Asymmetric Extraction Of AngleⅡdivision 1 Malocclusion

Objective: To disscuss the effectiveness of asymmetric extraction about the case of classⅡdivision1.Methods: An adult femal class Ⅱpatient from Dalian friendship hospital.She is13 years old.She present protrusion profile and shaped face;low angle;the lower right first molar had been treatmented and not good;the maxillary crowding is 8mm,and mandibular crowding is 8.5mm;the dental lower midline to left side 3mm.This patient has overbite and overjet.Especially the rigrht second premolar locked bite.By the analysis of model,cepholomitric,we made a plan for this patient :extact the lower right first molar and second primary tooth.Use coil spring for the upper right lateral incisor.After aligment and leveling,decreasing the overbite and overjet,adjustment the relationship of molar with classⅡelastic.Then compare the data between pre and post treatment. Analyses the data with the method of Tweed、Wits、Steiner、Downs and Kim.Result: Process of treatment lasts 28 months. By the analysis of models,after the treatmnet, both upper and lower dentition were in order, canines relationship become class Ⅰ. The midline still aligned, overjet and overbite decrease,nearly normal. The temporomandibular joint no abnormalities. By the analysis of cepholomitric :(1) ANB had an decrease of 3°,which shows the position more harmony between maxilla andmandible.(2) Both overbite and overjet decrease, change to 2mm and 4mm respectively.(3)Upper moved backword and no longer protrusion,because of the SNA decreased.(4)Z angle increse 4°, H angle decrease 5 °, U1-EP increase 3mm,L1-EP decrese1 mm.All these shows that facial profile immproved and more pefect.Conclusion: This case got a activity effect,because that it solve the big space after extracting first molar,and maintain the integrity of dental.Through the treatment,overbite and overjet gone and the profile become better.