title: A comparison of stress distribution and flexion among various designs of bar attachments for implant overdentures: a three dimensional finite element analysis.
abstract: BACKGROUND
  Bar overdentures are popular choices among clinicians worldwide but configurations that provide an optimal biomechanical distribution of stress are still debatable.
  
  
  OBJECTIVE
  To compare the stresses and elastic flexion between implant supported bar overdentures in various configurations using finite element analysis.
  
  
  METHODS
  A CAT scan of a human mandible was used to generate an anatomically accurate mechanical model.
  
  
  METHODS
  Three models with bars and clips in three different configurations were constructed. Model 1 had a single bar connecting two implants, Model 2 had three bars connecting all the four implants, and Model 3 had two bars connecting the medial and distal implants on the sides only. The models were loaded under static conditions with 100N load distributed at the approximate position of the clip. The mandibular boundary conditions were modeled considering the real geometry of its muscle supporting system. Maximum von Mises stress at the level of the bar and at the bone implant interface were compared in all three models. The flexion of mandible and the bar was also compared qualitatively.
  
  
  METHODS
  The analyses were accomplished using the ANSYS software program and were processed by a personal computer. Stress on these models was analyzed after loading conditions.
  
  
  RESULTS
  Qualitative comparisons showed that stress at the level of the bar and at the bone implant interface were in the following order: Model 1> Model 3> Model 2. The flexion of the mandible and the bar were in the following order: Model 2 > Model 1 > Model 3.
  
  
  CONCLUSIONS
  Four implant bar systems connected by bars on the sides only is a better choice than two implant bar systems and four implant bar systems with bars connecting all four implants.
authors.affiliation: Department of Prosthodontics, Manipal College of Dental Sciences, Manipal, Karnataka, 576 119, India. drvjprakash22@yahoo.co.in
authors.forename: Vijay
authors.initials: V
authors.lastname: Prakash
authors.forename: Mariette
authors.initials: M
authors.lastname: D'Souza
authors.forename: Raviraj
authors.initials: R
authors.lastname: Adhikari