title: Effects of horizontal misfit and bar framework material on the stress distribution of an overdenture-retaining bar system: a 3D finite element analysis.
abstract: OBJECTIVE
  To evaluate the influence of horizontal misfit change and bar framework material on the distribution of static stresses in an overdenture-retaining bar system using finite element (FE) analysis.
  
  
  METHODS
  A 3D FE model was created including two titanium implants and a bar framework placed in the anterior part of a severely resorbed jaw. The model set was exported to mechanical simulation software, where horizontal displacement (10, 50, 100, and 200 μm) was applied simulating the settling of the framework, which suffered shrinkage during laboratory procedures. Four bar materials (gold alloy, silver-palladium alloy, commercially pure titanium, and cobalt-chromium alloy) were also simulated in the analysis using 50 μm as the horizontal misfit. Data were qualitatively evaluated using von Mises stress, given by the software.
  
  
  RESULTS
  The misfit amplification presented a great increase in the stress levels in the inferior region of the bar, screw-retaining neck, cervical and medium third of the implant, and cortical bone tissue surrounding the implant. The higher stiffness of the bar presented a considerable increase in the stress levels in the bar framework only.
  
  
  CONCLUSIONS
  The levels of static stresses seem to be closely linked with horizontal misfit, such that its amplification caused increased levels of stress in the structures of the overdenture-retaining bar system. On the other hand, the stiffness of the bar framework presented a lower effect on the static stress levels.
authors.affiliation: Department of Prosthodontics, Dental School, Meridional Faculty (IMED), Passo Fundo, RS, Brazil. aospazzin@yahoo.com.br
authors.forename: Aloísio O
authors.initials: AO
authors.lastname: Spazzin
authors.forename: Mateus Bertolini Fernandes
authors.initials: MB
authors.lastname: Dos Santos
authors.forename: Lourenço Correr
authors.initials: LC
authors.lastname: Sobrinho
authors.forename: Rafael Leonardo X
authors.initials: RL
authors.lastname: Consani
authors.forename: Marcelo F
authors.initials: MF
authors.lastname: Mesquita
mesh_terms: D003198:Computer Simulation; D003722:Dental Alloys; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis / Q000379:methods; D003781:Denture Retention / Q000295:instrumentation*; D003828:Denture, Overlay; D020342:Finite Element Analysis; D006801:Humans; D008422:Materials Testing; D017755:Prosthesis Fitting; D013314:Stress, Mechanical
chemical_list: D003722:Dental Alloys