title: A comparison of torque expression between stainless steel, titanium molybdenum alloy, and copper nickel titanium wires in metallic self-ligating brackets.
abstract: OBJECTIVE
  The force moment providing rotation of the tooth around the x-axis (buccal-lingual) is referred to as torque expression in orthodontic literature. Many factors affect torque expression, including the wire material characteristics. This investigation aims to provide an experimental study into and comparison of the torque expression between wire types.
  
  
  METHODS
  With a worm-gear-driven torquing apparatus, wire was torqued while a bracket mounted on a six-axis load cell was engaged. Three 0.019 x 0.0195 inch wire (stainless steel, titanium molybdenum alloy [TMA], copper nickel titanium [CuNiTi]), and three 0.022 inch slot bracket combinations (Damon 3MX, In-Ovation-R, SPEED) were compared.
  
  
  RESULTS
  At low twist angles (<12 degrees), the differences in torque expression between wires were not statistically significant. At twist angles over 24 degrees, stainless steel wire yielded 1.5 to 2 times the torque expression of TMA and 2.5 to 3 times that of nickel titanium (NiTi). At high angles of torsion (over 40 degrees) with a stiff wire material, loss of linear torque expression sometimes occurred.
  
  
  CONCLUSIONS
  Stainless steel has the largest torque expression, followed by TMA and then NiTi.
authors.affiliation: Orthodontic Graduate Program, School of Dentistry, University of Alberta, Edmonton, AB, Canada.
authors.forename: Amy
authors.initials: A
authors.lastname: Archambault
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Major
authors.forename: Jason P
authors.initials: JP
authors.lastname: Carey
authors.forename: Giseon
authors.initials: G
authors.lastname: Heo
authors.forename: Hisham
authors.initials: H
authors.lastname: Badawi
authors.forename: Paul W
authors.initials: PW
authors.lastname: Major
mesh_terms: D000497:Alloys / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D003722:Dental Alloys / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D006801:Humans; D008422:Materials Testing; D009532:Nickel / Q000737:chemistry*; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D012399:Rotation; D013193:Stainless Steel / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D014025:Titanium / Q000737:chemistry*; D019415:Torque; D054159:Torsion, Mechanical; D014159:Transducers
chemical_list: D000497:Alloys; C415948:Copper NiTi; D003722:Dental Alloys; C525450:titanium molybdenum alloy; D013193:Stainless Steel; D003300:Copper; D009532:Nickel; D014025:Titanium