う蝕低罹患状況における第一大臼歯のう蝕罹患

We analyzed a dental caries index of an individual which was obtained from the "Checkup chart of teeth and mouths" data of 435 people extracted from the third grade of junior high-school of one city in southern Yamagata Prefecture of fiscal year 2003 at random, in order to clarify an early stage of dental caries at a low experience of dental caries and to check up the risk of dental caries according to the tooth type considering its eruption time. The following conclusions were obtained. 1. We carried out a follow up research on the group of low experience whose index was 2.32 teeth at the age of 2, during the first grade to the fourth grade. The DMFT Index was 1.17 tooth above the index 1 of the new dental mark when they became fourth graders. 2. The results of the follow up research concerning the tooth type shows that most of dental caries were on the first molar of the upper and lower jaws (1-4 graders). 3. The eruption of the first molars, which were about 50% on the upper jaw and about 65% on the lower jaw of the first graders, was attained until the fourth grader. We examined the number of the first molars contracting caries until the fourth grade and it was found that the number of decayed first molars with eruption of the first grader is much larger than that of those with eruption during the 2 to 4 grader. 4. It is significantly easy that the first molar contracts caries of the 2-4 grader compared with the 1 grader. The number of the decayed first molars of the 1 grader is 4.4-fold on the upper jaws and 2.2-fold on the lower jaws. 5. The comparative risk of caries of the first molar with eruption of the 1 grader to the first molar with eruption during the 2-4 grader is 2.57 at the upper jaws and 2.38 at the lower jaws. We judged the risk of the 1 grader was higher. The above-mentioned suggests that further effort is necessary from the concerned people to improve the dental health in the current state at a low experience in caries. Effective measures to prevent dental caries should be set up and executed for the lower classes of elementary school, especially for the first graders with the first molar

う蝕の罹患状況で変わるう蝕指標の役割

Recently, occurrences of dental caries have decreased dramatically. We studied the role of two parameters to establish the goals of dental health service and assess its activities properly. By using dental caries records of 53,417 of elementary school children and junior high school students in Yonezawa City, Yamagata Prefecture from 1997 to 2002, we concluded the following : 1. There were significant correlations observed between the rate at the beginning of the observation and the decrease of the rate for 5 years in the change of the DMFT index, but insignificant correlations in the change of the individual DMF rate. 2. There was a marked correlation logarithmic curve Y=26.7 log_e X+43.9 between the individual DMF rate (Y) and the DMFT index (X). There was a steep increase between 1 and 3 on the 3-point scale, thereafter a gradual increase. 3. The shifts of the group from DMFT index 5 to DMFT index 4, from DMFT index 4 to DMFT index 3, and from DMFT index 3 to DMFT index 2 were successful when the number of the pupils with a lot of caries decreased and the number of the pupils with a few decayed teeth or non-decayed teeth increased. But the shift of the group from DMFT index 2 to DMFT index 1 was successful when the number of each cluster decreased and the number of the pupils with non-decayed teeth drastically increased. From these results, the individual DMF rate would be seen to show a bigger change and a more sensitive response than the DMFT index in cases with a DMFT index of around 2. In the situation of the low incidence of caries, the main purpose of dental health service is to increase the number of pupils with non-decayed teeth. Therefore, using the individual DMF rate to describe the current situation of dental health service and its goals would make its activities and course clearer