title: Phase transformation behaviour and bending property of twisted nickel-titanium endodontic instruments.
abstract: OBJECTIVE
  To investigate the relationship between phase transformation behaviour and bending property of nickel-titanium endodontic instruments manufactured by a twisting process.
  
  
  METHODS
  The phase transformation behaviour and bending property of Twisted Files (TF; SybronEndo, Orange, CA, USA) and K3 (SybronEndo) with.06 taper and size 30 tip were investigated. K3 was used as control group. Phase transformation behaviour was estimated by differential scanning calorimetry (DSC). Transformation temperatures were calculated from the DSC curve. Bending load of the instruments was measured by cantilever-bending test at 37°C. Data were analysed by Student's t-test and Mann-Whitney U-test.
  
  
  RESULTS
  The phase transformation temperatures of TF were significantly higher (P<0.05) than those of K3. The bending load values were significantly lower for TF than that of K3 (P<0.05), both in the elastic and super-elastic ranges.
  
  
  CONCLUSIONS
  The new method of manufacturing NiTi instruments by twisting coupled with heat treatment might contribute to the increased phase transformation temperatures and superior flexibility.
authors.affiliation: Pulp Biology and Endodontics, Department of Restorative Sciences, Graduate School of Medical and Dental Sciences, Tokyo, Japan.
authors.forename: Xm
authors.initials: X
authors.lastname: Hou
authors.forename: Y
authors.initials: Y
authors.lastname: Yahata
authors.forename: Y
authors.initials: Y
authors.lastname: Hayashi
authors.forename: A
authors.initials: A
authors.lastname: Ebihara
authors.forename: T
authors.initials: T
authors.lastname: Hanawa
authors.forename: H
authors.initials: H
authors.lastname: Suda
mesh_terms: D003722:Dental Alloys / Q000737:chemistry*; D003762:Dental Instruments; D003799:Dental Stress Analysis; D004548:Elasticity; D004867:Equipment Design; D004868:Equipment Failure; D008422:Materials Testing; D008669:Metallurgy; D009532:Nickel / Q000737:chemistry*; D018583:Pliability; D018915:Root Canal Preparation / Q000295:instrumentation*; D013314:Stress, Mechanical; D014025:Titanium / Q000737:chemistry*; D044366:Transition Temperature
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium