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

Objective: 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. Methods: 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. Results: 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. Conclusions: 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.