title: An in vitro comparison of canal preparation using two automated rotary nickel-titanium instrumentation techniques.
abstract: OBJECTIVE
  The aim of this study was to compare the efficacy of root canal preparation using two automated rotary nickel-titanium instrumentation techniques with a double flared balanced forces hand preparation technique, using stainless steel files in extracted human teeth.
  
  
  METHODS
  Sixty root canals in extracted human teeth were matched for curvature, length and diameter and divided evenly between three groups (group 1 = double flare using Flexofiles, group 2 = rotary nickel-titanium using McXIM instruments and group 3 = rotary nickel-titanium using Profile .04 Taper Series 29 instruments). The instruments were used according to the manufacturer's instructions in a torque controlled motor and handpiece (groups 2 and 3) and according to a predetermined procedure in group 1. A standardized radiographic technique using mercury as a contrast medium was used to evaluate the canal shape before and after preparation in the plane of maximum curvature. The pre- and postoperative radiographic images were compared against each other and with a predicted 'ideal preparation' calculated from a projection of the final instrument dimensions. The outcome measures were changes in canal dimensions as quantified by measuring the changes in the position of the inner and outer wall at 1 mm intervals. Alteration in canal curvature could be inferred by comparison with the ideal preparation.
  
  
  RESULTS
  The degree of canal curvature did not influence the effectiveness of any of the techniques. The results showed no statistically significant differences in the outcome measures between the groups (two-way ANOVA). There were no significant differences in canal wall position changes at any level except the apical three, where significantly less change occurred in all groups (P = 1%). Instruments fractured in three canals, with acute curves in groups 2 and 3.
  
  
  CONCLUSIONS
  Canal curvatures were equally and well maintained following preparation in all the groups, as long as the instrument did not fracture.
authors: Eastman Dental Institute for Oral Health Care Sciences, University College London, London, UK.
authors: S J
authors: SJ
authors: Jardine
authors: K
authors: K
authors: Gulabivala
mesh_terms: D000704:Analysis of Variance; D001331:Automation; D001641:Bicuspid; D003287:Contrast Media; D003722:Dental Alloys; D003786:Dental Pulp Cavity / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D004867:Equipment Design; D004868:Equipment Failure; D006801:Humans; D008628:Mercury; D008963:Molar; D009532:Nickel; D011670:Pulpectomy / Q000295:instrumentation / Q000379:methods; D011859:Radiography; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods; D012399:Rotation; D013193:Stainless Steel; D013499:Surface Properties; D014025:Titanium; D019227:Tooth Apex / Q000000981:diagnostic imaging / Q000648:ultrastructure
chemical_list: D003287:Contrast Media; D003722:Dental Alloys; C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D014025:Titanium; D008628:Mercury