title: Stress analysis in edentulous mandibular bone supporting implant-retained 1-piece or multiple superstructures.
abstract: OBJECTIVE
  The aim of this study was to investigate the stress distribution in mandibular bone supporting a single or separate multiple implant-retained superstructures.
  
  
  METHODS
  Three-dimensional finite element models consisting of the mandibular bone, 8 implants, and 1 or more superstructures were created. Vertical and oblique loads were directed onto the occlusal areas of the superstructures to simulate the maximum intercuspal contacts and working contacts, such as the canine-protected and group function occlusion.
  
  
  RESULTS
  The unseparated 1-piece superstructure generated the lowest maximum equivalent stresses in the peri-implant bone, followed by the 2-piece superstructure separated at the midline. For the 3-piece superstructure, which was separated between the canine and the premolar, the maximum stress was lower when the canine on the working side was loaded than when the posterior teeth were loaded.
  
  
  CONCLUSIONS
  Separating the 1-piece superstructure into 2- to 4-piece superstructures increased the mechanical stress around supporting implants. Canine load on the working side is distributed well in 1-piece and 3-piece superstructures.
  
  
  CONCLUSIONS
  Based on the results of this finite element model study, canine protected occlusion is recommended for 1-piece and 3-piece superstructures. The unseparated superstructure was more effective in relieving stress concentration in the edentulous mandibular bone than the separated superstructures.
authors.affiliation: Implantology, Department of Masticatory Function Rehabilitation, Division of Oral Health Sciences, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan. sawako.impl@tmd.ac.jp
authors.forename: Sawako
authors.initials: S
authors.lastname: Yokoyama
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Wakabayashi
authors.forename: Makoto
authors.initials: M
authors.lastname: Shiota
authors.forename: Takashi
authors.initials: T
authors.lastname: Ohyama
mesh_terms: D001732:Bite Force; D003198:Computer Simulation; D003481:Cuspid / Q000502:physiology; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis / Q000379:methods*; D003826:Denture, Complete, Lower; D003830:Denture, Partial, Fixed; D020342:Finite Element Analysis; D006801:Humans; D007575:Jaw, Edentulous / Q000503:physiopathology*; D008334:Mandible / Q000503:physiopathology*