title: In vitro analysis of post-fatigue reverse-torque values at the dental abutment/implant interface for a unitarian abutment design.
abstract: OBJECTIVE
  This study analyzed baseline and post-fatigue reverse-torque values (RTVs) for a specific brand control abutment relative to a third party compatible abutment. The purpose of this study was to compare the abutments' fatigue resistance to simulated function, using RTVs as an indication of residual preload at the implant/abutment interface.
  
  
  METHODS
  Forty Straumann tissue-level implants were mounted in resin and divided into four groups (n = 10). Forty abutments were seated, 20 control and 20 third-party abutments, according to manufacturer guidelines. Ten abutments from each manufacturer were evaluated for RTV without fatigue loading, using a calibrated digital torque gauge to provide a baseline RTVs. Fatigue loading was carried out on the remaining ten specimens from each manufacturer according to ISO 14801 guidelines. A moving-magnet linear motor was used to load one specimen per sequence, alternating from 10 to 200 N at 15 Hz for 5×10(6) cycles. RTV was recorded post-fatigue loading. The results were subjected to two-sample t-testing and two-way ANOVA. Scanning electron microphotography was carried out on three specimens from both manufacturers at baseline and post-fatigue cycling to visualize thread geometry and the abutment/implant interface.
  
  
  RESULTS
  The data indicated that mean post-fatigue RTV observed for the control group was significantly higher than the third-party group (RTV 42.65 ± 6.70 N vs. 36.25 ± 2.63 N, p= 0.0161). Visual differences at the macro/microscopic level were also apparent for thread geometry, with third-party abutments demonstrating considerably greater variation in geometrical architecture than control specimens.
  
  
  CONCLUSIONS
  Within the limitations of this in vitro model, the effect of component manufacturer resulted in a significantly higher RTV in the control group (two-way ANOVA, p= 0.0032) indicating greater residual preload; however, there was no significant decrease in post-fatigue RTV for either manufacturer compared to baseline.
authors: Clinical Lecturer, Department of Prosthodontics, Eastman Dental Institute, University College London, London, United Kingdom. p.cashman@ucl.ac.uk
authors: Paul M
authors: PM
authors: Cashman
authors: Robert L
authors: RL
authors: Schneider
authors: Galen B
authors: GB
authors: Schneider
authors: Clark M
authors: CM
authors: Stanford
authors: James M
authors: JM
authors: Clancy
authors: Fang
authors: F
authors: Qian
mesh_terms: D059605:Dental Implant-Abutment Design; D003799:Dental Stress Analysis; D006801:Humans; D013314:Stress, Mechanical; D013499:Surface Properties; D054159:Torsion, Mechanical