title: The use of computed tomography when comparing nickel-titanium and stainless steel files during preparation of simulated curved canals.
abstract: OBJECTIVE
  The aim of this study was to compare canal preparations completed with Hedstrom and K-files of ISO size 15 - 40, made of nickel-titanium (Ni-Ti) and stainless steel (SS).
  
  
  METHODS
  Eighty simulated canals with 200 and 30 degrees C curvatures were prepared using the step-back technique and quarter turn/pull instrument manipulation. Middle and apical level canal sections were taken using computed tomography.
  
  
  RESULTS
  No significant difference was found between any of the file types at either level with respect to canal curvature (20 degrees or 30 degrees). At the middle level, the stainless steel files caused more enlargement toward the inner part, compared to nickel-titanium files. At the apical level, nickel-titanium canal files caused more enlargement toward the inner part, whereas more outward enlargement was caused by stainless steel instruments. No significant difference could be observed at the middle level (P > 0.05) related to the enlargement toward the outer side of the canal curvature. Transportation at both levels was significantly less (P < 0.001) for the Ni-Ti files than the SS ones. Centring ratios of the file types at the middle level were low, but not significantly different (P > 0.05), whereas at the apical level the centring ratios were significantly higher for the Ni-Ti files (P < 0.001).
  
  
  CONCLUSIONS
  Ni-Ti instruments produced preparations with adequate enlargement, less transportation, and a better centring ratio.
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Marmara University, Istanbul, Turkey. ygarip@yahoo.com
authors.forename: Y
authors.initials: Y
authors.lastname: Garip
authors.forename: M
authors.initials: M
authors.lastname: Günday
mesh_terms: D003762:Dental Instruments; D003786:Dental Pulp Cavity / Q000000981:diagnostic imaging; D008953:Models, Anatomic; D003765:Models, Dental; D009532:Nickel; D018915:Root Canal Preparation / Q000295:instrumentation*; D013193:Stainless Steel; D018709:Statistics, Nonparametric; D014025:Titanium; D014057:Tomography, X-Ray Computed
chemical_list: C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D014025:Titanium