FACTORS INFLUENCING SOFT TISSUE PROFILE CHANGES FOLLOWING ORTHODONTIC TREATMENT IN PATIENTS WITH CLASS II DIVISION 1 MALOCCLUSION

Abstract

The purposes of this study were to evaluate soft tissue profile changes of Thai patients with Class II Division 1 malocclusion following orthodontic treatment and study the factors influencing the soft tissue profile changes. The subjects comprised 104 Thai patients (50 boys, 54 girls) mean age 11.62±1.42 years old who presented Class II Division 1 malocclusion and were treated with different orthodontic modalities. Group I: 30 patients (15 boys, 15 girls) mean age 10.93±1.34 years old were treated with cervical headgear. Group II: 30 patients (15 boys, 15 girls) mean age 12.13±1.63 years old were treated with Class II traction. Group III: 44 patients (20 boys, 24 girls) mean age 11.73±1.15 years old were treated as an extraction of the four first premolars case. The profile changes were scrutinized from the lateral cephalograms before and after treatments by means of the x-y coordinate system. Significant differences of the profile changes within and between treatment groups were tested by paired-t test and one-way ANOVA at 0.05 significant level, respectively. The correlations between significantly soft tissue changes and independent variables comprising age, sex, treatment modality, pretreatment skeletal, dental and soft tissue morphology were evaluated by stepwise multiple regression analysis at 0.05 significant level. The result indicated that after treatment the headgear group presented downward and backward movements of the upper lip whereas the lower lip only moved downward and the chin moved downward and forward. In the Class II traction group, the upper lip moved downward, the lower lip moved downward and forward and the chin moved downward. In the four first premolar extraction group, the upper and lower lips moved downward and backward whereas the chin moved downward and forward. The multiple regression analysis indicated that not only different treatment modalities but also other factors comprising age, sex, pretreatment skeletal, dental and soft tissue morphology seemed to be related to the profile changes. The predictive power of these variables on the soft tissue profile changes ranged from 9.9% to 40.3%. In conclusion different treatment modalities and facial growth produce different soft tissue profile responses in Class II Division 1 patients. The prediction equation of profile change after treatment obtained from this study should be beneficial for selection of the treatment modalities for the individual patient.