title: Comparison of conventional and new-generation nickel-titanium files in regard to their physical properties.
abstract: BACKGROUND
  This study investigated the surface, fractured structure, and physicochemical properties related to cyclic fatigue in various nickel-titanium (NiTi) files.
  
  
  METHODS
  Among a total of 10 groups of NiTi files, conventional NiTi files (ProFile [Dentsply Maillefer, Ballaigues, Switzerland] and K3 [SybronEndo, Orange, CA]) and new-generation NiTi files (ProFile Vortex [PV; Tulsa Dental Specialties, Tulsa, OK], Vortex Blue [VB; Tulsa Dental Specialties], and K3 XF [XF; SybronEndo, Orange, CA]) with the same tip diameter (ISO size 25) and 2 types of taper (0.04 and 0.06) were used in this study. Scanning electron microscopy of the file surface structure, differential scanning calorimetry, and cyclic fatigue resistance tests were conducted.
  
  
  RESULTS
  Many mechanical grooves were recognized on the file surface. The surface in the ProFile group was extremely smooth compared with that observed for the other files. Many shallow hollows besides mechanical grooves were noted on the surface in the XF group. A smooth curve was observed in the ProFile, K3, and PV groups. Defined peaks in differential scanning calorimetry were observed in the VB and XF groups. The 0.04 taper files exhibited a statistically higher number of cycles to fracture than the 0.06 taper files in all groups (P < .05). Cracks along the mechanical grooves were observed in the NiTi files, with the exception of the XF group. The start of cracking was detected at U-shape sites in the ProFile group, the cutting edge in the PV and VB groups, and radial islands in the K3 and XF groups.
  
  
  CONCLUSIONS
  The present findings suggest that new-generation NiTi files are not necessarily improved compared with conventional files.
authors.affiliation: Department of Cariology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Tsujimoto
authors.affiliation: Department of Cariology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
authors.forename: Yuu
authors.initials: Y
authors.lastname: Irifune
authors.affiliation: Department of Endodontics, Nihon University School of Dentistry at Matsudo, Matsudo, Japan.
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Tsujimoto
authors.affiliation: Department of Cariology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
authors.forename: Shizuka
authors.initials: S
authors.lastname: Yamada
authors.affiliation: Department of Dental and Biomedical Materials Science, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
authors.forename: Ikuya
authors.initials: I
authors.lastname: Watanabe
authors.affiliation: Department of Cariology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan. Electronic address: hayashi@nagasaki-u.ac.jp.
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Hayashi
mesh_terms: D002152:Calorimetry, Differential Scanning; D055598:Chemical Phenomena; D003722:Dental Alloys / Q000737:chemistry*; D003799:Dental Stress Analysis; D004867:Equipment Design; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D009532:Nickel / Q000737:chemistry*; D018583:Pliability; D018915:Root Canal Preparation / Q000295:instrumentation*; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D014025:Titanium / Q000737:chemistry*; D019415:Torque
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium
keywords: Cyclic fatigue resistance test; differential scanning calorimetry; heat treatment; nickel-titanium files; scanning electron microscopy