Anterior alveolar bone and tooth inclination in different skeletal patterns: a cone-beam computed tomography study

BACKGROUND: Despite the importance of dentoalveolar compensation in orthodontic treatment, the inclination of alveolar bone and its relationship with the incisors remain unclear in patients with different skeletal malocclusions. This study aimed to assess anterior alveolar bone inclination (ABI), tooth inclination (TI), and the angulation between them in patients with different skeletal patterns, using a novel method to define ABI, and explore skeletal parameters correlated with ABI. METHODS: Based on cone-beam computed tomography images of 79 adult patients, the ABI, TI, and the angulation between them were measured in the central incisor region. The subjects were classified into skeletal Class I, Class II division 1, Class II division 2, and Class III groups, and hypodivergent, normodivergent, and hyperdivergent groups. One-way analysis of variance was performed for intergroup comparison. Craniofacial skeletal parameters were also measured to evaluate correlations with ABI through correlation analysis. RESULTS: The ABI and TI were smallest in skeletal Class II division 2 patients in maxilla and decreased gradually in skeletal Class II, I, III patients in mandible (P < 0.01). In terms of vertical skeletal patterns, the ABI in maxilla and the ABI and TI (related to the mandibular plane) in mandible decreased in hypodivergent, normodivergent, and hyperdivergent patients (P < 0.01). The angulation between ABI and TI in maxilla was smaller in hyperdivergent patients and largest in skeletal Class II division 2 patients (P < 0.05). Correlation analyses revealed that the ABI had correlations with TI, ANB, SN-MP, FHI, gonial angle, Y-axis angle, etc. CONCLUSIONS: The anterior ABI and TI, as well as the angulation between them, show significant variations across different skeletal patterns. ABI also exhibits correlations with several skeletal parameters. These variations should be considered in orthodontic treatment planning to reduce the risk of iatrogenic complications.