title: A comparative computational analysis of the mechanical behavior of two nickel-titanium rotary endodontic instruments.
abstract: BACKGROUND
  A finite element model of two nickel-titanium (Ni-Ti) rotary endodontic instruments (ProTaper and SystemGT; Dentsply-Maillefer, Ballaigues, Switzerland) was developed to investigate the mechanical behavior of these devices and to identify the benefits/limitations of different geometries during instrumentation in various root canals.
  
  
  METHODS
  Instrument shape, curved root canal geometry, and Ni-Ti alloy pseudo-elastic behavior were investigated in this study using computational techniques. Two different operating conditions were simulated: (1) the file insertion-removal cycle which resembles the standard working condition and (2) the file subjected to a torque in the counter-clockwise direction, which mimics the auto-reverse movement of the instrument when the tip is locked in the canal wall.
  
  
  RESULTS
  The simulations of standard and auto-reverse conditions produced bending and torsion loading conditions in the files, respectively. In the standard situation in which different canal shapes were considered, the strains in the SystemGT were generally lower than the strains in the ProTaper and always in the pseudo-elastic range; in only 1 case did the ProTaper overcame the pseudo-elastic range limit. In the auto-reverse situation, a better behavior of the ProTaper was detected.
  
  
  CONCLUSIONS
  The two simulated conditions highlighted the different mechanical properties of the files; the SystemGT showed slightly better performances under flexural solicitation, whereas the Protaper presented better behavior under torsion solicitations.
authors.affiliation: Laboratory of Biological Structure Mechanics, Department of Structural Engineering, Politecnico di Milano, 20133 Milan, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Necchi
authors.forename: Lorenza
authors.initials: L
authors.lastname: Petrini
authors.forename: Silvio
authors.initials: S
authors.lastname: Taschieri
authors.forename: Francesco
authors.initials: F
authors.lastname: Migliavacca
mesh_terms: D003198:Computer Simulation; D003722:Dental Alloys / Q000737:chemistry*; D003786:Dental Pulp Cavity / Q000033:anatomy & histology; D055119:Elastic Modulus; D004867:Equipment Design; D020342:Finite Element Analysis; D006801:Humans; D055595:Mechanical Phenomena; D008962:Models, Theoretical; D009532:Nickel / Q000737:chemistry*; D018583:Pliability; D018915:Root Canal Preparation / Q000295:instrumentation*; D012399:Rotation; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D019415:Torque; D054159:Torsion, Mechanical
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium