Beyond Linear Measurements: A Multidimensional Framework for Evaluating Sexual Dimorphism in Human Postcanine Tooth Size

Background: Sexual dimorphism in tooth size has been assessed on radiographs, dental casts, two-dimensional image analysis, and linear measurements are evaluated in two dimensions. These approaches evaluate isolated dimensions and may not adequately represent the three-dimensional complexity of tooth morphology. This study compared conventional odontometric measurements, centroid-based size assessments, and principal component-derived multidimensional size variables to determine whether overall tooth size exhibits sexual dimorphism. Methodology: A total of 120 dental casts (60 males and 60 females) were digitized using a laser surface scanner. Anatomical and geometric landmarks were identified on three-dimensional tooth models using 3D Slicer software. Mesiodistal, buccolingual, and diagonal dimensions were calculated from landmark coordinates, and two- and three-dimensional centroid sizes were derived. Principal component analysis was used to generate integrated multidimensional size variables. Sex differences were evaluated using independent Student’s t-tests, two one-sided tests (TOST) for equivalence, and random-effects meta-analysis. Results: Principal component analysis showed that conventional odontometric measurements and centroid sizes represented a common multidimensional size construct, explaining 79.1–91.3% of the variance across most tooth types. Centroid size demonstrated the highest component loadings, and principal component-derived variables correlated strongly with centroid size (r = 0.945–0.994; p < 0.001). No significant sex differences were observed for any principal component-derived size variable (p > 0.05). Equivalence testing and pooled meta-analysis demonstrated practical and statistical equivalence between males and females across principal component-derived variables, centroid sizes, and conventional odontometric measurements (all TOST p < 0.001). Conclusions: Conventional odontometric measurements, centroid sizes, and principal component-derived variables capture a common multidimensional construct of tooth size. Although isolated dimensions may differ, overall tooth size is practically equivalent between males and females.