Function and dysfunction of the masticatory system in individuals with dual bite

Abstract

A dual bite is present if the antero-posterior difference between the retruded and intercuspal positions exceeds 2 mm, and if two occlusal positions can easily be taken up. Twelve dual bite patients aged 11–60 years (median age 17 years) were studied clinically, radiographically and by means of dental casts. Three subjects had had no orthodontic treatment; three had had orthodontic treatment in the upper jaw, and six had been treated with an activator, alone or in combination with other appliances. There were few subjective and clinical symptoms of mandibular dysfunction among the youngest dual bite patients, but the dysfunction symptoms increased with age. Some of the subjects had marked occlusal wear. X-ray cephalometry showed that the mandible was more retrognathic than in an average series. Structural changes of the TMJs were found in two patients and were probably associated with earlier trauma to the mandible. The present study suggests that dual bite is not associated with a high prevalence of subjective symptoms of mandibular dysfunction. The risk of developing clinical signs of dysfunction and excessive tooth wear suggests, however, that treatment aimed at creating stable occlusion in or close to the RP is indicated in dual bite patients.