title: Influence of number and inclination angle of implants on stress distribution in mandibular cortical bone with All-on-4 Concept.
abstract: OBJECTIVE
  The All-on-4 is used in the therapy of edentulous mandibles. However, few studies have investigated the effect of such implants on supporting bone. To clarify differences in stress in peri-implant cortical bone between 2-patterns of 6 implants and 8-patterns of 4 implants with change in inclination angle based on the All-on-4.
  
  
  METHODS
  Three-dimensional finite element analysis models based on the mean value of the Japanese edentulous mandible were constructed. Implants 13 or 15 mm in length were inserted between the mental foramina. In the 6-implant model, implants were inserted in parallel. In the 4-implant model, the 2 anterior implants were inserted in parallel and the 2 posterior implants in parallel or on a slant. Implants were splinted with a superstructure. A 50 N load was applied to the occlusal surface under condition A, at 2mm distal from the distal implant, or condition B, at the distal end of the superstructure. Maximum von Mises stress on cortical bone was measured.
  
  
  RESULTS
  Stress was concentrated around the posterior-most implant on the right side. Under condition A, stress increased with 4 implants and increase in angulation. At 45°, stress increased by 23% of that in the 6-implant model. Under condition B, stress increased with 4 implants, although stress decreased with increase in angulation. At 45°, stress decreased by 45% of that in the 6 implants.
  
  
  CONCLUSIONS
  The use of 4 implants or inclined implants increased stress on peri-implant cortical bone. However, when used in conjunction with a short cantilever, inclined implants decreased stress on peri-implant cortical bone.
authors.affiliation: Department of Removable Prosthodontics and Gerodontology, Tokyo Dental College, 1-2-2 Masago, Mihama-ku, Chiba city, Chiba, 261-8502, Japan. takahashit@tdc.jp
authors.forename: Takeshi
authors.initials: T
authors.lastname: Takahashi
authors.forename: Ichiro
authors.initials: I
authors.lastname: Shimamura
authors.forename: Kaoru
authors.initials: K
authors.lastname: Sakurai
mesh_terms: D003758:Dental Implantation, Endosseous / Q000379:methods*; D015921:Dental Implants; D003799:Dental Stress Analysis; D008334:Mandible; D003765:Models, Dental; D013314:Stress, Mechanical
chemical_list: D015921:Dental Implants