title: Influence of bending mode on the mechanical properties of nickel-titanium archwires and correlation to differential scanning calorimetry measurements.
abstract: BACKGROUND
  Nickel-titanium orthodontic archwires are used with bonded appliances for initial leveling. However, precise bending of these archwires is difficult and can lead to changes within the crystal structure of the alloy, thus changing the mechanical properties unpredictably. The aim of this study was to evaluate different bending methods in relation to the subsequent mechanical characteristics of the alloy.
  
  
  METHODS
  The mechanical behaviors of 3 archwires (Copper NiTi 35°C [Ormco, Glendora, Calif], Neo Sentalloy F 80 [GAC International, Bohemia, NY], and Titanol Low Force [Forestadent, Pforzheim, Germany]) were investigated after heat-treatment in a dental furnace at 550-650°C, treatment with an electrical current (Memory-Maker, Forestadent), and cold forming. In addition, the change in A(f) temperature was registered by means of differential scanning calorimetry.
  
  
  RESULTS
  Heat-treatment in the dental furnace as well as with the Memory-Maker led to widely varying force levels for each product. Cold forming resulted in similar or slightly reduced force levels when compared to the original state of the wires. A(f) temperatures were in general inversely proportional to force levels.
  
  
  CONCLUSIONS
  Archwire shape can be modified by using either chair-side technique (Memory-Maker, cold forming) because the superelastic behavior of the archwires is not strongly affected. However it is important to know the specific changes in force levels induced for each individual archwire with heat-treatment. Cold forming resulted in more predictable forces for all products tested. Therefore, cold forming is recommended as a chair-side technique for the shaping of NiTi archwires.
authors.affiliation: Department of Orthodontics and Pedodontics, University of Basel, Switzerland. Lorenz.Brauchli@unibas.ch
authors.forename: Lorenz M
authors.initials: LM
authors.lastname: Brauchli
authors.forename: Heidi
authors.initials: H
authors.lastname: Keller
authors.forename: Christiane
authors.initials: C
authors.lastname: Senn
authors.forename: Andrea
authors.initials: A
authors.lastname: Wichelhaus
mesh_terms: D002152:Calorimetry, Differential Scanning / Q000379:methods*; D003080:Cold Temperature; D003722:Dental Alloys / Q000737:chemistry* / Q000145:classification; D004560:Electricity; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D055595:Mechanical Phenomena; D009532:Nickel / Q000737:chemistry* / Q000145:classification; D009969:Orthodontic Wires; D018583:Pliability; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors; D014025:Titanium / Q000737:chemistry* / Q000145:classification
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium