Effect of tooth agenesis on facial soft tissue profile.

This study examined the influence of tooth agenesis on the soft tissue facial profile in modern humans. The sample included 799 individuals, comprising 486 with tooth agenesis (mean = 2.5 missing teeth) and 313 controls without agenesis, including third molars. Soft tissue profile shape was quantified on pre-orthodontic lateral cephalometric radiographs using two curves and 36 fixed and sliding semi-landmarks. Shape configurations were processed through Procrustes superimposition and principal component analysis, and the resulting principal components were entered as dependent variables in sex-specific multivariate regression models. Six principal components captured approximately 90% of profile shape variation and revealed pronounced sexual dimorphism (P < 0.001). After adjusting for age, tooth agenesis significantly affected facial profile shape in both females (η² = 0.055; P < 0.001) and males (η² = 0.049; P = 0.013). Individuals with agenesis exhibited a less convex, flatter profile and reduced lip protrusion, with isolated third molar agenesis producing similar but weaker effects that reached statistical significance only in females. These findings indicate a global influence of tooth agenesis on soft tissue profile morphology, independent of the location of missing teeth, and are consistent with prior evidence of its effects on dentoalveolar and craniofacial structures. Understanding these associations may help clinicians anticipate aesthetic consequences and plan individualized treatments.