The Study Of The Effect On The Mandible Morphology And Position In Adolescent With Unilateral Posterior Crossbite

Objective: By comparing the difference of the morphological development and position characteristics of mandible in adolescent with unilateral posterior crossbite(UPCB)and those without UPCB,we analyze the two indexes in UPCB patients and investigate the mechanism of the effect of UPCB on the morphological development and position characteristics of adolescent mandible,aiming to provide a theoretical reference for formulating a reasonable diagnosis and treatment plan,and seizing the optimal time for treatment.Methods: 80 cases of Angle’s Class III in adolescent were selected which met with the inclusion criteria.The patients were divided into two groups according to the presence or absence of UPCB: the UPCB group,consisted of 40 patients(ten males,thirty females),the average age(13.73±1.32)years,is the experimental group;and the non-UPCB group was the control group with 40 cases(twelve males,twenty-eight females),the average age(13.58±1.43)years.The frontal and lateral cephalograms taken during the initial examination were selected,and the Winceph 9.0 software was used to measure the relevant hard tissue indexes of maxilla and mandible.SPSS 22.0 software was used for data analyzing and independent sample t-test were used for difference analysis between the obtained results,the transverse width of maxilla and mandible along with the correlated indexes of mandible were performed with Pearson correlation analysis.Results:1.The sagittal direction: the ANB,Wits values of group UPCB were smaller than non-UPCB group.2.The vertical direction: SN-Go Gn,PP-MP,articular angle,gonial angle,and the sum of the three angle in the UPCB group were larger than non-UPCB group;while posterior facial height,ratio of face height,S-Ar/Ar-Go,Ar-Go were smaller than non-UPCB group.3.The horizontal direction: Ag-Ag,Mx-Ag,Me-ML value in the UPCB group were larger than the non-UPCB group.4.Result of the Pearson test showed a positive correlation between Ag-Ag and SN-Go Gn(P<0.05),the Pearson coefficient r=0.341.Conclusions : 1.UPCB in adolescents has some impact on the sagittal position of mandible,making its position more protruded.2.UPCB also affect the vertical position and development of the mandible,giving it a clockwise growth tendency and increase of vertical height,while limiting the development of mandible ramus.3.UPCB is more likely to occur shift on chin point.