title: Mechanical behavior of three nickel-titanium rotary files: A comparison of numerical simulation with bending and torsion tests.
abstract: OBJECTIVE
  To assess the flexibility and torsional stiffness of three nickel-titanium rotary instruments by finite element analysis and compare the numerical results with the experiment.
  
  
  METHODS
  Mtwo (VDW, Munich, Germany) and RaCe (FKG Dentaire, La-Chaux-de-Fonds, Switzerland) size 25, .06 taper (0.25-mm tip diameter, 0.06% conicity) and PTU F1 (Dentsply Maillefer, Ballaigues, Switzerland) instruments were selected for this study. Experimental tests to assess the flexibility and torsional stiffness of the files were performed according to specification ISO 3630-1. Geometric models for finite element analysis were obtained by micro-CT scanning. Boundary conditions for the numerical analysis were based on the specification ISO 3630-1.
  
  
  RESULTS
  A good agreement between the simulation and the experiment moment-displacement curves was found for the three types of instruments studied. RaCe exhibited the highest flexibility and PTU presented the highest torsional stiffness. Maximum values of von Mises stress were found for the PTU F1 file (1185MPa) under bending, whereas the values of von Mises stress for the three instruments were quite similar under torsion. The stress patterns proved to be different in Mtwo under bending, according to the displacement orientation.
  
  
  CONCLUSIONS
  The favorable agreement found between simulation and experiment for the three types of instruments studied confirmed the potential of the numerical method to assess the mechanical behavior of endodontic instruments. Thus, a methodology is established to predict the failure of the instruments under bending and torsion.
authors.affiliation: Department of Metallurgical and Materials Engineering, School of Engineering, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brazil; Department of Structural Engineering, School of Engineering, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brazil.
authors.forename: Leandro
authors.initials: L
authors.lastname: de Arruda Santos
authors.affiliation: Group of Structural Mechanics and Materials Modeling (GEMM), Aragón Institute of Engineering Research (I3A), Universidad de Zaragoza, Zaragoza, Spain.
authors.forename: Javier Bayod
authors.initials: JB
authors.lastname: López
authors.affiliation: Department of Structural Engineering, School of Engineering, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brazil.
authors.forename: Estevam Barbosa
authors.initials: EB
authors.lastname: de Las Casas
authors.affiliation: Department of Restorative Dentistry, Faculty of Dentistry, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brazil.
authors.forename: Maria Guiomar
authors.initials: MG
authors.lastname: de Azevedo Bahia
authors.affiliation: Department of Metallurgical and Materials Engineering, School of Engineering, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brazil. Electronic address: vbuono@demet.ufmg.br.
authors.forename: Vicente Tadeu Lopes
authors.initials: VT
authors.lastname: Buono
mesh_terms: D020342:Finite Element Analysis; D008422:Materials Testing; D009532:Nickel / Q000737:chemistry*; D013314:Stress, Mechanical; D014025:Titanium / Q000737:chemistry*
chemical_list: C040654:titanium nickelide; D009532:Nickel; D014025:Titanium
keywords: Finite element analysis; Flexibility; NiTi endodontic instruments; Torsional stiffness