title: Physical and mechanical properties of a thermomechanically treated NiTi wire used in the manufacture of rotary endodontic instruments.
abstract: OBJECTIVE
  To compare physical and mechanical properties of one conventional and one thermomechanically treated nickel-titanium (NiTi) wire used to manufacture rotary endodontic instruments.
  
  
  METHODS
  Two NiTi wires 1.0 mm in diameter were characterized; one of them, C-wire (CW), was processed in the conventional manner, and the other, termed M-Wire (MW), received an additional heat treatment according to the manufacturer. Chemical composition was determined by energy-dispersive X-ray spectroscopy, phase constitution by XRD and the transformation temperatures by DSC. Tensile loading/unloading tests and Vickers microhardness measurements were performed to assess the mechanical behaviour. Data were analysed using analysis of variance (α = 0.05).
  
  
  RESULTS
  The two wires showed approximately the same chemical composition, close to the 1 : 1 atomic ratio, and the β-phase was the predominant phase present. B19' martensite and the R-phase were found in MW, in agreement with the higher transformation temperatures found in this wire compared with CW, whose transformation temperatures were below room temperature. Average Vickers microhardness values were similar for MW and CW (P = 0.91). The stress at the transformation plateau in the tensile load-unload curves was lower and more uniform in the M-Wire, which also showed the smallest stress hysteresis and apparent elastic modulus.
  
  
  CONCLUSIONS
  The M-Wire had physical and mechanical properties that can render endodontic instruments more flexible and fatigue resistant than those made with conventionally processed NiTi wires.
authors.affiliation: Department of Restorative Dentistry, Faculty of Dentistry, Universidade Federal de Minas Gerais, Belo Horizonte-MG, Brazil.
authors.forename: E S J
authors.initials: ES
authors.lastname: Pereira
authors.forename: I F C
authors.initials: IF
authors.lastname: Peixoto
authors.forename: A C D
authors.initials: AC
authors.lastname: Viana
authors.forename: I I
authors.initials: II
authors.lastname: Oliveira
authors.forename: B M
authors.initials: BM
authors.lastname: Gonzalez
authors.forename: V T L
authors.initials: VT
authors.lastname: Buono
authors.forename: M G A
authors.initials: MG
authors.lastname: Bahia
mesh_terms: D002152:Calorimetry, Differential Scanning; D055598:Chemical Phenomena; D003722:Dental Alloys / Q000737:chemistry*; D055119:Elastic Modulus; D004867:Equipment Design; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D055595:Mechanical Phenomena; D009532:Nickel / Q000737:chemistry*; D044367:Phase Transition; D018583:Pliability; D018915:Root Canal Preparation / Q000295:instrumentation*; D012399:Rotation; D013052:Spectrometry, X-Ray Emission; D013499:Surface Properties; D013718:Tensile Strength; D013816:Thermodynamics; D014025:Titanium / Q000737:chemistry*; D044366:Transition Temperature; D014961:X-Ray Diffraction
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; C093824:Martensite; D009532:Nickel; D014025:Titanium