The effect of on the incisor teeth of activator treatment: a follow-up study.

A follow-up study of the effect of activator treatment on the incisors is presented. Much of the effect of activator treatment is due to movement of the incisors. It has been claimed that the upper incisors become retroclined, however, a proclination of the lower incisors may also occur and this has been regarded by many as a contra-indication. This aspect has been studied in a material consisting of 40 Angle Class II:1 cases treated with the activator. Mean age at the start of treatment was 11 years and at the end of treatment 12.5 years. Incisor position and inclination were recorded on radiographs taken before and after treatment. The results indicate a significant improvement regarding upper incisor position and inclination whereas the lower incisors had moved forward 2.6 mm and proclined 1.6 degrees on average. A regression analysis suggested, however, that cases with proclined lower incisors prior to treatment underwent retroclination during treatment (p less than 0.001). Furthermore, 25 per cent of the patients studied showed retroclination of the lower incisors during activator treatment. It is thus concluded that proclined lower incisors is not necessarily a contra-indication for treatment using the activator.