Orthopedic and orthodontic effects resulting from the use of a functional appliance with different amounts of protrusive activation.

A functional appliance worn full-time was given to 50 consecutively treated girls aged 8 1/2 to 14 years. These patients were divided into three groups: in 14 patients, protrusive activation was maintained at 1 mm; in another 14 patients, it was maintained at 3 mm; and in 22 patients, there was an initial, large single advancement averaging 5 to 6 mm. These amounts of protrusion were checked and maintained every 2 months. Analysis of the data, using control patients matched for age and sex, indicated that there was no difference in either orthopedic or orthodontic variables between the 3 mm continuous-advancement group and the single large-advancement group. The 1 mm continuous-advancement group showed a diminished but still statistically significant response. Assuming linearity, it was calculated that, had the 1 mm activation group been treated long enough to have obtained the mandibular orthopedic effects of the other two groups, the orthodontic changes also would have been comparable.