Effects Of Orthodontic Treatment On The Condylar And Mandibular Positions Of Patients With Class Ⅲ Malocclusion In Mixed Dentition

Objective:To compare and analyse Helkimo index evaluation between the photographs of cephalometrics before and after orthodontics and control groups, to evaluate the effects of orthodontic treatment on the condylar and mandibular positions of patients with classⅢmalocclusion in mixed dentition. Methods:32 patients with Angle classⅢmalocclusions in mixed dentition were chosen (15 boys and 17 girls). The mean ages of the subjects in the beginning was 11.6±1.3 years. The average treatment time was 26 months. They were treated with maxillary protraction and straight wire technique. Helkimo index evaluation was made individually before and after treatment. Lateral cephalometric films were taken individually before and after treatment, and linear measurement were observed. Control groups:(1)Group one:43 cephalograms of the patients (21 boys and 22 girls) before their treatment started, which have the similar occlusal and skeletal characters with the treatment group. The mean ages of the subjects was 11.6±0.3 years. (2) Group two:43 cephalograms of the patients (22 boys and 21 giris) before their treatment started, which have the similar occlusal and skeletal characters with the treatment group. The mean ages of the subjects was 13.8±0.3 years, which is similar to the finishing age of the treatment group. Results:1. Treatment changes of Helkimo index:there were significant changes in Helkimo index in treatment group. Ai 0 level ratio was significantly higher, Ai II grade to reduce the proportion of zero.2. Cephalometric radiography:(1) Maxillary:A significant increase of SNA and ANS-Ptm (P<0.01) after treatment was observed. (2) Condyle and mandible:Co-y,Ar-y,Go-y,N-S-Ar,N-S-Go,N-S-Pg,ArGo'-SN,Y axia,facial angle were increased significantly (P＜0.05). Co-x,Pg-y,SNB,NP-FH were decreased significantly (P<0.05). And Ar-y,Go-y,Pg-y change in value before and after correction of the order increases, N-S-Ar,N-S-Go,N-S-Pg changes in the value of the order also increased. (3) The relationship between the maxillary and mandibular:ANB,Wits,NA-PA increased significantly (P<0.01). AB plane angle were decreased significantly (P<0.01). Conclusion:1. The treatment is effective in the correction Helkimo symptoms of mix dentition patients.2. A significant increase in maxillary forward growth, backward upward shift of condylar point, inhibition of mandibular forward growth, and clockwise rotation of the mandible were observed, which contribute to the correction of a skeletal class III relationship.