title: Torsional profiles of new and used revo-s rotary instruments: an in vitro study.
abstract: BACKGROUND
  This study investigated the torsional properties of new and used Revo-S Shaping Universal (SU) endodontic instruments.
  
  
  METHODS
  Torsional profiles were established following the American National Standards Institute/American Dental Association Specification No. 28. Unused SU instruments (group 1, control; n = 30) and instruments used in simulated root canals twice (group 2, n = 30) or six times (group 3, n = 30) were tested. Analysis of variance with the Bonferroni/Dunn post hoc test (α = 0.05) was used to analyze the torque and angle of rotation at fracture.
  
  
  RESULTS
  The maximum torque at fracture did not differ significantly among instruments in group 1 and groups 2 and 3. The angle of rotation at fracture decreased significantly (P < .01) from group 1 to groups 2 and 3.
  
  
  CONCLUSIONS
  The repeated use of the SU rotary instruments significantly reduced the angle of rotation at fracture but did not reduce the torque at fracture.
authors.affiliation: Discipline of Endodontics, University of Toronto, Toronto, Ontario, Canada. bettina.basrani@dentistry.utoronto.ca
authors.forename: Bettina
authors.initials: B
authors.lastname: Basrani
authors.forename: Karina
authors.initials: K
authors.lastname: Roth
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Sas
authors.forename: Anil
authors.initials: A
authors.lastname: Kishen
authors.forename: Ove A
authors.initials: OA
authors.lastname: Peters
mesh_terms: D003762:Dental Instruments; D003799:Dental Stress Analysis; D004867:Equipment Design; D004868:Equipment Failure; D017743:Equipment Reuse; D008422:Materials Testing; D018915:Root Canal Preparation / Q000295:instrumentation*; D019415:Torque; D054159:Torsion, Mechanical