title: Measurement of plastic and elastic deformation due to third-order torque in self-ligated orthodontic brackets.
abstract: BACKGROUND
  Control of root torque is often achieved by introducing a twist in a rectangular archwire. The purpose of this study was to investigate third-order torque on different types of self-ligated brackets by analyzing the bracket's elastic and plastic deformations in conjunction with the expressed torque at varying angles of twist.
  
  
  METHODS
  An orthodontic bracket was mounted to a load cell that measured forces and moments in all directions. The wire was twisted in the bracket via a stepper motor, controlled by custom software. Overhead images were taken by a camera through a microscope and processed by using optical correlation to measure deformation.
  
  
  RESULTS
  At the maximum torquing angle of 63° with 0.019 × 0.025-in stainless steel wire, the total elastic and plastic deformation values were 0.063, 0.033, and 0.137 mm for Damon Q (Ormco, Orange, Calif), In-Ovation R (GAC, Bohemia, NY), and Speed (Strite Industries, Cambridge, Ontario, Canada), respectively. The total plastic deformation values were 0.015, 0.006, and 0.086 mm, respectively, measured at 0° of unloading.
  
  
  CONCLUSIONS
  In-Ovation R had the least deformation due to torquing of the 3 investigated bracket types. Damon Q and Speed on average had approximately 2.5 and 14 times greater maximum plastic deformation, respectively, than did In-Ovation R.
authors: Department of Mechanical Engineering, Faculty of Engineering, University of Alberta, Edmonton, Alberta, Canada.
authors: Thomas W
authors: TW
authors: Major
authors: Jason P
authors: JP
authors: Carey
authors: David S
authors: DS
authors: Nobes
authors: Giseon
authors: G
authors: Heo
authors: Paul W
authors: PW
authors: Major
mesh_terms: D003722:Dental Alloys; D003799:Dental Stress Analysis; D004548:Elasticity; D016014:Linear Models; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D013193:Stainless Steel; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D019415:Torque
chemical_list: D003722:Dental Alloys; D013193:Stainless Steel