Face convexity changes in class Ⅱ malocclusion patients after Twin-block appliance therapy / 中国组织工程研究

ABSTRACT

BACKGROUND: Twin-block appliance has been confirmed to efficiently change hard tissue and the profile of soft tissue.Whether a linear relationship exists between soft tissue and hard tissue changes remains unclear.OBJECTIVE: To evaluate the face convexity changes of soft and hard tissues after Twin-block appliance therapy and compare with controls.METHODS: Thirty-one class Ⅱ division 1 malocclusion subjects with hand-wrist radiographs in FG-G stage were selected.Among the 31 patients,17 received Twin-block appliance therapy,serving as experimental group,and the remaining 14 subjects abandoned treatment,serving as control group.Cephalometric radiographs of each included subject were taken prior to and after treatment or observation.Face convexity of soft and hard tissues,as well as the face convexity changes,was compared between the experimental and control groups.Linear regression equation was employed to analyze the linear association between soft-and hard-tissue changes.Regression equations of experimental and control groups were compared.RESULTS AND CONCLUSION: Prior to and after Twin-block appliance therapy,a significant correlation existed between the position changes of superior and inferior alveolar sockets relative to the nose and mandible,and the position changes of upper and lower lip pits relative to the nose and mandible,i.e.,there was a linear correlation between A-E change and Ss-E change,and between B-E change and Si-E change.The largest Pearson's correlation coefficient(0.839)appeared between Si-E change and B-E change,indicating the best correlativity between these two changes.Statistical analysis revealed that the linear equations of face convexity changes of soft and hard tissues after Twin-block appliance therapy were Si-E=0.745 B-E,Ss-E=0.276 A-E.These linear equations would be helpful to explain mandible growth and face convexity change after Twin-block appliance therapy and predict the prognosis of face convexity change.