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Sample records for abutment screw loosening

  1. 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

  2. Does Abutment Collar Length Affect Abutment Screw Loosening After Cyclic Loading?

    PubMed

    Siadat, Hakimeh; Pirmoazen, Salma; Beyabanaki, Elaheh; Alikhasi, Marzieh

    2015-07-01

    A significant vertical space that is corrected with vertical ridge augmentation may necessitate selection of longer abutments, which would lead to an increased vertical cantilever. This study investigated the influence of different abutment collar heights on single-unit dental implant screw-loosening after cyclic loading. Fifteen implant-abutment assemblies each consisted of an internal hexagonal implant were randomly assigned to 3 groups: Group1, consisting of 5 abutments with 1.5 mm gingival height (GH); Group2, 5 abutments with 3.5 mm GH; and Group3, 5 abutments with 5.5 mm GH. Each specimen was mounted in transparent auto-polymerizing acrylic resin block, and the abutment screw was tightened to 35 Ncm with an electric torque wrench. After 5 minutes, initial torque loss (ITL) was recorded for all specimens. Metal crowns were fabricated with 45° occlusal surface and were placed on the abutments. A cyclic load of 75 N and frequency of 1 Hz were applied perpendicular to the long axis of each specimen. After 500 000 cycles, secondary torque loss (STL) was recorded. One-way ANOVA analysis was used to evaluate the effects of abutment collar height before and after cyclic loading. One-way ANOVA showed that ITL among the groups was not significantly different (P = .52), while STL was significantly different among the groups (P = .008). Post-hoc Tukey HSD tests showed that STL values were significantly different between the abutments with 1.5 mm GH (Group1) and with 5.5 mm GH (Group3) (P = .007). A paired comparison t-test showed that cyclic loading significantly influenced the STL in comparison with the ITL in each group. Within the limitations of this study, it can be concluded that increase in height of the abutment collar could adversely affect the torque loss of the abutment screw. PMID:26237093

  3. Screw- vs cement-implant-retained restorations: an experimental study in the Beagle. Part 1. Screw and abutment loosening.

    PubMed

    Assenza, Bartolomeo; Scarano, Antonio; Leghissa, Giulio; Carusi, Giorgio; Thams, Ulf; Roman, Fidel San; Piattelli, Adriano

    2005-01-01

    The causes of implant failures can be biological or mechanical. The mechanical causes include fracture of the implant, fracture of the abutment, and loosening of the abutment. Numerous studies show that abutment loosening constitutes one of the marked implant postsurgery complications requiring clinical intervention. The aim of the present study was to evaluate the incidence of the screw loosening in screwed or cemented abutments. Six adult male Beagles were used. In each dog, the first molars and 2 premolars were extracted. The sutures were removed after 7 days. After 3 months, 10 implants were placed in each dog, 5 in the right mandible and 5 in the left mandible. The abutments either were screwed in (n=30) by applying a total strength of 30 N/cm or were cemented (n=30). After 12 months, 8 (27%) loosened screws were present in screwed abutments, whereas no abutment loosening was observed in cemented abutments (P = .0001). Screwed abutments are often submitted to nonaxial loads that determine screw and abutment loosening. PMID:16265854

  4. Abutment screw loosening of endosseous dental implant body/abutment joint by cyclic torsional loading test at the initial stage.

    PubMed

    Katsuta, Yasuhiro; Watanabe, Fumihiko

    2015-01-01

    Cyclic torsional loading tests were carried out in the laboratory using various implant systems, in order to clarify differences between the systems in loosening of abutment screws. Six samples from six commercially available abutment systems were used, giving a total of 36 samples. Four of the systems used internal connections, and two used external connections. The abutment screw for each system was tightened to a torque value specified by the manufacturer, and after 5 min, the loosening torque was measured using a digital torque meter. Measurements were taken twice, and a second measurement was taken as a reference value. A cyclic torsional loading test with 100,000 cycles was performed on the sample, and the loosening torque was again measured after the test. In conclusion, loosening of the abutment screw occurred as a result of cyclic torsional loading, and the degree of loosening varied with each implant system. PMID:26632240

  5. Influence of the implant abutment types and the dynamic loading on initial screw loosening

    PubMed Central

    Kim, Eun-Sook

    2013-01-01

    PURPOSE This study examined the effects of the abutment types and dynamic loading on the stability of implant prostheses with three types of implant abutments prepared using different fabrication methods by measuring removal torque both before and after dynamic loading. MATERIALS AND METHODS Three groups of abutments were produced using different types of fabrication methods; stock abutment, gold cast abutment, and CAD/CAM custom abutment. A customized jig was fabricated to apply the load at 30° to the long axis. The implant fixtures were fixed to the jig, and connected to the abutments with a 30 Ncm tightening torque. A sine curved dynamic load was applied for 105 cycles between 25 and 250 N at 14 Hz. Removal torque before loading and after loading were evaluated. The SPSS was used for statistical analysis of the results. A Kruskal-Wallis test was performed to compare screw loosening between the abutment systems. A Wilcoxon signed-rank test was performed to compare screw loosening between before and after loading in each group (α=0.05). RESULTS Removal torque value before loading and after loading was the highest in stock abutment, which was then followed by gold cast abutment and CAD/CAM custom abutment, but there were no significant differences. CONCLUSION The abutment types did not have a significant influence on short term screw loosening. On the other hand, after 105 cycles dynamic loading, CAD/CAM custom abutment affected the initial screw loosening, but stock abutment and gold cast abutment did not. PMID:23509006

  6. Correlation between microleakage and screw loosening at implant-abutment connection

    PubMed Central

    Ayyildiz, Simel

    2014-01-01

    PURPOSE This study aimed to evaluate the correlation between microleakage and screw loosening at different types of implant-abutment connections and/or geometries measuring the torque values before and after the leakage tests. MATERIALS AND METHODS Three different abutment types (Intenal hex titanium, internal hex zirconium, morse tapered titaniuım) with different geometries were connected to its own implant fixture. All the abutments were tightened with a standard torque value then the composition was connected to the modified fluid filtration system. After the measurements of leakage removal torque values were re-measured. Kruskal-wallis test was performed for non-parametric and one-way ANOVA was performed for parametric data. The correlation was evaluated using Spearman Correlation Test (α=0.05). RESULTS Significantly higher microleakage was found at the connection of implant-internal hex zirconium abutment. Observed mean torque value loss was also significantly higher than other connection geometries. Spearman tests revealed a significant correlation between microleakage and screw loosening. CONCLUSION Microleakage may provoke screw loosening. Removing torque values rationally decrease with the increase of microleakage. PMID:24605204

  7. Effect of cement washout on loosening of abutment screws and vice versa in screw- and cement- retained implant-supported dental prosthesis

    PubMed Central

    Kim, Seok-Gyu; Son, Mee-Kyoung

    2015-01-01

    PURPOSE The purpose of this study was to examine the abutment screw stability of screw- and cement-retained implant-supported dental prosthesis (SCP) after simulated cement washout as well as the stability of SCP cements after complete loosening of abutment screws. MATERIALS AND METHODS Thirty-six titanium CAD/CAM-made implant prostheses were fabricated on two implants placed in the resin models. Each prosthesis is a two-unit SCP: one screw-retained and the other cemented. After evaluating the passive fit of each prosthesis, all implant prostheses were randomly divided into 3 groups: screwed and cemented SCP (Control), screwed and noncemented SCP (Group 1), unscrewed and cemented SCP (Group 2). Each prosthesis in Control and Group 1 was screwed and/or cemented, and the preloading reverse torque value (RTV) was evaluated. SCP in Group 2 was screwed and cemented, and then unscrewed (RTV=0) after the cement was set. After cyclic loading was applied, the postloading RTV was measured. RTV loss and decementation ratios were calculated for statistical analysis. RESULTS There was no significant difference in RTV loss ratio between Control and Group 1 (P=.16). No decemented prosthesis was found among Control and Group 2. CONCLUSION Within the limits of this in vitro study, the stabilities of SCP abutment screws and cement were not significantly changed after simulated cement washout or screw loosening. PMID:26140172

  8. Acrylic resin guide for locating the abutment screw access channel of cement-retained implant prostheses.

    PubMed

    Ahmed, Ayman; Maroulakos, Georgios; Garaicoa, Jorge

    2016-05-01

    Abutment screw loosening represents a common and challenging technical complication of cement-retained implant prostheses. This article describes the fabrication of a simple and accurate poly(methyl methacrylate) guide for identifying the location and angulation of the abutment screw access channel of a cement-retained implant prosthesis with a loosened abutment screw. PMID:26794698

  9. Access to Abutment Screw in Cement Retained Restorations: A Clinical Tip

    PubMed Central

    Harianawala, Husain; Kantharia, Nidhi; Sethi, Tania; Jambhekar, Shantanu

    2015-01-01

    Abutment screw loosening has been reported to be the most common prosthetic complications occurring in screw retained as well as cement retained implant restorations. Different methods to treat this issue have been reported in the literature so far; however these have their own short-comings. Retrievability of an implant restoration intact becomes a clinical challenge when the restoration is cement retained especially with an angulated abutment. This technique is aimed at accurately determining the position of the abutment screw in 3 dimensional relationships using a vacuum formed clear stent. This technique can be used as a viable protocol for management of screw loosening in cement retained implant restorations. PMID:25859535

  10. 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. PMID:21203705

  11. [Loosening of a Calcaneo-Stop Screw after Trampolining].

    PubMed

    Trieb, K; Fingernagel, T; Petershofer, A; Hofstaetter, S G

    2015-06-01

    Flexible flatfoot is a common malalignment in the paediatric population. Arthroereisis with a calcaneo-stop screw is an effective surgical procedure for treating juvenile flexible flatfoot after conservative measures have been fully exploited. In the present report, we describe the case of a loosening of a calcaneo-stop screw in a 12-year-old youth after excessive trampolining. PMID:25710392

  12. The applicability of PEEK-based abutment screws.

    PubMed

    Schwitalla, Andreas Dominik; Abou-Emara, Mohamed; Zimmermann, Tycho; Spintig, Tobias; Beuer, Florian; Lackmann, Justus; Müller, Wolf-Dieter

    2016-10-01

    The high-performance polymer PEEK (poly-ether-ether-ketone) is more and more being used in the field of dentistry, mainly for removable and fixed prostheses. In cases of screw-retained implant-supported reconstructions of PEEK, an abutment screw made of PEEK might be advantageous over a conventional metal screw due to its similar elasticity. Also in case of abutment screw fracture, a screw of PEEK could be removed more easily. M1.6-abutment screws of four different PEEK compounds were subjected to tensile tests to set their maximum tensile strengths in relation to an equivalent stress of 186MPa, which is aused by a tightening torque of 15Ncm. Two screw types were manufactured via injection molding and contained 15% short carbon fibers (sCF-15) and 40% (sCF-40), respectively. Two screw types were manufactured via milling and contained 20% TiO2 powder (TiO2-20) and >50% parallel orientated, continuous carbon fibers (cCF-50). A conventional abutments screw of Ti6Al4V (Ti; CAMLOG(®) abutment screw, CAMLOG, Wimsheim, Germany) served as control. The maximum tensile strength was 76.08±5.50MPa for TiO2-20, 152.67±15.83MPa for sCF-15, 157.29±20.11MPa for sCF-40 and 191.69±36.33MPa for cCF-50. The maximum tensile strength of the Ti-screws amounted 1196.29±21.4MPa. The results of the TiO2-20 and the Ti screws were significantly different from the results of the other samples, respectively. For the manufacturing of PEEK abutment screws, PEEK reinforced by >50% continuous carbon fibers would be the material of choice. PMID:27434650

  13. A technique for removal of a fractured implant abutment screw.

    PubMed

    Kurt, Murat; Güler, Ahmet Umut; Duran, İbrahim

    2013-12-01

    The aim of this technique report was to present a procedure for removal of a fractured implant abutment screw. Whatever the cause, when an abutment fracture has occurred, the fractured screw segment inside the implant must be removed. The methods used by the clinicians may include the use of an endo-explorer self-made screwdriver and the use of implant repair kit available for some implant systems. The advantage of the presented method is that it may be extended to other implant systems that do not have a special repair kit and also that the technique is simple and does not require special equipment. PMID:21905898

  14. Management of a fractured implant abutment screw: a clinical report.

    PubMed

    Canpolat, Ceyhun; Ozkurt-Kayahan, Zeynep; Kazazoğlu, Ender

    2014-07-01

    In an abutment screw fracture, it is generally a challenge for the clinician to remove fractured fragments. In some cases, the screw cannot be removed, and alternative solutions should be considered. This clinical report describes the replacement of a ball attachment with a fractured screw, which was impossible to retrieve, with a cast dowel with ball attachment. The patient who presented to the Department of Prosthodontics, Yeditepe University, Faculty of Dentistry was a 65-year-old woman, wearing a mandibular complete denture supported by two implants for 4 years. She complained about the loss of retention of the denture because of the fractured abutment screw, and it was found that another dentist had previously tried to retrieve the fractured screw with no success. It was decided to construct a cast dowel with ball attachment to improve retention without sacrificing the implant. The interior of the implant and the fractured screw were machined with a rotating instrument. An impression was taken with a metal strip and silicone-based materials. In the laboratory, a stone die was generated from the impression, and a custom-made cast dowel with ball attachment was constructed. It was then cemented with glass ionomer cement and connected to the denture with the direct method. The alternative procedure described in this clinical report was successful for the removal of the fractured abutment screw and use of the existing denture. PMID:24393481

  15. Effects of Repeated Screw Tightening on Implant Abutment Interfaces in Terms of Bacterial and Yeast Leakage in Vitro: One-Time Abutment Versus the Multiscrewing Technique.

    PubMed

    Calcaterra, Roberta; Di Girolamo, Michele; Mirisola, Concetta; Baggi, Luigi

    2016-01-01

    Screw loosening can damage the interfaces of implant components, resulting in susceptibility to contamination of the internal parts by microorganisms. The aim of this study was to investigate the impact of abutment screw retightening on the leakage of two different types of bacteria, Streptococcus sanguinis and Fusobacterium nucleatum, and of the yeast Candida albicans. Two types of implant-abutment systems with tube-in-tube interfaces were tested. Groups A and B each used a different type of system that consisted of 20 different pieces that were assembled according to the manufacturer's torque recommendations; four samples in each group were closed just one time, four samples three times, four samples five times, four samples seven times, and four samples nine times. The implants of groups A and B were contaminated with 0.1 μL of microbial solution just before being assembled for the last time to minimize the possibility of contamination. Results showed a direct correlation between the number of colony-forming units grown in the plates and the closing/opening cycles of the implant-abutment systems. Within the limitations of this study, the results indicate the possibility that repeated closing/opening cycles of the implant-abutment unit may influence bacterial/yeast leakage, most likely as a consequence of decreased precision of the coupling between the abutment and the internal part of the dental implant. These findings suggest that a one-time abutment technique may avoid microbiologic leakage in cases of implant-abutment systems with tube-in-tube interfaces. PMID:26901305

  16. Fracture resistance of abutment screws made of titanium, polyetheretherketone, and carbon fiber-reinforced polyetheretherketone.

    PubMed

    Neumann, Eduardo Aloisio Fleck; Villar, Cristina Cunha; França, Fabiana Mantovani Gomes

    2014-01-01

    Fractured abutment screws may be replaced; however, sometimes, the screw cannot be removed and the entire implant must be surgically removed and replaced. The aim of this study was to compare the fracture resistance of abutment retention screws made of titanium, polyetheretherketone (PEEK) and 30% carbon fiber-reinforced PEEK, using an external hexagonal implant/UCLA-type abutment interface assembly. UCLA-type abutments were fixed to implants using titanium screws (Group 1), polyetheretherketone (PEEK) screws (Group 2), and 30% carbon fiber-reinforced PEEK screws (Group 3). The assemblies were placed on a stainless steel holding apparatus to allow for loading at 45o off-axis, in a universal testing machine. A 200 N load (static load) was applied at the central point of the abutment extremity, at a crosshead speed of 5 mm/minute, until failure. Data was analyzed by ANOVA and Tukey's range test. The titanium screws had higher fracture resistance, compared with PEEK and 30% carbon fiber-reinforced PEEK screws (p < 0.05). In contrast, no statistically significant difference was observed between the fracture resistance of the PEEK and the 30% carbon fiber-reinforced PEEK screws (p> 0.05). Finally, visual analysis of the fractions revealed that 100% of them occurred at the neck of the abutment screw, suggesting that this is the weakest point of this unit. PEEK abutment screws have lower fracture resistance, in comparison with titanium abutment screws. PMID:25098826

  17. The Effects of Spinopelvic Parameters and Paraspinal Muscle Degeneration on S1 Screw Loosening

    PubMed Central

    Kim, Jin-Bum; Lee, Young-Seok; Nam, Taek-Kyun; Park, Yong-Sook; Kim, Young-Baeg

    2015-01-01

    Objective To investigate risk factors for S1 screw loosening after lumbosacral fusion, including spinopelvic parameters and paraspinal muscles. Methods We studied with 156 patients with degenerative lumbar disease who underwent lumbosacral interbody fusion and pedicle screw fixation including the level of L5-S1 between 2005 and 2012. The patients were divided into loosening and non-loosening groups. Screw loosening was defined as a halo sign larger than 1 mm around a screw. We checked cross sectional area of paraspinal muscles, mean signal intensity of the muscles on T2 weight MRI as a degree of fatty degeneration, spinopelvic parameters, bone mineral density, number of fusion level, and the characteristic of S1 screw. Results Twenty seven patients showed S1 screw loosening, which is 24.4% of total. The mean duration for S1 screw loosening was 7.3±4.1 months after surgery. Statistically significant risk factors were increased age, poor BMD, 3 or more fusion levels (p<0.05). Among spinopelvic parameters, a high pelvic incidence (p<0.01), a greater difference between pelvic incidence and lumbar lordotic angle preoperatively (p<0.01) and postoperatively (p<0.05). Smaller cross-sectional area and high T2 signal intensity in both multifidus and erector spinae muscles were also significant muscular risk factors (p<0.05). Small converging angle (p<0.001) and short intraosseous length (p<0.05) of S1 screw were significant screw related risk factors (p<0.05). Conclusion In addition to well known risk factors, spinopelvic parameters and the degeneration of paraspinal muscles also showed significant effects on the S1 screw loosening. PMID:26587190

  18. Management of a Fractured Multiunit Maxillary Implant-Supported Fixed Prosthesis with Stripped Abutment Screws Using a Hybrid Cement-Retained and Screw-Retained Design: A 5-Year Follow-Up Clinical Report.

    PubMed

    Al Amri, Mohammad D

    2016-06-01

    Fracture and loosening of implant-supported prostheses (ISPs) are complications encountered in routine dental practice. In the present report, management of a fractured maxillary full-arch cement-retained (CR) fixed dental prosthesis supported by six implants is presented. Due to stripped screws, complications were encountered that prevented the retrieval of two of the six abutment screws, which was managed by using a hybrid retention approach, whereby a single full-arch CR and screw-retained (SR) ISP was used. The techniques used to successfully retrieve four of the abutment screws are described. The final retention design involved a combination of three CR and three SR restorations, which offers the advantages of both retention designs. PMID:26713868

  19. Improving the long-term stability of Ti6Al4V abutment screw by coating micro/nano-crystalline diamond films.

    PubMed

    Xie, Youneng; Zhou, Jing; Wei, Qiuping; Yu, Z M; Luo, Hao; Zhou, Bo; Tang, Z G

    2016-10-01

    Abutment screw loosening is the most common complication of implanting teeth. Aimed at improving the long-term stability of them, well-adherent and homogeneous micro-crystalline diamond (MCD) and nano-crystalline diamond (NCD) were deposited on DIO(®) (Dong Seo, Korea) abutment screws using a hot filament chemical vapor deposition (HFCVD) system. Compared with bare DIO(®) screws, diamond coated ones showed higher post reverse toque values than the bare ones (p<0.05) after cyclic loading one million times under 100N, and no obvious flaking happened after loading test. Diamond coated disks showed lower friction coefficients of 0.15 and 0.18 in artificial saliva when countered with ZrO2 than that of bare Ti6Al4V disks of 0.40. Though higher cell apoptosis rate was observed on film coated disks, but no significant difference between MCD group and NCD group. And the cytotoxicity of diamond films was acceptable for the fact that the cell viability of them was still higher than 70% after cultured for 72h. It can be inferred that coating diamond films might be a promising modification method for Ti6Al4V abutment screws. PMID:27393893

  20. In vitro evaluation of the loosening characteristics of self-tapped and non-self-tapped cortical bone screws.

    PubMed

    Vangsness, C T; Carter, D R; Frankel, V H

    1981-06-01

    The heads of self-tapping and non-self-tapping screws in dog femurs were exposed to a cyclic shearing force of 110 N for 200 loading cycles. This cyclic shear loading created a decrease in pull-out strength for both screw types of approximately 11% (p less than 0.01). No statistically significant difference in pull-out strength was found between screw types either before or after cyclic loading. A linear relationship between pull-out force and cortical thickness was observed for both screw types. These tests corroborated past work which showed equal holding power for the self-tapping and non-self-tapping screw. The progressive loosening of the screws with cyclic shear loading was accompanied by increasing load-displacement hysteresis and screw head migration. Greater hysteresis suggested that the non-self-tapping screw might have loosened more than the self-tapping screw from this applied loading schedule. Bone microcracking around screw threads before and after cyclic loading was observed by scanning electron microscopy. Photomicrographs of one non-self-tapping screw type and two self-tapping screw types showed microcracks at the tip of the outer diameter of the screw thread. More microcracks were observed after application of cyclic shear loading. PMID:7249457

  1. Using a porcelain furnace to debond cement-retained implant crown from the abutment after screw fracture: a clinical report.

    PubMed

    Saponaro, Paola C; Heshmati, Reza H; Lee, Damian J

    2015-04-01

    When a screw fracture occurs on a cement-retained, implant-supported restoration, the abutment and restoration are completely separated from the implant's internal connection. Traditionally, an access hole is drilled through the crown to retrieve the broken screw, and the restoration can be placed again as a screw-retained restoration. This clinical report documents a patient whose broken abutment screw was retrieved from the restoration by burning off the cement and separating from the abutment without drilling an access hole. PMID:25316610

  2. In-vitro development of a temporal abutment screw to protect osseointegration in immediate loaded implants

    PubMed Central

    2015-01-01

    PURPOSE In this study, a temporal abutment fixation screw, designed to fracture in a controlled way upon application of an occlusal force sufficient to produce critical micromotion was developed. The purpose of the screw was to protect the osseointegration of immediate loaded single implants. MATERIALS AND METHODS Seven different screw prototypes were examined by fixing titanium abutments to 112 Mozo-Grau external hexagon implants (MG Osseous®; Mozo-Grau, S.A., Valladolid, Spain). Fracture strength was tested at 30° in two subgroups per screw: one under dynamic loading and the other without prior dynamic loading. Dynamic loading was performed in a single-axis chewing simulator using 150,000 load cycles at 50 N. After normal distribution of obtained data was verified by Kolmogorov-Smirnov test, fracture resistance between samples submitted and not submitted to dynamic loading was compared by the use of Student's t-test. Comparison of fracture resistance among different screw designs was performed by the use of one-way analysis of variance. Confidence interval was set at 95%. RESULTS Fractures occurred in all screws, allowing easy retrieval. Screw Prototypes 2, 5 and 6 failed during dynamic loading and exhibited statistically significant differences from the other prototypes. CONCLUSION Prototypes 2, 5 and 6 may offer a useful protective mechanism during occlusal overload in immediate loaded implants. PMID:25932315

  3. Noninvasive method for retrieval of broken dental implant abutment screw.

    PubMed

    Gooty, Jagadish Reddy; Palakuru, Sunil Kumar; Guntakalla, Vikram Reddy; Nera, Mahipal

    2014-04-01

    Dental implants made of titanium for replacement of missing teeth are widely used because of ease of technical procedure and high success rate, but are not free of complications and may fail. Fracturing of the prosthetic screw continues to be a problem in restorative practice and great challenge to remove the fractured screw conservatively. This case report describes and demonstrates the technique of using an ultrasonic scaler in the removal of the fracture screw fragment as a noninvasive method without damaging the hex of implants. PMID:24963261

  4. Noninvasive method for retrieval of broken dental implant abutment screw

    PubMed Central

    Gooty, Jagadish Reddy; Palakuru, Sunil Kumar; Guntakalla, Vikram Reddy; Nera, Mahipal

    2014-01-01

    Dental implants made of titanium for replacement of missing teeth are widely used because of ease of technical procedure and high success rate, but are not free of complications and may fail. Fracturing of the prosthetic screw continues to be a problem in restorative practice and great challenge to remove the fractured screw conservatively. This case report describes and demonstrates the technique of using an ultrasonic scaler in the removal of the fracture screw fragment as a noninvasive method without damaging the hex of implants. PMID:24963261

  5. Evaluation of implant loosening following segmental pedicle screw fixation in adolescent idiopathic scoliosis: a 2 year follow-up with low-dose CT

    PubMed Central

    2014-01-01

    Background The long term radiological status of screw fixation following scoliosis surgery with all pedicle screw construct is not previously studied. Aim To evaluate the incidence of loosening (implant failure) evaluated with low-dose CT two years following scoliosis surgery. Study design Retrospective study. Methods 81 consecutive patients with adolescent idiopathic scoliosis (AIS), aged 18 ± 3 years at 2 years follow-up (83% were female), subjected for scoliosis corrective surgery with all pedicle screw construct (total of 1666 screws) has been examined with plain radiography and with low dose CT 6 weeks and 2 years postoperatively. Results In 26 out of 81 (32%) patients there were signs of loosening of one or more screws, a maximum 3 screws. 47 out of 1666 (2.8%) screws showed evidence of loosening. Preoperative Cobb angle was 56° among patients with loosening compared with 53° among patients with no evidence of loosening (P = 0.288). In males there were signs of loosening in 8 out of 14 (57%) and in females 18 out of 67 (27%), (P = 0.027). Among cases with loosening, 14% had suboptimal screw placement at the first postoperative CT compared with 11% among patients with no evidence of loosening (P = 0.254). One patient with a loosened L4 screw had neurological deficit and subjected for revision of the construct. Out of 26 patients with evidence of loosening, 5 patients reported minor pain or discomfort, 1 patient had a minor proximal junctional kyphosis of about 15° and 3 patients showed evidence of pull-out of 3–5 mm at the upper end of the construct but no clinical complaint. With plain radiography loosening could be observed only in 11 out of 26 cases, 5 were in the lumbar region. Conclusions In a consecutive series of 81 cases with AIS who had underwent scoliosis surgery, one third showed, 2 years after the intervention, minor screw loosening. Males were more prone to develop screw loosening. In CT system that enables low

  6. Dynamic Abutment: A method of redirecting screw access for implant-supported restorations: Technical details and a clinical report.

    PubMed

    Berroeta, Eva; Zabalegui, Ion; Donovan, Terrence; Chee, Winston

    2015-06-01

    The esthetic outcome of implant-supported restorations is affected by the implant position. A well-placed implant will allow appropriate contours of the restoration and together with an adequate volume of soft tissue will result in a functional and esthetic restoration. When a screw-retained restoration is anticipated, an implant that is angled too far facially would be esthetically unacceptable. In 2004, an abutment called the Dynamic Abutment (Talladium International Implantology) became commercially available. This abutment can allow a deviation of the restoration screw access angle to the implant angle of up to 28 degrees while allowing a screw-retained restoration to be connected directly to the platform of the implant. The purpose of this article was to describe the components, technique, and clinical use of this abutment. PMID:25794919

  7. Influence of abutment screw design and surface coating on the bending flexural strength of the implant set.

    PubMed

    Prado, Célio Jesus do; Neves, Flávio Domingues das; Soares, Carlos José; Dantas, Kelly Abadia; Dantas, Talita Souza; Naves, Lucas Zago

    2014-04-01

    The purpose of this study was to analyze the influence of the setting and the presence of solid lubricant on the abutment screw surface on the flexural strength of the joint implant/abutment/screw. Forty abutments were connected to external hex implants, divided into 4 groups (n = 10): FE (titanium alloy screw threaded in the extremity), LE (titanium alloy screw with solid lubricant and thread in the extremity), FT (titanium alloy screw with threaded in all its length), and LT (titanium alloy screw with solid lubricant and thread in all its length). Through the mechanical flexural test, the implant/abutment resistance was evaluated with load applied perpendicular to the long axis in a mechanical testing machine (EMIC) under a speed of 0.5 mm/min. Data were submitted to a statistics test, and results showed statistically significant differences between the FE group and the other groups, and the FE group showed the lowest values. The LE group showed greater values than the LT group, and the values were statistically significant. According to the methodology used, it can be concluded that within noncoated titanium screws, a screw threaded along its entire length provided greater rigidity to the implant set, while with the screw containing solid lubricant, the screw threaded in all its length provided less rigidity of the implant set than screws with the thread only on the end. Among screws with the same geometry, those with the solid lubricant are statistically higher than those which do not have threads just at the end, but those with threads along their entire length do not show statistically significant differences. PMID:22251283

  8. Management of a malpositioned implant using custom abutment and screw-retained fixed dental prosthesis.

    PubMed

    Turkyilmaz, Ilser

    2014-01-01

    A 32-year-old woman with missing permanent mandibular right molars and left first molar presented for treatment. One of the implants were misaligned during the placement due to sudden mouth closure of the patient. All implants success fully osseointegrated. However, the misaligned implant resulted in substantial mechanical and esthetic restorative challenges. The prosthodontic treatment included a custom abutment and a screw-retained fixed dental prosthesis on the right side. The patient did not report any problems with the implants and restorations during the first year of service. The treatment presented in this clinical report may be an alternative option to restore malpositioned implants. PMID:25307826

  9. The Effect of Lumbar Lordosis on Screw Loosening in Dynesys Dynamic Stabilization: Four-Year Follow-Up with Computed Tomography

    PubMed Central

    Kuo, Chao-Hung; Chang, Peng-Yuan; Tu, Tsung-Hsi; Fay, Li-Yu; Chang, Hsuan-Kan; Wu, Jau-Ching; Huang, Wen-Cheng; Cheng, Henrich

    2015-01-01

    Introduction. This study aimed to evaluate the effects of Dynesys dynamic stabilization (DDS) on clinical and radiographic outcomes, including spinal pelvic alignment. Method. Consecutive patients who underwent 1- or 2-level DDS for lumbar spondylosis, mild degenerative spondylolisthesis, or degenerative disc disease were included. Clinical outcomes were evaluated by Visual Analogue Scale for back and leg pain, Oswestry Disability Index, and the Japanese Orthopedic Association scores. Radiographic outcomes were assessed by radiographs and computed tomography. Pelvic incidence and lumbar lordosis (LL) were also compared. Results. In 206 patients with an average follow-up of 51.1 ± 20.8 months, there were 87 screws (8.2%) in 42 patients (20.4%) that were loose. All clinical outcomes improved at each time point after operation. Patients with loosened screws were 45 years older. Furthermore, there was a higher risk of screw loosening in DDS involving S1, and these patients were more likely to have loosened screws if the LL failed to increase after the operation. Conclusions. The DDS screw loosening rate was overall 8.2% per screw and 20.4% per patient at more than 4 years of follow-up. Older patients, S1 involvement, and those patients who failed to gain LL postoperatively were at higher risk of screw loosening. PMID:26779532

  10. 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

  11. Effect of abutment screw length and cyclic loading on removal torque in external and internal hex implants

    PubMed Central

    Mohammed, Hnd Hadi; Lee, Jin-Han; Bae, Ji-Myung

    2016-01-01

    PURPOSE The purpose of this study was to evaluate the effects of abutment screw length and cyclic loading on the removal torque (RTV) in external hex (EH) and internal hex (IH) implants. MATERIALS AND METHODS Forty screw-retained single crowns were connected to external and internal hex implants. The prepared titanium abutment screws were classified into 8 groups based on the number of threads (n = 5 per group): EH 12.5, 6.5, 3.5, 2.5 and IH 6.5, 5, 3.5, 2.5 threads. The abutment screws were tightened with 20 Ncm torque twice with 10-minute intervals. After 5 minutes, the initial RTVs of the abutment screws were measured with a digital torque gauge (MGT12). A customized jig was constructed to apply a load along the implant long axis at the central fossa of the maxillary first molar. The post-loading RTVs were measured after 16,000 cycles of mechanical loading with 50 N at a 1-Hz frequency. Statistical analysis included one-way analysis of variance and paired t-tests. RESULTS The post-loading RTVs were significantly lower than the initial RTVs in the EH 2.5 thread and IH 2.5 thread groups (P<.05). The initial RTVs exhibited no significant differences among the 8 groups, whereas the post-loading RTVs of the EH 6.5 and EH 3.5 thread groups were higher than those of the IH 3.5 thread group (P<.05). CONCLUSION Within the limitations of this study, the external hex implants with short screw lengths were more advantageous than internal hex implants with short screw lengths in torque maintenance after cyclic loading. PMID:26949489

  12. Screw vs cement-implant-retained restorations: an experimental study in the beagle. Part 2. Immunohistochemical evaluation of the peri-implant tissues.

    PubMed

    Assenza, Bartolomeo; Artese, Luciano; Scarano, Antonio; Rubini, Corrado; Perrotti, Vittoria; Piattelli, Maurizio; Thams, Ulf; San Roman, Fidel; Piccirilli, Marcello; Piattelli, Adriano

    2006-01-01

    Crestal bone loss has been reported to occur around dental implants. Even if the causes of this bone loss are not completely understood, the presence of a microgap between implant and abutment with a possible contamination of the internal portion of the implants has been suggested. The aim of this study was to see if there were differences in the vascular endothelial growth factor (VEGF) expression, microvessel density (MVD), proliferative activity (MIB-1), and inflammatory infiltrate in the soft tissues around implants with screwed and cemented abutments. Sandblasted and acid-etched implants were inserted in the mandibles of 6 Beagle dogs. Ten 3.5- x 10-mm root-form implants were inserted in each mandible. A total of 60 implants (30 with screwed abutments and 30 with cemented abutments) were used. After 12 months, all the bridges were removed and all abutments were checked for mobility. A total of 8 loosened screws (27%) were found in the screwed abutments, whereas no loosening was observed in cemented abutments. A gingival biopsy was performed in 8 implants with cemented abutments, in 8 implants with screwed abutments, and in 8 implants with unscrewed abutments. No statistically significant differences were found in the inflammatory infiltrate and in the MIB-1 among the different groups. No statistically significant difference was found in the MVD between screwed and cemented abutments (P = .2111), whereas there was a statistically significant difference in MVD between screwed and unscrewed abutments (P = .0277) and between cemented and unscrewed abutments (P = .0431). A low intensity of VEGF was prevalent in screwed and in cemented abutments, whereas a high intensity of VEGF was prevalent in unscrewed abutments. These facts could be explained by the effects induced, in the abutments that underwent a screw loosening, by the presence of bacteria inside the hollow portion of the implants or by enhanced reparative processes. PMID:16526575

  13. Double-Step Image Superimposition Technique for Fabricating a Drilling Guide to Access the Abutment Screw in Implant Prostheses.

    PubMed

    Mai, Hang-Nga; Kim, Kyung-Rok; Lee, Du-Hyeong

    2016-01-01

    Limited retrievability is a major disadvantage of cement-retained implant restorations. Despite great progress in locating the abutment screw within crowns, the existing techniques are based on prior data or prefabricated devices and require significant work. This study introduces a new procedure for fabricating a guide template to drill a screw access hole using a double-step superimposition technique that incorporates intraoral optical scanning, cone beam computed tomography, and dental design software. The double-step superimposition technique with computer-aided design/computer-assisted manufacturing technology can enhance the convenience and accuracy of drilling the screw-access hole. PMID:27479352

  14. A Simple and Cost Effective Method used for Removal of a Fractured Implant Abutment Screw: A Case Report

    PubMed Central

    Satwalekar, Parth; Chander, K Subash; Reddy, B Anantha; Sandeep, N; Sandeep, N; Satwalekar, Tanushree

    2013-01-01

    The success of dental implants is based primarily on the extent of osseointegration. The failure of dental implants is not only due to biological factors, such as unsuccessful osseointegration or the presence of peri-implantitis, but may also result from technical complications. Fracture of the implant abutment screw can be a serious problem, as the fragment remaining inside the implant may prevent the implant from functioning efficiently as an anchor. A simple and cost effective procedure used for the removal of fractured screw fragments and the successful utilization of the existing prosthesis are described in this clinical report. How to cite this article: Satwalekar P, Chander KS, Reddy BA, Sandeep N, Sandeep N, Satwalekar T. A Simple and Cost Effective Method used for Removal of a Fractured Implant Abutment Screw: A Case Report. J Int Oral Health 2013; 5(5):120-3. PMID:24324315

  15. FRACTURE OF ABUTMENT SCREW SUPPORTING A CEMENTED IMPLANT-RETAINED PROSTHESIS WITH EXTERNAL HEXAGON CONNECTION: A CASE REPORT WITH SEM EVALUATION

    PubMed Central

    Santos, Mariana Diniz Bisi; Pfeifer, Arthur Braga; Silva, Marcos Rogério Pupo; Sendyk, Claudio Luiz; Sendyk, WIlson Roberto

    2007-01-01

    One of the causes of implant failures in cemented implant-retained prostheses is the fracture of abutment screw or UCLA abutment. This article reports a case of simultaneous fracture of two UCLA abutments screws occurring in an implant-supported prosthesis placed in the mandibular molar region. The fractured structures were examined under scanning electron microscopy to investigate the probable causes of the failure, which were not related to failures on materials or fabrication of the screws, but rather were due to shear forces. The misfit in cemented prostheses may be the most likely cause of shear force generation. PMID:19089120

  16. In vitro analysis of resistance to cyclic load and preload distribution of two implant/abutment screwed connections.

    PubMed

    Murmura, Giovanna; Di Iorio, Donato; Cicchetti, Angelo Raffaele; Sinjari, Bruna; Caputi, Sergio

    2013-06-01

    The aim of the present research is an in vitro evaluation of the preload distribution in screw-retained implant systems under cyclic load. Two implant systems with internal connection were tested: fifteen 4.5 × 10 mm implants with internal hexagon and fifteen 4.5 × 10 mm implants with internal octagon. Samples underwent cyclic load that was between 20 N and 200 N for 1 × 10(6) cycles. After mechanical tests, samples were sectioned along the long axis and analyzed under a scanning electron microscope. Five 4.5 × 10 mm implants with internal hexagon and five 4.5 × 10 mm implants with internal octagon were collected for photoelastic analysis. Each fixture was mounted in a wax-made parallelepiped measuring 20 mm × 20 mm × 10 mm. A mold was made for each wax parallelepiped/fixture assembly using a silicone-based impression material, and an epoxy resin was poured in each mold. After setting of the resin, 25° angled titanium abutments were screwed onto each replica; afterwards, assemblies underwent photoelastic analysis. After cyclic load, screw threads and heads were still in contact with internal fixture threads and abutment holes, respectively, suggesting that preload has not been lost during load. During load, SSO and Xsigñ implants behave in a different way. SSO samples revealed the presence of fringes radiating from the base of the abutment. Xsigñ implants showed the presence of fringes radiating from the threads of the retention screw. From the present in vitro research, it is possible to state that screw-retained abutment based on an internal octagonal connection is less likely to come loose after cyclic load. PMID:21231867

  17. The effect of different implant-abutment connections on screw joint stability.

    PubMed

    Michalakis, Konstantinos X; Calvani, Pasquale Lino; Muftu, Sinan; Pissiotis, Argiris; Hirayama, Hiroshi

    2014-04-01

    Dental implants with an internal connection have been designed to establish a better stress distribution when lateral external forces act on the prosthesis and minimize the forces transmitted to the fastening screw. In the present study, 10 externally and 10 internally hexed implants were tested with a compressive force applied with an Instron Universal machine. Four cycles of loading-unloading were applied to each specimen to achieve displacements of 0.5, 1, 2, and 2.5 mm. The mean loads for the first cycle were 256.70 N for the external connection and 256 N for the internal connection implants. The independent t test did not reveal any significant differences among the 2 tested groups (P = .780). For the second cycle, the mean loads needed for a displacement of 1 mm were 818.19 N and 780.20 N for the external connection and the internal connection implants, respectively. The independent t test revealed significant differences among the 2 tested groups (P < .001). In the third cycle, the mean load values for a 2-mm displacement were 1394.10 N and 1225.00 N. The independent t test revealed significant differences among the 2 tested groups (P < .001). The mean loads for the fourth cycle were 1488.00 N for the external connection and 1029.00 N for the internal connection implants. These loads were required for a displacement of 2.5 mm. The independent t test revealed significant differences among the 2 tested groups (P < .001). The results of this in vitro study suggest that the internal connection design of the examined implant system could not prevent screw loosening during overloading. No implant or prosthesis failure was noticed in either group. PMID:24779947

  18. 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

  19. Determination of fluid leakages in the different screw-retained implant-abutment connections in a mechanical artificial mouth.

    PubMed

    Martin-Gili, D; Molmeneu, M; Fernandez, M; Punset, M; Giner, Ll; Armengou, J; Gil, F Javier

    2015-07-01

    This study shows the potential risk of microfiltration between two different types of implant-abutment connections screwed at 45 Ncm: external and internal. For the first time the use of a mechanical artificial mouth is used with the values (compression and torsion loads with a frequency of 2 Hz) of the human chewing. The mechanical tests were performed with an artificial saliva at 37°C. The microgap in the connection was measured by an Image Analysis software incorporated in a high resolution scanning electron microscopy. Implant connections were filled with methylene blue by using self-adjustable precision pipettes and the quantity of leakage was determined by high sensitivity spectometry. We showed that the internal connection has lower microgaps compared to the external ones and these microgaps increased with the number of mechanical cycles. The leakage of methylene blue was higher when the external connection was performed. Microgaps and the influence of the mechanical loads are very important for the long-term behavior avoiding the bacteria colonization in the dental implants. These aspects should be known by the implantologists. PMID:26174348

  20. Immediate load and esthetic zone considerations to replace maxillary incisor teeth using a new zirconia implant abutment in the bone grafted anterior maxilla.

    PubMed

    Lee, Cameron Y S; Hasegawa, Henry

    2008-01-01

    The goal of this prospective clinical study is to evaluate a new all-ceramic implant abutment made from zirconium oxide during the immediate load of dental implants placed in the block grafted anterior maxilla. This new zirconia abutment gives the clinician the opportunity to provide the patient with an all-ceramic restorative system (abutment and crown) for an optimum esthetic result and a high level of patient satisfaction. A total of 9 hydroxyapatite-coated dental implants were surgically placed in 9 patients and were immediately loaded 5 to 7 days later with a custom composite provisional restoration that was placed out of functional occlusion. Each prefabricated, natural colored zirconia abutment was shaped and connected to the implant with a titanium screw. Provisional restorations were cemented to the zirconia abutment with the use of temporary cement. Twelve weeks later, the provisional restoration was replaced with an all-ceramic restoration. Over a 52-week observation period, no abutment fractures occurred, and no abutment screw loosening was observed. No implants failed. All 9 patients reported total satisfaction regarding esthetic quality of the all-ceramic restorative system (abutment and implant). Preliminary results of this clinical study indicate that this new zirconia abutment offers the clinician and the patient exceptional strength, optimal esthetics, and simplicity. It is of important clinical significance that use of this all-ceramic abutment eliminates the well-known disadvantages of metal abutments. PMID:19170292

  1. Long-term cumulative survival and mechanical complications of single-tooth Ankylos Implants: focus on the abutment neck fractures

    PubMed Central

    2015-01-01

    PURPOSE To evaluate the cumulative survival rate (CSR) and mechanical complications of single-tooth Ankylos® implants. MATERIALS AND METHODS This was a retrospective clinical study that analyzed 450 single Ankylos® implants installed in 275 patients between December 2005 and December 2012. The main outcomes were survival results CSR and implant failure) and mechanical complications (screw loosening, fracture, and cumulative fracture rate [CFR]). The main outcomes were analyzed according to age, sex, implant length or diameter, bone graft, arch, and position. RESULTS The 8-year CSR was 96.9%. Thirteen (2.9%) implants failed because of early osseointegration failure in 3, marginal bone loss in 6, and abutment fracture in 4. Screw loosening occurred in 10 implants (2.2%), and 10 abutment fractures occurred. All abutment fractures were located in the neck, and concurrent screw fractures were observed. The CSR and rate of screw loosening did not differ significantly according to factors. The CFR was higher in middle-aged patients (5.3% vs 0.0% in younger and older patients); for teeth in a molar position (5.8% vs 0.0% for premolar or 1.1% for anterior position); and for larger-diameter implants (4.5% for 4.5 mm and 6.7% for 5.5 mm diameter vs 0.5% for 3.5 mm diameter) (all P<.05). CONCLUSION The Ankylos® implant is suitable for single-tooth restoration in Koreans. However, relatively frequent abutment fractures (2.2%) were observed and some fractures resulted in implant failures. Middle-aged patients, the molar position, and a large implant diameter were associated with a high incidence of abutment fracture. PMID:26813443

  2. Adjacent-Level Hypermobility and Instrumented-Level Fatigue Loosening With Titanium and PEEK Rods for a Pedicle Screw System: An In Vitro Study.

    PubMed

    Agarwal, Aakas; Ingels, Marcel; Kodigudla, Manoj; Momeni, Narjes; Goel, Vijay; Agarwal, Anand K

    2016-05-01

    Adjacent-level disease is a common iatrogenic complication seen among patients undergoing spinal fusion for low back pain. This is attributed to the postsurgical differences in stiffness between the spinal levels, which result in abnormal forces, stress shielding, and hypermobility at the adjacent levels. In addition, as most patients undergoing these surgeries are osteoporotic, screw loosening at the index level is a complication that commonly accompanies adjacent-level disease. Recent studies indicate that a rod with lower rigidity than that of titanium may help to overcome these detrimental effects at the adjacent level. The present study was conducted in vitro using 12 L1-S1 specimens divided into groups of six, with each group instrumented with either titanium rods or PEEK (polyetheretherketone) rods. The test protocol included subjecting intact specimens to pure moments of 10 Nm in extension and flexion using an FS20 Biomechanical Spine Test System (Applied Test Systems) followed by hybrid moments on the instrumented specimens to achieve the same L1-S1 motion as that of the intact specimens. During the protocol's later phase, the L4-L5 units from each specimen were segmented for cyclic loading followed by postfatigue kinematic analysis to highlight the differences in motion pre- and postfatigue. The objectives included the in vitro comparison of (1) the adjacent-level motion before and after instrumentation with PEEK and titanium rods and (2) the pre- and postfatigue motion at the instrumented level with PEEK and titanium rods. The results showed that the adjacent levels above the instrumentation caused increased flexion and extension with both PEEK and titanium rods. The postfatigue kinematic data showed that the motion at the instrumented level (L4-L5) increased significantly in both flexion and extension compared to prefatigue motion in titanium groups. However, there was no significant difference in motion between the pre- and postfatigue data in the PEEK

  3. Experimental Study of Loosening of Threaded Fasteners due to Dynamic Shear Loads

    NASA Astrophysics Data System (ADS)

    PAI, N. G.; HESS, D. P.

    2002-06-01

    This paper presents a study on loosening of threaded fasteners subjected to dynamic shear loads. A fundamental analysis of loosening reveals that a fastener can loosen at lower loads than previously expected due to localized slip at the contact surfaces. Four different loosening processes of a screw under different conditions of slip at the head and thread contact regions are identified. Experimental results illustrating these loosening processes are presented. In addition, the minimum dynamic shear force required to initiate loosening is determined experimentally.

  4. Using a guide template with a handpiece sleeve to locate the abutment screw position of a cement-retained implant restoration.

    PubMed

    Kang, Hye-Won; Lee, Du-Hyeong

    2015-09-01

    The existing techniques for drilling a screw access hole in cement-retained restorations are limited by inaccurate drill guidance and ineffective cooling of the drilling area. An approach for fabricating a guide template to provide screw retrievability using computer-aided design and computer-aided manufacturing (CAD/CAM) is described. A handpiece sleeve was made by 3-dimensional printing and incorporating it into a vacuum-formed template. The handpiece sleeve not only guides the head of the handpiece accurately but also enables the cooling water to reach the area of drilling directly. PMID:26013071

  5. Custom-made laser-welded titanium implant prosthetic abutment.

    PubMed

    Iglesia-Puig, Miguel A

    2005-10-01

    A technique to create an individually modified implant prosthetic abutment is described. An overcasting is waxed onto a machined titanium abutment, cast in titanium, and joined to it with laser welding. With the proposed technique, a custom-made titanium implant prosthetic abutment is created with adequate volume and contour of metal to support a screw-retained, metal-ceramic implant-supported crown. PMID:16198181

  6. THE INFLUENCE OF SCREW TYPE, ALLOY AND CYLINDER POSITION ON THE MARGINAL FIT OF IMPLANT FRAMEWORKS BEFORE AND AFTER LASER WELDING

    PubMed Central

    Castilio, Daniela; Pedreira, Ana Paula Ribeiro do Vale; Rossetti, Paulo Henrique Orlato; Rossetti, Leylha Maria Nunes; Bonachela, Wellington Cardoso

    2006-01-01

    Misfit at the abutment-prosthetic cylinder interface can cause loss of preload, leading to loosening or fracture of gold and titanium screws. Objectives: To evaluate the influence of screw type, alloy, and cylinder position on marginal fit of implant frameworks before and after laser welding. Methods: After Estheticone-like abutments were screwed to the implants, thirty plastic prosthetic cylinders were mounted and waxed-up to fifteen cylindrical bars. Each specimen had three interconnected prosthetic components. Five specimens were one-piece cast in titanium and five in cobalt-chromium alloy. On each specimen, tests were conducted with hexagonal titanium and slotted gold screws separately, performing a total of thirty tested screws. Measurements at the interfaces were performed using an optical microscope with 5 μm accuracy. After sectioning, specimens were laser welded and new measurements were obtained. Data were submitted to a four-way ANOVA and Tukey's multiple comparisons test (α =0.05). Results: Slotted and hexagonal screws did not present significant differences regarding to the fit of cylinders cast in titanium, either in one-piece casting framework or after laser welding. When slotted and hexagonal screws were tested on the cobalt-chromium specimens, statistically significant differences were found for the one-piece casting condition, with the slotted screws presenting better fit (24.13μm) than the hexagonal screws (27.93 μm). Besides, no statistically significant differences were found after laser welding. Conclusions: 1) The use of different metal alloys do exert influence on the marginal fit, 2) The slotted and hexagonal screws play the exclusive role of fixing the prosthesis, and did not improve the fit of cylinders, and 3) cylinder position did not affect marginal fit values. PMID:19089035

  7. Fixation Strength of Caudal Pedicle Screws after Posterior Lumbar Interbody Fusion with the Modified Cortical Bone Trajectory Screw Method

    PubMed Central

    Miwa, Toshitada; Yamashita, Tomoya; Kuroda, Yusuke; Ohwada, Tetsuo

    2016-01-01

    Study Design Clinical case series. Purpose In the posterior lumbar interbody fusion (PLIF) procedure in our institute, the cephalad screw trajectory follows a mediolateral and caudocephalad directed path according to the original cortical bone trajectory (CBT) method. However, the starting point of the caudal screw is at the medial border of the pedicle on an articular surface of the superior articular process, and the trajectory takes a mediolateral path parallel to the cephalad endplate. The incidence of caudal screw loosening after PLIF with this modified CBT screw method was investigated, and significant risk factors for caudal screw loosening were evaluated. Overview of Literature A biomechanical study of this modified caudal screw trajectory using the finite element method reported about a 20% increase in uniaxial yield pullout load compared with the traditional trajectory. However, there has been no clinical study concerning the fixation strength of this modified caudal screw trajectory. Methods The subjects were 193 consecutive patients who underwent single-level PLIF with modified CBT screw fixation. Caudal screw loosening was checked in computed tomography at 6 months after surgery, and screw loosening was defined as a radiolucency of 1 mm or more at the bone-screw interface. Results The incidence of caudal screw loosening after lumbosacral PLIF (46.2%) was significantly higher than that after floating PLIF (6.0%). No significant differences in sex, brand of the instruments, and diameter and length of the caudal screw were evident between patients with and without caudal screw loosening. Patients with caudal screw loosening were significantly older at the time of surgery than patients without caudal screw loosening. Conclusions Fixation strength of the caudal screw after floating PLIF with this modified CBT screw technique was sufficiently acceptable. Fixation strength after the lumbosacral procedure was not. PMID:27559442

  8. Influence of abutment materials on the implant-abutment joint stability in internal conical connection type implant systems

    PubMed Central

    Jo, Jae-Young; Yang, Dong-Seok; Huh, Jung-Bo; Heo, Jae-Chan; Yun, Mi-Jung

    2014-01-01

    PURPOSE This study evaluated the influence of abutment materials on the stability of the implant-abutment joint in internal conical connection type implant systems. MATERIALS AND METHODS Internal conical connection type implants, cement-retained abutments, and tungsten carbide-coated abutment screws were used. The abutments were fabricated with commercially pure grade 3 titanium (group T3), commercially pure grade 4 titanium (group T4), or Ti-6Al-4V (group TA) (n=5, each). In order to assess the amount of settlement after abutment fixation, a 30-Ncm tightening torque was applied, then the change in length before and after tightening the abutment screw was measured, and the preload exerted was recorded. The compressive bending strength was measured under the ISO14801 conditions. In order to determine whether there were significant changes in settlement, preload, and compressive bending strength before and after abutment fixation depending on abutment materials, one-way ANOVA and Tukey's HSD post-hoc test was performed. RESULTS Group TA exhibited the smallest mean change in the combined length of the implant and abutment before and after fixation, and no difference was observed between groups T3 and T4 (P>.05). Group TA exhibited the highest preload and compressive bending strength values, followed by T4, then T3 (P<.001). CONCLUSION The abutment material can influence the stability of the interface in internal conical connection type implant systems. The strength of the abutment material was inversely correlated with settlement, and positively correlated with compressive bending strength. Preload was inversely proportional to the frictional coefficient of the abutment material. PMID:25551010

  9. Angled Screw Channel: An Alternative to Cemented Single-Implant Restorations--Three Clinical Examples.

    PubMed

    Gjelvold, Björn; Sohrabi, Majid Melvin; Chrcanovic, Bruno Ramos

    2016-01-01

    This article presents three cases of single labially tilted implants restored with screw-retained single crowns. Individualized abutments with an angled screw channel were used to avoid an unesthetic vestibular access channel. This individualized abutment allows the dentist and dental technician to use the screw-retained restorations where a cemented reconstruction would otherwise have been needed. PMID:26757334

  10. Failure modes of Y-TZP abutments with external hex implant-abutment connection determined by fractographic analysis.

    PubMed

    Basílio, Mariana de Almeida; Delben, Juliana Aparecida; Cesar, Paulo Francisco; Rizkalla, Amin Sami; Santos Junior, Gildo Coelho; Arioli Filho, João Neudenir

    2016-07-01

    Yttria-stabilized tetragonal zirconia (Y-TZP) was introduced as ceramic implant abutments due to its excellent mechanical properties. However, the damage patterns for Y-TZP abutments are limited in the literature. Fractographic analyses can provide insights as to the failure origin and related mechanisms. The purpose of this study was to analyze fractured Y-TZP abutments to establish fractographic patterns and then possible reasons for failure. Thirty two prefabricated Y-TZP abutments on external hex implants were retrieved from a single-load-to failure test according to the ISO 14801. Fractographic analyses were conducted under polarized-light estereo and scanning electro microscopy. The predominant fracture pattern was abutment fracture at the connecting region. Classic fractographic features such as arrest lines, hackle, and twist hackle established that failure started where Y-TZP abutments were in contact with the retention screw edges. The abutment screw design and the loading point were the reasons for localized stress concentration and fracture patterns. PMID:26807772

  11. The effect of a positioning index on the biomechanical stability of tapered implant-abutment connections.

    PubMed

    Villarinho, Eduardo Aydos; Cervieri, André; Shinkai, Rosemary Sadami Arai; Grossi, Márcio Lima; Teixeira, Eduardo Rolim

    2015-04-01

    The biomechanical stability of the implant-abutment connection is critical for the success of implant-supported restorations. This study investigated the effect of a positioning index on the abutment screw preload values of tapered connection implants. Twenty Morse taper implants presenting an internal locking hex received 10 solid and 10 straight screw retained abutments for cemented single-crown restorations. Ten abutments had a positioning index to fit the internal locking hex of the implant (straight), and 10 were locked only by the implant taper (solid). The preload values for each abutment screw after a tightening torque were registered by strain gauges. Prosthetic crowns were placed on each abutment and subjected to mechanical cycling. Detorque forces were applied to each abutment and compared with the initial torque values. Data were statistically analyzed using Kolmogorov-Smirnov and Student t tests. The nonindexed group presented higher initial preload (6.05 N ± 0.95 N) compared with the indexed group (4.88 N ± 0.92 N; P < .05). After cycling, the nonindexed group exhibited less reduction of preload (13.84% ± 6.43%) compared with the indexed group (52.65% ± 14.81%; P < .01). Indexed tapered abutments for single-crown restorations might represent greater biomechanical risk under function. PMID:23641735

  12. The effect of movement on the holding power of screws in bone.

    PubMed

    Schatzker, J; Horne, J G; Sumner-Smith, G

    1975-09-01

    Movement between screw threads and bone inhibits bone formation, revascularization and remodeling of dead bone. Movement causes the screw to become enveloped by fibrous tissue in response to necrosis and resorption of adjacent dead cortical bone. This results in a radiologically discernible radiolucent "halo" about the screw, a certain sign of screw loosening. PMID:1157420

  13. A comparative study of gold UCLA-type and CAD/CAM titanium implant abutments

    PubMed Central

    Park, Ji-Man; Lee, Jai-Bong; Heo, Seong-Joo

    2014-01-01

    PURPOSE The aim of this study was to evaluate the interface accuracy of computer-assisted designed and manufactured (CAD/CAM) titanium abutments and implant fixture compared to gold-cast UCLA abutments. MATERIALS AND METHODS An external connection implant system (Mark III, n=10) and an internal connection implant system (Replace Select, n=10) were used, 5 of each group were connected to milled titanium abutment and the rest were connected to the gold-cast UCLA abutments. The implant fixture and abutment were tightened to torque of 35 Ncm using a digital torque gauge, and initial detorque values were measured 10 minutes after tightening. To mimic the mastication, a cyclic loading was applied at 14 Hz for one million cycles, with the stress amplitude range being within 0 N to 100 N. After the cyclic loading, detorque values were measured again. The fixture-abutment gaps were measured under a microscope and recorded with an accuracy of ±0.1 µm at 50 points. RESULTS Initial detorque values of milled abutment were significantly higher than those of cast abutment (P<.05). Detorque values after one million dynamic cyclic loadings were not significantly different (P>.05). After cyclic loading, detorque values of cast abutment increased, but those of milled abutment decreased (P<.05). There was no significant difference of gap dimension between the milled abutment group and the cast abutment group after cyclic loading. CONCLUSION In conclusion, CAD/CAM milled titanium abutment can be fabricated with sufficient accuracy to permit screw joint stability between abutment and fixture comparable to that of the traditional gold cast UCLA abutment. PMID:24605206

  14. Mechanical and biological complication rates of the modified lateral-screw-retained implant prosthesis in the posterior region: an alternative to the conventional Implant prosthetic system

    PubMed Central

    2016-01-01

    PURPOSE The modified lateral-screw-retained implant prosthesis (LSP) is designed to combine the advantages of screw- and cement-retained implant prostheses. This retrospective study evaluated the mechanical and biological complication rates of implant-supported single crowns (ISSCs) inserted with the modified LSP in the posterior region, and determined how these complication rates are affected by clinical factors. MATERIALS AND METHODS Mechanical complications (i.e., lateral screw loosening [LSL], abutment screw loosening, lateral screw fracture, and ceramic fracture) and biological complications (i.e., peri-implant mucositis [PM] and peri-implantitis) were identified from the patients' treatment records, clinical photographs, periapical radiographs, panoramic radiographs, and clinical indices. The correlations between complication rates and the following clinical factors were determined: gender, age, position in the jaw, placement location, functional duration, clinical crown-to-implant length ratio, crown height space, and the use of a submerged or nonsubmerged placement procedure. RESULTS Mechanical and biological complications were present in 25 of 73 ISSCs with the modified LSP. LSL (n=11) and PM (n=11) were the most common complications. The incidence of mechanical complications was significantly related to gender (P=.018). The other clinical factors were not significantly associated with mechanical and biological complication rates. CONCLUSION Within the limitations of this study, the incidence of mechanical and biological complications in the posterior region was similar for both modified LSP and conventional implant prosthetic systems. In addition, the modified LSP is amenable to maintenance care, which facilitates the prevention and treatment of mechanical and biological complications. PMID:27141260

  15. Effects of vertical interarch space and abutment height on stress distributions: a 3D finite element analysis.

    PubMed

    Naveau, Adrien; Renault, Patrick; Pierrisnard, Laurent

    2009-06-01

    This three dimensional Finite Element Analysis study investigated stress distribution and intensity in implants restored with cemented or screwed crown. Two parameters varied: interarch space and abutment height. Highest stresses occurred at the cervical area in all models. Stresses increased mainly with vertical interarch space highness, and secondarily with abutments shortness. From a mechanical point of view, bone and prosthetics components supporting cemented crowns were not as solicited as with screwed crowns. PMID:19645311

  16. DETAIL OF WEST ABUTMENT, SHOWING ABUTMENT (1922) AND WINGWALL AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF WEST ABUTMENT, SHOWING ABUTMENT (1922) AND WINGWALL AND GIRDER (1929). VIEW TO NORTHEAST. - Hassayampa Bridge, Spanning Hassayampa River at old U.S. Highway 80, Arlington, Maricopa County, AZ

  17. Power-Tool Adapter For T-Handle Screws

    NASA Technical Reports Server (NTRS)

    Deloach, Stephen R.

    1992-01-01

    Proposed adapter enables use of pneumatic drill, electric drill, electric screwdriver, or similar power tool to tighten or loosen T-handled screws. Notched tube with perpendicular rod welded to it inserted in chuck of tool. Notched end of tube slipped over screw handle.

  18. Design and testing of external fixator bone screws.

    PubMed

    Evans, M; Spencer, M; Wang, Q; White, S H; Cunningham, J L

    1990-11-01

    In external fixation, bone screw loosening still presents a major clinical problem. For this study, the design factors influencing the mechanics of the bone-screw interface were analysed and various experimental screws designed with the intention of maximizing the strength and stiffness of the inserted screw. Push-in, pull-out and bending tests were then carried out on the three experimental screws, and on two commercially available screws in both a synthetic material and in cadaveric bone; photoelastic tests on different screw threadforms were also performed. The results of the push-in and pull-out tests indicate that both the screw threadform and cutting head have a significant effect on the holding strength of the screw. The photoelastic tests show that most of the applied load is distributed over the first few threads closest to the load, and that the area between the thread crests is subjected to high shear stresses. PMID:2266740

  19. 17. DETAIL, WEST ABUTMENT, FROM NORTH, SHOWING CONCRETE ABUTMENT, L0 ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    17. DETAIL, WEST ABUTMENT, FROM NORTH, SHOWING CONCRETE ABUTMENT, L0 JOINT AND BEARING, AND BEARING SEAT OF WEST ABUTMENT - Glendale Road Bridge, Spanning Deep Creek Lake on Glendale Road, McHenry, Garrett County, MD

  20. Effect of Vertical Misfit on Screw Joint Stability of Implant-Supported Crowns

    NASA Astrophysics Data System (ADS)

    Assunção, Wirley Gonçalves; Delben, Juliana Aparecida; Tabata, Lucas Fernando; Barão, Valentim Adelino Ricardo; Gomes, Érica Alves

    2011-08-01

    The passive fit between prosthesis and implant is a relevant factor for screw joint stability and treatment success. The aim of this study was to evaluate the influence of vertical misfit in abutment-implant interface on preload maintenance of retention screw of implant-supported crowns. The crowns were fabricated with different abutments and veneering materials and divided into 5 groups ( n = 12): Gold UCLA abutments cast in gold alloy veneered with ceramic (Group I) and resin (Group II), UCLA abutments cast in titanium veneered with ceramic (Group III) and resin (Group IV), and zirconia abutments with ceramic veneering (Group V). The crowns were attached to implants by gold retention screws with 35-N cm insertion torque. Specimens were submitted to mechanical cycling up to 106 cycles. Measurements of detorque and vertical misfit in abutment-implant interface were performed before and after mechanical cycling. ANOVA revealed statistically significant difference ( P < 0.05) among groups for vertical misfit measured before and after mechanical cycling. The abutments cast in titanium exhibited the highest misfit values. Pearson correlation test did not demonstrate significant correlation ( P > 0.05) between vertical misfit and detorque value. It was concluded that vertical misfit did not influence torque maintenance and the abutments cast in titanium exhibited the highest misfit values.

  1. Minimally Invasive Technique for PMMA Augmentation of Fenestrated Screws

    PubMed Central

    Kogias, Evangelos; Sircar, Ronen; Krüger, Marie T.; Volz, Florian; Scheiwe, Christian; Hubbe, Ulrich

    2015-01-01

    Purpose. To describe the minimally invasive technique for cement augmentation of cannulated and fenestrated screws using an injection cannula as well as to report its safety and efficacy. Methods. A total of 157 cannulated and fenestrated pedicle screws had been cement-augmented during minimally invasive posterior screw-rod spondylodesis in 35 patients from January to December 2012. Retrospective evaluation of cement extravasation and screw loosening was carried out in postoperative plain radiographs and thin-sliced triplanar computed tomography scans. Results. Twenty-seven, largely prevertebral cement extravasations were detected in 157 screws (17.2%). None of the cement extravasations was causing a clinical sequela like a new neurological deficit. One screw loosening was noted (0.6%) after a mean follow-up of 12.8 months. We observed no cementation-associated complication like pulmonary embolism or hemodynamic insufficiency. Conclusions. The presented minimally invasive cement augmentation technique using an injection cannula facilitates convenient and safe cement delivery through polyaxial cannulated and fenestrated screws during minimally invasive screw-rod spondylodesis. Nevertheless, the optimal injection technique and design of fenestrated screws have yet to be identified. This trial is registered with German Clinical Trials DRKS00006726. PMID:26075297

  2. A technique for fabricating single screw-retained implant-supported interim crowns in conjunction with implant surgery.

    PubMed

    McRory, M Eric; Cagna, David R

    2014-06-01

    This article presents an intraoral technique for fabricating single screw-retained implant-supported interim crowns immediately after surgical implant placement in extraction sites. The technique may be used with any implant system that provides a provisional abutment or an open-tray impression coping that can be modified for use as a provisional abutment. PMID:24461941

  3. Fabrication of a screw-retained restoration avoiding the facial access hole: a clinical report.

    PubMed

    Garcia-Gazaui, Sabrina; Razzoog, Michael; Sierraalta, Marianella; Saglik, Berna

    2015-11-01

    Dental implant restorations may be either screw-retained or cemented onto an abutment. While each method has its advantages and disadvantages, cemented restorations are commonly used in the maxillary arch, usually because of esthetic concerns. Available bone in the anterior maxilla dictates the placement of the implant, which may result in a facially positioned screw-access opening. Still, a growing volume of literature states that periimplant soft tissues respond more favorably to screw-retained crowns than cement-retained crowns. This clinical report outlines a treatment with a new method of fabricating a custom abutment-crown combination for a screw-retained restoration. The technique allows the channel for the screw to be placed at an angle other than parallel to the implant body. In this case, the practitioner may choose either a screw-retained or cement-retained implant restoration, where previously only a cemented restoration was possible. PMID:26344192

  4. Mechanical behavior of provisional implant prosthetic abutments

    PubMed Central

    Serra-Pastor, Blanca; Roig-Vanaclocha, Ana; Román-Rodriguez, Juan-Luis; Fons-Font, Antonio

    2015-01-01

    Introduction: Implant-supported prostheses have to overcome a major difficulty presented by the morphology and esthetics of peri-implant tissues in the anterior sector. Diverse therapeutic techniques are used for managing the mucosa adjacent to the implant and the most noteworthy is immediate/deferred fixed provisionalization. Objectives: In vitro testing of strength and deformation of implant prosthetic abutments made from different materials (Titanium/PEEK/methacrylate). Material and Methods: Forty Sweden&Martina® implant prosthetic abutments (n=40) were divided into five groups: Group MP: methacrylate provisional abutments with machined titanium base; Group PP: Poly ether ether ketone (PEEK) provisional abutments; Group TP: titanium provisional abutments; Group TAD: titanium anti-rotational definitive abutments; Group TRD: titanium rotational definitive abutments. Their mechanical behavior under static loading was analyzed. Samples were examined under a microscope to determine the type of fracture produced. Results and Conclusions: Definitive anti-rotational titanium abutments and definitive rotational titanium abutments achieved the best mean compression strength, while PEEK resin provisional abutments obtained the lowest. The group that showed the greatest elastic deformation was the group of titanium provisional abutments. Key words:Immediate loading, immediate provisionalization, implant prosthetic abutment, definitive implant prosthetic abutment. PMID:25129253

  5. A three-dimensional finite element study on the stress distribution pattern of two prosthetic abutments for external hexagon implants

    PubMed Central

    Moreira, Wagner; Hermann, Caio; Pereira, Jucélio Tomás; Balbinoti, Jean Anacleto; Tiossi, Rodrigo

    2013-01-01

    Objective: The purpose of this study was to evaluate the mechanical behavior of two different straight prosthetic abutments (one- and two-piece) for external hex butt-joint connection implants using three-dimensional finite element analysis (3D-FEA). Materials and Methods: Two 3D-FEA models were designed, one for the two-piece prosthetic abutment (2 mm in height, two-piece mini-conical abutment, Neodent) and another one for the one-piece abutment (2 mm in height, Slim Fit one-piece mini-conical abutment, Neodent), with their corresponding screws and implants (Titamax Ti, 3.75 diameter by 13 mm in length, Neodent). The model simulated the single restoration of a lower premolar using data from a computerized tomography of a mandible. The preload (20 N) after torque application for installation of the abutment and an occlusal loading were simulated. The occlusal load was simulated using average physiological bite force and direction (114.6 N in the axial direction, 17.1 N in the lingual direction and 23.4 N toward the mesial at an angle of 75° to the occlusal plan). Results: The regions with the highest von Mises stress results were at the bottom of the initial two threads of both prosthetic abutments that were tested. The one-piece prosthetic abutment presented a more homogeneous behavior of stress distribution when compared with the two-piece abutment. Conclusions: Under the simulated chewing loads, the von Mises stresses for both tested prosthetic-abutments were within the tensile strength values of the materials analyzed which thus supports the clinical use of both prosthetic abutments. PMID:24932125

  6. Mechanical behavior of single-layer ceramized zirconia abutments for dental implant prosthetic rehabilitation

    PubMed Central

    Jiménez-Melendo, Manuel; Llena-Blasco, Oriol; Bruguera, August; Llena-Blasco, Jaime; Yáñez-Vico, Rosa-María; García-Calderón, Manuel; Vaquero-Aguilar, Cristina; Velázquez-Cayón, Rocío; Gutiérrez-Pérez, José-Luis

    2014-01-01

    Objectives: This study was undertaken to characterize the mechanical response of bare (as-received) and single-layer ceramized zirconia abutments with both internal and external connections that have been developed to enhanced aesthetic restorations. Material and Methods: Sixteen zirconia implant abutments (ZiReal Post®, Biomet 3i, USA) with internal and external connections have been analyzed. Half of the specimens were coated with a 0.5mm-thick layer of a low-fusing fluroapatite ceramic. Mechanical tests were carried out under static (constant cross-head speed of 1mm/min until fracture) and dynamic (between 100 and 400N at a frequency of 1Hz) loading conditions. The failure location was identified by electron microscopy. The removal torque of the retaining screws after testing was also evaluated. Results: The average fracture strength was above 300N for all the abutments, regardless of connection geometry and coating. In most of the cases (94%), failure occurred by abutment fracture. No significant differences were observed either in fatigue behavior and removal torque between the different abutment groups. Conclusions: Mechanical behavior of Zireal zirconia abutments is independent of the type of internal/external connection and the presence/absence of ceramic coating. This may be clinically valuable in dental rehabilitation to improve the aesthetic outcome of zirconia-based dental implant systems. Key words:Dental implant, zirconia, ceramic structure, mechanical properties. PMID:25674313

  7. Thoracic Aortic Stent-Graft Placement for Safe Removal of a Malpositioned Pedicle Screw

    SciTech Connect

    Hu Hongtao; Shin, Ji Hoon Hwang, Jae-Yeon; Cho, Young Jun; Ko, Gi-Young; Yoon, Hyun-Ki

    2010-10-15

    We describe a case of percutaneous placement of a thoracic aortic stent-graft for safe removal of a malpositioned pedicle screw in a 52-year-old man. The patient had undergone posterior thoracic spinal instrumentation for pyogenic spondylitis and spinal deformity 8 months previously. Follow-up CT images showed a malpositioned pedicle screw which was abutting the thoracic aorta at the T5 level. After percutaneous stent-graft placement, the malpositioned pedicle screw was safely and successfully removed.

  8. Effect of cyclic load on vertical misfit of prefabricated and cast implant single abutment

    PubMed Central

    DE JESUS TAVAREZ, Rudys Rodolfo; BONACHELA, Wellington Cardoso; XIBLE, Anuar Antônio

    2011-01-01

    Objective The purpose of this in vitro study was to evaluate misfit alterations at the implant/abutment interface of external and internal connection implant systems when subjected to cyclic loading. Material and Methods Standard metal crowns were fabricated for 5 groups (n=10) of implant/abutment assemblies: Group 1, external hexagon implant and UCLA cast-on premachined abutment; Group 2, internal hexagon implant and premachined abutment; Group 3, internal octagon implant and prefabricated abutment; Group 4, external hexagon implant and UCLA cast-on premachined abutment; and Group 5, external hexagon implant and Ceraone abutment. For groups 1, 2, 3 and 5, the crowns were cemented on the abutments and in group 4 crowns were screwed directly on the implant. The specimens were subjected to 500,000 cycles at 19.1 Hz of frequency and non-axial load of 133 N in a MTS 810 machine. The vertical misfit (μm) at the implant/abutment interface was evaluated before (B) and after (A) application of the cyclic loading. Data were analyzed statistically by using two-away ANOVA and Tukey’s post-hoc test (p<0.05). Results Before loading values showed no difference among groups 2 (4.33±3.13), 3 (4.79±3.43) and 5 (3.86±4.60); between groups 1 (12.88±6.43) and 4 (9.67±3.08), and among groups 2, 3 and 4. However, groups 1 and 4 were significantly different from groups 2, 3 and 5. After loading values of groups 1 (17.28±8.77) and 4 (17.78±10.99) were significantly different from those of groups 2 (4.83±4.50), 3 (8.07±4.31) and 5 (3.81±4.84). There was a significant increase in misfit values of groups 1, 3 and 4 after cyclic loading, but not for groups 2 and 5. Conclusion The cyclic loading and type of implant/abutment connection may develop a role on the vertical misfit at the implant/abutment interface. PMID:21437464

  9. Cement leakage in pedicle screw augmentation: a prospective analysis of 98 patients and 474 augmented pedicle screws.

    PubMed

    Mueller, Jan U; Baldauf, Joerg; Marx, Sascha; Kirsch, Michael; Schroeder, Henry W S; Pillich, Dirk T

    2016-07-01

    OBJECTIVE Loosening and pullout of pedicle screws are well-known problems in pedicle screw fixation surgery. Augmentation of pedicle screws with bone cement, first described as early as 1975, increases the pedicle-screw interface and pullout force in osteoporotic vertebrae. The aim of the present study was to identify cement leakage and pulmonary embolism rates in a large prospective single-center series of pedicle screw augmentations. METHODS All patients who underwent cement-augmented pedicle screw placement between May 2006 and October 2010 at the authors' institution were included in this prospective cohort study. Perivertebral cement leakage and pulmonary cement embolism were evaluated with a CT scan of the area of operation and with a radiograph of the chest, respectively. RESULTS A total of 98 patients underwent placement of cement-augmented pedicle screws; 474 augmented screws were inserted in 237 vertebrae. No symptomatic perivertebral cement leakage or symptomatic pulmonary cement embolism was observed, but asymptomatic perivertebral cement leakage was seen in 88 patients (93.6%) and in 165 augmented vertebrae (73.3%). Cement leakage most often occurred in the perivertebral venous system. Clinically asymptomatic pulmonary cement embolism was found in 4 patients (4.1%). CONCLUSIONS Perivertebral cement leakage often occurs in pedicle screw augmentation, but in most cases, it is clinically asymptomatic. Cement augmentation should be performed under continuous fluoroscopy to avoid high-volume leakage. Alternative strategies, such as use of expandable screws, should be examined in more detail for patients at high risk of screw loosening. PMID:26943258

  10. Catalysts of plant cell wall loosening

    PubMed Central

    Cosgrove, Daniel J.

    2016-01-01

    The growing cell wall in plants has conflicting requirements to be strong enough to withstand the high tensile forces generated by cell turgor pressure while selectively yielding to those forces to induce wall stress relaxation, leading to water uptake and polymer movements underlying cell wall expansion. In this article, I review emerging concepts of plant primary cell wall structure, the nature of wall extensibility and the action of expansins, family-9 and -12 endoglucanases, family-16 xyloglucan endotransglycosylase/hydrolase (XTH), and pectin methylesterases, and offer a critical assessment of their wall-loosening activity PMID:26918182

  11. Pullout performance comparison of pedicle screws based on cement application and design parameters.

    PubMed

    Tolunay, Tolga; Başgül, Cemile; Demir, Teyfik; Yaman, Mesut E; Arslan, Arslan K

    2015-11-01

    Pedicle screws are the main fixation devices for certain surgeries. Pedicle screw loosening is a common problem especially for osteoporotic incidents. Cannulated screws with cement augmentation are widely used for that kind of cases. Dual lead dual cored pedicle screw has already given promising pullout values without augmentation. This study concentrates on the usage of dual lead dual core with cement augmentation as an alternative to cannulated and standard pedicle screws with cement augmentation. Five groups (dual lead dual core, normal pedicle screw and cannulated pedicle screw with augmentation, normal pedicle screw, dual lead dual cored pedicle screw) were designed for this study. Healthy bovine vertebrae and synthetic polyurethane foams (grade 20) were used as embedding test medium. Test samples were prepared in accordance with surgical guidelines and ASTM F543 standard testing protocols. Pullout tests were conducted with Instron 3300 testing frame. Load versus displacement values were recorded and maximum pullout loads were stated. The dual lead dual cored pedicle screw with poly-methyl methacrylate augmentation exhibited the highest pullout values, while dual lead dual cored pedicle screw demonstrated similar pullout strength as cannulated pedicle screw and normal pedicle screw with poly-methyl methacrylate augmentation. The dual lead dual cored pedicle screw with poly-methyl methacrylate augmentation can be used for osteoporotic and/or severe osteoporotic patients according to its promising results on animal cadaver and synthetic foams. PMID:26503840

  12. Intramedullary fixation with screwed, conical stems--unsolicited results from animal experiments.

    PubMed

    van Loon, P J; Weinans, H; Huiskes, R; de Groot, K; Slooff, T J

    1992-01-01

    For the purpose of studying bone remodeling around prostheses, a segmental replacement for the goat tibia was designed, using a conical, screw-threaded, hydroxyapatite-coated stem for fixation. Eight goats were provided with the implant, seven of which loosened within 10 days post-operatively, displaying progressive radiolucency and gross rotational motion. The eighth one also loosened radiographically, but developed a stabilizing callus bridge to prevent motion. A second design of similar shape and coating, but lacking the screw threads, was designed and also applied in eight animals. In this case, no loosening occurred in the first 6 weeks post-operatively. It is concluded that the application of screwed intramedullary stems for prosthetic fixation is not a viable concept, because the threads prevent the stem from subsiding and restabilizing when minor initial interface stress-relaxation and remodeling has occurred. PMID:10149986

  13. Influence of Prosthetic Screw Material on Joint Stability in Passive and Non-Passive Implant-Supported Dentures

    PubMed Central

    Spazzin, Aloísio Oro; Henriques, Guilherme Elias Pessanha; de Arruda Nóbilo, Mauro Antônio; Consani, Rafael Leonardo Xediek; Correr-Sobrinho, Lourenço; Mesquita, Marcelo Ferraz

    2009-01-01

    Objectives: This study evaluated the influence of prosthetic screw material on joint stability in implantsupported dentures at two levels of fit. Methods: Ten mandibular implant-supported dentures were fabricated. Twenty cast models were fabricated using these dentures. Four groups (n=10) were tested, according to the vertical fit of the dentures [passive and non-passive] and prosthetic screw materials [titanium (Ti) or gold (Au) alloy]. The one-screw test was performed to quantify the vertical misfits using an optic microscope. The loosening torque for the prosthetic screws was measured 24 hours after the tightening torque (10 Ncm) using a digital torque meter. Data were analyzed by two-way ANOVA and Tukey’s test (α=0.05). Results: Overall, dentures with passive fit and Ti screws resulted in significantly higher loosening torque of the prosthetic screws (p<0.05). No significant interaction was found between fit level and screw material (p=0.199). The prosthetic screw material and fit of implant-supported dentures have an influence on screw joint stability. Ti screws presented higher joint stability than Au screws and minimum of misfit should be found clinically to improve the mechanical behavior of the screw joint. PMID:20148135

  14. Spline-Screw Payload-Fastening System

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1994-01-01

    Payload handed off securely between robot and vehicle or structure. Spline-screw payload-fastening system includes mating female and male connector mechanisms. Clockwise (or counter-clockwise) rotation of splined male driver on robotic end effector causes connection between robot and payload to tighten (or loosen) and simultaneously causes connection between payload and structure to loosen (or tighten). Includes mechanisms like those described in "Tool-Changing Mechanism for Robot" (GSC-13435) and "Self-Aligning Mechanical and Electrical Coupling" (GSC-13430). Designed for use in outer space, also useful on Earth in applications needed for secure handling and secure mounting of equipment modules during storage, transport, and/or operation. Particularly useful in machine or robotic applications.

  15. A new Brånemark single tooth abutment: handling and early clinical experiences.

    PubMed

    Andersson, B; Odman, P; Carlsson, L; Brånemark, P I

    1992-01-01

    A new prosthetic concept, today available under the name CeraOne, for single tooth replacement with the Brånemark system is described. This concept is characterized by a new design of the prefabricated components. A mechanical torque driver is used together with a gold screw and a special counter-torque device to ensure that the screw is tightened in an optimal manner to resist screw loosening and only transmit minor stress to the fixture interface. Another characteristic is the use of a prefabricated cap of sintered aluminum oxide as the basis for the ceramic crown. The crown is cemented to provide better esthetic possibilities even in situations of somewhat unfavorable fixture placement. PMID:1398817

  16. Comparison of the fracture resistance of dental implants with different abutment taper angles.

    PubMed

    Wang, Kun; Geng, Jianping; Jones, David; Xu, Wei

    2016-06-01

    To investigate the effects of abutment taper angles on the fracture strength of dental implants with TIS (taper integrated screwed-in) connection. Thirty prototype cylindrical titanium alloy 5.0mm-diameter dental implants with different TIS-connection designs were divided into six groups and tested for their fracture strength, using a universal testing machine. These groups consisted of combinations of 3.5 and 4.0 mm abutment diameter, each with taper angles of 6°, 8° or 10°. 3-Dimensional finite element analysis (FEA) was also used to analyze stress states at implant-abutment connection areas. In general, the mechanical tests found an increasing trend of implant fracture forces as the taper angle enlarged. When the abutment diameter was 3.5 mm, the mean fracture forces for 8° and 10° taper groups were 1638.9 N ± 20.3 and 1577.1 N ± 103.2, respectively, both larger than that for the 6° taper group of 1475.0 N ± 24.4, with the largest increasing rate of 11.1%. Furthermore, the difference between 8° and 6° taper groups was significant, based on Tamhane's multiple comparison test (P<0.05). In 4.0 mm-diameter abutment groups, as the taper angle was enlarged from 6° to 8° and 10°, the mean fracture value was increased from 1066.7 N ± 56.1 to 1241.4 N ± 6.4 and 1419.3 N ± 20.0, with the largest increasing rate of 33.1%, and the differences among the three groups were significant (P<0.05). The FEA results showed that stress values varied in implants with different abutment taper angles and supported the findings of the static tests. In conclusion, increases of the abutment taper angle could significantly increase implant fracture resistance in most cases established in the study, which is due to the increased implant wall thickness in the connection part resulting from the taper angle enlargement. The increasing effects were notable when a thin implant wall was present to accommodate wide abutments. PMID:27040208

  17. An in vivo assessment of the effects of using different implant abutment occluding materials on implant microleakage and the peri-implant microbiome

    NASA Astrophysics Data System (ADS)

    Rubino, Caroline

    Microleakage may be a factor in the progression of peri-implant pathology. Microleakage in implant dentistry refers to the passage of bacteria, fluids, molecules or ions between the abutment-implant interface to and from the surrounding periodontal tissues. This creates a zone of inflammation and reservoir of bacteria at the implant-abutment interface. Bone loss typically occurs within the first year of abutment connection and then stabilizes. It has not yet been definitively proven that the occurrence of microleakage cannot contribute to future bone loss or impede the treatment of peri-implant disease. Therefore, strategies to reduce or eliminate microleakage are sought out. Recent evidence demonstrates that the type of implant abutment channel occluding material can affect the amount of microleakage in an in vitro study environment. Thus, we hypothesize that different abutment screw channel occluding materials will affect the amount of observed microleakage, vis-a-vis the correlation between the microflora found on the abutment screw channel occluding material those found in the peri-implant sulcus. Additional objectives include confirming the presence of microleakage in vivo and assessing any impact that different abutment screw channel occluding materials may have on the peri-implant microbiome. Finally, the present study provides an opportunity to further characterize the peri-implant microbiome. Eight fully edentulous patients restored with at dental implants supporting screw-retained fixed hybrid prostheses were included in the study. At the initial appointment (T1), the prostheses were removed and the implants and prostheses were cleaned. The prostheses were then inserted with polytetrafluoroethylene tape (PTFE, TeflonRTM), cotton, polyvinyl siloxane (PVS), or synthetic foam as the implant abutment channel occluding material and sealed over with composite resin. About six months later (T2), the prostheses were removed and the materials collected. Paper

  18. Prediction at long-term condyle screw fixation of temporomandibular joint implant: A numerical study.

    PubMed

    Ramos, A; Duarte, R J; Mesnard, M

    2015-05-01

    The fixation of commercial temporomandibular joint (TMJ) implant is accomplished by using screws, which, in some cases, can lead to loosening of the implant. The aim of this study was to predict the evolution of fixation success of a TMJ. Numerical models using a Christensen TMJ implant were developed to analyze strain distributions in the adjacent mandibular bone. The geometry of a human mandible was developed based on computed tomography (CT) scans from a cadaveric mandible on which a TMJ implant was subsequently placed. In this study, the five most important muscle forces acting were applied and the anatomical conditions replicated. The evolution of fixation was defined according to bone response methodology focused in strain distribution around the screws. Strain and micromotions were analyzed to evaluate implant stability, and the evolution process conduct at three different stages: start with all nine screws in place (initial stage); middle stage, with three screws removed (middle stage), and end stage, with only three screws in place (final stage). With regard to loosening, the implant success fixation changed the strains in the bone between 21% and 30%, when considering the last stage. The most important screw positions were #1, #7, and #9. It was observed that, despite the commercial Christensen TMJ implant providing nine screw positions for fixation, only three screws were necessary to ensure implant stability and fixation success. PMID:25819477

  19. Management of a complication with a fractured zirconia implant abutment in the esthetic zone.

    PubMed

    Joda, Tim; Brägger, Urs

    2015-01-01

    Technical complications in implant prosthetic cases represent a major challenge in dentistry. This case report describes minimally invasive management to recover an implant with a fractured remnant of a zirconia abutment, including provisional rehabilitation during a sequential treatment protocol in the esthetic zone. A patient was treated with a screw-retained one-piece implant-supported reconstruction made of a customized zirconia abutment with direct ceramic veneering in the maxillary right central incisor position. During the prosthetic try-in, a fracture in the apical portion of the abutment was evident. The first rescue attempt led to fracture of the retrieval instrument. Immediately, an individualized wired construction was applied to bond the existing fractured reconstruction to the neighboring teeth to maintain the peri-implant mucosal architecture. Because the implant screw canal was blocked, a customized round bur had to be manufactured and was placed in the implant axis with a specific bracket tool from the service set to protect the interior implant threads. Then, the drills of the service set were guided by the newly created access to remove the fractured remnants. The implant screw was retapped and the area rinsed with chlorhexidine solution. All remnants were removed without the need for surgical intervention. Neither the implant connection nor the bone-to-implant interface was damaged. The stepwise treatment approach with the customized round bur combined with the system-specific drills of the service set saved the blocked implant so that the patient could be successfully rehabilitated with a new implant reconstruction. PMID:25615928

  20. Computational simulations of stress shielding and bone resorption around existing and computer-designed orthopaedic screws.

    PubMed

    Gefen, A

    2002-05-01

    Failure of an orthopaedic fixation due to stress shielding and consequent screw loosening is a major concern among surgeons: the loosened screws could not only interfere with the healing process but also endanger adjacent anatomical structures. In this study, the effect of the screw's engineering design (dimensions, profile shape and material properties) on the load sharing with adjacent bone and consequent bone resorption was tested, using a set of two-dimensional computational (finite element) models. An algorithm simulating local bone adaptation to strain energy density (SED) mechanical stimuli was developed and used to evaluate the biomechanical performances of different commercial screws. Two new designs, a 'graded-stiffness' composite screw, with a reduced-stiffness titanium core and outer polymeric threads, and an active-compression hollow screw that generates compressive stresses on the surrounding bone, were also evaluated. A dimensionless set of stress transfer parameters (STPs) were utilised for ranking the performances of the different screws according to the expected screw-bone load sharing and its evolution with adaptation of the surrounding tissue. The results indicated that commercial wide (6 mm thread diameter) trapezoidal and rectangular screw profiles have superior biomechanical compatibility with bone (i.e. predicted to be stable after 2 years). The graded-stiffness and active-compression screws provided the best biomechanical performances: bone loading around them was predicted to decrease by no more than 15% after 3 years, compared with a decrease of 55-70% in bone loading around commercially available screws. Computer simulations of bone adaptation around orthopaedic screws are demonstrated to be effective means for objective and quantitative evaluation of the biomechanical aspects of implant-tissue compatibility. PMID:12195978

  1. Effect of implant connection and restoration design (screwed vs. cemented) in reliability and failure modes of anterior crowns.

    PubMed

    Freitas, Amilcar C; Bonfante, Estevam A; Rocha, Eduardo P; Silva, Nelson R F A; Marotta, Leonard; Coelho, Paulo G

    2011-08-01

    The mechanical performance of cemented or screw-retained implant-supported crowns with an internal or external configuration is yet to be understood. This in vitro study evaluated the effect of screw-retained and cement-retained prostheses on internal and external implant-abutment connections. Thereby, the reliability and failure modes of crowns were investigated. Eighty-four implants (Emfils; Colosso Evolution system) were divided into four groups (n=21 each): screw-retained and internal connection (Si), screw-retained and external connection (Se), cement-retained and internal connection (Ci), and cement-retained and external connection (Ce). Ti-6Al-4V abutments were torqued (30 Ncm) to the implants, and maxillary central incisor metal crowns were torqued (30 Ncm) or cemented (Rely X Unicem; 3M-ESPE) and subjected to accelerated life-testing in water. Use-level probability Weibull curves and reliability for 50,000 cycles at 150 N were calculated. The β values for Si (1.72), Se (1.50), Ci (1.34), and Ce (1.77) groups indicated that fatigue/damage accumulation accelerated their failure. The Ci group presented the highest reliability, the Se group presented the lowest reliability, and Si and Ce groups presented intermediate reliability. Screw-retained restorations presented mainly abutment fracture. Cement-retained restorations resulted in failures of the screw in the Ce group, but implant/screw fracture in the Ci group. PMID:21726295

  2. Biomechanical and Histological Evaluation of Roughened Surface Titanium Screws Fabricated by Electron Beam Melting

    PubMed Central

    Yang, Jun; Cai, Hong; Lv, Jia; Zhang, Ke; Leng, Huijie; Wang, Zhiguo; Liu, Zhongjun

    2014-01-01

    Background Various fabrication methods are used to improve the stability and osseointegration of screws within the host bone. The aim of this study was to investigate whether roughened surface titanium screws fabricated by electron beam melting can provide better stability and osseointegration as compared with smooth titanium screws in sheep cervical vertebrae. Methods Roughened surface titanium screws, fabricated by electron beam melting, and conventional smooth surface titanium screws were implanted into sheep for 6 or 12 weeks (groups A and B, respectively). Bone ingrowth and implant stability were assessed with three-dimensional imaging and reconstruction, as well as histological and biomechanical tests. Results No screws in either group showed signs of loosening. Fibrous tissue formation could be seen around the screws at 6 weeks, which was replaced with bone at 12 weeks. Bone volume/total volume, bone surface area/bone volume, and the trabecular number were significantly higher for a define region of interest surrounding the roughened screws than that surrounding the smooth screws at 12 weeks. Indeed, for roughened screws, trabecular number was significantly higher at 12 weeks than at 6 weeks. On mechanical testing, the maximum pullout strength was significantly higher at 12 weeks than at 6 weeks, as expected; however, no significant differences were found between smooth and roughened screws at either time point. The maximum torque to extract the roughened screws was higher than that required for the smooth screws. Conclusions Electron beam melting is a simple and effective method for producing a roughened surface on titanium screws. After 12 weeks, roughened titanium screws demonstrated a high degree of osseointegration and increased torsional resistance to extraction over smooth titanium screws. PMID:24788866

  3. Optimizing the biomechanical compatibility of orthopedic screws for bone fracture fixation.

    PubMed

    Gefen, A

    2002-06-01

    Progressive loosening of bone fixation screws is a well-documented phenomenon, induced by stress shielding and subsequent adaptive bone remodeling which results in bone loss around the screw. A set of two-dimensional computational (finite element) models was developed in order to test the effect of various engineering designs of fixation screws on the predicted screw-bone stress transfer, and consequently, on the biomechanical conditions for osteosynthesis. A dimensionless set of stress-transfer parameters (STP) was developed to quantify the screw-bone load sharing, enabling a convenient rating to be given of the biomechanical compatibility of practically any given screw design according to the nature of the simulated mechanical interaction. The results indicated that newly proposed screw designs, i.e. a "graded-stiffness" composite screw with a reduced-stiffness-titanium core and outer polymeric threads and an "active-compression" hollow screw which generates compressive stresses on the surrounding bone, are expected to provide significantly better biomechanical performances in terms of the STP criteria, compared with conservative screw designs. Accordingly, the present work demonstrates that finite element computer simulations can be used as a powerful tool for design and evaluation of bone screws, including geometrical features, material characteristics and even coatings. PMID:12052361

  4. Effect of cement fill ratio in loosening of hip implants

    PubMed Central

    Gunn, Elizabeth; Gundapaneni, Dinesh; Goswami, Tarun

    2012-01-01

    Femoral loosening is one of the most prevalent causes of revision orthopedic surgeries. Cement mantle thickness has been directly correlated with femoral loosening. If the mantle is too thick, there is an increased risk of radiolucent lines and inconsistent densities. Also, the more bone that is reamed out during the procedure can lead to instability, especially if the quality of the bone is compromised due to osteoporosis. Too thin of a mantle can lead to a higher probability for cement fracture, loosening the prosthetic even further. This study has shown that there is an ideal thickness range between two to five that should be kept. From radiographic images one can measure the thickness of the cement mantle showing the loosening characteristics. PMID:23507806

  5. WILLIAM SEAL USING A HAMMER TO LOOSEN A BEARDSLEY AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    WILLIAM SEAL USING A HAMMER TO LOOSEN A BEARDSLEY AND PIPER ROTOMOLD CORMATIC CORE FROM ITS CORE BOX. - Southern Ductile Casting Company, Core Making, 2217 Carolina Avenue, Bessemer, Jefferson County, AL

  6. Implant Fixture Heat Transfer During Abutment Preparation.

    PubMed

    Aleisa, Khalil; Alkeraidis, Abdullah; Al-Dwairi, Ziad Nawaf; Altahawi, Hamdi; Lynch, Edward

    2015-06-01

    The purpose of the study was to evaluate the effect of water flow rate on the heat transmission in implants during abutment preparation using a diamond bur in a high-speed dental turbine. Titanium-alloy abutments (n = 32) were connected to a titanium-alloy implant embedded in an acrylic resin within a water bath at a controlled temperature of 37°C. The specimens were equally distributed into 2 groups (16 each) according to the water flow rate used during the preparation phase. Group 1 had a water flow rate of 24 mL/min, and group 2 had a water flow rate of 40 mL/min. Each abutment was prepared in the axial plane for 1 minute and in the occlusal plane for 1 minute with a coarse tapered diamond bur using a high-speed dental handpiece. Thermocouples embedded at the cervix of the implant surface were used to record the temperature of heat transmission from the abutment preparation. Heat generation was measured at 3 distinct times (immediately and 30 seconds and 60 seconds after the end of preparation). Statistical analyses were carried out using 2-way analysis of variance and the Student t test. Water flow rates (24 mL vs 40 mL) and time interval had no statistically significant effect on the implant's temperature change during the abutment preparation stage (P = .431 and P = .064, respectively). Increasing the water flow rate from 24 to 40 mL/min had no influence on the temperature of the implant fixture recorded during preparation of the abutment. PMID:23713452

  7. Cemented and screw-retained implant-supported single-tooth restorations in the molar mandibular region: A retrospective comparison study after an observation period of 1 to 4 years

    PubMed Central

    Peñarrocha-Diago, Miguel; Pradíes, Guillermo; Sola-Ruiz, María-Fernanda; Agustín-Panadero, Rubén

    2015-01-01

    Objectives: The aim of this study was to evaluate the survival and compare the appearance of different mechanical and biological complications, in screw-retained and cemented-retained single-tooth implant-supported restorations localized in the molar mandibular region, over a period of 1 to 4 years. Material and Methods: A retrospective study was carried out with a total of eighty implant-supported restorations, which were placed in eighty patients for prosthetic rehabilitation of a mandibular molar. Forty patients were rehabilitated with a cemented-retained restoration and the other forty with a screw-retained restoration. The presence of the following complications was recorded for both types of prostheses: Fractures of the ceramic veneering, loosening screws, mucositis and peri-implantitis. Debonding of the restoration was analyzed in the cemented-retained restoration group. The clinical survival of crowns was analyzed with a Kaplan-Meier test and the clinical complications were compared, using a Student t test and Log-rank test. Results: 27 patients registered some complication. The average rate of complications was 37,5% for cemented-retained restorations and 30% for screw-retained restorations. The complications more common in the cemented-retained restoration were the presence of mucositis (14,87%), while in the screw-retained restorations was the loosening screw (20%). Student t test and Log-Rank test found significant differences (p=0,001) between the screw loosening and presence of mucositis. Conclusions: The cemented-retained restorations seem to prevent screw loosening, but the presence of cement seem to increase the complications around the soft tissues, however in the screw-retained restorations the presence of mucositis and peri-implantitis are lower than cemented-retained restorations. The incidence of fracture of ceramic veneering was similar in both groups. Key words:Screw-retained restorations, cemented-retained restorations, screw loosening

  8. 11. Southern bridge abutment and arches, taken from old bridge ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. Southern bridge abutment and arches, taken from old bridge abutment looking south. - Presumpscot Falls Bridge, Spanning Presumptscot River at Allen Avenue extension, 0.75 mile west of U.S. Interstate 95, Falmouth, Cumberland County, ME

  9. Simultaneous Use of Both Bilateral Intralaminar and Pedicle Screws for C2 Stabilization.

    PubMed

    Tarukado, Kiyoshi; Tono, Osamu; Doi, Toshio

    2015-10-01

    Four patients underwent stabilization surgery using both bilateral C2 pedicle screw (PS) and intralaminar screw (LS). Neural and vascular injury resulting from incorrect screw placement was assessed using computed tomography (CT). The evaluation of bone union was assessed by lateral flexion-extension X-ray films and CT. The symptoms were improved in all patients. There were no intraoperative complications. Furthermore, there were no cases of neurological worsening or vascular injury from incorrect screw placement. Failure of instrumentation or screw loosening during the follow-up period did not occur in any of the patients. All cases had accomplished bone union at the final follow-up. Theoretically, the stabilization technique using both bilateral C2 PS and LS at the same time can provide more stability than any other single technique. Simultaneous use of both bilateral C2 PS and LS is potentially a good choice for surgical repair. PMID:26435800

  10. Detail, north abutment, from southeast, showing original squared cut stone ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail, north abutment, from southeast, showing original squared cut stone masonry abutment and portion of non-original concrete apron at west base of abutment - Castle Garden Bridge, Township Route 343 over Bennetts Branch of Sinnemahoning Creek, Driftwood, Cameron County, PA

  11. 21 CFR 872.3630 - Endosseous dental implant abutment.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Endosseous dental implant abutment. 872.3630... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3630 Endosseous dental implant abutment. (a) Identification. An endosseous dental implant abutment is a premanufactured prosthetic...

  12. 21 CFR 872.3630 - Endosseous dental implant abutment.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Endosseous dental implant abutment. 872.3630... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3630 Endosseous dental implant abutment. (a) Identification. An endosseous dental implant abutment is a premanufactured prosthetic...

  13. 21 CFR 872.3630 - Endosseous dental implant abutment.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Endosseous dental implant abutment. 872.3630... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3630 Endosseous dental implant abutment. (a) Identification. An endosseous dental implant abutment is a premanufactured prosthetic...

  14. 21 CFR 872.3630 - Endosseous dental implant abutment.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Endosseous dental implant abutment. 872.3630... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3630 Endosseous dental implant abutment. (a) Identification. An endosseous dental implant abutment is a premanufactured prosthetic...

  15. 21 CFR 872.3630 - Endosseous dental implant abutment.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Endosseous dental implant abutment. 872.3630... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3630 Endosseous dental implant abutment. (a) Identification. An endosseous dental implant abutment is a premanufactured prosthetic...

  16. Laboratory technique for coloring titanium abutments to improve esthetics.

    PubMed

    Wadhwani, Chandur P K; O'Brien, Richard; Kattadiyil, Mathew T; Chung, Kwok-Hung

    2016-04-01

    Titanium alloys are used for implant abutments onto which prostheses are attached. One major disadvantage of titanium abutments is their esthetics; the metallic gray color may show through the restorative material or through surrounding tissues. A laboratory technique using readily available household items is described that can alter the abutment color by anodization. PMID:26723096

  17. Implant-abutment connections: influence of the design on the microgap and their fatigue and fracture behavior of dental implants.

    PubMed

    Gil, F J; Herrero-Climent, M; Lázaro, P; Rios, J V

    2014-07-01

    Microgap between implant and abutment can produce biological and mechanical problems such as peri-implantitis and/or fatigue failures. The aim of this study was to evaluate microgap size and fatigue behavior of external and internal connections. In both systems the torque to tighten the abutment screw of single crown abutments was 45 Ncm. Fifty implants for each connection type were studied. One subgroup (n = 5) was used by the observation and evaluation of the microgap, other (n = 5) was tested for fracture strength and the other (n = 40) was subjected to dynamic loading. The internal connection presents a lower microgap than the external ones. From fatigue results, the external hexagon interface showed superior result compared to the internal hexagon interfaces. The tolerances in the internal connections are better and favour the fatigue behavior but this factor alone is not sufficient to improve the fatigue response in relation to the external connections when the screw is subjected at the same torque. The external system presents a higher value of the area than the internal and it produces a better load distribution. Microgaps and mechanical properties are very important for the long-term behavior of the dental implants and these aspects should be known by the implantologists. PMID:24719176

  18. Clinical Use of Laser-Microtextured Abutments: A Case Series.

    PubMed

    Shapoff, Cary A; Babushkin, Jeffrey A; Wohl, David J

    2016-01-01

    This article discusses the clinical use of laser-microtextured abutments on dental implant restorations. Four cases are presented, each using one of the four commercially available laser-microtextured abutment styles. Numerous preclinical and clinical studies have shown the positive effects of laser microtexturing on the implant platform in limiting crestal bone loss and benefiting soft tissue stability. Other histologic studies of laser microtexturing on the implant abutment have demonstrated the ability of this specific feature to block epithelial downgrowth and provide a functional connective tissue attachment to the abutment surface. Other abutment designs, styles, and materials have only demonstrated a soft tissue seal with epithelial adhesion and a circular ring of connective tissue fibers around the abutment without direct contact. This article presents clinical and radiographic case examples from a private practice perspective on the longterm successful use of microtextured abutments with respect to crestal bone levels, exceptional soft tissue health, and stability with minimal sulcular depth. PMID:27560683

  19. Comparison of the bending performance of solid and cannulated spinal pedicle screws using finite element analyses and biomechanical tests.

    PubMed

    Shih, Kao-Shang; Hsu, Ching-Chi; Hou, Sheng-Mou; Yu, Shan-Chuen; Liaw, Chen-Kun

    2015-09-01

    Spinal pedicle screw fixations have been used extensively to treat fracture, tumor, infection, or degeneration of the spine. Cannulated spinal pedicle screws with bone cement augmentation might be a useful method to ameliorate screw loosening. However, cannulated spinal pedicle screws might also increase the risk of screw breakage. Thus, the purpose of this study was to investigate the bending performance of different spinal pedicle screws with either solid design or cannulated design. Three-dimensional finite element models, which consisted of the spinal pedicle screw and the screw's hosting material, were first constructed. Next, monotonic and cyclic cantilever bending tests were both applied to validate the results of the finite element analyses. Finally, both the numerical and experimental approaches were evaluated and compared. The results indicated that the cylindrical spinal pedicle screws with a cannulated design had significantly poorer bending performance. In addition, conical spinal pedicle screws maintained the original bending performance, whether they were solid or of cannulated design. This study may provide useful recommendations to orthopedic surgeons before surgery, and it may also provide design rationales to biomechanical engineers during the development of spinal pedicle screws. PMID:26208430

  20. Radiographic evaluation of HDPE cemented and cementless Lord and An.C.A. screwed acetabular models.

    PubMed

    Toni, A; Sudanese, A; Viceconti, M; Montina, P P; Ciaroni, D; Calista, F; Terzi, S; Giunti, A

    1992-01-01

    A total of 187 alumina screwed porous-ceramic coated sockets (An.C.A.), 48 screwed smooth-surfaced Lord sockets, and 251 cemented polyethylene sockets were radiographically evaluated at an average follow-up of 30, 51 and 96 months respectively. After 6 years the Lord prostheses revealed a 38% incidence of loosening, similar to that observed for cemented sockets 10-12 years after surgery. The An.C.A. prostheses revealed radiographic loosening equal to 12% (6 cases) in the first 50 implants, and only 0.7% in the remaining 137 cases: overall, the An.C.A. acetabular prosthesis revealed an index of radiographic loosening equal to 3.3% (7/187). To guarantee "osteointegration" of the porous coating of An.C.A. sockets optimal stability must be obtained when the prosthesis is screwed in. Because the mid-term follow-up for this clinical experience is relatively short (30 months), an opinion on the reliability of the screwed "porous" sockets must await confirmation. PMID:1297574

  1. Screw-locking wrench

    NASA Technical Reports Server (NTRS)

    Vranish, John M. (Inventor)

    2007-01-01

    A tool comprises a first handle and a second handle, each handle extending from a gripping end portion to a working end portion, the first handle having first screw threads disposed circumferentially about an inner portion of a first through-hole at the working end portion thereof, the second handle having second screw threads disposed circumferentially about an inner portion of a second through-hole at the working end portion thereof, the first and second respective through-holes being disposed concentrically about a common axis of the working end portions. First and second screw locks preferably are disposed concentrically with the first and second respective through-holes, the first screw lock having a plurality of locking/unlocking screw threads for engaging the first screw threads of the first handle, the second screw lock having a plurality of locking/unlocking screw threads for engaging the second screw threads of the second handle. A locking clutch drive, disposed concentrically with the first and second respective through-holes, engages the first screw lock and the second screw lock. The first handle and the second handle are selectively operable at their gripping end portions by a user using a single hand to activate the first and second screw locks to lock the locking clutch drive for either clockwise rotation about the common axis, or counter-clockwise rotation about the common axis, or to release the locking clutch drive so that the handles can be rotated together about the common axis either the clockwise or counter-clockwise direction without rotation of the locking clutch drive.

  2. Mechanical analysis of conventional and small diameter conical implant abutments

    PubMed Central

    Moris, Izabela Cristina Maurício; Faria, Adriana Cláudia Lapria; de Mattos, Maria da Gloria Chiarello; Ribeiro, Ricardo Faria

    2012-01-01

    PURPOSE The aim of the present study was to evaluate if a smaller morse taper abutment has a negative effect on the fracture resistance of implant-abutment connections under oblique compressive loads compared to a conventional abutment. MATERIALS AND METHODS Twenty morse taper conventional abutments (4.8 mm diameter) and smaller abutments (3.8 mm diameter) were tightened (20 Ncm) to their respective implants (3.5 × 11 mm) and after a 10 minute interval, implant/abutment assemblies were subjected to static compressive test, performed in a universal test machine with 1 mm/min displacement, at 45° inclination. The maximum deformation force was determined. Data were statistically analyzed by student t test. RESULTS Maximum deformation force of 4.8 mm and 3.8 mm abutments was approximately 95.33 kgf and 95.25 kgf, respectively, but no fractures were noted after mechanical test. Statistical analysis demonstrated that the evaluated abutments were statistically similar (P=.230). CONCLUSION Abutment measuring 3.8 mm in diameter (reduced) presented mechanical properties similar to 4.8 mm (conventional) abutments, enabling its clinical use as indicated. PMID:22977724

  3. Mechanical properties of resin glass fiber-reinforced abutment in comparison to titanium abutment

    PubMed Central

    Andreasi Bassi, Mirko; Bedini, Rossella; Pecci, Raffella; Ioppolo, Pietro; Lauritano, Dorina; Carinci, Francesco

    2015-01-01

    Purpose: So far, definitive implant abutments have been performed with high elastic modulus materials, which prevented any type of shock absorption of the chewing loads and as a consequence, the protection of the bone-fixture interface. This is particularly the case when the esthetic restorative material chosen is ceramic rather than composite resin. The adoption of an anisotropic abutment, characterized by an elastic deformability, could allow decreasing the impulse of chewing forces transmitted to the crestal bone. Materials and Methods: According to research protocol, the mechanical resistance to cyclical load was evaluated in a tooth-colored fiber-reinforced abutment (TCFRA) prototype and compared to that of a titanium abutment (TA), thus eight TCFRAs and eight TAs were adhesively cemented on as many titanium implants. The swinging that the two types of abutments showed during the application of sinusoidal load was also analyzed. Results: In the TA group, both fracture and deformation occurred in 12.5% of samples while debonding 62.5%. In the TCFRA group, only debonding was present in 37.5% of samples. In comparison to the TAs, the TCFRAs exhibited a greater swinging during the application of sinusoidal load. In the TA group, the extrusion prevailed, whereas in the TCFRA group, the intrusion was more frequent. Conclusion: The greater elasticity of TCFRA to the flexural load allows absorbing part of the transversal load applied on the fixture during the chewing function, thus reducing the stress on the bone-implant interface. PMID:26229266

  4. Survival of abutment teeth used for telescopic abutment retainers in removable partial dentures.

    PubMed

    Dittmann, Britta; Rammelsberg, Peter

    2008-01-01

    This retrospective clinical study investigated the survival of 385 abutment teeth retaining 117 removable partial dentures with 3 types of telescopic abutment retainers. Within a mean service time of 6.26 years, 8.8% of 385 abutment teeth were extracted. Cox regression analysis revealed a significantly higher risk of tooth loss for posterior teeth (odds ratio: 2.985) and for teeth with root canal treatment (odds ratio: 3.298), whereas age, sex, and number and type of telescopic retainer had no influence on survival. Root canal-treated teeth did not show a higher fracture rate, excluding this as an explanation for an increased risk of tooth loss. PMID:18717090

  5. Use of the talon hip compression screw in intertrochanteric fractures of the hip.

    PubMed

    Bramlet, Dale G

    2004-08-01

    A retrospective analysis of a compression hip screw with four reversibly deployable talons was done. Fifty-four patients had sufficient radiographs to be included in this analysis. One-year mortality was 17% and increased to 41% by 2 years. No lag screws cut out, and postoperative slide was reduced compared with that in many published series. Three patients had revision of a failed alternate-type hip pin with the Talon hip compression screw. Previous studies showed the talons provide the definitive difference in allowing enhanced compression at the time of surgery, preventing cut-out by enhanced rotational stability, and allowing immediate postoperative weightbearing without excessive limb shortening. The failure mode of the Talon compression hip screw seems to be side-plate loosening rather than varus deformity and lag screw cut-out. The Talon compression hip screw especially is effective with weak, osteoporotic bone and in unstable, three-part and four-part fractures. A previous study showed that Talon deployment notably improved interfragment compression and torsional strength, and that engagement or penetration into or through the cortical bone at the base of the femoral head-neck junction in the inferior lag screw position was the critical technical step to maximize the talon lag screw purchase. PMID:15292793

  6. Increase of stability in external fracture fixation by hydroxyapatite-coated bone screws.

    PubMed

    Augat, P; Claes, L; Hanselmann, K F; Suger, G; Fleischmann, W

    1995-01-01

    A major problem in fracture treatment by external fixation is screw loosening, which often results in reduced stability and can lead to prolonged treatment. A load-carrying experiment was conducted to determine whether coating implants with bioactive hydroxyapatite (HA) increases screw stability. Twelve HA-coated ASIF screws with 3 different macroporosities were inserted in 12 sheep that had already been fitted with a 6-pin external fixator for the treatment of a tibial osteotomy. The same number of uncoated polished steel screws served as controls. Although initial stability was not different for HA-coated screws, average removal torque after a 9-week implantation period increased with increasing macroporosity of the HA coating (p < .002). Instability of some screws was accompanied by histologic findings of cartilagenous tissue and proliferation of periosteal callus. Near the threads in the tibial cortex and in the shaft area of the screw were seen large numbers of HA particles that had been sheared off during implantation as well as during screw removal because of high contact forces between the HA coating and bone. Particulate debris of HA particles as well as the release of small bone fragments during explanation is likely to be unavoidable since HA adherence to bone is greater than adherence to steel after several weeks of implantation. PMID:7640445

  7. Development of Anti-Loosening Performance of Hyper Lock Nut

    NASA Astrophysics Data System (ADS)

    Nishiyama, Shuji; Migita, Hiroaki; Kataoka, Mitumasa; Nakasaki, Nobuyuki; Murano, Kohshi

    Bolted joints are widely used in mechanical structures as they allow easy disassembly for maintenance without high cost. However, vibration-induced loosening due to dynamic loading remains a long-unresolved issue. We have developed a new type of nut named the hyper lock nut (HLN) that offers anti-loosening performance without a complicated tightening process and tools. In this study, we investigated the mechanisms of joints bolted with the HLN, and tightening behavior was analyzed using the three-dimensional finite element method. The analytical results were compared with the experimental results for the HLN, and close qualitative agreement was observed between the two with respect to displacement, tightening force and tightening torque. We found a number of new aspects and plus points for joints bolted with the HLN in comparison to those fastened with JIS standard nuts. It was found that the tightening torque of the HLN is higher than that of JIS standard nuts, and that satisfactory anti-loosening performance can be realized through the thread contact force at the slit region and the angular face of the bearing surface.

  8. 6. SOUTHEAST ABUTMENT AT CALVERT STREET, SHOWING LEON HERMANT ALLEGORICAL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. SOUTHEAST ABUTMENT AT CALVERT STREET, SHOWING LEON HERMANT ALLEGORICAL RELIEF OF TRANSPORTATION BY AUTOMOBILE - Calvert Street Bridge, Spanning Rock Creek & Potomac Parkway, Washington, District of Columbia, DC

  9. 9. DETAIL VIEW OF SPANDREL WALL AT ABUTMENT AND INTERSECTION ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. DETAIL VIEW OF SPANDREL WALL AT ABUTMENT AND INTERSECTION WITH FOUNDATION OF ADJOINING BUILDING - Sanderson Avenue Bridge, Sanderson Avenue spanning Lackawanna River, Scranton, Lackawanna County, PA

  10. Perspective view of span over French Creek and east abutment, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Perspective view of span over French Creek and east abutment, looking NW. - Pennsylvania Railroad, French Creek Trestle, Spanning French Creek, north of Paradise Street, Phoenixville, Chester County, PA

  11. The influence of removable partial dentures on the periodontal health of abutment and non-abutment teeth

    PubMed Central

    Dula, Linda J.; Shala, Kujtim Sh.; Pustina–Krasniqi, Teuta; Bicaj, Teuta; Ahmedi, Enis F.

    2015-01-01

    Objective: The aim of this study was to evaluate the influence of removable partial dentures (RPD) on the periodontal health of abutment and non-abutment teeth. Materials and Methods: A total 107 patients with RPD participated in this study. It was examined 138 RPD, they were 87 with clasp-retained and 51 were RPD with attachments. The following periodontal parameters were evaluated for abutment and non-abutment teeth, plaque index (PLI), calculus index (CI), bleeding on probing (BOP), probing depth (PD) (mm) and tooth mobility (TM) index. These clinical measurements were taken immediately before insertion the RPD, then one and 3 months after insertion. The level of significance was set at (P < 0.05). Results: The mean scores for PLI, CI, BOP, PD, and TM index, of the abutment teeth and non-abutment teeth were no statistically significant at the time of insertion of RPD. After 1-month, PLI was statistically significant (0.57 ± 0.55 for abutment and 0.30 ± 0.46 for non-abutment teeth). After 3 months, there were significant differences between abutment and non-abutment teeth with regard to the BOP (1.53 ± 0.50 and 1.76 ± 0.43 respectively), PD (0.28 ± 0.45 and 0.12 ± 0.33 respectively) and PLI (1.20 ± 0.46 and 0.75 ± 0.64 respectively). No significant mean difference in TM and CI was found between the abutment and non-abutment teeth (P > 0.05). Conclusions: With carefully planned prosthetic treatment and adequate maintenance of the oral and denture hygiene, we can prevent the periodontal diseases. PMID:26430367

  12. [Microbial contamination of the implant-abutment connections: Review of the literature].

    PubMed

    Baixe, S; Tenenbaum, H; Etienne, O

    2016-02-01

    Today manufacturing process of dental implant parts allows for a precision of fit between implant and abutment of several microns. This microgap opens and closes under occlusal forces, leading to a pumping effect and to a contamination of the implant from bacteria and oral fluids. This kind of contamination is seen in all systems even if less often with internal connections that offers a better fit. Apart from this junction area, the screw well is another contamination pathway if the filling materials do not guarantee a hermetic sealing. The nature of contamination depends on the surrounding oral flora. When present, contamination leads to a persistent inflammatory reaction nearby the seal. The use of antiseptics or other materials for sealing the microgap decreases the risk of contamination and improves the gingival reaction. However, these solutions are time-limited. PMID:26746601

  13. Improved Screw-Thread Lock

    NASA Technical Reports Server (NTRS)

    Macmartin, Malcolm

    1995-01-01

    Improved screw-thread lock engaged after screw tightened in nut or other mating threaded part. Device does not release contaminating material during tightening of screw. Includes pellet of soft material encased in screw and retained by pin. Hammer blow on pin extrudes pellet into slot, engaging threads in threaded hole or in nut.

  14. [The significance of wear and material fatigue in loosening of hip prostheses].

    PubMed

    Willert, H G; Buchhorn, G H; Hess, T

    1989-09-01

    Particles created by wear and disintegration of implant materials give rise to foreign body reactions in the tissue surrounding joint endoprostheses. Histiocytes and foreign body giant cells phagocytize the particles released and form granulomas, which lead in turn to remodelling and resorption of the bone at the interface between implant and bone. As a consequence of this, osteolysis develops, which may lead to loosening and complete failure of fixation of the implant. Radiographically, the areas of osteolysis appear as localized, round, oval or oblong scalloping defects or as radiolucent lines in the endosteal sections of the bone immediately adjacent to the implants. This paper reports on 21 hip joint endoprostheses in which polyethylene and bone cement particles induced large areas of osteolysis at the bone/cement interface. In 8 cases the polyethylene particles originated from the convex joint surfaces of ball heads in "soft-top" endoprostheses (with or without simultaneous replacement of the acetabulum by a metal cup), and in 5 cases they originated from the anchoring surfaces of non-cemented cone-shaped screw-in sockets (Endler type); osteolysis and loosening of these endoprostheses appeared on average 48.2 and 76.6 months after implantation, respectively. The bone cement fragments came from the bone cement mantle of the femur, which had become fractured, disrupted and crushed, in 8 cases of total hip replacement with cemented prostheses; osteolysis appeared on average 87 months after primary implantation in these cases. Tissue samples taken at revision surgery from the joint capsule, the bone/cement interface and the osteolytic areas were processed into histological sections for microscopy and examined in the usual way. The type and amount of phagocytized material were subjected to semiquantitative analysis. We were able to show that osteolysis at the bone/cement interface can be induced by foreign body reactions to abraded polyethylene particles alone as

  15. Biomechanical comparison of different combinations of hook and screw in one spine motion unit - an experiment in porcine model

    PubMed Central

    2014-01-01

    Background The biomechanical performance of the hooks and screws in spinal posterior instrumentation is not well-characterized. Screw-bone interface failure at the uppermost and lowermost vertebrae is not uncommon. Some have advocated for the use of supplement hooks to prevent screw loosening. However, studies describing methods for combined hook and screw systems that fully address the benefits of these systems are lacking. Thus, the choice of which implant to use in a given case is often based solely on a surgeon’s experience instead of on the biomechanical features and advantages of each device. Methods We conducted a biomechanical comparison of devices instrumented with different combinations of hooks and screws. Thirty-six fresh low thoracic porcine spines were assigned to three groups (12 per group) according to the configuration used for of fixation: (1) pedicle screw; (2) lamina hook and (3) combination of pedicle screw and lamina hook. Axial pullout tests backward on transverse plane in the direction normal to the rods were performed using a material testing machine and a specially designed grip with self-aligned function. Results The pullout force for the pedicle screws group was significantly greater than for the hooks and the combination (p < 0.05). However, no significant difference was found between the hooks and the combination (p > 0.05). Conclusions Pedicle screws achieve the maximal pullout strength for spinal posterior instrumentation. PMID:24913189

  16. 23. VIEW LOOKING UPSTREAM AND TOWARD LEFT ABUTMENT OF DAM. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    23. VIEW LOOKING UPSTREAM AND TOWARD LEFT ABUTMENT OF DAM. NOTE FORMS FOR LEFT GRAVITY ABUTMENT AT UPPER RIGHT CORNER OF PICTURE. ARCHES 3, 4, 5, AND 7 COMPLETED TO ELEVATION 1795. 5 OR 7.5 FEET BELOW TOP OF PARAPET WALL. November 29, 1938 - Bartlett Dam, Verde River, Phoenix, Maricopa County, AZ

  17. 156. Humpback Mountain Viaduct. View shows the stone faced abutment. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    156. Humpback Mountain Viaduct. View shows the stone faced abutment. Due to the skew of the abutment, it doubles as a foundation for one of the piers. Looking south. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

  18. Apparatus for connecting aligned abutted tubes

    DOEpatents

    Williams, R.E.

    1984-11-29

    An apparatus for connecting abutted tubes and for maintaining their rotary alignment during connection. The apparatus comprises first and second tubes, a rotation prevention element, a collar and a retainer. Each tube has inside and outside walls, and first and second ends, each end having an inside and outside edge. The first tube has portions defining a first plurality of cavities located at the outside edge of its first end. An external threaded portion is on the outside wall of the first tube and next to the first plurality of cavities. The second tube has portions defining a second plurality of cavities located at the outside edge of its first end. The first plurality has a different number than the second plurality. The first ends of the first and second tubes have substantially the same outside diameter and are abutted during connection so that an orifice is formed whenever first and second tube cavities substantially overlap. A rotation prevension element is placed in the orifice to prevent rotation of the first and second tubes. A collar with an internal threaded portion is slidably disposed about the second tube. The internal threaded portion engages the external threaded portion of the first tube to connect the tubes. A lip connected to the collar prevents separation of the collar from the second tube.

  19. Fixture-abutment connection surface and micro-gap measurements by 3D micro-tomographic technique analysis.

    PubMed

    Meleo, Deborah; Baggi, Luigi; Di Girolamo, Michele; Di Carlo, Fabio; Pecci, Raffaella; Bedini, Rossella

    2012-01-01

    X-ray micro-tomography (micro-CT) is a miniaturized form of conventional computed axial tomography (CAT) able to investigate small radio-opaque objects at a-few-microns high resolution, in a non-destructive, non-invasive, and tri-dimensional way. Compared to traditional optical and electron microscopy techniques, which provide two-dimensional images, this innovative investigation technology enables a sample tri-dimensional analysis without cutting, coating or exposing the object to any particular chemical treatment. X-ray micro-tomography matches ideal 3D microscopy features: the possibility of investigating an object in natural conditions and without any preparation or alteration; non-invasive, non-destructive, and sufficiently magnified 3D reconstruction; reliable measurement of numeric data of the internal structure (morphology, structure and ultra-structure). Hence, this technique has multi-fold applications in a wide range of fields, not only in medical and odontostomatologic areas, but also in biomedical engineering, materials science, biology, electronics, geology, archaeology, oil industry, and semi-conductors industry. This study shows possible applications of micro-CT in dental implantology to analyze 3D micro-features of dental implant to abutment interface. Indeed, implant-abutment misfit is known to increase mechanical stress on connection structures and surrounding bone tissue. This condition may cause not only screw preload loss or screw fracture, but also biological issues in peri-implant tissues. PMID:22456016

  20. Ball Screw Actuator Including a Compliant Ball Screw Stop

    NASA Technical Reports Server (NTRS)

    Wingett, Paul T. (Inventor); Hanlon, Casey (Inventor)

    2015-01-01

    An actuator includes a ball nut, a ball screw, and a ball screw stop. The ball nut is adapted to receive an input torque and in response rotates and supplies a drive force. The ball screw extends through the ball nut and has a first end and a second end. The ball screw receives the drive force from the ball nut and in response selectively translates between a retract position and a extend position. The ball screw stop is mounted on the ball screw proximate the first end to translate therewith. The ball screw stop engages the ball nut when the ball screw is in the extend position, translates, with compliance, a predetermined distance toward the first end upon engaging the ball nut, and prevents further rotation of the ball screw upon translating the predetermined distance.

  1. Implant adaptation of stock abutments versus CAD/CAM abutments: a radiographic and Scanning Electron Microscopy study

    PubMed Central

    Apicella, Davide; Veltri, Mario; Chieffi, Nicoletta; Polimeni, Antonella; Giovannetti, Agostino; Ferrari, Marco

    2011-01-01

    Summary Introduction The study evaluated a null-hypothesis of no differences of fit between stock abutments and CAD/CAM titanium, gold sputtered and zirconia abutments when examined for radiographic adaptation and Scanning Electron Microcopy (SEM) at their inner aspect. The agreement between microscopic and radiographic fit was also assessed. Methods Implants (Osseospeed, Astra Tech, Mölndal, Sweden) were connected to titanium abutments (Ti-design, Astra Tech, Mölndal, Sweden) (control group n=12), to stock zirconia abutments (Zir-design, Astra Tech) (group 1 n=12) and to third party zirconia abutments (Aadva Zr abutment, GC, Tokyo, Japan) as observed under SEM (JEOL JSM-6060LV, Tokyo, Japan). Two independent operators blindly evaluated the images, according to a three-score scale: perfect adaptation, no complete adaptation, and clear evidence of no adaptation. A Kruskal-Wallis test was applied to assess significant differences in adaptation scores between the groups. Results All specimens showed precise SEM adaptation at all tested interfaces and no radiographically apparent gaps. No significant differences were found and therefore the null-hypothesis tested was accepted. Radiographic and SEM scores were in agreement. Discussion CAD/CAM titanium, gold sputtered and zirconia abutments and third-part CAD/CAM zirconia abutments show an adaptation to Astra Tech implants that is comparable to that of stock titanium and zirconia abutments. Clinicians might be able to verify such adaptation with an x-ray. In-vivo studies would be needed to evaluate the clinical outcome of CAD/CAM abutments. PMID:22238709

  2. In vitro biomechanical study of pedicle screw pull-out strength based on different screw path preparation techniques

    PubMed Central

    Moldavsky, Mark; Salloum, Kanaan; Bucklen, Brandon; Khalil, Saif; Mehta, Jwalant S

    2016-01-01

    Background: Poor screw-to-bone fixation is a clinical problem that can lead to screw loosening. Under-tapping (UT) the pedicle screw has been evaluated biomechanically in the past. The objective of the study was to determine if pedicle preparation with a sequential tapping technique will alter the screw-to-bone fixation strength using a stress relaxation testing loading protocol. Materials and Methods: Three thoracolumbar calf spines were instrumented with pedicle screws that were either probed, UT, standard-tapped (ST), or sequential tapped to prepare the pedicle screw track and a stress relaxation protocol was used to determine pull-out strength. The maximum torque required for pedicle screw insertion and pull-out strength was reported. A one-way ANOVA and Tukeys post-hoc test were used to determine statistical significance. Results: The pedicle screw insertion torques for the probed, UT, ST and sequentially tapped (SQT) techniques were 5.09 (±1.08) Nm, 5.39 (±1.61) Nm, 2.93 (±0.43) Nm, and 3.54 (±0.67) Nm, respectively. There is a significant difference between probed compared to ST (P ≤ 0.05), as well as UT compared to both ST and SQT (P ≤ 0.05). The pull-out strength for pedicle screws for the probed, UT, ST and SQT techniques was 2443 (±782) N, 2353(±918) N, 2474 (±521) N, and 2146 (±582) N, respectively, with no significant difference (P ≥ 0.05) between techniques. Conclusions: The ST technique resulted in the highest pull-out strength while the SQT technique resulted in the lowest. However, there was no significant difference in the pull-out strength for the various preparation techniques and there was no correlation between insertion torque and pull-out strength. This suggests that other factors such as bone density may have a greater influence on pull-out strength. PMID:27053808

  3. Accuracy combining different brands of implants and abutments

    PubMed Central

    Selva-Otaolaurruchi, Eduardo; Senent-Vicente, Gisela; González-de-Cossio, Inés; Amigó-Borrás, Vicente

    2013-01-01

    Objective: To evaluate the vertical misfit between different brands of dental implants and prosthetic abutments, with or without mechanical torque, and to study their possible combination. Study design: Five different brands of implant were used in the study: Biofit (Castemaggiore, Italy), Bioner S.A. (Barcelona, Spain), 3i Biomet (Palm Beach, U.S.A.), BTI (Alava, Spain) and Nobel Biocare (Göteborg, Sweden), with standard 4.1 mm heads and external hexagons, and their respective machined prosthetic abutments. The implant-to-abutment fit/misfit was evaluated at four points (vestibular, lingual/palatine, mesial and distal) between implants and abutments of the same brand and different brands, with or without mechanical torque, using SEM micrographs at 5000X. Image analysis was performed using NIS-Elements software (Nikon Instruments Europe B.V.). Results: Before applying torque, vertical misfit (microgaps) of the different combinations tested varied between 1.6 and 5.4 microns and after applying torque, between 0.9 and 5.9 microns, an overall average of 3.46±2.96 microns. For manual assembly without the use of mechanical torque, the best results were obtained with the combination of the 3i implant and the BTI abutment. The Nobel implant and Nobel abutment, 3i-3i and BTI-BTI and the combination of 3i implant with BTI or Nobel abutment provided the best vertical fit when mechanical torque was applied. Conclusions: The vertical fits obtained were within the limits considered clinically acceptable. The application of mechanical torque improved outcomes. There is compatibility between implants and abutments of different brand and so their combination is a clinical possibility. Key words:Vertical fit, implant, prosthetic abutment, combination. PMID:23229250

  4. Prosthetic management of malpositioned implant using custom cast abutment

    PubMed Central

    Chatterjee, Aishwarya; Ragher, Mallikarjuna; Patil, Sanket; Chatterjee, Debopriya; Dandekeri, Savita; Prabhu, Vishnu

    2015-01-01

    Two cases are reported with malpositioned implants. Both the implants were placed 6–7 months back. They had osseointegrated well with the surrounding bone. However, they presented severe facial inclination. Case I was restored with custom cast abutment with an auto polymerizing acrylic gingival veneer. Case II was restored with custom cast UCLA type plastic implant abutment. Ceramic was directly fired on the custom cast abutments. The dual treatment strategy resulted in functional and esthetic restorations despite facial malposition of the implants. PMID:26538957

  5. DETAIL OF SOUTHEAST CORNER OF ABUTMENT WITH SCALE. NOTE STAY ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF SOUTHEAST CORNER OF ABUTMENT WITH SCALE. NOTE STAY ROD EXTENDING FROM BOTTOM CHORD AND ANCHORED INTO ABUTMENT WITH IRON EYEHOOK. THIS FEATURE SECURED THE SUPERSTRUCTURE OF THE BRIDGE TO THE ABUTMENTS TO PREVENT THE TRUSS FROM BEING WASHED DOWNSTREAM IN FLOODS. NOTE ALSO THE CAST IRON PLATE ON WHICH THE ARCH BEARS, WHICH WAS DESIGNED TO PROLONG THE LIFE OF THE ARCH ENDS, ONE OF THE MOST VULNERABLE SPOTS ON A TIMBER BRIDGE. - West Union Bridge, Spanning Sugar Creek, CR 525W, West Union, Parke County, IN

  6. Magnesium inference screw supports early graft incorporation with inhibition of graft degradation in anterior cruciate ligament reconstruction

    NASA Astrophysics Data System (ADS)

    Cheng, Pengfei; Han, Pei; Zhao, Changli; Zhang, Shaoxiang; Zhang, Xiaonong; Chai, Yimin

    2016-05-01

    Patients after anterior cruciate ligament (ACL) reconstruction surgery commonly encounters graft failure in the initial phase of rehabilitation. The inhibition of graft degradation is crucial for the successful reconstruction of the ACL. Here, we used biodegradable high-purity magnesium (HP Mg) screws in the rabbit model of ACL reconstruction with titanium (Ti) screws as a control and analyzed the graft degradation and screw corrosion using direct pull-out tests, microCT scanning, and histological and immunohistochemical staining. The most noteworthy finding was that tendon graft fixed by HP Mg screws exhibited biomechanical properties substantially superior to that by Ti screws and the relative area of collagen fiber at the tendon-bone interface was much larger in the Mg group, when severe graft degradation was identified in the histological analysis at 3 weeks. Semi-quantitative immunohistochemical results further elucidated that the MMP-13 expression significantly decreased surrounding HP Mg screws with relatively higher Collagen II expression. And HP Mg screws exhibited uniform corrosion behavior without displacement or loosening in the femoral tunnel. Therefore, our results demonstrated that Mg screw inhibited graft degradation and improved biomechanical properties of tendon graft during the early phase of graft healing and highlighted its potential in ACL reconstruction.

  7. Magnesium inference screw supports early graft incorporation with inhibition of graft degradation in anterior cruciate ligament reconstruction.

    PubMed

    Cheng, Pengfei; Han, Pei; Zhao, Changli; Zhang, Shaoxiang; Zhang, Xiaonong; Chai, Yimin

    2016-01-01

    Patients after anterior cruciate ligament (ACL) reconstruction surgery commonly encounters graft failure in the initial phase of rehabilitation. The inhibition of graft degradation is crucial for the successful reconstruction of the ACL. Here, we used biodegradable high-purity magnesium (HP Mg) screws in the rabbit model of ACL reconstruction with titanium (Ti) screws as a control and analyzed the graft degradation and screw corrosion using direct pull-out tests, microCT scanning, and histological and immunohistochemical staining. The most noteworthy finding was that tendon graft fixed by HP Mg screws exhibited biomechanical properties substantially superior to that by Ti screws and the relative area of collagen fiber at the tendon-bone interface was much larger in the Mg group, when severe graft degradation was identified in the histological analysis at 3 weeks. Semi-quantitative immunohistochemical results further elucidated that the MMP-13 expression significantly decreased surrounding HP Mg screws with relatively higher Collagen II expression. And HP Mg screws exhibited uniform corrosion behavior without displacement or loosening in the femoral tunnel. Therefore, our results demonstrated that Mg screw inhibited graft degradation and improved biomechanical properties of tendon graft during the early phase of graft healing and highlighted its potential in ACL reconstruction. PMID:27210585

  8. Magnesium inference screw supports early graft incorporation with inhibition of graft degradation in anterior cruciate ligament reconstruction

    PubMed Central

    Cheng, Pengfei; Han, Pei; Zhao, Changli; Zhang, Shaoxiang; Zhang, Xiaonong; Chai, Yimin

    2016-01-01

    Patients after anterior cruciate ligament (ACL) reconstruction surgery commonly encounters graft failure in the initial phase of rehabilitation. The inhibition of graft degradation is crucial for the successful reconstruction of the ACL. Here, we used biodegradable high-purity magnesium (HP Mg) screws in the rabbit model of ACL reconstruction with titanium (Ti) screws as a control and analyzed the graft degradation and screw corrosion using direct pull-out tests, microCT scanning, and histological and immunohistochemical staining. The most noteworthy finding was that tendon graft fixed by HP Mg screws exhibited biomechanical properties substantially superior to that by Ti screws and the relative area of collagen fiber at the tendon-bone interface was much larger in the Mg group, when severe graft degradation was identified in the histological analysis at 3 weeks. Semi-quantitative immunohistochemical results further elucidated that the MMP-13 expression significantly decreased surrounding HP Mg screws with relatively higher Collagen II expression. And HP Mg screws exhibited uniform corrosion behavior without displacement or loosening in the femoral tunnel. Therefore, our results demonstrated that Mg screw inhibited graft degradation and improved biomechanical properties of tendon graft during the early phase of graft healing and highlighted its potential in ACL reconstruction. PMID:27210585

  9. Helical screw viscometer

    DOEpatents

    Aubert, J.H.; Chapman, R.N.; Kraynik, A.M.

    1983-06-30

    A helical screw viscometer for the measurement of the viscosity of Newtonian and non-Newtonian fluids comprising an elongated cylindrical container closed by end caps defining a circular cylindrical cavity within the container, a cylindrical rotor member having a helical screw or ribbon flight carried by the outer periphery thereof rotatably carried within the cavity whereby the fluid to be measured is confined in the cavity filling the space between the rotor and the container wall. The rotor member is supported by axle members journaled in the end caps, one axle extending through one end cap and connectable to a drive source. A pair of longitudinally spaced ports are provided through the wall of the container in communication with the cavity and a differential pressure meter is connected between the ports for measuring the pressure drop caused by the rotation of the helical screw rotor acting on the confined fluid for computing viscosity.

  10. Loosening xyloglucan accelerates the enzymatic degradation of cellulose in wood.

    PubMed

    Kaida, Rumi; Kaku, Tomomi; Baba, Kei'ichi; Oyadomari, Masafumi; Watanabe, Takashi; Nishida, Koji; Kanaya, Toshiji; Shani, Ziv; Shoseyov, Oded; Hayashi, Takahisa

    2009-09-01

    In order to create trees in which cellulose, the most abundant component in biomass, can be enzymatically hydrolyzed highly for the production of bioethanol, we examined the saccharification of xylem from several transgenic poplars, each overexpressing either xyloglucanase, cellulase, xylanase, or galactanase. The level of cellulose degradation achieved by a cellulase preparation was markedly greater in the xylem overexpressing xyloglucanase and much greater in the xylems overexpressing xylanase and cellulase than in the xylem of the wild-type plant. Although a high degree of degradation occurred in all xylems at all loci, the crystalline region of the cellulose microfibrils was highly degraded in the xylem overexpressing xyloglucanase. Since the complex between microfibrils and xyloglucans could be one region that is particularly resistant to cellulose degradation, loosening xyloglucan could facilitate the enzymatic hydrolysis of cellulose in wood. PMID:19825667

  11. Influences of implant condyle geometry on bone and screw strains in a temporomandibular implant.

    PubMed

    Mesnard, M; Ramos, A; Simões, J A

    2014-04-01

    A 3D finite element model of an in vitro implanted mandible was analysed. The load point was placed on the condyle in three positions (inside the mouth, centred and outside) to simulate different contact points between the mandible condyle and the temporal bone. The strain fields in the condyle were assessed and detailed around the surgical screws. The temporomandibular implant studied here was modelled on a commercial device that uses four screws to fix it in vivo in a very similar position. The boundary conditions of the numerical model simulated a load on the incisors with a 15 mm mouth aperture. The same contact loads were applied to the two condyles. Numerical results were successfully obtained for the three different contact points: the inside contact produced lower strains on the condyle. The first screw created a critical strain distribution in the bone, just under the screw. The study shows that centred and inside contact induces lower strain distributions. This suggests that spherical condyle geometry should be applied in order to reduce the strains in fixation. As the top screw was observed to play the most critical role, the third screw is in fact unnecessary, since the lower strain distribution suggests that it will be loosened. PMID:23726645

  12. Screw-Retaining Allen Wrench

    NASA Technical Reports Server (NTRS)

    Granett, D.

    1985-01-01

    Steadying screws with fingers unnecessary. Crimp in uncompressed spring wire slightly protrudes from one facet of Allen wrench. Compressed spring retains Allen screw. Tool used with Allen-head screws in cramped spaces with little or no room for fingers to hold fastener while turned by wrench.

  13. 12. DETAIL VIEW OF WEST ABUTMENT AT Lo, SHOWING BRIDGE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. DETAIL VIEW OF WEST ABUTMENT AT Lo, SHOWING BRIDGE SEAT, TIMBER PILES, STEEL SILL AND BACKWALL/WlNGWALL BOARDS, LOOKING NORTH - Cottonville Bridge, County Road D-61 at Farmer's Creek, Maquoketa, Jackson County, IA

  14. 14. BRIDGE ABUTMENT AND ARCH TRUSS MOUNTING PLATE SHOWING EYEBAR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    14. BRIDGE ABUTMENT AND ARCH TRUSS MOUNTING PLATE SHOWING EYE-BAR CONNECTION AND EYE-BAR PIN LOCATION - Spruce Street Bridge, East Spruce Street, 500 Block, spanning Power Canal, Sault Ste. Marie, Chippewa County, MI

  15. 10. DETAIL OF RUBBLE MASONRY ABUTMENT ON THE SOUTH BANK ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. DETAIL OF RUBBLE MASONRY ABUTMENT ON THE SOUTH BANK AND DISINTEGRATING CONCRETE FACING; VIEW FROM WEST. - Mitchell's Mill Bridge, Spanning Winter's Run on Carrs Mill Road, west of Bel Air, Bel Air, Harford County, MD

  16. 9. South abutment, detail of collapsed east wing wall; also ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. South abutment, detail of collapsed east wing wall; also detail of bottom lateral bracing and stringers; looking southeast - Dodd Ford Bridge, County Road 147 Spanning Blue Earth River, Amboy, Blue Earth County, MN

  17. 9. 64 foot pony truss south west bearing abutment ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. 64 foot pony truss - south west bearing abutment of the first pony, truss, showing the sheet piling and the added 'I' beam support. - Weidemeyer Bridge, Spanning Thomes Creek at Rawson Road, Corning, Tehama County, CA

  18. 15. DETAIL OF ROCKER BEARING AT SOUTH ABUTMENT. NOTE LOCKING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    15. DETAIL OF ROCKER BEARING AT SOUTH ABUTMENT. NOTE LOCKING MECHANISM AT LEFT OF FRAME. - Chicago, Milwaukee & St. Paul Railway, Bridge No. Z-2, Spanning North Branch Canal at North Cherry Avenue, Chicago, Cook County, IL

  19. 6. VIEW FROM WESTERN ABUTMENT, SHOWING SIDE ELEVATION OF BRIDGE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. VIEW FROM WESTERN ABUTMENT, SHOWING SIDE ELEVATION OF BRIDGE No. Z-6 IN OPEN POSITION. - Chicago, Milwaukee & St. Paul Railway, Bridge No. Z-6, Spanning North Branch of Chicago River, South of Cortland Street, Chicago, Cook County, IL

  20. 8. Detail, lower chord, looking west from southeastern abutment ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. Detail, lower chord, looking west from southeastern abutment - Hayden Bridge, Spanning McKenzie River at Southern Pacific Railroad (moved from Springfield, Lake County, OR), Springfield, Lane County, OR

  1. 4. VIEW UNDERNEATH BRIDGE, SHOWING STONE ABUTMENT AND THE DECK ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. VIEW UNDERNEATH BRIDGE, SHOWING STONE ABUTMENT AND THE DECK BEAMS, STRINGERS AND DIAGONAL BRACING OF DECK SUPPORT SYSTEM - John Bright No. 1 Iron Bridge, Spanning Poplar Creek at Havenport Road (TR 263), Carroll, Fairfield County, OH

  2. NORTH NORTHWEST, SHOWING ABUTMENTS AND PIER MADE OF CUT, SQUARED ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    NORTH NORTHWEST, SHOWING ABUTMENTS AND PIER MADE OF CUT, SQUARED STONE WITH MORTARED JOINTS. - Crum Bridge, Spanning Little Muskingum River, TR 384A (formerly Old Camp Road), Rinard Mills, Monroe County, OH

  3. 6. EASTERLY AERIAL VIEW SHOWING THE RIGHT ABUTMENT AND OUTLET ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. EASTERLY AERIAL VIEW SHOWING THE RIGHT ABUTMENT AND OUTLET CONTROL WORKS IN THE FOREGROUND.... Volume XX, No. 8, September 9, 1940. - Prado Dam, Santa Ana River near junction of State Highways 71 & 91, Corona, Riverside County, CA

  4. 14. Balustrade, sidewalk, and support detail at east abutment. View ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    14. Balustrade, sidewalk, and support detail at east abutment. View east - Ashton Viaduct, State Route 116 (Washington Highway) spanning Blackstone River, Blackstone Canal, & Providence & Worcester Railroad, Ashton, Providence County, RI

  5. 13. Balustrade and parapet detail at west abutment. View south ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    13. Balustrade and parapet detail at west abutment. View south - Ashton Viaduct, State Route 116 (Washington Highway) spanning Blackstone River, Blackstone Canal, & Providence & Worcester Railroad, Ashton, Providence County, RI

  6. 12. East abutment and approach span column detail. View east ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. East abutment and approach span column detail. View east - Ashton Viaduct, State Route 116 (Washington Highway) spanning Blackstone River, Blackstone Canal, & Providence & Worcester Railroad, Ashton, Providence County, RI

  7. Detail, northwest wingwall of north abutment, from west, showing original ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail, northwest wingwall of north abutment, from west, showing original squared cut stone masonry construction and portion of non-original concrete apron - Castle Garden Bridge, Township Route 343 over Bennetts Branch of Sinnemahoning Creek, Driftwood, Cameron County, PA

  8. 5. DETAIL VIEW OF JUNCTURE BETWEEN ARCH, AND ABUTMENT, SHOWING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. DETAIL VIEW OF JUNCTURE BETWEEN ARCH, AND ABUTMENT, SHOWING CANTILEVERED WALKWAY AND DECK BEAMS ON UNDERSIDE OF BRIDGE - Benson Street Concrete Bowstring Bridge, Spanning Mill Creek at Benson Street, Lockland, Hamilton County, OH

  9. 18. Understructure, view of south arch abutment showing arch ribs, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    18. Understructure, view of south arch abutment showing arch ribs, columns, sway bracing, floor beams, deck cantilever, railing; view to southwest. - Parks Bar Bridge, Spanning Yuba River at State Highway 20, Smartville, Yuba County, CA

  10. 12. DETAIL OF NORTH ABUTMENT, FROM BENEATH, SHOWING ARCH RIB ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. DETAIL OF NORTH ABUTMENT, FROM BENEATH, SHOWING ARCH RIB AND FLOOR BEAM. VIEW TO NORTHEAST. - Rock Valley Bridge, Spanning North Timber Creek at Old U.S. Highway 30, Marshalltown, Marshall County, IA

  11. 7. DETAIL OF EAST ABUTMENT, LOOKING SOUTHEAST. The easternmost bridge ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. DETAIL OF EAST ABUTMENT, LOOKING SOUTHEAST. The easternmost bridge span to shore was removed in the Spring of 1987. - Annisquam Bridge, Spanning Lobster Cove between Washington & River Streets, Gloucester, Essex County, MA

  12. 17. Underside of bridge and abutment with large boulder looking ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    17. Underside of bridge and abutment with large boulder looking ENE. - Great Smoky Mountains National Park Roads & Bridges, Roaring Fork Motor Nature Trail, Between Cherokee Orchard Road & U.S. Route 321, Gatlinburg, Sevier County, TN

  13. SOUTHEAST SIDE, TAKEN FROM LOWER PARKING LOT, WITH ABUTTING FACILITY ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    SOUTHEAST SIDE, TAKEN FROM LOWER PARKING LOT, WITH ABUTTING FACILITY 346 IN FOREGROUND. - U.S. Naval Base, Pearl Harbor, Joint Intelligence Center, Makalapa Drive in Makalapa Administration Area, Pearl City, Honolulu County, HI

  14. 2. VIEW SOUTH, PERSPECTIVE OF ABUTMENT AND INCLINED PLANE ON ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. VIEW SOUTH, PERSPECTIVE OF ABUTMENT AND INCLINED PLANE ON WEST SIDE OF PA ROUTE 56 - Laurel Hill Quarry, Incline Plane, Both sides of State Route 56, 2.4 miles East of State Route 711, Seward, Westmoreland County, PA

  15. 3. VIEW NORTHWEST, PERSPECTIVE OF ABUTMENT AND INCLINED PLANE ON ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. VIEW NORTHWEST, PERSPECTIVE OF ABUTMENT AND INCLINED PLANE ON WEST SIDE OF PA ROUTE 56 - Laurel Hill Quarry, Incline Plane, Both sides of State Route 56, 2.4 miles East of State Route 711, Seward, Westmoreland County, PA

  16. 4. VIEW FROM EAST ABUTMENT SHOWING BASCULE LEAFS AND DECK ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. VIEW FROM EAST ABUTMENT SHOWING BASCULE LEAFS AND DECK SUBSTRUCTURE. - Chicago River Bascule Bridge, Monroe Street, Spanning South Branch of Chicago River at Monroe Street, Chicago, Cook County, IL

  17. 2. EAST ABUTMENT RIVER PIER LOOKING AT BASCULE TRUSS LIVE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. EAST ABUTMENT RIVER PIER LOOKING AT BASCULE TRUSS LIVE LOAD SUPPORT COLUMN. - Chicago River Bascule Bridge, Monroe Street, Spanning South Branch of Chicago River at Monroe Street, Chicago, Cook County, IL

  18. 2. DETAIL OF RUBBLE ABUTMENT AT WEST END OF WEST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. DETAIL OF RUBBLE ABUTMENT AT WEST END OF WEST MULTNOMAH FALLS VIADUCT. - Historic Columbia River Highway, West Multnomah Falls Viaduct, West of Multnomah Falls on Historic Columbia River Highway, Troutdale, Multnomah County, OR

  19. 27. Otter Creek Bridge #5. Detail of the interior abutment ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    27. Otter Creek Bridge #5. Detail of the interior abutment wall. Wingwall, and facade thickness. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

  20. 23. DETAIL VIEW OF THE NORTHWEST ABUTMENT, SHOWING AN ORIGINAL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    23. DETAIL VIEW OF THE NORTHWEST ABUTMENT, SHOWING AN ORIGINAL LIGHT FIXTURE AND THE 'HISTORICAL TABLET,' LOOKING NORTH-NORTHEAST FROM BELOW Ryan - Benton Street Bridge, Spanning Iowa River at Benton Street, Iowa City, Johnson County, IA

  1. DETAIL OF NORTHEAST CUT STONE ABUTMENT FROM SOUTHWEST. Cataract ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF NORTHEAST CUT STONE ABUTMENT FROM SOUTHWEST. - Cataract Falls Bridge, Spanning Mill Creek, bypassed section of CR 279 (Cataract Falls Unit of Leiber State Recreation Area), Cataract, Owen County, IN

  2. 6. View southeast, west elevation, showing north arch span abutment ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. View southeast, west elevation, showing north arch span abutment and central pier with nose on upstream side - Edna Dean Proctor Bridge, Spanning Contoacook River at State Route 114, Henniker, Merrimack County, NH

  3. 25. Photocopy of photograph. VIEW, LOOKING EAST, SHOWING ABUTMENT. Photographer ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    25. Photocopy of photograph. VIEW, LOOKING EAST, SHOWING ABUTMENT. Photographer unknown, November 19, 1968. (Print in possession of the Washington County Highway Department.) - Hegeman-Hill Street Bridge, Spanning Batten Kill, .65 mile West of Greenwich, Easton, Washington County, NY

  4. 8. View east. East abutment, showing bearings on concrete pads, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. View east. East abutment, showing bearings on concrete pads, drainage pipes for approach, and scupper downspouts. - Walpole-Westminster Bridge, Spanning Connecticut River between Walpole, NH & Westminster, VT, Walpole, Cheshire County, NH

  5. 22. VIEW OF STEEL ARCH, SHOWING ABUTMENT INTERIOR, DETAIL OF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    22. VIEW OF STEEL ARCH, SHOWING ABUTMENT INTERIOR, DETAIL OF ARCH BEARINGS WITH HINGED SEATS AND LATERAL BRACING OF ARCHES, LOOKING NORTH - Notre Dame Bridge, Spanning Merrimack River on Bridge Street, Manchester, Hillsborough County, NH

  6. 5. West side of Fourth Street; concrete abutment pier and ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. West side of Fourth Street; concrete abutment pier and crib work, June 29, 1931. Photographer: unknown - Marquette Ore Dock No. 6, Approach, Between Fifth & Lake Streets, Marquette, Marquette County, MI

  7. 9. CABLE ANCHORAGE DETAIL, NORTHWEST ABUTMENT (NOTE MOSSCOVERED CONCRETE ANCHOR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. CABLE ANCHORAGE DETAIL, NORTHWEST ABUTMENT (NOTE MOSS-COVERED CONCRETE ANCHOR LEFT OF ANCHOR BOLTS) - Nisqually Suspension Bridge, Spanning Nisqually River on Service Road, Longmire, Pierce County, WA

  8. 14. Hell Gate Bridge south abutment tower. Queens, Queens Co., ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    14. Hell Gate Bridge south abutment tower. Queens, Queens Co., NY. Sec. 4207, MP 7.29. - Northeast Railroad Corridor, Amtrak Route between New Jersey/New York & New York/Connecticut State Lines, New York County, NY

  9. 69. View of downstream face from west or right abutment. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    69. View of downstream face from west or right abutment. Photographer Mark Durben. Source: Salt River Project. - Waddell Dam, On Agua Fria River, 35 miles northwest of Phoenix, Phoenix, Maricopa County, AZ

  10. 39. Pleasant Dam from east abutment with spillway visible at ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    39. Pleasant Dam from east abutment with spillway visible at center. Photographer unknown, 1927. Source: MWD. - Waddell Dam, On Agua Fria River, 35 miles northwest of Phoenix, Phoenix, Maricopa County, AZ

  11. BRIDGE ABUTMENTS WITH ARCH SEGMENTS ON RIVER BOTTOM. ARCHES COLLAPSED ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    BRIDGE ABUTMENTS WITH ARCH SEGMENTS ON RIVER BOTTOM. ARCHES COLLAPSED AROUND EIGHT YEARS BEFORE THIS DATE. - Whittlesey Road Bridge, Spanning Black River at Whittlesey Road, Lyons Falls, Lewis County, NY

  12. Prosthetic abutment influences bone biomechanical behavior of immediately loaded implants.

    PubMed

    Camargos, Germana de Villa; Sotto-Maior, Bruno Salles; Silva, Wander José da; Lazari, Priscilla Cardoso; Del Bel Cury, Altair Antoninha

    2016-05-31

    This study aimed to evaluate the influence of the type of prosthetic abutment associated to different implant connection on bone biomechanical behavior of immediately and delayed loaded implants. Computed tomography-based finite element models comprising a mandible with a single molar implant were created with different types of prosthetic abutment (UCLA or conical), implant connection (external hexagon, EH or internal hexagon, IH), and occlusal loading (axial or oblique), for both immediately and delayed loaded implants. Analysis of variance at 95%CI was used to evaluate the peak maximum principal stress and strain in bone after applying a 100 N occlusal load. The results showed that the type of prosthetic abutment influences bone stress/strain in only immediately loaded implants. Attachment of conical abutments to IH implants exhibited the best biomechanical behavior, with optimal distribution and dissipation of the load in peri-implant bone. PMID:27253141

  13. Detail view of the metal caisson and masonry abutment at ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail view of the metal caisson and masonry abutment at north end of through truss span - Crooked River Bridge, Spanning Crooked River on Elliot Lane (County Road 124) at Milepoint 1.38, Prineville, Crook County, OR

  14. 12. Detail showing concrete abutment on southwest side looking east, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. Detail showing concrete abutment on southwest side looking east, taken from below road surface. - Presumpscot Falls Bridge, Spanning Presumptscot River at Allen Avenue extension, 0.75 mile west of U.S. Interstate 95, Falmouth, Cumberland County, ME

  15. ERECTION PLAN FOR BEAM SPANS FROM WEST ABUTMENT TO BENT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    ERECTION PLAN FOR BEAM SPANS FROM WEST ABUTMENT TO BENT NO. 36 AT WEST APPROACH, APALACHICOLA RIVER BRIDGE, SHEET 5509-E1 - Apalachicola River Bridge, State Route 20 spanning the Apalachicola River, Blountstown, Calhoun County, FL

  16. 6. VIEW OF NORTHWEST RAILING TERMINATION AND NORTH ABUTMENT; VIEWED ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. VIEW OF NORTHWEST RAILING TERMINATION AND NORTH ABUTMENT; VIEWED FROM THE WEST - La Verkin Creek Bridge, Spanning La Verkin Creek on State Route 17, 0.7 miles northwest of La Verkin , La Verkin, Washington County, UT

  17. Mechanical testing of thin-walled zirconia abutments

    PubMed Central

    CANULLO, Luigi; COELHO, Paulo G.; BONFANTE, Estevam A.

    2013-01-01

    Although the use of zirconia abutments for implant-supported restorations has gained momentum with the increasing demand for esthetics, little informed design rationale has been developed to characterize their fatigue behavior under different clinical scenarios. However, to prevent the zirconia from fracturing, the use of a titanium connection in bicomponent aesthetic abutments has been suggested. Objective: Mechanical testing of customized thin-walled titanium-zirconia abutments at the connection with the implant was performed in order to characterize the fatigue behavior and the failure modes for straight and angled abutments. Material and Methods: Twenty custom-made bi-component abutments were tested according to ISO 14801:2007 either at a straight or a 25º angle inclination (n=10 each group). Fatigue was conducted at 15 Hz for 5 million cycles in dry conditions at 20ºC±5ºC. Mean values and standard deviations were calculated for each group. All comparisons were performed by t-tests assuming unequal variances. The level of statistical significance was set at p≤0.05. Failed samples were inspected in a polarized-light and then in a scanning electron microscope. Results: Straight and angled abutments mean maximum load was 296.7 N and 1,145 N, the dynamic loading mean Fmax was 237.4 N and 240.7 N, respectively. No significant differences resulted between the straight and angled bi-component abutments in both static (p=0.253) and dynamic testing (p=0.135). A significant difference in the bending moment required for fracture was detected between the groups (p=0.01). Fractures in the angled group occurred mainly at the point of load application, whereas in the straight abutments, fractures were located coronally and close to the thinly designed areas at the cervical region. Conclusion: Angled or straight thin-walled zirconia abutments presented similar Fmax under fatigue testing despite the different bending moments required for fracture. The main implication is

  18. Hemispheric titanium porous coated acetabular component without screw fixation.

    PubMed

    Dorr, L D; Wan, Z; Cohen, J

    1998-06-01

    One hundred fifteen hips in 108 patients with primary total hip arthroplasty using the anatomic porous replacement hemispheric acetabular component implanted without adjunctive screw fixation had a mean postoperative followup time of 6 years (range, 5-7.4 years). Clinical evaluation was performed using the Harris hip score and patient self assessment using a modified Short Form-36 questionnaire. Radiographs were measured for radiolucent lines, polyethylene wear, osteolysis, migration, and fractures. No acetabular metal shell had been revised for loosening or was radiographically loose with or without migration (more than 3 mm) at final followup. Reoperation was done in nine (8%) hips because of polyethylene insert wear or disassembly. No fracture of the acetabular bone occurred at the time of surgery or was observed on radiograph. Fixation of the metal shell was stable, with progressive radiolucent lines observed at final followup in 2% of the hips. Osteolysis was recorded in one patient with two acetabular components. The fixation of noncemented hemispheric porous coated acetabular components is more related to the technique of acetabular bone preparation and press fit implantation than to whether additional screws or peg fixation are used. Fixation of this acetabular component without screws at an average of 6 years after surgery is reproducible and predictable in primary hip arthroplasty. The design of modular polyethylene inserts has been improved and should reduce the wear rate of reoperations of the polyethylene insert. PMID:9646758

  19. Best estimation of spectrum profiles for diagnosing femoral prostheses loosening.

    PubMed

    Díaz-Pérez, Francisco; García-Nieto, Evelyn; Ros, Antonio; Claramunt, Rafael

    2014-02-01

    For the past few years, some authors have proposed several vibration analysis techniques to detect the prosthetic femoral stem loosening, having found some differences in the frequency response between secure and loose stems. Classical methods like periodogram have been used in most studies for the spectral estimation, and their conclusions have been reached only by visual inspection. A new metric called Non-linear Logarithmic Weighted Distance (NLWD), based on log-spectral distance is presented. As its name suggests, the spectral power is weighted in order to highlight discriminatory patterns of the spectral profiles. A Generalized Discriminant Ratio (GDR) based on NLWD metric has been also defined. In this study, experiments on a cadaveric dried bone with two kinds of fixation, Loose Stem class (LS) and Secure Stem class (SS), have been analyzed. To select the most discriminating approach to spectral estimation, five well known algorithms (Welch's, Burg's Auto-Regressive (AR), Auto-Regressive Moving Average (ARMA), Multiple Signal Classification (MUSIC) and Thomson's Multi-taper (MTM)) have been compared by using GDR. Finally, the use of the MTM method is proposed for the analysis of bone-stem interface vibratory signals, since it yields the most discriminatory profiles. PMID:24332977

  20. Effect of Misfit on Preload Maintenance of Retention Screws of Implant-Supported Prostheses

    NASA Astrophysics Data System (ADS)

    Assunção, Wirley Gonçalves; Dos Santos, Paulo Henrique; Delben, Juliana Aparecida; Gomes, Érica Alves; Barão, Valentim Adelino Ricardo; Tabata, Lucas Fernando

    2009-10-01

    The aim of this study was to evaluate the effect of unilateral misfit at different levels on a crown-implant-retention screw system of implant-supported crowns. Hexagon castable UCLA abutments were cast in Co-Cr alloy to fabricate 48 metallic crowns divided into four groups ( n = 12). Group A: crowns did not present misfit; Groups B, C and D: crowns were fabricated with unilateral misfit of 50, 100, and 200 μm, respectively. The crowns were attached by titanium retention screw with 30 N/cm to external hexagonal osseointegrated implants embedded in acrylic resin. After 2 min, the retention screw of each replica was submitted to detorque evaluation by an analogic torque gauge. Three retention screws were used to perform detorque evaluation at each replica and the procedure was repeated twice with each screw. Each group was submitted to 72 detorque measurements. Data were evaluated by ANOVA and Tukey test ( P < 0.05). All groups exhibited significant decrease ( P < 0.05) in preload and the lowest decrease occurred in Group A. Groups B, C, and D were statistically significant different from Group A ( P < 0.05), but there was no statistically significant difference between Groups B and D ( P > 0.05). Crowns with unilateral misfit presented higher preload decrease than crowns completely fitted to osseointegrated implants.

  1. A capillary Archimedes' screw

    NASA Astrophysics Data System (ADS)

    Darbois Texier, Baptiste; Dorbolo, Stephane

    2014-11-01

    As used by Egyptians for irrigation and reported by Archimedes, a screw turning inside a hollow pipe can pull out a fluid againt gravity. At a centimetric scale, an analagous system can be found with a drop pending on a rotating spiral which is tilted toward the horizontal. The ascent of the drop to the top of the spiral is considered and a theoretical model based on geometrical considerations is proposed. The climb of the drop is limited by the fluid deposition on the screw at high capillary number and by a centrifugation phenomenon. We find out the range of fluid proprities and spiral characteristics for which an ascending motion of the drop is possible. Finally we discuss the efficiency of such system to extract a fluid from a bath at a centrimetric scale.

  2. NUT SCREW MECHANISMS

    DOEpatents

    Glass, J.A.F.

    1958-07-01

    A reactor control mechanism is described wherein the control is achieved by the partial or total withdrawal of the fissile material which is in the form of a fuel rod. The fuel rod is designed to be raised and lowered from the reactor core area by means of two concentric ball nut and screw assemblies that may telescope one within the other. These screw mechanisms are connected through a magnetic clutch to a speed reduction gear and an accurately controllable prime motive source. With the clutch energized, the fuel rod may be moved into the reactor core area, and fine adjustments may be made through the reduction gearing. However, in the event of a power failure or an emergency signal, the magnetic clutch will become deenergized, and the fuel rod will drop out of the core area by the force of gravity, thus shutting down the operation of the reactor.

  3. [Effectivity and durability of telescopic dentures on abutment teeth].

    PubMed

    van den Wijngaarden, E; van Pelt, A W J; Meisberger, E W; Tams, J; Cune, M S

    2016-03-01

    In a study, the effectivity and durability of telescopic dentures on abutment teeth provided with telescope crowns were investigated. The prognosis for the prosthetic structure and for the abutment teeth were both investigated. The survival rate of 234 telescopic dentures (886 abutment teeth) in 147 patients in a general dental practice were retrospectively evaluated on the basis of a status study. The mean survival rate was calculated. This is the moment when 50% of the telescopic dentures had failed. For telescopic dentures in the maxilla, this was 22.3±2.8 years, which did not represent a statistically significant difference from the mandible (20.9±1.9 years). Of the 886 abutment teeth that were used, 127 (14.3%) were extracted after an average period of 11.7 years. Periodontal complications were the primary reason for extraction. Based on this investigation, one could conclude that telescopic dentures are also a durable and sustainable solution in the long term. Loss of abutment teeth is relatively rare and has limited influence on the survival of the prosthetic structure. PMID:26973985

  4. Development of a non-invasive diagnostic technique for acetabular component loosening in total hip replacements.

    PubMed

    Alshuhri, Abdullah A; Holsgrove, Timothy P; Miles, Anthony W; Cunningham, James L

    2015-08-01

    Current techniques for diagnosing early loosening of a total hip replacement (THR) are ineffective, especially for the acetabular component. Accordingly, new, accurate, and quantifiable methods are required. The aim of this study was to investigate the viability of vibrational analysis for accurately detecting acetabular component loosening. A simplified acetabular model was constructed using a Sawbones(®) foam block. By placing a thin silicone layer between the acetabular component and the Sawbones block, 2- and 4-mm soft tissue membranes were simulated representing different loosening scenarios. A constant amplitude sinusoidal excitation with a sweep range of 100-1500 Hz was used. Output vibration from the model was measured using an accelerometer and an ultrasound probe. Loosening was determined from output signal features such as the number and relative strength of observed harmonic frequencies. Both measurement methods were sufficient to measure the output vibration. Vibrational analysis reliably detected loosening corresponding to both 2 and 4 mm tissue membranes at driving frequencies between 100 and 1000 Hz (p < 0.01) using the accelerometer. In contrast, ultrasound detected 2-mm loosening at a frequency range of 850-1050 Hz (p < 0.01) and 4-mm loosening at 500-950 Hz (p < 0.01). PMID:26054805

  5. Strength comparison of allogenic bone screws, bioabsorbable screws, and stainless steel screw fixation.

    PubMed

    Rano, James A; Savoy-Moore, Ruth T; Fallat, Lawrence M

    2002-01-01

    Allogenic bone screws are new to the fixation market and have yet to be tested against current fixation materials. An in vitro comparison of the same sizes of stainless steel, bioabsorbable, and allogenic bone screws was undertaken to assess screw resistance to the forces of bending, pullout, and shear. Using aluminum plates to support the screws, forces up to 1000 Newtons were applied to six to eight samples of each type of screw. During each test, stainless steel screws withstood the maximum force that could be exerted by the testing apparatus without failing (bending, 113.9 +/- 11.8 N mean +/- SE; pullout 999.1 +/- 33.7 N; and shear, 997.5 +/- 108.8 N). In each test, compared to bioabsorbable screws, allogenic bone screws failed faster (pullout, allogenic: 12.4 +/- 1.1 seconds vs. bioabsorbable, 120.6 +/- 13.8 seconds; p = .001; bending, allogenic: 53.4 +/- 4.8 seconds vs. bioabsorbable, 201.9 +/- 11.1 seconds; p = .001; shear, allogenic 13.5 +/- 1.4 seconds vs. bioabsorbable, 43.8 +/- 0.9 seconds; p = .001) under equivalent (pullout: bioabsorbable, 385.0 +/- 18.4 N vs. allogenic, 401.0 +/- 35.9 N; p = .001) or lower (bending, allogenic: 4.7 +/- 0.2 N vs. bioabsorbable, 11.0 +/- 0.9 N; p = .675; shear, allogenic: 312.1 +/- 15.5 N vs. bioabsorbable 680.9 +/- 8.5 N; p = .001) loads, and in a highly variable fashion. Overall, the bioabsorbable screws withstood the forces of bending, pullout, and shear better than the allogenic screws, and stainless steel screws outperformed both bioabsorbable and allogenic screws. Despite these results, allogenic screws could still be useful in compliant patients who would benefit from their osteoconductive properties. PMID:11858609

  6. Low noise lead screw positioner

    NASA Technical Reports Server (NTRS)

    Perkins, Gerald S. (Inventor)

    1986-01-01

    A very precise and low noise lead screw positioner, for positioning a retroreflector in an interferometer is described. A gas source supplies inert pressurized gas, that flows through narrow holes into the clearance space between a nut and the lead screw. The pressurized gas keeps the nut out of contact with the screw. The gas flows axially along the clearance space, into the environment. The small amount of inert gas flowing into the environment minimizes pollution. By allowing such flow into the environment, no seals are required between the end of the nut and the screw.

  7. A Technique Elucidating the Retrieval of an Adhered Cover Screw in a Dental Implant – A Case Report

    PubMed Central

    Bhuvaneswarri, J.; Chandrasekaran, S.C.

    2013-01-01

    Dental implants have become one of the most popular and rapidly growing techniques for replacing missing teeth. While their predictability, functionality, and durability make them an attractive option for patients and clinicians alike, complications can arise at any stage from patient assessment to maintenance of therapy. Failure of dental implants not only occurs due to biological factors, like unsuccessful osseointegration or peri-implantitis but may also occur due to technical complications like, failures of implant-supported restorations relating those from the implant components, and those relating to the prosthesis. Technical problems related to implant components include abutment screw fractures and cover screw fractures. In this case report we have elucidated an adhered cover screw in an implant. PMID:24392429

  8. Replacing worn overdenture abutments of an unknown implant system by using laser welding: a clinical report.

    PubMed

    Mohunta, Vrinda V; Stevenson, James A; Lee, Damian J

    2014-09-01

    This clinical report describes a procedure for replacing worn ball abutments with low-profile resilient abutments by using laser welding when the implant system for a mandibular implant-supported overdenture could not be identified. PMID:24836281

  9. Findings of a Four-Year Randomized Controlled Clinical Trial Comparing Two-Piece and One-Piece Zirconia Abutments Supporting Single Prosthetic Restorations in Maxillary Anterior Region.

    PubMed

    Paolantoni, Guerino; Marenzi, Gaetano; Blasi, Andrea; Mignogna, Jolanda; Sammartino, Gilberto

    2016-01-01

    The purpose of this randomized controlled study is to investigate the clinical results obtained over four years and incidence of complications associated with one- versus two-piece custom made zirconia anchorages, in single tooth implant-supported restorations of the maxillary anterior region. Sixty-five patients, with a total of 74 missing maxillary teeth, were selected in the period from February 2007 to July 2010. Two different ways of custom made zirconia abutment and final prosthetic restoration were evaluated: a standard zirconia abutment associated with a pressed layer of lithium disilicate with an all-ceramic cemented restoration versus one-piece restoration with the facing porcelain fired and pressed straight to the custom made zirconia abutment. In 29 cases, the restoration consisted of an all-ceramic restoration for cementation (two pieces); in 45 cases the restoration was a screw-retained restoration (one piece). Three all-ceramic restorations broke during the observation time. Two one-piece restorations fractured after 26 months. At follow-up examination there were no significant differences between one-piece and two-piece groups regarding the PI, BI, and MBL. Awaiting studies with longer follow-up times, a careful conclusion is that zirconia anchorages for single-implant restorations seem to demonstrate good short-term technical and biological results. PMID:27027093

  10. Findings of a Four-Year Randomized Controlled Clinical Trial Comparing Two-Piece and One-Piece Zirconia Abutments Supporting Single Prosthetic Restorations in Maxillary Anterior Region

    PubMed Central

    Paolantoni, Guerino; Marenzi, Gaetano; Blasi, Andrea; Mignogna, Jolanda; Sammartino, Gilberto

    2016-01-01

    The purpose of this randomized controlled study is to investigate the clinical results obtained over four years and incidence of complications associated with one- versus two-piece custom made zirconia anchorages, in single tooth implant-supported restorations of the maxillary anterior region. Sixty-five patients, with a total of 74 missing maxillary teeth, were selected in the period from February 2007 to July 2010. Two different ways of custom made zirconia abutment and final prosthetic restoration were evaluated: a standard zirconia abutment associated with a pressed layer of lithium disilicate with an all-ceramic cemented restoration versus one-piece restoration with the facing porcelain fired and pressed straight to the custom made zirconia abutment. In 29 cases, the restoration consisted of an all-ceramic restoration for cementation (two pieces); in 45 cases the restoration was a screw-retained restoration (one piece). Three all-ceramic restorations broke during the observation time. Two one-piece restorations fractured after 26 months. At follow-up examination there were no significant differences between one-piece and two-piece groups regarding the PI, BI, and MBL. Awaiting studies with longer follow-up times, a careful conclusion is that zirconia anchorages for single-implant restorations seem to demonstrate good short-term technical and biological results. PMID:27027093

  11. [Interproximal tooth cleansing of abutment teeth and pontic design].

    PubMed

    Kocher, T; Plagmann, H C; Engelsmann, U; Schlüter, R

    1990-03-01

    This clinical study was an attempt to find out if a patient's home care plaque control at his or her abutment tooth is more effectively enhanced by a modified ridge lap or a hygienic pontic design. Oral hygiene was performed either with a tooth brush alone or in combination with an interdental brush. We found that the effectivity of interproximal toothcleaning was not influenced by the pontic design and that only interdental brushes permit a good plaque control at the proximal area of the abutment tooth. This implies that "self cleansing" is non-existent in these tooth areas. PMID:2257819

  12. The Effects of Screw Length on Stability of Simulated Osteoporotic Distal Radius Fractures Fixed with Volar Locking Plates

    PubMed Central

    Wall, Lindley B.; Brodt, Michael D.; Silva, Matthew J.; Boyer, Martin I.; Calfee, Ryan P.

    2013-01-01

    Purpose Volar plating for distal radius fractures has caused extensor tendon ruptures secondary to dorsal screw prominence. This study was designed to determine the biomechanical impact of placing unicortical distal locking screws and pegs in an extra-articular fracture model. Methods Volar-locking distal radius plates were applied to 30 osteoporotic distal radius models. Radii were divided into 5 groups based on distal locking fixation: bicortical locked screws, 3 lengths of unicortical locked screws (abutting the dorsal cortex [full length], 75% length, and 50% length to dorsal cortex), and unicortical locked pegs. Distal radius osteotomy simulated a dorsally comminuted, extra-articular, fracture. Each constructs stiffness was determined under physiologic loads (axial compression, dorsal bending volar bending) before and after 1000 cycles of axial conditioning and prior to axial loading to failure (2mm of displacement) and subsequent catastrophic failure. Results Cyclic conditioning did not alter constructs stiffness. Stiffness to volar bending and dorsal bending forces were similar between groups. Final stiffness(N/mm) under axial load was statistically equivalent for all groups: bicortical screws(230), full-length unicortical screws(227), 75% length unicortical screws(226), 50% length unicortical screws(187), unicortical pegs(226). Force(N) at 2 mm displacement was significantly less for 50% length unicortical screws(311) compared to bicortical screws(460), full-length unicortical screws(464), 75% length unicortical screws(400), and unicortical pegs(356). Force(N) to catastrophic fracture was statistically equivalent between groups but mean values for pegs(749) and 50% length unicortical(702) screws were 16-21% less than means for bicortical(892), full-length unicortical(860), and 75% length(894) unicortical constructs. Discussion Locked unicortical distal screws of at least 75% length produce construct stiffness similar to bicortical fixation. Unicortical

  13. Porous-coated acetabular components with screw fixation. Five to ten-year results.

    PubMed

    Latimer, H A; Lachiewicz, P F

    1996-07-01

    The results of 136 consecutive primary total hip arthroplasties performed by one surgeon with the Harris-Galante-I porous-coated acetabular component were reviewed at a mean of seven years (range, five to ten years). In all hips, the outer diameter of the acetabular component was the same as the diameter of the final reamer used in the preparation of the acetabulum. However, this reamer was used only briefly at the rim of the acetabulum, and therefore the components had so-called press-fit stability. A mean of four screws (range, three to six screws) were used for additional fixation of the component. The clinical evaluation was performed with use of the Harris hip score. Standardized anteroposterior radiographs of the pelvis were assessed for migration of the component, radiolucent and radiodense lines, linear wear of the polyethylene, and osteolysis. No acetabular component had been revised for loosening and none were radiographically loose at the time of the most recent follow-up evaluation. There were no complications related to the use of the screws, and no screw had bent or broken. A non-progressive radiolucent line was seen in one acetabular zone in thirty-four hips (25 per cent) and in two acetabular zones in six hips (4 per cent). No hip had a radiolucent line in all three acetabular zones. The mean rate of linear wear of the polyethylene was 0.1 millimeter per year. There was no dissociation of the acetabular liner from the metal shell. Two hips (1 per cent) had asymptomatic osteolysis in the ischium and adjacent to the rim of the acetabular component; this was treated with grafting at the site of the lesion and exchange of the femoral head and the worn polyethylene liner. Five femoral components inserted without cement and one inserted with cement were revised because of loosening. The data suggest that, at a mean of seven years, fixation of this porous-coated component was uniformly excellent. The low prevalence of radiolucent lines and the absence of

  14. Screw/stud removal tool

    NASA Technical Reports Server (NTRS)

    Daniels, K.; Herrick, D. E.; Rothermel, L.

    1980-01-01

    Tool removes stubborn panheaded screws or studs where conventional tools would be either too weak or inconvenient to use. Screws with damaged heads or slots can also be removed this way. Tool can be worked with one hand and easily fits limited-access and blind areas. It can be made in various sizes to fit different screwheads.

  15. Litanium expandable pedicle screw for the treatment of degenerative and traumatic spinal diseases in osteoporotic patients: preliminary experience.

    PubMed

    Gazzeri, Roberto; Roperto, Raffaelino; Fiore, Claudio

    2012-12-01

    Osteoporosis is a major global health problem, with over 10 million people currently diagnosed with the disease. Although 80% of osteoporotic patients are women, a considerable number of men are also affected. Also, due to increasing life expectancy, the number of elderly patients with osteoporosis affected by degenerative and traumatic spinal diseases will increase further. Osteoporosis reduces bone quality through negative bone remodelling. Low bone quality can reduce the pull-out strength of pedicle screw, and negative bone remodelling can cause delayed bone fusion. However, pedicle screw instrumentation of the osteoporotic spine carries an increased risk of screw loosening, pull-out, and fixation failure. Our preliminary study aims to investigate the efficiency of expandable pedicle screws (OsseoScrew-Spinal Fixation System, Alphatec Spine Inc., Carlsbad, CA) in osteoporotic spinal patients. All osteoporotic patients with degenerative and traumatic spinal diseases admitted in our department underwent a pre-operative spinal x-Ray and MRI or CT. Pre-operative clinical assesment of patients was based on the visual analog scale (VAS) and Owestry Disability (ODI) questionnaire-a disease-specific outcome measure. Ten osteoporotic patients were treated with expandable pedicle screws (OsseoScrew). Post-operative clinical assessment of patients was based on the VAS and ODI questionnaire at 3 months and 1 year of follow-up. Post-operative radiologic follow-up was performed after 3 days (CT, x-ray); 3 months (x-ray); 6 months (spinal CT); and 1 year (spinal CT). Expandable pedicle screws improved pull-out strength as compared to standard pedicle screws in osteoporotic patients with degenerative and traumatic spinal diseases. PMID:23023577

  16. An Innovative Universal Screw Removal Instrument

    PubMed Central

    Elmadağ, Mehmet; Uzer, Gökçer; Acar, Mehmet Ali

    2015-01-01

    Objective To present the clinical benefits of an instrument designed to facilitate removal of polyaxial screws during revision surgery. Methods All polyaxial screws can be removed without additional materials or a large amount of debridement using our newly designed instrument. Forty-two screws were removed from five patients without any complications using this instrument. Results We removed the cap screws and rods from the 42 polyaxial screws in five patients and made them monoaxial using the new screw removal apparatus. The screws and rods were removed quickly in a minimally invasive way with no complications. No damage to the pedicle or surrounding soft tissue occurred during screw removal. No neurogenic changes developed during revision surgery after changing the screws. Conclusion This newly designed screw removal instrument was used safely and effectively to remove all polyaxial and monoaxial pedicle screws. PMID:25883660

  17. Polypyrrole coating on poly-(lactide/glycolide)-β-tricalcium phosphate screws enhances new bone formation in rabbits.

    PubMed

    Zhao, Ming-Dong; Björninen, Miina; Cao, Lu; Wang, Hui-Ren; Pelto, Jani; Li, Xiang-Qian; Hyttinen, Jari; Jiang, Yun-Qi; Kellomäki, Minna; Miettinen, Susanna; Sándor, George K; Seppänen, Riitta; Haimi, Suvi; Dong, Jian

    2015-12-01

    Polypyrrole (PPy) has gained interest as an implant material due to its multifunctional properties and its high compatibility with several cell and tissue types. For the first time, the biocompatibility and osteointegration of PPy coating, incorporated with chondroitin sulfate (CS), were studied in vivo by implanting PPy-coated bioabsorbable bone fixation composite screws of poly-(lactide/glycolide) copolymer (PLGA) and β-tricalcium phosphate (TCP) into New Zealand white rabbits. Uncoated bioabsorbable polymer composite screws and commercially available stainless steel cortical screws were used as reference implants. The rabbits were euthanized 12 and 26 weeks after the implantation. The systemic effects were evaluated from food and water consumption, body weight, body temperature, clinical signs, blood samples, internal organ weights, and histological examination. Local effects were studied from bone tissue and surrounding soft tissue histology. New bone formation was evaluated by micro-computed tomography, tetracycline labeling and torsion tests. Torsion tests were performed in order to capture the peak value of the torsion force during the course of the screw's loosening. The coated screws induced significantly more bone formation than the uncoated screws. In addition, none of the implants induced any systemic or local toxicity. The results suggest that PPy is biocompatible with bone tissue and is a potential coating for enhancing osteointegration in orthopedic implants. PMID:26610717

  18. 71. VIEW SHOWING PROGRESS ON ABUTMENT A AND PIERS 9, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    71. VIEW SHOWING PROGRESS ON ABUTMENT A AND PIERS 9, 10, AND 11. CONCRETE BEING PLACED IN PIER 11-B, LOOKING NORTHWEST. Taken on August 8, 1935. - Upper Mississippi River 9-Foot Channel, Lock & Dam No. 10, Guttenberg, Clayton County, IA

  19. 21. Photocopy of drawing, Plan of Abutments for Bridge No. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    21. Photocopy of drawing, Plan of Abutments for Bridge No. 79B at Main & Washington Sts., South Norwalk, N.Y. Div., N.Y., N.H. and H.R.R., dated November 22, 1895. Original on file with Metro North Commuter Railroad. - South Norwalk Railroad Bridge, South Main & Washington Streets, Norwalk, Fairfield County, CT

  20. 12. DETAIL OF NORTH ABUTMENT (EAST SIDE) AND PIER. LOOKING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. DETAIL OF NORTH ABUTMENT (EAST SIDE) AND PIER. LOOKING NORTH. - Route 31 Bridge, New Jersey Route 31, crossing disused main line of Central Railroad of New Jersey (C.R.R.N.J.) (New Jersey Transit's Raritan Valley Line), Hampton, Hunterdon County, NJ

  1. Remains of abutments for Bridge No. 1575 at MD Rt. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Remains of abutments for Bridge No. 1575 at MD Rt. 51 in Spring Gap, Maryland, looking northeast. (Compare with HAER MD-115 photos taken 1988). - Western Maryland Railway, Cumberland Extension, Pearre to North Branch, from WM milepost 125 to 160, Pearre, Washington County, MD

  2. 28. VIEW SOUTHWEST, EAST ABUTMENT SHOWING BASCULE LEAF IN RAISED ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    28. VIEW SOUTHWEST, EAST ABUTMENT SHOWING BASCULE LEAF IN RAISED POSITION WITH THE EXTREME UPPER PORTION OF THE BASCULE RACK GEAR SHOWING IN THE LOWER RIGHT PORTION OF THE PHOTOGRAPH - Tomlinson Bridge, Spanning Quinnipiac River at Forbes Street (U.S. Route 1), New Haven, New Haven County, CT

  3. 27. VIEW NORTHEAST, EAST ABUTMENT SHOWING DRIVE GEAR 'D' IN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    27. VIEW NORTHEAST, EAST ABUTMENT SHOWING DRIVE GEAR 'D' IN LOWER CENTER OF PHOTOGRAPH AND RACKS ON CENTER BASCULE GIRDERS 'B' AND 'C' AT LEFT CENTER - Tomlinson Bridge, Spanning Quinnipiac River at Forbes Street (U.S. Route 1), New Haven, New Haven County, CT

  4. 38. VIEW EAST, WEST ABUTMENT, SOUTH SIDE VIEW OF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    38. VIEW EAST, WEST ABUTMENT, SOUTH SIDE - VIEW OF RACK GEAR ON BASCULE GIRDER 'D' - NOTE COUNTERWEIGHT AND COUNTERWEIGHT LINK AT UPPER LEFT OF PHOTOGRAPH - Tomlinson Bridge, Spanning Quinnipiac River at Forbes Street (U.S. Route 1), New Haven, New Haven County, CT

  5. 14. LOOKING NW FROM EASTERN ABUTMENT, WITH SWING SPAN IN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    14. LOOKING NW FROM EASTERN ABUTMENT, WITH SWING SPAN IN OPEN POSITION. NOTE BUMPER ON CURVED RACK AT BOTTOM LEFT OF FRAME. - Chicago, Milwaukee & St. Paul Railway, Bridge No. Z-6, Spanning North Branch of Chicago River, South of Cortland Street, Chicago, Cook County, IL

  6. 7. OBLIQUE VIEW OF WEST BRIDGE ELEVATION, SHOWING NORTHERN ABUTMENT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. OBLIQUE VIEW OF WEST BRIDGE ELEVATION, SHOWING NORTHERN ABUTMENT (LEFT), CANTILEVERED NORTHERN TRUSS SECTION (CENTER), AND PIER (RIGHT), FROM SOUTHWEST SIDE OF BRIDGE. FACING NORTHEAST. - Coverts Crossing Bridge, Spanning Mahoning River along Township Route 372 (Covert Road), New Castle, Lawrence County, PA

  7. SOUTH ABUTMENT AND BELOW DECK DETAIL. NOTE THE FLOOR BEAMS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    SOUTH ABUTMENT AND BELOW DECK DETAIL. NOTE THE FLOOR BEAMS ON THE APPROACH DO NOT REST ON THE LOWER CHORD BUT ARE SUSPENDED BELOW THE LOWER CHORDS BY MEANS LOOPED IRON HANGERS THAT WRAP AROUND WOODEN BLOCKS RESTING ON THE LOWER CHORD. - Crum Bridge, Spanning Little Muskingum River, TR 384A (formerly Old Camp Road), Rinard Mills, Monroe County, OH

  8. 5. GENERAL VIEW FROM EAST ABUTMENT ALONG AXIS OF DAM ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. GENERAL VIEW FROM EAST ABUTMENT ALONG AXIS OF DAM SHOWING STEEL SHEET PILE CUTOFF WALL COMPLETED, AND EMBANKMENT MATERIAL BEING COMPACTED INTO POSITION. Volume XVI, No. 11, July 21, 1939. - Prado Dam, Embankment, Santa Ana River near junction of State Highways 71 & 91, Corona, Riverside County, CA

  9. Detail of north abutment of Seventh Street Bridge. Notice pin ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail of north abutment of Seventh Street Bridge. Notice pin connection that serves to anchor eye-bar suspension cable after descending below roadway level inside of the compressed lower girder. The bridge is not anchored in the traditional sense. - Three Sisters Bridges, Seventh Street Bridge, Spanning Allegheny River at Seventh Street, Pittsburgh, Allegheny County, PA

  10. 11. 100 foot through truss north east bearing abutment ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. 100 foot through truss - north east bearing abutment of the second through truss, showing that the bearing point is to the backmost position of the concrete pier. This bearing point is on a concrete extension of the original bearing point now covered by rock and soil. - Weidemeyer Bridge, Spanning Thomes Creek at Rawson Road, Corning, Tehama County, CA

  11. 6. DETAIL OF SOUTHEAST ABUTMENT, SHOWING MANUFACTURER'S NAME ('PHOENIXUSA') ON ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. DETAIL OF SOUTHEAST ABUTMENT, SHOWING MANUFACTURER'S NAME ('PHOENIX-USA') ON HORIZONTAL MEMBER LEFT OF CENTER. - North Branch Quantico Creek Bridge, Prince William Forest Park, on NPS Route 406 spanning north branch of Quantico Creek, Dumfries, Prince William County, VA

  12. DESCHUTES PROJECT. WICKIUP RESERVOIR, COMPLETE EAST DIKE FROM LEFT ABUTMENT. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DESCHUTES PROJECT. WICKIUP RESERVOIR, COMPLETE EAST DIKE FROM LEFT ABUTMENT. Photocopy of historic photograph (original photograph on file at National Archives, Rocky Mountain Region, Denver, CO). R.A. Baker, photographer, August 29, 1947 - Wickiup Dam, Dikes and Spillway, Deschutes River, La Pine, Deschutes County, OR

  13. DESCHUTES PROJECT, OREGON, WICKIUP DAM, LOOKING NORTH FROM RIGHT ABUTMENT. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DESCHUTES PROJECT, OREGON, WICKIUP DAM, LOOKING NORTH FROM RIGHT ABUTMENT. BUREAU MAINTENANCE BUILDINGS LOCATED BELOW THE DAM WITH ROUND MOUNTAIN BEYOND. SHOW COVERED CULTUS MOUNTAIN TO THE LEFT. Photocopy of historic photographs (original photograph on file at National Archives, Rocky Mountain Region, Denver, CO). R.A. Baker, Photographer, April 25, 1950 - Wickiup Dam, Deschutes River, La Pine, Deschutes County, OR

  14. RUINS OF NORTH ABUTMENT OF OR & L RAILWAY TRESTLE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    RUINS OF NORTH ABUTMENT OF OR & L RAILWAY TRESTLE ON DOWNSTREAM SIDE OF BRIDGE NO. 3A, VIEW FROM THE EAST - Oahu Railway & Land Company Trestle Ruins, Spanning Makaha Stream between Makaha Beach & Farrington Highway, near Kili Drive, Honolulu, Honolulu County, HI

  15. RUINS OF FOUNDATIONS AND SOUTH ABUTMENT OF OR & L ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    RUINS OF FOUNDATIONS AND SOUTH ABUTMENT OF OR & L RAILWAY TRESTLE ON DOWNSTREAM SIDE OF BRIDGE NO. 3A, VIEW FROM THE SOUTH - Oahu Railway & Land Company Trestle Ruins, Spanning Makaha Stream between Makaha Beach & Farrington Highway, near Kili Drive, Honolulu, Honolulu County, HI

  16. RUINS OF FOUNDATIONS AND NORTH ABUTMENT OF OR & L ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    RUINS OF FOUNDATIONS AND NORTH ABUTMENT OF OR & L RAILWAY TRESTLE ON DOWNSTREAM SIDE OF BRIDGE NO. 3A, VIEW FROM THE SOUTHEAST - Oahu Railway & Land Company Trestle Ruins, Spanning Makaha Stream between Makaha Beach & Farrington Highway, near Kili Drive, Honolulu, Honolulu County, HI

  17. RUINS OF FOUNDATIONS AND SOUTH ABUTMENT OF OR & L ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    RUINS OF FOUNDATIONS AND SOUTH ABUTMENT OF OR & L RAILWAY TRESTLE ON DOWNSTREAM SIDE OF BRIDGE NO. 3, VIEW FROM THE NORTHWEST FROM BRIDGE NO. 3 - Oahu Railway & Land Company Trestle Ruins, Spanning Makaha Stream between Makaha Beach & Farrington Highway, near Kili Drive, Honolulu, Honolulu County, HI

  18. 4. Prefabricated concrete panel portion of Snowshed 29 abutting west ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. Prefabricated concrete panel portion of Snowshed 29 abutting west portal of Tunnel 41, view to east, 135mm lens. Function of the elevated portion is unknown, but it may help to channel exhaust fumes out of the shed and the two-mile long tunnel. - Central Pacific Transcontinental Railroad, Tunnel No. 41, Milepost 193.3, Donner, Placer County, CA

  19. 5. View of bearing on north abutment and first panel ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. View of bearing on north abutment and first panel point, note eye bar construction of chord and pin connection of panel point - Bridge No. 2.4, Spanning Boiling Fork Creek at Railroad Milepost JC-2.4, Decherd, Franklin County, TN

  20. 29. SECTION DRAWINGS OF HEADGATE IN RIGHT (WEST) ABUTMENT, SPILLWAY, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    29. SECTION DRAWINGS OF HEADGATE IN RIGHT (WEST) ABUTMENT, SPILLWAY, AND PENSTOCK Sections and profiles of dam and pipe line, Exhibit J(3). Prepared by C. F. Uhden, electrical engineer, for the Okanogan Valley Power Company, 1916. - Enloe Dam, On Similkameen River, Oroville, Okanogan County, WA

  1. Detail of north intermediate abutment pylon showing proximity of adjacent ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail of north intermediate abutment pylon showing proximity of adjacent 1001-1007 East First Street (James K. Hill and Sons Pickle Works Building), facing east - First Street Bridge, Spanning Los Angeles River at First Street, Los Angeles, Los Angeles County, CA

  2. 29. View of construction shops and housing from west abutment. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    29. View of construction shops and housing from west abutment. River bed, foreground, downstream from dam site, being excavated for aggregate material. Photographer unknown, 1927. Source: MWD. - Waddell Dam, On Agua Fria River, 35 miles northwest of Phoenix, Phoenix, Maricopa County, AZ

  3. 25. A QUIRK ON THE FACING OF THE NORTHEASTERN ABUTMENT. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    25. A QUIRK ON THE FACING OF THE NORTHEASTERN ABUTMENT. IT HAS BEEN CAST IN PLACE, THE GHOSTS OF THE WOODEN FORMERS CAN BE SEEN. EVEN THE MITRES WITHIN THE SUNK PORTIONS OF THE CASTING ARE VISIBLE. POISON IVY AND TRUMPET VINE CLING WELL TO THE ROUGH CONCRETE. - Main Street Bridge, Spanning East Fork Whitewater River, Richmond, Wayne County, IN

  4. 8. Detail showing concrete abutment, showing substructure of bridge, specifically ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. Detail showing concrete abutment, showing substructure of bridge, specifically west side of arch and substructure. - Presumpscot Falls Bridge, Spanning Presumptscot River at Allen Avenue extension, 0.75 mile west of U.S. Interstate 95, Falmouth, Cumberland County, ME

  5. 14. Looking slightly southeast, showing railing, some abutment and east ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    14. Looking slightly southeast, showing railing, some abutment and east side all the way across the bridge. - Presumpscot Falls Bridge, Spanning Presumptscot River at Allen Avenue extension, 0.75 mile west of U.S. Interstate 95, Falmouth, Cumberland County, ME

  6. PRELIMINARY COMMUNICATION: Abutment region dosimetry for sequential arc IMRT delivery

    NASA Astrophysics Data System (ADS)

    Low, Daniel A.; Mutic, Sasa

    1997-07-01

    Arc-based intensity modulated radiation therapy (IMRT) planning and delivery is available as a commercial product (Nomos Corp.). The dose distribution is delivered to 1.68 cm thick regions, and the patient moved in a precise manner between treatments. Assuming accurate patient positioning, the abutment region dose distribution near the gantry isocentre is delivered with no undesired dose heterogeneities. However, for regions far from the isocentre, the dose distribution may exhibit high- or low-dose regions due to uncompensated beam divergence for arc treatments of less than gantry angle length. A study has been initiated to characterize abutment region dose distribution heterogeneities for sequential arc IMRT delivery. Five dose distributions were optimized, each using 8 cm diameter target volumes at different distances from the isocentre, and the arc delivery limited to symmetric about the vertical axis. The target lengths were sufficient to require a treatment consisting of five couch positions, yielding four abutment regions. The dose within the abutment regions was measured using film and analysed as a function of off-axis position along both the vertical and horizontal directions. Little dependence on the dose heterogeneity was seen along the horizontal axis passing through the isocentre. However, the abutment regions along the vertical axis contained 15% low and 7% high doses at 7 cm above and below the isocentre respectively. This dose heterogeneity is not predicted by the current clinical release of the treatment planning software due to limitations of the dose calculation algorithm. The intensity of dose heterogeneity is considered sufficient to warrant further study.

  7. Split spline screw

    NASA Technical Reports Server (NTRS)

    Vranish, John M. (Inventor)

    1993-01-01

    A split spline screw type payload fastener assembly, including three identical male and female type split spline sections, is discussed. The male spline sections are formed on the head of a male type spline driver. Each of the split male type spline sections has an outwardly projecting load baring segment including a convex upper surface which is adapted to engage a complementary concave surface of a female spline receptor in the form of a hollow bolt head. Additionally, the male spline section also includes a horizontal spline releasing segment and a spline tightening segment below each load bearing segment. The spline tightening segment consists of a vertical web of constant thickness. The web has at least one flat vertical wall surface which is designed to contact a generally flat vertically extending wall surface tab of the bolt head. Mutual interlocking and unlocking of the male and female splines results upon clockwise and counter clockwise turning of the driver element.

  8. Percutaneous Sacroiliac Screw Technique.

    PubMed

    Tidwell, John; Cho, Rosa; Reid, J Spence; Boateng, Henry; Copeland, Carol; Sirlin, Edward

    2016-08-01

    Remembering that preoperative planning, surgical indications, and fracture reduction are paramount for this procedure, presented here is our technique for performing percutaneous sacroiliac screws, both transiliac-transsacral and sacral style. A combination of video, still pictures, and fluoroscopy images will guide the viewer through the process we routinely use highlighting specific details. Patient positioning and intraoperative fluoroscopy imaging are critical to a successful procedure. Although inlet and outlet films remain important, we find the procedure best started on the lateral sacral view to reduce the need for start site, trajectory, and imaging position changes during the case. A cannulated pig sticker (drill guide) used with long drill tip guide wires provide improved manual control to both finding a good start site and directing the trajectory. For patient safety, sacral anatomy and safe zones are discussed as well. Using these technical points will help make this a successful procedure. PMID:27441927

  9. Orientation of the "Lisfranc screw".

    PubMed

    Panchbhavi, Vinod K

    2012-11-01

    The reduction and stabilization of diastases between the medial cuneiform and the base of second metatarsal after a Lisfranc ligament injury is a crucial objective in the open reduction and internal fixation of these injuries. To achieve this objective, a single screw is used. The present practice is to insert the screw directed from the medial cuneiform bone into the base of the second metatarsal. This technique trick describes an easier method of insertion of the screw and one that possibly provides a better fixation. PMID:22549028

  10. The combined role of wear particles, macrophages and lymphocytes in the loosening of total joint prostheses.

    PubMed

    Revell, Peter A

    2008-11-01

    This review considers the causes of loosening of prosthetic joint replacement paying attention to the biological mechanisms rather than other effects that are physical, such as component fracture and other failure related to mechanical problems. Infection accounts for approximately 1.5 per cent of joint loosening and when it occurs it is a cause of serious concern to the surgeon. The loosening of prosthetic joints in the absence of infection is by far the most common reason for revision surgery and is known as aseptic loosening. While this may be multifactorial in terms of causation, and non-biological factors may contribute significantly in a particular individual, a significant part is undoubtedly played by the generation of wear debris, mainly from the bearing surfaces of the joint, and the cellular reaction to this in the implant bed. Phagocytic cells (macrophages and multinucleated giant cells) are the ones that remove foreign material from the tissues, and the ways in which these cells function in the interface between implant and bone are described. Mediators produced locally include numerous cytokines, enzymes and integrins. There is evidence for interactions between macrophages and locally recruited lymphocytes, which may or may not give rise to an immunologically mediated process.Sensitization of individuals having metal implants in place has been shown by positive skin tests or blood lymphocyte transformation tests and in these cases has been accompanied by loosening and failure of the replacement joint. The question remains as to whether this process is also present in a proportion of individuals with aseptic loosening in the absence of clearly defined clinical evidence of sensitization.Numerous studies performed by the author's group and, latterly, by others suggest that the cellular reactions detected in the tissues in cases of aseptic loosening are indeed those of contact sensitization. There is good evidence to show that a type IV cell

  11. 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. PMID:27129382

  12. Numerical Studies on Time-Varying Stiffness of Disk-Drum Type Rotor with Bolt Loosening

    NASA Astrophysics Data System (ADS)

    Qin, Zhaoye; Chu, Fulei

    2015-07-01

    Disk-drum type rotors are widely used in industry for their high stiffness and low weight properties. In disk-drum type rotors, the adjacent disks and drums are commonly connected by bolted joints. Those rotating joint interfaces are subjected to numerous combinations of loads during normal operation, where loosening of the connecting bolts might occur. The bolt loosening will change the local stiffness of the rotor, which in turn affect the rotor dynamics and even result in structural failures. In this paper, the local stiffness of a disk- drum rotor with bolt loosening is investigated numerically. A three-dimensional (3D) finite element (FE) model for the bolted disk-drum joint is established in ANSYS, where the bolt loosening is simulated by reducing the preloads of certain bolts, and removing those bolts as the limiting case. Simulations are performed on the FE model to evaluate the joint behaviour under static loads. Periodic variations of the joint deflections with respect to the rotation angle of the shaft are obtained, which implies the appearance of the time-varying local stiffness in the rotor system. The studies in this paper help accurate prediction of the rotor dynamics and early detection of bolt loosening.

  13. Occult Infection in Aseptic Joint Loosening and the Diagnostic Role of Implant Sonication

    PubMed Central

    Kempthorne, J. T.; Ailabouni, R.; Raniga, S.; Hammer, D.; Hooper, G.

    2015-01-01

    Our aim was to determine the incidence of occult infection and to examine the role of ultrasound sonication of the implants in cases of presumed aseptic loosening in a prospective trial. Joint swabs, aspirates, and deep tissue samples were obtained from around the prosthesis for routine microbiology. Each prosthesis was sonicated and the sonicate examined with Gram staining and extended cultures. There were 106 joints in the study of which 54 were revised for aseptic loosening and 52 were assigned to the control revision group. There were 9 positive cultures with 8/54 positive cultures in the aseptic loosening group and 1/52 in the control revision group (p = 0.017, associated OR 47.7). We found concordant results between sonication fluid culture and conventional samples in 5/9 cultures. Preoperative inflammatory markers were not prognostic for infection. Coagulase-negative Staphylococcus was the most commonly cultured organism (7/9). Previously unrecognised infection was present in 15% of patients undergoing revision for aseptic loosening. Ultrasound sonication of the removed prosthesis was less sensitive than conventional sampling techniques. We recommend routine intraoperative sampling for patients having revision for aseptic loosening, but we do not support the routine use of ultrasound sonication for its detection. PMID:26583149

  14. Self-energized screw coupling

    NASA Technical Reports Server (NTRS)

    Lefever, A. E.; Totah, R. S.

    1980-01-01

    Threaded coupling carries its own store of rotational energy. Originally developed to ease task of astronauts assembling structures in space, coupling offers same advantages in other hazardous operations, such as underwater and in and around nuclear reactors. Coupling consists of two parts: crew portion and receptacle. When screw portion is inserted into receptacle and given slight push by operator, trigger pins release ratchet, allowing energy stored in springs to rotate screw into nut in receptacle.

  15. Angulated abutments and perimplants stress: F.E.M. analysis

    PubMed Central

    CARDELLI, P.; MONTANI, M.; GALLIO, M.; BIANCOLINI, M.; BRUTTI, C.; BARLATTANI, A.

    2009-01-01

    SUMMARY The long-term success of an implant supported prosthesis depends on many variables. In addition to the osseointegration rules that are commonly acknowledged, a clinician should consider also the biomechanical concepts related to the manufacturing process of a prosthetic structure assembly and their effects on the bone/implant interface. These concepts are particularly important when the anatomical structures leads to angulate the prosthetic component with respect to the fixture. In this study the stress distribution on the bone and on the prosthetic components was evaluated by means of a Finite Element Analysis (FEA). The effect of abutment axis angle was investigated considering three different measures: 15°, 25° and 35°. The simulation of both 450N maximal biting and 100N functional forces, highlighted the stress trend, which suggests as a maximum limit to choose an abutment with an angulation of 25°. PMID:23285352

  16. Acid-etched splinting to a ceramometal abutment.

    PubMed

    Jordan, R D; Aquilino, S A; Krell, K V

    1986-05-01

    This technique describes an acid-etch metal splint with a ceramometal abutment. The internal surface of the DuraLingual Wing Form patterns provide undercuts necessary for composite bonding. The external surface provides a smooth solid metal surface when cast. Since this system uses mechanical undercuts, the resin-bonded splints can have multiple try-ins without the detrimental effects of burnishing and contamination that occur with electrolytically etched metal surfaces. If an abutment for a resin-retained fixed partial denture requires a ceramometal crown, a DuraLingual Wing Form can be incorporated onto its lingual surface thereby providing mechanical undercuts for bonding. The opposite undercuts of the crown and splint provide excellent bond strength for the system. PMID:3519944

  17. Evaluation of abutment scour prediction equations with field data

    USGS Publications Warehouse

    Benedict, S.T.; Deshpande, N.; Aziz, N.M.

    2007-01-01

    The U.S. Geological Survey, in cooperation with FHWA, compared predicted abutment scour depths, computed with selected predictive equations, with field observations collected at 144 bridges in South Carolina and at eight bridges from the National Bridge Scour Database. Predictive equations published in the 4th edition of Evaluating Scour at Bridges (Hydraulic Engineering Circular 18) were used in this comparison, including the original Froehlich, the modified Froehlich, the Sturm, the Maryland, and the HIRE equations. The comparisons showed that most equations tended to provide conservative estimates of scour that at times were excessive (as large as 158 ft). Equations also produced underpredictions of scour, but with less frequency. Although the equations provide an important resource for evaluating abutment scour at bridges, the results of this investigation show the importance of using engineering judgment in conjunction with these equations.

  18. "Security loop" tie: a new technique to overcome loosening of surgical knots.

    PubMed

    Alzacko, Saadallah Mohammad; Majid, Omer Waleed

    2007-11-01

    Sutures require knots so as to ensure optimal tissue closure strength. Loosening of surgical knots during or after tying can lead to an ineffective suture and compromise the final result. Loosening is affected mainly by the type of suture material and nature of surgical field. In palatal surgery, tying secure knots is a major consideration and may present a technical challenge. In this article, and after a review of the literature, we present a new modification of the usual knot-tying technique to maximize knot security and prevent knot loosening after the first throw is done. This technique was found to be effective, simple, fast, easy to learn, and saves time and material. PMID:17964468

  19. 10. 100 foot through truss north west bearing abutment ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. 100 foot through truss - north west bearing abutment of the second through truss, showing the diagonal sway bracing to its alternate pier. This bearing point is on a concrete extension of the original bearing point now covered by rock and soil. Note that the bearing point is to the backmost position on the concrete pier. - Weidemeyer Bridge, Spanning Thomes Creek at Rawson Road, Corning, Tehama County, CA

  20. The development and evaluation of individualized templates to assist transoral C2 articular mass or transpedicular screw placement in TARP-IV procedures: adult cadaver specimen study

    PubMed Central

    Li, Xue-Shi; Wu, Zeng-Hui; Xia, Hong; Ma, Xiang-Yang; Ai, Fu-Zhi; Zhang, Kai; Wang, Jian-Hua; Mai, Xiao-Hong; Yin, Qing-Shui

    2014-01-01

    OBJECTIVES: The transoral atlantoaxial reduction plate system treats irreducible atlantoaxial dislocation from transoral atlantoaxial reduction plate-I to transoral atlantoaxial reduction plate-III. However, this system has demonstrated problems associated with screw loosening, atlantoaxial fixation and concealed or manifest neurovascular injuries. This study sought to design a set of individualized templates to improve the accuracy of anterior C2 screw placement in the transoral atlantoaxial reduction plate-IV procedure. METHODS: A set of individualized templates was designed according to thin-slice computed tomography data obtained from 10 human cadavers. The templates contained cubic modules and drill guides to facilitate transoral atlantoaxial reduction plate positioning and anterior C2 screw placement. We performed 2 stages of cadaveric experiments with 2 cadavers in stage one and 8 in stage two. Finally, guided C2 screw placement was evaluated by reading postoperative computed tomography images and comparing the planned and inserted screw trajectories. RESULTS: There were two cortical breaching screws in stage one and three in stage two, but only the cortical breaching screws in stage one were ranked critical. In stage two, the planned entry points and the transverse angles of the anterior C2 screws could be simulated, whereas the declination angles could not be simulated due to intraoperative blockage of the drill bit and screwdriver by the upper teeth. CONCLUSIONS: It was feasible to use individualized templates to guide transoral C2 screw placement. Thus, these drill templates combined with transoral atlantoaxial reduction plate-IV, may improve the accuracy of transoral C2 screw placement and reduce related neurovascular complications. PMID:25518033

  1. Load-Bearing Capacity of Fiber-Reinforced Composite Abutments and One-Piece Implants.

    PubMed

    Etxeberria, Marina; Abdulmajeed, Aous A; Escuin, Tomas; Vinas, Miguel; Lassila, Lippo V J; Närhi, Timo O

    2015-06-01

    Fiber-reinforced composites (FRC) can potentially help in a physiologic stress transmission due to its excellent biomechanical matching with living tissues. Novel one-piece FRC implants and abutments with two different fiber orientations were loaded until failure to assess the load-bearing capacity, fracture patterns, and precision of fit. The one-piece FRC implants showed significantly higher load-bearing capacity compared to FRC abutments regardless of the fiber orientation (p < 0.001). For FRC abutments, bidirectional abutments showed significantly higher loads compared to unidirectional abutments (p < 0.001). The type of structure and fiber orientation are strong determinant factors of the load-bearing capacity of FRC implants and abutments. PMID:26373199

  2. Stress Reduction Effect and Anti-Loosening Performance of Outer Cap Nut by Finite Element Method

    NASA Astrophysics Data System (ADS)

    Noda, Nao-Aki; Kuhara, Masahiro; Xiao, Yang; Noma, Shunsuke; Saito, Kinjiro; Nagawa, Masato; Yumoto, Atsushi; Ogasawara, Ayako

    Previously several kinds of anti-loosening bolts and nuts were invented. However, they usually need a certain amount of prevailing torque even before the nut touches a clamped member. A new outer cap nut named “Super loose proof (SPR)” has been developed to overcome such inconvenience. At first this outer cap nut can be rotated smoothly by hand until the nut touching the clamped member. After fastening the outer cap nut, anti-loosening performance can be realized by deforming the outer cap and producing thread contact force at the outer cap region. In this study, stress concentration and tightening-loosening behavior are analyzed by axi-symmetric and three-dimensional finite element methods. Under a certain bolt-axial force, the load distribution of the first thread decreases more than 12% with increasing initial clearance of outer cap nut. Stress concentration appearing at the first thread of the bolt is about 10% smaller than that of conventional nut, reflecting the increase of the thread contact force at the outer cap region. On the other hands, it is found that anti-loosening performance of SPR can be realized when the outer cap has high yield stress.

  3. Bolt-loosening identification of bolt connections by vision image-based technique

    NASA Astrophysics Data System (ADS)

    Nguyen, Tuan-Cuong; Huynh, Thanh-Canh; Ryu, Joo-Young; Park, Jae-Hyung; Kim, Jeong-Tae

    2016-04-01

    In this study, an algorithm using image processing techniques is proposed to identify bolt-loosening in bolted connections of steel structures. Its basic concept is to identify rotation angles of nuts from a pictured image, and is mainly consisted of the following 3 steps: (1) taking a picture for a bolt joint, (2) segmenting the images for each nut by image processing techniques, and (3) identifying rotation angle of each nut and detecting bolt-loosening. By using the concept, an algorithm is designed for continuous monitoring and inspection of the bolt connections. As a key imageprocessing technique, Hough transform is used to identify rotation angles of nuts, and then bolt-loosening is detected by comparing the angles before and after bolt-loosening. Then the applicability of the proposed algorithm is evaluated by experimental tests for two lab-scaled models. A bolted joint model which consists of a splice plate and 8 sets of bolts and nuts with 2×4 array is used to simulate inspection of bridge connections, and a model which is consisted of a ring flange and 32 sets of bolt and nut is used to simulate continuous monitoring of bolted connections in wind turbine towers.

  4. The effect of hydroxyapatite coated screw in the lateral fragility fractures of the femur. A prospective randomized clinical study.

    PubMed

    Pesce, V; Maccagnano, G; Vicenti, G; Notarnicola, A; Moretti, L; Tafuri, S; Vanni, D; Salini, V; Moretti, B

    2014-01-01

    Due to a growing numbers of lateral fragility fractures of the femur and their high social costs the need to work out an effective strategy in order to find a better solution for these patients is warranted. From January 2010 to July 2011, we carried out a prospective randomized clinical study comparing the results of patients with femoral lateral fractures treated by nail and cephalic hydroxyapatite coated screws (study group including 27 patients) compared to the patients with the same fractures treated with nail and head standard screws (control group including 27 patients). We defined the two parts of the femoral neck as ROI 1 (under the head screw) and ROI 2 (above the femoral screw) on the AP view. The bone density of the two areas was calculated using DEXA at T0 (1st day post-surgery), at T1 (40th day post-surgery), at T2 (3 months later), at T3 (1 year later). The clinical-radiography evaluations were based on the Harris Hip Score (HHS), ADL test and x-ray views of the hip. As far as the bone mineral density average of ROI 1 and ROI 2 is concerned, we found a significant statistical increase at T1 and T3 in the study group, while it was not significant in the control group. We could account for this data through the higher mechanical stability of hydroxyapatite coated screws than standard screws. In fact, this material was responsible for improved implant osteointegration. Thanks to a 1 year follow-up we were able to demonstrate the implant utility associated with augmentation and the importance of densitometry exams such as easily repeatable and low cost diagnostics to prevent the onset of complications linked to screw loosening. PMID:24750798

  5. Expandable insert serves as screw anchor

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Expandable self-locking adapter secures components to panels having one accessible side. Mounting holes in the panels may not be threaded to accommodate screws, therefore, the adapter contains a female thread that will mate a mounting screw.

  6. A comparison between screw- and cement-retained implant prostheses. A literature review.

    PubMed

    Shadid, Rola; Sadaqa, Nasrin

    2012-06-01

    Implant-supported restorations can be secured to implants with screws (screw-retained), or they can be cemented to abutments which are attached to implants with screws (cement-retained). This literature review discusses the advantages and disadvantages of each method of retention from different aspects. These aspects include: ease of fabrication and cost, esthetics, access, occlusion, retention, incidence of loss of retention, retrievability, clinical prosthesis fit, restriction of implant position, effect on peri-implant tissue health, provisionalization, immediate loading, impression procedures, porcelain fracture, and clinical performance. Peer-reviewed literature published in the English language between 1955 and 2010 was reviewed using PubMed and hand searches. Since the choice of using either method of retention is still controversial, this review article offers some clinical situations that prefer one method of retention over the other. The review demonstrated that each method of retention has certain advantages and disadvantages; however, there are some clinical situations in which it is better to select one method of retention rather than the other. PMID:21091343

  7. [Arthroscopic distal ulna resection after post traumatic ulno carpal abutment].

    PubMed

    Mathoulin, C; Pagnotta, A

    2006-11-01

    Ulno carpal abutments secondary to the sequels of a fracture of the radius are often due to the inversion of the distal radio ulnar index by shortening relative to the radius. This positive ulnar variance eventually leads to an abutment between the head of the ulnar and the proximal articular face of the lunate with alteration of the cartilaginous carpal surfaces. The wrist arthroscopy makes diagnosis and treatment possible in a less invasive way. The patients are operated on as outpatients under local regional anaesthetic using a pneumatic tourniquet. The arthroscope is positioned using the 3-4 radio carpal opening permitting exploration of the joint. The surgical treatment is performed by arthroscopy using a burr and going in through the 6R radio carpal opening. In this way we use the technique of partial resection of the distal ulna. We have a series of 62 patients who have benefited from the technique of partial resection of the ulnar head by arthroscopy. There were 30 men and 32 women. The average age was 66 years old (between 45 and 82). Our average follow-up is 32 months (between 12 and 60 months). Recovery of mobility was immediate in all cases with persistent pain in the radio ulnar joint in 8 cases. Arthroscopic treatment of ulno carpal abutment has proved itself effective and innocuous. It should nevertheless be reserved for operations on small sized inversions of the distal radio ulnar index (less than 5 mm). In the event of larger ulnar variances we prefer ulnar shortening osteotomy. The other techniques will be restricted to cases where the distal radio ulnar joint has been impaired. PMID:17361890

  8. [Arthroscopic distal ulna resection after post traumatic ulno carpal abutment.

    PubMed

    Mathoulin, C; Pagnotta, A

    2006-11-01

    Ulno carpal abutments secondary to the sequels of a fracture of the radius are often due to the inversion of the distal radio ulnar index by shortening relative to the radius. This positive ulnar variance eventually leads to an abutment between the head of the ulnar and the proximal articular face of the lunate with alteration of the cartilaginous carpal surfaces. The wrist arthroscopy makes diagnosis and treatment possible in a less invasive way. The patients are operated on as outpatients under local regional anaesthetic using a pneumatic tourniquet. The arthroscope is positioned using the 3-4 radio carpal opening permitting exploration of the joint. The surgical treatment is performed by arthroscopy using a burr and going in through the 6R radio carpal opening. In this way we use the technique of partial resection of the distal ulna. We have a series of 62 patients who have benefited from the technique of partial resection of the ulnar head by arthroscopy. There were 30 men and 32 women. The average age was 66 years old (between 45 and 82). Our average follow-up is 32 months (between 12 and 60 months). Recovery of mobility was immediate in all cases with persistent pain in the radio ulnar joint in 8 cases. Arthroscopic treatment of ulno carpal abutment has proved itself effective and innocuous. It should nevertheless be reserved for operations on small sized inversions of the distal radio ulnar index (less than 5 mm). In the event of larger ulnar variances we prefer ulnar shortening osteotomy. The other techniques will be restricted to cases where the distal radio ulnar joint has been impaired. PMID:17349395

  9. Study of displacements of a bridge abutment using FEM

    NASA Astrophysics Data System (ADS)

    Wymysłowski, Michał; Kurałowicz, Zygmunt

    2016-06-01

    Steel sheet piles are often used to support excavations for bridge foundations. When they are left in place in the permanent works, they have the potential to increase foundation bearing capacity and reduce displacements; but their presence is not usually taken into account in foundation design. In this article, the results of finite element analysis of a typical abutment foundation, with and without cover of sheet piles, are presented to demonstrate these effects. The structure described is located over the Więceminka river in the town of Kołobrzeg, Poland. It is a single-span road bridge with reinforced concrete slab.

  10. Improved Abutting Edges For Welding In Keyhole Mode

    NASA Technical Reports Server (NTRS)

    Harwing, Dennis D.; Sanders, John M.

    1994-01-01

    Welds of better quality made, and/or heat input reduced. Improved shapes devised for abutting edges of metal pieces to be joined by plasma arc welding in keyhole mode, in which gas jet maintains molten hole ("keyhole") completely through thickness of weld joint. Edges of metal pieces to be welded together machined to provide required combination gap and shaped, thin sections. Shapes and dimensions chosen to optimize weld in various respects; e.g., to enhance penetration of keyhole or reduce heat input to produce joint of given thickness.

  11. Air-Lubricated Lead Screw

    NASA Technical Reports Server (NTRS)

    Perkins, G. S.

    1983-01-01

    Air lubricated lead screw and nut carefully machined to have closely matched closely fitting threads. Compressed air injected into two plenums encircle nut and flow through orifices to lubricate mating threads. Originally developed to position precisely interferometer retroreflector for airborne measurement of solar infrared radiation, device now has positioning accuracy of 0.25 micron.

  12. Bacterial adhesion and colonization differences between zirconia and titanium implant abutments: an in vivo human study

    PubMed Central

    de Oliveira, Greison Rabelo; Pozzer, Leandro; Cavalieri-Pereira, Lucas; de Moraes, Paulo Hemerson; de Albergaría Barbosa, Jose Ricardo

    2012-01-01

    Purpose Several parameters have been described for determining the success or failure of dental implants. The surface properties of transgingival implant components have had a great impact on the long-term success of dental implants. The purpose of this study was to compare the tendency of two periodontal pathogens to adhere to and colonize zirconia abutments and titanium alloys both in hard surfaces and soft tissues. Methods Twelve patients participated in this study. Three months after implant placement, the abutments were connected. Five weeks following the abutment connections, the abutments were removed, probing depth measurements were recorded, and gingival biopsies were performed. The abutments and gingival biopsies taken from the buccal gingiva were analyzed using real-time polymerase chain reaction to compare the DNA copy numbers of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and total bacteria. The surface free energy of the abutments was calculated using the sessile water drop method before replacement. Data analyses used the Mann Whitney U-test, and P-values below 0.05 find statistical significance. Results The present study showed no statistically significant differences between the DNA copy numbers of A. actinomycetemcomitans, P. gingivalis, and total bacteria for both the titanium and zirconia abutments and the biopsies taken from their buccal gingiva. The differences between the free surface energy of the abutments had no influence on the microbiological findings. Conclusions Zirconia surfaces have comparable properties to titanium alloy surfaces and may be suitable and safe materials for the long-term success of dental implants. PMID:23346465

  13. Platform switching and abutment emergence profile modification on peri-implant soft tissue.

    PubMed

    Dornbush, Jeffrey R; Reiser, Gary M; Ho, Daniel K

    2014-01-01

    Although the peri-implant hard tissue advantages of platform switching abutments have been well documented by many authors, the peri-implant soft tissue advantages of platform switching abutments has had limited mention. This article illustrates how the amount of peri-implant soft tissue volume is influenced by the dimensional extent of platform switching and the degree that an abutment's sulcular emergence profile has been modified. This article also introduces the term "abutment sulcular emergence profile enhancement" (ASEPE) to describe the combined effect of platform switching and abutment emergence profile modification. Three unrecognized clinical advantages of ASEPE are described by different clinical cases. First, elimination of excessive abutment impingement on gingival tissue adjacent to implants is achieved. Second, allowance for sufficient interproximal space between implant and adjacent tooth/implant for the entry of interproximal toothbrush is made possible. Third, excessive soft tissue blanching during abutment seating at prosthesis delivery is eliminated. Together, the combined application of platform switching and abutment emergence profile modification represents the opening of a new realm for managing soft tissue around implants to resolve dimensional problems. PMID:25269220

  14. The upper bound of abutment scour defined by selected laboratory and field data

    USGS Publications Warehouse

    Benedict, Stephen; Caldwell, Andral W.

    2015-01-01

    The U.S. Geological Survey, in cooperation with the South Carolina Department of Transportation, conducted a field investigation of abutment scour in South Carolina and used that data to develop envelope curves defining the upper bound of abutment scour. To expand upon this previous work, an additional cooperative investigation was initiated to combine the South Carolina data with abutment-scour data from other sources and evaluate the upper bound of abutment scour with the larger data set. To facilitate this analysis, a literature review was made to identify potential sources of published abutment-scour data, and selected data, consisting of 446 laboratory and 331 field measurements, were compiled for the analysis. These data encompassed a wide range of laboratory and field conditions and represent field data from 6 states within the United States. The data set was used to evaluate the South Carolina abutment-scour envelope curves. Additionally, the data were used to evaluate a dimensionless abutment-scour envelope curve developed by Melville (1992), highlighting the distinct difference in the upper bound for laboratory and field data. The envelope curves evaluated in this investigation provide simple but useful tools for assessing the potential maximum abutment-scour depth in the field setting.

  15. Metallurgical examination of gun barrel screws

    SciTech Connect

    Bird, E.L.; Clift, T.L.

    1996-06-01

    The examination was conducted to determine the extent of degradation that had occurred after a series of firings; these screws prevent live rounds of ammunition from being loaded into the firing chamber. One concern is that if the screw tip fails and a live round is accidentally loaded into the chamber, a live round could be fired. Another concern is that if the blunt end of the screw begins to degrade by cracking, pieces could become small projectiles during firing. All screws used in firing 100 rounds or more exhibited some degree degradation, which progressively worsened as the number of rounds fired increased. (SEM, metallography, x-ray analysis, and microhardness were used.) Presence of cracks in these screws after 100 fired rounds is a serious concern that warrants the discontinued use of these screws. The screw could be improved by selecting an alloy more resistant to thermal and chemical degradation.

  16. Evaluation of Maryland abutment scour equation through selected threshold velocity methods

    USGS Publications Warehouse

    Benedict, S.T.

    2010-01-01

    The U.S. Geological Survey, in cooperation with the Maryland State Highway Administration, used field measurements of scour to evaluate the sensitivity of the Maryland abutment scour equation to the critical (or threshold) velocity variable. Four selected methods for estimating threshold velocity were applied to the Maryland abutment scour equation, and the predicted scour to the field measurements were compared. Results indicated that performance of the Maryland abutment scour equation was sensitive to the threshold velocity with some threshold velocity methods producing better estimates of predicted scour than did others. In addition, results indicated that regional stream characteristics can affect the performance of the Maryland abutment scour equation with moderate-gradient streams performing differently from low-gradient streams. On the basis of the findings of the investigation, guidance for selecting threshold velocity methods for application to the Maryland abutment scour equation are provided, and limitations are noted.

  17. Potential of incorporated accelerometers for the in vivo assessment of hip stem loosening

    NASA Astrophysics Data System (ADS)

    Lowet, G.; Van der Perre, G.

    1994-09-01

    The detection of prosthesis loosening in total hip replacement remains a problematic issue. Common techniques such as radiography and arthrography have not been shown to be very effective. Although originally developed for the assessment of fracture healing, vibration analysis was proposed as a method for the detection of loose prostheses [1,2]. In this paper, we will discuss the principles used in the vibration analysis in relation with the detection of loose prothesis and discuss the potential and limitations.

  18. A Stereophotogrammetric System For The Detection Of Prosthesis Loosening In Total Hip Arthroplasty

    NASA Astrophysics Data System (ADS)

    Baumrind, Sheldon; Genant, Harry K.; Hunter, John; Miller, David; Moffitt, Francis; Murray, William R.; Ross, Steven E.

    1980-07-01

    Loosening of the prosthetic device occurs in about 5% of cases following placement of total hip prostheses (THP). Early detection of loosening is much desired but is difficult to achieve using conventional methods. Due to errors of projection, it is quite possible to fail to detect mobility of even as much as 5 mm on single x-ray films. We are attempting to develop a simplified photogrammetric system suitable for general hospital use which could detect loosening of 0.8 mm at the 95 % level of confidence without use of complex stereoplotting equipment. Metal reference markers are placed in the shaft of the femur and in the acetabular region of the pelvis at the time of surgery. The distances between these reference markers and certain unambiguous points on the prostheses are computed analytically using an X-Y acoustical digitizer (accuracy ± 0.1 mm) and software developed previously for craniofacial measurement. Separate stereopairs of the joint region are taken under weight-bearing and nonweight-bearing conditions. Differences in the measured distances between the bo-ne markers and the prosthetic components on the two stereopairs are taken as indicators of prosthesis loosening. Measurements on a phantom using ten different x-ray stereopairs taken from as many different perspectives have established that true linear distances between reference points and prostheses can be measured at the desired reliability with the present low precision system. Preliminary in vivo measurements indicate that the main unresolved problem is the movement of the subject between the two exposures of each single stereopair. Two possible solutions to this problem are discussed.

  19. The pedicle screw-rod system is an acceptable method of reconstructive surgery after resection of sacroiliac joint tumours

    PubMed Central

    Zhou, Yi-Jun; Yunus, Akbar; Tian, Zheng; Chen, Jiang-Tao; Wang, Chong; Xu, Lei-Lei

    2016-01-01

    Hemipelvic resections for primary bone tumours require reconstruction to restore weight bearing along anatomic axes. However, reconstruction of the pelvic arch remains a major surgical challenge because of the high rate of associated complications. We used the pedicle screw-rod system to reconstruct the pelvis, and the purpose of this investigation was to assess the oncology, functional outcome and complication rate following this procedure. The purpose of this study was to investigate the operative indications and technique of the pedicle screw-rod system in reconstruction of the stability of the sacroiliac joint after resection of sacroiliac joint tumours. The average MSTS (Musculoskeletal Tumour Society) score was 26.5 at either three months after surgery or at the latest follow-up. Seven patients had surgery-related complications, including wound dehiscence in one, infection in two, local necrosis in four (including infection in two), sciatic nerve palsy in one and pubic symphysis subluxation in one. There was no screw loosening or deep vein thrombosis occurring in this series. Using a pedicle screw-rod after resection of a sacroiliac joint tumour is an acceptable method of pelvic reconstruction because of its reduced risk of complications and satisfactory functional outcome, as well as its feasibility of reconstruction for type IV pelvis tumour resection without elaborate preoperative customisation. Level of evidence: Level IV, therapeutic study. PMID:27095944

  20. Retrieval study of uncemented metal-metal hip prostheses revised for early loosening.

    PubMed

    Reinisch, Georg; Judmann, Kurt P; Lhotka, Christian; Lintner, Felix; Zweymüller, Karl A

    2003-03-01

    A tribologic assessment was performed on 22 metal-metal hip prostheses from a single manufacturer, following removal for early aseptic loosening after a mean service life of 32 months (range, 12-59 months). The mean linear wear rate was 7.6 microm/year (range, 2.9-12.8 microm/year). This was below the rates previously observed in other modern metal-metal combinations. A novel contour analysis technique using a coordinate measuring machine showed the mean volumetric wear rate to be 2.02 mm(3)/year (range, 0.55-3.74 mm(3)/year), which corresponds to a mean gravimetric wear rate of 16.9 mg/year (range, 4.6-31.4 mg/year). The mean clearance of 39.8 microm (range, 30-50 microm) was within the optimal range for hard-hard bearing combinations. Evidence of abrasive, adhesive, and third-body wear was found on all bearing surfaces. The tribologic assessment did not indicate manufacturing defects as a cause of early loosening. Equally, third-body wear was too low to be considered a causative factor for early loosening. PMID:12504531

  1. A Novel RFID-Based Sensing Method for Low-Cost Bolt Loosening Monitoring

    PubMed Central

    Wu, Jian; Cui, Xingmei; Xu, Yunpeng

    2016-01-01

    In coal mines, bolt loosening in the cage guide is affected by the harsh environmental factors and cage hoist vibration, leading to significant threats to work safety. It is crucial, to this effect, to successfully detect the status of multipoint bolts of guide structures. This paper proposes a system to monitor bolt status in harsh environments established based on the RFID technique. A proof-of-concept model was demonstrated consisting of a bolt gearing system, passive UHF RFID tags, a reader, and monitoring software. A tinfoil metal film is fixed on the retaining plate and an RFID tag bonded to a large gear, with the bolt to be detected fixed in the center of a smaller gear. The radio-frequency signal cannot be received by the reader if the tag is completely obscured by the tinfoil, and if the bolt is loose, the tag’s antenna is exposed when the gear revolves. A radio-frequency signal that carries corresponding bolt’s information is transmitted by the RFID tag to the RFID reader due to coil coupling, identifying loose bolt location and reporting them in the software. Confirmatory test results revealed that the system indeed successfully detects bolt loosening and comparative test results (based on a reed switch multipoint bolt loosening monitor system) provided valuable information regarding the strengths and weaknesses of the proposed system. PMID:26828498

  2. A Novel RFID-Based Sensing Method for Low-Cost Bolt Loosening Monitoring.

    PubMed

    Wu, Jian; Cui, Xingmei; Xu, Yunpeng

    2016-01-01

    In coal mines, bolt loosening in the cage guide is affected by the harsh environmental factors and cage hoist vibration, leading to significant threats to work safety. It is crucial, to this effect, to successfully detect the status of multipoint bolts of guide structures. This paper proposes a system to monitor bolt status in harsh environments established based on the RFID technique. A proof-of-concept model was demonstrated consisting of a bolt gearing system, passive UHF RFID tags, a reader, and monitoring software. A tinfoil metal film is fixed on the retaining plate and an RFID tag bonded to a large gear, with the bolt to be detected fixed in the center of a smaller gear. The radio-frequency signal cannot be received by the reader if the tag is completely obscured by the tinfoil, and if the bolt is loose, the tag's antenna is exposed when the gear revolves. A radio-frequency signal that carries corresponding bolt's information is transmitted by the RFID tag to the RFID reader due to coil coupling, identifying loose bolt location and reporting them in the software. Confirmatory test results revealed that the system indeed successfully detects bolt loosening and comparative test results (based on a reed switch multipoint bolt loosening monitor system) provided valuable information regarding the strengths and weaknesses of the proposed system. PMID:26828498

  3. Replacement of missing anterior tooth using screw retained implant prosthesis in the esthetic zone: a case report with 3 years of follow up.

    PubMed

    Ahmad, Manawar; Dhanasekar, B; Aparna, I N; Naim, Hina

    2014-09-01

    As more and more dental practitioners are focusing on implant-supported fixed restorations, some clinicians favor the use of cement retained restorations while others consider screw-retained prosthesis to be the best choice. As both types of prostheses have certain advantages and disadvantages, clinicians should be aware of the limitations of each type. Screw-retained implant restorations have an advantage of predictable retention, retrievability and lack of potentially retained sub-gingival cement. However, a few disadvantages exist such as precise placement of the implant for optimal and esthetic location of the screw access hole and obtaining passive fit. On the other hand, cement retained restorations eliminates unaesthetic screw access holes; have passive fit of castings; reduce stress to splinted implants because of minor misfit of the framework; reduced complexity of lab procedures; enhanced esthetics; reduced cost factors and non disrupted morphology of the occlusal table. This case report presents the replacement of missing left central incisor using screw-retained implant prosthesis due to palatal trajectory of the implant placement and inadequate abutment height for retention of cement retained prosthesis. PMID:25183915

  4. Helical screw expander evaluation project

    NASA Technical Reports Server (NTRS)

    Mckay, R.

    1982-01-01

    A one MW helical rotary screw expander power system for electric power generation from geothermal brine was evaluated. The technology explored in the testing is simple, potentially very efficient, and ideally suited to wellhead installations in moderate to high enthalpy, liquid dominated field. A functional one MW geothermal electric power plant that featured a helical screw expander was produced and then tested with a demonstrated average performance of approximately 45% machine efficiency over a wide range of test conditions in noncondensing, operation on two-phase geothermal fluids. The Project also produced a computer equipped data system, an instrumentation and control van, and a 1000 kW variable load bank, all integrated into a test array designed for operation at a variety of remote test sites. Data are presented for the Utah testing and for the noncondensing phases of the testing in Mexico. Test time logged was 437 hours during the Utah tests and 1101 hours during the Mexico tests.

  5. Helical screw expander evaluation project

    NASA Astrophysics Data System (ADS)

    McKay, R.

    1982-03-01

    A one MW helical rotary screw expander power system for electric power generation from geothermal brine was evaluated. The technology explored in the testing is simple, potentially very efficient, and ideally suited to wellhead installations in moderate to high enthalpy, liquid dominated field. A functional one MW geothermal electric power plant that featured a helical screw expander was produced and then tested with a demonstrated average performance of approximately 45% machine efficiency over a wide range of test conditions in noncondensing, operation on two-phase geothermal fluids. The Project also produced a computer equipped data system, an instrumentation and control van, and a 1000 kW variable load bank, all integrated into a test array designed for operation at a variety of remote test sites. Data are presented for the Utah testing and for the noncondensing phases of the testing in Mexico. Test time logged was 437 hours during the Utah tests and 1101 hours during the Mexico tests.

  6. Screw-fed pump system

    SciTech Connect

    Sprouse, Kenneth M

    2014-11-25

    A pump system includes a pump that includes a first belt and a second belt that are spaced apart from each other to provide generally straight sides of a passage there between. There is an inlet at one end of the passage and an outlet at an opposite end of the passage, with a passage length that extends between the inlet and the outlet. The passage defines a gap distance in a width direction between the straight sides at the passage inlet. A hopper includes an interior space that terminates at a mouth at the passage inlet. At least one screw is located within the interior space of the hopper and includes a screw diameter in the width direction that is less than or equal to the gap distance.

  7. 1. West portal of the mudshed abutting the west portal ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. West portal of the mudshed abutting the west portal of Tunnel 5, view to the northwest, 135mm lens. The flat-roofed reinforced concrete mudsheds, rocksheds, and snowsheds are a common feature of the Natron Cutoff over the summit of the Cascades. With the railroad located on a sidehill bench cut into the precipitous slopes, the sheds protect the track from rock and mud slides, as well as from avalanches. With a solid wall on the uphill side and a series of columns on the downhill side, they form a gallery-like effect from within. This mudshed was built concurrent with the tunnel, in 1927. Though none of the mudsheds on the line are scheduled to be modified, this shed was documented as an integral element of Tunnel 5. - Southern Pacific Railroad Natron Cutoff, Tunnel 5, Milepost 545.2, McCredie Springs, Lane County, OR

  8. EARTHQUAKE PERFORMANCE OF A BRIDGE DECK AND ABUTMENT.

    USGS Publications Warehouse

    Celebi, M.; Brady, G.

    1985-01-01

    During the 24 April 1984 Morgan Hill Earthquake (M equals 6. 1), 15 channels of acceleration records were obtained at the site of the I-280-680/US 101 interchange 12 km west of the epicenter. These records include free field measurements as well as the acceleration response at one of the supporting column bases, and at three locations in one of the spans of the three-span continuous post-tensioned box-girder deck. The purpose of this paper is to review the performance of this bridge deck and its abutment through the study of these records. The objective in extensively instrumenting a bridge deck or any structure is to obtain relevant response data to study its behaviour during strong motion events and ultimately extrapolate conclusions for improved design.

  9. Metal debris concentrations in soft tissues adjacent to loosened femoral stems is higher in uncemented than cemented implants

    PubMed Central

    2014-01-01

    Background There are still many questions related to aseptic femoral stem loosening. Systemic and local immune responses to the implanted “foreign body” is one of the reasons for loosening. The purpose of the study was to measure metal ion concentration (Ti, Co, Cr, Mo, Ni, Al) around loosened femoral stems and compare their levels around uncemented and cemented implants. Methods This paper reports 50 hips operated for isolated stem loosening, in 50 patients at the mean age of 57 years (from 21 to 87). There were 25 cemented (Co,Cr29,Mo,Ni) and 25 uncemented (Ti, Al) stems. The mean follow-up from primary hip replacement to revision was 10.1 years (from 0.5 to 17). During the procedure, scar tissue around the stem was taken for analysis of metal ions. Results The concentrations of titanium and aluminium in soft tissues around uncemented loosened stems were higher than cemented ones (p < 0.001, p < 0.001 respectively). However, no statistically significant differences were observed between both types of stems in terms of ions of the metal of which cemented implants had been made of (Co, Cr, Mo, Ni). Conclusions In soft tissue around a loosened stem, the concentrations of metal ions from implants are much higher in case of uncemented stems than of cemented ones. Metal ions from vitalium femoral heads were found around uncemented stems in similar values to cemented streams. PMID:25098913

  10. Shock-Absorbent Ball-Screw Mechanism

    NASA Technical Reports Server (NTRS)

    Hirr, Otto A., Jr.; Meneely, R. W.

    1986-01-01

    Actuator containing two ball screws in series employs Belleville springs to reduce impact loads, thereby increasing life expectancy. New application of springs increases reliability of equipment in which ball screws commonly used. Set of three springs within lower screw of ball-screw mechanism absorbs impacts that result when parts reach their upper and lower limits of movement. Mechanism designed with Belleville springs as shock-absorbing elements because springs have good energy-to-volume ratio and easily stacked to attain any stiffness and travel.

  11. Human beta-defensin-3 producing cells in septic implant loosening.

    PubMed

    Levón, Jaakko; Al-Samadi, Ahmed; Mackiewicz, Zygmunt; Coer, Andrej; Trebse, Rihard; Waris, Eero; Konttinen, Yrjö T

    2015-02-01

    Human β-defensin-3 (hBD-3) has been found in synovial fluid and later in periprosthetic tissues in septic joint implant loosening. The aim of the present study was to identify its cellular sources. Tissue samples from 12 patients were analyzed. A fully automatic Leica BOND MAX staining robot was used. Affinity-purified rabbit anti-human hBD-3 IgG was applied in a two-layer horse radish peroxidase/anti-rabbit-labeled polymer method. Double immunofluorescence of hBD3 together with CD68, CD31, heat shock protein 47 (HSP47) and mast cell tryptase (MCT) staining was done. Human BD-3 was found in monocyte/macrophage-like cells, vascular endothelial cells and fibroblasts-like cells, but was weakly expressed in foreign body giant cells and negative in neutrophils. Human BD-3 was found in CD68 and CD31 immunoreactive cells, whereas HSP47 and MCT positive cells were hBD-3 negative. Immunostaining of hBD-3 was strong in some tissue areas but weak or absent in others. Monocyte/macrophages and endothelial cells were established in this study as the major cellular sources of hBD-3 in septic loosening, but fibroblasts and foreign body giant cells can also contribute to its production. The heterogeneous topological staining of hBD-3 suggests local regulation, possibly by bacterial products, damage-associated molecular patterns and cytokines. The results explain the increased synovial fluid/tissue concentrations of hBD-3 in septic loosening. PMID:25655501

  12. Regulation of Extracellular Matrix Remodeling Proteins by Osteoblasts in Titanium Nanoparticle-Induced Aseptic Loosening Model.

    PubMed

    Xie, Jing; Hou, Yanhua; Fu, Na; Cai, Xiaoxiao; Li, Guo; Peng, Qiang; Lin, Yunfeng

    2015-10-01

    Titanium (Ti)-wear particles, formed at the bone-implant interface, are responsible for aseptic loosening, which is a main cause of total joint replacement failure. There have been many studies on Ti particle-induced function changes in mono-cultured osteoblasts and synovial cells. However, little is known on extracellular matrix remodeling displayed by osteoblasts when in coexistence with Synovial cells. To further mimic the bone-implant interface environment, we firstly established a nanoscaled-Ti particle-induced aseptic loosening system by co-culturing osteoblasts and Synovial cells. We then explored the impact of the Synovial cells on Ti particle-engulfed osteoblasts in the mimicked flamed niche. The matrix metalloproteinases and lysyl oxidases expression levels, two protein families which are critical in osseointegration, were examined under induction by tumor necrosis factor-alpha. It was found that the co-culture between the osteoblasts and Synovial cells markedly increased the migration and proliferation of the osteoblasts, even in the Ti-particle engulfed osteoblasts. Importantly, the Ti-particle engulfed osteoblasts, induced by TNF-alpha after the co-culture, enhanced the release of the matrix metalloproteinases and reduced the expressions of lysyl oxidases. The regulation of extracellular matrix remodeling at the protein level was further assessed by investigations on gene expression of the matrix metalloproteinases and lysyl oxidases, which also suggested that the regulation started at the genetic level. Our research work has therefore revealed the critical role of multi cell-type interactions in the extracellular matrix remodeling within the peri-prosthetic tissues, which provides new insights on aseptic loosening and brings new clues about incomplete osseointegration between the implantation materials and their surrounding bones. PMID:26502645

  13. A Biomechanical Comparison of Expansive Pedicle Screws for Severe Osteoporosis: The Effects of Screw Design and Cement Augmentation.

    PubMed

    Tai, Ching-Lung; Tsai, Tsung-Ting; Lai, Po-Liang; Chen, Yi-Lu; Liu, Mu-Yi; Chen, Lih-Huei

    2015-01-01

    Expansive pedicle screws significantly improve fixation strength in osteoporotic spines. However, the previous literature does not adequately address the effects of the number of lengthwise slits and the extent of screw expansion on the strength of the bone/screw interface when expansive screws are used with or without cement augmentation. Herein, four designs for expansive pedicle screws with different numbers of lengthwise slits and different screw expansion levels were evaluated. Synthetic bones simulating severe osteoporosis were used to provide a comparative platform for each screw design. The prepared specimens were then tested for axial pullout failure. Regardless of screw design, screws with cement augmentation demonstrated significantly higher pullout strength than pedicle screws without cement augmentation (p < 0.001). For screws without cement augmentation, solid screws exhibited the lowest pullout strength compared to the four expansive groups (p < 0.01). No significant differences in pullout strength were observed between the expansive screws with different designs (p > 0.05). Taken together, our results show that pedicle screws combined with cement augmentation may greatly increase screw fixation regardless of screws with or without expansion. An increase in both the number of slits and the extent of screw expansion had little impact on the screw-anchoring strength. Cement augmentation is the most influential factor for improving screw pullout strength. PMID:26720724

  14. A Biomechanical Comparison of Expansive Pedicle Screws for Severe Osteoporosis: The Effects of Screw Design and Cement Augmentation

    PubMed Central

    Tai, Ching-Lung; Tsai, Tsung-Ting; Lai, Po-Liang; Chen, Yi-Lu; Liu, Mu-Yi; Chen, Lih-Huei

    2015-01-01

    Expansive pedicle screws significantly improve fixation strength in osteoporotic spines. However, the previous literature does not adequately address the effects of the number of lengthwise slits and the extent of screw expansion on the strength of the bone/screw interface when expansive screws are used with or without cement augmentation. Herein, four designs for expansive pedicle screws with different numbers of lengthwise slits and different screw expansion levels were evaluated. Synthetic bones simulating severe osteoporosis were used to provide a comparative platform for each screw design. The prepared specimens were then tested for axial pullout failure. Regardless of screw design, screws with cement augmentation demonstrated significantly higher pullout strength than pedicle screws without cement augmentation (p < 0.001). For screws without cement augmentation, solid screws exhibited the lowest pullout strength compared to the four expansive groups (p < 0.01). No significant differences in pullout strength were observed between the expansive screws with different designs (p > 0.05). Taken together, our results show that pedicle screws combined with cement augmentation may greatly increase screw fixation regardless of screws with or without expansion. An increase in both the number of slits and the extent of screw expansion had little impact on the screw-anchoring strength. Cement augmentation is the most influential factor for improving screw pullout strength. PMID:26720724

  15. Single Image X-Ray Photogrammetry System Used To Detect Total Joint Loosening

    NASA Astrophysics Data System (ADS)

    Lippert, F. G.; Veress, S. A.; Harrington, R. M.; EI-Garf, T.

    1983-07-01

    Loosening is the number one complication of total joint replacements. A direct method of measuring small motions between the prosthetic implant and the surrounding bone would allow the surgeon to evaluate replacement surgery or activity restrictions. Single plane x-ray photogrammetry uses stainless steel markers in the bone and prosthetic implant and a control frame in order to accomplish this measurement. Testing of models representing a total hip replacement and total knee replacement has shown that displacements can be measured with a root mean square error of less than 0.2 mm.

  16. True anteroposterior view pedicle screw insertion technique

    PubMed Central

    Bai, Jia-yue; Zhang, Wei; An, Ji-long; Sun, Ya-peng; Ding, Wen-yuan; Shen, Yong

    2016-01-01

    Background The wide use of minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) surgery in the treatment of degenerative disc disease of lumbar spine in spinal surgery highlights the gradual decrease in the use of traditional pedicle screw insertion technology. This study aims to analyze the accuracy of the true anteroposterior view pedicle screw insertion technique in MIS-TLIF surgery, compare it with conventional pedicle screw insertion technology, and discuss its clinical application value. Methods Fifty-two patients undergoing true anteroposterior view (group A) and 87 patients undergoing conventional pedicle screw insertion (group B) were diagnosed with lumbar disc herniation or lumbar spinal stenosis. Time for screw placement, intraoperative irradiation exposure, accuracy rate of pedicle screw insertion, and incidence of neurovascular injury were compared between the two groups. Results The time for screw placement and intraoperative irradiation exposure was significantly less in group A. Penetration rates of the paries lateralis of vertebral pedicle, medial wall of vertebral pedicle, and anterior vertebral wall were 1.44%, 0%, and 2.40%, respectively, all of which were significantly lower than that in group B. No additional serious complications caused by the placement of screw were observed during the follow-up period in patients in group A, but two patients with medial penetration underwent revision for unbearable radicular pain. Conclusion The application of true anteroposterior view pedicle screw insertion technique in MIS-TLIF surgery shortens time for screw placement and reduces the intraoperative irradiation exposure along with a higher accuracy rate of screw placement, which makes it a safe, accurate, and efficient technique. PMID:27418828

  17. Influence of Sealing of the Screw Access Hole on the Fracture Resistance of Implant-Supported Restorations.

    PubMed

    Pereira, Rodrigo de Paula; Rocha, Cibele Oliveira de Melo; Reis, José Maurício dos Santos Nunes; Arioli-Filho, João Neudenir

    2016-01-01

    The purpose of this study was to assess the influence of sealing of the screw access hole (SAH) on the fracture resistance of metal-ceramic implant-supported restorations. UCLA abutments were used to make 30 implant-retained mandibular molar restorations and divide equally into three groups: Group SRS: screw-retained restorations with SAH sealed; Group SRNS: screw-retained restorations with SAH not sealed; Group CR: cement-retained restorations. The following protocol was adopted to restore the SAH: the ceramic surface of the SAH was air-abraded with aluminum oxide; etched with 10% hydrofluoric acid; a silane coupling agent and a bonding agent were applied; cotton pellets were used as filling material and P-60 resin composite as restoring material. The cement-retained restorations were cemented with Rely-X U100. A metal rod with a spherical tip of 6.0 mm diameter was used to apply a vertical static load, simultaneously on the buccal and lingual incline cusps, at a crosshead speed of 0.5 mm/min until the fracture of the specimens. Data were analyzed using one-way ANOVA and Dunnet test (p<0.05) for multiples comparisons. The mode of failure was evaluated by a scanning electron microscopy (SEM). No significant difference between screw-retained restorations was found. The highest mean fracture resistance values were observed with CR group. Therefore, it was shown that SAH sealing did not influence the fracture resistance of the screw-retained restorations. PMID:27058376

  18. A comparative study of marginal fit of copings prepared with various techniques on different implant abutments.

    PubMed

    Koç, Esra; Öngül, Değer; Şermet, Bülent

    2016-01-01

    This study evaluated fabrication techniques of recently introduced all-ceramic copings' marginal adaptation on two different implant abutments with different finish lines. Five different copings were prepared (Casted chrome-cobalt metal coping, Zirkonzahn, Cercon, In Ceram Alumina and IPS e.max Press) on two cementable implant abutments with two marginal designs. Ten samples for each coping group were prepared (totally 100 samples). Copings were cemented to implant abutments and marginal gap measurements were done from 24 points with stereomicroscope and the datas were analyzed by the Kruskal-Wallis test before cementation. Cercon copings showed the lowest marginal fit scores and metal copings showed the highest scores. After cementation, all marginal gap values have been increased. All marginal gap values obtained from crown copings can be considered in clinically acceptable limits (<120 µm) except metal copings after cementation on abutment with 135 degrees shoulder group (123 µm). PMID:27252001

  19. Comparison of Observed and Predicted Abutment Scour at Selected Bridges in Maine

    USGS Publications Warehouse

    Lombard, Pamela J.; Hodgkins, Glenn A.

    2008-01-01

    Maximum abutment-scour depths predicted with five different methods were compared to maximum abutment-scour depths observed at 100 abutments at 50 bridge sites in Maine with a median bridge age of 66 years. Prediction methods included the Froehlich/Hire method, the Sturm method, and the Maryland method published in Federal Highway Administration Hydraulic Engineering Circular 18 (HEC-18); the Melville method; and envelope curves. No correlation was found between scour calculated using any of the prediction methods and observed scour. Abutment scour observed in the field ranged from 0 to 6.8 feet, with an average observed scour of less than 1.0 foot. Fifteen of the 50 bridge sites had no observable scour. Equations frequently overpredicted scour by an order of magnitude and in some cases by two orders of magnitude. The equations also underpredicted scour 4 to 14 percent of the time.

  20. NORTH ABUTMENT DETAIL. AveryBartholomew Patent Railroad Iron Bridge, Town ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    NORTH ABUTMENT DETAIL. - Avery-Bartholomew Patent Railroad Iron Bridge, Town park south of Route 222, west of Owasco Inlet (moved from Elm Street Extension spanning Fall Creek, Nubia, NY), Groton, Tompkins County, NY

  1. The Effect of Polymethyl Methacrylate Augmentation on the Primary Stability of Cannulated Bone Screws in an Anterolateral Plate in Osteoporotic Vertebrae: A Human Cadaver Study.

    PubMed

    Rüger, Matthias; Sellei, Richard M; Stoffel, Marcus; von Rüden, Christian

    2016-02-01

    Study Design Cohort study. Objective Expandable anterolateral plates facilitate the reduction of posttraumatic deformities of thoracolumbar spine injuries and are commonly used in cases of unstable injuries or compromised bone quality. In this in vitro study, the craniocaudal yield load of the osseous fixation of an anterior angular stable plate fixation system and the effect of polymethyl methacrylate (PMMA) screw augmentation on the primary stability of the screw-bone interface during kyphosis reduction was evaluated in 12 osteoporotic human thoracolumbar vertebrae. Methods The anterolateral stabilization device used for this study is comprised of two swiveling flanges and an expandable midsection. It facilitates the controlled reduction of kyphotic deformities in situ with a geared distractor. Single flanges were attached to 12 thoracolumbar vertebrae. Six specimens were augmented with PMMA by means of cannulated bone screws. The constructs were subjected to static, displacement-controlled craniocaudal loading to failure in a servohydraulic testing machine. Results The uncemented screws cut out at a mean 393 ± 66 N, whereas the cemented screws showed significantly higher yield load of 966 ± 166 N (p < 0.02). We detected no significant correlation between bone mineral density and yield load in this setting. Conclusion Our results indicate that PMMA augmentation is an effective method to increase two- to threefold the primary stability of the screw-bone interface of an anterolateral spine stabilization system in osteoporotic bone. We recommend it in cases of severely compromised bone quality to reduce the risk of screw loosening during initial kyphosis correction and to increase long-term construct stability. PMID:26835201

  2. Combined therapy for teeth with furcation involvement used as abutments for fixed restorations.

    PubMed

    Hürzeler, M B; Strub, J R

    1990-01-01

    Preprosthodontic and prosthodontic procedures for preparing molars with degree 3 furcation involvement for use as abutments for a fixed prosthesis are described. Periodontal surgery precedes endodontic and restorative pretreatment of the abutments, and the required root resection, root separation, or hemisection is performed. A long-term, provisional resin-veneered metal framework restoration is placed for 9 to 12 months. If neither biological nor technical failure occurs, the final metal ceramic fixed restoration may then be fabricated. PMID:2088385

  3. The BCL2 -938C>A Promoter Polymorphism Is Associated with Risk for and Time to Aseptic Loosening of Total Hip Arthroplasty

    PubMed Central

    Fuest, Lena; Kurscheid, Gina; Gehrke, Thorsten; Klenke, Stefanie; Jäger, Marcus; Kauther, Max D.; Bachmann, Hagen S.

    2016-01-01

    Aseptic loosening is a major cause of revision surgery of total hip arthroplasty (THA). Only few host factors affecting aseptic loosening have been identified until now, although they are urgently needed to identify and possibly treat those patients at higher risk for aseptic loosening. To determine whether the functional single nucleotide polymorphism (SNP) c.-938C>A (rs2279115), located in the promoter region of the BCL2 gene has an impact on aseptic loosening of THA we genotyped and analyzed 234 patients suffering from aseptic loosening and 231 patients after primary THA. The polymorphism is associated with risk for aseptic loosening with the CC genotype at highest risk for aseptic loosening, Odds Ratio CC vs. AA 1.93, 95%CI 1.15–3.25, p = 0.013. In contrast, low risk AA genotype carriers that still developed aseptic loosening showed a significantly shorter time to aseptic loosening than patients carrying the C allele (p = 0.004). These results indicate that the BCL2 -938C>A polymorphism influences the occurrence and course of aseptic loosening and suggests this polymorphism as an interesting candidate for prospective studies and analyses in THA registers. PMID:26881923

  4. The surface characteristics produced by various oral hygiene instruments and materials on titanium implant abutments.

    PubMed

    Rapley, J W; Swan, R H; Hallmon, W W; Mills, M P

    1990-01-01

    The purpose of this investigation was to determine the comparative surface roughness produced by various oral hygiene instruments and materials on titanium implant abutments. Ten Brånemark titanium abutment cylinders were used, with one serving as an untreated control. One abutment was used to evaluate each of nine oral hygiene instrumentation methods used for specified lengths of time or instrument strokes. Each abutment was sonically cleaned, air dried, and viewed with a scanning electron microscope. Polaroid photomicrographs were made of abutment surfaces at predetermined magnifications. They were analyzed by three investigators, who compared individual test parameters in terms of time application or stroke number. The resulting abutment surface roughness was also evaluated. The rubber cup with flour of pumice created a smoother surface than the control; the interdental brush, soft nylon toothbrush, plastic scaler, Eva plastic tip, rubber cup, and Cavi-jet left a surface comparable to the control; the metal scalers and the Cavitron created a severely roughened surface. PMID:2202669

  5. Influence of superstructure geometry on the mechanical behavior of zirconia implant abutments: a finite element analysis.

    PubMed

    Geringer, Alexander; Diebels, Stefan; Nothdurft, Frank P

    2014-12-01

    To predict the clinical performance of zirconia abutments, it is crucial to examine the mechanical behavior of different dental implant-abutment connection configurations. The international standard protocol for dynamic fatigue tests of dental implants (ISO 14801) allows comparing these configurations using standardized superstructure geometries. However, from a mechanical point of view, the geometry of clinical crowns causes modified boundary conditions. The purpose of this finite element (FE) study was to evaluate the influence of the superstructure geometry on the maximum stress values of zirconia abutments with a conical implant-abutment connection. Geometry models of the experimental setup described in ISO 14801 were generated using CAD software following the reconstruction of computerized tomography scans from all relevant components. These models served as a basis for an FE simulation. To reduce the numerical complexity of the FE model, the interaction between loading stamp and superstructure geometry was taken into account by defining the boundary conditions with regard to the frictional force. The results of the FE simulations performed on standardized superstructure geometry and anatomically shaped crowns showed a strong influence of the superstructure geometry and related surface orientations on the mechanical behavior of the underlying zirconia abutments. In conclusion, ISO testing of zirconia abutments should be accompanied by load-bearing capacity testing under simulated clinical conditions to predict clinical performance. PMID:25029078

  6. [Pathophysiology of implant-associated infections: From biofilm to osteolysis and septic loosening].

    PubMed

    Wagner, C; Hänsch, G M

    2015-12-01

    Biofilm formation is the key factor in the pathogenesis of implant-associated infections. The most common pathogens isolated are Staphylococcus species, opportunists belonging to the physiological flora of the skin. Biofilm formation starts with the adhesion of bacteria and colonisation preferentially occurs on the surfaces of the foreign body material. As an interactive symbiotic "city of microbes," biofilm formation represents an efficient survival strategy for bacteria. In clinically apparent infections the biofilm induces a local host response with infiltration of phagocytic immune cells. The proinflammatory microenvironment results in a stimulation of osteoclastogenesis, with local osteolysis, and finally septic loosening of the implant. According to the biofilm theory, retaining the implant in primary revision surgery is only recommended in early-stage infections with a stable implant; in late-stage infections, or when loosening occurs, the implant should be removed. Results of previous anti-biofilm therapies have not been satisfactory; therefore, current research is focused on prevention strategies, especially the modification of implant surfaces. Basic knowledge of the underlying pathophysiology is a prerequisite for the development of innovative interdisciplinary therapy and prevention strategies; in this context, essential aspects of biofilm formation, its consequences, and its relevance to diagnosis and therapy are described and discussed. PMID:26556489

  7. Proliferative cell response to loosening of total hip replacements: a cytofluorographic cell cycle analysis.

    PubMed

    Santavirta, S; Pajamäki, J; Eskola, A; Konttinen, Y T; Lindholm, T

    1991-01-01

    Monocyte/macrophages and fibroblasts are the major reactive cells in the periprosthetic connective tissue in a loose totally replaced hip. Monocyte/macrophages are bone-marrow-derived, hematogenous cells, whereas mesenchymal fibroblasts replenish by local proliferation. The cell-cycle-phase frequency distribution therefore reflects the local mitotic fibroblast response to the loose total hip replacement (THR) implant. In 13 patients who underwent revision of a loose THR implant, most of the local cells were in the resting G0/G1 phase (88.1 +/- 6.3%, mean +/- SD), whereas 8.6 +/- 3.7% were in the S phase of the cycle, and 3.4 +/- 2.9% had already reached the G2/M phase. The highest DNA values were recorded in an osteoarthritic patient undergoing revision 4 years after the primary uncemented THR, while the lowest values were observed in a rheumatoid arthritis patient with a loose cemented prosthesis 15 years after the primary operation. The results suggest that the local proliferative fibroblast response in general is uniform and does not seem to depend on the type of prosthesis or the use of cement. The responses in aggressive granulomatous-type loosening and the common type of loosening were similar. PMID:1772725

  8. Bone vibration measurement using ultrasound: application to detection of hip prosthesis loosening.

    PubMed

    Rowlands, A; Duck, F A; Cunningham, J L

    2008-04-01

    Hip prosthesis loosening can be determined in vivo using a vibration-based technique called vibrometry. In this technique, a low frequency (<1000Hz) sinusoidal vibration is applied to the femoral condyles and the resulting vibration is measured at the greater trochanter. If the prosthesis is securely fixed, the output vibration signal matches that of the input vibration, whereas if the prosthesis is loose, the output vibration signal is distorted and shows the marked presence of harmonics of the input frequency. One of the main problems with this application of this technique is in measuring the output vibration where significant amounts of soft tissue cover the measurement site. In order to circumvent this problem, an ultrasound probe, normally used for the measurement of blood flow, has been used to measure the output vibration. This has been evaluated by comparing the results obtained from the ultrasound probe with those from a conventional accelerometer in models representing a tight and loose hip prosthesis under simulated clinical conditions. The ultrasound probe was able to consistently detect the output vibration, for both the loose and secure prostheses. Under the test conditions used (which attempted to simulate a large thickness of soft tissue), the ultrasound probe was able to produce a greatly enhanced output vibration signal compared to the accelerometer. This suggests that the use of an ultrasound probe to detect mechanically induced vibration through significant amounts of soft tissue appears to be viable and could lead to enhanced detection of prosthesis loosening using this technique. PMID:17587635

  9. Application of a simple and cost-effective method for detection of bolt self-loosening in single lap joints

    NASA Astrophysics Data System (ADS)

    Esmaeel, Ramadan A.; Taheri, Farid

    2013-09-01

    One of the major advantages of bolted joints (BJs) over welded, riveted and adhesively bonded joints is the disassembling option. This option facilitates the manufacturing and transportation of large-scale structures that are commonly formed as assemblage of various large structural components. However, this option is not always problem free, in that, during the life cycle of such structures, the bolts used to fasten the joints may become loosened. Although several techniques have been developed to mitigate bolt self-loosening (BSL), nonetheless, development of a methodology for detecting BSL has consumed considerable attention in recent years. As a result, several researchers have been seeking simple and reliable methods for detecting bolt-loosening in BJs, without compromising their stability. In this study, piezoelectric sensors are used to collect the vibration signals of a laboratory-scale single lap joint, joining two steel plates with three bolts. The acquired signals are then processed using the empirical mode decomposition method and the energies of the respective signals are calculated. A recently developed effective method is then employed to establish the so-called energy damage index, evaluated based on the energy stored in certain modes of the collected signal, in both the damaged and healthy states of the system. This method is found to be quite effective in detecting bolt loosening and the progression of self-loosening.

  10. Long-term porous-coated cup survivorship using spikes, screws, and press-fitting for initial fixation.

    PubMed

    Engh, Charles A; Hopper, Robert H; Engh, C Anderson

    2004-10-01

    This study examined the long-term outcome of a single institution's experience with 4,289 primary total hip arthroplasties using hemispheric porous-coated cups. Initial fixation was achieved with spikes (255 AML TriSpike cups), by press-fitting with rim screws (427 Arthropor cups) or by press-fitting the component (83 Harris-Galante, 391 ACS Triloc+, 2,537 Duraloc, and 596 Pinnacle cups). Among 203 revised hips, only 18 cups were found to be loose at the time of revision. Using revision for any reason as an end point, 15-year survivorship was 82.9% +/- 5.6% (95% confidence interval) for spiked components, 71.6% +/- 8.5% for press-fit cups with adjunctive rim screws, and 72.0% +/- 12.6% for press-fit components (P<.001, log rank). Using revision for aseptic loosening as an end point, 15-year survivorship was 94.7% +/- 3.4% for spiked cups, 98.4% +/- 1.9% for press-fit cups with screws and 100% +/- 0.1% for press-fit cups. Despite an increasing incidence of polyethylene wear-related revisions, porous-coated acetabular components have demonstrated excellent long-term fixation. PMID:15457419

  11. Determination of Abutment Pressure in Coal Mines with Extremely Thick Alluvium Stratum: A Typical Kind of Rockburst Mines in China

    NASA Astrophysics Data System (ADS)

    Zhu, Sitao; Feng, Yu; Jiang, Fuxing

    2016-05-01

    This paper investigates the abutment pressure distribution in coal mines with extremely thick alluvium stratum (ETAS), which is a typical kind of mines encountering frequent intense rockbursts in China. This occurs due to poor understanding to abutment pressure distribution pattern and the consequent inappropriate mine design. In this study, a theoretical computational model of abutment pressure for ETAS longwall panels is proposed based on the analysis of load transfer mechanisms of key stratum (KS) and ETAS. The model was applied to determine the abutment pressure distribution of LW2302S in Xinjulong Coal Mine; the results of stress and microseismic monitoring verified the rationality of this model. The calculated abutment pressure of LW2302S was also used in the terminal mining line design of LW2301N for rockburst prevention, successfully protecting the main roadway from the adverse influence of the abutment pressure.

  12. A digital approach to fabricating an abutment replica to control cement volume in a cement-retained implant prosthesis.

    PubMed

    Lee, Ju-Hyoung; Park, In-Sook; Sohn, Dong-Seok

    2016-07-01

    If a cement-retained implant prosthesis is placed on an abutment, excess cement should be minimized or removed to prevent periimplant inflammation. Various methods for fabricating an abutment replica have been introduced to maintain tissue health and reduce clean-up time. The purpose of this article is to present an alternative technique for fabricating an abutment replica with computer-aided design/computer-aided manufacturing (CAD/CAM) technology. PMID:26946917

  13. Missed low-grade infection in suspected aseptic loosening has no consequences for the survival of total hip arthroplasty

    PubMed Central

    Boot, Willemijn; Moojen, Dirk Jan F; Visser, Els; Lehr, A Mechteld; De Windt, Tommy S; Van Hellemondt, Gijs; Geurts, Jan; Tulp, Niek J A; Schreurs, B Wim; Burger, Bart J; Dhert, Wouter J A; Gawlitta, Debby; Vogely, H Charles

    2015-01-01

    Background and purpose — Aseptic loosening and infection are 2 of the most common causes of revision of hip implants. Antibiotic prophylaxis reduces not only the rate of revision due to infection but also the rate of revision due to aseptic loosening. This suggests under-diagnosis of infections in patients with presumed aseptic loosening and indicates that current diagnostic tools are suboptimal. In a previous multicenter study on 176 patients undergoing revision of a total hip arthroplasty due to presumed aseptic loosening, optimized diagnostics revealed that 4–13% of the patients had a low-grade infection. These infections were not treated as such, and in the current follow-up study the effect on mid- to long-term implant survival was investigated. Patients and methods — Patients were sent a 2-part questionnaire. Part A requested information about possible re-revisions of their total hip arthroplasty. Part B consisted of 3 patient-related outcome measure questionnaires (EQ5D, Oxford hip score, and visual analog scale for pain). Additional information was retrieved from the medical records. The group of patients found to have a low-grade infection was compared to those with aseptic loosening. Results — 173 of 176 patients from the original study were included. In the follow-up time between the revision surgery and the current study (mean 7.5 years), 31 patients had died. No statistically significant difference in the number of re-revisions was found between the infection group (2 out of 21) and the aseptic loosening group (13 out of 152); nor was there any significant difference in the time to re-revision. Quality of life, function, and pain were similar between the groups, but only 99 (57%) of the patients returned part B. Interpretation — Under-diagnosis of low-grade infection in conjunction with presumed aseptic revision of total hip arthroplasty may not affect implant survival. PMID:26364842

  14. C1-c2 pedicle screw fixation for treatment of old odontoid fractures.

    PubMed

    Qi, Lei; Li, Mu; Zhang, Shuai; Si, Haipeng; Xue, Jingsong

    2015-02-01

    Nonunion and C1-C2 instability of odontoid fractures usually result from delayed diagnosis and inappropriate treatment. However, the available treatment options for odontoid fractures remain controversial. The authors evaluated the effectiveness of internal screw fixation via the C1 and C2 pedicle in cases of old odontoid fractures. This retrospective study included 21 patients with old odontoid fractures (13 men and 8 women; mean age, 46.5 years; range, 24-69 years). Internal screw fixation via the C1 and C2 pedicle was performed in all patients. Fracture reduction and C1-C2 fusion were assessed with imaging. The neck pain visual analog scale score and cervical spinal cord functional Japanese Orthopaedic Association score (for those who had cervical spinal cord injury) were used to evaluate the effectiveness of treatment. Postoperative complications were recorded. Postoperative imaging showed that the C1-C2 dislocation was satisfactorily repositioned in all patients. Bone fusion was observed 1 year after surgery in all patients. No loosening or breaking of internal fixation occurred. The preoperative neck pain visual analog scale score was 5.9±1.5 and improved significantly to 1.8±0.8 after surgery (P<.001). The Japanese Orthopaedic Association score in patients with cervical spinal injury (n=14) was 9.2±1.9 and also significantly improved to 13.8±1.9 at the last follow-up examination (P<.001), with an average improvement rate of 61.0%. No iatrogenic vertebral artery injury or severe spinal cord injury occurred. Screw fixation via the C1 and C2 pedicle was found to be an effective and safe surgical approach for the treatment of old odontoid fractures with C1-C2 dislocation or instability. PMID:25665108

  15. Head-locking durability of fixed and variable angle locking screws under repetitive loading.

    PubMed

    Lenz, Mark; Wahl, Dieter; Zderic, Ivan; Gueorguiev, Boyko; Jupiter, Jesse B; Perren, Stephan M

    2016-06-01

    Polyaxial locking screws are increasingly applied in fracture fixation. To investigate the durability of the head-locking mechanism, the removal torque of variable angle (VA) and fixed angle (FA) stainless steel and titanium locking screws was investigated without and after a cyclic loading test. Stainless steel (St) and titanium (Ti) 2.4 mm orthogonally inserted FA screws and 2.4 mm VA screws inserted in different inclinations (0°-15°) (n = 6 per group) were locked at 0.8 Nm. Removal torque was determined without (W) and after (A) cyclic loading (sinusoidal load, 5 Hz, constant amplitude of 25 N, up to 10'000 cycles, or failure). Significant differences in-between the groups were detected by Student's t-test (p < 0.05). Except VA Ti in 0deg and FA, all groups exhibited a drop in removal torque below the insertion torque without and after cyclic testing. The removal torque was (St: FA W:0.81 Nm ± 0.04 A:0.72Nm ± 0.04; VA0deg W:0.73 Nm ± 0.04 A:0.65 Nm ± 0.05; VA15deg W:0.51 Nm ± 0.05 A:0.50 Nm ± 0.08; Ti: FA W:0.82 Nm ± 0.03 A:0.70 Nm ± 0.04; VA0deg W:0.80 Nm ± 0.02 A:0.72 Nm ± 0.05; VA15deg W:0.55 Nm ± 0.03 A:0.54 Nm ± 0.06). In all groups, the removal torque after cyclic testing did not drop below 16% of the removal torque without cyclic testing. No head loosening was observed after cyclic testing. Stainless steel and titanium 2.4 mm fixed and variable angle locking screws provide a stable and lasting head-locking mechanism. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:949-952, 2016. PMID:26580296

  16. Scaphoid Fracture Fixation with an Acutrak(®) Screw.

    PubMed

    Loving, Vilert A; Richardson, Michael L

    2006-01-01

    We report a case of fixation of a scaphoid fracture using an Acutrak(®) screw. This screw is cannulated and headless, which allows it to be implanted below the surface of the bone. It uses the same concept of variable thread pitch as the Herbert screw, but unlike the Herbert screw, is fully threaded, with continuously varying pitch along its length. This variable pitch creates constant compression across a fracture as the screw is advanced, and gives the screw its unique appearance. This feature may improve internal holding power, as well as allow a fracture or osteotomy site to lie anywhere along the length of the screw. PMID:27298683

  17. Screw-released roller brake

    NASA Technical Reports Server (NTRS)

    Vranish, John M. (Inventor)

    1999-01-01

    A screw-released roller brake including an input drive assembly, an output drive assembly, a plurality of locking sprags, a mechanical tripper nut for unlocking the sprags, and a casing therefor. The sprags consist of three dimensional (3-D) sprag members having pairs of contact surface regions which engage respective pairs of contact surface regions included in angular grooves or slots formed in the casing and the output drive assembly. The sprags operate to lock the output drive assembly to the casing to prevent rotation thereof in an idle mode of operation. In a drive mode of operation, the tripper is either self actuated or motor driven and is translated linearly up and down against a spline and at the limit of its travel rotates the sprags which unlock while coupling the input drive assembly to the output drive assembly so as to impart a turning motion thereto in either a clockwise or counterclockwise direction.

  18. Full mouth rehabilitation of a patient with mandibular implant screw retained Fp-3 prosthesis opposing maxillary acrylic removable over-denture

    PubMed Central

    Jain, Ashish R.; Nallaswamy, Deepak; Ariga, Padma; Philip, Jacob Mathew

    2013-01-01

    A hybrid denture is one that is fabricated over a metal framework and retained by screws threaded into the implant abutments. The anterior part of a mandibular hybrid denture is fixed on implants while the posterior part of the denture is extended and cantilevered from implants. This article presents the fabrication of a maxillary over-denture opposing mandibular implant retained hybrid prosthesis. A total of four implants were placed in the mandibular arch. Castable abutments were used to produce the optimal angulations. Framework was waxed, cast recovered, and the fit was refined until the framework seated passively on the master cast. The mandibular denture teeth were waxed to the hybrid framework, and a final wax try-in was performed to verify and correct maxillomandibular relations before processing. The prosthesis was inserted after verification of occlusion, retention, and stability. The rehabilitation of edentulous patients with hybrid dentures has been observed to achieve greater masticatory function and psychological satisfaction than with conventional over-dentures. Producing a passive-fitting substructure for a fixed removable screw retained hybrid prosthesis is arguably one of the most technically complex tasks in implant dentistry. The technique presented may not initially produce a perfectly passive framework, but use of disclosing media and adjusting the internal aspect of the casting can result in non-binding, fully seated prostheses. PMID:24015016

  19. Reinforcement of osteosynthesis screws with brushite cement.

    PubMed

    Van Landuyt, P; Peter, B; Beluze, L; Lemaître, J

    1999-08-01

    The fixation of osteosynthesis screws remains a severe problem for fracture repair among osteoporotic patients. Polymethyl-methacrylate (PMMA) is routinely used to improve screw fixation, but this material has well-known drawbacks such as monomer toxicity, exothermic polymerization, and nonresorbability. Calcium phosphate cements have been developed for several years. Among these new bone substitution materials, brushite cements have the advantage of being injectable and resorbable. The aim of this study is to assess the reinforcement of osteosynthesis screws with brushite cement. Polyurethane foams, whose density is close to that of cancellous bone, were used as bone model. A hole was tapped in a foam sample, then brushite cement was injected. Trabecular osteosynthesis screws were inserted. After 24 h of aging in water, the stripping force was measured by a pull-out test. Screws (4.0 and 6.5 mm diameter) and two foam densities (0.14 and 0.28 g/cm3) were compared. Cements with varying solid/liquid ratios and xanthan contents were used in order to obtain the best screw reinforcement. During the pull-out test, the stripping force first increases to a maximum, then drops to a steady-state value until complete screw extraction. Both maximum force and plateau value increase drastically in the presence of cement. The highest stripping force is observed for 6.5-mm screws reinforced with cement in low-density foams. In this case, the stripping force is multiplied by 3.3 in the presence of cement. In a second experiment, cements with solid/liquid ratio ranging from 2.0 to 3.5 g/mL were used with 6.5-mm diameter screws. In some compositions, xanthan was added to improve injectability. The best results were obtained with 2.5 g/mL cement containing xanthan and with 3.0 g/mL cements without xanthan. A 0.9-kN maximal stripping force was observed with nonreinforced screws, while 1.9 kN was reached with reinforced screws. These first results are very promising regarding screw

  20. Vertical-Screw-Auger Conveyer Feeder

    NASA Technical Reports Server (NTRS)

    Walton, Otis (Inventor); Vollmer, Hubert J. (Inventor)

    2016-01-01

    A conical feeder is attached to a vertically conveying screw auger. The feeder is equipped with scoops and rotated from the surface to force-feed regolith the auger. Additional scoops are possible by adding a cylindrical section above the conical funnel section. Such then allows the unit to collect material from swaths larger in diameter than the enclosing casing pipe of the screw auger. A third element includes a flexible screw auger. All three can be used in combination in microgravity and zero atmosphere environments to drill and recover a wide area of subsurface regolith and entrained volatiles through a single access point on the surface.

  1. Guidelines for Clinical Management of Laser-Etched (Laser-Lok) Abutments in Two Different Clinical Scenarios: A Preclinical Laboratory Soft Tissue Assessment Study.

    PubMed

    Neiva, Rodrigo; Tovar, Nick; Jimbo, Ryo; Gil, Luiz F; Goldberg, Paula; Barbosa, Joao Pm; Lilin, Thomas; Coelho, Paulo G

    2016-01-01

    One-stage implants were placed in the mandibles of eight beagle dogs with laser-etched (LL) and machined abutments. After 4 weeks, half of the LL abutments were disconnected and reconnected after 10 minutes of saline storage, and the other half were replaced with a new LL abutment (impression simulation) with or without sulcus de-epithelialization. After abutment change, systems remained in vivo for 3 weeks. Results showed that LL abutments can be reconnected and that sulcus scoring prior to LL placement of one-stage implants receiving machined abutments may be beneficial. PMID:27100803

  2. The Harris-Galante porous acetabular component press-fit without screw fixation. Five-year radiographic analysis of primary cases.

    PubMed

    Schmalzried, T P; Wessinger, S J; Hill, G E; Harris, W H

    1994-06-01

    One hundred twenty-two primary total hip arthroplasties were followed for an average of 56 months (range, 48-66 months) in which the Harris-Galante (Zimmer, Warsaw, IN) porous ingrowth acetabular component had been press-fit into the innominate bone without screw fixation. There were no acetabular fractures. No socket was revised for loosening and none were radiographically loose. There was no evidence of disruption of the titanium porous mesh. There was no acetabular osteolysis. Compared to the authors' series of primary hip reconstructions using this same prosthesis inserted with line-to-line reaming and screw fixation, the data indicate that the tight peripheral fit associated with the press-fit technique is effective in reducing both the incidence and extent of bone-implant radiolucencies. However, the increased incidence of radiolucencies near the apex of the acetabulum also suggest that initial contact of the porous surface with live acetabular bone at this location is desirable in order to obtain and maintain an optimal bone-implant interface. Additional studies are necessary to further establish the relationship between the initial fit and long-term fixation of cementless acetabular components. Based on the data and other considerations for eliminating both vascular risk and the potential for fretting wear between the screws and shell, the authors recommend press-fitting without screw fixation for this acetabular component in primary cases when anatomy and bone stock permit. Full seating of the component is recommended in order to obtain dome contact. PMID:8077971

  3. Minifragment screw fixation of oblique metacarpal fractures: a biomechanical analysis of screw types and techniques.

    PubMed

    Liporace, Frank A; Kinchelow, Tosca; Gupta, Salil; Kubiak, Erik N; McDonnell, Matthew

    2008-12-01

    The lag screw technique has historically been a successful and accepted way to treat oblique metacarpal fractures. However, it does take additional time and involve multiple steps that can increase the risk of fracture propagation or comminution in the small hand bones of the hand. An alternate fixation technique uses bicortical interfragmentary screws. Other studies support the clinical effectiveness and ease of this technique. The purpose of this study is to biomechanically assess the strength of the bicortical interfragmentary screw versus that of the traditional lag screw. Using 48 cadaver metacarpals, oblique osteotomies were created and stabilized using one of four methods: 1.5 mm bicortical interfragmentary (IF) screw, 1.5 mm lag technique screw, 2.0 mm bicortical IF screw, or 2.0 mm lag technique screw. Biomechanical testing was performed to measure post cyclic displacement and load to failure. Data was analyzed using one-way analysis of variance (ANOVA). There was no significant difference among the fixation techniques with regard to both displacement and ultimate failure strength. There was a slight trend for a higher load to failure with the 2.0 mm IF screw and 2.0 mm lag screw compared to the 1.5 mm IF and 1.5 mm lag screws, but this was not significant. Our results support previously established clinical data that bicortical interfragmentary screw fixation is an effective treatment option for oblique metacarpal fractures. This technique has clinical importance because it is an option to appropriately stabilize the often small and difficult to control fracture fragments encountered in metacarpal fractures. PMID:18780019

  4. Prosthetic Abutment Height is a Key Factor in Peri-implant Marginal Bone Loss

    PubMed Central

    Galindo-Moreno, P.; León-Cano, A.; Ortega-Oller, I.; Monje, A.; Suárez, F.; ÓValle, F.; Spinato, S.; Catena, A.

    2014-01-01

    In this study, we analyzed the influence of prosthetic abutment height on marginal bone loss (MBL) around implants in the posterior maxilla. In this retrospective cohort study, the radiographically determined MBL was related to the height of the abutments of internal conical connection implants at 6 and 18 months post-loading. Data were gathered on age, sex, bone substratum, smoking habit, history of periodontitis, and prosthetic features, among other variables. A linear mixed model was used for statistical analysis. The study included 131 patients receiving 315 implants. MBL rates at 6 and 18 months were mainly affected by the abutment height but were also significantly influenced by the bone substratum, periodontitis, and smoking habit. MBL rates were higher for prosthetic abutment < 2 mm vs. ≥ 2 mm, for periodontal vs. non-periodontal patients, for grafted vs. pristine bone, and for a heavier smoking habit. The abutment height is a key factor in MBL. MBL rates followed a non-linear trend, with a greater MBL rate during the first 6 months post-loading than during the next 12 months. PMID:24621670

  5. Clinical evaluation of abutment teeth of removable partial denture by means of the Periotest method.

    PubMed

    Jorge, J H; Giampaolo, E T; Vergani, C E; Machado, A L; Pavarina, A C; Cardoso de Oliveira, M R

    2007-03-01

    Prosthodontics should be one of the means of establishing conditions for the maintenance of periodontal health. The forces applied to the abutment teeth and their effects are very important considerations in the design and construction of the removable partial dentures. This 6-month follow-up clinical study evaluated the degree of mobility of abutment teeth of distal extension and tooth supported removable partial dentures by using Periotest. Two types of clasp design were selected for evaluation. In cases with unilateral and bilateral distal-extension, a clasp design including a T clasp of Roach retentive arm, a rigid reciprocal arm and a mesial rest were used. For the abutments of tooth-supported removable partial dentures, a second clasp design with a cast circumferential buccal retentive arm, a rigid reciprocal clasp arm and a rest adjacent to the edentulous ridges was selected. A total of 68 abutment teeth was analysed. Periotest values were made at the time of denture placement (control) and at 1, 3 and 6 months after the denture placement. The statistical analysis was performed using Friedman test. All analysis was performed at a 0.05 level of significance. The results revelled that no significant changes in tooth mobility were observed during the 6-months follow-up (P > 0.05). In conclusion, our findings suggest that adequate oral hygiene instructions, careful prosthetic treatment planning and regular recall appointments play an important role in preventing changes in abutment tooth mobility caused by removable partial denture placement. PMID:17302951

  6. Evaluation of the marginal fit at implant-abutment interface by optical coherence tomography.

    PubMed

    Kikuchi, Keisuke; Akiba, Norihisa; Sadr, Alireza; Sumi, Yasunori; Tagami, Junji; Minakuchi, Shunsuke

    2014-05-01

    Vertical misfit of implant-abutment interface can affect the success of implant treatment; however, currently available modalities have limitations to detect these gaps. This study aimed to evaluate implant-abutment gaps in vitro using optical coherence tomography (OCT). Vertical misfit gaps sized 50, 100, 150, or 200 μm were created between external hexagonal implants and titanium abutments (Nobel Biocare, Göteborg, Sweden). A porcine gingival tissue slice, 0.5, 1.0, 1.5, or 2.0 mm in thickness, was placed on each implant-abutment interface. The gaps were evaluated by swept-source OCT at a center wavelength of 1330 nm (Panasonic Healthcare, Ehime, Japan) with beam angles of 90, 75 and 60 deg to the implant long-axis. The results suggested that while the measurements were precise, gap size and gingival thickness affected the sensitivity of detection. Gaps sized 100 μm and above could be detected with good accuracy under 0.5- or 1.0-mm-thick gingiva (GN). Around 70% of gaps sized 150 μm and above could be detected under 1.5-mm-thick GN. On the other hand, 80% of gaps under 2.0-mm-thick GN were not detected due to attenuation of near-infrared light through the soft tissue. OCT appeared as an effective tool for evaluating the misfit of implant-abutment under thin layers of soft tissue. PMID:24805806

  7. Evaluation of the marginal fit at implant-abutment interface by optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Kikuchi, Keisuke; Akiba, Norihisa; Sadr, Alireza; Sumi, Yasunori; Tagami, Junji; Minakuchi, Shunsuke

    2014-05-01

    Vertical misfit of implant-abutment interface can affect the success of implant treatment; however, currently available modalities have limitations to detect these gaps. This study aimed to evaluate implant-abutment gaps in vitro using optical coherence tomography (OCT). Vertical misfit gaps sized 50, 100, 150, or 200 μm were created between external hexagonal implants and titanium abutments (Nobel Biocare, Göteborg, Sweden). A porcine gingival tissue slice, 0.5, 1.0, 1.5, or 2.0 mm in thickness, was placed on each implant-abutment interface. The gaps were evaluated by swept-source OCT at a center wavelength of 1330 nm (Panasonic Healthcare, Ehime, Japan) with beam angles of 90, 75 and 60 deg to the implant long-axis. The results suggested that while the measurements were precise, gap size and gingival thickness affected the sensitivity of detection. Gaps sized 100 μm and above could be detected with good accuracy under 0.5- or 1.0-mm-thick gingiva (GN). Around 70% of gaps sized 150 μm and above could be detected under 1.5-mm-thick GN. On the other hand, 80% of gaps under 2.0-mm-thick GN were not detected due to attenuation of near-infrared light through the soft tissue. OCT appeared as an effective tool for evaluating the misfit of implant-abutment under thin layers of soft tissue.

  8. Tool Preloads Screw and Applies Locknut

    NASA Technical Reports Server (NTRS)

    Wood, K. E.

    1982-01-01

    Special tool reaches through structural members inside Space Shuttle fasten nut on preloaded screw that holds thermal protection tile against outside skin of vehicle. Tool attaches tiles with accuratelycontrolled tensile loading.

  9. Additional Drive Circuitry for Piezoelectric Screw Motors

    NASA Technical Reports Server (NTRS)

    Smythe, Robert; Palmer, Dean; Gursel, Yekta; Reder, Leonard; Savedra, Raymond

    2004-01-01

    Modules of additional drive circuitry have been developed to enhance the functionality of a family of commercially available positioning motors (Picomotor . or equivalent) that provide linear motion controllable, in principle, to within increments .30 nm. A motor of this type includes a piezoelectric actuator that turns a screw. Unlike traditional piezoelectrically actuated mechanisms, a motor of this type does not rely on the piezoelectric transducer to hold position: the screw does not turn except when the drive signal is applied to the actuator.

  10. Helical rotary screw expander power system

    NASA Technical Reports Server (NTRS)

    Mckay, R. A.; Sprankle, R. S.

    1974-01-01

    An energy converter for the development of wet steam geothermal fields is described. A project to evaluate and characterize a helical rotary screw expander for geothermal applications is discussed. The helical screw expander is a positive displacement machine which can accept untreated corrosive mineralized water of any quality from a geothermal well. The subjects of corrosion, mineral deposition, the expansion process, and experience with prototype devices are reported.

  11. Contributions of human tissue analysis to understanding the mechanisms of loosening and osteolysis in total hip replacement

    PubMed Central

    Gallo, Jiri; Vaculova, Jana; Goodman, Stuart B.; Konttinen, Yrjö T.; Thyssen, Jacob P.

    2015-01-01

    Aseptic loosening and osteolysis are the most frequent late complications of total hip arthroplasty (THA) leading to revision of the prosthesis. This review aims to demonstrate how histopathological studies contribute to our understanding of the mechanisms of aseptic loosening/osteolysis development. Only studies analysing periprosthetic tissues retrieved from failed implants in humans were included. Data from 101 studies (5532 patients with failure of THA implants) published in English or German between 1974 and 2013 were included. “Control” samples were reported in 45 of the 101 studies. The most frequently examined tissues were the bone-implant interface membrane and pseudosynovial tissues. Histopathological studies contribute importantly to determination of key cell populations underlying the biological mechanisms of aseptic loosening and osteolysis. The studies demonstrated the key molecules of the host response at the protein level (chemokines, cytokines, nitric oxide metabolites, metalloproteinases). However, these studies also have important limitations. Tissues harvested at revision surgery reflect specifically end-stage failure and may not adequately reveal the evolution of pathophysiological events that lead to prosthetic loosening and osteolysis. One possible solution is to examine tissues harvested from stable total hip arthroplasties that have been revised at various time periods due to dislocation or periprosthetic fracture in multicenter studies. PMID:24525037

  12. Long-term effects of deep soil loosening on root distribution and soil physical parameters in compacted lignite mine soils

    NASA Astrophysics Data System (ADS)

    Badorreck, Annika; Krümmelbein, Julia; Raab, Thomas

    2015-04-01

    Soil compaction is a major problem of soils on dumped mining substrates in Lusatia, Germany. Deep ripping and cultivation of deep rooting plant species are considered to be effective ways of agricultural recultivation. Six years after experiment start, we studied the effect of initial deep soil loosening (i.e. down to 65 cm) on root systems of rye (Secale cereale) and alfalfa (Medicago sativa) and on soil physical parameters. We conducted a soil monolith sampling for each treatment (deep loosened and unloosened) and for each plant species (in three replicates, respectively) to determine root diameter, length density and dry mass as well as soil bulk density. Further soil physical analysis comprised water retention, hydraulic conductivity and texture in three depths. The results showed different reactions of the root systems of rye and alfalfa six years after deep ripping. In the loosened soil the root biomass of the rye was lower in depths of 20-40 cm and the root biomass of alfalfa was also decreased in depths of 20-50 cm together with a lower root diameter for both plant species. Moreover, total and fine root length density was higher for alfalfa and vice versa for rye. The soil physical parameters such as bulk density showed fewer differences, despite a higher bulk density in 30-40cm for the deep loosened rye plot which indicates a more pronounced plough pan.

  13. [Evaluation of cermet fillings in abutment teeth in removable partial prostheses].

    PubMed

    Saulic, S; Tihacek-Sojic, Lj

    2001-01-01

    The aim of the study was to describe the clinical process of setting the purpose filling on abutment teeth, after finishing the removable partial dentures. The aim was also to investigate the use of cermet glass-ionomer cement for the purpose filling in the abutment teeth for removable partial dentures, as well as to investigate the surface of the purpose filling. For the clinical evaluation of purpose filling slightly modified criteria according to Ryg's were used in 20 patients with different type of edentulousness. Changes occurring on the surface of purpose filling have been experimentally established by the method of scanning electron microscopy on the half-grown third molars in seven patients. It could be concluded that cement glass-ionomer was not the appropriate material for the purpose fillings in abutment teeth for removable partial dentures. PMID:11858021

  14. Elasto-Viscoplastic Block Element Method and its Application to Arch Dam Abutment Slopes

    NASA Astrophysics Data System (ADS)

    Chen, S.-H.; Shahrour, I.; Egger, P.; Wang, W.-M.

    2002-08-01

    This paper presents an elasto-viscoplastic block element method and its application to the deformation and stability study of arch dam abutment slopes. The paper is composed of two parts. The first part concerns the numerical methods used in the analysis, which includes the identification of the rock blocky system, the algorithm of unconfined seepage flow in discontinuity network taking the grout curtain and drainage curtain into account, and the elasto-viscoplastic block element method as well. In the second part a complicated arch dam abutment slope is studied, from which the seepage flow, the deformation, and the safety factor of the abutment slope are obtained. Based on the analysis suggestions about the seepage control and stabilization measures are made.

  15. “NIMS technique” for minimally invasive spinal fixation using non-fenestrated pedicle screws: A technical note

    PubMed Central

    Rajesh, Alugolu; Pelluru, Pavan Kumar; Kumar, Ashish

    2015-01-01

    Study Design: Case series. Objective: To reduce the cost of minimally invasive spinal fixation. Background: Minimally invasive spine (MIS) surgery is an upcoming modality of managing a multitude of spinal pathologies. However, in a resource-limited situations, using fenestrated screws (FSs) may prove very costly for patients with poor affordability. We here in describe the Nizam's Institute of Medical Sciences (NIMS) experience of using routine non-FSs (NFSs) for transpedicular fixation by the minimally invasive way to bridge the economic gap. Materials and Methods: A total of 7 patients underwent NFS-minimally invasive spine (MIS) surgery. Male to female distribution was 6:1. The average blood loss was 50 ml and the mean operating time was 2 and 1/2 h. All patients were mobilized the very next day after confirming the position of implants on X-ray/computed tomography. Results: All 7 patients are doing well in follow-up with no complaints of a backache or fresh neurological deficits. There was no case with pedicle breach or screw pullout. The average cost of a single level fixation by FS and NFS was ₹1, 30,000/patient and ₹32,000/patient respectively (‘2166 and ‘530, respectively). At the end of 1-year follow-up, we had two cases of screw cap loosening and with a displacement of the rod cranio-caudally in one case which was revised through the same incisions. Conclusions: Transpedicular fixation by using NFS for thoracolumbar spinal pathologies is a cost-effective extension of MIS surgery. This may extend the benefits to a lower socioeconomic group who cannot afford the cost of fenestrated screw (FS). PMID:26692692

  16. Ball Screw Actuator Including a Stop with an Integral Guide

    NASA Technical Reports Server (NTRS)

    Wingett, Paul T. (Inventor); Perek, John (Inventor); Geck, Kellan (Inventor)

    2015-01-01

    An actuator includes a housing assembly, a ball nut, a ball screw, and a ball screw stop. The ball nut is rotationally mounted in the housing assembly, is adapted to receive an input torque, and is configured, upon receipt thereof, to rotate and supply a drive force. The ball screw is mounted within the housing assembly and extends through the ball nut. The ball screw has a first end and a second end, and is coupled to receive the drive force from the ball nut. The ball screw is configured, upon receipt of the drive force, to selectively translate between a stow position and a deploy position. The ball screw stop is mounted on the ball screw to translate therewith and is configured to at selectively engage the housing assembly while the ball screw is translating, and engage the ball nut when the ball screw is in the deploy position.

  17. Insertion Profiles of 4 Headless Compression Screws

    PubMed Central

    Hart, Adam; Harvey, Edward J.; Lefebvre, Louis-Philippe; Barthelat, Francois; Rabiei, Reza; Martineau, Paul A.

    2013-01-01

    Purpose In practice, the surgeon must rely on screw position (insertion depth) and tactile feedback from the screwdriver (insertion torque) to gauge compression. In this study, we identified the relationship between interfragmentary compression and these 2 factors. Methods The Acutrak Standard, Acutrak Mini, Synthes 3.0, and Herbert-Whipple implants were tested using a polyurethane foam scaphoid model. A specialized testing jig simultaneously measured compression force, insertion torque, and insertion depth at half-screw-turn intervals until failure occurred. Results The peak compression occurs at an insertion depth of −3.1 mm, −2.8 mm, 0.9 mm, and 1.5 mm for the Acutrak Mini, Acutrak Standard, Herbert-Whipple, and Synthes screws respectively (insertion depth is positive when the screw is proud above the bone and negative when buried). The compression and insertion torque at a depth of −2 mm were found to be 113 ± 18 N and 0.348 ± 0.052 Nm for the Acutrak Standard, 104 ± 15 N and 0.175 ± 0.008 Nm for the Acutrak Mini, 78 ± 9 N and 0.245 ± 0.006 Nm for the Herbert-Whipple, and 67 ± 2N, 0.233 ± 0.010 Nm for the Synthes headless compression screws. Conclusions All 4 screws generated a sizable amount of compression (> 60 N) over a wide range of insertion depths. The compression at the commonly recommended insertion depth of −2 mm was not significantly different between screws; thus, implant selection should not be based on compression profile alone. Conically shaped screws (Acutrak) generated their peak compression when they were fully buried in the foam whereas the shanked screws (Synthes and Herbert-Whipple) reached peak compression before they were fully inserted. Because insertion torque correlated poorly with compression, surgeons should avoid using tactile judgment of torque as a proxy for compression. Clinical relevance Knowledge of the insertion profile may improve our understanding of the implants, provide a better basis for comparing screws

  18. Bipolar hip arthroplasty as salvage treatment for loosening of the acetabular cup with significant bone defects

    PubMed Central

    Ghanem, Mohamed; Glase, Almuth; Zajonz, Dirk; Roth, Andreas; Heyde, Christoph-E.; Josten, Christoph; von Salis-Soglio, Georg

    2016-01-01

    Introduction: Revision arthroplasty of the hip is becoming increasingly important in recent years. Early primary arthroplasty and longer life expectancy of the patients increases the number of revision surgery. Revision surgery of hip arthroplasty is major surgery for the patients, especially the elderly, with significant risks concerning the general condition of the patient. The aim of this work is to evaluate the outcome of bipolar hip arthroplasty as a salvage procedure for treatment of loosening of the acetabular cup with significant acetabular bone defects after total hip replacement (THR) in multi-morbid patients. Patients and methods: During the period from January 1st 2007 to December 31st 2011 19 revision hip surgeries were performed in 19 patients, in which the loosened acetabular cup was replaced by a bipolar head. The examined patient group consisted exclusively of female patients with an average of 75 years. The predominant diagnosis was “aseptic loosening” (84.2%). All patients in our study were multi-morbid. We decided to resort to bipolar hip arthroplasty due to the compromised general condition of patients and the major acetabular bone defects, which were confirmed intraoperatively. The postoperative follow-up ranged from 0.5 to 67 months (average 19.1 months). Results: Evaluation of the modified Harris Hip Score showed an overall improvement of the function of the hip joint after surgery of approximately 45%. Surgery was less time consuming and thus adequate for patients with significantly poor general health condition. We noticed different complications in a significant amount of patients (68.4%). The most common complication encountered was the proximal migration of the bipolar head. The rate of revision following the use of bipolar hip arthroplasty in revision surgery of the hip in our patients was high (21%). Despite the high number of complications reported in our study, we have noticed significant improvement of hip joint function as

  19. Pullout strength of pedicle screws with cement augmentation in severe osteoporosis: A comparative study between cannulated screws with cement injection and solid screws with cement pre-filling

    PubMed Central

    2011-01-01

    Background Pedicle screws with PMMA cement augmentation have been shown to significantly improve the fixation strength in a severely osteoporotic spine. However, the efficacy of screw fixation for different cement augmentation techniques, namely solid screws with retrograde cement pre-filling versus cannulated screws with cement injection through perforation, remains unknown. This study aimed to determine the difference in pullout strength between conical and cylindrical screws based on the aforementioned cement augmentation techniques. The potential loss of fixation upon partial screw removal after screw insertion was also examined. Method The Taguchi method with an L8 array was employed to determine the significance of design factors. Conical and cylindrical pedicle screws with solid or cannulated designs were installed using two different screw augmentation techniques: solid screws with retrograde cement pre-filling and cannulated screws with cement injection through perforation. Uniform synthetic bones (test block) simulating severe osteoporosis were used to provide a platform for each screw design and cement augmentation technique. Pedicle screws at full insertion and after a 360-degree back-out from full insertion were then tested for axial pullout failure using a mechanical testing machine. Results The results revealed the following 1) Regardless of the screw outer geometry (conical or cylindrical), solid screws with retrograde cement pre-filling exhibited significantly higher pullout strength than did cannulated screws with cement injection through perforation (p = 0.0129 for conical screws; p = 0.005 for cylindrical screws). 2) For a given cement augmentation technique (screws without cement augmentation, cannulated screws with cement injection or solid screws with cement pre-filling), no significant difference in pullout strength was found between conical and cylindrical screws (p >0.05). 3) Cement infiltration into the open cell of the test block led to

  20. Aseptic stem loosening in primary THA: migration analysis of cemented and cementless fixation

    PubMed Central

    Kroell, Artur; Beaulé, Paul; Krismer, Martin; Behensky, Hannes; Stoeckl, Bernd

    2008-01-01

    Early migration has reportedly been predictive for later implant failure. Using four different migration patterns, this study aimed to analyse migration behaviour of the two types of implant fixation—cemented and cementless—throughout the process of loosening. Migrational behaviour of 69 revised stems (49 cemented, 20 uncemented) was analysed retrospectively with EBRA-FCA (Einzel-Bild-Röntgen-Analyse, Femoral Component Analysis). Uncemented stems failed after early and late onset migration alike, while late migration was the predominant pattern in cemented stems. Mean prosthetic failure after early migration occurred 5.8 (±4.4) years postoperatively due to insufficient primary stability. Initially stable stems with late onset migration were revised after 12.4 (±4.5) years. Measurement of early migration was found to be a valuable tool to screen short-term and mid-term failure. In the long run the method’s sensitivity decreased. Late onset migration, however, preceded long-term failure by a mean of three years. PMID:19066889

  1. Macrophage activation and migration in interface tissue around loosening total hip arthroplasty components.

    PubMed

    Ishiguro, N; Kojima, T; Ito, T; Saga, S; Anma, H; Kurokouchi, K; Iwahori, Y; Iwase, T; Iwata, H

    1997-06-01

    The bone-cement interface tissue of failed total hip arthroplasty (THA) has inflammatory characteristics, such as the presence of prostaglandin E2 and interleukin 1 (IL-1). We considered that the bone-cement interface tissue could be the site of granulomatous inflammation caused by a foreign-body reaction. It has been demonstrated that inflammatory cytokines and chemokines have an important role in granulomatous inflammation. Bone-cement interface tissue was obtained at revision from nine patients with failed cemented THA, and the role of macrophages was assessed by immunohistochemistry, electron microscopy, and molecular biological techniques. We used the reverse-transcriptional polymerase chain reaction to examine the expression of mRNA for IL-1 alpha, IL-1 beta, tumor necrosis factor alpha (TNF alpha), macrophage inflammatory protein (MIP)-1 alpha, MIP-1 beta, IL-8, and monocyte chemoattractant protein. Polyethylene debris surrounded by macrophages and phagocytosis of debris by macrophages was frequently observed in the interface tissue. Macrophage activation and the production of inflammatory cytokines such as IL-1 and TNF alpha might induce the development of interface tissue. Expression of chemokine mRNAs was also commonly seen, suggesting that this led to recruitment of macrophages into the bone-cement interface tissue. Debris released from implants appears to cause activation of macrophages and the production of inflammatory cytokines and chemokines that induce cellular recruitment into interface tissue. This mechanism might form a vicious cycle that aggravates THA loosening. PMID:9138074

  2. Apparatus to test insertion and removal torque of bone screws.

    PubMed

    Koistinen, A; Santavirta, S; Lappalainen, R

    2003-01-01

    This paper describes affordable equipment for testing bone screw torque, corresponding to ASTM standard F543-00 for testing metallic medical bone screws. Correct testing of thin and long bone screws is essential due to screw failures during insertion and removal of the screws. Furthermore, insertion torque is an important factor in predicting fixation strength, screw pull-out force and effects of surface treatment of screws. The capability of the custom-built tester was determined using polytetrafluoroethylene and wood disc samples and bone screws. Bovine cortical bones allowed testing to the failure limit, i.e. the torque increased in long screws to the fracture limit. For 2.7 and 3.5 mm thick self-tapping cortical bone screws, the failure torques were 30-50 per cent higher than the minimum values required by the standard (1.0 and 2.3 N m respectively). The equipment provided reproducible results and fulfilled the ASTM standard very well. Preliminary testing with amorphous diamond coated bone screws showed good durability of the coating and on average 10-15 per cent lower torque values compared with uncoated screws. The equipment can be used to measure insertion and removal torques as described in the standard. Furthermore, it also allows testing of normal screws and bolts. PMID:14702987

  3. Twin screw wet granulation: Binder delivery.

    PubMed

    Saleh, Mohammed F; Dhenge, Ranjit M; Cartwright, James J; Hounslow, Michael J; Salman, Agba D

    2015-06-20

    The effects of three ways of binder delivery into the twin screw granulator (TSG) on the residence time, torque, properties of granules (size, shape, strength) and binder distribution were studied. The binder distribution was visualised through the transparent barrel using high speed imaging as well as quantified using offline technique. Furthermore, the effect of binder delivery and the change of screw configuration (conveying elements only and conveying elements with kneading elements) on the surface velocity of granules across the screw channel were investigated using particle image velocimetry (PIV). The binder was delivered in three ways; all solid binder incorporated with powder mixture, 50% of solid binder mixed with powder mixture and 50% mixed with water, all the solid binder dissolved in water. Incorporation of all solid binder with powder mixture resulted in the relatively longer residence time and higher torque, narrower granule size distribution, more spherical granules, weaker big-sized granules, stronger small-sized granules and better binder distribution compared to that in other two ways. The surface velocity of granules showed variation from one screw to another as a result of uneven liquid distribution as well as shown a reduction while introducing the kneading elements into the screw configuration. PMID:25869451

  4. The effect of mucosal cuff shrinkage around dental implants during healing abutment replacement.

    PubMed

    Nissan, J; Zenziper, E; Rosner, O; Kolerman, R; Chaushu, L; Chaushu, G

    2015-10-01

    Soft tissue shrinkage during the course of restoring dental implants may result in biological and prosthodontic difficulties. This study was conducted to measure the continuous shrinkage of the mucosal cuff around dental implants following the removal of the healing abutment up to 60 s. Individuals treated with implant-supported fixed partial dentures were included. Implant data--location, type, length, diameter and healing abutments' dimensions--were recorded. Mucosal cuff shrinkage, following removal of the healing abutments, was measured in bucco-lingual direction at four time points--immediately after 20, 40 and 60 s. anova was used to for statistical analysis. Eighty-seven patients (49 women and 38 men) with a total of 311 implants were evaluated (120 maxilla; 191 mandible; 291 posterior segments; 20 anterior segments). Two-hundred and five (66%) implants displayed thick and 106 (34%) thin gingival biotype. Time was the sole statistically significant parameter affecting mucosal cuff shrinkage around dental implants (P < 0.001). From time 0 to 20, 40 and 60 s, the mean diameter changed from 4.1 to 4.07, 3.4 and 2.81 mm, respectively. The shrinkage was 1%, 17% and 31%, respectively. The gingival biotype had no statistically significant influence on mucosal cuff shrinkage (P = 0.672). Time required replacing a healing abutment with a prosthetic element should be minimised (up to 20/40 s), to avoid pain, discomfort and misfit. PMID:26132112

  5. 18. DETAIL, L0 JOINT AND BEARING SEAT AT WEST ABUTMENT, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    18. DETAIL, L0 JOINT AND BEARING SEAT AT WEST ABUTMENT, FROM NORTH, SHOWING RIVETED CONNECTION OF BOTTOM CHORD AND END POST AT JOINT, AND FIXED SHOE - Glendale Road Bridge, Spanning Deep Creek Lake on Glendale Road, McHenry, Garrett County, MD

  6. In-office technique for selectively etching titanium abutments to improve bonding for interim implant prostheses.

    PubMed

    Wadhwani, Chandur; Chung, Kwok-Hung

    2016-03-01

    A technique is described for increasing the surface area of a titanium abutment with hydrofluoric acid etching. This provides mechanical retention for acrylic resin and composite resins and can be easily and rapidly accomplished in both the laboratory and clinic. PMID:26553255

  7. 31. VIEW FROM SOUTHWEST TO CORNER WHERE SAMPLING/CRUSHING ADDITIONS ABUT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    31. VIEW FROM SOUTHWEST TO CORNER WHERE SAMPLING/CRUSHING ADDITIONS ABUT CRUSHED OXIDIZED ORE BIN. INTACT BARREN SOLUTION TANK VISIBLE IN FRONT OF CRUSHED ORE BIN. - Bald Mountain Gold Mill, Nevada Gulch at head of False Bottom Creek, Lead, Lawrence County, SD

  8. 13. Detail of abutment/arch rib juncture. Northeast end of bridge, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    13. Detail of abutment/arch rib juncture. Northeast end of bridge, looking east to west. - Presumpscot Falls Bridge, Spanning Presumptscot River at Allen Avenue extension, 0.75 mile west of U.S. Interstate 95, Falmouth, Cumberland County, ME

  9. Fatal complications after stereotactic body radiation therapy for central lung tumors abutting the proximal bronchial tree

    PubMed Central

    Haseltine, Justin M.; Rimner, Andreas; Gelblum, Daphna Y.; Modh, Ankit; Rosenzweig, Kenneth E.; Jackson, Andrew; Yorke, Ellen D.; Wu, Abraham J.

    2016-01-01

    Purpose Stereotactic body radiation therapy (SBRT) is associated with excess toxicity following treatment of central lung tumors. Risk-adapted fractionation appears to have mitigated this risk, but it remains unclear whether SBRT is safe for all tumors within the central lung zone, especially those abutting the proximal bronchial tree (PBT). We investigated the dependence of toxicity on tumor proximity to PBT and whether tumors abutting the PBT had greater toxicity than other central lung tumors after SBRT. Materials and methods A total of 108 patients receiving SBRT for central lung tumors were reviewed. Patients were classified based on closest distance from tumor to PBT. Primary endpoint was SBRT-related death. Secondary endpoints were overall survival, local control, and grade 3+ pulmonary adverse events. We compared tumors abutting the PBT to nonabutting and those ≤1 cm and >1 cm from PBT. Results Median follow-up was 22.7 months. Median distance from tumor to PBT was 1.78 cm. Eighty-eight tumors were primary lung and 20 were recurrent or metastatic; 23% of tumors were adenocarcinoma and 71% squamous cell. Median age was 77.5 years. Median dose was 4500 cGy in 5 fractions prescribed to the 100% isodose line. Eighteen patients had tumors abutting the PBT, 4 of whom experienced SBRT-related death. No other patients experienced death attributed to SBRT. Risk of SBRT-related death was significantly higher for tumors abutting the PBT compared with nonabutting tumors (P < .001). Two patients with SBRT-related death received anti-vascular endothelial growth factor therapy and experienced pulmonary hemorrhage. Patients with tumors ≤1 cm from PBT had significantly more grade 3+ events than those with tumors >1cm from PBT (P = .014). Conclusions Even with risk-adapted fractionation, tumors abutting PBT are associated with a significant and differential risk of SBRT-related toxicity and death. SBRT should be used with particular caution in central-abutting tumors

  10. The reaction of cortical bone to compression by screw threads.

    PubMed

    Schatzker, J; Horne, J G; Sumner-Smith, G

    1975-09-01

    Cortical bone subjected to compression by screw threads retains its integrity and is not resorbed. Screws which generate compression at the interface of their threads with bone can be expected to provide adequate fixation until bone union occurs. PMID:1157421

  11. [Cement augmentation of pedicle screws : Pros and cons].

    PubMed

    Schnake, K J; Blattert, T R; Liljenqvist, U

    2016-09-01

    Cement augmentation of pedicle screws biomechanically increases screw purchase in the bone. However, clinical complications may occur. The pros and cons of the technique are discussed from different clinical perspectives. PMID:27514827

  12. Impact of screw configuration on the particle size distribution of granules produced by twin screw granulation.

    PubMed

    Vercruysse, J; Burggraeve, A; Fonteyne, M; Cappuyns, P; Delaet, U; Van Assche, I; De Beer, T; Remon, J P; Vervaet, C

    2015-02-01

    Twin screw granulation (TSG) has been reported by different research groups as an attractive technology for continuous wet granulation. However, in contrast to fluidized bed granulation, granules produced via this technique typically have a wide and multimodal particle size distribution (PSD), resulting in suboptimal flow properties. The aim of the current study was to evaluate the impact of granulator screw configuration on the PSD of granules produced by TSG. Experiments were performed using a 25 mm co-rotating twin screw granulator, being part of the ConsiGma™-25 system (a fully continuous from-powder-to-tablet manufacturing line from GEA Pharma Systems). Besides the screw elements conventionally used for TSG (conveying and kneading elements), alternative designs of screw elements (tooth-mixing-elements (TME), screw mixing elements (SME) and cutters) were investigated using an α-lactose monohydrate formulation granulated with distilled water. Granulation with only conveying elements resulted in wide and multimodal PSD. Using kneading elements, the width of the PSD could be partially narrowed and the liquid distribution was more homogeneous. However, still a significant fraction of oversized agglomerates was obtained. Implementing additional kneading elements or cutters in the final section of the screw configuration was not beneficial. Furthermore, granulation with only TME or SME had limited impact on the width of the PSD. Promising results were obtained by combining kneading elements with SME, as for these configurations the PSD was narrower and shifted to the size fractions suitable for tableting. PMID:25562758

  13. Screw expander for light duty diesel engines

    NASA Technical Reports Server (NTRS)

    1983-01-01

    Preliminary selection and sizing of a positive displacement screw compressor-expander subsystem for a light-duty adiabatic diesel engine; development of a mathematical model to describe overall efficiencies for the screw compressor and expander; simulation of operation to establish overall efficiency for a range of design parameters and at given engine operating points; simulation to establish potential net power output at light-duty diesel operating points; analytical determination of mass moments of inertia for the rotors and inertia of the compressor-expander subsystem; and preparation of engineering layout drawings of the compressor and expander are discussed. As a result of this work, it was concluded that the screw compressor and expander designed for light-duty diesel engine applications are viable alternatives to turbo-compound systems, with acceptable efficiencies for both units, and only a moderate effect on the transient response.

  14. Low energy high pressure miniature screw valve

    DOEpatents

    Fischer, Gary J.; Spletzer, Barry L.

    2006-12-12

    A low energy high pressure screw valve having a valve body having an upper portion and a lower portion, said lower portion of said valve body defining an inlet flow passage and an outlet flow passage traversing said valve body to a valve seat, said upper portion of said valve body defining a cavity at said valve seat, a diaphragm restricting flow between said upper portion of said valve body and said lower portion, said diaphragm capable of engaging said valve seat to restrict fluid communication between said inlet passage and said outlet passage, a plunger within said cavity supporting said diaphragm, said plunger being capable of engaging said diaphragm with said valve seat at said inlet and outlet fluid passages, said plunger being in point contact with a drive screw having threads engaged with opposing threads within said upper portion of said valve body such engagement allowing motion of said drive screw within said valve body.

  15. Reuse of healing abutments: an in vitro model of plasma cleaning and common sterilization techniques.

    PubMed

    Vezeau, P J; Keller, J C; Wightman, J P

    2000-01-01

    The reuse of transgingival healing abutments has been advocated by several implant manufacturers, but cleaning and sterilization procedures to yield clean and optimal surfaces have yet to be developed. The objective of this in vitro project was to investigate various cleaning and sterilization regimens for the removal of biological debris to support reattachment of subgingival connective tissue. Simulated clinical healing abutment surfaces were exposed to culture medium with serum for 1 hour to simulate biological exposure. Simulated healing abutment surfaces not contaminated by serum were used to represent the "as-is" healing abutment surface without prior in vivo use. The discs were cleaned with detergent before sterilization by ultraviolet light (UV) or steam autoclaving (AC) both with and without 1- and 5-minute plasma cleaning (PC). A series of surface analytical techniques (XPS, AES, and surface contact angles) and in vitro analysis of cell attachment and spreading using gingival fibroblasts were performed. After exposure to the simulated biological conditions, clinical cleaning followed by UV resulted in contaminated surfaces and relatively high levels of cell attachment. PC before UV treatment enhanced surface energetics but did not affect cell attachment and spreading. AC increased surface wetting angles; which were decreased somewhat by previous PC. Cell attachment was significantly reduced by AC. Although some increase in cell attachment after longer plasma cleaning was noted in the AC group, no difference in cell spreading was seen in any AC group. Cell spreading seemed to be less for all AC groups compared with all UV, as-is, and control groups. Although certain cleaning (PC) and sterilization (UV) procedures can be effective for cleaning transgingival healing abutments, those using AC are questionable due to their propensity for organic and inorganic contamination and unfavorable surface alteration. PMID:11307410

  16. The Effect of Polymethyl Methacrylate Augmentation on the Primary Stability of Cannulated Bone Screws in an Anterolateral Plate in Osteoporotic Vertebrae: A Human Cadaver Study

    PubMed Central

    Rüger, Matthias; Sellei, Richard M.; Stoffel, Marcus; von Rüden, Christian

    2015-01-01

    Study Design Cohort study. Objective Expandable anterolateral plates facilitate the reduction of posttraumatic deformities of thoracolumbar spine injuries and are commonly used in cases of unstable injuries or compromised bone quality. In this in vitro study, the craniocaudal yield load of the osseous fixation of an anterior angular stable plate fixation system and the effect of polymethyl methacrylate (PMMA) screw augmentation on the primary stability of the screw–bone interface during kyphosis reduction was evaluated in 12 osteoporotic human thoracolumbar vertebrae. Methods The anterolateral stabilization device used for this study is comprised of two swiveling flanges and an expandable midsection. It facilitates the controlled reduction of kyphotic deformities in situ with a geared distractor. Single flanges were attached to 12 thoracolumbar vertebrae. Six specimens were augmented with PMMA by means of cannulated bone screws. The constructs were subjected to static, displacement-controlled craniocaudal loading to failure in a servohydraulic testing machine. Results The uncemented screws cut out at a mean 393 ± 66 N, whereas the cemented screws showed significantly higher yield load of 966 ± 166 N (p < 0.02). We detected no significant correlation between bone mineral density and yield load in this setting. Conclusion Our results indicate that PMMA augmentation is an effective method to increase two- to threefold the primary stability of the screw–bone interface of an anterolateral spine stabilization system in osteoporotic bone. We recommend it in cases of severely compromised bone quality to reduce the risk of screw loosening during initial kyphosis correction and to increase long-term construct stability. PMID:26835201

  17. SCREW MIGRATION IN TOTAL KNEE ARTHROPLASTY: CLINICAL REPORT

    PubMed Central

    Fonseca, Fernando; Tomé, José; Barreto, Manuel

    2015-01-01

    Complications from total knee arthroplasty caused by the implanted material are rare, with the exception of polyethylene wear. Descriptions of screw migration into the knee joint cavity are very rare. The authors report intra-articular migration of a polyethylene safety screw in a case of total knee arthroplasty, with sacrifice of the posterior cruciate ligament (TKA Performance; Biomet, Warsaw, IN, USA), which necessitated new surgery to remove the screw, replace the polyethylene insert and emplace a new fixation screw. PMID:27022526

  18. Esthetic Outcomes of Single-Tooth Implant-Supported Restorations Using Metal-Ceramic Restorations with Zirconia or Titanium Abutments: A Randomized Controlled Clinical Study.

    PubMed

    Baldini, Nicola; D'Elia, Chiara; Clementini, Marco; Carrillo de Albornoz, Ana; Sanz, Mariano; De Sanctis, Massimo

    2016-01-01

    The aim of this study was to test whether zirconia abutments exhibit the same clinical and esthetic outcomes as titanium abutments in single-tooth implant restorations in the esthetic area. The 24 treated patients were randomly assigned to a test (zirconia abutment) or control (titanium abutment) group. Objective evaluations were carried out using the Implant Crown Aesthetic Index (ICAI) and the Papilla Index (PI) at the 1-month and 12-month follow-up examinations after crown cementation. No significant differences, either in ICAI or in other periodontal or radiographic measurements, were observed. At 1 year, zirconia and titanium abutments exhibited the same esthetic outcomes. PMID:27333019

  19. Spline-Screw Multiple-Rotation Mechanism

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1994-01-01

    Mechanism functions like combined robotic gripper and nut runner. Spline-screw multiple-rotation mechanism related to spline-screw payload-fastening system described in (GSC-13454). Incorporated as subsystem in alternative version of system. Mechanism functions like combination of robotic gripper and nut runner; provides both secure grip and rotary actuation of other parts of system. Used in system in which no need to make or break electrical connections to payload during robotic installation or removal of payload. More complicated version needed to make and break electrical connections. Mechanism mounted in payload.

  20. Reversed-field pinch and screw pinch

    SciTech Connect

    Kito, M.; Yoshimura, H.

    1983-12-01

    The Electrotechnical Laboratory and the College of Science and Technology at Nihon University discuss the results, device parameters, and objectives of reversed-field pinch TPE-1R(M). This device is illustrated and tables are given of machine parameters, as well as plasma parameters and temperature and density scalings. Other reversed-field pinch (RFP) machines are discussed, and tables show the RFP devices of Japan and design parameters of TPE-2, a screw-pinch device with a noncircular cross section. The STP-3 screw-pinch device is also discussed.

  1. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Pedicle screw spinal system. 888.3070 Section 888.3070 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3070 Pedicle screw spinal system. (a) Identification. Pedicle screw spinal systems...

  2. Biomechanical evaluation of a new composite bioresorbable screw.

    PubMed

    Bailey, C A; Kuiper, J H; Kelly, C P

    2006-04-01

    A new bioresorbable composite cannulated screw has been developed for small bone fracture fixation. The LG ("Little Grafter") screw is manufactured from Biosteon, which is a composite of poly L-lactic acid and hydroxyapatite. This study aimed to compare interfragmentary compression generated by this new screw with conventional metal screws commonly used in scaphoid fracture fixation. Four small metallic screws were compared with the LG screw, using a bone model produced from rigid polyurethane foam. The screws included the Acutrak, Asnis III, Herbert and Herbert-Whipple screws. The mean maximum compression forces for the LG screw, the Asnis and the Acutrak were comparable (LG 32.3 N, Asnis 32.8 N, Acutrak 38.3 N), whereas those using the Herbert and the Herbert-Whipple screw were significantly lower (Herbert 21.8 N, Herbert-Whipple 19.9 N). The bioresorbable LG screw has been shown to have good compressive properties compared to commonly used small bone fragment compression screws. PMID:16361004

  3. Minimally Invasive Multilevel Percutaneous Pedicle Screw Fixation for Lumbar Spinal Diseases

    PubMed Central

    Son, Seong; Park, Chan Woo; Kim, Woo Kyung

    2012-01-01

    Objective There are rare reports on the result of multilevel (≥3 levels) percutaneous pedicle screw fixation (PPF). The purpose of this study was to report the clinical experiences for multilevel PPF of the lumbar spine. Methods A total of 17 patients of lumbar spinal disease (7 degenerative diseases, 6 infectious diseases, and 4 traumatic instabilities) underwent neural decompression and multilevel PPF. There were 8 men and 9 women with a mean age of 61.4 years (range, 25-84) and a mean follow-up period of 23.2 months (range, 13-48). The average PPF level was 3.7. A retrospective review of clinical, radiological, and surgical data was conducted. Results "Excellent" or "good" clinical results were obtained in 15 patients (88.2%) according to the Odom's criteria. The average improvement of visual analogue scale was 5.2 points (from 9.3 to 4.1), and the average improvement of Oswestry Disability Index was 36.2 (from 71.2 to 35.0) at the last visit (p<0.05). The fusion rate was 88.2%, but, screw loosening was occurred in 2 patients, and adjacent segmental degeneration was occurred in 2 patients. There was no statistical significance in the change of total lumbar lordotic angle. The average operation time was 5.9 hours, with an estimated blood loss of 550 ml and bed rest duration of 2.0 days. Conclusion Although the current study examined a small sample with relatively short term follow up periods, our study results demonstrate that multilevel PPF is feasible and safe for selective lumbar spinal diseases. PMID:25983845

  4. Comparison of The Effect of Implant Abutment Surface Modifications on Retention of Implant-Supported Restoration with A Polymer Based Cement

    PubMed Central

    Sahu, Nabaprakash; Lakshmi, Namratha; Azhagarasan, N.S.; Agnihotri, Yoshaskam; Rajan, Manoj; Hariharan, Ramasubramanian

    2014-01-01

    Background: In cement-retained implant-supported restoration it is important to gain adequate retention of definitive restoration as well as retrievability of prosthesis. The surface of the abutment, alloy of the restoration and the type of cement used influences the retention of the restoration. There is a need to analyze the influence of surface modifications of abutments on the retentive capabilities of provisional implant cements. Purpose of study: To compare the effect of implant abutment surface modifications on retention of implant-supported restoration cemented with polymer based cement. Materials and method: Thirty solid titanium implant abutments (ADIN), 8mm height, were divided into 3 groups. Ten abutments with retentive grooves (Group I) as supplied by the manufacturer, Ten abutments milled to 20 taper circumferentially (Group II), and Ten abutments milled and air-abraded with 110 μm aluminum oxide (Group III) were used in this study. Ni-Cr coping were casted for each abutment and polymer based cement was used to secure them to the respective abutments. Using a universal testing machine at a crosshead speed of 0.5 cm/minute, tensile bond strength was recorded (N). Results: Mean tensile bond strength of Group I, II and III were found to be 408.3, 159.9 and 743.8 Newton respectively. The values were statistically different from each other (p<0.001). Conclusion: Abutments with milled and sandblasted surface provide the highest retention followed by abutments with retentive grooves and then by abutments with milled surface when cast copings were cemented to implant abutments with polymer based cement. Clinical implications: Retention of restoration depends on the surface of the abutment as well as the luting agents used. Incorporation of retentive grooves or particle abrasion can enhance retention especially in situation of short clinical crown. PMID:24596785

  5. Analysis of screw pullout strength: a function of screw orientation in subtalar joint arthrodesis.

    PubMed

    McGlamry, Michael C; Robitaille, Melissa F

    2004-01-01

    The purpose of this cadaveric study was to compare the pullout strength and failure load of 2 different screw orientations for subtalar arthrodesis. Twenty-six specimens from 13 cadaver donors (1 left and 1 right each) were used. A 7.3- x 65-mm long-thread profile (32-mm length) cannulated screw inserted into the calcaneus from dorsal to plantar (calcaneal specimens) was compared with a 7.3- x 65-mm short-thread profile (16-mm length) cannulated screw inserted into the talus from plantar to dorsal (talar specimens). A torque screwdriver with a calibrated electronic vernier scale measured the torque of screw insertion. Screw pullout strength and load failure were measured by using a servohydraulic materials testing machine. Distraction was applied along the axis of the screw at a displacement rate of 25 mm/min. The peak torque of insertion in all calcaneal specimens was reached on initial insertion through the dorsal subchondral bone plate of the calcaneus; in talar specimens, it was reached as the screw threads were completely buried into the talus. A significant difference (P = .00647) was found between the mean torque of insertion for the calcaneal (1.50 Nm) and talar specimens (1.30 Nm). A comparison of pullout forces showed a significantly stronger mean failure load for calcaneal specimens (P = .000085). The mean failure load for paired calcaneal specimens was 1782 N compared with a mean 1245 N for talar specimens. Although the pullout force was clearly greater in the dorsal-to-plantar screw application, the pullout force in the plantar-to-dorsal orientation was also considerable. PMID:15480401

  6. Fatigue strength of common tibial intramedullary nail distal locking screws

    PubMed Central

    Griffin, Lanny V; Harris, Robert M; Zubak, Joseph J

    2009-01-01

    Background Premature failure of either the nail and/or locking screws with unstable fracture patterns may lead to angulation, shortening, malunion, and IM nail migration. Up to thirty percent of all unreamed nail locking screws can break after initial weight bearing is allowed at 8–10 weeks if union has not occurred. The primary problem this presents is hardware removal during revision surgery. The purposes of our study was to evaluate the relative fatigue resistance of distal locking screws and bolts from representative manufacturers of tibial IM nail systems, and develop a relative risk assessment of screws and materials used. Evaluations included quantitative and qualitative measures of the relative performance of these screws. Methods Fatigue tests were conducted to simulate a comminuted fracture that was treated by IM nailing assuming that all load was carried by the screws. Each screw type was tested ten times in a single screw configuration. One screw type was tested an additional ten times in a two-screw parallel configuration. Fatigue tests were performed using a servohydraulic materials testing system and custom fixturing that simulated screws placed in the distal region of an appropriately sized tibial IM nail. Fatigue loads were estimated based on a seventy-five kilogram individual at full weight bearing. The test duration was one million cycles (roughly one year), or screw fracture, whichever occurred first. Failure analysis of a representative sample of titanium alloy and stainless steel screws included scanning electron microscopy (SEM) and quantitative metallography. Results The average fatigue life of a single screw with a diameter of 4.0 mm was 1200 cycles, which would correspond roughly to half a day of full weight bearing. Single screws with a diameter of 4.5 mm or larger have approximately a 50 percent probability of withstanding a week of weight bearing, whereas a single 5.0 mm diameter screw has greater than 90 percent probability of

  7. Computer simulation of screw dislocation in aluminum

    NASA Technical Reports Server (NTRS)

    Esterling, D. M.

    1976-01-01

    The atomic structure in a 110 screw dislocation core for aluminum is obtained by computer simulation. The lattice statics technique is employed since it entails no artificially imposed elastic boundary around the defect. The interatomic potential has no adjustable parameters and was derived from pseudopotential theory. The resulting atomic displacements were allowed to relax in all three dimensions.

  8. Improvements In Ball-Screw Linear Actuators

    NASA Technical Reports Server (NTRS)

    Iskenderian, Theodore; Joffe, Benjamin; Summers, Robert

    1996-01-01

    Report describes modifications of design of type of ball-screw linear actuator driven by dc motor, with linear-displacement feedback via linear variable-differential transformer (LVDT). Actuators used to position spacecraft engines to direct thrust. Modifications directed toward ensuring reliable and predictable operation during planned 12-year cruise and interval of hard use at end of cruise.

  9. Computation of Flow in Screw Compressors

    NASA Astrophysics Data System (ADS)

    Kalitzin, Georgi; Cai, Xiaodan; Reba, Ramons; Medic, Gorazd

    2015-08-01

    A CFD model enabling accurate and computationally affordable simulation of unsteady flow in screw compressors has been developed. This paper focuses on computational aspects, including real-gas CFD using hybrid structured/unstructured moving grids, and specifics of grid generation for moving rotors and their communication with the discharge plenum.

  10. Improvements to the single screw extruder

    NASA Technical Reports Server (NTRS)

    Hiemenz, C.; Ziegmann, G.; Franzkoch, B.; Hoffmanns, W.; Michaeli, W.

    1977-01-01

    The extrusion on a single screw extruder is examined. The process is divided into several steps: the dosage of the materials to be conveyed; the modification of the shape of the feeding opening which influences the feeding process and consequently the throughput of the extruder; optimizing the shape of the feeding zone to meet the specific material requirements; and plasticizing and homogenizing.

  11. Nylon screws make inexpensive coil forms

    NASA Technical Reports Server (NTRS)

    Aucoin, G.; Rosenthal, C.

    1978-01-01

    Standard nylon screws act as coil form copper wire laid down in spiral thread. Completed coil may be bonded to printed-circuit board. However, it is impossible to tune coil by adjusting spacing between windings, technique sometimes used with air-core coils.

  12. Biomechanical testing of a new design for Schanz pedicle screws.

    PubMed

    Willett, K; Hearn, T C; Cuncins, A V

    1993-01-01

    Standard 5-mm AO Schanz pedicle screws were biomechanically compared with a new design, featuring 6-mm threads with a 5-mm core diameter continuous with the shaft. One each of the two screw designs was surgically inserted into the matching pedicles of 32 cadaveric vertebrae. The pull-out strengths of the screws were then determined by recording the peak force values during extraction under servohydraulic displacement control. The screws were also tested in three-point bending, varying the inner load point with respect to the shaft thread junction, within a clinically anticipated range. The mean pull-out strength for the 6-mm screw was 597 N, which was significantly greater than the mean strength of 405 N for the 5 mm screw (p = 0.002). The 6-mm screw was also stronger in three-point bending, and failed at the point of inner load application, with no evidence of a stress-raising effect at the shaft/thread junction. In contrast, the 5-mm screw withstood lower loads, and failed at the shaft/thread junction, regardless of the point of loading. Pedicle screw breakage and pull-out are the recognized modes of failure of spinal implants, which are dependent on pedicle screw fixation. The results suggest distinct biomechanical advantages for the 6-mm screw, which should be used whenever clinically feasible. PMID:8377050

  13. Surgical screw segmentation for mobile C-arm CT devices

    NASA Astrophysics Data System (ADS)

    Görres, Joseph; Brehler, Michael; Franke, Jochen; Wolf, Ivo; Vetter, Sven Y.; Grützner, Paul A.; Meinzer, Hans-Peter; Nabers, Diana

    2014-03-01

    Calcaneal fractures are commonly treated by open reduction and internal fixation. An anatomical reconstruction of involved joints is mandatory to prevent cartilage damage and premature arthritis. In order to avoid intraarticular screw placements, the use of mobile C-arm CT devices is required. However, for analyzing the screw placement in detail, a time-consuming human-computer interaction is necessary to navigate through 3D images and therefore to view a single screw in detail. Established interaction procedures of repeatedly positioning and rotating sectional planes are inconvenient and impede the intraoperative assessment of the screw positioning. To simplify the interaction with 3D images, we propose an automatic screw segmentation that allows for an immediate selection of relevant sectional planes. Our algorithm consists of three major steps. At first, cylindrical characteristics are determined from local gradient structures with the help of RANSAC. In a second step, a DBScan clustering algorithm is applied to group similar cylinder characteristics. Each detected cluster represents a screw, whose determined location is then refined by a cylinder-to-image registration in a third step. Our evaluation with 309 screws in 50 images shows robust and precise results. The algorithm detected 98% (303) of the screws correctly. Thirteen clusters led to falsely identified screws. The mean distance error for the screw tip was 0.8 +/- 0.8 mm and for the screw head 1.2 +/- 1 mm. The mean orientation error was 1.4 +/- 1.2 degrees.

  14. Pull-out strength of screws from polymethylmethacrylate cement.

    PubMed

    Motzkin, N E; Chao, E Y; An, K N; Wikenheiser, M A; Lewallen, D G

    1994-03-01

    We aimed to determine the optimal method of inserting a screw into polymethylmethacrylate (PMMA) cement to enhance fixation. We performed six groups of ten axial pull-out tests with two sizes of screw (3.5 and 4.5 mm AO cortical) and three methods of insertion. Screws were placed into 'fluid' PMMA, into 'solid' PMMA by drilling and tapping, or into 'curing' PMMA with quarter-revolution turns every 30 seconds until the PMMA had hardened. After full hardening, we measured the maximum load to failure for each screw-PMMA construct. We found no significant difference in the pull-out strengths between screw sizes or between screws placed in fluid or solid PMMA. Screws placed in curing PMMA were significantly weaker: the relative strengths of solid, fluid and curing groups were 100%, 97% and 71%, respectively. We recommend the use of either solid or fluid insertion according to the circumstances and the preference of the surgeon. PMID:8113302

  15. Esthetic Considerations for Reconstructing Implant Emergence Profile Using Titanium and Zirconia Custom Implant Abutments: Fifty Case Series Report.

    PubMed

    Kutkut, Ahmad; Abu-Hammad, Osama; Mitchell, Richard

    2015-10-01

    Titanium and zirconia custom implant abutments are now commonly used for esthetic implant dentistry. Custom implant abutments allow the clinician to improve an implant's emergence profile, to customize cervical margins in accordance with the anatomy of the natural root, and to compensate for poor implant angulation. All of these are essential for optimum esthetic outcomes. Computer-aided design/computer-aided machining (CAD/CAM) technology allows the clinician to design custom implant abutment configurations and create natural-looking superstructures that are in harmony with the adjacent dentition and soft tissue. The CAD/CAM technique provides precise fit, reduces the cost of the procedure, and eliminates dimensional inaccuracies inherent in the conventional waxing and casting technique. The aim of this report is to describe a simplified technique for reconstructing emergence profiles during implant restoration using milled titanium and zirconia custom implant abutments. The results of 50 consecutive cases are reported. PMID:24175922

  16. The use of CAD/CAM technology to fabricate a custom ceramic implant abutment: a clinical report.

    PubMed

    Bertolini, Martinna de Mendonça e; Kempen, Juan; Lourenço, Eduardo José Veras; Telles, Daniel de Moraes

    2014-05-01

    Well-placed dental implants are a prerequisite of functional and esthetically successful dental implant-supported crowns. The presence of soft tissue is essential for excellent esthetics because the dental implant or titanium abutment may become visible if the soft-tissue contour is not acceptable. This clinical report describes the use of a custom ceramic implant abutment designed with computer-aided design and computer-aided manufacturing (CAD/CAM) technology by milling a zirconia framework that was cemented extraorally to a prefabricated titanium abutment with a reduced diameter. This ceramic abutment has the strength and precise fit of a titanium interface and also the esthetic advantages of shaded custom-milled zirconia, with no visible metal. PMID:24433839

  17. Microscopical and chemical surface characterization of CAD/CAM zircona abutments after different cleaning procedures. A qualitative analysis

    PubMed Central

    2015-01-01

    PURPOSE To describe and characterize the surface topography and cleanliness of CAD/CAM manufactured zirconia abutments after steaming and ultrasonic cleaning. MATERIALS AND METHODS A total of 12 ceramic CAD/CAM implant abutments of various manufacturers were produced and randomly divided into two groups of six samples each (control and test group). Four two-piece hybrid abutments and two one-piece abutments made of zirconium-dioxide were assessed per each group. In the control group, cleaning by steam was performed. The test group underwent an ultrasonic cleaning procedure with acetone, ethyl alcohol and antibacterial solution. Groups were subjected to scanning electron microscope (SEM) analysis and Energy-dispersive X-ray spectroscopy (EDX) to verify and characterize contaminant chemical characterization non-quantitatively. RESULTS All zirconia CAD/CAM abutments in the present study displayed production-induced wear particles, debris as well as organic and inorganic contaminants. The abutments of the test group showed reduction of surface contamination after undergoing an ultrasonic cleaning procedure. However, an absolute removal of pollutants could not be achieved. CONCLUSION The presence of debris on the transmucosal surface of CAD/CAM zirconia abutments of various manufacturers was confirmed. Within the limits of the study design, the results suggest that a defined ultrasonic cleaning process can be advantageously employed to reduce such debris, thus, supposedly enhancing soft tissue healing. Although the adverse long-term influence of abutment contamination on the biological stability of peri-implant tissues has been evidenced, a standardized and validated polishing and cleaning protocol still has to be implemented. PMID:25932314

  18. Abutment-Supported Papilla: A Combined Surgical and Prosthetic Approach to Papilla Reformation.

    PubMed

    Urban, Istvan A; Klokkevold, Perry R; Takei, Henry H

    2016-01-01

    Restoration of lost interdental papilla remains one of the most challenging goals for clinicians. When a single tooth is replaced with an implant, the papilla between the tooth and the implant can often be maintained or predictably reconstructed as long as the periodontal attachment and bone of the adjacent tooth is preserved. However, if the periodontal support is compromised on the neighboring natural tooth, the papilla will often be deficient or missing. This article presents a multidisciplinary treatment approach to regenerate the interdental papilla between an implant and a periodontally compromised tooth using surgical procedures and a customized abutment. Specifically, an abutment with modified subgingival contours is used to enhance support of the surgically reformed papilla. PMID:27560670

  19. George Washington Bridge and stone abutment, from West 181st Street ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    George Washington Bridge and stone abutment, from West 181st Street and Riverside Drive overlook, looking west. HHP northbound, flanked by old Riverside Drive promenade (Hudson River Valley Greenway) with low masonry wall in center, and Fort Washington Park on right. Palisades Interstate Park across river in background. - Henry Hudson Parkway, Extending 11.2 miles from West 72nd Street to Bronx-Westchester border, New York County, NY

  20. Influence of Resin Cements on the Tension Force of Cast Frameworks Made by the Technique of Framework Cemented on Prepared Abutments.

    PubMed

    Perroni, Ana Paula; Gomes, Érica Alves; Bielemann, Amália Machado; Baseggio, Bruna; Federizzi, Leonardo; Spazzin, Aloísio Oro; dos Santos, Mateus Bertolini Fernandes

    2015-01-01

    This study evaluated the tension force of cast frameworks made by the technique of framework cemented on prepared abutments using two different resin cements. Forty multi-unit abutment analogs were individually fixed with chemically cured acrylic resin inside PVC cylinders using a parallelometer. Brass cylindrical abutments were tightened to the multi-unit abutments to be used as spacers and then castable UCLA abutments were positioned above. These abutments were cast with Ni-Cr and then divided into 4 groups (n=10): cemented with RelyX U100(r); cemented with RelyX U100(r) and simulation of acrylic resin polymerization process; cemented with Multilink(r); and cemented with Multilink(r) and simulation of acrylic resin polymerization process. Abutments were cemented according to manufacturers' instructions. In a universal testing machine, tensile strength was applied in the direction of the long axis of the abutments at 1 mm/min crosshead speed until displacement of the luted abutments was obtained. The values of maximum tensile force (N) required for the displacement of the luted abutments were tabulated and analyzed statistically by one-way ANOVA with a 95% confidence level. No statistically significant difference was found among the groups (p>0.05). There was an increase in mean tension force when the specimens were subjected to the simulation of acrylic resin polymerization process, but the results did not differ statistically. Both resin cements presented positive results as regards the retention of luted abutments on their respective multi-unit abutments. Both materials may be indicated for the technique of framework cemented on prepared abutments when professionals pursuit better adaptation of implant-supported frameworks. PMID:26312978

  1. Soft Tissue Response to Titanium Abutments with Different Surface Treatment: Preliminary Histologic Report of a Randomized Controlled Trial

    PubMed Central

    Canullo, Luigi; Dehner, Jan Friedrich; Penarrocha, David; Checchi, Vittorio; Mazzoni, Annalisa; Breschi, Lorenzo

    2016-01-01

    The aim of this preliminary prospective RCT was to histologically evaluate peri-implant soft tissues around titanium abutments treated using different cleaning methods. Sixteen patients were randomized into three groups: laboratory customized abutments underwent Plasma of Argon treatment (Plasma Group), laboratory customized abutments underwent cleaning by steam (Steam Group), and abutments were used as they came from industry (Control Group). Seven days after the second surgery, soft tissues around abutments were harvested. Samples were histologically analyzed. Soft tissues surrounding Plasma Group abutments predominantly showed diffuse chronic infiltrate, almost no acute infiltrate, with presence of few polymorphonuclear neutrophil granulocytes, and a diffuse presence of collagenization bands. Similarly, in Steam Group, the histological analysis showed a high variability of inflammatory expression factors. Tissues harvested from Control Group showed presence of few neutrophil granulocytes, moderate presence of lymphocytes, and diffuse collagenization bands in some sections, while they showed absence of acute infiltrate in 40% of sections. However, no statistical difference was found among the tested groups for each parameter (p > 0.05). Within the limit of the present study, results showed no statistically significant difference concerning inflammation and healing tendency between test and control groups. PMID:27366741

  2. Soft Tissue Response to Titanium Abutments with Different Surface Treatment: Preliminary Histologic Report of a Randomized Controlled Trial.

    PubMed

    Canullo, Luigi; Dehner, Jan Friedrich; Penarrocha, David; Checchi, Vittorio; Mazzoni, Annalisa; Breschi, Lorenzo

    2016-01-01

    The aim of this preliminary prospective RCT was to histologically evaluate peri-implant soft tissues around titanium abutments treated using different cleaning methods. Sixteen patients were randomized into three groups: laboratory customized abutments underwent Plasma of Argon treatment (Plasma Group), laboratory customized abutments underwent cleaning by steam (Steam Group), and abutments were used as they came from industry (Control Group). Seven days after the second surgery, soft tissues around abutments were harvested. Samples were histologically analyzed. Soft tissues surrounding Plasma Group abutments predominantly showed diffuse chronic infiltrate, almost no acute infiltrate, with presence of few polymorphonuclear neutrophil granulocytes, and a diffuse presence of collagenization bands. Similarly, in Steam Group, the histological analysis showed a high variability of inflammatory expression factors. Tissues harvested from Control Group showed presence of few neutrophil granulocytes, moderate presence of lymphocytes, and diffuse collagenization bands in some sections, while they showed absence of acute infiltrate in 40% of sections. However, no statistical difference was found among the tested groups for each parameter (p > 0.05). Within the limit of the present study, results showed no statistically significant difference concerning inflammation and healing tendency between test and control groups. PMID:27366741

  3. The Influence of Implant Abutment Surface Roughness and the Type of Cement on Retention of Implant Supported Crowns

    PubMed Central

    Reddy, M. Sushender; Reddy, C. Rajaneesh; Pithani, Padmaja; R, Santosh Kumar; Kulkarni, Ganesh

    2015-01-01

    Objectives: To provide relative data on the retentive characters of the commonly used cements on different implant abutment surfaces. Materials and Methods: A total of 20 implant abutments were divided into 2 groups. Ten implants were unaltered and ten were air borne particle abraded with 50μ aluminium oxide. Three luting agents (Tempbond, IRM and ImProv) were used to secure the crowns to abutments. All the crowns were removed from the abutment with an Instron machine at 0.5mm per minute and tensile bond strengths were recorded. Statistical analysis was performed using Anova, Paired t-test and Post-Hoc tests. Results: IRM showed the highest mean tensile strength among the three cements when used with treated and untreated implant abutment surfaces. Change in the abutment surface roughness had no effect on the mean tensile bond strength of TempBond and IRM cements, whereas ImProv cement showed reduced tensile strength with sandblasted surface. Conclusion: When increased retention is required IRM cement with either sandblasted or milled surface could be used and when retrievability is required cements of choice could be either TempBond or ImProv. PMID:25954694

  4. Three Dimensional Finite Element Analysis of Distal Abutment Stresses of Removable Partial Dentures with Different Retainer Designs

    PubMed Central

    Zarrati, Simindokht; Heidari, Fatemeh; Kashani, Jamal

    2015-01-01

    Objectives: This finite element method study aimed to compare the amount of stress on an isolated mandibular second premolar in two conventional reciprocal parallel interface designs of removable partial dentures (RPDs) and the same RPD abutment tooth (not isolated). Materials and Methods: A Kennedy Class 1, modification 1 RPD framework was simulated on a 3D model of mandible with three different designs: an isolated tooth with a mesial rest, an isolated tooth with mesial and distal rests and an abutment with a mesial rest (which was not isolated); 26 N occlusal forces were exerted bilaterally on the first molar sites. Stress on the abutment teeth was analyzed using Cosmos Works 2009 Software. Results: In all designs, the abutment tooth stress concentration was located in the buccal alveolar crest. In the first model, the von Mises stress distribution in the contact area of I-bar clasp and cervical portion of the tooth was 19 MPa and the maximum stress was 30 MPa. In the second model, the maximum von Mises stress distribution was 15 MPa in the cervical of the tooth. In the third model, the maximum von Mises stress was located in the cervical of the tooth and the distal proximal plate. Conclusion: We recommend using both mesial and distal rests on the distal abutment teeth of distal extension RPDs. The abutment of an extension base RPD, which is not isolated in presence of its neighboring more anterior tooth, may have a better biomechanical prognosis. PMID:26884772

  5. Addition of an anti-rotation screw to the dynamic hip screw for femoral neck fractures.

    PubMed

    Makki, Daoud; Mohamed, Ahmed M; Gadiyar, Rajeev; Patterson, Marc

    2013-07-01

    The authors investigated the use of an anti-rotation screw with the dynamic hip screw (DHS) during internal fixation of Garden I and II femoral neck fractures. Sixty-five patients with Garden I and II femoral neck fractures (mean age, 70 years) were treated with internal fixation at the authors' institution. In 31 patients, a 2-hole DHS was used alone (group 1), and in 34 patients, the DHS was combined with an anti-rotation screw placed in the cranial part of femoral head and neck (group 2). Patients' preinjury function and mental level were assessed using the Barthel index and the Abbreviated Mental test, respectively. The outcome measures included cost implications, operative time, and intraoperative radiation dose. The modified Harris Hip Score and a radiological assessment were performed at a mean of 11 months (range, 8-24 months) postoperatively. The use of the anti-rotation screw was associated with a longer operative time (mean, 44.54 minutes in group 1 vs 51.52 minutes in group 2; P<.0001) and more fluoroscopy screening (mean dose area product, 28.39 cGy/cm(2) in group 1 vs 44.33 cGy/cm(2) in group 2; P=.03). The additional cost of using an anti-rotation screw was £106 ($170) per case. No difference existed between the 2 groups with regard to radiological union, onset of avascular necrosis, and rate of revision surgeries. An anti-rotation screw, used with the dynamic hip screw, involves extra costs, prolongs operative time, and requires more intraoperative fluoroscopy screening but offers no advantages with regard to fracture union. PMID:23823042

  6. Correction of Malpositioned Implants through Periodontal Surgery and Prosthetic Rehabilitation Using Angled Abutment.

    PubMed

    de Avila, Erica Dorigatti; de Molon, Rafael Scaf; de Barros-Filho, Luiz Antônio Borelli; de Andrade, Marcelo Ferrarezi; Mollo, Francisco de Assis; de Barros, Luiz Antônio Borelli

    2014-01-01

    When dental implants are malpositioned in relation to the adjacent teeth and alveolar bone or in an excessive buccal or lingual position, the final prosthesis rehabilitation impairs the peri-implant health of the gingival tissues and the aesthetics of the patient. Thus, the purpose of this case was to report and discuss a multidisciplinary protocol for the treatment of a compromised maxillary tooth in a patient with an abscess in his right central incisor due to an excessive buccal implant position. The patient presented with an implant-supported provisional restoration on his right maxillary central incisor and a traumatic injury in his left central incisor. The treatment protocol consisted in (i) abutment substitution to compensate the incorrect angulation of the implant, (ii) clinical crown lengthening, (iii) atraumatic extraction of the left central incisor, and (iv) immediate implant placement. Finally, (v) a custom abutment was fabricated to obtain a harmonious gingival contour around the prosthetic crown. In conclusion, when implants are incorrectly positioned in relation to the adjacent teeth, associated with soft-tissue defects, the challenge to create a harmonious mucogingival contours may be achieved with an interdisciplinary approach and with the placement of an appropriate custom abutment. PMID:24955259

  7. Repeatability and reproducibility of individual abutment impression, assessed with a blue light scanner

    PubMed Central

    Kim, Dong-Yeon; Lee, Jae-Jun; Kim, Ji-Hwan

    2016-01-01

    PURPOSE We assessed the repeatability and reproducibility of abutment teeth dental impressions, digitized with a blue light scanner, by comparing the discrepancies in repeatability and reproducibility values for different types of abutment teeth. MATERIALS AND METHODS To evaluate repeatability, impressions of the canine, first premolar, and first molar, prepared for ceramic crowns, were repeatedly scanned to acquire 5 sets of 3-dimensional data via stereolithography (STL) files. Point clouds were compared and the error sizes were measured (n=10, per type). To evaluate reproducibility, the impressions were rotated by 10-20° on the table and scanned. These data were compared to the first STL data and the error sizes were measured (n=5, per type). One-way analysis of variance was used to assess the repeatability and reproducibility of the 3 types of teeth, and Tukey honest significant differences (HSD) multiple comparison test was used for post hoc comparisons (α=.05). RESULTS The differences with regard to repeatability were 4.5, 2.7, and 3.1 µm for the canine, premolar, and molar, indicating the poorest repeatability for the canine (P<.001). For reproducibility, the differences were 6.6, 5.8, and 11.0 µm indicating the poorest reproducibility for the molar (P=.007). CONCLUSION Our results indicated that impressions of individual abutment teeth, digitized with a blue light scanner, had good repeatability and reproducibility. PMID:27350856

  8. Correction of Malpositioned Implants through Periodontal Surgery and Prosthetic Rehabilitation Using Angled Abutment

    PubMed Central

    de Avila, Érica Dorigatti; de Barros-Filho, Luiz Antônio Borelli; de Andrade, Marcelo Ferrarezi; Mollo, Francisco de Assis; de Barros, Luiz Antônio Borelli

    2014-01-01

    When dental implants are malpositioned in relation to the adjacent teeth and alveolar bone or in an excessive buccal or lingual position, the final prosthesis rehabilitation impairs the peri-implant health of the gingival tissues and the aesthetics of the patient. Thus, the purpose of this case was to report and discuss a multidisciplinary protocol for the treatment of a compromised maxillary tooth in a patient with an abscess in his right central incisor due to an excessive buccal implant position. The patient presented with an implant-supported provisional restoration on his right maxillary central incisor and a traumatic injury in his left central incisor. The treatment protocol consisted in (i) abutment substitution to compensate the incorrect angulation of the implant, (ii) clinical crown lengthening, (iii) atraumatic extraction of the left central incisor, and (iv) immediate implant placement. Finally, (v) a custom abutment was fabricated to obtain a harmonious gingival contour around the prosthetic crown. In conclusion, when implants are incorrectly positioned in relation to the adjacent teeth, associated with soft-tissue defects, the challenge to create a harmonious mucogingival contours may be achieved with an interdisciplinary approach and with the placement of an appropriate custom abutment. PMID:24955259

  9. Comparison of the retro screw and standard interference screw for ACL reconstruction.

    PubMed

    Wang, Robert Y; Arciero, Robert A; Obopilwe, Elifho; Mazzocca, Augustus D

    2012-07-01

    The objective of the study was to compare the load to failure between a retro screw (RS) and a standard interference screw (IS) for tibial-sided anterior cruciate ligament (ACL) fixation. We used 20 bovine tibia and extensor tendons for the study. A group of 10 specimens underwent IS fixation while the other 10 underwent RS fixation. Within each group, five specimens had graft suture in contact (interdigitating) with the screw threads. All specimens were tested on the MTS 858 Mini Bionix II (MTS Systems, Shakopee, MN). There was no statistically significant difference between the RS and IS with respect to peak load to failure. IS with suture interdigitation failed at an average of 520 N (range: 358 to 793 N), while the RS with suture interdigitation failed at 613 N (range: 438 to 1089 N). The IS without suture interdigitation failed at 654 N and the RS without suture interdigitation at 531 N. Specimens with a whipstitch in contact with the screw did not demonstrate higher pull out strength. The RS fixation strength appears to equal the IS. Graft suture contact with screw threads does not increase fixation strength. Based on this study, using a RS for tibial ACL soft tissue graft fixation is feasible and provides equal fixation strength compared with the standard IS. PMID:23057142

  10. Translational mini-screw implant research.

    PubMed

    Rossouw, Emile

    2014-09-01

    It is important to thoroughly test new materials as well as techniques when these innovations are to be utilized in the human clinical situation. Translational research fills this important niche. The purpose of translational research is to establish the continuity of evidence from the laboratory to the clinic and in so-doing, provide evidence that the material is functioning appropriately and that the process in the human will be successful. This concept applies to the mini-screw implant; which, has been very successfully introduced into the orthodontic armamentarium over the last decade for application as a temporary anchorage device. The examples of translational research that will be illustrated in this paper have paved the way to ensure that clinicians have evidence to confidently utilize mini-screw implants in orthodontic practice. Needless to say, more studies are needed to ensure a safe, effective and efficient manner to practice orthodontics. PMID:25138369

  11. Analysis of Modeling Parameters on Threaded Screws.

    SciTech Connect

    Vigil, Miquela S.; Brake, Matthew Robert; Vangoethem, Douglas

    2015-06-01

    Assembled mechanical systems often contain a large number of bolted connections. These bolted connections (joints) are integral aspects of the load path for structural dynamics, and, consequently, are paramount for calculating a structure's stiffness and energy dissipation prop- erties. However, analysts have not found the optimal method to model appropriately these bolted joints. The complexity of the screw geometry cause issues when generating a mesh of the model. This paper will explore different approaches to model a screw-substrate connec- tion. Model parameters such as mesh continuity, node alignment, wedge angles, and thread to body element size ratios are examined. The results of this study will give analysts a better understanding of the influences of these parameters and will aide in finding the optimal method to model bolted connections.

  12. Biomechanical analysis of expansion screws and cortical screws used for ventral plate fixation on the cervical spine

    PubMed Central

    Ullrich, Bernhard; Huber, Gerd; Morlock, Michael M.

    2009-01-01

    Compared to bicortical screws, the surgical risk of injuring intraspinal structures can be minimized with the use of monocortical screws. However, this reduction should not be achieved at the expense of the stability of the fixation. With monocortical stabilization, the expansion screws have the potential of absorbing high loads. Therefore, they are expected to be a suitable alternative to bicortical screws for revision surgeries and in osteoporotic bone. The purpose of this in vitro study was to investigate the stiffness of the two screw-plate systems used for ventral stabilization of the cervical spine, by focusing on the suitability of expansion screws as tools for revision treatments. The study was conducted in ten functional units of human cervical spines. The device sample stiffness was determined for four conditions using a turning moment of 2.25 N m each around one of the three principle axes. The conditions were native, destabilized, primarily stabilized with one of the screw-plate systems, followed by secondary stabilization using the expansion screw implant. The stabilized samples achieved a comparable, in most cases higher stiffness than the native samples. The samples undergoing secondary stabilization using expansion screws tend to display greater stiffness for all three axes compared to the primarily stabilized samples. The achieved tightening moment of the screws was higher than the one achieved with primary fixation. Both plates revealed similar primary stability. Revision surgeries with secondary instrumentation achieve a high stiffness of the screwed up segments. Monocortical expansion screws combined with a trapezoidal plate allow ventral stabilization of the cervical spine that is comparable to the plate fixation using bicortical screws. PMID:19588171

  13. Sliding screw implants for extracapsular hip fractures.

    PubMed

    Mavrogenis, Andreas F; Kouvidis, George; Stavropoulos, Nikolaos A; Stavrakakis, Loannis; Katonis, Pavlos; Papagelopoulos, Panayiotis J

    2012-01-01

    Hip fractures are associated with significant mortality and morbidity for the patients, more dependent residual status, and increased socio-economic cost. Many hip-fracture patients experience severe functional impairment, and most never recover their pre-fracture level of function. Current research has sought to identify the most effective treatments to reduce the incidence of hip fractures, improve survival and quality of life, and minimize complications and disability. The treatment of these fractures in the elderly aims to return these people to their pre-fracture mobility and functional level. This article reviews the surgical treatment options for extracapsular hip fractures and discusses their associated advantages, disadvantages, and complications. Two types of implants are currently available: the dynamic hip screw (DHS), and the intramedullary hip nail with one or two sliding screws. In this review, no clear advantage of one implant over another for the treatment of extracapsular hip fractures was evident. Both the DHS and hip nails can be used successfully for the treatment of stable hip fractures; for unstable fractures and low subtrochanteric fractures, hip nails are preferred. Although hip nails are associated with limited exposure, lower blood loss and transfusion requirements, and shorter operative time, complications are more common with hip nails. Long-term survival and function are similar in the two approaches. Hip nails with two sliding screws do not seem to make the difference in clinical practice that is reported in biomechanical studies. PMID:23016784

  14. The effect of thread design on stress distribution in a solid screw implant: a 3D finite element analysis.

    PubMed

    Eraslan, Oğuz; Inan, Ozgür

    2010-08-01

    The biomechanical behavior of implant thread plays an important role on stresses at implant-bone interface. Information about the effect of different thread profiles upon the bone stresses is limited. The purpose of this study was to evaluate the effects of different implant thread designs on stress distribution characteristics at supporting structures. In this study, three-dimensional (3D) finite element (FE) stress-analysis method was used. Four types of 3D mathematical models simulating four different thread-form configurations for a solid screw implant was prepared with supporting bone structure. V-thread (1), buttress (2), reverse buttress (3), and square thread designs were simulated. A 100-N static axial occlusal load was applied to occlusal surface of abutment to calculate the stress distributions. Solidworks/Cosmosworks structural analysis programs were used for FE modeling/analysis. The analysis of the von Mises stress values revealed that maximum stress concentrations were located at loading areas of implant abutments and cervical cortical bone regions for all models. Stress concentration at cortical bone (18.3 MPa) was higher than spongious bone (13.3 MPa), and concentration of first thread (18 MPa) was higher than other threads (13.3 MPa). It was seen that, while the von Mises stress distribution patterns at different implant thread models were similar, the concentration of compressive stresses were different. The present study showed that the use of different thread form designs did not affect the von Mises concentration at supporting bone structure. However, the compressive stress concentrations differ by various thread profiles. PMID:19543925

  15. Assessment of the stress transmitted to dental implants connected to screw-retained bars using different casting techniques.

    PubMed

    Haselhuhn, Klaus; Marotti, Juliana; Tortamano, Pedro; Weiss, Claudia; Suleiman, Lubna; Wolfart, Stefan

    2014-12-01

    Passive fit of the prosthetic superstructure is important to avoid complications; however, evaluation of passive fit is not possible using conventional procedures. Thus, the aim of this study was to check and locate mechanical stress in bar restorations fabricated using two casting techniques. Fifteen patients received four implants in the interforaminal region of the mandible, and a bar was fabricated using either the cast-on abutment or lost-wax casting technique. The fit accuracy was checked according to the Sheffield's test criteria. Measurements were recorded on the master model with a gap-free, passive fit using foil strain gauges both before and after tightening the prosthetic screws. Data acquisition and processing was analyzed with computer software and submitted to statistical analysis (ANOVA). The greatest axial distortion was at position 42 with the cast-on abutment technique, with a mean distortion of 450 μm/m. The lowest axial distortion occurred at position 44 with the lost-wax casting technique, with a mean distortion of 100 μm/m. The minimal differences between the means of axial distortion do not indicate any significant differences between the techniques (P = 0.2076). Analysis of the sensor axial distortion in relation to the implant position produced a significant difference (P < 0.0001). Significantly higher measurements were recorded in the axial distortion analysis of the distal sensors of implants at the 34 and 44 regions than on the mesial positions at the 32 and 42 regions (P = 0.0481). The measuring technique recorded axial distortion in the implant-supported superstructures. Distortions were present at both casting techniques, with no significant difference between the sides. PMID:23270308

  16. Dual load path ball screw with rod end swivel

    NASA Technical Reports Server (NTRS)

    Wngett, Paul (Inventor)

    2002-01-01

    A dual drive ball has a ball screw shaft coupled at one end to a gear train and coupled at the other end to a ball screw nut. The ball screw shaft and ball screw nut are connected through complementary helical grooves filled with ball bearing balls. The outer surface of the ball screw nut is plined and can be driven by a second gear train. An output tube is coupled at one end to the ball screw nut and at its opposite end has a connector portion with a groove on its inner surface. A rod end has a coupling member for coupling to a surface to be actuated and a shaft portion with a groobe on its outer surface. This shaft portion is received with in the outputtube portion and the corresponding grooves are coupled through the use of a plurality of ball bearing balls.

  17. Loosening pattern in a cementless custom-made hip stem: X-ray analysis, finite-elements and photoelasticity measurements.

    PubMed

    Plath, J; Schuhr, T; Fethke, K; Zacharias, T; Johnson, M; Mach, J

    2000-01-01

    Thirty-three X-press cementless stems (Depuy) manufactured according to standardized X-rays were inserted from 1992 to 1994. The patients' mean age was 49 (range 15-79) years with a mean follow-up of 32 (+/-6) months. A characteristic radiographic pattern of aseptic loosening with erosion of the medial cortex by the tip of the stem occurred in 28 patients and a valgus shift of the implant in 14 cases. A radiolucent line with increased sclerosis below the tip (zone Gruen 4) was observed in 17 cases. Four stems were revised due to histologically confirmed aseptic loosening. Biomechanical investigation of one of the revised stems with the typical pattern of valgus angulation and medial cortex erosion included photoelasticity and finite-element analysis. The intertrochanteric fit and fill obviously resulted in an unfavorable distribution of contact areas, including peaks of high stress on the medial tip of the stem. These experimental findings are even evident for a postulated rotational stability. The clinical and radiographic results of the cementless X-press stems do not seem to support the fixation concept of intertrochanteric fit and fill of femoral components. PMID:10653115

  18. Isolation and characterization of beta-glucan synthase: A potential biochemical regulator of gravistimulated differential cell wall loosening

    NASA Technical Reports Server (NTRS)

    Kuzmanoff, K. M.

    1984-01-01

    In plants, gravity stimulates differential growth in the upper and lower halves of horizontally oriented organs. Auxin regulation of cell wall loosening and elongation is the basis for most models of this phenomenon. Auxin treatment of pea stem tissue rapidly increases the activity of Golgi-localized Beta-1,4-glucan synthase, an enzyme involved in biosynthesis of wall xyloglucan which apparently constitutes the substrate for the wall loosening process. The primary objective is to determine if auxin induces de novo formation of Golgi glucan synthase and increases the level of this glucan synthase mRNA. This shall be accomplished by (a) preparation of a monoclonal antibody to the synthase, (b) isolation, and characterization of the glucan synthase, and (c) examination for cross reactivity between the antibody and translation products of auxin induced mRNAs in pea tissue. The antibody will also be used to localize the glucan synthase in upper and lower halves of pea stem tissue before, during and after the response to gravity.

  19. Development of Thread Rolled Anti-Loosening Bolts Based on the Double Thread Mechanism and a Performance Evaluation

    NASA Astrophysics Data System (ADS)

    Takemasu, Teruie; Miyahara, Hiroshi

    It has already been proven that bolt fasteners based on the double thread mechanism have an excellent anti-loosening performance. The purpose of this study is to establish a mass production method for these double thread bolts (DTBs) by thread rolling. The pitch ratio of the coarse thread and the fine thread of the target DTB is set as 2 to 1. A two-die roller with a plunge feed is employed as the rolling method due to its fine processing precision. The roller dies used in the experiments have special grooves on the external surface which follow the same outline as the thread profiles of the DTB. Using these special dies, the DTB can be successfully formed in the same process as single thread bolts. The deformation of a workpiece during rolling is examined, and the examination shows that the formed material smoothly fills the die grooves in each cross section. The rolled DTBs completely pass the loosening test with extremely severe vibration and impact, as specified in NAS3354. The tensile fatigue strength of the rolled DTB is about 100% greater than that of the cutting DTB.

  20. Construct damage and loosening around glenoid implants: A longitudinal micro-CT study of five cadaver specimens.

    PubMed

    Lewis, Gregory S; Brenza, Jacob B; Paul, Emmanuel M; Armstrong, April D

    2016-06-01

    The evolution of failure of bone and cement leading to loosening of glenoid components following shoulder arthroplasty is not well understood. The purpose of this study was to identify and visualize potential mechanisms of mechanical failure within cadavers, cemented with two types of components, and subject to cyclic loading. Five glenoid cadaver bones were implanted with either a three-pegged polyethylene component, or prototype posteriorly augmented component which addresses posterior bone loss. Specimens were loaded by constant glenohumeral compression combined with cyclic anterior-posterior displacement of the humeral head relative to the glenoid. At six time points across 100,000 cycles, implant loosening micromotions were optically measured, and specimens were imaged by micro-computed tomography. Scans were 3D registered and inspected for crack initiation and progression, and micro-CT based time-lapse movies were created. Cement cracking initiated at stress concentrations and progressed with additional cyclic loading. Failure planes within trabecular bone and the bone-cement interface were identified in four of the five specimens. Implant subsidence increased to greater than 1.0 mm in two specimens. Cemented glenoid structural failure can occur within the cement, along planes of trabecular bone, or at the bone cement interface. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1053-1060, 2016. PMID:26630205

  1. Fracture fixation with two locking screws versus three non-locking screws

    PubMed Central

    Grawe, B.; Le, T.; Williamson, S.; Archdeacon, A.; Zardiackas, L.

    2012-01-01

    Objectives We aimed to further evaluate the biomechanical characteristics of two locking screws versus three standard bicortical screws in synthetic models of normal and osteoporotic bone. Methods Synthetic tubular bone models representing normal bone density and osteoporotic bone density were used. Artificial fracture gaps of 1 cm were created in each specimen before fixation with one of two constructs: 1) two locking screws using a five-hole locking compression plate (LCP) plate; or 2) three non-locking screws with a seven-hole LCP plate across each side of the fracture gap. The stiffness, maximum displacement, mode of failure and number of cycles to failure were recorded under progressive cyclic torsional and eccentric axial loading. Results Locking plates in normal bone survived 10% fewer cycles to failure during cyclic axial loading, but there was no significant difference in maximum displacement or failure load. Locking plates in osteoporotic bone showed less displacement (p = 0.02), but no significant difference in number of cycles to failure or failure load during cyclic axial loading (p = 0.46 and p = 0.25, respectively). Locking plates in normal bone had lower stiffness and torque during torsion testing (both p = 0.03), but there was no significant difference in rotation (angular displacement) (p = 0.84). Locking plates in osteoporotic bone showed lower torque and rotation (p = 0.008), but there was no significant difference in stiffness during torsion testing (p = 0.69). Conclusions The mechanical performance of locking plate constructs, using only two screws, is comparable to three non-locking screw constructs in osteoporotic bone. Normal bone loaded with either an axial or torsional moment showed slightly better performance with the non-locking construct. PMID:23610681

  2. The Effect of Laser-Etched Surface Design on Soft Tissue Healing of Two Different Implant Abutment Systems: An Experimental Study in Dogs.

    PubMed

    Neiva, Rodrigo; Tovar, Nick; Jimbo, Ryo; Gil, Luiz F; Goldberg, Paula; Barbosa, Joao Pm; Lilin, Thomas; Coelho, Paulo G

    2016-01-01

    This study describes the early soft tissue morphology around two different implant systems that received either smooth or laser-etched abutments in a beagle dog model. Implants were placed in the healed mandibular molar region of eight beagle dogs and allowed to heal for 7 weeks. When the most apical aspect of the junctional epithelium (JE) was above or within the upper half of the laser-etched region, fibers were oriented perpendicular to the abutment surface. In contrast, JE positioned within the lower half of the laser-etched region or within or below the implant-abutment gap level presented fibers oriented parallel to the abutment surface. PMID:27560671

  3. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...; spinal tumor; and failed previous fusion (pseudarthrosis). These pedicle screw spinal systems must comply... tumor, and failed previous fusion (pseudarthrosis). The safety and effectiveness of these devices...

  4. Screws, Propellers and Fans Based on a Mobius Strip

    NASA Technical Reports Server (NTRS)

    Seiner, John M.; Backley, Floyd D.; Gilinsky, Mikhail

    1998-01-01

    A Mobius strip concept is intended for improving the working efficiency of propellers and screws. Applications involve cooling, boat propellers, mixing in appliance, blenders, and helicopters. Several Mobius shaped screws for the average size kitchen mixers have been made and tested. The tests have shown that the mixer with the Mobius shaped screw pair is most efficient, and saves more than 30% of the electric power by comparison with the standard. The created video film about these tests illustrates efficiency of Mobius shaped screws.

  5. Use of polymethylmethacrylate to enhance screw fixation in bone.

    PubMed

    Cameron, H U; Jacob, R; Macnab, I; Pilliar, R M

    1975-07-01

    Pull-out testing of screws inserted into cement and bone under various conditions showed that the cement-screw complex was significantly stronger when the screw was placed in soft cement and the cement was allowed to polymerize without further manipulation. When screw fixation in osteoporotic bone was reinforced with cement, the bone was the weakest component in the system. Fixation under these conditions should be enhanced by increasing the area of contact between the cement and bone. By cooling the cement to prolong its working time, it could be injected with a syringe in such a way that maximum endosteal and periosteal contact was provided. PMID:1150708

  6. Finite Element Analysis of Osteosynthesis Screw Fixation in the Bone Stock: An Appropriate Method for Automatic Screw Modelling

    PubMed Central

    Wieding, Jan; Souffrant, Robert; Fritsche, Andreas; Mittelmeier, Wolfram; Bader, Rainer

    2012-01-01

    The use of finite element analysis (FEA) has grown to a more and more important method in the field of biomedical engineering and biomechanics. Although increased computational performance allows new ways to generate more complex biomechanical models, in the area of orthopaedic surgery, solid modelling of screws and drill holes represent a limitation of their use for individual cases and an increase of computational costs. To cope with these requirements, different methods for numerical screw modelling have therefore been investigated to improve its application diversity. Exemplarily, fixation was performed for stabilization of a large segmental femoral bone defect by an osteosynthesis plate. Three different numerical modelling techniques for implant fixation were used in this study, i.e. without screw modelling, screws as solid elements as well as screws as structural elements. The latter one offers the possibility to implement automatically generated screws with variable geometry on arbitrary FE models. Structural screws were parametrically generated by a Python script for the automatic generation in the FE-software Abaqus/CAE on both a tetrahedral and a hexahedral meshed femur. Accuracy of the FE models was confirmed by experimental testing using a composite femur with a segmental defect and an identical osteosynthesis plate for primary stabilisation with titanium screws. Both deflection of the femoral head and the gap alteration were measured with an optical measuring system with an accuracy of approximately 3 µm. For both screw modelling techniques a sufficient correlation of approximately 95% between numerical and experimental analysis was found. Furthermore, using structural elements for screw modelling the computational time could be reduced by 85% using hexahedral elements instead of tetrahedral elements for femur meshing. The automatically generated screw modelling offers a realistic simulation of the osteosynthesis fixation with screws in the adjacent

  7. Finite element analysis of osteosynthesis screw fixation in the bone stock: an appropriate method for automatic screw modelling.

    PubMed

    Wieding, Jan; Souffrant, Robert; Fritsche, Andreas; Mittelmeier, Wolfram; Bader, Rainer

    2012-01-01

    The use of finite element analysis (FEA) has grown to a more and more important method in the field of biomedical engineering and biomechanics. Although increased computational performance allows new ways to generate more complex biomechanical models, in the area of orthopaedic surgery, solid modelling of screws and drill holes represent a limitation of their use for individual cases and an increase of computational costs. To cope with these requirements, different methods for numerical screw modelling have therefore been investigated to improve its application diversity. Exemplarily, fixation was performed for stabilization of a large segmental femoral bone defect by an osteosynthesis plate. Three different numerical modelling techniques for implant fixation were used in this study, i.e. without screw modelling, screws as solid elements as well as screws as structural elements. The latter one offers the possibility to implement automatically generated screws with variable geometry on arbitrary FE models. Structural screws were parametrically generated by a Python script for the automatic generation in the FE-software Abaqus/CAE on both a tetrahedral and a hexahedral meshed femur. Accuracy of the FE models was confirmed by experimental testing using a composite femur with a segmental defect and an identical osteosynthesis plate for primary stabilisation with titanium screws. Both deflection of the femoral head and the gap alteration were measured with an optical measuring system with an accuracy of approximately 3 µm. For both screw modelling techniques a sufficient correlation of approximately 95% between numerical and experimental analysis was found. Furthermore, using structural elements for screw modelling the computational time could be reduced by 85% using hexahedral elements instead of tetrahedral elements for femur meshing. The automatically generated screw modelling offers a realistic simulation of the osteosynthesis fixation with screws in the adjacent

  8. Clinical Evaluation of Removable Partial Dentures on the Periodontal Health of Abutment Teeth: A Retrospective Study

    PubMed Central

    Dula, Linda J; Ahmedi, Enis F; Lila-Krasniqi, Zana D; Shala, Kujtim Sh

    2015-01-01

    The aim of this retrospective study was to evaluate the effect of removable partial dentures in periodontal abutment teeth in relation to the type of denture support and design of RPD in a five-year worn period. Methods : A total of 64 patients with removable partial dentures (RPDs), participated in this study. It were examined ninety-one RPDs. There were seventy-five RPDs with clasp-retained and sixteenth were RPDs with attachments. There were 28 females and 36 males, aged between 40-64 years, 41 maxillary and 50 mandible RPDs. For each subjects the following data were collected: denture design, denture support, and Kennedy classification. Abutment teeth were assessed for plaque index (PI), calculus index (CI), blending on probing (BOP), probing depth (PD), gingival recession (GR), tooth mobility (TM). Level of significance was set at p<0.05. Results : According to denture support of RPD, BOP, PD, PI, GR, CI and TM-index showed no statistically significant difference. Based on the denture design of RPD’s, BOP, PD, PI, CI, and TM-index proved no statistically significant difference. Except GR-index according to denture design confirmed statistically significant difference in RPD with clasp p<0.01. The higher values of all periodontal parameter as BOP, PD, PI, CI and TM were in patients with RPD’s with claps comparing with RPD’s with attachment. Conclusion : RPD’s with clasp increased level of gingival inflammation in regions covered by the dentures and below the clasp arms in abutment teeth. PMID:25926896

  9. Clinical evaluation of removable partial dentures on the periodontal health of abutment teeth: a retrospective study.

    PubMed

    Dula, Linda J; Ahmedi, Enis F; Lila-Krasniqi, Zana D; Shala, Kujtim Sh

    2015-01-01

    The aim of this retrospective study was to evaluate the effect of removable partial dentures in periodontal abutment teeth in relation to the type of denture support and design of RPD in a five-year worn period. Methods : A total of 64 patients with removable partial dentures (RPDs), participated in this study. It were examined ninety-one RPDs. There were seventy-five RPDs with clasp-retained and sixteenth were RPDs with attachments. There were 28 females and 36 males, aged between 40-64 years, 41 maxillary and 50 mandible RPDs. For each subjects the following data were collected: denture design, denture support, and Kennedy classification. Abutment teeth were assessed for plaque index (PI), calculus index (CI), blending on probing (BOP), probing depth (PD), gingival recession (GR), tooth mobility (TM). Level of significance was set at p<0.05. Results : According to denture support of RPD, BOP, PD, PI, GR, CI and TM-index showed no statistically significant difference. Based on the denture design of RPD's, BOP, PD, PI, CI, and TM-index proved no statistically significant difference. Except GR-index according to denture design confirmed statistically significant difference in RPD with clasp p<0.01. The higher values of all periodontal parameter as BOP, PD, PI, CI and TM were in patients with RPD's with claps comparing with RPD's with attachment. Conclusion : RPD's with clasp increased level of gingival inflammation in regions covered by the dentures and below the clasp arms in abutment teeth. PMID:25926896

  10. Bacterial contamination along implant-abutment interface in external and internal-hex dental implants

    PubMed Central

    de Oliveira, Greison Rabelo; Olate, Sergio; Pozzer, Leandro; Cavalieri-Pereira, Lucas; Rodrigues-Chessa, Jaime G; Albergaría-Barbosa, José Ricardo

    2014-01-01

    The aim of this research was to evaluate bacterial contamination along the implant-abutment interface in relation to the size of the interface. 80 brand name implants were used, 40 internal-hex and 40 external-hex. The implants were handled in a sterile atmosphere inside a box, where they were inoculated with 0.3 μl of the Streptococcus sanguis ATCC10556 bacterium in the interior and the abutment was immediately installed with a torque of 30 Ncm for the external-hex and 20 Ncm for the internal-hex; the system was included in an Eppendorf control for 30 seconds and then placed in an Eppendorf control for 30 days. The implants were removed and assessed under a scanning electron microscope while the Eppendorf controls were bred in blood agar to analyze the colonies formed. The data were analyzed using the Chi-squared, Kruskal-Wallis and Mann-Whitney tests, considering a value of p<0.05 to obtain statistical significance. Five implants were excluded due to probable external contamination. Microspaces of up to 86.8 μm were observed in the external-hex implants and up to 53.9 μm in the internal-hex implants with no significant differences between the different systems being observed (p>0.05). The contamination observed was produced mainly in the external-hex implants and statistically significant differences were observed between the different hex systems from the same company. No significant differences were observed between interface size and bacterial contamination. Within our limitations, there was no relation between the size of the implant-abutment interface and bacterial contamination with Streptococcus sanguis ATCC10556. PMID:24753751

  11. Modeling bicortical screws under a cantilever bending load.

    PubMed

    James, Thomas P; Andrade, Brendan A

    2013-12-01

    Cyclic loading of surgical plating constructs can precipitate bone screw failure. As the frictional contact between the plate and the bone is lost, cantilever bending loads are transferred from the plate to the head of the screw, which over time causes fatigue fracture from cyclic bending. In this research, analytical models using beam mechanics theory were developed to describe the elastic deflection of a bicortical screw under a statically applied load. Four analytical models were developed to simulate the various restraint conditions applicable to bicortical support of the screw. In three of the models, the cortical bone near the tip of the screw was simulated by classical beam constraints (1) simply supported, (2) cantilever, and (3) split distributed load. In the final analytical model, the cortices were treated as an elastic foundation, whereby the response of the constraint was proportional to screw deflection. To test the predictive ability of the new analytical models, 3.5 mm cortical bone screws were tested in a synthetic bone substitute. A novel instrument was developed to measure the bending deflection of screws under radial loads (225 N, 445 N, and 670 N) applied by a surrogate surgical plate at the head of the screw. Of the four cases considered, the analytical model utilizing an elastic foundation most accurately predicted deflection at the screw head, with an average difference of 19% between the measured and predicted results. Determination of the bending moments from the elastic foundation model revealed that a maximum moment of 2.3 N m occurred near the middle of the cortical wall closest to the plate. The location of the maximum bending moment along the screw axis was consistent with the fracture location commonly observed in clinical practice. PMID:24105350

  12. Magnesium Alloys as a Biomaterial for Degradable Craniofacial Screws

    PubMed Central

    Henderson, Sarah E.; Verdelis, Konstantinos; Maiti, Spandan; Pal, Siladitya; Chung, William L.; Chou, Da-Tren; Kumta, Prashant N.; Almarza, Alejandro J.

    2014-01-01

    Recently, magnesium (Mg) alloys have received significant attention as a potential biomaterial for degradable implants, and this study was directed at evaluating the suitability of Mg for craniofacial bone screws. The objective was to implant screws fabricated from commercially available Mg-alloys (pure Mg and AZ31) in-vivo in a rabbit mandible. First, Mg-alloy screws were compared to stainless steel screws in an in-vitro pull-out test and determined to have a similar holding strength (~40N). A finite element model of the screw was created using the pull-out test data, and the model can be used for future Mg-alloy screw design. Then, Mg-alloy screws were implanted for 4, 8, and 12 weeks, with two controls of an osteotomy site (hole) with no implant and a stainless steel screw implanted for 12 weeks. MicroCT (computed tomography) was used to assess bone remodeling and Mg-alloy degradation, both visually and qualitatively through volume fraction measurements for all time points. Histologic analysis was also completed for the Mg-alloys at 12 weeks. The results showed that craniofacial bone remodeling occurred around both Mg-alloy screw types. Pure Mg had a different degradation profile than AZ31, however bone growth occurred around both screw types. The degradation rate of both Mg-alloy screw types in the bone marrow space and the muscle were faster than in the cortical bone space at 12 weeks. Furthermore, it was shown that by alloying Mg, the degradation profile could be changed. These results indicate the promise of using Mg-alloys for craniofacial applications. PMID:24384125

  13. Influence of preparation depths on the fracture load of customized zirconia abutments with titanium insert

    PubMed Central

    Joo, Han-Sung; Yang, Hong-So; Park, Sang-Won; Kim, Hyun-Seung; Yun, Kwi-Dug; Ji, Min-Kyung

    2015-01-01

    PURPOSE This study evaluated the fracture load of customized zirconia abutments with titanium insert according to preparation depths, with or without 5-year artificial aging. MATERIALS AND METHODS Thirty-six identical lithium disilicate crowns (IPS e.max press) were fabricated to replace a maxillary right central incisor and cemented to the customized zirconia abutment with titanium insert on a 4.5×10 mm titanium fixture. Abutments were fabricated with 3 preparation depths (0.5 mm, 0.7 mm, and 0.9 mm). Half of the samples were then processed using thermocycling (temperature: 5-55℃, dwelling time: 120s) and chewing simulation (1,200,000 cycles, 49 N load). All specimens were classified into 6 groups depending on the preparation depth and artificial aging (non-artificial aging groups: N5, N7, N9; artificial aging groups: A5, A7, A9). Static load was applied at 135 degrees to the implant axis in a universal testing machine. Statistical analyses of the results were performed using 1-way ANOVA, 2-way ANOVA, independent t-test and multiple linear regression. RESULTS The fracture loads were 539.28 ± 63.11 N (N5), 406.56 ± 28.94 N (N7), 366.66 ± 30.19 N (N9), 392.61 ± 50.57 N (A5), 317.94 ± 30.05 N (A7), and 292.74 ± 37.15 N (A9). The fracture load of group N5 was significantly higher than those of group N7 and N9 (P<.017). Consequently, the fracture load of group A5 was also significantly higher than those of group A7 and A9 (P<.05). After artificial aging, the fracture load was significantly decreased in all groups with various preparation depths (P<.05). CONCLUSION The fracture load of a single anterior implant restored with lithium disilicate crown on zirconia abutment with titanium insert differed depending on the preparation depths. After 5-year artificial aging, the fracture loads of all preparation groups decreased significantly. PMID:26140169

  14. LOFT/FET complex. Construction view of abutment footings for arches of ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    LOFT/FET complex. Construction view of abutment footings for arches of hangar (TAN-629). Tunnels between basement of hangar and control building (TAN-630) had to fit between arches. (Note concrete work taking place at hole at lower edge of view. This photo may document unexpected bubble in underlying lava rock. It was dumped full of concrete and a footing made. Source: Interview with John DeClue). Date: December 19, 1957. Photographer: Jack L. Anderson. INEEL negative no. 57-6203 - Idaho National Engineering Laboratory, Test Area North, Scoville, Butte County, ID

  15. Single screw interrupted thread positive displacement mechanism

    NASA Astrophysics Data System (ADS)

    Boblitt, Wayne W.

    1992-07-01

    A single screw positive displacement compressor mechanism employing shallow gate rotor tooth penetration of the main rotor for purposes of reducing internal leakage and consequent compressor inefficiencies is presented. The invention is provided with an interrupted main rotor thread for purposes of insuring multiple gate rotor teeth meshing with the drive portion of the main rotor thread, thereby reducing gate rotor tooth flank loads in the compressor section of the device. Provision is also made for main rotor thread baffling between the main rotor chamber section and the mechanism inlet.

  16. Injection of coal by screw feed

    NASA Technical Reports Server (NTRS)

    Fisher, R.

    1977-01-01

    The use of the screw feeder for injecting solids through a 20 to 30 psi barrier is common practice in the cement making industry. An analytical extrapolation of that design, accounting for pressure holding characteristics of a column of solids, shows that coal can be fed to zones at several hundred psi with minimal or no loss of gas. A series of curves showing the calculated pressure gradient through a moving column of solids is presented. Mean particle size, solids velocity, and column length are parameters. Further study of this system to evaluate practicality is recommended.

  17. Comparisons of maximum deformation and failure forces at the implant–abutment interface of titanium implants between titanium-alloy and zirconia abutments with two levels of marginal bone loss

    PubMed Central

    2013-01-01

    Background Zirconia materials are known for their optimal aesthetics, but they are brittle, and concerns remain about whether their mechanical properties are sufficient for withstanding the forces exerted in the oral cavity. Therefore, this study compared the maximum deformation and failure forces of titanium implants between titanium-alloy and zirconia abutments under oblique compressive forces in the presence of two levels of marginal bone loss. Methods Twenty implants were divided into Groups A and B, with simulated bone losses of 3.0 and 1.5 mm, respectively. Groups A and B were also each divided into two subgroups with five implants each: (1) titanium implants connected to titanium-alloy abutments and (2) titanium implants connected to zirconia abutments. The maximum deformation and failure forces of each sample was determined using a universal testing machine. The data were analyzed using the nonparametric Mann–Whitney test. Results The mean maximum deformation and failure forces obtained the subgroups were as follows: A1 (simulated bone loss of 3.0 mm, titanium-alloy abutment) = 540.6 N and 656.9 N, respectively; A2 (simulated bone loss of 3.0 mm, zirconia abutment) = 531.8 N and 852.7 N; B1 (simulated bone loss of 1.5 mm, titanium-alloy abutment) = 1070.9 N and 1260.2 N; and B2 (simulated bone loss of 1.5 mm, zirconia abutment) = 907.3 N and 1182.8 N. The maximum deformation force differed significantly between Groups B1 and B2 but not between Groups A1 and A2. The failure force did not differ between Groups A1 and A2 or between Groups B1 and B2. The maximum deformation and failure forces differed significantly between Groups A1 and B1 and between Groups A2 and B2. Conclusions Based on this experimental study, the maximum deformation and failure forces are lower for implants with a marginal bone loss of 3.0 mm than of 1.5 mm. Zirconia abutments can withstand physiological occlusal forces applied in the anterior region. PMID

  18. The Bond Strength of Resin Bonded Bridge Retainers to Abutments of Differing Proportions of Enamel and Composite.

    PubMed

    Durey, Kathryn; Nattress, Brian

    2015-03-01

    Four groups of specimens were constructed using bovine enamel and composite resin. After a period of ageing, the specimens were roughened and acid etched before they were cemented to air abraded base metal alloy beams with a universal resin cement. After further ageing, tensile peel testing was carried out using a Universal Testing Machine. The force required to produce failure increased as the amount of composite resin on the bonding surface of the abutment increased. This difference reached statistical significance (p < 0.5) when the abutments contained > 50% composite. The mode of failure was mixed on the majority of retainers. Within the limitations of the study, findings suggest that RBB retainers can be cemented to abutments restored with composite resin without a reduction in bond strength. PMID:26415336

  19. Quantitative Anatomy of C7 Vertebra in Southern Chinese for Insertion of Lateral Mass Screws and Pedicle Screws

    PubMed Central

    Chan, Chi Hin; Wong, Kam Kwong; Wong, Wing Cheung

    2016-01-01

    Study Design Retrospective study. Purpose To analyze the quantitative anatomy of C7 vertebra for insertion of lateral mass screws and pedicle screws in Southern Chinese patients. Overview of Literature C7 lateral mass is smaller when compared to other subaxial cervical levels, which limits the length of lateral mass screws that can be used. Some studies have suggested pedicle screws for better fixation. But, this option is limited by the narrow pedicle width. Methods We have obtained computed tomography (CT) cervical spine data in 0.625 mm slices from our radiology department. The patients were adults. CTs were from May to August, 2015. The lateral mass screw length was measured using Margerl's technique and pedicle width and pedicle screw trajectory were determined in three-dimensional reformated images. Results CT scans of cervical spines of 94 patients were obtained and 188 lateral masses and pedicles of C7 vertebrae were measured. The mean lateral mass screw length was 13.2 mm (standard deviation [SD] 1.6 mm), mean outer pedicle width was 5.9 mm (SD 1.0 mm) and mean pedicle screw trajectory was 29.4 degrees (SD 3.6 degrees). Most (91.0%) of the pedicles had an outer diameter ≥4.5 mm. Conclusions The mean lateral mass screw length was longer when compared with other similar studies, while the mean outer pedicle width was narrower. Nearly 10% of the pedicles were unable to accommodate 3.5 mm screws. These findings favor the use of lateral mass screws to provide a safe and stable fixation for C7 vertebrae in Southern Chinese patients, while the final choice of fixation method should only be confirmed after careful preoperative planning with CT scan. PMID:27559451

  20. Application studies of CFRTP hexagon socket head cap screws

    NASA Astrophysics Data System (ADS)

    Sano, Akihiko; Matsumoto, Masaru

    PPS thermoplastic CFRP is used to fabricate screws via injection molding; these samples were tested for tensile strength and torque vs axial tension. Attention was given to the effects of various lubricants. When MoS2 was applied to the screw's threading, its axial tension increased from 10 to 16 kN.

  1. Periodic Stresses in Gyroscopic Bodies, with Applications to Air Screws

    NASA Technical Reports Server (NTRS)

    Zahm, A F

    1918-01-01

    Report discusses periodic stresses in gyroscopic bodies with applications to air screws caused by particle mass. Report concludes that all modern air screws obey the laws found for plane groups of particles. In particular the two-bladers exert on the shaft a rhythmic gyroscopic torque; the multibladers a steady one; both easily calculable for any given conditions of motion and mass distribution.

  2. 21 CFR 872.4880 - Intraosseous fixation screw or wire.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Intraosseous fixation screw or wire. 872.4880 Section 872.4880 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES.... (a) Identification. An intraosseous fixation screw or wire is a metal device intended to be...

  3. Use of small cannulated screws for fixation in foot surgery.

    PubMed

    Burns, A E

    2000-05-01

    Use of cannulated bone screws, as compared with use of traditional bone screws, has been reported to decrease surgical time, allow for more precise screw placement, and reduce sources of error. Cannulation of the smaller-size screws that are routinely used in foot surgery has not been available until the last few years. This article reports on the use of the small cannulated screws manufactured by Alphatec Manufacturing, Inc (Palm Desert, California). The screw sizes available in the Mini Lag Screw System are 2.7, 3.5, and 4.0 mm. A long-term clinical and radiographic prospective evaluation of 70 procedures performed on 49 patients was conducted. The follow-up time for all patients was 2 years. None of the 70 implants fractured, and seven procedures (in seven patients) resulted in some type of implant-fixation failure. All of the fixation failures, however, appeared to be related to an untoward event or patient noncompliance. These smaller cannulated screws proved to be a reliable and effective means of fixation in foot surgery. PMID:10833872

  4. The effect of platform switching on the levels of metal ion release from different implant–abutment couples

    PubMed Central

    Alrabeah, Ghada O; Knowles, Jonathan C; Petridis, Haralampos

    2016-01-01

    The improved peri-implant bone response demonstrated by platform switching may be the result of reduced amounts of metal ions released to the surrounding tissues. The aim of this study was to compare the levels of metal ions released from platform-matched and platform-switched implant–abutment couples as a result of accelerated corrosion. Thirty-six titanium alloy (Ti-6Al-4V) and cobalt–chrome alloy abutments were coupled with titanium cylinders forming either platform-switched or platform-matched groups (n=6). In addition, 18 unconnected samples served as controls. The specimens were subjected to accelerated corrosion by static immersion in 1% lactic acid for 1 week. The amount of metal ions ion of each test tube was measured using inductively coupled plasma mass spectrometry. Scanning electron microscope (SEM) images and energy dispersive spectroscopy X-ray analyses were performed pre- and post-immersion to assess corrosion at the interface. The platform-matched groups demonstrated higher ion release for vanadium, aluminium, cobalt, chrome, and molybdenum compared with the platform-switched groups (P<0.05). Titanium was the highest element to be released regardless of abutment size or connection (P<0.05). SEM images showed pitting corrosion prominent on the outer borders of the implant and abutment platform surfaces. In conclusion, implant–abutment couples underwent an active corrosion process resulting in metal ions release into the surrounding environment. The highest amount of metal ions released was recorded for the platform-matched groups, suggesting that platform-switching concept has a positive effect in reducing the levels of metal ion release from the implant–abutment couples. PMID:27357323

  5. The effect of platform switching on the levels of metal ion release from different implant-abutment couples.

    PubMed

    Alrabeah, Ghada O; Knowles, Jonathan C; Petridis, Haralampos

    2016-01-01

    The improved peri-implant bone response demonstrated by platform switching may be the result of reduced amounts of metal ions released to the surrounding tissues. The aim of this study was to compare the levels of metal ions released from platform-matched and platform-switched implant-abutment couples as a result of accelerated corrosion. Thirty-six titanium alloy (Ti-6Al-4V) and cobalt-chrome alloy abutments were coupled with titanium cylinders forming either platform-switched or platform-matched groups (n=6). In addition, 18 unconnected samples served as controls. The specimens were subjected to accelerated corrosion by static immersion in 1% lactic acid for 1 week. The amount of metal ions ion of each test tube was measured using inductively coupled plasma mass spectrometry. Scanning electron microscope (SEM) images and energy dispersive spectroscopy X-ray analyses were performed pre- and post-immersion to assess corrosion at the interface. The platform-matched groups demonstrated higher ion release for vanadium, aluminium, cobalt, chrome, and molybdenum compared with the platform-switched groups (P<0.05). Titanium was the highest element to be released regardless of abutment size or connection (P<0.05). SEM images showed pitting corrosion prominent on the outer borders of the implant and abutment platform surfaces. In conclusion, implant-abutment couples underwent an active corrosion process resulting in metal ions release into the surrounding environment. The highest amount of metal ions released was recorded for the platform-matched groups, suggesting that platform-switching concept has a positive effect in reducing the levels of metal ion release from the implant-abutment couples. PMID:27357323

  6. A comparison of retentive strength of implant cement depending on various methods of removing provisional cement from implant abutment

    PubMed Central

    Keum, Eun-Cheol

    2013-01-01

    PURPOSE This study evaluated the effectiveness of various methods for removing provisional cement from implant abutments, and what effect these methods have on the retention of prosthesis during the definitive cementation. MATERIALS AND METHODS Forty implant fixture analogues and abutments were embedded in resin blocks. Forty cast crowns were fabricated and divided into 4 groups each containing 10 implants. Group A was cemented directly with the definitive cement (Cem-Implant). The remainder were cemented with provisional cement (Temp-Bond NE), and classified according to the method for cleaning the abutments. Group B used a plastic curette and wet gauze, Group C used a rubber cup and pumice, and Group D used an airborne particle abrasion technique. The abutments were observed using a stereomicroscope after removing the provisional cement. The tensile bond strength was measured after the definitive cementation. Statistical analysis was performed using one-way analysis of variance test (α=.05). RESULTS Group B clearly showed provisional cement remaining, whereas the other groups showed almost no cement. Groups A and B showed a relatively smooth surface. More roughness was observed in Group C, and apparent roughness was noted in Group D. The tensile bond strength tests revealed Group D to have significantly the highest tensile bond strength followed in order by Groups C, A and B. CONCLUSION A plastic curette and wet gauze alone cannot effectively remove the residual provisional cement on the abutment. The definitive retention increased when the abutments were treated with rubber cup/pumice or airborne particle abraded to remove the provisional cement. PMID:24049563

  7. The Analysis of Soil Resistance During Screw Displacement Pile Installation

    NASA Astrophysics Data System (ADS)

    Krasinski, Adam

    2015-02-01

    The application of screw displacement piles (SDP) is still increasing due to their high efficiency and many advantages. However, one technological problem is a serious disadvantage of those piles. It relates to the generation of very high soil resistance during screw auger penetration, especially when piles are installed in non-cohesive soils. In many situations this problem causes difficulties in creating piles of designed length and diameter. It is necessary to find a proper method for prediction of soil resistance during screw pile installation. The analysis of screw resistances based on model and field tests is presented in the paper. The investigations were carried out as part of research project, financed by the Polish Ministry of Science and Higher Education. As a result of tests and analyses the empirical method for prediction of rotation resistance (torque) during screw auger penetration in non-cohesive subsoil based on CPT is proposed.

  8. Ball Screw Actuator Including an Axial Soft Stop

    NASA Technical Reports Server (NTRS)

    Wingett, Paul T. (Inventor); Forrest, Steven Talbert (Inventor); Abel, Steve (Inventor); Woessner, George (Inventor); Hanlon, Casey (Inventor)

    2016-01-01

    An actuator includes an actuator housing, a ball screw, and an axial soft stop assembly. The ball screw extends through the actuator housing and has a first end and a second end. The ball screw is coupled to receive a drive force and is configured, upon receipt of the drive force, to selectively move in a retract direction and an extend direction. The axial soft stop assembly is disposed within the actuator housing. The axial soft stop assembly is configured to be selectively engaged by the ball screw and, upon being engaged thereby, to translate, with compliance, a predetermined distance in the extend direction, and to prevent further movement of the ball screw upon translating the predetermined distance.

  9. Use of prefabricated titanium abutments and customized anatomic lithium disilicate structures for cement-retained implant restorations in the esthetic zone.

    PubMed

    Lin, Wei-Shao; Harris, Bryan T; Zandinejad, Amirali; Martin, William C; Morton, Dean

    2014-03-01

    This report describes the fabrication of customized abutments consisting of prefabricated 2-piece titanium abutments and customized anatomic lithium disilicate structures for cement-retained implant restorations in the esthetic zone. The heat-pressed lithium disilicate provides esthetic customized anatomic structures and crowns independently of the computer-aided design and computer-aided manufacturing process. PMID:24360007

  10. Accuracy of a proposed implant impression technique using abutments and metal framework

    PubMed Central

    Lee, Hyeok-Jae; Lim, Young-Jun; Kim, Chang-Whe; Choi, Jung-Han

    2010-01-01

    PURPOSE This study compared the accuracy of an abutment-framework (A-F) taken with open tray impression technique combining cementon crown abutments, a metal framework and resin cement to closed tray and resin-splinted open tray impression techniques for the 3-implant definitive casts. The effect of angulation on the accuracy of these 3 techniques was also evaluated. MATERIAL AND METHODS Three definitive casts, each with 3 linearly positioned implant analogs at relative angulations 0, 30, and 40 degrees, were fabricated with passively fitted corresponding reference frameworks. Ten impressions were made and poured, using each of the 3 techniques on each of the 3 definitive casts. To record the vertical gap between reference frameworks and analogs in duplicate casts, a light microscope with image processing was used. Data were analyzed by two-way analysis of variance and the Tukey test. RESULTS The open tray techniques showed significantly smaller vertical gaps compare to closed tray technique (P < .05). The closed tray and the resin-splinted open tray technique showed significantly different vertical gaps according to the angulation of implant (P < .05), but the A-F impression technique did not (P > .05). CONCLUSION The accuracy of the A-F impression technique was superior to that of conventional techniques, and was not affected by the angulation of the implants. PMID:21165184

  11. Twin screw granulation - review of current progress.

    PubMed

    Thompson, M R

    2015-01-01

    Twin screw granulation (TSG) is a new process of interest to the pharmaceutical community that can continuously wet granulate powders, doing so at lower liquid concentrations and with better product consistency than found by a high shear batch mixer. A considerable body of research has evolved over the short time since this process was introduced but generally with little comparison of results. A certain degree of confidence has been developed through these studies related to how process variables and many attributes of machinery configuration will affect granulation but some major challenges still lay ahead related to scalability, variations in the processing regimes related to degree of channel fill and the impact of wetting and granulation of complex powder formulations. This review examines the current literature for wet granulation processes studied in twin screw extrusion machinery, summarizing the influences of operational and system parameters affecting granule properties as well as strives to provide some practical observations to newly interested users of the technique. PMID:25402966

  12. Screw dislocations in GaN

    SciTech Connect

    Liliental-Weber, Zuzanna; Jasinski, Jacek B.; Washburn, Jack; O'Keefe, Michael A.

    2002-02-15

    GaN has received much attention over the past few years because of several new applications, including light emitting diodes, blue laser diodes and high-power microwave transistors. One of the biggest problems is a high density of structural defects, mostly dislocations, due to a lack of a suitable lattice-matched substrate since bulk GaN is difficult to grow in large sizes. Transmission Electron Microscopy (TEM) has been applied to study defects in plan-view and cross-sections on samples prepared by conventional techniques such as mechanical thinning and precision ion milling. The density of dislocations close to the sample surface of a 1 mm-thick HVPE sample was in the range of 3x109 cm-2. All three types of dislocations were present in these samples, and almost 50 percent were screw dislocations. Our studies suggest that the core structure of screw dislocations in the same material might differ when the material is grown by different methods.

  13. Asymmetric distribution in twin screw granulation.

    PubMed

    Chan Seem, Tim; Rowson, Neil A; Gabbott, Ian; de Matas, Marcel; Reynolds, Gavin K; Ingram, Andy

    2016-09-01

    Positron Emission Particle Tracking (PEPT) was successfully employed to validate measured transverse asymmetry in material distribution in the conveying zones of a Twin Screw Granulator (TSG). Flow asymmetry was established to be a property of the granulator geometry and dependent on fill level. The liquid distribution of granules as a function of fill level was determined. High flow asymmetry at low fill level negatively affects granule nucleation leading to high variance in final uniformity. Wetting of material during nucleation was identified as a critical parameter in determining final granule uniformity and fill level is highlighted as a crucial control factor in achieving this. Flow asymmetry of dry material in conveying zones upstream of binder fluid injection leads to poor non-uniform wetting at nucleation and results in heterogeneous final product. The granule formation mechanism of 60°F kneading blocks is suggested to be primarily breakage of agglomerates formed during nucleation. Optimisation of screw configuration would be required to provide secondary growth. This work shows how fill dependent flow regimes affect granulation mechanisms. PMID:26820919

  14. Axial cyclic behavior of the bone-screw interface.

    PubMed

    Inceoğlu, Serkan; Ehlert, Mike; Akbay, Atilla; McLain, Robert F

    2006-11-01

    Screw fixation strength is investigated by using a pullout test. Despite many screw pullout studies, the effects of loading rate on the pullout behavior of pedicle screws are not known. The objective of this study was to assess the effects of loading rate on the pullout stiffness and strength of pedicle screws. Sixty pedicle screws were inserted in foam blocks and pulled out at four different rates: 0.1, 1, 5 and 50 mm/min. Twenty of these 60 screws were cycled non-destructively at four different rates sequentially, i.e., 0.1, 1, 5 and 50 mm/min prior to pullout. Ten additional pedicle screws were inserted in five calf lumbar vertebrae, cycled as in foam group, and pulled out at a rate of either 0.1 or 50 mm/min. The results showed that the stiffness was higher at all rates compared to 0.1 mm/min in foam model but in bone model only 1 and 5 mm/min groups were higher compared to 0.1 mm/min. The pullout strength in 50 mm/min group was higher than that in 0.1 mm/min group in both foam and bone model. The results suggested that loading rate influenced the mechanics of the bone-screw interface. Therefore, a fair comparison between the pullout studies can be achieved under same loading rate conditions. Moreover, the cycling of the pedicle screws in axial direction within a pre-yield region showed an unusual hysteresis curve. Further studies are needed for a better understanding of the mechanics of the screw-bone interface. PMID:16458568

  15. A Surgical Method for Determining Proper Screw Length in ACDF

    PubMed Central

    Park, Hae-Gi; Kang, Moo-Sung; Kim, Kyung-Hyun; Park, Jeong-Yoon; Kim, Keun-Su

    2014-01-01

    Objective We describe a surgical tool that uses the distractor pin as a reference for determining proper screw length in ACDF. It is critical that screw purchase depth be as deep as possible without violating or penetrating the posterior cortical wall, which ensures strong pull out strength. Methods We enrolled 81 adult patients who underwent ACDF using an anterior cervical plate from 2010 to 2012. Patients were categorized into Groups A (42 patients: retractor pin used as a reference for screw length) and B (39 patients: control group). Intraoperative lateral x-rays were taken after screwing the retractor pin to confirm the approaching vertebral level. The ratio of retractor pin length to body anteroposterior (A-P) diameter was measured as a reference. Proper screw length was determined by comparison to the reference. Results The average distance from screw tip to posterior wall was 3.0±1.4mm in Group A and 4.1±2.3mm in Group B. The ratio of screw length to body sagittal diameter was 86.2±5.7% in Group A and 80.8±9.0% in Group B. Screw length to body sagittal diameter ratios higher than 4/5 occurred in 33 patients (90%) in Group A and 23 patients (59%) in Group B. No cases violated the posterior cortical wall. Conclusion We introduce a useful surgical method for determining proper screw length in ACDF using the ratio of retractor pin length to body A-P diameter as a reference. This method allows for deeper screw purchase depth without violation of the posterior cortical wall. PMID:25346756

  16. Lateral Movement of Screw Dislocations During Homoepitaxial Growth and Devices Yielded Therefrom Free of the Detrimental Effects of Screw Dislocations

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G. (Inventor); Powell, J. Anthony (Inventor)

    2004-01-01

    The present invention is related to a method that enables and improves wide bandgap homoepitaxial layers to be grown on axis single crystal substrates, particularly SiC. The lateral positions of the screw dislocations in epitaxial layers are predetermined instead of random, which allows devices to be reproducibly patterned to avoid performance degrading crystal defects normally created by screw dislocations.

  17. Limitation of total hip arthroplasty of the acetabular roof by press-fit without screw fixation: discussion of a biomechanical study.

    PubMed

    Kanda, Akio; Kaneko, Kazuo; Obayashi, Osamu; Mogami, Atsuhiko; Iwase, Hideaki

    2013-05-01

    In total hip arthroplasty of the acetabular roof fixed by press-fit without screw fixation, there is little possibility for loosening to occur, because it is difficult for wear debris to enter between the cup and the acetabular roof, as screw holes are not present. However, stability is provided only by contact. In the case of acetabular dysplasia, it is not well understood whether sufficient initial fixation power is provided. We performed a torsion test and a lever-out test. In the torsion test, in the case of a normal hip joint, as the cup grew bigger, the fixation power tended to increase in strength. In the acetabular dysplasia model, with cups of each size, as the protrusion angle increased, the fixation power of the cup tended to become weak. When the protrusion angle approaches 15 degrees, we must use a cup that is 4 mm larger than the original cup to achieve the same initial fixation power. Furthermore, when the protrusion angle is 15 degrees in cups that are over 48 mm in size, we obtain fixation power that is theoretically adequate, but when small cups, for example, 46 mm in size are set with protrusion, the initial fixation power decreases significantly, and we cannot obtain a fixation power that is theoretically adequate. PMID:23412291

  18. Review of the role of dynamic 18F-NaF PET in diagnosing and distinguishing between septic and aseptic loosening in hip prosthesis.

    PubMed

    Adesanya, Olu; Sprowson, Andrew; Masters, James; Hutchinson, Charles

    2015-01-01

    Joint replacements may fail due to infection, dislocation, peri-prosthetic fracture and loosening. Between 0.4 and 4% of joint replacements are known to be complicated by infection and aseptic loosening 2-18%. Differentiating between infection and aseptic loosening has an important bearing on the ongoing strategy for antimicrobial therapy and surgical intervention, but distinguishing one from the other can be difficult and will often require a battery of clinical and biochemical tests including the use of varying radiological modalities to accurately identify whether problematic joints are infected or aseptically loose. Prompt diagnosis is important due to the development of a biofilm on the surface of the infected prosthesis, which makes treatment difficult. There is no consensus among experts on the ideal imaging technique nor the methodology for image interpretation, but there is an increasing trend to apply hybrid imaging in the investigation of painful joint prosthesis and recent attempts have been made using PET-CT to identify aseptic loosening and infection with (18)F-fluorodeoxyglucose (FDG) and sodium fluoride (18)F-Na. The aim of this paper is to evaluate the role of (18)F-NaF sodium fluoride ((18)F-NaF) positron emission tomography (PET) in distinguishing between septic and aseptic failure in hip and knee replacements, in addition to evaluating the feasibility of using multi-sequential (18)F-NaF PET-CT for the assessment of painful lower limb prostheses. PMID:25592441

  19. Cortical bone trajectory screws for the middle-upper thorax

    PubMed Central

    Sheng, Sun-Ren; Chen, Jiao-Xiang; Chen, Wei; Xue, En-Xing; Wang, Xiang-Yang; Zhu, Qing-An

    2016-01-01

    Abstract To quantify the reference data concerning the morphometrics of the middle-upper thorax to guide the placement of cortical bone trajectory (CBT) screws. Eighty patients were studied on computed tomography (CT) scans. The reference anatomical parameters were measured. Next, 20 cadaveric specimens were implanted with CBT screws based on CT measurements. These specimens were then judged directly from the cadaveric vertebrae and X-ray. The maximum length of the trajectory, the maximum diameter, and the cephaled angle exhibited a slight increase trend while the transverse and sagittal angles of the pedicle tended to decrease from T3 to T8. We recommend that the width of CBT screw for middle-upper thoracic spine is 5.0 mm, the length is 25 to 35 mm. The cadaveric anatomical study revealed that 5/240 screws penetrated in the medial or lateral areas, 5/240 screws penetrated in the superior or inferior pedicle wall, and 2/240 screws did not fit into the superior endplate of the pedicle. The CBT screws are safe for the middle-upper thorax. This study provides a theoretical basis for clinical surgery. PMID:27583893

  20. Economics of water injected air screw compressor systems

    NASA Astrophysics Data System (ADS)

    Venu Madhav, K.; Kovačević, A.

    2015-08-01

    There is a growing need for compressed air free of entrained oil to be used in industry. In many cases it can be supplied by oil flooded screw compressors with multi stage filtration systems, or by oil free screw compressors. However, if water injected screw compressors can be made to operate reliably, they could be more efficient and therefore cheaper to operate. Unfortunately, to date, such machines have proved to be insufficiently reliable and not cost effective. This paper describes an investigation carried out to determine the current limitations of water injected screw compressor systems and how these could be overcome in the 15-315 kW power range and delivery pressures of 6-10 bar. Modern rotor profiles and approach to sealing and cooling allow reasonably inexpensive air end design. The prototype of the water injected screw compressor air system was built and tested for performance and reliability. The water injected compressor system was compared with the oil injected and oil free compressor systems of the equivalent size including the economic analysis based on the lifecycle costs. Based on the obtained results, it was concluded that water injected screw compressor systems could be designed to deliver clean air free of oil contamination with a better user value proposition than the oil injected or oil free screw compressor systems over the considered range of operations.

  1. Parametric analysis of orthopedic screws in relation to bone density.

    PubMed

    Zanetti, Elisabetta M; Salaorno, Massimiliano; Grasso, Giovanni; Audenino, Alberto L

    2009-01-01

    A global study of geometry and material properties of orthopedic screws was performed, considering not only the effect of each single factor (screw pitch, number of threads, fillet angle, etc.) but also their interactions with respect to bone density.The stress patterns resulting from different screw geometries and bone densities were analyzed using finite element techniques, taking into account different levels of osseointegration between the screw and the bone. These numerical models where validated through experimental pull-out tests, where a pull out force of 120 N produced localized failure of the last thread (stresses above 0.42 MPa). The results of the numerical simulations were then summarised using a multi-factorial parametric analysis. This demonstrated the great relevance of the interaction between bone density and screw pitch, showing that the optimal screw pitch can vary by more than 25% for different densities (0.35 g/cm(3) and 0.47 g/cm(3), respectively).The parameters calculated by means of the multi-factorial analysis allow the pull out force to be estimated for different osseointegration levels, different screw geometries and material properties, and for different bone densities. The final objective is to determine the best choice of implant for each individual patient. PMID:19587807

  2. Hydroxyapatite composite resin cement augmentation of pedicle screw fixation.

    PubMed

    Turner, Alexander W L; Gillies, R Mark; Svehla, Martin J; Saito, Masanobu; Walsh, William R

    2003-01-01

    Pedicle screw stability is poor in osteopenic vertebrae attributable, in part, to low screw-bone interface strength. The current authors examined cement augmentation using a low curing temperature hydroxyapatite and bis-phenol-A glycidol methacrylate-based composite resin. This cement may stiffen the screw-bone interface and reduce the harmful effects associated with polymethylmethacrylate regarding temperature and toxic monomer. Thirty-five lumbar vertebrae from human cadavers were instrumented with pedicle screws, with one pedicle previously injected with cement and the other as the control. Caudocephalad toggling of +/- 1 mm for 1600 cycles was applied to the pedicle screws, and the resulting forces supported by the implant-bone interface were captured by a load cell. A curve was constructed from the peak caudal load for each cycle and three mechanical measures parameterized this curve: (1) initial load; (2) rate of load decay during the first 400 cycles; and (3) final load. The initial load increased by 16% as a result of cement augmentation, the final load increased by 65%, and the rate of load decay decreased by 59%. Cement augmentation of pedicle screws increased the stiffness and stability of the screw-bone interface. PMID:12579026

  3. Biomechanical Analysis of Pedicle Screw Fixation for Thoracolumbar Burst Fractures.

    PubMed

    McDonnell, Matthew; Shah, Kalpit N; Paller, David J; Thakur, Nikhil A; Koruprolu, Sarath; Palumbo, Mark A; Daniels, Alan H

    2016-05-01

    Treatment of unstable thoracolumbar burst fractures remains controversial. Long-segment pedicle screw constructs may be stiffer and impart greater forces on adjacent segments compared with short-segment constructs, which may affect clinical performance and long-term out come. The purpose of this study was to biomechanically evaluate long-segment posterior pedicle screw fixation (LSPF) vs short-segment posterior pedicle screw fixation (SSPF) for unstable burst fractures. Six unembalmed human thoracolumbar spine specimens (T10-L4) were used. Following intact testing, a simulated L1 burst fracture was created and sequentially stabilized using 5.5-mm titanium polyaxial pedicle screws and rods for 4 different constructs: SSPF (1 level above and below), SSPF+L1 (pedicle screw at fractured level), LSPF (2 levels above and below), and LSPF+L1 (pedicle screw at fractured level). Each fixation construct was tested in flexion-extension, lateral bending, and axial rotation; range of motion was also recorded. Two-way repeated-measures analysis of variance was performed to identify differences between treatment groups and functional noninstrumented spine. Short-segment posterior pedicle screw fixation did not achieve stability seen in an intact spine (P<.01), whereas LSPF constructs were significantly stiffer than SSPF constructs and demonstrated more stiffness than an intact spine (P<.01). Pedicle screws at the fracture level did not improve either SSPF or LSPF construct stability (P>.1). Long-segment posterior pedicle screw fixation constructs were not associated with increased adjacent segment motion. Al though the sample size of 6 specimens was small, this study may help guide clinical decisions regarding burst fracture stabilization. [Orthopedics. 2016; 39(3):e514-e518.]. PMID:27135451

  4. Nutrients and bioactive compounds content of Baillonella toxisperma, Trichoscypha abut and Pentaclethra macrophylla from Cameroon.

    PubMed

    Fungo, Robert; Muyonga, John; Kaaya, Archileo; Okia, Clement; Tieguhong, Juius C; Baidu-Forson, Jojo J

    2015-07-01

    Baillonella toxisperma, Pentaclethra macrophylla and Trichoscypha abut are important foods for communities living around forests in Cameroon. Information on the nutritional value and bioactive content of these foods is required to establish their contribution to the nutrition and health of the communities. Samples of the three foods were obtained from four villages in east and three villages in south Cameroon. The foods were analyzed for proximate composition, minerals and bioactive content using standard chemical analysis methods. T. abut was found to be an excellent source of bioactive compounds; flavonoids (306 mg/100 g), polyphenols (947 mg/100 g), proanthocyanins (61.2 mg/100 g), vitamin C (80.05 mg/100 g), and total oxalates (0.6 mg/100 g). P. macrophylla was found to be a rich source of total fat (38.71%), protein (15.82%) and total fiber (17.10%) and some bioactive compounds; vitamin E (19.4 mg/100 g) and proanthocyanins (65.0 mg/100 g). B. toxisperma, was found to have high content of carbohydrates (89.6%), potassium (27.5 mg/100 g) and calcium (37.5 mg/100 g). Flavonoids, polyphenols, vitamins C and E are the main bioactive compounds in these forest foods. The daily consumption of some of these fruits may coffer protection against some ailments and oxidative stress. Approximately 200 g of either B. toxisperma or P. macrophylla, can supply 100% iron and zinc RDAs for children aged 1-3 years, while 300 g of the two forest foods can supply about 85% iron and zinc RDAs for non-pregnant non-lactating women. The three foods provide 100% daily vitamins C and E requirements for both adults and children. The results of this study show that Baillonella toxisperma, Pentaclethra macrophylla and Trichoscypha abut can considerably contribute towards the human nutrient requirements. These forest foods also contain substantial levels of health promoting phytochemicals notably flavonoids, polyphenols, vitamins C and E. These foods therefore have

  5. Nutrients and bioactive compounds content of Baillonella toxisperma, Trichoscypha abut and Pentaclethra macrophylla from Cameroon

    PubMed Central

    Fungo, Robert; Muyonga, John; Kaaya, Archileo; Okia, Clement; Tieguhong, Juius C; Baidu-Forson, Jojo J

    2015-01-01

    Baillonella toxisperma, Pentaclethra macrophylla and Trichoscypha abut are important foods for communities living around forests in Cameroon. Information on the nutritional value and bioactive content of these foods is required to establish their contribution to the nutrition and health of the communities. Samples of the three foods were obtained from four villages in east and three villages in south Cameroon. The foods were analyzed for proximate composition, minerals and bioactive content using standard chemical analysis methods. T. abut was found to be an excellent source of bioactive compounds; flavonoids (306 mg/100 g), polyphenols (947 mg/100 g), proanthocyanins (61.2 mg/100 g), vitamin C (80.05 mg/100 g), and total oxalates (0.6 mg/100 g). P. macrophylla was found to be a rich source of total fat (38.71%), protein (15.82%) and total fiber (17.10%) and some bioactive compounds; vitamin E (19.4 mg/100 g) and proanthocyanins (65.0 mg/100 g). B. toxisperma, was found to have high content of carbohydrates (89.6%), potassium (27.5 mg/100 g) and calcium (37.5 mg/100 g). Flavonoids, polyphenols, vitamins C and E are the main bioactive compounds in these forest foods. The daily consumption of some of these fruits may coffer protection against some ailments and oxidative stress. Approximately 200 g of either B. toxisperma or P. macrophylla, can supply 100% iron and zinc RDAs for children aged 1–3 years, while 300 g of the two forest foods can supply about 85% iron and zinc RDAs for non-pregnant non-lactating women. The three foods provide 100% daily vitamins C and E requirements for both adults and children. The results of this study show that Baillonella toxisperma, Pentaclethra macrophylla and Trichoscypha abut can considerably contribute towards the human nutrient requirements. These forest foods also contain substantial levels of health promoting phytochemicals notably flavonoids, polyphenols, vitamins C and E. These foods therefore have

  6. Optically driven Archimedes micro-screws for micropump applications: multiple blade design

    NASA Astrophysics Data System (ADS)

    Baldeck, Patrice L.; Lin, Chih-Lang; Lin, Yu-Sheng; Lin, Chin-Te; Chung, Tien-Tung; Bouriau, Michel; Vitrant, Guy

    2011-10-01

    We study the rotation of photo-driven Archimedes screw with multiple blades. The micron-sized Archimedes screws are readily made by the two-photon polymerization technique. Free-floating screws that are trapped by optical tweezers align in the laser irradiation direction, and rotate spontaneously. In this study we demonstrate that the rotation speeds of two-blade-screws is twice the rotation speed of one-blade-screw. However, more complex 3-blade-screws rotate slower than 2-blade-screws due to their limited geometry resolution at this micron scale.

  7. Vibration analysis of three-screw pumps under pressure loads and rotor contact forces

    NASA Astrophysics Data System (ADS)

    Li, Wanyou; Lu, Hanfeng; Zhang, Yue; Zhu, Chuan; Lu, Xiqun; Shuai, Zhijun

    2016-01-01

    Two main vibration sources in three-screw pumps, the fluid exciting force and the screw contact force, are studied to provide the basis for vibration control in this paper. A fluid exciting force model and a screw contact model are proposed to calculate these forces. An experimental test is carried out to obtain the vibration response of a three-screw pump. A calibrated finite element model of the three-screw pump is used to verify the vibration response under the fluid exciting force and the screw contact force obtained from the proposed models. The results show that the screw contact force is more dominant than the fluid exciting force.

  8. The biologic stability of alumina-zirconia implant abutments after 1 year of clinical service: a digital subtraction radiographic evaluation.

    PubMed

    Bae, Kyu-Hyun; Han, Jung-Suk; Seol, Yang-Jo; Butz, Frank; Caton, Jack; Rhyu, In-Chul

    2008-04-01

    The purpose of the present clinical study was to evaluate the biologic stability of alumina-zirconia implant abutments by histologic and radiographic examination. Nineteen partially edentulous patients were treated with 37 external-hexagon implants. After a healing period of 3 to 6 months, alumina-zirconia abutments were connected and restored with cemented single crowns or short-span fixed partial dentures. Periapical radiographs were taken at the time of prosthesis delivery and after 3, 6, and 12 months of follow-up. Crestal alveolar bone level changes were assessed by digital subtraction of consecutive images, and 1-way analysis of variance was used for statistical analysis. No implant, abutment, or restoration failed during the observation period. Bone level changes were statistically insignificant and histologic examination revealed no signs of inflammation. Stable and healthy soft and hard tissue conditions may be expected around alumina-zirconia abutments after 1 year of clinical service. However, long-term data are needed to confirm the present results. PMID:18546809

  9. Effect of abutment angulation in the retention and durability of three overdenture attachment systems: An in vitro study

    PubMed Central

    Ustrell, Raul; Mendes, Jose Manuel; Braga, Ana Cristina; Berastegui, Esther

    2016-01-01

    PURPOSE This in vitro study investigated and compared the durability and retention of three types of attachments. MATERIALS AND METHODS Three commercially available attachments were investigated: Clix®, Dalbo-Plus® and Locator®. In total, 72 samples of these attachments were placed in the acrylic resin forms and subjected to mechanical testing (5400 cycles of insertion and removal) over the respective ball or Locator abutments immersed in artificial saliva at pH 7 and 37℃. The abutments were placed at angulations of 0°, 10° and 20°. The retention force was recorded at the beginning and after 540, 1080, 2160, 3240, 4320 and 5400 insertion-removal cycles. RESULTS The results revealed that there were significant differences in the average values of the insertion/removal force due to angulation (F (2.48) = 343619, P<.05) and the type of attachment (F (7.48) = 23.220, P<.05). CONCLUSION Greater angulation of the abutments was found to influence the retention capacity of the attachments, and the fatigue test simulating 5 years of denture insertion and removal did not produce wear in the metal abutments. PMID:26949484

  10. Polyethylene wear particles do not induce inflammation or gelatinase (MMP-2 and MMP-9) activity in fibrous tissue interfaces of loosening total hip arthroplasties.

    PubMed

    De Jong, Pieter T; Tigchelaar, Wikky; Van Noorden, Cornelis J F; Van der Vis, Harm M

    2011-09-01

    In vitro and in vivo studies have suggested that polyethylene wear particles are the main cause for osteolysis in prosthetic loosening. Elevated amounts of proteases including gelatinases (or matrix metalloproteinases MMP-2 and MMP-9) have been found in fibrous tissue interfaces of loosened total hip arthroplasties suggesting that proteolysis plays a role in osteolysis. The presence of proteases does not mean that they are active, because activity of proteases is highly regulated at the post-translational level. We investigated whether the activity of two major proteases that are active extracellularly and have been associated with loosening, MMP-2 and MMP-9, is involved in loosening of non-cemented hip implants with polyethylene acetabular components. Eight interface tissues retrieved during revision were studied with light and electron microscopy and by in situ zymography to localize MMP-2 and MMP-9 activity in combination with immunohistochemistry to localize MMP-2 and MMP-9 proteins. All interface tissues contained large amounts of polyethylene wear particles, either in large accumulations or dispersed in the extracellular matrix or intracellularly in fibroblasts. Particles were not encountered in association with MMP-2 or MMP-9 activity or leukocytes. Inflammation was never found. MMP-9 activity was restricted to macrophages and MMP-2 activity was restricted to microvascular endothelial cells mainly outside areas where particles were present. Our data indicate that wear particles do not induce activation of leukocytes or MMP-2 or MMP-9 activity. Therefore, aseptic loosening may not be particle induced but initiated by other mechanisms such as mechanical stress. PMID:20656340

  11. Spline-Locking Screw Fastening Strategy (SLSFS)

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1991-01-01

    A fastener was developed by NASA Goddard for efficiently performing assembly, maintenance, and equipment replacement functions in space using either robotic or astronaut means. This fastener, the 'Spline Locking Screw' (SLS) would also have significant commercial value in advanced manufacturing. Commercial (or DoD) products could be manufactured in such a way that their prime subassemblies would be assembled using SLS fasteners. This would permit machines and robots to disconnect and replace these modules/parts with ease, greatly reducing life cycle costs of the products and greatly enhancing the quality, timeliness, and consistency of repairs, upgrades, and remanufacturing. The operation of the basic SLS fastener is detailed, including hardware and test results. Its extension into a comprehensive fastening strategy for NASA use in space is also outlined. Following this, the discussion turns toward potential commercial and government applications and the potential market significance of same.

  12. Spline-locking screw fastening strategy

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1992-01-01

    A fastener was developed by NASA Goddard for efficiently performing assembly, maintenance, and equipment replacement functions in space using either robotics or astronaut means. This fastener, the 'Spline Locking Screw' (SLS) would also have significant commercial value in advanced space manufacturing. Commercial (or DoD) products could be manufactured in such a way that their prime subassemblies would be assembled using SLS fasteners. This would permit machines and robots to disconnect and replace these modules/parts with ease, greatly reducing life cycle costs of the products and greatly enhancing the quality, timeliness, and consistency of repairs, upgrades, and remanufacturing. The operation of the basic SLS fastener is detailed, including hardware and test results. Its extension into a comprehensive fastening strategy for NASA use in space is also outlined. Following this, the discussion turns toward potential commercial and government applications and the potential market significance of same.

  13. Screw Compressor Characteristics for Helium Refrigeration Systems

    NASA Astrophysics Data System (ADS)

    Ganni, V.; Knudsen, P.; Creel, J.; Arenius, D.; Casagrande, F.; Howell, M.

    2008-03-01

    The oil injected screw compressors have practically replaced all other types of compressors in modern helium refrigeration systems due to their large displacement capacity, minimal vibration, reliability and capability of handling helium's high heat of compression. At the present state of compressor system designs for helium systems, typically two-thirds of the lost input power is due to the compression system. Therefore it is important to understand the isothermal and volumetric efficiencies of these machines to help properly design these compression systems to match the refrigeration process. This presentation summarizes separate tests that have been conducted on Sullair compressors at the Superconducting Super-Collider Laboratory (SSCL) in 1993, Howden compressors at Jefferson Lab (JLab) in 2006 and Howden compressors at the Spallation Neutron Source (SNS) in 2006. This work is part of an ongoing study at JLab to understand the theoretical basis for these efficiencies and their loss mechanisms, as well as to implement practical solutions.

  14. A comprehensive microbiological evaluation of fifty-four patients undergoing revision surgery due to prosthetic joint loosening.

    PubMed

    Bjerkan, Geir; Witsø, Eivind; Nor, Anne; Viset, Trond; Løseth, Kirsti; Lydersen, Stian; Persen, Leif; Bergh, Kåre

    2012-04-01

    The diagnosis of a chronic prosthetic joint infection (PJI) is challenging, and no consensus exists regarding how best to define the criteria required for microbiological identification. A general view is that culture of periprosthetic biopsies suffers from inadequate sensitivity. Recently, molecular analyses have been employed in some studies but the specificity of molecular analyses has been questioned, mainly due to contamination issues. In a prospective study of 54 patients undergoing revision surgery due to prosthetic joint loosening, we focused on two aspects of microbiological diagnosis of chronic PJI. First, by collecting diagnostic specimens in a highly standardized manner, we aimed at investigating the adequacy of various specimens by performing quantitative bacteriological culture. Second, we designed and performed real-time 16S rRNA gene PCR analysis with particular emphasis on minimizing the risk of false-positive PCR results. The specimens analysed included synovial fluid, periprosthetic biopsies from the joint capsule and the interface membrane, and specimens from the surface of the explanted prosthesis rendered accessible by scraping and sonication. No antibiotics were given prior to specimen collection. Based on five diagnostic criteria recently suggested, we identified 18 PJIs, all of which fulfilled the criterion of ≥2 positive cultures of periprosthetic specimens. The rate of culture-positive biopsies from the interface membrane was higher compared to specimens from the joint capsule and synovial fluid, and the interface membrane contained a higher bacterial load. Interpretational criteria were applied to differentiate a true-positive PCR from potential bacterial DNA contamination derived from the reagents used for DNA extraction and amplification. The strategy to minimize the risk of false-positive PCR results was successful as only two PCR results were false-positive out of 216 negative periprosthetic specimens. Although the PCR assays

  15. Bone Loss at Implant with Titanium Abutments Coated by Soda Lime Glass Containing Silver Nanoparticles: A Histological Study in the Dog

    PubMed Central

    Martinez, Arturo; Guitián, Francisco; López-Píriz, Roberto; Bartolomé, José F.; Cabal, Belén; Esteban-Tejeda, Leticia; Torrecillas, Ramón; Moya, José S.

    2014-01-01

    The aim of the present study was to evaluate bone loss at implants connected to abutments coated with a soda-lime glass containing silver nanoparticles, subjected to experimental peri-implantitis. Also the aging and erosion of the coating in mouth was studied. Five beagle dogs were used in the experiments. Three implants were placed in each mandible quadrant: in 2 of them, Glass/n-Ag coated abutments were connected to implant platform, 1 was covered with a Ti-mechanized abutment. Experimental peri-implantitis was induced in all implants after the submarginal placement of cotton ligatures, and three months after animals were euthanatized. Thickness and morphology of coating was studied in abutment cross-sections by SEM. Histology and histo-morphometric studies were carried on in undecalfied ground slides. After the induced peri-implantitis: 1.The abutment coating shown losing of thickness and cracking. 2. The histometry showed a significant less bone loss in the implants with glass/n-Ag coated abutments. A more symmetric cone of bone resorption was observed in the coated group. There were no significant differences in the peri-implantitis histological characteristics between both groups of implants. Within the limits of this in-vivo study, it could be affirmed that abutments coated with biocide soda-lime-glass-silver nanoparticles can reduce bone loss in experimental peri-implantitis. This achievement makes this coating a suggestive material to control peri-implantitis development and progression. PMID:24466292

  16. Bone loss at implant with titanium abutments coated by soda lime glass containing silver nanoparticles: a histological study in the dog.

    PubMed

    Martinez, Arturo; Guitián, Francisco; López-Píriz, Roberto; Bartolomé, José F; Cabal, Belén; Esteban-Tejeda, Leticia; Torrecillas, Ramón; Moya, José S

    2014-01-01

    The aim of the present study was to evaluate bone loss at implants connected to abutments coated with a soda-lime glass containing silver nanoparticles, subjected to experimental peri-implantitis. Also the aging and erosion of the coating in mouth was studied. Five beagle dogs were used in the experiments. Three implants were placed in each mandible quadrant: in 2 of them, Glass/n-Ag coated abutments were connected to implant platform, 1 was covered with a Ti-mechanized abutment. Experimental peri-implantitis was induced in all implants after the submarginal placement of cotton ligatures, and three months after animals were euthanatized. Thickness and morphology of coating was studied in abutment cross-sections by SEM. Histology and histo-morphometric studies were carried on in undecalfied ground slides. After the induced peri-implantitis: 1.The abutment coating shown losing of thickness and cracking. 2. The histometry showed a significant less bone loss in the implants with glass/n-Ag coated abutments. A more symmetric cone of bone resorption was observed in the coated group. There were no significant differences in the peri-implantitis histological characteristics between both groups of implants. Within the limits of this in-vivo study, it could be affirmed that abutments coated with biocide soda-lime-glass-silver nanoparticles can reduce bone loss in experimental peri-implantitis. This achievement makes this coating a suggestive material to control peri-implantitis development and progression. PMID:24466292

  17. Photon and electron collimator effects on electron output and abutting segments in energy modulated electron therapy

    SciTech Connect

    Olofsson, Lennart; Karlsson, Magnus G.; Karlsson, Mikael

    2005-10-15

    In energy modulated electron therapy a large fraction of the segments will be arranged as abutting segments where inhomogeneities in segment matching regions must be kept as small as possible. Furthermore, the output variation between different segments should be minimized and must in all cases be well predicted. For electron therapy with add-on collimators, both the electron MLC (eMLC) and the photon MLC (xMLC) contribute to these effects when an xMLC tracking technique is utilized to reduce the x-ray induced leakage. Two add-on electron collimator geometries have been analyzed using Monte Carlo simulations: One isocentric eMLC geometry with an isocentric clearance of 35 cm and air or helium in the treatment head, and one conventional proximity geometry with a clearance of 5 cm and air in the treatment head. The electron fluence output for 22.5 MeV electrons is not significantly affected by the xMLC if the shielding margins are larger than 2-3 cm. For small field sizes and 9.6 MeV electrons, the isocentric design with helium in the treatment head or shielding margins larger than 3 cm is needed to avoid a reduced electron output. Dose inhomogeneity in the matching region of electron segments is, in general, small when collimator positions are adjusted to account for divergence in the field. The effect of xMLC tracking on the electron output can be made negligible while still obtaining a substantially reduced x-ray leakage contribution. Collimator scattering effects do not interfere significantly when abutting beam techniques are properly applied.

  18. Accuracy of 3D white light scanning of abutment teeth impressions: evaluation of trueness and precision

    PubMed Central

    Jeon, Jin-Hun; Kim, Hae-Young; Kim, Ji-Hwan

    2014-01-01

    PURPOSE This study aimed to evaluate the accuracy of digitizing dental impressions of abutment teeth using a white light scanner and to compare the findings among teeth types. MATERIALS AND METHODS To assess precision, impressions of the canine, premolar, and molar prepared to receive all-ceramic crowns were repeatedly scanned to obtain five sets of 3-D data (STL files). Point clouds were compared and error sizes were measured (n=10 per type). Next, to evaluate trueness, impressions of teeth were rotated by 10°-20° and scanned. The obtained data were compared with the first set of data for precision assessment, and the error sizes were measured (n=5 per type). The Kruskal-Wallis test was performed to evaluate precision and trueness among three teeth types, and post-hoc comparisons were performed using the Mann-Whitney U test with Bonferroni correction (α=.05). RESULTS Precision discrepancies for the canine, premolar, and molar were 3.7 µm, 3.2 µm, and 7.3 µm, respectively, indicating the poorest precision for the molar (P<.001). Trueness discrepancies for teeth types were 6.2 µm, 11.2 µm, and 21.8 µm, respectively, indicating the poorest trueness for the molar (P=.007). CONCLUSION In respect to accuracy the molar showed the largest discrepancies compared with the canine and premolar. Digitizing of dental impressions of abutment teeth using a white light scanner was assessed to be a highly accurate method and provided discrepancy values in a clinically acceptable range. Further study is needed to improve digitizing performance of white light scanning in axial wall. PMID:25551007

  19. Effect of abutment shade, ceramic thickness, and coping type on the final shade of zirconia all-ceramic restorations: in vitro study of color masking ability

    PubMed Central

    Oh, Seon-Hee

    2015-01-01

    PURPOSE The aim of the study was to evaluate the effect of abutment shade, ceramic thickness, and coping type on the final shade of zirconia all-ceramic restorations. MATERIALS AND METHODS Three different types of disk-shaped zirconia coping specimens (Lava, Cercon, Zirkonzahn: ø10 mm × 0.4 mm) were fabricated and veneered with IPS e.max Press Ceram (shade A2), for total thicknesses of 1 and 1.5 mm. A total of sixty zirconia restoration specimens were divided into six groups based on their coping types and thicknesses. The abutment specimens (ø10 mm × 7 mm) were prepared with gold alloy, base metal (nickel-chromium) alloy, and four different shades (A1, A2, A3, A4) of composite resins. The average L*, a*, b* values of the zirconia specimens on the six abutment specimens were measured with a dental colorimeter, and the statistical significance in the effects of three variables was analyzed by using repeated measures analysis of variance (α=.05).The average shade difference (ΔE) values of the zirconia specimens between the A2 composite resin abutment and other abutments were also evaluated. RESULTS The effects of zirconia specimen thickness (P<.001), abutment shade (P<.001), and type of zirconia copings (P<.003) on the final shade of the zirconia restorations were significant. The average ΔE value of Lava specimens (1 mm) between the A2 composite resin and gold alloy abutments was higher (close to the acceptability threshold of 5.5 ΔE) than th ose between the A2 composite resin and other abutments. CONCLUSION This in-vitro study demonstrated that abutment shade, ceramic thickness, and coping type affected the resulting shade of zirconia restorations. PMID:26576252

  20. Screw-matrix method in dynamics of multibody systems

    NASA Astrophysics Data System (ADS)

    Yanzhu, Liu

    1988-05-01

    In the present paper the concept of screw in classical mechanics is expressed in matrix form, in order to formulate the dynamical equations of the multibody systems. The mentioned method can retain the advantages of the screw theory and avoid the shortcomings of the dual number notation. Combining the screw-matrix method with the tool of graph theory in Roberson/Wittenberg formalism. We can expand the application of the screw theory to the general case of multibody systems. For a tree system, the dynamical equations for each j-th subsystem, composed of all the outboard bodies connected by j-th joint can be formulated without the constraint reaction forces in the joints. For a nontree system, the dynamical equations of subsystems and the kinematical consistency conditions of the joints can be derived using the loop matrix. The whole process of calculation is unified in matrix form. A three-segment manipulator is discussed as an example.

  1. Adhesive-backed terminal board eliminates mounting screws

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Low-profile terminal board is used in dense electronic circuits where mounting and working space is limited. The board has a thin layer of pressure-sensitive adhesive backing which eliminates the need for mounting screws.

  2. Percutaneous screw fixation of acetabular fractures: applicability of hip arthroscopy.

    PubMed

    Yang, Jae-Hyuk; Chouhan, Devendra Kumar; Oh, Kwang-Jun

    2010-11-01

    Percutaneous screw fixation of the anterior column of the acetabulum has been a challenging task because of its unique anatomy and a risk of intra-articular penetration. Evidence is lacking for any tools to provide visual scrutiny of fracture reduction and intra-articular screw penetration. We report 2 cases of fracture of the acetabulum that developed in young female athletes, in which the anterior column was fixed with a percutaneous screw by use of hip arthroscopy as an assisting tool for intra-articular observation. In our experience this method was found to be promising in terms of anatomic reduction of the fracture site, avoiding articular penetration during screw insertion, with additional advantages of joint debridement, lavage, and reduction in radiation exposure. PMID:20888169

  3. 21. NBS SUIT LAB. THREE GLOVES, HELMET, AND SCREW DRIVER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    21. NBS SUIT LAB. THREE GLOVES, HELMET, AND SCREW DRIVER TORQUE WRENCH FOR ASSEMBLY AND REPAIR OF BOTH. - Marshall Space Flight Center, Neutral Buoyancy Simulator Facility, Rideout Road, Huntsville, Madison County, AL

  4. Structural and mechanical characterisation of the peri-prosthetic tissue surrounding loosened hip prostheses. An explorative study.

    PubMed

    Moerman, Astrid; Zadpoor, Amir A; Oostlander, Angela; Schoeman, Monique; Rahnamay Moshtagh, Parisa; Pouran, Behdad; Valstar, Edward

    2016-09-01

    Very little is known about the structure and properties of peri-prosthetic fibrous tissue that is found around loose orthopaedic implants. We describe a method for characterizing the structural organisation (histology, confocal microscopy) as well as the nano- and micro-scale mechanical behaviour (atomic force microscopy, nanoindentation) of peri-prosthetic fibrous tissue. The tissue was collected from 11 patients undergoing revision surgery due to aseptic loosening. Sirius Red and Movat histological staining procedures indicated that the tissue mainly consists of collagen fibres and ground substance. However, large inter- and intra-patient variations in the relative proportions of these tissue components were found, as well as in collagen fibre orientation and possibly also maturation. The nano-scale Young׳s moduli ranged from 0-950kPa, but showed large inter-patient variability. When the results per sample were presented in a probability density function, we could roughly discriminate one peak in the 0-100kPa range and/or one peak in the 100-500Pa range. These nano-scale moduli seem to respectively present the mechanical properties of glycosaminoglycan (GAG) and collagen molecules. The majority of the micro-scale Young׳s moduli ranged between 0.5 and 2.0kPa for all samples. This explorative study provides new insights in (the variations of) structural organisation and mechanical properties of peri-prosthetic tissue. PMID:27281163

  5. Innate immune response and implant loosening: Interferon gamma is inversely associated with early migration of total knee prostheses.

    PubMed

    Schoeman, Monique A E; Pijls, Bart G; Oostlander, Angela E; Keurentjes, Johan C; Valstar, Edward R; Nelissen, Rob G H H; Meulenbelt, Ingrid

    2016-01-01

    To allow prediction of the risk of loosening prior to surgery, we investigated the relationship between innate immune cytokine response via TLR2 stimulation and early migration of six different knee prostheses using RSA (radiostereometry). This study included 114 patients of a prospective RSA-cohort who received a total knee arthroplasty. Whole blood cytokine responses were obtained by ex vivo stimulation with tripalmitoyl-S-glycerylcysteine (Pam3Cys-SK4) for assessment of the TLR2 immune response. Early migration was calculated using the maximum total point motion (MTPM) 1 year post surgery. Principal component analysis (PCA) was applied to the cytokine data to reduce the correlated data of individual cytokines and identified two components. Subsequently, linear mixed model analyses were applied with adjustments for gender, age, BMI, time-to-blood sampling, and prosthesis type. Component 1, consisting of IFNγ, IL-12p40, IL-10, IL-1β, TNFα, and IL-6, showed a significant inverse association (β = -0.128; p = 0.041) with MTPM. Further analysis showed that IFNγ (β = -0.161, p = 0.008) had the highest contribution to this association and is particularly found in patients receiving another prosthesis than Nexgen (β = -0.239; p < 0.001). In conclusion, patients with high levels of IFNγ upon stimulation of TLR2 are at lower risk of early migration of their knee prosthesis. PMID:26212694

  6. Loosening of the total knee arthroplasty: detection by radionuclide bone scanning. [/sup 99m/Tc-methylene diphosphonate

    SciTech Connect

    Hunter, J.C.; Hattner, R.S.; Murray, W.R.; Genant, H.K.

    1980-07-01

    Pain after total knee arthroplasty is a common clinical problem in orthopedics, and prosthetic loosening, often requiring surgical revision, is usually the etiology. Since standard clinical and radiographic diagnostic measures have not proven totally satisfactory, a study of the utility of bone scintigraphy to assess stability of the knee prosthesis was done. Thirty-five patients with 39 prostheses were studied. Seventeen patients with 21 total knee arthroplasties served as controls and were asymptomatic, were stable at surgery, or improved with conservative management. Eighteen knees in 18 symptomatic patients composed the experimental group. Of these, 11 knees were loose at surgery and seven have had surgery recommended. Scintigrams of the knees were obtained using /sup 99m/Tc-MDP, and ranked 0-3 corresponding to increasingly abnormal localization by three observers. Highly significant differences were observed between the abnormal and control groups (p<0.001). Reciprocal changes in sensitivity and specificity with increasingly stringent criteria were shown. While it is apparent that the bone scan cannot be used as the sole diagnostic method for evaluation of prosthetic stability, it does seem to be a useful adjunct along with clinical criteria and radiographic studies.

  7. Structural health monitoring for bolt loosening via a non-invasive vibro-haptics human-machine cooperative interface

    NASA Astrophysics Data System (ADS)

    Pekedis, Mahmut; Mascerañas, David; Turan, Gursoy; Ercan, Emre; Farrar, Charles R.; Yildiz, Hasan

    2015-08-01

    For the last two decades, developments in damage detection algorithms have greatly increased the potential for autonomous decisions about structural health. However, we are still struggling to build autonomous tools that can match the ability of a human to detect and localize the quantity of damage in structures. Therefore, there is a growing interest in merging the computational and cognitive concepts to improve the solution of structural health monitoring (SHM). The main object of this research is to apply the human-machine cooperative approach on a tower structure to detect damage. The cooperation approach includes haptic tools to create an appropriate collaboration between SHM sensor networks, statistical compression techniques and humans. Damage simulation in the structure is conducted by releasing some of the bolt loads. Accelerometers are bonded to various locations of the tower members to acquire the dynamic response of the structure. The obtained accelerometer results are encoded in three different ways to represent them as a haptic stimulus for the human subjects. Then, the participants are subjected to each of these stimuli to detect the bolt loosened damage in the tower. Results obtained from the human-machine cooperation demonstrate that the human subjects were able to recognize the damage with an accuracy of 88 ± 20.21% and response time of 5.87 ± 2.33 s. As a result, it is concluded that the currently developed human-machine cooperation SHM may provide a useful framework to interact with abstract entities such as data from a sensor network.

  8. 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. PMID:26270750

  9. Crystal geometry of screw dislocation glide in tungsten nanocrystals

    NASA Astrophysics Data System (ADS)

    Sadanov, E. V.

    2015-02-01

    A zigzag pattern of low-temperature dislocation glide occurring in tungsten nanocrystals in the intersecting planes {110} and {211}, which belong to the <111> crystallographic zone, has been revealed using field ion microscopy. It has been shown that cores of 1/2[111] screw dislocations are undissociated within the limits of the resolution of the field ion microscope. It has been found experimentally that surface atoms are displaced into metastable positions in the region of the trace of screw dislocation motion.

  10. Screw thread parameter measurement system based on image processing method

    NASA Astrophysics Data System (ADS)

    Rao, Zhimin; Huang, Kanggao; Mao, Jiandong; Zhang, Yaya; Zhang, Fan

    2013-08-01

    In the industrial production, as an important transmission part, the screw thread is applied extensively in many automation equipments. The traditional measurement methods of screw thread parameter, including integrated test methods of multiparameters and the single parameter measurement method, belong to contact measurement method. In practical the contact measurement exists some disadvantages, such as relatively high time cost, introducing easily human error and causing thread damage. In this paper, as a new kind of real-time and non-contact measurement method, a screw thread parameter measurement system based on image processing method is developed to accurately measure the outside diameter, inside diameter, pitch diameter, pitch, thread height and other parameters of screw thread. In the system the industrial camera is employed to acquire the image of screw thread, some image processing methods are used to obtain the image profile of screw thread and a mathematics model is established to compute the parameters. The C++Builder 6.0 is employed as the software development platform to realize the image process and computation of screw thread parameters. For verifying the feasibility of the measurement system, some experiments were carried out and the measurement errors were analyzed. The experiment results show the image measurement system satisfies the measurement requirements and suitable for real-time detection of screw thread parameters mentioned above. Comparing with the traditional methods the system based on image processing method has some advantages, such as, non-contact, easy operation, high measuring accuracy, no work piece damage, fast error analysis and so on. In the industrial production, this measurement system can provide an important reference value for development of similar parameter measurement system.

  11. Solid and hollow pedicle screws affect the electrical resistance: A potential source of error with stimulus-evoked electromyography

    PubMed Central

    Wang, Hongwei; Liao, Xinhua; Ma, Xianguang; Li, Changqing; Han, Jianda; Zhou, Yue

    2013-01-01

    Background: Although stimulus evoked electromyography (EMG) is commonly used to confirm the accuracy of pedicle screw placement. There are no studies to differentiate between solid screws and hollow screws to the electrical resistance of pedicle screws. We speculate that the electrical resistance of the solid and hollow pedicle screws may be different and then a potential source of error with stimulus-evoked EMG may happen. Materials and Methods: Resistance measurements were obtained from 12 pedicle screw varieties (6 screws of each manufacturer) across the screw shank based on known constant current and measured voltage. The voltage was measured 5 times at each site. Results: Resistance of all solid screws ranged from 0.084 Ω to 0.151 Ω (mean =0.118 ± 0.024 Ω) and hollow screws ranged from 0.148 Ω to 0.402 Ω (mean = 0.285 ± 0.081 Ω). There was a significant difference of resistance between the solid screws and hollow screws (P < 0.05). The screw with the largest diameter no matter solid screws or hollow screws had lower resistance than screws with other diameters. No matter in solid screws group or hollow screws group, there were significant differences (P < 0.05) between the 5.0 mm screws and 6.0 mm screws, 6.0 mm screws and 7.0 mm screws, 5.0 mm screws and 7.0 mm screws, 4.5 mm screws and 5.5 mm screws, 5.5 mm screws and 6.5 mm screws, 4.5 mm screws and 6.5 mm screws. The resistance of hollow screws was much larger than the solid screws in the same diameter group (P < 0.05). Conclusions: Hollow pedicle screws have the potential for high electrical resistance compared to the solid pedicle screws and therefore may affect the EMG response during stimulus-evoked EMG testing in pedicle screw fixation especially in minimally invasive percutaneous pedical screw fixation surgery. PMID:23960278

  12. Pullout strength of misplaced pedicle screws in the thoracic and lumbar vertebrae - A cadaveric study

    PubMed Central

    Saraf, Shyam K; Singh, Ravindra P; Singh, Vakil; Varma, Ashish

    2013-01-01

    Background: The objective of this cadaveric study was to analyze the effects of iatrogenic pedicle perforations from screw misplacement on the mean pullout strength of lower thoracic and lumbar pedicle screws. We also investigated the effect of bone mineral density (BMD), diameter of pedicle screws, and the region of spine on the pullout strength of pedicle screws. Materials and Methods: Sixty fresh human cadaveric vertebrae (D10–L2) were harvested. Dual-energy X-ray absorptiometry (DEXA) scan of vertebrae was done for BMD. Titanium pedicle screws of different diameters (5.2 and 6.2 mm) were inserted in the thoracic and lumbar segments after dividing the specimens into three groups: a) standard pedicle screw (no cortical perforation); b) screw with medial cortical perforation; and c) screw with lateral cortical perforation. Finally, pullout load of pedicle screws was recorded using INSTRON Universal Testing Machine. Results: Compared with standard placement, medially misplaced screws had 9.4% greater mean pullout strength and laterally misplaced screws had 47.3% lesser mean pullout strength. The pullout strength of the 6.2 mm pedicle screws was 33% greater than that of the 5.2 mm pedicle screws. The pullout load of pedicle screws in lumbar vertebra was 13.9% greater than that in the thoracic vertebra (P = 0.105), but it was not statistically significant. There was no significant difference between pullout loads of vertebra with different BMD (P = 0.901). Conclusion: The mean pullout strength was less with lateral misplaced pedicle screws while medial misplaced pedicle screw had more pullout strength. The pullout load of 6.2 mm screws was greater than that of 5.2 mm pedicle screws. No significant correlation was found between bone mineral densities and the pullout strength of vertebra. Similarly, the pullout load of screw placed in thoracic and lumbar vertebrae was not significantly different. PMID:23798753

  13. Robot-assisted Anterior Odontoid Screw Fixation: A Case Report.

    PubMed

    Tian, Wei; Wang, Han; Liu, Ya-Jun

    2016-08-01

    Anterior odontoid screw fixation has been proved to be effective but technically challenging because the difficult approach is associated with high risks of screw malposition and damage to surrounding vital structures. Navigation techniques are therefore increasingly being used to improve safety and accuracy. However, no robot-assisted odontoid screw fixation has yet been reported. We here report a 61-year-old woman with a type II dens fracture on whom anterior odontoid screw fixation was performed under the guidance of a newly developed robotic system (TiRobot, co-designed by Beijing Jishuitan Hospital and TINAVI Medical Technologies). One odontoid screw was safely and accurately placed, the calculated deviation between the planned and actual positions being 0.9 mm. No intraoperative complications were identified and the patient was discharged on Day 5. Follow-up studies after 2 weeks showed good clinical and radiological results. We believe this is the first reported case of robot-assisted anterior odontoid screw fixation. We consider that complicated procedures can become feasible, safe and accurate using TiRobot systems. PMID:27627725

  14. Prediction of Deformity Correction by Pedicle Screw Instrumentation in Thoracolumbar Scoliosis Surgery

    NASA Astrophysics Data System (ADS)

    Kiriyama, Yoshimori; Yamazaki, Nobutoshi; Nagura, Takeo; Matsumoto, Morio; Chiba, Kazuhiro; Toyama, Yoshiaki

    In segmental pedicle screw instrumentation, the relationship between the combinations of pedicle screw placements and the degree of deformity correction was investigated with a three-dimensional rigid body and spring model. The virtual thoracolumbar scoliosis (Cobb’s angle of 47 deg.) was corrected using six different combinations of pedicle-screw placements. As a result, better correction in the axial rotation was obtained with the pedicle screws placed at or close to the apical vertebra than with the screws placed close to the end vertebrae, while the correction in the frontal plane was better with the screws close to the end vertebrae than with those close to the apical vertebra. Additionally, two screws placed in the convex side above and below the apical vertebra provided better correction than two screws placed in the concave side. Effective deformity corrections of scoliosis were obtained with the proper combinations of pedicle screw placements.

  15. Development and Testing of X-Ray Imaging-Enhanced Poly-L-Lactide Bone Screws.

    PubMed

    Chang, Wei-Jen; Pan, Yu-Hwa; Tzeng, Jy-Jiunn; Wu, Ting-Lin; Fong, Tsorng-Harn; Feng, Sheng-Wei; Huang, Haw-Ming

    2015-01-01

    Nanosized iron oxide particles exhibit osteogenic and radiopaque properties. Thus, iron oxide (Fe3O4) nanoparticles were incorporated into a biodegradable polymer (poly-L-lactic acid, PLLA) to fabricate a composite bone screw. This multifunctional, 3D printable bone screw was detectable on X-ray examination. In this study, mechanical tests including three-point bending and ultimate tensile strength were conducted to evaluate the optimal ratio of iron oxide nanoparticles in the PLLA composite. Both injection molding and 3D printing techniques were used to fabricate the PLLA bone screws with and without the iron oxide nanoparticles. The fabricated screws were implanted into the femoral condyles of New Zealand White rabbits. Bone blocks containing the PLLA screws were resected 2 and 4 weeks after surgery. Histologic examination of the surrounding bone and the radiopacity of the iron-oxide-containing PLLA screws were evaluated. Our results indicated that addition of iron oxide nanoparticles at 30% significantly decreased the ultimate tensile stress properties of the PLLA screws. The screws with 20% iron oxide exhibited strong radiopacity compared to the screws fabricated without the iron oxide nanoparticles. Four weeks after surgery, the average bone volume of the iron oxide PLLA composite screws was significantly greater than that of PLLA screws without iron oxide. These findings suggested that biodegradable and X-ray detectable PLLA bone screws can be produced by incorporation of 20% iron oxide nanoparticles. Furthermore, these screws had significantly greater osteogenic capability than the PLLA screws without iron oxide. PMID:26466309

  16. Development and Testing of X-Ray Imaging-Enhanced Poly-L-Lactide Bone Screws

    PubMed Central

    Tzeng, Jy-Jiunn; Wu, Ting-Lin; Fong, Tsorng-Harn; Feng, Sheng-Wei; Huang, Haw-Ming

    2015-01-01

    Nanosized iron oxide particles exhibit osteogenic and radiopaque properties. Thus, iron oxide (Fe3O4) nanoparticles were incorporated into a biodegradable polymer (poly-L-lactic acid, PLLA) to fabricate a composite bone screw. This multifunctional, 3D printable bone screw was detectable on X-ray examination. In this study, mechanical tests including three-point bending and ultimate tensile strength were conducted to evaluate the optimal ratio of iron oxide nanoparticles in the PLLA composite. Both injection molding and 3D printing techniques were used to fabricate the PLLA bone screws with and without the iron oxide nanoparticles. The fabricated screws were implanted into the femoral condyles of New Zealand White rabbits. Bone blocks containing the PLLA screws were resected 2 and 4 weeks after surgery. Histologic examination of the surrounding bone and the radiopacity of the iron-oxide-containing PLLA screws were evaluated. Our results indicated that addition of iron oxide nanoparticles at 30% significantly decreased the ultimate tensile stress properties of the PLLA screws. The screws with 20% iron oxide exhibited strong radiopacity compared to the screws fabricated without the iron oxide nanoparticles. Four weeks after surgery, the average bone volume of the iron oxide PLLA composite screws was significantly greater than that of PLLA screws without iron oxide. These findings suggested that biodegradable and X-ray detectable PLLA bone screws can be produced by incorporation of 20% iron oxide nanoparticles. Furthermore, these screws had significantly greater osteogenic capability than the PLLA screws without iron oxide. PMID:26466309

  17. Investigation of an 11mm diameter twin screw granulator: Screw element performance and in-line monitoring via image analysis.

    PubMed

    Sayin, Ridade; Martinez-Marcos, Laura; Osorio, Juan G; Cruise, Paul; Jones, Ian; Halbert, Gavin W; Lamprou, Dimitrios A; Litster, James D

    2015-12-30

    As twin screw granulation (TSG) provides one with many screw element options, characterization of each screw element is crucial in optimizing the screw configuration in order to obtain desired granule attributes. In this study, the performance of two different screw elements - distributive feed screws and kneading elements - was studied in an 11 mm TSG at different liquid-to-solid (L/S) ratios. The kneading element configuration was found to break large granules more efficiently, leading to narrower granule size distributions. While pharmaceutical industry shifts toward continuous manufacturing, inline monitoring and process control are gaining importance. Granules from an 11 mm TSG were analysed using the Eyecon™, a real-time high speed direct imaging system, which has been used to capture accurate particle size distribution and particle count. The size parameters and particle count were then assessed in terms of their ability to be a suitable control measure using the Shewhart control charts. d10 and particle count were found to be good indicators of the change in L/S ratio. However, d50 and d90 did not reflect the change, due to their inherent variability even when the process is at steady state. PMID:26385406

  18. Helical Screw Expander Evaluation Project. Final report

    SciTech Connect

    McKay, R.

    1982-03-01

    A functional 1-MW geothermal electric power plant that featured a helical screw expander was produced and then tested in Utah in 1978 to 1979 with a demonstrated average performance of approximately 45% machine efficiency over a wide range of test conditions in noncondensing operation on two-phase geothermal fluids. The Project also produced a computer-equipped data system, an instrumentation and control van, and a 1000-kW variable load bank, all integrated into a test array designed for operation at a variety of remote test sites. Additional testing was performed in Mexico in 1980 under a cooperative test program using the same test array, and machine efficiency was measured at 62% maximum with the rotors partially coated with scale, compared with approximately 54% maximum in Utah with uncoated rotors, confirming the importance of scale deposits within the machine on performance. Data are presented for the Utah testing and for the noncondensing phases of the testing in Mexico. Test time logged was 437 hours during the Utah tests and 1101 hours during the Mexico tests.

  19. Stem–Cement Porosity May Explain Early Loosening of Cemented Femoral Hip Components: Experimental-Computational In Vitro Study

    PubMed Central

    Mann, Kenneth A.; Damron, Leatha A.; Miller, Mark A.; Race, Amos; Clarke, Michael T.; Cleary, Richard J.

    2007-01-01

    A combination of laboratory experiment and computational simulation was performed to assess the role of interface porosity on stem migration. The early motion of in vitro prepared cemented femoral components was measured during application of cyclic stair climbing loads. Following testing, transverse sections were obtained and the distribution of pores at the stem–cement interface was determined. Finite element models of cemented stem constructs were developed and a scheme was implemented to randomly assign pores to the stem–cement interface. For a series of 14 in vitro prepared components, pore fractions at the stem–cement interface ranged from 23% to 67%. The majority of pores at the stem–cement interface were less than 1 mm in length with a mean length of 1.27 ± 2.7 mm and thickness of 0.12 ± 0.11 mm. For stems with large pore fractions, pores tended to coalesce in longer extended gaps over the stem surface. Finite element and experimental models both revealed strong positive correlations (r2 = 0.55–0.72; p < 0.0001) between stem–cement pore fraction and stem internal rotation, suggesting that the presence and extent of pores could explain the early motion of the stems. There was an increased volume of cement at risk of fatigue failure with increasing stem migration. Pore fractions greater than 30% resulted in large increases in stem internal rotation, suggesting that attempts to maintain surface porosity at or below this level may be desirable to minimize the risk of clinical loosening. PMID:17149748

  20. Combination gene therapy targeting on interleukin-1β and RANKL for wear debris-induced aseptic loosening.

    PubMed

    Wang, H; Jia, T-H; Zacharias, N; Gong, W; Du, H-X; Wooley, P H; Yang, S-Y

    2013-02-01

    This study investigated the efficacy of a combination gene therapy to repress interleukin-1 (IL-1) and receptor activator of nuclear factor NF-kappa B ligand (RANKL) for the treatment of particulate debris-induced aseptic loosening, and tried to explore the molecular mechanism of the exogenous gene modifications on osteoclastogenesis. RAW cells activated by titanium particles were transduced with DFG-IL-1Ra (retroviral vector encoding IL-1 receptor antagonist) and AAV-OPG (adeno-associated viral vectors-osteoprotegerin) individually or in combination for 4 weeks. Pro-inflammatory cytokines in culture media were determined by enzyme-linked immunosorbent assay, and gene expressions of RANK, IL-1β, c-Fos, TRAF6, JNK1 and CPK were examined using real-time PCR. An established knee-implant-failure mouse model was employed to evaluate the efficacy of the in vivo double-gene therapy. The surgical implantation of a titanium alloy pin into the proximal tibia was followed by monthly challenge with titanium debris. Peri-implant gene transfers of IL-1Ra and OPG (respectively or in combination) were given 3 weeks after surgery. The combination of OPG and IL-1Ra gene transfer exhibited strong synergetic effects in blockage of inflammation and osteoclastogenesis at 8 weeks after gene modification. The combination therapy reversed peri-implant bone resorption and restored implant stability when compared with either single gene transduction. Real-time PCR data indicated that the action of IL-1Ra gene therapy may be mediated via the JNK1 pathway, while the reduction of osteoclastogenesis by OPG gene modification may be regulated by c-Fos expression. In addition, both gene modifications resulted in significant diminishment of TRAF6 expression. PMID:22318091

  1. Comparison of the roles of IL-1, IL-6, and TNFα in cell culture and murine models of aseptic loosening1

    PubMed Central

    Taki, Naoya; Tatro, Joscelyn M.; Lowe, Robert; Goldberg, Victor M.; Greenfield, Edward M.

    2007-01-01

    Pro-inflammatory cytokines, such as IL-1, IL-6, and TNF, are considered to be major mediators of osteolysis and ultimately aseptic loosening. This study demonstrated that synergistic interactions among these cytokines are required for the in vitro stimulation of osteoclast differentiation by titanium particles. In contrast, genetic knock out of these cytokines or their receptors does not protect murine calvaria from osteolysis induced by titanium particles. Thus, the extent of osteolysis was not substantially altered in single knock out mice lacking either the IL-1 receptor or IL-6. Osteolysis also was not substantially altered in double knock out mice lacking both the IL-1 receptor and IL-6 or in double knock out mice lacking both TNF receptor-1 and TNF receptor-2. The differences between the in vivo and the cell culture results make it difficult to conclude whether the pro-inflammatory cytokines contribute to aseptic loosening. One alternative is that in vivo experiments are more physiological and that therefore the current results do not support a role for the pro-inflammatory cytokines in aseptic loosening. We however favor the alternative that, in this case, the cell culture experiments can be more informative. We favor this alternative because the role of the pro-inflammatory cytokines may be obscured in vivo by compensation by other cytokines or by the low signal to noise ratio found in measurements of particle-induced osteolysis. PMID:17236833

  2. Evaluation of removal forces of implant-supported zirconia copings depending on abutment geometry, luting agent and cleaning method during re-cementation

    PubMed Central

    Rödiger, Matthias; Rinke, Sven; Ehret-Kleinau, Fenja; Pohlmeyer, Franziska; Lange, Katharina; Bürgers, Ralf

    2014-01-01

    PURPOSE To evaluate the effects of different abutment geometries in combination with varying luting agents and the effectiveness of different cleaning methods (prior to re-cementation) regarding the retentiveness of zirconia copings on implants. MATERIALS AND METHODS Implants were embedded in resin blocks. Three groups of titanium abutments (pre-fabricated, height: 7.5 mm, taper: 5.7°; customized-long, height: 6.79 mm, taper: 4.8°; customized-short, height: 4.31 mm, taper: 4.8°) were used for luting of CAD/CAM-fabricated zirconia copings with a semi-permanent (Telio CS) and a provisional cement (TempBond NE). Retention forces were evaluated using a universal testing machine. Furthermore, the influence of cleaning methods (manually, manually in combination with ultrasonic bath or sandblasting) prior to re-cementation with a provisional cement (TempBond NE) was investigated with the pre-fabricated titanium abutments (height: 7.5 mm, taper: 5.7°) and SEM-analysis of inner surfaces of the copings was performed. Significant differences were determined via two-way ANOVA. RESULTS Significant interactions between abutment geometry and luting agent were observed. TempBond NE showed the highest level of retentiveness on customized-long abutments, but was negatively affected by other abutment geometries. In contrast, luting with Telio CS demonstrated consistent results irrespective of the varying abutment geometries. Manual cleaning in combination with an ultrasonic bath was the only cleaning method tested prior to re-cementation that revealed retentiveness levels not inferior to primary cementation. CONCLUSION No superiority for one of the two cements could be demonstrated because their influences on retentive strength are also depending on abutment geometry. Only manual cleaning in combination with an ultrasonic bath offers retentiveness levels after re-cementation comparable to those of primary luting. PMID:25006388

  3. Reducing Distortion of Implant- or Abutment-Level Impressions for Implant-Supported Prosthetic Rehabilitation: A Technique Report.

    PubMed

    Lanis, Alejandro; Padial-Molina, Miguel; Selman, Andrea; Alvarez Del Canto, Orlando

    2015-01-01

    Passive fit between prosthesis and implants or abutments is a significant factor in preventing mechanical and biologic failures of implant-supported prostheses. Therefore, impression techniques must transfer the 3D implant position as accurately as possible for a correct superstructure fabrication. A novel impression protocol that uses an individualized open tray design is proposed. It allows the clinician to splint the transfers between the copings, outside the impression area, and to the tray itself to create a rigid monoblock. Thus, distortions produced by the tear of impression material or by transfer abutments' micromovements during tray retrieval are limited and superstructure misfits are minimized. This technique is specifically recommended for long spanning or completely edentulous patients. PMID:26509993

  4. Evaluation of the Effect of Fixation Angle between Polyaxial Pedicle Screw Head and Rod on the Failure of Screw-Rod Connection.

    PubMed

    Çetin, Engin; Özkaya, Mustafa; Güler, Ümit Özgür; Acaroğlu, Emre; Demir, Teyfik

    2015-01-01

    Introduction. Polyaxial screws had been only tested according to the ASTM standards (when they were perpendicularly positioned to the rod). In this study, effects of the pedicle screws angled fixation to the rod on the mechanical properties of fixation were investigated. Materials and Method. 30 vertically fixed screws and 30 screws fixed with angle were used in the study. Screws were used in three different diameters which were 6.5 mm, 7.0 mm, and 7.5 mm, in equal numbers. Axial pull-out and flexion moment tests were performed. Test results compared with each other using appropriate statistical methods. Results. In pull-out test, vertically fixed screws, in 6.5 mm and 7.0 mm diameter, had significantly higher maximum load values than angled fixed screws with the same diameters (P < 0.01). Additionally, vertically fixed screws, in all diameters, had significantly greater stiffness according to corresponding size fixed with angle (P < 0.005). Conclusion. Fixing the pedicle screw to the rod with angle significantly decreased the pull-out stiffness in all diameters. Similarly, pedicle screw instrumentation fixed with angle decreased the minimum sagittal angle between the rod and the screw in all diameters for flexion moment test but the differences were not significant. PMID:27019578

  5. The best location for proximal locking screw for femur interlocking nailing: A biomechanical study

    PubMed Central

    Karaarslan, Ahmet A; Karakaşli, Ahmet; Aycan, Hakan; Çeçen, Berivan; Yildiz, Didem Venüs; Sesli, Erhan

    2016-01-01

    Background: Proximal locking screw deformation and screw fracture is a frequently seen problem for femur interlocking nailing that affects fracture healing. We realized that there is lack of literature for the right level for the proximal locking screw. We investigated the difference of locking screw bending resistance between the application of screws on different proximal femoral levels. Materials and Methods: We used a total of 80 proximal locking screws for eight groups, 10 screws for each group. Three-point bending tests were performed on four types of screws in two different trochanteric levels (the lesser trochanter and 20 mm proximal). We determined the yield points at three-point bending tests that a permanent deformation started in the locking screws using an axial compression testing machine. Results: The mean yield point value of 5 mm threaded locking screws applied 20 mm proximal of lesser trochanter was 1022 ± 49 (range 986–1057) (mean ± standard deviation, 95% confidence interval). On the other hand, the mean yield point value of the same type of locking screws applied on the lesser trochanteric level was 2089 ± 249 (range 1911–2268). Which means 103% increase of screw resistance between two levels (P = 0.000). In all screw groups, on the lesser trochanter line we determined 98–174% higher than the yield point values of the same type of locking screws in comparison with 20 mm proximal to the lesser trochanter (P = 0.000). Conclusion: According to our findings, there is twice as much difference in locking screw bending resistance between these two application levels. To avoid proximal locking screw deformation, locking screws should be placed in the level of the lesser trochanter in nailing of 1/3 middle and distal femur fractures. PMID:26955183

  6. Cement as a locking mechanism for screw heads in acetabular revision shells - a biomechanical analysis.

    PubMed

    Laflamme, G Y; Alami, G B; Zhim, F

    2008-01-01

    In acetabular revisions, polyethylene (PE) liners are often cemented into metal shells on top of acetabular screw heads. This study investigates the possibility of using this technique to obtain fixed-angle acetabular screws Eth a concept that has not yet been reported in the literature. Two groups of screws (n=8) were inserted into Trabecular Metal revision shells (Zimmer), into which PE liners were then cemented. Screws in Group 1, inserted in the shell's pre-fabricated holes, were countersunk, whereas screws in Group 2 were inserted in custom-drilled holes that make their heads protrude into, and interdigitate with, the overlying cement mantle. Perpendicular loading was then applied to the screw shafts both statically to failure and cyclically. A greater stiffness was observed for the protruding screws upon static loading; and while the countersunk screws all failed at the screw-cement junction (53.44 + or - 8.33 N), the protruding screws all failed at the screw shaft (1049.79 + or - 32.12 N) a 20-fold difference (p< 0.05). Under cyclic loading, only the protruding screw head specimen did not fail, undergoing an overall displacement within the limits of osseointegration.These results support the hypothesis that the protrusion of an acetabular screw head into an overlying cement mantle significantly increases its angular stability. Provided other variables are favorable, this locking effect may increase the initial stability of the whole implant, thus improving the ultimate success of complex acetabular revisions. PMID:18645971

  7. Periodontal and pulpal conditions of abutment teeth. Status after four to eight years following the incorporation of fixed reconstructions.

    PubMed

    Reichen-Graden, S; Lang, N P

    1989-01-01

    In the present retrospective clinical study, 58 patients were examined 4 to 8 years (median 77 months) following the incorporation of a fixed reconstruction. No regular maintenance care had been provided during the interval period. The periodontal conditions represented by the Plaque Control Record (PCR), the Gingival Index (GI) and pocket probing depths were examined on 182 abutment teeth of 94 reconstructions. Pulpal vitality and periapical pathology were assessed clinically as well as radiographically. The periodontal parameters of the abutment teeth were compared with homologous contralateral uncrowned teeth. Significantly higher plaque prevalence, gingival indices, and pocket probing depths were found in the crowned teeth. Also, bleeding on probing was observed more frequently whenever the crown margins were located subgingivally. At the end of the interval period, 3.7% of the originally vital abutments had lost their vitality. A technical failure rate of 7.4% with no apparent differences between conventional and extension bridges was noted. This study indicates that even with precise marginal fit and in the absence of a regular maintenance program, the supragingival location of the crown margin is more favourable than the subgingival location for the maintenance of oral health. PMID:2701195

  8. IN VITRO EVALUATION OF THE PRECISION OF WORKING CASTS FOR IMPLANT-SUPPORTED RESTORATION WITH MULTIPLE ABUTMENTS

    PubMed Central

    Castilho, Anderson Almeida; Kojima, Alberto Noriyuki; Pereira, Sarina Maciel Braga; de Vasconcellos, Diego Klee; Itinoche, Marcos Koiti; Faria, Renata; Bottino, Marco Antonio

    2007-01-01

    Objective: The purpose of this study was to compare the accuracy of two working cast fabrication techniques using strain- gauge analysis. Methods: Two working cast fabrication methods were evaluated. Based on a master model, 20 working casts were fabricated by means of an indirect impression technique using polyether after splinting the square transfer copings with acrylic resin. Specimens were assigned to 2 groups (n=10): Group A (GA): type IV dental stone was poured around the abutment analogs in the conventional way; Group B (GB), the dental stone was poured in two stages. Spacers were used over the abutment analogs (rubber tubes) and type IV dental stone was poured around the abutment analogs in the conventional way. After the stone had hardened completely, the spacers were removed and more stone was inserted in the spaces created. Six strain-gauges (Excel Ltd.), positioned in a cast bar, which was dimensionally accurate (perfect fit) to the master model, recorded the microstrains generated by each specimen. Data were analyzed statistically by the variance analysis (ANOVA) and Tukey's test (α= 5%). Results: The microstrain values (με) were (mean±SD): GA: 263.7±109.07με, and GB: 193.73±78.83με. Conclusion: There was no statistical difference between the two methods studied. PMID:19089137

  9. Focal adhesion linker proteins expression of fibroblast related to adhesion in response to different transmucosal abutment surfaces

    PubMed Central

    Moon, Yeon-Hee; Yoon, Mi-Kyeong; Moon, Jung-Sun; Kang, Jee-Hae; Kim, Sun-Hun; Yang, Hong-Seo

    2013-01-01

    PURPOSE To evaluate adherence of human gingival fibroblasts (HGFs) to transmucosal abutment of dental implant with different surface conditions with time and to investigate the roles of focal adhesion linker proteins (FALPs) involved in HGFs adhesion to abutment surfaces. MATERIALS AND METHODS Morphologies of cultured HGFs on titanium and ceramic discs with different surface were observed by scanning electron microscopy. Biocompatibility and focal adhesion were evaluated by ultrasonic wave application and cell viability assay. FALPs expression levels were assessed by RT-PCR and western blot. RESULTS There seemed to be little difference in biocompatibility and adhesion strength of HGFs depending on the surface conditions and materials. In all experimental groups, the number of cells remaining on the disc surface after ultrasonic wave application increased more than 2 times at 3 days after seeding compared to 1-day cultured cells and this continued until 7 days of culture. FALPs expression levels, especially of vinculin and paxillin, also increased in 5-day cultured cells compared to 1-day cultured fibroblasts on the disc surface. CONCLUSION These results might suggest that the strength of adhesion of fibroblasts to transmucosal abutment surfaces increases with time and it seemed to be related to expressions of FALPs. PMID:24049577

  10. Stress Analysis of Axial and Tilted Implants in Full-arch Fixed Dentures Under Different Abutment Conditions.

    PubMed

    Mazaro, José Vitor Quinelli; da Silva, Cristina Ramos; Filho, Humberto Gennari; Zavanelli, Adriana Cristina; de Mello, Caroline Cantieri; Lemos, Cleidiel Aparecido Araujo; Pellizzer, Eduardo Piza

    2016-05-01

    The aim of this study was to evaluate the stress distribution on full-arch prostheses, considering axial implants and tilted implants with or without abutments. Two photoelastic models were made, being that in 1 model the implants were inserted perpendicular, whereas in the other model 2 implants were inserted perpendicular and 2 implants were inserted with tilting 30° to the distal area. The prosthetic situations were evaluated: A-axial implants and nonsegmented full-arch prosthesis; B-axial implants and segmented full-arch prosthesis; C-tilted distal implants and nonsegmented full-arch prosthesis; D-tilted distal implants and segmented full-arch prosthesis, and was applied an axial load of 100 N at 5 points. The results showed greater stress concentration for axial implants than tilted implants in anterior and posterior loading. There was no difference in stress distribution to the use of abutment in the tilted implants. Shorter cantilever with tilted implants improved the stress distribution; the use of abutment did not influence the stress distribution. PMID:26999691

  11. Biomechanical efficacy of monoaxial or polyaxial pedicle screw and additional screw insertion at the level of fracture, in lumbar burst fracture: An experimental study

    PubMed Central

    Wang, Hongwei; Li, Changqing; Liu, Tao; Zhao, Wei-dong; Zhou, Yue

    2012-01-01

    Background: Use of a pedicle screw at the level of fracture, also known as an intermediate screw, has been shown to improve clinical results in managing lumbar fracture, but there is a paucity of biomechanical studies to support the claim. The aim of this study was to evaluate the effect of adding intermediate pedicle screws at the level of a fracture on the stiffness of a short-segment pedicle fixation using monoaxial or polyaxial screws and to compare the strength of monoaxial and polyaxial screws in the calf spine fracture model. Materials and Methods: Flexibility of 12 fresh-frozen calf lumbar spine specimens was evaluated in all planes. An unstable burst fracture model was created at the level of L3 by the pre-injury and dropped-mass technique. The specimens were randomly divided into monoaxial pedicle screw (MPS) and polyaxial pedicle screw (PPS) groups. Flexibility was retested without and with intermediate screws (MPSi and PPSi) placed at the level of fracture in addition to standard screws placed at L2 and L4. Results: The addition of intermediate screws significantly increased the stability of the constructs, as measured by a decreased range of motion (ROM) in flexion, extension, and lateral bending in both MPS and PPS groups (P < 0.05). There was neither any significant difference in the ROM in the spines of the two groups before injury, nor a difference in the ROM between the MPSi and PPSi groups (P > 0.05), but there was a significant difference between MPS and PPS in flexion and extension in the short-segment fixation group (P < 0.05). Conclusions: The addition of intermediate screws at the level of a burst fracture significantly increased the stability of short-segment pedicle screw fixation in both the MPS and PPS groups. However, in short-segment fixation group, monoaxial pedicle screw exhibited more stability in flexion and extension than the polyaxial pedicle screw. PMID:22912513

  12. Distal Locking Screws for Intramedullary Nailing of Tibial Fractures.

    PubMed

    Agathangelidis, Filon; Petsatodis, Georgios; Kirkos, John; Papadopoulos, Pericles; Karataglis, Dimitrios; Christodoulou, Anastasios

    2016-01-01

    Recently introduced tibial intramedullary nails allow a number of distal screws to be used to reduce the incidence of malalignment and loss of fixation of distal metaphyseal fractures. However, the number of screws and the type of screw configuration to be used remains obscure. This biomechanical study was performed to address this question. Thirty-six Expert tibial nails (Synthes, Oberdorf, Switzerland) were introduced in composite bone models. The models were divided into 4 groups with different distal locking configurations ranging from 2 to 4 screws. A 7-mm gap osteotomy was performed 72 mm from the tibial plafond to simulate a 42-C3 unstable distal tibial fracture. Each group was divided in 3 subgroups and underwent nondestructive biomechanical testing in axial compression, coronal bending, and axial torsion. The passive construct stiffness was measured and statistically analyzed with one-way analysis of variance. Although some differences were noted between the stiffness of each group, these were not statistically significant in compression (P=.105), bending (P=.801), external rotation (P=.246), and internal rotation (P=.370). This in vitro study showed that, when using the Expert tibial nail for unstable distal tibial fractures, the classic configuration of 2 parallel distal screws could provide the necessary stability under partial weight-bearing conditions. PMID:26840700

  13. Screw dislocations in GaN grown by different methods

    SciTech Connect

    Liliental-Weber, Z.; Zakharov, D.; Jasinski, J.; O'Keefe, M.A.; Morkoc, H.

    2003-05-27

    A study of screw dislocations in Hydride-Vapor-Phase-Epitaxy (HVPE) template and Molecular-Beam-Epitaxy (MBE) over-layers was performed using Transmission Electron Microscopy (TEM) in plan-view and in cross-section. It was observed that screw dislocations in the HVPE layers were decorated by small voids arranged along the screw axis. However, no voids were observed along screw dislocations in MBE overlayers. This was true both for MBE samples grown under Ga-lean and Ga-rich conditions. Dislocation core structures have been studied in these samples in the plan-view configuration. These experiments were supported by image simulation using the most recent models. A direct reconstruction of the phase and amplitude of the scattered electron wave from a focal series of high-resolution images was applied. It was shown that the core structures of screw dislocations in the studied materials were filled. The filed dislocation cores in an MBE samples were stoichiometric. However, in HVPE materials, single atomic columns show substantial differences in intensities and might indicate the possibility of higher Ga concentration in the core than in the matrix. A much lower intensity of the atomic column at the tip of the void was observed. This might suggest presence of lighter elements, such as oxygen, responsible for their formation.

  14. Numerical simulation of a twin screw expander for performance prediction

    NASA Astrophysics Data System (ADS)

    Papes, Iva; Degroote, Joris; Vierendeels, Jan

    2015-08-01

    With the increasing use of twin screw expanders in waste heat recovery applications, the performance prediction of these machines plays an important role. This paper presents a mathematical model for calculating the performance of a twin screw expander. From the mass and energy conservation laws, differential equations are derived which are then solved together with the appropriate Equation of State in the instantaneous control volumes. Different flow processes that occur inside the screw expander such as filling (accompanied by a substantial pressure loss) and leakage flows through the clearances are accounted for in the model. The mathematical model employs all geometrical parameters such as chamber volume, suction and leakage areas. With R245fa as working fluid, the Aungier Redlich-Kwong Equation of State has been used in order to include real gas effects. To calculate the mass flow rates through the leakage paths formed inside the screw expander, flow coefficients are considered as constant and they are derived from 3D Computational Fluid Dynamic calculations at given working conditions and applied to all other working conditions. The outcome of the mathematical model is the P-V indicator diagram which is compared to CFD results of the same twin screw expander. Since CFD calculations require significant computational time, developed mathematical model can be used for the faster performance prediction.

  15. Treatment of scaphoid waist fractures with the HCS screw

    PubMed Central

    Gehrmann, Sebastian V.; Grassmann, Jan-Peter; Wild, Michael; Jungbluth, Pascal; Kaufmann, Robert A.; Windolf, Joachim; Hakimi, Mohssen

    2014-01-01

    The aim of the study was to evaluate the clinical results of the Headless Compression Screw (HCS, Synthes) when used for treatment of acute scaphoid waist fractures. The new screw design generates interfragmentary compression with use of a compression sleeve. Twenty-one patients were treated for acute scaphoid waist fractures type B2 with HCS screws. The average time to the final follow-up examination was 12.8 months. All 21 fractures united after a mean time of 7.2 weeks. The mean DASH score was 7.1. The average motion of the wrist in extension was 61°, flexion was 46°, radial abduction reached 25° and the ulnar abduction was 31°. The maximally achieved grip strength was 86% compared to the uninjured side. Treatment of type B2 scaphoid fractures with the Headless Compression Screw showed good functional and radiographic results. The results are similar to those identified using other screw fixation systems. PMID:26504721

  16. Endovascular aortic injury repair after thoracic pedicle screw placement.

    PubMed

    Pesenti, S; Bartoli, M A; Blondel, B; Peltier, E; Adetchessi, T; Fuentes, S

    2014-09-01

    Our objective was to describe the management and prevention of thoracic aortic injuries caused by a malposition of pedicle screws in corrective surgery of major spine deformities. Positioning pedicle screws in thoracic vertebras by posterior approach exposes to the risk of injury of the elements placed ahead of the thoracic spine, as the descending thoracic aorta. This complication can result in a cataclysmic bleeding, needing urgent vascular care, but it can also be totally asymptomatic, resulting in the long run in a pseudoaneurysm, justifying the systematic removal of the hardware. We report the case of a 76-year-old woman who underwent spinal correction surgery for thoraco-lumbar degenerative kypho-scoliosis. Immediately after the surgery, a thoracic aortic injury caused by the left T7 pedicle screw was diagnosed. The patient underwent a two-step surgery. The first step was realized by vascular surgeons and aimed to secure the aortic wall by short endovascular aortic grafting. During the second step, spine surgeons removed the responsible screw by posterior approach. The patient was discharged in a rehabilitation center 7 days after the second surgery. When such a complication occurs, a co-management by vascular and spine surgeons is necessary to avoid major complications. Endovascular management of this kind of vascular injuries permits to avoid an open surgery that have a great rate of morbi-mortality in frail patients. Nowadays, technologies exist to prevent this kind of event and may improve the security when positioning pedicle screws. PMID:25023930

  17. Percutaneous iliac screws for minimally invasive spinal deformity surgery.

    PubMed

    Wang, Michael Y

    2012-01-01

    Introduction. Adult spinal deformity (ASD) surgeries carry significant morbidity, and this has led many surgeons to apply minimally invasive surgery (MIS) techniques to reduce the blood loss, infections, and other peri-operative complications. A spectrum of techniques for MIS correction of ASD has thus evolved, most recently the application of percutaneous iliac screws. Methods. Over an 18 months 10 patients with thoracolumbar scoliosis underwent MIS surgery. The mean age was 73 years (70% females). Patients were treated with multi-level facet osteotomies and interbody fusion using expandable cages followed by percutaneous screw fixation. Percutaneous iliac screws were placed bilaterally using the obturator outlet view to target the ischial body. Results. All patients were successfully instrumented without conversion to an open technique. Mean operative time was 302 minutes and the mean blood loss was 480 cc, with no intraoperative complications. A total of 20 screws were placed successfully as judged by CT scanning to confirm no bony violations. Complications included: two asymptomatic medial breaches at T10 and L5, and one patient requiring delayed epidural hematoma evacuation. Conclusions. Percutaneous iliac screws can be placed safely in patients with ASD. This MIS technique allows for successful caudal anchoring to stress-shield the sacrum and L5-S1 fusion site in long-segment constructs. PMID:22900162

  18. Performance monitoring of a short-span integral-abutment bridge using wireless sensor technology

    NASA Astrophysics Data System (ADS)

    Gangone, Michael V.; Whelan, Matthew J.; Fuchs, Michael P.; Janoyan, Kerop D.

    2007-04-01

    Discussed in this paper is the implementation of a wireless sensor system for performance monitoring of bridges. The advanced wireless sensor system, developed at Clarkson University's Laboratory for Intelligent Infrastructure and Transportation Technologies (LIITT), allows for structural monitoring of bridges. A short-span integral-abutment bridge located in New York State is instrumented with a wireless sensor system measuring acceleration, and strain to monitor the behavior of the structure under various loading conditions including ambient, environmental and traffic loading. Strain and acceleration measurements are recorded simultaneously and in real time to validate various performance characteristics of the bridge, including load distribution along an interior girder, as well as additional stiffness factors (end fixity and composite action of the beams and bridge deck), using existing bridge load testing and condition evaluation guidelines used by the New York State Department of Transportation (NYSDOT) and American Association of State Highway and Transportation Officials (AASHTO). Additionally, acceleration measurements are used to extract the superstructure's first five natural frequencies and corresponding mode shapes. Results are compared to a developed Finite Element Method (FEM) model based on the bridge as built drawings.

  19. Safety identifying of integral abutment bridges under seismic and thermal loads.

    PubMed

    Easazadeh Far, Narges; Barghian, Majid

    2014-01-01

    Integral abutment bridges (IABs) have many advantages over conventional bridges in terms of strength and maintenance cost. Due to the integrity of these structures uniform thermal and seismic loads are known important ones on the structure performance. Although all bridge design codes consider temperature and earthquake loads separately in their load combinations for conventional bridges, the thermal load is an "always on" load and, during the occurrence of an earthquake, these two important loads act on bridge simultaneously. Evaluating the safety level of IABs under combination of these loads becomes important. In this paper, the safety of IABs--designed by AASHTO LRFD bridge design code--under combination of thermal and seismic loads is studied. To fulfill this aim, first the target reliability indexes under seismic load have been calculated. Then, these analyses for the same bridge under combination of thermal and seismic loads have been repeated and the obtained reliability indexes are compared with target indexes. It is shown that, for an IAB designed by AASHTO LRFD, the indexes have been reduced under combined effects. So, the target level of safety during its design life is not provided and the code's load combination should be changed. PMID:25405232

  20. Safety Identifying of Integral Abutment Bridges under Seismic and Thermal Loads

    PubMed Central

    Easazadeh Far, Narges; Barghian, Majid

    2014-01-01

    Integral abutment bridges (IABs) have many advantages over conventional bridges in terms of strength and maintenance cost. Due to the integrity of these structures uniform thermal and seismic loads are known important ones on the structure performance. Although all bridge design codes consider temperature and earthquake loads separately in their load combinations for conventional bridges, the thermal load is an “always on” load and, during the occurrence of an earthquake, these two important loads act on bridge simultaneously. Evaluating the safety level of IABs under combination of these loads becomes important. In this paper, the safety of IABs—designed by AASHTO LRFD bridge design code—under combination of thermal and seismic loads is studied. To fulfill this aim, first the target reliability indexes under seismic load have been calculated. Then, these analyses for the same bridge under combination of thermal and seismic loads have been repeated and the obtained reliability indexes are compared with target indexes. It is shown that, for an IAB designed by AASHTO LRFD, the indexes have been reduced under combined effects. So, the target level of safety during its design life is not provided and the code's load combination should be changed. PMID:25405232

  1. Optically driven Archimedes micro-screws for micropump application.

    PubMed

    Lin, Chih-Lang; Vitrant, Guy; Bouriau, Michel; Casalegno, Roger; Baldeck, Patrice L

    2011-04-25

    Archimedes micro-screws have been fabricated by three-dimensional two-photon polymerization using a Nd:YAG Q-switched microchip laser at 532nm. Due to their small sizes they can be easily manipulated, and made to rotate using low power optical tweezers. Rotation rates up to 40 Hz are obtained with a laser power of 200 mW, i.e. 0.2 Hz/mW. A photo-driven micropump action in a microfluidic channel is demonstrated with a non-optimized flow rate of 6 pL/min. The optofluidic properties of such type of Archimedes micro-screws are quantitatively described by the conservation of momentum that occurs when the laser photons are reflected on the helical micro-screw surface. PMID:21643076

  2. C2 Pedicle Screw Placement: A Novel Teaching Aid

    PubMed Central

    Moisi, Marc; Chapman, Jens; Oskouian, Rod J; Tubbs, R. Shane

    2016-01-01

    The C2 pedicle screw is more biomechanically stable and provides patients with increased postoperative range of motion in comparison to other methods of C2 fixation. However, as a result of the proximity of the C2 pedicle to the transverse foramen, there is a considerable risk of intraoperative morbidity due to vertebral artery injury laterally or vertebral canal breach medially. Other than the use of cadavers for the demonstration and practice of C2 pedicle screw placement, there are currently few other readily available teaching aids for the training of residents and fellows. Herein, we describe a simple and cost effective modality for the demonstration, evaluation, and practice of C2 pedicle screw placement in a laboratory setting. PMID:27433409

  3. Experimental determination of bone cortex holding power of orthopedic screw.

    PubMed

    Bolliger Neto, R; Rossi, J D; Leivas, T P

    1999-01-01

    Cylindrical specimens of bone measuring 15 mm in diameter were obtained from the lateral cortical layer of 10 pairs of femurs and tibias. A central hole 3.2 mm in diameter was drilled in each specimen. The hole was tapped, and a 4.5 mm cortical bone screw was inserted from the outer surface. The montage was submitted to push-out testing up to a complete strip of the bone threads. The cortical thickness and rupture load were measured, and the shear stress was calculated. The results were grouped according to the bone segment from which the specimen was obtained. The results showed that bone cortex screw holding power is dependent on the bone site. Additionally, the diaphyseal cortical bone tissue is both quantitatively and qualitatively more resistant to screw extraction than the metaphyseal tissue. PMID:10881065

  4. Efficiency study of oil cooling of a screw compressor

    SciTech Connect

    Tree, D.R.; McKellar, M.G.

    1989-04-01

    One of the major goals of all compressor manufacturers is to build as efficient a compressor as possible. Over the last several years improvements to the design of screw compressors has made them efficiently competitive with other types of compressors, especially at large loads. The primary purpose of this research is to investigate four different methods of cooling a 250 horsepower compressor and determine their effects on the efficiency of the compressor. Two conventional methods, liquid injection and thermosyphon cooling, and two new methods, V-PLUS and Fresco oil injection, are investigated. The screw compressor used in the tests was a VRS-500 screw compressor made by the Vilter Manufacturing Corporation. 6 figs.

  5. Quantitative comparison between the straight-forward and anatomical insertion technique for pedicle screw placement

    NASA Astrophysics Data System (ADS)

    Knez, Dejan; Mohar, Janez; Likar, Boštjan; Pernuš, Franjo; Vrtovec, Tomaž

    2016-03-01

    Spinal deformity correction with vertebral fixation is nowadays the preferred surgical treatment, where pedicle screws are inserted through pedicles into corresponding vertebral bodies and afterwards connected with rods. In clinical practice, the straight-forward and anatomical insertion technique are currently being used for pedicle screw placement surgery. However, it is difficult to quantitatively compare both techniques and determine which technique is more adequate for each planned pedicle screw before surgery (i.e. preoperatively). In this paper, we therefore describe a framework for quantitative comparison between the straight-forward and anatomical insertion technique for pedicle screw placement surgery by evaluating the screw fastening strength. Quantitative comparisons were performed on computed tomography images of 11 patients with 74 manually planned pedicle screws, who underwent the vertebral fixation procedure. The first quantitative comparison was performed between the straight-forward and anatomical pedicle screw insertion technique, which resulted in a relatively high agreement with mean absolute difference of 0.0mm in screw diameter, 2.9mm in screw length, 1.2mm in pedicle crossing point and 6.5° in screw inclinations. The second quantitative comparison was performed between the best resulting pedicle screw insertion technique and manually obtained pedicle screw plans, which again resulted in a relatively high agreement with mean absolute difference of 0.5mm in screw diameter, 4.7mm in screw length, 2.4mm in pedicle crossing point and 6.0° in screw inclinations. Both the straight-forward and anatomical insertion technique proved approximately equal in terms of the screw fastening strength.

  6. Bending strength and holding power of tibial locking screws.

    PubMed

    Lin, J; Lin, S J; Chiang, H; Hou, S M

    2001-04-01

    The bending strength and holding power of two types of specially designed tibial locking devices, a both-ends-threaded screw and an unthreaded bolt, were studied and compared with four types of commercially available tibial interlocking screws: Synthes, Howmedica, Richards, and Osteo AG. To test bending strength, the devices were inserted into a high molecular weight polyethylene tube and loaded at their midpoint by a materials testing machine to simulate a three point bending test. Single loading yielding strength and cyclic loading fatigue life were measured. To test holding power, the devices were inserted into tubes made of polyurethane foam, and their tips were loaded axially to measure pushout strength. The devices were tested with two different densities of foam materials and two different sizes of pilot holes. Insertion torque and stripping torque of the screws were measured first. Pushout tests were performed with each screw inserted with a tightness equal to 60% of its stripping torque. Test results showed that the yielding strength and the fatigue life were related closely to the inner diameter of the screws. The stripping torque predicted the pushout strength more reliably than did the insertion torque. All tested devices showed greater holding power in the foam with the higher density and with the smaller pilot holes. The both-ends-threaded screw had the highest pushout strength and a satisfactory fatigue strength. The unthreaded bolt had the highest fatigue strength but only fair holding power. Clinical studies of the use of these two types of locking devices are worthwhile. PMID:11302315

  7. Virtual estimates of fastening strength for pedicle screw implantation procedures

    NASA Astrophysics Data System (ADS)

    Linte, Cristian A.; Camp, Jon J.; Augustine, Kurt E.; Huddleston, Paul M.; Robb, Richard A.; Holmes, David R.

    2014-03-01

    Traditional 2D images provide limited use for accurate planning of spine interventions, mainly due to the complex 3D anatomy of the spine and close proximity of nerve bundles and vascular structures that must be avoided during the procedure. Our previously developed clinician-friendly platform for spine surgery planning takes advantage of 3D pre-operative images, to enable oblique reformatting and 3D rendering of individual or multiple vertebrae, interactive templating, and placement of virtual pedicle implants. Here we extend the capabilities of the planning platform and demonstrate how the virtual templating approach not only assists with the selection of the optimal implant size and trajectory, but can also be augmented to provide surrogate estimates of the fastening strength of the implanted pedicle screws based on implant dimension and bone mineral density of the displaced bone substrate. According to the failure theories, each screw withstands a maximum holding power that is directly proportional to the screw diameter (D), the length of the in-bone segm,ent of the screw (L), and the density (i.e., bone mineral density) of the pedicle body. In this application, voxel intensity is used as a surrogate measure of the bone mineral density (BMD) of the pedicle body segment displaced by the screw. We conducted an initial assessment of the developed platform using retrospective pre- and post-operative clinical 3D CT data from four patients who underwent spine surgery, consisting of a total of 26 pedicle screws implanted in the lumbar spine. The Fastening Strength of the planned implants was directly assessed by estimating the intensity - area product across the pedicle volume displaced by the virtually implanted screw. For post-operative assessment, each vertebra was registered to its homologous counterpart in the pre-operative image using an intensity-based rigid registration followed by manual adjustment. Following registration, the Fastening Strength was computed

  8. New Screw Design for Securing Buried Distractors Usefulness and Ease of Removal.

    PubMed

    Fariña, Rodrigo; Hinojosa, Andrés; Sánchez, Martín; Olate, Sergio

    2015-07-01

    There are 2 types of distraction devices for mandibular distraction: buried and external. The advantage of buried devices is the stability, but the difficulty in removing the screws is the greatest disadvantage. To resolve this problem, an osteosynthesis screw (Fariña Screw) has been designed, which greatly facilitates its removal when buried distractors are used. PMID:26102540

  9. Bending strength and holding power of a prototype tibial locking screw.

    PubMed

    Lin, Jinn; Hou, Sheng-Mou

    2002-10-01

    To improve mechanical performance, a prototype tibial locking screw with two components was developed for the current study: a both-ends-threaded screw with a smooth shank and a small set screw inserted obliquely through the cap of the both-ends-threaded screw. The bending strength and holding power of this prototype screw were compared with that of five commercially available tibial locking screws: Synthes, Howmedica, Richards, Osteo AG, and Zimmer. To test bending strength, the screws were inserted into a polyethylene tube and loaded at their midpoint to simulate a three-point bending test. Single-loading yielding strength and cyclic-loading fatigue life then were measured. To test holding power, the screws were inserted into polyurethane foam tubes, and stripping torque and pushout strength were measured. The results showed that the yielding strength and the fatigue life were related closely to the inner diameter of the fully threaded screws. The stripping torque reflected the pushout strength, which also was estimated by the formula D[0.5 + 0.57735 (D - d)/2p] (D, outer diameter; d, inner diameter; p, pitch). Even though, among all of the tested screws, the prototype had the smallest outer diameter at its middle, it had the highest fatigue strength, and simultaneously preserved its high bone-holding power. A clinical trial using this prototype screw is warranted, one in which the difficult surgical technique of inserting the set screws should be investigated. PMID:12360032

  10. Posterior cervical spine arthrodesis with laminar screws: a report of two cases.

    PubMed

    Nakanishi, Kazuo; Tanaka, Masato; Sugimoto, Yoshihisa; Ozaki, Toshifumi

    2007-04-01

    We performed fixation using laminar screws in 2 patients in whom lateral mass screws, pedicle screws or transarticular screws could not be inserted. One was a 56-year-old woman who had anterior atlantoaxial subluxation (AAS). When a guide wire was inserted using an imaging guide, the hole bled massively. We thought the re-insertion of a guide wire or screw would thus increase the risk of vascular injury, so we used laminar screws. The other case was an 18-year-old man who had a hangman fracture. Preoperative magnetic resonance angiography showed occlusion of the left vertebral artery. A laminar screw was inserted into the patent side (i.e., the right side of C2). Cervical pedicle screws are the most biomechanically stable screws. However, their use carries a high risk of neurovascular complications during screw insertion, because the cervical pedicle is small and is adjacent laterally to the vertebral artery, medially to the spinal cord, and vertically to the nerve roots. Lateral mass screws are also reported to involve a risk of neurovascular injuries. The laminar screw method was thus thought to be useful, since arterial injuries could thus be avoided and it could also be used as a salvage modality for the previous misinsertion. PMID:17471313

  11. Comparison of pro-inflammatory cytokines and bone metabolism mediators around titanium and zirconia dental implant abutments following a minimum of six months of clinical function

    PubMed Central

    Barwacz, Christopher A.; Brogden, Kim A.; Stanford, Clark M.; Dawson, Deborah V.; Recker, Erica N.; Blanchette, Derek

    2014-01-01

    Objectives Dental implant abutments are fundamental prosthetic components within dentistry that require optimal biocompatibility. The primary aim of this cross-sectional study was to preliminarily assess differences in the pro-inflammatory cytokine and bone metabolism mediator protein expression in the peri-implant crevicular fluid adjacent to transmucosal abutments. Material and Methods Abutments were fabricated from either titanium or zirconia in patients previously receiving single-tooth implant therapy. All subjects sampled in this study had an identical implant system and implant-abutment connection. Participants (n=46) had an average time of clinical function for 22 months (6.2–72.8 months, ±SD 17.0 months) and received a clinical and radiographic exam of the implant site at the time of peri-implant crevicular fluid (PICF) sampling using a paper strip-based sampling technique. Cytokine, chemokine, and bone metabolism mediator quantities (picograms/30 s) were determined using a commercial 22-multiplexed fluorescent bead-based immunoassay instrument. A total of 19 pro-inflammatory cytokines and 7 bone metabolism mediators were evaluated. Results Multivariable analyses provided no evidence of a group (titanium or zirconia), gender, or age effect with regard to the expression of pro-inflammatory mediators evaluated. Significant (p=0.022) differences were observed for the bone-mediator leptin, with titanium abutments demonstrating significantly elevated levels in comparison to zirconia. Osteopontin demonstrated a significant (p=0.0044) correlation with age of the subjects. Conclusions No significant differences in pro-inflammatory cytokine or bone metabolism mediator profiles were observed biochemically, with the exception of leptin, for the abutment biomaterials of titanium or zirconia The molecular PICF findings support the observed clinical biocompatibility of both titanium and zirconia abutments. PMID:24417614

  12. Rotational Stability of Scaphoid Osteosyntheses: An In Vitro Comparison of Small Fragment Cannulated Screws to Novel Bone Screw Sets

    PubMed Central

    Erhart, Jochen; Unger, Ewald; Schefzig, Philip; Varga, Peter; Trulson, Inga; Gormasz, Anna; Trulson, Alexander; Reschl, Martin; Hagmann, Michael; Vecsei, Vilmos; Mayr, Winfried

    2016-01-01

    Background The current standard of care for operative repair of scaphoid fractures involves reduction and internal fixation with a single headless compression screw. However, a compression screw in isolation does not necessarily control rotational stability at a fracture or nonunion site. The single screw provides rotational control through friction and bone interdigitation from compression at the fracture site. We hypothesize that osteosyntheses with novel bone screw sets (BSS) equipped with anti-rotational elements provide improved rotational stability. Methods Stability of osteosynthesis under increasing cyclic torsional loading was investigated on osteotomized cadaveric scaphoids. Two novel prototype BSS, oblique type (BSS-obl.) and longitudinal type (BSS-long.) were compared to three conventional screws: Acutrak2®mini, HCS®3.0 and Twinfix®. Biomechanical tests were performed on scaphoids from single donors in paired comparison and analyzed by balanced incomplete random block design. Loading was increased by 50 mNm increments with 1,000 cycles per torque level and repeated until a rotational clearance of 10°. Primary outcome measure was the number of cycles to 10° clearance, secondary outcome measure was the maximum rotational clearance for each torque level. Findings BSS-obl. performed significantly better than Acutrak2®mini and HCS® (p = 0.015, p<0.0001). BSS-long. performed significantly better than HCS® (p = 0.010). No significant difference in performance between BSS-obl. and BSS-long. (p = 0.361), between BSS obl. and Twinfix® (p = 0.50) and BSS long. and Twinfix® (p = 0.667) was detected. Within the torque range up to 200 mNm, four of 21 (19%) BSS-long. and four of 21 (19%) BSS-obl. preparations showed early failure. The same loading led to early failure in four (29%) Twinfix®, seven (50%) Acutrak2®mini and 10 (71%) HCS® of 14 screw samples, respectively. Conclusions For both BSS and to a lesser extent for Twinfix® (as dual-component screw

  13. Screw fixation of medial malleolar fractures: a cadaveric biomechanical study challenging the current AO philosophy.

    PubMed

    Parker, L; Garlick, N; McCarthy, I; Grechenig, S; Grechenig, W; Smitham, P

    2013-12-01

    The AO Foundation advocates the use of partially threaded lag screws in the fixation of fractures of the medial malleolus. However, their threads often bypass the radiodense physeal scar of the distal tibia, possibly failing to obtain more secure purchase and better compression of the fracture. We therefore hypothesised that the partially threaded screws commonly used to fix a medial malleolar fracture often provide suboptimal compression as a result of bypassing the physeal scar, and proposed that better compression of the fracture may be achieved with shorter partially threaded screws or fully threaded screws whose threads engage the physeal scar. We analysed compression at the fracture site in human cadaver medial malleoli treated with either 30 mm or 45 mm long partially threaded screws or 45 mm fully threaded screws. The median compression at the fracture site achieved with 30 mm partially threaded screws (0.95 kg/cm(2) (interquartile range (IQR) 0.8 to 1.2) and 45 mm fully threaded screws (1.0 kg/cm(2) (IQR 0.7 to 2.8)) was significantly higher than that achieved with 45 mm partially threaded screws (0.6 kg/cm(2) (IQR 0.2 to 0.9)) (p = 0.04 and p < 0.001, respectively). The fully threaded screws and the 30mm partially threaded screws were seen to engage the physeal scar under an image intensifier in each case. The results support the use of 30 mm partially threaded or 45 mm fully threaded screws that engage the physeal scar rather than longer partially threaded screws that do not. A 45 mm fully threaded screw may in practice offer additional benefit over 30 mm partially threaded screws in increasing the thread count in the denser paraphyseal region. PMID:24293597

  14. The inhibitory effect of strontium-doped calcium polyphosphate particles on cytokines from macrophages and osteoblasts leading to aseptic loosening in vitro.

    PubMed

    Huang, Chengcheng; Li, Li; Yu, Xixun; Gu, Zhipeng; Zhang, Xu

    2014-04-01

    Aseptic loosening is a common cause of joint implant failure in humans. In order to enhance implant stability, we need to develop a new material that not only promotes the wear resistance of components of an artificial joint, but also possesses the pharmaceutical efficacy of protecting patients against aseptic loosening. Strontium-doped calcium polyphosphate (SCPP) has been found to have this potential ability. The goal of this study is to respectively quantify the levels of TNF-α (for macrophages), receptor activator of NF-kB ligand (RANKL) and osteoprotegerin (OPG) (for osteoblasts) when osteoblasts and macrophages are challenged with various particles (including SCPP). In this study, the osteoblasts ROS 17/2.8 and macrophages RAW 264.7 were challenged with various wear particles (8% SCPP, the molar percentage of Sr in SCPP is 8%, UHMWPE, hydroxyapatite (HA) and CPP). The secretion of TNF-α (from RAW 264.7), OPG and RANKL protein (from ROS 17/2.8) was analyzed by ELISA. The OPG and RANKL mRNA from ROS 17/2.8 was detected by RT-PCR. The data of ELISA indicated that the amount of TNF-α challenged with 8% SCPP particles was more than three-fold lower than that of all other test groups. The ratio of OPG/RANKL in the 8% SCPP group was significantly increased compared to that of all other test groups. The results of OPG and RANKL mRNA expression showed the same tendency as the ELISA results. In general, this study showed that 8% SCPP particles can inhibit the expression of TNF-α and RANKL, promote the expression of OPG so that SCPP can inhibit bone resorption and promote bone formation, and then inhibit aseptic loosening. Thus SCPP could be a promising material for the construction of artificial joints. PMID:24518283

  15. Covering the screw-access holes of implant restorations in the esthetic zone: a clinical report.

    PubMed

    Saboury, Abolfazl; Gooya, Ali

    2014-11-01

    Screw-retained implant restorations have an advantage of predictable retention as well as retrievability, and obviate the risk of excessive sub-gingival cement commonly associated with cement retained implant restorations. Screw-retained restorations generally have screw access holes, which can compromise esthetics and weaken the porcelain around the holes. The purpose of this study is to describe the use of a separate overcasting crown design to cover the screw access hole of implant screw-retained prosthesis for improved esthetics. PMID:25628703

  16. Covering the Screw-Access Holes of Implant Restorations in the Esthetic Zone: A Clinical Report

    PubMed Central

    Saboury, Abolfazl; Gooya, Ali

    2014-01-01

    Screw-retained implant restorations have an advantage of predictable retention as well as retrievability, and obviate the risk of excessive sub-gingival cement commonly associated with cement retained implant restorations. Screw-retained restorations generally have screw access holes, which can compromise esthetics and weaken the porcelain around the holes. The purpose of this study is to describe the use of a separate overcasting crown design to cover the screw access hole of implant screw-retained prosthesis for improved esthetics. PMID:25628703

  17. Granulation of increasingly hydrophobic formulations using a twin screw granulator.

    PubMed

    Yu, Shen; Reynolds, Gavin K; Huang, Zhenyu; de Matas, Marcel; Salman, Agba D

    2014-11-20

    The application of twin screw granulation in the pharmaceutical industry has generated increasing interest due to its suitability for continuous processing. However, an understanding of the impact of formulation properties such as hydrophobicity on intermediate and finished product quality has not yet been established. Hence, the current work investigated the granulation behaviour of three formulations containing increasing amounts of hydrophobic components using a Consigma™-1 twin screw granulator. Process conditions including powder feed rate, liquid to solid ratio, granulation liquid composition and screw configuration were also evaluated. The size of the wet granules was measured in order to enable exploration of granulation behaviour in isolation without confounding effects from downstream processes such as drying. The experimental observations indicated that the granulation process was not sensitive to the powder feed rate. The hydrophobicity led to heterogeneous liquid distribution and hence a relatively large proportion of un-wetted particles. Increasing numbers of kneading elements led to high shear and prolonged residence time, which acted to enhance the distribution of liquid and feeding materials. The bimodal size distributions considered to be characteristic of twin screw granulation were primarily ascribed to the breakage of relatively large granules by the kneading elements. PMID:25124058

  18. Dynamics of discrete screw dislocations on glide directions

    NASA Astrophysics Data System (ADS)

    Alicandro, R.; De Luca, L.; Garroni, A.; Ponsiglione, M.

    2016-07-01

    We consider a simple discrete model for screw dislocations in crystals. Using a variational discrete scheme we study the motion of a configuration of dislocations toward low energy configurations. We deduce an effective fully overdamped dynamics that follows the maximal dissipation criterion introduced in Cermelli and Gurtin (1999) and predicts motion along the glide directions of the crystal.

  19. INTERIOR VIEW OF JAMES HARRIS CUTTING SCREW THREADS INTO THE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    INTERIOR VIEW OF JAMES HARRIS CUTTING SCREW THREADS INTO THE INTERIOR OF FITTINGS ON ONE IN A BANK OF TAPPING MACHINES, EACH OPERATED BY THE SAME WORKER SIMULTANEOUSLY BUT TIMED TO REQUIRE WORKER ACTION AT INTERVALS THAT DO NOT INTERFERE WITH THE OTHER MACHINES. - Stockham Pipe & Fittings Company, Tapping Room, 4000 Tenth Avenue North, Birmingham, Jefferson County, AL

  20. Some refinements of the theory of the viscous screw pump.

    NASA Technical Reports Server (NTRS)

    Elrod, H. G.

    1972-01-01

    Recently performed analysis for herringbone thrust bearings has been incorporated into the theory of the viscous screw pump for Newtonian fluids. In addition, certain earlier corrections for sidewall and channel curvature effects have been simplified. The result is a single, refined formula for the prediction of the pressure-flow relation for these pumps.