Quantification of tooth displacement from cone-beam computed tomography images

Introduction: The objectives of this study were to demonstrate a method that could be used to quantify threedimensional (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. (Am J Orthod Dentofacial Orthop 2009; 136: 393-400)