Effect of premolar extraction and incisor retraction on the soft tissue in adult skeletal open bite subjects with miniplate anchored intrusion of maxillary posterior teeth

Objective: This study was conducted to determine the effect of premolar extraction and incisor retraction on the soft tissue profile of skeletal open bite adults following maxillary posterior teeth intrusion. Materials and Methods: Lateral cephalometric radiographs of 28 adults with skeletal open bite (age = 22.6 ± 2.1 years) were taken following molar intrusion with zygomatic miniplate skeletal anchorage and after four first premolars extraction. Several soft tissue variables were measured. Correlations, mean ratios and regression equations between the change in lip position and incisor retraction were calculated. Results:Both the upper and lower lips moved backwards by 3.46 mm ± 0.84 mm (P ≤0.01) and 0.87 mm ± 0.23 mm (P ≤ 0.05) respectively, with a significant reduction in the angle of convexity by 1.36° ± 0.24° (P ≤ 0.05). Strong correlations were found between the amount of upper incisor retraction and backward movement of the upper lip with a mean ratio of 1.04:1 (r = 0.812, P ≤ 0.01) and with the reduction of soft tissue convexity angle with a mean ratio of 2.65:1 (r = 0.814, P ≤ 0.01) and between the lower incisor retraction and backward movement of the lower lip with a mean ratio of 0.76:1 (r = 0.802, P ≤ 0.01). Conclusion: The pattern of change in soft tissue profile in this study was similar to studies of premolar extraction without prior molar intrusion. However, the ratio of change of upper lip position relative to the upper incisor retraction was higher compared to ratios reported in the literature which may be attributed to the underlying long face skeletal pattern.