A Comparative Study Of The Mechanism Of Activator And Twin-block Appliances In The Treatment Of AngleⅡ~1 Malocclusion

Objective: Based on the theory of orofacial harmony,the purpose of present study was to comparative investigate the changes of dentoskeletal and soft tissue profile following the use of Twin-Block appliance and Activator appliance in children of ClassⅡ division 1malocclusion.Methods : The study included 30 growing children of Angle Class Ⅱ division 1malocclusion(14 boys and 16 girls,aged 10 to 12.5 years,mean age 10.5 years old),whose hand wrist radiographs were at FG-G stage.16 patients were treated with Twin-Block appliances;while the remaining 14 were treated with Activator appliance.Gall line was used as a reference line,which is one ideal limit line for anterioposterior position of maxillary in Andrews′ six elements of orofacial harmony.Cephalometric preand post-functional treatment measurements were obtained and analyzed.Two independent samples t test was adopted to compare the means of two groups(Twin-Block and Activator groups)before treatment in order to determine whether the two-group means were significantly different.Then,the two-group values after treatments were obtained and compared with that before by paired-samples t test,respectively.Meanwhile,the amount of variations after therapies were also compared by two independent samples t test.P <0.05 was considered as being statistically significant.All data were analyzed via SPSS16.0 statistical software.Results: The treatment course in the Twin-Block group was carried out over 8.4 months,and the treatment course in the Activator group was carried out over 9.1 months.After treatments,the results of GALL line as the mark of the measurement indicators came to the same as the traditional indicator evaluations in the two groups.The length of Go-Gn and Co-Go in the two groups were significantly increased(P<0.01).The lower jaw forward obviously.Pos-GALL and the height of lower face(Sn-Mes)increased(P<0.01).While the Wits value,ANB angle and OJ(mm)were obviously decreased(P<0.01),The occlusal relationship was also improved obviously,and the maxillomandibular skeletal relationship in sagittal was more harmonious.The changes of Activator group’s soft tissue FCA(G-Sn-Pos)and U1FA-GALL were less than that of Twin-Block group(P<0.05).The changes of thickness of the lower lip LL-L1 and LL-GALL of Activator group were greater than that of Twin-Block group(P<0.05).The changes in the rest of the measuring projects before and after the treatment for comparison between the two groups have no statistical significance.After the treatment,the post-functional treatment measurements were closer to the standards of the theory of orofacial harmony.The soft tissue profile and facial esthetics were improved.Conclusions: Twin-Block appliance and Activator appliance can effectively improved the hard and soft tissue profile and facial esthetics of the children of ClassⅡ division 1malocclusion.This paper demonstrated that the method combining the theory of orofacial harmony could intutively reflect the changes of dento-maxillofacial profile of ClassⅡdivision 1 malocclusion children before and after treatments.