title: Influence of implant collar design on stress and strain distribution in the crestal compact bone: a three-dimensional finite element analysis.
abstract: OBJECTIVE
  To evaluate the influence of implant collar geometry on the distribution of stress and strain in the crestal compact bone contiguous to an implant collar for four types of bone under axial and oblique loads.
  
  
  METHODS
  Finite element models of threaded implants with three kinds of implant collar designs (divergent, straight, and convergent) with their corresponding suprastructures embedded in the posterior mandible were created with ANSYS software. Eight different test conditions incorporating four types of bone (orthotropic and effectively isotropic in part 1 and high and low densities in part 2) under separate 100-N axial and 35.6-degree oblique forces were created to investigate the stress and strain distributions in the crestal compact bone around the implant collars.
  
  
  RESULTS
  In all eight conditions, the divergent collar demonstrated the lowest maximum von Mises and principal stresses and strains in the crestal compact bone contiguous to the implant collar, followed by the straight and convergent collars. The oblique load induced higher peak values than the axial load. The orthotropic design amplified and increased the pathologic microstrains and tensile stresses in the crestal compact bone compared to the effectively isotropic design, especially in models with a convergent collar design. In part 2 of the study, the maximum von Mises stresses and strains increased with a decrease in the cancellous bone density. Under oblique loading, the convergent and straight collars showed pathologic microstrain values as well as excessive ultimate tensile stresses in the orthotropic bone model with low-density cancellous bone.
  
  
  CONCLUSIONS
  Within the limitations, it was concluded that stress and strain distributions in the adjacent compact bone are influenced by the implant collar design. The divergent implant collar design was associated with the lowest stress and strain concentrations in the crestal compact bone.
authors.affiliation: Department of Dentistry, National Yang-Ming University, Veterans General Hospital, No. 155 Sec. 2 Li-Non Street, Taipei, Taiwan.
authors.forename: Wan-Ling
authors.initials: WL
authors.lastname: Shen
authors.forename: Chen-Sheng
authors.initials: CS
authors.lastname: Chen
authors.forename: Ming-Lun
authors.initials: ML
authors.lastname: Hsu
mesh_terms: D000539:Alveolar Process / Q000502:physiology; D003198:Computer Simulation; D015921:Dental Implants; D017267:Dental Prosthesis Design; D003799:Dental Stress Analysis / Q000379:methods; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional; D008334:Mandible / Q000502:physiology; D008954:Models, Biological
chemical_list: D015921:Dental Implants