title: Cyclic Fatigue of ProFile Vortex and Vortex Blue Nickel-Titanium Files in Single and Double Curvatures.
abstract: BACKGROUND
  The aims of this study were to determine the flexibility of ProFile Vortex (VX) and Vortex Blue (VB) files (Dentsply Tulsa Dental Specialties, Tulsa, OK) and then to evaluate and compare their fatigue resistance in artificial single curvature and 2 different artificial double curvature canals.
  
  
  METHODS
  Flexibility of the files (size 25/.04) in bending was assessed according to ISO 3630-1. Both files were subjected to fatigue tests inside artificial canals with a single curvature (group 1: 60° curvature, 5-mm radius) and with 2 different double curvatures (group 2: first [coronal] curve of 60° curvature and 5-mm radius and the second one [apical] of 30° curvature and 2-mm radius and group 3: first curve of 60° curvature and 5-mm radius and the second one of 60° curvature and 2-mm radius). The number of cycles to fracture (NCF) was recorded, and the fracture surface of all fragments was examined with a scanning electron microscope.
  
  
  RESULTS
  The bending load was significantly lower for VB files than VX files (P < .05), and the 2 types of files followed different trajectories in identical canals. In group 1, the 2 files had significantly higher NCF than in groups 2 and 3 (P < .05). Both files had significantly higher NCF in group 2 than in group 3 (P < .05). In group 1, VB files had fatigue resistance superior to VX files (P < .05), whereas in groups 2 and 3 their fatigue resistance was not statistically different from each other. The crack initiation of a vast majority of files that fractured in double curvature canals (groups 2 and 3) was localized on either 1 of 2 of the 3 cutting edges.
  
  
  CONCLUSIONS
  Double curvature canals represent a much more stressful and challenging anatomy than single curvature canals, and, in them, fatigue resistance may be affected by the degrees and the radii of curvatures as well as by the bending properties of the files.
authors.affiliation: Department of Oral Biological and Medical Sciences, Faculty of Dentistry, The University of British Columbia, Vancouver, Canada.
authors.forename: Frederic
authors.initials: F
authors.lastname: Duke
authors.affiliation: Department of Oral Biological and Medical Sciences, Faculty of Dentistry, The University of British Columbia, Vancouver, Canada. Electronic address: yashen@dentistry.ubc.ca.
authors.forename: Ya
authors.initials: Y
authors.lastname: Shen
authors.affiliation: Center for Biomedical Materials and Engineering, Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin, China.
authors.forename: Huimin
authors.initials: H
authors.lastname: Zhou
authors.affiliation: Department of Oral Biological and Medical Sciences, Faculty of Dentistry, The University of British Columbia, Vancouver, Canada.
authors.forename: N Dorin
authors.initials: ND
authors.lastname: Ruse
authors.affiliation: Department of Oral Biological and Medical Sciences, Faculty of Dentistry, The University of British Columbia, Vancouver, Canada.
authors.forename: Zhe-jun
authors.initials: ZJ
authors.lastname: Wang
authors.affiliation: Department of Oral Biological and Medical Sciences, Faculty of Dentistry, The University of British Columbia, Vancouver, Canada.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Hieawy
authors.affiliation: Department of Oral Biological and Medical Sciences, Faculty of Dentistry, The University of British Columbia, Vancouver, Canada.
authors.forename: Markus
authors.initials: M
authors.lastname: Haapasalo
mesh_terms: D003722:Dental Alloys; D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D003799:Dental Stress Analysis; D004868:Equipment Failure; D006801:Humans; D009532:Nickel; D018915:Root Canal Preparation / Q000295:instrumentation*; D014025:Titanium
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium
keywords: Bending property; ProFile Vortex; Vortex Blue; double curvature; fatigue resistance; nickel-titanium files