Hard- and soft-tissue symmetry comparison in patients with Class III malocclusion

Our aim was to describe hard- and soft-tissue asymmetry in people who have a skeletal Class III malocclusion, and to compare with those without asymmetry. We also performed a regional analysis of a possible correlation between facial soft- and hard-tissue asymmetries.

This retrospective study was performed with the use of the computed tomographic scans of 60 subjects. The skeletal Class III subjects were categorized into 2 subgroups: soft-tissue menton deviation ≤4 mm (n = 20) versus >4 mm (n = 20). The Class III groups were compared with a Class I symmetry group (n = 20). Hard and soft tissues were segmented into different morphologic areas and deviation calculated. Pearson correlation coefficients were obtained, and 1-way analysis of variance was conducted for statistical analysis.

The highest deviation in the hard tissues of the Class III asymmetry group was in the corpus region (5.55 ± 3.05 mm), with the second highest in the angulus region (4.70 ± 2.43 mm). The highest average deviation in the soft tissues was seen in the lower cheek (7.04 ± 3.46 mm). In the different study groups, the amounts of asymmetry measured in anatomic structures on the mandible were found to be highly correlated between neighboring structures.

Clinically and statistically significant differences were found in the anatomic regions located in the middle and lower thirds of the face. There was a medium or high correlation between condyle, coronoid process, ramus, and angulus regions. A low level of correlation was observed between middle face and mandibular asymmetries in hard-tissue upper cheek and lower cheek regions were correlated with different mandibular regions.