title: Comparison of the effects of different implant apical designs on the magnitude and distribution of stress and strain in bone: a finite element analysis study.
abstract: OBJECTIVE
  The aim of this study was to investigate the effects of implant design on the apex area and on stress and stress patterns within surrounding bone.
  
  
  METHODS
  Three commercially available implants with the same diameter (3.5 mm), same length (10-11 mm), and same complement abutment were selected for modeling as follows: (1) flat apical design with light tapering degree, (2) dome-shaped apical design with light tapering, and (3) flat apical design with intense tapering in one-third of the apical area. According to human conebeam computed tomography (CBCT), the bone was modeled using a cortical thickness of 2 mm and cancellous bone. Forces of 100 N and 300 N in the vertical and 15° angle directions were applied to the entire abutment surface, and the equivalent stress and strain were calculated using finite element analysis (FEA) methods.
  
  
  RESULTS
  In all models, stress was concentrated on the cortical bone around the implant neck; in non-axial loads, stress was concentrated on the buccal side. The maximum strain recorded was a microstrain of 7200 μm μm-1 around the apex of sample C, which also showed the highest level of stress detected in cancellous bone (4.4 MPa). We observed the pathologic overload in the apical area of sample B (with a dome-shaped apex); however, the strain value was less than that of sample C.
  
  
  CONCLUSIONS
  FEA revealed that great sudden changes in diameter along the fixture increases stress and strain in peri-implant bone. Therefore, uniform tapering should be considered as a standard feature for most clinical situations, and a flat apical design, which creates a better stress and strain distribution in surrounding bone than dome-shaped bone, should also be used.
authors.affiliation: Dental Research Center, Research Institute of Dental Science of Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Mahdi
authors.initials: M
authors.lastname: Kadkhodazadeh
authors.affiliation: Periodontics Department, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Ardeshir
authors.initials: A
authors.lastname: Lafzi
authors.affiliation: Department of Periodontics, Dental Faculty, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Saeed
authors.initials: S
authors.lastname: Raoofi
authors.affiliation: Department of Periodontics, Dental Faculty, Ahwaz University of Medical Sciences, Ahwaz, Iran.
authors.forename: Maryam
authors.initials: M
authors.lastname: Khademi
authors.affiliation: Department of Periodontics, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Reza
authors.initials: R
authors.lastname: Amid
authors.affiliation: Manufacturing, Sharif University of Technology, Tehran, Iran.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Movahhedy
authors.affiliation: Department of Periodontics, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Hasti
authors.initials: H
authors.lastname: Torabi
mesh_terms: D001696:Biomechanical Phenomena; D000069343:Bone-Implant Interface / Q000502:physiology; D054893:Cone-Beam Computed Tomography / Q000379:methods; D000044:Dental Abutments; D015921:Dental Implants; D017267:Dental Prosthesis Design; D055119:Elastic Modulus; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008334:Mandible / Q000502:physiology*; D008954:Models, Biological; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D015921:Dental Implants