Preliminary Study on Methods Selection in Treatment of Class III Malocclusion in Mixed Dentition

Objective To help clinicians make a decision on treatment plan of Class Ⅲ malocclusion with undeveloped maxilla in mixed dentition. Methods The sample included orthodontic treatment and orthopedic treatment groups, which consisted of 15 patients, respectively, with Class Ⅲ malocclusion due to undeveloped maxilla. The selection criteria included (1) Anterior crossbites (2 ) - 2 ANB 1 ( 3 ) Cephalometric analysis showed undeveloped maxilla and normal growth of the mandible (4) Growing patients (5) Mild Concave profile. Patients in orthodontic group were treated with 2×4 appliance and with stable treatment effects after two years follow - up. Patients in orthopedic group were treated with reverse headgear when failure or relapse was noted after treatment with 2×4 appliance within one year. Cephalometric analysis was performed with pretreatment lateral cephalograms. T - test was assessed to compare significant difference between the two groups. Discriminate analysis was performed and its result helped to select the treatment method to Class Ⅲ malocclusion in mixed dentition. Results The average value of NSAr was significantly smaller in orthodontic treatment group ( p 0.01) , anterior cranial base length ( p 0.001) and posterior cranial base length (p0.01) was significantly larger in orthodontic treatment group. Prediction Index (PI) = -0.2 (NSAr) + 0.243 (anterior cranial base length) + 0.187 (posterior cranial base length) + 3.366. Conclusion With larger PI ( 0) , with greater success of treatment with 2×4 appliances in Class Ⅲ malocclusion in mixed dentition, due to undeveloped maxilla is expected.