Morphological analysis of 3DMRI in patients with mandibular asymmetry

Objectives: Accurate and reproducible three-dimensional (3D) reconstructed images are important for treatment planning of mandibular asymmetry. The purposes of this study were to investigate the differences in size of the mandible between deviated and non-deviated sides in patients with mandibular asymmetry, and to compare these parameters with values obtained in controls.

Methods: The study was carried out in 20 patients with skeletal mandibular asymmetry: ten females and ten males, 16-28 yrs of age. The discrepancy between the midline of the upper and lower incisors ranged from 3 to 11 mm. The controls (normal skull shape, normal occlusion, and no craniomandibular dysfunction) were 20 adults: ten females and ten males, 20-30 yrs of age. The distances and angles between landmarks (condyle, mandibular angle, mental edge, and incisor) measured on reconstructed high-resolution 3D MRI (Dr. View/PRO, AJS Co. Ltd.). Then, the ratio of the length of the condylar process to that of the ramus was calculated. The data of the deviated and non-deviated sides were statistically analyzed for significant difference. Each side of the deviated and non-deviated sides was compared with values in the controls.

Results: In patients, all data showed significant difference between the deviated and non-deviated sides (p < 0.01, paired t-test). Compared with controls, condylar process, from condyle to incisor or mental edge were longer on the non-deviated side of the patients than those values from controls (p < 0.01, t-test with Bonferroni). The ratio of the length of the condylar process to the ramus showed 44.5 in control; 44.3 (deviated side) and 48.2% (non-deviated side) in patients.

Conclusion: Overgrowth of the condylar process may exert an influence on the mandibular deviation in patients with mandibular asymmetry.

Supported by Grants in Aid of Scientific Research from the Ministry of Education, Japan (No. 19390479).