Morphological evaluation of the chin and symphysis and its relationship with occlusal planes in skeletal Class II malocclusions

Background: To investigate the correlation between the inclination of occlusal planes (OPs) and the morphologies of the chin and mandibular symphysis in skeletal Class II malocclusion. Methods: This retrospective study utilized cone beam computed tomography (CBCT) to explore the relationship of the occlusal plane (OP) inclinations with the chin and mandibular symphysis in different skeletal patterns. A total of 150 children aged 6–12 years were recruited for this study. The included cases were categorized into three groups: normodivergent skeletal Class I malocclusion (IN ), normodivergent skeletal class II malocclusion (IIN ) and hyperdivergent skeletal Class II malocclusion (IIH ). Each group consisted of 50 individuals. Results: In terms of the contours of the chin and mandibular symphysis, the IN group had the broadest and shortest shapes, whereas the IIH group had the thinnest and tallest morphologies. No significant differences in chin volume were found among the three groups. Compared with those in IN group, the anterior occlusal plane (AOP) and posterior occlusal plane (POP) were steeper in the groups with skeletal Class II malocclusion. In addition, there was a negative correlation between the OPs and the height and width of the chin and mandibular symphysis, as well as the position of the chin. Conclusions: In individuals with skeletal Class II malocclusion, the development of the height and width of the chin and mandibular symphysis may be related to the inclination of the OPs.