Comparison of the effects of Twin Block and activator treatment on the soft tissue profile

The aim of this study was to evaluate and compare the effects of activator and Twin Block (TB) appliances on the soft tissue profile. The study included 50 skeletal Class II patients (25 girls and 25 boys, mean age: 11.9 +/- 0.16 years) who were randomly allocated to one of two functional appliance treatment groups. The control group included 25 untreated skeletal Class II patients (13 boys and 12 girls, mean age: 10.11 +/- 0.91 years). Data were obtained from standardized lateral cephalograms taken at the beginning (T0) and end (T1) of appliance wear. The mean treatment time was 9 months for the activator group and 8 months for the TB group. The observation period of the control group was 8 months. Soft tissue profile changes were evaluated by means of 12 linear and five angular measurements. The groups were compared at T0 and T1 using analysis of variance, and treatment/observation differences (T1-T0) were evaluated with the Kruskal-Wallis test. Treatment changes in both appliance groups differed significantly (P < or = 0.001) from those in the control group, except for Ss-y, Ls-y, Li-E, and A-y measurements in the TB group and Ls-y, Li-E, nasolabial angle, and A-y measurements in the activator group. When the effects of the two appliances were compared, significant differences were observed only for SS-y (P < or = 0.05), Ss-E (P < or = 0.05), Si-E (P < or = 0.05), and nasolabial angle (P < or = 0.01). The effects of the activator and TB appliances on the soft tissue profile were similar; both significantly changed the soft tissue profile.