Shogoro Okada

Study on caries activity test. II. Caries prediction by simplified ST Media.

We applied the Snyder Test (Simplified S·T MEDIA®) to 4-month-olds and 18-month-olds. This caries activity test depends on the color change resulting from acid production by oral bacteria in a culture medium.In some samples, the pH measured by color comparison did not coincide with the pH measured by pH meter, and we called these misjudged samples. So we investigated the caries prediction by two evaluation methods, the color comparison and the pH measurement. To compare the oral status of the children, we used several indices such as caries prevalence, mean dft, caries severity index, and the caries types in deciduous teeth.As a result, we found that the evaluation of caries activity by pH measurement predicted caries occurence more accurately than the evaluation by color comparison. Therefore to predict caries activity more easily and more accurately, we concluded that the evaluation method of adding a drop of brom cresol green to culture medium after 72 hours culture and dividing caries activity into two groups was suitable.

Time series analysis of annual statistics of dental health checkup for 3-year-olds. 2 Secular changes in mean numbers of dmf primary teeth in 3-year-old Japanese children by prefectures.

Time-related trends in the prevalence of dental caries in 3-year-old Japanese children were determined by employing the Annual Statistics of Dental Health Checkup for 3-year-olds, extending over a span of two decades from 1963 to 1983 by prefectures. Geographic distribution of caries prevalence was compared at two-year intervals in computing mean numbers of dmf primary teeth. A significant increase in mean dmf was statistically observed during the first decade (1963-1972) without any consistent geographic variations. A substantial decline of caries experience among 3-year-old children has been seen since 1975 throughout the country, but marked geographic difference in caries prevalence has remained. Caries prevalence was much higher in the regions of Hokkaido, Tohoku, Kyushu, and Okinawa, ranging from 4.1 to 5.9 dmf per child, as compared to the nationwide figure of mean dmf (3.4) in 1983.

Electron microscopic study of bacterial colonization in fissures of rat molars during eruption period.

The fissures of the rat molars were examined by the SEM technique with the purpose of demonstrating the change in the bacterial colonization according to the period of tooth eruption. The bacteria began to adhere to the entrance of the fissures as soon as the molars appear in the oral cavity and the colonization extended up to the deeper places of the fissures with eruption. At the completion of eruption, the bacteria were observed at the lower part of the fissure. Only a slight difference was found in the formation ofthe bacterial plaque in the fissures when the rats were given different diets. Extracellular polysaccharide was observed in the fissures of rats provided with diet containing sucrose.

Studies on the Utilization of Oxidation-Reduction Indicator for Dental Plaque Disclosing

The aim of this investigation was to demonstrate the plaque maturity accumulated on tooth surface using Oxidation-Reduction Indicator in situ. The ingredients of this disclosing solution are Methylene Blue and 2, 3, 5-Triphenyltetrazolium Chloride generally used in histochemical investigations.No gingival inflammation and caries free subject was selected. The participant was told to abolish oral hygiene and allowed to develope the plaque on tooth surface for 7 days. On day 1, 3, 5 and 7 of no oral hygiene periods, new disclosing solution was topically applied on tooth surface.At the time of topical application on 3 days plaque, it was disclosed in blue tone, but gradually changed to red localized to the area of gingival margin. More typical results were obtained in 7 days mature plaque. The blue tone was instantly fading and blue plaque almost changed to red within 10min.The results of this experiments have demonstrated that it is possible to distinguish the old, thick mature plaque from new one. Patient can easily visualize the appearance of plaque changing in colour, so it is very usefull for patient motivation in periodontal practice.