[Correlations between first molar eruption, caries incidence and caries experience in primary school children]

A follow-up study was made on the results of oral health examinations which had been conducted for six years on a total of 871 primary school children in the 1st grade (age, 6 years) till they became sixth graders (460 boys and 411 girls). The findings are as follows: 1. When they were first graders, the oral health examination revealed their 56% had erupted the upper first molar, and 73% the lower first molar. 2. The incidence of caries in the upper first molar had occurred mostly between one and two years after eruption. After three to four years, more than half of the pupils had this particular tooth decayed. In the case of the lower first molar, caries had started to develop within one year after eruption. After two years, caries was evident in more than half of the examinees. 3. In the sixth graders, the number of DMF teeth per child came to 3.9 and the DMF teeth rate stood at 17%. Both the number of DMF teeth and the DMF teeth rate were larger in girls than in boys. The rate for an intact first molar teeth were 32% in the upper jaw and 15% in the lower jaw. These rates were lower in girls than in boys. 4. The shorter the period between the eruption of the first molars in both jaws and the caries incidence, the larger the number of the DMF teeth and the DMF teeth rate at sixth graders. For the prevention of caries in permanent teeth, special care should be taken during the short period of time following eruption.