Cone-beam computed tomography digital for measuring the inclination angle to the long axis of healthy maxillary anterior teeth and morphologically characterizing their labial bone plates

Abstract

We aim to determine the thickness of the labial plate, the distance between the cement-enamel junction (CEJ) and alveolar crest, and the inclination angle of the long axis of healthy maxillary anterior teeth by using cone- beam computed tomography (CBCT). A total of 345 CBCT volumes obtained by Newtom VGI® CBCT were analyzed by using the NNT software. The digital measurements of the labial bone plate thickness at level 4 mm below the CEJ, the midpoint of tooth root and the radiological tooth apex, the distance between the CEJ and alveolar crest, and the angle between the long axis of the teeth and the long axis of alveolar process were obtained from the mid-sagittal planes of maxillary incisors and canines. Plate thickness 4 mm below the CEJ was measured, and values below ≥1 mm were recorded. In the central incisor, 1) the angle between the long axis of the teeth and alveolar bone was 15.2°±6.2°, the distance between the CEJ and alveolar crest was (1.5±1.0) mm, labial bone plate thick-ness at 4 mm below the CEJ was (0.8±0.4) mm, the midpoint of tooth root was (0.6±0.4) mm, and the radiological tooth apex was (1.3±0.7) mm; in the lateral incisor, 16.2°±8.8°, (1.6±1.0) mm, (0.7±0.5) mm, (0.4±0.6) mm, and (1.1±0.7) mm, respectively; and in the canine, 19.0°±6.2°, (1.8±1.0) mm, (0.9±0.6) mm, (0.4±0.6) mm, and (1.2±0.7) mm, respectively. 2) The frequencies of plate thickness ≥1 mm were 28.3%, 25.8%, and 42.7% in the central incisor, lateral incisor, and canine, respectively. 3) The distance between the CEJ and alveolar crest was positively correlated with age. The correlation coefficients was 0.42 (P<0.01) in the central incisor, 0.50 (P<0.01) in the lateral incisor, and 0.62 (P<0.01) in the canine. The thickness of labial bone plate is thin, the distance from CEJ to alveolar crest increases with age, and the long axis of the teeth is more inclined than the long axis of alveolar process. Knowledge of these special morphological characteristics can improve the safety and result for many dental procedures.