The relationship between mandibular symphysis shape and lower incisor dentoalveolar compensation in Class I and Class III skeletal patterns: A CBCT study

Abstract

Aim: The aim of this study was to examine the relationship between the lower incisor dentoalveolar compensation mechanism and the morphology of the mandibular symphysis in patients with Class I and Class III malocclusions, who have different vertical growth patterns, using cone-beam computed tomography (CBCT).

Methodology: This retrospective study analyzed the CBCT scans of 60 patients, divided into four groups based on dental and skeletal characteristics: Class I normodivergent, Class I hyperdivergent, Class III normodivergent, and Class III hyperdivergent. Measurements focused on the midsagittal section of the right lower central incisor to assess the relationship between mandibular symphysis morphology and alveolar bone thickness.

​Results: There were no substantial differences observed in alveolar bone thickness or linear mandibular symphysis measures between the groups. However, significant differences were found in symphysis concavity, basal and dentoalveolar inclination, and Incisor Mandibular Plane Angle (IMPA) values (p=0.036, p=0.001, p=0.003, and p=​0.001, respectively). Further analysis revealed strong correlations between symphysial thickness, total symphysis height, dentoalveolar inclination, and convexity angle with mandibular symphysis-related alveolar bone thickness (p<0.05).

Conclusion: A positive correlation was observed between the dentoalveolar symphysis and alveolar bone thickness in all groups. In Class I patients, symphysis height was negatively correlated with alveolar bone thickness, whereas no correlation was found for symphysis thickness or inclination. In Class III patients, the symphysis shape provided some insight, but could not reliably estimate the alveolar bone thickness.