Correlation analysis of three-dimensional changes of hard and soft tissues in class III orthognathic surgery patients using cone-beam computed tomography

BACKGROUND: This study was to investigate the correlation between changes of the soft and hard tissues three-dimensionally in class III orthognathic patients using cone-beam computed tomography. METHODS: Cone-beam computed tomography images were obtained within 2 weeks before surgery and at 6 months after surgery in 18 adult class III patients who underwent Le Fort I osteotomy and bilateral intraoral vertical ramus osteotomy. Subjects were divided into group 1 with no mandibular asymmetry (menton deviation, <2 mm; n = 9) and group 2 with mandibular asymmetry (menton deviation, >4 mm; n = 9). Landmarks were designated on the reconstructed three-dimensional models. Correlations and proportions of changes of the soft tissue to hard tissue were calculated. RESULTS: There were significant correlations of ΔB' to ΔB and ΔPog' to ΔPog in both groups on the horizontal axis (P < 0.05), and their proportions were 0.53 and 0.67 in group 1 and 0.77 and 0.88 in group 2, respectively. There were significant correlations of ΔB' to ΔB, ΔPog' to ΔPog, and ΔMe' to ΔMe on the sagittal axis in both groups (P < 0.05), and their proportions were 0.94, 0.84, and 0.96 in group 1 and 0.95, 0.91, and 1.03 in group 2, respectively. There were significant correlations of the three-dimensional distances between ΔB' to ΔB, ΔPog' to ΔPog, and ΔMe' to ΔMe in both groups (P < 0.05), and their proportions were 0.92, 0.79, and 0.95 in group 1 and 0.92, 0.88, and 0.97 in group 2, respectively. However, there were no significant correlations between changes in soft and hard tissues on the vertical axis in both groups (P > 0.05). CONCLUSIONS: In class III orthognathic patients with mandibular asymmetry, the proportions of ΔB' to ΔB, ΔPog' to ΔPog, and ΔMe' to ΔMe on the horizontal and sagittal axes and the three-dimensional distances were different from patients with no mandibular asymmetry.