Do Asymmetric Faces Harbor Asymmetric Roots? A Morphologic Study of Mandibular Premolars in Human Cadavers

Mandibular first premolars exhibit notable anatomic variability, particularly in root canal morphology. Simultaneously, asymmetries between facial and dental midlines are frequently observed but rarely examined in relation to internal tooth structure. This study aimed to investigate whether midline-based anatomic asymmetry is correlated with root canal morphology.

Ten fixed cadaveric heads (6 female, 4 male) were examined. Intraoral measurements were taken using digital calipers to quantify asymmetry based on distances from mandibular premolars to facial and dental midlines. A composite asymmetry score was computed and categorized as low (≤3), moderate (3-6), or high (>6). Mandibular first premolars were extracted and sectioned to classify root canal morphology according to the Vertucci system. Statistical analyses included χ 2 , Kruskal-Wallis, Spearman correlation, and receiver operating characteristic curve analysis.

Among the 10 specimens, 5 displayed symmetrical and 5 asymmetric root canal configurations. Canal asymmetry was significantly associated with higher asymmetry scores (χ 2 , P =0.0067). The degree of canal type variation differed significantly among asymmetry categories (Kruskal-Wallis, P =0.0155). A strong positive correlation was found between total asymmetry score and canal type difference ( Ρ =0.871, P =0.001). Receiver operating characteristic analysis confirmed excellent predictive value of the asymmetry score for canal morphology asymmetry (AUC=1.00).

Facial and dental midline asymmetry is strongly associated with root canal morphologic variability. These findings suggest that asymmetry assessment could aid clinicians in anticipating complex root canal anatomies, thus optimizing diagnostic and therapeutic outcomes in endodontics.