Anatomical Proximity Between the Retromolar Canal and Mandibular Third Molars on Cone-Beam CT: A Retrospective Study

Background/Objectives: The retromolar canal (RMC) and retromolar foramen (RMF) are anatomical variations in the posterior mandible that may lie close to mandibular third molars and may contain neurovascular structures. This study aimed to characterize RMC/RMF–third-molar proximity on cone-beam computed tomography (CBCT), with close proximity defined a priori as a minimum distance < 2 mm. Methods: This retrospective CBCT study included 100 adults (200 hemimandibles). RMC/RMF morphology and morphometry, Pell and Gregory class and position, and Winter angulation were assessed. Generalized estimating equations accounted for within-patient clustering, and inter-observer reliability was quantified. Results: RMCs were identified in 41/200 hemimandibles (20.5%; patient-clustered 95% CI, 14.9–27.6%) and 32/100 patients (32.0%; 95% CI, 23.7–41.7%). Among RMC-positive hemimandibles that also contained a third molar (n = 26), 8 showed a minimum RMC/RMF–third-molar distance < 2 mm (30.8%; patient-clustered 95% CI, 14.9–52.9%). When all hemimandibles containing a third molar were considered (n = 121), the same close-proximity configuration was present in 8 (6.6%). No statistically significant association was detected between RMC presence and third-molar presence, Pell and Gregory class or position, or Winter angulation. Inter-observer agreement was high (κ = 0.757–0.951; ICC = 0.960–0.995). Conclusions: Close RMC/RMF–third-molar proximity occurred in a substantial subset of RMC-positive sites, although precision was limited. The findings suggest that direct assessment of the RMC/RMF may offer complementary anatomical information beyond conventional impaction classifications; this hypothesis requires confirmation in larger prospective studies.