The position of the inferior alveolar nerve at the mandibular angle:: an anatomic consideration for aesthetic mandibular angle reduction

Mandibular angle reduction is a popular contouring surgery in Asia. Avoidance of injury to the inferior alveolar nerve is crucial during these procedures. Anatomic data regarding the position of the nerve in the mandibular angle area are sparse. The purpose of this study was to use 3-dimensional computed tomographic data to evaluate the nerve in patients with prominent mandibular angles and to compare the nerve position with a normative group. A total of 28 female and 5 male adult patients who presented with a complaint of prominent angles or a "square-face" look, as well as 20 female and 22 male adult normal subjects were included, for a total of 150 hemimandibles for extraction of the inferior alveolar nerve. The nerve and the mandible were displayed. Point O was defined on the oblique line along the anterior cortex of ramus, where it intersected with a line extending from the alveolar arch. From the O point, linear distances were defined, including horizontal distances to the posterior cortex, oblique distances to the gonion, and the vertical distances to the inferior cortex. Mandibular width was defined as the distance between the 2 gonion points. Results demonstrated significant differences mainly in the oblique distances (ie, from the O point to the nerve [O1], from the nerve to the gonion [O2], and from the O point to the gonion [O1-O2]) in both female and male patients. The O2 distance was 23.69 mm versus 20.66 mm in women and 27.30 mm versus 23.28 mm in men (square face vs norm). The mandibular width was significantly larger in the male square-face patients, but the difference was not significant between the female groups. These results provide useful information for surgeons planning mandibular angle reduction. These findings suggest that the mandibular contouring procedure should be aimed at correcting regional osseous dysmorphology in the angle area and improving the relationship to the chin, rather than merely reducing the mandibular width.