A laminagraphic study of the alterations in the temporo-mandibular joint following activator treatment

Abstract

The effect of activator treatment is widely discussed. Although most authors agree on the dento-alveolar changes, the influence on the condyle and the temporo-mandibular region are only sparsely commented upon. The purpose of the present study has been to develop a standardized method of laminagraphy and to apply this to the evaluation of the changes in the temporo-mandibular region following activator treatment. Twenty three children, 15 boys and eight girls were included in the study. At the initiation of the study metallic implants were inserted in the upper and lower jaw according to the method of Björk. Fifteen of the patients, all exhibiting a Class II molar relationship and large overjet were treated with a Harvold-type activator to be worn 12–14 hours a day. One profile radiograph and two laminagraphs were produced in a standardized fashion before and after 10 months of treatment/observation. Changes in the temporo-mandibular region were described in a coordinate system related to the cranial base. Changes in the dento-alveolar region as well as condylar growth quantity and direction were related to the metallic implants of the jaws. It was shown that a major part of the activator effect could be ascribed to an anterior displacement of the mandible caused by an increase in the amount and a change in direction of the condylar growth as well as to a remodelling of the articular fossa.