Geometric morphometric analysis of maxillary molar sexual dimorphism: A cross-sectional study

The sexual dimorphism of permanent maxillary molars has been extensively documented through metric and subjective shape analysis. The aim of this study was to evaluate sexual dimorphism in the shape of permanent maxillary first (UM1) and second molars (UM2) using geometric morphometric analysis.

This cross-sectional study analysed digitized dental casts from 60 males and 60 females. The casts were scanned using a laser surface scanner, and 28 three-dimensional landmarks, defined based on anatomical and geometric landmarks, were marked using SlicerMorph software. The shape data was then analysed using Procrustes superimposition, principal components analysis, regression, and discriminant function analysis to test the shape changes, allometry, and differences between the sexes.

Centroid size did not differ significantly between sexes for UM1 and UM2 (p > 0.05). Shape differences were not significant in UM1 (p = 0.15) but were significant in UM2 (p = 0.01). Allometry was observed in both molars, with a greater contribution in UM2 (6.96%) compared to UM1 (2.39%) (p < 0.001). Discriminant function analysis identified patterns of shape variation between groups; however, these findings should be interpreted cautiously as no cross-validation was performed.

Geometric morphometric analysis identified significant shape differences in the maxillary second molar. These findings demonstrate the utility of 3D geometric morphometric analysis for assessing tooth shape variation and support its application to evaluating sexual dimorphism of maxillary molars. Further studies involving larger and more diverse populations are warranted to validate these findings.