Chen Jie, Li Shuning, Fang Shiaofen
Department of Mechanical Engineering, Indiana University Purdue University, Indianapolis, Indianapolis, IN 46202, USA.
Am J Orthod Dentofacial Orthop. 2009 Sep;136(3):393-400. doi: 10.1016/j.ajodo.2007.10.058.
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.
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.
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.
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.
本研究的目的是展示一种可用于从锥形束计算机断层扫描（CBCT）图像中量化三维（3D）牙齿位移并评估其准确性的方法。
使用在未进行治疗的情况下相隔2周拍摄的同一下颌骨的图像。四颗下颌牙齿——左侧切牙、左尖牙、左第一前磨牙和左第一磨牙——要么保持不动，要么在一张图像上以已知值进行人工位移以模拟治疗后的情况。使用迭代最近点法叠加下颌骨不变的骨部分，并找到牙齿位移前后两个位置之间的变换矩阵。根据变换矩阵计算牙齿位移。
获得了牙齿沿3个轴的平移和绕3个轴的旋转方面的所有6个位移分量。结果表明误差是可控的：平移误差小于5%，旋转误差小于10%。
可以从CBCT图像中获得三维牙齿位移，其准确性在临床应用中是可以接受的，并且当图像质量提高时可以得到改善。
