Study Of Adult Skeletal Class ? High Angle Malocclusion With Extracted Treatment By Passive Self-ligating Appliance

Objective:In this study,the skull lateral radiographs of adult skeletal Class II Malocclusion with high angle were measured and analyzed before and after the treatment of 4 premolars extracted with passive self-ligating appliance,to study the facial soft and hard tissue characteristics of skeletal Class II Malocclusion and to evaluate the effect of passive self-ligating appliance in the treatment of skeletal Class II High Angle malocclusion in order to provide reference for the future treatment of this malocclusion.Methods:In the Orthodontic Department of Jilin University,25 adult patients who had completed orthodontic treatment before November 2019 were selected according to inclusion criteria and exclusion criteria for Skeletal Class II High Angle malocclusion.The skull lateral radiographs of these patients were marked and measured by Dolphin Imaging 11.9 cephalometric analysis software,and then analyzed and summarized by Downs,Wylie,Ricketts and Huaxi comprehensive analysis methods.The data base of the measurement results is established,and the statistical analysis is carried out by the statistical analysis software.The results of the test items which fit the normal distribution are recorded in the form of mean standard deviation.Independent sample t test was used to compare the initial results with the standard values,and paired sample t test was used to compare the results before and after treatment.P<0.05 indicated the difference was statistically significant.Results:Compared with standard values,the values of patients with Skeletal Class II High Angle malocclusion showed increased SNA,NS-Me /N-Me,NP-FH,NA-PA,L1-NB angle,L1-NB distance,U1-AP and the upper lip protrusion-H line;decreased SNB,S-Go / N-Me,BaN-PtmGn,A-B plane angle,Y axis angle,U1-L1 angle,U1-NA distance and L1-OP.The differences are statistically significant(P <0.05);U1-SN angle,U1-NA angle.There is no statistical significance between the lower lip protrusion point-H line and the normal value(P> 0.05).After extracted treatment by passive self-ligating appliance,the values of patients with Skeletal Class II High Angle malocclusion showed increased S-Go,S-Go / N-Me,A-B plane angle,U1-L1 angle,L1-OP;decreased ANB,MP-SN,NA-PA,U1-SN angle,U1-NA angle,L1-NB angle,L1-NB distance,U1-AP and lower lip protrusion point-H line,the differences are statistically significant(P <0.05);but SNA,SNB,N-ANS,ANS-Me / N-Me,BaN-PtmGn,NP-FH,NA-PA,Y axis angle and NLA are not statistically significant after the treatment(P>0.05)Conclusion:1.The patients with skeletal Class ? high angle Malocclusion were characterized by high anterior and posterior low lower face,relatively underdeveloped mandible and inferior alveolar bone,sufficient chindevelopment,slightly protruding upper and lower incisors and labial inclination of the lower incisors.2.The passive self-ligating appliance was used for the patients with skeletal Class ? high angle Malocclusion and the tooth extraction scheme was adopted for fixed orthodontic treatment.The relative position of the mandible and alveolar bone and the labial inclination of the upper and lower incisors changed obviously,and the soft tissue profile was more coordinated.3.The values of mandible plane showed sightly increased S-Go,S-Go /N-Me and decreased MP-SN.The effect of counterclockwise rotation of the mandible is not obvious.4.In order to obtain better curative effect of mandible counterclockwise rotation,more vertical auxiliary devices can be added to carry out comprehensive treatment.