title: [Influence of loops on the torsion stiffness of rectangular wire].
abstract: OBJECTIVE
  To study the influence of loops on the torsion stiffness of rectangular wire.
  
  
  METHODS
  The torsion moments and angles of 0.018 inch x 0.025 inch rectangular orthodontic arch wires in single 0.022 inch bracket of the first maxillary incisor were measured with a torsion measurement apparatus, and the measured values were analyzed by two-way ANOVA. The wires included straight stainless steel rectangular wires, and 3.5 mm, 7 mm, 10.5 mm, 14 mm high vertical loop wires, and 3 mm, 6 mm, 9 mm, 12 mm long horizontal loop wires.
  
  
  RESULTS
  1. The torsion stiffnesses of straight wire and vertical and horizontal loop wires were 4.909, 4.544, 4.137, 3.851, 3.454, 3.448, 3.024, 2.686, 2.378 N.mm/degree respectively. 2. The arch wires will be twisted 19.143 degrees, 19.377 degrees, 19.851 degrees, 20.949 degrees, 21.632 degrees, 21.812 degrees, 22.418 degrees, 23.254 degrees, 24.316 degrees respectively to obtain 20 N.mm force.
  
  
  CONCLUSIONS
  The design of loop can reduce the torsion stiffness of rectangular wire. Compared with the length of loop, the shape of loop has more important effect on the reduction of torsion stiffness. The horizontal loop design as a factor for the control of the tongue is more effective than the vertical loop design.
authors.affiliation: Department of Orthodonic, West China School of Stomatology, Sichuan University, Chengdu 610041, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.forename: Ding
authors.initials: D
authors.lastname: Bai
authors.forename: Ming
authors.initials: M
authors.lastname: Gu
authors.forename: Na
authors.initials: N
authors.lastname: Kang
mesh_terms: D000704:Analysis of Variance; D008422:Materials Testing / Q000295:instrumentation; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D018583:Pliability; D012399:Rotation; D013314:Stress, Mechanical; D013499:Surface Properties