title: Cutting efficiency of twisted versus machined nickel-titanium endodontic files.
abstract: BACKGROUND
  The purpose of this study was to compare the efficacy of the cutting ability of two different instruments, concerning changes in the dentin thickness removed and root canal volume, by using multislice computed tomography scanning.
  
  
  METHODS
  Thirty single-rooted mandibular premolars were divided into two equal groups according to the preparation system used: the twisted file (TF) and ProTaper (Dentsply Maillefer, Ballaigues, Swizerland). Dentin thickness along the whole length of the root canal and canal volume were measured before and after instrumentation by using multislice computed tomography scanning and image analysis software.
  
  
  RESULTS
  ProTaper removed significantly more dentin from the mesiodistal and buccolingual directions of the root canal than the TF (P < .05). No significant difference was recorded for the changes in root canal volume between the two systems (P > .05).
  
  
  CONCLUSIONS
  The TF system was found to cut dentin efficiently with more uniform cutting than ProTaper system.
authors.affiliation: Endodontic Department, Faculty of Oral and Dental Medicine, Misr International University, Cairo, Egypt. aliafayyad222@yahoo.com
authors.forename: Dalia Mukhtar
authors.initials: DM
authors.lastname: Fayyad
authors.forename: Abeer A
authors.initials: AA
authors.lastname: Elhakim Elgendy
mesh_terms: D001641:Bicuspid; D003722:Dental Alloys; D003762:Dental Instruments; D003804:Dentin; D004867:Equipment Design; D006801:Humans; D009532:Nickel; D018915:Root Canal Preparation / Q000295:instrumentation*; D014025:Titanium; D014057:Tomography, X-Ray Computed
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium