Anatomical Study of the Mandibular Angle and Body in Wide Mandibular Angle Cases

Background: Mandibular angle reduction surgery is widely used for aesthetic purposes. Because inferior alveolar nerve injury is a common complication of this surgery, the anatomical location of this nerve must be known before surgery. This study investigated the relative location of the inferior alveolar nerve in mesofacial and brachyfacial groups.

Methods: Panoramic views of patients were divided into Groups A (gonial angle < 120°) and B (gonial angle > 120°). For the analysis, the magnification of each image was standardized and the following parameters were measured: (1) gonial angle; (2) distance from the alveolar ridge at the center of the first and second premolars and first and second molars to (a) the inferior margin of the inferior alveolar canal and (b) the inferior margin of the mandible; (3) distance from the posterior alveolar ridge to the gonial angle and to (a) on the same line; (4) size of the first and second molars.

Results: Statistical analysis showed that there were no significant differences (P > 0.05) between Group A and Group B with respect to the distance from the alveolar ridge to the inferior alveolar canal in the first premolar, second premolar, and first molar. The differences between Group A and Group B with respect to the distance from the alveolar ridge to the inferior margin of the mandible for the second premolar, first molar, second molar and gonial angle were 0.7, 1.5, 2.8, and 7.0 mm, respectively (P < 0.05). The differences between Group A and Group B with respect to the distances from the inferior margin of the inferior alveolar canal to the inferior margin of the mandible for the same landmarks were 0.7, 1.1, 1.3, and 5.7 mm, respectively (P < 0.05).

Conclusion: The difference in length from the alveolar ridge to the mandibular canal between the two groups was minimal, but the length to the gonial angle differed significantly. These results will help reduce inferior alveolar nerve injury during mandibular angle reduction surgery.

Level of Evidence IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.