Mandibular function before and after orthodontic treatment.

To determine the influence of orthodontic treatment on mandibular function, a longitudinal study was initiated on 245 consecutive prospective orthodontic patients before and after the orthodontic treatment. Of the 245 referred patients, eight declined treatment and 27 moved to other parts of the country before the treatment was completed. Thus, the longitudinal study was based on 210 patients. The functional examination was made according to Carlsson and Helkimo (1972) and Helkimo (1974), and by the same person (MO). Before the orthodontic treatment, symptoms of temporomandibular disorders (TMD) were found in 16.7 per cent of the patients and in 6.7 per cent after treatment. The number of subjects without signs or symptoms of TMD increased from 26.7 per cent before treatment to 46.2 per cent after. According to the dysfunction index (Helkimo, 1974), 31.4 per cent of the patients had a moderate and 13.8 per cent a severe mandibular dysfunction before the start of orthodontic treatment. After the treatment, the corresponding figures were 14.3 and 5.7 per cent, respectively. The material was divided into groups, consisting of boys and girls younger than 13 years, and 13 years and older at the start of treatment. Before treatment there was a higher prevalence of signs and symptoms of TMD in the older age group than in the younger, and higher in girls than in boys. After the orthodontic treatment, the prevalence was still higher in girls than in boys in both age groups, but not higher in the older age group than in the younger group.