title: Torque and force induced by ProTaper universal and ProTaper next during shaping of large and small root canals in extracted teeth.
abstract: BACKGROUND
  The purpose of this study was to compare peak torque and force between ProTaper Universal (PTU) and ProTaper Next (PTN) instruments during the preparation of large and small root canals in extracted teeth.
  
  
  METHODS
  Twelve maxillary incisors and each independent canal of 6 mesial roots of mandibular molars were randomly assigned to be prepared with a new set of either PTU or PTN instruments after a glide path was achieved. A total of 12 new sets of each instrument system were used. The tests were run in a standardized fashion in a torque-testing platform. Peak torques (Ncm) and force (N) were registered; analysis of variance and Tukey post hoc tests were then applied.
  
  
  RESULTS
  Among instruments in the same sequence, no significant differences in peak torque and force were found among PTN instruments when shaping small or large root canals, but some PTU instruments showed statistically lower peak torque and force (P < .01) than others for both types of canals. Whereas PTU instruments showed significant differences in peak torque and force (P < .05) between large and small root canals, PTN instruments showed significantly lower force (P < .04) in large canals, but peak torque was not significantly different for upper central incisors or mesial mandibular root canals.
  
  
  CONCLUSIONS
  Under the conditions of this study, instruments in ProTaper Next set showed greater regularity in peak torque for small and large canals than ProTaper Universal instruments.
authors.affiliation: Department of Endodontics, Arthur A. Dugoni School of Dentistry, University of the Pacific, San Francisco, California. Electronic address: aa@ana-arias.com.
authors.forename: Ana
authors.initials: A
authors.lastname: Arias
authors.affiliation: Department of Endodontics, Arthur A. Dugoni School of Dentistry, University of the Pacific, San Francisco, California.
authors.forename: Rupinderpal
authors.initials: R
authors.lastname: Singh
authors.affiliation: Department of Endodontics, Arthur A. Dugoni School of Dentistry, University of the Pacific, San Francisco, California.
authors.forename: Ove A
authors.initials: OA
authors.lastname: Peters
mesh_terms: D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D004867:Equipment Design; D004868:Equipment Failure; D006801:Humans; D007180:Incisor / Q000033:anatomy & histology; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D008963:Molar / Q000033:anatomy & histology; D011897:Random Allocation; D018915:Root Canal Preparation / Q000295:instrumentation*; D013314:Stress, Mechanical; D019227:Tooth Apex / Q000033:anatomy & histology; D019415:Torque
keywords: M-Wire; ProTaper Next; ProTaper Universal; torque