title: Determining cutting efficiency of nickel-titanium coronal flaring instruments used in lateral action.
abstract: OBJECTIVE
  To develop a method to evaluate the cutting behaviour of nickel-titanium (NiTi) coronal flaring instruments.
  
  
  METHODS
  BioRaCe BR0 (BR), HyFlex CM 1 (HY), ProFile OS No. 2 (PF) and ProTaper Sx (PT) instruments were used in simulated coronal flaring using a lateral action against bovine dentine blocks, at 250 and 500 rpm. Cutting efficiency was assessed by three methods: first, areas of notches produced by instruments were directly measured under a stereomicroscope. Second, dentine specimens were then analysed by surface profilometry to determine the maximum cutting depth and finally by microcomputed tomography to assess the volume of removed dentine. Data were compared using parametric tests with the significance level set at 0.05.
  
  
  RESULTS
  For all three methods, HY and PF were the most and the least cutting-efficient instruments, respectively (P < 0.05). Significant differences were detected between 250 and 500 rpm for HY and PT (area); for BR, HY and PT (depth); and for BR and HY (volume). There were strong positive correlations between the results obtained with those three different methods with r-values ranging from 0.81 to 0.92.
  
  
  CONCLUSIONS
  Measuring the amount of material removed in a specific time under stereomicroscopy is a simple and rational way to assess the cutting behaviour of NiTi rotary instruments in lateral action. HyFlex, manufactured with thermomechanically treated NiTi wire, was the most efficient instrument, and increased rotational speed was associated with increased cutting efficiency.
authors.affiliation: Department of Endodontics, Arthur A. Dugoni School of Dentistry, University of the Pacific, San Francisco, CA, USA.
authors.forename: O A
authors.initials: OA
authors.lastname: Peters
authors.forename: R D
authors.initials: RD
authors.lastname: Morgental
authors.forename: K A
authors.initials: KA
authors.lastname: Schulze
authors.forename: F
authors.initials: F
authors.lastname: Paqué
authors.forename: P M P
authors.initials: PM
authors.lastname: Kopper
authors.forename: F V
authors.initials: FV
authors.lastname: Vier-Pelisser
mesh_terms: D000818:Animals; D002417:Cattle; D003762:Dental Instruments; D004708:Endodontics / Q000295:instrumentation*; D009532:Nickel; D014025:Titanium; D055114:X-Ray Microtomography
chemical_list: D009532:Nickel; D014025:Titanium
keywords: coronal flaring; cutting efficiency; endodontics; nickel-titanium alloy; root canal preparation; rotational speed