title: Method to improve passive fit of frameworks on implant-supported prostheses: An in vitro study.
abstract: BACKGROUND
  The passivity of the superstructure to the abutments of implant-supported prostheses is necessary for implant-prosthesis success. Improvements are needed in the methods of verifying passivity.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to evaluate an inexpensive, easy to make, and user-friendly device to verify the position of the implant abutment replicas of the definitive cast and to avoid framework misfit before fabrication.
  
  
  METHODS
  Eighty stone devices were constructed on a metal base for the in vitro tests. The horizontal, vertical, and angled positions of the implant replicas were created to simulate misfits. The devices were fitted on the abutment replicas, and their ability to identify misfits was evaluated. A statistical analysis was not indicated, because the probability of fracture of the stone devices was 0 or 1. Two mathematical models were built using computer-aided design software (SolidWorks Premium; Dassault Systèmes SolidWorks Corp), and the finite element method was used (Ansys; ANSYS Inc) to simulate the structural behavior of 2 implant configurations (4 and 6 implants).
  
  
  RESULTS
  Horizontal misfits of 150 μm, vertical misfits of 50 μm, and angled misfits of 1 degree were detected during the in vitro tests. Different loads and bone quality in the mathematical models did not change stress in the prosthesis configurations on 4 or 6 implants in a relevant way.
  
  
  CONCLUSIONS
  The fabricated device was easily able to detect the misfits in accordance with the defined parameters.
authors.affiliation: Tutor, Surgical Science Department, Prosthodontic Section, Dental School C.I.R, University of Turin, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Manzella
authors.affiliation: Associate Professor, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Bignardi
authors.affiliation: Private practice, Turin, Italy.
authors.forename: Valerio
authors.initials: V
authors.lastname: Burello
authors.affiliation: Full Professor, Surgical Science Department, Prosthodontic Section, Dental School C.I.R, University of Turin, Turin, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Carossa
authors.affiliation: Associate Professor, Surgical Science Department, Prosthodontic Section, Dental School C.I.R, University of Turin, Turin, Italy. Electronic address: gianmario.schierano@unito.it.
authors.forename: Gianmario
authors.initials: G
authors.lastname: Schierano
mesh_terms: D059605:Dental Implant-Abutment Design / Q000379:methods*; D003760:Dental Impression Materials; D003761:Dental Impression Technique; D019094:Dental Prosthesis, Implant-Supported / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D066298:In Vitro Techniques
chemical_list: D003760:Dental Impression Materials