title: Three-point bending testing of fibre posts: critical analysis by finite element analysis.
abstract: OBJECTIVE
  To evaluate the effect of taper, specimen supports and the isotropic and orthotropic properties of the posts on flexure and stress response during three-point bending using finite element analysis.
  
  
  METHODS
  A three-dimensional finite element model of a fibre post was created. The occlusal portion was cylindrical whilst the apical portion was tapered. Five different support positions were evaluated during a simulated three-point bending test: M1 - support distance of 10 mm centralized and no tilt; M2 - 10 mm centralized with tilt; M3 - 10 mm not centralized and no tilt; M4 - 10 mm not centralized with tilt; M5 - 6 mm not centralized with no tilt. A sixth post model (M6) was a centralized post without tapered section. The applied properties were elastic and orthotropic.
  
  
  RESULTS
  Tilting the tapered posts to level them in the test setup had little effect on the outcome. Flexure increased when 50% of the bent portion involved taper (M1, M2). If only 20% of the bent post involved taper (M3, M4), the flexure values were close to M6 (no taper). The orthotropic properties also caused increased flexure compared to an isotropic post. Maximum stresses were only a little higher when 50% of the bend structure involved taper, whilst the orthotropic properties had little effect.
  
  
  CONCLUSIONS
  Regardless of levelling, the flexural stress determination with tapered fibre posts in the three-point bending test was valid as long as the tapered portion was limited in length.
authors.affiliation: Department of Operative Dentistry and Dental Materials, Dental School, Federal University of Uberlândia, Minas Gerais, Brazil.
authors.forename: V R
authors.initials: VR
authors.lastname: Novais
authors.forename: A
authors.initials: A
authors.lastname: Versluis
authors.forename: L
authors.initials: L
authors.lastname: Correr-Sobrinho
authors.forename: C J
authors.initials: CJ
authors.lastname: Soares
mesh_terms: D001696:Biomechanical Phenomena; D003198:Computer Simulation; D017267:Dental Prosthesis Design; D003799:Dental Stress Analysis; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional; D018583:Pliability; D011176:Post and Core Technique / Q000295:instrumentation*