抄録
The tooth axis is an important as a morphological reference axis. However, a general definition of the tooth axis has not been established. The aim of this study was to use cone beam computed tomography (CBCT) to determine three-dimensional tooth axes (PC-A) based on principal component analysis automatically, and to estimate errors in the axes compared with those determined using micro-computed tomography (μCT), the standard of reference. We compared the tooth axis PC-A using three differential modes of CBCT (spatial resolution: D-mode = 0.1 × 0.1 × 1.0 mm^3, I-mode = 0.19 × 0.19 × 1.0 mm^3, A-mode = 0.3125 x 0.3125 x 1.0 mm^3) and uCT (spatial resolution: 0.033 × 0.033 x 0.033 mm^3) imaging of 22 human teeth: three incisors, four canines, seven premolars, and eight molars. The average relative angular errors and distance errors of PC-A between μCT and I-mode of CBCT were 0.51 ± 0.22 deg. and 0.16 ± 0.10 mm, respectively. As experimental results using the 22 teeth, the average relative angular errors between the tooth axes manually specified by three dentists and the PC-A automatically calculated from I-mode of CBCT with the proposed method were 1.97 ± 0.60 deg. for incisors, 1.92 ± 0.96 deg. for canines, 3.05 ± 1.28 deg. for premolars and 3.98 ± 1.43 deg. for molars, respectively.
