title: Phase transformation behavior and mechanical properties of thermomechanically treated K3XF nickel-titanium instruments.
abstract: BACKGROUND
  The bending and torsional properties of thermomechanically treated K3XF (SybronEndo, Orange, CA) nickel-titanium instruments in relation to their phase transformation behavior were evaluated.
  
  
  METHODS
  NiTi instruments K3 (SybronEndo) and K3XF, both in sizes 25/.04 and 40/.04, were examined by differential scanning calorimetry and X-ray diffraction. The metal composition was determined by scanning electron microscopy with X-ray energy-dispersive spectrometric analyses. The bending property of K3 and K3XF instruments was measured in a cantilever-bending test with a maximum deflection of 4.00 mm. A torsional test of the instruments was evaluated according to the American National Standards Institute/American Dental Association Specification No. 28.
  
  
  RESULTS
  K3 and K3XF instruments had approximately the same chemical composition with a nickel content of 48-49 atomic %. The differential scanning calorimetry analyses showed that each segment of the K3XF instruments (24.89°C ± 1.98°C) had a higher austenite finish temperature than the K3 instruments (17.63°C ± 1.76°C) (P < .05). The bending load values were significantly lower for K3XF than for K3 in the superelastic ranges (P < .05). There was no statistically significant difference between K3 and K3XF in the maximum torque or maximum angular deflection before failure. The torque at fracture values of K3 and K3XF increased significantly with the diameter (P < .05).
  
  
  CONCLUSIONS
  K3XF exhibited different phase transformation behavior and flexibility when compared with K3, which may be attributed to the special heat treatment history of K3XF instruments.
authors.affiliation: Division of Endodontics, Department of Oral Biological and Medical Sciences, Faculty of Dentistry, The University of British Columbia, Vancouver, Canada.
authors.forename: Ya
authors.initials: Y
authors.lastname: Shen
authors.forename: Hui-Min
authors.initials: HM
authors.lastname: Zhou
authors.forename: Zhejun
authors.initials: Z
authors.lastname: Wang
authors.forename: Les
authors.initials: L
authors.lastname: Campbell
authors.forename: Yu-feng
authors.initials: YF
authors.lastname: Zheng
authors.forename: Markus
authors.initials: M
authors.lastname: Haapasalo
mesh_terms: D002152:Calorimetry, Differential Scanning; D055598:Chemical Phenomena; D003722:Dental Alloys / Q000737:chemistry*; D004548:Elasticity; D004867:Equipment Design; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D055595:Mechanical Phenomena; D008855:Microscopy, Electron, Scanning; D009532:Nickel / Q000737:chemistry*; D018583:Pliability; D018915:Root Canal Preparation / Q000295:instrumentation*; D013052:Spectrometry, X-Ray Emission; D013696:Temperature; D014025:Titanium / Q000737:chemistry*; D019415:Torque; D054159:Torsion, Mechanical; D014961:X-Ray Diffraction
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; C093826:Austenite; D009532:Nickel; D014025:Titanium