title: Micromotion and dynamic fatigue properties of the dental implant-abutment interface.
abstract: BACKGROUND
  Clinical loading may result in micromotion and metal fatigue in apparently stable implant screw joints. This micromotion may contribute to tissue inflammation and prosthesis failure.
  
  
  OBJECTIVE
  This study investigated dental implant screw joint micromotion and dynamic fatigue as a function of varied preload torque applied to abutment screws when tested under simulated clinical loading.
  
  
  METHODS
  Fifteen noble alloy single-tooth implant restorations, each containing a hexed UCLA-style gold cylinder, were randomly assigned to 3 preload groups (16, 32, and 48 N.cm). Each group consisted of 5 implants (each 3.75 x 15 mm) and 5 square gold alloy abutment screws. A mechanical testing machine applied a compressive cyclic sine wave load between 20 and 130 N at 6 Hz to a contact point on each implant crown. A liquid metal strain gauge recorded the micromotion of the screw joint interface after 100, 500, 1,000, 5,000, 10,000, 50,000, and 100,000 cycles. Baseline data at 0 N.cm were collected before the application of the specified preload torque.
  
  
  RESULTS
  The 16 N.cm group exhibited greater micromotion (P<.001) than both the 32 and 48 N.cm groups at all cycle intervals (2-way ANOVA, Tukey HSD). Micromotion of the implant-abutment interface remained constant (P=.99) for each of the preload groups through 105 cycles.
  
  
  CONCLUSIONS
  Under the loading parameters of this study, no measurable fatigue of the implant-abutment interface occurred. However, dental implant screw joints tightened to lower preload values exhibited significantly greater micromotion at the implant-abutment interface.
authors.affiliation: School of Dentistry, The University of Western Ontario, London, Ontario, Canada. dgratton@julian.uwo.ca
authors.forename: D G
authors.initials: DG
authors.lastname: Gratton
authors.forename: S A
authors.initials: SA
authors.lastname: Aquilino
authors.forename: C M
authors.initials: CM
authors.lastname: Stanford
mesh_terms: D000704:Analysis of Variance; D000044:Dental Abutments; D019250:Dental Implants, Single-Tooth; D017268:Dental Prosthesis Retention / Q000295:instrumentation*; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D019544:Equipment Failure Analysis; D006047:Gold Alloys; D006801:Humans; D008422:Materials Testing; D009038:Motion; D019415:Torque
chemical_list: D006047:Gold Alloys