Study On The Factors Affecting The Lip Retraction Of Adult Female Patients With Bimaxillary Protrusion

Objective:To explore the influencing factors of lip retraction in adult female patients with bimaxillary protrusion before and after orthodontic treatment,and to provide reference basis for predicting the changes of lip retraction after orthodontic treatment.Method:A total of 39 adult female patients with bimaxillary protrusion were selected for cephalometric analysis before and after treatment.A total of 28 items including dental tissue,hard tissue,soft tissue items and changes of soft tissue and hard tissue were measured before treatment.The sensitive factors affecting lip adduction were screened by multivariate linear regression(stepwise regression).Results:The sagittal changes of the lower lip edge were regarded as dependent variables,and the items of soft and hard tissue before treatment and the items of changes in treatment were taken as independent variables for multivariate linear regression.1.Four sensitive variables affecting the sagittal change of the upper lip were selected as follows: sagittal change of the cervical margin of the upper incisor,sagittal change of the incisal edge of the upper incisor,distance from the point of the upper lip to the line E and thickness of the chin.The prediction equation for the sagittal change of the upper lip is:?UL'-R=-5.114+0.911(?cUl-R)+0.564(UL'-E)+0.273(CT)2.Six sensitive variables affecting the sagittal change of the lower lip edge were selected as follows: sagittal change of the cervical margin of the inferior central incisor,sagittal change of the incisal edge of the inferior central incisor,distance from the point of the lower lip to the line E before treatment,and the tensity of the lower lip.The thickness of chin and the angle of mental lip.The equation for predicting the change of the sagittal direction of the lower lip is:?LL'-R=3.436+0.661(?cLl-R)+0.834(LL'-E)+0.394(LLT)+0.388(?tUl-R)+0.342(CT)-0.084(MLA)Conclusions:Features of soft and hard tissue in patients with bimaxillary protrusion before receiving treatment and the effect of treatment.For the upper lip : the greater the distance from the line to the E line and the thickness of the chin before treatment,the more the cervical margin and incisal margin of the upper incisor were adducted,and the more the upper lip adduces.For lower lip:before treatment,the distance between LL,and E line,the greater the tension of lower lip and the thickness of chin,the smaller the angle of mental lip,the more adducts in incisor and neck margin of lower teeth,and the more adduction in lower lip after treatment.