[Evaluation of condylar asymmetry in different skeletal patterns with cone-beam CT]

The aim of this study was to evaluate condylar asymmetry in different skeletal patterns with cone-beam CT (CBCT).

A total of 110 subjects aged from 18 to 30 years were selected from patients who had undergone CBCT examinations retrospectively. All the subjects were divided into three groups according to their skeletal patterns: Class Ⅰ (Cl Ⅰ: 0°≤ANB≤5°), Class Ⅱ (Cl Ⅱ: ANB>5°) and Class Ⅲ (Cl Ⅲ: ANB<0°). In addition, each group was further divided into two subgroups according to genders. Condylar (Co-Sig), ramus (Go-Sig) and condyle-plus-ramus (Co-Go) asymmetry were assessed by identifying landmarks on the reconstructed images with a 3-dimentional (3D) reference plane. The coordinates of the landmarks were calculated statistically. The data were analyzed statistically with SPSS17.0 software package.

The condyle-plus-ramus and ramus asymmetry (Co-Go R-L and Go-Sig R-L) were affected by the ANB angle (P<0.05) respectively, and the differences mainly came from the y coordinate (P<0.05). When comparing the two sides of the three groups respectively, the Co-Go, Go-Sig and Co-Sig of some patients had gender difference and left-right difference. The z coordinate of point Menton (Me) had significant difference (P<0.05) caused by different skeletal patterns, while the coordinates of x and y were similar (P>0.05).

Condyle-plus-ramus and the ramus asymmetry were affected by different skeletal patterns and the differences were caused by the height primarily. Patients of Class Ⅲ usually manifest mandibular protrusion while Class Ⅱ with mandibular retrognathism. Whether the degree of chin deviation differs according to the condylar asymmetry needs further investigation.