Evaluation of pre-tightening in abutments and prosthetic screws on different implant connections Avaliação do pré-aparafusamento em pilares e parafusos protéticos em diferentes conexões de implante (original) (raw)
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The International journal of oral & maxillofacial implants
This study aimed to evaluate the role of the implant/abutment system on torque maintenance of titanium retention screws and the vertical misfit of screw-retained implant-supported crowns before and after mechanical cycling. Three groups were studied: morse taper implants with conical abutments (MTC group), external-hexagon implants with conical abutments (EHC group), and external-hexagon implants with UCLA abutments (EHU group). Metallic crowns casted in cobalt-chromium alloy were used (n = 10). Retention screws received insertion torque and, after 3 minutes, initial detorque was measured. Crowns were retightened and submitted to cyclic loading testing under oblique loading (30 degrees) of 130 ± 10 N at 2 Hz of frequency, totaling 1 × 106 cycles. After cycling, final detorque was measured. Vertical misfit was measured using a stereomicroscope. Data were analyzed by analysis of variance, Tukey test, and Pearson correlation test (P < .05). All detorque values were lower than the in...
The International Journal of Oral & Maxillofacial Implants, 2019
L oosening torque of abutment screws is a frequent prosthetic complication in implant dentistry, 1,2 especially for external hexagon connections 3-5 ; the dental implant literature reports a higher incidence of complications related to this implant connection. 6 New solutions need to be developed for cases in which implants that were placed years ago are now presenting prosthetic complications. 7 Some authors have stated that the abutment screw design interferes with its application as a union agent. 8-11 A conical head screw design for a singletooth abutment (Fig 1) was developed to preserve the initial applied torque. 12 Abutment screws create a friction mechanism between the head of the screw and the inner surface of the abutment; it was hypothesized that the conical head screw shape increases the contact area, increasing friction and resistance to micromovements during loading. 12 In the present situation, the design of the conical head screw
Effect of Vertical Misfit on Screw Joint Stability of Implant-Supported Crowns
Journal of Materials Engineering and Performance, 2011
The passive fit between prosthesis and implant is a relevant factor for screw joint stability and treatment success. The aim of this study was to evaluate the influence of vertical misfit in abutment-implant interface on preload maintenance of retention screw of implant-supported crowns. The crowns were fabricated with different abutments and veneering materials and divided into 5 groups (n = 12): Gold UCLA abutments cast in gold alloy veneered with ceramic (Group I) and resin (Group II), UCLA abutments cast in titanium veneered with ceramic (Group III) and resin (Group IV), and zirconia abutments with ceramic veneering (Group V). The crowns were attached to implants by gold retention screws with 35-N cm insertion torque. Specimens were submitted to mechanical cycling up to 10 6 cycles. Measurements of detorque and vertical misfit in abutment-implant interface were performed before and after mechanical cycling. ANOVA revealed statistically significant difference (P < 0.05) among groups for vertical misfit measured before and after mechanical cycling. The abutments cast in titanium exhibited the highest misfit values. Pearson correlation test did not demonstrate significant correlation (P > 0.05) between vertical misfit and detorque value. It was concluded that vertical misfit did not influence torque maintenance and the abutments cast in titanium exhibited the highest misfit values.
Mechanical Testing of Implant-Supported Anterior Crowns with Different Implant/Abutment Connections
The International Journal of Oral & Maxillofacial Implants, 2013
S ingle-tooth replacement involving osseointegrated implants is among the most popular and successful treatment options, presenting 89.4% estimated survival rates after 10 years in function. 1 However, despite the high success rates reported for dental implant treatment, 2 mechanical complications in the prosthetic components, such as loosening and/or fracture of the abutment screws, have been reported and remain under investigation. 3-5 Once osseointegration has been achieved and maintained, the stability of the implantabutment connection becomes a key factor for the success of the restoration, especially in single-tooth replacements, where the incidence of mechanical complications is highest. 6 Therefore, failures should be explored to gain insight into the mechanical behavior of different implant-abutment connection configurations, since they may compromise function and quality of life. 7,8 From a biomechanical point of view, one major concern among different implant-abutment connection designs is the external force exerted on components via oral function, which is concentrated mainly on the abutment screw, especially in external-hexagon (EH) connections. 9,10 In contrast, internal-hexagon (IH) connections have been claimed to be more mechanically
Displacement of Screw-Retained Single Crowns into Implants with Conical Internal Connections
The International Journal of Oral & Maxillofacial Implants, 2013
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. Material and Methods: 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. Results: 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. Conclusion: Differences between hand tightening and torque tightening should be taken into consideration during laboratory and clinical adjustments to prevent esthetic and functional complications.
The Journal of Prosthetic Dentistry, 2021
STATEMENT OF PROBLEM The design of the implant-abutment connection has been widely researched, but the impact of different crown-abutment geometries remains unclear. PURPOSE The purpose of this in vitro study was to evaluate the effect of different crown-abutment margin geometries on the mechanical behavior and fit of screw-retained implant-supported single-crown restorations by using mechanical static and fatigue tests and mastication simulation. MATERIAL AND METHODS A total of 45 cobalt-chromium premolar-shaped metal frameworks were fabricated for single-unit implant-supported screw-retained restorations on stock abutments and internal hexagon Ø4.25×11-mm cylindrical implants. They were divided into 3 groups according to margin geometry: S, shoulder; C, chamfer; and F, feather-edge. Three static load until fracture and 24 dynamic load tests were performed by using the International Organization for Standardization 14801:2016 standard (ISO 14801:2016) (number of cycles limit: 5×106 cycles, frequency: 6 Hz). The ProFatigue software program was used to optimize the procedure (S, n=12 specimens; C, n=7 specimens; and F, n=5 specimens). Six additional specimens from each group were subjected to a mastication simulation (limit number of cycles: 1×106 cycles, cyclic loading from Pmin=30 N to Pmax=300 N, frequency: 6 Hz). Results from the fatigue tests were reported descriptively, and the Fisher exact test was used to analyze the difference in failure modes. Data from maximum misfit were evaluated by photogrammetry and statistically analyzed with the Anderson-Darling test and the Kruskal-Wallis and Dunn multiple comparison tests (α=.05). RESULTS The fatigue limit was 456 N for group S, 512 N for group C, and 514 N for group F. The mean ±standard deviation misfit was 2.6 ±0.1 μm for group S, 3.8 ±1.1 μm for group C, and 3.6 ±0.8 μm for group F. Differences in misfit between groups S and C and between groups S and F were statistically significant (P<.05). CONCLUSIONS Crown-abutment connections with chamfer and feather-edge margins showed better mechanical behavior, while shoulder margin exhibited better fit. However, high levels of fit were achieved for all the evaluated geometries.
International Journal of Medical and Biomedical Studies
Background: Dental implants have provided an alternative method of prosthetic rehabilitation with high long-term success rates. However, mechanical or biological complications may occur with implants amongst which loosening of the screw is very common. Loosening of the screw might cause misfit of implant‒abutment interface and may occur due to preload loss subsequent to inadequate initial torque, distortion of the screw, wear of the screw, overloading, and micro-movements because of functional loading. The implant-abutment connection design like internal hex, external hex and morse taper may affect the screw stability. The effect of various implant-abutment connections on the stability of abutment screw has been discussed in this systematic review. Aim: The aim of this review is to assess and compare effect of different abutment connections on loosening of the screw. Data Sources: An online search was made for the articles using Google Scholar and PubMed. Study Eligibility Criteria...
Effect of Misfit on Preload Maintenance of Retention Screws of Implant-Supported Prostheses
Journal of Materials Engineering and Performance, 2009
The aim of this study was to evaluate the effect of unilateral misfit at different levels on a crown-implantretention screw system of implant-supported crowns. Hexagon castable UCLA abutments were cast in Co-Cr alloy to fabricate 48 metallic crowns divided into four groups (n = 12). Group A: crowns did not present misfit; Groups B, C and D: crowns were fabricated with unilateral misfit of 50, 100, and 200 lm, respectively. The crowns were attached by titanium retention screw with 30 N/cm to external hexagonal osseointegrated implants embedded in acrylic resin. After 2 min, the retention screw of each replica was submitted to detorque evaluation by an analogic torque gauge. Three retention screws were used to perform detorque evaluation at each replica and the procedure was repeated twice with each screw. Each group was submitted to 72 detorque measurements. Data were evaluated by ANOVA and Tukey test (P < 0.05). All groups exhibited significant decrease (P < 0.05) in preload and the lowest decrease occurred in Group A. Groups B, C, and D were statistically significant different from Group A (P < 0.05), but there was no statistically significant difference between Groups B and D (P > 0.05). Crowns with unilateral misfit presented higher preload decrease than crowns completely fitted to osseointegrated implants.