Three-dimensional analysis of mandibular morphology asymmetry and temporomandibular joint position in patients with unilateral Brodie bite.

OBJECTIVE: Previous studies have shown unilateral posterior crossbite is associated with mandibular asymmetry in morphology and position. However, it remains unclear whether unilateral Brodie bite plays a similar role in mandibular development. Therefore, this study aims to investigate the morphological and positional symmetry of mandibles in patients with unilateral Brodie bite by three-dimensional anaylsis.

METHODS: Fourteen patients with unilateral Brodie bite (mean age 18.43 ± 4.24 years) and fourteen sex- and age-matched patients with normal occlusion (mean age 18.07 ± 5.48 years) underwent cone-beam computed tomography (CBCT) scans. 3D surface mesh models of their mandibles were established using Mimics Research 19.0. The surface matching percentage was compared between the original and mirrored mandible by Geomagic Control X software. Furthermore, the dimension and position of the temporomandibular joint (TMJ) were determined for both groups using InVivoDental 5.0.

RESULTS: For surface-to-surface deviation analysis, the percentage of mismatch in patients with unilateral Brodie bite was significantly higher than the control group at ±0.50 mm, ±0.75 mm, and ±1.00 mm tolerance (P < .001). In patients with unilateral Brodie syndrome, the condyles on the scissors-bite side showed a significantly more anterior position (P = .03), greater medial inclination (P < .01), and larger posterior TMJ space (P = .01) than the non-scissors-bite side.

CONCLUSION: Patients with unilateral Brodie bite exhibit a more asymmetrical mandibular morphology, with a greater anterior condylar position and posterior joint space on the scissors-bite side, indicating that early diagnosis and treatment may be necessary for patients with unilateral Brodie bite.