The Cephalometric Changes Of The Morphology Of The Symphysis After Extraction In Angle Class â…¡ Division 1 Malocclusion

Objective:To investigate the effects of extraction to the morphology of symphysis and the relationship between lower incisors retraction and the changes of the symphysis by evaluating the cephalograms of patients with Angle Class II Division 1 malocclusion.,in order to provide a reference to clinical treatment. Methods:A total of 45 subjects (20boys and 25 girls) treated with Edegewise appliance were divided into 3 groups with extracting 4 first premolars,extracting upper first premolars and lower second premolars,and nonextraction.Lateral head films in habitual occlusion from before and after a average treatment period of 1.37 years were evaluated. During the evaluation ,measure the morphology of symphysis ,the position of the incisors and the profile before and after treatment.Then analysed the data statistically. Result:1. In the two extraction groups,there are significant lower incisors retractions (p<0.01) ,the protrusion of upper and lower lips are decrease (p<0.01) ,the thickness of symphysis at infradentale ,apex, B point and the inclination of symphysis are all decreased significantly (p<0.01) ,the curve of the symphysis is also decreased (p<0.05) .