title: Effects of implant diameter and prosthesis retention system on the reliability of single crowns.
abstract: OBJECTIVE
  The probability of survival of implant-supported prostheses may be affected by the interplay between different implant diameters supporting screwed or cemented crowns. The purpose of this study was to investigate the effect of implant diameter and prosthesis retention system on the reliability and failure modes of single crowns.
  
  
  METHODS
  Internal-hexagon implants were divided into six groups (n = 21 each) according to implant diameter (3.3, 4.0, or 5.0 mm) and crown retention system (screwed or cemented). Abutments were torqued to the implants, and crowns were then fixed and subjected to step-stress accelerated life testing in water. Use-level probability Weibull curves and reliability for missions of 50,000 cycles at 100, 150, and 200 N were calculated. Failure analysis was performed.
  
  
  RESULTS
  Cemented systems presented higher reliability than screwed ones, except between 3.3-mm-diameter cemented and screwed systems at a load of 100 or 150 N. Failure modes were restricted to the abutment screw and varied with implant diameter only in the cement-retained groups.
  
  
  CONCLUSIONS
  Higher reliability was observed for cement-retained crowns and implants of larger diameter compared to screw-retained and smaller diameter. Failure modes differed between groups.
authors.forename: Estevam A
authors.initials: EA
authors.lastname: Bonfante
authors.forename: Erika O
authors.initials: EO
authors.lastname: Almeida
authors.forename: Fabio C
authors.initials: FC
authors.lastname: Lorenzoni
authors.forename: Paulo G
authors.initials: PG
authors.lastname: Coelho
mesh_terms: D002484:Cementation / Q000379:methods; D003442:Crowns; D003738:Dental Cements; D019250:Dental Implants, Single-Tooth / Q000592:standards*; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure / Q000706:statistics & numerical data; D003799:Dental Stress Analysis; D006801:Humans; D060489:Prosthesis Retention / Q000379:methods* / Q000592:standards; D015203:Reproducibility of Results
chemical_list: D003738:Dental Cements