title: The effects of simulated bone loss on the implant-abutment assembly and likelihood of fracture: an in vitro study.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Restorative Dentistry, King's College London Dental Institute, Guy's Hospital Campus, London, United Kingdom.
authors.forename: Behzad
authors.initials: B
authors.lastname: Manzoor
authors.forename: Mahmood
authors.initials: M
authors.lastname: Suleiman
authors.forename: Richard M
authors.initials: RM
authors.lastname: Palmer
mesh_terms: D016301:Alveolar Bone Loss / Q000150:complications* / Q000503:physiopathology; D059605:Dental Implant-Abutment Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000379:methods*; D011336:Probability; D015203:Reproducibility of Results; D018709:Statistics, Nonparametric; D016474:Weight-Bearing