Soft tissue effects of Twin Block and Herbst appliances in patients with Class II division 1 mandibular retrognathy.

The aim of this study was to evaluate and compare the changes in soft tissue profile related to treatment with Twin Block and Herbst appliances. Sixty Class II, division 1, mandibular retrognathic patients were divided into three groups. Forty patients were randomly allocated to one of two functional appliance treatment groups. The first group comprised 11 girls and 9 boys (mean age= 12.74 ± 1.43 years) treated with the Herbst appliance. The second group comprised 10 girls and 10 boys (mean age = 13.0 ± 1.32 years) who received treatment with Twin Block appliance. The untreated control group included 9 girls and 11 boys with a mean age of 12.17 ± 1.47 years. Mean treatment time was 15.81 ± 5.96 and 16.20 ± 7.54 months for Herbst and Twin Block groups, respectively. The observation period of the control group was 15.58 ± 3.13 months. Pre-treatment (T0) and post-treatment (T1) cephalograms were used to evaluate skeletal, dentoalveolar, and especially soft tissue changes. The groups were compared at T0 and T1 using analysis of variance, and treatment/observation differences (T1 - T0) were evaluated with paired samples t-test at P < 0.05 level. Soft tissue convexity, H angle, and mentolabial angle decreased in both treatment groups compared to control. Statistically significant treatment changes were found for mandibular soft tissue measurements in Twin Block group and to a lesser extend in Herbst group. Both appliances reduced the soft tissue profile convexity when the nose is not taken into consideration. Greater advancement of mandibular soft tissues was observed in Twin Block group.