title: Effect of bite force in occlusal adjustment of dental implants on the distribution of occlusal pressure: comparison among three bite forces in occlusal adjustment.
abstract: BACKGROUND
  The purpose of this study was to investigate the influence of occlusal forces (the contractile force of masticatory muscles) exerted during occlusal adjustment on the distribution of the forces among teeth, implants, and temporomandibular joints (TMJs) in intercuspal clenching in cases with bilateral missing molars and premolars by using finite element analysis.
  
  
  METHODS
  A three-dimensional finite element model of the mandible with eight implants in the premolar and molar regions was constructed. Linearly elastic material properties were defined for all elements except the periodontal ligament, which was defined as nonlinearly elastic. The TMJs and antagonists were simplified and replaced with nonlinear springs. Antagonists were assumed to be natural teeth or implants and had two- or three-stage displaceability. We constructed finite element (FE) models in which occlusal adjustment with three kinds of occlusal force (40 N as a light bite, 200 N as a hard bite, and 400 N as a maximum biting force) was performed. The clearance by occlusal adjustment was decided beforehand with a trial-and-error method so that the occlusal forces were distributed similarly to the distribution of the natural dentition. Each model was evaluated under loads of 40, 100, 200, 400, and 800 N to determine the distribution of occlusal forces on the teeth and implants.
  
  
  RESULTS
  The occlusal forces were concentrated on the most posterior implants while the load was larger, and the percentage of bearing force at the TMJ was small, and vice versa.
  
  
  CONCLUSIONS
  Maximum biting force was better for occlusal adjustment to prevent overloading of the most posterior implant.
authors.affiliation: Removable Prosthodontics, Hokkaido University Hospital, Hokkaido University, Kita-14, Nishi-5, Kita-Ku, Sapporo, 060-8648, Japan.|Department of Oral Functional Prosthodontics, Division of Oral Functional Science, Graduate School of Dental Medicine, Hokkaido University, Kita-13, Nishi-7, Kita-Ku, Sapporo, 060-8648, Japan.
authors.forename: Sho
authors.initials: S
authors.lastname: Kayumi
authors.affiliation: Removable Prosthodontics, Hokkaido University Hospital, Hokkaido University, Kita-14, Nishi-5, Kita-Ku, Sapporo, 060-8648, Japan. takayama@den.hokudai.ac.jp.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Takayama
authors.affiliation: Department of Oral Functional Prosthodontics, Division of Oral Functional Science, Graduate School of Dental Medicine, Hokkaido University, Kita-13, Nishi-7, Kita-Ku, Sapporo, 060-8648, Japan.
authors.forename: Atsuro
authors.initials: A
authors.lastname: Yokoyama
authors.affiliation: Removable Prosthodontics, Hokkaido University Hospital, Hokkaido University, Kita-14, Nishi-5, Kita-Ku, Sapporo, 060-8648, Japan.
authors.forename: Nana
authors.initials: N
authors.lastname: Ueda
keywords: Implants; Nonlinear finite element analysis; Occlusal adjustment