[A clinical study of the effect of a rigid open activator (ROA) in the treatment of Angle class II.1].

The study introduces a maximally weight and volume reduced rigid open activator (ROA) for wear by patients with Angle class II.1 deformities. The activator is worn from about the age of 9 until the end of the eruption of the permanent canines and the first and second premolars. Intensive wear of the activator leads to regular occlusion after only 4 months. Cephalometric parameters at the beginning of treatment compared with those following regular occlusion document and illustrate the impressive adaptation of the masticatory system achieved through wear of the ROA.