title: Stress distribution in implant retained finger prosthesis: a finite element study.
abstract: BACKGROUND
  Finger amputation may result from congenital cause, trauma, infection and tumours. The finger amputation may be rehabilitated with dental implant-retained finger prosthesis. The success of implant-retained finger prosthesis is determined by the implant loading. The type of the force is a determining factor in implant loading.
  
  
  OBJECTIVE
  To evaluate stress distributions in finger bone when the loading force is applied along the long axis of the implant using finite element analysis.
  
  
  METHODS
  The finite element models were created. The finger bone model containing cortical bone and cancellous bone was constructed by using radiograph. Astra Tech Osseo Speed bone level implant of 4.5 mm diameter and 14 mm length was selected. The force was applied to the top of the abutment along the long axis of the implant.
  
  
  RESULTS
  Finite element analysis indicated that the maximum stress was located at the head of abutment screw. The minimum stress was located in the apical third of the implant fixture. The weakest point was calculated by safety factor which is located in the spongy bone at apical third of the fixtures. Finally, 4.9 times yield stress of spongy bone was needed for the deformation of the spongy bone.
  
  
  CONCLUSIONS
  Finite element study showed that when the force was applied along the long axis of the implant, the maximum stress was located around the neck of the implant and the cortex bone received more stress than cancellous bone. So, to achieve long term success, the designers of implant systems must confront biomaterial and biomechanical problems including in vivo forces on implants, load transmission to the interface and interfacial tissue response.
authors.affiliation: Maxillofacial Prosthetic Clinic, Faculty of Dentistry, Mahidol University , Bangkok, Thailand .
authors.forename: Pokpong
authors.initials: P
authors.lastname: Amornvit
authors.affiliation: Maxillofacial Prosthetic Clinic, Faculty of Dentistry, Mahidol University , Bangkok, Thailand .
authors.forename: Dinesh
authors.initials: D
authors.lastname: Rokaya
authors.affiliation: Maxillofacial Surgery Clinic, Golden Jubilee, Medical Centre, Mahidol University , NakonPathom, Salaya, Thailand .
authors.forename: Konrawee
authors.initials: K
authors.lastname: Keawcharoen
authors.affiliation: Orthopaedic Surgery Clinic, Golden Jubilee, Medical Centre, Mahidol University , NakonPathom, Salaya, Thailand .
authors.forename: Nimit
authors.initials: N
authors.lastname: Thongpulsawasdi
keywords: Dental implant; Finger prosthesis; Finite element analysis; Stress