title: Theoretical study of the effects of tooth and implant mobility differences on occlusal force transmission in tooth/implant-supported partial prostheses.
abstract: BACKGROUND
  Despite their mobility differences under occlusal loads, a natural tooth and an implant are often used together to support fixed prostheses. In some situations, tooth/implant-supported partial prostheses include cantilever extensions, especially in the posterior region where the bone is inadequate for placement of an additional implant.
  
  
  OBJECTIVE
  In this study, engineering beam theory was used to study the effects of the mobility differences between the implant and the tooth on the force and moment distribution, due to occlusal loads in tooth/implant-supported prostheses.
  
  
  METHODS
  The prosthesis was treated as a linear elastic beam and the supports were modeled as springs with (vertical) translational and rotational stiffness. The bending moments and forces on the supports were calculated as functions of the parameters that describe the geometry, position of the occlusal load, and stiffness ratios (namely, implant or tooth) of the springs.
  
  
  RESULTS
  Bending moments on the supports were more sensitive to the relative rotational mobility between the supports and their individual values than to the relative translational mobility. The moment at the implant was minimized when the supports had similar mobilities. A preliminary design concept was introduced and eliminated the moment at the implant without significantly increasing the magnitude of the moment at the tooth. Cantilevering the prosthesis resulted in moderately increased bending moments and considerable tensile forces on the supports for a broad range of the parameters that describe the geometry and loading.
  
  
  CONCLUSIONS
  From this simulation, it is suggested that cantilever extensions should be avoided or supported by a short implant, which will only restrain the vertical movement of the cantilever end.
authors.affiliation: Department of Mechanical and Aerospace Engineering, Süleyman Demirel University, Turkey.
authors.forename: R
authors.initials: R
authors.lastname: Kayacan
authors.forename: R
authors.initials: R
authors.lastname: Ballarini
authors.forename: R L
authors.initials: RL
authors.lastname: Mullen
mesh_terms: D000465:Algorithms; D001698:Biomedical Engineering; D001732:Bite Force; D003198:Computer Simulation; D003758:Dental Implantation, Endosseous; D015921:Dental Implants; D017268:Dental Prosthesis Retention; D019094:Dental Prosthesis, Implant-Supported; D003779:Denture Design; D003830:Denture, Partial, Fixed; D004548:Elasticity; D006801:Humans; D008954:Models, Biological; D009068:Movement; D012399:Rotation; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D014070:Tooth / Q000502:physiology*; D014086:Tooth Mobility / Q000503:physiopathology; D019415:Torque
chemical_list: D015921:Dental Implants