The purpose of this study is to use a newly developed selective medium for Str. mutans in a cries activity test.
The medium contains an indicator dye, bromocresol purple, which changes from purple to yellow in the range of pH 6.8-5.2.
The optimum concentration of growth inhiditors in this medium, phenethyl alcohol and sodium azide, were 0.1% and 0.0075%, resepctively
Mannitol was utilized as a fermentable carbohydrate.
In this medium, the growth Str. mutans serotype a-g groups was not inhibited, butt he multiplication of other oral bacteria was.
When this medium was used to isolate Str. mutans from human plaque, large yellow colonies, rounded and smooth, were observed on the agar plate.
Therefor, we were interested in the application of this medium, which we named “KKY”, in acaries activity test based on the occurrence of Str. mutans in plaque material.
565 children aged from 4 to 6 yaars were tested.
The relation between the KKY test score and present oral status was statistically analyzed. The average number of decayed teeth was about 2 in the (-) group, about 3 in the (±) group, and about 5 in the (+) group, and we recognized a significant difference between each group.

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We have developed a new caries activity test, the “KKY test”, based on Str. mutans in plaque material measured by a colorimetric method.
For the purpose of analyzing the relation between the test score of the caries activity and the increase in caries, 436 kindergarteners were investigated, and their oral status was observed for 6 months.
The average number of increased caries after 6 months was less than 1 in the (-) group, about 1 in the (±) group, and about 1.5 in the (+) group.
A high statistical significance was shown in the relationship between the KKY test and the increase of decay.
Therefore, the KKY test seems useful for measuring caries activity.
It lends itself readily to dental practice, sine observation of color change is much easier than counting the number of bacterial colonies.
It also has the advantage that it can be understood by child patiets.
As a consequence it has value in patient education.

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In assessing enamel mottling and opacities, like dental fluorosis, on the photographs customarily taken with a stroboscope, it is often difficult to detect the affected areas because strongly reflected spots or areas are liable to appear on the tooth surface in the photograph.
To resolve the problem, we developed a non-reflective photography using two dichroic polarizers, one in front of the stroboscope and the other before the lens of the camera.
We applied the method to assess the severity of dental fluorosis of schoolchildren residing in a fluoride-rich water district. The method made the appearance of the mottling and opaque areas on dental enamel clearer than in customary photography. The severity grades of dental fluorosis assessed on the non-reflective photograph agreed with the grade levels from inspection in general, but had a tendency to be evaluated as severer in some cases.
To assess the mottling on dental enamel in dental fluorosis more objectively, it is recommendable to compare the findings from inspection, customary photographes, and non-reflective photographs of the object, to evaluate the three together, and then decide on a severity grade.
This technique can also be used for taking non-reflective photographes of other biological materials.

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Since the molar occlusal surface is most susceptible to dental caries, the degree of cleanliness of this surface is connected with dental caries.
For this reason, the Molar Occlusal Plaque Index (MOPI) was tested at a certain commercial establishment. The findings were compared with those of the OHI and PMAI methods for analysis.
The following conclusions were obtained:
1) Using the initial data as standard for one month, DI gave 52.3%, CI 76.6%, and OHI 64.3% as total values.
2) The reduction effect of MOPI in the first month was 31.5%. This rate was in agreement with that of 6 months.
3) The amount of plaque attachment tended to be larger on the maxilla than on the mandible. The central part had a pronouncedly higher value than the mesial-distal portion.
4) The correlation of MOPI with other indices was most noted for DI.
56 persons were selected for the present study, but we mean to try to increase this number in the future.

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It was reported previously that mutational phase I and phase III of Streptococcs mutans NCTC 10449 were different in their cariogenicity. The purpose of this study was to examine their utilization of tooth matrix and glucose metabolism, which may be involved in their caries-inducing properties.
Both strains were grown in trypticase soy broth containing 50 mM glucose. Change of pH and fermentation products in these cultures were determined. The pH of both cultures fell to about 4.3 in 24 hours and the main product from glucose was lactic acid when estimated by Gas Liquid Chromatography. No differences in the properties of either strain were observed.
For the assay of protease activity, strains were grown in brain heart infusion broth. The resulting cultures were separated into two fractions, i. e., the supernatant and the whole cells. Both fractions were searched for protease activity at pH 6.5, using casein as substrate. The activity was found only in the cell fraction of both strains, and phase I showed higher activity than phase III.
The utilization of bovine teeth powder by both strains was examined with the Warburg manometric technique. The utilization was expressed as the oxygen uptake for four hours at pH 7.0. The oxygen uptake by phase I was much higher than phase III. It is probable that phase I may have more ability to utilize dental tissues and grow on them.

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This program of caries prevention, using mainly the fluoride mouth rinsing method, was carried out for seven years from 1974 to 1981. All primary and junior high school children in Maki village, Niigata Prefecture, were subjected to the program. In order to measure the effect of the program, we compared the prevalence of dental caries between the commencement and the end of the program. A cost-value analysis was also done, using cost benefit analysis and cost effectiveness analysis
In primary and junior high school children, the DMF prevalence rate and the DMFT index decreased from 87.2% to 54.7%, and from 3.68 to 1.51 respectively. The incidence of dental caries in the schoolchildren decreased markedly.
In the cost benefit analysis, the cost was divided into two levels, the first for fluoride mouth rinsing and the second for promoting and maintaining the program. The first cost was calculated as 62.8 yen per child per year. The total of the first and second cost was 255.5 yen per child per year. The benefit was calculated by estimating the avoided cost of treating the caries and of traveling to the dentist's office. The standard used in estimating the expense for each case of caries treatment was the numerical rating of the health insurance. The Cost for caries treatment was calculated by the standard issued on April 1981, assuming that all DMF teeth were treated.
As the result of the calculation, the caries treatment avoided cost was 1455.4 yen per child per year and travel expense avoided was 53.5 yen. The total benefit was 1508.9 yen per child per year. The first cost and benefit ratio was 1: 24.0, and the total cost and benefit ratio was 1: 5.9.
As to the cost effectiveness analysis, the number of tooth surfaces which did not contract dental caries increased by 0.54 surfaces per child per year. The first cost effectiveness ratio was 116.3 yen, and the total cost effectiveness ratio was 473.1 yen.
Judging from this cost benefit analysis and cost effectiveness analysis, the economical benefit from the caries preventive program in Maki village was vary great.

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Five hundred and two 1st year children in junior high school from four different primary schools in the Tsubame district of Niigata prefecture were examined for dental caries and plaque accumulation by the blind recording method in May 1980. The children were divided into four groups, A, B, C and D. Groups A and B were not given noteworthy instruction or treatment for the care of their teeth in primary school. Group C was given instruction in brushing their teeth after lunch at school every day from the beginning of primary school. Group D rinsed their mouths with sodium fluoride solution three times a week from the first grade in primary school. The average number of DMF surfaces per child in groups A and B was 8.24 (SE=0.54) and 8.70 (0.54), respectively. In group C it was 7.99 (0.47) and in group D it was 4.56 (0.41). In comparison with the control group (average of A and B) the caries reducation rate in group C was 5.8%, which is not significant statistically. But in group D the caries reduction rate was 46.2%, which is significant statistically.
The mean plaque accumulation and treated carious teeth rate did not differ in the four groups.
The average number of DMF teeth per child in the 6 th grade in primary school children who will enter group D was 4. 84 (0.26) when the mouth rinsing program commenced in 1973, and after 8 years in 1981 it was 3.00 (0.27). The caries reduction rate was 38%, which is significant statistically.
Tooth brushing instruction after lunch every day in primary school was not effective for caries prevention. But mouth rinsing with sodium fluoride three times a week showed great effectiveness and the caries reduction rate was approximately 40%.
In conclusion, this paper discusses the most effective method for caries prevention in school dental health program.

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Mutanase and dextranase were shown to prevent the formation and the progress of experimental dental caries in golden hamsters.
Mutanase and dextranase were prepared from a Pseudomonas sp. and Corynebacterium pseudodiphtheriticum, respectively, which were isolated from soil in this laboratory. Both enzymes were given to hamsters with Diet 2000 and drinking water.
Either mutanase or dextranase prevented the caries formation when given immediately after infection with Streptococcus mutans OMZ 176 and daily thereafter. An especially, the pronounced effect was obtained when mutanase and dextranase were given together.
Furthermore, each of these enzymes had a dose dependent effect on prevention of dental caries.
Mutanase and dextranase inhibited the progress of the caries formation even when given after the caries had already formed. The progress of caries was not only delayed but also blocked in a group given both enzymes together.
These results suggest that the administration of both enzymes together may be more effective in the prevention and inhibition of dental caries.

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