External Facial Width as a Surrogate for Posterior Mandibular Canal Position: A CBCT-Based Morphometric Study

To determine whether bizygomatic width (Zy-Zy) is associated with posterior mandibular body width (W) at a standardized retromolar level and the relative buccolingual position of the inferior alveolar canal (IAC), expressed as the B/W ratio. This retrospective CBCT-based morphometric study included 120 adults (60 males, 60 females). Mandibular width (W) and buccal distance (B; canal center to buccal cortex) were measured bilaterally on the first coronal slice anterior to ramus disappearance, corresponding to a tooth-independent posterior mandibular body level. Bilateral measurements were averaged to obtain subject-level estimates. Sex differences were assessed using the Welch t test. Associations between Zy-Zy and mandibular variables were evaluated using Pearson correlation, with Spearman ρ as a robustness check, and multivariable regression assessed whether Zy-Zy independently predicted W or B/W after adjustment for sex. Mean Zy-Zy was 129.5±7.0 mm and was significantly greater in males (P<0.001). Mean W was 16.7±2.5 mm (P=0.020) and mean B/W was 0.44±0.08 (P=0.238). Zy-Zy showed a small association with W (Pearson r=0.162, P=0.078; Spearman ρ=0.195, P=0.033) but no association with B/W (Pearson r=0.069, P=0.456; Spearman ρ=0.037, P=0.685). In sex-adjusted regression models, Zy-Zy was not independently associated with W or B/W. Bizygomatic width shows at most a weak association with posterior mandibular body width and does not predict IAC position. CBCT evaluation remains essential for assessing posterior mandibular surgical risk.