title: Influence of implant number on the biomechanical behaviour of mandibular implant-retained/supported overdentures: a three-dimensional finite element analysis.
abstract: OBJECTIVE
  The aim of this study was to evaluate strain distribution in peri-implant bone, stress in the abutments and denture stability of mandibular overdentures anchored by different numbers of implants under different loading conditions, through three-dimensional finite element analysis (3D FEA).
  
  
  METHODS
  Four 3D finite element models of mandibular overdentures were established, using between one and four Straumann implants with Locator attachments. Three types of load were applied to the overdenture in each model: 100N vertical and inclined loads on the left first molar and a 100N vertical load on the lower incisors. The biomechanical behaviours of peri-implant bone, implants, abutments and overdentures were recorded.
  
  
  RESULTS
  Under vertical load on the lower incisors, the single-implant overdenture rotated over the implant from side to side, and no obvious increase of strain was found in peri-implant bone. Under the same loading conditions, the two-implant-retained overdenture showed more apparent rotation around the fulcrum line passing through the two implants, and the maximum equivalent stress in the abutments was higher than in the other models. In the three-implant-supported overdenture, no strain concentration was found in cortical bone around the middle implant under three loading conditions.
  
  
  CONCLUSIONS
  Single-implant-retained mandibular overdentures do not show damaging strain concentration in the bone around the only implant and may be a cost-effective treatment option for edentulous patients. A third implant can be placed between the original two when patients rehabilitated by two-implant overdentures report constant and obvious denture rotation around the fulcrum line.
authors.affiliation: Department of Prosthodontics, Peking University School and Hospital of Stomatology, No. 22 Zhongguancun Nandajie, Haidian District, Beijing 100081, PR China.
authors.forename: Jingyin
authors.initials: J
authors.lastname: Liu
authors.forename: Shaoxia
authors.initials: S
authors.lastname: Pan
authors.forename: Jing
authors.initials: J
authors.lastname: Dong
authors.forename: Zhongjun
authors.initials: Z
authors.lastname: Mo
authors.forename: Yubo
authors.initials: Y
authors.lastname: Fan
authors.forename: Hailan
authors.initials: H
authors.lastname: Feng
mesh_terms: D001696:Biomechanical Phenomena; D000044:Dental Abutments; D015921:Dental Implants; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis / Q000379:methods; D003781:Denture Retention; D003828:Denture, Overlay; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D008334:Mandible; D003765:Models, Dental
chemical_list: D015921:Dental Implants