title: Platform-Switching for Cemented Versus Screwed Fixed Dental Prostheses: Reliability and Failure Modes: An In Vitro Study.
abstract: OBJECTIVE
  The aim of this study was to evaluate the probability of survival of cemented and screwed three-unit implant-supported fixed dental prostheses (ISFDP) using different implant-abutment horizontal matching configurations (regular vs switching platforms).
  
  
  METHODS
  One hundred and sixty-eight implants with internal hexagon connection (4 mm diameter, 10 mm length, Emfils; Colosso Evolution System, Itú, SP, Brazil) were selected for this study according to the horizontal implant-abutment matching configuration (regular or switching) and retention method and divided in four groups (n = 21 per group) as follows: 1) regular platform cemented (IRC); 2) or screw-retained (IRS); 3) switched-platform cemented (ISC); or 4) screw-retained (ISS). Regular and platform-switched abutments (Colosso evolution, 4 mm and 3.3 mm, respectively) were torqued, and 84 three-unit metal bridges were fabricated (first molar pontic). Implants were embedded in polymethyl-methacrylate resin and subjected to step-stress accelerated life testing in water. Weibull distribution was used to determine the probability of survival for a mission of 100,000 cycles at 400 N (90% two-sided confidence intervals). Polarized light and scanning electron microscopes were used for fractographic analysis.
  
  
  RESULTS
  The β values of 0.50, 1.19, 1.25, and 1.95 for groups IRC, IRS, ISC, and ISS respectively, indicated that fatigue accelerated the failure for all groups, except IRC. The cement-retained groups presented significantly higher probability of survival (IRC - 98%, ISC - 59%) than screw-retained groups (IRS - 23% and ISS - 0%). Screw-retained FDPs exclusively failed by abutment-screw fractures, whereas cement-retained presented implant/screw/abutment fractures.
  
  
  CONCLUSIONS
  The probability of survival of cement-retained ISFDP was higher than screw-retained, irrespective of implant-abutment horizontal configuration.
authors.affiliation: Department of Biomaterials and Biomimetics, New York University, College of Dentistry, New York, NY, USA.|Department of Dental Materials and Prosthodontics, São Paulo State University, Araçatuba Dental School, Araçatuba, SP, Brazil.|Centro Universitario do Norte Paulista-UNORP, São José do Rio Preto, SP, Brazil.
authors.forename: Rodolfo Brunieira
authors.initials: RB
authors.lastname: Anchieta
authors.affiliation: Department of Biomaterials and Biomimetics, New York University, College of Dentistry, New York, NY, USA.|Department of Dental Materials and Prosthodontics, São Paulo State University, Araçatuba Dental School, Araçatuba, SP, Brazil.
authors.forename: Lucas Silveira
authors.initials: LS
authors.lastname: Machado
authors.affiliation: Department of Biomaterials and Biomimetics, New York University, College of Dentistry, New York, NY, USA.
authors.forename: Ronaldo
authors.initials: R
authors.lastname: Hirata
authors.affiliation: Department of Prosthodontics, University of São Paulo - Bauru College of Dentistry, Bauru, SP, Brazil.
authors.forename: Estevam Augusto
authors.initials: EA
authors.lastname: Bonfante
authors.affiliation: Department of Biomaterials and Biomimetics, New York University, College of Dentistry, New York, NY, USA.|Department of Periodontology and Implant Dentistry, New York University, College of Dentistry, New York, NY, USA.|Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
authors.forename: Paulo G
authors.initials: PG
authors.lastname: Coelho
mesh_terms: D003738:Dental Cements; D059605:Dental Implant-Abutment Design; D015921:Dental Implants; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D006801:Humans; D008855:Microscopy, Electron, Scanning
chemical_list: D003738:Dental Cements; D015921:Dental Implants
keywords: Weibull analysis; dental implant; fatigue; fixed dental prostheses; fractography; reliability