title: Quantification of tooth displacement from cone-beam computed tomography images.
abstract: BACKGROUND
  The objectives of this study were to demonstrate a method that could be used to quantify three-dimensional (3D) tooth displacement from cone-beam computed tomography (CBCT) images and to assess its accuracy.
  
  
  METHODS
  Images of the same mandible taken 2 weeks apart with no treatment were used. Four mandibular teeth-left lateral incisor, left canine, left first premolar, and left first molar-either remained unmoved or were artificially displaced with known values on 1 image to simulate after-treatment conditions. The iterative closest point method was used to superimpose the unchanged bony part of the mandible and to find the transformation matrix between a tooth's 2 positions, before and after displacement. Tooth displacement was calculated from the transformation matrix.
  
  
  RESULTS
  All 6 displacement components in terms of translations along and rotations about the 3 axes on the tooth were obtained. The results showed that the errors could be managed: they were less than 5% in translation and 10% in rotation.
  
  
  CONCLUSIONS
  The 3D tooth displacement can be obtained from CBCT images, and the accuracy is acceptable for clinical use and can be improved when the quality of the images improves.
authors.affiliation: Department of Mechanical Engineering, Indiana University Purdue University, Indianapolis, Indianapolis, IN 46202, USA. jchen3@iupui.edu
authors.forename: Jie
authors.initials: J
authors.lastname: Chen
authors.forename: Shuning
authors.initials: S
authors.lastname: Li
authors.forename: Shiaofen
authors.initials: S
authors.lastname: Fang
mesh_terms: D000328:Adult; D000465:Algorithms; D019412:Anatomy, Cross-Sectional; D001641:Bicuspid / Q000000981:diagnostic imaging; D002508:Cephalometry / Q000379:methods; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D003481:Cuspid / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D007180:Incisor / Q000000981:diagnostic imaging; D008334:Mandible / Q000000981:diagnostic imaging; D008963:Molar / Q000000981:diagnostic imaging; D015203:Reproducibility of Results; D012399:Rotation; D014070:Tooth / Q000000981:diagnostic imaging*; D014087:Tooth Movement Techniques