学童期における永久歯齲蝕発病率の統計学的研究

Abstract

Patterns of caries incidence were stuided on a population of primary school children residing in the same district by conducting personal follow-up check with every children's mouth for the number of the erupting permanent teeth at every four months intervals up to 16 months, and caries incidence rate during the whole period was studied statistically. Results obtained were summarized as follows. 1) T Rate (%) With respect to individual teeth of upper and lower jaws of both sexes, the trends of T rate by progressive months were very similar. When curves for this trends were plotted against semilogarithmic scale, T rate for each tooth rose higher to form a convex curve indicating an increase of the rate of increase with progressive months. The trend curve of T rate for individual teeth did not necessarily follow the same pattern, but the time required for the beginning and completion of eruption process differed from one kind of teeth to another. It was generally shown, however, that the teeth of lower jaw begun erupting in the mouth earlier than the homologous teeth of opposite jaw and likewise the teeth of female subjects showed earlier eruption than the ones of male subjects. 2) DMF-T Rate (%) When statistical difference was computed with respect to DMF-T prevalence rates found among homologous teeth of upper and lower jaws in both sexes, the prevalence rates in the 1st and 2nd molars of lower jaw proved higher than those of upper jaw, whereas the same rates in other teeth such as the 1st and 2nd premolars, central and lateral incisors proved higher with upper than with lower jaw. When DMF-T rates were compared between both sexes, the rate for the female was higher than the one for the male. The rates of DMF-T as studied in every teeth proved higher with progressive months and this monthly rise was more conspicuously seen in all teeth of upper jaw than in those of lower jaw with both sexes. Oral examinations on a single subject were conducted consecutively 5 times at every four months in search of dental health status and the percentage of newly developing DMF-T against total number of healthy teeth at each four-month period was defined as DMF-T incidence. According to this definition, DMF-T incidence was highest in the 1st molars of 4 quadrants in both sexes with about 10% during four months intervals and was below that in the remaining teeth. The incidence, however, rose to approximately 10% with the 1st and 2nd premolars and 2nd molars with progressive months by about 20 to 124 months. DMF-T incidence in the school age children of both sexes was prevalent in upper rather than lower jaws, and, on the basis of whole jaws, the incidence curve reached the peak of about 10% by approximately 92 to 96 months of age, sloping down slightly thereafter to about 6% and leveling off there. When individual teeth of whole mouth erupting successively onto both arches were classified into 5 groups by 4 months intervals, it was shown that the incidence of DMF-T was more prevalent in groups of earlier eruption than in groups of later eruption. DMF-T incidence was next studied at various times starting from zero month to every four months periods, and results indicated that DMF-T prevalence was highest at zero month, that is, at the time of initial examination of whole teeth and the rate continued to increase at successive examinations of four months intervals toward 16 months. In view of the foregoing results, much emphasis in public hygienic concern should be laid on the fact that dental caries of permanent teeth is very liable to prevail in younger population of school age. To protect them from this wide spread disease, parents and guardians are adviced to take every opportunity to participate in the programs of dental health education and practice of dental care and to bring the children to have deeper concern with their own teeth. In view of the urgent need for more intensive