Assessment of collum angle and alveolar bone plate thickness relative to tooth inclination in central incisors using CBCT: a retrospective cross-sectional study

Understanding the relationship between incisor inclination, Collum angle, and alveolar bone thickness is crucial for accurate orthodontic diagnosis and treatment planning. This study is one of the first to assess the Collum angle and buccal and lingual bone plate thickness of maxillary and mandibular central incisors with tooth inclination on cone-beam computed tomography (CBCT) scans. In this cross-sectional study, 112 CBCT scans of the maxilla and 112 CBCT scans of the mandible were three-dimensionally reconstructed using Ez3D-I version 4.1 software. The Collum angle and the labial and lingual bone plate thickness were measured on CBCT scans. The U1-palatal plane angle and the incisor mandibular plane angle (IMPA) were used to determine the inclination of maxillary and mandibular central incisors, respectively. Accordingly, the patients were assigned to three groups of low, normal, and high inclination. Data were analyzed by ANOVA, and the Kruskal-Wallis and Bonferroni tests (α = 0.05). The mean value of the Collum angle was significantly different among the three groups in both the maxilla and mandible (P < 0.001). The smallest value was recorded in the high inclination group, and the largest value was recorded in the low inclination group. The difference in labial and lingual bone plate thickness was significant among the three groups at the apex of maxillary central incisors, and at the apex and mid-root of mandibular central incisors (P < 0.05). Patients with highly inclined maxillary and mandibular central incisors had a significantly smaller Collum angle and vice versa. Tooth inclination had a significant effect on labial and lingual bone plate thickness at the apex of maxillary central incisors, and at the apex and mid-root of mandibular central incisors. Orthodontists should carefully evaluate these parameters during treatment planning to minimize the risk of complications such as root resorption and cortical bone perforation.