title: Selection of optimal expansion angle and length of an expandable implant in the osteoporotic mandible: a three-dimensional finite element analysis.
abstract: OBJECTIVE
  To identify from a biomechanical point of view the optimal parameters for an expandable implant in the osteoporotic mandible, a three-dimensional finite element model (FEM) of an expandable implant was created with variations in expansion angle and expansion length.
  
  
  METHODS
  FEMs of osteoporotic posterior mandibular segments with an expandable implant were created. An axial load of 100 N and a buccolingual load of 30 N were applied to the implant. The expansion angle ranged from 0 to 4 degrees, and the expansion length ratio ranged from 1/6 to 5/6. The maximum equivalent stress (max EQV stress) in jawbone and the implant-abutment complex and the maximum displacement in the implant-abutment complex were evaluated.
  
  
  RESULTS
  With changes in the expansion angle and expansion length ratio, the max EQV stress in cortical and cancellous bone increased by 12.4% and 73.9%, respectively, under axial loading, respectively, and by 38.6% and 69.1%, respectively, under buccolingual loading. The max EQV stress in the implant-abutment complex increased by 65.3% and 160% under axial and buccolingual loading, respectively. Maximum displacement in the implant-abutment complex increased by 3.66% and 19.73% under axial and buccolingual loading, respectively.
  
  
  CONCLUSIONS
  Expansion angles and the expansion length ratio favored stress distribution in jawbone under axial and buccolingual loads, respectively. An expansion angle between 1.5 and 2.5 degrees and an expansion length ratio between 2/6 and 3/6 provided optimal biomechanical properties for an expandable implant in the osteoporotic mandible.
authors.affiliation: Department of Oral and Maxillofacial Surgery, School of Stomatology, the fourth Military Medical University, Xi'an, P R China. xianjianrui@gmail.com
authors.forename: Jian-Rui
authors.initials: JR
authors.lastname: Xiao
authors.forename: Liang
authors.initials: L
authors.lastname: Kong
authors.forename: Yu-Xuan
authors.initials: YX
authors.lastname: Chen
authors.forename: Xiao-Xian
authors.initials: XX
authors.lastname: Han
authors.forename: Yong-Feng
authors.initials: YF
authors.lastname: Li
mesh_terms: D001696:Biomechanical Phenomena; D001732:Bite Force; D003198:Computer Simulation; D000044:Dental Abutments; D059605:Dental Implant-Abutment Design / Q000379:methods; D015921:Dental Implants; D017267:Dental Prosthesis Design; D003799:Dental Stress Analysis / Q000379:methods; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008334:Mandible / Q000503:physiopathology*; D010024:Osteoporosis / Q000503:physiopathology*; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical
chemical_list: D015921:Dental Implants