title: [Properties of NiTi wires with direct electric resistance heat treatment method in three-point bending tests].
abstract: OBJECTIVE
  To investigate the mechanical properties of Ni-Ti wires with direct electric resistance heat treatment (DERHT) method in three-point bending tests.
  
  
  METHODS
  Two superelastic Ni-Ti wires (wire A: Smart SE, wire B: SENTALLOY SE, 0.406 mm × 0.559 mm) and 2 heat-actived Ni-Ti wires (wire C: Smart SM, wire D: L&H TITAN, 0.406 mm × 0.559 mm) were selected. They were heat-treated using the DERHT method by a controlled electric current (6.36 A) applied for different period of time [0 (control), 1.0, 1.5, 2.0, 2.5 seconds). Then, a three-point bending test was performed under controlled temperature (37°C) to examine the relationships between the deflection and the load in the bending of wires.
  
  
  RESULTS
  After DERHT treatment, the plateau in the force-deflection curve of superelastic Ni-Ti wires and heat-activated Ni-Ti wires were increased. When the wires were heated for 2.0 seconds and deflected to 1.5 mm, the loading force of A, B, C and D Ni-Ti wires increased from (3.85 ± 0.11), (3.62 ± 0.07), (3.28 ± 0.09), (2.91 ± 0.23) N to (4.33 ± 0.07), (4.07 ± 0.05), (4.52 ± 0.08), (3.27 ± 0.15) N respectively.
  
  
  CONCLUSIONS
  DERHT method is very convenient for clinical use. It is possible to change the arch form and superelastic force of NiTi wires. The longer the heating time is, the more the superelastic characteristics of the wires are altered.
authors.affiliation: Department of Orthodontics, Capital Medical University School of Stomatology, Beijing 100050, China.
authors.forename: Hong-mei
authors.initials: HM
authors.lastname: Wang
authors.forename: Bang-kang
authors.initials: BK
authors.lastname: Wang
authors.forename: Chao-chao
authors.initials: CC
authors.lastname: Ren
authors.forename: Yu-xing
authors.initials: YX
authors.lastname: Bai
mesh_terms: D003799:Dental Stress Analysis; D004548:Elasticity; D006358:Hot Temperature; D008422:Materials Testing; D009532:Nickel / Q000737:chemistry*; D009969:Orthodontic Wires; D013314:Stress, Mechanical; D014025:Titanium / Q000737:chemistry*
chemical_list: C040654:titanium nickelide; D009532:Nickel; D014025:Titanium