Do Mandibular Functional Units Exhibit Inherent Asymmetry in Adults With a Normal Degree of Chin Deviation? a Cone-Beam Computed Tomography Study

Objectives: This study aimed to investigate the inherent asymmetry of mandibular functional units and to compare the degree of asymmetry between adults with a normal degree of chin deviation from different sagittal skeletal patterns using cone beam computed tomography (CBCTs)
Methods: Ninety CBCTs scans of normodivergent adults with a normal degree of chin deviation, representing different sagittal skeletal patterns (Classes I, II, and III) were included; 30 each. Three-dimensional mandibular models were generated, and volumetric and linear bilateral measurements were obtained for the hemimandible and the condylar, coronoid, ramus, angular, alveolar, body, and chin units. The degree of asymmetry was presented using the asymmetry index (AI) and between groups measurements were compared using ANOVA test and GEE model
Results: The mean AI values were significantly higher than 0% across all measurements for all sagittal skeletal patterns (P<0.001). Volumetric measurements yielded higher overall AI values than linear measurements (3.55 ± 0.13 vs 1.83 ± 0.06, P<0.001). Negative and positive correlation values were found between mandibular units, thus supporting the theory of compensatory mechanism of the mandible. In all groups, the coronoid process volume and angular unit length exhibited the highest degree of asymmetry, whereas the total body length and hemimandibular volume demonstrated the lowest. No significant differences were found in the AI of volumetric or linear measurements between sagittal skeletal patterns (P<0.05)
Conclusions: Volumetric and linear measurements of mandibular functional units exhibited a degree of asymmetry in normodivergent adults with a normal degree of chin deviation from different sagittal skeletal patterns