Torque Loss After Miniscrew Placement: An In-Vitro Study Followed by a Clinical Trial.

PubMed

Migliorati, Marco; Drago, Sara; Barberis, Fabrizio; Schiavetti, Irene; Dalessandri, Domenico; Benedicenti, Stefano; Biavati, Armando Silvestrini

2016-01-01

To evaluate torque loss a week after insertion, both in an in vivo and an in vitro experimental setup were designed. In the in vivo setup a total of 29 miniscrews were placed in 20 patients who underwent orthodontic treatment. Maximum insertion torque (MIT) was evaluated at insertion time (T1). A week later, insertion torque was measured again by applying a quarter turn (T2); no load was applied on the screw during the first week. In the in vitro setup a total of 20 miniscrews were placed in pig rib bone samples. MIT was evaluated at insertion time (T1). Bone samples were kept in saline solution and controlled environment for a week during which the solution was refreshed every day. Afterwards, torque was measured again by applying a quarter turn (T2). The comparison of MIT over time was done calculating the percentage difference of the torque values between pre- and post-treatment and using the parametric two independent samples t-test or the non-parametric Mann-Whitney test. After a week unloaded miniscrews showed a mean loss of rotational torque of 36.3% and 40.9% in in vitro and in in vivo conditions, respectively. No statistical differences were found between the two different setups. Torque loss was observed after the first week in both study models; in vitro experimental setup provided a reliable study model for studying torque variation during the first week after insertion.

Torque Loss After Miniscrew Placement: An In-Vitro Study Followed by a Clinical Trial

PubMed Central

Migliorati, Marco; Drago, Sara; Barberis, Fabrizio; Schiavetti, Irene; Dalessandri, Domenico; Benedicenti, Stefano; Biavati, Armando Silvestrini

2016-01-01

To evaluate torque loss a week after insertion, both in an in vivo and an in vitro experimental setup were designed. In the in vivo setup a total of 29 miniscrews were placed in 20 patients who underwent orthodontic treatment. Maximum insertion torque (MIT) was evaluated at insertion time (T1). A week later, insertion torque was measured again by applying a quarter turn (T2); no load was applied on the screw during the first week. In the in vitro setup a total of 20 miniscrews were placed in pig rib bone samples. MIT was evaluated at insertion time (T1). Bone samples were kept in saline solution and controlled environment for a week during which the solution was refreshed every day. Afterwards, torque was measured again by applying a quarter turn (T2). The comparison of MIT over time was done calculating the percentage difference of the torque values between pre- and post-treatment and using the parametric two independent samples t-test or the non-parametric Mann–Whitney test. After a week unloaded miniscrews showed a mean loss of rotational torque of 36.3% and 40.9% in in vitro and in in vivo conditions, respectively. No statistical differences were found between the two different setups. Torque loss was observed after the first week in both study models; in vitro experimental setup provided a reliable study model for studying torque variation during the first week after insertion. PMID:27386011

Biomechanical evaluation of macro and micro designed screw-type implants: an insertion torque and removal torque study in rabbits.

PubMed

Chowdhary, Ramesh; Jimbo, Ryo; Thomsen, Christian; Carlsson, Lennart; Wennerberg, Ann

2013-03-01

To investigate the combined effect of macro and pitch shortened threads on primary and secondary stability during healing, but before dynamic loading. Two sets of turned implants with different macro geometry were prepared. The test group possessed pitch shortened threads in between the large threads and the control group did not have thread alterations. The two implant groups were placed in both femur and tibiae of 10 lop-eared rabbits, and at the time of implant insertion, insertion torques were recorded. After 4 weeks, all implants were subjected to removal torque tests. The insertion torque values for the control and test groups for the tibia were 15.7 and 20.6 Ncm, respectively, and for the femur, 11.8, and 12.8 Ncm respectively. The removal torque values for the control and test groups in the tibia were 7.9 and 9.1 Ncm, respectively, and for the femur, 7.9 and 7.7 Ncm respectively. There was no statistically significant difference between the control and test groups. Under limited dynamic load, the addition of pitch shortened threads did not significantly improve either the primary or the secondary stability of the implants in bone. © 2011 John Wiley & Sons A/S.

Heat generation during implant placement in low-density bone: effect of surgical technique, insertion torque and implant macro design.

PubMed

Marković, Aleksa; Mišić, Tijana; Miličić, Biljana; Calvo-Guirado, Jose Luis; Aleksić, Zoran; Ðinić, Ana

2013-07-01

The study aimed to investigate the effect of surgical technique, implant macrodesign and insertion torque on bone temperature changes during implant placement. In the in vitro study, 144 self-tapping (blueSKY(®) 4 × 10 mm; Bredent) and 144 non-self-tapping (Standard implant(®) 4.1 × 10 mm; Straumann) were placed in osteotomies prepared in pig ribs by lateral bone condensing or bone drilling techniques. The maximum insertion torque values of 30, 35 and 40 Ncm were used. Real-time bone temperature measurement during implant placement was performed by three thermocouples positioned vertically, in tripod configuration around every osteotomy, at a distance of 5 mm from it and at depths of 1, 5 and 10 mm. Data were analysed using Kruskal-Wallis, Mann-Whitney U-tests and Regression analysis. Significant predictor of bone temperature at the osteotomy depth of 1 mm was insertion torque (P = 0.003) and at the depth of 10-mm implant macrodesign (P = 0.029), while no significant predictor at depth of 5 mm was identified (P > 0.05). Higher insertion torque values as well as non-self-tapping implant macrodesign were related to higher temperatures. Implant placement in sites prepared by bone drilling induced significantly higher temperature increase (P = 0.021) compared with bone condensing sites at the depth of 5 mm, while no significant difference was recorded at other depths. Compared with 30 Ncm, insertion torque values of 35 and 40 Ncm produced significantly higher temperature increase (P = 0.005; P = 0.003, respectively) at the depth of 1 mm. There was no significant difference in temperature change induced by 35 and 40 Ncm, neither by implant macrodesign at all investigated depths (P > 0.05). Placement of self-tapping implants with low insertion torque into sites prepared by lateral bone condensing technique might be advantageous in terms of thermal effect on bone. © 2012 John Wiley & Sons A/S.

Effect of implant macro-design on primary stability: A prospective clinical study.

PubMed

Lozano-Carrascal, Naroa; Salomó-Coll, Oscar; Gilabert-Cerdà, Marta; Farré-Pagés, Nuria; Gargallo-Albiol, Jordi; Hernández-Alfaro, Federico

2016-03-01

Implant restorations have become a high predictable treatment option. Several caracteristics such as surgical technique and implant design can influence the treatment outcomes. The aim of the present study was to evaluate the influence of implant macro-design on primary stability measured with resonance frequency analysis (RFA) and insertion torque (IT). Material and Mehods: A total of 47 implants divided in two groups: Test group (TI): 22 Tapered MIS® Seven implants; Control group (CI): 25 cylindrical Astra® Osseospeed implants. All implants were inserted following the manufacturers' standard protocols. Implant primary stability was measured at the moment of implant placement by registering insertion torque values (ITv) and ISQ values by means of Osstell™ Mentor (ISQv) (Integration Diagnostic Ltd., Goteborg, Sweden). In the mandible, mean ISQv for tapered implants (TI) was 71.67±5.16 and for cylindrical implants (CI) 57.15±4.83 (p=0.01). Mean insertion torque was 46.67±6.85 Ncm for TI and 35.77±6.72 Ncm for CI (p=0.01). In the maxilla, mean ISQ was 67.2±4.42 for tapered implants and 49.17±15.30 for cylindrical implants (p=0.01). Mean insertion torque for TI was 41.5±6.26 Ncm and for CI 39.17±6.34 Ncm (p>0.05). For tapered implants, no correlation could be found between implant diameter and primary stability. But for cylindrical implants there was a statistically significant correlation between implant diameter and primary stability: ITv (p=0.03); ISQv (p=0.04). Within the limits of the present study, tapered shaped implants achieve higher primary stability measured through ISQ and insertion torque values. Moreover, for cylindrical implants positive correlation has been established between implant diameter and primary stability.

The Effect of Tissue Entrapment on Screw Loosening at the Implant/Abutment Interface of External- and Internal-Connection Implants: An In Vitro Study.

PubMed

Zeno, Helios A; Buitrago, Renan L; Sternberger, Sidney S; Patt, Marisa E; Tovar, Nick; Coelho, Paulo; Kurtz, Kenneth S; Tuminelli, Frank J

2016-04-01

To compare the removal of torque values of machined implant abutment connections (internal and external) with and without soft tissue entrapment using an in vitro model. Thirty external- and 30 internal-connection implants were embedded in urethane dimethacrylate. Porcine tissue was prepared and measured to thicknesses of 0.5 and 1.0 mm. Six groups (n = 10) were studied: External- and internal-connection implants with no tissue (control), 0.5, and 1.0 mm of tissue were entrapped at the implant/abutment interface. Abutments were inserted to 20 Ncm for all six groups. Insertion torque values were recorded using a digital torque gauge. All groups were then immersed in 1 M NaOH for 48 hours to dissolve tissue. Subsequent reverse torque measurements were recorded. Mean and standard deviation were determined for each group, and one-way ANOVA and Bonferroni test were used for statistical analysis. All 60 specimens achieved a 20-Ncm insertion torque, despite tissue entrapment. Reverse torque measurements for external connection displayed a statistically significant difference (p < 0.05) between all groups with mean reverse torque values for the control (13.71 ± 1.4 Ncm), 0.5 mm (7.83 ± 2.4 Ncm), and 1.0 mm tissue entrapment (2.29 ± 1.4 Ncm) groups. Some statistically significant differences (p < 0.05) were found between internal-connection groups. In all specimens, tissue did not completely dissolve after 48 hours. External-connection implants were significantly affected by tissue entrapment; the thicker the tissue, the lower the reverse torque values noted. Internal-connection implants were less affected by tissue entrapment. © 2015 by the American College of Prosthodontists.

Mathematical evaluation of the influence of multiple factors on implant stability quotient values in clinical practice: a retrospective study

PubMed Central

Huang, Hairong; Wismeijer, Daniel; Shao, Xianhong; Wu, Gang

2016-01-01

Objectives The objective of this study is to mathematically evaluate the influence of multiple factors on implant stability quotient values in clinical practice. Patients and methods Resonance frequency analysis was performed at T1 (measured immediately at the time of implant placement) and at T2 (measured before dental restoration) in 177 patients (329 implants). Using a multivariate linear regression model, we analyzed the influence of the following eleven candidate factors: sex, age, maxillary/mandibular location, bone type, immediate/delayed implantation, bone grafting (presence or absence), insertion torque, I-/II-stage healing pattern, implant diameter, implant length, and T1–T2 time interval. Results The following factors were identified to significantly influence the implant stability quotient (ISQ) values at T1: insertion torque, bone grafting, I-/II-stage healing pattern, immediate/delayed implantation, maxillary/mandibular location, implant diameter, and sex. In contrast, the ISQ values at T2 were significantly influenced only by three factors: implant diameter, T1–T2 time interval, and insertion torque. Conclusion Among the eleven candidate factors, seven key factors were found to influence the T1-ISQ values, while only three key factors influenced the T2-ISQ values. Both T1 and T2-ISQ values were found to be influenced by implant diameter and insertion torque. T1 was influenced specifically by the sex of the patient, the location (maxillary or mandibular), the implantation mode (immediate/delayed implantation), the healing stage, and the absence or presence of bone graft materials. PMID:27785040

Bioactive ceramic coating of cancellous screws improves the osseointegration in the cancellous bone.

PubMed

Lee, Jae Hyup; Nam, Hwa; Ryu, Hyun-Seung; Seo, Jun-Hyuk; Chang, Bong-Soon; Lee, Choon-Ki

2011-05-01

A number of methods for coating implants with bioactive ceramics have been reported to improve osseointegration in bone, but the effects of bioactive ceramic coatings on the osseointegration of cancellous screws are not known. Accordingly, biomechanical and histomorphometric analyses of the bone-screw interface of uncoated cancellous screws and cancellous screws coated with four different bioactive ceramics were performed. After coating titanium alloy cancellous screws with calcium pyrophosphate (CPP), CaO-SiO(2)-B(2)O(3) glass-ceramics (CSG), apatite-wollastonite 1:3 glass-ceramics (W3G), and CaO-SiO(2)-P(2)O(5)-B(2)O(3) glass-ceramics (BGS-7) using an enameling method, the coated and the uncoated screws were inserted into the proximal tibia and distal femur metaphysis of seven male mongrel dogs. The torque values of the screws were measured at the time of insertion and at removal after 8 weeks. The bone-screw contact ratio was analyzed by histomorphometry. There was no significant difference in the insertion torque between the uncoated and coated screws. The torque values of the CPP and BGS-7 groups measured at removal after 8 weeks were significantly higher than those of the uncoated group. Moreover, the values of the CPP and BGS-7 groups were significantly higher than the insertion torques. The fraction of bone-screw interface measured from the undecalcified histological slide showed that the CPP, W3G, and BGS-7 groups had significantly higher torque values in the cortical bone area than the uncoated group, and the CPP and BGS-7 groups had significantly higher torque values in the cancellous bone area than the uncoated group. In conclusion, a cancellous screw coated with CPP and BGS-7 ceramic bonds directly to cancellous bone to improve the bone-implant osseointegration. This may broaden the indications for cancellous screws by clarifying their contribution to improving osseointegration, even in the cancellous bone area.

Torque removal evaluation of prosthetic screws after tightening and loosening cycles: an in vitro study.

PubMed

Cardoso, Mayra; Torres, Marcelo Ferreira; Lourenço, Eduardo José Veras; de Moraes Telles, Daniel; Rodrigues, Renata Cristina Silveira; Ribeiro, Ricardo Faria

2012-04-01

The aim of this study was to evaluate the variation in removal torque of implant prosthetic abutment screws after successive tightening and loosening cycles, in addition to evaluating the influence of the hexagon at the abutment base on screw removal torque. Twenty hexagonal abutments were tightened to 20 regular external hex implants with a titanium alloy screw, with an insertion torque of 32 N cm, measured with a digital torque gauge. The implant/abutment/screw assemblies were divided into two groups: (1) abutments without hexagon at the base and (2) abutments with a hexagon at the base. Each assembly received a provisional restoration and was submitted to mechanical loading cycles. After this, the screws were removed and the removal torque was measured. This sequence was repeated 10 times, then the screw was replaced by a new one, and another cycle was performed. Linear regression analysis was performed. Removal torque values tended to decrease as the number of insertion/removal cycles increased, for both groups. Comparisons of the slopes and the intercepts between groups showed no statistical difference. There was no significant difference between the mean values of last five cycles and the 11th cycle. Within the limitations of this in vitro study, it was concluded that (1) repeated insertion/removal cycles promoted gradual reduction in removal torque of screws, (2) replacing the screw with a new one after 10 cycles did not increase resistance to loosening, and (3) removal of the hexagon from the abutment base had no effect on the removal torque of the screws. © 2011 John Wiley & Sons A/S.

Effect of implant macro-design on primary stability: A prospective clinical study

PubMed Central

Lozano-Carrascal, Naroa; Salomó-Coll, Oscar; Gilabert-Cerdà, Marta; Farré-Pagés, Nuria; Hernández-Alfaro, Federico

2016-01-01

Background Implant restorations have become a high predictable treatment option. Several caracteristics such as surgical technique and implant design can influence the treatment outcomes. The aim of the present study was to evaluate the influence of implant macro-design on primary stability measured with resonance frequency analysis (RFA) and insertion torque (IT). Material and Methods A total of 47 implants divided in two groups: Test group (TI): 22 Tapered MIS® Seven implants; Control group (CI): 25 cylindrical Astra® Osseospeed implants. All implants were inserted following the manufacturers’ standard protocols. Implant primary stability was measured at the moment of implant placement by registering insertion torque values (ITv) and ISQ values by means of Osstell™ Mentor (ISQv) (Integration Diagnostic Ltd., Goteborg, Sweden). Results In the mandible, mean ISQv for tapered implants (TI) was 71.67±5.16 and for cylindrical implants (CI) 57.15±4.83 (p=0.01). Mean insertion torque was 46.67±6.85 Ncm for TI and 35.77±6.72 Ncm for CI (p=0.01). In the maxilla, mean ISQ was 67.2±4.42 for tapered implants and 49.17±15.30 for cylindrical implants (p=0.01). Mean insertion torque for TI was 41.5±6.26 Ncm and for CI 39.17±6.34 Ncm (p>0.05). For tapered implants, no correlation could be found between implant diameter and primary stability. But for cylindrical implants there was a statistically significant correlation between implant diameter and primary stability: ITv (p=0.03); ISQv (p=0.04). Conclusions Within the limits of the present study, tapered shaped implants achieve higher primary stability measured through ISQ and insertion torque values. Moreover, for cylindrical implants positive correlation has been established between implant diameter and primary stability. Key words:Primary stability, tapered, cylindrical, conical, implant macro-design. PMID:26827067

Effect of insertion torque on bone screw pullout strength.

PubMed

Lawson, K J; Brems, J

2001-05-01

The effect of insertion torque on the holding strength of 4.5-mm ASIF/AO cortical bone screws was studied in vitro. Screw holding strength was determined using an Instron materials testing machine (Bristol, United Kingdom) on 55 lamb femora and 30 human tibiocortical bone sections. Holding strength was defined as tensile stress at pullout with rapid loading to construct failure. Different insertion torques were tested, normalizing to the thickness of cortical bone specimen engaged. These represented low, intermediate, high, and thread-damaging insertion torque. All screws inserted with thread-damaging torque and single cortex engaging screws inserted to high torque tightening moments showed diminished holding strength. This loss of strength amounted to 40%-50% less than screws inserted with less torque.

Preloads generated with repeated tightening in three types of screws used in dental implant assemblies.

PubMed

Byrne, Declan; Jacobs, Stuart; O'Connell, Brian; Houston, Frank; Claffey, Noel

2006-01-01

Abutment screw loosening, especially in the case of cemented single tooth restorations, is a cause of implant restoration failure. This study compared three screws (titanium alloy, gold alloy, and gold-coated) with similar geometry by recording the preload induced when torques of 10, 20, and 35 Ncm were used for fixation. Two abutment types were used-prefabricated preparable abutments and cast-on abutments. A custom-designed rig was used to measure preload in the abutment-screw-implant assembly with a strain gauge. Ten screws of each type were sequentially tightened to 10, 20, and 35 Ncm on ten of the two abutment types. The same screws were then loosened and re-tightened. This procedure was repeated. Thus, each screw was tightened on three occasions to the three insertion torques. A linear regression model was used to analyze the effects on preload values of screw type and abutment type for each of the three insertion torques. The results indicated that the gold-coated screw generated the highest preloads for all insertion torques and for each tightening episode. Further analysis focused on the effects of screw type and abutment type for each episode of tightening and for each fixation torque. The gold-coated screw, fixed to the prefabricated abutment, displayed higher preloads for the first tightening at 10, 20, and 35 Ncm. Conversely, the same screw fixed to the cast-on abutment showed higher values for the second and third tightening for all fixation torques. All screws showed decay in preload with the number of times tightened. Given the higher preloads generated using the gold-coated screw with both abutment types, it is more likely that this type of screw will maintain a secure joint when tightened for the second and third time. All screw types displayed some decay in preload with repeated tightening, irrespective of abutment type and insertion torque. The gold-coated screw showed markedly higher preloads for all insertion torques and for all instances of tightening when compared with the uncoated screws.

Z-2 Threaded Insert Design and Testing Abstract

NASA Technical Reports Server (NTRS)

Rhodes, RIchard; Graziosi, Dave; Jones, Bobby; Ferl, Jinny; Scarborough, Steve; Sweeney, Mitch

2016-01-01

The Z-2 Prototype Planetary Extravehicular Space Suit Assembly is a continuation of NASA's Z series of spacesuits. The Z-2 is another step in the NASA's technology development roadmap leading to human exploration of the Martian surface. To meet a more challenging set of requirements than previous suit systems standard design features, such as threaded inserts, have been re-analyzed and improved. NASA's Z-2 prototype space suit contains several components fabricated from an advanced hybrid composite laminate consisting of IM10 carbon fiber and fiber glass. One requirement NASA levied on the suit composites was the ability to have removable, replaceable helicoil inserts to which other suit components would be fastened. An approach utilizing bonded in inserts with helicoils inside of them was implemented. The design of the interface flanges of the composites allowed some of the inserts to be a "T" style insert that was installed through the entire thickness of the laminate. The flange portion of the insert provides a mechanical lock as a redundancy to the adhesive aiding in the pullout load that the insert can withstand. In some locations it was not possible to utilize at "T" style insert and a blind insert was used instead. These inserts rely completely on the bond strength of the adhesive to resist pullout. It was determined during the design of the suit that the inserts did not need to withstand loads induced from pressure cycling but instead tension induced from torqueing the screws to bolt on hardware which creates a much higher stress on them. Bolt tension is determined by dividing the torque on the screw by a k value multiplied by the thread diameter of the bolt. The k value is a factor that accounts for friction in the system. A common value used for k for a non-lubricated screw is 0.2. The k value can go down by as much as 0.1 if the screw is lubricated which means for the same torque, a much larger tension could be placed on the bolt and insert. This paper summarizes testing that was performed to determine a k value for helicoil inserts in the Z2 suit and how the insert design was modified to resist a higher pull out tension.

Primary stability, insertion torque, and bone density of conical implants with internal hexagon: is there a relationship?

PubMed

Trisi, Paolo; Berardi, Davide; Paolantonio, Michele; Spoto, Giuseppe; D'Addona, Antonio; Perfetti, Giorgio

2013-05-01

Between implants and peri-implant bone, there should be a minimum gap, without micromotions over a threshold, which could cause resorption and fibrosis. The higher the implant insertion torque, the higher will be the initial stability. The aim was to evaluate in vitro the correlation between micromotions and insertion torque of implants in bone of different densities. The test was performed on bovine bone of hard, medium, and soft density: 150 implants were used, 10 for each torque (20, 35, 45, 70, and 100 N/cm). Samples were fixed on a loading device. On each sample, we applied a 25-N horizontal force. Insertion torque and micromotions are statistically correlated. In soft bone with an insertion force of 20 and 35 N/cm, the micromotion resulted significantly over the risk threshold, which was not found with an insertion force of 45 and 70 N/cm and in hard and medium bones with any insertion torque. The increase in insertion torque reduces the amount of micromotions between implant and bone. Therefore, the immediate loading may be considered a valid therapeutic choice, even in low-density bone, as long as at least 45 N/cm of insertion torque is reached.

Influence of Stepped Osteotomy on Primary Stability of Implants Inserted in Low-Density Bone Sites: An In Vitro Study.

PubMed

Degidi, Marco; Daprile, Giuseppe; Piattelli, Adriano

The aims of this study were to evaluate the ability of a stepped osteotomy to improve dental implant primary stability in low-density bone sites and to investigate possible correlations between primary stability parameters. The study was performed on fresh humid bovine bone classified as type III. The test group consisted of 30 Astra Tech EV implants inserted following the protocol provided by the manufacturer. The first control group consisted of 30 Astra Tech EV implants inserted in sites without the underpreparation of the apical portion. The second control group consisted of 30 Astra Tech TX implants inserted following the protocol provided by the manufacturer. Implant insertion was performed at the predetermined 30 rpm. The insertion torque data were recorded and exported as a curve; using a trapezoidal integration technique, the area underlying the curve was calculated: this area represents the variable torque work (VTW). Peak insertion torque (pIT) and resonance frequency analysis (RFA) were also recorded. A Mann-Whitney test showed that the mean VTW was significantly higher in the test group compared with the first control and second control groups; furthermore, statistical analysis showed that pIT also was significantly higher in the test group compared with the first and second control groups. Analyzing RFA values, only the difference between the test group and second control group showed statistical significance. Pearson correlation analysis showed a very strong positive correlation between pIT and VTW values in all groups; furthermore, it showed a positive correlation between pIT and RFA values and between VTW and RFA values only in the test group. Within the limitations of an in vitro study, the results show that stepped osteotomy can be a viable method to improve implant primary stability in low-density bone sites, and that, when a traditional osteotomy method is performed, RFA presents no correlation with pIT and VTW.

Significance of the Pars Interarticularis in the Cortical Bone Trajectory Screw Technique: An In Vivo Insertional Torque Study.

PubMed

Ninomiya, Koshi; Iwatsuki, Koichi; Ohnishi, Yu-Ichiro; Ohkawa, Toshika; Yoshimine, Toshiki

2016-10-01

Retrospective study. Cortical bone trajectory (CBT), a more medial-to-lateral and shorter path than the traditional one for spinal fusion, is thought to be effective for severely degenerated vertebrae because screws are primarily stabilized at the posterior elements. We evaluated the efficacy of this approach through in vivo insertional torque measurement. There has been only one prior in vivo study on CBT insertional torque. Between January 2013 and April 2014, a total of 22 patients underwent posterior lumbar fusion using the CBT technique. The maximum insertional torque, which covers the radial strength needed for insertion, was measured for 113 screws, 8 of which were inserted for L5 spondylolysis. The insertional torque for cases with (n=8) and without (n=31) spondylolysis of L5 were compared using one-way analysis of variance (ANOVA). To evaluate vertebral degeneration, we classified 53 vertebrae without spondylolysis by lumbar radiography using semiquantitative methods; the insertional torque for the 105 screws used was compared on the basis of this classification. Additionally, differences in insertional torque among cases grouped by age, sex, and lumbar level were evaluated for these 105 screws using ANOVA and the Tukey test. The mean insertional torque was significantly lower for patients with spondylolysis than for those without spondylolysis (4.25 vs. 8.24 in-lb). There were no statistical differences in insertional torque according to vertebral grading or level. The only significant difference in insertional torque between age and sex groups was in men <75 years and women ≥75 years (10 vs. 5.5 in-lb). Although CBT should be used with great caution in patient with lysis who are ≥75 years, it is well suited for dealing with severely degenerated vertebrae because the pars interarticularis plays a very important role in the implementation of this technique.

Implant Insertion Torque: Its Role in Achieving Primary Stability of Restorable Dental Implants.

PubMed

Greenstein, Gary; Cavallaro, John

2017-02-01

A literature review was conducted to determine the role of insertion torque in attaining primary stability of dental implants. The review is comprised of articles that discussed the amount of torque needed to achieve primary implant stability in healed ridges and fresh extraction sockets prior to immediate implant loading. Studies were appraised that addressed the effects of minimum and maximum forces that can be used to successfully place implants. The minimum torque that can be employed to attain primary stability is undefined. Forces ≥30 Ncm are routinely used to place implants into healed ridges and fresh extraction sockets prior to immediate loading of implants. Increased insertion torque (≥50 Ncm) reduces micromotion and does not appear to damage bone. In general, the healing process after implant insertion provides a degree of biologic stability that is similar whether implants are placed with high or low initial insertion torque. Primary stability is desirable when placing implants, but the absence of micromotion is what facilitates predictable implant osseointegration. Increased insertion torque helps achieve primary stability by reducing implant micromotion. Furthermore, tactile information provided by the first surgical twist drill can aid in selecting the initial insertion torque to achieve predictable stability of inserted dental implants.

Effect of the starting point of half-pin insertion on the insertional torque of the pin at the tibia.

PubMed

Kim, Sung Jae; Kim, Sung Hwan; Kim, Young Hwan; Chun, Yong Min

2015-01-01

The authors have observed a failure to achieve secure fixation in elderly patients when inserting a half-pin at the anteromedial surface of the tibia. The purpose of this study was to compare two methods for inserting a half-pin at tibia diaphysis in elderly patients. Twenty cadaveric tibias were divided into Group C or V. A half-pin was inserted into the tibias of Group C via the conventional method, from the anteromedial surface to the interosseous border of the tibia diaphysis, and into the tibias of Group V via the vertical method, from the anterior border to the posterior surface at the same level. The maximum insertion torque was measured during the bicortical insertion with a torque driver. The thickness of the cortex was measured by micro-computed tomography. The relationship between the thickness of the cortex engaged and the insertion torque was investigated. The maximum insertion torque and the thickness of the cortex were significantly higher in Group V than Group C. Both groups exhibited a statistically significant linear correlation between torque and thickness by Spearman's rank correlation analysis. Half-pins inserted by the vertical method achieved purchase of more cortex than those inserted by the conventional method. Considering that cortical thickness and insertion torque in Group V were significantly greater than those in Group C, we suggest that the vertical method of half-pin insertion may be an alternative to the conventional method in elderly patients.

Insertion torque recordings for the diagnosis of contact between orthodontic mini-implants and dental roots: a systematic review.

PubMed

Meursinge Reynders, Reint; Ladu, Luisa; Ronchi, Laura; Di Girolamo, Nicola; de Lange, Jan; Roberts, Nia; Plüddemann, Annette

2016-03-31

Most orthodontic mini-implants (OMIs) are inserted between dental roots. The prevalence of contacting these structures is high. Such contacts can cause permanent root damage and implant instability. Increased torque levels during implant insertion (the index test) could be a more accurate and immediate measure for diagnosing implant-root contact (the target condition) than radiographs (the reference standard) and could ultimately lead to a reduction or elimination of X-ray exposure. To address this issue, we asked three questions: (1) whether OMIs with root contact had higher insertion torque values than those without, (2) what is the accuracy of the index test compared with the reference standard to diagnose the target condition and what are the adverse effects of the index test, and (3) whether intermediate torque values have clinical diagnostic utility. Methods were conducted according to our published protocol, which was based on the PRISMA-P 2015 statement. We applied broad spectrum eligibility criteria that included randomized and non-randomized studies on clinical, animal, and cadaver models. Not including such models would be unethical because it could slow down knowledge creation on the adverse effects of implant insertion. We conducted searches in more than 40 electronic databases including MEDLINE and 10 journals were hand-searched. Grey literature and reference lists were also searched. All research procedures were conducted independently by three reviewers. Authors of selected studies were contacted to obtain additional information. Outcomes on the three different research models were analysed separately. Systematic error was assessed with the Cochrane 'Risk of bias tool' for non-randomized studies. One clinical, two animal, and two cadaver studies fulfilled the eligibility criteria of the first research question. All studies and subgroups demonstrated higher insertion torque values for OMIs with the target condition than those without. Mean differences (MD) between these effect estimates were statistically significant in one beagle model (MD, 4.64; 95 % CI, 3.50 to 5.79) and three subgroups of cadaver studies (MD, 2.70; 95 % CI, 1.42 to 3.98) (MD, 3.97; 95 % CI, 2.17 to 5.78) (MD, 0.93; 95 % CI, 0.67 to 1.20). Highest mean differences were identified in most self-drilling compared with pre-drilling groups. Clinical heterogeneity between studies was high, and many items were underreported. All studies except one cadaver study scored at least one domain as 'serious risk' of bias. No studies addressed the second research question. One cadaver study addressed the third question which showed the importance of recording torque levels during the entire implant insertion process. Responses of contacted authors were helpful, but often difficult to obtain. Implants fractured in one animal and in one cadaver model. All eligible studies scored higher insertion torque values for implants with root contact than those without, but none of these studies assessed the diagnostic accuracy of the index test. The inclusion of non-randomized and animal and cadaver models in this systematic review provided key findings that otherwise would have been wasted. Such studies are important in the context of the wide applicability of this test, the high prevalence of the target condition, and the underreporting of adverse effects of interventions. A protocol for a potential new diagnostic pathway was presented, and the importance of contacting authors was addressed. The applicability of the findings should be interpreted in the context of underreporting and the many limitations of the included studies.

In vivo analysis of insertional torque during pedicle screwing using cortical bone trajectory technique.

PubMed

Matsukawa, Keitaro; Yato, Yoshiyuki; Kato, Takashi; Imabayashi, Hideaki; Asazuma, Takashi; Nemoto, Koichi

2014-02-15

The insertional torque of pedicle screws using the cortical bone trajectory (CBT) was measured in vivo. To investigate the effectiveness of the CBT technique by measurement of the insertional torque. The CBT follows a mediolateral and caudocephalad directed path, engaging with cortical bone maximally from the pedicle to the vertebral body. Some biomechanical studies have demonstrated favorable characteristics of the CBT technique in cadaveric lumbar spine. However, no in vivo study has been reported on the mechanical behavior of this new trajectory. The insertional torque of pedicle screws using CBT and traditional techniques were measured intraoperatively in 48 consecutive patients. A total of 162 screws using the CBT technique and 36 screws using the traditional technique were compared. In 8 of 48 patients, the side-by-side comparison of 2 different insertional techniques for each vertebra were performed, which formed the H group. In addition, the insertional torque was correlated with bone mineral density. The mean maximum insertional torque of CBT screws and traditional screws were 2.49 ± 0.99 Nm and 1.24 ± 0.54 Nm, respectively. The CBT screws showed 2.01 times higher torque and the difference was significant between the 2 techniques (P < 0.01). In the H group, the insertional torque were 2.71 ± 1.36 Nm in the CBT screws and 1.58 ± 0.44 Nm in the traditional screws. The CBT screws demonstrated 1.71 times higher torque and statistical significance was achieved (P < 0.01). Positive linear correlations between maximum insertional torque and bone mineral density were found in both technique, the correlation coefficient of traditional screws (r = 0.63, P < 0.01) was higher than that of the CBT screws (r = 0.59, P < 0.01). The insertional torque using the CBT technique is about 1.7 times higher than the traditional technique. 2.

Evaluation of the Effect of Platelet-Released Growth Factor and Immediate Orthodontic Loading on the Removal Torque of Miniscrews.

PubMed

Bayani, Shahin; Masoomi, Fatemeh; Aghaabbasi, Sharereh; Farsinejad, Alireza

2016-01-01

The purpose of this study was to evaluate the effect of platelet-released growth factor (PRGF) and immediate orthodontic forces on the removal torque of miniscrews. This study was conducted on three male dogs aged 6 to 8 months with a body weight of 17.6 to 18.4 kg. Sixty miniscrews were inserted in the posterior aspect of the femur. There were four groups, including loaded miniscrews with application of PRGF, unloaded miniscrews without application of PRGF, unloaded miniscrews with PRGF, and loaded miniscrews without PRGF. Twenty miniscrews were inserted in the femoral bone of one foot of each dog, including all the aforementioned subgroups. After 12 weeks, the miniscrews were removed by a removal torque tester device and measured in newton centimeters. The mean removal torque values in four groups of immediately loaded screws with PRGF, unloaded screws with PRGF, immediately loaded screws without PRGF, and unloaded screws without PRGF were 19.68, 21.74, 13.65, and 15.46 Ncm, respectively. It was shown that the mean removal torque value for the group with PRGF was significantly higher than that in the other groups (P = .0001). Although there was a tendency toward a decrease in removal torque value with immediate loading, it was not statistically significant (P = .21). According to the results of this study, applying PRGF with miniscrews increased their stability, but the delivery of immediate force on miniscrews had no effect on the miniscrews' stability.

BIOMECHANICAL EVALUATION OF THE INFLUENCE OF CERVICAL SCREWS TAPPING AND DESIGN.

PubMed

Silva, Patricia; Rosa, Rodrigo César; Shimano, Antonio Carlos; Albuquerque de Paula, Francisco José; Volpon, José Batista; Aparecido Defino, Helton Luiz

2009-01-01

To assess if the screw design (self-drilling/self-tapping) and the pilot hole tapping could affect the insertion torque and screw pullout strength of the screw used in anterior fixation of the cervical spine. Forty self-tapping screws and 20 self-drilling screws were inserted into 10 models of artificial bone and 10 cervical vertebrae of sheep. The studied parameters were the insertion torque and pullout strength. The following groups were created: Group I-self-tapping screw insertion after pilot hole drilling and tapping; Group II-self-tapping screw insertion after pilot hole drilling without tapping; Group III-self-drilling screw insertion without drilling and tapping. In Groups I and II, the pilot hole had 14.0 mm in depth and was made with a 3mmn drill, while tapping was made with a 4mm tap. The insertion torque was measured and the pullout test was performed. The comparison between groups was made considering the mean insertion torque and the maximum mean pullout strength with the variance analysis (ANOVA; p≤ 0.05). Previous drilling and tapping of pilot hole significantly decreased the insertion torque and the pullout strength. The insertion torque and pullout strength of self-drilling screws were significantly higher when compared to self-tapping screws inserted after pilot hole tapping.

The effect of implant design and bone quality on insertion torque, resonance frequency analysis, and insertion energy during implant placement in low or low- to medium-density bone.

PubMed

Wang, Tong-Mei; Lee, Ming-Shu; Wang, Juo-Song; Lin, Li-Deh

2015-01-01

This study investigated the effect of implant design and bone quality on insertion torque (IT), implant stability quotient (ISQ), and insertion energy (IE) by monitoring the continuous change in IT and ISQ while implants were inserted in artificial bone blocks that simulate bone of poor or poor-to-medium quality. Polyurethane foam blocks (Sawbones) of 0.16 g/cm³ and 0.32 g/cm³ were respectively used to simulate low density and low- to medium-density cancellous bone. In addition, some test blocks were laminated with a 1-mm 0.80 g/cm³ polyurethane layer to simulate cancellous bone with a thin cortical layer. Four different implants (Nobel Biocare Mk III-3.75, Mk III-4.0, Mk IV-4.0, and NobelActive-4.3) were placed into the different test blocks in accordance with the manufacturer's instructions. The IT and ISQ were recorded at every 0.5-mm of inserted length during implant insertion, and IE was calculated from the torque curve. The peak IT (PIT), final IT (FIT), IE, and final ISQ values were statistically analyzed. All implants showed increasing ISQ values when the implant was inserted more deeply. In contrast to the ISQ, implants with different designs showed dissimilar IT curve patterns during the insertion. All implants showed a significant increase in the PIT, FIT, IE, and ISQ when the test-block density increased or when the 1-mm laminated layer was present. Tapered implants showed FIT or PIT values of more than 40 Ncm for all of the laminated test blocks and for the nonlaminated test blocks of low to medium density. Parallel-wall implants did not exhibit PIT or FIT values of more than 40 Ncm for all of the test blocks. NobelActive-4.3 showed a significantly higher FIT, but a significantly lower IE, than Mk IV-4.0. While the existence of cortical bone or implant designs significantly affects the dynamic IT profiles during implant insertion, it does not affect the ISQ to a similar extent. Certain implant designs are more suitable than others if high IT is required in bone of poor quality. The manner in which IT, IE, and ISQ represent the implant primary stability requires further study.

Modelling dental implant extraction by pullout and torque procedures.

PubMed

Rittel, D; Dorogoy, A; Shemtov-Yona, K

2017-07-01

Dental implants extraction, achieved either by applying torque or pullout force, is used to estimate the bone-implant interfacial strength. A detailed description of the mechanical and physical aspects of the extraction process in the literature is still missing. This paper presents 3D nonlinear dynamic finite element simulations of a commercial implant extraction process from the mandible bone. Emphasis is put on the typical load-displacement and torque-angle relationships for various types of cortical and trabecular bone strengths. The simulations also study of the influence of the osseointegration level on those relationships. This is done by simulating implant extraction right after insertion when interfacial frictional contact exists between the implant and bone, and long after insertion, assuming that the implant is fully bonded to the bone. The model does not include a separate representation and model of the interfacial layer for which available data is limited. The obtained relationships show that the higher the strength of the trabecular bone the higher the peak extraction force, while for application of torque, it is the cortical bone which might dictate the peak torque value. Information on the relative strength contrast of the cortical and trabecular components, as well as the progressive nature of the damage evolution, can be revealed from the obtained relations. It is shown that full osseointegration might multiply the peak and average load values by a factor 3-12 although the calculated work of extraction varies only by a factor of 1.5. From a quantitative point of view, it is suggested that, as an alternative to reporting peak load or torque values, an average value derived from the extraction work be used to better characterize the bone-implant interfacial strength. Copyright © 2017 Elsevier Ltd. All rights reserved.

[Tensile strength of bone fixation of hydroxyapatite coated Schanz screws of the Heidelberg External Fixation System (HEFS)--comparative torque measurements in clinical use and in cadaver tibia].

PubMed

Placzek, R; Deuretzbacher, G; Meiss, A L

2002-12-01

It is claimed in the literature that hydroxyapatite(HA)-coated screws of external fixators have superior fixation strength in bone, which is postulated to lead to a substantial decrease in loosening and infection rates. We report on a study of the maximum torque values developed while inserting and removing 30 HA-coated Schanz screws of 8 Heidelberg external fixation systems applied to the tibia to correct leg length differences and axial deformities. The infection rate was determined in accordance with defined criteria, and was found to be about 20% for the HA-coated screws. Screws without infection showed an extraction torque above insertion torque, screws with infection an extraction torque below. A significant correlation (p = 0.05) was seen between infection and decrease in fixation strength (quotient: loosening torque/tightening torque). To exclude the impact of such biological processes as osteointegration and bone remodelling, the clinical results were compared with the torques measured for coated and uncoated Schanz screws in a human cadaveric tibia. A significantly higher fixation strength in bone was found for HA-coated screws in comparison with uncoated screws (p = 0.002). These data warrant a clinical study directly comparing HA-coated and uncoated Schanz screws.

Two-Finger Tightness: What Is It? Measuring Torque and Reproducibility in a Simulated Model.

PubMed

Acker, William B; Tai, Bruce L; Belmont, Barry; Shih, Albert J; Irwin, Todd A; Holmes, James R

2016-05-01

Residents in training are often directed to insert screws using "two-finger tightness" to impart adequate torque but minimize the chance of a screw stripping in bone. This study seeks to quantify and describe two-finger tightness and to assess the variability of its application by residents in training. Cortical bone was simulated using a polyurethane foam block (30-pcf density) that was prepared with predrilled holes for tightening 3.5 × 14-mm long cortical screws and mounted to a custom-built apparatus on a load cell to capture torque data. Thirty-three residents in training, ranging from the first through fifth years of residency, along with 8 staff members, were directed to tighten 6 screws to two-finger tightness in the test block, and peak torque values were recorded. The participants were blinded to their torque values. Stripping torque (2.73 ± 0.56 N·m) was determined from 36 trials and served as a threshold for failed screw placement. The average torques varied substantially with regard to absolute torque values, thus poorly defining two-finger tightness. Junior residents less consistently reproduced torque compared with other groups (0.29 and 0.32, respectively). These data quantify absolute values of two-finger tightness but demonstrate considerable variability in absolute torque values, percentage of stripping torque, and ability to consistently reproduce given torque levels. Increased years in training are weakly correlated with reproducibility, but experience does not seem to affect absolute torque levels. These results question the usefulness of two-finger tightness as a teaching tool and highlight the need for improvement in resident motor skill training and development within a teaching curriculum. Torque measuring devices may be a useful simulation tools for this purpose.

Solid Rocket Booster Hydraulic Pump Port Cap Joint Load Testing

NASA Technical Reports Server (NTRS)

Gamwell, W. R.; Murphy, N. C.

2004-01-01

The solid rocket booster uses hydraulic pumps fabricated from cast C355 aluminum alloy, with 17-4 PH stainless steel pump port caps. Corrosion-resistant steel, MS51830 CA204L self-locking screw thread inserts are installed into C355 pump housings, with A286 stainless steel fasteners installed into the insert to secure the pump port cap to the housing. In the past, pump port cap fasteners were installed to a torque of 33 Nm (300 in-lb). However, the structural analyses used a significantly higher nut factor than indicated during tests conducted by Boeing Space Systems. When the torque values were reassessed using Boeing's nut factor, the fastener preload had a factor of safety of less than 1, with potential for overloading the joint. This paper describes how behavior was determined for a preloaded joint with a steel bolt threaded into steel inserts in aluminum parts. Finite element models were compared with test results. For all initial bolt preloads, bolt loads increased as external applied loads increased. For higher initial bolt preloads, less load was transferred into the bolt, due to external applied loading. Lower torque limits were established for pump port cap fasteners and additional limits were placed on insert axial deformation under operating conditions after seating the insert with an initial preload.

Effect of screw torque level on cortical bone pullout strength.

PubMed

Cleek, Tammy M; Reynolds, Karen J; Hearn, Trevor C

2007-02-01

The objectives of this study were 2-fold: (1) to perform detailed analysis of cortical screw tightening stiffness during automated insertion, and (2) to determine the effect of 3 torque levels on the holding strength of the bone surrounding the screw threads as assessed by screw pullout. Ten pairs of ovine tibiae were used with 3 test sites spaced 20 mm apart centered along the shaft. One side of each pair was used for measuring ultimate failure torque (Tmax). These Tmax and bone-density values were used to predict Tmax at contralateral tibia sites. Screws were inserted and tightened to 50%, 70%, and 90% of predicted Tmax at the contralateral sites to encompass the average clinical level of torque (86% Tmax). Pullout tests were performed and maximum force values were normalized by cortical thickness. Torque to failure tests indicated tightening to 86% Tmax occurs after yield and leads to an average 51% loss in stiffness. Normalized pullout strength for screws tightened to 50% Tmax, 70% Tmax, and 90% Tmax were 2525 +/- 244, 2707 +/- 280, and 2344 +/- 346 N, respectively, with a significant difference between 70% Tmax and 90% Tmax groups (P < 0.05). Within the limitations of our study involving the testing of 1 type of screw purchase in ovine tibiae, results demonstrate that clinical levels of lag screw tightening (86% Tmax) are past the yield point of bone. Tightening to these high torque levels can cause damage leading to compromised holding strength. Further research is still required to establish the appropriate level of torque required for achieving optimal fracture fixation and healing.

Efficacy of Sealing Agents on Preload Maintenance of Screw-Retained Implant-Supported Prostheses.

PubMed

Seloto, Camila Berbel; Strazzi Sahyon, Henrico Badaoui; Dos Santos, Paulo Henrique; Delben, Juliana Aparecida; Assunção, Wirley Gonçalves

The aim of this study was to evaluate the effect of sealing agents on preload maintenance of screw joints. A total of four groups (n = 10 in each group) of abutment/implant systems, including external hexagon implants and antirotational UCLA abutments with a metallic collar in cobalt-chromium alloy, were assessed. In the control group (CG), no sealing agent was used at the abutment screw/implant interface. In the other groups, three different sealing agents were used at the abutment screw/implant interface: anaerobic sealing agent for medium torque (ASMT), anaerobic sealing agent for high torque (ASHT), and cyanoacrylate-based bonding agent (CYAB). All abutments were attached to the implants at 32 ± 1 N.cm. After 48 ± 2 hours of initial tightening, loosing torque (detorque) was measured using a digital torque wrench. Data were analyzed using Shapiro-Wilk, Wilcoxon, and Kruskal-Wallis tests, at 5% level of significance. In the CG and ASMT groups, detorque was lower than the insertion torque (24.6 ± 1.5 N.cm and 24.3 ± 1.1 N.cm, respectively). In the ASHT and CYAB groups, mean detorque increased in comparison to the insertion torque (51.0 ± 7.4 N.cm and 47.7 ± 15.1 N.cm, respectively). The ASHT was more efficient than the other sealing agents, increasing the remaining preload (detorque value) 58.88%. Although the cyanoacrylate-based bonding agent also generated high detorque values, the high standard deviation suggested its lower reliability.

Effect of Off-Axis Screw Insertion, Insertion Torque, and Plate Contouring on Locked Screw Strength

PubMed Central

Gallagher, Bethany; Silva, Matthew J.; Ricci, William M.

2015-01-01

Objectives This study quantifies the effects of insertion torque, off-axis screw angulation, and plate contouring on the strength of locking plate constructs. Methods Groups of locking screws (n = 6–11 screws) were inserted at 50%, 100%, 150%, and 200% of the manufacturer-recommended torque (3.2 Nm) into locking compression plates at various angles: orthogonal (control), 5-degree angle off-axis, and 10-degree angle off-axis. Screws were loaded to failure by a transverse force (parallel to the plate) either in the same (“+”) or opposite direction (“−”) of the initial screw angulation. Separately, locking plates were bent to 5 and 10-degree angles, with the bend apex at a screw hole. Locking screws inserted orthogonally into the apex hole at 100% torque were loaded to failure. Results Orthogonal insertion resulted in the highest average load to failure, 2577 ± 141 N (range, 2413–2778 N), whereas any off-axis insertion significantly weakened constructs (165–1285 N, at 100% torque) (P < 0.05). For “+” loading, torque beyond 100% did not increase strength, but 50% torque reduced screw strength (P < 0.05). Loading in the “−” direction consistently resulted in higher strengths than “+” loading (P < 0.05). Plate contouring of 5-degree angle did not significantly change screw strength compared with straight plates but contouring of 10-degree angle significantly reduced load to failure (P < 0.05). Conclusions To maximize the screw plate interface strength, locking screws should be inserted without cross-threading. The mechanical stability of locked screws is significantly compromised by loose insertion, off-axis insertion, or severe distortion of the locking mechanism. PMID:24343255

Predicting cancellous bone failure during screw insertion.

PubMed

Reynolds, Karen J; Cleek, Tammy M; Mohtar, Aaron A; Hearn, Trevor C

2013-04-05

Internal fixation of fractures often requires the tightening of bone screws to stabilise fragments. Inadequate application of torque can leave the fracture unstable, while over-tightening results in the stripping of the thread and loss of fixation. The optimal amount of screw torque is specific to each application and in practice is difficult to attain due to the wide variability in bone properties including bone density. The aim of the research presented in this paper is to investigate the relationships between motor torque and screw compression during powered screw insertion, and to evaluate whether the torque during insertion can be used to predict the ultimate failure torque of the bone. A custom test rig was designed and built for bone screw experiments. By inserting cancellous bone screws into synthetic, ovine and human bone specimens, it was established that variations related to bone density could be automatically detected through the effects of the bone on the rotational characteristics of the screw. The torque measured during screw insertion was found to be directly related to bone density and can be used, on its own, as a good predictor of ultimate failure torque of the bone. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

Time-elapsed screw insertion with microCT imaging.

PubMed

Ryan, M K; Mohtar, A A; Cleek, T M; Reynolds, K J

2016-01-25

Time-elapsed analysis of bone is an innovative technique that uses sequential image data to analyze bone mechanics under a given loading regime. This paper presents the development of a novel device capable of performing step-wise screw insertion into excised bone specimens, within the microCT environment, whilst simultaneously recording insertion torque, compression under the screw head and rotation angle. The system is computer controlled and screw insertion is performed in incremental steps of insertion torque. A series of screw insertion tests to failure were performed (n=21) to establish a relationship between the torque at head contact and stripping torque (R(2)=0.89). The test-device was then used to perform step-wise screw insertion, stopping at intervals of 20%, 40%, 60% and 80% between screw head contact and screw stripping. Image data-sets were acquired at each of these time-points as well as at head contact and post-failure. Examination of the image data revealed the trabecular deformation as a result of increased insertion torque was restricted to within 1mm of the outer diameter of the screw thread. Minimal deformation occurred prior to the step between the 80% time-point and post-failure. The device presented has allowed, for the first time, visualization of the micro-mechanical response in the peri-implant bone with increased tightening torque. Further testing on more samples is expected to increase our understanding of the effects of increased tightening torque at the micro-structural level, and the failure mechanisms of trabeculae. Copyright © 2015 Elsevier Ltd. All rights reserved.

Locking design affects the jamming of screws in locking plates.

PubMed

Sandriesser, Sabrina; Rupp, Markus; Greinwald, Markus; Heiss, Christian; Augat, Peter; Alt, Volker

2018-06-01

The seizing of locking screws is a frequently encountered clinical problem during implant removal of locking compression plates (LCP) after completion of fracture healing. The aim of this study was to investigate the effect of two different locking mechanisms on the seizing of locking screws. Specifically, the removal torques before and after cyclic dynamic loading were assessed for screws inserted at the manufacturer-recommended torque or at an increased insertion torque. The seizing of 3.5-mm angular stable screws was assessed as a function of insertion torque for two different locking mechanisms (Thread & Conus and Thread Only). Locking screws (n=10 for each configuration) were inserted either according to the manufacturer-recommended torque or at an increased torque of 150% to simulate an over-insertion of the screw. Half of the screws were removed directly after insertion and the remaining half was removed after a dynamic load protocol of 100,000 cycles. The removal torques of locking screws exceeded the insertion torques for all tested conditions confirming the adequacy of the test setup in mimicking screw seizing in locked plating. Screw seizing was more pronounced for Thread Only design (+37%) compared to Thread & Conus design (+14%; P<0.0001). Cyclic loading of the locking construct consistently resulted in an increased seizing of the locking screws (P<0.0001). Clinical observations from patients treated with the Thread & Conus locking design confirm the biomechanical findings of reduction in seizing effect by using a Thread & Conus design. In conclusion, both over-tightening and cyclic loading are potential causes for screw seizing in locking plate implants. Both effects were found to be less pronounced in the Thread & Conus design as compared to the traditional Thread Only design. © 2018 Elsevier Ltd. All rights reserved.

Primary stability, insertion torque and bone density of cylindric implant ad modum Branemark: is there a relationship? An in vitro study.

PubMed

Trisi, Paolo; De Benedittis, Simona; Perfetti, Giorgio; Berardi, Davide

2011-05-01

Protocols of immediate loading have been reported in several studies. It has also been demonstrated that the cause of failure of immediate loaded implants is due to the micromotion on the bone-implant interface induced by immediate loading. There should be a minimum gap between the implant and the peri-implant bone, without micromotions occurring above a definite threshold risk as they induce bone resorption and fibrosis around the implant. Measurement of the torque necessary to insert an implant in the bone is a parameter for measuring initial stability. The higher the implant insertion torque, the higher the initial stability attained. The aim of this study was to evaluate in vitro the correlation between the micromotion of cylindric screw implants ad modum Branemark and the insertion torque in bone of different densities. The test was carried out on 2 × 2 cm samples of fresh bovine bone of three different densities: hard (H), medium (M) and soft (S). One hundred and fifty hexa implants ad modum Branemark were used, 3.75 mm in diameter and 9 mm long. To screw in the implants, a customized manual key was used, controlled digitally to evaluate the peak insertion torques. Ten implants were prepared for each torque (20, 35, 45, 70 and 100 N/cm). The bone sample was then fixed on a loading device, which allowed evaluating the micromotion. On each sample, we applied a 25 N horizontal force. The results indicate that the peak insertion torque and the implant micromotion are statistically correlated, and statistically significant differences in H and M bone were found compared with S bone. In S bone, we noted a micromotion significantly higher than the risk threshold, and it was not possible to reach peak insertion torque above 35 N/cm. In H and M bone, the micromotion is below the threshold of all insertion torques. Increasing the peak insertion torque, we can reduce the extent of the micromotion between the implant and the bone when submitted to lateral forces in vitro. In soft bone, the micromotion was always high; hence, immediate loading of implants in low-density bone should be evaluated with care. © 2010 John Wiley & Sons A/S.

Stability of smooth and rough mini-implants: clinical and biomechanical evaluation - an in vivostudy

PubMed Central

Vilani, Giselle Naback Lemes; Ruellas, Antônio Carlos de Oliveira; Elias, Carlos Nelson; Mattos, Cláudia Trindade

2015-01-01

Objective: To compare in vivo orthodontic mini-implants (MI) of smooth (machined) and rough (acid etched) surfaces, assessing primary and secondary stability. Methods: Thirty-six (36) MI were inserted in the mandibles of six (6) dogs. Each animal received six (6) MI. In the right hemiarch, three (3) MI without surface treatment (smooth) were inserted, whereas in the left hemiarch, another three (3) MI with acid etched surfaces (rough) were inserted. The two distal MI in each hemiarch received an immediate load of 1.0 N for 16 weeks, whereas the MI in the mesial extremity was not subject to loading. Stability was measured by insertion and removal torque, initial and final mobility and by inter mini-implant distance. Results: There was no statistical behavioral difference between smooth and rough MI. High insertion torque and reduced initial mobility were observed in all groups, as well as a reduction in removal torques in comparison with insertion torque. Rough MI presented higher removal torque and lower final mobility in comparison to smooth MI. MI did not remain static, with displacement of rough MI being smaller in comparison with smooth MI, but with no statistical difference. Conclusions: MI primary stability was greater than stability measured at removal. There was no difference in stability between smooth and rough MI when assessing mobility, displacement and insertion as well as removal torques. PMID:26560819

Functional Consequence of Distal Brachioradialis Tendon Release: A Biomechanical Study

PubMed Central

Tirrell, Timothy F.; Franko, Orrin I.; Bhola, Siddharth; Hentzen, Eric R.; Abrams, Reid A.; Lieber, Richard L.

2013-01-01

Purpose Open reduction and internal fixation of distal radius fractures often necessitates release of the brachioradialis from the radial styloid. However, this common procedure has the potential to decrease elbow flexion strength. To determine the potential morbidity associated with brachioradialis release, we measured the change in elbow torque as a function of incremental release of the brachioradialis insertion footprint. Methods In 5 upper extremity cadaveric specimens, the brachioradialis tendon was systematically released from the radius, and the resultant effect on brachioradialis elbow flexion torque was measured. Release distance was defined as the distance between the release point and the tip of the radial styloid. Results Brachioradialis elbow flexion torque dropped to 95%, 90% and 86% of its original value at release distances of 27mm, 46mm, and 52mm, respectively. Importantly, brachioradialis torque remained above 80% of its original value at release distances up to 7 centimeters. Conclusions Our data demonstrate that release of the brachioradialis tendon from its insertion has minor effects on its ability to transmit force to the distal radius. Clinical Relevance These data may imply that release of the distal brachioradialis tendon during distal radius open reduction internal fixation can be performed without meaningful functional consequences to elbow flexion torque. Even at large release distances, overall elbow flexion torque loss after brachioradialis release would be expected to be less than 5% due to the much larger contributions of the biceps and brachialis. Use of the brachioradialis as a tendon transfer donor should not be limited by concerns of elbow flexion loss, and the tendon could be considered as an autograft donor. PMID:23528425

Fracture strength of orthodontic mini-implants

PubMed Central

Assad-Loss, Tatiana Feres; Kitahara-Céia, Flávia Mitiko Fernandes; Silveira, Giordani Santos; Elias, Carlos Nelson; Mucha, José Nelson

2017-01-01

ABSTRACT Objective: This study aimed at evaluating the design and dimensions of five different brands of orthodontic mini-implants, as well as their influence on torsional fracture strength. Methods: Fifty mini-implants were divided into five groups corresponding to different manufactures (DEN, RMO, CON, NEO, SIN). Twenty-five mini-implants were subjected to fracture test by torsion in the neck and the tip, through arbors attached to a Universal Mechanical Testing Machine. The other 25 mini-implants were subjected to insertion torque test into blocks of pork ribs using a torquimeter and contra-angle handpiece mounted in a surgical motor. The shape of the active tip of the mini-implants was evaluated under microscopy. The non-parametric Friedman test and Snedecor’s F in analysis of variance (ANOVA) were used to evaluate the differences between groups. Results: The fracture torque of the neck ranged from 23.45 N.cm (DEN) to 34.82 N.cm (SIN), and of the tip ranged from 9.35 N.cm (CON) to 24.36 N.cm (NEO). Insertion torque values ranged from 6.6 N.cm (RMO) to 10.2 N.cm (NEO). The characteristics that most influenced the results were outer diameter, inner diameter, the ratio between internal and external diameters, and the existence of milling in the apical region of the mini-implant. Conclusions: The fracture torques were different for both the neck and the tip of the five types evaluated. NEO and SIN mini-implants showed the highest resistance to fracture of the neck and tip. The fracture torques of both tip and neck were higher than the torque required to insert mini-implants. PMID:28746487

Effect of various factors on pull out strength of pedicle screw in normal and osteoporotic cancellous bone models.

PubMed

Varghese, Vicky; Saravana Kumar, Gurunathan; Krishnan, Venkatesh

2017-02-01

Pedicle screws are widely used for the treatment of spinal instability by spine fusion. Screw loosening is a major problem of spine fusion, contributing to delayed patient recovery. The present study aimed to understand the factor and interaction effects of density, insertion depth and insertion angle on pedicle screw pull out strength and insertion torque. A pull out study was carried out on rigid polyurethane foam blocks representing osteoporotic to normal bone densities according to the ASTM-1839 standard. It was found that density contributes most to pullout strength and insertion torque. The interaction effect is significant (p < 0.05) and contributes 8% to pull out strength. Axial pullout strength was 34% lower than angled pull out strength in the osteoporotic bone model. Insertion angle had no significant effect (p > 0.05) on insertion torque. Pullout strength and insertion torque had no significant correlation (p > 0.05) in the case of the extremely osteoporotic bone model. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

Effect of Repeated Screw Joint Closing and Opening Cycles and Cyclic Loading on Abutment Screw Removal Torque and Screw Thread Morphology: Scanning Electron Microscopy Evaluation.

PubMed

Arshad, Mahnaz; Mahgoli, Hosseinali; Payaminia, Leila

To evaluate the effect of repeated screw joint closing and opening cycles and cyclic loading on abutment screw removal torque and screw thread morphology using scanning electron microscopy (SEM). Three groups (n = 10 in each group) of implant-abutment-abutment screw assemblies were created. There were also 10 extra abutment screws as new screws in group 3. The abutment screws were tightened to 12 Ncm with an electronic torque meter; then they were removed and removal torque values were recorded. This sequence was repeated 5 times for group 1 and 15 times for groups 2 and 3. The same screws in groups 1 and 2 and the new screws in group 3 were then tightened to 12 Ncm; this was also followed by screw tightening to 30 Ncm and retightening to 30 Ncm 15 minutes later. Removal torque measurements were performed after screws were subjected to cyclic loading (0.5 × 10⁶ cycles; 1 Hz; 75 N). Moreover, the surface topography of one screw from each group before and after cyclic loading was evaluated with SEM and compared with an unused screw. All groups exhibited reduced removal torque values in comparison to insertion torque in each cycle. However, there was a steady trend of torque loss in each group. A comparison of the last cycle of the groups before loading showed significantly greater torque loss value in the 15th cycle of groups 2 and 3 compared with the fifth cycle of group 1 (P < .05). Nonetheless, torque loss values after loading were not shown to be significantly different from each other. Using a new screw could not significantly increase the value of removal torque. It was concluded that restricting the amount of screw tightening is more important than replacing the screw with a new one when an abutment is definitively placed.

Effect of insertion torque on titanium implant osseointegration: an animal experimental study.

PubMed

Duyck, Joke; Roesems, Rutger; Cardoso, Marcio V; Ogawa, Toru; De Villa Camargos, Germana; Vandamme, Katleen

2015-02-01

To evaluate the effect of implant insertion torque on the peri-implant bone healing and implant osseointegration. Bilaterally in the tibia of five adult New Zealand white rabbits, 20 implants were installed, subdivided into four groups, corresponding to two insertion torque conditions (low, < 10 Ncm vs. high > 50 Ncm) and 2 experimental periods (2 weeks vs. 4 weeks of healing). The implant insertion torque was determined by the surgical drill diameter relative to the implant diameter. Implant osseointegration was evaluated by quantitative histology (bone-to-implant contact with host bone [BIC-host], with neoformed bone [BIC-de novo], with both bone types [BIC-total], and peri-implant bone [BA/TA]). Every response was modelled over time using GEE (general estimation equation) with an unstructured variance-covariance matrix to correct for dependency between the measurements from one animal. The statistical significance level of α = 0.05 was applied. Significantly, more BIC-host and BIC-total were recorded for H implants compared with L implants after 2 week of healing (P = 0.010 and P = 0.0001, respectively). However, this result was no longer found for the extended healing period. Furthermore, BIC-total significantly increased over time for L implants (P < 0.00001). In contrast, the significant increase in BA/TA over time was found for H implants (P < 0.01). Finally, H insertion torque led to an increased BA/TA after 4 week of healing (P < 0.02) compared with the L insertion protocol. L insertion torque implants installed in the rabbit tibial bone osseointegrate with considerable de novo bone formation. This bone neoformation enables L implants to catch up, already during the early osseointegration stage, the initial inferior amount BIC contact compared with that of H implants. A negative impact of the created strain environment accompanying H insertion torque implant installation on the biological process of osseointegration could not be observed, at least not at tissue level. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Coating dental implant abutment screws with diamondlike carbon doped with diamond nanoparticles: the effect on maintaining torque after mechanical cycling.

PubMed

Lepesqueur, Laura Soares; de Figueiredo, Viviane Maria Gonçalves; Ferreira, Leandro Lameirão; Sobrinho, Argemiro Soares da Silva; Massi, Marcos; Bottino, Marco Antônio; Nogueira Junior, Lafayette

2015-01-01

To determine the effect of maintaining torque after mechanical cycling of abutment screws that are coated with diamondlike carbon and coated with diamondlike carbon doped with diamond nanoparticles, with external and internal hex connections. Sixty implants were divided into six groups according to the type of connection (external or internal hex) and the type of abutment screw (uncoated, coated with diamondlike carbon, and coated with diamondlike carbon doped with diamond nanoparticles). The implants were inserted into polyurethane resin and crowns of nickel chrome were cemented on the implants. The crowns had a hole for access to the screw. The initial torque and the torque after mechanical cycling were measured. The torque values maintained (in percentages) were evaluated. Statistical analysis was performed using one-way analysis of variance and the Tukey test, with a significance level of 5%. The largest torque value was maintained in uncoated screws with external hex connections, a finding that was statistically significant (P = .0001). No statistically significant differences were seen between the groups with and without coating in maintaining torque for screws with internal hex connections (P = .5476). After mechanical cycling, the diamondlike carbon with and without diamond doping on the abutment screws showed no improvement in maintaining torque in external and internal hex connections.

Technical Errors May Affect Accuracy of Torque Limiter in Locking Plate Osteosynthesis.

PubMed

Savin, David D; Lee, Simon; Bohnenkamp, Frank C; Pastor, Andrew; Garapati, Rajeev; Goldberg, Benjamin A

2016-01-01

In locking plate osteosynthesis, proper surgical technique is crucial in reducing potential pitfalls, and use of a torque limiter makes it possible to control insertion torque. We conducted a study of the ways in which different techniques can alter the accuracy of torque limiters. We tested 22 torque limiters (1.5 Nm) for accuracy using hand and power tools under different rotational scenarios: hand power at low and high velocity and drill power at low and high velocity. We recorded the maximum torque reached after each torque-limiting event. Use of torque limiters under hand power at low velocity and high velocity resulted in significantly (P < .0001) different mean (SD) measurements: 1.49 (0.15) Nm and 3.73 (0.79) Nm. Use under drill power at controlled low velocity and at high velocity also resulted in significantly (P < .0001) different mean (SD) measurements: 1.47 (0.14) Nm and 5.37 (0.90) Nm. Maximum single measurement obtained was 9.0 Nm using drill power at high velocity. Locking screw insertion with improper technique may result in higher than expected torque and subsequent complications. For torque limiters, the most reliable technique involves hand power at slow velocity or drill power with careful control of insertion speed until 1 torque-limiting event occurs.

A strain gauge analysis comparing 4‐unit veneered zirconium dioxide implant‐borne fixed dental prosthesis on engaging and non‐engaging abutments before and after torque application

PubMed Central

Epprecht, Alyssa; Zeltner, Marco; Benic, Goran

2018-01-01

Abstract This study quantified the strain development after inserting implant‐borne fixed dental prosthesis (FDP) to various implant–abutment joints. Two bone‐level implants (∅ = 4.1 mm, RC, SLA 10 mm, Ti, Straumann) were inserted in polyurethane models (N = 3) in the area of tooth nos 44 and 47. Four‐unit veneered zirconium dioxide FDPs (n = 2) were fabricated, one of which was fixed on engaging (E; RC Variobase, ∅ = 4.5 mm, H = 3.5 mm) and the other on non‐engaging (NE) abutments (RC Variobase, ∅ = 4.5 mm, H = 5.5 mm). One strain gauge was bonded to the occlusal surface of pontic no. 46 on the FDP and the other two on the polyurethane model. Before (baseline) and after torque (35 Ncm), strain values were recorded three times. Data were analyzed using Kruskal–Wallis and Mann–Whitney U tests (α = 0.05). Mean strain values presented significant increase after torque for both E and NE implant–abutment connection type (baseline: E = 4.33 ± 4.38; NE = 4.85 ± 4.85; torque: E = 196.56 ± 188.02; NE = 275.63 ± 407.7; p < .05). Mean strain values based on implant level presented significant increase after torque for both E and NE implant–abutment connection (baseline: E = 4.94 ± 5.29; NE = 5.78 ± 5.69; torque: E = 253.78 ± 178.14; NE = 347.72 ± 493.06; p < .05). The position of the strain gauge on implants (p = .895), FDP (p = .275), and abutment connection type (p = .873) did not significantly affect the strain values. Strain levels for zirconium dioxide implant‐borne FDPs were not affected by the implant–abutment connection type. PMID:29744210

Preload evaluation of different screws in external hexagon joint.

PubMed

Assunção, Wirley Gonçalves; Delben, Juliana Aparecida; Tabata, Lucas Fernando; Barão, Valentim Adelino Ricardo; Gomes, Erica Alves; Garcia, Idelmo Rangel

2012-02-01

This study compared the maintenance of tightening torque in different retention screw types of implant-supported crowns. Twelve metallic crowns in UCLA abutments cast with cobalt-chromium alloy were attached to external hexagon osseointegrated implants with different retention screws: group A: titanium alloy retention screw; group B: gold alloy retention screw with gold coating; group C: titanium alloy retention screw with diamond-like carbon film coating; and group D: titanium alloy retention screw with aluminum titanium nitride coating. Three detorque measurements were obtained after torque insertion in each replica. Data were evaluated by analysis of variance (ANOVA), Tukey's test (P < 0.05), and t test (P < 0.05). Detorque value reduced in all groups (P < 0.05). Group A retained the highest percentage of torque in comparison with the other groups (P < 0.05). Groups B and D retained the lowest percentage of torque without statistically significant difference between them (P > 0.05). All screw types exhibited reduction in the detorque value. The titanium screw maintained the highest percentage of torque whereas the gold-coated screw and the titanium screw with aluminum titanium nitride coating retained the lowest percentage.

Implant stability and marginal bone level of microgrooved zirconia dental implants: A 3-month experimental study on dogs.

PubMed

Delgado-Ruiz, Rafael Arcesio; Marković, Aleksa; Calvo-Guirado, José Luís; Lazić, Zoran; Piattelli, Adriano; Boticelli, Daniele; Maté-Sánchez, José Eduardo; Negri, Bruno; Ramírez-Fernández, María Piedad; Mišić, Tijana

2014-05-01

The modification of implant surfaces could affect mechanical implant stability as well as dynamics and quality of peri-implant bone healing. The aim of this 3-month experimental study in dogs was to investigate implant stability, marginal bone levels and bone tissue response to zirconia dental implants with two laser-micro-grooved intraosseous surfaces in comparison with nongrooved sandblasted zirconia and sandblasted, high-temperature etched titanium implants. Implant surface characterization was performed using optical interferometric profilometty and energy dispersive X-ray spectroscopy. A total of 96 implants (4 mm in diameter and 10 mm in length) were inserted randomly in both sides of the lower jaw of 12 Fox Hound dogs divided into groups of 24 each: the control (titanium), the group A (sandblasted zirconia), the group B (sandolasted zirconia plus microgrooved neck) and the group C (sandblasted zirconia plus all microgrooved). All the implants were immediately loaded. Insertion torque, periotest values, radiographic crestal bone level and removal torque were recorded during the 3-month follow-up. Qualitative scanning electon microscope (SEM) analysis of the bone-implant interfaces of each group was performed. Insertion torque values were higher in the group C and control implants (p < 0.05). Periotest values increased in all the periods in proportion to the extent of microgrooving as follows: the group C > the control > the group B > the group A (p < 0.05). Radiographic measurements showed minimal crestal bone loss at 3 months for microgrooved zirconia implants (groups C and B) and control implants compared with the group A implants (p < 0.05). The removal torque values increased with time for all the groups as follows: the group C > the control > the group B > the group A (p < 0.05). SEM showed that implant surfaces of the groups B and C had an extra bone growth inside the microgrooves that corresponded to the shape and direction of the microgrooves. The addition of microgrooves to the entire intraosseous surface of zirconia dental implants enhances primary and secondary implant stability, promotes bone tissue ingrowth and preserves crestal bone levels.

Effect of Real-Time Feedback on Screw Placement Into Synthetic Cancellous Bone.

PubMed

Gustafson, Peter A; Geeslin, Andrew G; Prior, David M; Chess, Joseph L

2016-08-01

The objective of this study is to evaluate whether real-time torque feedback may reduce the occurrence of stripping when inserting nonlocking screws through fracture plates into synthetic cancellous bone. Five attending orthopaedic surgeons and 5 senior level orthopaedic residents inserted 8 screws in each phase. In phase I, screws were inserted without feedback simulating conventional techniques. In phase II, screws were driven with visual torque feedback. In phase III, screws were again inserted with conventional techniques. Comparison of these 3 phases with respect to screw insertion torque, surgeon rank, and perception of stripping was used to establish the effects of feedback. Seventy-three of 239 screws resulted in stripping. During the first phase, no feedback was provided and the overall strip rate was 41.8%; this decreased to 15% with visual feedback (P < 0.001) and returned to 35% when repeated without feedback. With feedback, a lower average torque was applied over a narrower torque distribution. Residents stripped 40.8% of screws compared with 20.2% for attending surgeons. Surgeons were poor at perceiving whether they stripped. Prevention and identification of stripping is influenced by surgeon perception of tactile sensation. This is significantly improved with utilization of real-time visual feedback of a torque versus roll curve. This concept of real-time feedback seems beneficial toward performance in synthetic cancellous bone and may lead to improved fixation in cancellous bone in a surgical setting.

Influence of Hydroxyapatite Stick on Pedicle Screw Fixation in Degenerative Lumbar Spine: Biomechanical and Radiologic Study.

PubMed

Shin, Sung Joon; Lee, Ji-Ho; Lee, Jae Hyup

2017-07-01

A prospective, within-patient, left-right comparative study. To evaluate the efficacy of hydroxyapatite (HA) stick augmentation method by comparing the insertional torque of the pedicle screw in osteoporotic and nonosteoporotic patients. Unsatisfactory clinical outcomes after spine surgery in osteoporotic patients are related to pedicle screw loosening or pull-outs. HA, as a bone graft extender, has a possibility to enhance the fixation strength at the bone-screw interface. From November 2009 to December 2010, among patients who required bilateral pedicle screw fixation for lumbar spine surgery, 22 patients were enrolled, who recieved unilateral HA stick augmentation and completed intraoperative insertional torque measurement of each pedicle screws. On the basis of preoperative evaluation of bone mineral density, patients with osteoporosis had 2 HA sticks inserted unilaterally, and 1 stick for patients without osteoporosis. Pedicle screw loosening and pull-outs were assessed using 12-month postoperative CT scans and follow-up radiographs. Clinical evaluation was done preoperatively and at 1 year postoperatively, based on Visual Analog Scale score, Oswestry Disability Index, and Short Form-36 Health Survey. Regardless of bone mineral density, the average torque value of all pedicle screws with HA stick insertion (HA stick inserted group) was significantly higher than that of all pedicle screws without HA insertion (control group) (P<0.0001). Same results were seen in the HA stick inserted subgroups and the control subgroups within both of the osteoporosis group (P=0.009) and the nonosteoporosis group (P=0.0004). There was no statistically significant difference of the rate of pedicle screw loosening in between the HA stick inserted group and the control group. Clinical evaluation also showed no statistically significant difference in between patients with loosening and those without. The enhancement of initial pedicle screw fixation strength in osteoporotic patients can be achieved by HA stick augmentation.

Evaluation of local cancellous bone amelioration by poly-L-DL-lactide copolymers to improve primary stability of dental implants: a biomechanical study in sheep.

PubMed

Stübinger, Stefan; Waser, Jasmin; Hefti, Thomas; Drechsler, Anika; Sidler, Michéle; Klein, Karina; von Rechenberg, Brigitte; Schlottig, Falko

2015-05-01

The aim of this study was to evaluate the clinical performance of local cancellous bone amelioration by a 70:30 poly-(L-lactide-co-D,L-Lacide) copolymer with two different implant designs on primary stability and after 4 and 12 weeks of healing time. In six sheep, n = 36 implants (TH) with a conditioned, sandblasted, thermal acid-etched micro-rough surface and n = 36 implants (NB) with a highly crystalline and phosphate-enriched anodized titanium oxide surface were placed in the pelvic bone. Using an ultrasound-based process named Constant Amelioration Process (CAP), half of peri-implant trabecular bone structures were locally tested with 70:30 poly-(L-lactide-co-D,L-Lacide) copolymer in both implant groups, TH and NB. The CAP technology employs ultrasonic energy to liquefy 70:30 poly-(L-lactide-co-D,L-Lacide) which enters the inter-trabecular space, leading to local reinforcement of the cancellous bone structure after solidification of the copolymer. The CAP test group was compared with reference implants placed with the conventional site preparation according to the manufacturers' description. Primary stability was assessed by the measurement of torque-in values and implant stability quotient (ISQ; n = 18 per group). Secondary stability was analyzed by biomechanical removal torque testing after 4 and 12 weeks (n = 9 per group). Insertion torque value (23.3 N cm ± 13.6) of reference TH implants demonstrated a statistically significant (P = 0.00) difference in comparison with test TH implants (41.9 N cm ± 19.5). Reference NB implants revealed a statistically significant (P = 0.03) lower insertion torque value (23.7 N cm ± 13.5) than test NB implants (39.7 N cm ± 18.6). ISQ values increased for all implants from initial implant placement until sacrifice at 12 weeks. Reference TH implants tended to result in an increase in torque values from 4 weeks (181.9 N cm ± 22.8) to 12 weeks (225.7 N cm ± 47.4). This trend could be also proven for implants of test sites (4 week: 176.8 N cm ± 24.1; 12 week: 201.5 N cm ± 53.4). For reference, NB implants a non-significant increase in removal torque values from 4 weeks (146. 7 N cm ± 18.0) to 12 weeks (170.2 N cm ± 40.4) was observed. Removal torque values of test NB implants did not increase from 4 weeks (153.3 N cm ± 21.5) to 12 weeks (146.1 N cm ± 37.5). Biomechanical data proved significantly enhanced primary stability of dental implants after local amelioration without long-term sequelae and irrespective of implant design. After 4- and 12-week healing time, removal torque of locally test implants was as high as for control implants, and osseointegration was therefore not influenced by the CAP process. No correlation between ISQ values and torque values was found. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Influence of Screw Length and Bone Thickness on the Stability of Temporary Implants

PubMed Central

Fernandes, Daniel Jogaib; Elias, Carlos Nelson; Ruellas, Antônio Carlos de Oliveira

2015-01-01

The purpose of this work was to study the influence of screw length and bone thickness on the stability of temporary implants. A total of 96 self-drilling temporary screws with two different lengths were inserted into polyurethane blocks (n = 66), bovine femurs (n = 18) and rabbit tibia (n = 12) with different cortical thicknesses (1 to 8 mm). Screws insertion in polyurethane blocks was assisted by a universal testing machine, torque peaks were collected by a digital torquemeter and bone thickness was monitored by micro-CT. The results showed that the insertion torque was significantly increased with the thickness of cortical bone from polyurethane (p < 0.0001), bovine (p = 0.0035) and rabbit (p < 0.05) sources. Cancellous bone improved significantly the mechanical implant stability. Insertion torque and insertion strength was successfully moduled by equations, based on the cortical/cancellous bone behavior. Based on the results, insertion torque and bone strength can be estimate in order to prevent failure of the cortical layer during temporary screw placement. The stability provided by a cortical thickness of 2 or 1 mm coupled to cancellous bone was deemed sufficient for temporary implants stability. PMID:28793582

Insertion torque recordings for the diagnosis of contact between orthodontic mini-implants and dental roots: protocol for a systematic review.

PubMed

Meursinge Reynders, Reint; Ladu, Luisa; Ronchi, Laura; Di Girolamo, Nicola; de Lange, Jan; Roberts, Nia; Plüddemann, Annette

2015-04-02

Hitting a dental root during the insertion of orthodontic mini-implants (OMIs) is a common adverse effect of this intervention. This condition can permanently damage these structures and can cause implant instability. Increased torque levels (index test) recorded during the insertion of OMIs may provide a more accurate and immediate diagnosis of implant-root contact (target condition) than radiographic imaging (reference standard). An accurate index test could reduce or eliminate X-ray exposure. These issues, the common use of OMIs, the high prevalence of the target condition, and because most OMIs are placed between roots warrant a systematic review. We will assess 1) the diagnostic accuracy and the adverse effects of the index test, 2) whether OMIs with root contact have higher insertion torque values than those without, and 3) whether intermediate torque values have clinical diagnostic utility. The Preferred Reporting Items for Systematic review and Meta-Analysis Protocols (PRISMA-P) 2015 statement was used as a the guideline for reporting this protocol. Inserting implants deliberately into dental roots of human participants would not be approved by ethical review boards and adverse effects of interventions are generally underreported. We will therefore apply broad spectrum eligibility criteria, which will include clinical, animal and cadaver models. Not including these models could slow down knowledge translation. Both randomized and non-randomized research studies will be included. Comparisons of interest and subgroups are pre-specified. We will conduct searches in MEDLINE and more than 40 other electronic databases. We will search the grey literature and reference lists and hand-search ten journals. All methodological procedures will be conducted by three reviewers. Study selection, data extraction and analyses, and protocols for contacting authors and resolving conflicts between reviewers are described. Designed specific risk of bias tools will be tailored to the research question. Different research models will be analysed separately. Parameters for exploring statistical heterogeneity and conducting meta-analyses are pre-specified. The quality of evidence for outcomes will be assessed through the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. The findings of this systematic review will be useful for patients, clinicians, researchers, guideline developers, policymakers, and surgical companies.

"Turn-of-the-Nut" Method Is Not Appropriate for Use in Cancellous Bone.

PubMed

Ryan, Melissa K; Mohtar, Aaron A; Costi, John J; Reynolds, Karen J

2015-11-01

The level to which bone screws are tightened is determined subjectively by the operating surgeon. It is likely that the tactile feedback that surgeons rely on is based on localized tissue yielding, which may predispose the screw-bone interface to failure. A limited number of studies have investigated the ratio between clinical tightening torque and stripping torque. The purpose of this study was to measure, for the first time, the ratio between yield torque (T yield) and stripping torque (T max) during screw insertion into the cancellous bone and to compare these torques with clinical levels of tightening reported in the literature. Additionally, a rotational limit was investigated as a potential end point for screw insertion in cancellous bone. A 6.5-mm outer diameter commercial cancellous bone screw was inserted into human femoral head specimens (n = 89). Screws were inserted to failure, while recording insertion torque, compression under the screw head, and rotation angle. The median, interquartile ranges, and coefficient of variation were calculated for each of the following parameters: T yield, T max, T yield/T max, slope, T plateau, and rotation angle. The median ratio of T yield/T max and rotation angle was 85.45% and 96.5 degrees, respectively. The coefficient of variation was greatest for the rotation angle compared with the ratio of T yield/T max (0.37 vs. 0.12). The detection of yield may be a more precise method than the rotation angle in cancellous bone; however, bone-screw constructs that exhibit a T yield close to T max may be more susceptible to stripping during insertion. Future work can identify factors that influence the ratio of T yield/T max may help to reduce the incidence of screw stripping.

Removal torque of nail interlocking screws is related to screw proximity to the fracture and screw breakage.

PubMed

White, Alexander A; Kubacki, Meghan R; Samona, Jason; Telehowski, Paul; Atkinson, Patrick J

2016-06-01

Studies have shown that titanium implants can be challenging to explant due to the material's excellent biocompatibility and resulting osseointegration. Clinically, titanium alloy nail interlocking screws may require removal to dynamize a construct or revise the nail due to nonunion, infection, pain, or periprosthetic fracture. This study was designed to determine what variables influence the removal torque for titanium alloy interlocking screws. An intramedullary nail with four interlocking screws was used to stabilize a 1-cm segmental femoral defect in a canine model for 16 weeks. The animals were observed to be active following a several-day recovery after surgery. In six animals, the femora and implanted nail/screws were first tested to failure in torsion to simulate periprosthetic fracture of an implant after which the screws were then removed. In four additional animals, the screws were removed without mechanical testing. Both intraoperative insertional and extraction torques were recorded for all screws. Mechanical testing to failure broke 10/24 screws. On average, the intact screws required 70% of the insertional torque during removal while broken screws only required 16% of the insertional torque (p < 0.001). In addition, intact screws closer to the fracture required 2.8 times more removal torque than the outboard distal screw (p < 0.005). On average, the angle of rotation to peak torque was ∼80°. The peak axial load did not significantly correlate with the torque required to remove the screws. On average, the removal torque was lower than at the time of insertion, and less torque was required to remove broken screws and screws remote to the fracture. However, broken screws will require additional time to retrieve the remaining screw fragment. This study suggests that broken screws and screws in prematurely active patients will require less torque to remove. © IMechE 2016.

Achievable accuracy of hip screw holding power estimation by insertion torque measurement.

PubMed

Erani, Paolo; Baleani, Massimiliano

2018-02-01

To ensure stability of proximal femoral fractures, the hip screw must firmly engage into the femoral head. Some studies suggested that screw holding power into trabecular bone could be evaluated, intraoperatively, through measurement of screw insertion torque. However, those studies used synthetic bone, instead of trabecular bone, as host material or they did not evaluate accuracy of predictions. We determined prediction accuracy, also assessing the impact of screw design and host material. We measured, under highly-repeatable experimental conditions, disregarding clinical procedure complexities, insertion torque and pullout strength of four screw designs, both in 120 synthetic and 80 trabecular bone specimens of variable density. For both host materials, we calculated the root-mean-square error and the mean-absolute-percentage error of predictions based on the best fitting model of torque-pullout data, in both single-screw and merged dataset. Predictions based on screw-specific regression models were the most accurate. Host material impacts on prediction accuracy: the replacement of synthetic with trabecular bone decreased both root-mean-square errors, from 0.54 ÷ 0.76 kN to 0.21 ÷ 0.40 kN, and mean-absolute-percentage errors, from 14 ÷ 21% to 10 ÷ 12%. However, holding power predicted on low insertion torque remained inaccurate, with errors up to 40% for torques below 1 Nm. In poor-quality trabecular bone, tissue inhomogeneities likely affect pullout strength and insertion torque to different extents, limiting the predictive power of the latter. This bias decreases when the screw engages good-quality bone. Under this condition, predictions become more accurate although this result must be confirmed by close in-vitro simulation of the clinical procedure. Copyright © 2018 Elsevier Ltd. All rights reserved.

Comparative evaluation of insertion torque and mechanical stability for self-tapping and self-drilling orthodontic miniscrews - an in vitro study.

PubMed

Tepedino, Michele; Masedu, Francesco; Chimenti, Claudio

2017-05-30

The aim of the present study was to evaluate the relationship between insertion torque and stability of miniscrews in terms of resistance against dislocation, then comparing a self-tapping screw with a self-drilling one. Insertion torque was measured during placement of 30 self-drilling and 31 self-tapping stainless steel miniscrews (Leone SpA, Sesto Fiorentino, Italy) in synthetic bone blocks. Then, an increasing pulling force was applied at an angle of 90° and 45°, and the displacement of the miniscrews was recorded. The statistical analysis showed a statistically significant difference between the mean Maximum Insertion Torque (MIT) observed in the two groups and showed that force angulation and MIT have a statistically significant effect on miniscrews stability. For both the miniscrews, an angle of 90° between miniscrew and loading force is preferable in terms of stability. The tested self-drilling orthodontic miniscrews showed higher MIT and greater resistance against dislocation than the self-tapping ones.

Biomechanical measurements of stopping and stripping torques during screw insertion in five types of human and artificial humeri.

PubMed

Aziz, Mina Sr; Tsuji, Matthew Rs; Nicayenzi, Bruce; Crookshank, Meghan C; Bougherara, Habiba; Schemitsch, Emil H; Zdero, Radovan

2014-05-01

During orthopedic surgery, screws are inserted by "subjective feel" in humeri for fracture fixation, that is, stopping torque, while trying to prevent accidental over-tightening that causes screw-bone interface failure, that is, stripping torque. However, no studies exist on stopping torque, stripping torque, or stopping/stripping torque ratio in human or artificial humeri. This study evaluated five types of humeri, namely, human fresh-frozen (n = 19), human embalmed (n = 18), human dried (n = 15), artificial "normal" (n = 13), and artificial "osteoporotic" (n = 13). An orthopedic surgeon used a torque screwdriver to insert 3.5-mm-diameter cortical screws into humeral shafts and 6.5-mm-diameter cancellous screws into humeral heads by "subjective feel" to obtain stopping and stripping torques. The five outcome measures were raw and normalized stopping torque, raw and normalized stripping torque, and stopping/stripping torque ratio. Normalization was done as raw torque/screw-bone interface area. For "gold standard" fresh-frozen humeri, cortical screw tests yielded averages of 1312 N mm (raw stopping torque), 30.4 N/mm (normalized stopping torque), 1721 N mm (raw stripping torque), 39.0 N/mm (normalized stripping torque), and 82% (stopping/stripping torque ratio). Similarly, fresh-frozen humeri gave cancellous screw average results of 307 N mm (raw stopping torque), 0.9 N/mm (normalized stopping torque), 392 N mm (raw stripping torque), 1.2 N/mm (normalized stripping torque), and 79% (stopping/stripping torque ratio). Of the five cortical screw parameters for fresh-frozen humeri versus other groups, statistical equivalence (p ≥ 0.05) occurred in four cases (embalmed), three cases (dried), four cases (artificial "normal"), and four cases (artificial "osteoporotic"). Of the five cancellous screw parameters for fresh-frozen humeri versus other groups, statistical equivalence (p ≥ 0.05) occurred in five cases (embalmed), one case (dried), one case (artificial "normal"), and zero cases (artificial "osteoporotic"). Stopping/stripping torque ratios were relatively constant for all groups at 77%-88% (cortical screws) and 79%-92% (cancellous screws). © IMechE 2014.

Bone quality assessment for total hip arthroplasty with intraoperative trabecular torque measurements.

PubMed

Klotz, Matthias C M; Beckmann, Nicholas A; Bitsch, Rudi G; Seebach, Elisabeth; Reiner, Tobias; Jäger, Sebastian

2014-11-13

In cases of poor bone quality, intraoperative torque measurement might be an alternative to preoperative dual-energy X-ray absorptiometry (DXA) to assess bone quality in total hip arthroplasty (THA). Trabecular peak torque measurement was applied in 14 paired fresh frozen human femurs. Here, a 6.5 × 23 mm wingblade was inserted into the proximal femur without harming the lateral cortical bone. Further tests of the proximal femur also evaluated bone strength (DXA, micro-computed tomography (μCT), monoaxial compression test), and the results were compared to the trabecular torque measurement. Student's t-test was used to compare the values of the groups. Pearson product-moment was applied to correlate the values of the peak torque measurement with the bone strength measured by DXA, μCT, and monoaxial compression test. In the femoral head, the mean trabecular peak torque was 4.38 ± 1.86 Nm. These values showed a strong correlation with the values of the DXA, the μCT, and the biomechanical load test (Pearson's product-moment: DXA: 0.86, μCT-BMD: 0.80, load test: 0.85). Furthermore, the torque measurement showed a more pronounced correlation with the biomechanical load test compared to the DXA. The use of this method provides highly diagnostic information about bone quality. Since the approach was adjusted for THA, no harm of the lateral bone stock will result from this measurement during surgery. The results of this initial study employing small sample sizes indicate that this new method is as sensitive as DXA in predicting bone quality and may function as an intraoperative alternative to DXA in THA. Nevertheless, before this method will turn into clinical use, more research and clinical trials are necessary.

Load Fatigue Performance Evaluation on Two Internal Tapered Abutment-Implant Connection Implants Under Different Screw Tightening Torques.

PubMed

Jeng, Ming-Dih; Liu, Po-Yi; Kuo, Jia-Hum; Lin, Chun-Li

2017-04-01

This study evaluates the load fatigue performance of different abutment-implant connection implant types-retaining-screw (RS) and taper integrated screwed-in (TIS) types under 3 applied torque levels based on the screw elastic limit. Three torque levels-the recommended torque (25 Ncm), 10% less, and 10% more than the ratio of recommended torque to screw elastic limits of different implants were applied to the implants to perform static and dynamic testing according to the ISO 14801 method. Removal torque loss was calculated for each group after the endurance limitation was reached (passed 5 × 10 6 cycles) in the fatigue test. The static fracture resistance results showed that the fracture resistance in the TIS-type implant significantly increased (P < .05) when the abutment screw was inserted tightly. The dynamic testing results showed that the endurance limitations for the RS-type implant were 229 N, 197 N, and 224 N and those for the TIS-type implant were 322 N, 364 N, and 376 N when the screw insertion torques were applied from low to high. The corresponding significant (P < .05) removal torque losses for the TIS-type implant were 13.2%, 5.3%, and 2.6% but no significant difference was found for the RS-type implant. This study concluded that the static fracture resistance and dynamic endurance limitation of the TIS-type implant (1-piece solid abutment) increased when torque was applied more tightly on the screw. Less torque loss was also found when increasing the screw insertion torque.

Primary stability and self-tapping blades: biomechanical assessment of dental implants in medium-density bone.

PubMed

Kim, Yung-Soo; Lim, Young-Jun

2011-10-01

The aim of this biomechanical study was to assess the influence of self-tapping blades in terms of primary implant stability between implants with self-tapping blades and implants without self-tapping blades using five different analytic methods, especially in medium-density bone. Two different types of dental implants (4 × 10 mm) were tested: self-tapping and non-self-tapping. The fixture design including thread profiles was exactly the same between the two groups; the only difference was the presence of cutting blades on one half of the apical portion of the implant body. Solid rigid polyurethane blocks with corresponding densities were selected to simulate medium-density bone. Five mechanical assessments (insertion torque, resonance frequency analysis [RFA], reverse torque, pull-out and push in test) were performed for primary stability. Implants without self-tapping blades showed significantly higher values (P<0.001) in four biomechanical assessments, except RFA (P=0.684). However, a statistically significant correlation could not be detected between insertion torque values with the four different outcome variables (P>0.05). The outcomes of the present study indicate that the implant body design without self-tapping blades has a good primary stability compared with that with self-tapping blades in medium-density bone. Considering the RFA, a distinct layer of cortical bone on marginal bone will yield implant stability quotient values similar to those in medium-bone density when implants have the same diameter. © 2011 John Wiley & Sons A/S.

Influence of underpreparation on primary stability of implants inserted in poor quality bone sites: an in vitro study.

PubMed

Degidi, Marco; Daprile, Giuseppe; Piattelli, Adriano

2015-06-01

The purpose of this present study was to investigate the relation between implant site underpreparation and primary stability in the presence of poor-quality bone. A study was performed on fresh humid bovine bone; samples presented no cortical layer with a cancellous structure inside and were obtained from the hip. The bones were firmly attached to a base device. Sixty sites were prepared according to the protocol provided by the manufacturer: a 2-mm pilot drill was introduced to the proper depth and then twist drills of 3 and 3.4 mm were used. After site preparation, 20 3.4- × 11-mm (standard protocol group), 20 3.8- × 11-mm (10% undersized group), and 20 4.5- × 11-mm (25% undersized group) implants were inserted at a calibrated maximum torque of 70 N-cm at the predetermined speed of 30 rpm. After implant insertion, variable torque work (VTW), maximum insertion torque (peak IT), and resonance frequency analysis (RFA) values were recorded. The standard protocol group showed a mean VTW of 565.77 ± 219.12 N-cm, a peak IT of 11.3 ± 4.44 N-cm, and an RFA of 69.35 ± 7.35 implant stability quotient (ISQ). The 10% undersized group showed a mean VTW of 1,240.24 ± 407.78 N-cm, a peak IT of 20.26 ± 7.03 N-cm, and an RFA of 73.40 ± 2.33 ISQ. The 25% undersized group showed a mean VTW of 1,254.96 ± 727.49 N-cm, a peak IT of 17.15 ± 10.39 N-cm, and an RFA of 72.30 ± 6.70 ISQ. For VTW, the difference between the standard and undersized protocol values was statistically significant; for peak IT, the difference between the standard and 10% undersized protocol values was statistically significant; no other statistical differences were found between mean values. In the presence of poor-bone quality, a 10% undersized protocol is sufficient to improve the primary stability of the implant; additional decreases do not seem to enhance primary stability values. Copyright © 2015 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.

Tilted orthodontic micro implants: a photoelastic stress analysis.

PubMed

Çehreli, Seçil; Özçırpıcı, Ayça Arman; Yılmaz, Alev

2013-10-01

The aim of this study was to examine peri-implant stresses around orthodontic micro implants upon torque-tightening and static load application by quasi-three-dimensional photoelastic stress analysis. Self-tapping orthodontic micro implants were progressively inserted into photoelastic models at 30, 45, 70, and 90 degrees and insertion torques were measured. Stress patterns (isochromatic fringe orders) were recorded by the quasi-three-dimensional photoelastic method using a circular polariscope after insertion and 250 g static force application. Torque-tightening of implants generated peri-implant stresses. Upon insertion, 90 degree placed implants displayed the lowest and homogeneous stress distribution followed by 30, 70, and 45 degree tilted implants. Static loading did not dramatically alter stress fields around the implants tested. The highest alteration in stress distribution was observed for the 90 degree placed implant, while 70 degree tilted implant had the lowest stresses among tilted implants. Torque-tightening of orthodontic micro implants creates a stress field that is not dramatically altered after application of static lateral moderate orthodontic loads, particularly at the cervical region of tilted implants.

External Tank (ET) Bipod Fitting Bolted Attachment Locking Insert Performance

NASA Technical Reports Server (NTRS)

Larsen, Curtis E.; Wilson, Tim R.; Elliott, Kenny B.; Raju, Ivatury S.; McManamen, John

2008-01-01

Following STS-107, the External Tank (ET) Project implemented corrective actions and configuration changes at the ET bipod fitting. Among the corrective actions, the existing bolt lock wire which provided resistance to potential bolt rotation was removed. The lock wire removal was because of concerns with creating voids during foam application and potential for lock wire to become debris. The bolts had been previously lubricated to facilitate assembly but, because of elimination of the lock wire, the ET Project wanted to enable the locking feature of the insert. Thus, the lubrication was removed from bolt threads and instead applied to the washer under the bolt head. Lubrication is necessary to maximize joint pre-load while remaining within the bolt torque specification. The locking feature is implemented by thread crimping in at four places in the insert. As the bolt is torqued into the insert the bolt threads its way past the crimped parts of the insert. This provides the locking of the bolt, as torque is required to loosen the joint after clamping.

Does maximum torque mean optimal pullout strength of screws?

PubMed

Tankard, Sara E; Mears, Simon C; Marsland, Daniel; Langdale, Evan R; Belkoff, Stephen M

2013-04-01

To determine the relationship between insertion torque and pullout strength of 3.5-mm-diameter cortical screws in cadaveric humeri with different bone mineral densities (BMDs). Five pairs of human humeri from each of 3 BMD groups (normal, osteopenic, and osteoporotic) were used. Holes were drilled in each humerus, and maximum insertion torque (T(max)) was measured by tightening a screw until stripping occurred. In the remaining holes, screws were tightened to 50%, 70%, or 90% of the T(max). A servohydraulic testing machine pulled each screw out at 1 mm/s while resulting force and axial displacement were recorded at 10 Hz. The authors checked for an effect of insertion torque (percent T(max)) on pullout strength using a general linearized and latent mixed model (Stata10), controlling for cortical thickness and BMD (T-score). Pullout strength for normal and osteoporotic bone was greatest for screws inserted to 50% T(max) and was significantly greater than that at T(max) but not significantly different from that at 70% or 90% T(max). For osteopenic bone, pullout strength was greatest at 70% peak torque, but it was not significantly different from the pullout strength at the 50% or 90% T(max) levels. Tightening screws beyond 50% T(max) does not increase pullout strength of the screw and may place bone at risk for damage that might result in loss of fixation. Even after adjusting for bone thickness and density, there is no clear relationship between pullout strength and screw torque.

Insertion torque, resonance frequency, and removal torque analysis of microimplants.

PubMed

Tseng, Yu-Chuan; Ting, Chun-Chan; Du, Je-Kang; Chen, Chun-Ming; Wu, Ju-Hui; Chen, Hong-Sen

2016-09-01

This study aimed to compare the insertion torque (IT), resonance frequency (RF), and removal torque (RT) among three microimplant brands. Thirty microimplants of the three brands were used as follows: Type A (titanium alloy, 1.5-mm × 8-mm), Type B (stainless steel, 1.5-mm × 8-mm), and Type C (titanium alloy, 1.5-mm × 9-mm). A synthetic bone with a 2-mm cortical bone and bone marrow was used. Each microimplant was inserted into the synthetic bone, without predrilling, to a 7 mm depth. The IT, RF, and RT were measured in both vertical and horizontal directions. One-way analysis of variance and Spearman's rank correlation coefficient tests were used for intergroup and intragroup comparisons, respectively. In the vertical test, the ITs of Type C (7.8 Ncm) and Type B (7.5 Ncm) were significantly higher than that of Type A (4.4 Ncm). The RFs of Type C (11.5 kHz) and Type A (10.2 kHz) were significantly higher than that of Type B (7.5 kHz). Type C (7.4 Ncm) and Type B (7.3 Ncm) had significantly higher RTs than did Type A (4.1 Ncm). In the horizontal test, both the ITs and RTs were significantly higher for Type C, compared with Type A. No significant differences were found among the groups, and the study hypothesis was accepted. Type A had the lowest inner/outer diameter ratio and widest apical facing angle, engendering the lowest IT and highest RF values. However, no significant correlations in the IT, RF, and RT were observed among the three groups. Copyright © 2016. Published by Elsevier Taiwan.

Bending stiffness, torsional stability, and insertion force of cementless femoral stems.

PubMed

Incavo, S J; Johnson, C C; Churchill, D L; Beynnon, B D

2001-04-01

In cementless total hip arthroplasty, increased femoral stem flexibility and decreased fracture propensity are desirable characteristics. The slotting and tapering of the stem have been introduced to achieve this. These features should not, however, be allowed to interfere with the ability of the distal stem to provide initial mechanical stability, especially under rotation. This study was done to investigate the ability of slotted and tapered stem designs to reduce stiffness and insertion force while still maintaining adequate torsional strength. The torsional strength, maximum insertion force, and insertional work of straight, slotted, and taper stems were measured by inserting each type into rigid polyurethane foam and torque testing to failure. Bending stiffness of each stem design was calculated using numerical methods. When compared to a straight stem, a unislot stem has similar torsional strength, maximum insertional force, and work of insertion. The bending stiffness is decreased by 19% to 82% depending on the bending direction. A trislot design decreased torque strength by 29%, maximal insertion force by 36%, and work by 11%. Bending stiffness was decreased by 74% and was not dependent on bending direction. A 0.5-mm taper decreased torque strength by 11% and insertional work by 14%. No difference was seen in maximum insertional force. We conclude that the design features studied (slots and taper) are effective in decreasing stem stiffness and reducing fracture propensity.

Experimental analysis of insertion torques and forces of threaded and press-fit acetabular cups by means of ex vivo and in vivo measurements.

PubMed

Vogel, Danny; Rathay, Andreas; Teufel, Stephanie; Ellenrieder, Martin; Zietz, Carmen; Sander, Manuela; Bader, Rainer

2017-01-01

In THA a sufficient primary implant stability is the precondition for successful secondary stability. Industrial foams of different densities have been used for primary stability investigations. The aim of this study was to analyse and compare the insertion behaviour of threaded and press-fit cups in vivo and ex vivo using bone substitutes with various densities. Two threaded (Bicon Plus®, Trident® TC) and one press-fit cup (Trident PSL®) were inserted by orthopaedic surgeons (S1, S2) into 10, 20 and 31 pcf blocks, using modified surgical instruments allowing measurements of the insertion forces and torques. Furthermore, the insertion behaviour of two cups were analysed intraoperatively. Torques for the threaded cups increased while bone substitute density increased. Maximum insertion torques were observed for S2 with 102 Nm for the Bicon Plus® in 20 pcf blocks and 77 Nm for the Trident® TC in 31 pcf blocks, which compares to the in vivo measurement (85 Nm). The average insertion forces for the press-fit cup varied from 5.2 to 6.8 kN (S1) and 7.2-11.5 kN (S2) ex vivo. Intraoperatively an average insertion force of 8.0 kN was determined. Implantation behaviour was influenced by acetabular cup design, bone substitute and experience of the surgeon. No specific density of bone substitute could be favoured for ex vivo investigations on the implantation behaviour of acetabular cups. The use synthetic bone blocks of high density (31 pcf) led to problems regarding cup orientation and seating. Therefore, bone substitutes used should be critically scrutinized in terms of the comparability to the in vivo situation.

Are insertion torque and early osseointegration proportional? A histologic evaluation.

PubMed

Campos, Felipe E B; Jimbo, Ryo; Bonfante, Estevam A; Barbosa, Darceny Z; Oliveira, Maiolino T F; Janal, Malvin N; Coelho, Paulo G

2015-11-01

The objective of this histologic study was to determine the effect of three drilling protocols (oversized, intermediate, and undersized) on biologic responses to a single implant type at early healing periods (2 weeks in vivo) in a beagle dog model. Ten beagle dogs were acquired and subjected to surgeries in the tibia 2 weeks before euthanasia. During surgery, each dog received three Unitite implants, 4 mm in diameter by 10 mm in length, in bone sites drilled to 3.5, 3.75, and 4.0 mm in final diameter. The insertion torque was recorded during surgery, and bone-to-implant contact (BIC), and bone area fraction occupied (BAFO) measured from the histology. Each outcome measure was compared between treatment conditions with the Wilcoxon signed-rank test. Bonferroni-corrected statistical significance was set to 95%. Insertion torque increased as an inverse function of drilling diameter, as indicated by significant differences in torque levels between each pair of conditions (P = 0.005). BIC and BAFO levels were highest and statistically similar in the recommended and undersized conditions and significantly reduced in the oversized condition (P < 0.01). Reduced drilling dimensions resulted in increased insertion torque (primary stability). While BIC and BAFO were maximized when drilling the recommended diameter hole, only the oversized hole resulted in evidence of statistically reduced integration. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Primary implant stability in augmented sinuslift-sites after completed bone regeneration: a randomized controlled clinical study comparing four subantrally inserted biomaterials

PubMed Central

Troedhan, Angelo; Schlichting, Izabela; Kurrek, Andreas; Wainwright, Marcel

2014-01-01

Implant-Insertion-Torque-Value (ITV) proved to be a significant clinical parameter to predict long term implant success-rates and to decide upon immediate loading. The study evaluated ITVs, when four different and commonly used biomaterials were used in sinuslift-procedures compared to natural subantral bone in two-stage-implant-procedures. The tHUCSL-INTRALIFT-method was chosen for sinuslifting in 155 sinuslift-sites for its minimal invasive transcrestal approach and scalable augmentation volume. Four different biomaterials were inserted randomly (easy-graft CRYSTAL n = 38, easy-graft CLASSIC n = 41, NanoBone n = 42, BioOss n = 34), 2 ccm in each case. After a mean healing period of 8,92 months uniform tapered screw Q2-implants were inserted and Drill-Torque-Values (DTV) and ITV were recorded and compared to a group of 36 subantral sites without need of sinuslifting. DTV/ITV were processed for statistics by ANOVA-tests. Mean DTV/ITV obtained in Ncm were: Control Group 10,2/22,2, Bio-Oss 12,7/26,2, NanoBone 17,5/33,3, easy-graft CLASSIC 20,3/45,9, easy-graft CRYSTAL 23,8/56,6 Ncm, significance-level of differences throughout p < 0,05. Within the limits of this study the results suggest self-hardening solid-block-like bone-graft-materials to achieve significantly better DTV/ITV than loose granulate biomaterials for its suspected improvement of vascularization and mineralization of the subantral scaffold by full immobilization of the augmentation site towards pressure changes in the human sinus at normal breathing. PMID:25073446

Primary implant stability in augmented sinuslift-sites after completed bone regeneration: a randomized controlled clinical study comparing four subantrally inserted biomaterials.

PubMed

Troedhan, Angelo; Schlichting, Izabela; Kurrek, Andreas; Wainwright, Marcel

2014-07-30

Implant-Insertion-Torque-Value (ITV) proved to be a significant clinical parameter to predict long term implant success-rates and to decide upon immediate loading. The study evaluated ITVs, when four different and commonly used biomaterials were used in sinuslift-procedures compared to natural subantral bone in two-stage-implant-procedures. The tHUCSL-INTRALIFT-method was chosen for sinuslifting in 155 sinuslift-sites for its minimal invasive transcrestal approach and scalable augmentation volume. Four different biomaterials were inserted randomly (easy-graft CRYSTAL n = 38, easy-graft CLASSIC n = 41, NanoBone n = 42, BioOss n = 34), 2 ccm in each case. After a mean healing period of 8,92 months uniform tapered screw Q2-implants were inserted and Drill-Torque-Values (DTV) and ITV were recorded and compared to a group of 36 subantral sites without need of sinuslifting. DTV/ITV were processed for statistics by ANOVA-tests. Mean DTV/ITV obtained in Ncm were: Control Group 10,2/22,2, Bio-Oss 12,7/26,2, NanoBone 17,5/33,3, easy-graft CLASSIC 20,3/45,9, easy-graft CRYSTAL 23,8/56,6 Ncm, significance-level of differences throughout p < 0,05. Within the limits of this study the results suggest self-hardening solid-block-like bone-graft-materials to achieve significantly better DTV/ITV than loose granulate biomaterials for its suspected improvement of vascularization and mineralization of the subantral scaffold by full immobilization of the augmentation site towards pressure changes in the human sinus at normal breathing.

In vitro and in vivo mechanical stability of orthodontic mini-implants.

PubMed

Cho, Il-Sik; Kim, Sung-Kyun; Chang, Young-Il; Baek, Seung-Hak

2012-07-01

To compare in vivo and in vitro mechanical stability of orthodontic mini-implants (OMIs) treated with a sandblasted, large-grit, and anodic-oxidation (SLAO) method vs those treated with a sandblasted, large-grit, and acid-etching (SLA) method. Fifty-four titanium OMIs (cylindrical shape, drill-free type; diameter  =  1.45 mm, length  =  8 mm, Biomaterials Korea Inc, Seoul, Korea) were allocated into control, SLA, and SLAO groups (N  =  12 for in vivo and N  =  6 for in vitro studies per group). In vitro study was carried out on a polyurethane foam bone block (Sawbones, Pacific Research Laboratories Inc, Vashon, Wash). In vivo study was performed in the tibias of Beagles (6 males, age  =  1 year, weight  =  10 to 13 kg; OMIs were removed at 8 weeks after installation). For insertion and removal of OMIs, the speed and maximum torque of the surgical engine were set to 30 rpm and 40 Ncm, respectively. Maximum torque (MT), total energy (TE), and near peak energy (NPE) during the insertion and removal procedures were statistically analyzed. In the in vitro study, although the control group had a higher insertion MT value than the SLA and SLAO groups (P < .01), no differences in insertion TE and NPE or in any of the removal variables were noted among the three groups. In the in vivo study, the control group exhibited higher values for all insertion variables compared with the SLA and SLAO groups (MT, P < .001; TE, P < .01; NPE, P < .001). Although no difference in removal TE and removal NPE was noted among the three groups, the SLAO group presented with a higher removal MT than the SLA and control groups (P < .001). SLAO treatment may be an effective tool in reducing insertion damage to surrounding tissue and improving the mechanical stability of OMIs.

Mechanical stability of a novel screw design after repeated insertion: can the double-thread screw serve as a back up?

PubMed

Wiendieck, Kurt; Müller, Helge; Buchfelder, Michael; Sommer, Björn

2018-06-01

We investigated mechanical pull-out behavior and tightening torque of a novel dual-core pedicle "6T screw" (6T). The aim of this study was to test if these changes in screw geometry are increasing the strength of the pedicle screw fixation after repeated insertion. Three different types of pedicle screws were inserted in rigid foam blocks. Tightening torque and pull-out strength were measured during two repetitive insertions of a standard 6.5×45-mm conical screw. The third insertion into the pilot hole was performed using either standard 6.5×45-mm or 7.2×45-mm conical screws or the novel 6.5×45-mm (6T) screw. Additionally, we performed a surface analysis to investigate the bone/screw interface. The maximal tightening torque at the third insertion of the novel 6T screw was 194% higher compared to the standard 6.5×45-mm conical screw and 135% higher compared to the standard 7.2×45-mm conical screw. The pull-out strength of the 6T screw showed no significant changes, and surface analysis revealed a compression of the screw-foam interface due to the different internal diameters. The modified geometrical design of the 6T screw seems to have no statistically significant effect on the pull-out strength, although it achieved a higher tightening torque. This might be due to the different pitch angle cutting a new thread into the material and also to the enlarged inner diameter.

Differences in crestal bone-to-implant contact following an under-drilling compared to an over-drilling protocol. A study in the rabbit tibia.

PubMed

Cohen, Omer; Ormianer, Zeev; Tal, Haim; Rothamel, Daniel; Weinreb, Miron; Moses, Ofer

2016-12-01

The objective of this study is to compare bone-to-implant contact (BIC) between implants inserted at high torque due to under-drilling of the crestal bone to those inserted at low torque due to over-drilling of the crestal bone. Forty implants with diameters of 3.75 mm (group A) or 3.55 mm (group B) were inserted in the proximal tibiae of NZW rabbits in two separate surgeries on day 0 or 21. Osteotomy of the crestal bone was finalized with a 3.65-mm drill. In group A, implants were inserted at torque ≥35 Ncm (under-drilling) and in group B with torque <10 Ncm (over-drilling). Implants and their surrounding bone were retrieved on day 42, thus creating 3- and 6-week observation periods, processed for non-decalcified histology and stained with toluidine blue. Crestal BIC (c-BIC) and total BIC (t-BIC) were measured. Wilcoxon test was used to evaluate differences between groups. Three weeks post-surgery, the mean c-BIC in group A was 16.3 ± 3.3 vs 31.5 ± 3.4 % in group B (P < 0.05). At 6 weeks, a similar trend was observed (group A: 28.7 ± 3.6 %; group B: 38.4 ± 4.9 %) (P > 0.05). No differences in t-BIC were noted at 3 weeks and at 6 weeks between the groups. Insertion of implants with an over-drilling protocol of the crestal aspect of the osteotomy resulted in increased short-term crestal bone-to-implant contact. Insertion of implants with a high torque following an under-drilling protocol, commonly used for immediate loading, may reduce crestal bone-to-implant contact at early healing stages.

Frequency and Type of Prosthetic Complications Associated with Interim, Immediately Loaded Full-Arch Prostheses: A 2-Year Retrospective Chart Review.

PubMed

Drago, Carl

2016-08-01

The purpose of this report was to retrospectively evaluate implant and immediate full-arch prosthesis survival rates over a 24-month period; patients were consecutively treated with immediate occlusal loading. Dental arch, gender, and implant orientation (vertical vs. tilted) were also noted. All Brånemark System implants (Nobel Active) and interim, all-acrylic resin prostheses placed in patients following an All-on-Four™ protocol, in a single private practice were assessed by retrospective patient chart review. The amount of space provided surgically for implant restorative components and prostheses was determined from measurements of the vertical heights of the interim prostheses in the right/left anterior and posterior segments. These measurements were made in the laboratory. Interim prosthetic repairs (type, frequency, length of time from insertion) were analyzed by type, arch, gender, and implant orientation. Implant survival and insertion torque values were also measured. Inclusion criteria consisted of all Brånemark System implants placed with the All-on-Four protocol from September 1, 2011, until August 31, 2013. Specific dietary instructions were given for the first 7 days immediately postoperatively and for the weeks prior to insertion of the definitive prostheses. One hundred twenty-nine patients, comprising 191 arches (766 implants) from September 1, 2011, until August 31, 2013, were included in the study. One patient experienced implant failure yielding an overall implant survival rate (SR) of 99.5% (762 of 766). Four hundred twenty-six of 430 maxillary implants and 336 of 336 mandibular implants survived for SRs of 99.1% and 100%, respectively. Regarding implant orientation, 415 of 417 tilted implants (SR 99.5%) and 343 of 345 (CSR 95.6%) vertical implants were noted to be clinically stable. Interim, all-acrylic resin prostheses were in place for a mean of 199.2 days; mandibular prostheses were in place for an average of 195.4 days; maxillary prostheses were in place for an average of 202.0 days. Thirty four of the 191 interim prostheses (17.8%) warranted at least one repair during the treatment period. The average overall implant insertion torque value was 60.74 Ncm; mandibular torque values averaged 63.08 Ncm; maxillary torque values averaged 59.00 Ncm. The results from this study suggest that dental arch, gender, and implant orientation for implants placed and immediately restored with interim, all-acrylic resin, full-arch prostheses per the All-on-Four protocol did not have significant statistical or clinical effects on prosthetic complications of the interim prostheses or implant survival. Only one of the 129 patients experienced implant failures, indicating that the All-on-Four treatment protocol used in this study is a viable alternative to other protocols for rehabilitating edentulous patients. © 2015 by the American College of Prosthodontists.

Impact of implant design on primary stability of orthodontic mini-implants.

PubMed

Wilmes, Benedict; Ottenstreuer, Stephanie; Su, Yu-Yu; Drescher, Dieter

2008-01-01

Skeletal anchorage with mini-implants has greatly broadened the treatment possibilities in orthodontics over the last few years. To reduce implant failure rates, it is advisable to obtain adequate primary stability. The aim of this study was to quantitatively analyze the impact of implant design and dimension on primary stability. Forty-two porcine iliac bone segments were prepared and embedded in resin. To evaluate the primary stability, we documented insertion torques of the following mini-implants: Aarhus Screw, AbsoAnchor, LOMAS, Micro-Anchorage-System, ORLUS and Spider Screw. In each bone, five Dual Top Screws were inserted for reference purposes to achieve comparability among the specimens. We observed wide variation in insertion torques and hence primary stability, depending on mini-implant design and dimension; the great impact that mini-implant diameter has on insertion torques was particularly conspicuous. Conical mini-implants achieved higher primary stabilities than cylindrical designs. The diameter and design of the mini-implant thread have a distinctive impact on primary stability. Depending on the region of insertion and local bone quality, the choice of the mini-implant design and size is crucial to establish sufficient primary stability.

Possibility of measuring the Abraham force using whispering gallery modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brevik, I.; Ellingsen, S. A.

2010-06-15

Critical experimental tests of the time-dependent Abraham force in phenomenological electrodynamics are scarce. In this paper, we analyze the possibility of making use of intensity-modulated whispering gallery modes in a microresonator for this purpose. Systems of this kind appear attractive, as the strong concentration of electromagnetic fields near the rim of the resonator serves to enhance the Abraham torque exerted by the field. We analyze mainly spherical resonators, although as an introductory step we consider also the cylinder geometry. The orders of magnitude of the Abraham torques are estimated by inserting reasonable and common values for the various input parameters.more » As expected, the predicted torques turn out to be very small, although probably not beyond reach experimentally. Our main idea is essentially a generalization of the method used by G. B. Walker et al.[Can. J. Phys. 53, 2577 (1975)] for low-frequency fields, to the optical case.« less

Ultrasound melted polymer sleeve for improved screw anchorage in trabecular bone--A novel screw augmentation technique.

PubMed

Schmoelz, W; Mayr, R; Schlottig, F; Ivanovic, N; Hörmann, R; Goldhahn, J

2016-03-01

Screw anchorage in osteoporotic bone is still limited and makes treatment of osteoporotic fractures challenging for surgeons. Conventional screws fail in poor bone quality due to loosening at the screw-bone interface. A new technology should help to improve this interface. In a novel constant amelioration process technique, a polymer sleeve is melted by ultrasound in the predrilled screw hole prior to screw insertion. The purpose of this study was to investigate in vitro the effect of the constant amelioration process platform technology on primary screw anchorage. Fresh frozen femoral heads (n=6) and vertebrae (n=6) were used to measure the maximum screw insertion torque of reference and constant amelioration process augmented screws. Specimens were cut in cranio-caudal direction, and the screws (reference and constant amelioration process) were implanted in predrilled holes in the trabecular structure on both sides of the cross section. This allowed the pairwise comparison of insertion torque for constant amelioration process and reference screws (femoral heads n=18, vertebrae n=12). Prior to screw insertion, a micro-CT scan was made to ensure comparable bone quality at the screw placement location. The mean insertion torque for the constant amelioration process augmented screws in both, the femoral heads (44.2 Ncm, SD 14.7) and the vertebral bodies (13.5 Ncm, SD 6.3) was significantly higher than for the reference screws of the femoral heads (31.7 Ncm, SD 9.6, p<0.001) and the vertebral bodies (7.1 Ncm, SD 4.5, p<0.001). The interconnection of the melted polymer sleeve with the surrounding trabecular bone in the constant amelioration process technique resulted in a higher screw insertion torque and can improve screw anchorage in osteoporotic trabecular bone. Copyright © 2016 Elsevier Ltd. All rights reserved.

Development of a Robotic Colonoscopic Manipulation System, Using Haptic Feedback Algorithm.

PubMed

Woo, Jaehong; Choi, Jae Hyuk; Seo, Jong Tae; Kim, Tae Il; Yi, Byung Ju

2017-01-01

Colonoscopy is one of the most effective diagnostic and therapeutic tools for colorectal diseases. We aim to propose a master-slave robotic colonoscopy that is controllable in remote site using conventional colonoscopy. The master and slave robot were developed to use conventional flexible colonoscopy. The robotic colonoscopic procedure was performed using a colonoscope training model by one expert endoscopist and two unexperienced engineers. To provide the haptic sensation, the insertion force and the rotating torque were measured and sent to the master robot. A slave robot was developed to hold the colonoscopy and its knob, and perform insertion, rotation, and two tilting motions of colonoscope. A master robot was designed to teach motions of the slave robot. These measured force and torque were scaled down by one tenth to provide the operator with some reflection force and torque at the haptic device. The haptic sensation and feedback system was successful and helpful to feel the constrained force or torque in colon. The insertion time using robotic system decreased with repeated procedures. This work proposed a robotic approach for colonoscopy using haptic feedback algorithm, and this robotic device would effectively perform colonoscopy with reduced burden and comparable safety for patients in remote site.

Resonance frequency analysis, insertion torque, and bone to implant contact of 4 implant surfaces: comparison and correlation study in sheep.

PubMed

Dagher, Maroun; Mokbel, Nadim; Jabbour, Gabriel; Naaman, Nada

2014-12-01

Primary stability is evaluated using resonance frequency analysis (RFA) and insertion torque (IT). Although there is a strong correlation between RFA and IT, studies failed to find a correlation between RFA and bone to implant contact (BIC) or IT and BIC. To compare RFA, IT, and BIC of SLA, SLActive, Euroteknika, and TiUnite implant surfaces and evaluate the correlation between them. Thirty-two implants were placed in 8 sheep. RFA and IT were recorded. Animals were killed at 1 and 2 months. A significant difference was found in RFA between the 4 surfaces. No significant difference was found for IT. Mean BIC was different between all 4 surfaces. A significant positive correlation was found between RFA and IT with SLA. No significant correlation was found between RFA and BIC and between IT and BIC at 1 and 2 months. Implants with 4 different surfaces have similar IT values but different RFA and BIC. Additionally irrespective of the implant surface, there is no correlation between IT and BIC and between RFA and BIC.

Drilling dimension effects in early stages of osseointegration and implant stability in a canine model

PubMed Central

Baires-Campos, Felipe-Eduardo; Jimbo, Ryo; Fonseca-Oliveira, Maiolino-Thomaz; Moura, Camila; Zanetta-Barbosa, Darceny; Coelho, Paulo-Guilherme

2015-01-01

Background This study histologically evaluated two implant designs: a classic thread design versus another specifically designed for healing chamber formation placed with two drilling protocols. Material and Methods Forty dental implants (4.1 mm diameter) with two different macrogeometries were inserted in the tibia of 10 Beagle dogs, and maximum insertion torque was recorded. Drilling techniques were: until 3.75 mm (regular-group); and until 4.0 mm diameter (overdrilling-group) for both implant designs. At 2 and 4 weeks, samples were retrieved and processed for histomorphometric analysis. For torque and BIC (bone-to-implant contact) and BAFO (bone area fraction occupied), a general-linear model was employed including instrumentation technique and time in vivo as independent. Results The insertion torque recorded for each implant design and drilling group significantly decreased as a function of increasing drilling diameter for both implant designs (p<0.001). No significant differences were detected between implant designs for each drilling technique (p>0.18). A significant increase in BIC was observed from 2 to 4 weeks for both implants placed with the overdrilling technique (p<0.03) only, but not for those placed in the 3.75 mm drilling sites (p>0.32). Conclusions Despite the differences between implant designs and drilling technique an intramembranous-like healing mode with newly formed woven bone prevailed. Key words: Histomorphometry, biomechanical, in vivo, initial stability, insertion torque, osseointegration. PMID:25858087

Pullout strength of cancellous screws in human femoral heads depends on applied insertion torque, trabecular bone microarchitecture and areal bone mineral density.

PubMed

Ab-Lazid, Rosidah; Perilli, Egon; Ryan, Melissa K; Costi, John J; Reynolds, Karen J

2014-12-01

For cancellous bone screws, the respective roles of the applied insertion torque (TInsert) and of the quality of the host bone (microarchitecture, areal bone mineral density (aBMD)), in contributing to the mechanical holding strength of the bone-screw construct (FPullout), are still unclear. During orthopaedic surgery screws are tightened, typically manually, until adequate compression is attained, depending on surgeons' manual feel. This corresponds to a subjective insertion torque control, and can lead to variable levels of tightening, including screw stripping. The aim of this study, performed on cancellous screws inserted in human femoral heads, was to investigate which, among the measurements of aBMD, bone microarchitecture, and the applied TInsert, has the strongest correlation with FPullout. Forty six femoral heads were obtained, over which microarchitecture and aBMD were evaluated using micro-computed tomography and dual X-ray absorptiometry. Using an automated micro-mechanical test device, a cancellous screw was inserted in the femoral heads at TInsert set to 55% to 99% of the predicted stripping torque beyond screw head contact, after which FPullout was measured. FPullout exhibited strongest correlations with TInsert (R=0.88, p<0.001), followed by structure model index (SMI, R=-0.81, p<0.001), bone volume fraction (BV/TV, R=0.73, p<0.001) and aBMD (R=0.66, p<0.01). Combinations of TInsert with microarchitectural parameters and/or aBMD did not improve the prediction of FPullout. These results indicate that, for cancellous screws, FPullout depends most strongly on the applied TInsert, followed by microarchitecture and aBMD of the host bone. In trabecular bone, screw tightening increases the holding strength of the screw-bone construct. Copyright © 2014 Elsevier Ltd. All rights reserved.

Primary stability of a hybrid self-tapping implant compared to a cylindrical non-self-tapping implant with respect to drilling protocols in an ex vivo model.

PubMed

Toyoshima, Takeshi; Wagner, Wilfried; Klein, Marcus Oliver; Stender, Elmar; Wieland, Marco; Al-Nawas, Bilal

2011-03-01

Modifications of implant design have been intending to improve primary stability. However, little is known about investigation of a hybrid self-tapping implant on primary stability. The aims of this study were to evaluate the primary stability of two hybrid self-tapping implants compared to one cylindrical non-self-tapping implant, and to elucidate the relevance of drilling protocols on primary stability in an ex vivo model. Two types of hybrid self-tapping implants (Straumann® Bone Level implant [BL], Straumann® Tapered Effect implant [TE]) and one type of cylindrical non-self-tapping implant (Straumann® Standard Plus implant [SP]) were investigated in the study. In porcine iliac cancellous bones, 10 implants each were inserted either using standard drilling or under-dimensioned drilling protocol. The evaluation of implant-bone interface stability was carried out by records of maximum insertion torque, the Periotest® (Siemens, Bensheim, Germany), the resonance frequency analysis (RFA), and the push-out test. In each drilling group, the maximum insertion torque values of BL and TE were significantly higher than SP (p=.014 and p=.047, respectively). In each group, the Periotest values of TE were significantly lower than SP (p=.036 and p=.033, respectively). The Periotest values of BL and TE were significantly lower in the group of under-dimensioned drilling than standard drilling (p=.002 and p=.02, respectively). In the RFA, no statistical significances were found in implants between two groups and between implants in each group. In each group, the push-out values of BL and TE were significantly higher than SP (p=.006 and p=.049, respectively). Hybrid self-tapping implants could achieve a high primary stability which predicts them for use in low-density bone. However, there is still a debate to clarify the influence of under-dimensioned drilling on primary stability. © 2009, Copyright the Authors. Journal Compilation © 2011, Wiley Periodicals, Inc.

Development of a Robotic Colonoscopic Manipulation System, Using Haptic Feedback Algorithm

PubMed Central

Woo, Jaehong; Choi, Jae Hyuk; Seo, Jong Tae

2017-01-01

Purpose Colonoscopy is one of the most effective diagnostic and therapeutic tools for colorectal diseases. We aim to propose a master-slave robotic colonoscopy that is controllable in remote site using conventional colonoscopy. Materials and Methods The master and slave robot were developed to use conventional flexible colonoscopy. The robotic colonoscopic procedure was performed using a colonoscope training model by one expert endoscopist and two unexperienced engineers. To provide the haptic sensation, the insertion force and the rotating torque were measured and sent to the master robot. Results A slave robot was developed to hold the colonoscopy and its knob, and perform insertion, rotation, and two tilting motions of colonoscope. A master robot was designed to teach motions of the slave robot. These measured force and torque were scaled down by one tenth to provide the operator with some reflection force and torque at the haptic device. The haptic sensation and feedback system was successful and helpful to feel the constrained force or torque in colon. The insertion time using robotic system decreased with repeated procedures. Conclusion This work proposed a robotic approach for colonoscopy using haptic feedback algorithm, and this robotic device would effectively perform colonoscopy with reduced burden and comparable safety for patients in remote site. PMID:27873506

Insertion torque in different bone models with different screw pitch: an in vitro study.

PubMed

Orlando, Bruno; Barone, Antonio; Giorno, Thierry M; Giacomelli, Luca; Tonelli, Paolo; Covani, Ugo

2010-01-01

Orthopedic surgeons use different types of screws for bone fixation. Whereas hard cortical bone requires a screw with a fine pitch, in softer cancellous bone a wider pitch might help prevent micromotion and eventually lead to greater implant stability. The aim of this study was to validate the assumption that fine-pitch implants are appropriate for cortical bone and wide-pitch implants are appropriate for cancellous bone. Wide-pitch and fine-pitch implants were inserted in both hard (D1 and D2) bone and soft (D3 and D4) bone, which was simulated by separate experimental blocks of cellular rigid polyurethane foam. A series of insertion sites in D1-D2 and D3-D4 experimental blocks were prepared using 1.5-mm and 2.5-mm drills. The final torque required to insert each implant was recorded. Wide-pitch implants displayed greater insertion torque (20% more than the fine-pitch implants) in cancellous bone and were therefore more suitable than fine-pitch implants. It is more appropriate to use a fine pitch design for implants, in conjunction with a 2.5-mm osteotomy site, in dense cortical bone (D1 or D2), whereas it is recommended to choose a wide-pitch design for implants, in conjunction with a 1.5-mm osteotomy site, in softer bone (D3 or D4).

Effect of tightening torque on the marginal adaptation of cement-retained implant-supported fixed dental prostheses

PubMed Central

Ghanbarzadeh, Jalil; Dashti, Hossin; Karamad, Reza; Alikhasi, Marzieh; Nakhaei, Mohammadreza

2015-01-01

Background: The final position of the abutment changes with the amount of tightening torque. This could eventually lead to loss of passivity and marginal misfit of prostheses. The aim of this study was to evaluate the effect of three different tightening torques on the marginal adaptation of 3-unit cement-retained implant-supported fixed dental prostheses (FDPs). Materials and Methods: Two implants (Straumann) were inserted in an acrylic block so that one of the implants was placed vertically and the other at a 15° vertical angle. A straight abutment and a 15° angulated abutment were connected to the vertically and obliquely installed implants, respectively, so that the two abutments were parallel. Then, 10 cement-retained FDPs were waxed and cast. Abutments were tightened with 10, 20, and 35 Ncm torques, respectively. Following each tightening torque, FDPs were luted on respective abutments with temporary cement. The marginal adaptation of the retainers was evaluated using stereomicroscope. FDPs were then removed from the abutments and were sectioned at the connector sites. The retainers were luted again on their respective abutments. Luting procedures and marginal adaptation measurement were repeated. Data were analyzed by ANOVA and least significant difference tests (α = 0.05). After cutting the FDP connectors, the independent samples t-test was used to compare misfit values (α = 0.05). Results: Following 10, 20, and 35 Ncm tightening torques, the marginal discrepancy of the retainers of FDPs significantly increased (P < 0.05). There was no significant difference between the marginal discrepancies of these two retainers (P > 0.05). The marginal gap values of angulated abutment retainers (ANRs) were significantly higher than those of the straight abutment after cutting the connectors (P = 0.026). Conclusion: Within the limitations of this study, the marginal misfit of cement-retained FDPs increased continuously when the tightening torque increased. After cutting the connectors, the marginal misfit of the ANRs was higher than those of the straight abutment retainers. PMID:26288627

Effect of tightening torque on the marginal adaptation of cement-retained implant-supported fixed dental prostheses.

PubMed

Ghanbarzadeh, Jalil; Dashti, Hossin; Karamad, Reza; Alikhasi, Marzieh; Nakhaei, Mohammadreza

2015-01-01

The final position of the abutment changes with the amount of tightening torque. This could eventually lead to loss of passivity and marginal misfit of prostheses. The aim of this study was to evaluate the effect of three different tightening torques on the marginal adaptation of 3-unit cement-retained implant-supported fixed dental prostheses (FDPs). Two implants (Straumann) were inserted in an acrylic block so that one of the implants was placed vertically and the other at a 15° vertical angle. A straight abutment and a 15° angulated abutment were connected to the vertically and obliquely installed implants, respectively, so that the two abutments were parallel. Then, 10 cement-retained FDPs were waxed and cast. Abutments were tightened with 10, 20, and 35 Ncm torques, respectively. Following each tightening torque, FDPs were luted on respective abutments with temporary cement. The marginal adaptation of the retainers was evaluated using stereomicroscope. FDPs were then removed from the abutments and were sectioned at the connector sites. The retainers were luted again on their respective abutments. Luting procedures and marginal adaptation measurement were repeated. Data were analyzed by ANOVA and least significant difference tests (α = 0.05). After cutting the FDP connectors, the independent samples t-test was used to compare misfit values (α = 0.05). Following 10, 20, and 35 Ncm tightening torques, the marginal discrepancy of the retainers of FDPs significantly increased (P < 0.05). There was no significant difference between the marginal discrepancies of these two retainers (P > 0.05). The marginal gap values of angulated abutment retainers (ANRs) were significantly higher than those of the straight abutment after cutting the connectors (P = 0.026). Within the limitations of this study, the marginal misfit of cement-retained FDPs increased continuously when the tightening torque increased. After cutting the connectors, the marginal misfit of the ANRs was higher than those of the straight abutment retainers.

Assessment of the correlation between insertion torque and resonance frequency analysis of implants placed in bone tissue of different densities.

PubMed

Filho, Luiz Carlos Magno; Cirano, Fabiano Ribeiro; Hayashi, Fernando; Feng, Hsu Shao; Conte, Alexandre; Dib, Luciano Lauria; Casati, Marcio Zaffalon

2014-06-01

The primary stability of dental implants is fundamental for osseointegration. Therefore, this study aimed to assess the correlation between insertion torque (IT) and resonance frequency analysis (RFA) of implants placed in mandibles and maxillas of different bone densities. Eighty dental implants were placed in maxillas and mandibles, and IT and the implant stability quotient (ISQ) were measured at the time of implant insertion. Bone density was assessed subjectively by the Lekholm and Zarb index. The type I and II densities were grouped together (group A)as were the type III and IV densities (group B). The IT in group A was higher (Student t test, P = .0013) than in group B (46.27 ± 18.51 Ncm, 33.62 ± 14.74 Ncm, respectively). The implants placed in group A showed higher ISQ (Student t test, P = .0004) than those placed in group B (70.09 ± 7.50, 63.66 ± 8.00, respectively). A significant correlation between IT and the ISQ value was observed for group A (Pearson correlation test; r = 0.35; P = .0213) and for group B (r = 0.37; P = .0224). Within the limitations of this study, it was possible to conclude that there is a correlation between IT and RFA of implants placed in mandibles and maxillas of different bone densities.

Spin-orbit torque induced magnetization switching in heavy metal/ferromagnet multilayers with bilayer of heavy metals

NASA Astrophysics Data System (ADS)

Bekele, Zelalem Abebe; Meng, Kangkang; Zhao, Bing; Wu, Yong; Miao, Jun; Xu, Xiaoguang; Jiang, Yong

2017-08-01

Symmetry breaking provides new insight into the physics of spin-orbit torque (SOT) and the switching without a magnetic field could lead to significant impact. In this work, we demonstrate the robust zero-field SOT switching of a perpendicular ferromagnet (FM) layer where the symmetry is broken by a bilayer of heavy metals (HMs) with the strong spin-orbit coupling (SOC). We observed the change of coercivity value by 31% after inserting Co2FeAl in the multilayer structure. These two HM layers (Ta and Pt) are used to strengthen the SOC by linear combination. With different angles between the magnetization and the current (i.e. parallel and anti-parallel), the structures show different switching behaviors such as clockwise or counterclockwise.

Torque Tension Testing of Fasteners used for NASA Flight Hardware Applications

NASA Technical Reports Server (NTRS)

Hemminger, Edgar G.; Posey, Alan J.; Dube, Michael J.

2014-01-01

The effect of various lubricants and other compounds on fastener torque-tension relationships is evaluated. Testing was performed using a unique test apparatus developed by Posey at the NASA Goddard Space Flight Center. A description of the test methodology, including associated data collection and analysis will be presented. Test results for 300 series CRES and A286 heat resistant fasteners, torqued into various types of inserts will be presented. The primary objective of this testing was to obtain torque-tension data for use on NASA flight projects.

Multiscale Analyses of the Bone-implant Interface

PubMed Central

Cha, J.Y.; Pereira, M.D.; Smith, A.A.; Houschyar, K.S.; Yin, X.; Mouraret, S.; Brunski, J.B.

2015-01-01

Implants placed with high insertion torque (IT) typically exhibit primary stability, which enables early loading. Whether high IT has a negative impact on peri-implant bone health, however, remains to be determined. The purpose of this study was to ascertain how peri-implant bone responds to strains and stresses created when implants are placed with low and high IT. Titanium micro-implants were inserted into murine femurs with low and high IT using torque values that were scaled to approximate those used to place clinically sized implants. Torque created in peri-implant tissues a distribution and magnitude of strains, which were calculated through finite element modeling. Stiffness tests quantified primary and secondary implant stability. At multiple time points, molecular, cellular, and histomorphometric analyses were performed to quantitatively determine the effect of high and low strains on apoptosis, mineralization, resorption, and collagen matrix deposition in peri-implant bone. Preparation of an osteotomy results in a narrow zone of dead and dying osteocytes in peri-implant bone that is not significantly enlarged in response to implants placed with low IT. Placing implants with high IT more than doubles this zone of dead and dying osteocytes. As a result, peri-implant bone develops micro-fractures, bone resorption is increased, and bone formation is decreased. Using high IT to place an implant creates high interfacial stress and strain that are associated with damage to peri-implant bone and therefore should be avoided to best preserve the viability of this tissue. PMID:25628271

Engineering spin-orbit torque in Co/Pt multilayers with perpendicular magnetic anisotropy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Kuo-Feng; Wang, Ding-Shuo; Lai, Chih-Huang, E-mail: chlai@mx.nthu.edu.tw

To address thermal stability issues for spintronic devices with a reduced size, we investigate spin-orbit torque in Co/Pt multilayers with strong perpendicular magnetic anisotropy. Note that the spin-orbit torque arises from the global imbalance of the spin currents from the top and bottom interfaces for each Co layer. By inserting Ta or Cu layers to strengthen the top-down asymmetry, the spin-orbit torque efficiency can be greatly modified without compromised perpendicular magnetic anisotropy. Above all, the efficiency builds up as the number of layers increases, realizing robust thermal stability and high spin-orbit-torque efficiency simultaneously in the multilayers structure.

A comparison of screw insertion torque and pullout strength.

PubMed

Ricci, William M; Tornetta, Paul; Petteys, Timothy; Gerlach, Darin; Cartner, Jacob; Walker, Zakiyyah; Russell, Thomas A

2010-06-01

Pullout strength of screws is a parameter used to evaluate plate screw fixation strength. However, screw fixation strength may be more closely related to its ability to generate sufficient insertion because stable nonlocked plate-screw fracture fixation requires sufficient compression between plate and bone such that no motion occurs between the plate and bone under physiological loads. Compression is generated by tightening of screws. In osteoporotic cancellous bone, sufficient screw insertion torque may not be generated before screw stripping. The effect of screw thread pitch on generation of maximum insertion torque (MIT) and pullout strength (POS) was investigated in an osteoporotic cancellous bone model and the relationship between MIT and POS was analyzed. Stainless steel screws with constant major (5.0 mm) and minor (2.7 mm) diameters but with varying thread pitches (1, 1.2, 1.5, 1.6, and 1.75 mm) were tested for MIT and POS in a validated osteoporotic surrogate for cancellous bone (density of 160 kg/m(3) [10 lbs/ft(3)]). MIT was measured with a torque-measuring hex driver for screws inserted through a one-third tubular plate. POS was measured after insertion of screws to a depth of 20 mm based on the Standard Specification and Test Methods for Metallic Medical Bone Screws (ASTM F 543-07). Five screws were tested for each failure mode and screw design. The relationship between MIT and compressive force between the plate and bone surrogate was evaluated using pressure-sensitive film. There was a significant difference in mean MIT based on screw pitch (P < 0.0001), whereas POS did not show statistically significant differences among the different screw pitches (P = 0.052). Small screw pitches (1.0 mm and 1.2 mm) had lower MIT and were distinguished from large pitches (1.5 mm, 1.6 mm, and the 1.75 mm) with higher MIT. For POS, only the 1-mm and 1.6-mm pitch screws were found to be different from each other. Linear regression analysis of MIT revealed a moderate correlation to the screw pitch (R(2) = 0.67, P < 0.0001), whereas the analysis of POS suggested no correlation to the screw pitch (R(2) = 0.28, P = 0.006). Pearson correlation analysis indicated no correlation between MIT and POS (P = 0.069, r = -0.37). A linear relationship of increased compression between the plate and bone surrogate was found for increasing screw torque (R(2) = 0.97). These results indicate that the ability of different screw designs to generate high screw insertion torque in a model of osteoporotic cancellous bone is unrelated to their pullout strength. Therefore, extrapolation of results for POS to identify optimal screw design for osteoporotic bone may not be valid. Screw designs that optimize MIT should be sought for fixation in osteoporotic bone.

The biomechanical effect of artificial and human bone density on stopping and stripping torque during screw insertion.

PubMed

Tsuji, Matthew; Crookshank, Meghan; Olsen, Michael; Schemitsch, Emil H; Zdero, Rad

2013-06-01

Orthopedic surgeons apply torque to metal screws manually by "subjective feel" to obtain adequate fracture fixation, i.e. stopping torque, and attempt to avoid accidental over-tightening that leads to screw-bone interface failure, i.e. stripping torque. Few studies have quantified stripping torque in human bone, and only one older study from 1980 reported stopping/ stripping torque ratio. The present aim was to measure stopping and stripping torque of cortical and cancellous screws in artificial and human bone over a wide range of densities. Sawbone blocks were obtained having densities from 0.08 to 0.80g/cm(3). Sixteen fresh-frozen human femurs of known standardized bone mineral density (sBMD) were also used. Using a torque screwdriver, 3.5-mm diameter cortical screws and 6.5-mm diameter cancellous screws were inserted for adequate tightening as determined subjectively by an orthopedic surgeon, i.e. stopping torque, and then further tightened until failure of the screw-bone interface, i.e. stripping torque. There were weak (R=0.25) to strong (R=0.99) linear correlations of absolute and normalized torque vs. density or sBMD. Maximum stopping torques normalized by screw thread area engaged by the host material were 15.2N/mm (cortical screws) and 13.4N/mm (cancellous screws) in sawbone blocks and 20.9N/mm (cortical screws) and 6.1N/mm (cancellous screws) in human femurs. Maximum stripping torques normalized by screw thread area engaged by the host material were 23.4N/mm (cortical screws) and 16.8N/mm (cancellous screws) in sawbone blocks and 29.3N/mm (cortical screws) and 8.3N/mm (cancellous screws) in human femurs. Combined average stopping/ stripping torque ratios were 80.8% (cortical screws) and 76.8% (cancellous screws) in sawbone blocks, as well as 66.6% (cortical screws) and 84.5% (cancellous screws) in human femurs. Surgeons should be aware of stripping torque limits for human femurs and monitor stopping torque during surgery. This is the first study of the effect of sawbone density or human bone sBMD on stopping and stripping torque. Copyright © 2013 Elsevier Ltd. All rights reserved.

Tapping insertional torque allows prediction for better pedicle screw fixation and optimal screw size selection.

PubMed

Helgeson, Melvin D; Kang, Daniel G; Lehman, Ronald A; Dmitriev, Anton E; Luhmann, Scott J

2013-08-01

There is currently no reliable technique for intraoperative assessment of pedicle screw fixation strength and optimal screw size. Several studies have evaluated pedicle screw insertional torque (IT) and its direct correlation with pullout strength. However, there is limited clinical application with pedicle screw IT as it must be measured during screw placement and rarely causes the spine surgeon to change screw size. To date, no study has evaluated tapping IT, which precedes screw insertion, and its ability to predict pedicle screw pullout strength. The objective of this study was to investigate tapping IT and its ability to predict pedicle screw pullout strength and optimal screw size. In vitro human cadaveric biomechanical analysis. Twenty fresh-frozen human cadaveric thoracic vertebral levels were prepared and dual-energy radiographic absorptiometry scanned for bone mineral density (BMD). All specimens were osteoporotic with a mean BMD of 0.60 ± 0.07 g/cm(2). Five specimens (n=10) were used to perform a pilot study, as there were no previously established values for optimal tapping IT. Each pedicle during the pilot study was measured using a digital caliper as well as computed tomography measurements, and the optimal screw size was determined to be equal to or the first size smaller than the pedicle diameter. The optimal tap size was then selected as the tap diameter 1 mm smaller than the optimal screw size. During optimal tap size insertion, all peak tapping IT values were found to be between 2 in-lbs and 3 in-lbs. Therefore, the threshold tapping IT value for optimal pedicle screw and tap size was determined to be 2.5 in-lbs, and a comparison tapping IT value of 1.5 in-lbs was selected. Next, 15 test specimens (n=30) were measured with digital calipers, probed, tapped, and instrumented using a paired comparison between the two threshold tapping IT values (Group 1: 1.5 in-lbs; Group 2: 2.5 in-lbs), randomly assigned to the left or right pedicle on each specimen. Each pedicle was incrementally tapped to increasing size (3.75, 4.00, 4.50, and 5.50 mm) until the threshold value was reached based on the assigned group. Pedicle screw size was determined by adding 1 mm to the tap size that crossed the threshold torque value. Torque measurements were recorded with each revolution during tap and pedicle screw insertion. Each specimen was then individually potted and pedicle screws pulled out "in-line" with the screw axis at a rate of 0.25 mm/sec. Peak pullout strength (POS) was measured in Newtons (N). The peak tapping IT was significantly increased (50%) in Group 2 (3.23 ± 0.65 in-lbs) compared with Group 1 (2.15 ± 0.56 in-lbs) (p=.0005). The peak screw IT was also significantly increased (19%) in Group 2 (8.99 ± 2.27 in-lbs) compared with Group 1 (7.52 ± 2.96 in-lbs) (p=.02). The pedicle screw pullout strength was also significantly increased (23%) in Group 2 (877.9 ± 235.2 N) compared with Group 1 (712.3 ± 223.1 N) (p=.017). The mean pedicle screw diameter was significantly increased in Group 2 (5.70 ± 1.05 mm) compared with Group 1 (5.00 ± 0.80 mm) (p=.0002). There was also an increased rate of optimal pedicle screw size selection in Group 2 with 9 of 15 (60%) pedicle screws compared with Group 1 with 4 of 15 (26.7%) pedicle screws within 1 mm of the measured pedicle width. There was a moderate correlation for tapping IT with both screw IT (r=0.54; p=.002) and pedicle screw POS (r=0.55; p=.002). Our findings suggest that tapping IT directly correlates with pedicle screw IT, pedicle screw pullout strength, and optimal pedicle screw size. Therefore, tapping IT may be used during thoracic pedicle screw instrumentation as an adjunct to preoperative imaging and clinical experience to maximize fixation strength and optimize pedicle "fit and fill" with the largest screw possible. However, further prospective, in vivo studies are necessary to evaluate the intraoperative use of tapping IT to predict screw loosening/complications. Published by Elsevier Inc.

Immediate versus early loading of two implants placed with a flapless technique supporting mandibular bar-retained overdentures: a single-blinded, randomised controlled clinical trial.

PubMed

Cannizzaro, Gioacchino; Leone, Michele; Esposito, Marco

2008-01-01

To evaluate the efficacy of immediate loading versus early loading at 6 weeks of bar-retained mandibular overdentures supported by two implants placed with a flapless technique. Sixty patients were randomised: 30 to the immediately loaded group and 30 to the early loaded group. To be immediately loaded, implants had to be inserted with a minimum torque > 48 Ncm. Outcome measures were prosthesis and implant failures, biological and biomechanical complications, patient satisfaction, and Implant Stability Quotient (ISQ) assessed with a resonance frequency analysis instrument. Sixty implants were placed in each group. Flaps had to be raised in nine patients to check drill direction or to better visualise the area after multiple teeth extraction. Two implants in two patients did not reach the planned insertion torque and were immediately replaced by larger diameters ones. After 1 year no drop out occurred and two early loaded implants failed in two patients. There were no statistically significant differences between groups for prosthesis failures, implant losses, complications, and mean ISQ values; however, patients in the immediately loaded group were significantly more satisfied than those loaded early. When comparing mean ISQ values taken 6 weeks after placement with 1-year data within each group, values decreased significantly. Mandibular overdentures can be successfully loaded the same day of implant placement with a minimally invasive surgery, increasing patient satisfaction while decreasing treatment time and patient discomfort. No apparent advantages were seen when loading the overdentures at 6 weeks.

Stability of the prosthetic screws of three types of craniofacial prostheses retention systems

PubMed Central

2016-01-01

Objectives This study aimed to evaluate the stability of prosthetic screws from three types of craniofacial prostheses retention systems (bar-clip, ball/O-ring, and magnet) when submitted to mechanical cycling. Materials and Methods Twelve models of acrylic resin were used with implants placed 20 mm from each other and separated into three groups: (1) bar-clip (Sistema INP, São Paulo, Brazil), (2) ball/O-ring (Sistema INP), and (3) magnet (Metalmag, São Paulo, Brazil), with four samples in each group. Each sample underwent a mechanical cycling removal and insertion test (f=0.5 Hz) to determine the torque and the detorque values of the retention screws. A servo-hydraulic MTS machine (810-Flextest 40; MTS Systems, Eden Prairie, MN, USA) was used to perform the cycling with 2.5 mm and a displacement of 10 mm/s. The screws of the retention systems received an initial torque of 30 Ncm and the torque values required for loosening the screw values were obtained in three cycles (1,080, 2,160, and 3,240). The screws were retorqued to 30 Ncm before each new cycle. Results The sample was composed of 24 screws grouped as follows: bar-clip (n=8), ball/O-ring (n=8), and magnet (n=8). There were significant differences between the groups, with greater detorque values observed in the ball/O-ring group when compared to the bar-clip and magnet groups for the first cycle. However, the detorque value was greater in the bar-clip group for the second cycle. Conclusion The results of this study indicate that all prosthetic screws will loosen slightly after an initial tightening torque, also the bar-clip retention system demonstrated greater loosening of the screws when compared with ball/O-ring and magnet retention systems. PMID:28053905

Initial stability of cementless acetabular cups: press-fit and screw fixation interaction--an in vitro biomechanical study.

PubMed

Tabata, Tomonori; Kaku, Nobuhiro; Hara, Katsutoshi; Tsumura, Hiroshi

2015-04-01

Press-fit and screw fixation are important technical factors to achieve initial stability of a cementless acetabular cup for good clinical results of total hip arthroplasty. However, how these factors affect one another in initial cup fixation remains unclear. Therefore, this study aimed to evaluate the mutual influence between press-fit and screw fixation on initial cup stability. Foam bone was subjected to exact hemispherical-shape machining to diameters of 48, 48.5 and 49 mm. A compressive force was applied to ensure seating of a 48-mm-diameter acetabular cup in the foam bone prior to testing. Screws were inserted in six different conditions and tightened in a radial direction at the same torque strength. Then, the socket was rotated with a twist-testing machine, and the torque value at the start of axial rotation between the socket and the foam bone was measured under each screw condition. The torque values for the 48-mm-diameter reaming were >20 N m higher than those for the 48.5- and 49-mm-diameter reaming in each screw condition, indicating that press-fit fixation is stronger than screw fixation. Meanwhile, torque values for the 48.5- and 49-mm-diameter reaming tended to increase with increasing the number of screws. According to our experiment, press-fit fixation of a cementless acetabular cup achieved rigid stability. Although the supplemental screws increased stability of the implant under good press-fit conditions, they showed little impact on whole-cup stability. In the case of insufficient press-fit fixation, cup stability depends on screw stability and increasing the number of additional screws increases cup stability.

Fastener starter tool

NASA Technical Reports Server (NTRS)

Chandler, Faith T. (Inventor); Arnett, Michael C. (Inventor); Garton, Harry L. (Inventor); Valentino, William D. (Inventor)

2003-01-01

A fastener starter tool includes a number of spring retention fingers for retaining a small part, or combination of parts. The tool has an inner housing, which holds the spring retention fingers, a hand grip, and an outer housing configured to slide over the inner housing and the spring retention fingers toward and away from the hand grip, exposing and opening, or respectively, covering and closing, the spring retention fingers. By sliding the outer housing toward (away from) the hand grip, a part can be released from (retained by) the tool. The tool may include replaceable inserts, for retaining parts, such as screws, and configured to limit the torque applied to the part, to prevent cross threading. The inner housing has means to transfer torque from the hand grip to the insert. The tool may include replaceable bits, the inner housing having means for transferring torque to the replaceable bit.

Evaluation of the effect of custom burr holes on a surgeon's sense of screw fixation in revision porous metal cups.

PubMed

Nyland, Mark A; Lanting, Brent A; Nikolov, Hristo N; Somerville, Lyndsay E; Teeter, Matthew G; Howard, James L

2016-12-01

It is common practice to burr custom holes in revision porous metal cups for screw insertion. The objective of this study was to determine how different hole types affect a surgeon's sense of screw fixation. Porous revision cups were prepared with pre-drilled and custom burred holes. Cups were held in place adjacent to synthetic bone material of varying density. Surgeons inserted screws through the different holes and materials. Surgeon subjective rating, compression, and torque was recorded. The torque achieved was greater ( p  = 0.002) for screws through custom holes than pre-fabricated holes in low and medium density material, with no difference for high density. Peak compression was greater ( p  = 0.026) through the pre-fabricated holes only in high density material. Use of burred holes affects the torque generated, and may decrease the amount of cup-acetabulum compression achieved.

The impact of a modified cutting flute implant design on osseointegration.

PubMed

Jimbo, R; Tovar, N; Marin, C; Teixeira, H S; Anchieta, R B; Silveira, L M; Janal, M N; Shibli, J A; Coelho, P G

2014-07-01

Information concerning the effects of the implant cutting flute design on initial stability and its influence on osseointegration in vivo is limited. This study evaluated the early effects of implants with a specific cutting flute design placed in the sheep mandible. Forty-eight dental implants with two different macro-geometries (24 with a specific cutting flute design - Blossom group; 24 with a self-tapping design - DT group) were inserted into the mandibular bodies of six sheep; the maximum insertion torque was recorded. Samples were retrieved and processed for histomorphometric analysis after 3 and 6 weeks. The mean insertion torque was lower for Blossom implants (P<0.001). No differences in histomorphometric results were observed between the groups. At 3 weeks, P=0.58 for bone-to-implant contact (BIC) and P=0.52 for bone area fraction occupied (BAFO); at 6 weeks, P=0.55 for BIC and P=0.45 for BAFO. While no histomorphometric differences were observed, ground sections showed different healing patterns between the implants, with better peri-implant bone organization around those with the specific cutting flute design (Blossom group). Implants with the modified cutting flute design had a significantly reduced insertion torque compared to the DT implants with a traditional cutting thread, and resulted in a different healing pattern. Copyright © 2014 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Comparison of removal torques between laser-treated and SLA-treated implant surfaces in rabbit tibiae

PubMed Central

Kang, Nam-Seok; Li, Lin-Jie

2014-01-01

PURPOSE The purpose of this study was to compare removal torques and surface topography between laser treated and sandblasted, large-grit, acid-etched (SLA) treated implants. MATERIALS AND METHODS Laser-treated implants (experimental group) and SLA-treated implants (control group) 8 mm in length and 3.4 mm in diameter were inserted into both sides of the tibiae of 12 rabbits. Surface analysis was accomplished using a field emission scanning electron microscope (FE-SEM; Hitachi S-4800; Japan) under ×25, ×150 and ×1,000 magnification. Surface components were analyzed using energy dispersive spectroscopy (EDS). Rabbits were sacrificed after a 6-week healing period. The removal torque was measured using the MGT-12 digital torque meter (Mark-10 Co., Copiague, NY, USA). RESULTS In the experimental group, the surface analysis showed uniform porous structures under ×25, ×150 and ×1,000 magnification. Pore sizes in the experimental group were 20-40 mm and consisted of numerous small pores, whereas pore sizes in the control group were 0.5-2.0 mm. EDS analysis showed no significant difference between the two groups. The mean removal torque in the laser-treated and the SLA-treated implant groups were 79.4 Ncm (SD = 20.4; range 34.6-104.3 Ncm) and 52.7 Ncm (SD = 17.2; range 18.7-73.8 Ncm), respectively. The removal torque in the laser-treated surface implant group was significantly higher than that in the control group (P=.004). CONCLUSION In this study, removal torque values were significantly higher for laser-treated surface implants than for SLA-treated surface implants. PMID:25177474

A Rotational and Axial Motion System Load Frame Insert for In Situ High Energy X-Ray Studies (Postprint)

DTIC Science & Technology

2015-09-08

N) without sample slippage. Equally critical is the applied tightening torque of the tapered compression nut in order to provide the necessary...preloaded linear ball spline which enables torque to be transferred to both the upper and lower rotation stages despite the fact that their vertical...interference fit, where a collet and tapered compression nut act to impart increasing pressure on the grip region of the specimen as increasing torque is

Orion - Super Koropon(Registered Trademark) Torque/Tension Report

NASA Technical Reports Server (NTRS)

Hemminger, Edgar G.; McLeod, Christopher; Peil, John

2012-01-01

The primary objective of this testing was to obtain torque tension data for the use of Super Koropon Primer Base which was proposed for use on the Orion project. This compound is a corrosion inhibitor/sealer used on threaded fasteners and inserts as specified per NASA/JSC PRC-4004, Sealing of Joints and Faying Surfaces. Some secondary objectives of this testing, were to identify the effect on torque coefficient of several variables. This document contains the outcome of the testing.

Intended and Achieved Torque of Implant Abutment's Screw using Manual Wrenches in Simulated Clinical Setting.

PubMed

Al-Otaibi, Hanan N

2016-11-01

To measure the difference between the intended torque and the achieved torque by the operator using the spring-style mechanical torque-limiting device (MTLD). Inexperienced and experienced clinicians used one spring-type MTLD to torque two abutment screws of each anterior and posterior implants, which were attached to two digital torque meters through a jaw model. The jaw model was part of a preclinical bench manikin attached to a dental chair. The intended torque value was 35 N cm (recommended by manufacturer) and the technique of torquing was observed for all the participants (instantaneous and repeated). The mean torque value was calculated for each subject for the anterior and posterior implants independently; t-test was used to compare between the intended and achieved torque values and to compare between the experienced and inexperienced clinicians (p ≤ 0.05). Thirty-seven clinicians participated, with an overall mean torque value of 34.30 N cm. The mean torque value of the achieved torque (34.30 ± 4.13 N cm) was statistically significantly less than the intended torque (p = 0.041). The male clinicians produced more statistically significantly accurate torque value (34.54 ± 3.78 N cm) than the female clinicians (p = 0.034), and the experienced clinicians produced more accurate torque values (34.9 ± 5.13 N cm) than the inexperienced clinicians (p = 0.048). Within the limitation of this study, the use of MTLDs did not always produce consistent torque values and the technique by which the operators use the MTLD might affect the torque value.

The insertion torque-depth curve integral as a measure of implant primary stability: An in vitro study on polyurethane foam blocks.

PubMed

Di Stefano, Danilo Alessio; Arosio, Paolo; Gastaldi, Giorgio; Gherlone, Enrico

2017-07-08

Recent research has shown that dynamic parameters correlate with insertion energy-that is, the total work needed to place an implant into its site-might convey more reliable information concerning immediate implant primary stability at insertion than the commonly used insertion torque (IT), the reverse torque (RT), or the implant stability quotient (ISQ). Yet knowledge on these dynamic parameters is still limited. The purpose of this in vitro study was to evaluate whether an energy-related parameter, the torque-depth curve integral (I), could be a reliable measure of primary stability. This was done by assessing if (I) measurement was operator-independent, by investigating its correlation with other known primary stability parameters (IT, RT, or ISQ) by quantifying the (I) average error and correlating (I), IT, RT, and ISQ variations with bone density. Five operators placed 200 implants in polyurethane foam blocks of different densities using a micromotor that calculated the (I) during implant placement. Primary implant stability was assessed by measuring the ISQ, IT, and RT. ANOVA tests were used to evaluate whether measurements were operator independent (P>.05 in all cases). A correlation analysis was performed between (I) and IT, ISQ, and RT. The (I) average error was calculated and compared with that of the other parameters by ANOVA. (I)-density, IT-density, ISQ-density, and RT-density plots were drawn, and their slopes were compared by ANCOVA. The (I) measurements were operator independent and correlated with IT, ISQ, and RT. The average error of these parameters was not significantly different (P>.05 in all cases). The (I)-density, IT-density, ISQ-density, and RT-density curves were linear in the 0.16 to 0.49 g/cm³ range, with the (I)-density curves having a significantly greater slope than those regarding the other parameters (P≤.001 in all cases). The torque-depth curve integral (I) provides a reliable assessment of primary stability and shows a greater sensitivity to density variations than other known primary stability parameters. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Spin-orbit torque based magnetization switching in Pt/Cu/[Co/Ni]5 multilayer structures

NASA Astrophysics Data System (ADS)

Ostwal, Vaibhav; Penumatcha, Ashish; Hung, Yu-Ming; Kent, Andrew D.; Appenzeller, Joerg

2017-12-01

Spin-Orbit Torque (SOT) in Heavy Metal/Ferromagnet (HM/FM) structures provides an important tool to control the magnetization of FMs and has been an area of interest for memory and logic implementation. Spin transfer torque on the FM in such structures is attributed to two sources: (1) the Spin Hall effect in the HM and (2) the Rashba-effect at the HM/FM interface. In this work, we study the SOT in a Pt/[Co,Ni] structure and compare its strength with the SOT in a Pt/Cu/[Co,Ni] structure where copper, a metal with a low spin-orbit interaction, is inserted between the Pt (HM) layer and the [Co,Ni] (FM) layer. We use an AC harmonic measurement technique to measure the strength of the SOT on the magnetic thin-film layer. Our measurements show that a significant SOT is exerted on the magnetization even after a 6 nm thick copper layer is inserted between the HM and the FM. Also, we find that this torque can be used to switch a patterned magnetic layer in the presence of an external magnetic field.

Stability comparison between commercially available mini-implants and a novel design: part 1.

PubMed

Hong, Christine; Lee, Haofu; Webster, Richard; Kwak, Jinny; Wu, Benjamin M; Moon, Won

2011-07-01

To compare mechanical stability among five mini-implant designs--a newly invented design and four commercially available designs that vary by shape and threading; to calculate external surface area of each design using high-resolution micro-computed tomography; and to evaluate the relationship between surface area and stability results. The four commercially available mini-implants--single-threaded and cylindrical (SC), single-threaded and tapered (ST), double-threaded and cylindrical (DC), double-threaded and tapered (DT)--and a new implant that is designed to engage mostly in cortical bone with shorter and wider dimensions (N1) were inserted in simulated bone with cortical and trabecular bone layers. The mechanical study consisted of torque measurements and lateral displacement tests. External surface area was computed using a 25-µm micro-CT. Maximum insertion torque, maximum removal torque, and force levels for displacements were the highest in N1, followed by DT, ST, DC, and SC (α  =  .05). The surface area was largest in DT, followed by N1, ST, DC, and SC. Surface area engaged in cortical bone, however, was the greatest in N1. The surface area of mini-implants had positive correlation with stability. Among commercial designs, both added tapering and double threading improved stability. N1 was the most stable design within this research design. The new design has the potential to be clinically superior; it has enhanced stability and there is diminished risk of endangering nearby anatomic structures during placement and orthodontic treatment, but the design requires refinements to reduce insertion torque to avoid clinical difficulty and patient discomfort.

Effects of a Short Drilling Implant Protocol on Osteotomy Site Temperature and Drill Torque.

PubMed

Mihali, Sorin G; Canjau, Silvana; Cernescu, Anghel; Bortun, Cristina M; Wang, Hom-Lay; Bratu, Emanuel

2018-02-01

To establish a protocol for reducing the drilling sequence during implant site preparation based on temperature and insertion torque. The traditional conventional drilling sequence (used several drills with 0.6-mm increment each time) was compared with the proposed short drilling protocol (only used 2 drills: initial and final drill). One hundred drilling osteotomies were performed in bovine and porcine bones. Sets of 2 osteotomy sites were created in 5 bone densities using 2 types of drilling protocols. Thermographic pictures were captured throughout all drilling procedures and analyzed using ThermaCAM Researcher Professional 2.10. Torque values were determined during drilling by measuring electrical input and drill speed. There were statistically significant differences in bone temperature between the conventional and short drilling protocols during implant site preparation (analysis of variance P = 0.0008). However, there were no significant differences between the 2 types of drilling protocols for both implant diameters. Implant site preparation time was significantly reduced when using the short drilling protocol compared with the conventional drilling protocol (P < 0.001). Within the limitations of the study, the short drilling protocol proposed herein may represent a safe approach for implant site preparation.

Measurement of the end-to-end distances between the femoral and tibial insertion sites of the anterior cruciate ligament during knee flexion and with rotational torque.

PubMed

Wang, Joon Ho; Kato, Yuki; Ingham, Sheila J M; Maeyama, Akira; Linde-Rosen, Monica; Smolinski, Patrick; Fu, Freddie H

2012-10-01

The aim of this study was to determine the end-to-end distance changes in anterior cruciate ligament (ACL) fibers during flexion/extension and internal/external rotation of the knee. The positional relation between the femur and tibia of 10 knees was digitized on a robotic system during flexion/extension and with an internal/external rotational torque (5 Nm). The ACL insertion site data, acquired by 3-dimensional scanning, were superimposed on the positional data. The end-to-end distances of 5 representative points on the femoral and tibial insertion sites of the ACL were calculated. The end-to-end distances of all representative points except the most anterior points were longest at full extension and shortest at 90°. The distances of the anteromedial (AM) and posterolateral (PL) bundles were 37.2 ± 2.1 mm and 27.5 ± 2.8 mm, respectively, at full extension and 34.7 ± 2.4 mm and 20.7 ± 2.3 mm, respectively, at 90°. Only 4 knees had an isometric point, which was 1 of the 3 anterior points. Under an internal torque, both bundles became longer with statistical meaning at all flexion angles (P = .005). The end-to-end distances of all points became longest with internal torque at full extension and shortest with an external torque at 90°. Only 4 of 10 specimens had an isometric point at a variable anterior point. The end-to-end distances of the AM and PL bundles were longer in extension and shorter in flexion. The nonisometric tendency of the ACL and the end-to-end distance change during knee flexion/extension and internal/external rotation should be considered during ACL reconstruction to avoid overconstraint of the graft. Copyright © 2012 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Accuracy and precision of as-received implant torque wrenches.

PubMed

Britton-Vidal, Eduardo; Baker, Philip; Mettenburg, Donald; Pannu, Darshanjit S; Looney, Stephen W; Londono, Jimmy; Rueggeberg, Frederick A

2014-10-01

Previous implant torque evaluation did not determine if the target value fell within a confidence interval for the population mean of the test groups, disallowing determination of whether a specific type of wrench met a standardized goal value. The purpose of this study was to measure both the accuracy and precision of 2 different configurations (spring style and peak break) of as-received implant torque wrenches and compare the measured values to manufacturer-stated values. Ten wrenches from 4 manufacturers, representing a variety of torque-limiting mechanisms and specificity of use (with either a specific brand or universally with any brand of implant product). Drivers were placed into the wrench, and tightening torque was applied to reach predetermined values using a NIST-calibrated digital torque wrench. Five replications of measurement were made for each wrench and averaged to provide a single value from that instrument. The target torque value for each wrench brand was compared to the 95% confidence interval for the true population mean of measured values to see if it fell within the measured range. Only 1 wrench brand (Nobel Biocare) demonstrated the target torque value falling within the 95% confidence interval for the true population mean. For others, the targeted torque value fell above the 95% confidence interval (Straumann and Imtec) or below (Salvin Torq). Neither type of torque-limiting mechanism nor designation of a wrench to be used as a dedicated brand-only product or to be used as a universal product on many brands affected the ability of a wrench to deliver torque values where the true population mean included the target torque level. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Steam sterilization effect on the accuracy of friction-style mechanical torque limiting devices.

PubMed

Sadr, Seyed Jalil; Fayyaz, Ali; Mahshid, Minoo; Saboury, Aboulfazl; Ansari, Ghassem

2014-01-01

This study was aimed to evaluate the effect of steam sterilization on the accuracy (within 10%) of friction-style mechanical torque limiting devices (F-S MTLDs) to achieve their target torque values. Fifteen new F-S MTLDs were selected from Astra Tech (25 Ncm, Hader SA, La Chaux-de-Fonds, Switzerland), BioHorizons (30 Ncm, Dynatorq ITL, Irvine, California, USA), Dr. Idhe (15-60 Ncm, Dr. Idhe Dental, Eching/Munich, Germany). Every peak torque measurement was tested ten times before steam sterilization using Tohnichi torque gauge (6Tohnichi-BTG (-S), Japan). Steam sterilization was performed using a 100 cycle autoclave. Preparation steps were carried out for the devices before each autoclave sterilization cycle. Peak torque measurements were repeated after every sterilization cycle. Mean difference between the measured and the targeted torque values were evaluated before and after aging. Repeated-measures of ANOVA were used to compare the differences of accuracy between subjects. Bonferroni post-hoc test was used for pairwise comparison. Autoclaving resulted in an increase in the error values (the difference between peak torque and target torque values) in all the three groups studied (P < 0.05), with only Astra Tech devices showing >10% (maximum 12%) difference from their torque values in 5% of the measurements. Steam sterilization effect differs between target torque and measured peak values with an increase trend. The peak torque values showed a significant decrease for BioHorizons, while a significant increase was noted for Astra Tech and no significant change in Dr. Idhe group after sterilization. Within the limitation of this study the torque output of each individual device deviated in varying degrees from target torque values. However, the majority of the new frictional-style devices tested in this study, delivered fairly consistent torque output within 10% of their preset target values after sterilization. Astra Tech devices were the only one showing more than 10% difference from their torque values in 5% of the measurements. Combined effects of sterilization and aging still needs to be determined.

The effect of sterilization and number of use on the accuracy of friction-style mechanical torque limiting devices for dental implants

PubMed Central

Fayaz, Ali; Mahshid, Minoo; Saboury, Aboulfazl; Sadr, Seyed Jalil; Ansari, Ghassem

2014-01-01

Background: Mechanical torque limiting devices (MTLDs) are necessary tools to control a peak torque and achieving target values of screw component of dental implants. Due to probable effect of autoclaving and number of use on the accuracy of these devices, this study aimed to evaluate the effect of sterilization and number of use on the accuracy of friction-style mechanical torque limiting devices (F-S MTLDs) in achieving their target torque values. Materials and Methods: Peak torque measurements of 15 new F-S MTLDs from three different manufacturers (Astra Tech, BioHorizons, Dr. Idhe) were measured ten times before and after 100 steam sterilization using a digital torque gauge. To simulate the clinical situation of aging (number of use) target torque application process was repeated 10 times after each sterilization cycle and the peak torque values were registered. Comparison of the mean differences with target torque in each cycle was performed using one sample t test. Considering the type of MTLDs as inter subject comparison, One-way repeated measure ANOVA was used to evaluate the absolute values of differences between devices of each manufacturer in each group (α = 0.05). Results: The results of this study in Dr. Idhe group showed that, mean of difference values significantly differed from the target torque (P = 0.002) until 75 cycles. In Astra Tech group, also mean of difference values with under estimation trend, showed a significant difference with the target torque (P < 0.001). Mean of difference values significantly differed from the target torque with under estimation trend during all the 100 cycles in BioHorizons group (P < 0.05). Conclusion: The torque output of each individual device stayed in 10% difference from target torque values before 100 sterilization cycles, but more than 10% difference from the target torque was seen in varying degrees during these consequent cycles. PMID:24688564

Accuracy of electronic implant torque controllers following time in clinical service.

PubMed

Mitrani, R; Nicholls, J I; Phillips, K M; Ma, T

2001-01-01

Tightening of the screws in implant-supported restorations has been reported to be problematic, in that if the applied torque is too low, screw loosening occurs. If the torque is too high, then screw fracture can take place. Thus, accuracy of the torque driver is of the utmost importance. This study evaluated 4 new electronic torque drivers (controls) and 10 test electronic torque drivers, which had been in clinical service for a minimum of 5 years. Torque values of the test drivers were measured and were compared with the control values using a 1-way analysis of variance. Torque delivery accuracy was measured using a technique that simulated the clinical situation. In vivo, the torque driver turns the screw until the selected tightening torque is reached. In this laboratory experiment, an implant, along with an attached abutment and abutment gold screw, was held firmly in a Tohnichi torque gauge. Calibration accuracy for the Tohnichi is +/- 3% of the scale value. During torque measurement, the gold screw turned a minimum of 180 degrees before contact was made between the screw and abutment. Three torque values (10, 20, and 32 N-cm) were evaluated, at both high- and low-speed settings. The recorded torque measurements indicated that the 10 test electronic torque drivers maintained a torque delivery accuracy equivalent to the 4 new (unused) units. Judging from the torque output values obtained from the 10 test units, the clinical use of the electronic torque driver suggests that accuracy did not change significantly over the 5-year period of clinical service.

Accuracy of mechanical torque-limiting devices for dental implants.

PubMed

L'Homme-Langlois, Emilie; Yilmaz, Burak; Chien, Hua-Hong; McGlumphy, Edwin

2015-10-01

A common complication in implant dentistry is unintentional implant screw loosening. The critical factor in the prevention of screw loosening is the delivery of the appropriate target torque value. Mechanical torque-limiting devices (MTLDs) are the most frequently recommended devices by the implant manufacturers to deliver the target torque value to the screw. Two types of MTLDs are available: friction-style and spring-style. Limited information is available regarding the influence of device type on the accuracy of MTLDs. The purpose of this study was to determine and compare the accuracy of spring-style and friction-style MTLDs. Five MTLDs from 6 different dental implant manufacturers (Astra Tech/Dentsply, Zimmer Dental, Biohorizons, Biomet 3i, Straumann [ITI], and Nobel Biocare) (n=5 per manufacturer) were selected to determine their accuracy in delivering target torque values preset by their manufacturers. All torque-limiting devices were new and there were 3 manufacturers for the friction-style and 3 manufacturers for the spring-style. The procedure of target torque measurement was performed 10 times for each device and a digital torque gauge (Chatillon Model DFS2-R-ND; Ametek) was used to record the measurements. Statistical analysis used nonparametric tests to determine the accuracy of the MTLDs in delivering target torque values and Bonferroni post hoc tests were used to assess pairwise comparisons. Median absolute difference between delivered torque values and target torque values of friction-style and spring-style MTLDs were not significantly different (P>.05). Accuracy of Astra Tech and Zimmer Dental friction-style torque-limiting devices were significantly different than Biohorizons torque-limiting devices (P<.05). There is no difference between the accuracy of new friction-style MTLDs and new spring-style MTLDs. All MTLDs fell within ±10% of the target torque value. Astra Tech and Zimmer Dental friction-style torque-limiting devices were significantly more accurate than Biohorizons (C) torque-limiting devices (P<.05); however, all the torque-limiting devices fell within ±10% of the target torque value preset by the manufacturers. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Effects of different abutment material and surgical insertion torque on the marginal adaptation of an internal conical interface: an in vitro study.

PubMed

Farronato, Davide; Pieroni, Stefano; Mangano, Francesco Guido; Briguglio, Francesco; Re, Dino

2014-10-01

To evaluate the marginal adaptation at implant-abutment connection of an implant featuring a conical (45° taper) internal hexagonal abutment with a connection depth of 2.5mm, comparing the performance of two identical abutments of different material (titanium grade-4 and Co-Cr-alloy). Twenty implants (3.75 mm×15 mm) were connected to non-matching abutments (5.5 mm×10 mm) of two different materials (titanium grade-4: n=10; Co-Cr-alloy: n=10). The specimens were separately embedded in epoxylite resin, inside copper cylinders, and submerged without covering the most coronal portion (5 mm) of the fixture. Five specimens per group were stressed simulating a surgical 100 Ncm insertion torque, while the others had no torque simulation. All specimens were subjected to a non-axial static load (100 N) in a universal testing machine, under an angle of 30° with respect to the implant axis. Once 100 N load was reached, low shrinkage self-curing resin was injected inside the cylinders, and load was maintained until complete resin polymerization. Specimens were cut and analyzed with optical and scanning-electron-microscope (SEM) to evaluate the marginal adaptation at the implant-abutment connection. Statistical analysis was performed using one-way ANOVA (p=0.02). None of the 20 samples failed. The implant-abutment connection was able to guarantee a good optical seal; SEM analysis confirmed the absence of microgaps. Within the limits of this study (small sample size, limited time) the marginal adaptation of the implant-abutment connection was not affected by the abutment material nor by the application of surgical insertion torque. Copyright © 2014 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

Bone cutting capacity and osseointegration of surface-treated orthodontic mini-implants.

PubMed

Kim, Ho-Young; Kim, Sang-Cheol

2016-11-01

The objective of the study was to evaluate the practicality and the validity of different surface treatments of self-drilling orthodontic mini-implants (OMIs) by comparing bone cutting capacity and osseointegration. Self-drilling OMIs were surface-treated in three ways: Acid etched (Etched), resorbable blasting media (RBM), partially resorbabla balsting media (Hybrid). We compared the bone cutting capacity by measuring insertion depths into artificial bone (polyurethane foam). To compare osseointegration, OMIs were placed in the tibia of 25 rabbits and the removal torque value was measured at 1, 2, 4, and 8 weeks after placement. The specimens were analyzed by optical microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The bone cutting capacity of the etched and hybrid group was lower than the machined (control) group, and was most inhibited in the RBM group ( p < 0.05). At 4 weeks, the removal torque in the machined group was significantly decreased ( p < 0.05), but was increased in the etched group ( p < 0.05). In the hybrid group, the removal torque significantly increased at 2 weeks, and was the highest among all measured values at 8 weeks ( p < 0.05). The infiltration of bone-like tissue surface was evaluated by SEM, and calcium and phosphorus were detected via EDS only in the hybrid group. Partial RBM surface treatment (hybrid type in this study) produced the most stable self-drilling OMIs, without a corresponding reduction in bone cutting capacity.

Bone cutting capacity and osseointegration of surface-treated orthodontic mini-implants

PubMed Central

Kim, Ho-Young

2016-01-01

Objective The objective of the study was to evaluate the practicality and the validity of different surface treatments of self-drilling orthodontic mini-implants (OMIs) by comparing bone cutting capacity and osseointegration. Methods Self-drilling OMIs were surface-treated in three ways: Acid etched (Etched), resorbable blasting media (RBM), partially resorbabla balsting media (Hybrid). We compared the bone cutting capacity by measuring insertion depths into artificial bone (polyurethane foam). To compare osseointegration, OMIs were placed in the tibia of 25 rabbits and the removal torque value was measured at 1, 2, 4, and 8 weeks after placement. The specimens were analyzed by optical microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). Results The bone cutting capacity of the etched and hybrid group was lower than the machined (control) group, and was most inhibited in the RBM group (p < 0.05). At 4 weeks, the removal torque in the machined group was significantly decreased (p < 0.05), but was increased in the etched group (p < 0.05). In the hybrid group, the removal torque significantly increased at 2 weeks, and was the highest among all measured values at 8 weeks (p < 0.05). The infiltration of bone-like tissue surface was evaluated by SEM, and calcium and phosphorus were detected via EDS only in the hybrid group. Conclusions Partial RBM surface treatment (hybrid type in this study) produced the most stable self-drilling OMIs, without a corresponding reduction in bone cutting capacity. PMID:27896213

Biomechanical and histologic basis of osseodensification drilling for endosteal implant placement in low density bone. An experimental study in sheep.

PubMed

Lahens, Bradley; Neiva, Rodrigo; Tovar, Nick; Alifarag, Adham M; Jimbo, Ryo; Bonfante, Estevam A; Bowers, Michelle M; Cuppini, Marla; Freitas, Helora; Witek, Lukasz; Coelho, Paulo G

2016-10-01

A bone drilling concept, namely osseodensification, has been introduced for the placement of endosteal implants to increase primary stability through densification of the osteotomy walls. This study investigated the effect of osseodensification on the initial stability and early osseointegration of conical and parallel walled endosteal implants in low density bone. Five male sheep were used. Three implants were inserted in the ilium, bilaterally, totaling 30 implants (n=15 conical, and n=15 parallel). Each animal received 3 implants of each type, inserted into bone sites prepared as follows: (i) regular-drilling (R: 2mm pilot, 3.2mm, and 3.8mm twist drills), (ii) clockwise osseodensification (CW), and (iii) counterclockwise (CCW) osseodensification drilling with Densah Bur (Versah, Jackson, MI, USA): 2.0mm pilot, 2.8mm, and 3.8mm multi-fluted burs. Insertion torque as a function of implant type and drilling technique, revealed higher values for osseodensification relative to R-drilling, regardless of implant macrogeometry. A significantly higher bone-to-implant contact (BIC) for both osseodensification techniques (p<0.05) was observed compared to R-drilling. There was no statistical difference in BIC as a function of implant type (p=0.58), nor in bone-area-fraction occupancy (BAFO) as a function of drilling technique (p=0.22), but there were higher levels of BAFO for parallel than conic implants (p=0.001). Six weeks after surgery, new bone formation along with remodeling sites was observed for all groups. Bone chips in proximity with the implants were seldom observed in the R-drilling group, but commonly observed in the CW, and more frequently under the CCW osseodensification technique. In low-density bone, endosteal implants present higher insertion torque levels when placed in osseodensification drilling sites, with no osseointegration impairment compared to standard subtractive drilling methods. Copyright © 2016 Elsevier Ltd. All rights reserved.

Spin-transfer torque in spin filter tunnel junctions

NASA Astrophysics Data System (ADS)

Ortiz Pauyac, Christian; Kalitsov, Alan; Manchon, Aurelien; Chshiev, Mairbek

2014-12-01

Spin-transfer torque in a class of magnetic tunnel junctions with noncollinear magnetizations, referred to as spin filter tunnel junctions, is studied within the tight-binding model using the nonequilibrium Green's function technique within Keldysh formalism. These junctions consist of one ferromagnet (FM) adjacent to a magnetic insulator (MI) or two FM separated by a MI. We find that the presence of the magnetic insulator dramatically enhances the magnitude of the spin-torque components compared to conventional magnetic tunnel junctions. The fieldlike torque is driven by the spin-dependent reflection at the MI/FM interface, which results in a small reduction of its amplitude when an insulating spacer (S) is inserted to decouple MI and FM layers. Meanwhile, the dampinglike torque is dominated by the tunneling electrons that experience the lowest barrier height. We propose a device of the form FM/(S)/MI/(S)/FM that takes advantage of these characteristics and allows for tuning the spin-torque magnitudes over a wide range just by rotation of the magnetization of the insulating layer.

The effects of two torque values on the screw preload of implant-supported prostheses with passive fit or misfit.

PubMed

Al-Otaibi, Hanan Nejer; Akeel, Riyadh Fadul

2014-01-01

To determine the effect of increased torque of the abutment screw and retorquing after 10 minutes on implant-supported fixed prostheses. Two strain gauges (SGs) were attached to four implants stabilized on an acrylic resin mandible. Four implant-supported frameworks were constructed to represent passive fit (PF) and different amounts of misfit (MF1, MF2, and MF3). Vertical misfit was measured using a traveling microscope. Each framework was torqued to 35 Ncm (the manufacturer's recommendation) and 40 Ncm, and the preload was recorded immediately and again after retorquing 10 minutes later (torque stage). The smallest gap was observed under the PF framework. Three-way analysis of variance revealed significant effects of the framework, torque value, and torque stage on preload. The PF showed the highest mean preload under both torque values. An independent-sample t test between the torque values revealed a statistically significant difference only for MF1 and MF2. A dependent-sample t test of the torque stage revealed a statistically significant difference at a torque value of 35 Ncm under the PF and MF3 frameworks. Increasing the torque value beyond the manufacturer's recommended amount and retorquing of the screws at 10 minutes after the initial torque did not necessarily lead to a significant increase in preload in full-arch implant-supported fixed prostheses, particularly under non-passively fitting frameworks.

Effect of surface anodization on stability of orthodontic microimplant

PubMed Central

Karmarker, Sanket; Yu, Wonjae

2012-01-01

Objective To determine the effect of surface anodization on the interfacial strength between an orthodontic microimplant (MI) and the rabbit tibial bone, particularly in the initial phase after placement. Methods A total of 36 MIs were driven into the tibias of 3 mature rabbits by using the self-drilling method and then removed after 6 weeks. Half the MIs were as-machined (n = 18; machined group), while the remaining had anodized surfaces (n = 18; anodized group). The peak insertion torque (PIT) and the peak removal torque (PRT) values were measured for the 2 groups of MIs. These values were then used to calculate the interfacial shear strength between the MI and cortical bone. Results There were no statistical differences in terms of PIT between the 2 groups. However, mean PRT was significantly greater for the anodized implants (3.79 ± 1.39 Ncm) than for the machined ones (2.05 ± 1.07 Ncm) (p < 0.01). The interfacial strengths, converted from PRT, were calculated at 10.6 MPa and 5.74 MPa for the anodized and machined group implants, respectively. Conclusions Anodization of orthodontic MIs may enhance their early-phase retention capability, thereby ensuring a more reliable source of absolute anchorage. PMID:23112925

Evaluation of the Accuracy and Related Factors of the Mechanical Torque-Limiting Device for Dental Implants

PubMed Central

Kazemi, Mahmood; Rohanian, Ahmad; Monzavi, Abbas; Nazari, Mohammad Sadegh

2013-01-01

Objective: Accurate delivery of torque to implant screws is critical to generate ideal preload in the screw joint and to offer protection against screw loosening. Mechanical torque-limiting devices (MTLDs) are available for this reason. In this study, the accuracy of one type of friction-style and two types of spring-style MTLDs at baseline, following fatigue conditions and sterilization processes were determined. Materials and Methods: Five unused MTLDs were selected from each of Straumann (ITI), Astra TECH and CWM systems. To measure the output of each MTLD, a digital torque gauge with a 3-jaw chuck was used to hold the driver. Force was applied to the MTLDs until either the friction styles released at a pre-calibrated torque value or the spring styles flexed to a pre-calibrated limit (target torque value). The peak torque value was recorded and the procedure was repeated 5 times for each MTLD. Then MTLDs were subjected to fatigue conditions at 500 and 1000 times and steam sterilization processes at 50 and 100 times and the peak torque value was recorded again at each stage. Results: Adjusted difference between measured torque values and target torque values differed significantly between stages for all 3 systems. Adjusted difference did not differ significantly between systems at all stages, but differed significantly between two different styles at baseline and 500 times fatigue stages. Conclusion: Straumann (ITI) devices differed minimally from target torque values at all stages. MTLDs with Spring-style were significantly more accurate than Friction-style device in achieving their target torque values at baseline and 500 times fatigue. PMID:23724209

Reference values of hip abductor torque among youth athletes: Influence of age, sex and sports.

PubMed

Bittencourt, Natália Franco Netto; Santos, Thiago Ribeiro Teles; Gonçalves, Gabriela Gomes Pavan; Coelho, Amanda Priscila; Gomes, Bárbara Gonçalves Braz de Magalhães; Mendonça, Luciana De Michelis; Fonseca, Sérgio Teixeira

2016-09-01

(1) To determine the reference values of hip abductor torque in youth athletes; (2) To investigate the influence of sex, age and sports on hip abductors torque. Cross-sectional. Sports clubs. 301 volleyball, basketball and futsal athletes between 10 and 19 years of age. Mean value of three maximal isometric hip abductor torques, evaluated using a hand-held dynamometer. The mean values of maximal isometric hip abductor torque ranged from 1.03 to 1.50 Nm/kg. The dominant hip abductor torque values were greater in 15-19 years old (1.41 ± 0.27 Nm/kg) than in 10-14 years old (1.12 ± 0.31 Nm/kg). In addition, the hip abductor torque values were smaller in basketball players (1.15 ± 0.31 Nm/kg) than futsal (1.34 ± 0.37 Nm/kg) and volleyball players (1.28 ± 0.25 Nm/kg). The comparison of hip abductor torque between futsal and volleyball players revealed no difference. The hip abductor torque values were greater in male volleyball athletes (1.28 ± 0.25 Nm/kg) than female volleyball athletes (1.13 ± 0.22 Nm/kg). This study established reference values for maximal isometric hip abductor torque in youth volleyball, basketball and futsal athletes. In addition, the results demonstrated that sex, age and sports influenced hip abductor torque. Copyright © 2015 Elsevier Ltd. All rights reserved.

The Accuracy of New and Aged Mechanical Torque Devices Employed in Five Dental Implant Systems.

PubMed

Erdem, Mehmet Ali; Karatasli, Burcin; Dinçer Kose, Onur; Kose, Taha Emre; Çene, Erhan; Aydın Aya, Serhan; Cankaya, Abdulkadir Burak

2017-01-01

Friction-style and spring-style torque wrenches are used to tighten implant abutments and prosthetic screws. The mechanical stability of these torque wrenches is crucial for the implant-abutment connection. The purposes of this study were to assess the performance of five brands (Straumann, Zimmer, Implant KA, Bredent, and Biohorizons) of wrench and to evaluate possible changes in applied torque values of aged wrenches. Five new and aged wrenches that had been used approximately 250 times in a 1-year period were tested. The torque applied by friction- and spring-style wrenches was measured with a specially designed strain gauge indicator. Descriptive statistics, the one-sample t -test, and the independent-samples t -test were used to analyze values obtained from all torque wrenches. The accuracy of new and aged torque devices of all brands except Bredent differed significantly from the target values, but the mean values for aged and new wrenches did not differ significantly from each other ( p > 0.05). Values for the spring- and friction-type torque wrenches deviated from the target values by 11.6% and 10.2%, respectively. The accuracy of aged torque wrenches is adequate for prosthetic screw tightening, but that of new torque wrenches is unsatisfactory and must be examined carefully before delivery.

The Effect of a Combination of Implant Controller and Handpiece from Different Manufacturers on the Torque Value.

PubMed

Lee, Du-Hyeong; Kim, Yong-Gun; Lee, Jong-Ho; Hong, Sam-Pyo; Lim, Young-Jun; Lee, Kyu-Bok

2015-01-01

To determine the accuracy of applied torque of different implant controller and handpiece combinations by using an electronic torque gauge. Four combinations of the following devices were tested: Surgic XT controller (NSK), XIP10 controller (Saeshin), X-SG20L handpiece (NSK), CRB26LX handpiece (Saeshin). For five torque settings, 30 measurements were recorded at 30 revolutions per minute by using an electronic torque gauge fixed to jigs, and means were calculated. Applied torques were generally higher than the set torque of 10 and 20 Ncm and lower than the set values of 40 and 50 Ncm. The average torque deviations differed significantly among the combinations (P < .05). At 10 and 20 Ncm, the Surgic XT/X-SG20L combination yielded the closest value to the intended torque, followed by the XIP10/X-SG20L combination. At 30 Ncm, the XIP10/X-SG20L combination showed the nearest value. At 40 Ncm, the Surgic XT/X-SG20L, XIP10/CRB26LX, and XIP10/X-SG20L combinations showed deviations within 10%. At 50 Ncm, all the combinations showed lower applied torque than the set value. Large standard deviations were observed in the Surgic XT/CRB26LX (13.288) and Surgic XT/X-SG20L (7.858) combinations. Different combinations of implant controllers and handpieces do not generate significant variations in applied torque. The actual torque varies according to the torque setting. It is necessary to calibrate devices before use to reduce potentially problematic torque.

The Accuracy of New and Aged Mechanical Torque Devices Employed in Five Dental Implant Systems

PubMed Central

Karatasli, Burcin; Dinçer Kose, Onur; Kose, Taha Emre; Çene, Erhan; Aydın Aya, Serhan

2017-01-01

Purpose Friction-style and spring-style torque wrenches are used to tighten implant abutments and prosthetic screws. The mechanical stability of these torque wrenches is crucial for the implant–abutment connection. The purposes of this study were to assess the performance of five brands (Straumann, Zimmer, Implant KA, Bredent, and Biohorizons) of wrench and to evaluate possible changes in applied torque values of aged wrenches. Materials and Methods Five new and aged wrenches that had been used approximately 250 times in a 1-year period were tested. The torque applied by friction- and spring-style wrenches was measured with a specially designed strain gauge indicator. Descriptive statistics, the one-sample t-test, and the independent-samples t-test were used to analyze values obtained from all torque wrenches. Results The accuracy of new and aged torque devices of all brands except Bredent differed significantly from the target values, but the mean values for aged and new wrenches did not differ significantly from each other (p > 0.05). Values for the spring- and friction-type torque wrenches deviated from the target values by 11.6% and 10.2%, respectively. Conclusion The accuracy of aged torque wrenches is adequate for prosthetic screw tightening, but that of new torque wrenches is unsatisfactory and must be examined carefully before delivery. PMID:29238725

ACL deficient potential copers and non-copers reveal different isokinetic quadriceps strength profiles in the early stage after injury

PubMed Central

Eitzen, I; Eitzen, TJ; Holm, I; Snyder-Mackler, L; Risberg, MA

2011-01-01

Background Isokinetic muscle strength tests using the peak torque value is the most frequently included quadriceps muscle strength measurement for anterior cruciate ligament (ACL) injured subjects. Aims The purpose of this study was to investigate quadriceps muscle performance during the whole isokinetic curve in ACL deficient subjects classified as potential copers or non-copers, and investigate whether these curve profiles were associated with single-leg hop performance. We hypothesized that quadriceps muscle torque at other knee flexion angles than peak torque would give more information about quadriceps muscle strength deficits. Furthermore, we hypothesized that there would be significant torque differences between potential copers and non-copers, and a significant relationship between angle specific torque values and single-leg hop performance. Study Design Cross-sectional study; Level of evidence, 2 Methods Seventy-six individuals with a complete unilateral ACL rupture within the last 3 months were included. The subjects were classified into potential copers and non-copers according to the criteria from Fitzgerald et al12. Isokinetic quadriceps muscle tests were performed at 60°/sec (Biodex 6000). Mean torque values were calculated for peak torque as well as for specific knee flexion angles. The one-leg hop and the 6 meter timed hop tests were included and symmetry indices were used. Results The peak torque value did not identify the largest quadriceps muscle strength deficit. Rather, these were established at knee flexion angles of less than 40°. There were significant differences in angle specific torque values between potential copers and non-copers (p<0.05). Moderate to strong associations were disclosed between angle specific torque values and single-leg hop performance, but only for non-copers (r≥0.32– 0.58). Conclusions Angle specific quadriceps muscle torque values of less than 40° of knee flexion provide more information on the quadriceps strength deficits after ACL injury compared to the commonly used peak torque values. PMID:20110458

Comparison of mechanical and biological properties of zirconia and titanium alloy orthodontic micro-implants.

PubMed

Choi, Hae Won; Park, Young Seok; Chung, Shin Hye; Jung, Min Ho; Moon, Won; Rhee, Sang Hoon

2017-07-01

The aim of this study was to compare the initial stability as insertion and removal torque and the clinical applicability of novel orthodontic zirconia micro-implants made using a powder injection molding (PIM) technique with those parameters in conventional titanium micro-implants. Sixty zirconia and 60 titanium micro-implants of similar design (diameter, 1.6 mm; length, 8.0 mm) were inserted perpendicularly in solid polyurethane foam with varying densities of 20 pounds per cubic foot (pcf), 30 pcf, and 40 pcf. Primary stability was measured as maximum insertion torque (MIT) and maximum removal torque (MRT). To investigate clinical applicability, compressive and tensile forces were recorded at 0.01, 0.02, and 0.03 mm displacement of the implants at angles of 0°, 10°, 20°, 30°, and 40°. The biocompatibility of zirconia micro-implants was assessed via an experimental animal study. There were no statistically significant differences between zirconia micro-implants and titanium alloy implants with regard to MIT, MRT, or the amount of movement in the angulated lateral displacement test. As angulation increased, the mean compressive and tensile forces required to displace both types of micro-implants increased substantially at all distances. The average bone-to-implant contact ratio of prototype zirconia micro-implants was 56.88 ± 6.72%. Zirconia micro-implants showed initial stability and clinical applicability for diverse orthodontic treatments comparable to that of titanium micro-implants under compressive and tensile forces.

Spin-orbit torques from interfacial spin-orbit coupling for various interfaces

NASA Astrophysics Data System (ADS)

Kim, Kyoung-Whan; Lee, Kyung-Jin; Sinova, Jairo; Lee, Hyun-Woo; Stiles, M. D.

2017-09-01

We use a perturbative approach to study the effects of interfacial spin-orbit coupling in magnetic multilayers by treating the two-dimensional Rashba model in a fully three-dimensional description of electron transport near an interface. This formalism provides a compact analytic expression for current-induced spin-orbit torques in terms of unperturbed scattering coefficients, allowing computation of spin-orbit torques for various contexts, by simply substituting scattering coefficients into the formulas. It applies to calculations of spin-orbit torques for magnetic bilayers with bulk magnetism, those with interface magnetism, a normal-metal/ferromagnetic insulator junction, and a topological insulator/ferromagnet junction. It predicts a dampinglike component of spin-orbit torque that is distinct from any intrinsic contribution or those that arise from particular spin relaxation mechanisms. We discuss the effects of proximity-induced magnetism and insertion of an additional layer and provide formulas for in-plane current, which is induced by a perpendicular bias, anisotropic magnetoresistance, and spin memory loss in the same formalism.

Spin-orbit torques from interfacial spin-orbit coupling for various interfaces.

PubMed

Kim, Kyoung-Whan; Lee, Kyung-Jin; Sinova, Jairo; Lee, Hyun-Woo; Stiles, M D

2017-09-01

We use a perturbative approach to study the effects of interfacial spin-orbit coupling in magnetic multilayers by treating the two-dimensional Rashba model in a fully three-dimensional description of electron transport near an interface. This formalism provides a compact analytic expression for current-induced spin-orbit torques in terms of unperturbed scattering coefficients, allowing computation of spin-orbit torques for various contexts, by simply substituting scattering coefficients into the formulas. It applies to calculations of spin-orbit torques for magnetic bilayers with bulk magnetism, those with interface magnetism, a normal metal/ferromagnetic insulator junction, and a topological insulator/ferromagnet junction. It predicts a dampinglike component of spin-orbit torque that is distinct from any intrinsic contribution or those that arise from particular spin relaxation mechanisms. We discuss the effects of proximity-induced magnetism and insertion of an additional layer and provide formulas for in-plane current, which is induced by a perpendicular bias, anisotropic magnetoresistance, and spin memory loss in the same formalism.

Spin-orbit torques from interfacial spin-orbit coupling for various interfaces

PubMed Central

Kim, Kyoung-Whan; Lee, Kyung-Jin; Sinova, Jairo; Lee, Hyun-Woo; Stiles, M. D.

2017-01-01

We use a perturbative approach to study the effects of interfacial spin-orbit coupling in magnetic multilayers by treating the two-dimensional Rashba model in a fully three-dimensional description of electron transport near an interface. This formalism provides a compact analytic expression for current-induced spin-orbit torques in terms of unperturbed scattering coefficients, allowing computation of spin-orbit torques for various contexts, by simply substituting scattering coefficients into the formulas. It applies to calculations of spin-orbit torques for magnetic bilayers with bulk magnetism, those with interface magnetism, a normal metal/ferromagnetic insulator junction, and a topological insulator/ferromagnet junction. It predicts a dampinglike component of spin-orbit torque that is distinct from any intrinsic contribution or those that arise from particular spin relaxation mechanisms. We discuss the effects of proximity-induced magnetism and insertion of an additional layer and provide formulas for in-plane current, which is induced by a perpendicular bias, anisotropic magnetoresistance, and spin memory loss in the same formalism. PMID:29333523

Fastener Design Manual

NASA Technical Reports Server (NTRS)

Barrett, Richard T.

1990-01-01

This manual was written for design engineers to enable them to choose appropriate fasteners for their designs. Subject matter includes fastener material selection, platings, lubricants, corrosion, locking methods, washers, inserts, thread types and classes, fatigue loading, and fastener torque. A section on design criteria covers the derivation of torque formulas, loads on a fastener group, combining simultaneous shear and tension loads, pullout load for tapped holes, grip length, head styles, and fastener strengths. The second half of this manual presents general guidelines and selection criteria for rivets and lockbolts.

In Vitro Measurement Of Insertion Torque, Removal Torque And Resonance Frequency Analysis Of Implants Placed Into Simulated Bony Defects

DTIC Science & Technology

2014-05-14

2002). "Healing after standardized clinical probing of perlimlant soft tissue seal; a histomorphometric study in dogs." Clinical oral Implants...implant and periodontal tissues . A study in the beagle dog." Clin Oral Implants Res3(1): 9-16. Luterbacher, S., Mayfield, L. (2000). "Diagnostic...encapsulation around the implant and soft tissue . This type of healing and encapsulation led to inflammation, infection, mobility and failure of the

Spin-Orbit Torque and Spin Pumping in YIG/Pt with Interfacial Insertion Layers (Postprint)

DTIC Science & Technology

2018-05-03

Distribution Statement A. Approved for public release: distribution unlimited. © 2018 AMERICAN INSTITUTE OF PHYSICS (STINFO COPY) AIR FORCE RESEARCH ...SPONSORING/MONITORING AGENCY ACRONYM(S) Air Force Research Laboratory Materials and Manufacturing Directorate Wright-Patterson Air Force Base, OH... observe a large enhancement of Gilbert damping with the insertion of Py that cannot be accounted for solely by spin pumping, revealing significant spin

Tool for Coupling a Torque Wrench to a Round Cable Connector

NASA Technical Reports Server (NTRS)

Hacker, Scott C.; Dean, Richard J.; Burge, Scott W.

2006-01-01

A tool makes it possible to couple a torque wrench to an externally knurled, internally threaded, round cable connector. The purpose served by the tool is to facilitate the tightening of multiple such connectors (or the repeated tightening of the same connector) to repeatable torques. The design of a prior cable-connector/ torque-wrench coupling tool provided for application of the torque-wrench jaws to a location laterally offset from the axis of rotation of the cable connector, making it necessary to correct the torque reading for the offset. Unlike the design of the prior tool, the design of the present tool provides for application of the torque-wrench jaws to a location on the axis of rotation, obviating correction of the torque reading for offset. The present tool (see figure) consists of a split collet containing a slot that provides clearance for inserting and bending the cable, a collet-locking sleeve, a collet-locking nut, and a torque-wrench adaptor that is press-fit onto the collet. Once the collet is positioned on the cable connector, the collet-locking nut is turned to force the collet-locking sleeve over the collet, compressing the collet through engagement of tapered surfaces on the outside of the collet and the inside of the locking sleeve. Because the collet is split and therefore somewhat flexible, this compression forces the collet inward to grip the connector securely. The torque wrench is then applied to the torque-wrench adaptor in the usual manner for torquing a nut or a bolt.

The Effect of Aging on the Accuracy of New Friction-Style Mechanical Torque Limiting Devices for Dental Implants

PubMed Central

Saboury, Aboulfazl; Sadr, Seyed Jalil; Fayaz, Ali; Mahshid, Minoo

2013-01-01

Objective: High variability in delivering the target torque is reported for friction-style mechanical torque limiting devices (F-S MTLDs). The effect of aging (number of use) on the accuracy of these devices is not clear. The purpose of this study was to assess the effect of aging on the accuracy (±10% of the target torque) of F-S MTLDs. Materials and Methods: Fifteen new F-S MTLDs and their appropriate drivers from three different implant manufacturers (Astra Tech, Biohorizon and Dr Idhe), five for each type, were selected. The procedure of peak torque measurement was performed in ten sequences before and after aging. In each sequence, ten repetitions of peak torque values were registered for the aging procedure. To measure the output of each device, a Tohnichi torque gauge was used. Results: Before aging, peak torque measurements of all the devices tested in this study falled within 10% of their preset target values. After aging, a significant difference was seen between raw error values of three groups of MTLDs (P<0.05). More than 50% of all peak torque measurements demonstrated more than 10% difference from their torque values after aging. Conclusion: Within the limitation of this study, aging as an independent factor affects the accuracy of F-S MTLDs. Astra Tech MTLDs presented the most consistent torque output for 25 Ncm target torque. PMID:23724202

The combined effect of dismantling for steam sterilization and aging on the accuracy of spring-style mechanical torque devices

PubMed Central

Mahshid, Minoo; Sadr, Seyed Jalil; Fayyaz, Ali; Kadkhodazadeh, Mahdi

2013-01-01

Purpose This study aimed to assess the combined effect of dismantling before sterilization and aging on the accuracy (±10% of the target torque) of spring-style mechanical torque devices (S-S MTDs). Methods Twenty new S-SMTDs from two different manufacturers (Nobel Biocare and Straumann: 10 of each type) were selected and divided into two groups, namely, case (group A) and control (group B). For sterilization, 100 cycles of autoclaving were performed in 100 sequences. In each sequence, 10 repetitions of peak torque values were registered for aging. To measure and assess the output of each device, a Tohnichi torque gauge was used (P<0.05). Results Before steam sterilization, all of the tested devices stayed within 10% of their target values. After 100 cycles of steam sterilization and aging with or without dismantling of the devices, the Nobel Biocare devices stayed within 10% of their target torque. In the Straumann devices, despite the significant difference between the peak torque and target torque values, the absolute error values stayed within 10% of their target torque. Conclusion Within the limitations of this study, there was no significant difference between the mean and absolute value of error between Nobel Biocare and Straumann S-S MTDs. PMID:24236244

Nonlinear SVM-DTC for induction motor drive using input-output feedback linearization and high order sliding mode control.

PubMed

Ammar, Abdelkarim; Bourek, Amor; Benakcha, Abdelhamid

2017-03-01

This paper presents a nonlinear Direct Torque Control (DTC) strategy with Space Vector Modulation (SVM) for an induction motor. A nonlinear input-output feedback linearization (IOFL) is implemented to achieve a decoupled torque and flux control and the SVM is employed to reduce high torque and flux ripples. Furthermore, the control scheme performance is improved by inserting a super twisting speed controller in the outer loop and a load torque observer to enhance the speed regulation. The combining of dual nonlinear strategies ensures a good dynamic and robustness against parameters variation and disturbance. The system stability has been analyzed using Lyapunov stability theory. The effectiveness of the control algorithm is investigated by simulation and experimental validation using Matlab/Simulink software with real-time interface based on dSpace 1104. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Do dual-thread orthodontic mini-implants improve bone/tissue mechanical retention?

PubMed

Lin, Yang-Sung; Chang, Yau-Zen; Yu, Jian-Hong; Lin, Chun-Li

2014-12-01

The aim of this study was to understand whether the pitch relationship between micro and macro thread designs with a parametrical relationship in a dual-thread mini-implant can improve primary stability. Three types of mini-implants consisting of single-thread (ST) (0.75 mm pitch in whole length), dual-thread A (DTA) with double-start 0.375 mm pitch, and dual-thread B (DTB) with single-start 0.2 mm pitch in upper 2-mm micro thread region for performing insertion and pull-out testing. Histomorphometric analysis was performed in these specimens in evaluating peri-implant bone defects using a non-contact vision measuring system. The maximum inserted torque (Tmax) in type DTA was found to be the smallest significantly, but corresponding values found no significant difference between ST and DTB. The largest pull-out strength (Fmax) in the DTA mini-implant was found significantly greater than that for the ST mini-implant regardless of implant insertion orientation. Mini-implant engaged the cortical bone well as observed in ST and DTA types. Dual-thread mini-implant with correct micro thread pitch (parametrical relationship with macro thread pitch) in the cortical bone region can improve primary stability and enhanced mechanical retention.

Comparison of design and torque measurements of various manual wrenches.

PubMed

Neugebauer, Jörg; Petermöller, Simone; Scheer, Martin; Happe, Arndt; Faber, Franz-Josef; Zoeller, Joachim E

2015-01-01

Accurate torque application and determination of the applied torque during surgical and prosthetic treatment is important to reduce complications. A study was performed to determine and compare the accuracy of manual wrenches, which are available in different designs with a large range of preset torques. Thirteen different wrench systems with a variety of preset torques ranging from 10 to 75 Ncm were evaluated. Three different designs were available, with a spring-in-coil or toggle design as an active mechanism or a beam as a passive mechanism, to select the preset torque. To provide a clinically relevant analysis, a total of 1,170 torque measurements in the range of 10 to 45 Ncm were made in vitro using an electronic torque measurement device. The absolute deviations in Ncm and percent deviations across all wrenches were small, with a mean of -0.24 ± 2.15 Ncm and -0.84% ± 11.72% as a shortfall relative to the preset value. The greatest overage was 8.2 Ncm (82.5%), and the greatest shortfall was 8.47 Ncm (46%). However, extreme values were rare, with 95th-percentile values of -1.5% (lower value) and -0.16% (upper value). A comparison with respect to wrench design revealed significantly higher deviations for coil and toggle-style wrenches than for beam wrenches. Beam wrenches were associated with a lower risk of rare extreme values thanks to their passive mechanism of achieving the selected preset torque, which minimizes the risk of harming screw connections.

The effect of steam sterilization on the accuracy of spring-style mechanical torque devices for dental implants

PubMed Central

Mahshid, Minoo; Saboury, Aboulfazl; Fayaz, Ali; Sadr, Seyed Jalil; Lampert, Friedrich; Mir, Maziar

2012-01-01

Background Mechanical torque devices (MTDs) are one of the most commonly recommended devices used to deliver optimal torque to the screw of dental implants. Recently, high variability has been reported about the accuracy of spring-style mechanical torque devices (S-S MTDs). Joint stability and survival rate of fixed implant supported prosthesis depends on the accuracy of these devices. Currently, there is limited information on the steam sterilization influence on the accuracy of MTDs. The purpose of this study was to assess the effect of steam sterilization on the accuracy (±10% of the target torque) of spring-style mechanical torque devices for dental implants. Materials and methods Fifteen new S-S MTDs and their appropriate drivers from three different manufacturers (Nobel Biocare, Straumann [ITI], and Biomet 3i [3i]) were selected. Peak torque of devices (5 in each subgroup) was measured before and after autoclaving using a Tohnichi torque gauge. Descriptive statistical analysis was used and a repeated-measures ANOVA with type of device as a between-subject comparison was performed to assess the difference in accuracy among the three groups of spring-style mechanical torque devices after sterilization. A Bonferroni post hoc test was used to assess pairwise comparisons. Results Before steam sterilization, all the tested devices stayed within 10% of their target values. After 100 sterilization cycles, results didn’t show any significant difference between raw and absolute error values in the Nobel Biocare and ITI devices; however the results demonstrated an increase of error values in the 3i group (P < 0.05). Raw error values increased with a predictable pattern in 3i devices and showed more than a 10% difference from target torque values (maximum difference of 14% from target torque was seen in 17% of peak torque measurements). Conclusion Within the limitation of this study, steam sterilization did not affect the accuracy (±10% of the target torque) of the Nobel Biocare and ITI MTDs. Raw error values increased with a predictable pattern in 3i devices and showed more than 10% difference from target torque values. Before expanding upon the clinical implications, the controlled and combined effect of aging (frequency of use) and steam sterilization needs more investigation. PMID:23674923

[Biomechanical testing of the new torque-segmented arch (TSA)].

PubMed

Wichelhaus, A; Sander, F G

1995-07-01

New torque-segmented arch wires are presented which consist of a superelastic anterior component with 30 degrees or 45 degrees torque and which are connected to 2 steel lateral components by means of a crimped connector. When using such torque-segmented arch wires, the crimped connector rests mesially to the canine bracket and the lateral components exhibit a torque of 0 degree. The use of the torque-segmented arch wires requires the practitioner to adjust the anterior tooth segment, to bend in first order bends in the steel lateral portion as well as to bend in a sweep to avoid an anterior tooth extrusion, and, if desired, to bend in third order bends to influence premolars and molars. In some cases the simultaneous application of palatal arches can become necessary, because each torque transfer results in a transversal enlargement in the molar area. Compared to conventional steel wires with dimensions of 0.016 x 0.022 in which an anterior tooth torque is bent, the torque segmented arch wires exhibit considerably fewer side effects, but there is a larger distally rotating moment for the molars. 1. When applying torque-segmented arch wires, the extrusive force transferred to the anterior teeth is considerably smaller. 2. The protrusive force acting on the anterior teeth is also considerably smaller, which results in a reduced demand being placed on the anchorage of the molars. 3. The torque transfer to the incisors rests in a quite moderate range, even in the case of a 50 degrees torque. For this reason, the practitioner can expect diminished or no resorptions at all compared to the aforementioned steel wires. 4. The Martensite plateau of the torque-segmented arch wires exhibit constant moments in large areas so that such arch wires can be used in almost every anterior tooth position. 5. The segmented wires presented here can be applied not only in the case of the standard edgewise technique but also in each case of the straight-wire technique. 6. These new arch wires require no readjustment of torque values. 7. To control the transferred torque values it is recommended that the already transferred torque values be monitored during each check-up with the help of the described torque key. 8. When the torque values of the brackets are known, the torque key renders frequent patient X-rays superfluous. 9. When the desired torque values are attained, treatment can proceed using conventional arch wires.

40 CFR 1054.505 - How do I test engines?

Code of Federal Regulations, 2010 CFR

2010-07-01

... following methods for confirming torque values for nonhandheld engines: (i) Calculate torque-related cycle... is valid. (ii) Evaluate each mode separately to validate the duty cycle. All torque feedback values recorded during non-idle sampling periods must be within ±2 percent of the reference value or within ±0.27...

Accuracy of torque-limiting devices: A comparative evaluation.

PubMed

Albayrak, Haydar; Gumus, Hasan Onder; Tursun, Funda; Kocaagaoglu, Hasan Huseyin; Kilinc, Halil Ibrahim

2017-01-01

To prevent the loosening of implant screws, clinicians should be aware of the output torque values needed to achieve the desired preload. Accurate torque-control devices are crucial in this regard; however, little information is currently available comparing the accuracy of mechanical with that of electronic torque-control devices. The purpose of this in vitro study was to identify and compare the accuracy of different types of torque-control devices. Devices from 5 different dental implant manufacturers were evaluated, including 2 spring-type (Straumann, Implance) mechanical devices (MTLD), 2 friction-type (Biohorizons, Dyna) MTLDs, and 1 (Megagen) electronic torque-control device (ETLD). For each manufacturer, 5 devices were tested 5 times with a digital torque tester, and the average for each device was calculated and recorded. The percentage of absolute deviations from the target torque values (PERDEV) were calculated and compared by using 1-way ANOVA. A 1-sample t test was used to evaluate the ability of each device to achieve its target torque value within a 95% confidence interval for the true population mean of measured values (α=.05 for all statistical analyses). One-way ANOVAs revealed statistically significant differences among torque-control devices (P<.001). ETLD showed higher PERDEVs (28.33 ±9.53) than MTLDs (P<.05), whereas PERDEVS of friction-type (7.56 ±3.64) and spring-type (10.85 ±4.11) MTLDs did not differ significantly. In addition, devices produced by Megagen had a significantly higher (P<.05) PERDEV (28.33 ±9.53) other devices, whereas no differences were found in devices manufactured by Biohorizons (7.31 ±5.34), Dyna (7.82 ±1.08), Implance (8.43 ±4.77), and Straumann (13.26 ±0.79). However, 1-sample t tests showed none of the torque-control devices evaluated in this study were capable of achieving their target torque values (P<.05). Within the limitations of this in vitro study, MTLDs were shown to be significantly more accurate than ETLDs. However, none of the torque-control devices evaluated were able to meet their target torque values successfully. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Correlation between the knee adduction torque and medial contact force for a variety of gait patterns.

PubMed

Zhao, Dong; Banks, Scott A; Mitchell, Kim H; D'Lima, Darryl D; Colwell, Clifford W; Fregly, Benjamin J

2007-06-01

The external knee adduction torque has been proposed as a surrogate measure for medial compartment load during gait. However, a direct link between these two quantities has not been demonstrated using in vivo measurement of medial compartment load. This study uses in vivo data collected from a single subject with an instrumented knee implant to evaluate this link. The subject performed five different overground gait motions (normal, fast, slow, wide, and toe-out) with simultaneous collection of instrumented implant, video motion, and ground reaction data. For each trial, the knee adduction torque was measured externally while the total axial force applied to the tibial insert was measured internally. Based on data collected from the same subject performing treadmill gait under fluoroscopic motion analysis, a regression equation was developed to calculate medial contact force from the implant load cell measurements. Correlation analyses were performed for the stance phase and entire gait cycle to quantify the relationship between the knee adduction torque and both the medial contact force and the medial to total contact force ratio. When the entire gait cycle was analyzed, R(2) for medial contact force was 0.77 when all gait trials were analyzed together and between 0.69 and 0.93 when each gait trial was analyzed separately (p < 0.001 in all cases). For medial to total force ratio, R(2) was 0.69 for all trials together and between 0.54 and 0.90 for each trial separately (p < 0.001 in all cases). When only the stance phase was analyzed, R(2) values were slightly lower. These results support the hypothesis that the knee adduction torque is highly correlated with medial compartment contact force and medial to total force ratio during gait. (c) 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Does rotational strain at screw tightening affect the attainment or maintenance of osseointegration?

PubMed

Moriya, Katsunori; Maruo, Yukinori; Minagi, Shogo

2006-08-01

This study investigated whether rotational strain affects osseointegration. A total of 135 male rats were divided into five groups: 2-w rotation, 4-w rotation, 8-w rotation, 12-w rotation and control. Two hundred and seventy implants were inserted in rat tibia. The control group received no strain, while the 2-w, 4-w, 8-w and 12-w rotation groups received rotational strain at 2, 4, 8 and 12 weeks after implant placement, respectively. Removal torque (N cm) was measured in vivo. Bone contact rate (%) was calculated histomorphologically. Immunostaining for osteonectin (ON), osteopontin (OPN) and osteocalcin (OCN) was performed. The removal torque and bone contact rate were analyzed using one-way analyses of variance and the Scheffé method. At 4 weeks, the torque was significantly higher in the 2-w rotation group (1.30+/-0.44 N cm) than in the control group (0.79+/-0.67 N cm). From 8 to 16 weeks, the strained groups showed no significant differences from the control group. From the bone contact rates, bone formation was larger in the 4-week rotation group (62.9+/-10.7%) than in the control group (42.1+/-17.9%) at 8 weeks. The 4-week rotation group showed higher bone contact rate (61.1+/-11.3%) compared with the other strained groups and maintained this higher value until 16 weeks, showing no significant difference from the control group (72+/-5.2%). At the implant-bone interface, OPN was widely distributed and OCN was detected at a low level; however, ON could not be observed in any group. The bone contact rate changed when rotational strain was exerted at different periods after implant placement. However, the removal torque and distribution of extracellular matrix proteins were not adversely affected by the rotational strain.

Comparing passive angle-torque curves recorded simultaneously with a load cell versus an isokinetic dynamometer during dorsiflexion stretch tolerance assessments.

PubMed

Buckner, Samuel L; Jenkins, Nathaniel D M; Costa, Pablo B; Ryan, Eric D; Herda, Trent J; Cramer, Joel T

2015-05-01

The purpose of the present study was to compare the passive angle-torque curves and the passive stiffness (PS, N m °(-)(1)) values recorded simultaneously from a load cell versus an isokinetic dynamometer during dorsiflexion stretch tolerance assessments in vivo. Nine healthy men (mean ± SD age = 21.4 ± 1.6 years) completed stretch tolerance assessments on a custom-built apparatus where passive torque was measured simultaneously from an isokinetic dynamometer and a load cell. Passive torque values that corresponded with the last 10° of dorsiflexion, verified by surface electromyographic amplitude, were analyzed for each device (θ1, θ2, θ3, …, θ10). Passive torque values measured with the load cell were greater (p ≤ 0.05) than the dynamometer torque values for θ4 through θ10. There were more statistical differentiations among joint angles for passive torque measured by the load cell, and the load cell measured a greater (p ≤ 0.01) increase in passive torque and PS than the isokinetic dynamometer. These findings suggested that when examining the angle-torque curves from passive dorsiflexion stretch tolerance tests, a load cell placed under the distal end of the foot may be more sensitive than the torque recorded from an isokinetic dynamometer. Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.

Installation Torque Tables for Noncritical Applications

NASA Technical Reports Server (NTRS)

Rivera-Rosario, Hazel T.; Powell, Joseph S.

2017-01-01

The objective of this project is to define torque values for bolts and screws when loading is not a concern. Fasteners require a certain torque to fulfill its function and prevent failure. NASA Glenn Research Center did not have a set of fastener torque tables for non-critical applications without loads, usually referring to hand-tight or wrench-tight torqueing. The project is based on two formulas, torque and pullout load. Torque values are calculated giving way to preliminary data tables. Testing is done to various bolts and metal plates, torqueing them until the point of failure. Around 640 torque tables were developed for UNC, UNF, and M fasteners. Different lengths of thread engagement were analyzed for the 5 most common materials used at GRC. The tables were put together in an Excel spreadsheet and then formatted into a Word document. The plan is to later convert this to an official technical publication or memorandum.

A One-year Follow-up Study of a Tapered Hydrophilic Implant Design Using Various Placement Protocols in the Maxilla

PubMed Central

Zwaan, Jakob; Vanden Bogaerde, Leonardo; Sahlin, Herman; Sennerby, Lars

2016-01-01

Purpose: To study the clinical/radiographic outcomes and stability of a tapered implant design with a hydrophilic surface when placed in the maxilla using various protocols and followed for one year. Methods: Ninety-seven consecutive patients treated as part of daily routine in two clinics with 163 tapered implants in healed sites, in extraction sockets and together with bone augmentation procedures in the maxilla were evaluated after one year in function. Individual healing periods varying from 0 to 6 months had been used. Insertion torque (IT) and resonance frequency analysis (RFA) measurements were made at baseline. Follow-up RFA registrations were made after 6 and 12 months of loading. The marginal bone levels were measured in intraoral radiographs from baseline and after 12 months. A reference group consisting of 163 consecutive straight maxillary implants was used for the comparison of baseline IT and RFA measurements. Results: Five implants failed before loading, giving an implant survival rate of 96.9% and a prosthesis survival rate of 99.4% after one year. The mean marginal bone loss after one year was 0.5 mm (SD 0.4). The mean IT was statistically significantly higher for tapered than for straight reference implants (41.3 ± 12.0 Ncm vs 33.6 ± 12.5 Ncm, p < 0.001). The tapered implants showed a statistically insignificantly higher mean ISQ value than the straight references implants (73.7 ± 6.4 ISQ vs 72.2 ± 8.0 ISQ, p=0.119). There was no correlation between IT and marginal bone loss. There was a correlation between IT and RFA measurements (p < 0.001). Conclusion: The tapered implant showed a high survival rate and minimal marginal bone loss after one year in function when using various protocols for placement. The tapered implant showed significantly higher insertion torque values than straight reference implants. PMID:28077972

Dynamic fatigue performance of implant-abutment assemblies with different tightening torque values.

PubMed

Xia, Dandan; Lin, Hong; Yuan, Shenpo; Bai, Wei; Zheng, Gang

2014-01-01

Implant-abutment assemblies are usually subject to long-term cyclic loading. To evaluate the dynamic fatigue performance of implant-abutment assemblies with different tightening torque values, thirty implant-abutment assemblies (Zimmer Dental, Carlsbad, CA, USA) were randomly assigned to three tightening groups (24 Ncm; 30 Ncm; 36 Ncm), each consisted of 10 implants. Five specimens from each group were unscrewed, and their reverse torque values recorded. The remaining specimens were subjected to a load between 30 N~300 N at a loading frequency of 15 Hz for 5 × 10(6) cycles. After fatigue tests, residual reverse torque values were recorded if available. In the 24 Ncm tightening group, all the implants fractured at the first outer thread of the implant after fatigue loading, with fatigue crack propagation at the fractured surface showed by SEM observation. For the 30 Ncm and 36 Ncm tightening groups, a statistical significant difference (p<0.05) between the unloaded and loaded groups was revealed. Compared with the unloaded specimens, the specimens went through fatigue loading had decreased reverse torque values. It was demonstrated that insufficient torque will lead to poor fatigue performance of dental implant-abutment assemblies and abutment screws should be tightened to the torque recommended by the manufacturer. It was also concluded that fatigue loading would lead to preload loss.

The overuse of the implant motor: effect on the output torque in overloading condition.

PubMed

Lee, Du-Hyeong; Cho, Sung-Am; Lee, Cheong-Hee; Lee, Kyu-Bok

2015-06-01

The overloading of the motor affects its performance. The output torque of the implant motor under overloading condition has not been reported. The purpose of this study was to determine the reliability and the tendency of the output torque when an implant motor is consecutively used. Three implant motors were evaluated: SurgicXT/X-SG20L (NSK), INTRAsurg300/CL3-09 (KaVo), and XIP10/CRB26LX (Saeshin). The output torque was measured using an electronic torque gauge fixed with jigs. For the 40 and 50 Ncm torque settings, 300 measurements were taken at 30 rpm. Repeated measures of analysis of variance (ANOVA) and one-way ANOVA were used to compare the torque values within each group and between the groups. As repeating measures, the output torque values decreased gradually compared with the baseline. In within-group analysis, the different torque value from the first measurement appeared earliest in NSK motor, followed in order by Saeshin and KaVo motors. NSK motor showed a different torque decrease between 40 and 50 Ncm settings (p < .05). Intergroup analysis revealed Saeshin motor to have the least deviation from the baseline, followed by KaVo motor. NSK motor had the most inconsistent torque at the 6, 8, 9, and 10 repeat counts (p < .05). The actual torque decreases when the surgical motor is continuously used. The NSK motor showed more significant decreases in torque than KaVo and Saeshin motors in overloading condition. © 2014 Wiley Periodicals, Inc.

Correlation Between Bone Density and Instantaneous Torque at Implant Site Preparation: A Validation on Polyurethane Foam Blocks of a Device Assessing Density of Jawbones.

PubMed

Di Stefano, Danilo Alessio; Arosio, Paolo

2016-01-01

Bone density at implant placement sites is one of the key factors affecting implant primary stability, which is a determinant for implant osseointegration and rehabilitation success. Site-specific bone density assessment is, therefore, of paramount importance. Recently, an implant micromotor endowed with an instantaneous torque-measuring system has been introduced. The aim of this study was to assess the reliability of this system. Five blocks with different densities (0.16, 0.26, 0.33, 0.49, and 0.65 g/cm(3)) were used. A single trained operator measured the density of one of them (0.33 g/cm(3)), by means of five different devices (20 measurements/device). The five resulting datasets were analyzed through the analysis of variance (ANOVA) model to investigate interdevice variability. As differences were not significant (P = .41), the five devices were each assigned to a different operator, who collected 20 density measurements for each block, both under irrigation (I) and without irrigation (NI). Measurements were pooled and averaged for each block, and their correlation with the actual block-density values was investigated using linear regression analysis. The possible effect of irrigation on density measurement was additionally assessed. Different devices provided reproducible, homogenous results. No significant interoperator variability was observed. Within the physiologic range of densities (> 0.30 g/cm(3)), the linear regression analysis showed a significant linear correlation between the mean torque measurements and the actual bone densities under both drilling conditions (r = 0.990 [I], r = 0.999 [NI]). Calibration lines were drawn under both conditions. Values collected under irrigation were lower than those collected without irrigation at all densities. The NI/I mean torque ratio was shown to decrease linearly with density (r = 0.998). The mean error introduced by the device-operator system was less than 10% in the range of normal jawbone density. Measurements performed with the device were linearly correlated with the blocks' bone densities. The results validate the device as an objective intraoperative tool for bone-density assessment that may contribute to proper jawbone-density evaluation and implant-insertion planning.

Evaluation of primary and secondary stability of titanium implants using different surgical techniques.

PubMed

Tabassum, Afsheen; Meijer, Gert J; Walboomers, X Frank; Jansen, John A

2014-04-01

To investigate the influence of different surgical techniques on the primary and secondary implant stability using trabecular bone of goats as an implantation model. In the iliac crest of eight goats, 48 cylindrical-screw-type implants with a diameter of 4.2 mm (Dyna(®) ; Bergen op Zoom, the Netherlands) were installed, using three different surgical techniques: (i) 5% undersized, using a final drill diameter of 4 mm; (ii) 15% undersized, using a final drill diameter of 3.6 mm; and (iii) 25% undersized, using a final drill diameter of 3.2 mm. Peak insertion torque values were measured by a Digital(®) (MARK-10 Corporation, New York, NY, USA) torque gauge instrument during placement. At 3 weeks after implantation, removal torque was measured. Histomorphometrically, the peri-implant bone volume was measured in three zones; the inner zone (0-500 μm), the middle zone (500-1000 μm) and the outer zone (1000-1500 μm). Evaluation of the obtained data demonstrated no statistically significant difference between different surgical techniques regarding removal torque values. With respect to the percentage peri-implant bone volume (%BV), also no significant difference could be observed between all three applied surgical techniques for both the inner, middle and outer zone. However, irrespective of the surgical technique, it was noticed that the %BV was significantly higher for the inner zone as compared to middle and outer zone (P < 0.05) around the implant. At 3 weeks after implant installation, independent of the used undersized surgical technique, the %BV in the inner zone (0-500 μm) peri-implant area was improved due to both condensation of the surrounding bone as also the translocation of host bone particles along the implant surface. Surprisingly, no mechanical beneficial effect of the 25% undersized surgical technique could be observed as compared to the 5% or 15% undersized surgical technique to improve primary or secondary implant stability. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Design, Fabrication, and Testing of a Composite Rack Prototype in Support of the Deep Space Habitat Program

NASA Technical Reports Server (NTRS)

Smith, Russ; Hagen, Richard

2015-01-01

In support of the Deep Space Habitat project a number of composite rack prototypes were developed, designed, fabricated and tested to various extents ( with the International Standard Payload Rack configuration, or crew quarters, as a baseline). This paper focuses specifically on a composite rack prototype with a direct tie in to Space Station hardware. The outlined prototype is an all composite construction, excluding metallic fasteners, washers, and their associated inserts. The rack utilizes braided carbon composite tubing for the frame with the sidewalls, backwall and flooring sections utilizing aircraft grade composite honeycomb sandwich panels. Novel additively manufactured thermoplastic joints and tube inserts were also developed in support of this effort. Joint and tube insert screening tests were conducted at a preliminary level. The screening tests allowed for modification, and enhancement, of the fabrication and design approaches, which will be outlined. The initial joint tests did not include mechanical fasteners. Adhesives were utilized at the joint to composite tube interfaces, along with mechanical fasteners during final fabrication (thus creating a stronger joint than the adhesive only variant). In general the prototype was focused on a potential in-space assembly approach, or kit-of-parts construction concept, which would not necessarily require the inclusion of an adhesive in the joint regions. However, given the tie in to legacy Station hardware (and potential flight loads with imbedded hardware mass loadings), the rack was built as stiff and strong as possible. Preliminary torque down tests were also conducted to determine the feasibility of mounting the composite honeycomb panels to the composite tubing sections via the additively manufactured tube inserts. Additional fastener torque down tests were also conducted with inserts (helicoils) imbedded within the joints. Lessons learned are also included and discussed.

Influence of Micro Threads Alteration on Osseointegration and Primary Stability of Implants: An FEA and In Vivo Analysis in Rabbits.

PubMed

Chowdhary, Ramesh; Halldin, Anders; Jimbo, Ryo; Wennerberg, Ann

2015-06-01

To describe the early bone tissue response to implants with and without micro threads designed to the full length of an oxidized titanium implant. A pair of two-dimensional finite element models was designed using a computer aided three-dimensional interactive application files of an implant model with micro threads in between macro threads and one without micro threads. Oxidized titanium implants with (test implants n=20) and without (control implants n=20) micro thread were prepared. A total of 12 rabbits were used and each received four implants. Insertion torque while implant placement and removal torque analysis after 4 weeks was performed in nine rabbits, and histomorphometric analysis in three rabbits, respectively. Finite element analysis showed less stress accumulation in test implant models with 31Mpa when compared with 62.2 Mpa in control implant model. Insertion and removal torque analysis did not show any statistical significance between the two implant designs. At 4 weeks, there was a significant difference between the two groups in the percentage of new bone volume and bone-to-implant contact in the femur (p< .05); however, not in the tibia. The effect of micro threads was prominent in the femur suggesting that micro threads promote bone formation. The stress distribution supported by the micro threads was especially effective in the cancellous bone. © 2013 Wiley Periodicals, Inc.

The effect of undersizing and tapping on bone to implant contact and implant primary stability: A histomorphometric study on bovine ribs.

PubMed

Di Stefano, Danilo Alessio; Perrotti, Vittoria; Greco, Gian Battista; Cappucci, Claudia; Arosio, Paolo; Piattelli, Adriano; Iezzi, Giovanna

2018-06-01

Implant site preparation may be adjusted to achieve the maximum possible primary stability. The aim of this investigation was to study the relation among bone-to-implant contact at insertion, bone density, and implant primary stability intra-operatively measured by a torque-measuring implant motor, when implant sites were undersized or tapped. Undersized (n=14), standard (n=13), and tapped (n=13) implant sites were prepared on 9 segments of bovine ribs. After measuring bone density using the implant motor, 40 implants were placed, and their primary stability assessed by measuring the integral of the torque-depth insertion curve. Bovine ribs were then processed histologically, the bone-to-implant contact measured and statistically correlated to bone density and the integral. Bone-to-implant contact and the integral of the torque-depth curve were significantly greater for undersized sites than tapped sites. Moreover, a correlation between bone to implant contact, the integral and bone density was found under all preparation conditions. The slope of the bone-to-implant/density and integral/density lines was significantly greater for undersized sites, while those corresponding to standard prepared and tapped sites did not differ significantly. The integral of the torque-depth curve provided reliable information about bone-to-implant contact and primary implant stability even in tapped or undersized sites. The linear relations found among the parameters suggests a connection between extent and modality of undersizing and the corresponding increase of the integral and, consequently, of primary stability. These results might help the physician determine the extent of undersizing needed to achieve the proper implant primary stability, according to the planned loading protocol.

Comparative Analysis of Screw Loosening With Prefabricated Abutments and Customized CAD/CAM Abutments.

PubMed

Paek, Janghyun; Woo, Yi-Hyung; Kim, Hyeong-Seob; Pae, Ahran; Noh, Kwantae; Lee, Hyeonjong; Kwon, Kung-Rock

2016-12-01

The aim of this study was to determine the stability of computer-aided design and manufacturing (CAD/CAM) and prefabricated abutment by measuring removal torque before and after cyclic loading. Three types of fixture and 2 types of abutments were used. Removable torque was measured after cyclic loading for 5000 cycles between 25 and 250 N for each group. The same procedure was performed twice. First, removal torque values (Newton centimeter) were measured for stock versus custom abutments as follows: group 1: 27.17 versus 26.67, group 2: 26.27 versus 26.33, and group 3: 37.33 versus 36.67. Second removal torque values (Newton centimeter) were also measured: group 1: 23 versus 23.5, group 2: 22.5 versus 22.33, and group 3: 32.67 versus 32.5. There was no significant difference between the stock and custom abutments in either the first or second removal torque values and also no significant difference among initial tightening torque, first or second removal torque (P > 0.05). With precise control of CAD/CAM abutments, good screw joint stability can be achieved.

Accuracy of dental torque wrenches.

PubMed

Wood, James S; Marlow, Nicole M; Cayouette, Monica J

2015-01-01

The aim of this in vitro study was to compare the actual torque of 2 manual wrench systems to their stated (target) torque. New spring- (Nobel Biocare USA, LLC) and friction-style (Zimmer Dental, Inc.) manual dental torque wrenches, as well as spring torque wrenches that had undergone sterilization and clinical use, were tested. A calibrated torque gauge was used to compare actual torque to target torque values of 15 and 35 N/cm. Data were statistically analyzed via mixed-effects regression model with Bonferroni correction. At a target torque of 15 N/cm, the mean torque of new spring wrenches (13.97 N/cm; SE, 0.07 N/cm) was significantly different from that of used spring wrenches (14.94 N/cm; SE, 0.06 N/cm; P < 0.0001). However, the mean torques of new spring and new friction wrenches (14.10 N/cm; SE, 0.07 N/cm; P = 0.21) were not significantly different. For torque measurements calibrated at 35 N/cm, the mean torque of new spring wrenches (35.29 N/cm; SE, 0.10 N/cm) was significantly different (P < 0.0001) from the means of new friction wrenches (36.20 N/cm; SE, 0.08 N/cm) and used spring wrenches (36.45 N/cm; SE, 0.08 N/cm). Discrepancies in torque could impact the clinical success of screw-retained dental implants. It is recommended that torque wrenches be checked regularly to ensure that they are performing to target values.

Removal torque of zirconia abutment screws under dry and wet conditions.

PubMed

Nigro, Frederico; Sendyk, Claudio L; Francischone, Carlos Eduardo; Francischone, Carlos Eduardo

2010-01-01

The aim of this study was to verify whether screw abutment lubrication can generate higher preload values compared to non-lubricated screws, a titanium abutment was screwed onto an implant analog and scanned with the Procera System to generate 20 zirconia abutments. MKIII Brånemark implants were clamped to a precision torque device, and the abutments were distributed in dry and wet groups with 10 specimens each. In the wet groups, the inner threads of the implants were filled with artificial saliva. All abutments were fastened with a Torqtite screw under 32 Ncm. Ten detorque measurements were performed per group pushing the reverse button of the Torque controller soon after screw tightening with values registered. The mean detorque values were calculated and compared by a Student's t test (α=0.05). The wet condition presented significantly higher mean detorque than the dry condition (31.5 ± 1.2 versus 27.5 ± 1.5 Ncm, respectively; p=0.0000024). In conclusion, there was always a loss in the initial torque values when the removal torque was measured under both conditions. The wet condition presented higher mean torque than the dry condition. Better preload values were established in the wet group, suggesting that the abutment screw must be lubricated in saliva to avoid further loosening.

Age-related reduction of trunk muscle torque and prevalence of trunk sarcopenia in community-dwelling elderly: Validity of a portable trunk muscle torque measurement instrument and its application to a large sample cohort study

PubMed Central

Sasaki, Shizuka; Chiba, Daisuke; Yamamoto, Yuji; Nawata, Atsushi; Tsuda, Eiichi; Nakaji, Shigeyuki; Ishibashi, Yasuyuki

2018-01-01

Trunk muscle weakness and imbalance are risk factors for postural instability, low back pain, and poor postoperative outcomes. The association between trunk muscle strength and aging is poorly understood, and establishing normal reference values is difficult. We aimed to establish the validity of a novel portable trunk muscle torque measurement instrument (PTMI). We then estimated reference data for healthy young adults and elucidated age-related weakness in trunk muscle strength. Twenty-four university students were enrolled to validate values for PTMI, and 816 volunteers from the general population who were recruited to the Iwaki Health Promotion Project were included to estimate reference data for trunk muscle strength. Trunk flexion and extension torque were measured with PTMI and KinCom, and interclass correlation coefficients (ICC) were estimated to evaluate the reliability of PTMI values. Furthermore, from the young adult reference, the age-related reduction in trunk muscle torque and the prevalence of sarcopenia among age-sex groups were estimated. The ICC in flexion and extension torque were 0.807 (p<0.001) and 0.789 (p<0.001), respectively. The prevalence of sarcopenia increased with age, and the prevalence due to flexion torque was double that of extension torque. Flexion torque decreased significantly after 60 years of age, and extension torque decreased after 70 years of age. In males over age 80, trunk muscle torque decreased to 49.1% in flexion and 63.5% in extension. In females over age 80, trunk muscle torque decreased to 60.7% in flexion and 68.4% in extension. The validity of PTMI was confirmed by correlation with KinCom. PTMI produced reference data for healthy young adults, and demonstrated age-related reduction in trunk muscle torque. Trunk sarcopenia progressed with aging, and the loss of flexion torque began earlier than extension torque. At age 80, trunk muscle torque had decreased 60% compared with healthy young adults. PMID:29471310

Age-related reduction of trunk muscle torque and prevalence of trunk sarcopenia in community-dwelling elderly: Validity of a portable trunk muscle torque measurement instrument and its application to a large sample cohort study.

PubMed

Sasaki, Eiji; Sasaki, Shizuka; Chiba, Daisuke; Yamamoto, Yuji; Nawata, Atsushi; Tsuda, Eiichi; Nakaji, Shigeyuki; Ishibashi, Yasuyuki

2018-01-01

Trunk muscle weakness and imbalance are risk factors for postural instability, low back pain, and poor postoperative outcomes. The association between trunk muscle strength and aging is poorly understood, and establishing normal reference values is difficult. We aimed to establish the validity of a novel portable trunk muscle torque measurement instrument (PTMI). We then estimated reference data for healthy young adults and elucidated age-related weakness in trunk muscle strength. Twenty-four university students were enrolled to validate values for PTMI, and 816 volunteers from the general population who were recruited to the Iwaki Health Promotion Project were included to estimate reference data for trunk muscle strength. Trunk flexion and extension torque were measured with PTMI and KinCom, and interclass correlation coefficients (ICC) were estimated to evaluate the reliability of PTMI values. Furthermore, from the young adult reference, the age-related reduction in trunk muscle torque and the prevalence of sarcopenia among age-sex groups were estimated. The ICC in flexion and extension torque were 0.807 (p<0.001) and 0.789 (p<0.001), respectively. The prevalence of sarcopenia increased with age, and the prevalence due to flexion torque was double that of extension torque. Flexion torque decreased significantly after 60 years of age, and extension torque decreased after 70 years of age. In males over age 80, trunk muscle torque decreased to 49.1% in flexion and 63.5% in extension. In females over age 80, trunk muscle torque decreased to 60.7% in flexion and 68.4% in extension. The validity of PTMI was confirmed by correlation with KinCom. PTMI produced reference data for healthy young adults, and demonstrated age-related reduction in trunk muscle torque. Trunk sarcopenia progressed with aging, and the loss of flexion torque began earlier than extension torque. At age 80, trunk muscle torque had decreased 60% compared with healthy young adults.

Local mechanical response of cells to the controlled rotation of magnetic nanorods.

PubMed

Castillo, Matias; Ebensperger, Roberto; Wirtz, Denis; Walczak, Magdalena; Hurtado, Daniel E; Celedon, Alfredo

2014-11-01

The mechanical response of the cytoplasm was investigated by the intracellular implantation of magnetic nanorods and exposure to low-frequency rotatory magnetic fields. Nanorods (Pt-Ni, ∼200 nm diameter) fabricated by electrodeposition in templates of porous alumina with lengths of approximately 2 and 5 µm were inserted into NIH/3T3 fibroblasts and manipulated with a rotational magnetic field. Nanorod rotation was observed only for torques greater than 3.0 × 10(-16) Nm, suggesting a Bingham-type behavior of the cytoplasm. Higher torques produced considerable deformation of the intracellular material. The cell nucleus and cell membrane were significantly deformed by nanorods actuated by 4.5 × 10(-15) Nm torques. Our results demonstrate that nanorods under magnetic fields are an effective tool to mechanically probe the intracellular environment. We envision that our findings may contribute to the noninvasive and direct mechanical characterization of the cytoplasm. © 2014 Wiley Periodicals, Inc.

Local mechanical response of cells to the controlled rotation of magnetic nanorods

PubMed Central

Castillo, Matias; Ebensperger, Roberto; Wirtz, Denis; Walczak, Magdalena; Hurtado, Daniel E.; Celedon, Alfredo

2015-01-01

The mechanical response of the cytoplasm was investigated by the intracellular implantation of magnetic nanorods and exposure to low-frequency rotatory magnetic fields. Nanorods (Pt-Ni, ~200 nm diameter) fabricated by electrodeposition in templates of porous alumina with lengths of approximately 2 and 5 μm were inserted into NIH/ 3T3 fibroblasts and manipulated with a rotational magnetic field. Nanorod rotation was observed only for torques greater than 3.0 × 10−16 Nm, suggesting a Bingham-type behavior of the cytoplasm. Higher torques produced considerable deformation of the intracellular material. The cell nucleus and cell membrane were significantly deformed by nanorods actuated by 4.5 × 10−15 Nm torques. Our results demonstrate that nanorods under magnetic fields are an effective tool to mechanically probe the intracellular environment. We envision that our findings may contribute to the noninvasive and direct mechanical characterization of the cytoplasm. PMID:24700696

In vitro effect of chlorhexidine gel on torque and detorque values of implant abutment screw.

PubMed

Asli, Hamid Neshandar; Saberi, Bardia Vadiati; Fatemi, Arezoo Sadat

2017-01-01

Use of chlorhexidine (CHX) gel to eliminate the malodor of implant cavity may decrease the friction coefficient and effective preload and result in abutment screw loosening. This study aimed to assess the effect of CHX gel on the preload, torque, and detorque values. This in vitro experimental study was conducted on three groups of five implants. Group A (G1) was the control group and no material was applied to the implant cavity. In Group B (G2), implant cavity was filled with saliva before abutment screw tightening. In Group C (G3), implant cavity was first filled with saliva and then with CHX gel. The abutments were torqued to 24 N/cm2 according to the manufacturer's instructions and were then loosened. These processes were repeated five times. The ratio of the mean percentage of detorque to torque values was measured in all groups. The collected data were analyzed using ANOVA and post hoc Tukey's test. No significant difference was noted between G1 and G2. Group G2 had significantly higher detorque value (p < 0.05). ANOVA detected a significant difference in the mean torque (p < 0.05) and detorque (p < 0.001) values among the three groups. G3 showed maximum difference between torque and detorque values; the minimum difference was noted in G2. Application of CHX gel (to decrease the malodor of the implant cavity) decreases the detorque and preload values and increases the risk of screw loosening.

Somatotype variables related to muscle torque and power in judoists.

PubMed

Lewandowska, Joanna; Buśko, Krzysztof; Pastuszak, Anna; Boguszewska, Katarzyna

2011-12-01

The purpose of this study was to examine the relationship between somatotype, muscle torque and power output in judoists. Thirteen judoists (age 18.4±3.1 years, body height 178.6±8.2 cm, body mass 82.3±15.9 kg) volunteered to participate in this study. Somatotype was determined using the Heath-Carter method. Maximal muscle torques of elbow, shoulder, knee, hip and trunk flexors as well as extensors were measured under static conditions. Power outputs were measured in 5 maximal cycle ergometer exercise bouts, 10 s each, at increasing external loads equal to 2.5, 5.0, 7.5, 10.0 and 12.5% of body weight. The Pearson's correlation coefficients were calculated between all parameters. The mean somatotype of judoists was: 3.5-5.9-1.8 (values for endomorphy, mesomorphy and ectomorphy, respectively). The values (mean±SD) of sum of muscle torque of ten muscle groups (TOTAL) was 3702.2±862.9 N x m. The power output ranged from 393.2±79.4 to 1077.2±275.4 W. The values of sum of muscle torque of right and left upper extremities (SUE), sum of muscle torque of right and left lower extremities (SLE), sum of muscle torque of the trunk (ST) and TOTAL were significantly correlated with the mesomorphic component (0.68, 0.80, 0.71 and 0.78, respectively). The ectomorphic component correlated significantly with values of SUE, SLE, ST and TOTAL (-0.69, -0.81, -0.71 and -0.79, respectively). Power output was also strongly correlated with both mesomorphy (positively) and ectomorphy (negatively). The results indicated that the values of mesomorphic and ectomorphic somatotype components influence muscle torque and power output, thus body build could be an important factor affecting results in judo.

76 FR 53312 - Airworthiness Directives; Agusta S.p.A. Model A109A and A109AII Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-26

... disassembling the tail rotor hub and blades assembly and inspecting for damage. If the tightening torque value..., and no further action is required. If the tightening torque value is greater than 700 kgcm, the hub plug must be replaced with an airworthy part. Torque the new hub plug to the specified tightening...

Dynamic Torque and Vertical Force Analysis during Nickel-titanium Rotary Root Canal Preparation with Different Modes of Reciprocal Rotation.

PubMed

Tokita, Daisuke; Ebihara, Arata; Nishijo, Miki; Miyara, Kana; Okiji, Takashi

2017-10-01

The purpose of the present study was to compare 2 modes of reciprocal movement (torque-sensitive and time-dependent reciprocal rotation) with continuous rotation in terms of torque and apical force generation during nickel-titanium rotary root canal instrumentation. A custom-made automated root canal instrumentation and torque/force analyzing device was used to prepare simulated canals in resin blocks and monitor the torque and apical force generated in the blocks during preparation. Experimental groups (n = 7, each) consisted of (1) torque-sensitive reciprocal rotation with torque-sensitive vertical movement (group TqR), (2) time-dependent reciprocal rotation with time-dependent vertical movement (group TmR), and (3) continuous rotation with time-dependent vertical movement (group CR). The canals were instrumented with TF Adaptive SM1 and SM2 rotary files (SybronEndo, Orange, CA), and the torque and apical force were measured during instrumentation with SM2. The mean and maximum torque and apical force values were statistically analyzed using 1-way analysis of variance and the Tukey test (α = 0.05). The recordings showed intermittent increases of upward apical force and clockwise torque, indicating the generation and release of screw-in forces. The maximum upward apical force values in group TmR were significantly smaller than those in group CR (P < .05). The maximum torque values in clockwise and counterclockwise directions in groups TqR and TmR were significantly smaller than those in group CR (P < .05). Under the present experimental conditions using TF Adaptive instruments, both torque-sensitive and time-dependent reciprocal rotation generated significantly lower maximum torque and may have advantages in reducing stress generation caused by screw-in forces when compared with continuous rotation. Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Influence on grip of knife handle surface characteristics and wearing protective gloves.

PubMed

Claudon, Laurent

2006-11-01

Ten subjects were asked to apply maximum torques on knife handles with either their bare hand or their hand wearing a Kevlar fibre protective glove. Four knife handles (2 roughnesses, 2 hardnesses) were tested. Surface electromyograms of 6 upper limb and shoulder muscles were recorded and subject opinions on both knife handle hardness and friction in the hand were also assessed. The results revealed the significant influence of wearing gloves (p<0.0001), knife type (p<0.0005) and handle hardness (p<0.005) on the applied torque. Wearing Kevlar fibre gloves greatly increased the torque independently of the other two parameters. Under the bare hand condition, a 90 degrees ShA slightly rough handle provided the greatest torque. Subject opinion agreed with the observed effects on recorded torque values except for the hardness factor, for which a preference for the 70 degrees ShA value over the 90 degrees ShA value emerged.

Measurement of clinicians' ability to hand torque dental implant components.

PubMed

Kanawati, Ali; Richards, Mark W; Becker, Jeffery J; Monaco, Natalie E

2009-01-01

There is a varying degree of hand torque abilities using finger drivers among clinicians. Calibrating one's own abilities requires complicated instruments not readily available. This study evaluated a simple-to-use method that allows dental practitioners to have a quantifiable clinical assessment of relative torque ability using finger drivers to torque down dental implant components. A typodont that includes dental implants was mounted in a mannequin placed in a patient-reclined position. The subjects were asked to torque as tightly as they could a new healing abutment to an implant secured firmly in resin within the typodont. All participants wore moistened gloves when using a finger driver. The healing abutment was countertorqued using a certified precalibrated precision torque measurement device. The reading on the torque driver was recorded when the healing abutment disengaged. An average of torque values of dentists and dental students was calculated. Fifty subjects had an average maximum torque ability of 24 Ncm (male dentists: 28 Ncm; students: 22 Ncm; male students: 24 Ncm; female students: 19 Ncm). Maximum torque values for all participants ranged from 11 Ncm to 38 Ncm. There was no significant difference between groups. This study showed a varying degree of hand torquing abilities using a finger driver. Clinicians should regularly calibrate their ability to torque implant components to more predictably perform implant dentistry. Dental implant manufacturers should more precisely instruct clinicians as to maximum torque, as opposed to "finger tighten only".

Antimicrobial efficacy of external fixator pins coated with a lipid stabilized hydroxyapatite/chlorhexidine complex to prevent pin tract infection in a goat model.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dejong, E. Schuyler; Deberardino, T. M.; Brooks, D. E.

Background: Pin tract infection is a common complication of external fixation. An antiinfective external fixator pin might help to reduce the incidence of pin tract infection and improve pin fixation. Methods: Stainless steel and titanium external fixator pins, with and without a lipid stabilized hydroxyapatite/chlorhexidine coating, were evaluated in a goat model. Two pins contaminated with an identifiable Staphylococcus aureus strain were inserted into each tibia of 12 goats. The pin sites were examined daily. On day 14, the animals were killed, and the pin tips cultured. Insertion and extraction torques were measured. Results: Infection developed in 100% of uncoatedmore » pins, whereas coated pins demonstrated 4.2% infected, 12.5% colonized, and the remainder, 83.3%, had no growth (p < 0.01). Pin coating decreased the percent loss of fixation torque over uncoated pins (p = 0.04). Conclusion: These results demonstrate that the lipid stabilized hydroxyapatite/chlorhexidine coating was successful in decreasing infection and improving fixation of external fixator pins.« less

Comparison of conventional twist drill protocol and piezosurgery for implant insertion: an ex vivo study on different bone types.

PubMed

Sagheb, Keyvan; Kumar, Vinay V; Azaripour, Adriano; Walter, Christian; Al-Nawas, Bilal; Kämmerer, Peer W

2017-02-01

The aim of this ex vivo study was to compare implant insertion procedures using piezosurgery and conventional drilling in different qualities of bone. Implant bed preparation time, generated heat, and primary implant stability were analyzed. Fresh ex vivo porcine bone block samples (cancellous, mixed, and cortical bone) were obtained. The bone quality was quantified by ultrasound transmission velocity (UTV). Each bone sample received three implants of the same diameter using each of the techniques of piezosurgery and conventional twist drills. Time for preparation was taken and the temperature while performing the osteotomy was measured using infrared spectroscopy. The primary implant stability after osteotomy was measured using resonance frequency analysis (RFA) and extrusion torque (ET). ANOVA with post hoc Tukey test was carried out to compare the values for the three different groups. The UTV values strongly correlated with the density of the bone samples. There was a significant increase in time (threefold, P < 0.05 [302 s vs. 122 s in cortical bone]) but no difference in the temperature for the piezo group (~37°C in cortical bone). Regardless of the osteotomy technique, there was a statistically significant increase in RFA and ET values in implants inserted in cancellous bone (RFA: piezo 77, drill 76; ET: piezo 22, drill 21), mixed bone (RFA: piezo 85, drill 86; ET: piezo 105, drill 61), and cortical bone (RFA: piezo 90, drill 87; ET piezo 184, drill 79) samples, respectively (P < 0.05). In between the different osteotomy groups, there was no difference in the RFA values but significant higher ET values in mixed/cortical bone samples in favor for the piezosurgery group. Piezosurgery and conventional implant bed drilling procedure do have similar mechanical outcomes regarding primary stability with high RFA values, but the preparation does need more time for piezosurgery group, so that piezosurgery might be a valuable tool in only very specific cases for implant bed preparation. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Forearm Torque and Lifting Strength: Normative Data.

PubMed

Axelsson, Peter; Fredrikson, Per; Nilsson, Anders; Andersson, Jonny K; Kärrholm, Johan

2018-02-10

To establish reference values for new methods designed to quantitatively measure forearm torque and lifting strength and to compare these values with grip strength. A total of 499 volunteers, 262 males and 237 females, aged 15 to 85 (mean, 44) years, were tested for lifting strength and forearm torque with the Kern and Baseline dynamometers. These individuals were also tested for grip strength with a Jamar dynamometer. Standardized procedures were used and information about sex, height, weight, hand dominance, and whether their work involved high or low manual strain was collected. Men had approximately 70% higher forearm torque and lifting strength compared with females. Male subjects aged 26 to 35 years and female subjects aged 36 to 45 years showed highest strength values. In patients with dominant right side, 61% to 78% had a higher or equal strength on this side in the different tests performed. In patients with dominant left side, the corresponding proportions varied between 41% and 65%. There was a high correlation between grip strength and forearm torque and lifting strength. Sex, body height, body weight, and age showed a significant correlation to the strength measurements. In a multiple regression model sex, age (entered as linear and squared) could explain 51% to 63% of the total variances of forearm torque strength and 30% to 36% of lifting strength. Reference values for lifting strength and forearm torque to be used in clinical practice were acquired. Grip strength has a high correlation to forearm torque and lifting strength. Sex, age, and height can be used to predict forearm torque and lifting strength. Prediction equations using these variables were generated. Normative data of forearm torque and lifting strength might improve the quality of assessment of wrist and forearm disorders as well as their treatments. Copyright © 2018 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

Analyzing the Influence of a New Dental Implant Design on Primary Stability.

PubMed

Valente, Mariana Lima da Costa; de Castro, Denise Tornavoi; Shimano, Antonio Carlos; Lepri, César Penazzo; dos Reis, Andréa Cândido

2016-02-01

The macrogeometry of dental implants strongly influences the primary stability and hence the osseointegration process. Compare the performance of conventional and modified implant models in terms of primary stability. A total of 36 implants (Neodent®) with two different formats (n = 18): Alvim CM (Conical CM, Ø 4.3 mm × 10 mm in length) and Titamax Ti (Cylindrical HE, Ø 4.0 mm × 11 mm in length) were inserted into artificial bone blocks. Nine implants from each set were selected to undergo external geometry changes. The primary stability was quantified by insertion torque and resonance frequency using an Osstell device and the pullout test. One-way analysis of variance and Tukey's test were used for statistical evaluation. The comparative analysis of the implants showed a significant increase of the insertion torque for the modified Conical CM implants (p = 0.000) and Cylindrical HE (p = 0.043); for the resonance frequency the modified Cylindrical HE showed a lower statistical mean (p = 0.002) when compared to the conventional model, and in the pullout test both modified implants showed significant reduction (p = 0.000). Within the limitations of this study, the proposed modification showed good stability levels and advantages when compared to the conventional implants. © 2015 Wiley Periodicals, Inc.

Haptic feedback for virtual assembly

NASA Astrophysics Data System (ADS)

Luecke, Greg R.; Zafer, Naci

1998-12-01

Assembly operations require high speed and precision with low cost. The manufacturing industry has recently turned attenuation to the possibility of investigating assembly procedures using graphical display of CAD parts. For these tasks, some sort of feedback to the person is invaluable in providing a real sense of interaction with virtual parts. This research develops the use of a commercial assembly robot as the haptic display in such tasks. For demonstration, a peg-hole insertion task is studied. Kane's Method is employed to derive the dynamics of the peg and the contact motions between the peg and the hole. A handle modeled as a cylindrical peg is attached to the end effector of a PUMA 560 robotic arm. The arm is handle modeled as a cylindrical peg is attached to the end effector of a PUMA 560 robotic arm. The arm is equipped with a six axis force/torque transducer. The use grabs the handle and the user-applied forces are recorded. A 300 MHz Pentium computer is used to simulate the dynamics of the virtual peg and its interactions as it is inserted in the virtual hole. The computed torque control is then employed to exert the full dynamics of the task to the user hand. Visual feedback is also incorporated to help the user in the process of inserting the peg into the hole. Experimental results are presented to show several contact configurations for this virtually simulated task.

The effect of screw taper on interference fit during load to failure at the soft tissue/bone interface.

PubMed

Mann, Charles J; Costi, John J; Stanley, Richard M; Dobson, Peter J

2005-10-01

The effect of screw geometry on the pullout strength of an anterior cruciate ligament reconstruction is well documented. The effect of a truly tapered screw has not been previously investigated. Thirty bovine knees in right and left knee pairs were collected. Superficial digital flexors from the hind legs of sheep were harvested to form a quadruple tendon graft. For each knee pair, one tendon graft was fixed using a tapered screw (n=15) and the other with a non-tapered screw (n=15). Interference screws were manufactured from stainless steel, and apart from the tapered or non-tapered profile were identical. The screws were inserted into a tibial tunnel already containing the tendon graft. The interference fit was tested by extensile load to failure tests. The insertion torque of the screws and first sign of load to failure (by pullout) of the interference fit were recorded. Results were analysed using paired t-tests. The results indicated that tapered screws have significantly higher resistance to interference failure (p=0.007) and insertion torque (p<0.001) than non-tapered screws. The improved biomechanical performance of tapered screws demonstrated in this study may translate into superior clinical results, particularly at the tibial attachment of hamstring anterior cruciate ligament reconstruction, and also of hamstring fixation to the medial femoral condyle for patella instability.

40 CFR 92.116 - Engine output measurement system calibrations.

Code of Federal Regulations, 2010 CFR

2010-07-01

... spaced torque values as indicated by the master load-cell for each in-use range used. (v) The in-use torque measurement must be within 2 percent of the torque measured by the master system for each load... the calibration equipment described in this section. (2) The engine flywheel torque feedback signals...

The Enhancement of spin Hall torque efficiency and Reduction of Gilbert damping in spin Hall metal/normal metal/ferromagnetic trilayers

NASA Astrophysics Data System (ADS)

Nguyen, Minh-Hai; Pai, Chi-Feng; Ralph, Daniel C.; Buhrman, Robert A.

2015-03-01

The spin Hall effect (SHE) in ferromagnet/heavy metal bilayer structures has been demonstrated to be a powerful means for producing pure spin currents and for exerting spin-orbit damping-like and field-like torques on the ferromagnetic layer. Large spin Hall (SH) angles have been reported for Pt, beta-Ta and beta-W films and have been utilized to achieve magnetic switching of in-plane and out-of-plane magnetized nanomagnets, spin torque auto-oscillators, and the control of high velocity domain wall motion. For many of the proposed applications of the SHE it is also important to achieve an effective Gilbert damping parameter that is as low as possible. In general the spin orbit torques and the effective damping are predicted to depend directly on the spin-mixing conductance of the SH metal/ferromagnet interface. This opens up the possibility of tuning these properties with the insertion of a very thin layer of another metal between the SH metal and the ferromagnet. Here we will report on experiments with such trilayer structures in which we have observed both a large enhancement of the spin Hall torque efficiency and a significant reduction in the effective Gilbert damping. Our results indicate that there is considerable opportunity to optimize the effectiveness and energy efficiency of the damping-like torque through engineering of such trilayer structures. Supported in part by NSF and Samsung Electronics Corporation.

Quantification of bone strength by intraoperative torque measurement: a technical note.

PubMed

Suhm, Norbert; Haenni, Markus; Schwyn, Ronald; Hirschmann, Michael; Müller, Andreas Marc

2008-06-01

Bone strength describes the resistance of bone against mechanical failure. Bone strength depends on both the amount of bone and the bone's quality, and the bone strength may be looked upon as a relevant parameter to judge an osteosynthesis' stability. Information about bone strength was barely available intraoperatively in the past. The previous work of our group reported on development and laboratory evaluation of mechanical torque measurement as a method for the intraoperative quantification of bone strength. With the clinical series presented here we intend to verify that the im gesamten Text DensiProbe instrumentation for intraoperative torque measurement and the related measurement method are eligible for intraoperative use based on the following criteria: application of the method may not create complications, the measurement can be performed by the surgeon himself and may only cause a limited increase in the procedure time. From December 2006 until May 2007 ten patients with a pertrochanteric femoral fracture or a lateral femoral neck fracture eligible for stabilization with DHS were included in the study after having received informed consent. Any medication and comorbidity that might have influenced bone quality or bone mineral density (BMD) in these patients was documented. Bone strength was intraoperatively measured with DensiProbe. Complications that were obviously related with torque measurement were documented as well as any deviation from the suggested procedure; 6 and 12 weeks postoperative follow-up included clinical and radiological examination. The time required for torque measurement, the overall operating time and the number of persons present in the operating room were protocolled. BMD values of the contralateral femoral neck were postoperatively assessed by dual energy X-ray absorptiometry (DEXA) and compared to intraoperative peak torque values measured by DensiProbe. No major complication was observed during intraoperative application of DensiProbe by trained surgeons. The unintended extraction of the guide wire together with the torque measurement probe was reported only once and is looked upon as a minor complication. Fracture healing was uneventful in all patients. The mean time for torque measurement was 2.35 +/- 0.9 min accounting for 2.2 +/- 1.1% of total surgery time. The presence of an additional person was not required to perform torque measurement but to protocol the data. There was a tendency towards correlation between BMD values of the femoral neck and intraoperative peak torque values. The data presented clearly indicate that the DensiProbe instrumentation and measurement principle are eligible for routine intraoperative use by trained surgeons. Interpretation of possible correlations between BMD values measured by means of DEXA and the Peak Torque values assessed by DensiProbe has to be considered very carefully, because BMD and Peak Torque analyse bone at a different scale. Only within the framework of a multicenter study it will be possible to include a sufficient number of patients for calculation of the methods' predictive value towards implant failure and to verify acceptance of the method by the surgeons.

The effect of different torque wrenches on rotational stiffness in compressive femoral nails: a biomechanical study.

PubMed

Karaarslan, A A; Acar, N

2018-02-01

Rotation instability and locking screws failure are common problems. We aimed to determine optimal torque wrench offering maximum rotational stiffness without locking screw failure. We used 10 conventional compression nails, 10 novel compression nails and 10 interlocking nails with 30 composite femurs. We examined rotation stiffness and fracture site compression value by load cell with 3, 6 and 8 Nm torque wrenches using torsion apparatus with a maximum torque moment of 5 Nm in both directions. Rotational stiffness of composite femur-nail constructs was calculated. Rotational stiffness of composite femur-compression nail constructs compressed by 6 Nm torque wrench was 3.27 ± 1.81 Nm/angle (fracture site compression: 1588 N) and 60% more than that compressed with 3 Nm torque wrench (advised previously) with 2.04 ± 0.81 Nm/angle (inter fragmentary compression: 818 N) (P = 0.000). Rotational stiffness of composite-femur-compression nail constructs compressed by 3 Nm torque wrench was 2.04 ± 0.81 Nm/angle (fracture site compression: 818 N) and 277% more than that of interlocking nail with 0.54 ± 0.08 Nm/angle (fracture site compression: 0 N) (P = 0.000). Rotational stiffness and fracture site compression value produced by 3 Nm torque wrench was not satisfactory. To obtain maximum rotational stiffness and fracture site compression value without locking screw failure, 6 Nm torque wrench in compression nails and 8 Nm torque wrench in novel compression nails should be used.

A comparison of preload values in gold and titanium dental implant retaining screws.

PubMed

Doolabh, R; Dullabh, H D; Sykes, L M

2014-08-01

This in vitro investigation compared the effect of using either gold or titanium retaining screws on preload in the dental implant- abutment complex. Inadequate preload can result in screw loosening, whilst fracture may occur if preload is excessive. These are the most commonly reported complications in implant-retained prostheses, and result in unscheduled, costly and time-consuming visits for the patient and the clinician. This study investigated changes in preload generation after repeated torque applications to gold and titanium screws. The test set-up consisted of an implant body, a cylindrical transmucosa abutment, and the test samples of gold and of titanium retaining screws. The implant bodies were anchored using a load cell, and the transmucosal abutments were attached using either gold or titanium retaining screws. A torque gauge was used to apply torque of 20Ncm, 32Ncm, and 40Ncm to the retaining screws. The preloads generated in each screw type were compared at each torque setting, and after repeated tightening episodes. In addition, the effect of applying torque beyond the manufacturers' recommendations was also examined. Gold retaining screws were found to achieve consistently higher preload values than titanium retaining screws. Preload values were not significantly different from the first to the tenth torque cycle. Titanium screws showed more consistent preload values, albeit lower than those of the gold screws. However due to possible galling of the internal thread of the implant body by titanium screws, gold screws remain the retaining screw of choice. Based on the findings of this study, gold retaining screws generate better preload than titanium. Torque beyond the manufacturers' recommendations resulted in a more stable implant complex. However, further investigations, with torque applications repeated until screw breakage, are needed to advise on ideal maintenance protocols.

Somatotype Variables Related to Muscle Torque and Power in Judoists

PubMed Central

Lewandowska, Joanna; Buśko, Krzysztof; Pastuszak, Anna; Boguszewska, Katarzyna

2011-01-01

The purpose of this study was to examine the relationship between somatotype, muscle torque and power output in judoists. Thirteen judoists (age 18.4±3.1 years, body height 178.6±8.2 cm, body mass 82.3±15.9 kg) volunteered to participate in this study. Somatotype was determined using the Heath-Carter method. Maximal muscle torques of elbow, shoulder, knee, hip and trunk flexors as well as extensors were measured under static conditions. Power outputs were measured in 5 maximal cycle ergometer exercise bouts, 10 s each, at increasing external loads equal to 2.5, 5.0, 7.5, 10.0 and 12.5% of body weight. The Pearson’s correlation coefficients were calculated between all parameters. The mean somatotype of judoists was: 3.5-5.9-1.8 (values for endomorphy, mesomorphy and ectomorphy, respectively). The values (mean±SD) of sum of muscle torque of ten muscle groups (TOTAL) was 3702.2±862.9 N x m. The power output ranged from 393.2±79.4 to 1077.2±275.4 W. The values of sum of muscle torque of right and left upper extremities (SUE), sum of muscle torque of right and left lower extremities (SLE), sum of muscle torque of the trunk (ST) and TOTAL were significantly correlated with the mesomorphic component (0.68, 0.80, 0.71 and 0.78, respectively). The ectomorphic component correlated significantly with values of SUE, SLE, ST and TOTAL (−0.69, −0.81, −0.71 and −0.79, respectively). Power output was also strongly correlated with both mesomorphy (positively) and ectomorphy (negatively). The results indicated that the values of mesomorphic and ectomorphic somatotype components influence muscle torque and power output, thus body build could be an important factor affecting results in judo. PMID:23487284

The effect of repeated torque in small diameter implants with machined and premachined abutments.

PubMed

Saboury, Abolfazl; Neshandar Asli, Hamid; Vaziri, Shahram

2012-05-01

Detorquing value is an important factor in the amount of preload stresses during abutment screw fastening. This study evaluated the percentage of detorque values in two-piece machined titanium and premachined cast abutments in small diameter implants. Three groups of five samples were evaluated. Group 1 (G1), machined titanium abutments, group 2 (G2), premachined cast straight abutments that cast with gold-palladium, and group 3 (G3), premachined angled cast abutments that cast with the same alloy, were angled before casting. Each abutment was torque to 24 Ncm according to the manufacturer's instructions and detorqued five times. The means of detorquing and torquing values in all groups were recorded. The mean of detorque in each group as a percentage of the toque value was calculated. The data for all groups were compared and calculated using analysis of variance (ANOVA) and t-test. Mean detorque values in G1, G2, and G3 were 88.1 ± 1.69, 93.1 ± 2.68, and 80.9 ± 4.95%, respectively. The ANOVA showed significant differences in mean of applied detorque (p < .001) and torque (p = .06) tightening among different groups. G2 had significantly greater detorque values (p < .05). No significant differences were found between G1 and G2. Surprisingly, abutment screw fracture occurred in three samples of G3. G3 showed significant percentage torque reduction (p < .05) and exhibited abutment screw fracture during evaluation. G2 presented the lowest torque reduction. Screw fracture occurred only in G3. © 2012 Wiley Periodicals, Inc.

Self-tapping ability of carbon fibre reinforced polyetheretherketone suture anchors.

PubMed

Feerick, Emer M; Wilson, Joanne; Jarman-Smith, Marcus; Ó'Brádaigh, Conchur M; McGarry, J Patrick

2014-10-01

An experimental and computational investigation of the self-tapping ability of carbon fibre reinforced polyetheretherketone (CFR-PEEK) has been conducted. Six CFR-PEEK suture anchor designs were investigated using PEEK-OPTIMA® Reinforced, a medical grade of CFR-PEEK. Experimental tests were conducted to investigate the maximum axial force and torque required for self-taping insertion of each anchor design. Additional experimental tests were conducted for some anchor designs using pilot holes. Computational simulations were conducted to determine the maximum stress in each anchor design at various stages of insertion. Simulations also were performed to investigate the effect of wall thickness in the anchor head. The maximum axial force required to insert a self-tapping CFR-PEEK suture anchor did not exceed 150 N for any anchor design. The maximum torque required to insert a self-tapping CFR-PEEK suture anchor did not exceed 0.8 Nm. Computational simulations reveal significant stress concentrations in the region of the anchor tip, demonstrating that a re-design of the tip geometry should be performed to avoid fracture during self-tapping, as observed in the experimental component of this study. This study demonstrates the ability of PEEK-OPTIMA Reinforced suture anchors to self-tap polyurethane foam bone analogue. This provides motivation to further investigate the self-tapping ability of CFR-PEEK suture anchors in animal/cadaveric bone. An optimised design for CFR-PEEK suture anchors offers the advantages of radiolucency, and mechanical properties similar to bone with the ability to self-tap. This may have positive implications for reducing surgery times and the associated costs with the procedure. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

40 CFR 1039.515 - What are the test procedures related to not-to-exceed standards?

Code of Federal Regulations, 2010 CFR

2010-07-01

...; however, use the power value corresponding to the engine operation at 30% of maximum torque at the B speed... 50% torque/power points) and below the line formed by connecting the two points in paragraphs (b)(2)(ii) and (iii) of this section (the 50% and 70% torque/power points). The 30%, 50%, and 70% torque...

Estimation of muscle torque in various combat sports.

PubMed

Pędzich, Wioletta; Mastalerz, Andrzej; Sadowski, Jerzy

2012-01-01

The purpose of the research was to compare muscle torque of elite combat groups. Twelve taekwondo WTF athletes, twelve taekwondo ITF athletes and nine boxers participated in the study. Measurements of muscle torques were done under static conditions on a special stand which belonged to the Department of Biomechanics. The sum of muscle torque of lower right and left extremities of relative values was significantly higher for taekwondo WTF athletes than for boxers (16%, p < 0.001 for right and 10%, p < 0.05 for left extremities) and taekwondo ITF (10%, p < 0.05 for right and 8% for left extremities). Taekwondo ITF athletes attained significantly higher absolute muscle torque values than boxers for elbow flexors (20%, p < 0.05 for right and 11% for left extremities) and extensors (14% for right and 18%, p < 0.05 for left extremities) and shoulder flexors (10% for right and 12%, p < 0.05 for left extremities) and extensors (11% for right and 1% for left extremities). Taekwondo WTF and taekwondo ITF athletes obtained significantly different relative values of muscle torque of the hip flexors (16%, p < 0.05) and extensors (11%, p < 0.05) of the right extremities.

Measurements of Repeated Tightening and Loosening Torque of Seven Different Implant/Abutment Connection Designs and Their Modifications: An In Vitro Study.

PubMed

Butkevica, Alena; Nathanson, Dan; Pober, Richard; Strating, Herman

2018-02-01

Repeated tightening and loosening of the abutment screw may alter its mechanical and physical properties affecting the optimal torque and ultimate reliability of an implant/abutment connection. The purpose of this study was to evaluate the effect of repeated tightening and loosening of implant/abutment screws on the loosening torque of implant/abutment connections of commercially available implant systems. Seven different implant/abutment connections and their modifications were tested. The screws of each system were tightened according to the manufacturer's specifications. After 20 minutes the screws were loosened. This procedure was repeated ten times, and the differences between the 1st and 10th cycle were expressed as a percentage change RTq(%) and correlated with initial torque, the number of threads, the length of shank, and thread surface area employing Spearman's analysis. All systems showed significant differences in residual torque (RTq) value (p < 0.05) between the 1st and 10th cycle except groups 6 and 11 (p > 0.05). All connections but group 3 (p = 1.000) showed a significant change from the initial torque (ITq) to the RTq values. The first successive RTq values increased in two connection groups 1 and 2. The remaining connections showed reduced RTq values ranging from -1.2 % (group 5) to -23.5% (group 6). The RTq values declined gradually with every repeated tightening in groups 1, 2, 3, 8, 9, 11, 12. In group 2, after the tenth tightening the RTq was still above the ITq value. Only length of shank demonstrated a correlation with the RTq(%) change over the successive tightening loosening cycles (p < 0.05). Repeated tightening and loosening of implant/abutment screws caused varying torque level changes among the different systems. These observations can probably be attributed to connection design. Limiting the number of tightening/loosening cycles in clinical and laboratory procedures is advisable for most of the implant systems tested. © 2016 by the American College of Prosthodontists.

Intraoperative mechanical bone strength determination in tibiotalocalcaneal fusion: a biomechanical investigation.

PubMed

Klos, Kajetan; Windolf, Markus; Schwieger, Karsten; Kuhn, Philipp; Hänni, Markus; Gueorguiev, Boyko; Hofmann, Gunther O; Mückley, Thomas

2009-12-01

Bone strength is currently measured with indirect techniques. We investigated the use of an intraoperative mechanical measurement for local bone strength determination and prediction of intramedullary-nail fusion failure. We investigated whether intraoperative local bone strength determination may be useful to the surgeon in predicting intramedullary nail hindfoot fusion performance. In seven human specimens, bone mineral density (BMD) was determined with qCT. A device (DensiProbe) specially devised for nailed tibiotalocalcaneal arthrodesis (TTCA) was inserted at the intended calcaneal screw sites of an intramedullary nail, and the cancellous break-away torque was measured. The constructs were then cyclically loaded to failure in dorsiflexion-plantarfexion. The BMD range was wide (42.8 to 185.9 mg HA/cm(3)). The proximal-screw site peak torque was 0.47 to 1.61 Nm; distal-screw site peak torque was 0.24 to 1.06 Nm. The number of cycles to failure correlated with peak torque both proximally (p = 0.021; r(2) = 0.69) and distally (p = 0.001; r(2) = 0.92). Proximally, peak torque did not correlate with BMD (p = 0.060; r(2) = 0.54); distally, it correlated significantly (p = 0.003; r(2) = 0.86). DensiProbe measurements can be used in the hindfoot to assess bone strength. In this study, specimens that failed early could be identified. However, in clinical practice fusion failure is multifactorial in origin, and failure prediction cannot be based upon peak torque measurements alone. The technique described here may be of use to give an intraoperative decision aid to predict intramedullary nail hindfoot fusion performance.

Sensitivity and specificity of radiographic methods for predicting insertion torque of dental implants.

PubMed

Cortes, Arthur Rodriguez Gonzalez; Eimar, Hazem; Barbosa, Jorge de Sá; Costa, Claudio; Arita, Emiko Saito; Tamimi, Faleh

2015-05-01

Subjective radiographic classifications of alveolar bone have been proposed and correlated with implant insertion torque (IT). The present diagnostic study aims to identify quantitative bone features influencing IT and to use these findings to develop an objective radiographic classification for predicting IT. Demographics, panoramic radiographs (taken at the beginning of dental treatment), and cone-beam computed tomographic scans (taken for implant surgical planning) of 25 patients receiving 31 implants were analyzed. Bone samples retrieved from implant sites were assessed with dual x-ray absorptiometry, microcomputed tomography, and histology. Odds ratio, sensitivity, and specificity of all variables to predict high peak IT were assessed. A ridge cortical thickness >0.75 mm and a normal appearance of the inferior mandibular cortex were the most sensitive variables for predicting high peak IT (87.5% and 75%, respectively). A classification based on the combination of both variables presented high sensitivity (90.9%) and specificity (100%) for predicting IT. Within the limitations of this study, the results suggest that it is possible to predict IT accurately based on radiographic findings of the patient. This could be useful in the treatment plan of immediate loading cases.

Computing the motor torque of Escherichia coli.

PubMed

Das, Debasish; Lauga, Eric

2018-06-13

The rotary motor of bacteria is a natural nano-technological marvel that enables cell locomotion by powering the rotation of semi-rigid helical flagellar filaments in fluid environments. It is well known that the motor operates essentially at constant torque in counter-clockwise direction but past work have reported a large range of values of this torque. Focusing on Escherichia coli cells that are swimming and cells that are stuck on a glass surface for which all geometrical and environmental parameters are known (N. C. Darnton et al., J. Bacteriol., 2007, 189, 1756-1764), we use two validated numerical methods to compute the value of the motor torque consistent with experiments. Specifically, we use (and compare) a numerical method based on the boundary integral representation of Stokes flow and also develop a hybrid method combining boundary element and slender body theory to model the cell body and flagellar filament, respectively. Using measured rotation speed of the motor, our computations predict a value of the motor torque in the range 440 pN nm to 829 pN nm, depending critically on the distance between the flagellar filaments and the nearby surface.

40 CFR Appendix B to Subpart E of... - Tables

Code of Federal Regulations, 2010 CFR

2010-07-01

... Variable-Speed Engines Test segment Mode number Engine speed 1 Observed torque 2 (percent of max. observed...'s specifications. Idle speed is specified by the manufacturer. 2 Torque (non-idle): Throttle fully open for 100 percent points. Other non-idle points: ± 2 percent of engine maximum value. Torque (idle...

Torque characteristics of a 122-centimeter butterfly valve with a hydro/pneumatic actuator

NASA Technical Reports Server (NTRS)

Lin, F. N.; Moore, W. I.; Lundy, F. E.

1981-01-01

Actuating torque data from field testing of a 122-centimeter (48 in.) butterfly valve with a hydro/pneumatic actuator is presented. The hydraulic cylinder functions as either a forward or a reverse brake. Its resistance torque increases when the valve speeds up and decreases when the valve slows down. A reduction of flow resistance in the hydraulic flow path from one end of the hydraulic cylinder to the other will effectively reduce the hydraulic resistance torque and hence increase the actuating torque. The sum of hydrodynamic and friction torques (combined resistance torque) of a butterfly valve is a function of valve opening time. An increase in the pneumatic actuating pressure will result in a decrease in both the combined resistance torque and the actuator opening torque; however, it does shorten the valve opening time. As the pneumatic pressure increases, the valve opening time for a given configuration approaches an asymptotical value.

Effects of Velocity on Electromyographic, Mechanomyographic, and Torque Responses to Repeated Eccentric Muscle Actions.

PubMed

Hill, Ethan C; Housh, Terry J; Camic, Clayton L; Smith, Cory M; Cochrane, Kristen C; Jenkins, Nathaniel D M; Cramer, Joel T; Schmidt, Richard J; Johnson, Glen O

2016-06-01

The purposes of this study were to examine the effects of the velocity of repeated eccentric muscle actions on the torque and neuromuscular responses during maximal isometric and eccentric muscle actions. Twelve resistance-trained men performed 30 repeated, maximal, eccentric, isokinetic muscle actions at randomly ordered velocities of 60, 120, or 180°·s on separate days. Maximal voluntary isometric contractions (MVICs) were performed before (pretest) and after (posttest) the repeated eccentric muscle actions on each day. Eccentric isokinetic peak torque (EIPT) values were the averages of the first 3 and last 3 repetitions of the 30 repeated eccentric muscle actions. During the EIPT and MVIC muscle actions, electromyographic (EMG) and mechanomyographic (MMG) amplitude (EMG AMP and MMG AMP) and mean power frequency (EMG MPF and MMG MPF) values were assessed. These results indicated that the repeated eccentric muscle actions had no effects on EIPT, or the EMG AMP, EMG MPF, or MMG MPF values assessed during the EIPT muscle actions, but decreased MMG AMP. The repeated eccentric muscle actions, however, decreased MVIC torque, and also the EMG AMP and MMG MPF values assessed during the MVIC muscle actions, but increased MMG AMP. The results indicated that the velocity of the repeated eccentric muscle actions affected the MVIC torque responses, but not EIPT or any of the neuromuscular parameters. Furthermore, there are differences in the torque and neuromuscular responses for isometric vs. eccentric muscle actions after repeated eccentric muscle actions.

Evaluation of the sealing capability of implants to titanium and zirconia abutments against Porphyromonas gingivalis, Prevotella intermedia, and Fusobacterium nucleatum under different screw torque values.

PubMed

Smith, Nicole A; Turkyilmaz, Ilser

2014-09-01

When evaluating long-term implant success, clinicians have always been concerned with the gap at the implant-abutment junction, where bacteria can accumulate and cause marginal bone loss. However, little information regarding bacterial leakage at the implant-abutment junction, or microgap, is available. The purpose of this study was to evaluate sealing at 2 different implant-abutment interfaces under different screw torque values. Twenty sterile zirconia abutments and 20 sterile titanium abutments were screwed into 40 sterile implants and placed in test tubes. The ability of a bacterial mixture of Prevotella intermedia, Porphyromonas gingivalis, and Fusobacterium nucleatum to leak through an implant-titanium abutment seal under 20 and 35 Ncm torque values and an implant-zirconia abutment seal under 20 and 35 Ncm torque values was evaluated daily until leakage was noted. Once a unit demonstrated leakage, a specimen was plated. After 4 days, the number of colonies on each plate was counted with an electronic colony counter. Plating was used to verify whether or not bacterial leakage occurred and when leakage first occurred. The implant-abutment units were removed and rinsed with phosphate buffered saline solution and evaluated with a stereomicroscope. The marginal gap between the implant and the abutment was measured and correlated with the amount of bacterial leakage. The data were analyzed with ANOVA. Bacterial leakage was noted in all specimens, regardless of material or screw torque value. With titanium abutments, changing the screw torque value from 20 to 35 Ncm did not significantly affect the amount of bacterial leakage. However, with zirconia abutments, changing the screw torque value from 20 to 35 Ncm was statistically significant (P<.017). Overall, the marginal gap noted was larger at the zirconia-abutment interface (5.25 ±1.99 μm) than the titanium-abutment interface (12.38 ±3.73 μm), irrespective of the screw torque value. Stereomicroscopy revealed a nonuniform marginal gap in all specimens. The results of this study showed that, over time, bacteria will leak through the implant-abutment microgap at the implant-abutment interface. Implants with a titanium abutment demonstrate a smaller microgap than implants with a zirconia abutment. Tightening the zirconia abutment screw from 20 to 35 Ncm decreases the size of the microgap, which suggests a more intimate fit between the implant and the abutment. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Friction torque in thrust ball bearings grease lubricated

NASA Astrophysics Data System (ADS)

Ianuş, G.; Dumitraşcu, A. C.; Cârlescu, V.; Olaru, D. N.

2016-08-01

The authors investigated experimentally and theoretically the friction torque in a modified thrust ball bearing having only 3 balls operating at low axial load and lubricated with NGLI-00 and NGLI-2 greases. The experiments were made by using spin-down methodology and the results were compared with the theoretical values based on Biboulet&Houpert's rolling friction equations. Also, the results were compared with the theoretical values obtained with SKF friction model adapted for 3 balls. A very good correlation between experiments and Biboulet_&_Houpert's predicted results was obtained for the two greases. Also was observed that the theoretical values for the friction torque calculated with SKF model adapted for a thrust ball bearing having only 3 balls are smaller that the experimental values.

Mechanics of the taper integrated screwed-in (TIS) abutments used in dental implants.

PubMed

Bozkaya, Dinçer; Müftü, Sinan

2005-01-01

The tapered implant-abutment interface is becoming more popular due to the mechanical reliability of retention it provides. Consequently, understanding the mechanical properties of the tapered interface with or without a screw at the bottom has been the subject of a considerable amount of studies involving experiments and finite element (FE) analysis. This paper focuses on the tapered implant-abutment interface with a screw integrated at the bottom of the abutment. The tightening and loosening torques are the main factors in determining the reliability and the stability of the attachment. Analytical formulas are developed to predict tightening and loosening torque values by combining the equations related to the tapered interface with screw mechanics equations. This enables the identification of the effects of the parameters such as friction, geometric properties of the screw, the taper angle, and the elastic properties of the materials on the mechanics of the system. In particular, a relation between the tightening torque and the screw pretension is identified. It was shown that the loosening torque is smaller than the tightening torque for typical values of the parameters. Most of the tightening load is carried by the tapered section of the abutment, and in certain combinations of the parameters the pretension in the screw may become zero. The calculations performed to determine the loosening torque as a percentage of tightening torque resulted in the range 85-137%, depending on the values of taper angle and the friction coefficient.

Improving socket design to prevent difficult removal of locking screws.

PubMed

Lin, Chen-Huei; Chao, Ching-Kong; Tang, Yi-Hsuan; Lin, Jinn

2018-03-01

Reports of driver slippage leading to difficult locking screw removals have increased since the adoption of titanium for screw fabrication; the use of titanium is known to cause cross-threading and cold welding. Such problems occur most frequently in screws with hex sockets, and may cause serious surgical complications. This study aimed to improve screw socket design to prevent slippage and difficult screw removal. Three types of small sockets (hex, Torx, and cruciate) and six types of large sockets (hex, Torx, Octatorx, Torx+ I, Torx+ II, and Torx+ III) with screw head diameters of 5.5 mm were manufactured from titanium, and corresponding screwdrivers were manufactured from stainless steel. The screw heads and drivers were mounted on a material testing machine, and torsional tests were conducted to simulate screw usage in clinical settings at two insertion depths: 1 and 2 mm. Ten specimens were tested from each design, and the maximum torque and failure patterns were recorded and compared. For small sockets in 2 mm conditions, the hex with the largest driver core had the highest torque, followed by Torx and cruciate. In these tests, the drivers were twisted off in all specimens. However, under the 1 mm condition, the hex slipped and the torque decreased markedly. Overall, torque was higher for large sockets than for small sockets. The Octatorx, with a large core and simultaneous deformation of the driver and socket lobes, had the highest torque at almost twice that of the small hex. The hex had the lowest torque, a result of slippage in both the 1 and 2 mm conditions. Torx plus designs, with more designed degrees of freedom, were able to maintain a higher driving angle and larger core for higher torque. The hex design showed slipping tendencies with a marked decrease in torque, especially under conditions with inadequate driver engagement. Large sockets allowed for substantial increases in torque. The Torx, Octatorx, and Torx plus designs displayed better performance than the hexes. Improvements to the socket design could effectively prevent slippage and solve difficult screw removal problems. Copyright © 2018. Published by Elsevier Ltd.

SATURATED TORQUE FORMULA FOR PLANETARY MIGRATION IN VISCOUS DISKS WITH THERMAL DIFFUSION: RECIPE FOR PROTOPLANET POPULATION SYNTHESIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masset, F. S.; Casoli, J., E-mail: masset@fis.unam.m, E-mail: jules.casoli@cea.f, E-mail: masset@fis.unam.m

2010-11-10

We provide torque formulae for low-mass planets undergoing type I migration in gaseous disks. These torque formulae put special emphasis on the horseshoe drag, which is prone to saturation: the asymptotic value reached by the horseshoe drag depends on a balance between coorbital dynamics (which tends to cancel out or saturate the torque) and diffusive processes (which tend to restore the unperturbed disk profiles, thereby desaturating the torque). We entertain the question of this asymptotic value and derive torque formulae that give the total torque as a function of the disk's viscosity and thermal diffusivity. The horseshoe drag features twomore » components: one that scales with the vortensity gradient and another that scales with the entropy gradient and constitutes the most promising candidate for halting inward type I migration. Our analysis, which is complemented by numerical simulations, recovers characteristics already noted by numericists, namely, that the viscous timescale across the horseshoe region must be shorter than the libration time in order to avoid saturation and that, provided this condition is satisfied, the entropy-related part of the horseshoe drag remains large if the thermal timescale is shorter than the libration time. Side results include a study of the Lindblad torque as a function of thermal diffusivity and a contribution to the corotation torque arising from vortensity viscously created at the contact discontinuities that appear at the horseshoe separatrices. For the convenience of the reader mostly interested in the torque formulae, Section 8 is self-contained.« less

40 CFR 86.1333-90 - Transient test cycle generation.

Code of Federal Regulations, 2012 CFR

2012-07-01

... zero percent speed specified in the engine dynamometer schedules (appendix I (f)(1), (f)(2), or (f)(3... feedback torque equal to zero (using, for example, clutch disengagement, speed to torque control switching... reference speed and reference torque are zero percent values. For each idle segment that is ten seconds or...

40 CFR 86.1333-90 - Transient test cycle generation.

Code of Federal Regulations, 2013 CFR

2013-07-01

... zero percent speed specified in the engine dynamometer schedules (appendix I (f)(1), (f)(2), or (f)(3... feedback torque equal to zero (using, for example, clutch disengagement, speed to torque control switching... reference speed and reference torque are zero percent values. For each idle segment that is ten seconds or...

40 CFR 86.1333-90 - Transient test cycle generation.

Code of Federal Regulations, 2011 CFR

2011-07-01

... zero percent speed specified in the engine dynamometer schedules (appendix I (f)(1), (f)(2), or (f)(3... feedback torque equal to zero (using, for example, clutch disengagement, speed to torque control switching... reference speed and reference torque are zero percent values. For each idle segment that is ten seconds or...

Stereoscopic, Force-Feedback Trainer For Telerobot Operators

NASA Technical Reports Server (NTRS)

Kim, Won S.; Schenker, Paul S.; Bejczy, Antal K.

1994-01-01

Computer-controlled simulator for training technicians to operate remote robots provides both visual and kinesthetic virtual reality. Used during initial stage of training; saves time and expense, increases operational safety, and prevents damage to robots by inexperienced operators. Computes virtual contact forces and torques of compliant robot in real time, providing operator with feel of forces experienced by manipulator as well as view in any of three modes: single view, two split views, or stereoscopic view. From keyboard, user specifies force-reflection gain and stiffness of manipulator hand for three translational and three rotational axes. System offers two simulated telerobotic tasks: insertion of peg in hole in three dimensions, and removal and insertion of drawer.

Enhancement of the anti-damping spin torque efficacy of platinum by interface modification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Minh-Hai; Pai, Chi-Feng; Nguyen, Kayla X.

2015-06-01

We report a strong enhancement of the efficacy of the spin Hall effect (SHE) of Pt for exerting anti-damping spin torque on an adjacent ferromagnetic layer by the insertion of ≈0.5 nm layer of Hf between a Pt film and a thin, ≤2 nm, Fe{sub 60}Co{sub 20}B{sub 20} ferromagnetic layer. This enhancement is quantified by measurement of the switching current density when the ferromagnetic layer is the free electrode in a magnetic tunnel junction. The results are explained as the suppression of spin pumping through a substantial decrease in the effective spin-mixing conductance of the interface, but without a concomitant reduction ofmore » the ferromagnet's absorption of the SHE generated spin current.« less

How do geometry-related parameters influence the clinical performance of orthodontic mini-implants? A systematic review and meta-analysis.

PubMed

Cunha, A C; da Veiga, A M A; Masterson, D; Mattos, C T; Nojima, L I; Nojima, M C G; Maia, L C

2017-12-01

The aim of this systematic review and meta-analysis was to investigate how parameters related to geometry influence the clinical performance of orthodontic mini-implants (MIs). Systematic searches were performed in electronic databases including MEDLINE, Scopus, Web of Science, Virtual Health Library, and Cochrane Library and reference lists up to March 2016. Eligibility criteria comprised clinical studies involving patients who received MIs for orthodontic anchorage, with data for categories of MI dimension, shape, and thread design and insertion site, and evaluated by assessment of primary and secondary stability. Study selection, data extraction, quality assessment, and a meta-analysis were carried out. Twenty-seven studies were included in the qualitative synthesis: five randomized, eight prospective, and 14 retrospective clinical studies. One study with a serious risk of bias was later excluded. Medium and short MIs (1.4-1.9mm diameter and 5-8mm length) presented the highest success rates (0.87, 95% CI 0.80-0.92). A maximum insertion torque of 13.28Ncm (standard error 0.34) was observed for tapered self-drilling MIs in the mandible, whereas cylindrical MIs in the maxilla presented a maximum removal torque of 10.01Ncm (standard error 0.17). Moderate evidence indicates that the clinical performance of MIs is influenced by implant geometry parameters and is also related to properties of the insertion site. However, further research is necessary to support these associations. Copyright © 2017 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Validity of Torque-Data Collection at Multiple Sites: A Framework for Collaboration on Clinical-Outcomes Research in Sports Medicine.

PubMed

Kuenze, Christopher; Eltouhky, Moataz; Thomas, Abbey; Sutherlin, Mark; Hart, Joseph

2016-05-01

Collecting torque data using a multimode dynamometer is common in sports-medicine research. The error in torque measurements across multiple sites and dynamometers has not been established. To assess the validity of 2 calibration protocols across 3 dynamometers and the error associated with torque measurement for each system. Observational study. 3 university laboratories at separate institutions. 2 Biodex System 3 dynamometers and 1 Biodex System 4 dynamometer. System calibration was completed using the manufacturer-recommended single-weight method and an experimental calibration method using a series of progressive weights. Both calibration methods were compared with a manually calculated theoretical torque across a range of applied weights. Relative error, absolute error, and percent error were calculated at each weight. Each outcome variable was compared between systems using 95% confidence intervals across low (0-65 Nm), moderate (66-110 Nm), and high (111-165 Nm) torque categorizations. Calibration coefficients were established for each system using both calibration protocols. However, within each system the calibration coefficients generated using the single-weight (System 4 = 2.42 [0.90], System 3a = 1.37 [1.11], System 3b = -0.96 [1.45]) and experimental calibration protocols (System 4 = 3.95 [1.08], System 3a = -0.79 [1.23], System 3b = 2.31 [1.66]) were similar and displayed acceptable mean relative error compared with calculated theoretical torque values. Overall, percent error was greatest for all 3 systems in low-torque conditions (System 4 = 11.66% [6.39], System 3a = 6.82% [11.98], System 3b = 4.35% [9.49]). The System 4 significantly overestimated torque across all 3 weight increments, and the System 3b overestimated torque over the moderate-torque increment. Conversion of raw voltage to torque values using the single-calibration-weight method is valid and comparable to a more complex multiweight calibration process; however, it is clear that calibration must be done for each individual system to ensure accurate data collection.

Effects of recycling on the biomechanical characteristics of retrieved orthodontic miniscrews

PubMed Central

Yun, Soon-Dong; Choi, Sung-Hwan; Cha, Jung-Yul; Yu, Hyung-Seog; Kim, Kwang-Mahn; Kim, Jin

2017-01-01

Objective The aim of this study was to compare recycled and unused orthodontic miniscrews to determine the feasibility of reuse. The comparisons included both miniscrews with machined surfaces (MS), and those with etched surfaces (ES). Methods Retrieved MS and ES were further divided into three subgroups according to the assigned recycling procedure: group A, air-water spray; group B, mechanical cleaning; and group C, mechanical and chemical cleaning. Unused screws were used as controls. Scanning electron microscopy, energy-dispersive X-ray spectrometry, insertion time and maximum insertion torque measurements in artificial bone, and biological responses in the form of periotest values (PTV), bone–implant contact ratio (BIC), and bone volume ratio (BV) were assessed. Results Morphological changes after recycling mainly occurred at the screw tip, and the cortical bone penetration success rate of recycled screws was lower than that of unused screws. Retrieved ES needed more thorough cleaning than retrieved MS to produce a surface composition similar to that of unused screws. There were no significant differences in PTV or BIC between recycled and unused screws, while the BV of the former was significantly lower than that of the latter (p < 0.05). Conclusions These results indicate that reuse of recycled orthodontic miniscrews may not be feasible from the biomechanical aspect. PMID:28670565

Intramuscular pressure and torque during isometric, concentric and eccentric muscular activity

NASA Technical Reports Server (NTRS)

Styf, J.; Ballard, R.; Aratow, M.; Crenshaw, A.; Watenpaugh, D.; Hargens, A. R.

1995-01-01

Intramuscular pressures, electromyography (EMG) and torque generation during isometric, concentric and eccentric maximal isokinetic muscle activity were recorded in 10 healthy volunteers. Pressure and EMG activity were continuously and simultaneously measured side by side in the tibialis anterior and soleus muscles. Ankle joint torque and position were monitored continuously by an isokinetic dynamometer during plantar flexion and dorsiflexion of the foot. The increased force generation during eccentric muscular activity, compared with other muscular activity, was not accompanied by higher intramuscular pressure. Thus, this study demonstrated that eccentric muscular activity generated higher torque values for each increment of intramuscular pressure. Intramuscular pressures during antagonistic co-activation were significantly higher in the tibilis anterior muscle (42-46% of maximal agonistic activity) compared with the soleus muscle (12-29% of maximal agonistic activity) and was largely due to active recruitment of muscle fibers. In summary, eccentric muscular activity creates higher torque values with no additional increase of the intramuscular pressure compared with concentric and isometric muscular activity.

Evaluation of fracture torque resistance of orthodontic mini-implants.

PubMed

Dalla Rosa, Fernando; Burmann, Paola Fp; Ruschel, Henrique C; Vargas, Ivana A; Kramer, Paulo F

2016-12-01

This study sought to assess the fracture torque resistance of mini-implants used for orthodontic anchorage. Five commercially available brands of mini-implants were used (SIN®, CONEXÃO®, NEODENT®, MORELLI®, andFORESTADENT®). Ten mini-implants of each diameter of each brand were tested, for a total 100 specimens. The mini-implants were subject to a static torsion test as described in ASTMstandard F543. Analysis of variance (ANOVA) with the Tukey multiple comparisons procedure was used to assess results. Overall, mean fracture strength ranged from 15.7 to 70.4 N·cm. Mini-implants with larger diameter exhibited higher peak torque values at fracture and higher yield strength, regardless of brand. In addition, significant differences across brands were observed when implants were stratified by diameter. In conclusion, larger mini-implant diameter is associated with increased fracture torque resistance. Additional information on peak torque values at fracture of different commercial brands of mini-implants may increase the success rate of this orthodontic anchorage modality. Sociedad Argentina de Investigación Odontológica.

VHDL-AMS modelling and simulation of a planar electrostatic micromotor

NASA Astrophysics Data System (ADS)

Endemaño, A.; Fourniols, J. Y.; Camon, H.; Marchese, A.; Muratet, S.; Bony, F.; Dunnigan, M.; Desmulliez, M. P. Y.; Overton, G.

2003-09-01

System level simulation results of a planar electrostatic micromotor, based on analytical models of the static and dynamic torque behaviours, are presented. A planar variable capacitance (VC) electrostatic micromotor designed, fabricated and tested at LAAS (Toulouse) in 1995 is simulated using the high level language VHDL-AMS (VHSIC (very high speed integrated circuits) hardware description language-analog mixed signal). The analytical torque model is obtained by first calculating the overlaps and capacitances between different electrodes based on a conformal mapping transformation. Capacitance values in the order of 10-16 F and torque values in the order of 10-11 N m have been calculated in agreement with previous measurements and simulations from this type of motor. A dynamic model has been developed for the motor by calculating the inertia coefficient and estimating the friction-coefficient-based values calculated previously for other similar devices. Starting voltage results obtained from experimental measurement are in good agreement with our proposed simulation model. Simulation results of starting voltage values, step response, switching response and continuous operation of the micromotor, based on the dynamic model of the torque, are also presented. Four VHDL-AMS blocks were created, validated and simulated for power supply, excitation control, micromotor torque creation and micromotor dynamics. These blocks can be considered as the initial phase towards the creation of intellectual property (IP) blocks for microsystems in general and electrostatic micromotors in particular.

Influence of obstructive sleep apnea syndrome in the fluctuation of the submaximal isometric torque of knee extensors in patients with early-grade osteoarthritis

PubMed Central

Silva, Andressa; Mello, Marco T.; Serrão, Paula R.; Luz, Roberta P.; Bittencourt, Lia R.; Mattiello, Stela M.

2015-01-01

OBJECTIVE: The aim of this study was to investigate whether obstructive sleep apnea (OSA) alters the fluctuation of submaximal isometric torque of the knee extensors in patients with early-grade osteoarthritis (OA). METHOD: The study included 60 male volunteers, aged 40 to 70 years, divided into four groups: Group 1 (G1) - Control (n=15): without OA and without OSA; Group 2 (G2) (n=15): with OA and without OSA; Group 3 (G3) (n=15): without OA and with OSA; and Group 4 (G4) (n=15) with OA and with OSA. Five patients underwent maximal isometric contractions of 10 seconds duration each, with the knee at 60° of flexion to determine peak torque at 60°. To evaluate the fluctuation of torque, 5 submaximal isometric contractions (50% of maximum peak torque) of 10 seconds each, which were calculated from the standard deviation of torque and coefficient of variation, were performed. RESULTS: Significant differences were observed between groups for maximum peak torque, while G4 showed a lower value compared with G1 (p=0.005). Additionally, for the average torque exerted, G4 showed a lower value compared to the G1 (p=0.036). However, no differences were found between the groups for the standard deviation (p=0.844) and the coefficient of variation (p=0.143). CONCLUSION: The authors concluded that OSA did not change the parameters of the fluctuation of isometric submaximal torque of knee extensors in patients with early-grade OA. PMID:26443974

Model of the multipolar engine with decreased cogging torque by asymmetrical distribution of the magnets

NASA Astrophysics Data System (ADS)

Goryca, Zbigniew; Paduszyński, Kamil; Pakosz, Artur

2018-03-01

This paper presents the results of field calculations of cogging torque for a 12-pole torque motor with an 18-slot stator. A constant angular velocity magnet and the same size gap between n-1 magnets were assumed. In these conditions, the effect of change of the n-th gap between magnets on the cogging torque was tested. Due to considerable length of the machine the calculations were performed using a 2D model. The n-th gap for which the cogging torque assumed the lowest value was evaluated. The cogging torque of the machine with symmetrical magnetic circuit (the same size of gap between magnets) was compared to the one of the asymmetrical machine. With proper choice of asymmetry, the cogging torque for the machine decreased by four times.

Effect of environmental torques on short-term attitude prediction for a rolling-wheel spacecraft in a sun-synchronous orbit

NASA Technical Reports Server (NTRS)

Hodge, W. F.

1972-01-01

A numerical evaluation and an analysis of the effects of environmental disturbance torques on the attitude of a hexagonal cylinder rolling wheel spacecraft were performed. The resulting perturbations caused by five such torques were found to be very small and exhibited linearity such that linearized equations of motion yielded accurate results over short periods and the separate perturbations contributed by each torque were additive in the sense of superposition. Linearity of the torque perturbations was not affected by moderate system design changes and persisted for torque-to-angular momentum ratios up to 100 times the nominal expected value. As these conditions include many possible applications, similar linear behavior might be anticipated for other rolling-wheel spacecraft.

Coordinating bracket torque and incisor inclination : Part 3: Validity of bracket torque values in achieving norm inclinations.

PubMed

Zimmer, Bernd; Sino, Hiba

2018-03-19

To analyze common values of bracket torque (Andrews, Roth, MBT, Ricketts) for their validity in achieving incisor inclinations that are considered normal by different cephalometric standards. Using the equations developed in part 1 (eU1 (BOP) = 90° - BT (U1) - TCA (U1) + α 1 - α 2 and eL1 (BOP) = 90° - BT (L1) - TCA (L1) + β 1 - β 2 ) (abbreviations see part 1) and the mean values (± SD) obtained as statistical measures in parts 1 and 2 of the study (α 1 and β 1 [1.7° ± 0.7°], α 2 [3.6° ± 0.3°], β 2 [3.2° ± 0.4°], TCA (U1) [24.6° ± 3.6°] and TCA (L1) [22.9° ± 4.3°]) expected (= theoretically anticipated) values were calculated for upper and lower incisors (U1 and L1) and compared to targeted (= cephalometric norm) values. For U1, there was no overlapping between the ranges of expected and targeted values, as the lowest targeted value of (58.3°; Ricketts) was higher than the highest expected value (56.5°; Andrews) relative to the bisected occlusal plane (BOP). Thus all of these torque systems will aim for flatter inclinations than prescribed by any of the norm values. Depending on target values, the various bracket systems fell short by 1.8-5.5° (Andrews), 6.8-10.5° (Roth), 11.8-15.5° (MBT), or 16.8-20.5° (Ricketts). For L1, there was good agreement of the MBT system with the Ricketts and Björk target values (Δ0.1° and Δ-0.8°, respectively), and both the Roth and Ricketts systems came close to the Bergen target value (both Δ2.3°). Depending on target values, the ranges of deviation for L1 were 6.3-13.2° for Andrews (Class II prescription), 2.3°-9.2° for Roth, -3.7 to -3.2° for MBT, and 2.3-9.2° for Ricketts. Common values of upper incisor bracket torque do not have acceptable validity in achieving normal incisor inclinations. A careful selection of lower bracket torque may provide satisfactory matching with some of the targeted norm values.

Torsional stability of interference screws derived from bovine bone - a biomechanical study

PubMed Central

2010-01-01

Background In the present biomechanical study, the torsional stability of different interference screws, made of bovine bone, was tested. Interference screws derived from bovine bone are a possible biological alternative to conventional metallic or bioabsorbable polymer interference screws. Methods In the first part of the study we compared the torsional stability of self-made 8 mm Interference screws (BC) and a commercial 8 mm interference screw (Tutofix®). Furthermore, we compared the torsional strength of BC screws with different diameters. For screwing in, a hexagon head and an octagon head were tested. Maximum breaking torques in polymethyl methacrylate resin were recorded by means of an electronic torque screw driver. In the second part of the study the tibial part of a bone-patellar tendon-bone graft was fixed in porcine test specimens using an 8 mm BC screw and the maximum insertion torques were recorded. Each interference screw type was tested 5 times. Results There was no statistically significant difference between the different 8 mm interference screws (p = 0.121). Pairwise comparisons did not reveal statistically significant differences, either. It was demonstrated for the BC screws, that a larger screw diameter significantly leads to higher torsional stability (p = 9.779 × 10-5). Pairwise comparisons showed a significantly lower torsional stability for the 7 mm BC screw than for the 8 mm BC screw (p = 0.0079) and the 9 mm BC screw (p = 0.0079). Statistically significant differences between the 8 mm and the 9 mm BC screw could not be found (p = 0.15). During screwing into the tibial graft channel of the porcine specimens, insertion torques between 0.5 Nm and 3.2 Nm were recorded. In one case the hexagon head of a BC screw broke off during the last turn. Conclusions The BC screws show comparable torsional stability to Tutofix® interference screws. As expected the torsional strength of the screws increases significantly with the diameter. The safety and in vivo performance of products derived from xenogeneic bone should be the focus of further investigations. PMID:20433761

A rationale method for evaluating unscrewing torque values of prosthetic screws in dental implants

PubMed Central

SALIBA, Felipe Miguel; CARDOSO, Mayra; TORRES, Marcelo Ferreira; TEIXEIRA, Alexandre Carvalho; LOURENÇO, Eduardo José Veras; TELLES, Daniel de Moraes

2011-01-01

Objectives Previous studies that evaluated the torque needed for removing dental implant screws have not considered the manner of transfer of the occlusal loads in clinical settings. Instead, the torque used for removal was applied directly to the screw, and most of them omitted the possibility that the hexagon could limit the action of the occlusal load in the loosening of the screws. The present study proposes a method for evaluating the screw removal torque in an anti-rotational device independent way, creating an unscrewing load transfer to the entire assembly, not only to the screw. Material and methods Twenty hexagonal abutments without the hexagon in their bases were fixed with a screw to 20 dental implants. They were divided into two groups: Group 1 used titanium screws and Group 2 used titanium screws covered with a solid lubricant. A torque of 32 Ncm was applied to the screw and then a custom-made wrench was used for rotating the abutment counterclockwise, to loosen the screw. A digital torque meter recorded the torque required to loosen the abutment. Results There was a significant difference between the means of Group 1 (38.62±6.43 Ncm) and Group 2 (48.47±5.04 Ncm), with p=0.001. Conclusion This methodology was effective in comparing unscrewing torque values of the implant-abutment junction even with a limited sample size. It confirmed a previously shown significant difference between two types of screws. PMID:21437472

Primary implant stability in a bone model simulating clinical situations for the posterior maxilla: an in vitro study

PubMed Central

2016-01-01

Purpose The aim of this study was to determine the influence of anatomical conditions on primary stability in the models simulating posterior maxilla. Methods Polyurethane blocks were designed to simulate monocortical (M) and bicortical (B) conditions. Each condition had four subgroups measuring 3 mm (M3, B3), 5 mm (M5, B5), 8 mm (M8, B8), and 12 mm (M12, B12) in residual bone height (RBH). After implant placement, the implant stability quotient (ISQ), Periotest value (PTV), insertion torque (IT), and reverse torque (RT) were measured. Two-factor ANOVA (two cortical conditions×four RBHs) and additional analyses for simple main effects were performed. Results A significant interaction between cortical condition and RBH was demonstrated for all methods measuring stability with two-factor ANOVA. In the analyses for simple main effects, ISQ and PTV were statistically higher in the bicortical groups than the corresponding monocortical groups, respectively. In the monocortical group, ISQ and PTV showed a statistically significant rise with increasing RBH. Measurements of IT and RT showed a similar tendency, measuring highest in the M3 group, followed by the M8, the M5, and the M12 groups. In the bicortical group, all variables showed a similar tendency, with different degrees of rise and decline. The B8 group showed the highest values, followed by the B12, the B5, and the B3 groups. The highest coefficient was demonstrated between ISQ and PTV. Conclusions Primary stability was enhanced by the presence of bicortex and increased RBH, which may be better demonstrated by ISQ and PTV than by IT and RT. PMID:27588215

The effects of cortical bone thickness and trabecular bone strength on noninvasive measures of the implant primary stability using synthetic bone models.

PubMed

Hsu, Jui-Ting; Fuh, Lih-Jyh; Tu, Ming-Gene; Li, Yu-Fen; Chen, Kuan-Ting; Huang, Heng-Li

2013-04-01

This study investigated how the primary stability of a dental implant as measured by the insertion torque value (ITV), Periotest value (PTV), and implant stability quotient (ISQ) is affected by varying thicknesses of cortical bone and strengths of trabecular bone using synthetic bone models. Four synthetic cortical shells (with thicknesses of 0, 1, 2, and 3 mm) were attached to four cellular rigid polyurethane foams (with elastic moduli of 137, 47.5, 23, and 12.4 MPa) and one open-cell rigid polyurethane foam which mimic the osteoporotic bone (with an elastic modulus 6.5 MPa), to represent the jawbones with various cortical bone thicknesses and strengths of trabecular bone. A total of 60 bone specimens accompanied with implants was examined by a torque meter, Osstell resonance frequency analyzer, and Periotest electronic device. All data were statistically analyzed by two-way analysis of variance. In addition, second-order nonlinear regression was utilized to assess the correlations of the primary implant stability with the four cortex thicknesses and five strengths of trabecular bone. ITV, ISQ, and PTV differed significantly (p < .05) and were strongly correlated with the thickness of cortical bone (R(2) > 0.9) and the elastic modulus of trabecular bone (R(2) = 0.74-0.99). The initial stability at the time of implant placement is influenced by both the cortical bone thickness and the strength of trabecular bone; however, these factors are mostly nonlinearly correlated with ITV, PTV, and ISQ. Using ITV and PTV seems more suitable for identifying the primary implant stability in osteoporotic bone with a thin cortex. © 2011 Wiley Periodicals, Inc.

77 FR 12450 - Airworthiness Directives; BRP-Powertrain GmbH & Co KG Rotax Reciprocating Engines

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-01

... have been tightened to the correct torque value, i.e. not in accordance with the specification. This... AD requires performing a one-time inspection of the oil system for leaks and a torque check of the... performing a one-time inspection of the oil system for leaks and a torque check of the oil pump attachment...

76 FR 9513 - Airworthiness Directives; BURKHART GROB LUFT-UND Model G 103 C Twin III SL Gliders

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-18

... plate) and tighten it, applying the torque following page 6.12 of the G 103 C TWIN III SL Maintenance...: The torque values and tolerances of the upper pulley wheel grooved nut have been standardized in the..., before further flight, readjust the torque of the upper pulley wheel grooved nut using the updated...

Displaying Force and Torque of A Manipulator

NASA Technical Reports Server (NTRS)

Bejczy, A. K.; Dotson, R. S.; Primus, H. C.

1984-01-01

Display combines bar charts, vector diagrams, and numerical values to inform operator of forces and torques exerted by end effector of manipulator. On voice or keyboard command, eight-channel strip-chart recorder traces force and torque components and claw position of raw measurements from eight strain gage sensors in end effector. Especially helpful when operator's view of end effector is obscured.

Evaluation of screw loosening on new abutment screws and after successive tightening.

PubMed

Barbosa, Gustavo Seabra; Silva-Neto, João Paulo da; Simamoto-Júnior, Paulo Cezar; Neves, Flávio Domingues das; Mattos, Maria da Gloria Chiarello de; Ribeiro, Ricardo Faria

2011-01-01

This study evaluated the loss of the torque applied after use of new screws and after successive tightening. Four infrastructures (IE), using UCLA castable abutment type, were cast in cobalt-chromium alloy and new abutment screws (G1) were used in a first moment. Subsequently, the same abutment screws were used a second time (G2) and more than two times (G3). The values of the torques applied and detorques were measured with a digital torque wrench to obtain the values of initial tightening loss (%). Data were analyzed by ANOVA and Tukey's test (?=0.05). Significant differences were observed between the G1 (50.71% ± 11.36) and G2 (24.01% ± 3.33) (p=0.000) and between G1 (50.71% ± 11.36) and G3 (25.60% ± 4.64) (p=0.000). There was no significant difference between G2 and G3 (p=0.774). Within the limitations of the study, it may be concluded that the percentage of the initial torque loss is lower when screws that already suffered the application of an initial torque were used, remaining stable after application of successive torques.

Design optimization of an axial-field eddy-current magnetic coupling based on magneto-thermal analytical model

NASA Astrophysics Data System (ADS)

Fontchastagner, Julien; Lubin, Thierry; Mezani, Smaïl; Takorabet, Noureddine

2018-03-01

This paper presents a design optimization of an axial-flux eddy-current magnetic coupling. The design procedure is based on a torque formula derived from a 3D analytical model and a population algorithm method. The main objective of this paper is to determine the best design in terms of magnets volume in order to transmit a torque between two movers, while ensuring a low slip speed and a good efficiency. The torque formula is very accurate and computationally efficient, and is valid for any slip speed values. Nevertheless, in order to solve more realistic problems, and then, take into account the thermal effects on the torque value, a thermal model based on convection heat transfer coefficients is also established and used in the design optimization procedure. Results show the effectiveness of the proposed methodology.

Variation in the total lengths of abutment/implant assemblies generated with a function of applied tightening torque in external and internal implant-abutment connection.

PubMed

Kim, Ki-Seong; Lim, Young-Jun; Kim, Myung-Joo; Kwon, Ho-Beom; Yang, Jae-Ho; Lee, Jai-Bong; Yim, Soon-Ho

2011-08-01

Settling (embedment relaxation), which is the main cause for screw loosening, is developed by microroughness between implant and abutment metal surface. The objective of this study was to evaluate and compare the relationship between the level of applied torque and the settling of abutments into implants in external and internal implant-abutment connection. Five different implant-abutment connections were used (Ext, External butt joint + two-piece abutment; Int-H2, Internal hexagon + two-piece abutment; Int-H1, Internal hexagon + one-piece abutment; Int-O2, Internal octagon + two-piece abutment; Int-O1, Internal octagon + one-piece abutment). All abutments of each group were assembled and tightened with corresponding implants by a digital torque gauge. The total lengths of implant-abutment samples were measured at each torque (5, 10, 30 N cm and repeated 30 N cm with 10-min interval) by an electronic digital micrometer. The settling values were calculated by changes between the total lengths of implant-abutment samples. All groups developed settling with repeated tightening. The Int-H2 group showed markedly higher settling for all instances of tightening torque and the Ext group was the lowest. Statistically significant differences were found in settling values between the groups and statistically significant increases were observed within each group at different tightening torques (P<0.05). After the second tightening of 30 N cm, repeated tightening showed almost constant settling values. Results from the present study suggested that to minimize the settling effect, abutment screws should be retightened at least twice at 30 N cm torque at a 10-min interval in all laboratory and clinical procedures. © 2010 John Wiley & Sons A/S.

Friction losses in a lubricated thrust-loaded cageless angular-contract bearing

NASA Technical Reports Server (NTRS)

Townsend, D. P.; Allen, C. W.; Zaretsky, E. V.

1973-01-01

The NASA spinning torque apparatus was modified to measure the spinning torque on a cageless ball thrust bearing. Friction torque was measured for thrust loads varying from 44.5 to 403 newtons (10 to 90 lb) at speeds of 1000, 2000, and 3000 rpm. Tests were conducted with di-2-ethylhexyl sebacate and a synthetic paraffinic oil. These tests were run with either oil jet lubrication or with a thin surface film of lubricant only. An analytical model which included rolling resistance was developed and extended from previous models for spinning torque and lubricant rheology. The model was extended by the inclusion of rolling resistance. The computed values were in fair agreement with the experimental results and confirmed previous hypotheses that a thin lubricant film gives minimum bearing torque and an oil jet flow of a viscous lubricant will result in considerable rolling torque in addition to the torque due to ball spin.

Torque Control of a Rehabilitation Teaching Robot Using Magneto-Rheological Fluid Clutches

NASA Astrophysics Data System (ADS)

Hakogi, Hokuto; Ohaba, Motoyoshi; Kuramochi, Naimu; Yano, Hidenori

A new robot that makes use of MR-fluid clutches for simulating torque is proposed to provide an appropriate device for training physical therapy students in knee-joint rehabilitation. The feeling of torque provided by the robot is expected to correspond to the torque performance obtained by physical therapy experts in a clinical setting. The torque required for knee-joint rehabilitation, which is a function of the rotational angle and the rotational angular velocity of a knee movement, is modeled using a mechanical system composed of typical spring-mass-damper elements. The robot consists of two MR-fluid clutches, two induction motors, and a feedback control system. In the torque experiments, output torque is controlled using the spring and damper coefficients separately. The values of these coefficients are determined experimentally. The experimental results show that the robot would be suitable for training physical therapy students to experience similar torque feelings as needed in a clinical situation.

Influence of the implant-abutment connection design and diameter on the screw joint stability.

PubMed

Shin, Hyon-Mo; Huh, Jung-Bo; Yun, Mi-Jeong; Jeon, Young-Chan; Chang, Brian Myung; Jeong, Chang-Mo

2014-04-01

This study was conducted to evaluate the influence of the implant-abutment connection design and diameter on the screw joint stability. Regular and wide-diameter implant systems with three different joint connection designs: an external butt joint, a one-stage internal cone, and a two-stage internal cone were divided into seven groups (n=5, in each group). The initial removal torque values of the abutment screw were measured with a digital torque gauge. The postload removal torque values were measured after 100,000 cycles of a 150 N and a 10 Hz cyclic load had been applied. Subsequently, the rates of the initial and postload removal torque losses were calculated to evaluate the effect of the joint connection design and diameter on the screw joint stability. Each group was compared using Kruskal-Wallis test and Mann-Whitney U test as post-hoc test (α=0.05). THE POSTLOAD REMOVAL TORQUE VALUE WAS HIGH IN THE FOLLOWING ORDER WITH REGARD TO MAGNITUDE: two-stage internal cone, one-stage internal cone, and external butt joint systems. In the regular-diameter group, the external butt joint and one-stage internal cone systems showed lower postload removal torque loss rates than the two-stage internal cone system. In the wide-diameter group, the external butt joint system showed a lower loss rate than the one-stage internal cone and two-stage internal cone systems. In the two-stage internal cone system, the wide-diameter group showed a significantly lower loss rate than the regular-diameter group (P<.05). The results of this study showed that the external butt joint was more advantageous than the internal cone in terms of the postload removal torque loss. For the difference in the implant diameter, a wide diameter was more advantageous in terms of the torque loss rate.

Influence of the implant-abutment connection design and diameter on the screw joint stability

PubMed Central

Shin, Hyon-Mo; Huh, Jung-Bo; Yun, Mi-Jeong; Jeon, Young-Chan; Chang, Brian Myung

2014-01-01

PURPOSE This study was conducted to evaluate the influence of the implant-abutment connection design and diameter on the screw joint stability. MATERIALS AND METHODS Regular and wide-diameter implant systems with three different joint connection designs: an external butt joint, a one-stage internal cone, and a two-stage internal cone were divided into seven groups (n=5, in each group). The initial removal torque values of the abutment screw were measured with a digital torque gauge. The postload removal torque values were measured after 100,000 cycles of a 150 N and a 10 Hz cyclic load had been applied. Subsequently, the rates of the initial and postload removal torque losses were calculated to evaluate the effect of the joint connection design and diameter on the screw joint stability. Each group was compared using Kruskal-Wallis test and Mann-Whitney U test as post-hoc test (α=0.05). RESULTS The postload removal torque value was high in the following order with regard to magnitude: two-stage internal cone, one-stage internal cone, and external butt joint systems. In the regular-diameter group, the external butt joint and one-stage internal cone systems showed lower postload removal torque loss rates than the two-stage internal cone system. In the wide-diameter group, the external butt joint system showed a lower loss rate than the one-stage internal cone and two-stage internal cone systems. In the two-stage internal cone system, the wide-diameter group showed a significantly lower loss rate than the regular-diameter group (P<.05). CONCLUSION The results of this study showed that the external butt joint was more advantageous than the internal cone in terms of the postload removal torque loss. For the difference in the implant diameter, a wide diameter was more advantageous in terms of the torque loss rate. PMID:24843398

Torquing preload in a lubricated bolt

NASA Technical Reports Server (NTRS)

Seegmiller, H. L.

1978-01-01

The tension preload obtained by torquing a 7/8 in. diam UNC high strength bolt was determined for lubricated and dry conditions. Consistent preload with a variation of + or - 3% was obtained when the bolt head area was lubricated prior to each torque application. Preload tensions nearly 70% greater than the value predicted with the commonly used formula occurred with the lubricated bolt. A reduction to 39% of the initial preload was observed during 50 torque applications without relubrication. Little evidence of wear was noted after 203 cycles of tightening.

The Effects of Racket Inertia Tensor on Elbow Loadings and Racket Behavior for Central and Eccentric Impacts

PubMed Central

Nesbit, Steven M.; Elzinga, Michael; Herchenroder, Catherine; Serrano, Monika

2006-01-01

This paper discusses the inertia tensors of tennis rackets and their influence on the elbow swing torques in a forehand motion, the loadings transmitted to the elbow from central and eccentric impacts, and the racket acceleration responses from central and eccentric impacts. Inertia tensors of various rackets with similar mass and mass center location were determined by an inertia pendulum and were found to vary considerably in all three orthogonal directions. Tennis swing mechanics and impact analyses were performed using a computer model comprised of a full-body model of a human, a parametric model of the racket, and an impact function. The swing mechanics analysis of a forehand motion determined that inertia values had a moderate linear effect on the pronation-supination elbow torques required to twist the racket, and a minor effect on the flexion-extension and valgus-varus torques. The impact analysis found that mass center inertia values had a considerable effect on the transmitted torques for both longitudinal and latitudinal eccentric impacts and significantly affected all elbow torque components. Racket acceleration responses to central and eccentric impacts were measured experimentally and found to be notably sensitive to impact location and mass center inertia values. Key Points Tennis biomechanics. Racket inertia tensor. Impact analysis. Full-body computer model. PMID:24260004

Probabilistic analysis of preload in the abutment screw of a dental implant complex.

PubMed

Guda, Teja; Ross, Thomas A; Lang, Lisa A; Millwater, Harry R

2008-09-01

Screw loosening is a problem for a percentage of implants. A probabilistic analysis to determine the cumulative probability distribution of the preload, the probability of obtaining an optimal preload, and the probabilistic sensitivities identifying important variables is lacking. The purpose of this study was to examine the inherent variability of material properties, surface interactions, and applied torque in an implant system to determine the probability of obtaining desired preload values and to identify the significant variables that affect the preload. Using software programs, an abutment screw was subjected to a tightening torque and the preload was determined from finite element (FE) analysis. The FE model was integrated with probabilistic analysis software. Two probabilistic analysis methods (advanced mean value and Monte Carlo sampling) were applied to determine the cumulative distribution function (CDF) of preload. The coefficient of friction, elastic moduli, Poisson's ratios, and applied torque were modeled as random variables and defined by probability distributions. Separate probability distributions were determined for the coefficient of friction in well-lubricated and dry environments. The probabilistic analyses were performed and the cumulative distribution of preload was determined for each environment. A distinct difference was seen between the preload probability distributions generated in a dry environment (normal distribution, mean (SD): 347 (61.9) N) compared to a well-lubricated environment (normal distribution, mean (SD): 616 (92.2) N). The probability of obtaining a preload value within the target range was approximately 54% for the well-lubricated environment and only 0.02% for the dry environment. The preload is predominately affected by the applied torque and coefficient of friction between the screw threads and implant bore at lower and middle values of the preload CDF, and by the applied torque and the elastic modulus of the abutment screw at high values of the preload CDF. Lubrication at the threaded surfaces between the abutment screw and implant bore affects the preload developed in the implant complex. For the well-lubricated surfaces, only approximately 50% of implants will have preload values within the generally accepted range. This probability can be improved by applying a higher torque than normally recommended or a more closely controlled torque than typically achieved. It is also suggested that materials with higher elastic moduli be used in the manufacture of the abutment screw to achieve a higher preload.

Advantages and disadvantages of new torque-controlled endodontic motors and low-torque NiTi rotary instrumentation.

PubMed

Gambarini, G

2001-12-01

The main problem with the NiTi rotary instrumentation technique is instrument failure. During shaping procedures, rotary instruments might lock and/or screw into canals and, consequently, be subjected to high levels of stress. This may frequently lead to instrument separation or deformation. If a high-torque motor is used, the applied forces are usually very high and the instrument-fracture limit is often exceeded, thus increasing the risk of intracanal failure. A possible solution of this problem is to use a low-torque endodontic motor, which operates below the maximum permissible torque limit of each and every rotary instrument. During clinical instrumentation of root canals, if a torque-controlled motor is loaded right up to the instrument-specific torque, the motor stops momentarily and/or starts rotating counter-clockwise (auto-reverse function) to disengage the locked instrument. These safety mechanisms were developed to reduce the risk of instrument fracture. The author fully discusses the rationale for selecting lower torque values in everyday endodontic practice, and provides clinicians with useful information on the advantages and disadvantages of new endodontic motors with torque control.

Comparing of cogging torque reduction methods in permanent magnet machines with fractional slot windings

NASA Astrophysics Data System (ADS)

Pristup, A. G.; Toporkov, D. M.

2017-10-01

The results of the investigation of the cogging torque in permanent magnet synchronous machines, which is caused by the stator slotting and the rotor eccentricity, are presented in the paper. A new design of the machine has been developed in the course of the investigation, and the value of the cogging torque in this construction is less considerably compared to other constructions. In contrast to the available methods of the cogging torque reduction, the solution suggested not only decreases the level of the cogging torque but also has negligibly small influence on characteristics of the machine with the rotor eccentricity which is typical of the mass production and long-term usage.

Current induced domain wall dynamics in the presence of spin orbit torques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boulle, O., E-mail: Olivier.boulle@cea.fr; Buda-Prejbeanu, L. D.; Jué, E.

2014-05-07

Current induced domain wall (DW) motion in perpendicularly magnetized nanostripes in the presence of spin orbit torques is studied. We show using micromagnetic simulations that the direction of the current induced DW motion and the associated DW velocity depend on the relative values of the field like torque (FLT) and the Slonczewski like torques (SLT). The results are well explained by a collective coordinate model which is used to draw a phase diagram of the DW dynamics as a function of the FLT and the SLT. We show that a large increase in the DW velocity can be reached bymore » a proper tuning of both torques.« less

Multivariate linear regression analysis to identify general factors for quantitative predictions of implant stability quotient values

PubMed Central

Huang, Hairong; Xu, Zanzan; Shao, Xianhong; Wismeijer, Daniel; Sun, Ping; Wang, Jingxiao

2017-01-01

Objectives This study identified potential general influencing factors for a mathematical prediction of implant stability quotient (ISQ) values in clinical practice. Methods We collected the ISQ values of 557 implants from 2 different brands (SICace and Osstem) placed by 2 surgeons in 336 patients. Surgeon 1 placed 329 SICace implants, and surgeon 2 placed 113 SICace implants and 115 Osstem implants. ISQ measurements were taken at T1 (immediately after implant placement) and T2 (before dental restoration). A multivariate linear regression model was used to analyze the influence of the following 11 candidate factors for stability prediction: sex, age, maxillary/mandibular location, bone type, immediate/delayed implantation, bone grafting, insertion torque, I-stage or II-stage healing pattern, implant diameter, implant length and T1-T2 time interval. Results The need for bone grafting as a predictor significantly influenced ISQ values in all three groups at T1 (weight coefficients ranging from -4 to -5). In contrast, implant diameter consistently influenced the ISQ values in all three groups at T2 (weight coefficients ranging from 3.4 to 4.2). Other factors, such as sex, age, I/II-stage implantation and bone type, did not significantly influence ISQ values at T2, and implant length did not significantly influence ISQ values at T1 or T2. Conclusions These findings provide a rational basis for mathematical models to quantitatively predict the ISQ values of implants in clinical practice. PMID:29084260

A torque balance measurement of anisotropy of the magnetic susceptibility in white matter.

PubMed

van Gelderen, Peter; Mandelkow, Hendrik; de Zwart, Jacco A; Duyn, Jeff H

2015-11-01

Recent MRI studies have suggested that the magnetic susceptibility of white matter (WM) in the human brain is anisotropic, providing a new contrast mechanism for the visualization of fiber bundles and allowing the extraction of cellular compartment-specific information. This study provides an independent confirmation and quantification of this anisotropy. Anisotropic magnetic susceptibility results in a torque exerted on WM when placed in a uniform magnetic field, tending to align the WM fibers with the field. To quantify the effect, excised spinal cord samples were placed in a torque balance inside the magnet of a 7 T MRI system and the magnetic torque was measured as function of orientation. All tissue samples (n = 5) showed orienting effects, confirming the presence of anisotropic susceptibility. Analysis of the magnetic torque resulted in reproducible values for the WM volume anisotropy that ranged from 13.6 to 19.2 ppb. The independently determined anisotropy values confirm estimates inferred from MRI experiments and validate the use of anisotropy to extract novel information about brain fiber structure and myelination. © 2014 Wiley Periodicals, Inc.

Evaluation of MSFC-STD-486, ''Threaded Fasteners, Torque Limits For'' for use in the construction of aerospace vhicles

NASA Technical Reports Server (NTRS)

Hart, J. F.

1973-01-01

MSFC-STD-486, Threaded Fasteners, Torque Limits For, is a relatively new standard that has not had much user experience. This test was run to provide such experience and verify the values in MSFC-STD-486. This was accomplished by plotting torque-tension curves on aluminum and alloy steel aircraft quality bolts and nuts through 1/2 inch in diameter.

Reduction of Risk for Low Back Injury in Theater of Operations

DTIC Science & Technology

2015-06-01

Assessed for eligibility (n = 698) 14 Figure 4. Predicted (from regression) isometric lumbar extension strength ( torque ) mean values (adjusted by...resistance exercise to the lumbar extensors in the ranges required for strength development, torque production from the gluteals and hamstrings must be...the small lumbar muscles play only a minor role in trunk extension torque production.17 Thus, they are considered to be the weak link in trunk

Muscle activation and the isokinetic torque-velocity relationship of the human triceps surae.

PubMed

Harridge, S D; White, M J

1993-01-01

The influence of muscle activation and the time allowed for torque generation on the angle-specific torque-velocity relationship of the triceps surae was studied during plantar flexion using supramaximal electrical stimulation and a release technique on six male subjects [mean (SD) age 25 (4) years]. Torque-velocity data were obtained under different levels of constant muscle activation by varying the stimulus frequency and the time allowed for isometric torque generation prior to release and isokinetic shortening. To eliminate the effects of the frequency response on absolute torque the isokinetic data were normalized to the maximum isometric torque values at 0.44 rad. There were no significant differences in the normalized torques generated at any angular velocity using stimulus frequencies of 20, 50 or 80 Hz. When the muscle was stimulated at 50 Hz the torques obtained after a 400 ms and 1 s pre-release isometric contraction did not differ significantly. However, with no pre-release contraction significantly less torque was generated at all angular velocities beyond 1.05 rad.s-1 when compared with either the 200, 400 ms or 1 s condition. With a 200 ms pre-release contraction significantly less torque was generated at angular velocities beyond 1.05 rad.s-1 when compared with the 400 ms or 1 s conditions. It would seem that the major factor governing the shape of the torque-velocity curve at a constant level of muscle activation is the time allowed for torque generation.

Effect of plyometric training on lower limb biomechanics in females.

PubMed

Baldon, Rodrigo de Marche; Moreira Lobato, Daniel F; Yoshimatsu, Andre P; dos Santos, Ana Flávia; Francisco, Andrea L; Pereira Santiago, Paulo R; Serrão, Fábio V

2014-01-01

To verify the effects of plyometric training on lower limb kinematics, eccentric hip and knee torques, and functional performance. Cohort study. Research laboratory. Thirty-six females were divided into a training group (TG; n = 18) that carried out the plyometric training for 8 weeks, and a control group (CG; n = 18) that carried out no physical training. Twenty-four plyometric training sessions during approximately 8 weeks with 3 sessions per week on alternate days. Lower limb kinematics (maximum excursion of hip adduction, hip medial rotation, and knee abduction during the single leg squat), eccentric hip (abductor, adductor, medial, and lateral rotator) isokinetic peak torques and knee (flexor and extensor) isokinetic peak torques, and functional performance (triple hop test and the 6-m timed hop test). After 8 weeks, only the TG significantly reduced the values for the maximum excursion of knee abduction (P = 0.01) and hip adduction (P < 0.001). Similarly, only the TG significantly increased the eccentric hip abductor (P < 0.001) and adductor (P = 0.01) torques. Finally, only the TG significantly increased the values in the triple hop test (P < 0.001) and significantly decreased the values in the 6-m timed hop test (P < 0.001) after intervention. Plyometric training alters lower limb kinematics and increases eccentric hip torque and functional performance, suggesting the incorporation of these exercises in preventive programs for ACL injuries.

Loosening torque of Universal Abutment screws after cyclic loading: influence of tightening technique and screw coating.

PubMed

Bacchi, Atais; Regalin, Alexandre; Bhering, Claudia Lopes Brilhante; Alessandretti, Rodrigo; Spazzin, Aloisio Oro

2015-10-01

The purpose of this study was to evaluate the influence of tightening technique and the screw coating on the loosening torque of screws used for Universal Abutment fixation after cyclic loading. Forty implants (Titamax Ti Cortical, HE, Neodent) (n=10) were submerged in acrylic resin and four tightening techniques for Universal Abutment fixation were evaluated: A - torque with 32 Ncm (control); B - torque with 32 Ncm holding the torque meter for 20 seconds; C - torque with 32 Ncm and retorque after 10 minutes; D - torque (32 Ncm) holding the torque meter for 20 seconds and retorque after 10 minutes as initially. Samples were divided into subgroups according to the screw used: conventional titanium screw or diamond like carbon-coated (DLC) screw. Metallic crowns were fabricated for each abutment. Samples were submitted to cyclic loading at 10(6) cycles and 130 N of force. Data were analyzed by two-way ANOVA and Tukey's test (5%). The tightening technique did not show significant influence on the loosening torque of screws (P=.509). Conventional titanium screws showed significant higher loosening torque values than DLC (P=.000). The use of conventional titanium screw is more important than the tightening techniques employed in this study to provide long-term stability to Universal Abutment screws.

A data-driven soft sensor for needle deflection in heterogeneous tissue using just-in-time modelling.

PubMed

Rossa, Carlos; Lehmann, Thomas; Sloboda, Ronald; Usmani, Nawaid; Tavakoli, Mahdi

2017-08-01

Global modelling has traditionally been the approach taken to estimate needle deflection in soft tissue. In this paper, we propose a new method based on local data-driven modelling of needle deflection. External measurement of needle-tissue interactions is collected from several insertions in ex vivo tissue to form a cloud of data. Inputs to the system are the needle insertion depth, axial rotations, and the forces and torques measured at the needle base by a force sensor. When a new insertion is performed, the just-in-time learning method estimates the model outputs given the current inputs to the needle-tissue system and the historical database. The query is compared to every observation in the database and is given weights according to some similarity criteria. Only a subset of historical data that is most relevant to the query is selected and a local linear model is fit to the selected points to estimate the query output. The model outputs the 3D deflection of the needle tip and the needle insertion force. The proposed approach is validated in ex vivo multilayered biological tissue in different needle insertion scenarios. Experimental results in five different case studies indicate an accuracy in predicting needle deflection of 0.81 and 1.24 mm in the horizontal and vertical lanes, respectively, and an accuracy of 0.5 N in predicting the needle insertion force over 216 needle insertions.

Mechanical torque measurement predicts load to implant cut-out: a biomechanical study investigating DHS anchorage in femoral heads.

PubMed

Suhm, Norbert; Hengg, Clemens; Schwyn, Ronald; Windolf, Markus; Quarz, Volker; Hänni, Markus

2007-08-01

Bone strength plays an important role in implant anchorage. Bone mineral density (BMD) is used as surrogate parameter to quantify bone strength and to predict implant anchorage. BMD can be measured by means of quantitative computer tomography (QCT) or dual energy X-ray absorptiometry (DXA). These noninvasive methods for BMD measurement are not available pre- or intra-operatively. Instead, the surgeon could determine bone strength by direct mechanical measurement. We have evaluated mechanical torque measurement for (A) its capability to quantify local bone strength and (B) its predictive value towards load at implant cut-out. Our experimental study was performed using sixteen paired human cadaver proximal femurs. BMD was determined for all specimens by QCT. The torque to breakaway of the cancellous bone structure (peak torque) was measured by means of a mechanical probe at the exact position of subsequent DHS placement. The fixation strength of the DHS achieved was assessed by cyclic loading in a stepwise protocol beginning with 1,500 N increasing 500 N every 5,000 cycles until 4,000 N. A highly significant correlation of peak torque with BMD (QCT) was found (r = 0.902, r (2) = 0.814, P < 0.001). Peak torque correlated highly significant with the load at implant cut-out (r = 0.795, P < 0.001). All specimens with a measured peak torque below 6.79 Nm failed at the first load level of 1,500 N. The specimens with a peak torque above 8.63 Nm survived until the last load level of 4,000 N. Mechanical peak torque measurement is able to quantify bone strength. In an experimental setup, peak torque identifies those specimens that are likely to fail at low load. In clinical routine, implant migration and cut-out depend on several parameters, which are difficult to control, such as fracture type, fracture reduction achieved, and implant position. The predictive value of peak torque towards cut-out in a clinical set-up therefore has to be carefully validated.

The Effects of Gravitational Instabilities on Gas Giant Planet Migration in Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Michael, Scott A.; Durisen, R. H.

2010-05-01

In this paper we conduct several three-dimensional radiative hydrodynamic simulations to explore the effect of the inclusion of gas giant planets in gravitationally unstable protoplanetary disks. We compare several simulations carried out with the CHYMERA code including: a baseline simulation without a planet, and three simulations including planets of various masses 0.3, 1 and 3 Jupiter masses. The planets are inserted into the baseline simulation after the gravitational instabilities (GIs) have grown to non-linear amplitude. The planets are inserted at the same radius, which coincides with the co-rotation radius of the dominant global mode in the baseline simulation. We examine the effect that the GIs have on migration rates as well as the potential of halting inward migration. We also examine the effect the insertion of the planet has on the global torques caused by the GIs. Furthermore, we explore the relationship between planet mass and migration rates and effect on GIs.

Circuit increases capability of hysteresis synchronous motor

NASA Technical Reports Server (NTRS)

Markowitz, I. N.

1967-01-01

Frequency and phase detector circuit enables a hysteresis synchronous motor to drive a load of given torque value at a precise speed determined by a stable reference. This technique permits driving larger torque loads with smaller motors and lower power drain.

Mechanical and Histological Effects of Resorbable Blasting Media Surface Treatment on the Initial Stability of Orthodontic Mini-Implants

PubMed Central

2016-01-01

Introduction. This study aimed to evaluate the effects of resorbable blasting media (RBM) treatment on early stability of orthodontic mini-implants by mechanical, histomorphometric, and histological analyses. Methods. Ninety-six (64 for mechanical study and 32 for histological study and histomorphometric analysis) titanium orthodontic mini-implants (OMIs) with machined (machined group) or RBM-treated (CaP) surface (RBM group) were implanted in the tibiae of 24 rabbits. Maximum initial torque (MIT) was measured during insertion, and maximum removal torque (MRT) and removal angular momentum (RAM) were measured at 2 and 4 weeks after implantation. Bone-to-implant contact (BIC) and bone area (BA) were analyzed at 4 weeks after implantation. Results. RBM group exhibited significantly lower MIT and significantly higher MRT and RAM at 2 weeks than machined group. No significant difference in MRT, RAM, and BIC between the two groups was noted at 4 weeks, although BA was significantly higher in RBM group than in machined group. RBM group showed little bone resorption, whereas machined group showed new bone formation after bone resorption. Conclusions. RBM surface treatment can provide early stability of OMIs around 2 weeks after insertion, whereas stability of machined surface OMIs may decrease in early stages because of bone resorption, although it can subsequently recover by new bone apposition. PMID:26942200

In-plane current-driven spin-orbit torque switching in perpendicularly magnetized films with enhanced thermal tolerance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Di; Department of Optical Science and Engineering, Key Laboratory of Micro and Nano Photonic Structures; Yu, Guoqiang, E-mail: guoqiangyu@ucla.edu

2016-05-23

We study spin-orbit-torque (SOT)-driven magnetization switching in perpendicularly magnetized Ta/Mo/Co{sub 40}Fe{sub 40}B{sub 20} (CoFeB)/MgO films. The thermal tolerance of the perpendicular magnetic anisotropy (PMA) is enhanced, and the films sustain the PMA at annealing temperatures of up to 430 °C, due to the ultra-thin Mo layer inserted between the Ta and CoFeB layers. More importantly, the Mo insertion layer also allows for the transmission of the spin current generated in the Ta layer due to spin Hall effect, which generates a damping-like SOT and is able to switch the perpendicular magnetization. When the Ta layer is replaced by a Pt layer,more » i.e., in a Pt/Mo/CoFeB/MgO multilayer, the direction of the SOT-induced damping-like effective field becomes opposite because of the opposite sign of spin Hall angle in Pt, which indicates that the SOT-driven switching is dominated by the spin current generated in the Ta or Pt layer rather than the Mo layer. Quantitative characterization through harmonic measurements reveals that the large SOT effective field is preserved for high annealing temperatures. This work provides a route to applying SOT in devices requiring high temperature processing steps during the back-end-of-line processes.« less

First principles calculation for Gilbert damping constants in ferromagnetic/non-magnetic junctions

NASA Astrophysics Data System (ADS)

Hiramatsu, R.; Miura, D.; Sakuma, A.

2018-05-01

We evaluated an intrinsic α in ferromagnetic (FM)/non-magnetic (NM) junctions from first principles (FM = Co, Fe, and Ni and NM = Cu, Pd, and Pt) to investigate the effects of the inserted NM layer. α is calculated by liner muffin-tin orbital methods based on the torque-correlation model. We confirmed that Gilbert damping is enhanced and saturated as NM thickness increases, and that the enhancement is greater in NM materials having a stronger spin-orbital interaction. By contrast, the calculated FM thickness dependences of α show that Gilbert damping tends to decrease and be saturated as the FM thickness increases. Under the torque-correlation model, the dependences of α on FM and NM thickness can be explained by considering the electronic structure of the total system, including junction interfaces, which exhibit similar behaviors derived by spin pumping theory.

Giant Spin Hall Effect and Switching Induced by Spin-Transfer Torque in a W /Co40Fe40B20/MgO Structure with Perpendicular Magnetic Anisotropy

NASA Astrophysics Data System (ADS)

Hao, Qiang; Xiao, Gang

2015-03-01

We obtain robust perpendicular magnetic anisotropy in a β -W /Co40Fe40B20/MgO structure without the need of any insertion layer between W and Co40Fe40B20 . This is achieved within a broad range of W thicknesses (3.0-9.0 nm), using a simple fabrication technique. We determine the spin Hall angle (0.40) and spin-diffusion length for the bulk β form of tungsten with a large spin-orbit coupling. As a result of the giant spin Hall effect in β -W and careful magnetic annealing, we significantly reduce the critical current density for the spin-transfer-torque-induced magnetic switching in Co40Fe40B20 . The elemental β -W is a superior candidate for magnetic memory and spin-logic applications.

Analysis Method of Friction Torque and Weld Interface Temperature during Friction Process of Steel Friction Welding

NASA Astrophysics Data System (ADS)

Kimura, Masaaki; Inoue, Haruo; Kusaka, Masahiro; Kaizu, Koichi; Fuji, Akiyoshi

This paper describes an analysis method of the friction torque and weld interface temperature during the friction process for steel friction welding. The joining mechanism model of the friction welding for the wear and seizure stages was constructed from the actual joining phenomena that were obtained by the experiment. The non-steady two-dimensional heat transfer analysis for the friction process was carried out by calculation with FEM code ANSYS. The contact pressure, heat generation quantity, and friction torque during the wear stage were calculated using the coefficient of friction, which was considered as the constant value. The thermal stress was included in the contact pressure. On the other hand, those values during the seizure stage were calculated by introducing the coefficient of seizure, which depended on the seizure temperature. The relationship between the seizure temperature and the relative speed at the weld interface in the seizure stage was determined using the experimental results. In addition, the contact pressure and heat generation quantity, which depended on the relative speed of the weld interface, were solved by taking the friction pressure, the relative speed and the yield strength of the base material into the computational conditions. The calculated friction torque and weld interface temperatures of a low carbon steel joint were equal to the experimental results when friction pressures were 30 and 90 MPa, friction speed was 27.5 s-1, and weld interface diameter was 12 mm. The calculation results of the initial peak torque and the elapsed time for initial peak torque were also equal to the experimental results under the same conditions. Furthermore, the calculation results of the initial peak torque and the elapsed time for initial peak torque at various friction pressures were equal to the experimental results.

Estimations of One Repetition Maximum and Isometric Peak Torque in Knee Extension Based on the Relationship Between Force and Velocity.

PubMed

Sugiura, Yoshito; Hatanaka, Yasuhiko; Arai, Tomoaki; Sakurai, Hiroaki; Kanada, Yoshikiyo

2016-04-01

We aimed to investigate whether a linear regression formula based on the relationship between joint torque and angular velocity measured using a high-speed video camera and image measurement software is effective for estimating 1 repetition maximum (1RM) and isometric peak torque in knee extension. Subjects comprised 20 healthy men (mean ± SD; age, 27.4 ± 4.9 years; height, 170.3 ± 4.4 cm; and body weight, 66.1 ± 10.9 kg). The exercise load ranged from 40% to 150% 1RM. Peak angular velocity (PAV) and peak torque were used to estimate 1RM and isometric peak torque. To elucidate the relationship between force and velocity in knee extension, the relationship between the relative proportion of 1RM (% 1RM) and PAV was examined using simple regression analysis. The concordance rate between the estimated value and actual measurement of 1RM and isometric peak torque was examined using intraclass correlation coefficients (ICCs). Reliability of the regression line of PAV and % 1RM was 0.95. The concordance rate between the actual measurement and estimated value of 1RM resulted in an ICC(2,1) of 0.93 and that of isometric peak torque had an ICC(2,1) of 0.87 and 0.86 for 6 and 3 levels of load, respectively. Our method for estimating 1RM was effective for decreasing the measurement time and reducing patients' burden. Additionally, isometric peak torque can be estimated using 3 levels of load, as we obtained the same results as those reported previously. We plan to expand the range of subjects and examine the generalizability of our results.

Effect of long-term steam autoclaving on changes in torque delivery of spring- and friction-type torque wrenches.

PubMed

Yilmaz, Burak; L'Homme-Langlois, Emilie; Beck, Frank M; McGlumphy, Edwin

2016-06-01

Two types of mechanical torque-limiting devices (MTLD) are available: friction-style and spring-style. Limited information is available regarding the accuracy of different types of MTLDs after sterilization. The purpose of this in vitro study was to determine the accuracy of MTLDs after sterilization. Three new friction-style and 3 new spring-style MTLDs (Astra Tech/Dentsply, Zimmer Dental, Biohorizons, Biomet 3i, Straumann [ITI] and Nobel Biocare; n=5 per manufacturer; 30 total) were selected to evaluate their accuracy in delivering the target torque values preset by their manufacturers before and after sterilization. Target torque measurements were made with a digital torque gauge (model DFS2-R-ND; Chatillon) 10 times for each device. All MTLDs were sterilized following the manufacturers' recommendations. The sterilization procedure was repeated 100 times, and the accuracy of all MTLDs was retested. Absolute torque differences were analyzed using a repeated measures analysis of variance with instrument as the repeated factor. MTLD type (friction or spring) and MTLD status (new or autoclaved) were the independent variables. Post hoc testing was done using the Tukey method for balanced data. No significant difference was found between the spring-style and friction-style MTLDs or within the spring-style and friction-style MTLDs before and after sterilization (P>.05). After 100 cycles of steam autoclaving, the accuracy of spring-style and friction-style MTLDs was similar. All MTLDs fell within ±10% of the target torque value before and after sterilization. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Influence of Different Screw Torque Levels on the Biomechanical Behavior of Tapered Prosthetic Abutments.

PubMed

Herbst, Paulo Eduardo; de Carvalho, Eduardo Bortolas; Salatti, Rafael C; Valgas, Laiz; Tiossi, Rodrigo

To study the force used for tightening tapered one-piece prosthetic abutments and their influence on the removal torque value and stress level of the prosthetic abutment after cyclic loading. Fourteen implants and prosthetic abutments were divided into two groups (n = 7): G1, 20 Ncm; and G2, 32 Ncm (manufacturer recommended). A 20-mm T-shaped horizontal bar was adapted to the abutments. A 12-Hz cyclic loading was applied to the specimens in an electrodynamic testing system with the maximum number of cycles set to 10 6 . Specimens were inclined by 15 degrees from the vertical axis, and a 5-mm off-center vertical load was applied to generate a combination of bending and torquing moments on the tapered connections. Progressive loads (from 164.85 to 362.85 N) were applied when the previous sample survived 10 6 cycles. The paired t test compared the screw removal torque with the initial tightening torque for each group (α = .05). A finite element analysis (FEA) of the mechanical testing analyzed the regions of stress concentration. No specimens failed after 10 6 cyclic loadings. The mean screw removal torque for both groups was similar to the initial abutment torque value applied for each group (G1, 20.36 ± 8.73 Ncm; and G2, 35.61 ± 6.99 Ncm) (P > .05). FEA showed similar stress behavior for both groups in the study despite the different simulated screw preloads (G1: 200 N; G2: 320 N). The coronal region of the implant body presented the highest strain values in both groups. Tightening tapered one-piece prosthetic abutments at 20 and 32 Ncm maintains a stable connection after cyclic loading. The stresses generated by the different tightening forces during cyclic loading are highest at the coronal level of the connection.

Design of a 7-DOF slave robot integrated with a magneto-rheological haptic master

NASA Astrophysics Data System (ADS)

Hwang, Yong-Hoon; Cha, Seung-Woo; Kang, Seok-Rae; Choi, Seung-Bok

2017-04-01

In this study, a 7-DOF slave robot integrated with the haptic master is designed and its dynamic motion is controlled. The haptic master is made using a controllable magneto-rheological (MR) clutch and brake and it provides the surgeon with a sense of touch by using both kinetic and kinesthetic information. Due to the size constraint of the slave robot, a wire actuating is adopted to make the desired motion of the end-effector which has 3-DOF instead of a conventional direct-driven motor. Another motions of the link parts that have 4-DOF use direct-driven motor. In total system, for working as a haptic device, the haptic master need to receive the information of repulsive forces applied on the slave robot. Therefore, repulsive forces on the end-effector are sensed by using three uniaxial torque transducer inserted in the wire actuating system and another repulsive forces applied on link part are sensed by using 6-axis transducer that is able to sense forces and torques. Using another 6-axis transducer, verify the reliability of force information on final end of slave robot. Lastly, integrated with a MR haptic master, psycho-physical test is conducted by different operators who can feel the different repulsive force or torque generated from the haptic master which is equivalent to the force or torque occurred on the end-effector to demonstrate the effectiveness of the proposed system.

Assessment of isometric muscle strength and rate of torque development with hand-held dynamometry: Test-retest reliability and relationship with gait velocity after stroke.

PubMed

Mentiplay, Benjamin F; Tan, Dawn; Williams, Gavin; Adair, Brooke; Pua, Yong-Hao; Bower, Kelly J; Clark, Ross A

2018-04-27

Isometric rate of torque development examines how quickly force can be exerted and may resemble everyday task demands more closely than isometric strength. Rate of torque development may provide further insight into the relationship between muscle function and gait following stroke. Aims of this study were to examine the test-retest reliability of hand-held dynamometry to measure isometric rate of torque development following stroke, to examine associations between strength and rate of torque development, and to compare the relationships of strength and rate of torque development to gait velocity. Sixty-three post-stroke adults participated (60 years, 34 male). Gait velocity was assessed using the fast-paced 10 m walk test. Isometric strength and rate of torque development of seven lower-limb muscle groups were assessed with hand-held dynamometry. Intraclass correlation coefficients were calculated for reliability and Spearman's rho correlations were calculated for associations. Regression analyses using partial F-tests were used to compare strength and rate of torque development in their relationship with gait velocity. Good to excellent reliability was shown for strength and rate of torque development (0.82-0.97). Strong associations were found between strength and rate of torque development (0.71-0.94). Despite high correlations between strength and rate of torque development, rate of torque development failed to provide significant value to regression models that already contained strength. Assessment of isometric rate of torque development with hand-held dynamometry is reliable following stroke, however isometric strength demonstrated greater relationships with gait velocity. Further research should examine the relationship between dynamic measures of muscle strength/torque and gait after stroke. Copyright © 2018 Elsevier Ltd. All rights reserved.

Differential Motion and Compression Between the Plantaris and Achilles Tendons: A Contributing Factor to Midportion Achilles Tendinopathy?

PubMed

Stephen, Joanna M; Marsland, Daniel; Masci, Lorenzo; Calder, James D F; Daou, Hadi El

2018-03-01

The plantaris tendon (PT) has been thought to contribute to symptoms in a proportion of patients with Achilles midportion tendinopathy, with symptoms improving after PT excision. There is compression and differential movement between the PT and Achilles tendon (AT) during ankle plantarflexion and dorsiflexion. Descriptive laboratory study. Eighteen fresh-frozen cadaveric ankles (mean ± SD age: 35 ± 7 years, range = 27-48 years; men, n = 9) were mounted in a customized testing rig, where the tibia was fixed but the forefoot could be moved freely. A Steinmann pin was drilled through the calcaneus, enabling a valgus torque to be applied. The soleus, gastrocnemius, and plantaris muscles were loaded with 63 N with a weighted pulley system. The test area was 40 to 80 mm above the os calcis, corresponding to where the injury is observed clinically. Medially, the AT and PT were exposed, and a calibrated flexible pressure sensor was inserted between the tendons. Pressure readings were recorded with the ankle in full dorsiflexion, full plantarflexion, and plantargrade and repeated in these positions with a 5 N·m torque, simulating increased hindfoot valgus. The pressure sensor was removed and the PT and AT marked with ink at the same level, with the foot held in neutral rotation and plantargrade. Videos and photographs were taken to assess differential motion between the tendons. After testing, specimens were dissected to identify the PT insertion. One-way analysis of variance and paired t tests were performed to make comparisons. The PT tendons with an insertion separate from the AT demonstrated greater differential motion through range (14 ± 4 mm) when compared with those directly adherent to the AT (2 ± 2 mm) ( P < .001). Mean pressure between the PT and AT rose in terminal plantarflexion for all specimens ( P < .001) and was more pronounced with hindfoot valgus ( P < .001). The PT inserting directly into the calcaneus resulted in significantly greater differential motion as compared with the AT. Tendon compression was elevated in terminal plantarflexion, suggesting that adapting rehabilitation tendon-loading programs to avoid this position may be beneficial. The insertion pattern of the PT may be a factor in plantaris-related midportion Achilles tendinopathy. Terminal range plantarflexion and hindfoot valgus both increased AT and PT compression, suggesting that these should be avoided in this patient population.

Method and system for determining the torque required to launch a vehicle having a hybrid drive-train

DOEpatents

Hughes, Douglas A.

2006-04-04

A method and system are provided for determining the torque required to launch a vehicle having a hybrid drive-train that includes at least two independently operable prime movers. The method includes the steps of determining the value of at least one control parameter indicative of a vehicle operating condition, determining the torque required to launch the vehicle from the at least one determined control parameter, comparing the torque available from the prime movers to the torque required to launch the vehicle, and controlling operation of the prime movers to launch the vehicle in response to the comparing step. The system of the present invention includes a control unit configured to perform the steps of the method outlined above.

Measurement of plastic and elastic deformation due to third-order torque in self-ligated orthodontic brackets.

PubMed

Major, Thomas W; Carey, Jason P; Nobes, David S; Heo, Giseon; Major, Paul W

2011-09-01

Control of root torque is often achieved by introducing a twist in a rectangular archwire. The purpose of this study was to investigate third-order torque on different types of self-ligated brackets by analyzing the bracket's elastic and plastic deformations in conjunction with the expressed torque at varying angles of twist. An orthodontic bracket was mounted to a load cell that measured forces and moments in all directions. The wire was twisted in the bracket via a stepper motor, controlled by custom software. Overhead images were taken by a camera through a microscope and processed by using optical correlation to measure deformation. At the maximum torquing angle of 63° with 0.019 × 0.025-in stainless steel wire, the total elastic and plastic deformation values were 0.063, 0.033, and 0.137 mm for Damon Q (Ormco, Orange, Calif), In-Ovation R (GAC, Bohemia, NY), and Speed (Strite Industries, Cambridge, Ontario, Canada), respectively. The total plastic deformation values were 0.015, 0.006, and 0.086 mm, respectively, measured at 0° of unloading. In-Ovation R had the least deformation due to torquing of the 3 investigated bracket types. Damon Q and Speed on average had approximately 2.5 and 14 times greater maximum plastic deformation, respectively, than did In-Ovation R. Copyright © 2011 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

Stability Study of Anthropomorphic Robot Antares under External Load Action

NASA Astrophysics Data System (ADS)

Kodyakov, A. S.; Pavlyuk, N. A.; Budkov, V. Yu; Prakapovich, R. A.

2017-01-01

The paper presents the study of the behavior of the major structural elements of the lower limbs of anthropomorphic robot Antares under the influence of different types of loads (torsion, fracture). We have determined the required values for actuators torques for motion of the robot in space. The maximum values of torques are 5 Nm and 5.2 Nm respectively, and are able to withstand the upper and lower leg structures.

Muscle shear elastic modulus is linearly related to muscle torque over the entire range of isometric contraction intensity.

PubMed

Ateş, Filiz; Hug, François; Bouillard, Killian; Jubeau, Marc; Frappart, Thomas; Couade, Mathieu; Bercoff, Jeremy; Nordez, Antoine

2015-08-01

Muscle shear elastic modulus is linearly related to muscle torque during low-level contractions (<60% of Maximal Voluntary Contraction, MVC). This measurement can therefore be used to estimate changes in individual muscle force. However, it is not known if this relationship remains valid for higher intensities. The aim of this study was to determine: (i) the relationship between muscle shear elastic modulus and muscle torque over the entire range of isometric contraction and (ii) the influence of the size of the region of interest (ROI) used to average the shear modulus value. Ten healthy males performed two incremental isometric little finger abductions. The joint torque produced by Abductor Digiti Minimi was considered as an index of muscle torque and elastic modulus. A high coefficient of determination (R(2)) (range: 0.86-0.98) indicated that the relationship between elastic modulus and torque can be accurately modeled by a linear regression over the entire range (0% to 100% of MVC). The changes in shear elastic modulus as a function of torque were highly repeatable. Lower R(2) values (0.89±0.13 for 1/16 of ROI) and significantly increased absolute errors were observed when the shear elastic modulus was averaged over smaller ROI, half, 1/4 and 1/16 of the full ROI) than the full ROI (mean size: 1.18±0.24cm(2)). It suggests that the ROI should be as large as possible for accurate measurement of muscle shear modulus. Copyright © 2015 Elsevier Ltd. All rights reserved.

Fabrication of nanotweezers and their remote actuation by magnetic fields.

PubMed

Iss, Cécile; Ortiz, Guillermo; Truong, Alain; Hou, Yanxia; Livache, Thierry; Calemczuk, Roberto; Sabon, Philippe; Gautier, Eric; Auffret, Stéphane; Buda-Prejbeanu, Liliana D; Strelkov, Nikita; Joisten, Hélène; Dieny, Bernard

2017-03-27

A new kind of nanodevice that acts like tweezers through remote actuation by an external magnetic field is designed. Such device is meant to mechanically grab micrometric objects. The nanotweezers are built by using a top-down approach and are made of two parallelepipedic microelements, at least one of them being magnetic, bound by a flexible nanohinge. The presence of an external magnetic field induces a torque on the magnetic elements that competes with the elastic torque provided by the nanohinge. A model is established in order to evaluate the values of the balanced torques as a function of the tweezers opening angles. The results of the calculations are confronted to the expected values and validate the overall working principle of the magnetic nanotweezers.

Loosening torque of Universal Abutment screws after cyclic loading: influence of tightening technique and screw coating

PubMed Central

Regalin, Alexandre; Bhering, Claudia Lopes Brilhante; Alessandretti, Rodrigo; Spazzin, Aloisio Oro

2015-01-01

PURPOSE The purpose of this study was to evaluate the influence of tightening technique and the screw coating on the loosening torque of screws used for Universal Abutment fixation after cyclic loading. MATERIALS AND METHODS Forty implants (Titamax Ti Cortical, HE, Neodent) (n=10) were submerged in acrylic resin and four tightening techniques for Universal Abutment fixation were evaluated: A - torque with 32 Ncm (control); B - torque with 32 Ncm holding the torque meter for 20 seconds; C - torque with 32 Ncm and retorque after 10 minutes; D - torque (32 Ncm) holding the torque meter for 20 seconds and retorque after 10 minutes as initially. Samples were divided into subgroups according to the screw used: conventional titanium screw or diamond like carbon-coated (DLC) screw. Metallic crowns were fabricated for each abutment. Samples were submitted to cyclic loading at 106 cycles and 130 N of force. Data were analyzed by two-way ANOVA and Tukey's test (5%). RESULTS The tightening technique did not show significant influence on the loosening torque of screws (P=.509). Conventional titanium screws showed significant higher loosening torque values than DLC (P=.000). CONCLUSION The use of conventional titanium screw is more important than the tightening techniques employed in this study to provide long-term stability to Universal Abutment screws. PMID:26576253

Prevailing Torque Locking Feature in Threaded Fasteners Using Anaerobic Adhesive

NASA Technical Reports Server (NTRS)

Hernandez, Alan; Hess, Daniel P.

2016-01-01

This paper presents results from tests to assess the use of anaerobic adhesive for providing a prevailing torque locking feature in threaded fasteners. Test procedures are developed and tests are performed on three fastener materials, four anaerobic adhesives, and both unseated assembly conditions. Five to ten samples are tested for each combination. Tests for initial use, reuse without additional adhesive, and reuse with additional adhesive are performed for all samples. A 48-hour cure time was used for all initial use and reuse tests. Test data are presented as removal torque versus removal angle with the specification required prevailing torque range added for performance assessment. Percent specification pass rates for the all combinations of fastener material, adhesive, and assembly condition are tabulated and reveal use of anaerobic adhesive as a prevailing torque locking feature is viable. Although not every possible fastener material and anaerobic adhesive combination provides prevailing torque values within specification, any combination can be assessed using the test procedures presented. Reuse without additional anaerobic adhesive generally provides some prevailing torque, and in some cases within specification. Reuse with additional adhesive often provides comparable removal torque data as in initial use.

Neoclassical Toroidal Viscosity Torque Induced by Plasma Response in a Low- β Tokamak with Edge Pedestal

NASA Astrophysics Data System (ADS)

Yan, Xingting; Zhu, Ping; Sun, Youwen

2016-10-01

The characteristic profile and magnitude are predicted in theory for the neoclassical toroidal viscosity (NTV) torque induced by the plasma response to the resonant magnetic perturbation (RMP) in a tokamak with an edge pedestal, using the newly developed module coupling the NIMROD and the NTVTOK codes. For a low β equilibrium, the NTV torque is mainly induced by the dominant toroidal mode of plasma response. The NTV torque profile is radially localized and peaked, which is determined by profiles of both the equilibrium temperature and the plasma response fields. In general, the peak of NTV torque profile is found to trace the pedestal location. The magnitude of NTV torque is extremely sensitive to the β of pedestal top; for a given plasma response, the peak value of NTV torque can increase by three orders of magnitude, when the pedestal β increases by only one order of magnitude. This suggests a more significant role of NTV torque in higher plasma β regimes. Supported by the National Magnetic Confinement Fusion Program of China under Grant Nos. 2014GB124002 and 2015GB101004, and the 100 Talent Program of the Chinese Academy of Sciences.

Atmospheric Torques on the Solid Earth and Oceans Based on the GEOS-1 General Circulation Model

NASA Technical Reports Server (NTRS)

Sanchez, Braulio V.; Au, Andrew Y.

1998-01-01

The GEOS-1 general circulation model has been used to compute atmospheric torques on the oceans and solid Earth for the period 1980-1995. The time series for the various torque components have been analyzed by means of Fourier transform techniques. It was determined that the wind stress torque over land is more powerful than the wind stress torque over water by 55%, 42%, and 80% for the x, y, and z components respectively. This is mainly the result of power in the high frequency range. The pressure torques due to polar flattening, equatorial ellipticity, marine geoid, and continental orography were computed. The orographic or "mountain torque" components are more powerful than their wind stress counterparts (land plus ocean) by 231% (x), 191% (y), and 77% (z). The marine pressure torques due to geoidal undulations are much smaller than the orographic ones, as expected. They are only 3% (x), 4% (y), and 5% (z) of the corresponding mountain torques. The geoidal pressure torques are approximately equal in magnitude to those produced by the equatorial ellipticity of the Earth. The pressure torque due to polar flattening makes the largest contributions to the atmospheric torque budget. It has no zonal component, only equatorial ones. Most of the power of the latter, between 68% and 69%, is found in modes with periods under 15 days. The single most powerful mode has a period of 361 days. The gravitational torque ranks second in power only to the polar flattening pressure torque. Unlike the former, it does produce a zonal component, albeit much smaller (1%) than the equatorial ones. The gravitational and pressure torques have opposite signs, therefore, the gravitational torque nullifies 42% of the total pressure torque. Zonally, however, the gravitational torque amounts to only 6% of the total pressure torque. The power budget for the total atmospheric torque yields 7595 and 7120 Hadleys for the equatorial components and 966 Hadleys for the zonal. The x-component exhibits a large mean value (1811 H), mainly the result of polar flattening pressure torque acting on the ocean surfaces. Atmospheric torque modes with periods of 408, 440, and 476 days appear in the spectrum of the equatorial components.

Atmospheric Torques on the Solid Earth and Oceans Based on the GEOS-1 General Circulation Model

NASA Technical Reports Server (NTRS)

Sanchez, Braulio

1999-01-01

The GEOS-1 general circulation model has been used to compute atmospheric torques on the oceans and solid Earth for the period 1980-1995. The time series for the various torque components have been analyzed by means of Fourier transform techniques. It was determined that the wind stress torque over land is more powerful than the wind stress torque over water by 55\\%, 42\\%, and 80\\t for the x, y, and z components respectively. This is mainly the result of power in the high frequency range. The pressure torques due to polar flattening, equatorial ellipticity, marine geoid, and continental orography were computed. The orographic or "mountain torque" components are more powerful than their wind stress counterparts (land plus ocean) by 231\\% (x), 191\\% (y), and 77\\% (z). The marine pressure torques due to geoidal undulations are much smaller than the orographic ones, as expected. They are only 3\\% (x), 4\\% (y), and 5\\% (z) of the corresponding mountain torques. The geoidal pressure torques are approximately equal in magnitude to those produced by the equatorial ellipticity of the Earth. The pressure torque due to polar flattening makes the largest contributions to the atmospheric'torque budget. It has no zonal component, only equatorial ones. Most of the power of the latter, between 68\\% and 69 %, is found in modes with periods under 15 days. The single most powerful mode has a period of 361 days. The gravitational torque ranks second in power only to the polar flattening pressure torque. Unlike the former, it does produce a zonal component, albeit much smaller (1\\ ) than the equatorial ones. The gravitational and pressure torques have opposite signs, therefore, the gravitational torque nullifies 42\\% of the total pressure torque. Zonally, however, the gravitational torque amounts to only 6\\% of the total pressure torque. The power budget for the total atmospheric torque yields 7595 and 7120 Hadleys for the equatorial components and 966 Hadleys for the zonal. The x-component exhibits a large mean value (1811 H), mainly the result of polar flattening pressure torque acting on the ocean surfaces. Atmospheric torque modes with periods of 408, 440, and 476 days appear in the spectrum of the equatorial components.

Mathematical model of the solar radiation force and torques acting on the components of a spacecraft

NASA Technical Reports Server (NTRS)

Georgevic, R. M.

1971-01-01

General expressions for the solar radiation force and torques are derived in the vectorial form for any given reflecting surface, provided that the reflecting characteristics of the surface, as well as the value of the solar constant, are known. An appropriate choice of a spacecraft-fixed frame of reference leads to relatively simple expressions for the solar radiation forces and torques in terms of the functions of the sun-spacecraft-earth angle.

The effect of vertical bracket positioning on torque and the resultant stress in the periodontal ligament--a finite element study.

PubMed

Sardarian, Ahmadreza; Danaei, Shahla Momeni; Shahidi, Shoaleh; Boushehri, Sahar Ghodsi; Geramy, Allahyar

2014-01-01

The ideal built-in tip and torque values of the straight wire appliance reduce the need for wire bending and hence reduce chair time. The vertical position of the bracket on the tooth surface can alter the torque exerted on the tooth. This is a result of the altered surface curvature observed at each vertical position. To further clarify the role of vertical bracket positioning on the applied torque and the resultant stresses in the periodontal ligament (PDL), we designed a mandibular first premolar using finite element modeling. Cone beam computed tomography of 52 patients (83 lower first premolars) was selected to be included in the study. Curvature was measured for points along the labial surface with increasing distances (0.5 mm increments) from the cusp tip by calculating the angle between tangents drawn from these points and the axis joining the cusp tip and the root apex. The mean values for each distance were calculated, and a finite element model was designed incorporating these mean values. The resultant stress and hydrostatic pressure in the PDL were calculated using finite element analysis. The labial surface of the mandibular first premolar demonstrated a 26.39° change from 2.5 to 6 mm from the cusp tip. The maximum Von-Mises stress and hydrostatic pressure in the PDL were observed at the root apex for all of the bracket positions, and these values demonstrated, respectively, a change of up to 0.059 and 0.186 MPa between two successive points. It can be concluded that the variation in the vertical position of the bracket can have an important effect on the torque and subsequently on the stresses and pressures in the PDL.

Assessment of dimensional accuracy of preadjusted metal injection molding orthodontic brackets.

PubMed

Alavi, Shiva; Tajmirriahi, Farnaz

2016-09-01

the aim of this study is to evaluate the dimensional accuracy of McLaughlin, Bennett, and Trevisi (MBT) brackets manufactured by two different companies (American Orthodontics and Ortho Organizers) and determine variations in incorporation of values in relation to tip and torque in these products. In the present analytical/descriptive study, 64 maxillary right central brackets manufactured by two companies (American Orthodontics and Ortho Organizers) were selected randomly and evaluated for the accuracy of the values in relation to torque and angulation presented by the manufacturers. They were placed in a video measuring machine using special revolvers under them and were positioned in a manner so that the light beams would be directed on the floor of the slot without the slot walls being seen. Then, the software program of the same machine was used to determine the values of each bracket type. The means of measurements were determined for each sample and were analyzed with independent t -test and one-sample t -test. Based on the confidence interval, it can be concluded that at 95% probability, the means of tip angles of maxillary right central brackets of these two brands were 4.1-4.3° and the torque angles were 16.39-16.72°. The tips in these samples were at a range of 3.33-4.98°, and the torque was at a range of 15.22-18.48°. In the present study, there were no significant differences in the angulation incorporated into the brackets from the two companies; however, they were significantly different from the tiP values for the MBT prescription. In relation to torque, there was a significant difference between the American Orthodontic brackets exhibited significant differences with the reported 17°, too.

PRELOAD AND TORQUE REMOVAL EVALUATION OF THREE DIFFERENT ABUTMENT SCREWS FOR SINGLE STANDING IMPLANT RESTORATIONS

PubMed Central

Stüker, Rafael Augusto; Teixeira, Eduardo Rolim; Beck, João Carlos Pinheiro; da Costa, Nilza Pereira

2008-01-01

Several authors still consider the mechanical problems of fracture and component loosening as the main causes of failure of implant-supported restorations. The purpose of this in vitro study was to compare the preload of three types of screw for transmucosal abutment attachment used in single implant-supported prosthesis through strain gauge and removal torque measurements. Three external hex fixtures were used, and each received a transmucosal abutment (Cera One®), which was fixed to the implant with its respective screw: Group A- gold screw, Group B- titanium screw and Group C- surface-treated titanium screw (Ti-Tite®). Ten screws of each type were attached applying a 30.07±0.28 Ncm torque force and maintained in position for 5 minutes. After this, the preload values were measured using strain gauges and a measurement cell. Gold screws presented higher preload values (131.72±8.98 N), followed by surface-treated titanium screws (97.78±4.68 N) and titanium screws (37.03±5.69 N). ANOVA (p<0.05) and Tukey's test (p<0.05) were applied. Statistically significant differences were found among the groups for both preload and removal torque values. In conclusion, gold screws may be indicated to achieve superior longevity of the abutment-implant connection and, consequently, prosthetic restoration due to greater preload values yielded. PMID:19089290

Influence of spore moisture content on the dry-heat resistance of Bacillus subtilis var. niger.

PubMed

Angelotti, R; Maryanski, J H; Butler, T F; Peeler, J T; Campbell, J E

1968-05-01

The dry-heat resistance of Bacillus subtilis var. niger spores located in or on various materials was determined as D and z values in the range of 105 through 160 C. The systems tested included spores located on steel and paper strips, spores located between stainless-steel washers mated together under 150 inch-lb and 12 inch-lb of torque, and spores encapsulated in methylmethacrylate and epoxy plastics. D values for a given temperature varied with the test system. High D values were observed for the systems in which spores were encapsulated or under heavy torque, whereas lower D values were observed for the steel and paper strip systems and the lightly torqued system. Similar z values were obtained for the plastic and steel strip systems (z(D) = 21 C), but an unusually low z for spores on paper (z(D) = 12.9 C) and an unusually high z for spores on steel washers mated at 150 inch-lb of torque (z(D) = 32 C) were observed. The effect of spore moisture content on the D value of spores encapsulated in water-impermeable plastic was determined, and maximal resistance was observed for spores with a water activity (a(w)) of 0.2 to 0.4. Significantly decreased D values were observed for spores with moisture contents below a(w) 0.2 or above a(w) 0.4. The data indicate that the important factors to be considered when measuring the dry heat resistance of spores are (i) the initial moisture content of the spore, (ii) the rate of spore desiccation during heating, (iii) the water retention capacity of the material in or on which spores are located, and (iv) the relative humidity of the system at the test temperature.

Results and Analysis from Space Suit Joint Torque Testing

NASA Technical Reports Server (NTRS)

Matty, Jennifer

2010-01-01

A space suit's mobility is critical to an astronaut's ability to perform work efficiently. As mobility increases, the astronaut can perform tasks for longer durations with less fatigue. Mobility can be broken down into two parts: range of motion (ROM) and torque. These two measurements describe how the suit moves and how much force it takes to move. Two methods were chosen to define mobility requirements for the Constellation Space Suit Element (CSSE). One method focuses on range of motion and the second method centers on joint torque. A joint torque test was conducted to determine a baseline for current advanced space suit joint torques. This test utilized the following space suits: Extravehicular Mobility Unit (EMU), Advanced Crew Escape Suit (ACES), I-Suit, D-Suit, Enhanced Mobility (EM)- ACES, and Mark III (MK-III). Data was collected data from 16 different joint movements of each suit. The results were then reviewed and CSSE joint torque requirement values were selected. The focus of this paper is to discuss trends observed during data analysis.

30 CFR 7.308 - Lockwasher equivalency test.

Code of Federal Regulations, 2014 CFR

2014-07-01

... hole and continuously and uniformly tightened at a speed not to exceed 30 rpm until the fastening's... cycles. (b) Acceptable performance. The minimum torque value required to start removal of the fastening from the installed position (minimum breakway torque) for any cycle of any test sample shall be greater...

30 CFR 7.308 - Lockwasher equivalency test.

Code of Federal Regulations, 2011 CFR

2011-07-01

... hole and continuously and uniformly tightened at a speed not to exceed 30 rpm until the fastening's... cycles. (b) Acceptable performance. The minimum torque value required to start removal of the fastening from the installed position (minimum breakway torque) for any cycle of any test sample shall be greater...

30 CFR 7.308 - Lockwasher equivalency test.

Code of Federal Regulations, 2013 CFR

2013-07-01

... hole and continuously and uniformly tightened at a speed not to exceed 30 rpm until the fastening's... cycles. (b) Acceptable performance. The minimum torque value required to start removal of the fastening from the installed position (minimum breakway torque) for any cycle of any test sample shall be greater...

30 CFR 7.308 - Lockwasher equivalency test.

Code of Federal Regulations, 2012 CFR

2012-07-01

... hole and continuously and uniformly tightened at a speed not to exceed 30 rpm until the fastening's... cycles. (b) Acceptable performance. The minimum torque value required to start removal of the fastening from the installed position (minimum breakway torque) for any cycle of any test sample shall be greater...

30 CFR 7.308 - Lockwasher equivalency test.

Code of Federal Regulations, 2010 CFR

2010-07-01

... hole and continuously and uniformly tightened at a speed not to exceed 30 rpm until the fastening's... cycles. (b) Acceptable performance. The minimum torque value required to start removal of the fastening from the installed position (minimum breakway torque) for any cycle of any test sample shall be greater...

QUICK RELEASABLE DRIVE

DOEpatents

Dickson, J.J.

1958-07-01

A quick releasable mechanical drive system suitable for use in a nuclear reactor is described. A small reversible motor positions a control rod by means of a worm and gear speed reducer, a magnetic torque clutch, and a bell crank. As the control rod is raised to the operating position, a heavy coil spring is compressed. In the event of an emergency indicated by either a''scram'' signal or a power failure, the current to the magnetic clutch is cut off, thereby freeing the coil spring and the bell crank positioner from the motor and speed reduction gearing. The coil spring will immediately act upon the bell crank to cause the insertion of the control rod. This arrangement will allow the slow, accurate positioning of the control rod during reactor operation, while providing an independent force to rapidly insert the rod in the event of an emergency.

The Zig-zag Instability of Streamlined Bodies

NASA Astrophysics Data System (ADS)

Guillet, Thibault; Coux, Martin; Quere, David; Clanet, Christophe

2017-11-01

When a floating bluff body, like a sphere, impacts water with a vertical velocity, its trajectory is straight and the depth of its dive increases with its initial velocity. Even though we observe the same phenomenon at low impact speed for axisymmetric streamlined bodies, the trajectory is found to deviate from the vertical when the velocity overcomes a critical value. This instability results from a competition between the destabilizing torque of the lift and the stabilizing torque of the Archimede's force. Balancing these torques yields a prediction on the critical velocity above which the instability appears. This theoretical value is found to depend on the position of the gravity center of the projectile and predicts with a full agreement the behaviour observed in our different experiments. Project funded by DGA.

The Simulation Study of Horizontal Axis Water Turbine Using Flow Simulation Solidworks Application

NASA Astrophysics Data System (ADS)

Prasetyo, H.; Budiana, EP; Tjahjana, DDDP; Hadi, S.

2018-02-01

The design of Horizontal Axis Water Turbine in pico hydro power plants involves many parameters. To simplify that, usually using computer simulation is applied. This research performs simulation process variation on turbine blade number, turbine blade curvature angle, turbine bucket angle and blocking system tilt angle. Those four variations were combined in order to obtain the best design of turbine. The study used Flow Simulation Solidworks application, and obtain data on turbine speed, pressure, force, and torque. However, this research focused on turbine torque value. The best design of turbine was obtained in the turbine with 6 blades, blade curvature angle of 65° and bucket angle of 10°, and blocking system tilt angle of 40°. In the best turbine, the produced torque value was 8.464 Nm.

Can maximal and rapid isometric torque characteristics predict playing level in division I American collegiate football players?

PubMed

Thompson, Brennan J; Ryan, Eric D; Sobolewski, Eric J; Smith, Doug B; Conchola, Eric C; Akehi, Kazuma; Buckminster, Tyler

2013-03-01

The purpose of this study was to determine if maximal and rapid isometric torque characteristics could discriminate starters from nonstarters in elite Division I American collegiate football players. Sixteen starters (mean ± SD: age = 20.81 ± 1.28 years; height = 184.53 ± 6.58 cm; and mass = 108.69 ± 22.16 kg) and 15 nonstarters (20.40 ± 1.68 years; 182.27 ± 10.52 cm; and 104.60 ± 22.44 kg) performed isometric maximal voluntary contractions (MVCs) of the leg flexor and extensor muscle groups. Peak torque (PT), rate of torque development (RTD), the time to peak RTD (TTRTDpeak), contractile impulse (IMPULSE), and absolute torque values (TORQUE) at specific time intervals were calculated from a torque-time curve. The results indicated significant and nonsignificant differences between starters and nonstarters for the early rapid leg flexion torque characteristics that included RTD, IMPULSE, and TORQUE at 30 and 50 milliseconds, and TTRTDpeak. These variables also demonstrated the largest effect sizes of all the variables examined (0.71-0.82). None of the leg extensor variables, leg flexion PT, or later leg flexion rapid torque variables (≥ 100 milliseconds) were significant discriminators of playing level. These findings suggest that the early rapid leg flexion torque variables may provide an effective and sensitive muscle performance measurement in the identification of collegiate football talent. Further, coaches and practitioners may use these findings when designing training programs for collegiate football players with the intent to maximize rapid leg flexion characteristics.

Axial displacement of abutments into implants and implant replicas, with the tapered cone-screw internal connection, as a function of tightening torque.

PubMed

Dailey, Bruno; Jordan, Laurence; Blind, Olivier; Tavernier, Bruno

2009-01-01

The passive fit of a superstructure on implant abutments is essential to success. One source of error when using a tapered cone-screw internal connection may be the difference between the tightening torque level applied to the abutments by the laboratory technician compared to that applied by the treating clinician. The purpose of this study was to measure the axial displacement of tapered cone-screw abutments into implants and their replicas as a function of the tightening torque level. Twenty tapered cone-screw abutments were selected. Two groups were created: 10 abutments were secured into 10 implants, and 10 abutments were secured into 10 corresponding implant replicas. Each abutment was tightened in increasing increments of 5 Ncm, from 0 Ncm to 45 Ncm, with a torque controller. The length of each sample was measured repeatedly with an Electronic Digital Micrometer. The mean axial displacement for the implant group and the replica group was calculated. The data were analyzed by the Mann-Whitney and Spearman tests. For both groups, there was always an axial displacement of the abutment upon each incremental application of torque. The mean axial displacement values varied between 7 and 12 microm for the implant group and between 6 and 21 microm for the replica group at each 5-Ncm increment. From 0 to 45 Ncm, the total mean axial displacement values were 89 microm for the implant group and 122 microm for the replica group. There was a continuous axial displacement of the abutments into implants and implant replicas when the applied torque was raised from 0 to 45 Ncm. Torque applied above the level recommended by the manufacturer increased the difference in displacement between the two groups.

Comparison of regression models for estimation of isometric wrist joint torques using surface electromyography

PubMed Central

2011-01-01

Background Several regression models have been proposed for estimation of isometric joint torque using surface electromyography (SEMG) signals. Common issues related to torque estimation models are degradation of model accuracy with passage of time, electrode displacement, and alteration of limb posture. This work compares the performance of the most commonly used regression models under these circumstances, in order to assist researchers with identifying the most appropriate model for a specific biomedical application. Methods Eleven healthy volunteers participated in this study. A custom-built rig, equipped with a torque sensor, was used to measure isometric torque as each volunteer flexed and extended his wrist. SEMG signals from eight forearm muscles, in addition to wrist joint torque data were gathered during the experiment. Additional data were gathered one hour and twenty-four hours following the completion of the first data gathering session, for the purpose of evaluating the effects of passage of time and electrode displacement on accuracy of models. Acquired SEMG signals were filtered, rectified, normalized and then fed to models for training. Results It was shown that mean adjusted coefficient of determination (Ra2) values decrease between 20%-35% for different models after one hour while altering arm posture decreased mean Ra2 values between 64% to 74% for different models. Conclusions Model estimation accuracy drops significantly with passage of time, electrode displacement, and alteration of limb posture. Therefore model retraining is crucial for preserving estimation accuracy. Data resampling can significantly reduce model training time without losing estimation accuracy. Among the models compared, ordinary least squares linear regression model (OLS) was shown to have high isometric torque estimation accuracy combined with very short training times. PMID:21943179

On structural transitions, thermodynamic equilibrium, and the phase diagram of DNA and RNA duplexes under torque and tension.

PubMed

Wereszczynski, Jeff; Andricioaei, Ioan

2006-10-31

A precise understanding of the flexibility of double stranded nucleic acids and the nature of their deformed conformations induced by external forces is important for a wide range of biological processes including transcriptional regulation, supercoil and catenane removal, and site-specific recombination. We present, at atomic resolution, a simulation of the dynamics involved in the transitions from B-DNA and A-RNA to Pauling (P) forms and to denatured states driven by application of external torque and tension. We then calculate the free energy profile along a B- to P-transition coordinate and from it, compute a reversible pathway, i.e., an isotherm of tension and torque pairs required to maintain P-DNA in equilibrium. The reversible isotherm maps correctly onto a phase diagram derived from single molecule experiments, and yields values of elongation, twist, and twist-stretch coupling in agreement with measured values. We also show that configurational entropy compensates significantly for the large electrostatic energy increase due to closer-packed P backbones. A similar set of simulations applied to RNA are used to predict a novel structure, P-RNA, with its associated free energy, equilibrium tension, torque and structural parameters, and to assign the location, on the phase-diagram, of a putative force-torque-dependent RNA "triple point."

Electromagnetic processes during phase commutation in field regulated reluctance machine

NASA Astrophysics Data System (ADS)

Shishkov, A. N.; Sychev, D. A.; Zemlyansky, A. A.; Krupnova, M. N.; Funk, T. A.; Ishmet'eva, V. D.

2018-03-01

The processes of currents switching in stator windings have been explained by the existence of the electromagnetic torque ripples in the electric drive with the field-regulated reluctance machine. The maximum value of ripples in the open loop control system for the six-phase machine can reach 20 percent from the developed electromagnetic torque. This method allows one to make calculation of ripple spike towards average torque developed by the electromotor for the different number of phases. Application of a trapezoidal form of current at six phases became the solution. In case of a less number of phases than six, a ripple spike considerably increases, which is inadmissible. On the other hand, increasing the number of phases tends to the increase of the semiconductor inverter external dimensions based on the inconspicuous decreasing of a ripple spike. The creation and usage of high-speed control loops of current (HCLC) have been recommended for a reduction of the electromagnetic torque’s ripple level, as well as the appliance of positive current feedback in switching phase currents. This decision allowed one to receive a mean value of the torque more than 10%, compared to system without change, to reduce greatly ripple spike of the electromagnetic torque. The possibility of the electric drive effective operation with FRRM in emergency operation has been shown.

Mechanical effects of third-order movement in self-ligated brackets by the measurement of torque expression.

PubMed

Major, Thomas W; Carey, Jason P; Nobes, David S; Heo, Giseon; Major, Paul W

2011-01-01

Axial rotation of orthodontic wire produces buccal or lingual root movement and is often referred to as third-order movement or "torque expression." The objective of this study was to quantify torque expression in 3 self-ligation bracket systems (Damon Q, Ormco, Orange, Calif; In-Ovation R, GAC, Bohemia, NY; and Speed, Strite Industries, Cambridge, Ontario, Canada) during loading and unloading. A stepper motor was used to rotate a wire in a fixed bracket slot from -15° to 63° in 3° increments, and then back to -15°. The bracket was mounted on top of a load cell that measured forces and moments in all directions. Damon's and In-Ovation's maximum average torque values at 63° were 105 and 113 Nmm, respectively. Many Speed brackets experienced premature loss of torque between 48° and 63°, and the average maximum was 82 Nmm at 54°. The torque plays for Damon, In-Ovation, and Speed were 11.3°, 11.9°, and 10.8°, respectively. Generally, In-Ovation expressed the most torque at a given angle of twist, followed by Damon and then Speed. However, there was no significant difference between brackets below 34 Nmm of torque. From a clinical perspective, the torque plays between brackets were virtually indistinguishable. Copyright © 2011 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

Selective laser melting of titanium alloy enables osseointegration of porous multi-rooted implants in a rabbit model.

PubMed

Peng, Wei; Xu, Liangwei; You, Jia; Fang, Lihua; Zhang, Qing

2016-07-21

Osseointegration refers to the direct connection between living bone and the surface of a load-bearing artificial implant. Porous implants with well-controlled porosity and pore size can enhance osseointegration. However, until recently implants were produced by machining solid core titanium rods. The aim of this study was to develop a multi-rooted dental implant (MRI) with a connected porous surface structure to facilitate osseointegration. MRIs manufactured by selective laser melting (SLM) and commercial implants with resorbable blasting media (RBM)-treated surfaces were inserted into the hind limbs of New Zealand white rabbits. Osseointegration was evaluated periodically over 12 weeks by micro-computerized tomography (CT) scanning, histological analysis, mechanical push-out tests, and torque tests. Bone volume densities were consistently higher in the MRI group than in the RBM group throughout the study period, ultimately resulting in a peak value of 48.41 % for the MRI group. Histological analysis revealed denser surrounding bone growth in the MRIs; after 4 and 8 weeks, bone tissue had grown into the pore structures and root bifurcation areas, respectively. Biomechanics tests indicated binding of the porous MRIs to the neobone tissues, as push-out forces strengthened from 294.7 to 446.5 N and maximum mean torque forces improved from 81.15 to 289.57 N (MRI), versus 34.79 to 87.8 N in the RBM group. MRIs manufactured by SLM possess a connected porous surface structure that improves the osteogenic characteristics of the implant surface.

Charts for Determining Preliminary Values of Span-load, Shear, Bending-moment, and Accumulated-torque Distributions of Swept Wings of Various Taper Ratios

NASA Technical Reports Server (NTRS)

Wollner, Bertram C

1948-01-01

Contains charts for use in determining preliminary values of the spanwise-load, shear, bending-moment, and accumulated-torque distributions of swept wings. The charts are based on strip theory and include four aerodynamic-load distributions, two section-moment distributions, and two inertia-load distributions. The taper ratios considered cover the range from 1.0 to 0 and the results are applicable to any angle of sweep.

Friction measurement in a hip wear simulator.

PubMed

Saikko, Vesa

2016-05-01

A torque measurement system was added to a widely used hip wear simulator, the biaxial rocking motion device. With the rotary transducer, the frictional torque about the drive axis of the biaxial rocking motion mechanism was measured. The principle of measuring the torque about the vertical axis above the prosthetic joint, used earlier in commercial biaxial rocking motion simulators, was shown to sense only a minor part of the total frictional torque. With the present method, the total frictional torque of the prosthetic hip was measured. This was shown to consist of the torques about the vertical axis above the joint and about the leaning axis. Femoral heads made from different materials were run against conventional and crosslinked polyethylene acetabular cups in serum lubrication. Regarding the femoral head material and the type of polyethylene, there were no categorical differences in frictional torque with the exception of zirconia heads, with which the lowest values were obtained. Diamond-like carbon coating of the CoCr femoral head did not reduce friction. The friction factor was found to always decrease with increasing load. High wear could increase the frictional torque by 75%. With the present system, friction can be continuously recorded during long wear tests, so the effect of wear on friction with different prosthetic hips can be evaluated. © IMechE 2016.

Assessing the therapeutic effect of 625-nm light-emitting diodes

NASA Astrophysics Data System (ADS)

Mao, Zongzhen; Xu, Guodong; Yang, Yi

2014-09-01

To evaluate the effects of red Light-Emitting Diodes on elbow extensor and flexor strength and the recovery of exercise induced fatigue, the torque values from the isokinetic dynamometer as well as biochemistry parameters were used as outcome measures. A randomized double-blind placebo-controlled crossover trial was performed with twenty male young tennis athletes. Active LED therapy (LEDT, with wavelength 625nm, 10 minutes total irradiation time, irradiated area amount to 30cm2, and 900J of total energy irradiated) or an identical placebo was delivered under double-blinded conditions to the left elbow just before exercise. The isokinetic muscle strength was measured immediately after irradiation. The blood lactate levels were sampled pre-exercise and post-exercise. The peak torque values of elbow extensor strength were significantly different between two groups. As in elbow flexor strength, the difference of peak torque was not significant. The blood lactate concentration of LEDT group post-exercise was significantly lower than those of placebo group. The results indicate that 625nm LED therapy is effective in preventing muscle fatigue as it can significantly reduce peak torque value of elbow extensors and blood lactate concentration. It has no effect on the strength of left elbow flexor or backhand performance in tennis.

Mechanical torque measurement for in vivo quantification of bone strength in the proximal femur.

PubMed

Mueller, Marc Andreas; Hengg, Clemens; Hirschmann, Michael; Schmid, Denise; Sprecher, Christoph; Audigé, Laurent; Suhm, Norbert

2012-10-01

Bone strength determines fracture risk and fixation strength of osteosynthesis implants. In vivo, bone strength is currently measured indirectly by quantifying bone mineral density (BMD) which is however only one determinant of the bone's biomechanical competence besides the bone's macro- and micro-architecture and tissue related parameters. We have developed a measurement principle (DensiProbe™ Hip) for direct, mechanical quantification of bone strength within the proximal femur upon hip fracture fixation. Previous cadaver tests indicated a close correlation between DensiProbe™ Hip measurements, 3D micro-CT analysis and biomechanical indicators of bone strength. The goal of this study was to correlate DensiProbe™ Hip measurements with areal bone mineral density (BMD). Forty-three hip fracture patients were included in this study. Intraoperatively, DensiProbe™ Hip was inserted to the subsequent hip screw tip position within the femoral head. Peak torque to breakaway of local cancellous bone was registered. Thirty-seven patients underwent areal BMD measurements of the contralateral proximal femur. Failure of fixation was assessed radio graphically 6 and 12 weeks postoperatively. Peak torque and femoral neck BMD showed significant correlations (R=0.60, P=0.0001). In regression analysis, areal BMD explained 46% of femoral neck BMD variance in a quadratic relationship. Throughout the 12-week follow-up period, no failure of fixation was observed. DensiProbe™ Hip may capture variations of bone strength beyond areal BMD which are currently difficult to measure in vivo. A multicenter study will clarify if peak torque predicts fixation failure. Copyright © 2012 Elsevier Ltd. All rights reserved.

Oscillation characteristics of zero-field spin transfer oscillators with field-like torque

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Yuan-Yuan; Xue, Hai-Bin, E-mail: xuehaibin@tyut.edu.cn; Department of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024

2015-05-15

We theoretically investigate the influence of the field-like spin torque term on the oscillation characteristics of spin transfer oscillators, which are based on MgO magnetic tunnel junctions (MTJs) consisting of a perpendicular magnetized free layer and an in-plane magnetized pinned layer. It is demonstrated that the field-like torque has a strong impact on the steady-state precession current region and the oscillation frequency. In particular, the steady-state precession can occur at zero applied magnetic field when the ratio between the field-like torque and the spin transfer torque takes up a negative value. In addition, the dependence of the oscillation properties onmore » the junction sizes has also been analyzed. The results indicate that this compact structure of spin transfer oscillator without the applied magnetic field is practicable under certain conditions, and it may be a promising configuration for the new generation of on-chip oscillators.« less

Counterrotating-Shoulder Mechanism for Friction Stir Welding

NASA Technical Reports Server (NTRS)

Nunes, Arthur C., Jr.

2007-01-01

A counterrotating-shoulder mechanism has been proposed as an alternative to the mechanism and fixtures used in conventional friction stir welding. The mechanism would internally react most or all of the forces and torques exerted on the workpiece, making it unnecessary to react the forces and torques through massive external fixtures. In conventional friction stir welding, a rotating pin tool is inserted into, and moved along, a weld seam. As the pin tool moves, it stirs together material from the opposite sides of the seam to form the weld. A large axial plunge force must be exerted upon the workpiece through and by the pin tool and a shoulder attached above the pin tool in order to maintain the pressure necessary for the process. The workpiece is secured on top of an anvil, which supports the workpiece against the axial plunge force and against the torque exerted by the pin tool and shoulder. The anvil and associated fixtures must be made heavy (and, therefore, are expensive) to keep the workpiece stationary. In addition, workpiece geometries must be limited to those that can be accommodated by the fixtures. The predecessor of the proposed counterrotating-shoulder mechanism is a second-generation, self-reacting tool, resembling a bobbin, that makes it possible to dispense with the heavy anvil. This tool consists essentially of a rotating pin tool with opposing shoulders. Although the opposing shoulders maintain the necessary pressure without need to externally apply or react a large plunge force, the torque exerted on the workpiece remains unreacted in the absence of a substantial external fixture. Depending on the RPM and the thickness of the workpiece, the torque can be large. The proposed mechanism (see figure) would include a spindle attached to a pin tool with a lower shoulder. The spindle would be coupled via splines to the upper one of three bevel gears in a differential drive. The middle bevel gear would be the power-input gear and would be coupled to the upper and lower bevel gears. The lower bevel gear would be attached to the upper shoulder and would slide and rotate freely over the spindle. The spindle would be fastened by its threaded upper end to an external submechanism that would exert axial tension on the spindle to load the workpiece in compression between the shoulders. By reducing or eliminating (relative to the use of a self reacting tool) the torque that must be reacted externally, the use of the proposed tool would reduce the tendency toward distortion or slippage of the workpiece. To begin a weld, the spindle would be inserted through a hole in the workpiece or run-on tab at the beginning of the seam and fastened to the loading submechanism. Rotation and axial loading would be increased gradually from zero and, after a time to be determined by trial and error, translation along the weld seam would be increased gradually from zero to a steady weld speed. The weld would be ended by running the mechanism off the workpiece or, if the lower shoulder were detachable, by detaching the lower shoulder from the spindle and pulling the pin tool out.

Unusual negative permeability of single magnetic nanowire excited by the spin transfer torque effect

NASA Astrophysics Data System (ADS)

Han, Mangui; Zhou, Wu

2018-07-01

Due to the effect of spin transfer torque, negative imaginary parts of permeability (μ″ < 0) are reported in a ferromagnetic nanowire. It is found that negative μ″ values are resulted from the interaction of spin polarized conduction electrons with the spatially non-uniform distributed magnetic moments at both ends of nanowires. The results are well explained from the effect of spin transfer torque on the precession of magnetization under the excitation of both the pulsed magnetic field and static electric field.

The Passive Series Stiffness That Optimizes Torque Tracking for a Lower-Limb Exoskeleton in Human Walking

PubMed Central

Zhang, Juanjuan; Collins, Steven H.

2017-01-01

This study uses theory and experiments to investigate the relationship between the passive stiffness of series elastic actuators and torque tracking performance in lower-limb exoskeletons during human walking. Through theoretical analysis with our simplified system model, we found that the optimal passive stiffness matches the slope of the desired torque-angle relationship. We also conjectured that a bandwidth limit resulted in a maximum rate of change in torque error that can be commanded through control input, which is fixed across desired and passive stiffness conditions. This led to hypotheses about the interactions among optimal control gains, passive stiffness and desired quasi-stiffness. Walking experiments were conducted with multiple angle-based desired torque curves. The observed lowest torque tracking errors identified for each combination of desired and passive stiffnesses were shown to be linearly proportional to the magnitude of the difference between the two stiffnesses. The proportional gains corresponding to the lowest observed errors were seen inversely proportional to passive stiffness values and to desired stiffness. These findings supported our hypotheses, and provide guidance to application-specific hardware customization as well as controller design for torque-controlled robotic legged locomotion. PMID:29326580

Influence of Drilling Parameters on Torque during Drilling of GFRP Composites Using Response Surface Methodology

NASA Astrophysics Data System (ADS)

Mohan, N. S.; Kulkarni, S. M.

2018-01-01

Polymer based composites have marked their valuable presence in the area of aerospace, defense and automotive industry. Components made of composite, are assembled to main structure by fastener, which require accurate, precise high quality holes to be drilled. Drilling the hole in composite with accuracy require control over various processes parameters viz., speed, feed, drill bit size and thickens of specimen. TRIAC VMC machining center is used to drill the hole and to relate the cutting and machining parameters on the torque. MINITAB 14 software is used to analyze the collected data. As a function of cutting and specimen parameters this method could be useful for predicting torque parameters. The purpose of this work is to investigate the effect of drilling parameters to get low torque value. Results show that thickness of specimen and drill bit size are significant parameters influencing the torque and spindle speed and feed rate have least influence and overlaid plot indicates a feasible and low region of torque is observed for medium to large sized drill bits for the range of spindle speed selected. Response surface contour plots indicate the sensitivity of the drill size and specimen thickness to the torque.

40 CFR Appendix A to Subpart D of... - Tables

Code of Federal Regulations, 2010 CFR

2010-07-01

...-test and post-test values) kPa Pv Saturation pressure at dew point temperature kPa Ra Relative humidity...) CONTROL OF EMISSIONS FROM NEW AND IN-USE NONROAD COMPRESSION-IGNITION ENGINES Emission Test Equipment... Percent torque related to maximum torque for the test mode % mass Pollutant mass flow g/h nd, i Engine...

40 CFR Appendix A to Subpart D of... - Tables

Code of Federal Regulations, 2011 CFR

2011-07-01

... post-test values) kPa Ra Relative humidity of the ambient air percent T Absolute temperature at air...) CONTROL OF EMISSIONS FROM NONROAD SPARK-IGNITION ENGINES AT OR BELOW 19 KILOWATTS Emission Test Equipment... torque related to maximum torque for the test mode percent mass Pollutant mass flow g/h nd, i Engine...

40 CFR Appendix A to Subpart D of... - Tables

Code of Federal Regulations, 2013 CFR

2013-07-01

... post-test values) kPa Ra Relative humidity of the ambient air percent T Absolute temperature at air...) CONTROL OF EMISSIONS FROM NONROAD SPARK-IGNITION ENGINES AT OR BELOW 19 KILOWATTS Emission Test Equipment... torque related to maximum torque for the test mode percent mass Pollutant mass flow g/h nd, i Engine...

40 CFR Appendix A to Subpart D of... - Tables

Code of Federal Regulations, 2010 CFR

2010-07-01

... post-test values) kPa Ra Relative humidity of the ambient air percent T Absolute temperature at air...) CONTROL OF EMISSIONS FROM NONROAD SPARK-IGNITION ENGINES AT OR BELOW 19 KILOWATTS Emission Test Equipment... torque related to maximum torque for the test mode percent mass Pollutant mass flow g/h nd, i Engine...

40 CFR Appendix A to Subpart D of... - Tables

Code of Federal Regulations, 2014 CFR

2014-07-01

...-test and post-test values) kPa Pv Saturation pressure at dew point temperature kPa Ra Relative humidity...) CONTROL OF EMISSIONS FROM NEW AND IN-USE NONROAD COMPRESSION-IGNITION ENGINES Emission Test Equipment... Percent torque related to maximum torque for the test mode % mass Pollutant mass flow g/h nd, i Engine...

40 CFR Appendix A to Subpart D of... - Tables

Code of Federal Regulations, 2011 CFR

2011-07-01

...-test and post-test values) kPa Pv Saturation pressure at dew point temperature kPa Ra Relative humidity...) CONTROL OF EMISSIONS FROM NEW AND IN-USE NONROAD COMPRESSION-IGNITION ENGINES Emission Test Equipment... Percent torque related to maximum torque for the test mode % mass Pollutant mass flow g/h nd, i Engine...

40 CFR Appendix A to Subpart D of... - Tables

Code of Federal Regulations, 2012 CFR

2012-07-01

...-test and post-test values) kPa Pv Saturation pressure at dew point temperature kPa Ra Relative humidity...) CONTROL OF EMISSIONS FROM NEW AND IN-USE NONROAD COMPRESSION-IGNITION ENGINES Emission Test Equipment... Percent torque related to maximum torque for the test mode % mass Pollutant mass flow g/h nd, i Engine...

40 CFR Appendix A to Subpart D of... - Tables

Code of Federal Regulations, 2012 CFR

2012-07-01

... post-test values) kPa Ra Relative humidity of the ambient air percent T Absolute temperature at air...) CONTROL OF EMISSIONS FROM NONROAD SPARK-IGNITION ENGINES AT OR BELOW 19 KILOWATTS Emission Test Equipment... torque related to maximum torque for the test mode percent mass Pollutant mass flow g/h nd, i Engine...

40 CFR Appendix A to Subpart D of... - Tables

Code of Federal Regulations, 2014 CFR

2014-07-01

... post-test values) kPa Ra Relative humidity of the ambient air percent T Absolute temperature at air...) CONTROL OF EMISSIONS FROM NONROAD SPARK-IGNITION ENGINES AT OR BELOW 19 KILOWATTS Emission Test Equipment... torque related to maximum torque for the test mode percent mass Pollutant mass flow g/h nd, i Engine...

40 CFR Appendix A to Subpart D of... - Tables

Code of Federal Regulations, 2013 CFR

2013-07-01

...-test and post-test values) kPa Pv Saturation pressure at dew point temperature kPa Ra Relative humidity...) CONTROL OF EMISSIONS FROM NEW AND IN-USE NONROAD COMPRESSION-IGNITION ENGINES Emission Test Equipment... Percent torque related to maximum torque for the test mode % mass Pollutant mass flow g/h nd, i Engine...

78 FR 56601 - Airworthiness Directives; Fokker Services B.V. Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-13

... torque values of nuts on circuit breakers, contactors, and terminal blocks of the EPC and battery relay... blocks of the EPC and battery relay panel, as applicable; and do all applicable adjustments of the torque... contacts and nuts on circuit breakers, contactors, and terminal blocks of the EPC and battery relay panel...

Actuation crosstalk in free-falling systems: Torsion pendulum results for the engineering model of the LISA pathfinder gravitational reference sensor

NASA Astrophysics Data System (ADS)

Bassan, M.; Cavalleri, A.; De Laurentis, M.; De Marchi, F.; De Rosa, R.; Di Fiore, L.; Dolesi, R.; Finetti, N.; Garufi, F.; Grado, A.; Hueller, M.; Marconi, L.; Milano, L.; Minenkov, Y.; Pucacco, G.; Stanga, R.; Vetrugno, D.; Visco, M.; Vitale, S.; Weber, W. J.

2018-01-01

In this paper we report on measurements on actuation crosstalk, relevant to the gravitational reference sensors for LISA Pathfinder and LISA. In these sensors, a Test Mass (TM) falls freely within a system of electrodes used for readout and control. These measurements were carried out on ground with a double torsion pendulum that allowed us to estimate both the torque injected into the sensor when a control force is applied and, conversely, the force leaking into the translational degree of freedom due to the applied torque.The values measured on our apparatus (the engineering model of the LISA Pathfinder sensor) agree to within 0.2% (over a maximum measured crosstalk of 1%) with predictions of a mathematical model when measuring force to torque crosstalk, while it is somewhat larger than expected (up to 3.5%) when measuring torque to force crosstalk. However, the values in the relevant range, i.e. when the TM is well centered ( ± 10 μm) in the sensor, remain smaller than 0.2%, satisfying the LISA Pathfinder requirements.

Modeling and Control of Needles with Torsional Friction

PubMed Central

Reed, Kyle B.; Okamura, Allison M.; Cowan, Noah J.

2010-01-01

A flexible needle can be accurately steered by robotically controlling the bevel tip orientation as the needle is inserted into tissue. Friction between the long, flexible needle shaft and the tissue can cause a significant discrepancy between the orientation of the needle tip and the orientation of the base where the needle angle is controlled. Our experiments show that several common phantom tissues used in needle steering experiments impart substantial friction forces to the needle shaft, resulting in a lag of over 45° for a 10 cm insertion depth in some phantoms; clinical studies report torques large enough to cause similar errors during needle insertions. Such angle discrepancies will result in poor performance or failure of path planners and image-guided controllers, since the needles used in percutaneous procedures are too small for state-of-the-art imaging to accurately measure the tip angle. To compensate for the angle discrepancy, we develop an estimator using a mechanics-based model of the rotational dynamics of a needle being inserted into tissue. Compared to controllers that assume a rigid needle in a frictionless environment, our estimator-based controller improves the tip angle convergence time by nearly 50% and reduces the path deviation of the needle by 70%. PMID:19695979

The influence of tip shape on bending force during needle insertion

PubMed Central

van de Berg, Nick J.; de Jong, Tonke L.; van Gerwen, Dennis J.; Dankelman, Jenny; van den Dobbelsteen, John J.

2017-01-01

Steering of needles involves the planning and timely modifying of instrument-tissue force interactions to allow for controlled deflections during the insertion in tissue. In this work, the effect of tip shape on these forces was studied using 10 mm diameter needle tips. Six different tips were selected, including beveled and conical versions, with or without pre-bend or pre-curve. A six-degree-of-freedom force/torque sensor measured the loads during indentations in tissue simulants. The increased insertion (axial) and bending (radial) forces with insertion depth — the force-displacement slopes — were analyzed. Results showed that the ratio between radial and axial forces was not always proportional. This means that the tip load does not have a constant orientation, as is often assumed in mechanics-based steering models. For all tip types, the tip-load assumed a more radial orientation with increased axial load. This effect was larger for straight tips than for pre-bent or pre-curved tips. In addition, the force-displacement slopes were consistently higher for (1) increased tip angles, and for (2) beveled tips compared to conical tips. Needles with a bent or curved tip allow for an increased bending force and a decreased variability of the tip load vector orientation. PMID:28074939

Discharge properties of motor units during steady isometric contractions performed with the dorsiflexor muscles

PubMed Central

Klass, Malgorzata; Duchateau, Jacques; Enoka, Roger M.

2012-01-01

The purpose of this study was to record the discharge characteristics of tibialis anterior motor units over a range of target forces and to import these data, along with previously reported observations, into a computational model to compare experimental and simulated measures of torque variability during isometric contractions with the dorsiflexor muscles. The discharge characteristics of 44 motor units were quantified during brief isometric contractions at torques that ranged from recruitment threshold to an average of 22 ± 14.4% maximal voluntary contraction (MVC) torque above recruitment threshold. The minimal [range: 5.8–19.8 pulses per second (pps)] and peak (range: 8.6–37.5 pps) discharge rates of motor units were positively related to the recruitment threshold torque (R2 ≥ 0.266; P < 0.001). The coefficient of variation for interspike interval at recruitment was positively associated with recruitment threshold torque (R2 = 0.443; P < 0.001) and either decreased exponentially or remained constant as target torque increased above recruitment threshold torque. The variability in the simulated torque did not differ from the experimental values once the recruitment range was set to ∼85% MVC torque, and the association between motor twitch contraction times and peak twitch torque was defined as a weak linear association (R2 = 0.096; P < 0.001). These results indicate that the steadiness of isometric contractions performed with the dorsiflexor muscle depended more on the distributions of mechanical properties than discharge properties across the population of motor units in the tibialis anterior. PMID:22442023

Discharge properties of motor units during steady isometric contractions performed with the dorsiflexor muscles.

PubMed

Jesunathadas, Mark; Klass, Malgorzata; Duchateau, Jacques; Enoka, Roger M

2012-06-01

The purpose of this study was to record the discharge characteristics of tibialis anterior motor units over a range of target forces and to import these data, along with previously reported observations, into a computational model to compare experimental and simulated measures of torque variability during isometric contractions with the dorsiflexor muscles. The discharge characteristics of 44 motor units were quantified during brief isometric contractions at torques that ranged from recruitment threshold to an average of 22 ± 14.4% maximal voluntary contraction (MVC) torque above recruitment threshold. The minimal [range: 5.8-19.8 pulses per second (pps)] and peak (range: 8.6-37.5 pps) discharge rates of motor units were positively related to the recruitment threshold torque (R(2) ≥ 0.266; P < 0.001). The coefficient of variation for interspike interval at recruitment was positively associated with recruitment threshold torque (R(2) = 0.443; P < 0.001) and either decreased exponentially or remained constant as target torque increased above recruitment threshold torque. The variability in the simulated torque did not differ from the experimental values once the recruitment range was set to ∼85% MVC torque, and the association between motor twitch contraction times and peak twitch torque was defined as a weak linear association (R(2) = 0.096; P < 0.001). These results indicate that the steadiness of isometric contractions performed with the dorsiflexor muscle depended more on the distributions of mechanical properties than discharge properties across the population of motor units in the tibialis anterior.

Self-cutting blades and their influence on primary stability of tapered dental implants in a simulated low-density bone model: a laboratory study.

PubMed

Kim, Duck-Rae; Lim, Young-Jun; Kim, Myung-Joo; Kwon, Ho-Beom; Kim, Sung-Hun

2011-11-01

This study tested the hypothesis that there would be differences in primary stability due to the presence of self cutting blades. We investigated the effect of a self-cutting blade implant design on the primary stability of tapered dental implants in a simulated low-density bone model. Implant fixtures with 2 different designs, one with self-cutting blades and the other without self-cutting blades, were fabricated in the same implant system. Insertion torque, resonance frequency analysis, reverse torque, and pull-out and push-in tests were evaluated in grade no. 10 solid rigid polyurethane foam. All 5 assessments of the group without self-cutting blades were significantly higher than those of the self-cutting group (P < .001). The implants without self-cutting blades create a lateral compression with increased contact surface area and consequently improve the primary stability in a simulated low-density bone model. Copyright © 2011 Mosby, Inc. All rights reserved.

Clinical measurement of force systems upon activation of transpalatal arch in the treatment of unilateral crossbite.

PubMed

Yoshida, N; Koga, Y; Jost-Brinkmann, P G; Kobayashi, K

2003-01-01

in this study, forces and moments acting on the molars were theoretically determined by means of small-deflection analysis when an asymmetric third-order activation of the TPA was carried out. the transpalatal arch (TPA) is used to correct unilateral crossbites through the application of buccal root torque to the anchorage molar and lingual root torque to the contralateral molar in crossbite, combined with expansion. Unfortunately, the complex force systems created at the molars upon activation of the TPA cannot be easily estimated. our computations revealed that the vertical forces developed on the molars when both ends of the TPA are inserted into the lingual sheaths (two-couple system) is four-times greater than those when only one end is tied to the lingual sheath as a single-point contact (one-couple system). we propose a method of clinical estimation of the force system in a two-couple system by directly measuring the vertical force produced by the one-couple system.

Biomechanical Stability of Dental Implants in Augmented Maxillary Sites: Results of a Randomized Clinical Study with Four Different Biomaterials and PRF and a Biological View on Guided Bone Regeneration

PubMed Central

Angelo, Troedhan; Marcel, Wainwright; Andreas, Kurrek; Izabela, Schlichting

2015-01-01

Introduction. Bone regenerates mainly by periosteal and endosteal humoral and cellular activity, which is given only little concern in surgical techniques and choice of bone grafts for guided bone regeneration. This study investigates on a clinical level the biomechanical stability of augmented sites in maxillary bone when a new class of moldable, self-hardening calcium-phosphate biomaterials (SHB) is used with and without the addition of Platelet Rich Fibrin (aPRF) in the Piezotome-enhanced subperiosteal tunnel-technique (PeSPTT). Material and Methods. 82 patients with horizontal atrophy of anterior maxillary crest were treated with PeSPTT and randomly assigned biphasic (60% HA/40% bTCP) or monophasic (100% bTCP) SHB without or with addition of aPRF. 109 implants were inserted into the augmented sites after 8.3 months and the insertion-torque-value (ITV) measured as clinical expression of the (bio)mechanical stability of the augmented bone and compared to ITVs of a prior study in sinus lifting. Results. Significant better results of (bio)mechanical stability almost by two-fold, expressed by higher ITVs compared to native bone, were achieved with the used biomaterials and more constant results with the addition of aPRF. Conclusion. The use of SHB alone or combined with aPRF seems to be favourable to achieve a superior (bio)mechanical stable restored alveolar bone. PMID:25954758

Algorithm Optimally Allocates Actuation of a Spacecraft

NASA Technical Reports Server (NTRS)

Motaghedi, Shi

2007-01-01

A report presents an algorithm that solves the following problem: Allocate the force and/or torque to be exerted by each thruster and reaction-wheel assembly on a spacecraft for best performance, defined as minimizing the error between (1) the total force and torque commanded by the spacecraft control system and (2) the total of forces and torques actually exerted by all the thrusters and reaction wheels. The algorithm incorporates the matrix vector relationship between (1) the total applied force and torque and (2) the individual actuator force and torque values. It takes account of such constraints as lower and upper limits on the force or torque that can be applied by a given actuator. The algorithm divides the aforementioned problem into two optimization problems that it solves sequentially. These problems are of a type, known in the art as semi-definite programming problems, that involve linear matrix inequalities. The algorithm incorporates, as sub-algorithms, prior algorithms that solve such optimization problems very efficiently. The algorithm affords the additional advantage that the solution requires the minimum rate of consumption of fuel for the given best performance.

Estimation of Electrically-Evoked Knee Torque from Mechanomyography Using Support Vector Regression.

PubMed

Ibitoye, Morufu Olusola; Hamzaid, Nur Azah; Abdul Wahab, Ahmad Khairi; Hasnan, Nazirah; Olatunji, Sunday Olusanya; Davis, Glen M

2016-07-19

The difficulty of real-time muscle force or joint torque estimation during neuromuscular electrical stimulation (NMES) in physical therapy and exercise science has motivated recent research interest in torque estimation from other muscle characteristics. This study investigated the accuracy of a computational intelligence technique for estimating NMES-evoked knee extension torque based on the Mechanomyographic signals (MMG) of contracting muscles that were recorded from eight healthy males. Simulation of the knee torque was modelled via Support Vector Regression (SVR) due to its good generalization ability in related fields. Inputs to the proposed model were MMG amplitude characteristics, the level of electrical stimulation or contraction intensity, and knee angle. Gaussian kernel function, as well as its optimal parameters were identified with the best performance measure and were applied as the SVR kernel function to build an effective knee torque estimation model. To train and test the model, the data were partitioned into training (70%) and testing (30%) subsets, respectively. The SVR estimation accuracy, based on the coefficient of determination (R²) between the actual and the estimated torque values was up to 94% and 89% during the training and testing cases, with root mean square errors (RMSE) of 9.48 and 12.95, respectively. The knee torque estimations obtained using SVR modelling agreed well with the experimental data from an isokinetic dynamometer. These findings support the realization of a closed-loop NMES system for functional tasks using MMG as the feedback signal source and an SVR algorithm for joint torque estimation.

Torque loss of different abutment sizes before and after cyclic loading.

PubMed

Moris, Izabela Cristina; Faria, Adriana Cláudia; Ribeiro, Ricardo Faria; Rodrigues, Renata Cristina

2015-01-01

The aim of this study was to compare 3.8- and 4.8-mm abutments submitted to simulations of masticatory cycles to examine whether abutment diameter and cemented vs screw-retained crowns affect torque loss of the abutments and crowns. Forty implant/abutment sets were divided into the following groups (n = 10 in each group): (1) G4.8S included 4.8-mm abutment with screw-retained crown; (2) G4.8C included 4.8-mm abutment with cemented crown; (3) G3.8S included 3.8-mm abutment with screw-retained crown; and (4) G3.8C included 3.8-mm abutment with cemented crown. All abutments were tightened with torque values of 20 Ncm, and 10 Ncm for screw-retained crowns. Torque loss was measured before and after cycling loading (300,000 cycles). Torque loss of screw-retained crowns significantly increased after cycling in abutments of groups G3.8S (P ≤ .05) and G4.8S (P = .001). No difference was noted between the abutments before cycling (P = .735), but G3.8S abutments presented greater torque loss than the other groups after cycling (P = .008). Significant differences were noted in the abutment torque loss before and after cycling loading only for the G3.8C group (P ≤ .05). The abutment diameter affects torque loss of screw-retained crowns and leads to failure during the test; mechanical cycling increases torque loss of abutment screw and screw-retained crowns.

Role of magnetic exchange interaction due to magnetic anisotropy on inverse spin Hall voltage at FeSi3%/Pt thin film bilayer interface

NASA Astrophysics Data System (ADS)

Shah, Jyoti; Ahmad, Saood; Chaujar, Rishu; Puri, Nitin K.; Negi, P. S.; Kotnala, R. K.

2017-12-01

In our recent studies inverse spin Hall voltage (ISHE) was investigated by ferromagnetic resonance (FMR) using bilayer FeSi3%/Pt thin film prepared by pulsed laser deposition (PLD) technique. In ISHE measurement microwave signal was applied on FeSi3% film along with DC magnetic field. Higher magnetization value along the film-plane was measured by magnetic hysteresis (M-H) loop. Presence of magnetic anisotropy has been obtained by M-H loop which showed easy direction of magnetization when applied magnetic field is parallel to the film plane. The main result of this study is that FMR induced inverse spin Hall voltage 12.6 μV at 1.0 GHz was obtained across Pt layer. Magnetic exchange field at bilayer interface responsible for field torque was measured 6 × 1014 Ω-1 m-2 by spin Hall magnetoresistance. The damping torque and spin Hall angle have been evaluated as 0.084 and 0.071 respectively. Presence of Si atom in FeSi3% inhomogenize the magnetic exchange field among accumulated spins at bilayer interface and feebly influenced by spin torque of FeSi3% layer. Weak field torque suppresses the spin pumping to Pt layer thus low value of inverse spin Hall voltage is obtained. This study provides an excellent opportunity to investigate spin transfer torque effect, thus motivating a more intensive experimental effort for its utilization at maximum potential. The improvement in spin transfer torque may be useful in spin valve, spin battery and spin transistor application.

The effect of different screw-rod design on the anti-rotational torque: a biomechanical comparison of three conventional screw-rod constructs.

PubMed

Huang, Zifang; Wang, Chongwen; Fan, Hengwei; Sui, Wenyuan; Li, Xueshi; Wang, Qifei; Yang, Junlin

2017-07-28

Screw-rod constructs have been widely used to correct spinal deformities, but the effects of different screw-rod systems on anti-rotational torque have not been determined. This study aimed to analyze the biomechanical effect of different rod-screw constructs on anti-rotational torque. Three conventional spinal screw-rod systems (Legacy, RF-F-10 and USSII) were used to test the anti-rotational torque in the material test machine. ANOVA was performed to evaluate the anti-rotational capacity of different pedicle screws-rod constructs. The anti-rotational torque of Legacy group, RF-F-10 group and USSII group were 12.3 ± 1.9 Nm, 6.8 ± 0.4 Nm, and 3.9 ± 0.8 Nm, with a P value lower than 0.05. This results indicated that the Legacy screws-rod construct could provide a highest anti-rotation capacity, which is 68% and 210% greater than RF-F-10 screw-rod construct and USSII screw-rod respectively. The anti-rotational torque may be mainly affected by screw cap and groove design. Our result showed the anti-rotational torque are: Legacy system > RF-F-10 system > USSII system, suggesting that appropriate rod-screw constructs selection in surgery may be vital for anti-rotational torque improvement and preventing derotation correction loss.

Stress Induced in the Periodontal Ligament under Orthodontic Loading (Part I): A Finite Element Method Study Using Linear Analysis.

PubMed

Hemanth, M; Deoli, Shilpi; Raghuveer, H P; Rani, M S; Hegde, Chatura; Vedavathi, B

2015-08-01

Orthodontic tooth movement is a complex procedure that occurs due to various biomechanical changes in the periodontium. Optimal orthodontic forces yield maximum tooth movement whereas if the forces fall beyond the optimal threshold it can cause deleterious effects. Among various types of tooth movements intrusion and lingual root torque are associated with causing root resoprtion, especially with the incisors. Therefore in this study, the stress patterns in the periodontal ligament (PDL) were evaluated with intrusion and lingual root torque using finite element method (FEM). A three-dimensional (3D) FEM model of the maxillary incisors was generated using SOLIDWORKS modeling software. Stresses in the PDL were evaluated with intrusive and lingual root torque movements by a 3D FEM using ANSYS software using linear stress analysis. It was observed that with the application of intrusive load compressive stresses were distributed at the apex whereas tensile stress was seen at the cervical margin. With the application of lingual root torque maximum compressive stress was distributed at the apex and tensile stress was distributed throughout the PDL. For intrusive and lingual root torque movements stress values over the PDL was within the range of optimal stress value as proposed by Lee, with a given force system by Proffit as optimum forces for orthodontic tooth movement using linear properties.

Stress Induced in the Periodontal Ligament under Orthodontic Loading (Part I): A Finite Element Method Study Using Linear Analysis

PubMed Central

Hemanth, M; deoli, Shilpi; Raghuveer, H P; Rani, M S; Hegde, Chatura; Vedavathi, B

2015-01-01

Background: Orthodontic tooth movement is a complex procedure that occurs due to various biomechanical changes in the periodontium. Optimal orthodontic forces yield maximum tooth movement whereas if the forces fall beyond the optimal threshold it can cause deleterious effects. Among various types of tooth movements intrusion and lingual root torque are associated with causing root resoprtion, especially with the incisors. Therefore in this study, the stress patterns in the periodontal ligament (PDL) were evaluated with intrusion and lingual root torque using finite element method (FEM). Materials and Methods: A three-dimensional (3D) FEM model of the maxillary incisors was generated using SOLIDWORKS modeling software. Stresses in the PDL were evaluated with intrusive and lingual root torque movements by a 3D FEM using ANSYS software using linear stress analysis. Results: It was observed that with the application of intrusive load compressive stresses were distributed at the apex whereas tensile stress was seen at the cervical margin. With the application of lingual root torque maximum compressive stress was distributed at the apex and tensile stress was distributed throughout the PDL. Conclusion: For intrusive and lingual root torque movements stress values over the PDL was within the range of optimal stress value as proposed by Lee, with a given force system by Proffit as optimum forces for orthodontic tooth movement using linear properties. PMID:26464555

[Magnetic resonance compatibility research for coronary mental stents].

PubMed

Wang, Ying; Liu, Li; Wang, Shuo; Shang, Ruyao; Wang, Chunren

2015-01-01

The objective of this article is to research magnetic resonance compatibility for coronary mental stents, and to evaluate the magnetic resonance compatibility based on laboratory testing results. Coronary stents magnetic resonance compatibility test includes magnetically induced displacement force test, magnetically induced torque test, radio frequency induced heating and evaluation of MR image. By magnetic displacement force and torque values, temperature, and image distortion values to determine metal coronary stent demagnetization effect. The methods can be applied to test magnetic resonance compatibility for coronary mental stents and evaluate its demagnetization effect.

Life test results for the advanced very high resolution radiometer scanner

NASA Technical Reports Server (NTRS)

Lenz, James

1996-01-01

The following paper reports the results obtained during a 3.33-year life test on the TIROS Advanced Very High Resolution Radiometer/3 (AVHRR/3) Scanner. The bearing drag torque and lubricant loss over life will be compared to predicted values developed through modeling. The condition of the lubricant at the end of the test will be described and a theory presented to explain the results obtained. The differences (if any) in the predicted and measured values of drag torque and lubricant loss will be discussed and possible reasons for these examined.

Automated Bone Screw Tightening to Adaptive Levels of Stripping Torque.

PubMed

Reynolds, Karen J; Mohtar, Aaron A; Cleek, Tammy M; Ryan, Melissa K; Hearn, Trevor C

2017-06-01

To use relationships between tightening parameters, related to bone quality, to develop an automated system that determines and controls the level of screw tightening. An algorithm relating current at head contact (IHC) to current at construct failure (Imax) was developed. The algorithm was used to trigger cessation of screw insertion at a predefined tightening level, in real time, between head contact and maximum current. The ability of the device to stop at the predefined level was assessed. The mean (±SD) current at which screw insertion ceased was calculated to be [51.47 ± 9.75% × (Imax - IHC)] + IHC, with no premature bone failures. A smart screwdriver was developed that uses the current from the motor driving the screw to predict the current at which the screw will strip the bone threads. The device was implemented and was able to achieve motor shut-off and cease tightening at a predefined threshold, with no premature bone failures.

Machined and plastic copings in three-element prostheses with different types of implantabutment joints: a strain gauge comparative analysis

PubMed Central

NISHIOKA, Renato Sussumu; NISHIOKA, Lea Nogueira Braulino de Melo; ABREU, Celina Wanderley; de VASCONCELLOS, Luis Gustavo Oliveira; BALDUCCI, Ivan

2010-01-01

Objective Using strain gauge (SG) analysis, the aim of this in vitro study was quantify the strain development during the fixation of three-unit screw implant-supported fixed partial dentures, varying the types of implant-abutment joints and the type of prosthetic coping. The hypotheses were that the type of hexagonal connection would generate different microstrains and the type of copings would produce similar microstrains after prosthetic screws had been tightened onto microunit abutments. Materials and methods Three dental implants with external (EH) and internal (IH) hexagonal configurations were inserted into two polyurethane blocks. Microunit abutments were screwed onto their respective implant groups, applying a torque of 20 Ncm. Machined Co-Cr copings (M) and plastic prosthetic copings (P) were screwed onto the abutments, which received standard wax patterns. The wax patterns were cast in Co-Cr alloy (n=5), forming four groups: G1) EH/M; G2) EH/P; G3) IH/M and G4) IH/P. Four SGs were bonded onto the surface of the block tangentially to the implants, SG 1 mesially to implant 1, SG 2 and SG 3 mesially and distally to implant 2, respectively, and SG 4 distally to implant 3. The superstructure’s occlusal screws were tightened onto microunit abutments with 10 Ncm torque using a manual torque driver. The magnitude of microstrain on each SG was recorded in units of microstrain (µε). The data were analyzed statistically by ANOVA and Tukey’s test (p<0.05). Results Microstrain values of each group were: G1= 338.1±223.0 µε; G2= 363.9±190.9 µε; G3= 415.1±53.5 µε; G4= 363.9±190.9 µε. No statistically significant difference was found between EH and IH, regardless of the type of copings (p>0.05). The hypotheses were partially accepted. Conclusions It was concluded that the type of hexagonal connection and coping presented similar mechanical behavior under tightening conditions. PMID:20856998

Thermomechanical conditions and stresses on the friction stir welding tool

NASA Astrophysics Data System (ADS)

Atthipalli, Gowtam

Friction stir welding has been commercially used as a joining process for aluminum and other soft materials. However, the use of this process in joining of hard alloys is still developing primarily because of the lack of cost effective, long lasting tools. Here I have developed numerical models to understand the thermo mechanical conditions experienced by the FSW tool and to improve its reusability. A heat transfer and visco-plastic flow model is used to calculate the torque, and traverse force on the tool during FSW. The computed values of torque and traverse force are validated using the experimental results for FSW of AA7075, AA2524, AA6061 and Ti-6Al-4V alloys. The computed torque components are used to determine the optimum tool shoulder diameter based on the maximum use of torque and maximum grip of the tool on the plasticized workpiece material. The estimation of the optimum tool shoulder diameter for FSW of AA6061 and AA7075 was verified with experimental results. The computed values of traverse force and torque are used to calculate the maximum shear stress on the tool pin to determine the load bearing ability of the tool pin. The load bearing ability calculations are used to explain the failure of H13 steel tool during welding of AA7075 and commercially pure tungsten during welding of L80 steel. Artificial neural network (ANN) models are developed to predict the important FSW output parameters as function of selected input parameters. These ANN consider tool shoulder radius, pin radius, pin length, welding velocity, tool rotational speed and axial pressure as input parameters. The total torque, sliding torque, sticking torque, peak temperature, traverse force, maximum shear stress and bending stress are considered as the output for ANN models. These output parameters are selected since they define the thermomechanical conditions around the tool during FSW. The developed ANN models are used to understand the effect of various input parameters on the total torque and traverse force during FSW of AA7075 and 1018 mild steel. The ANN models are also used to determine tool safety factor for wide range of input parameters. A numerical model is developed to calculate the strain and strain rates along the streamlines during FSW. The strain and strain rate values are calculated for FSW of AA2524. Three simplified models are also developed for quick estimation of output parameters such as material velocity field, torque and peak temperature. The material velocity fields are computed by adopting an analytical method of calculating velocities for flow of non-compressible fluid between two discs where one is rotating and other is stationary. The peak temperature is estimated based on a non-dimensional correlation with dimensionless heat input. The dimensionless heat input is computed using known welding parameters and material properties. The torque is computed using an analytical function based on shear strength of the workpiece material. These simplified models are shown to be able to predict these output parameters successfully.

Variable Torque Prescription: State of Art.

PubMed Central

Lacarbonara, Mariano; Accivile, Ettore; Abed, Maria R.; Dinoi, Maria Teresa; Monaco, Annalisa; Marzo, Giuseppe; Capogreco, Mario

2015-01-01

The variable prescription is widely described under the clinical aspect: the clinics is the result of the evolution of the state-of-the-art, aspect that is less considered in the daily literature. The state-of-the-art is the key to understand not only how we reach where we are but also to learn how to manage propely the torque, focusing on the technical and biomechanical purpos-es that led to the change of the torque values over time. The aim of this study is to update the clinicians on the aspects that affect the torque under the biomechanical sight, helping them to understand how to managing it, following the “timeline changes” in the different techniques so that the Variable Prescription Orthodontic (VPO) would be a suitable tool in every clinical case. PMID:25674173

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiong, Qi-lin, E-mail: xiongql@hust.edu.cn; Hubei Key Laboratory of Engineering Structural Analysis and Safety Assessment, Luoyu Road 1037, Wuhan 430074; Tian, Xiao Geng

The torsional mechanical properties of hexagonal single-walled boron nitride nanotubes (SWBNNTs), single-walled carbon nanotubes (SWCNTs), and their hybrid structures (SWBN-CNTs) are investigated using molecular dynamics (MD) simulation. Two approaches - force approach and energy approach, are adopted to calculate the shear moduli of SWBNNTs and SWCNTs, the discrepancy between two approaches is analyzed. The results show that the shear moduli of single-walled nanotubes (SWNTs), including SWBNNTs and SWCNTs are dependent on the diameter, especially for armchair SWNTs. The armchair SWNTs show the better ability of resistance the twisting comparable to the zigzag SWNTs. The effects of diameter and length onmore » the critical values of torque of SWNTs are obtained by comparing the torsional behaviors of SWNTs with different diameters and different lengths. It is observed that the MD results of the effect of diameter and length on the critical values of torque agrees well with the prediction of continuum shell model. The shear modulus of SWBN-CNT has a significant dependence on the percentages of SWCNT and the hybrid style has also an influence on shear modulus. The critical values of torque of SWBN-CNTs increase with the increase of the percentages of SWCNT. This phenomenon can be interpreted by the function relationship between the torque of different bonds (B-N-X, C-C-X, C-B-X, C-N-X) and the angles of bonds.« less

A Computational Model of Torque Generation: Neural, Contractile, Metabolic and Musculoskeletal Components

PubMed Central

Callahan, Damien M.; Umberger, Brian R.; Kent-Braun, Jane A.

2013-01-01

The pathway of voluntary joint torque production includes motor neuron recruitment and rate-coding, sarcolemmal depolarization and calcium release by the sarcoplasmic reticulum, force generation by motor proteins within skeletal muscle, and force transmission by tendon across the joint. The direct source of energetic support for this process is ATP hydrolysis. It is possible to examine portions of this physiologic pathway using various in vivo and in vitro techniques, but an integrated view of the multiple processes that ultimately impact joint torque remains elusive. To address this gap, we present a comprehensive computational model of the combined neuromuscular and musculoskeletal systems that includes novel components related to intracellular bioenergetics function. Components representing excitatory drive, muscle activation, force generation, metabolic perturbations, and torque production during voluntary human ankle dorsiflexion were constructed, using a combination of experimentally-derived data and literature values. Simulation results were validated by comparison with torque and metabolic data obtained in vivo. The model successfully predicted peak and submaximal voluntary and electrically-elicited torque output, and accurately simulated the metabolic perturbations associated with voluntary contractions. This novel, comprehensive model could be used to better understand impact of global effectors such as age and disease on various components of the neuromuscular system, and ultimately, voluntary torque output. PMID:23405245

[Application of plasma sprayed zirconia coating in dental implant: study in implant].

PubMed

Huang, Z F; Wang, Z F; Li, C H; Hao, D; Lan, J

2018-04-09

Objective: To investigate the osseointegration of a novel coating-plasma-sprayed zirconia in dental implant. Methods: Zirconia coating on non-thread titanium implant was prepared using plasma spraying, the implant surface morphology, surface roughness and wettability were measured. In vivo , zirconia coated implants were inserted in rabbit tibia and animals were respectively sacrificed at 2, 4, 8 and 12 weeks after implantation. The bond strength between implant and bone was measured by push-out test. The osseointegration was observed by scanning electron microscopy (SEM), micro CT and histological analyses. Quantified parameters including removal torque, and bone-implant contact (BIC) percentage were calculated. Results: The surface roughness (1.6 µm) and wettability (54.6°) of zirconia coated implant was more suitable than those of titanium implant (0.6 µm and 74.4°) for osseointegration. At 12 weeks, the push-out value of zirconia coated implant and titanium implant were (64.9±3.0) and (50.4±2.9) N, and BIC value of these two groups were (54.7±3.6)% and (41.5±3.6)%. All these differences had statistical significance. Conclusions: The surface characters of zirconia coated implant were more suitable for osseointegration and present better osseointegration than smooth titanium implant in vivo , especially at early stage.

A Randomized Case-Series Study Comparing the Stability of Implant with Two Different Surfaces Placed in Fresh Extraction Sockets and Immediately Loaded

PubMed Central

Vanden Bogaerde, Leonardo; Sennerby, Lars

2016-01-01

Background. Hydrophilic and moderately rough implant surfaces have been proposed to enhance the osseointegration response. Aim. The aim of this study was to compare early changes of stability for two implants with identical macrodesign but with different surface topographies. Materials and Methods. In 11 patients, a total of 22 implants (11 bimodal (minimally rough, control) and 11 proactive (moderately rough and hydrophilic, test), Neoss Ltd., Harrogate, UK) were immediately placed into fresh extraction sockets and immediately loaded. The peak insertion torque (IT) was measured in Ncm at placement. Resonance Frequency Analysis (RFA) measurements were made at baseline and 2, 4, 6, and 12 weeks after surgery. Results. The two implant types showed similar IT and RFA values at placement (NS). A dip of RFA values after 2 weeks followed by an increase was observed, where the test implant showed a less pronounced decrease and a more rapid recovery than the control implant. The test implants were significantly more stable than the control ones after 12 weeks. Conclusions. The results from the present study indicated that the hydrophilic and rougher test implant was more resistant to immediate loading and showed a significantly higher stability than the smoother control implant after 12 weeks. PMID:27042180

Influence of Spore Moisture Content on the Dry-Heat Resistance of Bacillus subtilis var. niger

PubMed Central

Angelotti, Robert; Maryanski, James H.; Butler, Thomas F.; Peeler, James T.; Campbell, Jeptha E.

1968-01-01

The dry-heat resistance of Bacillus subtilis var. niger spores located in or on various materials was determined as D and z values in the range of 105 through 160 C. The systems tested included spores located on steel and paper strips, spores located between stainless-steel washers mated together under 150 inch-lb and 12 inch-lb of torque, and spores encapsulated in methylmethacrylate and epoxy plastics. D values for a given temperature varied with the test system. High D values were observed for the systems in which spores were encapsulated or under heavy torque, whereas lower D values were observed for the steel and paper strip systems and the lightly torqued system. Similar z values were obtained for the plastic and steel strip systems (zD = 21 C), but an unusually low z for spores on paper (zD = 12.9 C) and an unusually high z for spores on steel washers mated at 150 inch-lb of torque (zD = 32 C) were observed. The effect of spore moisture content on the D value of spores encapsulated in water-impermeable plastic was determined, and maximal resistance was observed for spores with a water activity (aw) of 0.2 to 0.4. Significantly decreased D values were observed for spores with moisture contents below aw 0.2 or above aw 0.4. The data indicate that the important factors to be considered when measuring the dry heat resistance of spores are (i) the initial moisture content of the spore, (ii) the rate of spore desiccation during heating, (iii) the water retention capacity of the material in or on which spores are located, and (iv) the relative humidity of the system at the test temperature. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 7 PMID:4968962

Influence of second-order bracket-archwire misalignments on loads generated during third-order archwire rotation in orthodontic treatment.

PubMed

Romanyk, Dan L; George, Andrew; Li, Yin; Heo, Giseon; Carey, Jason P; Major, Paul W

2016-05-01

To investigate the influence of a rotational second-order bracket-archwire misalignment on the loads generated during third-order torque procedures. Specifically, torque in the second- and third-order directions was considered. An orthodontic torque simulator (OTS) was used to simulate the third-order torque between Damon Q brackets and 0.019 × 0.025-inch stainless steel archwires. Second-order misalignments were introduced in 0.5° increments from a neutral position, 0.0°, up to 3.0° of misalignment. A sample size of 30 brackets was used for each misalignment. The archwire was then rotated in the OTS from its neutral position up to 30° in 3° increments and then unloaded in the same increments. At each position, all forces and torques were recorded. Repeated-measures analysis of variance was used to determine if the second-order misalignments significantly affected torque values in the second- and third-order directions. From statistical analysis of the experimental data, it was found that the only statistically significant differences in third-order torque between a misaligned state and the neutral position occurred for 2.5° and 3.0° of misalignment, with mean differences of 2.54 Nmm and 2.33 Nmm, respectively. In addition, in pairwise comparisons of second-order torque for each misalignment increment, statistical differences were observed in all comparisons except for 0.0° vs 0.5° and 1.5° vs 2.0°. The introduction of a second-order misalignment during third-order torque simulation resulted in statistically significant differences in both second- and third-order torque response; however, the former is arguably clinically insignificant.

Spin-transfer torque in multiferroic tunnel junctions with composite dielectric/ferroelectric barriers

NASA Astrophysics Data System (ADS)

Velev, Julian P.; Merodio, Pablo; Pollack, Cesar; Kalitsov, Alan; Chshiev, Mairbek; Kioussis, Nicholas

2017-12-01

Using model calculations, we demonstrate a very high level of control of the spin-transfer torque (STT) by electric field in multiferroic tunnel junctions with composite dielectric/ferroelectric barriers. We find that, for particular device parameters, toggling the polarization direction can switch the voltage-induced part of STT between a finite value and a value close to zero, i.e. quench and release the torque. Additionally, we demonstrate that under certain conditions the zero-voltage STT, i.e. the interlayer exchange coupling, can switch sign with polarization reversal, which is equivalent to reversing the magnetic ground state of the tunnel junction. This bias- and polarization-tunability of the STT could be exploited to engineer novel functionalities such as softening/hardening of the bit or increasing the signal-to-noise ratio in magnetic sensors, which can have important implications for magnetic random access memories or for combined memory and logic devices.

Impact of lubricant parameters on rotary instrument torque and force.

PubMed

Boessler, Claudia; Peters, Ove A; Zehnder, Matthias

2007-03-01

In the current study, the impact of lubricant parameters on simulated root canal instrumentation was investigated. Using size 30 ProFile .06 instruments in milled artificial root canals in human dentin, the effects of sodium hypochlorite (1% NaOCl) and a chelator (18% etidronic acid) in aqueous irrigants on maximum torque, full torsional load, and maximum force values were gauged using a torque testing platform. Furthermore, the impact of the time a chelating lubricant was exposed to dentin as well as its galenic form (aqueous vs. gel-type) on the above outcome variables was evaluated. Aqueous lubricants significantly (p < 0.05, ANOVA, Newman-Keuls) reduced all outcome variables compared to dry conditions. The incorporation of a chelator further reduced these values (p < 0.05), whereas hypochlorite behaved similar to water. The chelator effect was immediate and did not increase with time. An aqueous lubricant was more beneficial than a gel-type counterpart.

Disturbance torque rejection properties of the NASA/JPL 70-meter antenna axis servos

NASA Technical Reports Server (NTRS)

Hill, R. E.

1989-01-01

Analytic methods for evaluating pointing errors caused by external disturbance torques are developed and applied to determine the effects of representative values of wind and friction torque. The expressions relating pointing errors to disturbance torques are shown to be strongly dependent upon the state estimator parameters, as well as upon the state feedback gain and the flow versus pressure characteristics of the hydraulic system. Under certain conditions, when control is derived from an uncorrected estimate of integral position error, the desired type 2 servo properties are not realized and finite steady-state position errors result. Methods for reducing these errors to negligible proportions through the proper selection of control gain and estimator correction parameters are demonstrated. The steady-state error produced by a disturbance torque is found to be directly proportional to the hydraulic internal leakage. This property can be exploited to provide a convenient method of determining system leakage from field measurements of estimator error, axis rate, and hydraulic differential pressure.

Experimental Observations for Determining the Maximum Torque Values to Apply to Composite Components Mechanically Joined With Fasteners (MSFC Center Director's Discretionary Fund Final Report, Proj. 03-13}

NASA Technical Reports Server (NTRS)

Thomas, F. P.

2006-01-01

Aerospace structures utilize innovative, lightweight composite materials for exploration activities. These structural components, due to various reasons including size limitations, manufacturing facilities, contractual obligations, or particular design requirements, will have to be joined. The common methodologies for joining composite components are the adhesively bonded and mechanically fastened joints and, in certain instances, both methods are simultaneously incorporated into the design. Guidelines and recommendations exist for engineers to develop design criteria and analyze and test composites. However, there are no guidelines or recommendations based on analysis or test data to specify a torque or torque range to apply to metallic mechanical fasteners used to join composite components. Utilizing the torque tension machine at NASA s Marshall Space Flight Center, an initial series of tests were conducted to determine the maximum torque that could be applied to a composite specimen. Acoustic emissions were used to nondestructively assess the specimens during the tests and thermographic imaging after the tests.

Effect of microthreads on removal torque and bone-to-implant contact: an experimental study in miniature pigs

PubMed Central

Kwon, Yee-Seo; Namgoong, Hee; Kim, Jung-Hoon; Cho, In Hee; Kim, Myung Duk; Eom, Tae Gwan

2013-01-01

Purpose The objective of this study was to evaluate the effect of microthreads on removal torque and bone-to-implant contact (BIC). Methods Twelve miniature pigs for each experiment, a total of 24 animals, were used. In the removal torque analysis, each animal received 2 types of implants in each tibia, which were treated with sandblasting and acid etching but with or without microthreads at the marginal portion. The animals were sacrificed after 4, 8, or 12 weeks of healing. Each subgroup consisted of 4 animals, and the tibias were extracted and removal torque was measured. In the BIC analysis, each animal received 3 types of implants. Two types of implants were used for the removal torque test and another type of implant served as the control. The BIC experiment was conducted in the mandible of the animals. The P1-M1 teeth were extracted, and after a 4-month healing period, 3 each of the 2 types of implants were placed, with one type on each side of the mandible, for a total of 6 implants per animal. The animals were sacrificed after a 2-, 4-, or 8-week healing period. Each subgroup consisted of 4 animals. The mandibles were extracted, specimens were processed, and BIC was analyzed. Results No significant difference in removal torque value or BIC was found between implants with and without microthreads. The removal torque value increased between 4 and 8 weeks of healing for both types of implants, but there was no significant difference between 8 and 12 weeks. The percentage of BIC increased between 2 and 4 weeks for all types of implants, but there was no significant difference between 4 and 8 weeks. Conclusions The existence of microthreads was not a significant factor in mechanical and histological stability. PMID:23508085

Tennis in hot and cool conditions decreases the rapid muscle torque production capacity of the knee extensors but not of the plantar flexors

PubMed Central

Girard, Olivier; Racinais, Sébastien; Périard, Julien D

2014-01-01

Objectives To assess the time course of changes in rapid muscle force/torque production capacity and neuromuscular activity of lower limb muscles in response to prolonged (∼2 h) match-play tennis under heat stress. Methods The rates of torque development (RTD) and electromyographic activity (EMG; ie, root mean square) rise were recorded from 0 to 30, –50, –100 and –200 ms during brief (3–5 s) explosive maximal isometric voluntary contractions (MVC) of the knee extensors (KE) and plantar flexors (PF), along with the peak RTD within the entirety of the torque-time curve. These values were recorded in 12 male tennis players before (prematch) and after (postmatch, 24 and 48 h) match-play in HOT (∼37°C) and COOL (∼22°C) conditions. Results The postmatch core temperature was greater in the HOT (∼39.4°C) vs COOL (∼38.7°C) condition (p<0.05). Reductions in KE RTD occurred within the 0–200 ms epoch after contraction onset postmatch and at 24 h, compared with prematch, independent of environmental conditions (p<0.05). A similar reduction in the KE peak RTD was also observed postmatch relative to prematch (p<0.05). No differences in KE RTD values were observed after normalisation to MVC torque. Furthermore, the rate of KE EMG activity rise remained unchanged. Conversely, the PF contractile RTD and rate of EMG activity rise were unaffected by the exercise or environmental conditions. Conclusions In the KE, a reduction in maximal torque production capacity following prolonged match-play tennis appears to account for the decrease in the rate of torque development, independent of environmental conditions, while remaining unchanged in the PF. PMID:24668381

Final report on the torque key komparison CCM.T-K1.2 measurand torque: 0 N.m, 500 N.m, 1000 N.m

NASA Astrophysics Data System (ADS)

Röske, Dirk

2015-01-01

The purpose of the CIPM subsequent bilateral comparison CCM.T-K1.2 was to link another participant, namely the National Institute of Metrology (Thailand), in short NIMT, to the CCM.T-K1 torque key comparison. The measuring capabilities up to 1000 N.m of dead-weight torque standard machines with supported lever were investigated. The pilot laboratory was the same in both comparisons—it was the Physikalisch-Technische Bundesanstalt (PTB, Braunschweig, Germany). The same two very stable torque transducers with well-known properties were used as travelling standards. The measurements at the participating laboratory were carried out between November 2007 and February 2008. According to the technical protocol, torque steps of 500 N.m and 1000 N.m had to be measured both in clockwise and anticlockwise directions. Corrections had to be applied to the results reported by the participants taking into account the use of different amplifiers, the creep (due to different loading times of the machines) and the environmental conditions in the laboratories (temperature and relative humidity of the ambient air). The results of the pilot laboratory in this bilateral comparison are in very good agreement with the same results obtained in the CCM.T-K1 comparison. For each of the transducers, the two torque steps and both senses of direction of the torque vector, the key comparison reference value of the CCM.T-K1 was taken, and the results of participant NIMT were calculated with respect to these values. The agreement between the results is very good. The smallest expanded (k = 2) relative uncertainty of the machine stated by the participant is 1 × 10-4. The results of the comparison support this uncertainty statement. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Rail Impact Testing. Test Operations Procedure (TOP)

DTIC Science & Technology

2008-09-15

impact test. The rail impact test is used to verify structural integrity of the test item and the adequacy of the tie-down system and tie-down...strength of provisions, connection and supporting structural frame, paragraph 5.2.3 ** Superscript...parts, to include outriggers and booms) without advanced approval by SDDCTEA. Torque nuts on wire rope clips to their correct value. Torque cable

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Chang-Sheng; Zhang, Shuang-Nan; Li, Xiang-Dong, E-mail: zhangsn@ihep.ac.cn

We re-estimate the surface magnetic fields of neutron stars (NSs) in Be X-ray binaries (BeXBs) with different models of torque, improved beyond Klus et al. In particular, a new torque model is applied to three models of magnetosphere radius. Unlike the previous models, the new torque model does not lead to divergent results for any fastness parameter. The inferred surface magnetic fields of these NSs for the two compressed magnetosphere models are much higher than that for the uncompressed magnetosphere model. The new torque model using the compressed magnetosphere radius leads to unique solutions near spin equilibrium in all cases, unlike other modelsmore » that usually give two branches of solutions. Although our conclusions are still affected by the simplistic assumptions about the magnetosphere radius calculations, we show several groups of possible surface magnetic field values with our new models when the interaction between the magnetosphere and the infalling accretion plasma is considered. The estimated surface magnetic fields for NSs BeXBs in the Large Magellanic Cloud, the Small Magellanic Cloud and the Milk Way are between the quantum critical field and the maximum “virial” value by the spin equilibrium condition.« less

ACL Fibers Near the Lateral Intercondylar Ridge Are the Most Load Bearing During Stability Examinations and Isometric Through Passive Flexion.

PubMed

Nawabi, Danyal H; Tucker, Scott; Schafer, Kevin A; Zuiderbaan, Hendrik Aernout; Nguyen, Joseph T; Wickiewicz, Thomas L; Imhauser, Carl W; Pearle, Andrew D

2016-10-01

The femoral insertion of the anterior cruciate ligament (ACL) has direct and indirect fiber types located within the respective high (anterior) and low (posterior) regions of the femoral footprint. The fibers in the high region of the ACL footprint carry more force and are more isometric than the fibers in the low region of the ACL footprint. Controlled laboratory study. Ten fresh-frozen cadaveric knees were mounted to a robotic manipulator. A 134-N anterior force at 30° and 90° of flexion and combined valgus (8 N·m) and internal (4 N·m) rotation torques at 15° of flexion were applied simulating tests of anterior and rotatory stability. The ACL was sectioned at the femoral footprint by detaching either the higher band of fibers neighboring the lateral intercondylar ridge in the region of the direct insertion or the posterior, crescent-shaped fibers in the region of the indirect insertion, followed by the remainder of the ACL. The kinematics of the ACL-intact knee was replayed, and the reduction in force due to each sectioned portion of insertion fibers was measured. Isometry was assessed at anteromedial, center, and posterolateral locations within the high and low regions of the femoral footprint. With an anterior tibial force at 30° of flexion, the high fibers carried 83.9% of the total anterior ACL load compared with 16.1% in the low fibers (P < .001). The high fibers also carried more anterior force than the low fibers at 90° of flexion (95.2% vs 4.8%; P < .001). Under combined torques at 15° of flexion, the high fibers carried 84.2% of the anterior ACL force compared with 15.8% in the low fibers (P < .001). Virtual ACL fibers placed at the anteromedial portion of the high region of the femoral footprint were the most isometric, with a maximum length change of 3.9 ± 1.5 mm. ACL fibers located high within the femoral footprint bear more force during stability testing and are more isometric during flexion than low fibers. It may be advantageous to create a "higher" femoral tunnel during ACL reconstruction at the lateral intercondylar ridge. © 2016 The Author(s).

Conventional multi-slice computed tomography (CT) and cone-beam CT (CBCT) for computer-assisted implant placement. Part I: relationship of radiographic gray density and implant stability.

PubMed

Arisan, Volkan; Karabuda, Zihni Cüneyt; Avsever, Hakan; Özdemir, Tayfun

2013-12-01

The relationship of conventional multi-slice computed tomography (CT)- and cone beam CT (CBCT)-based gray density values and the primary stability parameters of implants that were placed by stereolithographic surgical guides were analyzed in this study. Eighteen edentulous jaws were randomly scanned by a CT (CT group) or a CBCT scanner (CBCT group) and radiographic gray density was measured from the planned implants. A total of 108 implants were placed, and primary stability parameters were measured by insertion torque value (ITV) and resonance frequency analysis (RFA). Radiographic and subjective bone quality classification (BQC) was also classified. Results were analyzed by correlation tests and multiple regressions (p < .05). CBCT-based gray density values (765 ± 97.32 voxel value) outside the implants were significantly higher than those of CT-based values (668.4 ± 110 Hounsfield unit, p < .001). Significant relations were found among the gray density values outside the implants, ITV (adjusted r(2)  = 0.6142, p = .001 and adjusted r(2)  = 0.5166, p = .0021), and RFA (adjusted r(2)  = 0.5642, p = .0017 and adjusted r(2)  = 0.5423, p = .0031 for CT and CBCT groups, respectively). Data from radiographic and subjective BQC were also in agreement. Similar to the gray density values of CT, that of CBCT could also be predictive for the subjective BQC and primary implant stability. Results should be confirmed on different CBCT scanners. © 2012 Wiley Periodicals, Inc.

Experimental investigation of the fracture torque of orthodontic anchorage screws.

PubMed

Reimann, Susanne; Ayubi, Mustafa; McDonald, Fraser; Bourauel, Christoph

2016-07-01

In contrast to dental implants that remain in the bone, orthodontic anchorage screws serve as temporary anchorage for orthodontic tooth movement and are removed after completion of treatment. The aim of the present study was to evaluate the stability of various commercially available orthodontic anchorage screws against torsion. The torsional deflection of ten different orthodontic anchorage screws from different manufacturers [Ortho Easy Pin (Forestadent), Benefit, quattro (both PSM Medical Solutions), Vector TAS (Ormco), AbsoAnchor(®) (DENTOS Inc.), OrthoLox, Dual-Top JA (both Promedia Medizintechnik), TAD (3M Unitek), INFINITAS (ODS) and tomas(®) (Dentaurum)] was tested in vitro in relation to the rotation angle using a self-developed set-up. The screws were positioned in a resin model with bone-like material properties. Shear tests were performed using the manufacturers' own screwdrivers. Ten screws each were turned manually until a sudden drop in the measured torque occurred. At this point, the screw head was twisted off. Fracture torque and the torque at which the screws deformed plastically were evaluated. Mean values and standard deviations were calculated. According to the German industrial standard, the torque of orthodontic anchorage screws should reach at least 20 Ncm. The majority of the screws reached this nominal torque; however, a few screws fractured before reaching this value. Five screw types displayed plastic deformation below the threshold, at approximately 16 Ncm. The results suggest that orthodontic anchorage screws generally meet the requirements of the standard and ensure safe clinical use. However, according to the present data, it may be assumed that a portion of the screws will be plastically deformed upon removal.

Research on parallel load sharing principle of piezoelectric six-dimensional heavy force/torque sensor

NASA Astrophysics Data System (ADS)

Liu, Wei; Li, Ying-jun; Jia, Zhen-yuan; Zhang, Jun; Qian, Min

2011-01-01

In working process of huge heavy-load manipulators, such as the free forging machine, hydraulic die-forging press, forging manipulator, heavy grasping manipulator, large displacement manipulator, measurement of six-dimensional heavy force/torque and real-time force feedback of the operation interface are basis to realize coordinate operation control and force compliance control. It is also an effective way to raise the control accuracy and achieve highly efficient manufacturing. Facing to solve dynamic measurement problem on six-dimensional time-varying heavy load in extremely manufacturing process, the novel principle of parallel load sharing on six-dimensional heavy force/torque is put forward. The measuring principle of six-dimensional force sensor is analyzed, and the spatial model is built and decoupled. The load sharing ratios are analyzed and calculated in vertical and horizontal directions. The mapping relationship between six-dimensional heavy force/torque value to be measured and output force value is built. The finite element model of parallel piezoelectric six-dimensional heavy force/torque sensor is set up, and its static characteristics are analyzed by ANSYS software. The main parameters, which affect load sharing ratio, are analyzed. The experiments for load sharing with different diameters of parallel axis are designed. The results show that the six-dimensional heavy force/torque sensor has good linearity. Non-linearity errors are less than 1%. The parallel axis makes good effect of load sharing. The larger the diameter is, the better the load sharing effect is. The results of experiments are in accordance with the FEM analysis. The sensor has advantages of large measuring range, good linearity, high inherent frequency, and high rigidity. It can be widely used in extreme environments for real-time accurate measurement of six-dimensional time-varying huge loads on manipulators.

Spacecraft attitude and velocity control system

NASA Technical Reports Server (NTRS)

Paluszek, Michael A. (Inventor); Piper, Jr., George E. (Inventor)

1992-01-01

A spacecraft attitude and/or velocity control system includes a controller which responds to at least attitude errors to produce command signals representing a force vector F and a torque vector T, each having three orthogonal components, which represent the forces and torques which are to be generated by the thrusters. The thrusters may include magnetic torquer or reaction wheels. Six difference equations are generated, three having the form ##EQU1## where a.sub.j is the maximum torque which the j.sup.th thruster can produce, b.sub.j is the maximum force which the j.sup.th thruster can produce, and .alpha..sub.j is a variable representing the throttling factor of the j.sup.th thruster, which may range from zero to unity. The six equations are summed to produce a single scalar equation relating variables .alpha..sub.j to a performance index Z: ##EQU2## Those values of .alpha. which maximize the value of Z are determined by a method for solving linear equations, such as a linear programming method. The Simplex method may be used. The values of .alpha..sub.j are applied to control the corresponding thrusters.

The validation of a human force model to predict dynamic forces resulting from multi-joint motions

NASA Technical Reports Server (NTRS)

Pandya, Abhilash K.; Maida, James C.; Aldridge, Ann M.; Hasson, Scott M.; Woolford, Barbara J.

1992-01-01

The development and validation is examined of a dynamic strength model for humans. This model is based on empirical data. The shoulder, elbow, and wrist joints were characterized in terms of maximum isolated torque, or position and velocity, in all rotational planes. This data was reduced by a least squares regression technique into a table of single variable second degree polynomial equations determining torque as a function of position and velocity. The isolated joint torque equations were then used to compute forces resulting from a composite motion, in this case, a ratchet wrench push and pull operation. A comparison of the predicted results of the model with the actual measured values for the composite motion indicates that forces derived from a composite motion of joints (ratcheting) can be predicted from isolated joint measures. Calculated T values comparing model versus measured values for 14 subjects were well within the statistically acceptable limits and regression analysis revealed coefficient of variation between actual and measured to be within 0.72 and 0.80.

Macroscopic and microscopic evaluation of a new implant design supporting immediately loaded full arch rehabilitation

PubMed Central

Tetè, Stefano; Zizzari, Vincenzo; De Carlo, Alessandro; Sinjari, Bruna; Gherlone, Enrico

2012-01-01

Summary The purpose of this study is to evaluate macroscopic and microscopic appearance of a new implant design, with particular emphasis given to the type of prosthesis connection. Two dental implants of the same type (Torque Type®, WinSix®, BioSAFin. S.r.l. - Ancona, Italy), with sandblasted and acid etched surfaces (Micro Rough Surface®), but differing from each other for the prosthesis connection system, were examined by scanning electron microscope (SEM) analysis at different magnifications: TTI implant, with a hexagonal internal connection, and TTX implant, with a hexagonal external connection. SEM analysis showed that the Torque Type® implant is characterized by a truncated cone shape with tapered tips. The implant body showed a double loop thread and double pitch with blunt tips. For both types of connection, the implant neck was 0.7 mm in height with a 3% taper. This implant design may be able to guarantee osteotomic properties at the time of insertion in a surgical site suitably prepared, a facilitated screwing, thanks to the thread pitch and to the broad and deep draining grooves, thereby ensuring a good primary stability. The different connection design appears defined and precise, in order to ensure a good interface between the fixture and the prosthetic components. Therefore, this design appears to be particularly suitable in cases where a good primary stability is necessary and a precise coupling between endosseous and prosthetic components, as it allows an easy insertion of the fixture even in conditions of reduced bone availability, and in cases of immediately loaded full-arch rehabilitations. PMID:23087785

A stepwise under-prepared osteotomy technique improves primary stability in shallow-placed implants: a preliminary study for simultaneous vertical ridge augmentation.

PubMed

Ueno, Daisuke; Nakamura, Kei; Kojima, Kousuke; Toyoshima, Takeshi; Tanaka, Hideaki; Ueda, Kazuhiko; Koyano, Kiyoshi; Kodama, Toshiro

2018-04-01

Simultaneous vertical ridge augmentation (VRA) can reduce treatment procedures and surgery time, but the concomitant reduction in primary stability (PS) of a shallow-placed implant imparts risk to its prognosis. Although several studies have reported improvements in PS, there is little information from any simultaneous VRA model. This study aimed to evaluate whether tapered implants with stepwise under-prepared osteotomy could improve the PS of shallow-placed implants in an in vitro model of simultaneous VRA. Tapered implants (Straumann ® Bone Level Tapered implant; BLT) and hybrid implants (Straumann ® Bone Level implant; BL) were investigated in this study. A total of 80 osteotomies of different depths (4, 6, 8, 10 mm) were created in rigid polyurethane foam blocks, and each BLT and BL was inserted by either standard (BLT-S, BL-S) or a stepwise under-prepared (BLT-U, BL-U) osteotomy protocol. The PS was evaluated by measuring maximum insertion torque (IT), implant stability quotient (ISQ), and removal torque (RT). The significance level was set at P < 0.05. There were no significant differences in IT, ISQ or RT when comparing BLT-S and BL-S or BLT-U and BL-U at placement depths of 6 and 8 mm. When comparison was made between osteotomy protocols, IT was significantly greater in BLT-U than in BLT-S at all placement depths. A stepwise under-prepared osteotomy protocol improves initial stability of a tapered implant even in a shallow-placed implant model. BLT-U could be a useful protocol for simultaneous VRA.

Macroscopic and microscopic evaluation of a new implant design supporting immediately loaded full arch rehabilitation.

PubMed

Tetè, Stefano; Zizzari, Vincenzo; De Carlo, Alessandro; Sinjari, Bruna; Gherlone, Enrico

2012-04-01

The purpose of this study is to evaluate macroscopic and microscopic appearance of a new implant design, with particular emphasis given to the type of prosthesis connection. Two dental implants of the same type (Torque Type(®), WinSix(®), BioSAFin. S.r.l. - Ancona, Italy), with sandblasted and acid etched surfaces (Micro Rough Surface(®)), but differing from each other for the prosthesis connection system, were examined by scanning electron microscope (SEM) analysis at different magnifications: TTI implant, with a hexagonal internal connection, and TTX implant, with a hexagonal external connection. SEM analysis showed that the Torque Type(®) implant is characterized by a truncated cone shape with tapered tips. The implant body showed a double loop thread and double pitch with blunt tips. For both types of connection, the implant neck was 0.7 mm in height with a 3% taper. This implant design may be able to guarantee osteotomic properties at the time of insertion in a surgical site suitably prepared, a facilitated screwing, thanks to the thread pitch and to the broad and deep draining grooves, thereby ensuring a good primary stability. The different connection design appears defined and precise, in order to ensure a good interface between the fixture and the prosthetic components. Therefore, this design appears to be particularly suitable in cases where a good primary stability is necessary and a precise coupling between endosseous and prosthetic components, as it allows an easy insertion of the fixture even in conditions of reduced bone availability, and in cases of immediately loaded full-arch rehabilitations.

Electromagnetic Torque in Tokamaks with Toroidal Asymmetries

NASA Astrophysics Data System (ADS)

Logan, Nikolas Christopher

Toroidal rotation and rotation shear strongly influences stability and confinement in tokamaks. Breaking of the toroidal symmetry by fields orders of magnitude smaller than the axisymmetric field can, however, produce electromagnetic torques that significantly affect the plasma rotation, stability and confinement. These electromagnetic torques are the study of this thesis. There are two typical types of electromagnetic torques in tokamaks: 1) "resonant torques" for which a plasma current defined by a single toroidal and single poloidal harmonic interact with external currents and 2) "nonresonant torques" for which the global plasma response to nonaxisymmetric fields is phase shifted by kinetic effects that drive the rotation towards a neoclassical offset. This work describes the diagnostics and analysis necessary to evaluate the torque by measuring the rate of momentum transfer per unit area in the vacuum region between the plasma and external currents using localized magnetic sensors to measure the Maxwell stress. These measurements provide model independent quantification of both the resonant and nonresonant electromagnetic torques, enabling direct verification of theoretical models. Measured values of the nonresonant torque are shown to agree well with the perturbed equilibrium nonambipolar transport (PENT) code calculation of torque from cross field transport in nonaxisymmetric equilibria. A combined neoclassical toroidal viscosity (NTV) theory, valid across a wide range of kinetic regimes, is fully implemented for the first time in general aspect ratio and shaped plasmas. The code captures pitch angle resonances, reproducing previously inaccessible collisionality limits in the model. The complete treatment of the model enables benchmarking to the hybrid kinetic MHD stability codes MARS-K and MISK, confirming the energy-torque equivalency principle in perturbed equilibria. Experimental validations of PENT results confirm the torque applied by nonaxisymmetric coils is often proportional to the energy put into the dominant ideal MHD kink mode. This reduces the control of nonresonant torque to a single mode model, enabling efficient feed forward optimization of applied fields. Initial results including the anisotropic kinetic pressure tensor directly in the plasma eigenmode calculations are presented here, and may eventually provide accurate metrics for multimodal coupling similar to the established single mode metrics.

Hydrodynamic Torques and Rotations of Superparamagnetic Bead Dimers

NASA Astrophysics Data System (ADS)

Pease, Christopher; Etheridge, J.; Wijesinghe, H. S.; Pierce, C. J.; Prikockis, M. V.; Sooryakumar, R.

Chains of micro-magnetic particles are often rotated with external magnetic fields for many lab-on-a-chip technologies such as transporting beads or mixing fluids. These applications benefit from faster responses of the actuated particles. In a rotating magnetic field, the magnetization of superparamagnetic beads, created from embedded magnetic nano-particles within a polymer matrix, is largely characterized by induced dipoles mip along the direction of the field. In addition there is often a weak dipole mop that orients out-of-phase with the external rotating field. On a two-bead dimer, the simplest chain of beads, mop contributes a torque Γm in addition to the torque from mip. For dimers with beads unbound to each other, mop rotates individual beads which generate an additional hydrodynamic torque on the dimer. Whereas, mop directly torques bound dimers. Our results show that Γm significantly alters the average frequency-dependent dimer rotation rate for both bound and unbound monomers and, when mop exceeds a critical value, increases the maximum dimer rotation frequency. Models that include magnetic and hydrodynamics torques provide good agreement with the experimental findings over a range of field frequencies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Z. X.; Wang, W. X.; Diamond, P. H.

We report that intrinsic torque, which can be generated by turbulent stresses, can induce toroidal rotation in a tokamak plasma at rest without direct momentum injection. Reversals in intrinsic torque have been inferred from the observation of toroidal velocity changes in recent lower hybrid current drive (LHCD) experiments. Here we focus on understanding the cause of LHCD-induced intrinsic torque reversal using gyrokinetic simulations and theoretical analyses. A new mechanism for the intrinsic torque reversal linked to magnetic shear (sˆ) effects on the turbulence spectrum is identified. This reversal is a consequence of the ballooning structure at weak sˆ . Basedmore » on realistic profiles from the Alcator C-Mod LHCD experiments, simulations demonstrate that the intrinsic torque reverses for weak sˆ discharges and that the value of sˆ crit is consistent with the experimental results sˆ exp crit [Rice et al., Phys. Rev. Lett. 111, 125003 (2013)]. In conclusion, the consideration of this intrinsic torque feature in our work is important for the understanding of rotation profile generation at weak and its consequent impact on macro-instability stabilization and micro-turbulence reduction, which is crucial for ITER. It is also relevant to internal transport barrier formation at negative or weakly positive sˆ .« less

A pressure-based force and torque prediction technique for the study of fish-like swimming

PubMed Central

Dabiri, John O.; Lauder, George V.

2017-01-01

Many outstanding questions about the evolution and function of fish morphology are linked to swimming dynamics, and a detailed knowledge of time-varying forces and torques along the animal’s body is a key component in answering many of these questions. Yet, quantifying these forces and torques experimentally represents a major challenge that to date prevents a full understanding of fish-like swimming. Here, we develop a method for obtaining these force and torque data non-invasively using standard 2D digital particle image velocimetry in conjunction with a pressure field algorithm. We use a mechanical flapping foil apparatus to model fish-like swimming and measure forces and torques directly with a load cell, and compare these measured values to those estimated simultaneously using our pressure-based approach. We demonstrate that, when out-of-plane flows are relatively small compared to the planar flow, and when pressure effects sufficiently dominate shear effects, this technique is able to accurately reproduce the shape, magnitude, and timing of locomotor forces and torques experienced by a fish-like swimmer. We conclude by exploring of the limits of this approach and its feasibility in the study of freely-swimming fishes. PMID:29216264

Evoked EMG-based torque prediction under muscle fatigue in implanted neural stimulation

NASA Astrophysics Data System (ADS)

Hayashibe, Mitsuhiro; Zhang, Qin; Guiraud, David; Fattal, Charles

2011-10-01

In patients with complete spinal cord injury, fatigue occurs rapidly and there is no proprioceptive feedback regarding the current muscle condition. Therefore, it is essential to monitor the muscle state and assess the expected muscle response to improve the current FES system toward adaptive force/torque control in the presence of muscle fatigue. Our team implanted neural and epimysial electrodes in a complete paraplegic patient in 1999. We carried out a case study, in the specific case of implanted stimulation, in order to verify the corresponding torque prediction based on stimulus evoked EMG (eEMG) when muscle fatigue is occurring during electrical stimulation. Indeed, in implanted stimulation, the relationship between stimulation parameters and output torques is more stable than external stimulation in which the electrode location strongly affects the quality of the recruitment. Thus, the assumption that changes in the stimulation-torque relationship would be mainly due to muscle fatigue can be made reasonably. The eEMG was proved to be correlated to the generated torque during the continuous stimulation while the frequency of eEMG also decreased during fatigue. The median frequency showed a similar variation trend to the mean absolute value of eEMG. Torque prediction during fatigue-inducing tests was performed based on eEMG in model cross-validation where the model was identified using recruitment test data. The torque prediction, apart from the potentiation period, showed acceptable tracking performances that would enable us to perform adaptive closed-loop control through implanted neural stimulation in the future.

Process Sensitivity, Performance, and Direct Verification Testing of Adhesive Locking Features

NASA Technical Reports Server (NTRS)

Golden, Johnny L.; Leatherwood, Michael D.; Montoya, Michael D.; Kato, Ken A.; Akers, Ed

2012-01-01

Phase I: The use of adhesive locking features or liquid locking compounds (LLCs) (e.g., Loctite) as a means of providing a secondary locking feature has been used on NASA programs since the Apollo program. In many cases Loctite was used as a last resort when (a) self-locking fasteners were no longer functioning per their respective drawing specification, (b) access was limited for removal & replacement, or (c) replacement could not be accomplished without severe impact to schedule. Long-term use of Loctite became inevitable in cases where removal and replacement of worn hardware was not cost effective and Loctite was assumed to be fully cured and working. The NASA Engineering & Safety Center (NESC) and United Space Alliance (USA) recognized the need for more extensive testing of Loctite grades to better understand their capabilities and limitations as a secondary locking feature. These tests, identified as Phase I, were designed to identify processing sensitivities, to determine proper cure time, the correct primer to use on aerospace nutplate, insert and bolt materials such as A286 and MP35N, and the minimum amount of Loctite that is required to achieve optimum breakaway torque values. The .1900-32 was the fastener size tested, due to wide usage in the aerospace industry. Three different grades of Loctite were tested. Results indicate that, with proper controls, adhesive locking features can be successfully used in the repair of locking features and should be considered for design. Phase II: Threaded fastening systems used in aerospace programs typically have a requirement for a redundant locking feature. The primary locking method is the fastener preload and the traditional redundant locking feature is a self-locking mechanical device that may include deformed threads, non-metallic inserts, split beam features, or other methods that impede movement between threaded members. The self-locking resistance of traditional locking features can be directly verified during assembly by measuring the dynamic prevailing torque. Adhesive locking features or LLCs are another method of providing redundant locking, but a direct verification method has not been used in aerospace applications to verify proper installation when using LLCs because of concern for damage to the adhesive bond. The reliability of LLCs has also been questioned due to failures observed during testing with coupons for process verification, although the coupon failures have often been attributed to a lack of proper procedures. It is highly desirable to have a direct method of verifying the LLC cure or bond integrity. The purpose of the Phase II test program was to determine if the torque applied during direct verification of an adhesive locking feature degrades that locking feature. This report documents the test program used to investigate the viability of such a direct verification method. Results of the Phase II testing were positive, and additional investigation of direct verification of adhesive locking features is merited.

A frequency and pulse-width co-modulation strategy for transcutaneous neuromuscular electrical stimulation based on sEMG time-domain features

NASA Astrophysics Data System (ADS)

Zhou, Yu-Xuan; Wang, Hai-Peng; Bao, Xue-Liang; Lü, Xiao-Ying; Wang, Zhi-Gong

2016-02-01

Objective. Surface electromyography (sEMG) is often used as a control signal in neuromuscular electrical stimulation (NMES) systems to enhance the voluntary control and proprioceptive sensory feedback of paralyzed patients. Most sEMG-controlled NMES systems use the envelope of the sEMG signal to modulate the stimulation intensity (current amplitude or pulse width) with a constant frequency. The aims of this study were to develop a strategy that co-modulates frequency and pulse width based on features of the sEMG signal and to investigate the torque-reproduction performance and the level of fatigue resistance achieved with our strategy. Approach. We examined the relationships between wrist torque and two stimulation parameters (frequency and pulse width) and between wrist torque and two sEMG time-domain features (mean absolute value (MAV) and number of slope sign changes (NSS)) in eight healthy volunteers. By using wrist torque as an intermediate variable, customized and generalized transfer functions were constructed to convert the two features of the sEMG signal into the two stimulation parameters, thereby establishing a MAV/NSS dual-coding (MNDC) algorithm. Wrist torque reproduction performance was assessed by comparing the torque generated by the algorithms with that originally recorded during voluntary contractions. Muscle fatigue was assessed by measuring the decline percentage of the peak torque and by comparing the torque time integral of the response to test stimulation trains before and after fatigue sessions. Main Results. The MNDC approach could produce a wrist torque that closely matched the voluntary wrist torque. In addition, a smaller decay in the wrist torque was observed after the MNDC-coded fatigue stimulation was applied than after stimulation using pulse-width modulation alone. Significance. Compared with pulse-width modulation stimulation strategies that are based on sEMG detection, the MNDC strategy is more effective for both voluntary muscle force reproduction and muscle fatigue reduction.

Removal Torque and Biofilm Accumulation at Two Dental Implant-Abutment Joints After Fatigue.

PubMed

Pereira, Jorge; Morsch, Carolina S; Henriques, Bruno; Nascimento, Rubens M; Benfatti, Cesar Am; Silva, Filipe S; López-López, José; Souza, Júlio Cm

2016-01-01

The aim of this study was to evaluate the removal torque and in vitro biofilm penetration at Morse taper and hexagonal implant-abutment joints after fatigue tests. Sixty dental implants were divided into two groups: (1) Morse taper and (2) external hexagon implant-abutment systems. Fatigue tests on the implant-abutment assemblies were performed at a normal force (FN) of 50 N at 1.2 Hz for 500,000 cycles in growth medium containing human saliva for 72 hours. Removal torque mean values (n = 10) were measured after fatigue tests. Abutments were then immersed in 1% protease solution in order to detach the biofilms for optical density and colony-forming unit (CFU/cm²) analyses. Groups of implant-abutment assemblies (n = 8) were cross-sectioned at 90 degrees relative to the plane of the implant-abutment joints for the microgap measurement by field-emission guns scanning electron microscopy. Mean values of removal torque on abutments were significantly lower for both Morse taper (22.1 ± 0.5 μm) and external hexagon (21.1 ± 0.7 μm) abutments after fatigue tests than those recorded without fatigue tests (respectively, 24 ± 0.5 μm and 24.8 ± 0.6 μm) in biofilm medium for 72 hours (P = .04). Mean values of microgap size for the Morse taper joints were statistically signicantly lower without fatigue tests (1.7 ± 0.4 μm) than those recorded after fatigue tests (3.2 ± 0.8 μm). Also, mean values of microgap size for external hexagon joints free of fatigue were statistically signicantly lower (1.5 ± 0.4 μm) than those recorded after fatigue tests (8.1 ± 1.7 μm) (P < .05). The optical density of biofilms and CFU mean values were lower on Morse taper abutments (Abs630nm at 0.06 and 2.9 × 10⁴ CFU/cm²) than that on external hexagon abutments (Abs630nm at 0.08 and 4.5 × 10⁴ CFU/cm²) (P = .01). The mean values of removal torque, microgap size, and biofilm density recorded at Morse taper joints were lower in comparison to those recorded at external hexagon implant-abutment joints after fatigue tests in a simulated oral environment for 72 hours.

Brake blending strategy for a hybrid vehicle

DOEpatents

Boberg, Evan S.

2000-12-05

A hybrid electric powertrain system is provided including a transmission for driving a pair of wheels of a vehicle and a heat engine and an electric motor/generator coupled to the transmission. A friction brake system is provided for applying a braking torque to said vehicle. A controller unit generates control signals to the electric motor/generator and the friction brake system for controllably braking the vehicle in response to a drivers brake command. The controller unit determines and amount of regenerative torque available and compares this value to a determined amount of brake torque requested for determining the control signals to the electric motor/generator and the friction brake system.

Receding horizon online optimization for torque control of gasoline engines.

PubMed

Kang, Mingxin; Shen, Tielong

2016-11-01

This paper proposes a model-based nonlinear receding horizon optimal control scheme for the engine torque tracking problem. The controller design directly employs the nonlinear model exploited based on mean-value modeling principle of engine systems without any linearizing reformation, and the online optimization is achieved by applying the Continuation/GMRES (generalized minimum residual) approach. Several receding horizon control schemes are designed to investigate the effects of the integral action and integral gain selection. Simulation analyses and experimental validations are implemented to demonstrate the real-time optimization performance and control effects of the proposed torque tracking controllers. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Variable frequency inverter for ac induction motors with torque, speed and braking control

NASA Technical Reports Server (NTRS)

Nola, F. J. (Inventor)

1975-01-01

A variable frequency inverter was designed for driving an ac induction motor which varies the frequency and voltage to the motor windings in response to varying torque requirements for the motor so that the applied voltage amplitude and frequency are of optimal value for any motor load and speed requirement. The slip frequency of the motor is caused to vary proportionally to the torque and feedback is provided so that the most efficient operating voltage is applied to the motor. Winding current surge is limited and a controlled negative slip causes motor braking and return of load energy to a dc power source.

Power-Factor and Torque Calculation under Consideration of Cross Saturation of the Interior Permanent Magnet Synchronous Motor with Brushless Field Excitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Seong T; Burress, Timothy A; Tolbert, Leon M

2009-01-01

This paper introduces a new method for calculating the power factor and output torque by considering the cross saturation between direct-axis (d-axis) and quadrature-axis (q-axis) of an interior permanent magnet synchronous motor (IPMSM). The conventional two-axis IPMSM model is modified to include the cross saturation effect by adding the cross-coupled inductance terms. This paper also contains the new method of calculating the cross-coupled inductance values as well as self-inductance values in d- and q-axes. The analyzed motor is a high-speed brushless field excitation machine that offers high torque per ampere per core length at low speed and weakened flux atmore » high speed, which was developed for the traction motor of a hybrid electric vehicle. The conventional two-axis IPMSM model was modified to include the cross-saturation effect by adding the cross-coupled inductance terms Ldq and Lqd. By the advantage of the excited structure of the experimental IPMSM, the analyzing works were performed under two conditions, the highest and lowest excited conditions. Therefore, it is possible to investigate the cross-saturation effect when a machine has higher magnetic flux from its rotor. The following is a summary of conclusions that may be drawn from this work: (1) Considering cross saturation of an IPMSM offers more accurate expected values of motor parameters in output torque calculation, especially when negative d-axis current is high; (2) A less saturated synchronous machine could be more affected by the cross-coupled saturation effect; (3) Both cross-coupled inductances, L{sub qd} and L{sub dq}, are mainly governed by d-axis current rather than q-axis current; (4) The modified torque equation, can be used for the dynamic model of an IPMSM for developing a better control model or control strategy; and (5) It is possible that the brushless field excitation structure has a common magnetic flux path on both d- and q-axis, and as a result, the reluctance torque of the machine could be reduced.« less

The Influence of Tactile Perception on Classification of Bone Tissue at Dental Implant Insertion.

PubMed

Linck, Gláucia Kelly Silva Barbosa; Ferreira, Geovane Miranda; De Oliveira, Rubelisa Cândido Gomes; Lindh, Christina; Leles, Cláudio Rodrigues; Ribeiro-Rotta, Rejane Faria

2016-06-01

Various ways of using the Lekholm and Zarb (L&Z) classification have added to the lack of scientific evidence of the effectiveness of this clinical method in the evaluation of implant treatment. The study aims to assess subjective jawbone classifications in patients referred for implant treatment, using L&Z classification with and without surgeon's hand perception at implant insertion. The association between bone type classifications and quantitative parameters of primary implant stability was also assessed. One hundred thirty-five implants were inserted using conventional loading protocol. Three surgeons classified bone quality at implant sites using two methods: one based on periapical and panoramic images (modified L&Z) and one based on the same images associated with the surgeon's tactile perception during drilling (original L&Z). Peak insertion torque and implant stability quotient (ISQ) were recorded. The modified and original L&Z were strongly correlated (rho = 0.79; p < .001); Wilcoxon signed-rank test showed no significant difference in the distribution of bone type classification between pairs using the two methods (p = .538). Spearman correlation tested the association between primary stability parameters and bone type classifications (-0.34 to -0.57 [p < .001]). Tactile surgical perception has a minor influence on rating of subjective bone type for dental implant treatment using the L&Z classification. © 2015 Wiley Periodicals, Inc.

Inductive detection of fieldlike and dampinglike ac inverse spin-orbit torques in ferromagnet/normal-metal bilayers

NASA Astrophysics Data System (ADS)

Berger, Andrew J.; Edwards, Eric R. J.; Nembach, Hans T.; Karenowska, Alexy D.; Weiler, Mathias; Silva, Thomas J.

2018-03-01

Functional spintronic devices rely on spin-charge interconversion effects, such as the reciprocal processes of electric field-driven spin torque and magnetization dynamics-driven spin and charge flow. Both dampinglike and fieldlike spin-orbit torques have been observed in the forward process of current-driven spin torque and dampinglike inverse spin-orbit torque has been well studied via spin pumping into heavy metal layers. Here, we demonstrate that established microwave transmission spectroscopy of ferromagnet/normal metal bilayers under ferromagnetic resonance can be used to inductively detect the ac charge currents driven by the inverse spin-charge conversion processes. This technique relies on vector network analyzer ferromagnetic resonance (VNA-FMR) measurements. We show that in addition to the commonly extracted spectroscopic information, VNA-FMR measurements can be used to quantify the magnitude and phase of all ac charge currents in the sample, including those due to spin pumping and spin-charge conversion. Our findings reveal that Ni80Fe20/Pt bilayers exhibit both dampinglike and fieldlike inverse spin-orbit torques. While the magnitudes of both the dampinglike and fieldlike inverse spin-orbit torque are of comparable scale to prior reported values for similar material systems, we observed a significant dependence of the dampinglike magnitude on the order of deposition. This suggests interface quality plays an important role in the overall strength of the dampinglike spin-to-charge conversion.

Effect of strength and speed of torque development on balance recovery with the ankle strategy.

PubMed

Robinovitch, Stephen N; Heller, Britta; Lui, Andrew; Cortez, Jeffrey

2002-08-01

In the event of an unexpected disturbance to balance, the ability to recover a stable upright stance should depend not only on the magnitude of torque that can be generated by contraction of muscles spanning the lower extremity joints but also on how quickly these torques can be developed. In the present study, we used a combination of experimental and mathematical models of balance recovery by sway (feet in place responses) to test this hypothesis. Twenty-three young subjects participated in experiments in which they were supported in an inclined standing position by a horizontal tether and instructed to recover balance by contracting only their ankle muscles. The maximum lean angle where they could recover balance without release of the tether (static recovery limit) averaged 14.9 +/- 1.4 degrees (mean +/- SD). The maximum initial lean angle where they could recover balance after the tether was unexpectedly released and the ankles were initially relaxed (dynamic recovery limit) averaged 5.9 +/- 1.1 degrees, or 60 +/- 11% smaller than the static recovery limit. Peak ankle torque did not differ significantly between the two conditions (and averaged 116 +/- 32 Nm), indicating the strong effect on recovery ability of latencies in the onset and subsequent rates of torque generation (which averaged 99 +/- 13 ms and 372 +/- 267 N. m/s, respectively). Additional experiments indicated that dynamic recovery limits increased 11 +/- 14% with increases in the baseline ankle torques prior to release (from an average value of 31 +/- 18 to 54 +/- 24 N. m). These trends are in agreement with predictions from a computer simulation based on an inverted pendulum model, which illustrate the specific combinations of baseline ankle torque, rate of torque generation, and peak ankle torque that are required to attain target recovery limits.

Barbell deadlift training increases the rate of torque development and vertical jump performance in novices.

PubMed

Thompson, Brennan J; Stock, Matt S; Shields, JoCarol E; Luera, Micheal J; Munayer, Ibrahim K; Mota, Jacob A; Carrillo, Elias C; Olinghouse, Kendra D

2015-01-01

The primary purpose of this study was to examine the effects of 10 weeks of barbell deadlift training on rapid torque characteristics of the knee extensors and flexors. A secondary aim was to analyze the relationships between training-induced changes in rapid torque and vertical jump performance. Fifty-four subjects (age, mean ± SD = 23 ± 3 years) were randomly assigned to a control (n = 20) or training group (n = 34). Subjects in the training group performed supervised deadlift training twice per week for 10 weeks. All subjects performed isometric strength testing of the knee extensors and flexors and vertical jumps before and after the intervention. Torque-time curves were used to calculate rate of torque development (RTD) values at peak and at 50 and 200 milliseconds from torque onset. Barbell deadlift training induced significant pre- to post-increases of 18.8-49.0% for all rapid torque variables (p < 0.01). Vertical jump height increased from 46.0 ± 11.3 to 49.4 ± 11.3 cm (7.4%; p < 0.01), and these changes were positively correlated with improvements in RTD for the knee flexors (r = 0.30-0.37, p < 0.01-0.03). These findings showed that a 10-week barbell deadlift training program was effective at enhancing rapid torque capacities in both the knee extensors and flexors. Changes in rapid torque were associated with improvements in vertical jump height, suggesting a transfer of adaptations from deadlift training to an explosive, performance-based task. Professionals may use these findings when attempting to design effective, time-efficient resistance training programs to improve explosive strength capacities in novices.

Specifiers Properties Information Exchange (SPie): Minimum Building Information Model (BIM) Object Definitions

DTIC Science & Technology

2013-03-01

Weave Welding Method Wheel Assembly Wind Load Wind Loads Wind Uplift Resistance Wind Uplift Resistance Class Window Category Window Finish Window... wind - blast Elongation UFGS 2.1 percent Insert Value Visual Defects UFGS 2.1 n/a Insert Value ERDC/CERL CR-13-1 39 Attribute Source...Sustainability COBie Guide n/a insert reqts FRP Strengthening UFGS 1.2 n/a seismic - wind - blast Elongation UFGS 2.2 percent Insert Value Tensile

Does increased topside conformity in modular total knee arthroplasty lead to increased backside wear?

PubMed

Schwarzkopf, Ran; Scott, Richard D; Carlson, Evan M; Currier, John H

2015-01-01

Modular metal-backed tibia components allow surgeons intraoperative flexibility. Although it is known that modular tibia components introduce the possibility for backside wear resulting from relative motion between the polyethylene insert and the tibial baseplate, it is not known to what degree variability in the conformity of the tibial polyethylene liner itself might contribute to backside wear. The purpose of this study was to determine whether a flat, cruciate-retaining tibial polyethylene bearing generates less backside wear than a more conforming (curved) tibial polyethylene bearing in an analysis of specimens explanted during revision surgery. The study included 70 total knee inserts explanted at revision surgery, all implanted and explanted by the same surgeon. Two different cruciate-retaining insert options in an otherwise similar knee system were used: one with a curved-on-flat (17) articular geometry and one with a highly conforming curved-on-curved design (53); both groups were sequential cohorts. The composite backside wear depth for the insert as well as the volume of backside wear was measured and compared between groups. The median linear backside-normalized wear for the posterior lipped inserts was 0.0063 mm/year (range, 0-0.085 mm/year), which was lower than for the curved inserts at 0.05 mm/year (range, 0.00003-0.14 mm/year) (p<0.001). The median calculated volumetric backside-normalized wear for the posterior lipped inserts was 14.2 mm3/year (range, 0-282.8 mm3/year) compared with 117 mm3/year (range, 2.1-312 mm3/year) for the curved inserts (p<0.001). In this retrieval study, more conforming tibial inserts demonstrated more backside-normalized wear than the flatter designs. This suggests that in this modular total knee arthroplasty design, higher articular conformity to address the issues of high bearing contact stress comes at a price: increased torque transmitted to the backside insert-to-tray interface. We suggest further work be undertaken to examine newer insert designs to evaluate if our conclusions hold true with the newer generation locking mechanism, tibial tray finish and polyethylene designs, as more highly conforming tibial inserts are introduced into the market. Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Electric Machine with Boosted Inductance to Stabilize Current Control

NASA Technical Reports Server (NTRS)

Abel, Steve

2013-01-01

High-powered motors typically have very low resistance and inductance (R and L) in their windings. This makes the pulse-width modulated (PWM) control of the current very difficult, especially when the bus voltage (V) is high. These R and L values are dictated by the motor size, torque (Kt), and back-emf (Kb) constants. These constants are in turn set by the voltage and the actuation torque-speed requirements. This problem is often addressed by placing inductive chokes within the controller. This approach is undesirable in that space is taken and heat is added to the controller. By keeping the same motor frame, reducing the wire size, and placing a correspondingly larger number of turns in each slot, the resistance, inductance, torque constant, and back-emf constant are all increased. The increased inductance aids the current control but ruins the Kt and Kb selections. If, however, a fraction of the turns is moved from their "correct slot" to an "incorrect slot," the increased R and L values are retained, but the Kt and Kb values are restored to the desired values. This approach assumes that increased resistance is acceptable to a degree. In effect, the heat allocated to the added inductance has been moved from the controller to the motor body, which in some cases is preferred.

Recovery of pectoralis major and triceps brachii after bench press exercise.

PubMed

Ferreira, Diogo V; Gentil, Paulo; Soares, Saulo Rodrigo Sampaio; Bottaro, Martim

2017-11-01

The present study evaluated and compared the recovery of pectoralis major (PM) and triceps brachii (TB) muscles of trained men after bench press exercise. Eighteen volunteers performed eight sets of bench press exercise to momentary muscle failure and were evaluated for TB and PM peak torque and total work on an isokinetic dynamometer. PM peak torque and total work remained lower than baseline for 72 and 96 h, respectively. TB peak torque was only different from baseline immediately post training, while total work was significantly lower than baseline immediately and 48 h after training. Normalized peak torque values were only different between TB and PM at 48 h after training. Considering the small and nonsignificant difference between the recovery of TB and PM muscles, the results suggest that bench press exercise may promote a similar stress on these muscles. Muscle Nerve 56: 963-967, 2017. © 2016 Wiley Periodicals, Inc.

Torque of the shank rotating muscles in patients with knee joint injuries.

PubMed

Hrycyna, Mariusz; Zieliński, Jacek

2011-01-01

The aim of the study was to evaluate the torque of the shank rotating muscles in patients with reconstructed anterior cruciate ligament (ACL) and rehabilitation accomplished in comparison with a control group. The study was carried out on the group of 187 males. For the purpose of the study a prototype testing device for the shank rotating muscles' torque under static conditions was used. The study was based on the measurement of maximal torque at selected angles (-30°, 0°, 45°) of the shank rotation as well as on the angle (30°, 60°, 90°) of flexion of the knee joint. The results obtained in the group with reconstructed anterior cruciate ligament (ACL) and rehabilitation accomplished were comparable to those the control group and mostly of no statistical significance. Lack of significant differences between the values of shank rotating muscles' torque achieved in an injured limb compared to an uninjured one may testify to an effective rehabilitation process. The results of the research can serve as a diagnostic tool for the rehabilitation process development.

Enhanced bone screw fixation with biodegradable bone cement in osteoporotic bone model.

PubMed

Juvonen, Tiina; Koistinen, Arto; Kröger, Heikki; Lappalainen, Reijo

2012-09-27

The purpose of this study was to study the potential of novel biodegradable PCL bone cement to improve bone screw fixation strength in osteoporotic bone. The biomechanical properties of bone cement (ε-polycaprolactone, PCL) and fixation strength were studied using biomechanical tests and bone screws fixed in an osteoporotic bone model. Removal torques and pullout strengths were assessed for cortical, self-tapping, and cancellous screws inserted in the osteoporotic bone model (polyurethane foam blocks with polycarbonate plate) with and without PCL bone cement. Open cell and cellular rigid foam blocks with a density of 0.12 g/cm3 were used in this model. Removal torques were significantly (more than six-fold) improved with bone cement for cancellous screws. Furthermore, the bone cement improved pullout strengths three to 12 times over depending on the screw and model material. Biodegradable bone cement turned out to be a very potential material to stabilize screw fixation in osteoporotic bone. The results warrant further research before safe clinical use, especially to clarify clinically relevant factors using real osteoporotic bone under human body conditions and dynamic fatigue testing for long-term performance.

Angular velocity affects trunk muscle strength and EMG activation during isokinetic axial rotation.

PubMed

Fan, Jian-Zhong; Liu, Xia; Ni, Guo-Xin

2014-01-01

To evaluate trunk muscle strength and EMG activation during isokinetic axial rotation at different angular velocities. Twenty-four healthy young men performed isokinetic axial rotation in right and left directions at 30, 60, and 120 degrees per second angular velocity. Simultaneously, surface EMG was recorded on external oblique (EO), internal oblique (IO), and latissimus dorsi (LD) bilaterally. In each direction, with the increase of angular velocity, peak torque decreased, whereas peak power increased. During isokinetic axial rotation, contralateral EO as well as ipsilateral IO and LD acted as primary agonists, whereas, ipsilateral EO as well as contralateral IO and LD acted as primary antagonistic muscles. For each primary agonist, the root mean square values decreased with the increase of angular velocity. Antagonist coactiviation was observed at each velocity; however, it appears to be higher with the increase of angular velocity. Our results suggest that velocity of rotation has great impact on the axial rotation torque and EMG activity. An inverse relationship of angular velocity was suggested with the axial rotation torque as well as root mean square value of individual trunk muscle. In addition, higher velocity is associated with higher coactivation of antagonist, leading to a decrease in torque with the increase of velocity.

Somatotype-variables related to muscle torque and power output in female volleyball players.

PubMed

Buśko, Krzysztof; Lewandowska, Joanna; Lipińska, Monika; Michalski, Radosław; Pastuszak, Anna

2013-01-01

The purpose of this study was to investigate the relationship between somatotype, muscle torque, maximal power output and height of rise of the body mass centre measured in akimbo counter movement jump (ACMJ), counter movement jump (CMJ) and spike jump (SPJ), and power output measured in maximal cycle ergometer exercise bouts in female volleyball players. Fourteen players participated in the study. Somatotype was determined using the Heath-Carter method. Maximal muscle torque was measured under static conditions. Power output was measured in 5 maximal cycle ergometer exercise bouts, 10 s each, at increasing external loads equal to 2.5, 5.0, 7.5, 10.0 and 12.5% of body weight (BW). All jump trials (ACMJ, SPJ and CMJ) were performed on a force plate. The mean somatotype of volleyball players was: 4.9-3.5-2.5. The value of the sum of muscle torque of the left upper extremities was significantly correlated only with mesomorphic component. Mesomorphic and ectomorphic components correlated significantly with values of maximal power measured during ACMJ and CMJ. Power output measured in maximal cycle ergometer exercise bouts at increasing external loads equal to 2.5, 5.0 and 7.5% of BW was significantly correlated with endomorphy, mesomorphy and ectomorphy.

Optimization of diesel engine performance by the Bees Algorithm

NASA Astrophysics Data System (ADS)

Azfanizam Ahmad, Siti; Sunthiram, Devaraj

2018-03-01

Biodiesel recently has been receiving a great attention in the world market due to the depletion of the existing fossil fuels. Biodiesel also becomes an alternative for diesel No. 2 fuel which possesses characteristics such as biodegradable and oxygenated. However, there are facts suggested that biodiesel does not have the equivalent features as diesel No. 2 fuel as it has been claimed that the usage of biodiesel giving increment in the brake specific fuel consumption (BSFC). The objective of this study is to find the maximum brake power and brake torque as well as the minimum BSFC to optimize the condition of diesel engine when using the biodiesel fuel. This optimization was conducted using the Bees Algorithm (BA) under specific biodiesel percentage in fuel mixture, engine speed and engine load. The result showed that 58.33kW of brake power, 310.33 N.m of brake torque and 200.29/(kW.h) of BSFC were the optimum value. Comparing to the ones obtained by other algorithm, the BA produced a fine brake power and a better brake torque and BSFC. This finding proved that the BA can be used to optimize the performance of diesel engine based on the optimum value of the brake power, brake torque and BSFC.

Development of a sliding mode control model for quiet upright stance.

PubMed

Zhang, Hongbo; Nussbaum, Maury A; Agnew, Michael J

2016-02-01

Human upright stance appears maintained or controlled intermittently, through some combination of passive and active ankle torques, respectively representing intrinsic and contractile contributions of the ankle musculature. Several intermittent postural control models have been proposed, though it has been challenging to accurately represent actual kinematics and kinetics and to separately estimate passive and active ankle torque components. Here, a simplified single-segment, 2D (sagittal plane) sliding mode control model was developed for application to track kinematics and kinetics during upright stance. The model was implemented and evaluated using previous experimental data consisting of whole body angular kinematics and ankle torques. Tracking errors for the whole-body center-of-mass (COM) angle and angular velocity, as well as ankle torque, were all within ∼10% of experimental values, though tracking performance for COM angular acceleration was substantially poorer. The model also enabled separate estimates of the contributions of passive and active ankle torques, with overall contributions estimated here to be 96% and 4% of the total ankle torque, respectively. Such a model may have future utility in understanding human postural control, though additional work is needed, such as expanding the model to multiple segments and to three dimensions. Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Z. X.; Tynan, G.; Center for Momentum Transport and Flow Organization and Center for Astrophysics and Space Science, University of California, San Diego, California 92093

Intrinsic torque, which can be generated by turbulent stresses, can induce toroidal rotation in a tokamak plasma at rest without direct momentum injection. Reversals in intrinsic torque have been inferred from the observation of toroidal velocity changes in recent lower hybrid current drive (LHCD) experiments. This work focuses on understanding the cause of LHCD-induced intrinsic torque reversal using gyrokinetic simulations and theoretical analyses. A new mechanism for the intrinsic torque reversal linked to magnetic shear (s{sup ^}) effects on the turbulence spectrum is identified. This reversal is a consequence of the ballooning structure at weak s{sup ^}. Based on realisticmore » profiles from the Alcator C-Mod LHCD experiments, simulations demonstrate that the intrinsic torque reverses for weak s{sup ^} discharges and that the value of s{sup ^}{sub crit} is consistent with the experimental results s{sup ^}{sub crit}{sup exp}≈0.2∼0.3 [Rice et al., Phys. Rev. Lett. 111, 125003 (2013)]. The consideration of this intrinsic torque feature in our work is important for the understanding of rotation profile generation at weak s{sup ^} and its consequent impact on macro-instability stabilization and micro-turbulence reduction, which is crucial for ITER. It is also relevant to internal transport barrier formation at negative or weakly positive s{sup ^}.« less

Resonance at the wrist demonstrated by the use of a torque motor: an instrumental analysis of muscle tone in man.

PubMed Central

Lakie, M; Walsh, E G; Wright, G W

1984-01-01

The resonance of the relaxed wrist for flexion-extension movements in the horizontal plane has been investigated by using rhythmic torques generated by a printed motor. In the normal subject the resonant frequency of the wrist is ca. 2 Hz unless the torque is reduced below a certain critical value when the system is no longer linear and the resonant frequency rises. This critical torque level, and the damping are both less in women than men. The resonant frequency is uninfluenced by surgical anaesthesia. With added bias the increase of resonant frequency at low torques still occurs although the hand is now oscillating about a displaced mean position. It follows that the stiffening implied by this elevation of resonant frequency for small movements is neither the result of pre-stressing of the muscles nor of reflex activity. With velocity feed-back of appropriate polarity the system will oscillate spontaneously at its resonant frequency. If the peak driving torque is progressively reduced the resonant frequency increases abruptly, indicating that the system has stiffened. Perturbations delivered to the wrist may reduce its stiffness. The postural system is thixotropic with a 'memory time' of 1-2 s. The resonant frequency is elevated in voluntary stiffening. PMID:6481624

In Vitro Evaluation of Manual Torque Values Applied to Implant-Abutment Complex by Different Clinicians and Abutment Screw Loosening.

PubMed

Dincer Kose, Onur; Karataslı, Burcin; Demircan, Sabit; Kose, Taha Emre; Cene, Erhan; Aya, Serhan Aydın; Erdem, Mehmet Ali; Cankaya, Abdulkadir Burak

2017-01-01

Preload is applied to screws manually or using a torque wrench in dental implant systems, and the preload applied must be appropriate for the purpose. The aim of this study was to assess screw loosening and bending/torsional moments applied by clinicians of various specialties following application of manual tightening torque to combinations of implants and abutments. Ten-millimeter implants of 3.7 and 4.1 mm diameters and standard or solid abutments were used. Each group contained five implant-abutment combinations. The control and experimental groups comprised 20 and 160 specimens, respectively. Implants in the experimental group were tightened by dentists of different specialties. Torsional and bending moments during tightening were measured using a strain gauge. Control group and implants with preload values close to the ideal preload were subjected to a dynamic loading test at 150 N, 15 Hz, and 85,000 cycles. The implants that deformed in this test were examined using an optical microscope to assess deformities. Manual tightening did not yield the manufacturer-recommended preload values. Dynamic loading testing suggested early screw loosening/fracture in samples with insufficient preload.

In Vitro Evaluation of Manual Torque Values Applied to Implant-Abutment Complex by Different Clinicians and Abutment Screw Loosening

PubMed Central

Demircan, Sabit; Cene, Erhan; Aya, Serhan Aydın; Erdem, Mehmet Ali; Cankaya, Abdulkadir Burak

2017-01-01

Preload is applied to screws manually or using a torque wrench in dental implant systems, and the preload applied must be appropriate for the purpose. The aim of this study was to assess screw loosening and bending/torsional moments applied by clinicians of various specialties following application of manual tightening torque to combinations of implants and abutments. Ten-millimeter implants of 3.7 and 4.1 mm diameters and standard or solid abutments were used. Each group contained five implant-abutment combinations. The control and experimental groups comprised 20 and 160 specimens, respectively. Implants in the experimental group were tightened by dentists of different specialties. Torsional and bending moments during tightening were measured using a strain gauge. Control group and implants with preload values close to the ideal preload were subjected to a dynamic loading test at 150 N, 15 Hz, and 85,000 cycles. The implants that deformed in this test were examined using an optical microscope to assess deformities. Manual tightening did not yield the manufacturer-recommended preload values. Dynamic loading testing suggested early screw loosening/fracture in samples with insufficient preload. PMID:28473988

'Neo-Suterian' pump-turbine characteristics and their benefits

NASA Astrophysics Data System (ADS)

Dörfler, P. K.

2010-08-01

Conventional representations of the various operation modes of a pump-turbine (4-quadrant characteristics) have important disadvantages. While curves of Q11 vs n11 have singularities at E=0 and multiple values in the 'unstable' ranges, the curves EnD(QnD) get singular at n=0. As a remedy, one may split the characteristics into separate parts, and switch between them. Another approach introduced by P. Suter (1966, [1]) defines a different set of variables which avoids singularity and always remains unique-valued. Suter described this artifice for non-regulated pumps; but using it for regulated machines without modifications is not practical due to large distortions at small guide vane opening. A decisive improvement has been described by C.S. Martin [4]. It avoids the distortion of the head-vs-flow curves at low load. The present paper describes how further improvement is possible, in particular with regard to the representation of torque. A modified torque parameter is obtained by subtracting the shutoff torque; this parameter can be handled in the same practical way as the discharge. Other improvements concern the correction for leakage at small guide vane opening, and the treatment of very small and zero opening. These details are concerned with the problem of closed gate where Suter's concept does not work. Applications are demonstrated, not only how to represent the hydraulic performance (head vs. discharge and torque vs. discharge), but also for other characteristics, such as the development of pressure and pressure pulsation in various locations, or the steady-state and unsteady guide vane torque. The advantage of a set of continuous, single-valued functions for all those physical properties greatly simplifies computation of their behavior during transients. Moreover, the, Suterized' properties of pump-turbines of different specific speed are less different from each other than the conventional ones, a fact that facilitates application of available test data for later projects.

Effect of the coefficient of friction and tightening speed on the preload induced at the dental implant complex with the finite element method.

PubMed

Bulaqi, Haddad Arabi; Mousavi Mashhadi, Mahmoud; Geramipanah, Farideh; Safari, Hamed; Paknejad, Mojgan

2015-05-01

To prevent screw loosening, a clear understanding of the factors influencing secure preload is necessary. The purpose of this study was to investigate the effect of coefficient of friction and tightening speed on screw tightening based on energy distribution method with exact geometric modeling and finite element analysis. To simulate the proper boundary conditions of the screw tightening process, the supporting bone of an implant was considered. The exact geometry of the implant complex, including the Straumann dental implant, direct crown attachment, and abutment screw were modeled with Solidworks software. Abutment screw/implant and implant/bone interfaces were designed as spiral thread helixes. The screw-tightening process was simulated with Abaqus software, and to achieve the target torque, an angular displacement was applied to the abutment screw head at different coefficients of friction and tightening speeds. The values of torque, preload, energy distribution, elastic energy, and efficiency were obtained at the target torque of 35 Ncm. Additionally, the torque distribution ratio and preload simulated values were compared to theoretically predicted values. Upon reducing the coefficient of friction and enhancing the tightening speed, the angle of turn increased at the target torque. As the angle of turn increased, the elastic energy and preload also increased. Additionally, by increasing the coefficient of friction, the frictional dissipation energy increased but the efficiency decreased, whereas the increase in tightening speed insignificantly affected efficiency. The results of this study indicate that the coefficient of friction is the most influential factor on efficiency. Increasing the tightening speed lowered the response rate to the frictional resistance, thus diminishing the coefficient of friction and slightly increasing the preload. Increasing the tightening speed has the same result as reducing the coefficient of friction. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Tool For Driving Many Fasteners Simultaneously

NASA Technical Reports Server (NTRS)

Cook, Joseph S., Jr.

1995-01-01

Proposed tool tightens or loosens several bolts, screws, nuts, or other threaded fasteners arranged in circle on compressor head, automotive wheel, pipe-end flange, or similar object. Enables assembly or disassembly in fraction of time needed to tighten fasteners one at a time. Simultaneously applies same torque to all fasteners, preventing distortion and enhancing reliability. Concept not limited to circular fastener patterns. Adapted to rectangular configurations like on engine intake manifolds, by adding gears to drive train to provide proper spacing. Designed to deliver fixed or adjustable maximum torque. To ensure even seal loading, piston pressure simultaneously ramped from initial to final values to maintain relatively constant torque loading on all fasteners until final specifications limit achieved.

Stretching, twisting and supercoiling in short, single DNA molecules

NASA Astrophysics Data System (ADS)

Lam, Pui-Man; Zhen, Yi

2018-02-01

We had combined the Neukirch-Marko model that describes the extension, torque and supercoiling in single, stretched and twisted DNA of infinite contour length, with a form of the free energy suggested by Sinha and Samuels to describe short DNA, with contour length only a few times the persistence length. We find that the free energy of the stretched but untwisted DNA, is significantly modified from its infinitely length value and this in turn modifies significantly the torque and supercoiling. We show that this is consistent with short DNA being more flexible than infinitely long DNA. We hope our results will stimulate experimental investigation of torque and supercoiling in short DNA.

Biomechanical evaluation of dental implants with three different designs: Removal torque and resonance frequency analysis in rabbits.

PubMed

Gehrke, Sergio Alexandre; Marin, Giovanni Wiel

2015-05-01

The objective of this study was to investigate the effect of implant design on stability and resistance to reverse torque in the tibia of rabbits. Three test groups were prepared using the different characteristics of each implant model: square threads with progressive depth to the apex, a cervical portion without threads and a self-tapping system that is quite pronounced and aggressive (Group 1); triangular threads with flat tips with increasing thread depth from the cervical portion to the apex and a small self-tapping portion with a short thread pitch (Group 2); long thread pitch, progressive thread depth, an apical area with a small self-tapping portion (Group 3). For the two last groups, a final single-use drill was provided for each implant. Nine rabbits received 54 conical implants with a same surface treatment. The resonance frequency was analysed four times (0, 6, 8 and 12 weeks), and removal torque values were measured at three time intervals after the implantations (6, 8 and 12 weeks). In comparing the implant stability quotient at the four time points, highly significant statistic differences were found (p = 1.29(-10)). The reverse torque at the three time points was also significantly different among the groups (p = 0.00015). The implants of Group 2, with seemingly less aggressive design, more quickly reached high values of stability and removal torque. Under the limitations of this study, however, it is possible that in cases in which there may be low osseointegration response, the implant design should be evaluated. Copyright © 2014 Elsevier GmbH. All rights reserved.

Rotation of artificial rotor axles in rotary molecular motors

PubMed Central

Baba, Mihori; Iwamoto, Kousuke; Ueno, Hiroshi; Hara, Mayu; Nakanishi, Atsuko; Kishikawa, Jun-ichi; Noji, Hiroyuki; Yokoyama, Ken

2016-01-01

F1- and V1-ATPase are rotary molecular motors that convert chemical energy released upon ATP hydrolysis into torque to rotate a central rotor axle against the surrounding catalytic stator cylinder with high efficiency. How conformational change occurring in the stator is coupled to the rotary motion of the axle is the key unknown in the mechanism of rotary motors. Here, we generated chimeric motor proteins by inserting an exogenous rod protein, FliJ, into the stator ring of F1 or of V1 and tested the rotation properties of these chimeric motors. Both motors showed unidirectional and continuous rotation, despite no obvious homology in amino acid sequence between FliJ and the intrinsic rotor subunit of F1 or V1. These results showed that any residue-specific interactions between the stator and rotor are not a prerequisite for unidirectional rotation of both F1 and V1. The torque of chimeric motors estimated from viscous friction of the rotation probe against medium revealed that whereas the F1-FliJ chimera generates only 10% of WT F1, the V1-FliJ chimera generates torque comparable to that of V1 with the native axle protein that is structurally more similar to FliJ than the native rotor of F1. This suggests that the gross structural mismatch hinders smooth rotation of FliJ accompanied with the stator ring of F1. PMID:27647891

Analysis of mechanical preparations in extracted teeth using ProTaper rotary instruments: value of the safety quotient.

PubMed

Blum, J Y; Machtou, P; Ruddle, C; Micallef, J P

2003-09-01

The purpose of this study was to apply the Endographe to analyze the vertical forces and torque developed during mechanical preparations in extracted teeth. The data collected in this study may be used to calculate the safety quotient (SQ) as proposed by J.T. McSpadden. The SQ formula is defined as the torque required to break a file at D3 divided by the mean working torque required to cut dentin. The Endographe is a unique force-analyzer device equipped to measure, record, and generate graphs of the vertical forces and torque exerted during root canal preparation. All preparations were performed by endodontists in roots with narrow, more restrictive canals, larger, more open canals, or in roots sectioned in two halves. All canals, including the sectioned canals, were prepared with ProTaper files in accordance with the manufacturer's guidelines for use. For narrow canals, the mean values of the generated vertical forces (g) and torque (g.cm) varied from 80 (+/- 20) g (SX) to 232 (+/- 60) g (F2) and from 80 (+/- 24) g x cm (F1) to 150 (+/- 45) g x cm (S2), respectively. For large canals, the mean values of the generated vertical forces (g) and torque (g x cm) varied from 80 (+/- 20) g (SX) to 340 (+/- 20) g (F1) and from 31 (+/- 9) g x cm (S2) to 96 (+/- 35) g x cm (SX), respectively. The SQ varied from 0.93 to 7.95 for narrow canals and from 1.58 to 14.50 for large canals. The SQ is intended to provide values that can be analyzed to predict whether a rotary file will have a tendency to break or will work safely during clinical use. However, if the formula is going to provide useful information, it must index the "rotation to failure torque" with the "mean working torque" at a specific location along the cutting blades of a file. Additionally, this mathematical formula does not account for factors such as the concentration of forces, the way the instruments are used, or the wear of the instruments. A precise protocol for canal preparation should emphasize using small flexible stainless steel hand files to create or verify that within any portion of a root canal there is sufficient space for rotary instruments to follow. When there is a confirmed smooth, reproducible glide path, then a "secured" space exists to safely guide the more flexible terminal extent of a rotary NiTi file. Endogrammes provide an innovative approach to the analysis of mechanical preparations and suggest that the ProTaper shaping files are best used with lateral forces to decrease the coronal screwing effect. The ProTaper finishing files should be used with slow penetration and be introduced only into canals that have a confirmed smooth and reproducible glide path. When any part of the overall length of a canal has been secured, then the number of instruments, the time spent utilizing each instrument, and the overall time progressing through a sequence of instruments to shape this region of the canal is reduced.

Comparison of fit accuracy and torque maintenance of zirconia and titanium abutments for internal tri-channel and external-hex implant connections.

PubMed

Siadat, Hakimeh; Beyabanaki, Elaheh; Mousavi, Niloufar; Alikhasi, Marzieh

2017-08-01

This in vitro study aimed to evaluate the effect of implant connection design (external vs. internal) on the fit discrepancy and torque loss of zirconia and titanium abutments. Two regular platform dental implants, one with external connection (Brånemark, Nobel Biocare AB) and the other with internal connection (Noble Replace, Nobel Biocare AB), were selected. Seven titanium and seven customized zirconia abutments were used for each connection design. Measurements of geometry, marginal discrepancy, and rotational freedom were done using video measuring machine. To measure the torque loss, each abutment was torqued to 35 Ncm and then opened by means of a digital torque wrench. Data were analyzed with two-way ANOVA and t-test at α=0.05 of significance. There were significant differences in the geometrical measurements and rotational freedom between abutments of two connection groups ( P <.001). Also, the results showed significant differences between titanium abutments of internal and external connection implants in terms of rotational freedom ( P <.001). Not only customized internal abutments but also customized external abutments did not have the exact geometry of prefabricated abutments ( P <.001). However, neither connection type ( P =.15) nor abutment material ( P =.38) affected torque loss. Abutments with internal connection showed less rotational freedom. However, better marginal fit was observed in externally connected abutments. Also, customized abutments with either connection could not duplicate the exact geometry of their corresponding prefabricated abutment. However, neither abutment connection nor material affected torque loss values.

“All talk no torque”- A novel set of metrics to quantify muscle fatigue through isometric dynamometry in Functional Electrical Stimulation (FES) muscle studies

NASA Astrophysics Data System (ADS)

Taylor, M. J.; Fornusek, C.; de Chazal, P.; Ruys, A. J.

2017-10-01

Functional Electrical Stimulation (FES) activates nerves and muscles that have been ravished and rendered paralysed by disease. As such, it is advantageous to study joint torques that arise due to electrical stimulation of muscle, to measure fatigue in an indirect, minimally-invasive way. Dynamometry is one way in which this can be achieved. In this paper, torque data is presented from an FES experiment on quadriceps, using isometric dynamometry to measure torque. A library of fatigue metrics to quantify these data are put forward. These metrics include; start and end torque peaks, percentage changes in torque over time, and maximum and minimum torque period algorithms (MTPA 1 and 2), and associated torque-time plots. It is illustrated, by example, how this novel library of metrics can model fatigue over time. Furthermore, these methods are critiqued by a qualitative assessment and compared against one another for their utility in modelling fatigue. Linear trendlines with coefficients of correlation (R 2) and qualitative descriptions of data are used to achieve this. We find that although arduous, individual peak plots yield the most relevant values upon which fatigue can be assessed. Methods to calculate peaks in data have less of a utility, offset by an order of magnitude of ˜101 in comparison with theoretically expected peak numbers. In light of this, we suggest that future methods would be well-inclined to investigate optimized form of peak analysis.

Effects of Screw Configuration on the Preload Force of Implant-Abutment Screws.

PubMed

Zipprich, Holger; Rathe, Florian; Pinz, Sören; Schlotmann, Luca; Lauer, Hans-Christoph; Ratka, Christoph

The aim of this study was to investigate the effects of tightening torque, screw head angle, and thread number on the preload force of abutment screws. The test specimens consisted of three self-manufactured components (ie, a thread sleeve serving as an implant analog, an abutment analog, and an abutment screw). The abutment screws were fabricated with metric M1.6 external threads. The thread number varied between one and seven threads. The screw head angles were produced in eight varying angles (30 to 180 degrees). A sensor unit simultaneously measured the preload force of the screw and the torsion moment inside the screw shank. The tightening of the screw with the torque wrench was performed in five steps (15 to 35 Ncm). The torque wrench was calibrated before each step. Only the tightening torque and screw head angle affected the resulting preload force of the implant-abutment connection. The thread number had no effect. There was an approximately linear correlation between tightening torque and preload force. The tightening torque and screw head angle were the only study parameters that affected the resulting preload force of the abutment screw. The results obtained from this experiment are valid only for a single torque condition. Further investigations are needed that analyze other parameters that affect preload force. Once these parameters are known, it will add value for a strong, but detachable connection between the implant and abutment. Short implants and flat-to-flat connections especially will benefit significantly from this knowledge.

Control of interjoint coordination during the swing phase of normal gait at different speeds

PubMed Central

Shemmell, Jonathan; Johansson, Jennifer; Portra, Vanessa; Gottlieb, Gerald L; Thomas, James S; Corcos, Daniel M

2007-01-01

Background It has been suggested that the control of unconstrained movements is simplified via the imposition of a kinetic constraint that produces dynamic torques at each moving joint such that they are a linear function of a single motor command. The linear relationship between dynamic torques at each joint has been demonstrated for multijoint upper limb movements. The purpose of the current study was to test the applicability of such a control scheme to the unconstrained portion of the gait cycle – the swing phase. Methods Twenty-eight neurologically normal individuals walked along a track at three different speeds. Angular displacements and dynamic torques produced at each of the three lower limb joints (hip, knee and ankle) were calculated from segmental position data recorded during each trial. We employed principal component (PC) analysis to determine (1) the similarity of kinematic and kinetic time series at the ankle, knee and hip during the swing phase of gait, and (2) the effect of walking speed on the range of joint displacement and torque. Results The angular displacements of the three joints were accounted for by two PCs during the swing phase (Variance accounted for – PC1: 75.1 ± 1.4%, PC2: 23.2 ± 1.3%), whereas the dynamic joint torques were described by a single PC (Variance accounted for – PC1: 93.8 ± 0.9%). Increases in walking speed were associated with increases in the range of motion and magnitude of torque at each joint although the ratio describing the relative magnitude of torque at each joint remained constant. Conclusion Our results support the idea that the control of leg swing during gait is simplified in two ways: (1) the pattern of dynamic torque at each lower limb joint is produced by appropriately scaling a single motor command and (2) the magnitude of dynamic torque at all three joints can be specified with knowledge of the magnitude of torque at a single joint. Walking speed could therefore be altered by modifying a single value related to the magnitude of torque at one joint. PMID:17466065

Constant strain rate experiments and constitutive modeling for a class of bitumen

NASA Astrophysics Data System (ADS)

Reddy, Kommidi Santosh; Umakanthan, S.; Krishnan, J. Murali

2012-08-01

The mechanical properties of bitumen vary with the nature of the crude source and the processing methods employed. To understand the role of the processing conditions played in the mechanical properties, bitumen samples derived from the same crude source but processed differently (blown and blended) are investigated. The samples are subjected to constant strain rate experiments in a parallel plate rheometer. The torque applied to realize the prescribed angular velocity for the top plate and the normal force applied to maintain the gap between the top and bottom plate are measured. It is found that when the top plate is held stationary, the time taken by the torque to be reduced by a certain percentage of its maximum value is different from the time taken by the normal force to decrease by the same percentage of its maximum value. Further, the time at which the maximum torque occurs is different from the time at which the maximum normal force occurs. Since the existing constitutive relations for bitumen cannot capture the difference in the relaxation times for the torque and normal force, a new rate type constitutive model, incorporating this response, is proposed. Although the blended and blown bitumen samples used in this study correspond to the same grade, the mechanical responses of the two samples are not the same. This is also reflected in the difference in the values of the material parameters in the model proposed. The differences in the mechanical properties between the differently processed bitumen samples increase further with aging. This has implications for the long-term performance of the pavement.

Analysis of a Precambrian Resonance-Stabilized Day Length

NASA Astrophysics Data System (ADS)

Bartlett, B. C.; Stevenson, D. J.

2014-12-01

Calculations indicate the average rate of decrease of Earth's angular momentum must have been less than its present value in the past; otherwise, the Earth should have a longer day length. Existing stromatolite data suggests the Earth's rotational frequency would have been near that of the atmospheric resonance frequency toward the end of the Precambrian era, approximately 600Ma. The semidiurnal atmospheric tidal torque would have reached a maximum near this day length of 21hr. At this point, the atmospheric torque would have been comparable in magnitude but opposite in direction to the lunar torque, creating a stabilizing effect which could preserve a constant day length while trapped in this resonant state, as suggested by Zahnle and Walker (1987). We examine the hypothesis that this resonant stability was encountered and sustained for a large amount of time during the Precambrian era and was broken by a large and relatively fast increase in global temperature, possibly in the deglaciation period following a snowball event. Computational simulations of this problem were performed, indicating that a persistent increase in temperature larger than around 10K over a period of time less than 107 years will break resonance (though these values vary with Q), but that the resonant stability is not easily broken by random high-amplitude high-frequency atmospheric temperature fluctuation or other forms of thermal noise. Further work also indicates it is possible to escape resonance simply by increasing the lunar tidal torque on the much longer timescale of plate tectonics, particularly for low atmospheric Q-factors, or that resonance could have never formed in the first place, had the lunar torque been very high or Q been very low when the Earth's rotational frequency was near the atmospheric resonance frequency. However, the need to explain the present day length given the current lunar torque favors the interpretation we offer, in which Earth's length of day was stabilized for hundreds of millions of years, escaping this stability in the aftermath of a sudden global temperature change.

Implant Stability in the Posterior Maxilla: A Controlled Clinical Trial

PubMed Central

de Vasconcelos, Mario Ramalho; Lopes Guerra, Isabel Maria; de Campos Felino, Antonio Cabral

2017-01-01

Aim To evaluate the primary and secondary stability of implants in the posterior maxilla. Methods Patients were allocated into three groups: (A) native bone, (B) partially regenerated bone, and (C) nearly totally regenerated bone. Insertion torque (IT) and implant stability quotient (ISQ) were measured at placement, to evaluate whether satisfactory high primary stability (IT ≥ 45 N/cm; ISQ ≥ 60) was achieved; ISQ was measured 15, 30, 45, and 60 days after placement, to investigate the evolution to secondary stability. Results 133 implants (Anyridge®, Megagen) were installed in 59 patients: 55 fixtures were placed in Group A, 57 in Group B, and 21 in Group C. Fifty-two implants had satisfactory high primary stability (IT ≥ 45 N/cm; ISQ ≥ 60). A positive correlation was found between all variables (IT, ISQ at t = 0, t = 60), and statistically higher IT and ISQ values were found for implants with satisfactory high primary stability. Significant differences were found for IT and ISQ between the groups (A, B, and C); however, no drops were reported in the median ISQ values during the healing period. Conclusions The evaluation of the primary and secondary implant stability may contribute to higher implant survival/success rates in critical areas, such as the regenerated posterior maxilla. The present study is registered in the ISRCTN registry with ID ISRCTN33469250. PMID:28626763

The effect of lavender oil on stress, bispectral index values, and needle insertion pain in volunteers.

PubMed

Kim, Sioh; Kim, Hyun-Jae; Yeo, Jin-Seok; Hong, Sung-Jung; Lee, Ji-Min; Jeon, Younghoon

2011-09-01

The purpose of this study was to investigate whether lavender oil aromatherapy can reduce the bispectral index (BIS) values and stress and decrease the pain of needle insertion in 30 volunteers. Thirty (30) healthy volunteers were randomly allocated to 2 groups: the experimental group received oxygen with a face mask coated with lavender oil for 5 minutes, and the control group received oxygen through a face mask with no lavender oil for 5 minutes. The stress level (0=no stress, 10=maximum stress), BIS value, and pain intensity of needle insertion (0=no pain, 10=worst pain imaginable) were measured. There were no significant differences in age, sex, height, and weight between the two groups. Stress level, BIS value, and pain intensity of needle insertion before aromatherapy were similar between the two groups. However, the stress values (p<0.001) and BIS value (p<0.001) after aromatherapy were significantly reduced compared with the control. In addition, the pain intensity of needle insertion was significantly decreased after aromatherapy compared with the control (p<0.001). Lavender aromatherapy in volunteers provided a significant decrease in the stress levels and in the BIS values. In addition, it significantly reduced the pain intensity of needle insertion.

Examination of the torque required to passively palmar abduct the thumb CMC joint in a pediatric population with hemiplegia and stroke.

PubMed

Stirling, Leia; Ahmad, Mona Qureshi; Kelty-Stephen, Damian; Correia, Annette

2015-12-16

Many activities of daily living involve precision grasping and bimanual manipulation, such as putting toothpaste on a toothbrush or feeding oneself. However, children afflicted by stroke, cerebral palsy, or traumatic brain injury may have lost or never had the ability to actively and accurately control the thumb. To translate insights from adult rehabilitation robotics to innovative therapies for hand rehabilitation in pediatric care, specifically for thumb deformities, an understanding of the torque needed to abduct the thumb to assist grasping tasks is required. Participants (n=16, 10 female, 13.2±3.1 years) had an upper extremity evaluation and measures were made of their passive range of motion, anthropometrics, and torques to abduct the thumb for both their affected and non-affected sides. Torque measures were made using a custom wrist orthosis that was adjusted for each participant. The torque to achieve maximum abduction was 1.47±0.61inlb for the non-affected side and 1.51±0.68inlb for the affected side, with a maximum recorded value of 4.87inlb. The overall maximum applied torque was observed during adduction and was 5.10inlb. We saw variation in the applied torque, which could have been due to the applied torques by the Occupational Therapist or the participant actively assisting or resisting the motion rather than remaining passive. We expect similar muscle and participant variation to exist with an assistive device. Thus, the data presented here can be used to inform the specifications for the development of an assistive thumb orthosis for children with "thumb-in-palm" deformity. Copyright © 2015 Elsevier Ltd. All rights reserved.

Torque balance, Taylor's constraint and torsional oscillations in a numerical model of the geodynamo

NASA Astrophysics Data System (ADS)

Dumberry, Mathieu; Bloxham, Jeremy

2003-11-01

Theoretical considerations and observations suggest that, to a first approximation, the Earth's dynamo is in a quasi-Taylor state, where the axial Lorentz torque on cylindrical surfaces co-axial with the rotation axis vanishes, except for the part involved in torsional oscillations. The latter are rigid azimuthal accelerations of cylindrical surfaces which oscillate with typical periods of decades. We present a solution of a numerical model of the geodynamo in which rigid accelerations of cylinder surfaces are observed. The underlying dynamic state in the model is not a Taylor state because the Reynolds stresses and viscous torque remain large and provide an effective way to balance a large Lorentz torque. This is a consequence of the limited parameter regime which can be attained numerically. Nevertheless, departures in the torque equilibrium are primarily counterbalanced by rigid accelerations of cylindrical surfaces, which, in turn, excite rigid azimuthal oscillations of the surfaces. We show that the azimuthal motion is indeed quasi-rigid, though the torsional oscillations that are produced in the model probably differ from those in the Earth's core because of the large influence of the Reynolds stresses on their dynamics. We also show that the continual excitation of rigid cylindrical accelerations is produced by the advection of the non-axisymmetric structure of the fields by a mean differential rotation of the cylindrical surfaces which produces disconnections and reconnections and continual fluctuations in the Lorentz torque and Reynolds stresses. We propose that the torque balance in Earth's core may evolve in a similar chaotic fashion, except that the influence of the Reynolds stresses is probably weaker. If this is the case, the Lorentz torque on a cylindrical surface is continually fluctuating, even though its time-averaged value vanishes and satisfies Taylor's constraint. Rigid accelerations of cylindrical surfaces are continually excited by the fluctuations in the Lorentz torque, and the torsional oscillations observed in the geomagnetic data are a mixture of forced and free oscillations.

Emergence of Chiral Phases in Active Torque Dipole Systems

NASA Astrophysics Data System (ADS)

Fialho, Ana; Tjhung, Elsen; Cates, Michael; Marenduzzo, Davide

The common description of active particles as active force dipoles fails to take into account that active processes in biological systems often exhibit chiral asymmetries, generating active chiral processes and torque dipoles. Examples of such systems include cytoskeleton filaments which interact with motor proteins and beating cilia and flagella. In particular, the generation of active torques by the actomyosin cytoskeleton has been linked to the break of chiral symmetry at a cellular level. This phenomenon could constitute the primary determinant for the break of left-right symmetry in many living organisms, e.g. the position of the human heart within the human body. In order to account for the effects of chirality, we consider active torque dipoles which generate a chiral active stress. We characterize quasi-1D and 2D systems of torque dipoles, using a combination of linear stability analysis and numerical simulations (Lattice Boltzmann). Our results show that activity drives a spontaneous breaking of chiral symmetry, leading to the self-assembly of a chiral phase, in the absence of any thermodynamic interactions favoring cholesteric ordering. At high values of activity, we also observe labyrinthine patterns where the activity-induced chiral ordering is highly frustrated.

Tightening of healing abutments: influence of torque on bacterial proliferation risk, an in vitro investigation.

PubMed

Bousquet, Philippe; Bennasar, Isabelle Calas; Tramini, Paul; Jacquemot, Maxime; Cuisinier, Frédéric

2014-12-01

Gap at the implant-healing abutment junction can increase the risk of bacterial proliferation. In this study, we determined the leakage at the microgap, and we evaluated hand screwing among clinicians. The torques tested with nitrogen gas flow were 10, 15, 20, and 30 N cm, and 54 clinicians were asked to torque down a healing abutment as for a surgical procedure. There were no significant differences between 10 and 15 N cm, with a total lack of tightness. For 20 and 30 N cm, there was a notable decrease in leakage. The torque achieved by hand was <10 N cm for 61.7% of the clinicians, between 10 and 15 N cm for 29.1%, between 15 and 20 N cm for 8.0%, and between 20 and 25 N cm for 1.2%. There was a significant difference related to the strength of tightening. Under the conditions of our experiment, the gap of connection was reduced with a torque of ≥20 N cm. Only a small portion of the clinicians could obtain these values by hand. Therefore, a dynamometrical manual wrench should be used to minimize the gap during the osseointegration period.

Torsional Tribological Behavior and Torsional Friction Model of Polytetrafluoroethylene against 1045 Steel

PubMed Central

Wang, Shibo; Niu, Chengchao

2016-01-01

In this work, the plane-on-plane torsional fretting tribological behavior of polytetrafluoroethylene (PTFE) was studied. A model of a rigid, flat-ended punch acting on an elastic half-space was built according to the experimental conditions. The results indicate that the shape of T–θ curves was influenced by both the torsional angle and the normal load. The torsion friction torque and wear rate of PTFE exponentially decreased when the torsion angle rose. The torsional torque increased from 0.025 N·m under a normal load of 43 N to 0.082 N·m under a normal load of 123 N. With sequentially increasing normal load, the value of torque was maintained. With rising normal load, the wear mass loss of PTFE disks was increased and the wear rate was decreased. Good agreement was found with the calculated torque according to the model and the experimental torque except for that under a normal load of 163 N. The difference under a normal load of 163 N was caused by the coefficient of friction. Usually the coefficient of friction of a polymer decreases with increasing normal load, whereas a constant coefficient of friction was applied in the model. PMID:26799324

Derivation of the Torque Associated to Tesseral Resonances

NASA Astrophysics Data System (ADS)

El Moutamid, Maryame

2018-04-01

A so-called m+1:m Tesseral Resonance is simply equivalent to an inner m+1:m Lindblad Resonance or an outer Lindblad Resonance, where m is an integer. They are generated between a gravity anomaly that rotates with the primary and a test particle evolving around this primary, instead of being caused by a secondary, meaning that in this case the particle and the secondary do not share the same orbit. We show in this work that the torque is stronger for small values of |m|; as |m| tends to infinity, the torque tends to zero and that the Lagrange points are displaced away from the usual triangular configuration. These simple results have interesting implications on Saturn, Chariklo and Mars.

Development of an empirically based dynamic biomechanical strength model

NASA Technical Reports Server (NTRS)

Pandya, A.; Maida, J.; Aldridge, A.; Hasson, S.; Woolford, B.

1992-01-01

The focus here is on the development of a dynamic strength model for humans. Our model is based on empirical data. The shoulder, elbow, and wrist joints are characterized in terms of maximum isolated torque, position, and velocity in all rotational planes. This information is reduced by a least squares regression technique into a table of single variable second degree polynomial equations determining the torque as a function of position and velocity. The isolated joint torque equations are then used to compute forces resulting from a composite motion, which in this case is a ratchet wrench push and pull operation. What is presented here is a comparison of the computed or predicted results of the model with the actual measured values for the composite motion.

Torque and power outputs on different subjects during manual wheelchair propulsion under different conditions

NASA Astrophysics Data System (ADS)

Hwang, Seonhong; Kim, Seunghyeon; Son, Jongsang; Kim, Youngho

2012-02-01

Manual wheelchair users are at a high risk of pain and injuries to the upper extremities due to mechanical inefficiency of wheelchair propulsion motion. The kinetic analysis of the upper extremities during manual wheelchair propulsion in various conditions needed to be investigated. We developed and calibrated a wheelchair dynamometer for measuring kinetic parameters during propulsion. We utilized the dynamometer to investigate and compare the propulsion torque and power values of experienced and novice users under four different conditions. Experienced wheelchair users generated lower torques with more power than novice users and reacted alertly and sensitively to changing conditions. We expect that these basic methods and results may help to quantitatively evaluate the mechanical efficiency of manual wheelchair propulsion.

Development and application of a direct method to observe the implant/bone interface using simulated bone.

PubMed

Yamaguchi, Yoko; Shiota, Makoto; FuJii, Masaki; Sekiya, Michi; Ozeki, Masahiko

2016-01-01

Primary stability after implant placement is essential for osseointegration. It is important to understand the bone/implant interface for analyzing the influence of implant design on primary stability. In this study rigid polyurethane foam is used as artificial bone to evaluate the bone-implant interface and to identify where the torque is being generated during placement. Five implant systems-Straumann-Standard (ST), Straumann-Bone Level (BL), Straumann-Tapered Effect (TE), Nobel Biocare-Brånemark MKIII (MK3), and Nobel Biocare-Brånemark MKIV (MK4)-were used for this experiment. Artificial bone blocks were prepared and the implant was installed. After placement, a metal jig and one side artificial bone block were removed and then the implant embedded in the artificial bone was exposed for observing the bone-implant interface. A digital micro-analyzer was used for observing the contact interface. The insertion torque values were 39.35, 23.78, 12.53, 26.35, and 17.79 N cm for MK4, BL, ST, TE, and MK3, respectively. In ST, MK3, TE, MK4, and BL the white layer areas were 61 × 103 μm(2), 37 × 103 μm(2), 103 × 103 μm(2) in the tapered portion and 84 × 03 μm(2) in the parallel portion, 134 × 103 μm(2), and 98 × 103 μm(2) in the tapered portion and 87 × 103 μm(2) in the parallel portion, respectively. The direct observation method of the implant/artificial bone interface is a simple and useful method that enables the identification of the area where implant retention occurs. A white layer at the site of stress concentration during implant placement was identified and the magnitude of the stress was quantitatively estimated. The site where the highest torque occurred was the area from the thread crest to the thread root and the under and lateral aspect of the platform. The artificial bone debris created by the self-tapping blade accumulated in both the cutting chamber and in the space between the threads and artificial bone.

Analytic Theory for the Yarkovsky-O Effect on Obliquity

NASA Astrophysics Data System (ADS)

Nesvorný, David; Vokrouhlický, David

2008-07-01

The Yarkovsky-O'Keefe-Radzievski-Paddack (YORP) effect is a thermal radiation torque that causes small objects to speed up or slow down their rotation and modify their spin vector orientation. This effect has important implications for spin dynamics of diameter D lsim 50 km asteroids. In our previous work we developed an analytic theory for the component of the YORP torque that affects the spin rate. Here we extend these calculations to determine the effect of the YORP torque on obliquity. Our theory is limited to objects with near-spherical shapes. Two limiting cases are studied: (1) immediate emission of the thermal energy that occurs for surface thermal conductivity K = 0; (2) the effects of K ≠ 0 in the limit of small temporal variations of the surface temperature. We use the linearized heat transport equation to model (2). The results include explicit scaling of the YORP torque on obliquity with physical and dynamical parameters such as the thermal conductivity and spin rate. The dependence of torques on the obliquity is given as series of the Legendre polynomials. Comparisons show excellent agreement of the analytic results with the numerically calculated YORP torques for objects such as asteroids 1998 KY26 and (66391) 1999 KW4. We suggest that an important fraction of main belt asteroids may have specific obliquity values (generalized Slivan states) arising from the roots of the Legendre polynomials.

The role of shoe design on the prediction of free torque at the shoe-surface interface using pressure insole technology.

PubMed

Weaver, Brian Thomas; Fitzsimons, Kathleen; Braman, Jerrod; Haut, Roger

2016-09-01

The goal of the current study was to expand on previous work to validate the use of pressure insole technology in conjunction with linear regression models to predict the free torque at the shoe-surface interface that is generated while wearing different athletic shoes. Three distinctly different shoe designs were utilised. The stiffness of each shoe was determined with a material's testing machine. Six participants wore each shoe that was fitted with an insole pressure measurement device and performed rotation trials on an embedded force plate. A pressure sensor mask was constructed from those sensors having a high linear correlation with free torque values. Linear regression models were developed to predict free torques from these pressure sensor data. The models were able to accurately predict their own free torque well (RMS error 3.72 ± 0.74 Nm), but not that of the other shoes (RMS error 10.43 ± 3.79 Nm). Models performing self-prediction were also able to measure differences in shoe stiffness. The results of the current study showed the need for participant-shoe specific linear regression models to insure high prediction accuracy of free torques from pressure sensor data during isolated internal and external rotations of the body with respect to a planted foot.

Clinical evaluation of immediate loading of electroeroded screw-retained titanium fixed prostheses supported by tilted implant: a multicenter retrospective study.

PubMed

Acocella, Alessandro; Ercoli, Carlo; Geminiani, Alessandro; Feng, Changyong; Billi, Mauro; Acocella, Gabriele; Giannini, Domenico; Sacco, Roberto

2012-05-01

Immediate occlusal loading of dental implants in the edentulous mandible has proven to be an effective, reliable, and predictable treatment protocol. However, there is limited long-term data available in the literature, when an electroeroded definitive cast-titanium fixed prosthesis is used for this treatment protocol. The aim of this study was to evaluate the clinical effectiveness of dental implants (Astra Tech Dental, Mölndal, Sweden) in the edentulous mandible immediately loaded with an electroeroded cast-titanium screw-retained fixed prosthesis. Forty-five patients received five implants each in the interforaminal area. All the implants were inserted with torque up to 40 Ncm and the distal implants were distally tilted approximately 20 to 30 degrees to minimize the length of posterior cantilevers. Implants were loaded within 48 hours of placement with an acrylic resin-titanium screw-retained prosthesis fabricated by electroerosion. Two of the 225 inserted implants failed after 3 and 16 months of healing, respectively, with a cumulative survival rate of 99.1% and a prosthetic survival rate of 97.8%. Immediate loading of tilted dental implants inserted in the edentulous mandible with a screw-retained titanium definitive prosthesis fabricated with electrical discharge machining provide reliable and predictable results. © 2011 Wiley Periodicals, Inc.

Effects of acoustic treatment on the interior noise levels of a twin-engine propeller aircraft - Experimental flight results and theoretical predictions

NASA Technical Reports Server (NTRS)

Beyer, T. B.; Powell, C. A.; Daniels, E. F.; Pope, L. D.

1984-01-01

In-flight noise level measurements were made within two cabin configurations of a general aviation business aircraft. The Fairchild Merlin IVC twin-engine aircraft was tested with bare walls and fiberglass insulation and in an executive trim configuration. Narrow-band and octave format data were subjected to analyses which permitted identification of the blade passage harmonics (BPH). Cabin noise level reductions (insertion losses) due to added insulation varied with position in the cabin, the BPH number, cabin pressure, and engine torque. The measurements were closely predicted using the propeller aircraft interior noise (PAIN) mode.

Torque efficiency of different archwires in 0.018- and 0.022-inch conventional brackets.

PubMed

Sifakakis, Iosif; Pandis, Nikolaos; Makou, Margarita; Eliades, Theodore; Katsaros, Christos; Bourauel, Christoph

2014-01-01

To compare the archwires inserted during the final stages of the orthodontic treatment with the generated moments at 0.018- and 0.022-inch brackets. The same bracket type, in terms of prescription, was evaluated in both slot dimensions. The brackets were bonded on two identical maxillary acrylic resin models, and each model was mounted on the orthodontic measurement and simulation system. Ten 0.017 × 0.025-inch TMA and ten 0.017 × 0.025-inch stainless steel archwires were evaluated in the 0.018-inch brackets. In the 0.022-inch brackets, ten 0.019 × 0.025-inch TMA and ten 0.019 × 0.025-inch stainless steel archwires were measured. A 15° buccal root torque (+15°) and then a 15° palatal root torque (-15°) were gradually applied to the right central incisor bracket, and the moments were recorded at these positions. A t-test was conducted to compare the generated moments between wires within the 0.018- and 0.022-inch bracket groups separately. The 0.017 × 0.025-inch archwire in the 0.018-inch brackets generated mean moments of 9.25 Nmm and 14.2 Nmm for the TMA and stainless steel archwires, respectively. The measured moments in the 0.022-inch brackets with the 0.019 × 0.025-inch TMA and stainless steel archwires were 6.6 Nmm and 9.3 Nmm, respectively. The 0.017 × 0.025-inch stainless steel and β-Ti archwires in the 0.018-inch slot generated higher moments than the 0.019 × 0.025-inch archwires because of lower torque play. This difference is exaggerated in steel archwires, in comparison with the β-Ti, because of differences in stiffness. The differences of maximum moments between the archwires of the same cross-section but different alloys were statistically significant at both slot dimensions.

Stability Control of Grasping Objects with Different Locations of Center of Mass and Rotational Inertia

PubMed Central

Slota, Gregory P.; Suh, Moon Suk; Latash, Mark L.; Zatsiorsky, Vladimir M.

2012-01-01

The objective of this study was to observe how the digits of the hand adjust to varying location of the center of mass (CoM) above/below the grasp and rotational inertia (RI) of a hand held object. Such manipulations do not immediately affect the equilibrium equations while stability control is affected. Participants were instructed to hold a handle, instrumented with five force/torque transducers and a 3-D rotational tilt sensor, while either the location of the CoM or the RI values were adjusted. On the whole, people use two mechanisms to adjust to the changed stability requirements; they increase the grip force and redistribute the total moment between the normal and tangential forces offsetting internal torques. The increase in grip force, an internal force, and offsetting internal torques allows for increases in joint and hand rotational apparent stiffness while not creating external forces/torques which would unbalance the equations of equilibrium. PMID:22456054

Integrated Orbit, Attitude, and Structural Control System Design for Space Solar Power Satellites

NASA Technical Reports Server (NTRS)

Woods-Vedeler, Jessica (Technical Monitor); Moore, Chris (Technical Monitor); Wie, Bong; Roithmayr, Carlos

2001-01-01

The major objective of this study is to develop an integrated orbit, attitude, and structural control system architecture for very large Space Solar Power Satellites (SSPS) in geosynchronous orbit. This study focuses on the 1.2-GW Abacus SSPS concept characterized by a 3.2 x 3.2 km solar-array platform, a 500-m diameter microwave beam transmitting antenna, and a 500 700 m earth-tracking reflector. For this baseline Abacus SSPS configuration, we derive and analyze a complete set of mathematical models, including external disturbances such as solar radiation pressure, microwave radiation, gravity-gradient torque, and other orbit perturbation effects. The proposed control system architecture utilizes a minimum of 500 1-N electric thrusters to counter, simultaneously, the cyclic pitch gravity-gradient torque, the secular roll torque caused by an o.set of the center-of-mass and center-of-pressure, the cyclic roll/yaw microwave radiation torque, and the solar radiation pressure force whose average value is about 60 N.

Integrated Orbit, Attitude, and Structural Control Systems Design for Space Solar Power Satellites

NASA Technical Reports Server (NTRS)

Wie, Bong; Roithmayr, Carlos M.

2001-01-01

The major objective of this study is to develop an integrated orbit, attitude, and structural control systems architecture for very large Space Solar Power Satellites (SSPS) in geosynchronous orbit. This study focuses on the 1.2-GW Abacus SSPS concept characterized by a 3.2 x 3.2 km solar-array platform, a 500-m diameter microwave beam transmitting antenna, and a 500 x 700 m earth-tracking reflector. For this baseline Abacus SSPS configuration, we derive and analyze a complete set of mathematical models, including external disturbances such as solar radiation pressure, microwave radiation, gravity-gradient torque, and other orbit perturbation effects. The proposed control systems architecture utilizes a minimum of 500 1-N electric thrusters to counter, simultaneously, the cyclic pitch gravity-gradient torque, the secular roll torque caused by an offset of the center-of-mass and center-of-pressure, the cyclic roll/yaw microwave radiation torque, and the solar radiation pressure force whose average value is about 60 N.

Prevalence of Torque teno virus in healthy donors of Paraná State, southern Brazil

PubMed Central

Mazzola, Jocimara Costa; Saito, Patrícia Keiko; Yamakawa, Roger Haruki; Watanabe, Maria Angélica Ehara; da Silva Junior, Waldir Veríssimo; Matta, Alessandra Cristina Gobbi; Borelli, Sueli Donizete

2015-01-01

Objective To determine the prevalence of the Torque teno virus in healthy donors in the northern and northwestern regions of the state of Paraná, southern Brazil. Methods The Torque teno virus was detected by a nested polymerase chain reaction using a set of oligoprimers for the N22 region. Results The prevalence of the virus was 69% in 551 healthy blood donors in southern Brazil. There was no statistically significant difference between the presence of the virus and the variables gender, ethnicity and marital status. There was significant difference in the prevalence of the virus regarding the age of the donors (p-value = 0.024) with a higher incidence (74.7%) in 18- to 24-year-old donors. Conclusion A high prevalence of Torque teno virus was observed in the population studied. Further studies are needed to elucidate the routes of contamination and the clinical implications of the virus in the healthy population. PMID:26408369

Variability in Laboratory vs. Field Testing of Peak Power, Torque, and Time of Peak Power Production Among Elite Bicycle Motocross Cyclists.

PubMed

Rylands, Lee P; Roberts, Simon J; Hurst, Howard T

2015-09-01

The aim of this study was to ascertain the variation in elite male bicycle motocross (BMX) cyclists' peak power, torque, and time of power production during laboratory and field-based testing. Eight elite male BMX riders volunteered for the study, and each rider completed 3 maximal sprints using both a Schoberer Rad Messtechnik (SRM) ergometer in the laboratory and a portable SRM power meter on an Olympic standard indoor BMX track. The results revealed a significantly higher peak power (p ≤ 0.001, 34 ± 9%) and reduced time of power production (p ≤ 0.001, 105 ± 24%) in the field tests when compared with laboratory-derived values. Torque was also reported to be lower in the laboratory tests but not to an accepted level of significance (p = 0.182, 6 ± 8%). These results suggest that field-based testing may be a more effective and accurate measure of a BMX rider's peak power, torque, and time of power production.

Spatiotemporal evolution of hairpin eddies, Reynolds stress, and polymer torque in polymer drag-reduced turbulent channel flows.

PubMed

Kim, Kyoungyoun; Sureshkumar, Radhakrishna

2013-06-01

To study the influence of dynamic interactions between turbulent vortical structures and polymer stress on turbulent friction drag reduction, a series of simulations of channel flow is performed. We obtain self-consistent evolution of an initial eddy in the presence of polymer stresses by utilizing the finitely extensible nonlinear elastic-Peterlin (FENE-P) model. The initial eddy is extracted by the conditional averages for the second quadrant event from fully turbulent Newtonian flow, and the initial polymer conformation fields are given by the solutions of the FENE-P model equations corresponding to the mean shear flow in the Newtonian case. At a relatively low Weissenberg number We(τ) (=50), defined as the ratio of the polymer relaxation time to the wall time scale, the generation of new vortices is inhibited by polymer-induced countertorques. Thus fewer vortices are generated in the buffer layer. However, the head of the primary hairpin is unaffected by the polymer stress. At larger We(τ) values (≥100), the hairpin head becomes weaker and vortex autogeneration and Reynolds stress growth are almost entirely suppressed. The temporal evolution of the vortex strength and polymer torque magnitude reveals that polymer extension by the vortical motion results in a polymer torque that increases in magnitude with time until a maximum value is reached over a time scale comparable to the polymer relaxation time. The polymer torque retards the vortical motion and Reynolds stress production, which in turn weakens flow-induced chain extension and torque itself. An analysis of the vortex time scales reveals that with increasing We(τ), vortical motions associated with a broader range of time scales are affected by the polymer stress. This is qualitatively consistent with Lumley's time criterion for the onset of drag reduction.

Design of Revolute Joints for In-Mold Assembly Using Insert Molding.

PubMed

Ananthanarayanan, Arvind; Ehrlich, Leicester; Desai, Jaydev P; Gupta, Satyandra K

2011-12-01

Creating highly articulated miniature structures requires assembling a large number of small parts. This is a very challenging task and increases cost of mechanical assemblies. Insert molding presents the possibility of creating a highly articulated structure in a single molding step. This can be accomplished by placing multiple metallic bearings in the mold and injecting plastic on top of them. In theory, this idea can generate a multi degree of freedom structures in just one processing step without requiring any post molding assembly operations. However, the polymer material has a tendency to shrink on top of the metal bearings and hence jam the joints. Hence, until now insert molding has not been used to create articulated structures. This paper presents a theoretical model for estimating the extent of joint jamming that occurs due to the shrinkage of the polymer on top of the metal bearings. The level of joint jamming is seen as the effective torque needed to overcome the friction in the revolute joints formed by insert molding. We then use this model to select the optimum design parameters which can be used to fabricate functional, highly articulating assemblies while meeting manufacturing constraints. Our analysis shows that the strength of weld-lines formed during the in-mold assembly process play a significant role in determining the minimum joint dimensions necessary for fabricating functional revolute joints. We have used the models and methods described in this paper to successfully fabricate the structure for a minimally invasive medical robot prototype with potential applications in neurosurgery. To the best of our knowledge, this is the first demonstration of building an articulated structure with multiple degrees of freedom using insert molding.

Comparison of fit accuracy and torque maintenance of zirconia and titanium abutments for internal tri-channel and external-hex implant connections

PubMed Central

Siadat, Hakimeh; Beyabanaki, Elaheh; Mousavi, Niloufar

2017-01-01

PURPOSE This in vitro study aimed to evaluate the effect of implant connection design (external vs. internal) on the fit discrepancy and torque loss of zirconia and titanium abutments. MATERIALS AND METHODS Two regular platform dental implants, one with external connection (Brånemark, Nobel Biocare AB) and the other with internal connection (Noble Replace, Nobel Biocare AB), were selected. Seven titanium and seven customized zirconia abutments were used for each connection design. Measurements of geometry, marginal discrepancy, and rotational freedom were done using video measuring machine. To measure the torque loss, each abutment was torqued to 35 Ncm and then opened by means of a digital torque wrench. Data were analyzed with two-way ANOVA and t-test at α=0.05 of significance. RESULTS There were significant differences in the geometrical measurements and rotational freedom between abutments of two connection groups (P<.001). Also, the results showed significant differences between titanium abutments of internal and external connection implants in terms of rotational freedom (P<.001). Not only customized internal abutments but also customized external abutments did not have the exact geometry of prefabricated abutments (P<.001). However, neither connection type (P=.15) nor abutment material (P=.38) affected torque loss. CONCLUSION Abutments with internal connection showed less rotational freedom. However, better marginal fit was observed in externally connected abutments. Also, customized abutments with either connection could not duplicate the exact geometry of their corresponding prefabricated abutment. However, neither abutment connection nor material affected torque loss values. PMID:28874994

Relationships between explosive and maximal triple extensor muscle performance and vertical jump height.

PubMed

Chang, Eunwook; Norcross, Marc F; Johnson, Sam T; Kitagawa, Taichi; Hoffman, Mark

2015-02-01

The purpose of this study was to examine the relationships between maximum vertical jump height and (a) rate of torque development (RTD) calculated during 2 time intervals, 0-50 milliseconds (RTD50) and 0-200 milliseconds (RTD200) after torque onset and (b) peak torque (PT) for each of the triple extensor muscle groups. Thirty recreationally active individuals performed maximal isometric voluntary contractions (MVIC) of the hip, knee and ankle extensors, and a countermovement vertical jump. Rate of torque development was calculated from 0 to 50 (RTD50) and 0 to 200 (RTD200) milliseconds after the onset of joint torque. Peak torque was identified and defined as the maximum torque value during each MVIC trial. Greater vertical jump height was associated with greater knee and ankle extension RTD50, RTD200, and PT (p ≤ 0.05). However, hip extension RTD50, RTD200, and PT were not significantly related to maximal vertical jump height (p > 0.05). The results indicate that 47.6 and 32.5% of the variability in vertical jump height was explained by knee and ankle extensor RTD50, respectively. Knee and ankle extensor RTD50 also seemed to be more closely related to vertical jump performance than RTD200 (knee extensor: 28.1% and ankle extensor: 28.1%) and PT (knee extensor: 31.4% and ankle extensor: 13.7%). Overall, these results suggest that training specifically targeted to improve knee and ankle extension RTD, especially during the early phases of muscle contraction, may be effective for increasing maximal vertical jump performance.

Angular momentum and torques in a simulation of the atmosphere's response to the 1982-83 El Nino

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ponte, R.M.; Rosen, R.D.; Boer, G.J.

Anomalies in the angular momentum of the atmosphere (M) during the 1982-83 El Nino event and the torques responsible for these anomalies are investigated using output from the Canadian Climate Centre general circulation model. Model values of M during the year of the event are generally larger than those for the model climatology, thereby capturing the observed tendency toward higher values of M during El Nino. Differences exist between the model and observations in the timing and amplitude of the largest anomalies, but these differences may be due to natural variability and not necessarily directly associated with the 1982-83 Elmore » Nino conditions. In late September and October 1982, the model atmosphere acquires momentum more rapidly than usual, leading to the development of the largest deviations from mean conditions at the end of October. A secondary maximum in the departure from mean M values occurs in January 1983 and is related to a general strengthening of westerly momentum anomalies over the model's tropical and midlatitude regions. Both mountain and tangential stress torques are involved in this episode, but no particular mechanism or region dominates the anomalous exchange of momentum. 24 refs., 10 figs., 1 tab.« less

Effect of cyclic loading and retightening on reverse torque value in external and internal implants.

PubMed

Cho, Woong-Rae; Huh, Yoon-Hyuk; Park, Chan-Jin; Cho, Lee-Ra

2015-08-01

The aim of this study was to evaluate the effect of cyclic loading and screw retightening on reverse torque value (RTV) in external and internal type implants. Cement-retained abutments were connected with 30 Ncm torque to external and internal type implants. Experimental groups were classified according to implant connection type and retightening/loading protocol. In groups with no retightening, RTV was evaluated after cyclic loading for 100,000 cycles. In groups with retightening, RTV was measured after 3, 10, 100 cycles as well as every 20,000 cycles until 100,000 cycles of loading. Every group showed decreased RTV after cyclic loading. Before and after cyclic loading, external type implants had significantly higher RTVs than internal type implants. In external type implants, retightening did not affect the decrease in RTV. In contrast, retightening 5 times and retightening after 10 cycles of dynamic loading was effective for maintaining RTV in internal type implants. Retightening of screws is more effective in internal type implants than external type implants. Retightening of screws is recommended in the early stage of functional loading.

Biomimetics of throwing at basketball

NASA Astrophysics Data System (ADS)

Merticaru, E.; Budescu, E.; Iacob, R. M.

2016-08-01

The paper deals with the inverse dynamics of a kinematic chain of the human upper limb when throwing the ball at the basketball, aiming to calculate the torques required to put in action the technical system. The kinematic chain respects the anthropometric features regarding the length and mass of body segments. The kinematic parameters of the motion were determined by measuring the angles of body segments during a succession of filmed pictures of a throw, and the interpolation of these values and determination of the interpolating polynomials for each independent geometric coordinate. Using the Lagrange equations, there were determined the variations with time of the required torques to put in motion the kinematic chain of the type of triple physical pendulum. The obtained values show, naturally, the fact that the biggest torque is that for mimetic articulation of the shoulder, being comparable with those obtained by the brachial biceps muscle of the analyzed human subject. Using the obtained data, there can be conceived the mimetic technical system, of robotic type, with application in sports, so that to perform the motion of ball throwing, from steady position, at the basket.

Peri-implant bone formation and surface characteristics of rough surface zirconia implants manufactured by powder injection molding technique in rabbit tibiae.

PubMed

Park, Young-Seok; Chung, Shin-Hye; Shon, Won-Jun

2013-05-01

To evaluate osseointegration in rabbit tibiae and to investigate surface characteristics of novel zirconia implants made by powder injection molding (PIM) technique, using molds with and without roughened inner surfaces. A total of 20 rabbits received three types of external hex implants with identical geometry on the tibiae: machined titanium implants, PIM zirconia implants without mold etching, and PIM zirconia implants with mold etching. Surface characteristics of the three types of implant were evaluated. Removal torque tests and histomorphometric analyses were performed. The roughness of PIM zirconia implants was higher than that of machined titanium implants. The PIM zirconia implants exhibited significantly higher bone-implant contact and removal torque values than the machined titanium implants (P < 0.001). The PIM zirconia implants using roughened mold showed significantly higher removal torque values than PIM zirconia implants without using roughened mold (P < 0.001). It is concluded that the osseointegration of PIM zirconia implant is promising and PIM using roughened mold etching technique can produce substantially rough surfaces on zirconia implants. © 2012 John Wiley & Sons A/S.

Control Performance of General Electric Fuel and Torque Regulator Operating on T31-3 Turbine-Propeller Engine in Sea-Level Test Stand

NASA Technical Reports Server (NTRS)

Oppenheimer, Frank L.; Lazar, James

1951-01-01

A .General Electric fuel and torque regulator was tested in conjunction with a T31-3 turbine-propeller engine in the sea-level static test stand at the NACA Lewis laboratory. The engine and control were operated over the entire speed range: 11,000 rpm, nominal flight idle, to 13,000 rpm, full power. Steady-state and transient data were recorded and are presented with a description of the four control loops being used in the system. Results of this investigation indicated that single-lever control operation was satisfactory under conditions of test. Transient data presented showed that turbine-outlet temperature did overshoot maximum operating value on acceleration but that the time duration of overshoot did not exceed approximately 1 second. This temperature limiting resulted from a control on fuel flow as a function of engine speed. Speed and torque first reached their desired values 0.4 second from the time of change in power-setting lever position. Maximum speed overshoot was 3 percent.

Single-Resonance Longitudinal and Torsional Vibrator Combination-Type Motor: Improvement of Motor Characteristics

NASA Astrophysics Data System (ADS)

Shimanuki, Masaharu; Aoyagi, Manabu; Tomikawa, Yoshiro

1994-05-01

The present paper deals with the single-resonance longitudinal and torsional vibrator combination-type motor, which is one of the ultrasonic motors with a relatively large torque. To improve the characteristics of this motor, the authors studied the calculation method of the resonance frequencies and designed the motor so that the resonance frequencies of the longitudinal and torsional vibrations were very close to the measured ones, because it was thought that the motor characteristics were largely affected by the degree of approximation of the resonance frequencies. Experimental results have proven that the prototype motor produced large torque with a maximum of 14.0 kgf·cm under a total electrical input power of 30 W; this value was 1.5 times as large as that reported previously. That is, it has been clarified that with sufficient degree of approximation of the resonance frequencies, as mentioned above, the output torque of the motor could be greatly improved; however, its efficiency (maximum of 13.1%) was maintained at almost the same value as before.

The importance of understanding: Model space moderates goal specificity effects.

PubMed

Kistner, Saskia; Burns, Bruce D; Vollmeyer, Regina; Kortenkamp, Ulrich

2016-01-01

The three-space theory of problem solving predicts that the quality of a learner's model and the goal specificity of a task interact on knowledge acquisition. In Experiment 1 participants used a computer simulation of a lever system to learn about torques. They either had to test hypotheses (nonspecific goal), or to produce given values for variables (specific goal). In the good- but not in the poor-model condition they saw torque depicted as an area. Results revealed the predicted interaction. A nonspecific goal only resulted in better learning when a good model of torques was provided. In Experiment 2 participants learned to manipulate the inputs of a system to control its outputs. A nonspecific goal to explore the system helped performance when compared to a specific goal to reach certain values when participants were given a good model, but not when given a poor model that suggested the wrong hypothesis space. Our findings support the three-space theory. They emphasize the importance of understanding for problem solving and stress the need to study underlying processes.

Test-retest reliability of biodex system 4 pro for isometric ankle-eversion and -inversion measurement.

PubMed

Tankevicius, Gediminas; Lankaite, Doanata; Krisciunas, Aleksandras

2013-08-01

The lack of knowledge about isometric ankle testing indicates the need for research in this area. to assess test-retest reliability and to determine the optimal position for isometric ankle-eversion and -inversion testing. Test-retest reliability study. Isometric ankle eversion and inversion were assessed in 3 different dynamometer foot-plate positions: 0°, 7°, and 14° of inversion. Two maximal repetitions were performed at each angle. Both limbs were tested (40 ankles in total). The test was performed 2 times with a period of 7 d between the tests. University hospital. The study was carried out on 20 healthy athletes with no history of ankle sprains. Reliability was assessed using intraclass correlation coefficient (ICC2,1); minimal detectable change (MDC) was calculated using a 95% confidence interval. Paired t test was used to measure statistically significant changes, and P <.05 was considered statistically significant. Eversion and inversion peak torques showed high ICCs in all 3 angles (ICC values .87-.96, MDC values 3.09-6.81 Nm). Eversion peak torque was the smallest when testing at the 0° angle and gradually increased, reaching maximum values at 14° angle. The increase of eversion peak torque was statistically significant at 7 ° and 14° of inversion. Inversion peak torque showed an opposite pattern-it was the smallest when measured at the 14° angle and increased at the other 2 angles; statistically significant changes were seen only between measures taken at 0° and 14°. Isometric eversion and inversion testing using the Biodex 4 Pro system is a reliable method. The authors suggest that the angle of 7° of inversion is the best for isometric eversion and inversion testing.

Age-related differences in rates of torque development and rise in EMG are eliminated by normalization.

PubMed

Jenkins, Nathaniel D M; Buckner, Samuel L; Cochrane, Kristen C; Bergstrom, Haley C; Palmer, Ty B; Johnson, Glen O; Schmidt, Richard J; Housh, Terry J; Cramer, Joel T

2014-09-01

The purpose of this study was to compare the voluntary and evoked, absolute and normalized leg extension rates of torque development (RTD) and rates of rise in electromyography (RER) during commonly reported time intervals in young and old men. Fourteen young men (21.9±3.2years) and 16 older men (72.3±7.3years) completed three evoked and three voluntary isometric leg extension muscle actions to quantify absolute voluntary (peak, 30, 50, 100, and 200ms) and evoked (peak, 30, 50, and 100ms) RTD and RER. All RTD values were normalized (nRTD) to peak torque, while RER values were normalized (nRER) to peak-to-peak M-wave amplitude (MPP). Absolute voluntary RTDs and RERs were 58-122% and 70-76% greater (p≤0.05) for the young men, respectively. However, there were no age-related differences (p>0.05) for voluntary nRTDs, absolute and normalized evoked RTDs, or voluntary nRER. MPP and evoked RER and nRER were greater (p≤0.05) for the young men. In addition, voluntary RTD was more reliable in the young than the older men. Normalizing RTD to peak torque and RER to M-wave amplitude eliminated the age-related differences and suggested that the age-related declines in RTD and RER were a result of reduced muscle strength and M-wave amplitude, respectively. Therefore, our findings questioned the value of RTD and RER measurements in the various time intervals for explaining sarcopenia and suggested that maximal strength and M-wave amplitude may be sufficient. Copyright © 2014 Elsevier Inc. All rights reserved.

Accelerated testing of an optimized closing system for automotive fuel tank

NASA Astrophysics Data System (ADS)

Gligor, A.; Ilie, S.; Nicolae, V.; Mitran, G.

2015-11-01

Taking into account the legal prescriptions which are in force and the new regulatory requirements that will be mandatory to implement in the near future regarding testing characteristics of automotive fuel tanks, resulted the necessity to develop a new testing methodology which allows to estimate the behaviour of the closing system of automotive fuel tank over a long period of time (10-15 years). Thus, were designed and conducted accelerated tests under extreme assembling and testing conditions (high values for initial tightening torques, extreme values of temperature and pressure). In this paper are presented two of durability tests which were performed on an optimized closing system of fuel tank: (i) the test of exposure to temperature with cyclical variation and (ii) the test of continuous exposure to elevated temperature. In these experimental tests have been used main components of the closing system manufactured of two materials variants, both based on the polyoxymethylene, material that provides higher mechanical stiffness and strength in a wide temperature range, as well as showing increased resistance to the action of chemical agents and fuels. The tested sample included a total of 16 optimized locking systems, 8 of each of 2 versions of material. Over deploying the experiments were determined various parameters such as: the initial tightening torque, the tightening torque at different time points during measurements, the residual tightening torque, defects occurred in the system components (fissures, cracks, ruptures), the sealing conditions of system at the beginning and at the end of test. Based on obtained data were plotted the time evolution diagrams of considered parameter (the residual tightening torque of the system consisting of locking nut and threaded ring), in different temperature conditions, becoming possible to make pertinent assessments on the choice between the two types of materials. By conducting these tests and interpreting the obtained results, it can be created a clear picture of the capacity of closing system of fuel tank to fulfil the functional requirements following the exposure to values of testing parameters significantly above the values that may appear throughout the entire service life of the vehicle. The proposed accelerated testing method shows the main advantage of simulation in a limited time all the situations which may be encountered in a much longer period of time, namely the service life of the vehicle.

The influence of bone graft procedures on primary stability and bone change of implants placed in fresh extraction sockets.

PubMed

Jun, Sang Ho; Park, Chang-Joo; Hwang, Suk-Hyun; Lee, Youn Ki; Zhou, Cong; Jang, Hyon-Seok; Ryu, Jae-Jun

2018-12-01

This study was to evaluate the effect of bone graft procedure on the primary stability of implants installed in fresh sockets and assess the vertical alteration of peri-implant bone radiographically. Twenty-three implants were inserted in 18 patients immediately after tooth extraction. The horizontal gap between the implant and bony walls of the extraction socket was grafted with xenografts. The implant stability before and after graft procedure was measured by Osstell Mentor as implant stability quotient before bone graft (ISQ bbg) and implant stability quotient after bone graft (ISQ abg). Peri-apical radiographs were taken to measure peri-implant bone change immediately after implant surgery and 12 months after implant placement. Data were analyzed by independent t test; the relationships between stability parameters (insertion torque value (ITV), ISQ abg, and ISQ bbg) and peri-implant bone changes were analyzed according to Pearson correlation coefficients. The increase of ISQ in low primary stability group (LPSG) was 6.87 ± 3.62, which was significantly higher than the increase in high primary stability group (HPSG). A significant correlation between ITV and ISQ bbg ( R  = 0.606, P  = 0.002) was found; however, age and peri-implant bone change were not found significantly related to implant stability parameters. It was presented that there were no significant peri-implant bone changes at 1 year after bone graft surgery. Bone graft procedure is beneficial for increasing the primary stability of immediately placed implants, especially when the ISQ of implants is below 65 and that bone grafts have some effects on peri-implant bone maintenance.

Validation of value of actual micromotion as a direct measure of implant micromobility after healing (secondary implant stability). An in vivo histologic and biomechanical study.

PubMed

Trisi, Paolo; Berardini, Marco; Falco, Antonello; Podaliri Vulpiani, Michele

2016-11-01

The osseointegration process replaces the surgically damaged bone with newly formed bone in contact to the implant surface. This involves some loss of primary stability, which will continue until new bone is formed providing a new stability, known as "secondary stability." A direct measurement of secondary implant stability appears fundamental to determine the period and modalities for implant loading. The aim of this study was to validate the measurement of the implant micromotion to test secondary implant stability. Twenty-four 3.8 × 11.5 mm implants (Dynamix, Cortex, Shlomi, Israel) were inserted in sheep iliac crests. The animals were sacrificed after 2 months, and the freshly retrieved bone blocks were immediately fixed on a customized device to calculate the value of actual micromotion (VAM) according to a previously described technique. Implant stability quotient (ISQ) values, reverse torque value (RTV), %bone-to-implant contact (%BIC), bone volume percentage (%BV) and crestal bone loss (CBL) were also calculated for each implant. Statistical correlations between VAM and the other parameters were calculated. Data correlation analysis between the examined parameters showed that VAM significantly correlates (P < 0.05) to RTV, %BIC, ISQ and CBL. As VAM showed to be statistical correlated to the other parameters of osseointegration, it may be used to clinically check the amount of implant osseointegration, secondary stability and CBL. Future studies are needed to confirm these results moreover. An instrument to measure VAM in the oral cavity still needs to be developed. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Sensor-less pseudo-sinusoidal drive for a permanent-magnet brushless ac motor

NASA Astrophysics Data System (ADS)

Liu, Li-Hsiang; Chern, Tzuen-Lih; Pan, Ping-Lung; Huang, Tsung-Mou; Tsay, Der-Min; Kuang, Jao-Hwa

2012-04-01

The precise rotor-position information is required for a permanent-magnet brushless ac motor (BLACM) drive. In the conventional sinusoidal drive method, either an encoder or a resolver is usually employed. For position sensor-less vector control schemes, the rotor flux estimation and torque components are obtained by complicated coordinate transformations. These computational intensive methods are susceptible to current distortions and parameter variations. To simplify the method complexity, this work presents a sensor-less pseudo-sinusoidal drive scheme with speed control for a three-phase BLACM. Based on the sinusoidal drive scheme, a floating period of each phase current is inserted for back electromotive force detection. The zero-crossing point is determined directly by the proposed scheme, and the rotor magnetic position and rotor speed can be estimated simultaneously. Several experiments for various active angle periods are undertaken. Furthermore, a current feedback control is included to minimize and compensate the torque fluctuation. The experimental results show that the proposed method has a competitive performance compared with the conventional drive manners for BLACM. The proposed scheme is straightforward, bringing the benefits of sensor-less drive and negating the need for coordinate transformations in the operating process.

Torque and mechanomyogram relationships during electrically-evoked isometric quadriceps contractions in persons with spinal cord injury.

PubMed

Ibitoye, Morufu Olusola; Hamzaid, Nur Azah; Hasnan, Nazirah; Abdul Wahab, Ahmad Khairi; Islam, Md Anamul; Kean, Victor S P; Davis, Glen M

2016-08-01

The interaction between muscle contractions and joint loading produces torques necessary for movements during activities of daily living. However, during neuromuscular electrical stimulation (NMES)-evoked contractions in persons with spinal cord injury (SCI), a simple and reliable proxy of torque at the muscle level has been minimally investigated. Thus, the purpose of this study was to investigate the relationships between muscle mechanomyographic (MMG) characteristics and NMES-evoked isometric quadriceps torques in persons with motor complete SCI. Six SCI participants with lesion levels below C4 [(mean (SD) age, 39.2 (7.9) year; stature, 1.71 (0.05) m; and body mass, 69.3 (12.9) kg)] performed randomly ordered NMES-evoked isometric leg muscle contractions at 30°, 60° and 90° knee flexion angles on an isokinetic dynamometer. MMG signals were detected by an accelerometer-based vibromyographic sensor placed over the belly of rectus femoris muscle. The relationship between MMG root mean square (MMG-RMS) and NMES-evoked torque revealed a very high association (R(2)=0.91 at 30°; R(2)=0.98 at 60°; and R(2)=0.97 at 90° knee angles; P<0.001). MMG peak-to-peak (MMG-PTP) and stimulation intensity were less well related (R(2)=0.63 at 30°; R(2)=0.67 at 60°; and R(2)=0.45 at 90° knee angles), although were still significantly associated (P≤0.006). Test-retest interclass correlation coefficients (ICC) for the dependent variables ranged from 0.82 to 0.97 for NMES-evoked torque, between 0.65 and 0.79 for MMG-RMS, and from 0.67 to 0.73 for MMG-PTP. Their standard error of measurements (SEM) ranged between 10.1% and 31.6% (of mean values) for torque, MMG-RMS and MMG-PTP. The MMG peak frequency (MMG-PF) of 30Hz approximated the stimulation frequency, indicating NMES-evoked motor unit firing rate. The results demonstrated knee angle differences in the MMG-RMS versus NMES-isometric torque relationship, but a similar torque related pattern for MMG-PF. These findings suggested that MMG was well associated with torque production, reliably tracking the motor unit recruitment pattern during NMES-evoked muscle contractions. The strong positive relationship between MMG signal and NMES-evoked torque production suggested that the MMG might be deployed as a direct proxy for muscle torque or fatigue measurement during leg exercise and functional movements in the SCI population. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

Supervisory control of drilling of composite materials

NASA Astrophysics Data System (ADS)

Ozaki, Motoyoshi

Composite materials have attractive features, such as high ratios of strength-to-weight and stiffness-to-weight. However, they are easily damaged when they are machined. A typical damage is delamination, which can occur when fiber reinforced composite laminates are drilled. The objective of this research is to study the drilling processes of carbon fiber reinforced laminates, and to develop and test a supervisory control strategy for their delamination-free drilling. Characterization of thrust force and torque is achieved through constant feedrate drilling experiments. The average values of thrust force and torque during the full engagement of the drill are utilized to obtain the Shaw's equations' parameters. The thrust force profile just before exit is given special attention. The Hocheng-Dharan equations, which give conservative values of delamination at the entrance and at the exit, are modified to express the influence of one lamina thickness explicitly. They are utilized not only for the characterization of thrust force but also for the determination of the thrust force reference for force control. In the design of the controllers of thrust force and torque, both thrust force and torque are assumed to be proportional to FPHR (Feed Per Half Revolution). A discrete-time dynamic model is established for the case when the time interval for a half revolution of the drill is divided by the sampling time, and the model is extended to the case of general spindle speeds. PI controllers are designed for the dynamic models of thrust force and torque. Root-locus techniques are used in the analysis. The phases of the drilling process are introduced and the control strategy at each phase is explained. The supervisory controller chooses not only the best control strategy for each phase, but also the reference value and the controller gain that are suitable at each drill position. Drilling experiments are conducted to show the usefulness of the concepts introduced in this dissertation, and to give an example of installing the control parameters, which were derived from data obtained in this research, on the supervisory controller. Efficient Delamination-free drilling is given special emphasis in the experiments.

Ankle and toe muscle strength characteristics in runners with a history of medial tibial stress syndrome.

PubMed

Saeki, Junya; Nakamura, Masatoshi; Nakao, Sayaka; Fujita, Kosuke; Yanase, Ko; Morishita, Katsuyuki; Ichihashi, Noriaki

2017-01-01

A high proportion of flexor digitorum longus attachment is found at the posteromedial border of the tibia, which is the most common location of medial tibial stress syndrome (MTSS). Therefore, plantar flexion strength of the lesser toes could be related to MTSS; however, the relationship between MTSS and muscle strength of the hallux and lesser toes is not yet evaluated due to the lack of quantitative methods. This study investigated the muscle strength characteristics in runners with a history of MTSS by using a newly developed device to measure the muscle strength of the hallux, lesser toes, and ankle. This study comprised 27 collegiate male runner participants (20.0 ± 1.6 years, 172.1 ± 5.1 cm, 57.5 ± 4.0 kg). Maximal voluntary isometric contraction (MVIC) torque of the plantar flexion, dorsiflexion, inversion, and eversion of the ankle were measured by using an electric dynamometer. MVIC torque of the 1st metatarsophalangeal joint (MTPJ) and 2nd-5th MTPJ were measured by using a custom-made torque-measuring device. MVIC torques were compared between runners with and without a history of MTSS. MVIC torque of the 1st MTPJ plantar flexion was significantly higher in runners with a history of MTSS than in those without it. In contrast, there were no significant differences in the MVIC torque values of the 2nd-5th MTPJ plantar flexion and each MVIC torque of the ankle between runners with and without a history of MTSS. A history of MTSS increased the isometric FHL strength.

Predictive momentum management for a space station measurement and computation requirements

NASA Technical Reports Server (NTRS)

Adams, John Carl

1986-01-01

An analysis is made of the effects of errors and uncertainties in the predicting of disturbance torques on the peak momentum buildup on a space station. Models of the disturbance torques acting on a space station in low Earth orbit are presented, to estimate how accurately they can be predicted. An analysis of the torque and momentum buildup about the pitch axis of the Dual Keel space station configuration is formulated, and a derivation of the Average Torque Equilibrium Attitude (ATEA) is presented, for the case of no MRMS (Mobile Remote Manipulation System) motion, Y vehicle axis MRMS motion, and Z vehicle axis MRMS motion. Results showed the peak momentum buildup to be approximately 20000 N-m-s and to be relatively insensitive to errors in the predicting torque models, for Z axis motion of the MRMS was found to vary significantly with model errors, but not exceed a value of approximately 15000 N-m-s for the Y axis MRMS motion with 1 deg attitude hold error. Minimum peak disturbance momentum was found not to occur at the ATEA angle, but at a slightly smaller angle. However, this minimum peak momentum attitude was found to produce significant disturbance momentum at the end of the predicting time interval.

Planetary Torque in 3D Isentropic Disks

NASA Astrophysics Data System (ADS)

Fung, Jeffrey; Masset, Frédéric; Lega, Elena; Velasco, David

2017-03-01

Planetary migration is inherently a three-dimensional (3D) problem, because Earth-size planetary cores are deeply embedded in protoplanetary disks. Simulations of these 3D disks remain challenging due to the steep resolution requirements. Using two different hydrodynamics codes, FARGO3D and PEnGUIn, we simulate disk-planet interaction for a one to five Earth-mass planet embedded in an isentropic disk. We measure the torque on the planet and ensure that the measurements are converged both in resolution and between the two codes. We find that the torque is independent of the smoothing length of the planet’s potential (r s), and that it has a weak dependence on the adiabatic index of the gaseous disk (γ). The torque values correspond to an inward migration rate qualitatively similar to previous linear calculations. We perform additional simulations with explicit radiative transfer using FARGOCA, and again find agreement between 3D simulations and existing torque formulae. We also present the flow pattern around the planets that show active flow is present within the planet’s Hill sphere, and meridional vortices are shed downstream. The vertical flow speed near the planet is faster for a smaller r s or γ, up to supersonic speeds for the smallest r s and γ in our study.

Muscular activity and torque of the foot dorsiflexor muscles during decremental isometric test: A cross-sectional study.

PubMed

Ruiz-Muñoz, Maria; González-Sánchez, Manuel; Martín-Martín, Jaime; Cuesta-Vargas, Antonio I

2017-06-01

To analyse the torque variation level that could be explained by the muscle activation (EMG) amplitude of the three major foot dorsiflexor muscles (tibialis anterior (TA), extensor digitorum longus (EDL), extensor hallucis longus (EHL)) during isometric foot dorsiflexion at different intensities. In a cross-sectional study, forty-one subjects performed foot dorsiflexion at 100%, 75%, 50% and 25% of maximal voluntary contractions (MVC) with the hip and knee flexed 90° and the ankle in neutral position (90° between leg and foot). Three foot dorsiflexions were performed for each intensity. Outcome variables were: maximum (100% MVC) and relative torque (75%, 50%, 25% MVC), maximum and relative EMG amplitude. A linear regression analysis was calculated for each intensity of the isometric foot dorsiflexion. The degree of torque variation (dependent variable) from the independent variables explain (EMG amplitude of the three major foot dorsiflexor muscles) the increases when the foot dorsiflexion intensity is increased, with values of R 2 that range from 0.194 (during 25% MVC) to 0.753 (during 100% MVC). The reliability of the outcome variables was excellent. The EMG amplitude of the three main foot dorsiflexors exhibited more variance in the dependent variable (torque) when foot dorsiflexion intensity increases. Copyright © 2016 Elsevier Ltd. All rights reserved.

Experimental Study of Split-Path Transmission Load Sharing

NASA Technical Reports Server (NTRS)

Krantz, Timothy L.; Delgado, Irebert R.

1996-01-01

Split-path transmissions are promising, attractive alternatives to the common planetary transmissions for helicopters. The split-path design offers two parallel paths for transmitting torque from the engine to the rotor. Ideally, the transmitted torque is shared equally between the two load paths; however, because of manufacturing tolerances, the design must be sized to allow for other than equal load sharing. To study the effect of tolerances, experiments were conducted using the NASA split-path test gearbox. Two gearboxes, nominally identical except for manufacturing tolerances, were tested. The clocking angle was considered to be a design parameter and used to adjust the load sharing of an otherwise fixed design. The torque carried in each path was measured for a matrix of input torques and clocking angles. The data were used to determine the optimal value and a tolerance for the clocking angles such that the most heavily loaded split path carried no greater than 53 percent of an input shaft torque of 367 N-m. The range of clocking angles satisfying this condition was -0.0012 +/- 0.0007 rad for box 1 and -0.0023 +/- 0.0009 rad for box 2. This study indicates that split-path gearboxes can be used successfully in rotorcraft and can be manufactured with existing technology.

Within- and between-session reliability of the maximal voluntary knee extension torque and activation.

PubMed

Park, Jihong; Hopkins, J Ty

2013-01-01

A ratio between the torque generated by maximal voluntary isometric contraction (MVIC) and exogenous electrical stimulus, central activation ratio (CAR), has been widely used to assess quadriceps function. To date, no data exist regarding between-session reliability of this measurement. Thirteen neurologically sound volunteers underwent three testing sessions (three trials per session) with 48 hours between-session. Subjects performed MVICs of the quadriceps with the knee locked at 90° flexion and the hip at 85°. Once the MVIC reached a plateau, an electrical stimulation from superimposed burst technique (SIB: 125 V with peak output current 450 mA) was manually delivered and transmitted directly to the quadriceps via stimulating electrodes. CAR was calculated by using the following equation: CAR = MVIC torque/MVIC + SIB torque. Intraclass correlation coefficients (ICC) were calculated within- (ICC((2,1))) and between-session (ICC((2,k))) for MVIC torques and CAR values. Our data show that quadriceps MVIC and CAR are very reliable both within- (ICC((2,1)) = 0.99 for MVIC; 0.94 for CAR) and between-measurement sessions (ICC((2,k)) = 0.92 for MVIC; 0.86 for CAR) in healthy young adults. For clinical research, more data of the patients with pathological conditions are required to ensure reproducibility of calculation of CAR.

Effects of Structural Deformations of the Crank-Slider Mechanism on the Estimation of the Instantaneous Engine Friction Torque

NASA Astrophysics Data System (ADS)

CHALHOUB, N. G.; NEHME, H.; HENEIN, N. A.; BRYZIK, W.

1999-07-01

The focus on the current study is to assess the effects of structural deformations of the crankshaft/connecting-rod/piston mechanism on the computation of the instantaneous engine friction torque. This study is performed in a fully controlled environment in order to isolate the effects of structural deformations from those of measurement errors or noise interference. Therefore, a detailed model, accounting for the rigid and flexible motions of the crank-slider mechanism and including engine component friction formulations, is considered in this study. The model is used as a test bed to generate the engine friction torque,Tfa, and to predict the rigid and flexible motions of the system in response to the cylinder gas pressure. The torsional vibrations and the rigid body angular velocity of the crankshaft, as predicted by the detailed model of the crank-slider mechanism, are used along with the engine load torque and the cylinder gas pressure in the (P-ω) method to estimate the engine friction torque,Tfe. This method is well suited for the purpose of this study because its formulation is based on the rigid body model of the crank-slider mechanism. The digital simulation results demonstrate that the exclusion of the structural deformations of the crank-slider mechanism from the formulation of the (P-ω) method leads to an overestimation of the engine friction torque near the top-dead-center (TDC) position of the piston under firing conditions. Moreover, for the remainder of the engine cycle, the estimated friction torque exhibits large oscillations and takes on positive numerical values as if it is inducing energy into the system. Thus, the adverse effects of structural deformations of the crank-slider mechanism on the estimation of the engine friction torque greatly differ in their nature from one phase of the engine cycle to another.

Displacement of screw-retained single crowns into implants with conical internal connections.

PubMed

Yilmaz, Burak; Seidt, Jeremy D; McGlumphy, Edwin A; Clelland, Nancy L

2013-01-01

Internal conical implant-abutment connections without platforms may lead to axial displacement of crowns during screw tightening. This displacement may affect proximal contacts, incisal edge position, or occlusion. This study aimed to measure the displacement of screw-retained single crowns into an implant in three dimensions during screw tightening by hand or via torque driver. A stereolithic acrylic resin cast was created using computed tomography data from a patient missing the maxillary right central incisor. A 4.0- × 11-mm implant was placed in the edentulous site. Five porcelain-fused-to-metal single crowns were made using "cast-to" abutments. Crowns were tried on the stereolithic model, representing the patient, and hand tightened. The spatial relationship of crowns to the model after hand tightening was determined using three-dimensional digital image correlation (3D DIC), an optical measurement technique. The crowns were then tightened using a torque driver to 20 Ncm and the relative crown positions were again recorded. Testing was repeated three times for each crown, and displacement of the crowns was compared between the hand-tightened and torqued states. Commercial image correlation software was used to analyze the data. Mean vertical and horizontal crown displacement values were calculated after torqueing. The interproximal contacts were evaluated before and after torquing using an 8-μm aluminum foil shim. There were vertical and horizontal differences in crown positions between hand tightening and torqueing. Although these were small in magnitude, detectable displacements occurred in both apical and facial directions. After hand tightening, the 8-μm shim could be dragged without tearing. However, after torque tightening, the interproximal contacts were too tight and the 8-μm shim could not be dragged without tearing. Differences between hand tightening and torque tightening should be taken into consideration during laboratory and clinical adjustments to prevent esthetic and functional complications.

Evaluation of stability of interface between CCM (Co-Cr-Mo) UCLA abutment and external hex implant.

PubMed

Yoon, Ki-Joon; Park, Young-Bum; Choi, Hyunmin; Cho, Youngsung; Lee, Jae-Hoon; Lee, Keun-Woo

2016-12-01

The purpose of this study is to evaluate the stability of interface between Co-Cr-Mo (CCM) UCLA abutment and external hex implant. Sixteen external hex implant fixtures were assigned to two groups (CCM and Gold group) and were embedded in molds using clear acrylic resin. Screw-retained prostheses were constructed using CCM UCLA abutment and Gold UCLA abutment. The external implant fixture and screw-retained prostheses were connected using abutment screws. After the abutments were tightened to 30 Ncm torque, 5 kg thermocyclic functional loading was applied by chewing simulator. A target of 1.0 × 10 6 cycles was applied. After cyclic loading, removal torque values were recorded using a driving torque tester, and the interface between implant fixture and abutment was evaluated by scanning electronic microscope (SEM). The means and standard deviations (SD) between the CCM and Gold groups were analyzed with independent t-test at the significance level of 0.05. Fractures of crowns, abutments, abutment screws, and fixtures and loosening of abutment screws were not observed after thermocyclic loading. There were no statistically significant differences at the recorded removal torque values between CCM and Gold groups ( P >.05). SEM analysis revealed that remarkable wear patterns were observed at the abutment interface only for Gold UCLA abutments. Those patterns were not observed for other specimens. Within the limit of this study, CCM UCLA abutment has no statistically significant difference in the stability of interface with external hex implant, compared with Gold UCLA abutment.

Titanium alloy vs. stainless steel miniscrews: an in vivo split-mouth study.

PubMed

Bollero, P; Di Fazio, V; Pavoni, C; Cordaro, M; Cozza, P; Lione, R

2018-04-01

To compare in vivo Titanium Alloy (TiA) with Stainless Steel (SS) miniscrews Temporary Anchorage Devices (TADs) using removal torque and Scanning Electron Microscopic (SEM) analysis. 15 subjects (6 males and 9 females) who required maximum anchorage were recruited. For each patient, a TiA TAD and a SS TAD with same length and width were implanted following a randomized split-mouth study design. Retraction was carried out with nickel-titanium spring ligated directly from the anterior hooks of the archwire to the TADs to produce 90 to 100 g of force. When no further anchorage supplementation was needed, the TADs were removed. The removal torque values were registered with a digital screwdriver. After removal, the TADs were collected in a fixed solution and examined using SEM and X-ray microanalysis. All TADs remained intact, with a 100% success rate. There was no difference in removal torque between TiA and SS miniscrews (4.4 ± 1.3 N-cm and 5.1 ± 0.7 N-cm, respectively). All specimens' loss of gloss with signs of biological contaminations resulted in a dull implant surface. SEM photomicrographs of TiA miniscrews showed predominantly blood cells while SS miniscrews showed the precipitation of an amorphous layer with low cellular component. There was no difference in spectroscopic analysis between TiA and SS miniscrews. TiA and SS miniscrews had comparable removal torque values. SEM photomicrographs showed no evidence of osseointegration with both TADs having similar biological responses.

Fastener Starter

NASA Technical Reports Server (NTRS)

Chandler, Faith; Garton, Harry; Valentino, Bill; Amett, Mike

2005-01-01

The Fastener Starter is a creative solution to prevent the loss of small fasteners during their installation. This is the only currently available tool that can firmly grip and hold a single screw, bolt, nut, washer, spacer, or any combination of these parts. Other commercially available fastener starters are unable to accommodate a variety of parts simultaneously. The Fastener Starter is a more capable and easier tool to use than prior tools. Its compact size allows it to be used effectively in cramped, difficult-to-see locations. Its design also allows it to be used with or without handles and extenders in other difficult-to-reach locations. It provides better protection against cross threading and loss of fasteners and associated parts. The Fastener Starter is non-magnetic and does not off-gas, thus meeting flight hardware requirements. The Fastener Starter incorporates a combination of features of several commercially available tools, providing an improved means of installing small fasteners. The Fastener Starter includes a custom molded insert that can be removed easily and replaced with a conventional tool bit (e.g., a screwdriver or hex-driver bit). When used with the insert, the Fastener Starter prevents cross threading and damage to internal threaded holes. This is achieved by allowing the fastener to slip within the tool insert when used without a conventional tool bit. Alternatively, without the insert and with a tool bit, the Fastener Starter can torque a fastener. The Fastener Starter has a square recess hole that accepts a conventional square drive handle or extension to accommodate a variety of applications by providing flexibility in handle style and length.

Procedure to Measure Effect of Excess Body Mass on Musculoskeleture: II. Implementation

NASA Astrophysics Data System (ADS)

Shaibani, Saami J.

2008-03-01

There are a number of ways in which the musculoskeletal system can be affected by excess body mass. One representative quantity for these is the torque exerted on the spinal column about a horizontal lateral axis; hence, its use as an illustrative mechanical indicator in the research reported here. Values of the torque are determined for all subjects in an exceptionally broad adult population that was developed during a companion study. Increases in body mass index caused nearly uniform increases in torque for all height percentiles in both sexes. Overweight individuals had torques that were 35 and 30 percent greater (females and males, respectively) than those for healthy individuals of the same height. Corresponding increases for obese individuals occurred at the much higher levels of 75 and 66 percent. Any resulting musculosketal damage from this is in addition to other problems arising from obesity, such as heart disease, diabetes, and high blood pressure. However, whereas the latter can be treated or managed with medication, some facets of the former might be irreversible and/or irremediable.

Roles of coercivity and remanent flux density of permanent magnet in interior permanent magnet synchronous motor (IPMSM) performance for electric vehicle applications

NASA Astrophysics Data System (ADS)

Won, Hoyun; Hong, Yang-Ki; Lee, Woncheol; Choi, Minyeong

2018-05-01

We used four rotor topologies of an interior permanent magnet synchronous motor (IPMSM) to investigate the effects of remanent flux density (Br) and coercivity (Hc) of permanent magnet on motor performance. Commercial strontium hexaferrite (SrFe12O19: energy product, (BH)max, of 4.62 MGOe) and Nd-Fe-B ((BH)max of 38.2 MGOe) magnets were used for the rotor designs. The same machine specifications and magnet volume keep constant, while the Hc and Br vary to calculate torque and energy efficiency with the finite-element analysis. A combination of high Hc and low Br more effectively increased maximum torque of IPMSM when the hexaferrite magnet was used. For Nd-Fe-B magnet, the same combination did not affect maximum torque, but increased energy efficiency at high speed. Therefore, the Hc value of a permanent magnet is more effective than the Br in producing high maximum torque for SrM-magnet based IPMSM and high energy efficiency at high speed for Nd-Fe-B magnet based IPMSM.

Recommended placement torque when tightening an orthodontic mini-implant.

PubMed

Motoyoshi, Mitsuru; Hirabayashi, Masayuki; Uemura, Miwa; Shimizu, Noriyoshi

2006-02-01

To determine an adequate placement torque for obtaining a better success rate of mini-implants that are screwed into the buccal alveolar bone of the posterior region as an anchor for orthodontic treatment, implant placement torque (IPT) was measured. The subjects were 41 orthodontic patients (124 implants), with an average age of 24.9 years (SD 6.5 years), who had surgery to place titanium mini-implants. The peak value of IPT was measured using a torque screwdriver. The success rate of the mini-implant anchor for 124 implants was 85.5%. The mean IPT ranged from 7.2 to 13.5 N cm, depending on the location of the implants. There was a significant difference in the IPT between maxilla and mandible. The IPT in the mandible was, unexpectedly, significantly higher in the failure group than in the success group. Therefore, a large IPT should not be used always. According to our calculations of the risk ratio for failure, to raise the success rate of 1.6-mm diameter mini-implants, the recommended IPT is within the range from 5 to 10 N cm.

Magnetic moment of inertia within the torque-torque correlation model.

PubMed

Thonig, Danny; Eriksson, Olle; Pereiro, Manuel

2017-04-19

An essential property of magnetic devices is the relaxation rate in magnetic switching which strongly depends on the energy dissipation. This is described by the Landau-Lifshitz-Gilbert equation and the well known damping parameter, which has been shown to be reproduced from quantum mechanical calculations. Recently the importance of inertia phenomena have been discussed for magnetisation dynamics. This magnetic counterpart to the well-known inertia of Newtonian mechanics, represents a research field that so far has received only limited attention. We present and elaborate here on a theoretical model for calculating the magnetic moment of inertia based on the torque-torque correlation model. Particularly, the method has been applied to bulk itinerant magnets and we show that numerical values are comparable with recent experimental measurements. The theoretical analysis shows that even though the moment of inertia and damping are produced by the spin-orbit coupling, and the expression for them have common features, they are caused by very different electronic structure mechanisms. We propose ways to utilise this in order to tune the inertia experimentally, and to find materials with significant inertia dynamics.

Validation of a Biofeedback System for Wheelchair Propulsion Training

PubMed Central

Guo, Liyun; Kwarciak, Andrew M.; Rodriguez, Russell; Sarkar, Nilanjan; Richter, W. Mark

2011-01-01

This paper describes the design and validation of the OptiPush Biofeedback System, a commercially available, instrumented wheel system that records handrim biomechanics and provides stroke-by-stroke biofeedback and targeting for 11 propulsion variables. Testing of the system revealed accurate measurement of wheel angle (0.02% error), wheel speed (0.06% error), and handrim loads. The maximum errors in static force and torque measurements were 3.80% and 2.05%, respectively. Measured forces were also found to be highly linear (0.985 < slope < 1.011) and highly correlated to the reference forces (r 2 > .998). Dynamic measurements of planar forces (F x and F y) and axle torque also had low error (−0.96 N to 0.83 N for force and 0.10 Nm to 0.14 Nm for torque) and were highly correlated (r > .986) with expected force and torque values. Overall, the OptiPush Biofeedback System provides accurate measurement of wheel dynamics and handrim biomechanics and may be a useful tool for improving manual wheelchair propulsion. PMID:22110977

Influence of implant diameter in the displacement of dental implants in trabecular bovine bone under a static lateral load: experimental results and computational modeling.

PubMed

Engelke, Wilfried; Decco, Oscar A; Cura, Andrea C; Maldonado, Isai; Crippa, Federico G

2014-12-01

Primary stability and micromovement of dental implants depend on structural properties of the surrounding bone and on implant dimension and design. The purpose of this study was to provide objective data for the influence of implant diameter on the displacement of titanium screw implants. Ninety Semados implants (length 15 mm, diameter 3.25, 3.75, and 4.5 mm; Bego, Bremen, Germany) were inserted in trabecular bone specimens. All implants were inserted with a torque up to 30 N·cm and loaded horizontally with 10, 20, and 30 N for 2 seconds. All implants showed primary stability. With increasing force, a gradual increase of micromovement was observed (Kruskal-Wallis test, P = 0.000). No significant differences were found (Kruskal-Wallis test, P = 0.148) comparing different diameters for every force. Variation of the diameter of standard implants between 3.25 and 4.5 mm does not seem to influence the primary stability in trabecular bone specimen. Differences between experimental and computational results may be due to the simplification used when modeling.

Using multiple sensors for printed circuit board insertion

NASA Technical Reports Server (NTRS)

Sood, Deepak; Repko, Michael C.; Kelley, Robert B.

1989-01-01

As more and more activities are performed in space, there will be a greater demand placed on the information handling capacity of people who are to direct and accomplish these tasks. A promising alternative to full-time human involvement is the use of semi-autonomous, intelligent robot systems. To automate tasks such as assembly, disassembly, repair and maintenance, the issues presented by environmental uncertainties need to be addressed. These uncertainties are introduced by variations in the computed position of the robot at different locations in its work envelope, variations in part positioning, and tolerances of part dimensions. As a result, the robot system may not be able to accomplish the desired task without the help of sensor feedback. Measurements on the environment allow real time corrections to be made to the process. A design and implementation of an intelligent robot system which inserts printed circuit boards into a card cage are presented. Intelligent behavior is accomplished by coupling the task execution sequence with information derived from three different sensors: an overhead three-dimensional vision system, a fingertip infrared sensor, and a six degree of freedom wrist-mounted force/torque sensor.

Rotation and neoclassical ripple transport in ITER

DOE PAGES

Paul, Elizabeth Joy; Landreman, Matt; Poli, Francesca M.; ...

2017-07-13

Neoclassical transport in the presence of non-axisymmetric magnetic fields causes a toroidal torque known as neoclassical toroidal viscosity (NTV). The toroidal symmetry of ITER will be broken by the finite number of toroidal field coils and by test blanket modules (TBMs). The addition of ferritic inserts (FIs) will decrease the magnitude of the toroidal field ripple. 3D magnetic equilibria in the presence of toroidal field ripple and ferromagnetic structures are calculated for an ITER steady-state scenario using the Variational Moments Equilibrium Code (VMEC). Furthermore, neoclassical transport quantities in the presence of these error fields are calculated using the Stellarator Fokker-Planckmore » Iterative Neoclassical Conservative Solver (SFINCS).« less

Rotation and neoclassical ripple transport in ITER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paul, Elizabeth Joy; Landreman, Matt; Poli, Francesca M.

Neoclassical transport in the presence of non-axisymmetric magnetic fields causes a toroidal torque known as neoclassical toroidal viscosity (NTV). The toroidal symmetry of ITER will be broken by the finite number of toroidal field coils and by test blanket modules (TBMs). The addition of ferritic inserts (FIs) will decrease the magnitude of the toroidal field ripple. 3D magnetic equilibria in the presence of toroidal field ripple and ferromagnetic structures are calculated for an ITER steady-state scenario using the Variational Moments Equilibrium Code (VMEC). Furthermore, neoclassical transport quantities in the presence of these error fields are calculated using the Stellarator Fokker-Planckmore » Iterative Neoclassical Conservative Solver (SFINCS).« less

Development of a Hardware-in-the-Loop Simulator for Control Moment Gyroscope-Based Attitude Control Systems

DTIC Science & Technology

2015-12-01

angular momentum is simply the scalar value projected along the axis of rotation of the momentum wheel (see Figure 1). Since reaction wheels are fixed ...CMGs generate torque by gimbaling a momentum wheel rotating at a nominally fixed rate [2]. The torque output of a CMG is the cross product of the...notably the fixed skew angle of the original system. The goal of this research is to build upon the previous redesign efforts and develop a four-CMG HIL

Experimental study of a variable-capacitance micromotor with electrostatic suspension

NASA Astrophysics Data System (ADS)

Han, F. T.; Wu, Q. P.; Wang, L.

2010-11-01

A variable-capacitance micromotor where the rotor is supported electrostatically in five degrees of freedom was designed, fabricated and tested in order to study the behavior of this electrostatic motor. The micromachined device is based on a glass/silicon/glass stack bonding structure, fabricated by bulk micromachining and initially operated in atmospheric environment. The analytical torque model is obtained by calculating the capacitances between different stator electrodes and the rotor. Capacitance values in the order of 10-13 pF and torque values in the order of 10-10 N m have been calculated from the motor geometry and attainable drive voltage. A dynamic model of the motor is proposed by further estimating the air-film damping effect in an effort to explain the experimental rotation measurements. Experimental results of starting voltage, continuous operation, switching response and electric bearing of the micromotor are presented and discussed. Preliminary measurements indicate that a rotor rotating speed of 73.3 r min-1 can be achieved at a drive voltage of 28.3 V, equivalent to a theoretical motive torque of 517 pN m. Starting voltage results obtained from experimental measurement are in agreement with the developed dynamic model.

Effect of cyclic loading and retightening on reverse torque value in external and internal implants

PubMed Central

Cho, Woong-Rae; Huh, Yoon-Hyuk; Park, Chan-Jin

2015-01-01

PURPOSE The aim of this study was to evaluate the effect of cyclic loading and screw retightening on reverse torque value (RTV) in external and internal type implants. MATERIALS AND METHODS Cement-retained abutments were connected with 30 Ncm torque to external and internal type implants. Experimental groups were classified according to implant connection type and retightening/loading protocol. In groups with no retightening, RTV was evaluated after cyclic loading for 100,000 cycles. In groups with retightening, RTV was measured after 3, 10, 100 cycles as well as every 20,000 cycles until 100,000 cycles of loading. RESULTS Every group showed decreased RTV after cyclic loading. Before and after cyclic loading, external type implants had significantly higher RTVs than internal type implants. In external type implants, retightening did not affect the decrease in RTV. In contrast, retightening 5 times and retightening after 10 cycles of dynamic loading was effective for maintaining RTV in internal type implants. CONCLUSION Retightening of screws is more effective in internal type implants than external type implants. Retightening of screws is recommended in the early stage of functional loading. PMID:26330975

Shortening-induced torque depression in old men: implications for age-related power loss.

PubMed

Power, Geoffrey A; Makrakos, Demetri P; Stevens, Daniel E; Herzog, Walter; Rice, Charles L; Vandervoort, Anthony A

2014-09-01

Following active muscle shortening, the steady-state isometric torque at the final muscle length is lower than the steady-state torque obtained for a purely isometric contraction at that same final muscle length. This well-documented property of skeletal muscle is termed shortening-induced torque depression (TD). Despite many investigations into the mechanisms of weakness and power loss in old age, the influence of muscle shortening on the history dependence of isometric torque production remains to be elucidated. Thus, it is unclear whether older adults are disadvantaged for torque and power production following a dynamic shortening contraction. The purpose of this study was to evaluate shortening-induced TD in older adults, and to determine whether shortening-induced TD is related to power loss. Maximal voluntary isometric dorsiflexion contractions (MVC; 10s) in 8 young (25.5±3.7years) and 9 old (76.1±5.4years) men were performed on a HUMAC NORM dynamometer as a reference, and then again following an active shortening of 40° joint excursion (40°PF-0°PF) at angular velocities of 15°/s and 120°/s. Work and instantaneous power were derived during shortening. Shortening-induced TD was calculated and expressed as a percentage by determining the mean torque value over 1s during the isometric steady state of the MVC following shortening, divided by the mean torque value for the same 1s time period during the isometric reference MVC. To assess muscle activation, electromyography (root mean square; EMGRMS) of the tibialis anterior (TA) and soleus (SOL) was calculated at identical time points used in assessing shortening-induced TD, and voluntary activation (VA) was assessed using the interpolated twitch technique. Old were 18% weaker than young for MVC, and ~40% less powerful for 15°/s and 120°/s of shortening. Old produced 37% and 21% less work for 15°/s and 120°/s than young, respectively. Furthermore, old experienced 60% and 70% greater shortening-induced TD than young for 15°/s and 120°/s, respectively with similar EMGRMS and VA across all conditions. A significant relationship between shortening-induced TD and instantaneous power was found only at the fast angular velocity for both the old (R(2)=0.32) and young (R(2)=0.45) men. The older men experienced greater shortening-induced TD than young while maintaining similar levels of voluntary activation. This previously unaccounted for history-dependent property of muscle may provide insight into power loss in old age. Copyright © 2014 Elsevier Inc. All rights reserved.

Sensorimotor adaptations to microgravity in humans.

PubMed

Edgerton, V R; McCall, G E; Hodgson, J A; Gotto, J; Goulet, C; Fleischmann, K; Roy, R R

2001-09-01

Motor function is altered by microgravity, but little detail is available as to what these changes are and how changes in the individual components of the sensorimotor system affect the control of movement. Further, there is little information on whether the changes in motor performance reflect immediate or chronic adaptations to changing gravitational environments. To determine the effects of microgravity on the neural control properties of selected motor pools, four male astronauts from the NASA STS-78 mission performed motor tasks requiring the maintenance of either ankle dorsiflexor or plantarflexor torque. Torques of 10 or 50% of a maximal voluntary contraction (MVC) were requested of the subjects during 10 degrees peak-to-peak sinusoidal movements at 0.5 Hz. When 10% MVC of the plantarflexors was requested, the actual torques generated in-flight were similar to pre-flight values. Post-flight torques were higher than pre- and in-flight torques. The actual torques when 50% MVC was requested were higher in- and post-flight than pre-flight. Soleus (Sol) electromyographic (EMG) amplitudes during plantarflexion were higher in-flight than pre- or post-flight for both the 10 and 50% MVC tasks. No differences in medial gastrocnemius (MG) EMG amplitudes were observed for either the 10 or 50% MVC tasks. The EMG amplitudes of the tibialis anterior (TA), an antagonist to plantarflexion, were higher in- and post-flight than pre-flight for the 50% MVC task. During the dorsiflexion tasks, the torques generated in both the 10 and 50% MVC tasks did not differ pre-, in- and post-flight. TA EMG amplitudes were significantly higher in- than pre-flight for both the 10 or 50% MVC tasks, and remained elevated post-flight for the 50% MVC test. Both the Sol and MG EMG amplitudes were significantly higher in-flight than either pre- or post-flight for both the 10 and 50% MVC tests. These data suggest that the most consistent response to space flight was an elevation in the level of contractions of agonists and antagonists when attempting to maintain constant torques at a given level of MVC. Also, the chronic levels of EMG activity in selected ankle flexor and extensor muscles during space flight and during routine activities on Earth were recorded. Compared with pre- and post-flight values, there was a marked increase in the total EMG activity of the TA and the Sol and no change in the MG EMG activity in-flight. These data indicate that space flight, as occurs on shuttle missions, is a model of elevated activation of both flexor and extensor muscles, probably reflecting the effects of programmed work schedules in flight rather than a direct effect of microgravity.

Sensorimotor adaptations to microgravity in humans

NASA Technical Reports Server (NTRS)

Edgerton, V. R.; McCall, G. E.; Hodgson, J. A.; Gotto, J.; Goulet, C.; Fleischmann, K.; Roy, R. R.

2001-01-01

Motor function is altered by microgravity, but little detail is available as to what these changes are and how changes in the individual components of the sensorimotor system affect the control of movement. Further, there is little information on whether the changes in motor performance reflect immediate or chronic adaptations to changing gravitational environments. To determine the effects of microgravity on the neural control properties of selected motor pools, four male astronauts from the NASA STS-78 mission performed motor tasks requiring the maintenance of either ankle dorsiflexor or plantarflexor torque. Torques of 10 or 50% of a maximal voluntary contraction (MVC) were requested of the subjects during 10 degrees peak-to-peak sinusoidal movements at 0.5 Hz. When 10% MVC of the plantarflexors was requested, the actual torques generated in-flight were similar to pre-flight values. Post-flight torques were higher than pre- and in-flight torques. The actual torques when 50% MVC was requested were higher in- and post-flight than pre-flight. Soleus (Sol) electromyographic (EMG) amplitudes during plantarflexion were higher in-flight than pre- or post-flight for both the 10 and 50% MVC tasks. No differences in medial gastrocnemius (MG) EMG amplitudes were observed for either the 10 or 50% MVC tasks. The EMG amplitudes of the tibialis anterior (TA), an antagonist to plantarflexion, were higher in- and post-flight than pre-flight for the 50% MVC task. During the dorsiflexion tasks, the torques generated in both the 10 and 50% MVC tasks did not differ pre-, in- and post-flight. TA EMG amplitudes were significantly higher in- than pre-flight for both the 10 or 50% MVC tasks, and remained elevated post-flight for the 50% MVC test. Both the Sol and MG EMG amplitudes were significantly higher in-flight than either pre- or post-flight for both the 10 and 50% MVC tests. These data suggest that the most consistent response to space flight was an elevation in the level of contractions of agonists and antagonists when attempting to maintain constant torques at a given level of MVC. Also, the chronic levels of EMG activity in selected ankle flexor and extensor muscles during space flight and during routine activities on Earth were recorded. Compared with pre- and post-flight values, there was a marked increase in the total EMG activity of the TA and the Sol and no change in the MG EMG activity in-flight. These data indicate that space flight, as occurs on shuttle missions, is a model of elevated activation of both flexor and extensor muscles, probably reflecting the effects of programmed work schedules in flight rather than a direct effect of microgravity.

Neural and Muscular Contributions to the Age-Related Reductions in Rapid Strength.

PubMed

Gerstner, Gena R; Thompson, Brennan J; Rosenberg, Joseph G; Sobolewski, Eric J; Scharville, Michael J; Ryan, Eric D

2017-07-01

The purposes of this study were to investigate the age-related differences in absolute and normalized plantarflexion rate of torque development (RTD) at early (0-50 ms) and late (100-200 ms) time intervals and to examine specific neural and muscular mechanisms contributing to these differences. Thirty-two young (20.0 ± 2.1 yr) and 20 older (69.5 ± 3.3 yr) recreationally active men performed rapid plantarflexion isometric muscle actions to examine absolute and normalized RTD and muscle activation using EMG at early and late time intervals. Ultrasonography was used to examine medial gastrocnemius muscle size, echo intensity (EI), and muscle architecture (fascicle length [FL] and pennation angle [PA]). The older men were weaker (23.9%, P < 0.001) and had lower later absolute and normalized RTD (P = 0.001-0.034) variables when compared with the young men. The older men also had higher EI (P < 0.001), smaller PA (P = 0.004), and lower later EMG amplitude values (P = 0.009-0.046). However, there were no differences in early RTD and EMG amplitude values, muscle size, or FL between groups (P = 0.097-0.914). Lower late RTD values were related to higher EI, smaller PA, and lower EMG amplitude values (r = -0.28-0.59, P = 0.001-0.044); however, late RTD values were no longer related to PA after normalizing to peak torque. Age-related alterations in muscle quality (EI), architecture, and muscle activation may influence rapid torque production at late time intervals (≥100 ms) from contraction onset. These findings highlight specific neuromuscular factors that influence the age-related reductions in RTD, which has been shown to significantly influence function and performance in older adults.

A Ground-Based Comparison of the Muscle Atrophy Research and Exercise System (MARES) and a Standard Isokinetic Dynamometer

NASA Technical Reports Server (NTRS)

Hackney, K. J.; English, K. L.; Redd, E.; DeWitt, J. K.; Ploutz-Snyder, R.; Ploutz-Snyder, L. L.

2010-01-01

PURPOSE: 1) To compare the test-to-test reliability of Muscle Atrophy Research and Exercise System (MARES) with a standard laboratory isokinetic dynamometer (ISOK DYN) and; 2) to determine if measures of peak torque and total work differ between devices. METHODS: Ten subjects (6M, 4F) completed two trials on both MARES and an ISOK DYN in a counterbalanced order. Peak torque values at 60 deg & 180 deg / s were obtained from five maximal repetitions of knee extension (KE) and knee flexion (KF). Total work at 180 deg / s was determined from the area under the torque vs. displacement curve during twenty maximal repetitions of KE and KF. Reliability of measures within devices was interpreted from the intraclass correlation coefficient (ICC) and compared between devices using the ratio of the within-device standard deviations. Indicators of agreement for the two devices were evaluated from: 1) a calculation of concordance (rho) and; 2) the correlation between the mean of measures versus the delta difference between measures (m u vs delta). RESULTS: For all outcome measures ICCs were high for both the ISOK DYN (0.95-0.99) and MARES (0.90-0.99). However, ratios of the within-device standard deviation were 1.3 to 4.3 times higher on MARES. On average, a wide range (3.3 to 1054 Nm) of differences existed between the values obtained. Only KE peak torque measured at 60 deg & 180 deg / s showed similarities between devices (rho = 0.91 & 0.87; Pearson's r for m u vs delta = -0.22 & -0.37, respectively). CONCLUSION: Although MARES was designed for use in microgravity it was quite reliable during ground-based testing. However, MARES was consistently more variable than an ISOK DYN. Future longitudinal studies evaluating a change in isokinetic peak torque or total work should be limited within one device.

Magnetic anisotropies and rotational hysteresis in Ni81Fe19/Fe50Mn50 films: A study by torque magnetometry and anisotropic magnetoresistance

NASA Astrophysics Data System (ADS)

da Silva, O. E.; de Siqueira, J. V.; Kern, P. R.; Garcia, W. J. S.; Beck, F.; Rigue, J. N.; Carara, M.

2018-04-01

Exchange bias properties of NiFe/FeMn thin films have been investigated through X-ray diffraction, hysteresis loops, angular measurements of anisotropic magnetoresistance (AMR) and magnetic torque. As first predicted by Meiklejohn and Bean we found a decrease on the bias field as the NiFe layer thickness increases. However such reduction is not as strong as expected and it was attributed to the increase on the number of uncompensed antiferromagnetic spins resulting from the increase on the number of FeMn grains at the interface as the thickness of the NiFe layer is increased. The angular evolution of AMR and the magnetic torque were calculated and compared to the experimental ones using the minimization of the free magnetic energy and finding the magnetization equilibrium angle. The free energy, for each grain of the polycrystalline sample, is composed by the following terms: Zeeman, uniaxial, unidirectional and the rotatable energies. While from the AMR curves we obtain stable anisotropy fields independently on the measuring fields, from the torque curves we obtain increasing values of the uniaxial and rotatable fields, as the measuring field is increased. These results were attributed to the physical origin and sensitivity of the two different techniques. Magnetoresistance is mainly sensitive to the inner portion of the ferromagnetic layer, and the torque brings out information of the whole ferromagnetic layer including the interface of the layers. In this way, we believe that the increase in the uniaxial and rotatable values were due to an increase on the volume of the ferromagnetic layer, near the interfaces, which is made to rotate with the measuring field. Studying the rotational hysteresis by both techniques allows to separately obtain the contributions coming from the inner portion of ferromagnetic layer and from the interface.

Engine-driven preparation of curved root canals: measuring cyclic fatigue and other physical parameters.

PubMed

Peters, Ove A; Kappeler, Stefan; Bucher, Willi; Barbakow, Fred

2002-04-01

An increasing number of engine-driven rotary systems are marketed to shape root canals. Although these systems may improve the quality of canal preparations, the risk for instrument fracture is also increased. Unfortunately, the stresses generated in rotary instruments when shaping curved root canals have not been adequately studied. Consequently, the aim of an ongoing project was to develop a measurement platform that could more accurately detail physical parameters generated in a simulated clinical situation. Such a platform was constructed by fitting a torque-measuring device between the rotating endodontic instrument and the motor driving it. Apically directed force and instrument insertion depth were also recorded. Additional devices were constructed to assess cyclic fatigue and static fracture loads. The current pilot study evaluated GT rotary instruments during the shaping of curved canals in plastic blocks as well as "ISO 3630-1 torque to fracture" and number of rotations required for fatigue fracture. Results indicated that torques in excess of 40 Nmm were generated by rotary GT-Files, a significantly higher figure than static fracture loads (less than 13 Nmm for the size 20. 12 GT-File). Furthermore, the number of rotations needed to shape simulated canals with a 5 mm radius of curvature in plastic blocks was 10 times lower than the number of rotations needed to fracture instruments in a "cyclic fatigue test". Apical forces were always greater than 1 N, and in some specimens, scores of 8 N or more were recorded. Further studies are required using extracted natural teeth, with their wide anatomical variation, in order to reduce the incidence of fracture of rotary instruments. In this way, the clinical potential of engine-driven rotary instruments to safely prepare curved canals can be fully appreciated.

Influence of abutment type and esthetic veneering on preload maintenance of abutment screw of implant-supported crowns.

PubMed

Delben, Juliana Aparecida; Barão, Valentim Adelino Ricardo; Dos Santos, Paulo Henrique; Assunção, Wirley Gonçalves

2014-02-01

The effect of veneering materials on screw joint stability remains inconclusive. Thus, this study evaluated the preload maintenance of abutment screws of single crowns fabricated with different abutments and veneering materials. Sixty crowns were divided into five groups (n = 12): UCLA abutment in gold alloy with ceramic (group GC) and resin (group GR) veneering, UCLA abutment in titanium with ceramic (group TiC) and resin (group TiR) veneering, and zirconia abutment with ceramic veneering (group ZiC). Abutment screws made of gold were used with a 35 Ncm insertion torque. Detorque measurements were obtained initially and after mechanical cycling. Data were analyzed by ANOVA and Fisher's exact test at a significance level of 5%. For the initial detorque means (in Ncm), group TiC (21.4 ± 1.78) exhibited statistically lower torque maintenance than groups GC (23.9 ± 0.91), GR (24.1 ± 1.34), and TiR (23.2 ± 1.33) (p < 0.05, Fisher's exact test). Group ZiC (21.9 ± 2.68) exhibited significantly lower torque maintenance than groups GC, GR, and TiR (p < 0.05, Fisher's exact test). After mechanical cycling, there was a statistically significant difference between groups TiC (22.1 ± 1.86) and GR (23.8 ± 1.56); between groups ZiC (21.7 ± 2.02) and GR; and also between groups ZiC and TiR (23.6 ± 1.30) (p < 0.05, Fisher's exact test). Detorque reduction occurred regardless of abutment type and veneering material. More irregular surfaces in the hexagon area of the castable abutments were observed. The superiority of any veneering material concerning preload maintenance was not established. © 2013 by the American College of Prosthodontists.

Relationships between eccentric hip isokinetic torque and functional performance.

PubMed

Baldon, Rodrigo de Marche; Lobato D, Ferreira Moreira; Carvalho, Lívia Pinheiro; Wun P, Yan Lam; Presotti, Cátia Valéria; Serrão, Fábio Viadanna

2012-02-01

Recently, attention in sports has been given to eccentric hip-muscle function, both in preventing musculoskeletal injuries and improving performance. To determine the key isokinetic variables of eccentric hip torque that predict the functional performance of women in the single-leg triple long jump (TLJ) and the timed 6-m single-leg hop (TH). Within-subject correlational study. Musculoskeletal laboratory. 32 healthy women age 18-25 y. The participants performed 2 sets of 5 eccentric hip-abductor/adductor and lateral/medial-rotator isokinetic contractions (30°/s) and 3 attempts in the TLJ and TH. The independent variables were the eccentric hip-abductor and -adductor and medial- and lateral-rotator isokinetic peak torque, normalized according to body mass (Nm/kg). The dependent variables were the longest distance achieved in the TLJ normalized according to body height and the shortest time spent during the execution of the TH. The forward-stepwise-regression analysis showed that the combination of the eccentric hip lateral-rotator and -abductor isokinetic peak torque provided the most efficient estimate of both functional tests, explaining 65% of the TLJ variance (P < .001) and 55% of the TH variance (P < .001). Higher values for eccentric hip lateral-rotator and hip-abductor torques reflected better performance. Thus, the eccentric action of these muscles should be considered in the development of physical training programs that aim to increase functional performance.

Field testing advanced geothermal turbodrill (AGT). Phase 1 final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maurer, W.C.; Cohen, J.H.

1999-06-01

Maurer Engineering developed special high-temperature geothermal turbodrills for LANL in the 1970s to overcome motor temperature limitations. These turbodrills were used to drill the directional portions of LANL`s Hot Dry Rock Geothermal Wells at Fenton Hill, New Mexico. The Hot Dry Rock concept is to drill parallel inclined wells (35-degree inclination), hydraulically fracture between these wells, and then circulate cold water down one well and through the fractures and produce hot water out of the second well. At the time LANL drilled the Fenton Hill wells, the LANL turbodrill was the only motor in the world that would drill atmore » the high temperatures encountered in these wells. It was difficult to operate the turbodrills continuously at low speed due to the low torque output of the LANL turbodrills. The turbodrills would stall frequently and could only be restarted by lifting the bit off bottom. This allowed the bit to rotate at very high speeds, and as a result, there was excessive wear in the bearings and on the gauge of insert roller bits due to these high rotary speeds. In 1998, Maurer Engineering developed an Advanced Geothermal Turbodrill (AGT) for the National Advanced Drilling and Excavation Technology (NADET) at MIT by adding a planetary speed reducer to the LANL turbodrill to increase its torque and reduce its rotary speed. Drilling tests were conducted with the AGT using 12 1/2-inch insert roller bits in Texas Pink Granite. The drilling tests were very successful, with the AGT drilling 94 ft/hr in Texas Pink Granite compared to 45 ft/hr with the LANL turbodrill and 42 ft/hr with a rotary drill. Field tests are currently being planned in Mexico and in geothermal wells in California to demonstrate the ability of the AGT to increase drilling rates and reduce drilling costs.« less

Evaluation of stability of interface between CCM (Co-Cr-Mo) UCLA abutment and external hex implant

PubMed Central

Yoon, Ki-Joon; Park, Young-Bum; Choi, Hyunmin; Cho, Youngsung; Lee, Jae-Hoon

2016-01-01

PURPOSE The purpose of this study is to evaluate the stability of interface between Co-Cr-Mo (CCM) UCLA abutment and external hex implant. MATERIALS AND METHODS Sixteen external hex implant fixtures were assigned to two groups (CCM and Gold group) and were embedded in molds using clear acrylic resin. Screw-retained prostheses were constructed using CCM UCLA abutment and Gold UCLA abutment. The external implant fixture and screw-retained prostheses were connected using abutment screws. After the abutments were tightened to 30 Ncm torque, 5 kg thermocyclic functional loading was applied by chewing simulator. A target of 1.0 × 106 cycles was applied. After cyclic loading, removal torque values were recorded using a driving torque tester, and the interface between implant fixture and abutment was evaluated by scanning electronic microscope (SEM). The means and standard deviations (SD) between the CCM and Gold groups were analyzed with independent t-test at the significance level of 0.05. RESULTS Fractures of crowns, abutments, abutment screws, and fixtures and loosening of abutment screws were not observed after thermocyclic loading. There were no statistically significant differences at the recorded removal torque values between CCM and Gold groups (P>.05). SEM analysis revealed that remarkable wear patterns were observed at the abutment interface only for Gold UCLA abutments. Those patterns were not observed for other specimens. CONCLUSION Within the limit of this study, CCM UCLA abutment has no statistically significant difference in the stability of interface with external hex implant, compared with Gold UCLA abutment. PMID:28018564

Dynamic nature of abutment screw retightening: finite element study of the effect of retightening on the settling effect.

PubMed

Bulaqi, Haddad Arabi; Mousavi Mashhadi, Mahmoud; Safari, Hamed; Samandari, Mohammad Mahdi; Geramipanah, Farideh

2015-05-01

A fundamental problem in fully understanding the dynamic nature of screw loosening is lack of recognition of the entire process of screw tightening and retightening. The purpose of this study was to explain the dynamic nature of abutment screw retightening by using finite element methods to investigate the effect of the coefficient of friction and retightening on the settling effect. Precise computer models were designed of a Straumann dental implant, a directly attached crown, an abutment screw, and the bone surrounding the implant. All threaded interfaces were designed with a spiral thread helix with a specific coefficient of static and kinetic friction, and the surfaces were characterized as fine, regular, and rough. Abaqus software was used for dynamic simulation, which involved applying rotational displacement to the abutment screw and torque controlling during the steps of tightening, relaxation, retightening, and second relaxation and at different coefficients of friction. The obtained torque and preload values were compared to the predicted values. When surfaces changed from fine to rough, the remaining torque and preload decreased, and the settling effect increased. Upon retightening, the remaining torque and preload increased, and the settling effect also decreased. The reduction of the coefficient of friction contributes to increases in the preload and decreases in the settling effect. Retightening reduced the settling effect and had an insignificant effect on the preload. At high coefficients of friction, the retightening effect was intensified. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

The tribological behaviour of different clearance MOM hip joints with lubricants of physiological viscosities.

PubMed

Hu, X Q; Wood, R J K; Taylor, A; Tuke, M A

2011-11-01

Clearance is one of the most influential parameters on the tribological performance of metal-on-metal (MOM) hip joints and its selection is a subject of considerable debate. The objective of this paper is to study the lubrication behaviour of different clearances for MOM hip joints within the range of human physiological and pathological fluid viscosities. The frictional torques developed by MOM hip joints with a 50 mm diameter were measured for both virgin surfaces and during a wear simulator test. Joints were manufactured with three different diametral clearances: 20, 100, and 200 microm. The fluid used for the friction measurements which contained different ratios of 25 percent newborn calf serum and carboxymethyl cellulose (CMC) with the obtained viscosities values ranging from 0.001 to 0.71 Pa s. The obtained results indicate that the frictional torque for the 20 microm clearance joint remains high over the whole range of the viscosity values. The frictional torque of the 100 microm clearance joint was low for the very low viscosity (0.001 Pa s) lubricant, but increased with increasing viscosity value. The frictional torque of the 200 microm clearance joint was high at very low viscosity levels, however, it reduced with increasing viscosity. It is concluded that a smaller clearance level can enhance the formation of an elastohydrodynamic lubrication (EHL) film, but this is at the cost of preventing fluid recovery between the bearing surfaces during the unloaded phase of walking. Larger clearance bearings allow a better recovery of lubricant during the unloaded phase, which is necessary for higher viscosity lubricants. The selection of the clearance value should therefore consider both the formation of the EHL film and the fluid recovery as a function of the physiological viscosity in order to get an optimal tribological performance for MOM hip joints. The application of either 25 per cent bovine serum or water in existing in vitro tribological study should also be revised to consider the relevance of clinic synovial fluid viscosities and to avoid possible misleading results.

A ROBUST MEASURE OF DARK MATTER HALO ELLIPTICITIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Evslin, Jarah

2016-08-01

In simulations of the standard cosmological model (ΛCDM), dark matter halos are aspherical. However, so far the asphericity of an individual galaxy’s halo has never been robustly established. We use the Jeans equations to define a quantity that robustly characterizes a deviation from rotational symmetry. This quantity is essentially the gravitational torque and it roughly provides the ellipticity projected along the line of sight. We show that the Thirty Meter Telescope (TMT), with a single epoch of observations combined with those of the Gaia Space Telescope , can distinguish the ΛCDM value of the torque from zero for each Sculptor-likemore » dwarf galaxy with a confidence between 0 and 5 σ , depending on the orientation of each halo. With two epochs of observations, TMT will achieve a 5 σ discovery of torque and thus asphericity for most such galaxies, thus providing a new and powerful test of the ΛCDM model.« less

Modeling Attitude Dynamics in Simulink: A Study of the Rotational and Translational Motion of a Spacecraft Given Torques and Impulses Generated by RMS Hand Controllers

NASA Technical Reports Server (NTRS)

Mauldin, Rebecca H.

2010-01-01

In order to study and control the attitude of a spacecraft, it is necessary to understand the natural motion of a body in orbit. Assuming a spacecraft to be a rigid body, dynamics describes the complete motion of the vehicle by the translational and rotational motion of the body. The Simulink Attitude Analysis Model applies the equations of rigid body motion to the study of a spacecraft?s attitude in orbit. Using a TCP/IP connection, Matlab reads the values of the Remote Manipulator System (RMS) hand controllers and passes them to Simulink as specified torque and impulse profiles. Simulink then uses the governing kinematic and dynamic equations of a rigid body in low earth orbit (LE0) to plot the attitude response of a spacecraft for five seconds given known applied torques and impulses, and constant principal moments of inertia.

Alterations of the in vivo torque-velocity relationship of human skeletal muscle following 30 days exposure to simulated microgravity

NASA Technical Reports Server (NTRS)

Dudley, Gary A.; Duvoisin, Marc; Convertino, Victor A.; Buchanan, Paul

1989-01-01

The effect of a continuous 30-d-long 6-deg headdown bedrest (BR) on the force output ability of skeletal muscles was investigated in human subjects by measuring peak angle specific torque of the knee extensor (KE) and knee flexor (KF) muscle groups of both limbs during unilateral efforts at four speeds (0.52. 1.74, 2.97, and 4.19 rad/sec) during eccentric action. It was found that, for the KE muscle group, the headdown BR resulted in decreases, by 19 percent on the average, of peak angle specific torque; on the other hand, the strength of the KF muscles was not altered significantly. A post-BR recovery for 30 days was found to restore muscle strength of the KE muscle group to about 92 percent of the pre-BR values. Changes of strength were not affected by the type of speed of muscle action.

Torque limit of PM motors for field-weakening region operation

DOEpatents

Royak, Semyon [Beachwood, OH; Harbaugh, Mark M [Richfield, OH

2012-02-14

The invention includes a motor controller and technique for controlling a permanent magnet motor. In accordance with one aspect of the present technique, a permanent magnet motor is controlled by receiving a torque command, determining a physical torque limit based on a stator frequency, determining a theoretical torque limit based on a maximum available voltage and motor inductance ratio, and limiting the torque command to the smaller of the physical torque limit and the theoretical torque limit. Receiving the torque command may include normalizing the torque command to obtain a normalized torque command, determining the physical torque limit may include determining a normalized physical torque limit, determining a theoretical torque limit may include determining a normalized theoretical torque limit, and limiting the torque command may include limiting the normalized torque command to the smaller of the normalized physical torque limit and the normalized theoretical torque limit.

Sensitivity and Specificity of Stability Criteria for Immediately Loaded Splinted Maxillary Implants.

PubMed

Wentaschek, Stefan; Scheller, Herbert; Schmidtmann, Irene; Hartmann, Sinsa; Weyhrauch, Michael; Weibrich, Gernot; Lehmann, Karl Martin

2015-10-01

To assess the suitability of dental implants for immediate loading, primary stability is usually evaluated intraoperatively. This retrospective study aimed to assess the suitability of three stability parameters - namely, insertion torque (IT), implant stability quotient (ISQ; measured by resonance frequency analysis), and Periotest (PT) values - as potential predictors for the risk of nonosseointegration of immediately loaded splinted implants. The stability parameters were routinely collected under immediate loading. Nineteen patients with 11 edentulous and 8 partially edentulous maxillae were treated with 105 dental implants, which were immediately loaded using temporary fixed dentures. The IT results, PT values, and ISQ results were recorded. Receiver operating characteristic analysis was performed to assess the quality of each parameter as a diagnostic test. After a 3-month observation period, 11 implants in four patients were not osseointegrated. The IT and ISQ (IT 25.0 ± 12.5 Ncm and 8.4 ± 2.3 Ncm; PT -1.5 ± 3.0 and +2.7 ± 3.0; and ISQ 62.6 ± 6.7 and 54.7 ± 6.2) differed significantly between the osseointegrated and failed implants (p < .005). The IT showed the greatest specificity at a sensitivity of 1 and the greatest area under the curve (AUC; 0.929), followed by the PT value (AUC = 0.836) and ISQ (AUC = 0.811). Among the intraoperative parameters analyzed, IT showed the highest specificity at a high sensitivity of 1. Therefore, the IT can be considered the most valid prognostic factor for osseointegration of immediately loaded splinted dental implants. © 2014 Wiley Periodicals, Inc.

Thermodynamics of relation-based systems with applications in econophysics, sociophysics, and music

NASA Astrophysics Data System (ADS)

Gündüz, Güngör

2012-10-01

A methodology was developed to analyze relation-based systems evolving in time by using the fundamental concepts of thermodynamics. The behavior of such systems can be tracked from the scattering matrix which is actually a network of directed vectors (or pathways) connecting subsequent values, which characterize an event, such as the index values in stock markets. A system behaves in a rigid (elastic) way to an external effect and resists permanent deformation, or it behaves in a viscous (or soft) way and deforms in an irreversible way. It was shown in the past that a formula derived using the slope of paths gives a measure about the extent of viscoelastic behavior of relation-based systems Gündüz (2009) [5] Gündüz and Gündüz (2010) [6]. In this research the ‘work’ associated with ‘elastic’ component, and ‘heat’ associated with ‘viscous’ component were discussed and elaborated. In a simple two subsequent pathway system in a scattering diagram the first vector represents ‘the cause’ and the second ‘the effect’. By using work and heat energy relations that involve force and also storage and loss modulus terms, respectively, one can calculate the energy involved in relation-based systems. The modulus values can be found from the parallel and vertical components of the second vector with respect to the first vector. Once work-like and heat-like terms were determined the internal energy is also easily found from their summation. The parallel and vertical components can also be used to calculate the magnitude of torque and torque energy in the system. Three cases, (i) the behavior of the NASDAQ-100 index, (ii) a social revolt, and (iii) the structure of a melody were analyzed for their ‘work-like’, ‘heat-like’, and ‘torque-like’ energies in the course of their evolution. NASDAQ-100 exhibits highly dissipative behavior, and its work terms are very small but heat terms are of large magnitude. Its internal energy highly fluctuates in time. In the social revolt studied work and heat terms are of comparable magnitude. The melody depicts highly organized structure, and usually has larger work terms than heat terms, but at some intervals heat terms burst out and attain very large magnitudes. Torque terms reach high values when the system is recovering from a minimum value.

PULPAL BLOOD FLOW CHANGES IN ABUTMENT TEETH OF REMOVABLE PARTIAL DENTURES

PubMed Central

Kunt, Göknil Ergün; Kökçü, Deniz; Ceylan, Gözlem; Yılmaz, Nergiz; Güler, Ahmet Umut

2009-01-01

The purpose of this study was to investigate the effect of tooth supported (TSD) and toothtissue supported (TTSD) removable partial denture wearing on pulpal blood flow (PBF) of the abutment teeth by using Laser Doppler Flowmeter (LDF). Measurements were carried out on 60 teeth of 28 patients (28 teeth and 12 patients of TTSD group, 32 teeth and 16 patients of TSD group) who had not worn any type of removable partial dentures before, had no systemic problems and were non smokers. PBF values were recorded by LDF before insertion (day 0) and after insertion of dentures at day 1, day 7 and day 30. Statistical analysis was performed by student t test and covariance analyses of repeated measurements. In the group TTSD, the mean values of PBF decreased statistically significantly at day 1 after insertion when compared with PBF values before insertion (p<0,01). There was no statistically significant difference among PBF mean values on 1st, 7th and 30th day. However, in the group TSD, there was no statistically significant difference among PBF mean values before insertion and on 1st, 7th and 30th day. In other words, PBF mean values in group TSD continued without changing statistically significant on 1st, 7th and 30th day. TTSD wearing may show negative effect on the abutment teeth due to decreasing basal PBF. PMID:20001995

Torque Generation of Enterococcus hirae V-ATPase*

PubMed Central

Ueno, Hiroshi; Minagawa, Yoshihiro; Hara, Mayu; Rahman, Suhaila; Yamato, Ichiro; Muneyuki, Eiro; Noji, Hiroyuki; Murata, Takeshi; Iino, Ryota

2014-01-01

V-ATPase (VoV1) converts the chemical free energy of ATP into an ion-motive force across the cell membrane via mechanical rotation. This energy conversion requires proper interactions between the rotor and stator in VoV1 for tight coupling among chemical reaction, torque generation, and ion transport. We developed an Escherichia coli expression system for Enterococcus hirae VoV1 (EhVoV1) and established a single-molecule rotation assay to measure the torque generated. Recombinant and native EhVoV1 exhibited almost identical dependence of ATP hydrolysis activity on sodium ion and ATP concentrations, indicating their functional equivalence. In a single-molecule rotation assay with a low load probe at high ATP concentration, EhVoV1 only showed the “clear” state without apparent backward steps, whereas EhV1 showed two states, “clear” and “unclear.” Furthermore, EhVoV1 showed slower rotation than EhV1 without the three distinct pauses separated by 120° that were observed in EhV1. When using a large probe, EhVoV1 showed faster rotation than EhV1, and the torque of EhVoV1 estimated from the continuous rotation was nearly double that of EhV1. On the other hand, stepping torque of EhV1 in the clear state was comparable with that of EhVoV1. These results indicate that rotor-stator interactions of the Vo moiety and/or sodium ion transport limit the rotation driven by the V1 moiety, and the rotor-stator interactions in EhVoV1 are stabilized by two peripheral stalks to generate a larger torque than that of isolated EhV1. However, the torque value was substantially lower than that of other rotary ATPases, implying the low energy conversion efficiency of EhVoV1. PMID:25258315

A comparative assessment of torque generated by lingual and conventional brackets.

PubMed

Sifakakis, Iosif; Pandis, Nikolaos; Makou, Margarita; Eliades, Theodore; Katsaros, Christos; Bourauel, Christoph

2013-06-01

The aim of this study was to assess the effect of bracket type on the labiopalatal moments generated by lingual and conventional brackets. Incognito™ lingual brackets (3M Unitek), STb™ lingual brackets (Light Lingual System; ORMCO), In-Ovation L lingual brackets (DENTSPLY GAC), and conventional 0.018 inch slot brackets (Gemini; 3M Unitek) were bonded on identical maxillary acrylic resin models with levelled and aligned teeth. Each model was mounted on the orthodontic measurement and simulation system and 10 0.0175 × 0.0175 TMA wires were used for each bracket type. The wire was ligated with elastomerics into the Incognito, STb, and conventional brackets and each measurement was repeated once after religation. A 15 degrees buccal root torque (+15 degrees) and then a 15 degrees palatal root torque (-15 degrees) were gradually applied to the right central incisor bracket. After each activation, the bracket returned to its initial position and the moments in the sagittal plane were recorded during these rotations of the bracket. One-way analysis of variance with post hoc multiple comparisons (Tukey test at 0.05 error rate) was conducted to assess the effect on bracket type on the generated moments. The magnitude of maximum moment at +15 degrees ranged 8.8, 8.2, 7.1, and 5.8 Nmm for the Incognito, STb, conventional Gemini, and the In-Ovation L brackets, respectively; similar values were recorded at -15 degrees: 8.6, 8.1, 7.0, and 5.7 Nmm, respectively. The recorded differences of maximum moments were statistically significant, except between the Incognito and STb brackets. Additionally, the torque angles were evaluated at which the crown torque fell well below the minimum levels of 5.0 Nmm, as well as the moment/torque ratio at the last part of the activation/deactivation curve, between 10 and 15 degrees. The lowest torque expression was observed at the self-ligating lingual brackets, followed by the conventional brackets. The Incognito and STb lingual brackets generated the highest moments.

Polyaxial Screws in Locked Plating of Tibial Pilon Fractures.

PubMed

Yenna, Zachary C; Bhadra, Arup K; Ojike, Nwakile I; Burden, Robert L; Voor, Michael J; Roberts, Craig S

2015-08-01

This study examined the axial and torsional stiffness of polyaxial locked plating techniques compared with fixed-angle locked plating techniques in a distal tibia pilon fracture model. The effect of using a polyaxial screw to cross the fracture site was examined to determine its ability to control relative fracture site motion. A laboratory experiment was performed to investigate the biomechanical stiffness of distal tibia fracture models repaired with 3.5-mm anterior polyaxial distal tibial plates and locking screws. Sawbones Fourth Generation Composite Tibia models (Pacific Research Laboratories, Inc, Vashon, Washington) were used to model an Orthopaedic Trauma Association 43-A1.3 distal tibia pilon fracture. The polyaxial plates were inserted with 2 central locking screws at a position perpendicular to the cortical surface of the tibia and tested for load as a function of axial displacement and torque as a function of angular displacement. The 2 screws were withdrawn and inserted at an angle 15° from perpendicular, allowing them to span the fracture and insert into the opposing fracture surface. Each tibia was tested again for axial and torsional stiffness. In medial and posterior loading, no statistically significant difference was found between tibiae plated with the polyaxial plate and the central screws placed in the neutral position compared with the central screws placed at a 15° position. In torsional loading, a statistically significant difference was noted, showing greater stiffness in tibiae plated with the polyaxial plate and the central screws placed at a 15° position compared with tibiae plated with the central screws placed at a 0° (or perpendicular) position. This study showed that variable angle constructs show similar stiffness properties between perpendicular and 15° angle insertions in axial loading. The 15° angle construct shows greater stiffness in torsional loading. Copyright 2015, SLACK Incorporated.

Nerve damage related to implant dentistry: incidence, diagnosis, and management.

PubMed

Greenstein, Gary; Carpentieri, Joseph R; Cavallaro, John

2015-10-01

Proper patient selection and treatment planning with respect to dental implant placement can preclude nerve injuries. Nevertheless, procedures associated with implant insertion can inadvertently result in damage to branches of the trigeminal nerve. Nerve damage may be transient or permanent; this finding will depend on the cause and extent of the injury. Nerve wounding may result in anesthesia, paresthesia, or dysesthesia. The type of therapy to ameliorate the condition will be dictated by clinical and radiographic assessments. Treatment may include monitoring altered sensations to see if they subside, pharmacotherapy, implant removal, reverse-torquing an implant to decompress a nerve, combinations of the previous therapies, and/or referral to a microsurgeon for nerve repair. Patients manifesting altered sensations due to various injuries require different therapies. Transection of a nerve dictates immediate referral to a microsurgeon for evaluation. If a nerve is compressed by an implant or adjacent bone, the implant should be reverse-torqued away from the nerve or removed. When an implant is not close to a nerve, but the patient is symptomatic, the patient can be monitored and treated pharmacologically as long as symptoms improve or the implant can be removed. There are diverse opinions in the literature concerning how long an injured patient should be monitored before being referred to a microsurgeon.

Mode control using two electrodes on HBT-EP

NASA Astrophysics Data System (ADS)

Stewart, I. G.; Brooks, J. W.; Levesque, J. P.; Mauel, M. E.; Navratil, G. A.

2017-10-01

Understanding the effects of plasma rotation on magnetohydrodynamic (MHD) modes and tokamak plasma stability is important for performance enhancement of current magnetic confinement experiments and to future fusion devices such as ITER. In order to control plasma rotation, two molybdenum electrodes have been installed on HBT-EP toroidally separated by 144 degrees. This allows independent biasing of the two probes both spatially and temporally. When the bias probes are inserted into the edge of the plasma and a voltage is applied, the probes drive radial currents and produce plasma flow from the torque induced by the currents. If the bias probe voltage is sufficiently positive, the MHD mode rotation transitions into a state with a rapid mode rotation frequency (in excess of 25 kHz) in the direction opposite to mode rotation without bias. The transition into this reversed rotation state occurs when the torque exceeds a threshold, which can depend upon the phase of an applied n = 1 error field. We present recent studies of the two-electrode system on mode rotation, mode stability, and the toroidal symmetry of the radial current through the scrape-off-layer (SOL) during MHD activity and applied magnetic perturbations. Supported by U.S. DOE Grant DE-FG02-86ER53222.

3D finite element analysis of tightening process of bolt and nut connections with pitch difference

NASA Astrophysics Data System (ADS)

Liu, X.; Noda, N.-A.; Sano, Y.; Huang, Y. T.; Takase, Y.

2018-06-01

In a wide industrial field, the bolt-nut joint is unitized as an important machine element and anti-loosening performance is always required. In this paper, the effect of a slight pitch difference between a bolt and nut is studied. Firstly, by varying the pitch difference, the prevailing torque required for the nut rotation, before the nut touches the clamped body, is measured experimentally. Secondly, the tightening torque is determined as a function of the axial force of the bolt after the nut touches the clamped body. The results show that a large value of pitch difference may provide large prevailing torque that causes an anti-loosening effect although a very large pitch difference may deteriorate the bolt axial force under a certain tightening torque. Thirdly, a suitable pitch difference is determined taking into account the anti-loosening and clamping abilities. Furthermore, the chamfered corners at nut ends are considered, and it is found that the 3D finite element analysis with considering the chamfered nut threads has a good agreement with the experimental observation. Finally, the most desirable pitch difference required for improving anti-loosening is proposed.