Post-treatment cephalometric changes in adolescent patients with Class II malocclusion treated using two different functional appliance systems for an extended time period: a randomized clinical trial

Objectives: To assess the post-treatment changes in Class II adolescent patients treated with two different functional appliances for an extended time period. Design: Randomized clinical trial. Setting: One university and one district general hospital in the UK. Participants: Caucasian adolescent patients with a Class II malocclusion. Methods: Pairs of patients of similar age and gender were randomly allocated to one of two functional appliance systems, the Twin Block or Dynamax appliance. The appliances were used for 15 months full time. Changes were measured from lateral cephalograms taken at the start (T1) and at the end of treatment at 15 months (T2) and 30 months (T3). Results: Hundred patients completed the trial, 52 Twin Block and 48 Dynamax. Mandibular forward movement was 3.5 mm (+/- 2.5) in the Twin Block group and 1.7 mm (+/- 2.1) in the Dynamax group (P < 0.01; T1-T2) and, subsequently, by 0.3 mm (+/- 2.6) and 0.9 mm (+/- 2.5), respectively (P = 0.3; T2-T3). Mandibular length increased by 6.3 mm (+/- 2.7) in the Twin Block group and 4.0 mm (+/- 2.5) in the Dynamax group (P < 0.01; T1-T2) with treatment and, subsequently, by 0.5 mm (+/- 2.3) and 1.5 mm (+/- 3.1; P = 0.05). Anterior face height increased in both groups. Conclusions: Treatment resulted in greater mandibular growth with the Twin Block than the Dynamax. In the follow-up period, there was less growth in the Twin Block group compared to the Dynamax