title: Shaping ability of nickel-titanium rotary instruments in curved root canals.
abstract: BACKGROUND
  Disinfection and subsequent obturation of the root canal space require adequate mechanical enlargement of the canals. The purpose of this in vitro study was to compare the shaping ability of Mtwo, RaCe and Medin rotary instruments during the preparation of curved root canals.
  
  
  METHODS
  Sixty mesiobuccal root canals of mandibular molars with severe curvatures between 25-35(°) and radius of 4-9 mm were randomly divided into three groups of 20 canals each. Using pre- and post-instrumentation radiographs, straightening of the canal and the apical transportation were determined with AutoCAD software. The data were analyzed using Chi square, analysis of variance, and post-hoc tests and the significance level was set at P<0.05.
  
  
  RESULTS
  Mtwo instruments maintained the canal curvature significantly better than Race and Medin instruments (P<0.05). There was significant difference between the rotary instruments for iatrogenic transportation of the major foramen (P>0.05).
  
  
  CONCLUSIONS
  Under the conditions of this in vitro study, Mtwo instruments seemed superior to the two other rotary instruments.
authors.affiliation: Dental Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Ali
authors.initials: A
authors.lastname: Talati
authors.forename: Saeed
authors.initials: S
authors.lastname: Moradi
authors.forename: Maryam
authors.initials: M
authors.lastname: Forghani
authors.forename: Ali
authors.initials: A
authors.lastname: Monajemzadeh
keywords: Dental Instruments; NiTi Alloy; Root Canal; Root Canal Preparation