Diagnosis of Mandibular Asymmetry using 3D Mirroring

Methods: Surface models were constructed from CBCT scans of 50 patients with facial asymmetry. For the first approach, the midsagittal plane was defined as the plane passing through Nasion, ANS, and Basion. The second approach was to mirror each patient's model on an arbitrary plane and then register the original and the arbitrarily mirrored images on the cranial base. Surface distances between right and left hemimandibles and mirrors were calculated for nine anatomic regions. Paired T and the cochran-Mantel-Haenszel tests were used to test differences between the two approaches.

Results: The differences with the two methods varied at different anatomic locations. Significant differences between the two approaches were observed at the ramus (p= 0.04), body (p= 0.01), and symphysis (p= 0.005) at the right side, and the lateral pole of the condyle at the left side (p= 0.02). Positive correlations between the degree of asymmetry and the differences between the two approaches were observed at the right inferior border (p=0.048), left posterior border (p=0.04), and medial pole of left condyle (p=0.03). There was no statistically significant difference in the measurements between the left and the right side mirrors for all anatomic locations using the registered mirror approach. However a significant difference was observed in the ramus (p=0.02), the body of the mandible (p=0.03), and the symphysis area (p=0.04) when mirroring used the midsagittal plane.

Conclusion: Both mirroring techniques provided similar quantification of mandibular asymmetry in this patients' cohort. Registration on the cranial base has the potential to aid diagnosis of mandibular asymmetry. Supported by NIDCR DE-017727 and DE-018962.