Stability of results and function of the masticatory system in patients treated with the Herren type of activator

Abstract

Forty-nine individuals, aged 15–24 years, who had been out of retention for 3–8 years after treatment of distal occlusion with the Herren type of activator were examined for stability of the treatment results and the function of the masticatory system. The examination comprised measurements on dental casts of the overjet, overbite, molar relation and length, widths and relative space of the dental arches. Facial morphology was analysed from profile cephalograms and the function of the masticatory system by means of a questionnaire and a clinical examination. The treatment had brought about a substantial reduction of the overjet that was essentially stable after retention. The long-term effect on the overbite was slight. After retention, a partial relapse in the molar relation improvement achieved during active treatment occured in the majority of subjects. The changes in upper arch widths were within the limits for normal growth. There were no marked changes in lower arch widths but the width between the lower canines tended to decrease. The dental arch lengths decreased and the crowding increased in both arches after retention. The morphology of the face at the follow-up examination was within normal limits except for a total facial retrognathism. The treatment had generally not brought about a lasting proclination of the lower incisors. The lip profile was also normal. The prevalence of symptoms and signs of mandibular dysfunction was in agreement with that found in random samples of untreated individuals. The prevalence of a large distance between the retruded contact and intercuspal positions of the mandible was high, however, indicating a functionally less statisfactory occlusion in part of the sample.