Dentoalveolar characteristics in subjects with different anteroposterior relationships: a retrospective...

The collum angle, tooth dimensions, root length, and alveolar bone thickness have a significant impact on orthodontic diagnosis and treatment planning. The boundaries of orthodontic tooth movement are determined by alveolar bone thickness and dimensions while the collum angle determines the appropriate positioning of the root relative to the cortical plate. This study aimed to compare the collum angle, crown dimensions, root length, and alveolar bone thickness of the upper and lower incisors, canines, and premolars in subjects with varying anteroposterior relationships.

Cone Beam Computed Tomography (CBCT) images of 89 patients (178 teeth/tooth type) were included in the study. The patients were divided into 4 subgroups according to the incisor relationship. Group 1: Class I (64/tooth type), Group 2: Class II Div 1 (28/ tooth type), Group 3: Class II Div 2 (28/tooth type), and Group 4: Class III (58/ tooth type). The following variables were measured using Carestream CS 3D imaging software on coronal, sagittal, oblique, and reconstructed panoramic views: collum angle, mesiodistal crown width, crown height and thickness, root length, and alveolar bone thickness.

In Class II Div 2 subjects, the collum angles of the upper central and upper lateral incisors were increased. Class III subjects had an increased root length of the upper first premolars, upper central incisors, and lower first and second premolars compared to other groups. In Class II Div 2 subjects, the mesiodistal crown widths were increased in the lower canines compared to Class I and Class III and in the lower central incisors compared to Class II Div 1 and Class III, the height of the crowns was increased in the upper lateral incisors compared to Class III and Class I and in the upper central incisors compared to Class I and Class II Div 1, the buccolingual thickness of teeth was increased in the upper central incisors compared to Class I, Class II Div 1, and Class III and the alveolar bone thickness was increased compared to other groups.

Class II Div 2 subjects exhibited increased collum angle, large crown width, height, and thickness, and increased alveolar bone thickness. Class III subjects had a longer root length compared to other groups.