title: Three-dimensional canine displacement patterns in response to translation and controlled tipping retraction strategies.
abstract: OBJECTIVE
  To validate whether applying a well-defined initial three-dimensional (3D) load can create consistently expected tooth movement in patients.
  
  
  METHODS
  Twenty-one patients who needed bilateral canine retraction to close extraction space were selected for this split-mouth clinical trial. After initial alignment and leveling, two canines in each patient were randomly assigned to receive either translation (TR) or controlled tipping (CT) load. The load was delivered by segmental T-loops designed to give specific initial moment/force ratios to the canines in each treatment interval (TI), verified with an orthodontic force tester. Maxillary dental casts were made before canine retraction and after each TI. The casts were digitized with a 3D laser scanner. The digital models were superimposed on the palatal rugae region. The 3D canine displacements and the displacement patterns in terms of TR, CT, and torque were calculated for each TI.
  
  
  RESULTS
  The method can reliably detect a TR displacement greater than 0.3 mm and a rotation greater than 1.5°. Ninety-two TIs had displacements that were greater than 0.3 mm and were used for further analysis. Most displacements were oriented within ±45° from the distal direction. The displacement pattern in terms of TR or CT was not uniquely controlled by the initial moment/force ratio.
  
  
  CONCLUSIONS
  The initial load system is not the only key factor controlling tooth movement. Using a segmental T-loop with a well-controlled load system, large variations in canine displacement can be expected clinically.
authors.affiliation: a  Postdoctoral Fellow, Department of Mechanical Engineering, Indiana University Purdue University Indianapolis, Indianapolis, Ind.
authors.forename: Shuning
authors.initials: S
authors.lastname: Li
authors.forename: Zeyang
authors.initials: Z
authors.lastname: Xia
authors.forename: Sean Shih-Yao
authors.initials: SS
authors.lastname: Liu
authors.forename: George
authors.initials: G
authors.lastname: Eckert
authors.forename: Jie
authors.initials: J
authors.lastname: Chen
mesh_terms: D001696:Biomechanical Phenomena; D003481:Cuspid / Q000473:pathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007834:Lasers; D008297:Male; D016382:Orthodontic Appliance Design; D019516:Orthodontic Space Closure / Q000379:methods; D009969:Orthodontic Wires; D012399:Rotation; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques / Q000295:instrumentation / Q000379:methods*; D019415:Torque; D055815:Young Adult
keywords: Controlled tipping; Orthodontic tooth movement; Translation