Abstract: Objective To analyze the sagittal root position of anterior teeth of alveolar bone in young adults with normal occlusion. Methods The subjects consisted of 73 young adults with normal occlusion, including 9 males cases and 64 female cases. And their ages ranged from 19 to 22 years, with an average of (19.89±0.70) years. Cone beam CT (CBCT) images of the subjects' craniofacial region were selected, and the data were imported into the professional software. The angle between the axis of root and the axis of alveolar bone of anterior teeth and the position of the root in the alveolar bone were measured. The relationship between the mandibular plane angle and the inclination of the central incisor and the alveolar bone thickness of the apex of anterior teeth were respectively analyzed. Results The mean of the angle between the axis of root and the axis of alveolar bone of central incisors and lateral incisors was smaller than that of canine with normal occlusion (P < 0.01). Most of the roots of maxillary anterior teeth were located at the labial of alveolar bone (94.98%), a few at the center of alveolar bone (5.02%), while most of mandibular anterior teeth were located at the center of alveolar bone (48.18%), a few at the labial of alveolar bone (34.24%). The least was located at the lingual side of alveolar bone (17.58%). With the increase of SN-MP, the SN-U1, MP-L1 and the alveolar bone thickness in mandibular apical (LW) decreased (r were -0.498, -0.421 and -0.383 respectively, P＜0.01). Conclusion In normal occlusion, roots of the maxillary anterior teeth are mostly located on the labial side of the alveolar bone, but they are mostly located on the labial side or the center of the alveolar bone in mandibular. Compared with the low-angle people, the angle of central incisors of the high-angle people is upright and the alveolar bone thickness of mandibular central incisors in the apical area is thin.

Key words: orthodontics, corrective, spiral cone-beam computed tomography, tooth apex, normal occlusion, anterior teeth