Quantitative evaluation of cortical bone thickness in mandibular prognathic patients with neurosensory disturbance after bilateral sagittal split osteotomy.

[PURPOSE] The buccal cortical thickness (BCT) between the mandibular canal and the corresponding external cortical surface was compared in patients with and without neurosensory disturbance (NSD) after they underwent a bilateral sagittal split osteotomy (BSSO) to correct mandibular prognathism.

[PATIENTS AND METHODS] This prospective cohort study was conducted in 146 patients (95 women, 65.1%; 51 men, 34.9%) 18 to 39 years old who underwent bimaxillary surgery (ie, Le Fort I osteotomy and BSSO) to correct mandibular prognathism. NSD was identified using a light touch test with a Semmes-Weinstein monofilament and a pricking pain test with a sharp dental explorer 1 week after surgery. Preoperative cone-beam computed tomographic (CBCT) imaging was used to visualize the bone contacts or fusion of the mandibular canal to the buccal cortical bone and to decrease injury to the mandibular nerve during surgical dissection. Preoperative CBCT imaging also was used to assess the BCT every 2 mm from the mandibular foramen to the furcation of the mandibular first molar in the NSD group and the sensory normal (N) group.

[RESULTS] The incidence of NSD was 32.5% at 1 week after surgery. There was no statistically significant difference between men and women, the side affected, or genioplasty at the time of undergoing BSSO. Of the total sample group, decreased BCT was identified throughout the observed length of the mandibular canal in the NSD group compared with the N group. Statistically significant decreased BCTs were 16 to 20 mm and 24 mm in the total sample, 6 to 8 mm in the female group, and 16 to 18 mm in the male group.

[CONCLUSION] Compared with the N group, BCTs in the NSD group were always decreased, especially those located at 16 to 20 mm and 24 mm in the total sample, 6 to 8 mm in the female group, and 16 to 18 mm in the male group.