title: Deformation and warping of the bracket slot in select self-ligating orthodontic brackets due to an applied third order torque.
abstract: OBJECTIVE
  To measure the plastic deformation of three different self-ligated brackets as a result of third order torque by analysing slot dimensions and determine its impact on torque play.
  
  
  METHODS
  Three different self-ligating orthodontic brackets (0·022-inch slot) were investigated: Damon Q®, In-Ovation R®, and Speed® (30 per group). A digital SLR camera coupled to a microscope was used to capture images of the slot profile of each bracket before and after torquing. Each bracket was torqued to 63° in the same manner using a 0·019×0·025-inch SS wire.
  
  
  RESULTS
  The mean change in slot height as measured at the top of the slot was 0·013 mm (SD 0·020), 0·007 mm (SD 0·010) and 0·070 mm (SD 0·03) for Damon Q®, In-Ovation R® and Speed®, respectively. Slot taper increased 0·75° (SD 0·96), 0·41° (SD 1·05) and 9·30° (SD 4·24), respectively. Increase in torque play was calculated to be 0·9, 0·6 and 7·7° respectively, as calculated using the novel formula presented in this study.
  
  
  CONCLUSIONS
  Damon Q® and In-Ovation R® maintain high levels of linearity in the shape of the slot walls and experience small, but significant amounts of plastic deformation that are physically insignificant. Speed® demonstrates the most plastic deformation with visually identifiable warping in the bracket slot.
authors.affiliation: Paul William Major, Department of Dentistry, Faculty of Medicine and Dentistry, 5 - 748, Edmonton Clinic Health Academy (ECHA), University of Alberta, 11405-87 Avenue, Edmonton, AB, Canada. major@ualberta.ca
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Major
authors.forename: Jason P
authors.initials: JP
authors.lastname: Carey
authors.forename: David S
authors.initials: DS
authors.lastname: Nobes
authors.forename: Giseon
authors.initials: G
authors.lastname: Heo
authors.forename: Paul William
authors.initials: PW
authors.lastname: Major
mesh_terms: D003799:Dental Stress Analysis; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D023861:Photography, Dental / Q000295:instrumentation; D054159:Torsion, Mechanical