OBJECTIVETo evaluate whether there was any difference on the clinical effects of Twin-block, Activator and Herbst appliances on the clinical effects of growing children with skeletal Class II malocclusion.

METHODS60 patients with skeletal Angle Class II malocclusion were divided into three groups (Twin-block group, Activator group, Herbst group), 20 in each group. The patients of three groups were respectively treated by Twin-block, Activator and Herbst appliances. The patients were 10-13 years old(mean 11.6) before treatment, and were mainly with mandibular retrognathia. Data of pre- and post-treatment were measured and analyzed.

RESULTSThere was statistically significance of ANB, SNB, Go-Gn, Co-Gn, L1-MP in sagittal changes, and N-Me, ANS-Me, S-Go, SN-MP, Co-Go in vertical changes after treatment of three groups. Herbst group was more effective than Twin-block group and Activator group in the increase of L1-MP, but the effects on maxilla were not significant among them. There was no statistical significance of Ptm-A, OB, N-Me, ANS-Me, S-Go and Co-Go between 3 groups.

CONCLUSIONTreatment effects of three different functional appliances (Twin-block, Activator and Herbst) are similar in the early treatment of skeletal Class II malocclusion. Compared with Twin-block and Activator, Herbst has more effects on orthopedic of mandibular and lower anterior teeth.