Longitudinal course of temporomandibular joint sounds in Japanese children and adolescents

BACKGROUND: Many epidemiological studies of temporomandibular disorders (TMDs) in children and adolescents have been performed. However, the results of such studies have varied, and a comprehensive view of the prevalence and severity of symptoms and signs is difficult to obtain. In the present study, temporomandibular joint (TMJ) sounds, which are the most common signs and symptoms of TMD, were observed longitudinally, and the need for treatment was evaluated. METHODS: Seventy individuals in six age groups (5, 6, 7, 8, 9, and 10 years old at the beginning of the observation period) participated in an epidemiological investigation conducted between 1987 and 1992. During each clinical examination, the following parameters were examined: maximum unassisted jaw opening, TMJ clicking, and the coincidence or difference between the midlines of the upper central incisors and the lower central incisors. In addition, the bilateral bite force was recorded, and the numbers of erupted, decayed, and filled teeth were recorded. RESULTS: Eight individuals dropped out because they moved. No TMJ dysfunction requiring treatment was observed in this series. TMJ clicking was observed in 30 subjects (48%); however, this symptom was temporary in most of subjects (26 subjects; 42%), and only 3 subjects (5%) had persistent clicking (continuing until the end of the observation period). The incidences of clicking were not significantly different among the six groups (x(2 )= 4.265). Clicking was significantly more common among girls (19 subjects) than among boys (11 subjects; P = 0.042). A significantly lower bite force (17 ± 18 kg) was recorded for the subjects with persistent clicking, compared with that of the other subjects (8- and 9-year-olds; mixed dentition) without persistent clicking (32 ± 17 kg). The persistent clicking began at an age of 11 or 12 years (permanent dentition). CONCLUSION: Most of the clicking observed in the children and adolescents was temporary, and no difference in the incidence of clicking was observed among the six age groups. Girls had a significantly higher incidence of clicking than boys.