title: A comparison of stainless steel hand and rotary nickel-titanium instrumentation using a silicone impression technique.
abstract: BACKGROUND
  Root canal preparation using rotary nickel-titanium instruments has been reported to be superior to hand instrumentation in terms of root canal shape, centring and frequency of procedural errors. The purpose of this study was to evaluate canal preparations using a sequential silicone impression technique to assess root canal morphology.
  
  
  METHODS
  Pre-operative canal impressions were obtained from 24 extracted single-rooted premolars. Canals were randomly assigned to be firstly, instrumented with stainless steel K-type files or rotary nickel-titanium instruments (Profile), then further apically enlarged with rotary nickel-titanium instruments (Profile or Lightspeed). Post instrumentation impressions were taken and digitally photographed in a bucco-lingual and mesio-distal orientation at low-power magnification. Images were evaluated for procedural defects, changes in canal curvature, canal enlargement and canal rounding at 1, 3 and 7mm from the working length.
  
  
  RESULTS
  Silicone impressions could accurately reproduce the detailed root canal morphology of single-canal premolars. Repeated impressions of each canal using a standardized procedure allowed a detailed comparison of instrumentation techniques at various stages. Hand instrumentation incurred more errors than rotary nickel-titanium instrumentation (Profile). Further apical enlargement using Lightspeed instruments incurred fewer errors than with Profile instruments. Differences among techniques were highly significant (p<0.005). All techniques resulted in slight canal straightening, as well as rounder and enlarged canals particularly in the apical third.
  
  
  CONCLUSIONS
  Rotary nickel-titanium instrumentation, especially Lightspeed, may produce better canal shape by reducing procedural errors.
authors.affiliation: School of Dental Science, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne.
authors.forename: J L
authors.initials: JL
authors.lastname: Chen
authors.forename: H H
authors.initials: HH
authors.lastname: Messer
mesh_terms: D000704:Analysis of Variance; D001641:Bicuspid; D003760:Dental Impression Materials; D003761:Dental Impression Technique; D003762:Dental Instruments; D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D006801:Humans; D019300:Medical Errors; D009532:Nickel; D011897:Random Allocation; D015203:Reproducibility of Results; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods; D012828:Silicones; D013193:Stainless Steel; D014025:Titanium
chemical_list: D003760:Dental Impression Materials; D012828:Silicones; C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D014025:Titanium