title: Evaluation of stress distribution in overdenture-retaining bar with different levels of vertical misfit.
abstract: OBJECTIVE
  To evaluate the effects of different levels of vertical misfit between implant and bar framework on distribution of static stresses in an overdenture-retaining bar system using finite element analysis.
  
  
  METHODS
  A 3D finite element model (11,718 elements and 21,625 nodes) was created and included two titanium implants and a bar framework placed in the medial region of the anterior part of a severely reabsorbed-jaw. All materials were presumed to be linear elastic, homogenous, and isotropic. Mechanical simulation software (NEiNastran 9.0) was used, where displacements were applied on the end of the bar framework to simulate the closure of the vertical misfits (5, 25, 50, 100, 200, and 300 μm) after tightening of the screws. Data were qualitatively evaluated using Von Mises stress given by the software.
  
  
  RESULTS
  The models showed stress concentration in cortical bone, corresponding to the cervical part of the implant, and in cancellous bone, corresponding to the apical part of the implant; however, in these regions few changes were observed in stress to the misfits studied. While in the bar framework, retaining-screw neck, and implant platform, a considerable stress increase proportional to the misfit amplification was observed.
  
  
  CONCLUSIONS
  The different levels of vertical misfit did not considerably influence the static stress levels in the peri-implant bone tissue; however, the mechanical components of the overdenture-retaining bar system are more sensitive to lack of passive fit.
authors.affiliation: Department of Prosthodontics and Periodontics, Piracicaba Dental School, State University of Campinas, Piracicaba, Brazil.
authors.forename: Aloísio O
authors.initials: AO
authors.lastname: Spazzin
authors.forename: Ricardo T
authors.initials: RT
authors.lastname: Abreu
authors.forename: Pedro Y
authors.initials: PY
authors.lastname: Noritomi
authors.forename: Rafael Leonardo X
authors.initials: RL
authors.lastname: Consani
authors.forename: Marcelo F
authors.initials: MF
authors.lastname: Mesquita
mesh_terms: D016301:Alveolar Bone Loss / Q000503:physiopathology; D003198:Computer Simulation; D015921:Dental Implants; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000379:methods; D003781:Denture Retention / Q000295:instrumentation*; D003828:Denture, Overlay; D020342:Finite Element Analysis; D006047:Gold Alloys; D006801:Humans; D007575:Jaw, Edentulous / Q000503:physiopathology; D017755:Prosthesis Fitting; D013314:Stress, Mechanical; D014716:Vertical Dimension
chemical_list: D015921:Dental Implants; D006047:Gold Alloys