Does the mandible alter its functional position during activator treatment?

Abstract

The study aimed at revealing possible changes, in activator-free periods, in the positions and movements of the mandible induced by the wearing of an activator. Twenty-one children being treated with three different types of activator for the correction of Angle Class II, Division 1 malocclusion were studied. The movement capacity of the mandible, the rest position, and the position of tooth contact during chewing were recorded with a Sirognathograph before treatment and repeatedly during the first year of treatment. With the exception of a slight increase in the maximal protrusion, no changes in mandibular movement capacity were found. The anteroposterior position of the mandible in the rest position was constant during the period of treatment, but the freeway space increased. No changes in the position of the point of tooth contact during chewing were found. The study produced no evidence of a treatment-induced forward positioning of the mandible in activator-free periods.