Mandibular asymmetry: Is there a difference in the bone and soft tissue thickness between both sides?

Abstract

Objective: The asymmetric mandible presents the clinician with unique anatomic challenges in orthognathic surgery correction. This study aims to investigate these characteristics of the asymmetric mandible: mandible bone thickness, soft tissue thickness, and the proximity of the bone cortex to the inferior alveolar nerve (IAN) canal.

Study design: Three-dimensional virtual models were created of 35 participants of Asian descent with mandibular asymmetry. Mandibular bone thicknesses and soft tissue thicknesses were measured at certain landmarks. Statistical analysis of the thicknesses of both sides of the mandible was performed. Comparison of thicknesses between patients with minor and major asymmetry were also performed.

Results: The bone was significantly thinner at the longer side at all 4 mandible landmarks (P < .001). The bone lateral to the IAN was significantly thinner at the longer side, as well (P < .001). The soft tissue thickness did not differ significantly across sides, except at 1 landmark. These findings were even more exaggerated in the major asymmetry group.

Conclusions: The longer side of the asymmetric mandible bone was thinner, and the bone lateral to the IAN was also thinner as a result. This asymmetric thinness was exaggerated in patients with severe asymmetry, which may predispose the longer side to IAN injury and unfavorable fractures. The differences in bone thickness in the asymmetric mandible may also result in residual postoperative asymmetry.