Analysis Of Chin Soft And Hard Tissues In Class Ⅱ Division 1 Malocclusion With Extraction Treatment In Adult Patients

Objective:The changes of chin soft and hard tissues in Class Ⅱ division 1 malocclusion with extraction treatment in adult patients were analyzed by lateral cephalometry,and the correlation between the different vertical facial patterns and chin morphology was further explored in order to provide reference for clinical treatment.Materials and Methods:Based on the experimental inclusion criteria,40 patients with Class Ⅱ division 1 malocclusion were selected from the Dalian Stomatological Hospital from September 2016 to December 2018,half of them with hyperdivergent subjects and others with normodivergent.There were 15 males and 25 females with an average age of 21.39±2.42.All patients were treated with straight wire arching technique.At the same time,the first premolars of upper and lower jaws were extracted.Finally we got Class I relationship of posterior molars and canines,and normal overbite and ovetjet of anterior teeth.Before and after treatment,the German ORTHOPHOS XG5 X-ray machine was used to take lateral cephalometry by radiologists according to the same standards.WinCeph 9.0 software was used to measure the relative angle and line spacing of the chin soft and hard tissues,and then observed the changes of chin soft and hard tissues.Chin hard tissue measurement items include chin thickness(B-Me),chin height(C-C’),chin minimum thickness(B-B’),chin anterior thickness(B-C’),chin posterior thickness(B-C’),chin angle,chin depression and curvature.Chin soft tissue measurement items include the pononion of soft tissue thickness(Pog-Pog’),the gnathion of soft tissue thickness(Gn-Gn’),the submental point thickness(Me-Me’),the chin-lip groove depth(Si-LLPog’),the chin-lip angle(LL-Si-Pog’),and the chin groove inclination(Pog’Si-FH).Finally,the SPSS 21.0 software was used to analyze the datas.Paired t-test was used to measure the indicators before and after treatment in each group.Independent sample t-test was used to measure the indicators between the two groups.Pearson correlation analysis was used to compare the correlations.Results:1.After extraction,C-C’/B-Me.B-B’,B-B’/C’,chin angle,SNA,U1-NA(mm),U1-NA,U1-SN,Y axis decreased in the hyperdivergent group,and Pog’Si-FH,NPog-FH,L1-U1 increased.In the normodivergent group,C-C’/B-Me and U1-SN decreased after treatment,B-C,B-C/B-C’,Pog’Si-FH,L1-U1 increased.And the appearance of both groups improved after treatment.2.Before treatment,hyperdivergent group chin depression and Pog’Si-FH were smaller than the normodivergent group.After treatment,hyperdivergent group with the B-B’,B-B’/C-C’,Pog’Si-FH were smaller than the normodivergent group.3.Mental anterior point had a negative correlation with C-C’,B-B’ and B-C.Mental vertex with the L1NB angle had a positive correlation,with the C-C’ had a negative correlation.Menton point and SNB,the L1NB angle had a positive correlation.Menton point and C-C’,C-C’/B-Me,B-B’,B-B’/C-C’,B-C’,mental angle had a negative correlation.Mental lip angle and U1NA angle had a negative correlation.Conclusions:1.Adult patients with Class II division 1 malocclusion have a better profile with tooth extraction.The changes of hyperdivergent profile is more obvious than normodivergent’s.And the chin morphology also improved in hyperdivergent group,but the effect is not as obvious as normodivergent group.2.There is a certain correlation between the chin soft and hard tissues and the lower incisor.Mental vertex and menton have a positive correlation with the angle of lower incisor.Mental anterior point and mental vertex have a negative clrrelation with the chin thickness.In order to make the chin soft tissues more pretty,the lower incisor torque should be controlled during treatment.