title: Differences in cyclic fatigue resistance between ProTaper Next and ProTaper Universal instruments at different levels.
abstract: BACKGROUND
  New designs and alloys have been developed to increase cyclic fatigue (CF) resistance of rotary files. The aim of this study was to compare CF resistance of ProTaper Universal (PTU; Dentsply Tulsa Dental, Tulsa, OK) and ProTaper Next (PTN, Dentsply Tulsa Dental) instruments at different points of curvature.
  
  
  METHODS
  A total of 420 files (240 PTU, S1, F1, F2, and F3 and 180 PTN, X1, X2, and X3) were divided in 14 groups of 30 instruments each. Instruments in groups S1-5, F1-5, X1-5, F2-5, X2-5, F3-5, and X3-5 were tested at 5 mm from the tip. Groups S1-12, X1-12, and F1-12 were tested at 12 mm from the tip because S1, X1, and F1 instruments have the same diameter at that level. Groups F2-8, X2-8, F3-8, and X3-8 were tested at 8 mm (F2/X2 and F3/X3, respectively, had the same diameter at 8 mm). All files were rotated at 300 rpm until fracture. CF resistance was tested in stainless steel curved canals (60°, r = 3 mm). Time to fracture was recorded. The mean half-life and beta and eta were calculated for each group and were compared with Weibull analysis.
  
  
  RESULTS
  PTN instruments will last significantly longer than PTU files with a probability higher than 98% at all tested levels except for S1, which was the significantly the most resistant instrument to CF at 5 mm from the tip.
  
  
  CONCLUSIONS
  PTU S1 was significantly the most resistant instrument at 5 mm from the tip. PTN files were significantly more resistant to CF than PTU instruments at all the other tested levels.
authors.affiliation: Department of Conservative Dentistry, School of Dentistry, Complutense University, Madrid, Spain.
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Pérez-Higueras
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 Conservative Dentistry, School of Dentistry, Complutense University, Madrid, Spain.
authors.forename: José C
authors.initials: JC
authors.lastname: de la Macorra
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: D003722:Dental Alloys / Q000737:chemistry*; D004867:Equipment Design; D004868:Equipment Failure; D019544:Equipment Failure Analysis; D006801:Humans; D008422:Materials Testing; D009532:Nickel / Q000737:chemistry*; D018915:Root Canal Preparation / Q000295:instrumentation*; D012399:Rotation; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors; D014025:Titanium / Q000737:chemistry*
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium
keywords: Cyclic fatigue resistance; M-Wire; ProTaper Next; ProTaper Universal; Weibull analysis