Automatic Three-Dimensional Tooth Axis Using In Vivo Cone-Beam CT Images

Abstract

The tooth axis is important as a morphological reference axis; however, a general definition of the tooth axis has not been established. This study presented a novel method of automatically calculating three-dimensional tooth axes on in vivo Cone-Beam Computed Tomography (CBCT) images. In this study, 36 teeth were obtained from 12 central and lateral incisors, and canines of 3 human subjects, respectively. Human in vivo images were obtained using a CBCT at a spatial resolution of 0.183 mm³ . The automatically tooth axis (PC-A) was calculated using principal component (PC) analysis of the segmented tooth and mandible. In experimental results using 36 teeth, the average relative angular errors between the tooth axes T-A manually specified by three dentists and the PC-A automatically calculated by the proposed method were 2.2 ± 1.4° for central incisors, 1.7 ± 1.0° for lateral incisors, 2.3 ± 1.4° for canines, respectively. The relative distance errors between the T-A and the PC-A were 0.39 ± 0.17 mm, 0.39 ± 0.21 mm and 0.63 ± 0.34 mm for central incisors, lateral incisors and canines, respectively. The experimental results of this study demonstrate that the proposed method of CBCT can accurately and automatically identify individual three-dimensional tooth axes.