The purpose of the present epidemiological study was to survey the incidence of the temporomandibular joint (TMJ) dysfunction in children (3 yrs to 15 yrs old age). A total of 1893 children (941 girls and 952 boys) from one kindergarden, three primary schools and one junior high school located in Gifu, were examined in the sutdy. The subjects were divided into four age groups according to class in school such as pre-school (PS,3 to 6 yrs), junior class group of primary school (JPS,6 to 9 yrs), senior class group of primary school (SPS,9 to 12 yrs) and junior high school (JHS,12 to 15 yrs).
The results obtained were as follows:
1. The numbers and incidence of the children with TMJ dysfunction were 275(14.5%) out of 1893. In each group, PS, JPS, SPS and JHS were 13 (8.2%),57 (9.4%),115 (20.2%) and 90 (16.9%) respectively. There were no differences based on sex in each group.
2. Since considerable differences among groups, such as PS and SPS, JPS and SPS, JPS and JHS groups were noticed, the incidence of the TMJ dysfunction is likely increase with the age.
3. Among the three major symptoms found in the TMJ dysfunction, TMJ sound was the most frequent of 11.8% (223 of 1893), followed by TMJ and/or masticatory muscles pain of 3.4% (65). Children with these two symptoms combined were 1.1 % (13), whereas there were no children who complained of mouth opening difficulties in all groups.
4. The incidences of TMJ sounds in the PS, JPS, SPS and JHS groups were 8.2%,7.6%,13.0% and 16.0%, respectively. Significant differences TMJ sounds were noticed among groups, with differences based on sex no found in any group.