title: Prediction of Cyclic Fatigue Life of Nickel-Titanium Rotary Files by Virtual Modeling and Finite Elements Analysis.
abstract: BACKGROUND
  The finite element method (FEM) has been proposed as a method to analyze stress distribution in nickel-titanium (NiTi) rotary instruments but has not been assessed as a method of predicting the number of cycles to failure (NCF). The objective of this study was to predict NCF and failure location of NiTi rotary instruments by FEM virtual simulation of an experimental nonstatic fatigue test.
  
  
  METHODS
  ProTaper Next (PTN) X1, X2, and X3 files (Dentsply Maillefer, Baillagues, Switzerland) (n = 20 each) were tested to failure using a customized fatigue testing device. The device and file geometries were replicated with computer-aided design software. Computer-aided design geometries (geometric model) were imported and discretized (numeric model). The typical material model of an M-Wire alloy was applied. The numeric model of the device and file geometries were exported for finite element analysis (FEA). Multiaxial random fatigue methodology was used to analyze stress history and predict instrument life. Experimental data from PTN X2 and X3 were used for virtual model tuning through a reverse engineering approach to optimize material mechanical properties. Tuned material parameters were used to predict the average NCF and failure locations of PTN X1 by FEA; t tests were used to compare FEA and experimental findings (P < .05).
  
  
  RESULTS
  Experimental NCF and failure locations did not differ from those predicted with FEA (P = .098).
  
  
  CONCLUSIONS
  File NCF and failure location may be predicted by FEA. Virtual design, testing, and analysis of file geometries could save considerable time and resources during instrument development.
authors.affiliation: Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Scattina
authors.affiliation: Division of Endodontics, Department of Surgical Sciences, University of Turin Dental School, Turin, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Alovisi
authors.affiliation: Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy.
authors.forename: Davide Salvatore
authors.initials: DS
authors.lastname: Paolino
authors.affiliation: Division of Endodontics, Department of Surgical Sciences, University of Turin Dental School, Turin, Italy. Electronic address: damiano.pasqualini@unito.it.
authors.forename: Damiano
authors.initials: D
authors.lastname: Pasqualini
authors.affiliation: Division of Endodontics, Department of Surgical Sciences, University of Turin Dental School, Turin, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Scotti
authors.affiliation: Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Chiandussi
authors.affiliation: Division of Endodontics, Department of Surgical Sciences, University of Turin Dental School, Turin, Italy.
authors.forename: Elio
authors.initials: E
authors.lastname: Berutti
mesh_terms: D000497:Alloys; D003722:Dental Alloys; D004868:Equipment Failure; D020342:Finite Element Analysis; D006801:Humans; D008422:Materials Testing; D018915:Root Canal Preparation / Q000295:instrumentation*; D054159:Torsion, Mechanical
chemical_list: D000497:Alloys; D003722:Dental Alloys; C013616:nitinol
keywords: C-S criterion; finite element analysis; multiaxial random fatigue; nickel-titanium rotary instrument; virtual modeling