CBCT-Based Assessment of Mandibular Canal Position and Bone Morphology at Critical Osteotomy Sites for Sagittal Split Ramus Osteotomy.

Background/Objectives: Variation in the mandibular canal and surrounding bone may affect surgical risk during sagittal split ramus osteotomy (SSRO). This study examined whether canal position and bone morphology at SSRO-relevant sites differ according to mandibular sagittal position. Methods: This retrospective cone-beam computed tomography study included 72 adults classified as retrognathic, normal, or prognathic according to the SNB angle. Bilateral measurements from 144 mandibular canals were obtained at the mandibular foramen entrance, ramus-corpus transition, and mesial aspect of the second molar. Cortical and cancellous bone thicknesses, canal diameter, and canal-to-cortex distances were compared using one-way analysis of variance with Tukey's post hoc test. Repeated measurements showed high reproducibility, with intraclass correlation coefficients exceeding 0.90. Results: At the mandibular foramen entrance, retrognathic patients had greater fusion of the buccal and lingual cortices-to-foramen and buccal cortex-to-canal distances than normal patients (both p < 0.05). Lingual cortical bone at the ramus-corpus transition was also thicker in the retrognathic group (p = 0.006). At the second molar level, the prognathic group showed greater buccal, lingual, and inferior cortical thicknesses but lower buccal cancellous bone thickness (all p < 0.05). Mandibular canal diameter did not differ significantly among the groups. Conclusions: Mandibular sagittal position was associated with regional differences in the bone surrounding the mandibular canal. Lower buccal cancellous bone thickness in prognathic patients may indicate less bony separation between the canal and the surgical field. These findings may inform patient-specific CBCT assessment and SSRO planning, although their relationship with surgical complications requires prospective clinical validation.