title: Threaded versus porous-surfaced implants as anchorage units for orthodontic treatment: three-dimensional finite element analysis of peri-implant bone tissue stresses.
abstract: OBJECTIVE
  A 3-dimensional finite element model was developed to investigate the cause of different crestal bone loss patterns observed around sintered porous-surfaced and machined (turned) threaded dental implants used for orthodontic anchorage in a previously reported animal study.
  
  
  METHODS
  Twenty-noded structural solid elements with parabolic interpolation between nodes were used for modeling the bone-implant interface zone. A 3-N traction force acting between either 2 porous-surfaced or 2 machined threaded implants placed in canine premolar mandibular sites and bone profiles observed at initiation and 22 weeks of orthodontic loading were modeled.
  
  
  RESULTS
  Higher maximum stresses in peri-implant bone next to the coronal region of the implants were predicted with the machined threaded implants at both the initial and final time points, with the values 20% greater than those predicted after the 22-week loading period. These values were approximately 200% greater than those predicted for the porous-surfaced implants, for which a more uniform stress distribution was predicted.
  
  
  CONCLUSIONS
  The finite element model results indicated that the observed greater retention of crestal bone next to the porous-surfaced implants was attributable to lower peak stresses developing in crestal peri-implant bone with this design, which decreased the probability of bone loss related to local overstressing and bone microfracture.
  
  
  CONCLUSIONS
  The predicted lower stresses were a result of the more uniform transfer of force from implant to bone with the porous-surfaced implants, which was a consequence of the interlocking of bone and implant possible with this design.
authors.affiliation: Faculty of Dentistry, Institute of Biomaterials and Biomedical Engineering, University of Toronto, Canada. bob.pilliar@utoronto.ca
authors.forename: Robert M
authors.initials: RM
authors.lastname: Pilliar
authors.forename: Genadijs
authors.initials: G
authors.lastname: Sagals
authors.forename: Shaker A
authors.initials: SA
authors.lastname: Meguid
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Oyonarte
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Deporter
mesh_terms: D016301:Alveolar Bone Loss / Q000503:physiopathology; D000539:Alveolar Process / Q000033:anatomy & histology / Q000502:physiology; D000818:Animals; D001641:Bicuspid; D003198:Computer Simulation; D015921:Dental Implants; D017267:Dental Prosthesis Design; D004285:Dogs; D020342:Finite Element Analysis; D021621:Imaging, Three-Dimensional; D008334:Mandible / Q000033:anatomy & histology / Q000502:physiology*; D008954:Models, Biological; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D009969:Orthodontic Wires; D016348:Osseointegration / Q000502:physiology; D016062:Porosity; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors
chemical_list: D015921:Dental Implants