title: Maxillary incisor retraction: evaluation of different mechanisms.
abstract: OBJECTIVE
  To mechanically evaluate different systems used for incisors retraction.
  
  
  METHODS
  Three different methods for incisors retraction using 0.019 x 0.025-in stainless steel wire were evaluated. The samples were divided into three groups: Group A (retraction arch with 7-mm high vertical hooks); Group G3 (elastic chain attached to the mini-implant and to the 3-mm stainless steel hook welded to the retraction arch); Group G6 (elastic chain attached to the mini-implant and to the 6-mm stainless steel hook welded to the retraction arch). A dental mannequin was used for evaluation in order to simulate the desired movements when the device was exposed to a heat source. The analysis of variance (ANOVA) and the Tukey test were used (p < 0.05).
  
  
  RESULTS
  The results demonstrated that Groups G3 and G6 exhibited less extrusion and less incisor inclination during the retraction phase (p < 0.05). With regard to incisor extrusion, statistically significant differences were observed between Groups A and G3, and between Groups A and G6 (p < 0.05). Regarding incisor inclination, statistically significant differences were observed between the three evaluated systems (p < 0.05).
  
  
  CONCLUSIONS
  Arches with 6-mm vertical hooks allow the force to be applied on the center of resistance of the incisors, thus improving mechanical control, when compared with the other two systems.
authors.affiliation: Federal University of Rio de Janeiro - UFRJ, Brazil. antonioruellas@yahoo.com.br
authors.forename: Antônio Carlos de Oliveira
authors.initials: AC
authors.lastname: Ruellas
authors.forename: Matheus Melo
authors.initials: MM
authors.lastname: Pithon
authors.forename: Rogério Lacerda
authors.initials: RL
authors.lastname: dos Santos
mesh_terms: D000704:Analysis of Variance; D015921:Dental Implants; D006801:Humans; D007180:Incisor / Q000473:pathology*; D008310:Malocclusion / Q000628:therapy*; D008348:Manikins; D008437:Maxilla / Q000473:pathology*; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation* / Q000379:methods; D009969:Orthodontic Wires; D014087:Tooth Movement Techniques / Q000295:instrumentation* / Q000379:methods
chemical_list: D015921:Dental Implants
keywords: Fixed orthodontics; Malocclusion; Maxillary incisors