title: Nickel titanium T-loop wire dimensions for en masse retraction.
abstract: OBJECTIVE
  To compare the force system produced by nickel-titanium T-loop springs made with wires of different dimensions.
  
  
  METHODS
  Thirty compound T-loop springs were divided into three groups according to the dimensions of the nickel-titanium wire used for its design: 0.016" × 0.022", 0.017" × 0.025", and 0.018" × 0.025". The loops were tested on the Orthodontic Force Tester machine at an interbracket distance of 23 mm and activated 9 mm. The force in the y-axis and the moment in the x-axis were registered while the calculated moment to force ratio was recorded at each .5 mm of deactivation. The data were analyzed by three analyses of variance of repeated measures to detect differences and interactions between deactivation and wire size on force, moment, and moment-force ratios (M/F).
  
  
  RESULTS
  All groups had significantly different forces (P < .001). The 0.016" × 0.022" wire produced 1.78N of force while the 0.017" × 0.025" and the 0.018" × 0.025" produced 2.81 N and 3.25 N, respectively. The 0.016" × 0.022" wire produced lower moments (11.6 Nmm) than the 0.017" × 0.025" and 0.018" × 0.025" wires, which produced similar moments (13.9 Nmm and 14.4Nmm, respectively). The M/F produced was different for all groups; 0.016" × 0.022" T-loops produced 6.7 mm while the 0.017" × 0.025" and 0.018" × 0.025" T-loops produced 5.0 mm and 4.5 mm, respectively. An interaction was detected for all variables between deactivation and groups.
  
  
  CONCLUSIONS
  The larger wires tested produced higher forces with slight increase on the moments, but the M/F produced by the 0.016" × 0.022" wire was the highest found.
authors.affiliation: a  Graduate student, Program of Orthodontics, Universidade Estadual Paulista, Araraquara, Brazil.
authors.forename: Layene
authors.initials: L
authors.lastname: Almeida
authors.affiliation: b  Private practice, Natal, Brazil.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Ribeiro
authors.affiliation: c  Private Practice and Adjunct Professor, Program of Orthodontics, Universidade Estadual Paulista, Araraquara, Brazil.
authors.forename: Renato
authors.initials: R
authors.lastname: Parsekian Martins
authors.affiliation: d  Associate Professor, Department of Orthodontics, Loma Linda University, Loma Linda, Calif.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Viecilli
authors.affiliation: e  Professor, Department of Orthodontics, Universidade Estadual Paulista, Araraquara, Brazil.
authors.forename: Lídia
authors.initials: L
authors.lastname: Parsekian Martins
mesh_terms: D000497:Alloys; D003722:Dental Alloys; D006801:Humans; D008422:Materials Testing; D009532:Nickel; D016382:Orthodontic Appliance Design; D009969:Orthodontic Wires; D013314:Stress, Mechanical; D014025:Titanium
chemical_list: D000497:Alloys; D003722:Dental Alloys; C013616:nitinol; D009532:Nickel; D014025:Titanium
keywords: NiTi; Orthodontics; T-loop