Implant abutment deformation during prosthetic cylinder screw tightening: an in vitro study.

PubMed

Neto, Rafael Tobias Moretti; Moura, Marcio Silva; Souza, Edson Antonio Capello; Rubo, José Henrique

2009-01-01

Nonpassive fit frameworks are believed to lead to implant overload and consequently loss of osseointegration. This is one of the most commonly reported failures of implant prostheses. In an ideal situation of passive fit, when torque is applied to bring the abutment-cylinder interface together some amount of deformation can be expected, and it should be homogeneous along the periphery of the abutment. The aim of this study was to verify the amount of abutment deformation that can be expected when a free-standing cylinder is screwed into place. This could give insight into what should be accepted as passive fit. Strain gauges were bonded to the sides of five standard abutments that had machined palladium-silver cylinders or cobalt-chromium cast cylinders screwed into place. Measurements were taken to verify the deformation at each site. Values of abutment deformation after abutment screw tightening ranged from -127.70 to -590.27 microepsilon. The deformation recorded for palladium-silver prosthetic cylinder tightening ranged from 56.905 to -381.50 microepsilon (mean: 173.298 microepsilon) and from -5.62638 to -383.86 microepsilon (mean: 200.474 microepsilon) for cobalt-chromium cylinders. There was no statistically significant difference among the two groups. Both abutment screw tightening and prosthetic cylinder screw tightening result in abutment deformation, which is compressive most of the time.

Influence of abutment screw preload on stress distribution in marginal bone.

PubMed

Khraisat, Ameen

2012-01-01

Changes in an implant assembly after abutment connection might possibly cause deformation in the implant/abutment joint and even in the marginal bone. The aim of this study was to evaluate the influence of abutment screw preload through the implant collar on marginal bone stress without external load application. Models of three implant parts made of titanium (implant, abutment, and abutment screw) and cortical bone were built and positioned with computer-aided design software. Meshing and generation of boundary conditions, loads, and interactions were performed. Each part was meshed independently. The sole load applied to the model was a torque of 32 Ncm on the abutment screw about its axis of rotation. The implant collar was deformed axially after the screw was tightened (3 μm). This deformation resulted in 60 MPa of stress in the marginal bone. Moreover, pressure on the marginal bone in a radial direction was observed. It can be concluded that, without any external load application, abutment screw preload exerts stresses on the implant collar and the marginal bone. These findings should help guide the development of new implant/abutment joint designs that exert less stress on the marginal bone.

Evaluation of torque maintenance of abutment and cylinder screws with Morse taper implants.

PubMed

Ferreira, Mayara Barbosa; Delben, Juliana Aparecida; Barão, Valentim Adelino Ricardo; Faverani, Leonardo Perez; Dos Santos, Paulo Henrique; Assunção, Wirley Gonçalves

2012-11-01

The screw loosening of implant-supported prostheses is a common mechanical failure and is related to several factors as insertion torque and preload. The aim of this study was to evaluate the torque maintenance of retention screws of tapered abutments and cylinders of Morse taper implants submitted to retightening and detorque measurements. Two groups were obtained (n = 12): group I-tapered abutment connected to the implant with titanium retention screw and group II-cylinder with metallic base connected to tapered abutment with titanium retention screw. The detorque values were measured by an analogic torque gauge after 3 minutes of torque insertion. The detorque was measured 10 times for each retention screw of groups I and II, totalizing 120 detorque measurements in each group. Data were submitted to ANOVA and Fisher exact test (P < 0.05). Both groups presented reduced detorque value (P < 0.05) in comparison to the insertion torque in all measurement periods. There was a statistically significant difference (P < 0.05) between the detorque values of the first measurement and the other measurement periods for the abutment screw. However, there was no statistically significant difference (P > 0.05) for the detorque values of all measurement periods for the cylinder screw. In conclusion, the abutment and cylinder screws exhibited torque loss after insertion, which indicates the need for retightening during function of the implant-supported prostheses.

Influence of repeated screw tightening on bacterial leakage along the implant-abutment interface.

PubMed

do Nascimento, Cássio; Pedrazzi, Vinícius; Miani, Paola Kirsten; Moreira, Larissa Daher; de Albuquerque, Rubens Ferreira

2009-12-01

Bacterial penetration along the implant-abutment interface as a consequence of abutment screw loosening has been reported in a number of recent studies. The aim of this in vitro study was to investigate the influence of repeated tightening of the abutment screw on leakage of Streptococcus mutans along the interface between implants and pre-machined abutments. Twenty pre-machined abutments with a plastic sleeve were used. The abutment screws were tightened to 32 N cm in group 1 (n=10 - control) and to 32 N cm, loosened and re-tightened with the same torque twice in group 2 (n=10). The assemblies were completely immersed in 5 ml of Tryptic Soy Broth medium inoculated with S. mutans and incubated for 14 days. After this period, contamination of the implant internal threaded chamber was evaluated using the DNA Checkerboard method. Microorganisms were found on the internal surfaces of both groups evaluated. However, bacterial counts in group 2 were significantly higher than that in the control group (P<0.05). These results suggest that bacterial leakage between implants and abutments occurs even under unloaded conditions and at a higher intensity when the abutment screw is tightened and loosened repeatedly.

Influence of abutment type and esthetic veneering on preload maintenance of abutment screw of implant-supported crowns.

PubMed

Delben, Juliana Aparecida; Barão, Valentim Adelino Ricardo; Dos Santos, Paulo Henrique; Assunção, Wirley Gonçalves

2014-02-01

The effect of veneering materials on screw joint stability remains inconclusive. Thus, this study evaluated the preload maintenance of abutment screws of single crowns fabricated with different abutments and veneering materials. Sixty crowns were divided into five groups (n = 12): UCLA abutment in gold alloy with ceramic (group GC) and resin (group GR) veneering, UCLA abutment in titanium with ceramic (group TiC) and resin (group TiR) veneering, and zirconia abutment with ceramic veneering (group ZiC). Abutment screws made of gold were used with a 35 Ncm insertion torque. Detorque measurements were obtained initially and after mechanical cycling. Data were analyzed by ANOVA and Fisher's exact test at a significance level of 5%. For the initial detorque means (in Ncm), group TiC (21.4 ± 1.78) exhibited statistically lower torque maintenance than groups GC (23.9 ± 0.91), GR (24.1 ± 1.34), and TiR (23.2 ± 1.33) (p < 0.05, Fisher's exact test). Group ZiC (21.9 ± 2.68) exhibited significantly lower torque maintenance than groups GC, GR, and TiR (p < 0.05, Fisher's exact test). After mechanical cycling, there was a statistically significant difference between groups TiC (22.1 ± 1.86) and GR (23.8 ± 1.56); between groups ZiC (21.7 ± 2.02) and GR; and also between groups ZiC and TiR (23.6 ± 1.30) (p < 0.05, Fisher's exact test). Detorque reduction occurred regardless of abutment type and veneering material. More irregular surfaces in the hexagon area of the castable abutments were observed. The superiority of any veneering material concerning preload maintenance was not established. © 2013 by the American College of Prosthodontists.

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.

Effect of lubricant on the reliability of dental implant abutment screw joint: An in vitro laboratory and three-dimension finite element analysis.

PubMed

Wu, Tingting; Fan, Hongyi; Ma, Ruiyang; Chen, Hongyu; Li, Zhi; Yu, Haiyang

2017-06-01

Biomechanical factors play a key role in the success of dental implants. Fracture and loosening of abutment screws are major issues. This study investigated the effect of lubricants on the stability of dental implant-abutment connection. As lubricants, graphite and vaseline were coated on the abutment screw surface, respectively, and a blank without lubricant served as the control. The total friction coefficient (μ tot ), clamping force, fatigue behavior and detorque of the joint combined with dynamic cyclic loading were measured under different lubricating conditions. Further, a three-dimensional finite element analysis was used to investigate stress distribution, in conjunction with experimental images. The results showed that the lubricant reduced μ tot , which in turn led to an increase in clamping force. Decrease in loading increased the fatigue life of the screw. However, use of lubricant at high load reduced the fatigue life. Ductile fracture at the first thread of the screw was the chief failure mode, which was due to maximum von Mises stress. Higher stress levels occurred in the lubricant groups. Lubricated screws resulted in lower detorque which made the joint easier to loosen. In conclusion, the lubricant cannot effectively improve the reliability of dental implant-abutment connection. Keeping the interfaces of implant-screw uncontaminated and strengthening the surface of the screw may be recommend for clinical operation and future design. Copyright © 2016 Elsevier B.V. All rights reserved.

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

PubMed Central

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

2008-01-01

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

The influence of abutment angulation on screw loosening of implants in the anterior maxilla.

PubMed

Ha, Chun-Yeo; Lim, Yung-Jun; Kim, Myung-Joo; Choi, Jung-Han

2011-01-01

This study compared the removal torque values (RTVs) of different abutments (straight, angled, and gold premachined UCLA-type) in external- and internal-hex implants after dynamic cyclic loading with the clinical situation of the anterior maxilla simulated. An ideal cast of a maxilla with a missing right central incisor was fabricated in dental stone, and an implant analog was embedded in this model at a 15-degree angle labial to the long axis of the left central incisor. Thirty external-hex and 30 internal-hex implants were used. A total of 10 straight abutments, 10 angled abutments, and 10 gold premachined UCLA-type abutments of each system and 60 abutment screws were tested. Initial RTVs were measured after each assembly was tightened to 30 Ncm. Straight abutments and angled abutments were prepared and gold-premachined UCLA-type abutments were waxed and cast with low-fusing gold alloy for the central incisor. RTVs were then measured again. After each assembly was tightened, a metal crown was temporarily cemented. After cyclic loading of 20 to 200 N was applied 1 million times, RTVs were measured for a third time. Statistical analysis (alpha = .05) was performed to evaluate the results. The angled abutment group showed significantly higher RTVs than the straight abutment and gold premachined UCLA-type abutment groups in external-hex implants. However, no significant difference in RTVs was found among abutments in internal-hex implants. The time of analysis of RTV was found to significantly influence mean RTVs. Mean RTVs of external- and internal-hex implants showed significant differences. Within the limitations of this study, there were significant differences in RTVs among different abutment groups in external-hex implants. There were no significant differences in RTVs among different abutment groups in internal-hex implants.

The influence of implant-abutment connection on the screw loosening and microleakage.

PubMed

Tsuruta, Katsuhiro; Ayukawa, Yasunori; Matsuzaki, Tatsuya; Kihara, Masafumi; Koyano, Kiyoshi

2018-04-09

There are some spaces between abutment and implant body which can be a reservoir of toxic substance, and they can penetrate into subgingival space from microgap at the implant-abutment interface. This penetration may cause periimplantitis which is known to be one of the most important factors associated with late failure. In the present study, three kinds of abutment connection system, external parallel connection (EP), internal parallel connection (IP), and internal conical connection (CC), were studied from the viewpoint of microleakage from the gap between the implant and the abutment and in connection with the loosening of abutment screw. We observed dye leakage from abutment screw hole to outside through microgap under the excessive compressive and tensile load and evaluated the anti-leakage characteristics of these connection systems. During the experiment, one abutment screw for EP and two screws for IP, out of seven samples in each group, were fractured. After the 2000 cycles of compressive tensile loadings, removal torque value (RTV) of abutment screw represented no statistical differences among three groups. Standard deviation was largest in the RTV of EP and smallest in that of CC. The results of microleakage of toluidine blue from implant-abutment connection indicated that microleakage generally increased as loading procedure progressed. The amount of microleakage was almost plateau at 2000 cycles in CC, but still increasing in other two groups. The value of microleakage greatly scattered in EP, but the deviation of that in CC is significantly smaller. At 500 cycles of loading, there were no significant differences in the amount of microleakage among the groups, but at 1000, 1500, and 2000 cycles of loading, the amount of microleakage in CC was significantly smaller than that in IP. Throughout the experiment, the amount of microleakage in EP was largest, but no statistical difference was indicated due to the high standard deviation. Within the

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

PubMed

Bozkaya, Dinçer; Müftü, Sinan

2005-01-01

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

Removal torque evaluation of three different abutment screws for single implant restorations after mechanical cyclic loading.

PubMed

Paepoemsin, T; Reichart, P A; Chaijareenont, P; Strietzel, F P; Khongkhunthian, P

2016-01-01

The aim of this study was to evaluate the removal torque of three different abutment screws and pull out strength of implant-abutment connection for single implant restorations after mechanical cyclic loading. The study was performed in accordance with ISO 14801:2007. Three implant groups (n=15) were used: group A, PW Plus® with flat head screw; group B, PW Plus® with tapered screw; and group C, Conelog® with flat head screw. All groups had the same implant-abutment connection feature: cone with mandatory index. All screws were tightened with manufacturer's recommended torque. Ten specimens in each group underwent cyclic loading (1×106 cycles, 10 Hz, and 250 N). Then, all specimens were un-tightened, measured for the removal torque, and underwent a tensile test. The force that dislodged abutment from implant fixture was recorded. The data were analysed using independent sample t-test, ANOVA and Tukey HSD test. Before cyclic loading, removal torque in groups A, B and C were significantly different (B> A> C, P<.05). After cyclic loading, removal torque in all groups decreased significantly (P<.05). Group C revealed significantly less removal torque than groups A and B (P<.005). Tensile force in all groups significantly increased after cyclic loading (P<.05), group A had significantly less tensile force than groups B and C (P<.005). Removal torque reduced significantly after cyclic loading. Before cyclic loading, tapered screws maintained more preload than did flat head screws. After cyclic loading, tapered and flat head screws maintained even amounts of preload. The tensile force that dislodged abutment from implant fixture increased immensely after cyclic loading.

Removal torque evaluation of three different abutment screws for single implant restorations after mechanical cyclic loading

PubMed Central

PAEPOEMSIN, T.; REICHART, P. A.; CHAIJAREENONT, P.; STRIETZEL, F. P.; KHONGKHUNTHIAN, P.

2016-01-01

SUMMARY Purpose The aim of this study was to evaluate the removal torque of three different abutment screws and pull out strength of implant-abutment connection for single implant restorations after mechanical cyclic loading. Methods The study was performed in accordance with ISO 14801:2007. Three implant groups (n=15) were used: group A, PW Plus® with flat head screw; group B, PW Plus® with tapered screw; and group C, Conelog® with flat head screw. All groups had the same implant-abutment connection feature: cone with mandatory index. All screws were tightened with manufacturer’s recommended torque. Ten specimens in each group underwent cyclic loading (1×106 cycles, 10 Hz, and 250 N). Then, all specimens were un-tightened, measured for the removal torque, and underwent a tensile test. The force that dislodged abutment from implant fixture was recorded. The data were analysed using independent sample t-test, ANOVA and Tukey HSD test. Results Before cyclic loading, removal torque in groups A, B and C were significantly different (B> A> C, P<.05). After cyclic loading, removal torque in all groups decreased significantly (P<.05). Group C revealed significantly less removal torque than groups A and B (P<.005). Tensile force in all groups significantly increased after cyclic loading (P<.05), group A had significantly less tensile force than groups B and C (P<.005). Conclusions Removal torque reduced significantly after cyclic loading. Before cyclic loading, tapered screws maintained more preload than did flat head screws. After cyclic loading, tapered and flat head screws maintained even amounts of preload. The tensile force that dislodged abutment from implant fixture increased immensely after cyclic loading. PMID:28042450

Detorque evaluation of dental abutment screws after immersion in a fluoridated artificial saliva solution.

PubMed

Duarte, Antônio R C; Neto, João P Silva; Souza, Júlio C M; Bonachela, Wellington C

2013-06-01

Implant-abutment connections still present failures in the oral cavity due to the loosening of mechanical integrity by detorque and corrosion of the abutment screws. The objective of this study was to evaluate the detorque of dental abutment screws before and after immersion in fluoridated solutions. Five commercial implant-abutment assemblies were assessed in this investigation: (C) Conexão®, (E) Emfils®, (I) INP®, (S) SIN®, and (T) Titanium Fix®. The implants were embedded in an acrylic resin and then placed in a holding device. The abutments were first connected to the implants and torqued to 20 Ncm using a handheld torque meter. The detorque values of the abutments were evaluated after 10 minutes. After applying a second torque of 20 Ncm, implant-abutment assemblies were withdrawn every 3 hours for 12 hours in a fluoridated solution over a period of 90 days. After that period, detorque of the abutments was examined. Scanning electronic microscopy (SEM) associated to energy dispersive spectroscopy (EDS) was applied to inspect the surfaces of abutments. Detorque values of systems C, E, and I immersed in the fluoridated solution were significantly higher than those of the initial detorque. ANOVA demonstrated no significant differences in detorque values between designs S and T. Signs of localized corrosion could not be detected by SEM although chemical analysis by EDS showed the presence of elements involved in corrosive processes. An increase of detorque values recorded on abutments after immersion in fluoridated artificial saliva solutions was noticed in this study. Regarding chemical analysis, such an increase of detorque can result from a corrosion layer formed between metallic surfaces at static contact in the implant-abutment joint during immersion in the fluoridated solutions. © 2012 by the American College of Prosthodontists.

In Vitro Evaluation of Manual Torque Values Applied to Implant-Abutment Complex by Different Clinicians and Abutment Screw Loosening.

PubMed

Dincer Kose, Onur; Karataslı, Burcin; Demircan, Sabit; Kose, Taha Emre; Cene, Erhan; Aya, Serhan Aydın; Erdem, Mehmet Ali; Cankaya, Abdulkadir Burak

2017-01-01

Preload is applied to screws manually or using a torque wrench in dental implant systems, and the preload applied must be appropriate for the purpose. The aim of this study was to assess screw loosening and bending/torsional moments applied by clinicians of various specialties following application of manual tightening torque to combinations of implants and abutments. Ten-millimeter implants of 3.7 and 4.1 mm diameters and standard or solid abutments were used. Each group contained five implant-abutment combinations. The control and experimental groups comprised 20 and 160 specimens, respectively. Implants in the experimental group were tightened by dentists of different specialties. Torsional and bending moments during tightening were measured using a strain gauge. Control group and implants with preload values close to the ideal preload were subjected to a dynamic loading test at 150 N, 15 Hz, and 85,000 cycles. The implants that deformed in this test were examined using an optical microscope to assess deformities. Manual tightening did not yield the manufacturer-recommended preload values. Dynamic loading testing suggested early screw loosening/fracture in samples with insufficient preload.

In Vitro Evaluation of Manual Torque Values Applied to Implant-Abutment Complex by Different Clinicians and Abutment Screw Loosening

PubMed Central

Demircan, Sabit; Cene, Erhan; Aya, Serhan Aydın; Erdem, Mehmet Ali; Cankaya, Abdulkadir Burak

2017-01-01

Preload is applied to screws manually or using a torque wrench in dental implant systems, and the preload applied must be appropriate for the purpose. The aim of this study was to assess screw loosening and bending/torsional moments applied by clinicians of various specialties following application of manual tightening torque to combinations of implants and abutments. Ten-millimeter implants of 3.7 and 4.1 mm diameters and standard or solid abutments were used. Each group contained five implant-abutment combinations. The control and experimental groups comprised 20 and 160 specimens, respectively. Implants in the experimental group were tightened by dentists of different specialties. Torsional and bending moments during tightening were measured using a strain gauge. Control group and implants with preload values close to the ideal preload were subjected to a dynamic loading test at 150 N, 15 Hz, and 85,000 cycles. The implants that deformed in this test were examined using an optical microscope to assess deformities. Manual tightening did not yield the manufacturer-recommended preload values. Dynamic loading testing suggested early screw loosening/fracture in samples with insufficient preload. PMID:28473988

In vitro evaluation of reverse torque value of abutment screw and marginal opening in a screw- and cement-retained implant fixed partial denture design.

PubMed

Kim, Seok-Gyu; Park, Jae-Uk; Jeong, Jae-Heon; Bae, Chang; Bae, Tae-Soo; Chee, Winston

2009-01-01

The purpose of this study was to evaluate the clinical efficacy of implant prostheses retained by screws and cement (SCPs) by examining the reverse torque values (RTVs) of the abutment screws and the marginal openings of the implant prostheses. Two implants (3.8 x 13 mm; Camlog Biotechnologies) were embedded in an acrylic resin block 5 mm apart. Eighteen copies of this resin specimen were fabricated and randomly divided into two groups. Two-unit implant prostheses with two different designs-purely cement-retained implant prostheses (group 1) and SCPs (group 2)-were made out of type IV gold alloy and placed on the implants. After tightening to about 30 Ncm, the preloading RTVs of the abutment screws were measured. After retightening the abutment screws or cementing the prostheses, followed by cyclic loading, the postloading RTVs of the abutment screws were examined. Also, the marginal openings of the prostheses in the two groups were measured under a stereomicroscope. These measurements were compared statistically. The postloading RTVs and their differences from the preloading RTVs of the abutment screws demonstrated no significant differences between groups (P > .05). Group 2 prostheses showed significantly smaller marginal openings than group 1 prostheses (P < .05). The forces generated when torquing the abutment screw of the SCP did not cause more loosening of the abutment screws than the purely cement-retained implant prosthesis. The SCP showed better marginal adaptation of the cement-retained part than the purely cement-retained implant prosthesis, possibly as a result of the screw-retained abutment seating the restoration. Within the limitations of this in vitro test, the SCP showed no significant difference in RTV of the abutment screw and a smaller marginal gap compared to a purely cement-retained implant prosthesis.

The effect of 3 torque delivery systems on gold screw preload at the gold cylinder-abutment screw joint.

PubMed

Tan, Keson B; Nicholls, Jack I

2002-01-01

This study measured the gold screw preload at the gold cylinder-abutment screw joint interface obtained by 3 torque delivery systems. Using a precalibrated, strain-gauged standard abutment as the load cell, 3 torque delivery systems tested were shown to have significant differences in gold screw preload when a gold cylinder was attached. Mean preloads measured were 291.2 N for hand torque drivers set at 10 Ncm, 340.3 N for electronic torque controllers at low setting/10 Ncm, 384.4 N for electronic torque controllers at high setting/10 Ncm; and 140.8 N for hand-tightening with a prosthetic slot screwdriver. Significant differences in screw preload were also found between operators using a hand torque driver. Hand-tightening delivered insufficient preload and cannot be recommended for final gold screw tightening. Different electronic torque controller units set at 10 Ncm induced mean gold screw preloads that ranged from 264.1 N to as high as 501.2 N. Electronic torque controllers should be regularly recalibrated to ensure optimal output.

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

PubMed

García-Roncero, Herminio; Caballé-Serrano, Jordi; Cano-Batalla, Jordi; Cabratosa-Termes, Josep; Figueras-Álvarez, Oscar

2015-04-01

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. 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%. 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. Prototypes 2, 5 and 6 may offer a useful protective mechanism during occlusal overload in immediate loaded implants.

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

Abutments with reduced diameter for both cement and screw retentions: analysis of failure modes and misfit of abutment-crown-connections after cyclic loading.

PubMed

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

2017-04-01

The aim of this study was to analyze failure modes and misfit of abutments with reduced diameter for both cement and screw retentions after cyclic loading. Forty morse-taper abutment/implant sets of titanium were divided into four groups (N = 10): G4.8S-4.8 abutment with screw-retained crown; G4.8C-4.8 abutment with cemented crown; G3.8S-3.8 abutment with screw-retained crown; and G3.8C-3.8 abutment with cemented crown. Copings were waxed on castable cylinders and cast by oxygen gas flame and injected by centrifugation. After, esthetic veneering ceramic was pressed on these copings for obtaining metalloceramic crowns of upper canine. Cemented crowns were cemented on abutments with provisional cement (Temp Bond NE), and screw-retained crowns were tightened to their abutments with torque recommended by manufacturer (10 N cm). The misfit was measured using a stereomicroscope in a 10× magnification before and after cyclic loading (300,000 cycles). Tests were visually monitored, and failures (decementation, screw loosening and fractures) were registered. Misfit was analyzed by mixed linear model while failure modes by chi-square test (α = 0.05). Cyclic loading affected misfit of 3.8C (P ≤ 0.0001), 3.8S (P = 0.0055) and 4.8C (P = 0.0318), but not of 4.8S (P = 0.1243). No differences were noted between 3.8S with 4.8S before (P = 0.1550) and after (P = 0.9861) cyclic loading, but 3.8C was different from 4.8C only after (P = 0.0015) loading. Comparing different types of retentions at the same diameter abutment, significant difference was noted before and after cyclic loading for 3.8 and 4.8 abutments. Analyzing failure modes, retrievable failures were present at 3.8S and 3.8C groups, while irretrievable were only present at 3.8S. The cyclic loading decreased misfit of cemented and screw-retained crowns on reduced diameter abutments, and misfit of cemented crowns is greater than screw-retained ones. Abutments of reduced diameter failed more than

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

PubMed

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

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

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

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

PubMed

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

2017-01-01

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

Immediate prosthesis over implants retained using abutments with flexible screws: A preliminary study

PubMed Central

Peñarrocha-Oltra, David; Serra-Pastor, Blanca; Balaguer-Martí, José-Carlos; Agustín-Panadero, Rubén

2017-01-01

Background Immediate loading protocols for the rehabilitation of edentulous or partially edentulous patients have become very popular, due to the conveniences they afford in comparison with conventional loading techniques. Material and Methods A preliminary study was carried out with 8 patients subjected to dental implant treatment with an immediate loading protocol involving a novel system of abutments with flexible screws. Implant survival was analyzed, together with marginal bone loss and patient and dentist satisfaction. Results A total of 35 implants were subjected to immediate loading using the abutments with flexible screws. The mean patient and dentist satisfaction score was 9.1 and 8.5, respectively. After 12 months the dental implant survival rate was 95.8%, with a mean marginal bone loss of 0.51 ± 0.12 mm. Conclusions The novel system of abutments with flexible screws offers a good alternative to conventional immediate loading, since it allows rapid and simple manufacture of a reliable passive fit, fixed interim prosthesis after surgery. Key words:Dental implants, Flexafit®, Immediate loading, Immediate prosthesis. PMID:29410752

Immediate prosthesis over implants retained using abutments with flexible screws: A preliminary study.

PubMed

Peñarrocha-Oltra, David; Serra-Pastor, Blanca; Balaguer-Martí, José-Carlos; Peñarrocha-Diago, Miguel; Agustín-Panadero, Rubén

2017-12-01

Immediate loading protocols for the rehabilitation of edentulous or partially edentulous patients have become very popular, due to the conveniences they afford in comparison with conventional loading techniques. A preliminary study was carried out with 8 patients subjected to dental implant treatment with an immediate loading protocol involving a novel system of abutments with flexible screws. Implant survival was analyzed, together with marginal bone loss and patient and dentist satisfaction. A total of 35 implants were subjected to immediate loading using the abutments with flexible screws. The mean patient and dentist satisfaction score was 9.1 and 8.5, respectively. After 12 months the dental implant survival rate was 95.8%, with a mean marginal bone loss of 0.51 ± 0.12 mm. The novel system of abutments with flexible screws offers a good alternative to conventional immediate loading, since it allows rapid and simple manufacture of a reliable passive fit, fixed interim prosthesis after surgery. Key words: Dental implants, Flexafit®, Immediate loading, Immediate prosthesis.

Stress distribution pattern of screw-retained restorations with segmented vs. non-segmented abutments: A finite element analysis

PubMed Central

Aalaei, Shima; Rajabi Naraki, Zahra; Nematollahi, Fatemeh; Beyabanaki, Elaheh; Shahrokhi Rad, Afsaneh

2017-01-01

Background. Screw-retained restorations are favored in some clinical situations such as limited inter-occlusal spaces. This study was designed to compare stresses developed in the peri-implant bone in two different types of screw-retained restorations (segmented vs. non-segmented abutment) using a finite element model. Methods. An implant, 4.1 mm in diameter and 10 mm in length, was placed in the first molar site of a mandibular model with 1 mm of cortical bone on the buccal and lingual sides. Segmented and non-segmented screw abutments with their crowns were placed on the simulated implant in each model. After loading (100 N, axial and 45° non-axial), von Mises stress was recorded using ANSYS software, version 12.0.1. Results. The maximum stresses in the non-segmented abutment screw were less than those of segmented abutment (87 vs. 100, and 375 vs. 430 MPa under axial and non-axial loading, respectively). The maximum stresses in the peri-implant bone for the model with segmented abutment were less than those of non-segmented ones (21 vs. 24 MPa, and 31 vs. 126 MPa under vertical and angular loading, respectively). In addition, the micro-strain of peri-implant bone for the segmented abutment restoration was less than that of non-segmented abutment. Conclusion. Under axial and non-axial loadings, non-segmented abutment showed less stress concentration in the screw, while there was less stress and strain in the peri-implant bone in the segmented abutment. PMID:29184629

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

PubMed

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

2008-09-01

Screw loosening is a problem for a percentage of implants. A probabilistic analysis to determine the cumulative probability distribution of the preload, the probability of obtaining an optimal preload, and the probabilistic sensitivities identifying important variables is lacking. The purpose of this study was to examine the inherent variability of material properties, surface interactions, and applied torque in an implant system to determine the probability of obtaining desired preload values and to identify the significant variables that affect the preload. Using software programs, an abutment screw was subjected to a tightening torque and the preload was determined from finite element (FE) analysis. The FE model was integrated with probabilistic analysis software. Two probabilistic analysis methods (advanced mean value and Monte Carlo sampling) were applied to determine the cumulative distribution function (CDF) of preload. The coefficient of friction, elastic moduli, Poisson's ratios, and applied torque were modeled as random variables and defined by probability distributions. Separate probability distributions were determined for the coefficient of friction in well-lubricated and dry environments. The probabilistic analyses were performed and the cumulative distribution of preload was determined for each environment. A distinct difference was seen between the preload probability distributions generated in a dry environment (normal distribution, mean (SD): 347 (61.9) N) compared to a well-lubricated environment (normal distribution, mean (SD): 616 (92.2) N). The probability of obtaining a preload value within the target range was approximately 54% for the well-lubricated environment and only 0.02% for the dry environment. The preload is predominately affected by the applied torque and coefficient of friction between the screw threads and implant bore at lower and middle values of the preload CDF, and by the applied torque and the elastic modulus of the abutment

Heat generation during removal of an abutment screw fragment from dental implants.

PubMed

Arias, Sergio R; Rueggeberg, Frederick A; Mettenburg, Donald; Sharawy, Mohamed; Looney, Stephen; Elsayed, Ranya; Elsalanty, Mohammed E

2018-04-01

Little information is available on the effect of drilling speed on surrounding bone during the removal of an abutment screw fragment. The purpose of this in vitro study was to compare, in vitro, the peak temperature increase during the removal of fractured abutment screws from implants placed in a porcine mandible, using drilling speeds of 600 or 2000 rpm. Twenty 4.3×13-mm dental implants were placed in 10 dissected porcine mandibles: 2 implants per mandible, 1 on each side. Localized defects were created in 20 surface-treated abutment screws, which were then tightened into each implant until a reproducible fracture occurred in each screw. The fractured screws were removed with a handpiece removal kit and irrigated with room-temperature water at either 600 or 2000 rpm. The temperature rise at the implant surface was measured at 3 levels with 3 type-K thermocouples. Repeated measure ANOVA was performed with the Tukey-Kramer post hoc test for mean pair-wise comparisons (α=.05 for all tests). Mean peak temperatures were significantly higher at 2000 rpm than at 600 rpm in the mid-body (P<.001) and crestal (P=.003) regions but not in the apical (P=.225) implant locations. No significant differences in mean peak temperatures were found among the 3 locations using 600 rpm (P=.179). In the 2000-rpm group, mean peak temperature in the mid-body area was consistently higher than that in the apical (P<.001) area, and more instances of temperature rise above 56°C and 60°C were observed. In 1 implant from this group, the estimated peak temperature exceeded the bone damage threshold value (50°C for 30 seconds). A drilling speed of 2000 rpm during the removal of abutment screw fragments caused overheating of the outer surface of the implant which may damage the surrounding bone; a speed of 600 rpm appears to be safe. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Experimental conical-head abutment screws on the microbial leakage through the implant-abutment interface: an in vitro analysis using target-specific DNA probes.

PubMed

Pita, Murillo S; do Nascimento, Cássio; Dos Santos, Carla G P; Pires, Isabela M; Pedrazzi, Vinícius

2017-07-01

The aim of this in vitro study was to identify and quantify up to 38 microbial species from human saliva penetrating through the implant-abutment interface in two different implant connections, external hexagon and tri-channel internal connection, both with conventional flat-head or experimental conical-head abutment screws. Forty-eight two-part implants with external hexagon (EH; n = 24) or tri-channel internal (TI; n = 24) connections were investigated. Abutments were attached to implants with conventional flat-head or experimental conical-head screws. After saliva incubation, Checkerboard DNA-DNA hybridization was used to identify and quantify up to 38 bacterial colonizing the internal parts of the implants. Kruskal-Wallis test followed by Bonferroni's post-tests for multiple comparisons was used for statistical analysis. Twenty-four of thirty-eight species, including putative periodontal pathogens, were found colonizing the inner surfaces of both EH and TI implants. Peptostreptococcus anaerobios (P = 0.003), Prevotella melaninogenica (P < 0.0001), and Candida dubliniensis (P < 0.0001) presented significant differences between different groups. Means of total microbial count (×10 4 , ±SD) for each group were recorded as follows: G1 (0.27 ± 2.04), G2 (0 ± 0), G3 (1.81 ± 7.50), and G4 (0.35 ± 1.81). Differences in the geometry of implant connections and abutment screws have impacted the microbial leakage through the implant-abutment interface. Implants attached with experimental conical-head abutment screws showed lower counts of microorganisms when compared with conventional flat-head screws. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

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.

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

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

PubMed

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

2014-04-01

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

Effect of modifying the screw access channels of zirconia implant abutment on the cement flow pattern and retention of zirconia restorations.

PubMed

Wadhwani, Chandur; Chung, Kwok-Hung

2014-07-01

The effect of managing the screw access channels of zirconia implant abutments in the esthetic zone has not been extensively evaluated. The purpose of this study was to determine the effect of an insert placed within the screw access channel of an anterior zirconia implant abutment on the amount of cement retained within the restoration-abutment system and on the dislodging force. Thirty-six paired zirconia abutments and restorations were fabricated by computer-aided design and computer-aided manufacturing and were divided into 3 groups: open abutment, with the screw access channel unfilled; closed abutment, with the screw access channel sealed; and insert abutment, with a thin, tubular metal insert projection continuous with the screw head and placed into the abutment screw access channel. The restorations were cemented to the abutments with preweighed eugenol-free zinc oxide cement (TempBond NE). Excess cement was removed, and the weight of the cement that remained in the restoration-abutment system was measured. Vertical tensile dislodging forces were recorded at a crosshead speed of 5 mm/min after incubation in a 37°C water bath for 24 hours. The specimens were examined for the cement flow pattern into the screw access channel after dislodgement. Data were analyzed with ANOVA, followed by multiple comparisons by using the Tukey honestly significant difference test (α = .05). The mean (standard deviation) of retentive force values ranged from 108.1 ± 29.9 N to 148.3 ± 21.0 N. The retentive force values differed significantly between the insert abutment and both the open abutment (P < .05) and closed abutment groups (P < .01). Distinct patterns of cement failure were noted. The weight of the cement that remained in the system differed significantly, with both open abutment and insert abutment being greater than closed abutment (P < .05). Modifying the internal configuration of the screw access channel of an esthetic zirconia implant abutment with a metal

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

PubMed

Smith, Nicole A; Turkyilmaz, Ilser

2014-09-01

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

[Dynamic analysis of the rigid fixed bridge and related tissue after intrusion of abutment with micro screw implant].

PubMed

Zhu, Lin; Xu, Pei-cheng; Lu, Liu-lei

2013-08-01

To study the variety of mechanical behavior of fixed bridge after abutments being intruded by micro screw implant and to provide theoretical principles for clinical practice of teeth preparation after intrusion of abutments under dynamic loads. Two-dimensional images of maxilla, teeth and supporting tissues of healthy people were scanned by spiral CT and were synthesized by Mimics10.01, Ansys13.0, etc. The three-dimensional finite element mathematical model of rigid fixed bridge repairing on double end of maxillary molar was developed. Under the condition of 10% simulative abutment alveolar absorption, vertical and oblique dynamic forces were applied in a circle of mastication(0.875 s) to build mathematical model after the abutment had been intruded for 0.5, 1.0, 1.5 and 2.0 mm. Stress variety of prosthesis, teeth, periodontal ligaments and supporting tissues were compared before and after intrusion of abutments. Stress variety of the prosthesis occurred, which had close relationship with the structure of prosthesis and teeth, the areas of periodontal ligaments increased, stress on the whole decreased along with the increase of the length of intrusion. With time accumulating, the stress value in prosthesis, teeth, periodontal ligaments and supporting tissues increased gradually and loads in oblique direction induced peak value stress in a masticatory cycle. Some residual stress left after unloading. By preparing the fixed bridge after abutment intrusion by micro screw implant, the service life of abutment and fixed bridge prosthesis can be reduced. The abutment and its related tissue have time-dependent mechanical behaviors during one mastication. The influence of oblique force on stress was greater than vertical force. There is some residual stress left after one mastication period. With the increase of the intrusion on abutment, residual stress reduced.

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

PubMed

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

2016-02-01

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. 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. 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). 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.

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

Dynamic nature of abutment screw retightening: finite element study of the effect of retightening on the settling effect.

PubMed

Bulaqi, Haddad Arabi; Mousavi Mashhadi, Mahmoud; Safari, Hamed; Samandari, Mohammad Mahdi; Geramipanah, Farideh

2015-05-01

A fundamental problem in fully understanding the dynamic nature of screw loosening is lack of recognition of the entire process of screw tightening and retightening. The purpose of this study was to explain the dynamic nature of abutment screw retightening by using finite element methods to investigate the effect of the coefficient of friction and retightening on the settling effect. Precise computer models were designed of a Straumann dental implant, a directly attached crown, an abutment screw, and the bone surrounding the implant. All threaded interfaces were designed with a spiral thread helix with a specific coefficient of static and kinetic friction, and the surfaces were characterized as fine, regular, and rough. Abaqus software was used for dynamic simulation, which involved applying rotational displacement to the abutment screw and torque controlling during the steps of tightening, relaxation, retightening, and second relaxation and at different coefficients of friction. The obtained torque and preload values were compared to the predicted values. When surfaces changed from fine to rough, the remaining torque and preload decreased, and the settling effect increased. Upon retightening, the remaining torque and preload increased, and the settling effect also decreased. The reduction of the coefficient of friction contributes to increases in the preload and decreases in the settling effect. Retightening reduced the settling effect and had an insignificant effect on the preload. At high coefficients of friction, the retightening effect was intensified. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

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

PubMed

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

2017-04-01

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

Critical bending moment of implant-abutment screw joint interfaces: effect of torque levels and implant diameter.

PubMed

Tan, Ban Fui; Tan, Keson B; Nicholls, Jack I

2004-01-01

Critical bending moment (CBM), the moment at which the external nonaxial load applied overcomes screw joint preload and causes loss of contact between the mating surfaces of the implant screw joint components, was measured with 2 types of implants and 2 types of abutments. Using 4 test groups of 5 implant-abutment pairs, CBM at the implant-abutment screw joint was measured at 25%, 50%, 75%, and 100% of the manufacturer's recommended torque levels. Regular Platform (RP) Nobel Biocare implants (3.75 mm diameter), Wide Platform (WP) Nobel Biocare implants (5.0 mm diameter), CeraOne abutments, and Multiunit abutments were used. Microstrain was measured as loads were applied to the abutment at various distances from the implant-abutment interface. Strain instrumentation logged the strain data dynamically to determine the point of gap opening. All torque applications and strain measurements were repeated 5 times. For the CeraOne-RP group, the mean CBMs were 17.09 Ncm, 35.35 Ncm, 45.63 Ncm, and 62.64 Ncm at 25%, 50%, 75%, and 100% of the recommended torque level, respectively. For the CeraOne-WP group, mean CBMs were 28.29 Ncm, 62.97 Ncm, 92.20 Ncm, and 127.41 Ncm; for the Multiunit-RP group, 16.08 Ncm, 21.55 Ncm, 34.12 Ncm, and 39.46 Ncm; and for the Multiunit-WP group, 15.90 Ncm, 32.86 Ncm, 43.29 Ncm, and 61.55 Ncm at the 4 different torque levels. Two-way analysis of variance (ANOVA) (P < .001) revealed significant effects for the test groups (F = 2738.2) and torque levels (F = 2969.0). The methodology developed in this study allows confirmation of the gap opening of the screw joint for the test groups and determination of CBM at different torque levels. CBM was found to differ among abutment systems, implant diameters, and torque levels. The torque levels recommended by the manufacturer should followed to ensure screw joint integrity.

Bacterial adhesion on commercially pure titanium and anatase-coated titanium healing screws: an in vivo human study.

PubMed

Scarano, Antonio; Piattelli, Adriano; Polimeni, Antonella; Di Iorio, Donato; Carinci, Francesco

2010-10-01

Little is known about the mechanisms of bacterial interaction with implant materials in the oral cavity. Other surface characteristics, in addition to surface roughness, seem to be extremely important in relation to plaque formation. Different adhesion affinities of bacteria were reported for different materials. Anatase is a nanoparticle that can be applied to titanium surfaces as a coating. The anatase coating gives special characteristics to the implant surface, including some genetic effects on osteoblasts. In this study, the antibacterial effect of anatase is investigated. The aim of this study is to characterize the percentages of surfaces covered by bacteria on commercially pure (cp) titanium and anatase-coated healing screws. Ten patients participated in this study. The protocol of the study was approved by the ethics committee of the University of Chieti-Pescara. A total of 20 healing screws (10 test and 10 control screws) were used in the study. The control screws were made of cp titanium, whereas the test screws were coated with anatase. Cleaning procedures and agents for chemical plaque control were not applied to the healing screws for the complete duration of the test period. After 7 days, all healing screws were removed, substituted, and processed under scanning electron microscopy for evaluation of the portions of the surfaces covered by bacteria. The supracrestal screw surfaces covered by bacteria on test specimens were not significantly lower than those of control screws (P = 0.174). The subcrestal screw surfaces and threads covered by bacteria on test specimens were significantly lower than those of control screws, and P values were 0.001 and 0.000, respectively. Results show that anatase could be a suitable material for coating implant abutments, with a low colonization potential.

An Indirect Method to Measure Abutment Screw Preload: A Pilot Study Based on Micro-CT Scanning.

PubMed

Rezende, Carlos Eduardo E; Griggs, Jason Alan; Duan, Yuanyuan; Mushashe, Amanda M; Nolasco, Gisele Maria Correr; Borges, Ana Flávia Sanches; Rubo, José Henrique

2015-01-01

This study aimed to measure the preload in different implant platform geometries based on micro-CT images. External hexagon (EH) implants and Morse Tapered (MT) implants (n=5) were used for the preload measurement. The abutment screws were scanned in micro-CT to obtain their virtual models, which were used to record their initial length. The abutments were screwed on the implant with a 20 Ncm torque and the set composed by implant, abutment screw and abutment were taken to the micro-CT scanner to obtain virtual slices of the specimens. These slices allowed the measurement of screw lengths after torque application and based on the screw elongation. Preload values were calculated using the Hooke's Law. The preloads of both groups were compared by independent t-test. Removal torque of each specimen was recorded. To evaluate the accuracy of the micro-CT technique, three rods with known lengths were scanned and the length of their virtual model was measured and compared with the original length. One rod was scanned four times to evaluate the measuring method variation. There was no difference between groups for preload (EH = 461.6 N and MT = 477.4 N), but the EH group showed higher removal torque values (13.8 ± 4.7 against 8.2 ± 3.6 N cm for MT group). The micro-CT technique showed a variability of 0.053% and repeatability showed an error of 0.23 to 0.28%. Within the limitations of this study, there was no difference between external hexagon and Morse taper for preload. The method using micro-CT may be considered for preload calculation.

The effects of loading on the preload and dimensions of the abutment screw for a 3-unit cantilever-fixed prosthesis design.

PubMed

Setia, Gaurav; Yousef, Hoda; Ehrenberg, David; Luke, Allyn; Weiner, Saul

2013-08-01

The purpose of this study was to use an in vitro model system to compare the effects on the screw torque and screw dimensions within 2 commercially available implant systems from occlusal loading on a cantilevered-fixed partial denture. Cantilevered implant-supported 3-unit prostheses with 2 premolar abutments and 1 premolar pontic (7.3 mm in length) were made on resin casts containing 2 implant analogs for 2 implant systems: BioLok Silhouette Tapered Implant System (Birmingham, AL) and Zimmer Tapered Screw-Vent Implant System (Carlsbad, CA) with 10 samples in each group. Each sample was loaded with either of 2 protocols: (1) a load of 50 N on the cantilevered pontic unit and (2) a loading of 150 N on all 3 units. The outcome measures were (1) changes in residual torque of the abutment screws and (2) changes in screw dimension. The BioLok Silhouette Tapered Implant group demonstrated slight but statistically significant torque loss 18.8% to 28.5% in both abutment screws for both protocols, P ≤ 0.05, without any changes in screw dimension. In the Zimmer Tapered Screw-Vent Implant group, there was a significant elongation of the abutment screws and a markedly significant 44.4%, (P ≤ 0.01) loss in torque in the mesial screw and a 28.5%, (P ≤ 0.05) loss in torque in the distal screw when the cantilever alone was loaded. Differences in screw design influence the maintenance of preload and distortion of the shank. The influence of the interface design, namely an internal hex of 1 mm versus an external hex did not influence the preload. Cantilevered prostheses can cause loss of torque and dimensional changes in abutment screws.

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

PubMed

Al-Otaibi, Hanan N

2016-11-01

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

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

PubMed

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

2009-01-01

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

Can the Hydroxyapatite-Coated Skin-Penetrating Abutment for Bone Conduction Hearing Implants Integrate with the Surrounding Skin?

PubMed

van Hoof, Marc; Wigren, Stina; Duimel, Hans; Savelkoul, Paul H M; Flynn, Mark; Stokroos, Robert Jan

2015-01-01

Percutaneous implants, such as bone conduction hearing implants, suffer from complications that include inflammation of the surrounding skin. A sealed skin-abutment interface can prevent the ingress of bacteria, which should reduce the occurrence of peri-abutment dermatitis. It was hypothesized that a hydroxyapatite (HA)-coated abutment in conjunction with soft tissue preservation surgery should enable integration with the adjacent skin. Previous research has confirmed that integration is never achieved with as-machined titanium abutments. Here, we investigate, in vivo, if skin integration is achievable in patients using a HA-coated abutment. One titanium abutment (control) and one HA-coated abutment (case) together with the surrounding skin were surgically retrieved from two patients who had a medical indication for this procedure. Histological sections of the skin were investigated using light microscopy. The abutment was qualitatively analyzed using scanning electron microscopy. The titanium abutment only had a partial and thin layer of attached amorphous biological material. The HA-coated abutment was almost fully covered by a pronounced thick layer of organized skin, composed of different interconnected structural layers. Proof-of-principle evidence that the HA-coated abutment can achieve integration with the surrounding skin was presented for the first time.

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

PubMed

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

2006-01-01

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

Effect of the Coronal Wall Thickness of Dental Implants on the Screw Joint Stability in the Internal Implant-Abutment Connection.

PubMed

Lee, Ji-Hye; Huh, Yoon-Hyuk; Park, Chan-Jin; Cho, Lee-Ra

2016-01-01

To evaluate the effect of implant coronal wall thickness on load-bearing capacity and screw joint stability. Experimental implants were customized after investigation of the thinnest coronal wall thickness of commercially available implant systems with a regular platform diameter. Implants with four coronal wall thicknesses (0.2, 0.3, 0.4, and 0.5 mm) were fabricated. Three sets of tests were performed. The first set was a failure test to evaluate load-bearing capacity and elastic limit. The second and third sets were cyclic and static loading tests. After abutment screw tightening of each implant, vertical cyclic loading of 250 N or static loading from 250 to 800 N was applied. Coronal diameter expansion, axial displacement, and removal torque values of the implants were compared. Repeated measures analysis of variance (ANOVA) was used for statistical analysis (α = .05). Implants with 0.2-mm coronal wall thickness demonstrated significantly low load-bearing capacity and elastic limit (both P < .05). These implants also showed significantly large coronal diameter expansion and axial displacement after screw tightening (both P < .05). Greater vertical load and thinner coronal wall thickness significantly increased coronal diameter expansion of the implant, axial displacement of the abutment, and removal torque loss of the abutment screw (all P < .05). Implant coronal wall thickness of 0.2 mm produces significantly inferior load-bearing capacity and screw joint stability.

Evaluation of Titanium-Coated Pedicle Screws: In Vivo Porcine Lumbar Spine Model.

PubMed

Kim, Do-Yeon; Kim, Jung-Ryul; Jang, Kyu Yun; Kim, Min Gu; Lee, Kwang-Bok

2016-07-01

Many studies have addressed the problem of loosening pedicle screws in spinal surgery, which is a serious concern. Titanium coating of medical implants (arthroplasty) is common, but few studies involving in vivo spine models have been reported. We evaluated the radiological, mechanical, and histological characteristics of titanium-coated pedicle screws compared with uncoated or hydroxyapatite-coated pedicle screws. Three different types of pedicle screws, i.e., uncoated, hydroxyapatite-coated, and titanium-coated, were implanted into the lumbar 3-4-5 levels of 9 mature miniature pigs. Radiological evaluation of loosening of pedicle screws was performed. Peak torsional extraction torque was tested in the 42 screws from 7 miniature pigs at 12 weeks postoperatively. The implant-bone interface of the remaining 12 pedicle screws from 2 miniature pigs in each group was assessed by micro-computed tomography and histologic studies. The incidence of loosening at 12 weeks postoperatively was not significantly different between the titanium-coated pedicle screw group and the other groups. The titanium-coated pedicle screw group exhibited the greatest mean extraction torsional peak torque at 12 weeks postoperatively (P < 0.05). Quantitative micro-computed tomography data were greatest in the titanium-coated pedicle screw group (P < 0.05). Histologic findings showed osteointegration with densely packed new bone formation at the screw coating-bone interface in the titanium-coated pedicle screw group. Fixation strength was greatest in the titanium-coated pedicle screw group. Osteointegration at the interface between the titanium-coated implant and bone produced prominent and firm bonding. The titanium-coated pedicle screw is a promising device for application in spinal surgery. Copyright © 2016 Elsevier Inc. All rights reserved.

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

PubMed

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

2014-12-01

This study evaluated the influence of abutment materials on the stability of the implant-abutment joint in internal conical connection type implant systems. 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. 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). 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.

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

Scanning Electron Microscopy Analysis of the Adaptation of Single-Unit Screw-Retained Computer-Aided Design/Computer-Aided Manufacture Abutments After Mechanical Cycling.

PubMed

Markarian, Roberto Adrian; Galles, Deborah Pedroso; Gomes França, Fabiana Mantovani

To measure the microgap between dental implants and custom abutments fabricated using different computer-aided design/computer-aided manufacture (CAD/CAM) methods before and after mechanical cycling. CAD software (Dental System, 3Shape) was used to design a custom abutment for a single-unit, screw-retained crown compatible with a 4.1-mm external hexagon dental implant. The resulting stereolithography file was sent for manufacturing using four CAD/CAM methods (n = 40): milling and sintering of zirconium dioxide (ZO group), cobalt-chromium (Co-Cr) sintered via selective laser melting (SLM group), fully sintered machined Co-Cr alloy (MM group), and machined and sintered agglutinated Co-Cr alloy powder (AM group). Prefabricated titanium abutments (TI group) were used as controls. Each abutment was placed on a dental implant measuring 4.1× 11 mm (SA411, SIN) inserted into an aluminum block. Measurements were taken using scanning electron microscopy (SEM) (×4,000) on four regions of the implant-abutment interface (IAI) and at a relative distance of 90 degrees from each other. The specimens were mechanically aged (1 million cycles, 2 Hz, 100 N, 37°C) and the IAI width was measured again using the same approach. Data were analyzed using two-way analysis of variance, followed by the Tukey test. After mechanical cycling, the best adaptation results were obtained from the TI (2.29 ± 1.13 μm), AM (3.58 ± 1.80 μm), and MM (1.89 ± 0.98 μm) groups. A significantly worse adaptation outcome was observed for the SLM (18.40 ± 20.78 μm) and ZO (10.42 ± 0.80 μm) groups. Mechanical cycling had a marked effect only on the AM specimens, which significantly increased the microgap at the IAI. Custom abutments fabricated using fully sintered machined Co-Cr alloy and machined and sintered agglutinated Co-Cr alloy powder demonstrated the best adaptation results at the IAI, similar to those obtained with commercial prefabricated titanium abutments after mechanical cycling. The

Diamondlike carbon coating as a galvanic corrosion barrier between dental implant abutments and nickel-chromium superstructures.

PubMed

Ozkomur, Ahmet; Erbil, Mehmet; Akova, Tolga

2013-01-01

The objectives of this study were to evaluate the galvanic corrosion behavior between titanium and nickel-chromium (Ni-Cr) alloy, to investigate the effect of diamondlike carbon (DLC) coating over titanium on galvanic corrosion behavior between titanium and Ni-Cr alloy, and to evaluate the effect of DLC coating over titanium abutments on the fit and integrity of prosthetic assemblies by scanning electron microcopy (SEM). Five Ni-Cr and 10 titanium disks with a diameter of 5 mm and thickness of 3 mm were prepared. DLC coating was applied to five titanium disks. Electrode samples were prepared, and open circuit potential measurements, galvanic current measurements over platinum electrodes, and potentiodynamic polarization tests were carried out. For the SEM evaluation, 20 Ni-Cr alloy and 10 gold alloy superstructures were cast and prepared over 30 abutments. DLC coating was applied to 10 of the abutments. Following the fixation of prosthetic assemblies, the samples were embedded in acrylic resin and cross sectioned longitudinally. Internal fit evaluations were carried out through examination of the SEM images. Titanium showed more noble and electrochemically stable properties than Ni-Cr alloy. DLC coating over the cathode electrode served as an insulating film layer over the surface and prevented galvanic coupling. Results of the SEM evaluations indicated that the DLC-coated and titanium abutments showed no statistically significant difference in fit. Hence, no adverse effects on the adaptation of prosthetic components were found with the application of DLC coating over abutment surfaces. DLC coating might serve as a galvanic corrosion barrier between titanium abutments and Ni-Cr superstructures.

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

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

PubMed

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

2011-05-01

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

Preload evaluation of different screws in external hexagon joint.

PubMed

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

2012-02-01

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

Analysis of plastic deformation in cortical bone after insertion of coated and non-coated self-tapping orthopaedic screws.

PubMed

Koistinen, A P; Korhonen, H; Kiviranta, I; Kröger, H; Lappalainen, R

2011-07-01

Insertion of internal fracture fixation devices, such as screws, mechanically weakens the bone. Diamond-like carbon has outstanding tribology properties which may decrease the amount of damage in tissue. The purpose of this study was to investigate methods for quantification of cortical bone damage after orthopaedic bone screw insertion and to evaluate the effect of surface modification on tissue damage. In total, 48 stainless steel screws were inserted into cadaver bones. Half of the screws were coated with a smooth amorphous diamond coating. Geometrical data of the bones was determined by peripheral quantitative computed tomography. Thin sections of the bone samples were prepared after screw insertion, and histomorphometric evaluation of damage was performed on images obtained using light microscopy. Micro-computed tomography and scanning electron microscopy were also used to examine tissue damage. A positive correlation was found between tissue damage and the geometric properties of the bone. The age of the cadaver significantly affected the bone mineral density, as well as the damage perimeter and diameter of the screw hole. However, the expected positive effect of surface modification was probably obscured by large variations in the results and, thus, statistically significant differences were not found in this study. This can be explained by natural variability in bone tissue, which also made automated image analysis difficult.

Influence of space size of abutment screw access channel on the amount of extruded excess cement and marginal accuracy of cement-retained single implant restorations.

PubMed

Al Amri, Mohammad D; Al-Johany, Sulieman S; Al-Qarni, Mohammed N; Al-Bakri, Ahmed S; Al-Maflehi, Nassr S; Abualsaud, Haythem S

2018-02-01

The detrimental effect of extruded excess cement on peri-implant tissue has been well documented. Although several techniques have been proposed to reduce this effect by decreasing the amount of extruded cement, how the space size of the abutment screw access channel (SAC) affects the amount of extruded cement and marginal accuracy is unclear. The purpose of this in vitro study was to evaluate the effect of the size of the unfilled space of the abutment SAC on the amount of extruded excess cement and the marginal accuracy of zirconia copings. Twelve implant replicas and corresponding standard abutments were attached and embedded in acrylic resin blocks. Computer-aided design and computer-aided manufacturing (CAD-CAM) zirconia copings with a uniform 30-μm cement space were fabricated by 1 dental technician using the standard method. The copings were temporarily cemented 3 times at different sizes of the left space of the SAC as follows: the nonspaced group (NS), in which the entire SAC was completely filled, the 1-mm-spaced group (1MMS), and the 2-mm-spaced group (2MMS). Abutments and crowns were ultrasonically cleaned, steam cleaned, and air-dried. The excess cement was collected and weighed. To measure the marginal accuracy, 20 measurements were made every 18 degrees along the coping margin at ×300 magnification and compared with the pre-cementation readings. One-way ANOVA was calculated to determine whether the amount of extruded excess cement differed among the 3 groups, and the Tukey test was applied for multiple comparisons (α=.05). The mean weights (mg) of extruded excess cement were NS (33.53 ±1.5), 1MMS (22.97 ±5.4), and 2MMS (15.17 ±5.9). Multiple comparisons showed significant differences in the amount of extruded excess cement among the 3 test groups (P<.001). The mean marginal discrepancy (μm) of the pre-cemented group (29.5 ±8.2) was significantly different (P<.01) from that of the NS (72.3 ±13.7), the 1MMS (70.1 ±19), and the 2MMS group

Clinical Performance of One-Piece, Screw-Retained Implant Crowns Based on Hand-Veneered CAD/CAM Zirconia Abutments After a Mean Follow-up Period of 2.3 Years.

PubMed

Schnider, Nicole; Forrer, Fiona Alena; Brägger, Urs; Hicklin, Stefan Paul

The aim of this study was to evaluate the clinical performance of one-piece, screw-retained implant crowns based on hand-veneered computer-aided design/computer-aided manufacture (CAD/CAM) zirconium dioxide abutments with a crossfit connection at least 1 year after insertion of the crown. Consecutive patients who had received at least one Straumann bone level implant and one-piece, screw-retained implant crowns fabricated with CARES zirconium dioxide abutments were reexamined. Patient satisfaction, occlusal and peri-implant parameters, mechanical and biologic complications, radiologic parameters, and esthetics were recorded. A total of 50 implant crowns in the anterior and premolar region were examined in 41 patients. The follow-up period of the definitive reconstructions ranged from 1.1 to 3.8 years. No technical and no biologic complications had occurred. At the reexamination, 100% of the implants and reconstructions were in situ. Radiographic evaluation revealed a mean distance from the implant shoulder to the first visible bone-to-implant contact of 0.06 mm at the follow-up examination. Screw-retained crowns based on veneered CAD/CAM zirconium dioxide abutments with a crossfit connection seem to be a promising way to replace missing teeth in the anterior and premolar region. In the short term, neither failures of components nor complications were noted, and the clinical and radiographic data revealed stable hard and soft tissue conditions.

Radiological, histological, and hematological evaluation of hydroxyapatite-coated resorbable magnesium alloy screws placed in rabbit tibia.

PubMed

Lim, Ho-Kyung; Byun, Soo-Hwan; Lee, Jin-Yong; Lee, Jung-Woo; Kim, Sae-Mi; Lee, Sung-Mi; Kim, Hyoun-Ee; Lee, Jong-Ho

2017-08-01

Titanium (Ti) screw has excellent mechanical property, and osseointegration capacity. However, they require surgery for removal. In contrast, polymer screws are resorbable, but they have poor mechanical properties. In this research, magnesium alloy screws (WE43: Mg-Y-Nd-Zr) that have advantages of titanium and polymer were manufactured. In addition, to increase biocompatibility and control degradation rate, the Mg alloy was coated with hydroxyapatite (HA). Torsion test and corrosion test were performed in vitro. For clinical, radiological and histological evaluation, on the eight rabbits, two HA-coated screws were installed in left tibia, and two noncoated screws were installed in right tibia. Each four rabbits were sacrificed 6 and 12 weeks postoperatively. For hematological evaluation, the same type of screws were installed on both legs. Complete blood count (CBC), Mg 2+ concentrate were sampled from the ear central artery on the operation day for a control point, and at 1, 2, 4, 6, 8, and 12 weeks. Mg alloy screws have no differences of biocompatibility according to the HA coating. However, resorption of screw was slower in case of the HA coating. The hematological problem related releasing of Mg was not found. The results suggest that Mg alloy screws have feasibility for clinical application. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1636-1644, 2017. © 2016 Wiley Periodicals, Inc.

Wear resistance of thick diamond like carbon coatings against polymeric materials used in single screw plasticizing technology

NASA Astrophysics Data System (ADS)

Zitzenbacher, G.; Liu, K.; Forsich, C.; Heim, D.

2015-05-01

Wear on the screw and barrel surface accompany polymer single screw plasticizing technology from the beginning. In general, wear on screws can be reduced by using nitrided steel surfaces, fused armour alloys on the screw flights and coatings. However, DLC-coatings (Diamond Like Carbon) comprise a number of interesting properties such as a high hardness, a low coefficient of friction and an excellent corrosion resistance due to their amorphous structure. The wear resistance of about 50 µm thick DLC-coatings against polyamide 6.6, polybutylene terephthalate and polypropylene is investigated in this paper. The tribology in the solids conveying zone of a single screw extruder until the beginning of melting is evaluated using a pin on disc tribometer and a so called screw tribometer. The polymeric pins are pressed against coated metal samples using the pin on disc tribometer and the tests are carried out at a defined normal force and sliding velocity. The screw tribometer is used to perform tribological experiments between polymer pellets and rotating coated metal shafts simulating the extruder screw. Long term experiments were performed to evaluate the wear resistance of the DLC-coating. A reduction of the coefficient of friction can be observed after a frictional distance of about 20 kilometers using glass fibre reinforced polymeric materials. This reduction is independent on the polymer and accompanied by a black layer on the wear surface of the polymeric pins. The DLC-coated metal samples show an up to 16 µm deep wear track after the 100 kilometer test period against the glass fiber filled materials only.

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

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

PubMed

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

2002-12-01

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

Loss of preload in screwed implant joints as a function of time and tightening/untightening sequences.

PubMed

Bernardes, Sérgio Rocha; da Gloria Chiarello de Mattos, Maria; Hobkirk, John; Ribeiro, Ricardo Faria

2014-01-01

The purpose of this study was to determine whether abutment screw tightening and untightening influenced loss of preload in three different implant/abutment interfaces, or on the implant body. Five custom-fabricated machined titanium implants were used, each with its respective abutment, with different connection types, retention screws, and torque values (external hexagon with titanium screw/32 Ncm, external hexagon with coated screw/32 Ncm, internal hexagon/20 Ncm and internal conical/20 and 32 Ncm). Each implant tested had two strain gauges attached and was submitted to five tightening/untightening sequences. External hexagons resulted in the lowest preload values generated in the implant cervical third (mean of 27.75 N), while the internal hexagon had the highest values (mean of 219.61 N). There was no immediate significant loss of preload after screw tightening. Tightening/untightening sequences, regardless of the implant/abutment interface design or type of screw used in the study, did not result in any significant loss of initial preload. Conical implant connections demonstrated greater structural reinforcement within the internal connections.

Influence of Diamondlike Carbon Coating of Screws on Axial Tightening Force and Stress Distribution on Overdenture Bar Frameworks with Different Fit Levels and Materials.

PubMed

dos Santos, Mateus Bertolini Fernandes; Bacchi, Atais; Consani, Rafael Leonardo Xediek; Correr-Sobrinho, Lourenço

2015-01-01

The aim of this study was to evaluate the axial tightening force applied by conventional and diamondlike carbon (DLC)-coated screws and to verify, through three-dimensional finite element analysis (FEA), the stress distribution caused by different framework materials and prosthetic screws in overdenture frameworks with different misfit levels. The axial tightening force applied by the screw was evaluated by means of a titanium matrix connected to a load cell. Conventional titanium or DLC-coated screws were tightened with a digital torque wrench, and the load values were recorded. The values were applied in an FEA to a bar-clip attachment system connected to two 4.0 × 11-mm external-hexagon titanium implants placed in an anterior edentulous arch. DLC-coated and conventional screws were modeled with their respective axial forces obtained on the experimental evaluation for three bar framework materials (titanium, nickel-chromium, and cobalt-chromium) and three levels of misfit (100, 150, and 200 μm). Von Mises stresses for prosthetic components and maximum principal stress and microstrains (maximum principal strains) for bone tissue were measured. The mean force applied by the conventional screw was 25.55 N (± 1.78); the prosthetic screw coated with a DLC layer applied a mean force of 31.44 N (± 2.11), a statistically significant difference. In the FEA, the DLC screw led to higher stresses on the framework; however, the prosthetic screw suffered lower stress. No influence of screw type was seen in the bone tissue. Titanium frameworks reduced the stress transmitted to the bone tissue and the bar framework but had no influence on the screws. Higher misfit values resulted in an increased stress/strain in bone tissue and bar framework, which was not the case for retention screws.

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

PubMed

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

2016-04-01

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

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

PubMed

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

2015-01-01

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

Stability of Uncemented Cups - Long-Term Effect of Screws, Pegs and HA Coating: A 14-Year RSA Follow-Up of Total Hip Arthroplasty.

PubMed

Otten, Volker T C; Crnalic, Sead; Röhrl, Stephan M; Nivbrant, Bo; Nilsson, Kjell G

2016-01-01

Screws, pegs and hydroxyapatite-coating are used to enhance the primary stability of uncemented cups. We present a 14-year follow-up of 48 hips randomized to four groups: press-fit only, press-fit plus screws, press-fit plus pegs and hydroxyapatite-coated cups. Radiostereometric migration measurements showed equally good stability regardless cup augmentation. The mean wear rate was high, 0.21 mm/year, with no differences between the groups. Seven hips had radiographical osteolysis but only in hips with augmented cups. Cups without screw-holes compared with cups with screw-holes resulted in better clinical outcome at the 14-year follow-up. Thus, augmentation of uncemented cups with screws, pegs, or hydroxyapatite did not appear to improve the long-term stability compared with press-fit only. Copyright © 2016 Elsevier Inc. All rights reserved.

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. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

The Influence of Torque Tightening on the Position Stability of the Abutment in Conical Implant-Abutment Connections.

PubMed

Hogg, Wiebke Semper; Zulauf, Kris; Mehrhof, Jürgen; Nelson, Katja

2015-01-01

The influence of repeated system-specific torque tightening on the position stability of the abutment after de- and reassembly of the implant components was evaluated in six dental implant systems with a conical implant-abutment connection. An established experimental setup was used in this study. Rotation, vertical displacement, and canting moments of the abutment were observed; they depended on the implant system (P = .001, P < .001, P = .006, respectively). Repeated torque tightening of the abutment screw does not eliminate changes in position of the abutment.

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.

Does Ferrule Effect Affect Implant-Abutment Stability?

PubMed

Mohajerfar, Maryam; Beyabanaki, Elaheh; Geramy, Allahyar; Siadat, Hakimeh; Alikhasi, Marzieh

2016-12-01

This study investigated the influence of placing implant-supported crowns on the torque loss of the abutment screw before and after loading. Twenty implant-abutment assemblies were randomly assigned to two groups. The first group was consisted of abutments with abutment-level finishing line (abutment-level), and in the second group the crown margin was placed on the implant shoulder (implant-level). Initial torque loss was recorded for all specimens. After 500000 cyclic load of 75 N and frequency of 2 Hz, post loading torque loss was recorded. Finite element model of each group was also modeled and screw energy, and stress were analyzed and compared between two groups. ANOVA for repeated measurements showed that the torque loss did not change significantly after cyclic loading (P=0.73). Crown margin also had no significant effect on the torque loss (P=0.56). However, the energy and stress of screw in abutment-level model (4.49 mJ and 22.74 MPa) was higher than implant-level model (3.52 mJ and 20.81 MPa). Although embracing the implant with crown produced less stress and energy in the abutment-implant screw, it did not have any significant influence on the torque loss of the screw. Copyright© 2016 Dennis Barber Ltd

Effect of zirconium nitride physical vapor deposition coating on preosteoblast cell adhesion and proliferation onto titanium screws.

PubMed

Rizzi, Manuela; Gatti, Giorgio; Migliario, Mario; Marchese, Leonardo; Rocchetti, Vincenzo; Renò, Filippo

2014-11-01

Titanium has long been used to produce dental implants. Problems related to its manufacturing, casting, welding, and ceramic application for dental prostheses still limit its use, which highlights the need for technologic improvements. The aim of this in vitro study was to evaluate the biologic performance of titanium dental implants coated with zirconium nitride in a murine preosteoblast cellular model. The purpose of this study was to evaluate the chemical and morphologic characteristics of titanium implants coated with zirconium nitride by means of physical vapor deposition. Chemical and morphologic characterizations were performed by scanning electron microscopy and energy dispersive x-ray spectroscopy, and the bioactivity of the implants was evaluated by cell-counting experiments. Scanning electron microscopy and energy dispersive x-ray spectroscopy analysis found that physical vapor deposition was effective in covering titanium surfaces with zirconium nitride. Murine MC-3T3 preosteoblasts were seeded onto titanium-coated and zirconium nitride-coated screws to evaluate their adhesion and proliferation. These experiments found a significantly higher number of cells adhering and spreading onto zirconium nitride-coated surfaces (P<.05) after 24 hours; after 7 days, both titanium and zirconium nitride surfaces were completely covered with MC-3T3 cells. Analysis of these data indicates that the proposed zirconium nitride coating of titanium implants could make the surface of the titanium more bioactive than uncoated titanium surfaces. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Evaluation of stability of interface between CCM (Co-Cr-Mo) UCLA abutment and external hex implant.

PubMed

Yoon, Ki-Joon; Park, Young-Bum; Choi, Hyunmin; Cho, Youngsung; Lee, Jae-Hoon; Lee, Keun-Woo

2016-12-01

The purpose of this study is to evaluate the stability of interface between Co-Cr-Mo (CCM) UCLA abutment and external hex implant. Sixteen external hex implant fixtures were assigned to two groups (CCM and Gold group) and were embedded in molds using clear acrylic resin. Screw-retained prostheses were constructed using CCM UCLA abutment and Gold UCLA abutment. The external implant fixture and screw-retained prostheses were connected using abutment screws. After the abutments were tightened to 30 Ncm torque, 5 kg thermocyclic functional loading was applied by chewing simulator. A target of 1.0 × 10 6 cycles was applied. After cyclic loading, removal torque values were recorded using a driving torque tester, and the interface between implant fixture and abutment was evaluated by scanning electronic microscope (SEM). The means and standard deviations (SD) between the CCM and Gold groups were analyzed with independent t-test at the significance level of 0.05. Fractures of crowns, abutments, abutment screws, and fixtures and loosening of abutment screws were not observed after thermocyclic loading. There were no statistically significant differences at the recorded removal torque values between CCM and Gold groups ( P >.05). SEM analysis revealed that remarkable wear patterns were observed at the abutment interface only for Gold UCLA abutments. Those patterns were not observed for other specimens. Within the limit of this study, CCM UCLA abutment has no statistically significant difference in the stability of interface with external hex implant, compared with Gold UCLA abutment.

Loss of mechanical properties in vivo and bone-implant interface strength of AZ31B magnesium alloy screws with Si-containing coating.

PubMed

Tan, Lili; Wang, Qiang; Lin, Xiao; Wan, Peng; Zhang, Guangdao; Zhang, Qiang; Yang, Ke

2014-05-01

In this study the loss of mechanical properties and the interface strength of coated AZ31B magnesium alloy (a magnesium-aluminum alloy) screws with surrounding host tissues were investigated and compared with non-coated AZ31B, degradable polymer and biostable titanium alloy screws in a rabbit animal model after 1, 4, 12 and 21weeks of implantation. The interface strength was evaluated in terms of the extraction torque required to back out the screws. The loss of mechanical properties over time was indicated by one-point bending load loss of the screws after these were extracted at different times. AZ31B samples with a silicon-containing coating had a decreased degradation rate and improved biological properties. The extraction torque of Ti6Al4V, poly-l-lactide (PLLA) and coated AZ31B increased significantly from 1week to 4weeks post-implantation, indicating a rapid osteosynthesis process over 3weeks. The extraction torque of coated AZ31B increased with implantation time, and was higher than that of PLLA after 4weeks of implantation, equalling that of Ti6Al4V at 12weeks and was higher at 21weeks. The bending loads of non-coated AZ31B and PLLA screws degraded sharply after implantation, and that of coated AZ31B degraded more slowly. The biodegradation mechanism, the coating to control the degradation rate and the bioactivity of magnesium alloys influencing the mechanical properties loss over time and bone-implant interface strength are discussed in this study and it is concluded that a suitable degradation rate will result in an improvement in the mechanical performance of magnesium alloys, making them more suitable for clinical application. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

SEM and fractography analysis of screw thread loosening in dental implants.

PubMed

Scarano, A; Quaranta, M; Traini, T; Piattelli, M; Piattelli, A

2007-01-01

Biological and technical failures of implants have already been reported. Mechanical factors are certainly of importance in implant failures, even if their exact nature has not yet been established. The abutment screw fracture or loosening represents a rare, but quite unpleasant failure. The aim of the present research is an analysis and structural examination of screw thread or abutment loosening compared with screw threads or abutment without loosening. The loosening of screw threads was compared to screw thread without loosening of three different implant systems; Branemark (Nobel Biocare, Gothenburg, Sweden), T.B.R. implant systems (Benax, Ancona, Italy) and Restore (Lifecore Biomedical, Chaska, Minnesota, USA). In this study broken screws were excluded. A total of 16 screw thread loosenings were observed (Group I) (4 Branemark, 4 T.B.R and 5 Restore), 10 screw threads without loosening were removed (Group II), and 6 screw threads as received by the manufacturer (unused) (Group III) were used as control (2 Branemark, 2 T.B.R and 2 Restore). The loosened abutment screws were retrieved and analyzed under SEM. Many alterations and deformations were present in concavities and convexities of screw threads in group I. No macroscopic alterations or deformations were observed in groups II and III. A statistical difference of the presence of microcracks were observed between screw threads with an abutment loosening and screw threads without an abutment loosening.

Reliability and Failure Modes of a Hybrid Ceramic Abutment Prototype.

PubMed

Silva, Nelson Rfa; Teixeira, Hellen S; Silveira, Lucas M; Bonfante, Estevam A; Coelho, Paulo G; Thompson, Van P

2018-01-01

A ceramic and metal abutment prototype was fatigue tested to determine the probability of survival at various loads. Lithium disilicate CAD-milled abutments (n = 24) were cemented to titanium sleeve inserts and then screw attached to titanium fixtures. The assembly was then embedded at a 30° angle in polymethylmethacrylate. Each (n = 24) was restored with a resin-cemented machined lithium disilicate all-ceramic central incisor crown. Single load (lingual-incisal contact) to failure was determined for three specimens. Fatigue testing (n = 21) was conducted employing the step-stress method with lingual mouth motion loading. Failures were recorded, and reliability calculations were performed using proprietary software. Probability Weibull curves were calculated with 90% confidence bounds. Fracture modes were classified with a stereomicroscope, and representative samples imaged with scanning electron microscopy. Fatigue results indicated that the limiting factor in the current design is the fatigue strength of the abutment screw, where screw fracture often leads to failure of the abutment metal sleeve and/or cracking in the implant fixture. Reliability for completion of a mission at 200 N load for 50K cycles was 0.38 (0.52% to 0.25 90% CI) and for 100K cycles was only 0.12 (0.26 to 0.05)-only 12% predicted to survive. These results are similar to those from previous studies on metal to metal abutment/fixture systems where screw failure is a limitation. No ceramic crown or ceramic abutment initiated fractures occurred, supporting the research hypothesis. The limiting factor in performance was the screw failure in the metal-to-metal connection between the prototyped abutment and the fixture, indicating that this configuration should function clinically with no abutment ceramic complications. The combined ceramic with titanium sleeve abutment prototype performance was limited by the fatigue degradation of the abutment screw. In fatigue, no ceramic crown or ceramic

In vitro and in vivo corrosion, mechanical properties and biocompatibility evaluation of MgF2-coated Mg-Zn-Zr alloy as cancellous screws.

PubMed

Li, Zhen; Shizhao, Sun; Chen, Minfang; Fahlman, Bradley Dean; Debao Liu; Bi, Hongwei

2017-06-01

Magnesium (Mg) and its alloys as biodegradable materials have received much attention in the orthopedics applications; however, the corrosion behavior of these metals in vivo remains challenging. In this work, a dense and nanoscale magnesium fluoride (MgF 2 ) coating was deposited on the surface of Mg-Zn-Zr (MZZ) alloy cancellous screw. The MZZ cancellous screw with MgF 2 coating maintained an integrated shape and high yield tensile stress after 30days immersion in SBF, comparing with the bare screw. Hydrogen releasing rate of the MZZ samples was suppressed at a lower level at the initial stage, which is in favour of the adhesion of the cells. And in vivo experiments indicated that MgF 2 -coated MZZ screws presented advantages in cytocompatibility, osteoconductivity and osteogenesis of cancellous bone in rabbits. Corrosion rate in vivo perfusion environment increased very slowly with time in long-term study, which was an opposite trend in vitro static immersion test. Moreover, maximum corrosion rate (CR max ), a critical calculation method of corrosion rate was introduced to predict fracture regions of the sample. The MZZ alloy with MgF 2 coating possesses a great potential for clinical applications for internal fracture fixation repair. Copyright © 2017 Elsevier B.V. All rights reserved.

Sinking and fit of abutment of locking taper implant system

PubMed Central

Moon, Seung-Jin; Kim, Hee-Jung; Son, Mee-Kyoung

2009-01-01

STATEMENT OF PROBLEM Unlike screw-retention type, fixture-abutment retention in Locking taper connection depends on frictional force so it has possibility of abutment to sink. PURPOSE In this study, Bicon® Implant System, one of the conical internal connection implant system, was used with applying loading force to the abutments connected to the fixture. Then the amount of sinking was measured. MATERIAL AND METHODS 10 Bicon® implant fixtures were used. First, the abutment was connected to the fixture with finger force. Then it was tapped with a mallet for 3 times and loads of 20 kg corresponding to masticatory force using loading application instrument were applied successively. The abutment state, slightly connected to the fixture without pressure was considered as a reference length, and every new abutment length was measured after each load's step was added. The amount of abutment sinking (mm) was gained by subtracting the length of abutment-fixture under each loading condition from reference length. RESULTS It was evident, that the amount of abutment sinking in Bicon® Implant System increased as loads were added. When loads of 20 kg were applied more than 5 - 7 times, sinking stopped at 0.45 ± 0.09 mm. CONCLUSION Even though locking taper connection type implant shows good adaption to occlusal force, it has potential for abutment sinking as loads are given. When locking taper connection type implant is used, satisfactory loads are recommended for precise abutment location. PMID:21165262

Surface characteristics of clinically used dental implant screws

NASA Astrophysics Data System (ADS)

Han, Myung-Ju; Choe, Han-Cheol; Chung, Chae-Heon

2005-12-01

Surface alteration of implant screws after function may be associated with mechanicalffailure. This type of metal fatigue appears to be the most common cause of structural failure. The purpose of this study was to evaluate surface alteration of implant screws after function through an examination of used and unused implant screws via scanning electron microscopy (SEM). In this study, abutment screws (Steri-oss, 3i, USA), gold retaining screws (3i, USA), and titanium retaining screws (3i, USA) were retrieved from patients, New, unused abutment, and retaining screws were prepared for a control group. Each of the old, used screws was retrieved with a screwdriver. The retrieved implant complex of a Steri-oss system was also prepared for this study. SEM investigation and energy dispersive spectroscopy (EDS) analysis of the abutment and retaining screws were then performed, as well as SEM investigation of a cross-sectioned sample of the retrieved implant complex in the case of new, unused implant screws, as-manufactured circumferential grooves were regularly examined and screw threads were sharply maintained. Before ultrasonic cleansing of old, used implant screws, there was a large amount of debris accumulation and corrosion products. After ultrasonic cleansing of old, used implant screws, circumferential grooves were examined were found to be randomly deepened and scratching increased. Also, dull screw fhreads were observed. More surface alterations after function were observed in titanium screws than in gold screws. Furthermore, more surface alteration was observed when the screws were retrieved with a driver than without a driver. These surface alterations after function may result in screw instability. Regular cleansing and exchange of screws is therefore recommended. We also recommend the use of gold screws over titanium screws, and careful manipulation of the driver.

FEA and microstructure characterization of a one-piece Y-TZP abutment.

PubMed

da Silva, Lucas Hian; Ribeiro, Sebastião; Borges, Alexandre Luís Souto; Cesar, Paulo Francisco; Tango, Rubens Nisie

2014-11-01

The most important drawback of dental implant/abutment assemblies is the need for a fixing screw. This study aimed to develop an esthetic one-piece Y-TZP abutment to suppress the use of the screw. Material characterization was performed using a bar-shaped specimen obtained by slip-casting to validate the method prior to prototype abutment fabrication by the same process. The mechanical behavior of the prototype abutment was verified and compared with a conventional abutment by finite element analysis (FEA). The abutment was evaluated by micro-CT analysis and its density was measured. FEA showed stress concentration at the first thread pitch during installation and in the cervical region during oblique loading for both abutments. However, stress concentration was observed at the base of the screw head and stem in the conventional abutment. The relative density for the fabricated abutment was 95.68%. Micro-CT analysis revealed the presence of elongated cracks with sharp edges over the surface and porosity in the central region. In the light of these findings, the behavior of a one-piece abutment is expected to be better than that of the conventional model. New studies should be conducted to clarify the performance and longevity of this one-piece Y-TZP abutment. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Critical bending moment of four implant-abutment interface designs.

PubMed

Lee, Frank K; Tan, Keson B; Nicholls, Jack I

2010-01-01

Critical bending moment (CBM), defined as the bending moment at which the external nonaxial load applied overcomes screw joint preload and causes loss of contact between the mating surfaces of the implant screw joint components, was measured for four different implants and their single-tooth replacement abutments. CBM at the implant-abutment screw joint for four implant-abutment test groups was measured in vitro at 80%, 100%, and 120% of the manufacturers' recommended torque levels. Regular-platform implants with their corresponding single-tooth abutments were used. Microstrain was measured while known loads were applied to the abutment at known distances from the implant-abutment interface. Strain instrumentation was used to record the strain data dynamically to determine the point of gap opening. All torque applications and strain measurements were repeated five times for the five samples in each group. For the Branemark/CeraOne assemblies, the mean CBMs were 72.14 Ncm, 102.21 Ncm, and 119.13 Ncm, respectively, at 80%, 100%, and 120% of the manufacturer's recommended torque. For the Replace/Easy assemblies, mean CBMs were 86.20 Ncm, 109.92 Ncm, and 120.93 Ncm; for the Biomet 3i/STA assemblies, they were 67.97 Ncm, 83.14 Ncm, and 91.81 Ncm; and for the Lifecore/COC assemblies, they were 58.32 Ncm, 76.79 Ncm, and 78.93 Ncm. Two-way analysis of variance revealed significant effects for the test groups and torque levels. Subsequent tests confirmed that significant differences existed between test groups and torque levels. The results appear to confirm the primary role of the compressive preload imparted by the abutment screw in maintaining screw joint integrity. CBM was found to differ among implant systems and torque levels. Torque levels recommended by the manufacturer should be followed to ensure screw joint integrity.

Comparative Evaluation of Fracture Resistance and Mode of Failure of Zirconia and Titanium Abutments with Different Diameters.

PubMed

Shabanpour, Reza; Mousavi, Niloufar; Ghodsi, Safoura; Alikhasi, Marzieh

2015-08-01

The purpose of the current study was to compare the fracture resistance and mode of failure of zirconia and titanium abutments with different diameters. Fourteen groups of abutments including prefabricated zirconia, copy-milled zirconia and titanium abutments of an implant system (XiVE, Dentsply) were prepared in different diameters. An increasing vertical load was applied to each specimen until failure occurred. Fracture resistance was measured in each group using the universal testing machine. Moreover, the failure modes were studied and categorized as abutment screw fracture, connection area fracture, abutment body fracture, abutment body distortion, screw distortion and connection area distortion. Groups were statistically compared using univariate and post-hoc tests. The level of statistical significance was set at 5%. Fabrication method (p = 0.03) and diameter (p < 0.001) had significant effect on the fracture resistance of abutments. Fracture resistance of abutments with 5.5 mm diameter was higher than other diameters (p < 0.001). The observed modes of failure were dependent on the abutment material as well. All of the prefabricated titanium abutments fractured within the abutment screw. Abutment screw distortion, connection area fracture, and abutment body fracture were the common failure type in other groups. Diameter had a significant effect on fracture resistance of implant abutments, as abutments with greater diameters were more resistant to static loads. Copy-milled abutments showed lower fracture resistance as compared to other experimental groups. Although zirconia abutments have received great popularity among clinicians and even patients selecting them for narrow implants should be with caution.

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.

Implant-abutment connections on single crowns: a systematic review.

PubMed

Ceruso, F M; Barnaba, P; Mazzoleni, S; Ottria, L; Gargari, M; Zuccon, A; Bruno, G; DI Fiore, A

2017-01-01

Different implant-abutment connections have been developed in the effort of reducing mechanical and biological failure. The most frequent complications are screw loosening, abutment or implant fracture and marginal bone loss due to overload and bacterial micro-leakage. Ideal connection should work as a one-piece implant avoiding the formation of a micro-gap at the implant-abutment interface. Different in vitro and in vivo researches have been published to compare the implant-abutment connections actually available: external hexagon, internal hexagon and conical finding different amount of micro-gap, micro-leakage and marginal bone loss. The aim of this article is to describe, according to the most recent literature, different kind of fixture-abutment connections and their clinical and mechanical advantages or disadvantages.

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. Copyright © 2016 Elsevier Ltd. All rights reserved.

Strain analysis of 9 different abutments for cement-retained crowns on an internal hexagonal implant.

PubMed

Salaita, Louai G; Yilmaz, Burak; Seidt, Jeremy D; Clelland, Nancy L; Chien, Hua-Hong; McGlumphy, Edwin A

2017-08-01

Many aftermarket abutments for cement-retained crowns are available for the tapered screw-vent implant. Aftermarket abutments vary widely, from stock to custom abutments and in materials such as zirconia, titanium, or a combination of the two. How these aftermarket abutments perform under occlusal loads with regard to strain distribution is not clear. The purpose of this in vitro study was to measure and compare the different strains placed upon the bone around implants by 9 different abutments for cement-retained crowns on an implant with an internal hexagonal platform. Nine 4.1×11.5-mm tapered screw-vent implants were placed into a 305×51×8-mm resin block for strain measurements. Five abutment specimens of each of the 9 different abutments (N=45) were evaluated with 1 of the 9 implants. Monolithic zirconia crowns were then fabricated for each of the 9 different abutments, the crowns were cyclically loaded (maximum force 225 N) at 30 degrees, twice at a frequency of 2 Hz, and the strain was measured and recorded. The strain to the resin block was determined using a 3-dimensional digital image correlation (3D DIC) technique. Commercial image correlation software was used to analyze the strain around the implants. Data for maximal and minimal principal strains were compared using analysis of variance with a Tukey-Kramer post hoc test (α=.05). Strain measurements showed no significant differences among any of the abutments for minimal (compression) principal strains (P>.05). For maximal (tensile) principal strains, the zirconia abutment showed the highest, and the patient-specific abutment showed the second-highest strain around the implant, with the zirconia being significantly greater than all abutments, with the exception of the patient-specific abutment, and the patient-specific abutment being significantly greater than the straight contoured abutment in titanium and also zirconia (P<.05). The name brand patient specific titanium and Atlantis zirconia

Evaluation of stability of interface between CCM (Co-Cr-Mo) UCLA abutment and external hex implant

PubMed Central

Yoon, Ki-Joon; Park, Young-Bum; Choi, Hyunmin; Cho, Youngsung; Lee, Jae-Hoon

2016-01-01

PURPOSE The purpose of this study is to evaluate the stability of interface between Co-Cr-Mo (CCM) UCLA abutment and external hex implant. MATERIALS AND METHODS Sixteen external hex implant fixtures were assigned to two groups (CCM and Gold group) and were embedded in molds using clear acrylic resin. Screw-retained prostheses were constructed using CCM UCLA abutment and Gold UCLA abutment. The external implant fixture and screw-retained prostheses were connected using abutment screws. After the abutments were tightened to 30 Ncm torque, 5 kg thermocyclic functional loading was applied by chewing simulator. A target of 1.0 × 106 cycles was applied. After cyclic loading, removal torque values were recorded using a driving torque tester, and the interface between implant fixture and abutment was evaluated by scanning electronic microscope (SEM). The means and standard deviations (SD) between the CCM and Gold groups were analyzed with independent t-test at the significance level of 0.05. RESULTS Fractures of crowns, abutments, abutment screws, and fixtures and loosening of abutment screws were not observed after thermocyclic loading. There were no statistically significant differences at the recorded removal torque values between CCM and Gold groups (P>.05). SEM analysis revealed that remarkable wear patterns were observed at the abutment interface only for Gold UCLA abutments. Those patterns were not observed for other specimens. CONCLUSION Within the limit of this study, CCM UCLA abutment has no statistically significant difference in the stability of interface with external hex implant, compared with Gold UCLA abutment. PMID:28018564

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

PubMed

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

2011-08-01

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

Salvaging an angled implant abutment with damaged internal threads: a clinical report.

PubMed

Imam, Ahmad Y; Yilmaz, Burak; Özçelik, Tuncer Burak; McGlumphy, Edwin

2013-05-01

This clinical report describes a technique to fit an existing fixed detachable implant-supported prosthesis to a zygomatic implant abutment with stripped internal threads. The threads of the abutment were retapped and a wide diameter/wide head retaining screw was used to secure the existing prosthesis on the abutment. Care is needed in the retrieval of broken screws so as not to damage the internal threads of the implants, which might lead to irreversible complications. Copyright © 2013 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

Cone-morse implant connection system significantly reduces bacterial leakage between implant and abutment: an in vitro study.

PubMed

Baj, A; Bolzoni, A; Russillo, A; Lauritano, D; Palmieri, A; Cura, F; Silvestre, F J; Giannì, A B

2017-01-01

Osseointegrated implants are very popular dental treatments today in the world. In osseointegrated implants, the occlusal forces are transmitted from prosthesis through an abutment to a dental implant. The abutment is connected to the implant by mean of a screw. A screw is the most used mean for connecting an implant to an abutment. Frequently the screws break and are lost. There is an alternative to screw retained abutment systems: the cone-morse connection (CMC). The CMC, thanks to the absence of the abutment screw, guarantees no micro-gaps, no micro-movements, and a reduction of bacterial leakage between implant and abutment. As P. gingivalis and T. forsythia penetration might have clinical relevance, it was the purpose of this investigation to evaluate molecular leakage of these two bacteria in a new CMC implants systems (Leone Spa®, Florence, Italy). To identify the capability of the implant to protect the internal space from the external environment, the passage of genetically modified Escherichia coli across implant-abutment interface was evaluated. Four cone-morse Leone implants (Leone® Spa, Florence, Italy) were immerged in a bacterial culture for 24 h and bacteria amount was then measured inside implant-abutment interface with Real-time PCR. Bacteria were detected inside all studied implants, with a median percentage of 3% for P. gingivalis and 4% for T. forsythia. Cone-morse connection implant system has very low bacterial leakage percentage and is similar to one-piece implants.

[Dental implant restoration abutment selection].

PubMed

Bin, Shi; Hao, Zeng

2017-04-01

An increasing number of implant restoration abutment types are produced with the rapid development of dental implantology. Although various abutments can meet different clinical demands, the selection of the appropriate abutment is both difficult and confusing. This article aims to help clinicians select the appropriate abutment by describing abutment design, types, and selection criteria.

Three-Dimensional Finite Element Analysis on Stress Distribution of Internal Implant-Abutment Engagement Features.

PubMed

Cho, Sung-Yong; Huh, Yun-Hyuk; Park, Chan-Jin; Cho, Lee-Ra

To investigate the stress distribution in an implant-abutment complex with a preloaded abutment screw by comparing implant-abutment engagement features using three-dimensional finite element analysis (FEA). For FEA modeling, two implants-one with a single (S) engagement system and the other with a double (D) engagement system-were placed in the human mandibular molar region. Two types of abutments (hexagonal, conical) were connected to the implants. Different implant models (a single implant, two parallel implants, and mesial and tilted distal implants with 1-mm bone loss) were assumed. A static axial force and a 45-degree oblique force of 200 N were applied as the sum of vectors to the top of the prosthetic occlusal surface with a preload of 30 Ncm in the abutment screw. The von Mises stresses at the implant-abutment and abutment-screw interfaces were measured. In the single implant model, the S-conical abutment type exhibited broader stress distribution than the S-hexagonal abutment. In the double engagement system, the stress concentration was high in the lower contact area of the implant-abutment engagement. In the tilted implant model, the stress concentration point was different from that in the parallel implant model because of the difference in the bone level. The double engagement system demonstrated a high stress concentration at the lower contact area of the implant-abutment interface. To decrease the stress concentration, the type of engagement features of the implant-abutment connection should be carefully considered.

Implant-Abutment Contact Surfaces and Microgap Measurements of Different Implant Connections Under 3-Dimensional X-Ray Microtomography.

PubMed

Scarano, Antonio; Valbonetti, Luca; Degidi, Marco; Pecci, Raffaella; Piattelli, Adriano; de Oliveira, P S; Perrotti, Vittoria

2016-10-01

The presence of a microgap between implant and abutment could produce a bacterial reservoir which could interfere with the long-term health of the periimplant tissues. The aim of this article was to evaluate, by x-ray 3-dimensional microtomography, implant-abutment contact surfaces and microgaps at the implant-abutment interface in different types of implant-abutment connections. A total of 40 implants were used in this in vitro study. Ten implants presented a screw-retained internal hexagon abutment (group I), 10 had a Morse Cone taper internal connection (group II), 10 another type of Morse Cone taper internal connection (group III), and 10 had a screwed trilobed connection (group IV). In both types of Morse Cone internal connections, there was no detectable separation at the implant-abutment in the area of the conical connection, and there was an absolute congruity without any microgaps between abutment and implant. No line was visible separating the implant and the abutment. On the contrary, in the screwed abutment implants, numerous gaps and voids were present. The results of this study support the hypothesis that different types of implant-abutment joints are responsible for the observed differences in bacterial penetration.

Pedicle screws with a thin hydroxyapatite coating for improving fixation at the bone-implant interface in the osteoporotic spine: experimental study in a porcine model.

PubMed

Ohe, Makoto; Moridaira, Hiroshi; Inami, Satoshi; Takeuchi, Daisaku; Nohara, Yutaka; Taneichi, Hiroshi

2018-03-30

OBJECTIVE Instrumentation failure caused by the loosening of pedicle screws (PSs) in patients with osteoporosis is a serious problem after spinal surgery. The addition of a thin hydroxyapatite (HA) surface coating applied by using a sputtering process was reported recently to be a promising method for providing bone conduction around an implant without a significant risk of coating-layer breakage. In this study, the authors evaluated the biomechanical and histological features of the bone-implant interface (BII) of PSs with a thin HA coating in an in vivo porcine osteoporotic spine model. METHODS Three types of PSs (untreated/standard [STPS], sandblasted [BLPS], and HA-coated [HAPS] PSs) were implanted into the thoracic and lumbar spine (T9-L6) of 8 mature Clawn miniature pigs (6 ovariectomized [osteoporosis group] and 2 sham-operated [control group] pigs). The spines were harvested from the osteoporosis group at 0, 2, 4, 8, 12, or 24 weeks after PS placement and from the control group at 0 or 24 weeks. Their bone mineral density (BMD) was measured by peripheral quantitative CT. Histological evaluation of the BIIs was conducted by performing bone volume/tissue volume and bone surface/implant surface measurements. The strength of the BII was evaluated with extraction torque testing. RESULTS The BMD decreased significantly in the osteoporosis group (p < 0.01). HAPSs exhibited the greatest mean extraction peak torque at 8 weeks, and HAPSs and BLPSs exhibited significantly greater mean torque than the STPSs at 12 weeks (p < 0.05). The bone surface/implant surface ratio was significantly higher for HAPSs than for STPSs after 2 weeks (p < 0.05), and bonding between bone and the implant surface was maintained until 24 weeks with no detachment of the coating layer. In contrast, the bone volume/tissue volume ratio was significantly higher for HAPSs than for BLPSs or STPSs only at 4 weeks. CONCLUSIONS Using PSs with a thin HA coating applied using a sputtering process

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

A finite element analysis of novel vented dental abutment geometries for cement‐retained crown restorations

PubMed Central

Rodriguez, Lucas C.; Saba, Juliana N.; Meyer, Clark A.; Chung, Kwok‐Hung; Wadhwani, Chandur

2016-01-01

Abstract Recent literature indicates that the long‐term success of dental implants is, in part, attributed to how dental crowns are attached to their associated implants. The commonly utilized method for crown attachment – cementation, has been criticized because of recent links between residual cement and peri‐implant disease. Residual cement extrusion from crown‐abutment margins post‐crown seating is a growing concern. This study aimed at (1) identifying key abutment features, which would improve dental cement flow characteristics, and (2) understanding how these features would impact the mechanical stability of the abutment under functional loads. Computational fluid dynamic modeling was used to evaluate cement flow in novel abutment geometries. These models were then evaluated using 3D‐printed surrogate models. Finite element analysis also provided an understanding of how the mechanical stability of these abutments was altered after key features were incorporated into the geometry. The findings demonstrated that the key features involved in improved venting of the abutment during crown seating were (1) addition of vents, (2) diameter of the vents, (3) location of the vents, (4) addition of a plastic screw insert, and (5) thickness of the abutment wall. This study culminated in a novel design for a vented abutment consisting of 8 vents located radially around the abutment neck‐margin plus a plastic insert to guide the cement during seating and provide retrievability to the abutment system.Venting of the dental abutment has been shown to decrease the risk of undetected residual dental cement post‐cement‐retained crown seating. This article will utilize a finite element analysis approach toward optimizing dental abutment designs for improved dental cement venting. Features investigated include (1) addition of vents, (2) diameter of vents, (3) location of vents, (4) addition of plastic screw insert, and (5) thickness of abutment wall. PMID

A finite element analysis of novel vented dental abutment geometries for cement-retained crown restorations.

PubMed

Rodriguez, Lucas C; Saba, Juliana N; Meyer, Clark A; Chung, Kwok-Hung; Wadhwani, Chandur; Rodrigues, Danieli C

2016-11-01

Recent literature indicates that the long-term success of dental implants is, in part, attributed to how dental crowns are attached to their associated implants. The commonly utilized method for crown attachment - cementation, has been criticized because of recent links between residual cement and peri-implant disease. Residual cement extrusion from crown-abutment margins post-crown seating is a growing concern. This study aimed at (1) identifying key abutment features, which would improve dental cement flow characteristics, and (2) understanding how these features would impact the mechanical stability of the abutment under functional loads. Computational fluid dynamic modeling was used to evaluate cement flow in novel abutment geometries. These models were then evaluated using 3D-printed surrogate models. Finite element analysis also provided an understanding of how the mechanical stability of these abutments was altered after key features were incorporated into the geometry. The findings demonstrated that the key features involved in improved venting of the abutment during crown seating were (1) addition of vents, (2) diameter of the vents, (3) location of the vents, (4) addition of a plastic screw insert, and (5) thickness of the abutment wall. This study culminated in a novel design for a vented abutment consisting of 8 vents located radially around the abutment neck-margin plus a plastic insert to guide the cement during seating and provide retrievability to the abutment system.Venting of the dental abutment has been shown to decrease the risk of undetected residual dental cement post-cement-retained crown seating. This article will utilize a finite element analysis approach toward optimizing dental abutment designs for improved dental cement venting. Features investigated include (1) addition of vents, (2) diameter of vents, (3) location of vents, (4) addition of plastic screw insert, and (5) thickness of abutment wall.

Experimental research on the relationship between fit accuracy and fracture resistance of zirconia abutments.

PubMed

Sui, Xinxin; Wei, Huasha; Wang, Dashan; Han, Yan; Deng, Jing; Wang, Yongliang; Wang, Junjun; Yang, Jianjun

2014-10-01

The purpose of the study was to investigate the correlation between fit accuracy and fracture resistance of zirconia abutments, as well as its feasibility for clinical applications. Twenty self-made zirconia abutments were tested with 30 Osstem GSII implants. First, 10 Osstem GSII implants were cut into two parts along the long axis and assembled with the zirconia abutments. The microgaps between the implants and the zirconia abutments were measured under a scanning electron microscope. Second, the zirconia abutments were assembled with 20 un-cut implants and photographed before and after being fixed with a central screw of 30-Ncm torque. The dental films were measured by Digora for Windows 2.6 software. Then the fracture resistance of zirconia abutments was measured using the universal testing machine at 90°. All results were analyzed using SPSS13.0 software. The average internal-hexagon microgaps between the implants and zirconia abutments were 19.38±1.34μm. The average Morse taper microgap in the implant-abutment interface was 17.55±1.68μm. The dental film showed that the Morse taper gap in the implant-abutment interface disappeared after being fixed with a central screw of 30-Ncm torque, and the average moving distance of the zirconia abutments to the implants was 0.19±0.02mm. The average fracture resistance of zirconia abutments was 282.93±17.28N. The internal-hexagon microgap between the implants and zirconia abutments was negatively related to the fracture resistance of the abutments (r1=-0.97, p<0.01). The Morse taper microgap in the implant-abutment interface was negatively related to the fracture resistance of the abutments (r2=-0.84, p<0.01). The microgap between implant and abutment was negatively related to the fracture resistance of the abutment, while the internal-hexagon microgap has better correlation than the Morse taper microgap. The closure of microgap is helpful to improve the fracture resistance of zirconia abutments. The fracture

Three-Dimensional Finite Element Analysis of the Stress Distribution at the Internal Implant-Abutment Connection.

PubMed

Cho, Sung-Yong; Huh, Yoon-Hyuk; Park, Chan-Jin; Cho, Lee-Ra

2016-01-01

This study investigated stress distribution in four different implant-abutment interface conditions in the internal tapered connection implant system. Four different implant diameters (3.5 mm, 4.0 mm, 4.5 mm, and 5.0 mm) and two abutment types (hexagonal and conical) were simulated. Four unique implant-abutment interface conditions were assumed based on wall thickness, mating surface length, distance to the vertical stop, and abutment shape. Axial and oblique loading was applied during abutment screw preload, and the Von Mises stresses were measured at the implant-abutment and abutment-screw interfaces. The implant-abutment interface stress decreased as the wall thickness increased. As the mating surface increased, the stress distribution trended downward, and when the distance to the implant vertical stop was 0 μm, the Von Mises stress was extremely high at the vertical stop. Despite their different shapes, the abutments showed similar stress distributions. However, the maximum Von Mises stress was higher in the conical connection than in the hexagonal connection, particularly at the contralateral side to loading. To decrease the stress distribution at the implant-abutment interface, the implant wall thickness, mating surface contact length, distance to the vertical stop, and abutment shape should be carefully considered.

Fracture loads and failure modes of customized and non-customized zirconia abutments.

PubMed

Moris, Izabela Cristina Maurício; Chen, Yung-Chung; Faria, Adriana Cláudia Lapria; Ribeiro, Ricardo Faria; Fok, Alex Sui-Lun; Rodrigues, Renata Cristina Silveira

2018-05-05

This study aimed to evaluate the fracture load and pattern of customized and non-customized zirconia abutments with Morse-taper connection. 18 implants were divided into 3 groups according to the abutments used: Zr - with non-customized zirconia abutments; Zrc - with customized zirconia abutments; and Ti - with titanium abutments. To test their load capacity, a universal test machine with a 500-kgf load cell and a 0.5-mm/min speed were used. After, one implant-abutment assembly from each group was analyzed by Scanning Electron Microscopy (SEM). For fractographic analysis, the specimens were transversely sectioned above the threads of the abutment screw in order to examine their fracture surfaces using SEM. A significant difference was noted between the groups (Zr=573.7±11.66N, Zrc=768.0±8.72N and Ti=659.1±7.70N). Also, the zirconia abutments fractured while the titanium abutments deformed plastically. Zrc presented fracture loads significantly higher than Zr (p=0.009). All the zirconia abutments fractured below the implant platform, starting from the area of contact between the abutment and implant and propagating to the internal surface of the abutment. All the zirconia abutments presented complete cleavage in the mechanical test. Fractography detected differences in the position and pattern of fracture between the two groups with zirconia abutments, probably because of the different diameters in the transmucosal region. Customization of zirconia abutments did not affect their fracture loads, which were comparable to that of titanium and much higher than the maximum physiological limit for the anterior region of the maxilla. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

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

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.

Fracture Resistance and Mode of Failure of Ceramic versus Titanium Implant Abutments and Single Implant-Supported Restorations.

PubMed

Sghaireen, Mohd G

2015-06-01

The material of choice for implant-supported restorations is affected by esthetic requirements and type of abutment. This study compares the fracture resistance of different types of implant abutments and implant-supported restorations and their mode of failure. Forty-five Oraltronics Pitt-Easy implants (Oraltronics Dental Implant Technology GmbH, Bremen, Germany) (4 mm diameter, 10 mm length) were embedded in clear autopolymerizing acrylic resin. The implants were randomly divided into three groups, A, B and C, of 15 implants each. In group A, titanium abutments and metal-ceramic crowns were used. In group B, zirconia ceramic abutments and In-Ceram Alumina crowns were used. In group C, zirconia ceramic abutments and IPS Empress Esthetic crowns were used. Specimens were tested to failure by applying load at 130° from horizontal plane using an Instron Universal Testing Machine. Subsequently, the mode of failure of each specimen was identified. Fracture resistance was significantly different between groups (p < .05). The highest fracture loads were associated with metal-ceramic crowns supported by titanium abutments (p = .000). IPS Empress crowns supported by zirconia abutments had the lowest fracture loads (p = .000). Fracture modes of metal-ceramic crowns supported by titanium abutments included screw fracture and screw bending. Fracture of both crown and abutment was the dominant mode of failure of In-Ceram/IPS Empress crowns supported by zirconia abutments. Metal-ceramic crowns supported by titanium abutments were more resistant to fracture than In-Ceram crowns supported by zirconia abutments, which in turn were more resistant to fracture than IPS Empress crowns supported by zirconia abutments. In addition, failure modes of restorations supported by zirconia abutments were more catastrophic than those for restorations supported by titanium abutments. © 2013 Wiley Periodicals, Inc.

Effect of Cyclic Loading on Micromotion at the Implant-Abutment Interface.

PubMed

Karl, Matthias; Taylor, Thomas D

2016-01-01

Cyclic loading may cause settling of abutments mounted on dental implants, potentially affecting screw joint stability and implant-abutment micromotion. It was the goal of this in vitro study to compare micromotion of implant-abutment assemblies before and after masticatory simulation. Six groups of abutments (n = 5) for a specific tissue-level implant system with an internal octagon were subject to micromotion measurements. The implant-abutment assemblies were loaded in a universal testing machine, and an apparatus and extensometers were used to record displacement. This was done twice, in the condition in which they were received from the abutment manufacturer and after simulated loading (100,000 cycles; 100 N). Statistical analysis was based on analysis of variance, two-sample t tests (Welch tests), and Pearson product moment correlation (α = .05). The mean values for micromotion ranged from 33.15 to 63.41 μm and from 30.03 to 42.40 μm before and after load cycling. The general trend toward reduced micromotion following load cycling was statistically significant only for CAD/CAM zirconia abutments (P = .036) and for one type of clone abutment (P = .012), with no significant correlation between values measured before and after cyclic loading (Pearson product moment correlation; P = .104). While significant differences in micromotion were found prior to load cycling, no significant difference among any of the abutment types tested could be observed afterward (P > .05 in all cases). A quantifiable settling effect at the implant-abutment interface seems to result from cyclic loading, leading to a decrease in micromotion. This effect seems to be more pronounced in low-quality abutments. For the implant system tested in this study, retightening of abutment screws is recommended after an initial period of clinical use.

Two Different Percutaneous Bone-Anchored Hearing Aid Abutment Systems: Comparative Clinical Study.

PubMed

Polat, Beldan; İşeri, Mete; Orhan, Kadir Serkan; Yılmazer, Ayça Başkadem; Enver, Necati; Ceylan, Didem; Kara, Ahmet; Güldiken, Yahya; Çomoğlu, Şenol

2016-04-01

To compare two different percutaneous bone-anchored hearing aid (BAHA) abutment systems regarding operation time, scar healing, quality of life, implant stability, audiologic results, and complications. The study involves a prospective multi-center clinical evaluation. Thirty-two consecutive patients who had undergone BAHA surgery from January 2011 to January 2013 in two tertiary centers were included in the study. The Glasgow Inventory Benefit Score was used to assess the patients at least 6 months after surgery. The operation time and complications were recorded. Implant stability quotient (ISQ) values were recorded using resonance frequency analysis. Holger's classification was used to evaluate skin reactions. The mean length of the operation was 39.2±4 min for standard abutment and 18.3±5.7 min for hydroxyapatite-coated abutment. ISQ scores were significantly better for standard abutment in all tests. The mean total Glasgow Inventory Benefit Score was 39.3±19 for the standard abutment and 46.3±24.5 for the hydroxyapatite-coated abutment groups, but there was no statistical significance between the two groups. There was no difference in audiological improvement between the two groups after surgery. Hydroxyapatite-coated abutment provided a shorter operation time that was significantly different from standard abutment. There were no significant differences between standard abutment and hydroxyapatite-coated abutment regarding audiologic improvement, quality of life, loading time, and complications.

Three-Dimensional Displacement of Nine Different Abutments for an Implant with an Internal Hexagon Platform.

PubMed

Gilbert, Andy B; Yilmaz, Burak; Seidt, Jeremy D; McGlumphy, Edwin A; Clelland, Nancy L; Chien, Hua-Hong

2015-01-01

Clinicians need to know whether there are any differences among the many abutment options available for restoring a particular implant. This study aims to compare nine abutments for one implant system for positional changes between hand tightening and torqueing. Nine Tapered Screw-Vent (TSV) implants were placed into a resin block. Five specimens of nine different abutments (n = 45) were tried in one of the nine implants. Initially, the abutments were torqued to 20 Ncm to represent hand tightening. Abutments were tightened to 30 Ncm using a torque driver as recommended by the manufacturer for final seating. Images were recorded in 12-second intervals for approximately 10 minutes after the torque was applied. The spatial relationship of the abutments to the resin block was determined using three-dimensional digital image correlation. Commercial image correlation software was used to analyze the displacements. Mean displacements for the nine different abutments were calculated in all three dimensions and for overall displacement in space. A t test with a step-down Bonferroni correction was used for a pairwise comparison of each abutment's mean displacements to the other abutments to determine statistical differences (α = .05). The Atlantis titanium, Inclusive titanium, and Legacy zirconia abutments showed mean displacements that were statistically significantly higher than other abutments in the horizontal direction. The overall three-dimensional displacement of the Atlantis titanium abutment after an applied 30-Ncm torque was significantly higher than that of six of the other eight abutments (P < .0144). Within the limitations of this in vitro study, the Zimmer PSA demonstrated less displacement between hand tightening and torqueing than the Atlantis titanium or Inclusive titanium abutments when used to restore a TSV implant.

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

PubMed

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

2012-04-01

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

Comparison of fracture resistance of pressable metal ceramic custom implant abutment with a commercially fabricated CAD/CAM zirconia implant abutment.

PubMed

Protopapadaki, Maria; Monaco, Edward A; Kim, Hyeong-Il; Davis, Elaine L

2013-11-01

The predictable nature of the hot pressing ceramic technique has several applications, but no study was identified that evaluated its application to the fabrication of custom implant abutments. The purpose of this study was to compare the fracture resistance of an experimentally designed pressable metal ceramic custom implant abutment (PR) with that of a duplicate zirconia abutment (ZR). Two groups of narrow platform (NP) (Nobel Replace) implant abutment specimens were fabricated (n=10). The experimental abutment (PR) had a metal substructure cast with ceramic alloy (Lodestar) and veneered with leucite pressable glass ceramic (InLine PoM). Each PR abutment was individually scanned and 10 duplicate CAD/CAM ZR abutments were fabricated for the control group. Ceramic crowns (n=20) with the average dimensions of a human lateral incisor were pressed with lithium disilicate glass ceramic (IPS e.max Press) and bonded on the abutments with a resin luting agent (Multilink Automix). The specimens were subjected to thermocycling, cyclic loading, and finally static loading to failure with a computer-controlled Universal Testing Machine. An independent t test (1 sided) determined whether the mean values of the fracture load differed significantly (α=.05) between the 2 groups. No specimen failed during cyclic loading. Upon static loading, the mean (SD) load to failure was significantly higher for the PR group (525.89 [143.547] N) than for the ZR group (413.70 [35.515] N) for internal connection narrow platform bone-level implants (P=.025). Failure was initiated at the screw and internal connection level for both groups. It is possible to fabricate PR abutments that are stronger than ZR abutments for Nobel Biocare internal connection NP bone-level implants. The screw and the internal connection are the weak links for both groups. Copyright © 2013 Editorial Council for the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

Minimally Invasive Sacroiliac Joint Fusion Using a Novel Hydroxyapatite-Coated Screw: Preliminary 1-Year Clinical and Radiographic Results of a 2-Year Prospective Study.

PubMed

Rappoport, Louis H; Luna, Ingrid Y; Joshua, Gita

2017-05-01

Proper diagnosis and treatment of sacroiliac joint (SIJ) pain remains a clinical challenge. Dysfunction of the SIJ can produce pain in the lower back, buttocks, and extremities. Triangular titanium implants for minimally invasive surgical arthrodesis have been available for several years, with reputed high levels of success and patient satisfaction. This study reports on a novel hydroxyapatite-coated screw for surgical treatment of SIJ pain. Data were prospectively collected on 32 consecutive patients who underwent minimally invasive SIJ fusion with a novel hydroxyapatite-coated screw. Clinical assessments and radiographs were collected and evaluated at 3, 6, and 12 months postoperatively. Mean (standard deviation) patient age was 55.2 ± 10.7 years, and 62.5% were female. More patients (53.1%) underwent left versus right SIJ treatment, mean operative time was 42.6 ± 20.4 minutes, and estimated blood loss did not exceed 50 mL. Overnight hospital stay was required for 84% of patients, and the remaining patients needed a 2-day stay (16%). Mean preoperative visual analog scale back and leg pain scores decreased significantly by 12 months postoperatively (P < 0.01). Mechanical stability was achieved in 93.3% (28/30) of patients, and all patients who were employed preoperatively returned to work within 3 months. Two patients who required revision surgery reported symptom improvement within 3 weeks and did not require subsequent surgery. Positive clinical outcomes are reported 1 year postoperatively after implantation of a novel implant to treat sacroiliac joint pain. Future clinical studies with larger samples are warranted to assess long-term patient outcomes. Copyright © 2017 Elsevier Inc. All rights reserved.

Effect of intentional abutment disconnection on the micro-movements of the implant-abutment assembly: a 3D digital image correlation analysis.

PubMed

Messias, Ana; Rocha, Salomão; Calha, Nuno; Neto, Maria Augusta; Nicolau, Pedro; Guerra, Fernando

2017-01-01

Implant-abutment assembly stability is critical for the success of implant-supported rehabilitation. The intentional removal of the prosthetic components may hamper the achievement of the essential stability due to preload reduction in the screw joint and implant-screw mating surface changes. To evaluate the effect of intentional abutment disconnection and reconnection in the stability of internal locking hex implants and corresponding abutments using the method of 3D digital image correlation. Ten conical shape and internal hexagon connection implants were embedded in acrylic resin and assembled to prosthetic abutments with 30 Ncm torque and assigned to two groups: group 1 - tested for static load-bearing capacity at 30° off-axis for two times and group 2 - underwent intentional disconnection and reconnection between tests. Micro-movements were captured with two high-speed photographic cameras and analyzed with video correlation system in three spacial axes U, V and W. Screw abutment and internal implant thread morphology was observed with a field-emission scanning electron microscopy. After the intentional disconnection of the abutment, group 2 showed generally higher maximum displacements for U and V directions. Under 50N load, mean difference was 24.7 μm (P = 0.008) for U direction and -7.7 μm (P = 0.008) for V direction. No significant differences were found for maximum and minimum displacements in the W direction. Mean displacement of the speckle surface presented was statistically different in the two groups (P = 0.016). SEM revealed non-homogenous screw surfaces with scoring on group 2 plus striations and debris in the implant threads. Micro-movements were higher for the group submitted to intentional disconnection and reconnection of the abutment, particularly under average bite forces. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

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

PubMed

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

2012-05-01

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

The fracture strength by a torsion test at the implant-abutment interface.

PubMed

Watanabe, Fumihiko; Hiroyasu, Kazuhiko; Ueda, Kazuhiko

2015-12-01

Fractured connections between implants and implant abutments or abutment screws are frequently encountered in a clinical setting. The purpose of this study was to investigate fracture strength using a torsion test at the interface between the implant and the abutment. Thirty screw-type implant with diameters of 3.3, 3.8, 4.3, 5.0, and 6.0 mm were submitted to a torsion test. Implants of each size were connected to abutments with abutment screws tightened to 20 N · cm. Mechanical stress was applied with a rotational speed of 3.6 °/min until fracture occurred, and maximum torque (fracture torque) and torsional yield strength were measured. The mean values were calculated and then compared using Tukey's test. The abutments were then removed, and the implant-abutment interfaces were examined using a scanning electron microscope (SEM). No significant differences in mean fracture torque were found among 3.3, 3.8, and 4.3 mm-diameter implants, but significant differences were found between these sizes and 5.0 and 6.0 mm-diameter implants (p < 0.01). Concerning mean torsional yield strength, significant differences were found between 3.3, 3.8, and 4.3 mm-diameter and 5.0 and 6.0 mm-diameter implants (p < 0.01). Observations under the SEM showed that all the projections of the abutment corresponding to the internal notches of the implant body had been destroyed. Smaller diameter implants demonstrated lower fracture torque and torsional yield strength than implants with larger diameters. In internal tube-in-tube connections, three abutment projections corresponding to rotation-prevention notches were destroyed in each implant.

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

PubMed

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

2014-08-01

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

6. VIEW OF SOUTH ABUTMENT. MASONRY ON BOTH ABUTMENTS IS ...

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

6. VIEW OF SOUTH ABUTMENT. MASONRY ON BOTH ABUTMENTS IS LAID UP IN SEMI-COURSED RUBBLE PATTERN. VIEW LOOKING SOUTHEAST. - Montgomery County Bridge No. 221, Metz Road spanning Towamencin Creek, Skippack, Montgomery County, PA

14. DETAIL, NORTH ABUTMENT, FROM EAST, SHOWING ABUTMENT, PORTION OF ...

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

14. DETAIL, NORTH ABUTMENT, FROM EAST, SHOWING ABUTMENT, PORTION OF SIMPLY ORNAMENTED EAST PARAPET, AND REMNANT OF STONE MASONRY ABUTMENT OF ORIGINAL (1890) FIFTH STREET VIADUCT - Fifth Street Viaduct, Spanning Bacon's Quarter Branch Valley on Fifth Street, Richmond, Independent City, VA

Self-Inflicted Drywall Screws in the Sagittal Sinus.

PubMed

Guppy, Kern H; Ochi, Calvin

2018-02-01

A 30-year-old right-handed man with a history of schizophrenia presented with 2 self-inflicted drywall screws in the skull. The patient was sleepy but easily arousable; blood tests showed he had taken methamphetamines. Computed tomography and computed tomography angiography of the head showed the frontal screw abutted left of the superior sagittal sinus, and the posterior screw went through the superior sagittal sinus with no extravasation of contrast material at either site. Both screws were removed with exposure of the sagittal sinus using U-shaped craniectomies. There was no bleeding on the removal of the screws. It appears the posterior screw entered between the leaflets of the sagittal sinus dura mater. The patient had returned to work without any sequelae 1 month after injury. Copyright © 2017 Elsevier Inc. All rights reserved.

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

SciTech Connect

Hu Hongtao; Shin, Ji Hoon, E-mail: jhshin@amc.seoul.kr; Hwang, Jae-Yeon

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.

Biomechanical evaluation of different abutment-implant connections - A nonlinear finite element analysis

NASA Astrophysics Data System (ADS)

Ishak, Muhammad Ikman; Shafi, Aisyah Ahmad; Rosli, M. U.; Khor, C. Y.; Zakaria, M. S.; Rahim, Wan Mohd Faizal Wan Abd; Jamalludin, Mohd Riduan

2017-09-01

The success of dental implant surgery is majorly dependent on the stability of prosthesis to anchor to implant body as well as the integration of implant body to bone. The attachment between dental implant body and abutment plays a vital role in attributing to the stability of dental implant system. A good connection between implant body cavity to abutment may minimize the complications of abutment loosening and implant fractures as widely reported in clinical findings. The aim of this paper is to investigate the effect of different abutment-implant connections on stress dispersion within the abutment and implant bodies as well as displacement of implant body via three-dimensional (3-D) finite element analysis (FEA). A 3-D model of mandible was reconstructed from computed tomography (CT) image datasets using an image-processing software with the selected region of interest was the left side covering the second premolar, first molar and second molar regions. The bone was modelled as compact (cortical) and porous (cancellous) structures. Besides, three implant bodies and three generic models of abutment with different types of connections - tapered interference fit (TIF), tapered integrated screwed-in (TIS) and screw retention (SR) were created using computer-aided design (CAD) software and all models were then analysed via 3D FEA software. Occlusal forces of 114.6 N, 17.2 N and 23.4 N were applied in the axial, lingual and mesio-distal directions, respectively, on the top surface of first molar crown. All planes of the mandibular bone model were rigidly fixed. The result exhibited that abutment with TIS connection produced the most favourable stress and displacement outcomes as compared to other attachment types. This is due to the existence of integrated screw at the bottom portion of tapered abutment which increases the motion resistance.

The bacterial sealing capacity of morse taper implant-abutment systems in vitro.

PubMed

Ranieri, Rogerio; Ferreira, Andreia; Souza, Emmanuel; Arcoverde, Joao; Dametto, Fabio; Gade-Neto, Cicero; Seabra, Flavio; Sarmento, Carlos

2015-05-01

The use of Morse taper systems in dental implantology has been associated widely with a more precise adaptation between implants and their respective abutments. This may lead to an increase in the stability of the implant system and may also prevent microbial invasion through the implant-abutment interface. The aim of this study was to investigate in vitro the ability of four commercially available Morse taper system units to impede bacterial penetration through their implant-abutment interfaces. Abutments were screwed onto the implants, and the units were subsequently immersed in Streptococcus sanguinis bacterial broth (1 × 10(8) colony forming units/mL) for 48 hours. The units were examined by scanning electron microscopy (SEM) under three conditions: 1) with the implant-abutment components assembled as units to investigate for both the existence of microgaps and the presence of bacteria; 2) with the implants and abutments separated for examination of internal surfaces; and 3) with the implant-abutment components again assembled as units to measure any microgaps detected. The mean size of the microgaps in each unit was determined by measuring, under SEM, their width in four equidistant points. Microgaps were detected in all units with no significant differences in dimension (Kruskal-Wallis test, P >0.05). Within all units, the presence of bacteria was also observed. The seals provided by the interfaces of the commercially available Morse taper implant-abutment units tested were not sufficiently small to shield the implant from bacterial penetration.

Displacement comparison of CAD-CAM titanium and zirconia abutments to implants with different conical connections.

PubMed

Yilmaz, Burak; Hashemzadeh, Shervin; Seidt, Jeremy D; Clelland, Nancy L

2018-04-01

To compare the displacements of CAD-CAM zirconia and titanium abutments into different internal connection systems after torquing. OsseoSpeed EV and OsseoSpeed TX implants (n=10) were placed in resin blocks. Zirconia and titanium abutments (n=5) were first hand tightened and then tightened to the recommended torque (20Ncm for TX and 25Ncm for EV). Displacements of abutments between screw tightening by hand and torque driver was measured using three-dimensional digital image correlation (3D DIC) technique. Displacements were measured in U (front/back), V (into/outward), W (right/left) directions and 3-dimensionally (3D). ANOVA with restricted maximum likelihood estimation method was used to analyze the data. Bonferroni-corrected t tests was used to determine the statistical differences (α=0.05). 3D displacement of zirconia and titanium abutments was significantly greater in OsseoSpeed EV implant (P<0.001). Displacement of zirconia and titanium abutments was not significantly different within implant systems, 3D (P≥0.386) and in each direction (P≥0.382). In U and V directions, zirconia and titanium abutments displaced significantly more towards negative in OsseoSpeed EV implant (P<0.019). Within the OsseoSpeed TX system, abutments displaced significantly more in V direction compared to the U and W (P≤0.005), and within the Osseospeed EV system, abutment displacements were significantly different amongst directions and displacements in V were the greatest (P<0.001). Abutments displaced more in the implant that required higher torque values to tighten the abutment. The amount of displacement in both systems was clinically small. Abutment material did not affect the magnitude of displacement. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

Effect of Abutment Modification and Cement Type on Retention of Cement-Retained Implant Supported Crowns

PubMed Central

Farzin, Mitra; Torabi, Kianoosh; Ahangari, Ahmad Hasan; Derafshi, Reza

2014-01-01

Objective: Provisional cements are commonly used to facilitate retrievability of cement-retained fixed implant restorations; but compromised abutment preparation may affect the retention of implant-retained crowns.The purpose of this study was to investigate the effect of abutment design and type of luting agent on the retentive strength of cement-retained implant restorations. Materials and Method: Two prefabricated abutments were attached to their corresponding analogs and embedded in an acrylic resin block. The first abutment (control group) was left intact without any modifications. The screw access channel for the first abutment was completely filled with composite resin. In the second abutment, (test group) the axial wall was partially removed to form an abutment with 3 walls. Wax models were made by CAD/CAM. Ten cast copings were fabricated for each abutment. The prepared copings were cemented on the abutments by Temp Bond luting agent under standardized conditions (n=20). The assemblies were stored in 100% humidity for one day at 37°C prior to testing. The cast crown was removed from the abutment using an Instron machine, and the peak removal force was recorded. Coping/abutment specimens were cleaned after testing, and the testing procedure was repeated for Dycal luting agent (n=20). Data were analyzed with two- way ANOVA (α=0.05). Results: There was no significant difference in the mean transformed retention (Ln-R) between intact abutments (4.90±0.37) and the abutments with 3 walls (4.83±0.25) using Dycal luting agent. However, in TempBond group, the mean transformed retention (Ln-R) was significantly lower in the intact abutment (3.9±0.23) compared to the abutment with 3 walls (4.13±0.33, P=0.027). Conclusion: The retention of cement-retained implant restoration can be improved by the type of temporary cement used. The retention of cast crowns cemented to implant abutments with TempBond is influenced by the wall removal. PMID:25628660

Impact of Intentional Overload on Joint Stability of Internal Implant-Abutment Connection System with Different Diameter.

PubMed

Lee, Ji-Hye; Lee, Won; Huh, Yoon-Hyuk; Park, Chan-Jin; Cho, Lee-Ra

2017-09-05

To evaluate the axial displacement of the implant-abutment assembly of different implant diameter after static and cyclic loading of overload condition. An internal conical connection system with three diameters (Ø 4.0, 4.5, and 5.0) applying identical abutment dimension and the same abutment screw was evaluated. Axial displacement of abutment and reverse torque loss of abutment screw were evaluated under static and cyclic loading conditions. Static loading test groups were subjected to vertical static loading of 250, 400, 500, 600, 700, and 800 N consecutively. Cyclic loading test groups were subjected to 500 N cyclic loading to evaluate the effect of excessive masticatory loading. After abutment screw tightening for 30 Ncm, axial displacement was measured upon 1, 3, 10, and 1,000,000 cyclic loadings of 500 N. Repeated-measure ANOVA and 2-way ANOVA were used for statistical analysis (α = 0.05). The increasing magnitude of vertical load and thinner wall thickness of implant increased axial displacement of abutment and reverse torque loss of abutment screw (p < 0.05). Implants in the Ø 5.0 diameter group demonstrated significantly low axial displacement, and reverse torque loss after static loading than Ø 4.0 and Ø 4.5 diameter groups (p < 0.05). In the cyclic loading test, all diameter groups of implant showed significant axial displacement after 1 cycle of loading of 500 N (p < 0.05). There was no significant axial displacement after 3, 10, or 1,000,000 cycles of loading (p = 0.603). Implants with Ø 5.0 diameter demonstrated significantly low axial displacement and reverse torque loss after the cyclic and static loading of overload condition. © 2017 by the American College of Prosthodontists.

Proposal for monitoring concrete painting as a preventive maintenance tool (Abutments and pier caps).

DOT National Transportation Integrated Search

2017-07-01

One of the growing number of preventive bridge maintenance activities conducted by the Kentucky Transportation Cabinet (KYTC) is washing and applying thin film protective coatings to bridge abutments and piers. Previous work conducted by Kentucky Tra...

Wear at the titanium-titanium and the titanium-zirconia implant-abutment interface: a comparative in vitro study.

PubMed

Stimmelmayr, Michael; Edelhoff, Daniel; Güth, Jan-Frederik; Erdelt, Kurt; Happe, Arndt; Beuer, Florian

2012-12-01

The purpose of this study was to determine and measure the wear of the interface between titanium implants and one-piece zirconia abutments in comparison to titanium abutments. 6 implants were secured into epoxy resin blocks. The implant interface of these implants and 6 corresponding abutments (group Zr: three one-piece zirconia abutments; group Ti: three titanium abutments) were examined by a microscope and scanning electron micrograph (SEM). Also the implants and the abutments were scanned by 3D-Micro Computer Tomography (CT). The abutments were connected to the implants and cyclically loaded with 1,200,000 cycles at 100N in a two-axis fatigue testing machine. Afterwards, all specimens were unscrewed and the implants and abutments again were scanned by microscope, SEM and CT. The microscope and SEM images were compared, the CT data were superimposed and the wear was calculated by inspection software. The statistical analysis was carried out with an unpaired t-test. Abutment fracture or screw loosening was not observed during cyclical loading. Comparing the microscope and SEM images more wear was observed on the implants connected to zirconia abutments. The maximum wear on the implant shoulder calculated by the inspection software was 10.2μm for group Zr, and 0.7μm for group Ti. The influence of the abutment material on the measured wear was statistically significant (p≤0.001; Levene-test). Titanium implants showed higher wear at the implant interface following cyclic loading when connected to one-piece zirconia implant abutments compared to titanium abutments. The clinical relevance is not clear; hence damage of the internal implant connection could result in prosthetic failures up to the need of implant removal. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Prospective assessment of CAD/CAM zirconia abutment and lithium disilicate crown restorations: 2.4 year results.

PubMed

Cooper, Lyndon F; Stanford, Clark; Feine, Jocelyne; McGuire, Michael

2016-07-01

Single-tooth implant restorations are commonly used to replace anterior maxillary teeth. The esthetic, functional, and biologic outcomes are, in part, a function of the abutment and crown. The purpose of this clinical study was to describe the implant, abutment, and crown survival and complication rates for CAD/CAM zirconia abutment and lithium disilicate crown restorations for single-tooth implants. As part of a broader prospective investigation that enrolled and treated 141 participants comparing tissue responses at the conical interface (CI; AstraTech OsseoSpeed), flat-to-flat interface (FI; NobelSpeedy), and platform-switch interface (PS; NanoTite Certain Prevail) of single-tooth implants, computer-aided design and computer-aided manufacturing (CAD/CAM) zirconia abutments (ATLANTIS Abutment) and cemented lithium disilicate (e.max) crowns were used in the restoration of all implants. After 2.4 years in function (3 years after implant placement), the implant, abutment, and crown of 110 participants were evaluated. Technical and biologic complications were recorded. Demographic results were tabulated as percentages with mean values and standard deviations. Abutment survival was calculated with the Kaplan-Meier method. After 2.4 years, no abutments or crowns had been lost. Abutment complications (screw loosening, screw fracture, fracture) were absent for all 3 implant groups. Crown complications were limited to 2 crowns debonding and 1 with excess cement (2.5%). Five biological complications (4.0%) were recorded. The overall complication rate was 6.5%. CAD/CAM zirconia abutments restored with cemented lithium disilicate crowns demonstrated high survival on 3 different implant-abutment interface designs. No abutment or abutment screw fracture occurred. The technical complications observed after 2.4 years were minor and reversible. The use of CAD/CAM zirconia abutments with cemented lithium disilicate crowns is associated with high technical and biologic success at 2

The Evaluation of Unscrewing Torque Values of Implant-Abutment Connections: An In Vitro Study.

PubMed

Bruna, Ezio; Fabianelli, Andrea; Mastriforti, Giacomo; Papacchini, Federica

This study investigated the stability of titanium screws in implant-abutment connections by measuring the force necessary to induce unscrewing. A total of 60 implant-abutment couplings were assigned to two groups (n = 30 each). The sequence 10-20-32 Ncm was tested in Group 1; the sequence 10-20-32-32-32 Ncm was tested in Group 2. The force necessary to unscrew each abutment-implant sample was recorded and statistically analyzed. The significance level was set at P < .05. Significant differences were found between the two sequences. Group 2 required higher forces than Group 1 to unscrew. The stability of the implant-abutment joint may be improved by tightening with the sequence 10-20-32-32-32 Ncm.

Comparison of Customized Abutments Made from Titanium and a Machinable Precious Alloy.

PubMed

Lee, Jee-Ho; Park, Ji-Man; Park, Eun-Jin; Koak, Jai-Young; Kim, Seong-Kyun; Heo, Seong-Joo

2016-01-01

To investigate the clinical usefulness, a customized abutment produced with the Pd-Ag-In alloy was compared with a customized abutment produced with the conventional titanium alloy for discoloration and mechanical accuracy. Discoloration and resistance to corrosion of the Pd-Ag-In alloy were evaluated using chemical solutions. Marginal adaptation of internal-type implants and abutments was compared using 10 titanium abutments and 10 Pd-Ag-In abutments using a surface measuring system. A detorque test was performed on 12 implant-abutment complexes of each control and experimental group to investigate screw joint stability. Cyclic loading simulating a human's mastication movement for 1 year was applied after 30 Ncm initial tightening, and the removal torque was measured using a digital torque gauge. The noninferiority test was conducted to compare the Pd-Ag-In alloy with a titanium abutment with a 10% margin. The Pd-Ag-In alloy had a warm yellow color and displayed stable resistance to discoloration and corrosion, resulting in an advantageous esthetic property. When compared to the titanium alloy, it did not show noninferiority with respect to the gap between the implant and the abutment; the gap was approximately 13.3 μm on average, which was not significantly different from those observed in previous studies. After long-term use, it displayed statistically significant noninferiority in the removal torque value compared to the titanium group. The Pd-Ag-In alloy-based customized abutment had good mechanical properties of the implant-abutment complex as well as a superior esthetic property, and can provide favorable outcomes in anterior implant restoration.

Platform-Switching for Cemented Versus Screwed Fixed Dental Prostheses: Reliability and Failure Modes: An In Vitro Study.

PubMed

Anchieta, Rodolfo Brunieira; Machado, Lucas Silveira; Hirata, Ronaldo; Bonfante, Estevam Augusto; Coelho, Paulo G

2016-08-01

The aim of this study was to evaluate the probability of survival of cemented and screwed three-unit implant-supported fixed dental prostheses (ISFDP) using different implant-abutment horizontal matching configurations (regular vs switching platforms). One hundred and sixty-eight implants with internal hexagon connection (4 mm diameter, 10 mm length, Emfils; Colosso Evolution System, Itú, SP, Brazil) were selected for this study according to the horizontal implant-abutment matching configuration (regular or switching) and retention method and divided in four groups (n = 21 per group) as follows: 1) regular platform cemented (IRC); 2) or screw-retained (IRS); 3) switched-platform cemented (ISC); or 4) screw-retained (ISS). Regular and platform-switched abutments (Colosso evolution, 4 mm and 3.3 mm, respectively) were torqued, and 84 three-unit metal bridges were fabricated (first molar pontic). Implants were embedded in polymethyl-methacrylate resin and subjected to step-stress accelerated life testing in water. Weibull distribution was used to determine the probability of survival for a mission of 100,000 cycles at 400 N (90% two-sided confidence intervals). Polarized light and scanning electron microscopes were used for fractographic analysis. The β values of 0.50, 1.19, 1.25, and 1.95 for groups IRC, IRS, ISC, and ISS respectively, indicated that fatigue accelerated the failure for all groups, except IRC. The cement-retained groups presented significantly higher probability of survival (IRC - 98%, ISC - 59%) than screw-retained groups (IRS - 23% and ISS - 0%). Screw-retained FDPs exclusively failed by abutment-screw fractures, whereas cement-retained presented implant/screw/abutment fractures. The probability of survival of cement-retained ISFDP was higher than screw-retained, irrespective of implant-abutment horizontal configuration. © 2015 Wiley Periodicals, Inc.

Connective Tissue Characteristics around Healing Abutments of Different Geometries: New Methodological Technique under Circularly Polarized Light.

PubMed

Delgado-Ruiz, Rafael Arcesio; Calvo-Guirado, Jose Luis; Abboud, Marcus; Ramirez-Fernandez, Maria Piedad; Maté-Sánchez de Val, José Eduardo; Negri, Bruno; Gomez-Moreno, Gerardo; Markovic, Aleksa

2015-08-01

To describe contact, thickness, density, and orientation of connective tissue fibers around healing abutments of different geometries by means of a new method using coordinates. Following the bilateral extraction of mandibular premolars (P2, P3, and P4) from six fox hound dogs and a 2-month healing period, 36 titanium implants were inserted, onto which two groups of healing abutments of different geometry were screwed: Group A (concave abutments) and Group B (wider healing abutment). After 3 months the animals were sacrificed and samples extracted containing each implant and surrounding soft and hard tissues. Histological analysis was performed without decalcifying the samples by means of circularly polarized light under optical microscope and a system of vertical and horizontal coordinates across all the connective tissue in an area delimited by the implant/abutment, epithelium, and bone tissue. In no case had the connective tissue formed a connection to the healing abutment/implant in the internal zone; a space of 35 ± 10 μm separated the connective tissue fibers from the healing abutment surface. The total thickness of connective tissue in the horizontal direction was significantly greater in the medial zone in Group B than in Group A (p < .05). The orientation of the fibers varied according to the coordinate area so that internal coordinates showed a higher percentage of parallel fibers in Group A (p < .05) and a higher percentage of oblique fibers in Group B (p < .05); medial coordinates showed more oblique fibers (p < .05); and the area of external coordinates showed the highest percentage of perpendicular fibers (p < .05). The fiber density was higher in the basal and medial areas (p < .05). Abutment geometry influences the orientation of collagen fibers; therefore, an abutment with a profile wider than the implant platform favors oblique and perpendicular orientation of collagen fibers and greater connective tissue thickness

The effect of the use of a counter-torque device on the abutment-implant complex.

PubMed

Lang, L A; May, K B; Wang, R F

1999-04-01

Little is known about the condition of the abutment-screw joint before loading, after the development of the preload. This study examined the tightening force transmitted to the implant with and without the use of a counter-torque device during the tightening of the abutment screw. Forty Brânemark implants and 10 CeraOne, Estheticone, Procera, and AurAdapt abutments formed the experimental populations. Samples in each group were further divided into 2 groups, 1 group was tightened with a torque controller without the use of a counter-torque device, whereas the other used the counter-torque device. Samples were positioned in a special holder within the grips of a Tohnichi BTG-6 torque gauge for measuring transmitted forces. There were significant differences (P =. 0001) in the tightening forces transmitted to the implant with and without the use of a counter-torque device when tightening the abutment screws. An average of 91% of the recommended preload tightening torque was transmitted to the implant-bone interface in the absence of a counter-torque device. In all abutment systems, less than 10% of the recommended preload tightening torque was transmitted to the implant when the counter-torque device was used.

Investigating the micromorphological differences of the implant-abutment junction and their clinical implications: a pilot study.

PubMed

Mattheos, Nikos; Li, Xiaona; Zampelis, Antonios; Ma, Li; Janda, Martin

2016-11-01

The aim of this pilot study was to investigate the morphological micro-features of three commercially available implant-abutment joints, using compatible and original prosthetic components. Furthermore, possible correlations between the micromorphology and potential functional complications were investigated with the use of finite element analysis. Three abutments (one original and two compatibles) were torqued on original Straumann RN implants, as according to each of the manufacturer's instructions. The implant-abutment units were sliced in the microtome and photographed under different magnifications (10×-500×) through a scanning electron microscope. Finite element analysis models were reconstructed for each of the implant-abutment units using the precise measurements from the SEM. Differences in stress, strain and deformation for the three different abutments were then calculated using ANSYS Workbench v13. Major dimensional differences were identified between all studied contact areas of the three units. The tight contact in the implant shoulder was similar in all three units, but engagement of the internal connection and, in particular, the anti-rotation elements was seriously compromised in the compatible abutments. One compatible abutment demonstrated compromised engagement of the abutment screw as well. Equivalent stress and strain in the FEA were much higher for the compatible abutments. An evaluation of the sequence of preload application revealed differences in the pattern of deformation between the original and compatible abutments, which can have serious clinical implications. Compatible abutments can present critical morphological differences from the original ones. The differences in the cross-sectional geometry result in large differences in the overall contact areas, both in terms of quality and quantity which could have serious implications for the long-term stability of the prosthesis. © 2015 John Wiley & Sons A/S. Published by John Wiley

A prospective, split-mouth study comparing tilted implants with angulated connection versus conventional implants with angulated abutment.

PubMed

Van Weehaeghe, Manú; De Bruyn, Hugo; Vandeweghe, Stefan

2017-12-01

An angulation of the implant connection could overcome the problems related to angulated abutments. This study compares conventional implants with angulated abutment to tilted implants with an angulated connection. Twenty patients were treated in the edentulous mandible. In the posterior jaw locations, one conventional tilted implant with angulated abutment and one angulated implant without abutment were placed. In the anterior jaw, two conventional implants were placed, one with and one without abutment. Implants were immediately loaded and 3 months later, the final bridge (PFM or monolithic zirconia) was placed. After a follow-up of 48 months, 17 patients were available for clinical examination. The mean overall marginal bone loss (MBL) was 1.26 mm. No significant differences in implant survival, MBL, periodontal indices, patients' satisfaction, or complications was found between implants restored on abutment or implant level, between the posteriorly located angulated implant nor angulated abutment, and between both anterior implants with or without abutment. The posterior implants demonstrated less MBL compared to the anterior implants (P < .001). There was no significant difference in MBL between the implants restored with zirconia or PFM bridges (P = .294). Overall mean pocket depth was 2.83 mm. More plaque was found in the PFM group compared to the full-zirconia group, at the bridge (P = .042) and the implants (P = .029). There was no difference between both materials in pocket depth (P = .635) or bleeding (P = .821). One zirconia bridge fractured, two angulated abutment were replaced and four loose bridge screws connected to the angulated abutments had to be tightened. Patients were overall satisfied (4.74/5). An implant with angulated connection may results in a stronger connection but does not affect the marginal bone loss. No difference in MBL was seen between implants restored on abutment or implant level. Zirconia seems to reduce

Influence of implant location on the clinical outcomes of implant abutments: a systematic review and meta-analysis

PubMed Central

ElHoussiney, Amr G; Zhang, He; Song, Jinlin; Ji, Ping; Wang, Lu; Yang, Sheng

2018-01-01

Purpose To compare the failure events and incidence of complications of different abutment materials in anterior and posterior regions. Failure was defined as complete loss of the abutment requiring replacement by a new abutment. Materials and methods Electronic searches using PubMed/Medline and Google Scholar complemented with manual searches were performed with specific search terms. Searches were restricted to publications in English between January 2006 and March 2016. Results A total of 863 and 1,264 implants were inserted in the anterior and posterior regions, respectively, in a total of 1,529 patients. No titanium abutments failed in anterior or posterior regions. On the other hand, 1.6% of zirconia abutments failed in the anterior region and 1.5% failed in the posterior region. Technical complications occurred mostly in the posterior region and mostly involved zirconia abutment. Meta-analysis was possible only for zirconia-abutment failure, due to considerable heterogeneity of studies and outcome variables. No significant difference in failure rate was found between anterior and posterior zirconia abutments (risk ratio 1.53, 95% CI 0.49–4.77; P=0.47). Conclusion This systematic review and meta-analysis showed similar outcomes of different abutment materials when used in anterior and posterior regions in terms of failure events and biological and aesthetic complications. The only significant finding was the increased incidence of technical complications in the posterior region, mostly involving zirconia abutments. Abutment-screw loosening was the most common technical complication. PMID:29520162

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

PubMed

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

2013-10-01

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). 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). 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. 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.

In Vitro Microbiological Analysis of Bacterial Seal in Hybrid Zirconia Abutment Tapered Connection.

PubMed

Harlos, Maurício Marcelo; Bezerra da Silva, Thiago; Peruzzo, Daiane C; Napimoga, Marcelo H; Joly, Julio Cesar; Martinez, Elizabeth F

2017-04-01

The aim of this study was to evaluate the bacterial seal at the implant-hybrid zirconia abutment interface and Morse taper-type connections through in vitro microbiological analysis. Sixteen implants and their respective abutments were divided into 3 groups: test (10 sets), positive control (3 sets), and negative control (3 sets). In the test group, 10 implants were contaminated with Escherichia coli using a sterile inoculating loop to the inner portion of the implants, followed by torque application to the abutment (30 N·cm). The positive controls were also contaminated, but no torque was applied to the abutment screw. The negative control consisted of uncontaminated sets. All specimens were immersed in test tubes containing 5 mL brain heart infusion (BHI) broth, maintained in a microbiological incubator for 14 days at 37°C under aerobic conditions, and monitored every 24 hours for evidence of bacterial growth. During the 14 days of incubation, no significant increase in the number of cloudy culture media was observed in the test group (P = 0.448). No significant difference in broth turbidity ratio was observed (P > 0.05). Hybrid zirconia abutments can create an effective seal at the tapered abutment-implant interface with a 30-N·cm installation torque.

Load fatigue performance of four implant-abutment interface designs: effect of torque level and implant system.

PubMed

Quek, H C; Tan, Keson B; Nicholls, Jack I

2008-01-01

Biomechanical load-fatigue performance data on single-tooth implant systems with different implant-abutment interface designs is lacking in the literature. This study evaluated the load fatigue performance of 4 implant-abutment interface designs (Brånemark-CeraOne; 3i Osseotite-STA abutment; Replace Select-Easy abutment; and Lifecore Stage-1-COC abutment system). The number of load cycles to fatigue failure of 4 implant-abutment designs was tested with a custom rotational load fatigue machine. The effect of increasing and decreasing the tightening torque by 20% respectively on the load fatigue performance was also investigated. Three different tightening torque levels (recommended torque, -20% recommended torque, +20% recommended torque) were applied to the 4 implant systems. There were 12 test groups with 5 samples in each group. The rotational load fatigue machine subjected specimens to a sinusoidally applied 35 Ncm bending moment at a test frequency of 14 Hz. The number of cycles to failure was recorded. A cutoff of 5 x 10(6) cycles was applied as an upper limit. There were 2 implant failures and 1 abutment screw failure in the Brånemark group. Five abutment screw failures and 4 implant failures was recorded for the 3i system. The Replace Select system had 1 implant failure. Five cone screw failures were noted for the Lifecore system. Analysis of variance revealed no statistically significant difference in load cycles to failure for the 4 different implant-abutment systems torqued at recommended torque level. A statistically significant difference was found between the -20% torque group and the +20% torque group (P < .05) for the 3i system. Load fatigue performance and failure location is system specific and related to the design characteristics of the implant-abutment combination. It appeared that if the implant-abutment interface was maintained, load fatigue failure would occur at the weakest point of the implant. It is important to use the torque level

Effects of artificial aging conditions on yttria-stabilized zirconia implant abutments.

PubMed

Basílio, Mariana de Almeida; Cardoso, Kátia Vieira; Antonio, Selma Gutierrez; Rizkalla, Amin Sami; Santos Junior, Gildo Coelho; Arioli Filho, João Neudenir

2016-08-01

Most ceramic abutments are fabricated from yttria-stabilized tetragonal zirconia (Y-TZP). However, Y-TZP undergoes hydrothermal degradation, a process that is not well understood. The purpose of this in vitro study was to assess the effects of artificial aging conditions on the fracture load, phase stability, and surface microstructure of a Y-TZP abutment. Thirty-two prefabricated Y-TZP abutments were screwed and tightened down to external hexagon implants and divided into 4 groups (n = 8): C, control; MC, mechanical cycling (1×10(6) cycles; 10 Hz); AUT, autoclaving (134°C; 5 hours; 0.2 MPa); and TC, thermal cycling (10(4) cycles; 5°/55°C). A single-load-to-fracture test was performed at a crosshead speed of 0.5 mm/min to assess the assembly's resistance to fracture (ISO Norm 14801). X-ray diffraction (XRD) analysis was applied to observe and quantify the tetragonal-monoclinic (t-m) phase transformation. Representative abutments were examined with high-resolution scanning electron microscopy (SEM) to observe the surface characteristics of the abutments. Load-to-fracture test results (N) were compared by ANOVA and Tukey test (α=.05). XRD measurements revealed the monoclinic phase in some abutments after each aging condition. All the aging conditions reduced the fracture load significantly (P<.001). Mechanical cycling reduced the fracture load more than autoclaving (P=.034). No differences were found in the process of surface degradation among the groups; however, the SEM detected grinding-induced surface flaws and microcracks. The resistance to fracture and the phase stability of Y-TZP implant abutments were susceptible to hydrothermal and mechanical conditions. The surface microstructure of Y-TZP abutments did not change after aging conditions. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Soft tissues stability of cad-cam and stock abutments in anterior regions: 2-year prospective multicentric cohort study.

PubMed

Lops, Diego; Bressan, Eriberto; Parpaiola, Andrea; Sbricoli, Luca; Cecchinato, Denis; Romeo, Eugenio

2015-12-01

Aim of this study was to verify if the type of implant abutment manufacturing, stock or cad-cam, could influence the maintenance of stable gingival margins around single restorations in anterior areas. After 16 weeks of healing, implants (Osseospeed, Astra Tech Dental Implant) were positioned. Depending on the different fixture inclination and the thickness of buccal peri-implant soft tissue, abutment selection resulted in four groups: Group 1 (patients with zirconia ZirDesign(®) stock abutments), Group 2 (titanium stock TiDesign(®) abutments), Group 3 (zirconia cad-cam abutments), and Group 4 (titanium cad-cam abutments). The following parameters were assessed: buccal gingival margin modification (BGM). The modification of the implant gingival margin was followed at 1 and 2 years of follow-up. A computerized analysis was performed for measurements. Differences between soft tissue margin at baseline and after 2 years measured the gingival margin recession. A general linear model was used to evaluate each group in relation to gingival recession after two years. Tukey's post hoc test was used to compare the mean REC indexes of each group of abutments. Seventy-two healthy patients (39 males and 33 females; mean age of 46 years) scheduled for single gap rehabilitation in anterior areas were enrolled. A 100% of implant survival rate was observed after 24 months of function. One failure occurred due to fracture of a Zirconia cad-cam abutment. Moreover, two abutment screw unscrewing were observed. Both for zirconia and titanium stock abutments (Group 1 and 2), the mean recession of implant buccal soft tissue was of 0.3 mm (SD of 0.3 and 0.4 mm, respectively). Soft tissue mean recession of zirconia and titanium cad-cam abutments (Group 3 and 4) was of 0.1 and -0.3 mm, respectively (SD of 0.3 and 0.4 mm, respectively). REC values of cad-cam titanium abutments (Group 4) were significantly lower than that of Group 1 (-0.57 mm), Group 2 (-0.61 mm), and Group 3 (-0.40 mm

Salivary bacterial leakage into implant-abutment connections: preliminary results of an in vitro study.

PubMed

Mencio, F; Papi, P; Di Carlo, S; Pompa, G

2016-06-01

The occurrence of bacterial leakage in the internal surface of implants, through implant-abutment interface (IAI), is one of the parameters for analyzing the fabrication quality of the connections. The aim of this in vitro study is to evaluate two different types of implant-abutment connections: the screwed connection (Group 1) and the cemented connection (Group 2), analyzing the permeability of the IAI to bacterial colonization, using human saliva as culture medium. A total of twelve implants were tested, six in each experimental group. Five healthy patients were enrolled in this study. Two milliliters of non-stimulated saliva were collected from each subject and mixed in a test tube. After 14 days of incubation of the bacteria sample in the implant fixtures, a PCR-Real Time analysis was performed. Fisher's exact test was used to compare the proportions of implant-abutment assembled structures detected with bacterial leakage. Differences in the bacterial counts of the two groups were compared using the Mann-Whitney U test. A p value < 0.05 was considered significant. The results showed a decreased stability with the screwed implant-abutment connections compared to the cemented implant-abutment connections. A mean total bacterial count of 1.2E+07 (± 0.25E+07) for Group 1 and of 7.2E+04 (± 14.4E+04) for Group 2 was found, with a high level of significance, p = .0001. Within the limitations of this study it can be concluded that bacterial species from human saliva may penetrate along the implant-abutment interface in both connections, however the cemented connection implants showed the lowest amount of bacterial colonization.

Resistance of three implant-abutment interfaces to fatigue testing

PubMed Central

RIBEIRO, Cleide Gisele; MAIA, Maria Luiza Cabral; SCHERRER, Susanne S.; CARDOSO, Antonio Carlos; WISKOTT, H. W. Anselm

2011-01-01

The design and retentive properties of implant-abutment connectors affect the mechanical resistance of implants. A number of studies have been carried out to compare the efficacy of connecting mechanisms between abutment and fixture. Objectives The aims of this study were: 1) to compare 3 implant-abutment interfaces (external hexagon, internal hexagon and cone-in-cone) regarding the fatigue resistance of the prosthetic screw, 2) to evaluate the corresponding mode of failure, and 3) to compare the results of this study with data obtained in previous studies on Nobel Biocare and Straumann connectors. Materials and Methods In order to duplicate the alternating and multivectorial intraoral loading pattern, the specimens were submitted to the rotating cantilever beam test. The implants, abutments and restoration analogs were spun around their longitudinal axes while a perpendicular force was applied to the external end. The objective was to determine the force level at which 50% of the specimens survived 106 load cycles. The mean force levels at which 50% failed and the corresponding 95% confidence intervals were determined using the staircase procedure. Results The external hexagon interface presented better than the cone-in-cone and internal hexagon interfaces. There was no significant difference between the cone-in-cone and internal hex interfaces. Conclusion Although internal connections present a more favorable design, this study did not show any advantage in terms of strength. The external hexagon connector used in this study yielded similar results to those obtained in a previous study with Nobel Biocare and Straumann systems. However, the internal connections (cone-in-cone and internal hexagon) were mechanically inferior compared to previous results. PMID:21710094

Development of a new quantitative gas permeability method for dental implant-abutment connection tightness assessment

PubMed Central

2011-01-01

Background Most dental implant systems are presently made of two pieces: the implant itself and the abutment. The connection tightness between those two pieces is a key point to prevent bacterial proliferation, tissue inflammation and bone loss. The leak has been previously estimated by microbial, color tracer and endotoxin percolation. Methods A new nitrogen flow technique was developed for implant-abutment connection leakage measurement, adapted from a recent, sensitive, reproducible and quantitative method used to assess endodontic sealing. Results The results show very significant differences between various sealing and screwing conditions. The remaining flow was lower after key screwing compared to hand screwing (p = 0.03) and remained different from the negative test (p = 0.0004). The method reproducibility was very good, with a coefficient of variation of 1.29%. Conclusions Therefore, the presented new gas flow method appears to be a simple and robust method to compare different implant systems. It allows successive measures without disconnecting the abutment from the implant and should in particular be used to assess the behavior of the connection before and after mechanical stress. PMID:21492459

Design of piles for integral abutment bridges.

DOT National Transportation Integrated Search

1984-08-01

More and more, integral abutment bridges are being used in place : of the more traditional bridge designs with expansion releases. In : this study, states which use integral abutment bridges were surveyed : to determine their current practice in the ...

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

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

PubMed

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

2014-01-01

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

Non-linear 3D evaluation of different oral implant-abutment connections.

PubMed

Streckbein, P; Streckbein, R G; Wilbrand, J F; Malik, C Y; Schaaf, H; Howaldt, H P; Flach, M

2012-12-01

Micro-gaps and osseous overload in the implant-abutment connection are the most common causes of peri-implant bone resorption and implant failure. These undesirable events can be visualized on standardized three-dimensional finite element models and by radiographic methods. The present study investigated the influence of 7 available implant systems (Ankylos, Astra, Bego, Brånemark, Camlog, Straumann, and Xive) with different implant-abutment connections on bone overload and the appearance of micro-gaps in vitro. The individual geometries of the implants were transferred to three-dimensional finite element models. In a non-linear analysis considering the pre-loading of the occlusion screw, friction between the implant and abutment, the influence of the cone angle on bone strain, and the appearance of micro-gaps were determined. Increased bone strains were correlated with small (< 15°) cone angles. Conical implant-abutment connections efficiently avoided micro-gaps but had a negative effect on peri-implant bone strain. Bone strain was reduced in implants with greater wall thickness (Ankylos) or a smaller cone angle (Bego). The results of our in silico study provide a solid basis for the reduction of peri-implant bone strain and micro-gaps in the implant-abutment connection to improve long-term stability.

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

PubMed

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

2018-02-01

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

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

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

PubMed

Shim, Hye Won; Yang, Byoung-Eun

2015-12-01

To evaluate the cumulative survival rate (CSR) and mechanical complications of single-tooth Ankylos® implants. 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. 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). 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.

GRS bridge piers and abutments.

DOT National Transportation Integrated Search

2001-01-01

This report presents the following three recent projects on load testing of geosynthetic-reinforced soil (GRS) bridge abutments and piers: a full-scale bridge pier load test conducted by the Turner-Fairbank Highway Research Center, Federal Highway Ad...

Fracture Resistance of Implant Abutments Following Abutment Alterations by Milling the Margins: An In Vitro Study.

PubMed

Patankar, Anuya; Kheur, Mohit; Kheur, Supriya; Lakha, Tabrez; Burhanpurwala, Murtuza

2016-12-01

This in vitro study evaluated the effect of different levels of preparation of an implant abutment on its fracture resistance. The study evaluated abutments that incorporated a platform switch (Myriad Plus Abutments, Morse Taper Connection) and Standard abutments (BioHorizons Standard Abutment, BioHorizons Inc). Each abutment was connected to an appropriate implant and mounted in a self-cured resin base. Based on the abutment preparation depths, 3 groups were created for each abutment type: as manufactured, abutment prepared 1 mm apical to the original margin, and abutment prepared 1.5 mm to the original margin. All the abutments were prepared in a standardized manner to incorporate a 0.5 mm chamfer margin uniformly. All the abutments were torqued to 30 Ncm on their respective implants. They were then subjected to loading until failure in a universal testing machine. Abutments with no preparation showed the maximum resistance to fracture for both groups. As the preparation depth increased, the fracture resistance decreased. The fracture resistance of implant abutment junction decreases as the preparation depth increases.

Long-term outcome of cemented versus screw-retained implant-supported partial restorations.

PubMed

Nissan, Joseph; Narobai, Demitri; Gross, Ora; Ghelfan, Oded; Chaushu, Gavriel

2011-01-01

The present study was designed to compare the long-term outcome and complications of cemented versus screw-retained implant restorations in partially edentulous patients. Consecutive patients with bilateral partial posterior edentulism comprised the study group. Implants were placed, and cemented or screw-retained restorations were randomly assigned to the patients in a split-mouth design. Follow-up (up to 15 years) examinations were performed every 6 months in the first year and every 12 months in subsequent years. The following parameters were evaluated and recorded at each recall appointment: ceramic fracture, abutment screw loosening, metal frame fracture, Gingival Index, and marginal bone loss. Thirty-eight patients were treated with 221 implants to support partial prostheses. No implants during the follow-up period (mean follow-up, 66 ± 47 months for screw-retained restorations [range, 18 to 180 months] and 61 ± 40 months for cemented restorations [range, 18 to 159 months]). Ceramic fracture occurred significantly more frequently (P < .001) in screw-retained (38% ± 0.3%) than in cemented (4% ± 0.1%) restorations. Abutment screw loosening occurred statistically significantly more often (P = .001) in screw-retained (32% ± 0.3%) than in cement-retained (9% ± 0.2%) restorations. There were no metal frame fractures in either type of restoration. The mean Gingival Index scores were statistically significantly higher (P < .001) for screw-retained (0.48 ± 0.5) than for cemented (0.09 ± 0.3) restorations. The mean marginal bone loss was statistically significantly higher (P < .001) for screw-retained (1.4 ± 0.6 mm) than for cemented (0.69 ± 0.5 mm) restorations. The long-term outcome of cemented implant-supported restorations was superior to that of screw-retained restorations, both clinically and biologically.

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.

Effect of framework soldering on the deformation of implant abutments after framework seating: a study with strain gauges.

PubMed

Mendes, Stella de N C; Edwards Rezende, Carlos E; Moretti Neto, Rafael T; Capello Sousa, Edson A; Henrique Rubo, José

2013-04-01

Passive fit has been considered an important requirement for the longevity of implant-supported prostheses. Among the different steps of prostheses construction, casting is a feature that can influence the precision of fit and consequently the uniformity of possible deformation among abutments upon the framework connection. This study aimed at evaluating the deformation of abutments after the connection of frameworks either cast in one piece or after soldering. A master model was used to simulate a human mandible with 5 implants. Ten frameworks were fabricated on cast models and divided into 2 groups. Strain gauges were attached to the mesial and distal sides of the abutments to capture their deformation after the framework's screw retentions were tightened to the abutments. The mean values of deformation were submitted to a 3-way analysis of variance that revealed significant differences between procedures and the abutment side. The results showed that none of the frameworks presented a complete passive fit. The soldering procedure led to a better although uneven distribution of compression strains on the abutments.

Influence of Abutment Color and Mucosal Thickness on Soft Tissue Color.

PubMed

Ferrari, Marco; Carrabba, Michele; Vichi, Alessandro; Goracci, Cecilia; Cagidiaco, Maria Crysanti

Zirconia (ZrO₂) and titanium nitride (TiN) implant abutments were introduced mainly for esthetic purposes, as titanium's gray color can be visible through mucosal tissues. This study was aimed at assessing whether ZrO₂ and TiN abutments could achieve better esthetics in comparison with titanium (Ti) abutments, regarding the appearance of soft tissues. Ninety patients were included in the study. Each patient was provided with an implant (OsseoSpeed, Dentsply Implant System). A two-stage surgical technique was performed. Six months later, surgical reentry was performed. After 1 week, provisional restorations were screwed onto the implants. After 8 weeks, implant-level impressions were taken and soft tissue thickness was recorded, ranking thin (≤ 2 mm) or thick (≥ 2 mm). Patients were randomly allocated to three experimental groups, based on abutment type: (1) Ti, (2) TiN, and (3) ZrO₂. After 15 weeks, the final restorations were delivered. The mucosal area referring to each abutment was measured for color using a clinical spectrophotometer (Easyshade, VITA); color measurements of the contralateral areas referring to natural teeth were performed at the same time. The data were collected using the Commission Internationale de l'Eclairage (CIE) L*a*b* color system, and ΔE was calculated between peri-implant and contralateral soft tissues. A critical threshold of ΔE = 3.7 was selected. The chi-square test was used to identify statistically significant differences in ΔE between thin and thick mucosal tissues and among the abutment types. Three patients were lost at follow-up. No statistically significant differences were noticed as to the abutment type (P = .966). Statistically significant differences in ΔE were recorded between thick and thin peri-implant soft tissues (P < .001). Only 2 out of 64 patients with thick soft tissues showed a ΔE higher than 3.7: 1 in the TiN group and 1 in the ZrO₂ group. All the patients with thin soft tissues reported color

The effect of photodynamic therapy on pathogenic bacteria around peri-implant sulcus and in the cavity between abutment and implant after healing phase: A prospective clinical study.

PubMed

Zhou, Lin-Yi; Shi, Jun-Yu; Zhu, Yu; Qian, Shu-Jiao; Lai, Hong-Chang; Gu, Ying-Xin

2018-05-14

To compare levels of pathogens from peri-implant sulcus versus abutment screw cavities after photodynamic therapy. Twenty patients were included. Photodynamic therapy (PDT) was applied both in sulcus and cavities after sampling following suprastructures loading, and repeated after 2 weeks. Two samples each containing four paper points were collected for each implant at baseline, 2 weeks, 3 months: (i) peri-implant sulcus and (ii) abutment screw cavities. Seventy-five percent ethanol was applied in another 20 patients as the control group in the same way. qPCR was used to quantify periodontal pathogens: Porphyromonas gingivalis, Fusobacterium nucleatum, Streptococcus mutans. PDT showed a better bacterial reduction than ethanol. P. g. and F. n. were most frequently detected, while less for S. m. P. gingivalis' proportion from both sites was significantly higher than the other two bacteria (P < 0.05), except for 2 weeks' peri-implant sulcus sample. Bacteria counts from abutment screw cavities were always less than those from peri-implant sulcus and was significantly lower for total bacteria at 3 months (P < 0.05). Total bacterial from abutment screw cavities significantly reduced at 3 months compared to baseline (P < 0.05). PDT appears to be effective in bacterial reduction compared to ethanol and can reduce P. gingivalis with short time intervals, as well as decreasing total bacteria counts within abutment screw cavities in the long run, suggesting PDT an effective way sterilizing inner surface of oral implant suprastrutures. Lasers Surg. Med. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

Behavior and analysis of an integral abutment bridge.

DOT National Transportation Integrated Search

2013-08-01

As a result of abutment spalling on the integral abutment bridge over 400 South Street in Salt Lake City, Utah, the Utah Department of Transportation (UDOT) instigated research measures to better understand the behavior of integral abutment bridges. ...

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

[Effect of zirconia abutment angulation on stress distribution in the abutment and the bone around implant: a finite element study].

PubMed

Yang, Yan-zhong; Tian, Xiao-hua; Zhou, Yan-min

2015-08-01

To investigate the effect of three different zirconia angular abutments on the stress distribution in bone and abutment using three-dimensional finite element analysis, and provide instruction for clinical application. Finite element analysis (FEA) was applied to analyze the stress distribution of three different zirconia/titanium angular abutments and bone around implant. The maximum Von Minses stress that existed in abutment, bolt and bone of the angular abutment model was significantly higher than that existed in the straight abutment model. The maximum Von Minses stress that existed in abutment, bolt and bone of the 20 ° angular abutment model was significantly higher than that existed in 15 ° angular abutment model. There was no significant difference between zirconia abutment model and titanium abutment model. The abutment angulation has a significant influence on the stress distribution in the abutment, bolt and bone, and exacerbates as the angulation increases, which suggest that we should take more attention to the implant orientation and use straight abutment or little angular abutment. The zirconia abutment can be used safely, and there is no noticeable difference between zirconia abutment and titanium abutment on stress distribution.

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.

An In Vitro Evaluation of the Loosening of Different Interchangeable Abutments in Internal-Connection-Type Implants.

PubMed

Park, Ji-Man; Baek, Chang-Hyun; Heo, Seong-Joo; Kim, Seong-Kyun; Koak, Jai-Young; Kim, Shin-Koo; Belser, Urs C

The aim of this study was to compare the loosening of interchangeable one-piece abutments connected to internal-connection-type implants after cyclic loading. Four implant abutment groups (n = 7 in each group) with Straumann tissue-level implants were assessed: Straumann solid abutment (group S), Southern Implants solid abutment (group SI), Implant Direct straight abutment (group ID), and Blue Sky Bio regular platform abutment (group BSB). The implant was firmly held in a special jig to ensure fixation. Abutment screws were tightened to manufacturers' recommended torque with a digital torque gauge. The hemispherical loading members were fabricated for the load cell of a universal testing machine to evenly distribute the force on the specimens and to fulfill the ISO 14801:2007 standard. A cyclic loading of 25 N at 30 degrees to the implant's long axis was applied for a duty of a half million cycles. Tightening torques were measured prior to the loading. Removal torques were measured after cyclic loading. The data were analyzed with one-way analysis of variance (ANOVA), and the significance level was set at P < .05. The mean removal torques after cyclic loading were 34.0 ± 1.1 Ncm (group S), 25.0 ± 1.5 Ncm (group SI), 23.9 ± 2.1 Ncm (group ID), and 27.9 ± 1.3 Ncm (group BSB). Removal torques of each group were statistically different in the order of group S > group BSB > groups SI and ID (P < .05). The mean reduction rates were -2.9% ± 3.2% (group S), -21.9% ± 4.8% (group SI), -20.2% ± 7.2% (group ID), and -6.9% ± 4.3% (group BSB) after a half million cycles, respectively. Reduction rates of groups S and BSB were statistically lower than those of groups SI and ID (P < .01). The standard deviation of group S was lower than group BSB. The removal torque of the original Straumann abutment was significantly higher than those of the copy abutments. The reduction rate of the groups S and BSB abutments was lower than those of the other copy abutments.

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. Copyright © 2016 Elsevier B.V. All rights reserved.

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.

Ball Screw Actuator Including a Compliant Ball Screw Stop

NASA Technical Reports Server (NTRS)

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

2017-01-01

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.

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

PubMed

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

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

An in vitro biomechanical comparison of hydroxyapatite coated and uncoated ao cortical bone screws for a limited contact: dynamic compression plate fixation of osteotomized equine 3rd metacarpal bones.

PubMed

Durham, Myra E; Sod, Gary A; Riggs, Laura M; Mitchell, Colin F

2015-02-01

To compare the monotonic biomechanical properties of a broad 4.5 mm limited contact-dynamic compression plate (LC-DCP) fixation secured with hydroxyapatite (HA) coated cortical bone screws (HA-LC-DCP) versus uncoated cortical bone screws (AO-LC-DCP) to repair osteotomized equine 3rd metacarpal (MC3) bones. Experimental. Adult equine cadaveric MC3 bones (n = 12 pair). Twelve pairs of equine MC3 were divided into 3 test groups (4 pairs each) for: (1) 4 point bending single cycle to failure testing; (2) 4 point bending cyclic fatigue testing; and (3) torsional single cycle to failure testing. For the HA-LC-DCP-MC3 construct, an 8-hole broad LC-DCP (Synthes Ltd, Paoli, PA) was secured on the dorsal surface of each randomly selected MC3 bone with a combination of four 5.5 mm and four 4.5 mm HA-coated cortical screws. For the AO-LC-DCP-MC3 construct, an 8-hole 4.5 mm broad LC-DCP was secured on the dorsal surface of the contralateral MC3 bone with a combination of four 5.5 mm and four 4.5 mm uncoated cortical screws. All MC3 bones had mid-diaphyseal osteotomies. Mean test variable values for each method were compared using a paired t-test within each group. Significance was set at P < .05. Mean yield load, yield bending moment, composite rigidity, failure load, and failure bending moment, under 4 point bending, single cycle to failure, of the HA-LC-DCP fixation were significantly greater than those of the AO-LC-DCP fixation. Mean ± SD values for the HA-LC-DCP and the AO-LC-DCP fixation techniques, respectively, in single cycle to failure under 4 point bending were: yield load, 26.7 ± 2.15 and 16.3 ± 1.38 kN; yield bending moment, 527.4 ± 42.4 and 322.9 ± 27.2 N-m; composite rigidity, 5306 ± 399 and 3003 ± 300 N-m/rad; failure load, 40.6 ± 3.94 and 26.5 ± 2.52 kN; and failure bending moment, 801.9 ± 77.9 and 522.9 ± 52.2 N-m. Mean cycles to failure in 4 point bending of the HA

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.

Measurement of the rotational misfit and implant-abutment gap of all-ceramic abutments.

PubMed

Garine, Wael N; Funkenbusch, Paul D; Ercoli, Carlo; Wodenscheck, Joseph; Murphy, William C

2007-01-01

The specific aims of this study were to measure the implant and abutment hexagonal dimensions, to measure the rotational misfit between implant and abutments, and to correlate the dimension of the gap present between the abutment and implant hexagons with the rotational misfit of 5 abutment-implant combinations from 2 manufacturers. Twenty new externally hexed implants (n = 10 for Nobel Biocare; n = 10 for Biomet/3i) and 50 new abutments were used (n = 10; Procera Zirconia; Procera Alumina; Esthetic Ceramic Abutment; ZiReal; and GingiHue post ZR Zero Rotation abutments). The mating surfaces of all implants and abutments were imaged with a scanning electron microscope before and after rotational misfit measurements. The distances between the corners and center of the implant and abutment hexagon were calculated by entering their x and y coordinates, measured on a measuring microscope, into Pythagoras' theorem. The dimensional difference between abutment and implant hexagons was calculated and correlated with the rotational misfit, which was recorded using a precision optical encoder. Each abutment was rotated (3 times/session) clockwise and counterclockwise until binding. Analysis of variance and Student-Newman-Keuls tests were used to compare rotational misfit among groups (alpha = .05). With respect to rotational misfit, the abutment groups were significantly different from one another (P < .001), with the exception of the Procera Zirconia and Esthetic Ceramic groups (P = .4). The mean rotational misfits in degrees were 4.13 +/- 0.68 for the Procera Zirconia group, 3.92 +/- 0.62 for the Procera Alumina group, 4.10 +/- 0.67 for the Esthetic Ceramic group, 3.48 +/- 0.40 for the ZiReal group, and 1.61 +/- 0.24 for the GingiHue post ZR group. There was no correlation between the mean implant-abutment gap and rotational misfit. Within the limits of this study, machining inconsistencies of the hexagons were found for all implants and abutments tested. The GingiHue Post

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.

Microleakage of the prosthetic abutment/implant interface with internal and external connection: in vitro study.

PubMed

Larrucea Verdugo, Carlos; Jaramillo Núñez, Guido; Acevedo Avila, Ariel; Larrucea San Martín, Carlo

2014-09-01

This study determined the degree of marginal microleakage of the abutment-implant interface on platforms with Morse taper connection and external connection. For this in vitro study, 42 implants, 21 with external connection and 21 with Morse taper connection, were used, immersed in acrylic resin cylinders. Each implant was joined by a prosthetic abutment screw tightened at different degrees, forming the six study groups: (1) External connection, manual tightening (2) External connection, 20 Newton (N) tightening (3) External connection, 30 N tightening (4) Morse taper connection, manual tightening (5) Morse taper connection, 20 N tightening (6) orse taper connection, 30 N tightening. All samples were subjected to load cycling and thermocycling. Then, they were submerged in a solution of 0.2% methylene blue for 24 h. Finally, the microleakage was measured via 20× optical microscopy in each study group, average was obtained, and Mann-Whitney test was applied. Statistically significant differences (P < 0.001) were found between the levels of microleakage presented in the Morse taper connection implants (1.48) and external connection implants (2.8) in all three types of tightening. Microleakage levels decreases when increasing torque is applied to the screws. Morse taper connection implants showed lower levels of microleakage than external connection implants; also, it was observed that microleakage decreases in the way torque increases. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Dental implants as strategic supplementary abutments for implant-tooth-supported telescopic crown-retained maxillary dentures: a retrospective follow-up study for up to 9 years.

PubMed

Krennmair, Gerald; Krainhöfner, Martin; Waldenberger, Otmar; Piehslinger, Eva

2007-01-01

The aim of this retrospective study was to present the results of implants and natural teeth used as combined abutments to support maxillary telescopic prostheses. Between 1997 and 2004, 22 patients with residual maxillary teeth underwent prosthodontic rehabilitation with supplementary implant placement of implant-tooth-supported telescopic prostheses. A total of 60 supplementary implants (mean: 2.9 implants; SD: 1.6; range: 1 to 5 per patient) were placed in strategic position and connected with 48 natural abutment teeth (mean: 2.2 teeth; SD: 0.9; range: 1 to 4 per patient) using telescopic crowns. The follow-up registration included implant and natural tooth survival rates and peri-implant and periodontal parameters, along with prosthodontic maintenance. Natural tooth abutments were additionally followed to compare their periodontal parameters at baseline to the follow-up examination. After a mean of 38 months (12 to 108 months) no implants or natural tooth abutments were lost (survival rate: 100%). There was no fracture, endodontic treatment, loss, or intrusion of natural teeth used for telescopic abutments. Implant abutments showed high stability and excellent periimplant soft tissue conditions. Natural tooth abutments used for double crowns also showed uneventful progress. A low rate of prosthodontic maintenance was seen, with implant screw abutment loosening as the most severe complication (3 of 60 implants; 5%). On the basis of this retrospective clinical review, the following conclusions were drawn: (1) successful function over a prolonged period and a minor complication rate of implant-tooth-supported telescopic maxillary dentures may be anticipated, and (2) the great variety of treatment modalities offered by tooth-implant support for telescopic prostheses appears to be useful as a treatment option for the maxilla in elderly patients.

Incidence of undetected cement on CAD/CAM monolithic zirconia crowns and customized CAD/CAM implant abutments. A prospective case series.

PubMed

Wasiluk, Grzegorz; Chomik, Ewa; Gehrke, Peter; Pietruska, Małgorzata; Skurska, Anna; Pietruski, Jan

2017-07-01

The aim of this study was to assess the frequency of cement residues after cementation of CAD/CAM monolithic zirconia crowns on customized CAD/CAM titanium abutments. Sixty premolars and molars were restored on Astra Tech Osseospeed TX ™ implants using single monolithic zirconia crowns fixed on two types of custom-made abutments: Atlantis ™ titanium or Atlantis ™ Gold Hue. Occlusal openings providing access to the abutment screws were designed for retrievability of the crown/abutment connection. After fixation with glass ionomer cement, the crown/abutment units were unscrewed to evaluate the presence of residual cement. Dichotomous assessment of the presence or absence of cement at the crown/abutment unit and peri-implant tissues was performed. Clinically undetected cement excess was visible on 44 of 60 restorations (73.3%). There was no interdependency between residual cement presence and implant location or diameter. However, a dependency between the presence of residual cement and the aspect of the abutment/crown connection could be noted. The majority of the residues were observed on the distal (17.9%) and mesial (15%) aspects. While on the palatal/lingual aspect, the cement was visible in 8.8%; only 3.4% of all surfaces displayed cement residues. Within the limitations of the study, it can be concluded that the use of customized CAD/CAM abutments do not guarantee avoidance of subgingival cement residues after crown cementation. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Oral mucosa tissue response to titanium cover screws.

PubMed

Olmedo, Daniel G; Paparella, María L; Spielberg, Martín; Brandizzi, Daniel; Guglielmotti, María B; Cabrini, Rómulo L

2012-08-01

Titanium is the most widely used metal in dental implantology. The release of particles from metal structures into the biologic milieu may be the result of electrochemical processes (corrosion) and/or mechanical disruption during insertion, abutment connection, or removal of failing implants. The aim of the present study is to evaluate tissue response of human oral mucosa adjacent to titanium cover screws. One hundred fifty-three biopsies of the supra-implant oral mucosa adjacent to the cover screw of submerged dental implants were analyzed. Histologic studies were performed to analyze epithelial and connective tissue as well as the presence of metal particles, which were identified using microchemical analysis. Langerhans cells, macrophages, and T lymphocytes were studied using immunohistochemical techniques. The surface of the cover screws was evaluated by scanning electron microscopy (SEM). Forty-one percent of mucosa biopsies exhibited metal particles in different layers of the section thickness. Particle number and size varied greatly among specimens. Immunohistochemical study confirmed the presence of macrophages and T lymphocytes associated with the metal particles. Microchemical analysis revealed the presence of titanium in the particles. On SEM analysis, the surface of the screws exhibited depressions and irregularities. The biologic effects seen in the mucosa in contact with the cover screws might be associated with the presence of titanium or other elements, such as aluminum or vanadium. The potential long-term biologic effects of particles on soft tissues adjacent to metallic devices should be further investigated because these effects might affect the clinical outcome of the implant.

Method for partially coating laser diode facets

NASA Technical Reports Server (NTRS)

Dholakia, Anil R. (Inventor)

1990-01-01

Bars of integral laser diode devices cleaved from a wafer are placed with their p regions abutting and n regions abutting. A thin BeCu mask having alternate openings and strips of the same width as the end facets is used to mask the n region interfaces so that multiple bars can be partially coated over their exposed p regions with a reflective or partial reflective coating. The partial coating permits identification of the emitting facet from the fully coated back facet during a later device mounting procedure.

19. DETAIL, WEST ABUTMENT, FROM NORTH, SHOWING SQUARED STONE MASONRY ...

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

19. DETAIL, WEST ABUTMENT, FROM NORTH, SHOWING SQUARED STONE MASONRY ABUTMENT, WITH PORTION OF SUPERSTRUCTURE - Virginia Department of Transportation Bridge No. 6051, Spanning Catoctin Creek at State Route 673 (Featherbottom Road), Waterford, Loudoun County, VA

18. DETAIL, WEST ABUTMENT, FROM NORTHEAST, SHOWING SQUARED STONE MASONRY ...

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

18. DETAIL, WEST ABUTMENT, FROM NORTHEAST, SHOWING SQUARED STONE MASONRY ABUTMENT, WITH STRINGERS AND LATERAL BRACING - Virginia Department of Transportation Bridge No. 6051, Spanning Catoctin Creek at State Route 673 (Featherbottom Road), Waterford, Loudoun County, VA

4. South Elevation Columbia Island Abutment Four; South Elevation ...

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

4. South Elevation - Columbia Island Abutment Four; South Elevation - Washington Abutment One - Arlington Memorial Bridge, Spanning Potomac River between Lincoln Memorial & Arlington National Cemetery, Washington, District of Columbia, DC

The influence of different screw tightening forces on the vertical misfit of implant-supported frameworks.

PubMed

Vasconcellos, Diego Klee de; Bottino, Marco Antonio; Nishioka, Renato Sussumu; Valandro, Luiz Felipe; Costa, Elza Maria Valadares da

2005-06-01

The present in vitro study was designed to compare the differences in the vertical misfit of implant-supported frameworks using three different forces for tightening the bridge locking screws: fastening by hand until first resistance, and using torque drivers with 10 and 20Ncm. The investigation was conducted based on the results given by 9 six-unit nickel-chromium (2 abutments/ 4 pontics) screw-retained implant-supported frameworks. The structures were exposed to simulated porcelain firings. The marginal misfit measurements were made using a traveling measuring microscope at selected screw tightening forces: fastening by hand until first resistance, and using torque drivers with 10 and 20Ncm. The results were submitted to one-way ANOVA with repeated measures on one factor, and post hoc pairwise comparisons using Tukey test (5%). The mean marginal misfit of the frameworks, fastening the screws by hand until first resistance, was 41.56µm (SD±12.45µm). The use of torque driver devices caused a significant reduction in marginal opening (p<0.05). With the lowest torque available (10Ncm), the mean marginal discrepancy at the abutment-framework interface was reduced an average of 52% to a mean marginal opening of 19.71µm (SD±2.97µm). After the use of the 20Ncm torque driver, the mean marginal discrepancy of the frameworks was reduced an average of 69% to a mean marginal opening of 12.82µm (SD±4.0µm). Comparing the use of torque drivers with 10 and 20 Ncm torque, the means are not significantly different from one another. The seating force has an important effect on the vertical misfit measurements, once it may considerably narrow the vertical misfit gaps at the abutment-framework interface, thus leading to a misjudgment of the real marginal situation.

Evaluation of Heat Transfer to the Implant-Bone Interface During Removal of Metal Copings Cemented onto Titanium Abutments.

PubMed

Cakan, Umut; Cakan, Murat; Delilbasi, Cagri

2016-01-01

The aim of this investigation was to measure the temperature increase due to heat transferred to the implant-bone interface when the abutment screw channel is accessed or a metal-ceramic crown is sectioned buccally with diamond or tungsten carbide bur using an air rotor, with or without irrigation. Cobalt-chromium copings were cemented onto straight titanium abutments. The temperature changes during removal of the copings were recorded over a period of 1 minute. The sectioning of coping with diamond bur and without water irrigation generated the highest temperature change at the cervical part of the implant. Both crown removal methods resulted in an increase in temperature at the implant-bone interface. However, this temperature change did not exceed 47°C, the potentially damaging threshold for bone reported in the literature.

Stresses in Implant-Supported Fixed Complete Dentures with Different Screw-Tightening Sequences and Torque Application Modes.

PubMed

Barcellos, Leonardo H; Palmeiro, Marina Lobato; Naconecy, Marcos M; Geremia, Tomás; Cervieri, André; Shinkai, Rosemary S

2018-05-17

To compare the effects of different screw-tightening sequences and torque applications on stresses in implant-supported fixed complete dentures supported by five abutments. Strain gauges fixed to the abutments were used to test the sequences 2-4-3-1-5; 1-2-3-4-5; 3-2-4-1-5; and 2-5-4-1-3 with direct 10-Ncm torque or progressive torque (5 + 10 Ncm). Data were analyzed using analysis of variance and standardized effect size. No effects of tightening sequence or torque application were found except for the sequence 3-2-4-1-5 and some small to moderate effect sizes. Screw-tightening sequences and torque application modes have only a marginal effect on residual stresses.

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.

The influence of screw type, alloy and cylinder position on the marginal fit of implant frameworks before and after laser welding.

PubMed

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

2006-04-01

Misfit at the abutment-prosthetic cylinder interface can cause loss of preload, leading to loosening or fracture of gold and titanium screws. To evaluate the influence of screw type, alloy, and cylinder position on marginal fit of implant frameworks before and after laser welding. 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 5mm 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 (alpha=0.05). 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 (24.13 microm) than the hexagonal screws (27.93 microm). Besides, no statistically significant differences were found after laser welding. 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.

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

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.

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 component...

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 component...

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 component...

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 component...

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 component...

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

6. View of east side abutment and wing wall. The ...

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

6. View of east side abutment and wing wall. The detail of this abutment and wing wall is the same for the similar abutment treatment at the west side. - Tipp-Elizabeth Road Bridge, Spanning Great Miami River, Tipp City, Miami County, OH

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.

Biomechanical Comparison of External Fixation and Compression Screws for Transverse Tarsal Joint Arthrodesis.

PubMed

Latt, L Daniel; Glisson, Richard R; Adams, Samuel B; Schuh, Reinhard; Narron, John A; Easley, Mark E

2015-10-01

Transverse tarsal joint arthrodesis is commonly performed in the operative treatment of hindfoot arthritis and acquired flatfoot deformity. While fixation is typically achieved using screws, failure to obtain and maintain joint compression sometimes occurs, potentially leading to nonunion. External fixation is an alternate method of achieving arthrodesis site compression and has the advantage of allowing postoperative compression adjustment when necessary. However, its performance relative to standard screw fixation has not been quantified in this application. We hypothesized that external fixation could provide transverse tarsal joint compression exceeding that possible with screw fixation. Transverse tarsal joint fixation was performed sequentially, first with a circular external fixator and then with compression screws, on 9 fresh-frozen cadaveric legs. The external fixator was attached in abutting rings fixed to the tibia and the hindfoot and a third anterior ring parallel to the hindfoot ring using transverse wires and half-pins in the tibial diaphysis, calcaneus, and metatarsals. Screw fixation comprised two 4.3 mm headless compression screws traversing the talonavicular joint and 1 across the calcaneocuboid joint. Compressive forces generated during incremental fixator foot ring displacement to 20 mm and incremental screw tightening were measured using a custom-fabricated instrumented miniature external fixator spanning the transverse tarsal joint. The maximum compressive force generated by the external fixator averaged 186% of that produced by the screws (range, 104%-391%). Fixator compression surpassed that obtainable with screws at 12 mm of ring displacement and decreased when the tibial ring was detached. No correlation was found between bone density and the compressive force achievable by either fusion method. The compression across the transverse tarsal joint that can be obtained with a circular external fixator including a tibial ring exceeds that

Upper bound of abutment scour in laboratory and field data

USGS Publications Warehouse

Benedict, Stephen

2016-01-01

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 those data to develop envelope curves that define the upper bound of abutment scour. To expand on this previous work, an additional cooperative investigation was initiated to combine the South Carolina data with abutment scour data from other sources and evaluate upper bound patterns with this larger data set. To facilitate this analysis, 446 laboratory and 331 field measurements of abutment scour were compiled into a digital database. This extensive database was used to evaluate the South Carolina abutment scour envelope curves and to develop additional envelope curves that reflected the upper bound of abutment scour depth for the laboratory and field data. The envelope curves provide simple but useful supplementary tools for assessing the potential maximum abutment scour depth in the field setting.

In vivo degradation of a new concept of magnesium-based rivet-screws in the minipig mandibular bone.

PubMed

Schaller, Benoit; Saulacic, Nikola; Beck, Stefan; Imwinkelried, Thomas; Goh, Bee Tin; Nakahara, Ken; Hofstetter, Willy; Iizuka, Tateyuki

2016-12-01

Self-tapping of magnesium screws in hard bone may be a challenge due to the limited torsional strength of magnesium alloys in comparison with titanium. To avoid screw failure upon implantation, the new concept of a rivet-screw was applied to a WE43 magnesium alloy. Hollow cylinders with threads on the outside were expanded inside drill holes of minipig mandibles. During the expansion with a hexagonal mandrel, the threads engaged the surrounding bone and the inside of the screw transformed into a hexagonal screw drive to allow further screwing in or out of the implant. The in vivo degradation of the magnesium implants and the performance of the used coating were studied in a human standard-sized animal model. Four magnesium alloy rivet-screws were implanted in each mandible of 12 minipigs. Six animals received the plasmaelectrolytically coated magnesium alloy implants; another six received the uncoated magnesium alloy rivet-screws. Two further animals received one titanium rivet-screw each as control. In vivo radiologic examination was performed at one, four, and eight weeks. Euthanasia was performed for one group of seven animals (three animals with coated, three with uncoated magnesium alloy implants and one with titanium implant) at 12weeks and for the remaining seven animals at 24weeks. After euthanasia, micro-computed tomography and histological examination with histomorphometry were performed. Significantly less void formation as well as higher bone volume density (BV/TV) and bone-implant contact area (BIC) were measured around the coated implants compared to the uncoated ones. The surface coating was effective in delaying degradation despite plastic deformation. The results showed potential for further development of magnesium hollow coated screws for bone fixation. Copyright © 2016 Elsevier B.V. All rights reserved.

Displacement of Implant Abutments Following Initial and Repeated Torqueing.

PubMed

Yilmaz, Burak; Gilbert, Andy B; Seidt, Jeremy D; McGlumphy, Edwin A; Clelland, Nancy L

2015-01-01

To measure and compare the three-dimensional (3D) position of nine different abutments manufactured by different manufacturers after repeated torqueing on an internal-hexagon implant. Nine tapered implants were placed into an acrylic resin block. Five specimens each of nine different abutments (n = 45) were placed into one of nine implants. The abutments were handtightened and then torqued to the manufacturer-recommended torque of 30 Ncm. After 10 minutes, 30 Ncm of torque was reapplied. Another 10 minutes elapsed before testing was completed. Images were recorded in 12-second intervals. The spatial relationship of the abutments to the resin block was determined using 3D digital image correlation. Commercial image correlation software was used to analyze the displacements. Mean displacements for the abutments were calculated in three dimensions and overall for both torque applications. Statistical comparisons were done with a t test and a step-down Bonferroni correction. The overall 3D displacement of the Atlantis Titanium abutment after the second applied torque was significantly greater than that of two of the eight other abutments. Displacement in all three dimensions for the Atlantis Titanium abutment changed direction between the first and second torque applications. All abutments moved further in the same direction except for the Atlantis Titanium abutment, which moved back toward its original hand-tightened position horizontally after the second torque application. Re-torqueing of abutments after a 10-minute interval leads to minor displacement of varying degrees between the abutment and a tapered implant. A potential effect of embedment relaxation and/or manufacturing errors should be taken into consideration when selecting an abutment for a cement-retained crown on a tapered implant. Accordingly, clinicians may benefit from adjusting cement-retained implant crowns after re-torqueing the abutments to prevent potential occlusal and interproximal contact

Support Ratio Between Abutment and Soft Tissue Under Overdentures: A Comparison Between Use of Two and Four Abutments.

PubMed

Abe, Manami; Yang, Tsung-Chieh; Maeda, Yoshionobu; Ando, Takanori; Wada, Masahiro

The purpose of this preliminary in vivo study was to compare force distribution on abutments (tooth or implant) and tissues supporting overdentures with two or four abutments. A convenience sample of five subjects with tooth and/or implant-supported overdentures was enrolled. Recordings were completed on each subject using a force-measuring system mounted on a metal framework with four anteroposterior spread abutments (A), four abutments with denture bases (B), and on two anterior abutments with denture bases (C). The tissue-support ratio (TSR) was calculated as (A-B)/A or (A-C)/A. TSR values changed 1.5 to 2 times when the number of abutments was reduced from four to two. The amount of tissue strain on the posterior residual ridge increased when the number of abutments was reduced.

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

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.

The screw propeller

NASA Astrophysics Data System (ADS)

Larrabee, E. E.

1980-07-01

Marine and air screw propellers are considered in terms of theoretical hydrodynamics as developed by Joukowsky, Prandtl, and Betz. Attention is given to the flow around wings of finite span where spanwise flow exists and where lift and the bound vorticity must all go smoothly to zero at the wing tips. The concept of a trailing vortex sheet made up of infinitesimal line vortexes roughly aligned with the direction of flight is discussed in this regard. Also considered is induced velocity, which tends to convect the sheet downward at every stage in the roll-up process, the vortex theory of propellers and the Betz-Prandtl circulation distribution. The performance of the Gossamer Albatross and of a pedal-driven biplane called the Chrysalis are also discussed.

Efficiency considerations for the purely tapered interference fit (TIF) abutments used in dental implants.

PubMed

Bozkaya, Dinçer; Müftü, Sinan

2004-08-01

A tapered interference fit provides a mechanically reliable retention mechanism for the implant-abutment interface in a dental implant. Understanding the mechanical properties of the tapered interface with or without a screw at the bottom has been the subject of a considerable amount of studies involving experiments and finite element (FE) analysis. In this paper, approximate closed-form formulas are developed to analyze the mechanics of a tapered interference fit. In particular, the insertion force, the efficiency, defined as the ratio of the pull-out force to insertion force, and the critical insertion depth, which causes the onset of plastic deformation, are analyzed. It is shown that the insertion force is a function of the taper angle, the contact length, the inner and outer radii of the implant, the static and the kinetic coefficients of friction, and the elastic modulii of the implant/abutment materials. The efficiency of the tapered interference fit, which is defined as the ratio of the pull-out force to insertion force, is found to be greater than one, for taper angles that are less than 6 deg when the friction coefficient is 0.3. A safe range of insertion forces has been shown to exist. The lower end of this range depends on the maximum pull-out force that may occur due to occlusion in the multiple tooth restorations and the efficiency of the system; and the upper end of this range depends on the plastic deformation of the abutment and the implant due to interference fit. It has been shown that using a small taper angle and a long contact length widens the safe range of insertion forces.

Abutment tooth loss in patients with overdentures.

PubMed

Ettinger, Ronald L; Qian, Fang

2004-06-01

Since the 1960s, the use of natural teeth as overdenture abutments has become part of accepted clinical practice. Several longitudinal studies have been conducted, but tooth loss has not been reported to be a significant problem. The aim of this study was to identify the incidence and causes of tooth loss in a prospective cohort study of subjects wearing overdentures. The study, conducted between 1973 and 1994, evaluated 273 subjects (62.3 percent male) with a mean age of 59.6 years. Of the 273 subjects with 666 abutments, 74 lost 133 abutments. The most common cause of tooth loss was periodontal disease (29.3 percent) followed by periapical lesions (18.8 percent) and caries (16.5 percent). Through logistic regression, the authors found that subjects who lost teeth were more likely to have medical problems that could cause soft-tissue lesions of the oral mucosa, were less likely to use fluoride daily and were less likely to return for yearly recall visits. The authors found 22 vertical fractures in 17 subjects. Chi2 analysis revealed that overdenture teeth in the maxillary arch that were opposed by natural teeth were more likely to experience vertical fractures. In a study that followed up some patients for as long as 22 years, the rate of tooth loss was 20.0 percent. Many of these failures could have been prevented if patients had practiced better oral hygiene. The findings suggest that if a dentist recommends overdenture therapy, the patient needs to be examined regularly to reduce the risk of experiencing caries and periodontal disease. Also, if the abutments are in the maxilla and are opposed by natural teeth, the dentist should consider using thimble crowns to reduce the risk of vertical fractures.

Tightening of healing abutments: influence of torque on bacterial proliferation risk, an in vitro investigation.

PubMed

Bousquet, Philippe; Bennasar, Isabelle Calas; Tramini, Paul; Jacquemot, Maxime; Cuisinier, Frédéric

2014-12-01

Gap at the implant-healing abutment junction can increase the risk of bacterial proliferation. In this study, we determined the leakage at the microgap, and we evaluated hand screwing among clinicians. The torques tested with nitrogen gas flow were 10, 15, 20, and 30 N cm, and 54 clinicians were asked to torque down a healing abutment as for a surgical procedure. There were no significant differences between 10 and 15 N cm, with a total lack of tightness. For 20 and 30 N cm, there was a notable decrease in leakage. The torque achieved by hand was <10 N cm for 61.7% of the clinicians, between 10 and 15 N cm for 29.1%, between 15 and 20 N cm for 8.0%, and between 20 and 25 N cm for 1.2%. There was a significant difference related to the strength of tightening. Under the conditions of our experiment, the gap of connection was reduced with a torque of ≥20 N cm. Only a small portion of the clinicians could obtain these values by hand. Therefore, a dynamometrical manual wrench should be used to minimize the gap during the osseointegration period.

Intramedullary nails with two lag screws.

PubMed

Brown, C J; Wang, C J; Yettram, A L; Procter, P

2004-06-01

To investigate the structural integrity of intramedullary nails with two lag screws, and to give guidance to orthopaedic surgeons in the choice of appropriate devices. Alternative designs of the construct are considered, and the use of a slotted upper lag screw insertion hole is analysed. Intramedullary fixation devices with a single lag screw have been known to fail at the lag screw insertion hole. Using two lag screws is considered. It has also been proposed to use a slot in the nail for the upper lag screw to prevent the upper lag screw from sticking. Bending and torsion load cases are analysed using finite element method. Consideration of both load conditions is essential. The results present the overall stiffness of the assembly, the load sharing between lag screws, and the possibility for cut-out to occur. While the slot for the upper lag screw might be advantageous with regard to the stresses in the lag screws, it could be detrimental for cut-out occurring adjacent to the lag screws. Comparative analyses demonstrate that two lag screws may be advantageous in patients whose cancellous bone quality is good and who impose large loads on the lag screw/nail interface. However, the use of two screws might pre-dispose to failure by cut-out of the lag screws. The addition of a slotted hole for the upper lag screw appears to do nothing significant to reduce the risk of such a failure. Copyright 2004 Elsevier Ltd.

Comparison of 3D displacements of screw-retained zirconia implant crowns into implants with different internal connections with respect to screw tightening.

PubMed

Rebeeah, Hanadi A; Yilmaz, Burak; Seidt, Jeremy D; McGlumphy, Edwin; Clelland, Nancy; Brantley, William

2018-01-01

Internal conical implant-abutment connections without horizontal platforms may lead to crown displacement during screw tightening and torque application. This displacement may affect the proximal contacts and occlusion of the definitive prosthesis. The purpose of this in vitro study was to evaluate the displacement of custom screw-retained zirconia single crowns into a recently introduced internal conical seal implant-abutment connection in 3D during hand and torque driver screw tightening. Stereolithic acrylic resin models were printed using computed tomography data from a patient missing the maxillary right central incisor. Two different internal connection implant systems (both ∼11.5 mm) were placed in the edentulous site in each model using a surgical guide. Five screw-retained single zirconia computer-aided design and computer-aided manufacturing (CAD-CAM) crowns were fabricated for each system. A pair of high-resolution digital cameras was used to record the relationship of the crown to the model. The crowns were tightened according to the manufacturers' specifications using a torque driver, and the cameras recorded their relative position again. Three-dimensional image correlation was used to measure and compare crown positions, first hand tightened and then torque driven. The displacement test was repeated 3 times for each crown. Commercial image correlation software was used to extract the data and compare the amount of displacement vertically, mesiodistally, and buccolingually. Repeated-measures ANOVA calculated the relative displacements for all 5 specimens for each implant for both crown screw hand tightening and after applied torque. A Student t test with Bonferroni correction was used for pairwise comparison of interest to determine statistical differences between the 2 implants (α=.05). The mean vertical displacements were statistically higher than the mean displacements in the mesiodistal and buccolingual directions for both implants (P<.001

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

OBLIQUE VIEW FROM SOUTHEAST LOOKING NORTHEAST. NOTE CORNERSTONE IN ABUTMENT. ...

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

OBLIQUE VIEW FROM SOUTHEAST LOOKING NORTHEAST. NOTE CORNERSTONE IN ABUTMENT. - Jackson Covered Bridge, Spanning Sugar Creek, CR 775N (Changed from Spanning Sugar Creek), Bloomingdale, Parke County, IN

Structural details below roadway, looking north from south abutment. ...

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

Structural details below roadway, looking north from south abutment. - Pleasantville Covered Bridge, Spanning Little Manatawny Creek at Covered Bridge Road (State Route 1030), Manatawny, Berks County, PA

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

Torsional stiffness after subtalar arthrodesis using second generation headless compression screws: Biomechanical comparison of 2-screw and 3-screw fixation.

PubMed

Riedl, Markus; Glisson, Richard R; Matsumoto, Takumi; Hofstaetter, Stefan G; Easley, Mark E

2017-06-01

Subtalar joint arthrodesis is a common operative treatment for symptomatic subtalar arthrosis. Because excessive relative motion between the talus and calcaneus can delay or prohibit fusion, fixation should be optimized, particularly in patients at risk for subtalar arthrodesis nonunion. Tapered, fully-threaded, variable pitch screws are gaining popularity for this application, but the mechanical properties of joints fixed with these screws have not been characterized completely. We quantified the torsion resistance of 2-screw and 3-screw subtalar joint fixation using this type of screw. Ten pairs of cadaveric subtalar joints were prepared for arthrodesis and fixed using Acutrak 2-7.5 screws. One specimen from each pair was fixed with two diverging posterior screws, and the contralateral joint was fixed using two posterior screws and a third screw directed through the anterior calcaneus into the talar neck. Internal and external torsional loads were applied and joint rotation and torsional stiffness were measured at two torque levels. Internal rotation was significantly less in specimens fixed with three screws. No difference was detectable between 2-screw and 3-screw fixation in external rotation or torsional stiffness in either rotation direction. Both 2-screw and 3-screw fixation exhibited torsion resistance surpassing that reported previously for subtalar joints fixed with two diverging conventional lag screws. Performance of the tapered, fully threaded, variable pitch screws exceeded that of conventional lag screws regardless of whether two or three screws were used. Additional resistance to internal rotation afforded by a third screw placed anteriorly may offer some advantage in patients at risk for nonunion. Copyright © 2017. Published by Elsevier Ltd.

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

PubMed

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

2016-06-01

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

A simplified method to reduce prosthetic misfit for a screw-retained, implant-supported complete denture using a luting technique and laser welding.

PubMed

Longoni, Salvatore; Sartori, Matteo; Davide, Roberto

2004-06-01

An important aim of implant-supported prostheses is to achieve a passive fit of the framework with the abutments to limit the amount of stress transfer to the bone-implant interface. An efficient and standardized technique is proposed. A definitive screw-retained, implant-supported complete denture was fabricated for an immediately loaded provisional screw-retained implant-supported complete denture. Precise fit was achieved by the use of industrial titanium components and the passivity, by an intraoral luting sequence and laser welding.

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

PubMed

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

2015-01-01

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. 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). 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). With carefully planned prosthetic treatment and adequate maintenance of the oral and denture hygiene, we can prevent the periodontal diseases.

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

Physicochemical and microscopic characterization of implant–abutment joints

PubMed Central

Lopes, Patricia A.; Carreiro, Adriana F. P.; Nascimento, Rubens M.; Vahey, Brendan R.; Henriques, Bruno; Souza, Júlio C. M.

2018-01-01

Objective: The purpose of this study was to investigate Morse taper implant–abutment joints by chemical, mechanical, and microscopic analysis. Materials and Methods: Surfaces of 10 Morse taper implants and the correlated abutments were inspected by field emission gun-scanning electron microscopy (FEG-SEM) before connection. The implant–abutment connections were tightened at 32 Ncm. For microgap evaluation by FEG-SEM, the systems were embedded in epoxy resin and cross-sectioned at a perpendicular plane of the implant–abutment joint. Furthermore, nanoindentation tests and chemical analysis were performed at the implant–abutment joints. Statistics: Results were statistically analyzed via one-way analysis of variance, with a significance level of P < 0.05. Results: Defects were noticed on different areas of the abutment surfaces. The minimum and maximum size of microgaps ranged from 0.5 μm up to 5.6 μm. Furthermore, defects were detected throughout the implant–abutment joint that can, ultimately, affect the microgap size after connection. Nanoindentation tests revealed a higher hardness (4.2 ± 0.4 GPa) for abutment composed of Ti6Al4V alloy when compared to implant composed of commercially pure Grade 4 titanium (3.2 ± 0.4 GPa). Conclusions: Surface defects produced during the machining of both implants and abutments can increase the size of microgaps and promote a misfit of implant–abutment joints. In addition, the mismatch in mechanical properties between abutment and implant can promote the wear of surfaces, affecting the size of microgaps and consequently the performance of the joints during mastication. PMID:29657532

Physicochemical and microscopic characterization of implant-abutment joints.

PubMed

Lopes, Patricia A; Carreiro, Adriana F P; Nascimento, Rubens M; Vahey, Brendan R; Henriques, Bruno; Souza, Júlio C M

2018-01-01

The purpose of this study was to investigate Morse taper implant-abutment joints by chemical, mechanical, and microscopic analysis. Surfaces of 10 Morse taper implants and the correlated abutments were inspected by field emission gun-scanning electron microscopy (FEG-SEM) before connection. The implant-abutment connections were tightened at 32 Ncm. For microgap evaluation by FEG-SEM, the systems were embedded in epoxy resin and cross-sectioned at a perpendicular plane of the implant-abutment joint. Furthermore, nanoindentation tests and chemical analysis were performed at the implant-abutment joints. Results were statistically analyzed via one-way analysis of variance, with a significance level of P < 0.05. Defects were noticed on different areas of the abutment surfaces. The minimum and maximum size of microgaps ranged from 0.5 μm up to 5.6 μm. Furthermore, defects were detected throughout the implant-abutment joint that can, ultimately, affect the microgap size after connection. Nanoindentation tests revealed a higher hardness (4.2 ± 0.4 GPa) for abutment composed of Ti6Al4V alloy when compared to implant composed of commercially pure Grade 4 titanium (3.2 ± 0.4 GPa). Surface defects produced during the machining of both implants and abutments can increase the size of microgaps and promote a misfit of implant-abutment joints. In addition, the mismatch in mechanical properties between abutment and implant can promote the wear of surfaces, affecting the size of microgaps and consequently the performance of the joints during mastication.

Clinical Characteristics of Abutment Teeth with Gingival Discoloration.

PubMed

Ristic, Ljubisa; Dakovic, Dragana; Postic, Srdjan; Lazic, Zoran; Bacevic, Miljana; Vucevic, Dragana

2017-04-06

The grey-bluish discoloration of gingiva (known as "amalgam tattoo") does not appear only in the presence of amalgam restorations. It may also be seen in cases of teeth restored with cast dowels and porcelain-fused-to-metal (PFM) restorations. The aim of this article was to determine the clinical characteristics of abutment teeth with gingival discoloration. This research was conducted on 25 patients referred for cast dowel and PFM restorations. These restorations were manufactured from Ni-Cr alloys. Ninety days after cementing the fixed prosthodontic restorations, the abutment teeth (n = 61) were divided into a group with gingival discoloration (GD) (n = 25) and without gingival discoloration (NGD) (n = 36). The control group (CG) comprised the contralateral teeth (n = 61). Plaque index, gingival index, clinical attachment level, and probing depth were assessed before fabrication and also 90 days after cementation of the PFM restorations. The gingival index, clinical attachment level, and probing depths of the abutment teeth that had GD were statistically higher before restoration, in comparison with the abutment teeth in the NGD and control groups. Ninety days after cementation, the abutment teeth with GD had significantly lower gingival indexes and probing depths, compared to the abutment teeth in the NGD group. Both abutment teeth groups (GD and NGD) had significantly higher values of clinical attachment levels when compared to the control group. There were no statistically significant differences in plaque index values between the study groups. The results of this study indicated that impairment of periodontal status of abutment teeth seemed to be related to the presence of gingival discolorations. Therefore, fabrication of fixed prosthodontic restorations requires careful planning and abutment teeth preparation to minimize the occurrence of gingival discolorations. With careful preparation of abutment teeth for cast dowels and crown restorations it may be

The effects of simulated bone loss on the implant-abutment assembly and likelihood of fracture: an in vitro study.

PubMed

Manzoor, Behzad; Suleiman, Mahmood; Palmer, Richard M

2013-01-01

The crestal bone level around a dental implant may influence its strength characteristics by offering protection against mechanical failures. Therefore, the present study investigated the effect of simulated bone loss on modes, loads, and cycles to failure in an in vitro model. Different amounts of bone loss were simulated: 0, 1.5, 3.0, and 4.5 mm from the implant head. Forty narrow-diameter (3.0-mm) implant-abutment assemblies were tested using compressive bending and cyclic fatigue testing. Weibull and accelerated life testing analysis were used to assess reliability and functional life. Statistical analyses were performed using the Fisher-Exact test and the Spearman ranked correlation. Compressive bending tests showed that the level of bone loss influenced the load-bearing capacity of implant-abutment assemblies. Fatigue testing showed that the modes, loads, and cycles to failure had a statistically significant relationship with the level of bone loss. All 16 samples with bone loss of 3.0 mm or more experienced horizontal implant body fractures. In contrast, 14 of 16 samples with 0 and 1.5 mm of bone loss showed abutment and screw fractures. Weibull and accelerated life testing analysis indicated a two-group distribution: the 0- and 1.5-mm bone loss samples had better functional life and reliability than the 3.0- and 4.5-mm samples. Progressive bone loss had a significant effect on modes, loads, and cycles to failure. In addition, bone loss influenced the functional life and reliability of the implant-abutment assemblies. Maintaining crestal bone levels is important in ensuring biomechanical sustainability and predictable long-term function of dental implant assemblies.

Dynamic locking screw improves fixation strength in osteoporotic bone: an in vitro study on an artificial bone model.

PubMed

Pohlemann, Tim; Gueorguiev, Boyko; Agarwal, Yash; Wahl, Dieter; Sprecher, Christoph; Schwieger, Karsten; Lenz, Mark

2015-04-01

The novel dynamic locking screw (DLS) was developed to improve bone healing with locked-plate osteosynthesis by equalising construct stiffness at both cortices. Due to a theoretical damping effect, this modulated stiffness could be beneficial for fracture fixation in osteoporotic bone. Therefore, the mechanical behaviour of the DLS at the screw-bone interface was investigated in an artificial osteoporotic bone model and compared with conventional locking screws (LHS). Osteoporotic surrogate bones were plated with either a DLS or a LHS construct consisting of two screws and cyclically axially loaded (8,500 cycles, amplitude 420 N, increase 2 mN/cycle). Construct stiffness, relative movement, axial screw migration, proximal (P) and distal (D) screw pullout force and loosening at the bone interface were determined and statistically evaluated. DLS constructs exhibited a higher screw pullout force of P 85 N [standard deviation (SD) 21] and D 93 N (SD 12) compared with LHS (P 62 N, SD 28, p = 0.1; D 57 N, SD 25, p < 0.01) and a significantly lower axial migration over cycles compared with LHS (p = 0.01). DLS constructs showed significantly lower axial construct stiffness (403 N/mm, SD 21, p < 0.01) and a significantly higher relative movement (1.1 mm, SD 0.05, p < 0.01) compared with LHS (529 N/mm, SD 27; 0.8 mm, SD 0.04). Based on the model data, the DLS principle might also improve in vivo plate fixation in osteoporotic bone, providing enhanced residual holding strength and reducing screw cutout. The influence of pin-sleeve abutment still needs to be investigated.

Management of overdenture abutments health by an innovative cleaning aid

PubMed Central

Mall, Priyanka; Singh, Kamleshwar; Singh, Saumyendra Vikram; Agrawal, Kaushal Kishor; Siddharth, Ramashanker; Chand, Pooran

2012-01-01

This article describes a method for fabrication of a custom-made device for cleaning dome-shaped overdenture abutments. A kid toothbrush and a rubber cup were used for fabrication of a prophylactic device. After regular use of this device periodontal health status of the overdenture abutments patients improved satisfactorily. PMID:23230248

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

Retrospective evaluation of complete-arch fixed partial dentures connecting teeth and implant abutments in patients with normal and reduced periodontal support.

PubMed

Cordaro, Luca; Ercoli, Carlo; Rossini, Carlo; Torsello, Ferruccio; Feng, Changyong

2005-10-01

The clinical outcome of complete-arch fixed prostheses supported by implants and natural tooth abutments in patients with normal or reduced periodontal support has been reported by few studies, with controversial results. The purpose of this study was to report on the implant success rate, prosthetic complications, and the occurrence of tooth intrusion, when complete-arch fixed prostheses, supported by a combination of implants and teeth, were fabricated for patients with normal and reduced periodontal support. Nineteen patients with residual teeth that served as abutments were consecutively treated with combined tooth- and implant-supported complete-arch fixed prostheses and were retrospectively evaluated after a period varying from 24 to 94 months. Nine patients showed reduced periodontal support as a result of periodontal disease and treatment (RPS group), and 10 patients had normal periodontal support of the abutment teeth (more than 2/3 of periodontal support [NPS group]). Ninety implants and 72 tooth abutments were used to support 19 fixed partial dentures. Screw- and cement-retained metal-ceramic and metal-resin prostheses were fabricated with rigid and nonrigid connectors. Implant survival and success rates, occurrence of caries and tooth intrusion, and prosthetic complications were recorded. The number of teeth, implants, prosthetic units, fixed partial dentures, and nonrigid connectors were compared with a t test to assess differences between the 2 groups, while data for the occurrence of intrusions and prosthetic complications were compared with the Fisher exact test (alpha=.05). One of the 90 implants was lost (99% survival rate) over 24 to 94 months, while 3 implants showed more than 2 mm of crestal bone loss (96% success rate) over the same period. No caries were detected, but 5.6% (4/72) of the abutment teeth exhibited intrusion. Intrusion of abutment teeth was noted in 3 patients who had normal periodontal support (13% of teeth in NPS group) of the

Scour around vertical wall abutment in cohesionless sediment bed

NASA Astrophysics Data System (ADS)

Pandey, M.; Sharma, P. K.; Ahmad, Z.

2017-12-01

At the time of floods, failure of bridges is the biggest disaster and mainly sub-structure (bridge abutments and piers) are responsible for this failure of bridges. It is very risky if these sub structures are not constructed after proper designing and analysis. Scour is a natural phenomenon in rivers or streams caused by the erosive action of the flowing water on the bed and banks. The abutment undermines due to river-bed erosion and scouring, which generally recognized as the main cause of abutment failure. Most of the previous studies conducted on scour around abutment have concerned with the prediction of the maximum scour depth (Lim, 1994; Melvill, 1992, 1997 and Dey and Barbhuiya, 2005). Dey and Barbhuiya (2005) proposed a relationship for computing maximum scour depth near an abutment, based on laboratory experiments, for computing maximum scour depth around vertical wall abutment, which was confined to their experimental data only. However, this relationship needs to be also verified by the other researchers data in order to support the reliability to the relationship and its wider applicability. In this study, controlled experimentations have been carried out on the scour near a vertical wall abutment. The collected data in this study along with data of the previous investigators have been carried out on the scour near vertical wall abutment. The collected data in this study along with data of the previous have been used to check the validity of the existing equation (Lim, 1994; Melvill, 1992, 1997 and Dey and Barbhuiya, 2005) of maximum scour depth around the vertical wall abutment. A new relationship is proposed to estimate the maximum scour depth around vertical wall abutment, it gives better results all relationships.

The Biocompatibility of Degradable Magnesium Interference Screws: An Experimental Study with Sheep

PubMed Central

Thormann, Ulrich; Alt, Volker; Heimann, Lydia; Gasquere, Cyrille; Heiss, Christian; Szalay, Gabor; Franke, Jörg; Schnettler, Reinhard; Lips, Katrin Susanne

2015-01-01

Screws for ligament reconstruction are nowadays mostly made of poly-L-lactide (PLLA). However, magnesium-based biomaterials are gathering increased interest in this research field because of their good mechanical property and osteoanabolic influence on bone metabolism. The aim of this pilot study was to evaluate the biocompatibility of an interference screw for ligament reconstruction made of magnesium alloy W4 by diecasting and milling and using different PEO-coatings with calcium phosphates. PLLA and titanium screws were used as control samples. The screws were implanted in the femur condyle of the hind leg of a merino sheep. The observation period was six and twelve weeks and one year. Histomorphometric, immunohistochemical, immunofluorescence, and molecular biological evaluation were conducted. Further TEM analysis was done. In all magnesium screws a clinically relevant gas formation in the vicinity of the biomaterial was observed. Except for the PLLA and titanium control samples, no screw was fully integrated in the surrounding bone tissue. Regarding the fabrication process, milling seems to produce less gas liberation and has a better influence on bone metabolism than diecasting. Coating by PEO with calcium phosphates could not reduce the initial gas liberation but rather reduced the bone metabolism in the vicinity of the biomaterial. PMID:25717474

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.

Degradation behaviour of LAE442-based plate-screw-systems in an in vitro bone model.

PubMed

Wolters, Leonie; Besdo, Silke; Angrisani, Nina; Wriggers, Peter; Hering, Britta; Seitz, Jan-Marten; Reifenrath, Janin

2015-04-01

The use of absorbable implant materials for fixation after bone fracture helps to avoid a second surgery for implant removal and the risks and costs involved. Magnesium (Mg) is well known as a potential metallic material for degradable implants. The aim of the present in vitro study was to evaluate if degradable LAE442-based magnesium plate-screw-systems are suitable candidates for osteosynthesis implants in load-bearing bones. The corrosion behaviour was tested concerning the influence of different surface treatments, coatings and screw torques. Steel plates and screws of the same size served as control. Plates without special treatment screwed on up to a specified torque of 15cNm or 7cNm, NaOH treated plates (15cNm), magnesium fluoride coated plates (15cNm) and steel plates as control (15cNm) were examined in pH-buffered, temperature-controlled SBF solution for two weeks. The experimental results indicate that the LAE442 plates and screws coated with magnesium fluoride revealed a lower hydrogen evolution in SBF solution as well as a lower weight loss and volume decrease in μ-computed tomography (μCT). The nanoindentation and SEM/EDX measurements at several plate areas showed no significant differences. Summarized, the different screw torques did not affect the corrosion behaviour differently. Also the NaOH treatment seemed to have no essential influence on the degradation kinetics. The plates coated with magnesium fluoride showed a decreased corrosion rate. Hence, it is recommended to consider this coating for the next in vivo study. Copyright © 2015 Elsevier B.V. All rights reserved.

Microleakage Evaluation at Implant-Abutment Interface Using Radiotracer Technique

PubMed Central

Siadat, Hakimeh; Arshad, Mahnaz; Mahgoli, Hossein-Ali; Fallahi, Babak

2016-01-01

Objectives: Microbial leakage through the implant-abutment (I-A) interface results in bacterial colonization in two-piece implants. The aim of this study was to compare microleakage rates in three types of Replace abutments namely Snappy, GoldAdapt, and customized ceramic using radiotracing. Materials and Methods: Three groups, one for each abutment type, of five implants and one positive and one negative control were considered (a total of 17 regular body implants). A torque of 35 N/cm was applied to the abutments. The samples were immersed in thallium 201 radioisotope solution for 24 hours to let the radiotracers leak through the I-A interface. Then, gamma photons received from the radiotracers were counted using a gamma counter device. In the next phase, cyclic fatigue loading process was applied followed by the same steps of immersion in the radioactive solution and photon counting. Results: Rate of microleakage significantly increased (P≤0.05) in all three types of abutments (i.e. Snappy, GoldAdapt, and ceramic) after cyclic loading. No statistically significant differences were observed between abutment types after cyclic loading. Conclusions: Microleakage significantly increases after cyclic loading in all three Replace abutments (GoldAdapt, Snappy, ceramic). Lowest microleakage before and after cyclic loading was observed in GoldAdapt followed by Snappy and ceramic. PMID:28392814

Implant-level prostheses in the edentulous maxilla: a comparison with conventional abutment-level prostheses after 5 years of use.

PubMed

Hjalmarsson, Lars; Smedberg, Jan-Ivan; Pettersson, Mattias; Jemt, Torsten

2011-01-01

Long-term comparisons of frameworks at the implant or abutment level are not available, and knowledge of the clinical function of cobalt-chromium (Co-Cr) alloy frameworks is limited. Primarily, the aim of this study was to compare the 5-year clinical performance of frameworks with or without abutment connections to implants. Secondly, the outcomes of prostheses made from Co-Cr alloy with porcelain veneers to those made of commercially pure titanium (CP Ti) with acrylic veneers were compared. The test groups comprised patients treated with screw-retained fixed prostheses made at the implant level according to the Cresco method in either dental porcelain-veneered Co-Cr alloy (n = 15) or acrylic-veneered CP Ti (n = 25). A control group of 40 randomly selected patients were provided with prostheses made at the standard abutment level in CP Ti with acrylic veneers. For all patients, clinical and radiologic 5-year data were retrospectively collected and evaluated. Five-year implant cumulative survival rates (CSRs) were 98.6% and 97.6% for test and control groups, respectively (P > .05). No major differences in bone level were demonstrated between the groups after 5 years (P > .05). Significantly more complications occurred in the test groups compared to the control group (P < .01), with the most common complications being mucositis and fracture of veneers. After 5 years, the clinical outcomes of implant-level prostheses made of porcelain-veneered Co-Cr or acrylic-veneered CP Ti seem comparable to acrylic-veneered titanium prostheses made at the standard abutment level regarding implant CSR and bone levels. However, more complications were registered in implant-level prostheses compared to the standard abutment-level prostheses.

Fracture resistance of implant- supported monolithic crowns cemented to zirconia hybrid-abutments: zirconia-based crowns vs. lithium disilicate crowns

PubMed Central

Nawafleh, Noor; Öchsner, Andreas; George, Roy

2018-01-01

PURPOSE The aim of this in vitro study was to investigate the fracture resistance under chewing simulation of implant-supported posterior restorations (crowns cemented to hybrid-abutments) made of different all-ceramic materials. MATERIALS AND METHODS Monolithic zirconia (MZr) and monolithic lithium disilicate (MLD) crowns for mandibular first molar were fabricated using computer-aided design/computer-aided manufacturing technology and then cemented to zirconia hybrid-abutments (Ti-based). Each group was divided into two subgroups (n=10): (A) control group, crowns were subjected to single load to fracture; (B) test group, crowns underwent chewing simulation using multiple loads for 1.2 million cycles at 1.2 Hz with simultaneous thermocycling between 5℃ and 55℃. Data was statistically analyzed with one-way ANOVA and a Post-Hoc test. RESULTS All tested crowns survived chewing simulation resulting in 100% survival rate. However, wear facets were observed on all the crowns at the occlusal contact point. Fracture load of monolithic lithium disilicate crowns was statistically significantly lower than that of monolithic zirconia crowns. Also, fracture load was significantly reduced in both of the all-ceramic materials after exposure to chewing simulation and thermocycling. Crowns of all test groups exhibited cohesive fracture within the monolithic crown structure only, and no abutment fractures or screw loosening were observed. CONCLUSION When supported by implants, monolithic zirconia restorations cemented to hybrid abutments withstand masticatory forces. Also, fatigue loading accompanied by simultaneous thermocycling significantly reduces the strength of both of the all-ceramic materials. Moreover, further research is needed to define potentials, limits, and long-term serviceability of the materials and hybrid abutments. PMID:29503716

Simple New Screw Insertion Technique without Extraction for Broken Pedicle Screws.

PubMed

Kil, Jin-Sang; Park, Jong-Tae

2018-05-01

Spinal transpedicular screw fixation is widely performed. Broken pedicle screw rates range from 3%-7.1%. Several techniques have been described for extraction of broken pedicle screws. However, most of these techniques require special instruments. We describe a simple, modified technique for management of broken pedicle screws without extraction. No special instruments or drilling in an adjacent pedicle are required. We used a high-speed air drill with a round burr. With C-arm fluoroscopy guidance, the distal fragment of a broken pedicle screw was palpated using free-hand technique through the screw entry hole. A high-speed air drill with a round burr (not a diamond burr) was inserted through the hole. Drilling began slowly and continued until enough space was obtained for new screw insertion. Using this space, we performed new pedicle screw fixation medially alongside the distal fragment of the broken pedicle screw. We performed the insertion with a previously used entry hole and pathway in the pedicle. The same size pedicle screw was used. Three patients were treated with this modified technique. New screw insertion was successful in all cases after partial drilling of the distal broken pedicle screw fragment. There were no complications, such as screw loosening, dural tears, or root injury. We describe a simple, modified technique for management of broken pedicle screws without extraction. This technique is recommended in patients who require insertion of a new screw. Copyright © 2017. Published by Elsevier Inc.

A Comparison of Removal Rates of Headless Screws Versus Headed Screws in Calcaneal Osteotomy.

PubMed

Kunzler, Daniel; Shazadeh Safavi, Pejma; Jupiter, Daniel; Panchbhavi, Vinod K

2017-11-01

Calcaneal osteotomy has been used to successfully treat both valgus and varus hindfoot deformities. Pain associated with implanted hardware may lead to further surgical intervention for hardware removal. Headless screws have been used to reduce postoperative hardware-associated pain and accompanying hardware removal, but data proving their effectiveness in this regard is lacking. The purpose of this study is to compare the rates of removal of headed and headless screws utilized in calcaneal osteotomy. We conducted a retrospective chart review of 74 patients who underwent calcaneal osteotomy between January 2010 and December 2014. The cohort was divided into 2 groups by fixation method: a headed screw and a headless screw group. Bivariate associations between infection or hardware removal, and screw type, screw head width, gender, smoking status, alcohol, hypertension, diabetes, hyperlipidemia, age, and body mass index were assessed using t-tests and Fisher's exact/χ 2 tests for continuous and discrete variables, respectively. Headed screws were removed more frequently than headless screws (P < .0001): 15 of 30 (50%) feet that received headed screws and 4 of 44 (9%) of feet that received headless screws underwent subsequent revision for screw removal. In all cases, screws were removed because of pain. The calcaneal union rate was 100% in both cohorts. The rate of screw removal in calcaneal osteotomies is significantly lower in patients who receive headless screws than in those receiving headed screws. Level IV.

Displacement of screw-retained single crowns into implants with conical internal connections.

PubMed

Yilmaz, Burak; Seidt, Jeremy D; McGlumphy, Edwin A; Clelland, Nancy L

2013-01-01

Internal conical implant-abutment connections without platforms may lead to axial displacement of crowns during screw tightening. This displacement may affect proximal contacts, incisal edge position, or occlusion. This study aimed to measure the displacement of screw-retained single crowns into an implant in three dimensions during screw tightening by hand or via torque driver. A stereolithic acrylic resin cast was created using computed tomography data from a patient missing the maxillary right central incisor. A 4.0- × 11-mm implant was placed in the edentulous site. Five porcelain-fused-to-metal single crowns were made using "cast-to" abutments. Crowns were tried on the stereolithic model, representing the patient, and hand tightened. The spatial relationship of crowns to the model after hand tightening was determined using three-dimensional digital image correlation (3D DIC), an optical measurement technique. The crowns were then tightened using a torque driver to 20 Ncm and the relative crown positions were again recorded. Testing was repeated three times for each crown, and displacement of the crowns was compared between the hand-tightened and torqued states. Commercial image correlation software was used to analyze the data. Mean vertical and horizontal crown displacement values were calculated after torqueing. The interproximal contacts were evaluated before and after torquing using an 8-μm aluminum foil shim. There were vertical and horizontal differences in crown positions between hand tightening and torqueing. Although these were small in magnitude, detectable displacements occurred in both apical and facial directions. After hand tightening, the 8-μm shim could be dragged without tearing. However, after torque tightening, the interproximal contacts were too tight and the 8-μm shim could not be dragged without tearing. Differences between hand tightening and torque tightening should be taken into consideration during laboratory and clinical

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

Evaluation of Dynamic Characteristics of the Footbridge with Integral Abutments

NASA Astrophysics Data System (ADS)

Pańtak, Marek; Jarek, Bogusław

2017-09-01

The paper presents the results of dynamic field tests and numerical analysis of the footbridge designed as a three-span composite structure with integral abutments. The adopted design solution which has allowed to achieve a high resistance of the structure to dynamic loads and to meet the requirements of the criteria of comfort of use with a large reserve has been characterized. For comparative purposes, numerical analyzes of three construction variants of the footbridge were presented: F-1 - construction with integral abutments (realized variant), F-2 - construction with girders anchored in the abutments by means of tension rocker bearings, F-3 - construction with concrete side spans.

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.

Fracture strength of zirconia implant abutments on narrow diameter implants with internal and external implant abutment connections: A study on the titanium resin base concept.

PubMed

Sailer, Irena; Asgeirsson, Asgeir G; Thoma, Daniel S; Fehmer, Vincent; Aspelund, Thor; Özcan, Mutlu; Pjetursson, Bjarni E

2018-04-01

There is limited knowledge regarding the strength of zirconia abutments with internal and external implant abutment connections and zirconia abutments supported by a titanium resin base (Variobase, Straumann) for narrow diameter implants. To compare the fracture strength of narrow diameter abutments with different types of implant abutment connections after chewing simulation. Hundred and twenty identical customized abutments with different materials and implant abutment connections were fabricated for five groups: 1-piece zirconia abutment with internal connection (T1, Cares-abutment-Straumann BL-NC implant, Straumann Switzerland), 1-piece zirconia abutment with external hex connection (T2, Procera abutment-Branemark NP implant, Nobel Biocare, Sweden), 2-piece zirconia abutments with metallic insert for internal connection (T3, Procera abutment-Replace NP implant, Nobel Biocare), 2-piece zirconia abutment on titanium resin base (T4, LavaPlus abutment-VarioBase-Straumann BL-NC implant, 3M ESPE, Germany) and 1-piece titanium abutment with internal connection (C, Cares-abutment-Straumann BL-NC implant, Straumann, Switzerland). All implants had a narrow diameter ranging from 3.3 to 3.5 mm. Sixty un-restored abutments and 60 abutments restored with glass-ceramic crowns were tested. Mean bending moments were compared using ANOVA with p-values adjusted for multiple comparisons using Tukey's procedure. The mean bending moments were 521 ± 33 Ncm (T4), 404 ± 36 Ncm (C), 311 ± 106 Ncm (T1) 265 ± 22 Ncm (T3) and 225 ± 29 (T2) for un-restored abutments and 278 ± 84 Ncm (T4), 302 ± 170 Ncm (C), 190 ± 55 Ncm (T1) 80 ± 102 Ncm (T3) and 125 ± 57 (T2) for restored abutments. For un-restored abutments, C and T4 had similar mean bending moments, significantly higher than those of the three other groups (p < .05). Titanium abutments (C) had significantly higher bending moments than identical zirconia abutments (T1) (p < .05). Zirconia

Microbiological and clinical assessment of the abutment and non-abutment teeth of partial removable denture wearers.

PubMed

Costa, Luciana; do Nascimento, Cássio; de Souza, Valéria Oliveira Pagnano; Pedrazzi, Vinícius

2017-03-01

The aim of this study was assessing the changes in both clinical and microbiological parameters of healthy individuals after rehabilitation with removable partial denture (RPD). 11 women received unilateral or bilateral free-end saddle RPD in the mandibular arch. Clinical and microbiological parameters of abutment, non-abutment, and antagonist teeth were assessed at baseline (RPD installation) and after 7, 30, 90, and 180days of function. The Checkerboard DNA-DNA hybridization technique was used to identify and quantify up to 43 different microbial species from subgingival biofilm samples. Probing depth, gingival recession, and bleeding on probing were also investigated over time. The total and individual microbial genome counts were shown significantly increased after 180days with no significant differences between abutment, non-abutment, or antagonist teeth. Streptococcus spp., Aggregatibacter actinomycetemcomitans, and other species associated to periodontitis (Peptostreptococcus anaerobius, Prevotella nigrescens, and Tannerella forsythia), as well as opportunistic Candida spp., were recovered in moderate counts. Abutment teeth presented higher values of gingival recession when compared with non-abutment or antagonist teeth, irrespectively time of sampling (p<0.05). No significant differences were found between groups regarding bleeding on probing or probing depth over time. Overall, the microbial counts significantly increased after 6 months of denture loading for both abutment and non-abutment teeth with no significant differences regarding the microbial profile over time. Bleeding on probing and probing depth showed no significant difference between groups over time whereas gingival recession increased in the abutment teeth. Copyright © 2016 Elsevier Ltd. All rights reserved.

Automated Erosion System to Protect Highway Bridge Crossings at Abutments

DOT National Transportation Integrated Search

2010-06-01

A new instrument (Photo-Electronic Erosion Pin, or PEEP) was examined in collecting field data and remotely monitoring bank erosion near bridge abutments during floods. The performance of PEEPs was evaluated through a detailed field study to determin...

17. DETAIL OF DAM CREST FROM WEST ABUTMENT, SHOWING SERVICE ...

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

17. DETAIL OF DAM CREST FROM WEST ABUTMENT, SHOWING SERVICE ROAD AND PARAPET WALL, WITH DEDICATION PLAQUE MOUNTED ON WALL IN LEFT FOREGROUND. VIEW TO NORTHEAST. - Owyhee Dam, Across Owyhee River, Nyssa, Malheur County, OR

Integral abutment bridge for Louisiana's soft and stiff soils.

DOT National Transportation Integrated Search

2008-02-01

The proposed research will be to field instrument, monitor, and analyze the design and construction of full integral abutment bridges for Louisianas soft and stiff soil conditions. Comparison of results will be submitted to the Louisiana Departmen...

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

Deterioration of J-bar reinforcement in abutments and piers.

DOT National Transportation Integrated Search

2011-12-31

Deterioration and necking of J-bars has been reportedly observed at the interface of the footing and stem wall during the demolition : of older retaining walls and bridge abutments. Similar deterioration has been reportedly observed between the pier ...

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

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

Trestle #1, detail of southwest abutment and deck. View to ...

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

Trestle #1, detail of southwest abutment and deck. View to south - Promontory Route Railroad Trestles, S.P. Trestle 779.91, One mile southwest of junction of State Highway 83 and Blue Creek, Corinne, Box Elder County, UT

Trestle #1, southwest abutment and wing wall. View to west ...

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

Trestle #1, southwest abutment and wing wall. View to west - Promontory Route Railroad Trestles, S.P. Trestle 779.91, One mile southwest of junction of State Highway 83 and Blue Creek, Corinne, Box Elder County, UT

Trestle #1, northeast abutment and wing walls. View to north ...

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

Trestle #1, northeast abutment and wing walls. View to north - Promontory Route Railroad Trestles, S.P. Trestle 779.91, One mile southwest of junction of State Highway 83 and Blue Creek, Corinne, Box Elder County, UT

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

Small Smooth Units ('Young' Lavas?) Abutting Lobate Scarps on Mercury

NASA Astrophysics Data System (ADS)

Malliband, C. C.; Rothery, D. A.; Balme, M. R.; Conway, S. J.

2018-05-01

We have identified small units abutting, and so stratigraphy younger than, lobate scarps. This post dates the end of large scale smooth plains formation at the onset of global contraction. This elaborates the history of volcanism on Mercury.

7. VIEW OF NORTHWEST PYLONS ON NORTH ABUTMENT, SUSPENSION CABLE ...

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

7. VIEW OF NORTHWEST PYLONS ON NORTH ABUTMENT, SUSPENSION CABLE AND 'U'-BOLT CONNECTIONS, LOOKING SOUTH - San Rafael Bridge, Spanning San Rafael River near Buckhorn Wash, Castle Dale, Emery County, UT

Performance assessment of MSE abutment walls in Indiana : final report.

DOT National Transportation Integrated Search

2017-05-01

This report presents a numerical investigation of the behavior of steel strip-reinforced mechanically stabilized earth (MSE) direct bridge abutments under static loading. Finite element simulations were performed using an advanced two-surface boundin...

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

Evaluation of DOTD semi-integral bridge and abutment system.

DOT National Transportation Integrated Search

2005-03-01

The Louisiana Department of Transportation and Development (LADOTD) designed and constructed its first prototype semi-integral abutment bridge in 1989. In this design, large longitudinal movements due to expansion and contraction, creep, shrinkage, a...

Long-term behavior of integral abutment bridges.

DOT National Transportation Integrated Search

2011-01-01

Integral abutment (IA) construction has become the preferred method over conventional construction for use with typical : highway bridges. However, the use of these structures is limited due to state mandated length and skew limitations. To : expand ...

Long-term behavior of integral abutment bridges : [technical summary].

DOT National Transportation Integrated Search

2011-01-01

Integral abutment bridges, a type of jointless bridge, are the construction option of choice when designing highway bridges in many parts of the country. Rather than providing an expansion joint to separate the substructure from the superstructure to...

GENERAL VIEW OF NORTH SAN GABRIEL RIVER BRIDGE, NORTH ABUTMENT, ...

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

GENERAL VIEW OF NORTH SAN GABRIEL RIVER BRIDGE, NORTH ABUTMENT, LOOKING NORTHWEST. - North San Gabriel River Bridge, Spanning North Fork of San Gabriel River at Business Route 35, Georgetown, Williamson County, TX

GENERAL VIEW OF SOUTH SAN GABRIEL RIVER BRIDGE, SOUTH ABUTMENT, ...

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

GENERAL VIEW OF SOUTH SAN GABRIEL RIVER BRIDGE, SOUTH ABUTMENT, LOOKING SOUTHWEST. - South San Gabriel River Bridge, Spanning South Fork of San Gabriel River at Georgetown at Business Route 35, Georgetown, Williamson County, TX

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

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

Integral bridge abutment-to-approach slab connection.

DOT National Transportation Integrated Search

2008-06-01

The Iowa Department of Transportation has long recognized that approach slab pavements of integral abutment bridges are prone to settlement and cracking, which manifests as the "bump at the end of the bridge". A commonly recommended solution is to in...

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

Integral abutment bridges under thermal loading : field monitoring and analysis.

DOT National Transportation Integrated Search

2017-08-01

Integral abutment bridges (IABs) have gained popularity throughout the United States due to their low construction and maintenance costs. Previous research on IABs has been heavily focused on substructure performance, leaving a need for better unders...

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

10. VIEW TO NORTHEAST ALONG NORTHWEST SPILLWAY ABUTMENT; SERVICE VEHICLE ...

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

10. VIEW TO NORTHEAST ALONG NORTHWEST SPILLWAY ABUTMENT; SERVICE VEHICLE GARAGE IN BACKGROUND. - Prado Dam, Spillway, Santa Ana River near junction of State Highways 71 & 91, Corona, Riverside County, CA

20. Detail view of west swing span abutment through swing ...

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

20. Detail view of west swing span abutment through swing span truss, looking north - India Point Railroad Bridge, Spanning Seekonk River between Providence & East Providence, Providence, Providence County, RI

9. LOOKING NORTHWEST, A VIEW OF THE NORTH ABUTMENT, THE ...

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

9. LOOKING NORTHWEST, A VIEW OF THE NORTH ABUTMENT, THE DITCH AND THE EAST SIDE OF THE STRUCTURE FROM BELOW. - Wells County Bridge No. 74, Spanning Rock Creek Ditch at County Road 400, Bluffton, Wells County, IN

Maintenance and design of steel abutment piles in Iowa bridges.

DOT National Transportation Integrated Search

2014-09-01

Soil consolidation and erosion caused by roadway runoff have exposed the upper portions of steel piles at the abutments of : numerous bridges, leaving them susceptible to accelerated corrosion rates due to the abundance of moisture, oxygen, and : chl...

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

2. VIEW OF NORTH FACE SHOWING SUBSTRUCTURE AND ABUTMENTS OF ...

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

2. VIEW OF NORTH FACE SHOWING SUBSTRUCTURE AND ABUTMENTS OF BRIDGE CROSSING THE SOUTH FORK OF THE TUOLUMNE RIVER. - South Fork Tuolumne River Bridge, Spanning South Fork Tuolumne River on Tioga Road, Mather, Tuolumne County, CA

3. Concrete and stone abutment at southeast end of Cedar ...

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

3. Concrete and stone abutment at southeast end of Cedar Avenue Bridge. - Delaware, Lackawanna & Western Railroad, Scranton Yards, Cedar Avenue Bridge, Spanning Cedar Avenue at Railroad Alley, Scranton, Lackawanna County, PA

Geosynthetic reinforced soil for low-volume bridge abutments.

DOT National Transportation Integrated Search

2012-01-01

This report presents a review of literature on geosynthetic reinforced soil (GRS) bridge abutments, and test results and analysis from two : field demonstration projects (Bridge 1 and Bridge 2) conducted in Buchanan County, Iowa, to evaluate the feas...

5. DETAIL OF SOUTHERN ARCH. PIER AND ABUTMENTS HAVE BEEN ...

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

5. DETAIL OF SOUTHERN ARCH. PIER AND ABUTMENTS HAVE BEEN REINFORCED WITH CONCRETE. INTRADOS HAS BEEN PARGED WITH MORTAR. - Core Creek County Bridge, Spanning Core Creek, approximately 1 mile South of State Route 332 (Newtown Bypass), Newtown, Bucks County, PA

9. VIEW OF SOUTHERN ROCKFACED DRESSED AND MORTARED STONE ABUTMENT, ...

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

9. VIEW OF SOUTHERN ROCKFACED DRESSED AND MORTARED STONE ABUTMENT, SHOWING STEEL CROSSBEAMS, TORSIONAL DIAGONAL STRUTS, AND WOODEN STRINGERS. FACING SOUTHWEST. - Coverts Crossing Bridge, Spanning Mahoning River along Township Route 372 (Covert Road), New Castle, Lawrence County, PA

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

Creep and shrinkage effects on integral abutment bridges

NASA Astrophysics Data System (ADS)

Munuswamy, Sivakumar

Integral abutment bridges provide bridge engineers an economical design alternative to traditional bridges with expansion joints owing to the benefits, arising from elimination of expensive joints installation and reduced maintenance cost. The superstructure for integral abutment bridges is cast integrally with abutments. Time-dependent effects of creep, shrinkage of concrete, relaxation of prestressing steel, temperature gradient, restraints provided by abutment foundation and backfill and statical indeterminacy of the structure introduce time-dependent variations in the redundant forces. An analytical model and numerical procedure to predict instantaneous linear behavior and non-linear time dependent long-term behavior of continuous composite superstructure are developed in which the redundant forces in the integral abutment bridges are derived considering the time-dependent effects. The redistributions of moments due to time-dependent effects have been considered in the analysis. The analysis includes nonlinearity due to cracking of the concrete, as well as the time-dependent deformations. American Concrete Institute (ACI) and American Association of State Highway and Transportation Officials (AASHTO) models for creep and shrinkage are considered in modeling the time dependent material behavior. The variations in the material property of the cross-section corresponding to the constituent materials are incorporated and age-adjusted effective modulus method with relaxation procedure is followed to include the creep behavior of concrete. The partial restraint provided by the abutment-pile-soil system is modeled using discrete spring stiffness as translational and rotational degrees of freedom. Numerical simulation of the behavior is carried out on continuous composite integral abutment bridges and the deformations and stresses due to time-dependent effects due to typical sustained loads are computed. The results from the analytical model are compared with the

Long-term behavior of integral abutment bridges : appendix E, INDOT design manual : selected recommendations for integral abutment bridges.

DOT National Transportation Integrated Search

2011-01-01

Integral abutment (IA) construction has become the preferred method over conventional construction for use with typical highway bridges. However, the use of these structures is limited due to state mandated length and skew limitations. To expand thei...

The effect of different screw-tightening techniques on the stress generated on an internal-connection implant superstructure.

PubMed

Choi, Jung-Han; Lim, Young-Jun; Kim, Chang-Whe; Kim, Myung-Joo

2009-01-01

This study evaluated the effect of different screw-tightening sequences, forces, and methods on the stresses generated on a well-fitting internal-connection implant (Astra Tech) superstructure. A metal framework directly connected to four parallel implants was fabricated on a fully edentulous mandibular resin model. Six stone casts with four implant replicas were made from a pickup impression of the superstructure to represent a "well-fitting" situation. Stresses generated by four screw-tightening sequences (1-2-3-4, 4-3-2-1, 2-4-3-1, and 2-3-1-4), two forces (10 and 20 Ncm), and two methods (one-step and two-step) were evaluated. In the two-step method, screws were tightened to the initial torque (10 Ncm) in a predetermined screw-tightening sequence and then to the final torque (20 Ncm) in the same sequence. Stresses were recorded twice by three strain gauges attached to the framework (superior face midway between abutments). Deformation data were analyzed using multiple analysis of variance at a .05 level of statistical significance. In all stone casts, stresses were produced by the superstructure connection, regardless of screw-tightening sequence, force, and method. No statistically significant differences for superstructure preload stresses were found based on screw-tightening sequences (-180.0 to -181.6 microm/m) or forces (-163.4 and -169.2 microm/m) (P > .05). However, different screw-tightening methods induced different stresses on the superstructure. The two-step screw-tightening method (-180.1 microm/m) produced significantly higher stress than the one-step method (-169.2 microm/m) (P = .0457). Within the limitations of this in vitro study, screw-tightening sequence and force were not critical factors in the stress generated on a well-fitting internal-connection implant superstructure. The stress caused by the two-step method was greater than that produced using the one-step method. Further studies are needed to evaluate the effect of screw

Biomechanical Comparison of Inter-fragmentary Compression Pressures: Lag Screw versus Herbert Screw for Anterior Odontoid Screw Fixation.

PubMed

Park, Jin-Woo; Kim, Kyoung-Tae; Sung, Joo-Kyung; Park, Seong-Hyun; Seong, Ki-Woong; Cho, Dae-Chul

2017-09-01

The purpose of the present study was to compare inter-fragmentary compression pressures after fixation of a simulated type II odontoid fracture with the headless compression Herbert screw and a half threaded cannulated lag screw. We compared inter-fragmentary compression pressures between 40- and 45-mm long 4.5-mm Herbert screws (n=8 and n=9, respectively) and 40- and 45-mm long 4.0-mm cannulated lag screws (n=7 and n=10, respectively) after insertion into rigid polyurethane foam test blocks (Sawbones, Vashon, WA, USA). A washer load cell was placed between the two segments of test blocks to measure the compression force. Because the total length of each foam block was 42 mm, the 40-mm screws were embedded in the cancellous foam, while the 45-mm screws penetrated the denser cortical foam at the bottom. This enabled us to compare inter-fragmentary compression pressures as they are affected by the penetration of the apical dens tip by the screws. The mean compression pressures of the 40- and 45-mm long cannulated lag screws were 50.48±1.20 N and 53.88±1.02 N, respectively, which was not statistically significant (p=0.0551). The mean compression pressures of the 40-mm long Herbert screw was 52.82±2.17 N, and was not statistically significant compared with the 40-mm long cannulated lag screw (p=0.3679). However, 45-mm Herbert screw had significantly higher mean compression pressure (60.68±2.03 N) than both the 45-mm cannulated lag screw and the 40-mm Herbert screw (p=0.0049 and p=0.0246, respectively). Our results showed that inter-fragmentary compression pressures of the Herbert screw were significantly increased when the screw tip penetrated the opposite dens cortical foam. This can support the generally recommended surgical technique that, in order to facilitate maximal reduction of the fracture gap using anterior odontoid screws, it is essential to penetrate the apical dens tip with the screw.

Screw-fed pump system

DOEpatents

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.

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.

Effect of screw position on load transfer in lumbar pedicle screws: A non-idealized finite element analysis

PubMed Central

Newcomb, Anna G. U. S.; Baek, Seungwon; Kelly, Brian P.; Crawford, Neil R.

2016-01-01

Angled screw insertion has been advocated to enhance fixation strength during posterior spine fixation. Stresses on a pedicle screw and surrounding vertebral bone with different screw angles were studied by finite element analysis during simulated multidirectional loading. Correlations between screw-specific vertebral geometric parameters and stresses were studied. Angulations in both the sagittal and axial planes affected stresses on the cortical and cancellous bones and the screw. Pedicle screws pointing laterally (vs. straight or medially) in the axial plane during superior screw angulation may be advantageous in terms of reducing the risk of both screw loosening and screw breakage. PMID:27454197

Microleakage at the Different Implant Abutment Interface: A Systematic Review

PubMed Central

Chowdhary, Ramesh; Kumari, Shail

2017-01-01

Introduction Presence of gap at the implant-abutment interface, leads to microleakage and accumulation of bacteria which can affect the success of dental implants. Aim To evaluate the sealing capability of different implant connections against microleakage. Materials and Methods In January 2017 an electronic search of literature was performed, in Medline, EBSCO host and Pubmed data base. The search was focused on ability of different implant connections in preventing microleakage. The related titles and abstracts available in English were screened, and the articles that fulfilled the inclusion criteria were selected for full text reading. Results In this systematic review, literature search initially resulted in 78 articles among which 30 articles only fulfilled the criteria for inclusion and were finally included in the review. Almost all the studies showed that there was some amount of microleakage at abutment implant interface. Microleakage was very less in Morse taper implants in comparison to other implant connections. Majority of studies showed less microleakage in static loading conditions and microleakage increases in dynamic loading conditions. Conclusion In this systematic review maximum studies showed that there was some amount of microleakage at abutment implant interface. External hexagon implants failed completely to prevent microleakage in both static and dynamic loading conditions of implants. Internal hexagon implants mainly internal conical (Morse taper) implants are very promising in case of static loading and also showed less microleakage in dynamic loading conditions. Torque recommended by manufacturer should be followed strictly to get a better seal at abutment implant interface. Zirconia abutments are more to microleakage than Titanium abutments and there use should be discouraged. Zirconia abutments should be only restricted to cases where there was very high demand of aesthetics. PMID:28764310

The effect of different screw-tightening techniques on the strain generated on an internal-connection implant superstructure. Part 2: Models created with a splinted impression technique.

PubMed

Choi, Jung-Han

2011-01-01

This study aimed to evaluate the effect of different screw-tightening sequences, torques, and methods on the strains generated on an internal-connection implant (Astra Tech) superstructure with good fit. An edentulous mandibular master model and a metal framework directly connected to four parallel implants with a passive fit to each other were fabricated. Six stone casts were made from a dental stone master model by a splinted impression technique to represent a well-fitting situation with the metal framework. Strains generated by four screw-tightening sequences (1-2-3-4, 4-3-2-1, 2-4-3-1, and 2-3-1-4), two torques (10 and 20 Ncm), and two methods (one-step and two-step) were evaluated. In the two-step method, screws were tightened to the initial torque (10 Ncm) in a predetermined screw-tightening sequence and then to the final torque (20 Ncm) in the same sequence. Strains were recorded twice by three strain gauges attached to the framework (superior face midway between abutments). Deformation data were analyzed using multiple analysis of variance at a .05 level of statistical significance. In all stone casts, strains were produced by connection of the superstructure, regardless of screw-tightening sequence, torque, and method. No statistically significant differences in superstructure strains were found based on screw-tightening sequences (range, -409.8 to -413.8 μm/m), torques (-409.7 and -399.1 μm/m), or methods (-399.1 and -410.3 μm/m). Within the limitations of this in vitro study, screw-tightening sequence, torque, and method were not critical factors for the strain generated on a well-fitting internal-connection implant superstructure by the splinted impression technique. Further studies are needed to evaluate the effect of screw-tightening techniques on the preload stress in various different clinical situations.

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.

Pedicle screw placement using image guided techniques.

PubMed

Merloz, P; Tonetti, J; Pittet, L; Coulomb, M; Lavalleé, S; Sautot, P

1998-09-01

Clinical evaluation of a computer assisted spine surgical system is presented. Eighty pedicle screws were inserted using computer assisted technology in thoracic and lumbar vertebrae for treatment of different types of disorders including fractures, spondylolisthesis, and scoliosis. Fifty-two patients with severe fractures, spondylolisthesis, or pseudoarthrosis of T10 to L5 were treated using a computer assisted technique on 1/2 the patients and performing the screw insertion manually for the other 1/2. At the same time, 28 pedicle screws were inserted in T12 to L4 vertebrae for scoliosis with the help of the computer assisted technique. Surgery was followed in all cases (66 vertebrae; 132 pedicle screws) by postoperative radiographs and computed tomographic examination, on which measurements of screw position relative to pedicle position could be done. For fractures, spondylolisthesis, or pseudarthrosis, comparison between the two groups showed that four screws in 52 (8%) vertebrae had incorrect placement with computer assisted technique whereas 22 screws in 52 (42%) vertebrae had incorrect placement with manual insertion. In patients with scoliosis, four screws in 28 (14%) vertebrae had incorrect placement. In all of the patients (132 pedicle screws) there were no neurologic complications. These results show that a computer assisted technique is much more accurate and safe than manual insertion.

Scalloped Implant-Abutment Connection Compared to Conventional Flat Implant-Abutment Connection: a Systematic Review and Meta-Analysis

PubMed Central

Christensen, Ann-Eva; Lorenzen, Henning

2017-01-01

ABSTRACT Objectives The objective was to test the hypothesis of no difference in implant treatment outcome after installation of implants with a scalloped implant-abutment connection compared to a flat implant-abutment connection. Material and Methods A MEDLINE (PubMed), Embase and Cochrane library search in combination with a hand-search of relevant journals was conducted. No language or year of publication restriction was applied. Results The search provided 298 titles. Three studies fulfilled the inclusion criteria. The included studies were characterized by low or moderate risk of bias. Survival of suprastructures has never been compared within the same study. High implant survival rate was reported in all the included studies. Significantly more peri-implant marginal bone loss, higher probing depth score, bleeding score and gingival score was observed around implants with a scalloped implant-abutment connection. There were no significant differences between the two treatment modalities regarding professional or patient-reported outcome measures. Meta-analysis disclosed a mean difference of peri-implant marginal bone loss of 1.56 mm (confidence interval: 0.87 to 2.25), indicating significant more bone loss around implants with a scalloped implant-abutment connection. Conclusions A scalloped implant-abutment connection seems to be associated with higher peri-implant marginal bone loss compared to a flat implant-abutment connection. Therefore, the hypothesis of the present systematic review must be rejected. However, further long-term randomized controlled trials assessing implant treatment outcome with the two treatment modalities are needed before definite conclusions can be provided about the beneficial use of implants with a scalloped implant-abutment connection on preservation of the peri-implant marginal bone level. PMID:28496962

Scalloped Implant-Abutment Connection Compared to Conventional Flat Implant-Abutment Connection: a Systematic Review and Meta-Analysis.

PubMed

Starch-Jensen, Thomas; Christensen, Ann-Eva; Lorenzen, Henning

2017-01-01

The objective was to test the hypothesis of no difference in implant treatment outcome after installation of implants with a scalloped implant-abutment connection compared to a flat implant-abutment connection. A MEDLINE (PubMed), Embase and Cochrane library search in combination with a hand-search of relevant journals was conducted. No language or year of publication restriction was applied. The search provided 298 titles. Three studies fulfilled the inclusion criteria. The included studies were characterized by low or moderate risk of bias. Survival of suprastructures has never been compared within the same study. High implant survival rate was reported in all the included studies. Significantly more peri-implant marginal bone loss, higher probing depth score, bleeding score and gingival score was observed around implants with a scalloped implant-abutment connection. There were no significant differences between the two treatment modalities regarding professional or patient-reported outcome measures. Meta-analysis disclosed a mean difference of peri-implant marginal bone loss of 1.56 mm (confidence interval: 0.87 to 2.25), indicating significant more bone loss around implants with a scalloped implant-abutment connection. A scalloped implant-abutment connection seems to be associated with higher peri-implant marginal bone loss compared to a flat implant-abutment connection. Therefore, the hypothesis of the present systematic review must be rejected. However, further long-term randomized controlled trials assessing implant treatment outcome with the two treatment modalities are needed before definite conclusions can be provided about the beneficial use of implants with a scalloped implant-abutment connection on preservation of the peri-implant marginal bone level.

Management of major vascular injury during pedicle screw instrumentation of thoracolumbar spine.

PubMed

Mirza, Aleem K; Alvi, Mohammed Ali; Naylor, Ryan M; Kerezoudis, Panagiotis; Krauss, William E; Clarke, Michelle J; Shepherd, Daniel L; Nassr, Ahmad; DeMartino, Randall R; Bydon, Mohamad

2017-12-01

Vascular injury is a rare complication of spinal instrumentation. Presentation can vary from immediate hemorrhage to pseudoaneurysm formation. In the literature, surgical approach to repair has varied based on anatomy, acuity of diagnosis, infection, and available technology. In this manuscript, we aim to describe our institutional experience with vascular injuries in thoraco-lumbar spine surgery. We report our institutional experience of three cases of vascular injury secondary to pedicle screw misplacement and their management, as well as a review of the literature. The first case had a history of previous instrumentation and presented with back pain and fever. The patient was taken for instrumentation exploration via a posterior approach. Aortic violation was discovered at T6 intraoperatively during instrumentation removal and the patient underwent emergent endovascular repair. The second case presented with chronic back pain after multiple prior posterior fusions and CT angiogram showing screw perforation on the aorta at T10. The patient underwent elective endovascular repair with synchronous removal of the instrumentation. The third case presented with radicular leg pain 6 months after L4-S1 posterior lumbar interbody fusion, with CT scan demonstrating the left S1 screw abutting the L5 nerve root and common iliac vein. The patient underwent elective instrumentation revision with intraoperative venography. Major vascular injury is a known complication of spinal surgery, especially if it involves instrumentation with pedicle screws. Treatment approach has evolved with the advancement of endovascular technology; however, open surgery remains an option when anatomy or infection is prohibitive. In the elective setting, preoperative planning with attention to surgical approach, positioning, and contingencies, should occur in a multidisciplinary fashion. Repair with an aortic stent-graft cuff may minimize unnecessary coverage of the descending thoracic aorta and

Bacterial adhesion affinities of various implant abutment materials.

PubMed

Yamane, Koichi; Ayukawa, Yasunori; Takeshita, Toru; Furuhashi, Akihiro; Yamashita, Yoshihisa; Koyano, Kiyoshi

2013-12-01

To investigate bacterial adhesion to various abutment materials. Thirty volunteers participated in this study. Resin splints were fabricated, and five types of disks were fabricated from pure titanium, gold-platinum alloy, zirconia, alumina, and hydroxyapatite with uniform surface roughness and attached to the buccal surface of each splint. After 4 days of use by the subjects, the plaque accumulated on the disk surfaces was analyzed. The bacterial community structure was evaluated using 16S rRNA gene profiling with terminal restriction fragment length polymorphism analysis. The total bacterial count on each disk was estimated using quantitative polymerase chain reaction. Terminal restriction fragment length polymorphism profiles were more similar between tested materials than between subjects, suggesting that the bacterial community structures on the abutment material were influenced more by the individuals than by the type of material. However, the total number of bacteria attached to a disk was significantly different among five materials (P < 0.001, Brunner-Langer test for longitudinal data). Fewer bacteria were attached to the gold-platinum alloy than to the other materials. Gold-platinum alloy appears to be useful material for abutments when considering the accumulation of plaque. However, alternative properties of the abutment material, such as effects on soft tissue healing, should also be taken into consideration when choosing an abutment material. © 2012 John Wiley & Sons A/S.

Fatigue induced changes in conical implant-abutment connections.

PubMed

Blum, Kai; Wiest, Wolfram; Fella, Christian; Balles, Andreas; Dittmann, Jonas; Rack, Alexander; Maier, Dominik; Thomann, Ralf; Spies, Benedikt Christopher; Kohal, Ralf Joachim; Zabler, Simon; Nelson, Katja

2015-11-01

Based on the current lack of data and understanding of the wear behavior of dental two-piece implants, this study aims for evaluating the microgap formation and wear pattern of different implants in the course of cyclic loading. Several implant systems with different conical implant-abutment interfaces were purchased. The implants were first evaluated using synchrotron X-ray high-resolution radiography (SRX) and scanning electron microscopy (SEM). The implant-abutment assemblies were then subjected to cyclic loading at 98N and their microgap was evaluated after 100,000, 200,000 and 1 million cycles using SRX, synchrotron micro-tomography (μCT). Wear mechanisms of the implant-abutment connection (IAC) after 200,000 cycles and 1 million cycles were further characterized using SEM. All implants exhibit a microgap between the implant and abutment prior to loading. The gap size increased with cyclic loading with its changes being significantly higher within the first 200,000 cycles. Wear was seen in all implants regardless of their interface design. The wear pattern comprised adhesive wear and fretting. Wear behavior changed when a different mounting medium was used (brass vs. polymer). A micromotion of the abutment during cyclic loading can induce wear and wear particles in conical dental implant systems. This feature accompanied with the formation of a microgap at the IAC is highly relevant for the longevity of the implants. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Pre-load on oral implants after screw tightening fixed full prostheses: an in vivo study.

PubMed

Duyck, J; Van Oosterwyck, H; Vander Sloten, J; De Cooman, M; Puers, R; Naert, I

2001-03-01

The fit of implant supported fixed prostheses is said to be of clinical concern because of the rigid fixation of an oral implant in its surrounding bone. The influence of the torque sequence of the set screws during fixation of implant supported fixed full prostheses on the final pre-load was investigated in vitro. No significant effect of the torque sequence of the set screws on the final pre-load was observed. The main objective of this study was to quantify and qualify the pre-load in vivo on implants supporting a fixed full prosthesis. This was performed when the prostheses were supported by all five or six implants and was repeated when the prostheses were supported by only four and three implants. A total of 13 patients with a fixed full implant supported prosthesis were selected. The existing abutments were changed for strain gauged abutments. After tightening the set screws with a torque of 10 N cm, the pre-load conditions were registered. The average (SEM) axial forces and bending moments in case of five or six, four and three supporting implants were 323 N (43 N), 346 N (59 N), 307 N (60 N) 21 N cm (3 N cm) and 21 N cm (2 N cm), 23 N cm (5 N cm), respectively. In addition, the pre-load was registered after fixation of a machined gold cylinder, as delivered by the manufacturer, on each of the supporting implants, representing the 'optimal fit' situation. The corresponding average (SEM) axial forces and bending moments in case of five or six, four and three supporting implants were 426 N (36 N), 405 N (40 N), 413 N (46 N) and 8 N cm (1 N cm), 8 N cm (1 N cm), 8 N cm (1 N cm), respectively. The induced axial forces after tightening the prostheses were significantly lower then after tightening the gold cylinder in case of five or six supporting implants (P < 0.02). The induced bending moments after tightening the prostheses were statistically significantly higher (P < 0.0001) then after tightening the gold cylinder in all test conditions (five or six, four or

Soil-structure interaction studies for understanding the behavior of integral abutment bridges.

DOT National Transportation Integrated Search

2012-03-01

Integral Abutment Bridges (IAB) are bridges without any joints within the bridge deck or between the : superstructure and the abutments. An IAB provides many advantages during construction and maintenance of : a bridge. Soil-structure interactions at...

Stability of rock riprap for protection at the toe of abutments located at the floodplain.

DOT National Transportation Integrated Search

1991-09-01

This report presents the results of a research conducted in a hydraulic flume to : determine the stability of rock riprap protecting abutments located on flood : plains. The observed vulnerable zone for rock riprap failure is presented for : two abut...

Hydraulic Performance of Shallow Foundations for the Support of Vertical-Wall Bridge Abutments

DOT National Transportation Integrated Search

2017-02-01

This study combined abutment flume experiments with numerical modeling using computational fluid dynamics (CFD) to investigate flow fields and scour at vertical-wall abutments with shallow foundations. The focus was situations dominated by flow contr...

Pedicle screw anchorage of carbon fiber-reinforced PEEK screws under cyclic loading.

PubMed

Lindtner, Richard A; Schmid, Rene; Nydegger, Thomas; Konschake, Marko; Schmoelz, Werner

2018-03-01

Pedicle screw loosening is a common and significant complication after posterior spinal instrumentation, particularly in osteoporosis. Radiolucent carbon fiber-reinforced polyetheretherketone (CF/PEEK) pedicle screws have been developed recently to overcome drawbacks of conventional metallic screws, such as metal-induced imaging artifacts and interference with postoperative radiotherapy. Beyond radiolucency, CF/PEEK may also be advantageous over standard titanium in terms of pedicle screw loosening due to its unique material properties. However, screw anchorage and loosening of CF/PEEK pedicle screws have not been evaluated yet. The aim of this biomechanical study therefore was to evaluate whether the use of this alternative nonmetallic pedicle screw material affects screw loosening. The hypotheses tested were that (1) nonmetallic CF/PEEK pedicle screws resist an equal or higher number of load cycles until loosening than standard titanium screws and that (2) PMMA cement augmentation further increases the number of load cycles until loosening of CF/PEEK screws. In the first part of the study, left and right pedicles of ten cadaveric lumbar vertebrae (BMD 70.8 mg/cm 3  ± 14.5) were randomly instrumented with either CF/PEEK or standard titanium pedicle screws. In the second part, left and right pedicles of ten vertebrae (BMD 56.3 mg/cm 3  ± 15.8) were randomly instrumented with either PMMA-augmented or nonaugmented CF/PEEK pedicle screws. Each pedicle screw was subjected to cyclic cranio-caudal loading (initial load ranging from - 50 N to + 50 N) with stepwise increasing compressive loads (5 N every 100 cycles) until loosening or a maximum of 10,000 cycles. Angular screw motion ("screw toggling") within the vertebra was measured with a 3D motion analysis system every 100 cycles and by stress fluoroscopy every 500 cycles. The nonmetallic CF/PEEK pedicle screws resisted a similar number of load cycles until loosening as the contralateral standard

In Vitro and In Vivo Evaluations of Nano-Hydroxyapatite/Polyamide 66/Glass Fibre (n-HA/PA66/GF) as a Novel Bioactive Bone Screw

PubMed Central

Su, Bao; Peng, Xiaohua; Jiang, Dianming; Wu, Jun; Qiao, Bo; Li, Weichao; Qi, Xiaotong

2013-01-01

In this study, we prepared nano-hydroxyapatite/polyamide 66/glass fibre (n-HA/PA66/GF) bioactive bone screws. The microstructure, morphology and coating of the screws were characterised, and the adhesion, proliferation and viability of MC3T3-E1 cells on n-HA/PA66/GF scaffolds were determined using scanning electron microscope, CCK-8 assays and cellular immunofluorescence analysis. The results confirmed that n-HA/PA66/GF scaffolds were biocompatible and had no negative effect on MC3T3-E1 cells in vitro. To investigate the in vivo biocompatibility, internal fixation properties and osteogenesis of the bioactive screws, both n-HA/PA66/GF screws and metallic screws were used to repair intercondylar femur fractures in dogs. General photography, CT examination, micro-CT examination, histological staining and biomechanical assays were performed at 4, 8, 12 and 24 weeks after operation. The n-HA/PA66/GF screws exhibited good biocompatibility, high mechanical strength and extensive osteogenesis in the host bone. Moreover, 24 weeks after implantation, the maximum push-out load of the bioactive screws was greater than that of the metallic screws. As shown by their good cytocompatibility, excellent biomechanical strength and fast formation and ingrowth of new bone, n-HA/PA66/GF screws are thus suitable for orthopaedic clinical applications. PMID:23861888

Wear at the Implant-Abutment Interface of Zirconia Abutments Manufactured by Three CAD/CAM Systems.

PubMed

Pinheiro Tannure, Ana Luiza; Cunha, Alfredo Gonçalves; Borges Junior, Luiz Antônio; da Silva Concílio, Laís Regiane; Claro Neves, Ana Christina

To evaluate the changes in the external-hexagon surface of the titanium (Ti) implant before and after mechanical cycling, when coupled with zirconia (Zr) abutments (A) manufactured by three computer-aided design/computer-aided manufacturing (CAD/CAM) systems (Neodent Digital, Zirkonzahn, and AmannGirrbach) and the ZrTi abutment manufactured by Neodent. Four groups were formed (n = 6): titanium implant with Zr AmannGirrbach abutment (AZrAG), with Zr Zirkonzahn abutment (AZrZ), with Zr Neodent abutment (AZrN), and with Zr abutment with infrastructure in Ti Neodent (AZrTiN). Standardized abutments were made from three identical abutments milled in wax. Images of the surface of each side of the hexagons of the implant were obtained by scanning electron microscopy, before and after mechanical cycling, to evaluate the parameters: (1) scratches in the hexagon face; (2) hexagon superior shoulder kneading; (3) hexagon shoulder wear; (4) alterations on the hexagon base; and (5) scratches on the hexagon top. The abutments were coupled with the implants, and Cr-Co crowns were cemented. The implant/abutment/crown assemblies were submitted to mechanical cycling (400 N, 8.0 Hz) for 1 million cycles. The observed changes were classified as follows: absence (0), mild (1), moderate (2), and severe (3). The results were analyzed using the Mann-Whitney, Kruskal-Wallis, and Dunn tests (P < .05). For parameter 1, a significant difference (P = .008) was observed between AZrZ and AZrAG, with more scratches in AZrZ; and between AZrN and AZrTiN (P = .006), with more scratches in AZrN. For parameter 2, a significant difference (P < .05) was observed between AZrZ and AZrAG and between AZrZ and AZrN, with greater kneading in AZrZ; among AZrN and AZrTiN, there was no significant difference (P = .103). For parameter 3, a significant difference (P < .05) was observed between AZrZ and the other groups of Zr, with more wear in AZrZ; between AZrN and AZrTiN, there was no significant difference (P

The effect of repeated torque tightening on total lengths of implant abutments in different internal implant‒abutment connections.

PubMed

Saleh Saber, Fariba; Abolfazli, Nader; Jannatii Ataei, Soheil; Taghizade Motlagh, Mahsa; Gharekhani, Vahede

2017-01-01

Background. Since the misfit of crown has an important role in clinical performance of implant-supported prostheses, and due to the impact of the settling effect on misfit, the aim of this study was to investigate the impact of torque forces on the total lengths of narrow and short implant abutments in different internal implant‒abutment connections. Methods. In four different implant‒abutment connections, 8 analog implants with a normal diameter (4 mm) and narrow abutment (4.5 mm) were selected from groups of internal hex, internal octagon, morse hex 6° and morse hex 11°. Each of them was mounted within plaster type IV, and 32 samples were obtained. Then, the amount of vertical displacement was measured by closing the impression copings and applying torques of 20 25 and 30 Ncm. This stage was repeated for the abutment. In the next stage, the resin pattern was built and measurements were performed after applying the torques mentioned. Finally, after making the frame, this stage was repeated, and the settling effect was statistically analyzed with ANOVA. Results. In the stages of impression coping, resin pattern and final prosthesis, HEXAGONE had significantly the highest and OCTAGONE had the lowest rates of settling, and the settling of morse hex 11° and 6° was between them. Conclusion. Octagon implant had significantly the lowest settling in various clinical and laboratory stages by applying different torques.

The effect of repeated torque tightening on total lengths of implant abutments in different internal implant‒abutment connections

PubMed Central

Saleh Saber, Fariba; Abolfazli, Nader; Jannatii Ataei, Soheil; Taghizade Motlagh, Mahsa; Gharekhani, Vahede

2017-01-01

Background. Since the misfit of crown has an important role in clinical performance of implant-supported prostheses, and due to the impact of the settling effect on misfit, the aim of this study was to investigate the impact of torque forces on the total lengths of narrow and short implant abutments in different internal implant‒abutment connections. Methods. In four different implant‒abutment connections, 8 analog implants with a normal diameter (4 mm) and narrow abutment (4.5 mm) were selected from groups of internal hex, internal octagon, morse hex 6° and morse hex 11°. Each of them was mounted within plaster type IV, and 32 samples were obtained. Then, the amount of vertical displacement was measured by closing the impression copings and applying torques of 20 25 and 30 Ncm. This stage was repeated for the abutment. In the next stage, the resin pattern was built and measurements were performed after applying the torques mentioned. Finally, after making the frame, this stage was repeated, and the settling effect was statistically analyzed with ANOVA. Results. In the stages of impression coping, resin pattern and final prosthesis, HEXAGONE had significantly the highest and OCTAGONE had the lowest rates of settling, and the settling of morse hex 11° and 6° was between them. Conclusion. Octagon implant had significantly the lowest settling in various clinical and laboratory stages by applying different torques. PMID:28748052

Predicting cancellous bone failure during screw insertion.

PubMed

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

2013-04-05

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

Twin-Screw Extruders in Ceramic Extrusion

NASA Astrophysics Data System (ADS)

Wiedmann, Werner; Hölzel, Maria

The machines mainly used for compounding plastics, chemicals and food are co-rotating, closely intermeshing twin-screw extruders. Some 30 000 such extruders are in use worldwide, about 1/3 are ZSKs from Coperion Werner & Pfleiderer, Stuttgart. In the chemical industry more and more batch mixers are being replaced by continuous twin-screw kneaders.

Comparison of observed and predicted abutment scour at selected bridges in Maine.

DOT National Transportation Integrated Search

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 Froehli...

Safe and accurate midcervical pedicle screw insertion procedure with the patient-specific screw guide template system.

PubMed

Kaneyama, Shuichi; Sugawara, Taku; Sumi, Masatoshi

2015-03-15

Clinical trial for midcervical pedicle screw insertion using a novel patient-specific intraoperative screw guiding device. To evaluate the availability of the "Screw Guide Template" (SGT) system for insertion of midcervical pedicle screws. Despite many efforts for accurate midcervical pedicle screw insertion, there still remain unacceptable rate of screw malpositioning that might cause neurovascular injuries. We developed patient-specific SGT system for safe and accurate intraoperative screw navigation tool and have reported its availability for the screw insertion to C2 vertebra and thoracic spine. Preoperatively, the bone image on computed tomography was analyzed and the trajectories of the screws were designed in 3-dimensional format. Three types of templates were created for each lamina: location template, drill guide template, and screw guide template. During the operations, after engaging the templates directly with the laminae, drilling, tapping, and screwing were performed with each template. We placed 80 midcervical pedicle screws for 20 patients. The accuracy and safety of the screw insertion by SGT system were evaluated using postoperative computed tomographic scan by calculation of screw deviation from the preplanned trajectory and evaluation of screw breach of pedicle wall. All templates fitted the laminae and screw navigation procedures proceeded uneventfully. All screws were inserted accurately with the mean screw deviation from planned trajectory of 0.29 ± 0.31 mm and no neurovascular complication was experienced. We demonstrated that our SGT system could support the precise screw insertion in midcervical pedicle. SGT prescribes the safe screw trajectory in a 3-dimensional manner and the templates fit and lock directly to the target laminae, which prevents screwing error along with the change of spinal alignment during the surgery. These advantages of the SGT system guarantee the high accuracy in screw insertion, which allowed surgeons to insert

Settling of abutments into implants and changes in removal torque in five different implant-abutment connections. Part 1: Cyclic loading.

PubMed

Kim, Ki-Seong; Han, Jung-Suk; Lim, Young-Jun

2014-01-01

The aim of this study was to evaluate and compare the settling of abutments into implants and the removal torque values (RTVs) before and after cyclic loading. Five different implant-abutment connections were tested: Ext = external butt joint + two-piece abutment; Int-H2 = internal hexagon + two-piece abutment; Int-H1 = internal hexagon + one-piece abutment; Int-O2 = internal octagon + two-piece abutment; and Int-O1 = internal octagon + one-piece abutment. Ten abutments from each group were secured to their corresponding implants (total n = 50). All samples were tested in a universal testing machine with a vertical load of 250 N for 100,000 cycles of 14 Hz. The amount of settling of the abutment into the implant was calculated from the change in the total length of the implant-abutment sample before and after loading, as measured with an electronic digital micrometer. The RTV after cyclic loading was compared to the initial RTV with a digital torque gauge. Statistical analysis was performed at a 5% significance level. A multiple-comparison test showed specific significant differences in settling values in each group after 250 N cyclic loading (Int-H1, Ext < Int-H2 < Int-O2 < Int-O1). There were statistically significant decreases in RTVs after loading compared to the initial RTVs in the Int-H2 and Int-O2 groups. No statistically significant differences were found in the Ext, Int-H1, and Int-O1 groups. The results of this study demonstrated that the settling amount and RTV (loss of preload) after cyclic loading were specific to the abutment type and related to the design characteristics of the implant-abutment connection.

Trestle #1, detail of bolts on northeast abutment lower vertical ...

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

Trestle #1, detail of bolts on northeast abutment lower vertical support timbers. View to north - Promontory Route Railroad Trestles, S.P. Trestle 779.91, One mile southwest of junction of State Highway 83 and Blue Creek, Corinne, Box Elder County, UT

Trestle #1, detail of southwest abutment lower sill and gabion ...

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

Trestle #1, detail of southwest abutment lower sill and gabion baskets. View to west - Promontory Route Railroad Trestles, S.P. Trestle 779.91, One mile southwest of junction of State Highway 83 and Blue Creek, Corinne, Box Elder County, UT

Trestle #1, wing wall on northwest side of northeast abutment. ...

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

Trestle #1, wing wall on northwest side of northeast abutment. View to northeast - Promontory Route Railroad Trestles, S.P. Trestle 779.91, One mile southwest of junction of State Highway 83 and Blue Creek, Corinne, Box Elder County, UT

Trestle #1, detail of southwest abutment upper timbers and gabion ...

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

Trestle #1, detail of southwest abutment upper timbers and gabion basket. View to west - Promontory Route Railroad Trestles, S.P. Trestle 779.91, One mile southwest of junction of State Highway 83 and Blue Creek, Corinne, Box Elder County, UT

Integral abutment bridge for Louisiana's soft and stiff soils.

DOT National Transportation Integrated Search

2016-03-01

Integral abutment bridges (IABs) have been designed and constructed in a few US states in the past few : decades. The initial purpose of building such bridges was to eliminate the expansion joints and resolve the : joint-induced problems. Although IA...

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

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

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

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

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

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

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

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

9. SEATING OF GIRDER SPAN AT SOUTH ABUTMENT. FABRICATOR'S PLATE ...

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

9. SEATING OF GIRDER SPAN AT SOUTH ABUTMENT. FABRICATOR'S PLATE READS 'VIRGINIA BRIDGE COMPANY 1950,' ACCOMPANIED BY THE LOGO OF UNITED STATES STEEL. - George P. Coleman Memorial Bridge, Spanning York River at U.S. Route 17, Yorktown, York County, VA

9. Terminal connection of arch structural member to concrete abutment ...

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

9. Terminal connection of arch structural member to concrete abutment on east of south end of bridge. Slightly oblique detail view west-northwest (from beside bridge). 150 mm lens. - Gault Bridge, Spanning Deer Creek at South Pine Street, Nevada City, Nevada County, CA

33. EAST ABUTMENT, VIEW NORTHEAST OF OPERATING MACHINERY SMALL ...

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

33. EAST ABUTMENT, VIEW NORTHEAST OF OPERATING MACHINERY - SMALL GEAR IS IDENTIFIED AS 'C' - LARGE GEAR IS 'B' REFER TO GEARING DIAGRAMS - STRAUSS SHEET #15 FOR POWER TRAIN RELATIONSHIPS - Tomlinson Bridge, Spanning Quinnipiac River at Forbes Street (U.S. Route 1), New Haven, New Haven County, CT

34. VIEW SOUTHEAST, WEST ABUTMENT OF OPERATING MACHINERY LARGE ...

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

34. VIEW SOUTHEAST, WEST ABUTMENT OF OPERATING MACHINERY - LARGE GEAR AT LEFT CENTER IS 'D' - REFER TO STRAUSS SHEETS #15 AND #18 FOR POWER TRAIN RELATIONSHIPS - Tomlinson Bridge, Spanning Quinnipiac River at Forbes Street (U.S. Route 1), New Haven, New Haven County, CT

35. VIEW SOUTHEAST, WEST ABUTMENT OF OPERATING MACHINERY BASCULE ...

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

35. VIEW SOUTHEAST, WEST ABUTMENT OF OPERATING MACHINERY - BASCULE LEAF RAISED - LARGE GEAR AT LEFT CENTER IS 'D' - REFER TO STRAUSS SHEETS #15 AND #18 FOR POWER TRAIN RELATIONSHIPS - Tomlinson Bridge, Spanning Quinnipiac River at Forbes Street (U.S. Route 1), New Haven, New Haven County, CT

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.

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.

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

Axial displacements in external and internal implant-abutment connection.

PubMed

Lee, Ji-Hye; Kim, Dae-Gon; Park, Chan-Jin; Cho, Lee-Ra

2014-02-01

The purpose of this study was to evaluate the axial displacement of the abutments during clinical procedures by the tightening torque and cyclic loading. Two different implant-abutment connection systems were used (external butt joint connection [EXT]; internal tapered conical connection [INT]). The master casts with two implant replicas, angulated 10° from each other, were fabricated for each implant connection system. Four types of impression copings were assembled and tightened with the corresponding implants (hex transfer impression coping, non-hex transfer impression coping, hex pick-up impression coping, non-hex pick-up impression coping). Resin splinted abutments and final prosthesis were assembled. The axial displacement was measured from the length of each assembly, which was evaluated repeatedly, after 30 Ncm torque tightening. After 250 N cyclic loading of final prosthesis for 1,000,000 cycles, additional axial displacement was recorded. The mean axial displacement was statistically analyzed (repeated measured ANOVA). There was more axial displacement in the INT group than that of the EXT group in impression copings, resin splinted abutments, and final prosthesis. Less axial displacement was found at 1-piece non-hex transfer type impression coping than other type of impression copings in the INT group. There was more axial displacement at the final prosthesis than resin splinted abutments in the INT and the EXT groups. After 250 N cyclic loading of final prosthesis, the INT group showed more axial displacement than that of the EXT group. Internal tapered conical connection demonstrated a varying amount of axial displacement with tightening torque and cyclic loading. © 2012 John Wiley & Sons A/S. Published by Blackwell Publishing Ltd.

Retention of cast crown copings cemented to implant abutments.

PubMed

Dudley, J E; Richards, L C; Abbott, J R

2008-12-01

The cementation of crowns to dental implant abutments is an accepted form of crown retention that requires consideration of the properties of available cements within the applied clinical context. Dental luting agents are exposed to a number of stressors that may reduce crown retention in vivo, not the least of which is occlusal loading. This study investigated the influence of compressive cyclic loading on the physical retention of cast crown copings cemented to implant abutments. Cast crown copings were cemented to Straumann synOcta titanium implant abutments with three different readily used and available cements. Specimens were placed in a humidifier, thermocycled and subjected to one of four quantities of compressive cyclic loading. The uniaxial tensile force required to remove the cast crown copings was then recorded. The mean retention values for crown copings cemented with Panavia-F cement were statistically significantly greater than both KetacCem and TempBond non-eugenol cements at each compressive cyclic loading quantity. KetacCem and TempBond non-eugenol cements produced relatively low mean retention values that were not statistically significantly different at each quantity of compressive cyclic loading. Compressive cyclic loading had a statistically significant effect on Panavia-F specimens alone, but increased loading quantities produced no further statistically significant difference in mean retention. Within the limitations of the current in vitro conditions employed in this study, the retention of cast crown copings cemented to Straumann synOcta implant abutments with a resin, glass ionomer and temporary cement was significantly affected by cement type but not compressive cyclic loading. Resin cement is the cement of choice for the definitive non-retrievable cementation of cast crown copings to Straumann synOcta implant abutments out of the three cements tested.

Feasibility of detecting orthopaedic screw overtightening using acoustic emission.

PubMed

Pullin, Rhys; Wright, Bryan J; Kapur, Richard; McCrory, John P; Pearson, Matthew; Evans, Sam L; Crivelli, Davide

2017-03-01

A preliminary study of acoustic emission during orthopaedic screw fixation was performed using polyurethane foam as the bone-simulating material. Three sets of screws, a dynamic hip screw, a small fragment screw and a large fragment screw, were investigated, monitoring acoustic-emission activity during the screw tightening. In some specimens, screws were deliberately overtightened in order to investigate the feasibility of detecting the stripping torque in advance. One set of data was supported by load cell measurements to directly measure the axial load through the screw. Data showed that acoustic emission can give good indications of impending screw stripping; such indications are not available to the surgeon at the current state of the art using traditional torque measuring devices, and current practice relies on the surgeon's experience alone. The results suggest that acoustic emission may have the potential to prevent screw overtightening and bone tissue damage, eliminating one of the commonest sources of human error in such scenarios.

Comparison of the impact of scaler material composition on polished titanium implant abutment surfaces.

PubMed

Hasturk, Hatice; Nguyen, Daniel Huy; Sherzai, Homa; Song, Xiaoping; Soukos, Nikos; Bidlack, Felicitas B; Van Dyke, Thomas E

2013-08-01

The purpose of this study was to compare the impact of the removal of biofilm with hand scalers of different material composition on the surface of implant abutments by assessing the surface topography and residual plaque after scaling using scanning electron microscopy (SEM). Titanium implant analogs from 3 manufacturers (Straumann USA LLC, Andover, Maine, Nobel BioCare USA LLC, Yorba Linda, Cali, Astra Tech Implant Systems, Dentsply, Mölndal, Sweden) were mounted in stone in plastic vials individually with authentic prosthetic abutments. Plaque samples were collected from a healthy volunteer, inoculated into growth medium and incubated with the abutments anaerobically for 1 week. A blinded, calibrated hygienist performed scaling to remove the biofilm using 6 implant scalers (in triplicate), 1 scaler for 1 abutment. The abutments were mounted on an imaging stand and processed for SEM. Images were captured in 3 randomly designated areas of interest on each abutment. Analysis of the implant polished abutment surface and plaque area measurements were performed using ImageJ image analysis software. Surface alterations were characterized by the number, length, depth and the width of the scratches observed. Glass filled resin scalers resulted in significantly more and longer scratches on all 3 abutment types compared to other scalers, while unfilled resin scalers resulted in the least surface change (p < 0.05). Filled resin-graphite reinforced scalers, carbon fiber reinforced resin scalers and titanium scalers resulted in more superficial scratches compared to glass filled resin, as well as more scratches than unfilled resin. No statistically significant differences were found between scalers and abutments with regard to plaque removal. The impact of scalers on implant abutment surfaces varies between abutment types presumably due to different surface characteristics with no apparent advantage of one abutment type over the other with regard to resistance to surface

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

PubMed Central

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

2015-01-01

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

Mixed zirconia calcium phosphate coatings for dental implants: tailoring coating stability and bioactivity potential.

PubMed

Pardun, Karoline; Treccani, Laura; Volkmann, Eike; Streckbein, Philipp; Heiss, Christian; Li Destri, Giovanni; Marletta, Giovanni; Rezwan, Kurosch

2015-03-01

Enhanced coating stability and adhesion are essential for long-term success of orthopedic and dental implants. In this study, the effect of coating composition on mechanical, physico-chemical and biological properties of coated zirconia specimens is investigated. Zirconia discs and dental screw implants are coated using the wet powder spraying (WPS) technique. The coatings are obtained by mixing yttria-stabilized zirconia (TZ) and hydroxyapatite (HA) in various ratios while a pure HA coating served as reference material. Scanning electron microscopy (SEM) and optical profilometer analysis confirm a similar coating morphology and roughness for all studied coatings, whereas the coating stability can be tailored with composition and is probed by insertion and dissections experiments in bovine bone with coated zirconia screw implants. An increasing content of calcium phosphate (CP) resulted in a decrease of mechanical and chemical stability, while the bioactivity increased in simulated body fluid (SBF). In vitro experiments with human osteoblast cells (HOB) revealed that the cells grew well on all samples but are affected by dissolution behavior of the studied coatings. This work demonstrates the overall good mechanical strength, the excellent interfacial bonding and the bioactivity potential of coatings with higher TZ contents, which provide a highly interesting coating for dental implants. Copyright © 2014 Elsevier B.V. All rights reserved.

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.

Esthetic and Clinical Performance of Implant-Supported All-Ceramic Crowns Made with Prefabricated or CAD/CAM Zirconia Abutments: A Randomized, Multicenter Clinical Trial.

PubMed

Wittneben, J G; Gavric, J; Belser, U C; Bornstein, M M; Joda, T; Chappuis, V; Sailer, I; Brägger, U

2017-02-01

Patients' esthetic expectations are increasing, and the options of the prosthetic pathways are currently evolving. The objective of this randomized multicenter clinical trial was to assess and compare the esthetic outcome and clinical performance of anterior maxillary all-ceramic implant crowns (ICs) based either on prefabricated zirconia abutments veneered with pressed ceramics or on CAD/CAM zirconia abutments veneered with hand buildup technique. The null hypothesis was that there is no statistically significant difference between the 2 groups. Forty implants were inserted in sites 14 to 24 (FDI) in 40 patients in 2 centers, the Universities of Bern and Geneva, Switzerland. After final impression, 20 patients were randomized into group A, restored with a 1-piece screw-retained single crown made of a prefabricated zirconia abutment with pressed ceramic as the veneering material using the cut-back technique, or group B using an individualized CAD/CAM zirconia abutment (CARES abutment; Institut Straumann AG) with a hand buildup technique. At baseline, 6 mo, and 1 y clinical, esthetic and radiographic parameters were assessed. Group A exhibited 1 dropout patient and 1 failure, resulting in a survival rate of 94.7% after 1 y, in comparison to 100% for group B. No other complications occurred. Clinical parameters presented stable and healthy peri-implant soft tissues. Overall, no or only minimal crestal bone changes were observed with a mean DIB (distance from the implant shoulder to the first bone-to-implant contact) of -0.15 mm (group A) and 0.12 mm (group B) at 1 y. There were no significant differences at baseline, 6 mo, and 1 y for DIB values between the 2 groups. Pink esthetic score (PES) and white esthetic score (WES) values at all 3 examinations indicated stability over time for both groups and pleasing esthetic outcomes. Both implant-supported prosthetic pathways represent a valuable treatment option for the restoration of single ICs in the anterior maxilla

Displacement of screw-retained splinted and nonsplinted restorations into implants with conical internal connections.

PubMed

Yilmaz, Burak; Seidt, Jeremy D; Clelland, Nancy L

2014-01-01

Variable abutment displacement could potentially affect proximal contacts, incisal edge position, or occlusion of implant-supported prostheses. This study aimed to measure and compare displacements of splinted and nonsplinted restorations into implants featuring internal conical connections as screws were tightened by hand or by torque driver. A stereolithic resin model was printed using computed tomography data from a patient missing mandibular left first and second molars. Two 5.0 × 11-mm implants were placed in the edentulous site using a surgical guide. Two sets (splinted and nonsplinted) of gold screw-retained prostheses were made indirectly to fit the implants in the stereolithic model representing the patient. The axial position of the crowns relative to a fixed location on the model was recorded following hand tightening using the three-dimensional image correlation technique and image correlation software. A pair of high-resolution digital cameras provided a synchronized view of the model during the experiment. Relative crown positions were again recorded after tightening with a torque driver to 25 Ncm. Testing was repeated randomly three times for each set of crowns. Displacement data after torque tightening were compared using a factorial analysis of variance with JMP 9.0 software (SAS) followed by a Tukey-Kramer post hoc test (α = .05). Interproximal contacts were evaluated using an 8-μm tin foil shim after tightening by hand and torque driver. Displacements for splinted and nonsplinted restorations differed only in a buccal direction. The nonsplinted crowns displaced significantly more than splinted crowns. Discernible differences were observed for the tin foil shim when dragged through proximal contacts following hand versus torque tightening. Differences between screw tightening by hand or torque driver should be taken into consideration during laboratory and clinical adjustments to prevent esthetic and functional complications.

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.

Effect of Steam Autoclaving on the Tensile Strength of Resin Cements Used for Bonding Two-Piece Zirconia Abutments.

PubMed

Fadanelli, Marcos Alexandre; Amaral, Flávia Lucisano Botelho do; Basting, Roberta Tarkany; Turssi, Cecilia Pedroso; Sotto-Maior, Bruno Salles; França, Fabiana Mantovani Gomes

2017-04-01

The purpose of this study was to evaluate the effects of steam autoclave sterilization on the tensile strength of two types of resin cements used to bond customized CAD/CAM zirconia abutments onto titanium bases. Forty sets of zirconia abutments cemented to screwed titanium bases of implants analogs were divided into 4 groups (n = 10). Two groups were treated with a conventional chemically activated resin cement (ML, Multilink Ivoclar Vivadent) and the other two groups with a self-adhesive dual resin cement (RelyX U200, 3M ESPE). One group from each cement was submitted to steam autoclaving. The autoclave sterilization cycle was performed after 72 hours of cementation for 15 minutes at 121°C and 2.1 Kgf/cm 2 . The samples were subjected to tensile strength testing in a universal testing machine (200 Kgf, 0.5 mm/min), from which the means and standard deviations were obtained in Newtons. Results showed (via ANOVA and Tukey's test; α = 0.05) that in the absence of steam autoclaving, no difference was observed in tensile strength between the cements tested: ML: 344.87 (93.79) and U200: 280 (92.42) (P = .314). Steam autoclaving, however, significantly increased tensile strength for the ML: 465.42 (87.87) compared to U200: 289.10 (49.02) (P < .001). Despite the significant increase in the ML samples (P = .013), autoclaving did not affect the tensile strength of the U200 samples (P > 0.05). The authors concluded that steam autoclaving increases the mean tensile strength of the chemically activated cement compared to the dual-cure self-adhesive cement. The performance of both cements evaluated was similar if the sterilization step was disconsidered.

Evaluation in a Dog Model of Three Antimicrobial Glassy Coatings: Prevention of Bone Loss around Implants and Microbial Assessments

PubMed Central

López-Píriz, Roberto; Solá-Linares, Eva; Rodriguez-Portugal, Mercedes; Malpica, Beatriz; Díaz-Güemes, Idoia; Enciso, Silvia; Esteban-Tejeda, Leticia; Cabal, Belén; Granizo, Juan José; Moya, José Serafín; Torrecillas, Ramón

2015-01-01

Objectives The aim of the present study is to evaluate, in a ligature-induced peri-implantitis model, the efficacy of three antimicrobial glassy coatings in the prevention of biofilm formation, intrasulcular bacterial growth and the resulting peri-implant bone loss. Methods Mandibular premolars were bilaterally extracted from five beagle dogs. Four dental implants were inserted on each hemiarch. Eight weeks after, one control zirconia abutment and three with different bactericidal coatings (G1n-Ag, ZnO35, G3) were connected. After a plaque control period, bacterial accumulation was allowed and biofilm formation on abutments was observed by Scanning Electron Microscopy (SEM). Peri-implantitis was induced by cotton ligatures. Microbial samples and peri-implant crestal bone levels of all implant sites were obtained before, during and after the breakdown period. Results During experimental induce peri-implantitis: colony forming units counts from intrasulcular microbial samples at implants with G1n-Ag coated abutment remained close to the basal inoculum; G3 and ZnO35 coatings showed similar low counts; and anaerobic bacterias counts at control abutments exhibited a logarithmic increase by more than 2. Bone loss during passive breakdown period was no statistically significant. Additional bone loss occurred during ligature-induce breakdown: 0.71 (SD 0.48) at G3 coating, 0.57 (SD 0.36) at ZnO35 coating, 0.74 (SD 0.47) at G1n-Ag coating, and 1.29 (SD 0.45) at control abutments; and statistically significant differences (p<0.001) were found. The lowest bone loss at the end of the experiment was exhibited by implants dressing G3 coated abutments (mean 2.1; SD 0.42). Significance Antimicrobial glassy coatings could be a useful tool to ward off, diminish or delay peri-implantitis progression. PMID:26489088

Evaluation in a Dog Model of Three Antimicrobial Glassy Coatings: Prevention of Bone Loss around Implants and Microbial Assessments.

PubMed

López-Píriz, Roberto; Solá-Linares, Eva; Rodriguez-Portugal, Mercedes; Malpica, Beatriz; Díaz-Güemes, Idoia; Enciso, Silvia; Esteban-Tejeda, Leticia; Cabal, Belén; Granizo, Juan José; Moya, José Serafín; Torrecillas, Ramón

2015-01-01

The aim of the present study is to evaluate, in a ligature-induced peri-implantitis model, the efficacy of three antimicrobial glassy coatings in the prevention of biofilm formation, intrasulcular bacterial growth and the resulting peri-implant bone loss. Mandibular premolars were bilaterally extracted from five beagle dogs. Four dental implants were inserted on each hemiarch. Eight weeks after, one control zirconia abutment and three with different bactericidal coatings (G1n-Ag, ZnO35, G3) were connected. After a plaque control period, bacterial accumulation was allowed and biofilm formation on abutments was observed by Scanning Electron Microscopy (SEM). Peri-implantitis was induced by cotton ligatures. Microbial samples and peri-implant crestal bone levels of all implant sites were obtained before, during and after the breakdown period. During experimental induce peri-implantitis: colony forming units counts from intrasulcular microbial samples at implants with G1n-Ag coated abutment remained close to the basal inoculum; G3 and ZnO35 coatings showed similar low counts; and anaerobic bacterias counts at control abutments exhibited a logarithmic increase by more than 2. Bone loss during passive breakdown period was no statistically significant. Additional bone loss occurred during ligature-induce breakdown: 0.71 (SD 0.48) at G3 coating, 0.57 (SD 0.36) at ZnO35 coating, 0.74 (SD 0.47) at G1n-Ag coating, and 1.29 (SD 0.45) at control abutments; and statistically significant differences (p<0.001) were found. The lowest bone loss at the end of the experiment was exhibited by implants dressing G3 coated abutments (mean 2.1; SD 0.42). Antimicrobial glassy coatings could be a useful tool to ward off, diminish or delay peri-implantitis progression.

Fracture resistance of zirconia-based implant abutments after artificial long-term aging.

PubMed

Alsahhaf, Abdulaziz; Spies, Benedikt Christopher; Vach, Kirstin; Kohal, Ralf-Joachim

2017-02-01

To investigate the survival rate, fracture strength, bending moments, loading to fracture and fracture modes of different designs of zirconia abutments after dynamic loading with thermocycling, and compare these values to titanium abutments. A total of 80 abutment samples were divided into 5 test groups of 16 samples in each group. The study included the following groups, "Group 1" CAD/CAM produced all-zirconia abutments, "Group 2" titanium abutments, "Group 3" zirconia-abutments adhesively luted to a titanium base, "Group 4" prefabricated all-zirconia abutments and "Group 5" zirconia-abutments glass soldered to a titanium base. Half the number of samples in each group was exposed to 1.2 million loading cycles (5-years simulation) in the chewing simulator. The samples that survived the artificial aging were later tested for fracture strength in a universal testing machine. The remaining 8 samples of the group were directly tested for fracture strength. All samples exposed to the 5-years artificial aging survived except of six samples in one group (Group 1). The surviving samples were later fracture tested in the universal testing machine. The bending moments (Ncm) values were as follow: Exposed groups: "Group 1" 94.5Ncm; "Group 2" 599.2Ncm; "Group 3" 477.5Ncm; "Group 4" 314.4Ncm; "Group 5" 509.4Ncm. Non-exposed groups: "Group 1" 269.3Ncm; "Group 2" 474.2Ncm; "Group 3" 377.6Ncm; "Group 4" 265.4Ncm; "Group 5" 372.4Ncm. Except in Group 1, the values were higher in the exposed groups, although, statistically there was no difference (p>0.05). The one-piece ZrO2-abutment group (Group 1 and Group 4) exhibited lower values, while the two-piece ZrO2-abutment groups (Group 3 and Group 5) showed similar values and fracture modes like the titanium abutment group. The titanium abutment group showed the highest values of bending moments among all groups. The implant-abutment connection area appeared to influence the bending moment value and the fracture mode of the tested

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.

Numerical simulation of abutment pressure redistribution during face advance

NASA Astrophysics Data System (ADS)

Klishin, S. V.; Lavrikov, S. V.; Revuzhenko, A. F.

2017-12-01

The paper presents numerical simulation data on the abutment pressure redistribution in rock mass during face advance, including isolines of maximum shear stress and pressure epures. The stress state of rock in the vicinity of a breakage heading is calculated by the finite element method using a 2D nonlinear model of a structurally heterogeneous medium with regard to plasticity and internal self-balancing stress. The thus calculated stress field is used as input data for 3D discrete element modeling of the process. The study shows that the abutment pressure increases as the roof span extends and that the distance between the face breast and the peak point of this pressure depends on the elastoplastic properties and internal self-balancing stress of a rock medium.

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.

Comparative study of torque resistance and microgaps between a combined Octatorx-cone connection and an internal hexagon implant-abutment connection.

PubMed

Khongkhunthian, Pathawee; Khongkhunthian, Sakornratana; Weerawatprachya, Winai; Pongpat, Kanuengnit; Aunmeungtong, Weerapan

2015-05-01

Although the implant-abutment connection may prevent crestal bone loss around dental implants, its failure often leads to treatment failure. Microgap and micromovement of the implant-abutment connection could be causes of bone resorption around dental implant neck. The purpose of this study was to compare torque resistance and microgaps between a new cone and index connection (Octatorx) and an internal hexagon implant-abutment connection (Internal hex). Twenty Octatorx and 20 internal hexagon connections were attached with retaining screws at 30 Ncm. In a torsion resistance test, 10 of each type of connection were attached to a universal testing machine. Torque resistance with 90 degrees per minute rotation speed was recorded. For microgap measurement, each of 10 connections was embedded in clear acrylic resin. The blocks were cut longitudinally. Twenty specimens of each connection were evaluated. Twelve measurements of microgaps (6 on each side of specimen) were recorded under scanning electron microscopy. The average torsion resistance of Octatorx (203.6 ±17.4 Ncm) was significantly greater than that of the internal hexagon (146.4 ±16.1 Ncm, P<.05). For the microgap, there was a significant difference (P=.001) between the median values of Octatorx (1.19 μm) and the internal hexagon (3.80 μm). In this study, the new connection, Octatorx, had a smaller microgap and greater torque resistance than the internal hexagon connection. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

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

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

PubMed

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

2013-08-01

There is currently no reliable technique for intraoperative assessment of pedicle screw fixation strength and optimal screw size. Several studies have evaluated pedicle screw insertional torque (IT) and its direct correlation with pullout strength. However, there is limited clinical application with pedicle screw IT as it must be measured during screw placement and rarely causes the spine surgeon to change screw size. To date, no study has evaluated tapping IT, which precedes screw insertion, and its ability to predict pedicle screw pullout strength. The objective of this study was to investigate tapping IT and its ability to predict pedicle screw pullout strength and optimal screw size. In vitro human cadaveric biomechanical analysis. Twenty fresh-frozen human cadaveric thoracic vertebral levels were prepared and dual-energy radiographic absorptiometry scanned for bone mineral density (BMD). All specimens were osteoporotic with a mean BMD of 0.60 ± 0.07 g/cm(2). Five specimens (n=10) were used to perform a pilot study, as there were no previously established values for optimal tapping IT. Each pedicle during the pilot study was measured using a digital caliper as well as computed tomography measurements, and the optimal screw size was determined to be equal to or the first size smaller than the pedicle diameter. The optimal tap size was then selected as the tap diameter 1 mm smaller than the optimal screw size. During optimal tap size insertion, all peak tapping IT values were found to be between 2 in-lbs and 3 in-lbs. Therefore, the threshold tapping IT value for optimal pedicle screw and tap size was determined to be 2.5 in-lbs, and a comparison tapping IT value of 1.5 in-lbs was selected. Next, 15 test specimens (n=30) were measured with digital calipers, probed, tapped, and instrumented using a paired comparison between the two threshold tapping IT values (Group 1: 1.5 in-lbs; Group 2: 2.5 in-lbs), randomly assigned to the left or right pedicle on each

[Clinical application of percutaneous iliosacral screws combined with pubic ramus screws in Tile B pelvic fracture].

PubMed

Xu, Qi-Fei; Lin, Kui-Ran; Zhao, Dai-Jie; Zhang, Song-Qin; Feng, Sheng-Kai; Li, Chen

2017-03-25

To investigate the application and effect of minimally invasive percutaneous anterior pelvic pubic ramus screw fixation in Tile B fractures. A retrospective review was conducted on 56 patients with posterior pelvic ring injury combined with fractures of anterior pubic and ischiadic ramus treated between May 2010 and August 2015, including 31 males and 25 females with an average age of 36.8 years old ranging from 35 to 65 years old. Based on the Tile classification, there were 13 cases of Tile B1 type, 28 cases of Tile B2 type and 15 cases of Tile B3 type. Among them, 26 patients were treated with sacroiliac screws combined with external fixation (external fixator group) and the other 30 patients underwent sacroiliac screw fixation combined with anterior screw fixation (pubic ramus screw group). Postoperative complications, postoperative ambulation time, fracture healing, blood loss, Majeed pelvic function score and visual analogue scale(VAS) were compared between two groups. Fifty-four patients were followed up from 3 to 24 months with a mean of 12 months. There were no significant difference in the peri-operative bleeding and operation time between two groups( P >0.05). The postoperative activity time and fracture healing time of pubic ramus screw group were shorter than those of the external fixator group, the differences were statistically significant( P <0.05). The Majeed score, VAS score of pubic ramus screw group were higher than those of the external fixator group, the differences were statistically significant( P <0.05). The incidence of postoperative complications of pubic ramus screw was lower than that of the external fixator group, the difference was statistically significant ( P <0.05). Percutaneous iliosacral screws fixation combined with the pubic ramus screw is an effective and safty treatment method to the Tile B pelvic fracture. It has advantages of early ambulation, relief of the pain and few complications.

Standard Waste Box Lid Screw Removal Option Testing

SciTech Connect

Anast, Kurt Roy

This report provides results from test work conducted to resolve the removal of screws securing the standard waste box (SWB) lids that hold the remediated nitrate salt (RNS) drums. The test work evaluated equipment and process alternatives for removing the 42 screws that hold the SWB lid in place. The screws were secured with a red Loctite thread locker that makes removal very difficult because the rivets that the screw threads into would slip before the screw could be freed from the rivet, making it impossible to remove the screw and therefore the SWB lid.

Fracture resistance of inter-joined zirconia abutment of dental implant system with injection molding technique.

PubMed

Yang, Jianjun; Wang, Ke; Liu, Guangyuan; Wang, Dashan

2013-11-01

Zirconia powder in nanometers can be fabricated into inter-joined abutment of dental implant system with the injection shaping technique. This study was to detect the resistance of inter-joined zirconia abutment with different angle loading for clinical applications. The inter-joined abutments were shaped with the technique of injection of zirconia powder in nanometers. Sixty Osstem GSII 5 × 10 mm implants were used with 30 zirconia abutments and 30 Osstem GSII titanium abutments for fixation using 40 N torque force. The loading applications included 90°, 30°, and 0° formed by the long axis of abutments and pressure head of universal test machine. The fracture resistances of zirconia and titanium abutments were documented and analyzed. The inter-joined zirconia abutments were assembled to the Osstem GSII implants successfully. In the 90° loading mode, the fracture resistance of zirconia abutment group and titanium abutment group were 301.5 ± 15.4 N and 736.4 ± 120.1 N, respectively. And those in the 30° groups were 434.7 ± 36.1 N and 1073.1 ± 74 N, correspondingly. Significant difference in the two groups was found using t-test and Wilcoxon test. No damage on the abutments of the two groups but S-shaped bending on the implants was found when the 0° loading was 1300-2000 N. Through the assembly of Zirconia abutments and implants, all the components presented sufficient resistance acquired for the clinical application under loadings with different angle. © 2012 John Wiley & Sons A/S.

Impact of abutment material on peri-implant soft tissue color. An in vitro study.

PubMed

Sala, Leticia; Bascones-Martínez, Antonio; Carrillo-de-Albornoz, Ana

2017-09-01

The objectives of the present study is to determine the differences in peri-implant soft tissue color with the utilization of titanium, titanium gold-plated, white zirconia, Vita Classical (VC) A4-shaded zirconia, and fluorescent white zirconia abutments and to establish the influence of gingival thickness on the resulting color. Four implants were contralaterally inserted in 19 fresh pig mandibles, and the color of the peri-implant mucosa with the different abutments was spectrophotometrically measured at 1-, 2-, and 3-mm height from the margin. At 1-mm height, titanium significantly differed from all zirconia abutments in lightness (L*), chroma along red axis (a*), and chroma along yellow-blue axis (b*) parameters. At 2 mm, all zirconia abutments differed from titanium in b* but only fluorescent zirconia in a*. At 3 mm, titanium differed from VC A4-shaded and fluorescent zirconia abutments in b*. At soft tissue thicknesses <1 and 1-2 mm, titanium differed from fluorescent zirconia in a* and b* and from VC A4-shaded zirconia in b*; at thickness >2 mm, no differences were found among abutments. All abutments differed from natural teeth in a* and b* at all heights and thicknesses except for fluorescent zirconia at thickness >2 mm. The Euclidean distance (ΔΕ) differed between titanium abutments and gold, VC A4, and fluorescent zirconia at <1- and 1-2-mm thicknesses. The natural gingival color was not reproduced with any abutment at gingival thicknesses <2 mm. The worst color match was with titanium abutments and the best with fluorescent zirconia, followed by VC A4-shaded zirconia. At gingival thicknesses >2 mm, no differences were detected among abutments. This study demonstrates that the type of abutment and the gingival thickness affect the resulting peri-implant gingival color.

The total occlusal convergence of the abutment of a partial fixed dental prosthesis: A definition and a clinical technique for its assessment

PubMed Central

Mamoun, John S.

2013-01-01

The abutment(s) of a partial fixed dental prosthesis (PFDP) should have a minimal total occlusal convergence (TOC), also called a taper, in order to ensure adequate retention of a PFDP that will be made for the abutment(s), given the height of the abutment(s). This article reviews the concept of PFDP abutment TOC and presents an alternative definition of what TOC is, defining it as the extent to which the shape of an abutment differs from an ideal cylinder shape of an abutment. This article also reviews experimental results concerning what is the ideal TOC in degrees and explores clinical techniques of estimating the TOC of a crown abutment. The author suggests that Dentists use high magnification loupes (×6-8 magnification or greater) or a surgical operating microscope when preparing crown abutments, to facilitate creating a minimum abutment TOC. PMID:24932130

Influence of reverse torque values in abutments with or without internal hexagon indexes.

PubMed

Cerutti-Kopplin, Daiane; Rodrigues Neto, Dimas João; Lins do Valle, Accácio; Pereira, Jefferson Ricardo

2014-10-01

The mechanical stability of the implant-abutment connection is of fundamental importance for successful implant-supported restorations. Therefore, understanding removal torque values is essential. The purpose of this study was to evaluate the reverse torque values of indexed and nonindexed abutments of the Morse Taper system. Twelve Morse taper implants with their respective abutments were divided into 2 groups (n=6): group NI, nonindexed abutments; and group IN, indexed abutments. Each abutment received a sequence of 2 consecutive torques for insertion (15 Ncm) at an interval of 10 minutes, and 1 reverse torque, all measured with a digital torque wrench. The Student t test with a 5% significance level was used to evaluate the data. Statistical analysis showed no significant difference in reverse torque values between nonindexed and indexed abutments (P=.57). When comparing insertion torque and reverse torque values between the groups, group NI presented a mean torque loosening percentage of 8% (P=.013), whereas group IN presented a loosening of 15.33% (P<.001). The use of indexed abutments for the Morse taper system presented similar biomechanical stability when compared with nonindexed abutments, both with a significant reduction in reverse torque values. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Application of reverse engineering in the production of individual dental abutments.

NASA Astrophysics Data System (ADS)

Yunusov, A. V.; Kashapov, R. N.; Kashapov, L. N.; Statsenko, E. O.

2017-09-01

The purpose of the research is to develop a method of manufacturing individual dental abutments for a variety of dental implants. System of industrial X-ray microtomography Phoenix V|tome|X S 240 has been applied for creation of highly accurate model of the dental abutment. Scanning of dental abutment and the optimization of model was produced. The program of milling the individual abutment with a standard conical neck of hexagon was produced for the five-axis milling machine imes - icore 450i from the materials titanium and zirconium oxide.

Fracture resistance of different implant abutments supporting 
all-ceramic single crowns after aging.

PubMed

Stimmelmayr, Michael; Heiß, Philipp; Erdelt, Kurt; Schweiger, Josef; Beuer, Florian

To test the mechanical properties of three different restorative materials for implant abutments supporting all-ceramic single crowns. Thirty implants with butt-joint connections were distributed into three test groups: Group A with 10 one-piece zirconia abutments, Group U with 10 titanium abutments, and Group T with 10 titanium-zirconia hybrid abutments. Monolithic zirconia single crowns were cemented and artificially aged. The crowns were loaded at a 30-degree angle in a universal testing machine until fracture or bending. Additionally, after removal of the restorations, the implant-abutment interface of the fixtures was inspected using a scanning electron microscope (SEM). In Group A, the abutments failed on average at 336.78 N, in Group U at 1000.12 N, and in Group T at 1296.55 N. The mean values between Groups T and U (P = 0.009), and between Group A and Groups T and U (P < 0.001) were significantly different. The abutments in Group A failed early due to fractures of the internal parts and parts close to the implant neck. In Groups T and U, failures occurred due to bending of the implant neck. This experimental study proves that hybrid and titanium abutments have similar mechanical properties. One-piece abutments made of zirconia showed significantly lower fracture resistance.

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. Copyright © 2015 Elsevier B.V. All rights reserved.

Low energy high pressure miniature screw valve

DOEpatents

Fischer, Gary J [Sandia Park, NM; Spletzer, Barry L [Albuquerque, NM

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.

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.

The accuracy and the safety of individualized 3D printing screws insertion templates for cervical screw insertion.

PubMed

Deng, Ting; Jiang, Minghui; Lei, Qing; Cai, Lihong; Chen, Li

2016-12-01

Clinical trial for cervical screw insertion by using individualized 3-dimensional (3D) printing screw insertion templates device. The objective of this study is to evaluate the safety and accuracy of the individualized 3D printing screw insertion template in the cervical spine. Ten patients who underwent posterior cervical fusion surgery with cervical pedicle screws, laminar screws or lateral mass screws between December 2014 and December 2015 were involved in this study. The patients were examined by CT scan before operation. The individualized 3D printing templates were made with photosensitive resin by a 3D printing system to ensure the screw shafts entered the vertebral body without breaking the pedicle or lamina cortex. The templates were sterilized by a plasma sterilizer and used during the operation. The accuracy and the safety of the templates were evaluated by CT scans at the screw insertion levels after operation. The accuracy of this patient-specific template technique was demonstrated. Only one screw axis greatly deviated from the planned track and breached the cortex of the pedicle because the template was split by rough handling and then we inserted the screws under the fluoroscopy. The remaining screws were inserted in the track as preoperative design and the screw axis deviated by less than 2 mm. Vascular or neurologic complications or injuries did not happen. And no infection, broken nails, fracture of bone structure, or screw pullout occurred. This study verified the safety and the accuracy of the individualized 3D printing screw insertion templates in the cervical spine as a kind of intraoperative screw navigation. This individualized 3D printing screw insertion template was user-friendly, moderate cost, and enabled a radiation-free cervical screw insertion.

An investigation of heat transfer to the implant-bone interface when drilling through a zirconia crown attached to a titanium or zirconia abutment.

PubMed

Mason, Amy G; Sutton, Alan; Turkyilmaz, Ilser

2014-11-01

Thermal injury to the implant-bone interface may lead to bone necrosis and loss of osseointegration. This is a concern during manipulation of the implant throughout the restorative phase of treatment. The risk of heat transfer to the implant-bone interface during abutment preparation or prosthesis removal should be considered. The purpose of the study was to examine the amount of heat transferred to the implant-bone interface when a zirconia crown is drilled to access the screw channel or section a crown with a high-speed dental handpiece. Of the 64 ceramic-veneered zirconia crowns fabricated, 32 had a coping thickness of 0.5 mm and 32 had a coping thickness of 1.0 mm. The crowns were cemented on either titanium stock abutments or zirconia stock abutments. Each group was further subdivided to evaluate heat transfer when the screw channel was accessed or the crown was sectioned with a high-speed handpiece with or without irrigation. Temperature change was recorded for each specimen at the cervical and apical aspect of the implant with thermocouples and a logging thermometer. ANOVA was used to assess the statistical significance in temperature change between the test combinations, and nonparametric Mann-Whitney U tests were used to evaluate the findings. The use of irrigation during both crown removal processes yielded an average temperature increase of 3.59 ±0.35°C. Crown removal in the absence of irrigation yielded an average temperature increase of 18.76 ±3.09°C. When all parameter combinations in the presence of irrigation were evaluated, the maximum temperature change was below the threshold of thermal injury to bone. The maximum temperature change was above the threshold for thermal injury at the coronal aspect of the implant and below the threshold at the apical aspect in the absence of irrigation. Within the limitations of this investigation, the use of irrigation with a high-speed dental handpiece to remove a ceramic-veneered zirconia crown results in

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.

Impact of abutment rotation and angulation on marginal fit: theoretical considerations.

PubMed

Semper, Wiebke; Kraft, Silvan; Mehrhof, Jurgen; Nelson, Katja

2010-01-01

Rotational freedom of various implant positional index designs has been previously calculated. To investigate its clinical relevance, a three-dimensional simulation was performed to demonstrate the influence of rotational displacements of the abutment on the marginal fit of prosthetic superstructures. Idealized abutments with different angulations (0, 5, 10, 15, and 20 degrees) were virtually constructed (SolidWorks Office Premium 2007). Then, rotational displacement was simulated with various degrees of rotational freedom (0.7, 0.95, 1.5, 1.65, and 1.85 degrees). The resulting horizontal displacement of the abutment from the original position was quantified in microns, followed by a simulated pressure-less positioning of superstructures with defined internal gaps (5 µm, 60 µm, and 100 µm). The resulting marginal gap between the abutment and the superstructure was measured vertically with the SolidWorks measurement tool. Rotation resulted in a displacement of the abutment of up to 157 µm at maximum rotation and angulation. Interference of a superstructure with a defined internal gap of 5 µm placed on the abutment resulted in marginal gaps up to 2.33 mm at maximum rotation and angulation; with a 60-µm internal gap, the marginal gaps reached a maximum of 802 µm. Simulation using a superstructure with an internal gap of 100 µm revealed a marginal gap of 162 µm at abutment angulation of 20 degrees and rotation of 1.85 degrees. The marginal gaps increased with the degree of abutment angulation and the extent of rotational freedom. Rotational displacement of the abutment influenced prosthesis misfit. The marginal gaps between the abutment and the superstructure increased with the rotational freedom of the index and the angulation of the abutment.

A comparative finite elemental analysis of glass abutment supported and unsupported cantilever fixed partial denture.

PubMed

Ramakrishaniah, Ravikumar; Al Kheraif, Abdulaziz A; Elsharawy, Mohamed A; Alsaleh, Ayman K; Ismail Mohamed, Karem M; Rehman, Ihtesham Ur

2015-05-01

The purpose of this study was to investigate and compare the load distribution and displacement of cantilever prostheses with and without glass abutment by three dimensional finite element analysis. Micro-computed tomography was used to study the relationship between the glass abutment and the ridge. The external surface of the maxilla was scanned, and a simplified finite element model was constructed. The ZX-27 glass abutment and the maxillary first and second premolars were created and modified. The solid model of the three-unit cantilever fixed partial denture was scanned, and the fitting surface was modified with reference to the created abutments using the 3D CAD system. The finite element analysis was completed in ANSYS. The fit and total gap volume between the glass abutment and dental model were determined by Skyscan 1173 high-energy spiral micro-CT scan. The results of the finite element analysis in this study showed that the cantilever prosthesis supported by the glass abutment demonstrated significantly less stress on the terminal abutment and overall deformation of the prosthesis under vertical and oblique load. Micro-computed tomography determined a gap volume of 6.74162 mm(3). By contacting the mucosa, glass abutments transfer some amount of masticatory load to the residual alveolar ridge, thereby preventing damage to the periodontal microstructures of the terminal abutment. The passive contact of the glass abutment with the mucosa not only preserves the health of the mucosa covering the ridge but also permits easy cleaning. It is possible to increase the success rate of cantilever FPDs by supporting the cantilevered pontic with glass abutments. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.