Background/Objectives: This study aimed to clarify the differences in the position of cone beam computed tomography (CBCT) landmarks according to different midsagittal planes (MSPs) in patients with skeletal Class III facial asymmetry.
Materials/Methods: Pre-treatment CBCT data from 60 patients with skeletal Class III were used. These patients were classified into symmetric (menton deviations of <2 mm) or asymmetric (menton deviations of >4 mm) group. Notably, six MSPs were established based on the previous research, and three-dimensional analyses were performed with respect to the planes in both groups. Subsequently, the measurement outcomes were statistically compared.
Results: A statistically significant interaction (P < 0.01) was observed between MSPs and facial asymmetry. No significant difference was observed among the MSPs in the symmetric group. Conversely, in the asymmetric group, significant differences in the linear measurements were identified among the MSPs; specifically, the upper facial MSP clearly revealed both maxillary and mandibular transverse asymmetry. Meanwhile, the anterior nasal spine (ANS)-associated MSP could not identify the maxillary asymmetry. Especially, the menton deviation was approximately 3 mm lower when estimated using the ANS-associated MSP compared to the estimate using the upper facial MSP.
Conclusions/Implications: When diagnosing a patient with asymmetry, the choice of MSP can significantly affect the treatment outcome. Therefore, in actual clinical practice, care should be taken when selecting an MSP.

Keywords: facial asymmetry, midsagittal plane, cone-beam CT, diagnosis