title: The influence of torque and manual glide path on the defect or separation rate of NiTi rotary instruments in root canal therapy.
abstract: BACKGROUND
  One of the effecting factors in prognosis of root canal therapy is accidental procedure as broken files that may be unpreventable. Many manufacturers have designed and marketed various electromotors that can control rotational speed and torque. On the other hand, some studies have recommended applying a manual glide path to diminish contact area between the file and canal walls. The purpose of this study was evaluation of the effect of torque and a manual glide path on defects as separation of Nickel-titanium (NiTi) rotary files.
  
  
  METHODS
  This ex vivo randomized controlled trial study was carried out on 160 canals of human's matured molars with mild curvature (15-338). After initial preparation of samples and checking for inclusion criteria, in first group, preparation was carried out with air-driven handpiece, and in group two, Endo IT was used as electromotor. In both groups, Mtwo files with simultaneous technique were used for preparation. Then all data were collected and analyzed with Mann Whitny, Mantel Cox, and t-test.
  
  
  RESULTS
  No significant differences between two groups (P < 0.05) were observed. Based on survival analysis, safety probability of files after preparation of nine canals is 64% in group one and 69.9% in group two. There was no significant differences between this safety probability in two groups (P = 0.272).
  
  
  CONCLUSIONS
  Usage of torque control handpiece is not an important factor, comparing instrumentation technique.
authors.affiliation: Department of Endodontics, Member of Dental Research Center, Dental School, Tehran, Iran.
authors.forename: M H
authors.initials: MH
authors.lastname: Zarrabi
authors.forename: M
authors.initials: M
authors.lastname: Javidi
authors.forename: M
authors.initials: M
authors.lastname: Vatanpour
authors.forename: H
authors.initials: H
authors.lastname: Esmaeili
mesh_terms: D003722:Dental Alloys; D003762:Dental Instruments; D004868:Equipment Failure; D004869:Equipment Safety; D006801:Humans; D008963:Molar; D009532:Nickel; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods*; D018709:Statistics, Nonparametric; D014025:Titanium; D019415:Torque
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium