Fumiko Ozaki

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.

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.