Changes and Correlation Ratio between Soft and Hard Tissue in Class III Patients Treatded by Bimaxillary Surgery

Objective:To predict soft tissue changes through study the changes and the correlation ratio between soft and hard tissue in skeletal class Ⅲ patients treated by bimaxillary surgery.Methods:29 patients with skeletal class Ⅲ who underwent bimaxillary surgery were included.A cephalometric study of pre-and post-operation was undertaken to evaluate the correlation between soft and hard tissue change.Results:Point of Sn remaind mostly unchanged.The thickness and the convexity of upper lip underwent a slight changed(P0.05).There were significant differences between pre-and post-surgery for almost all variables in lower lip and chin(P0.001).The weak or poor correlations included the landmarks which were located at the nasal tip(r0.6).The correlation between soft and incisor movements for corresponding landmarks was the highest(r0.8).Apart from lower lip,all mandibular soft tissue landmark were strongly correlated with hard tissue landmarks(r0.8).Conclusion:The correlation between nasal tip and hard tissue was poor.The correlation of upper lip to incisal was more significant than other hard tissue.The moderate correlation occurred for the landmark in the lower lip.The high correlation occurred for landmark in the chin,which should help to predict the change of the soft tissue after the surgery.