Study On The Effect Of Chin Morphology On Skeletal ClassⅠ Malocclusion Patients Orthodontic Treatment

Objective:To investigate the effect of different soft tissue morphology on the treatment of skeletal class Ⅰ malocclusion patients by analyzing the measurement data before and after treatment.Methods:Pre-and post-treament lateral cephalograms of 55 adult female patients were collected in Department of Orthodontics,Hospital of stomatology,Jilin University from January 2012 to December 2020.According to the chin of soft tissue morphology in the lateral cranial radiographs,the patients were divided into abnormal chin morphology group and normal chin morphology group,and the relevant soft and hard tissue indexes were selected to study in-group varieties and inter-group differences of different chin morphology before and after treatment.Results:1.The Chin-lip angle,mandibular chin Angle,mandibular chin vertex Angle,LL-E,UL-E,chin thickness and B-B’ thickness in the abnormal chin morphology group were significantly higher than those in the normal chin morphology group(P < 0.05);m: BMe and n: B’Mes were significantly lower than those in normal chin morphology group(P < 0.05).2.After treatment,the mandibular chin Angle,mandibular chin vertex Angle,U1-SN,L1-MP,LL-E,UL-E,SNA,SNB and B-B’ thickness of the abnormal chin morphology group were significantly decreased(P< 0.05);Nasolabial Angle,PP-MP,m: BMe,n: B’Mes and chin thickness were significantly increased(P < 0.05).3.After treatment,in normal chin morphology group,U1-SN,L1-MP,LL-E,UL-E and B-B’ thickness decreased significantly(P < 0.05);Nasolabial Angle were significantly increased(P < 0.05).4.After treatment,The Chin-lip angle,mandibular chin Angle,PP-MP,LL-E,UL-E,B-B’ thickness in the abnormal chin morphology group were significantly higher than those in the normal chin morphology group(P < 0.05);Me-Mes thickness,m: BMe and n: B’Mes were significantly lower than those in normal chin morphology group(P <0.05).5.m: BMe and n: B’Mes are positively correlated.Conclusion:1.Chin morphology affects the formulation of treament plans.Compared with normal chin morphology group,abnormal chin morphology group require a larger retraction of incisors.2.Although the chin of soft tissue morphology is related to the morphology of bone,the changes of soft tissue chin after treament cannot be directly predicted according to the changes of bone.3.Soft tissue Chin morphology affects the aesthetic assessment of soft tissue lateral profile and the change of soft tissue before and after treatment,and the prediction of the change of soft tissue chin after treatment should take the morphology of the soft tissue chin into account.