Three-dimensional comparison of mandibular shape variability across skeletal classes: Cross-sectional geometric morphometric study.

INTRODUCTION

This study aimed to compare the 3-dimensional (3D) variability of mandibular morphology across different age groups and skeletal classes.

METHODS

A retrospective analysis was conducted on cone-beam computed tomography scans from 282 patients aged 9-50 years. The participants were stratified into 6 age groups using random stratified sampling: group (G)1 (n = 51), G2 (n = 51), G3 (n = 52), G4 (n = 56), G5 (n = 41), and G6 (n = 31). Each patient was categorized according to the skeletal classification (I, II, and III). The 3D mandibular models were created using specialized software, with 32 anatomic landmarks placed on each model. Landmark configurations were aligned through generalized Procrustes analysis. Shape variation was evaluated using principal component analysis, permutational multivariate analysis of variance, and canonical variate analysis, followed by pairwise comparisons.

RESULTS

Significant differences in mandibular shape were found among age groups, especially in younger patients, whereas skeletal class showed no significant effect. The most notable differences were observed in canonical variables 1 and 2, particularly between younger groups (G1 and G2) and older groups (P <0.001). These differences involved changes in the basal mandibular contour, bicondylar width, and bigonial width. Skeletal class had no significant impact on mandibular morphology.

CONCLUSIONS

The 3D modeling revealed significant age-related changes in mandibular basal contour, transverse expansion, chin projection, ramus height and thickness, gonial angle, and anterior body curvature. This highlights the value of 3D models for precise analysis of changes in mandibular shape across ages.