title: Effect of the number of implants on stress distribution of anterior implant-supported fixed prostheses combined with a removable partial denture: a finite element analysis.
abstract: OBJECTIVE
  The main goal of this study was to evaluate differences in stress distribution relevant to the number of implants under an anterior bridge when combined with a removable partial denture in the posterior region.
  
  
  METHODS
  Four three-dimensional finite element models (3D FEM) were designed from a mandible containing an implant-supported bridge extending between canines, and a bilateral distal extension removable partial denture. A nonrigid connection was selected as the attachment method between the partial denture and the anterior implant-supported fixed prosthesis; 2, 3, 4 and 5 implants supporting the bridge all with 10mm length and 3.8 mm diameter were assessed. With the aid of the finite element program ANSYS 8.0, the models were loaded and von Mises stresses were evaluated.
  
  
  RESULTS
  In spongy bone, stress forces showed a decrease from 2 implants to 4 implants but showed an increase in the 5-implant model. Stresses on cortical bone of terminal implants were in similar range in the 2-, 3- and 4-implant models. While, in the 5-implant model the amount of stresses on terminal implants increased dramatically. The stresses on implants were nearly similar in all models, with the greatest amount on terminal implants.
  
  
  CONCLUSIONS
  Within the limitations of this study, 2-, 3- and 4-implant models showed less stress on cortical and spongy bone in comparison with the 5-implant model. The stresses transferred to implants were nearly similar.
authors: Associate Professor, Prosthodontics Department, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors: Minoo
authors: M
authors: Mahshid
authors: Professor, Dental Research Center Dentistry Research Institute & Department of Orthodontics, Tehran University of Medical Sciences, Tehran, Iran.
authors: Allahyar
authors: A
authors: Geramy
authors: Assistant Professor, Prosthodontics Department, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors: Massoud
authors: M
authors: Ejlali
authors: Assistant Professor, Prosthodontics Department, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors: Majid
authors: M
authors: Sedaghat Monfared
authors: Assistant Professor, Prosthodontics Department, Dental School,Qazvin University of Medical Sciences, Qazvin, Iran.
authors: Shirin
authors: S
authors: Rezvani Habib Abadi
keywords: Finite Element Analysis; Implants; Removable Partial Denture
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