title: Failure of ProFile instruments used with high and low torque motors.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the failure incidence of ProFile nickel-titanium rotary instruments when used in conjunction with different motors and a specific instrumentation technique.
  
  
  METHODS
  ProFile Ni-Ti rotary instruments (PRI) with 0.06 taper were used in a crown-down technique. In groups 1, 2 and 3, an air, a high torque and a low torque motor were used, respectively. Each group included 30 canals in extracted human molars. One set of PRI sizes 40-15 was used for each canal; they were sterilized before each case. A 2.5% NaOCl solution was used as an irrigant. The number of deformed and separated instruments was recorded for the various experimental groups.
  
  
  RESULTS
  Instrument separation did not occur in any of the three groups. One and two instruments were deformed when using the air and high torque motors, respectively.
  
  
  CONCLUSIONS
  The results indicated no difference between the three motors with respect to the incidence of instrument failure. The results suggest that the use of PRI in a crown-down manner with air control motors was safe.
authors.affiliation: Discipline of Endodontics, Faculty of Dentistry, University of Toronto, Canada. g.yared@utoronto.ca
authors.forename: G M
authors.initials: GM
authors.lastname: Yared
authors.forename: F E
authors.initials: FE
authors.lastname: Bou Dagher
authors.forename: P
authors.initials: P
authors.lastname: Machtou
mesh_terms: D003754:Dental High-Speed Equipment; D003762:Dental Instruments; D004868:Equipment Failure; D006801:Humans; D008963:Molar; D009532:Nickel; D018915:Root Canal Preparation / Q000295:instrumentation*; D014025:Titanium; D019415:Torque
chemical_list: C040654:titanium nickelide; D009532:Nickel; D014025:Titanium