Introduction: Because transverse dental compensation prevents lateral movement of the mandible in orthognathic surgery, it should be removed through the preoperative orthodontic treatment. We analyzed the extent of transverse dental decompensation using computer tomography.

Patients and methods: We analyzed 23 patients who were referred to Seoul Asan Medical Center to get orthognathic surgery with preoperative orthodontic treatment to restore facial asymmetry from January 2007 to March 2011. Cone Beam CT scan was taken to diagnose and plan orthognathic surgery. We measured inclination angle of the buccolingual tooth axis of the first molar and inclination angle of the mandibular body in the deviated side and the non-deviated side.

Results: We used nonparametric Wilcoxon rank sum test to analyze corresponding pairs of variables. Deviated side mandibular molar tooth axis inclination tends to be smaller than that of non-deviated side. It shows statistically significant difference ( p = 0.016). Deviated side body inclination tends to be smaller than non-deviated side body inclination. Deviated side maxillary molar tooth axis inclination tends to be larger than that of the non-deviated side. But these are not statistically significant.

Conclusion: We evaluated the transverse dental decompensation after preoperative orthodontic treatment. There was statistically significant difference between both side mandibular molar tooth axis inclinations. Therefore, we found that preoperative orthodontic treatment was unable to get the complete transverse dental decompensation. To get over these limitations, we had to consider increased buccal overjet or posterior scissor bite especially in severe cases.

Conflict of interest: None declared.