In Niigata Prefecture, Japan, 282 elementary schools (about 40% of all) in 70 of all municipalities (112) carried out a program of oral rinsing with sodium fluoride solution in December, 1986.
In this study, a great amount of available data concerning the community dental health in Niigata Prefecture was fed in to a data base system. The relationship between the measures for dental health in elementary school and caries prevalence of permanent teeth was analyzed with this data base system, and the effectiveness of the fluoride mouth rinsing program in Niigata Prefecture, that is the community effectiveness, was evaluated on the basis of schools and municipalities.
1. Analysis of the measures for school dental health as factors influencing on caries prevalance in permanent teeth:
A multiple-regression analysis was carried out, in order to ascertain the relationship between DMFT-index of sixth grade children of 459 elementary schools in 1985 (as an independent variable) and items such as school dental health education or administration (as dependent variables). The result showed that the period during which children had participated in the fluoride mouth rinsing program was the most influential factor on caries prevalence, and other measures of school dental health were not significant.
2. The effectiveness of the fluoride mouth rinsing program
1) An Analysis based on schools: Sixth grade children of 64 elementary schools in which carried out the fluoride mouth rinsing program in 1985, were classified according to their grade when the program began. Reduction rates of DMFT-index were calculated in comparison to the baseline score of children who were examined in the year when the rinsing program began. Children who continued to rinse from first grade had a caries reduction of 32.9%, and children who conti nued from preschool, 40.6%. In each school, the DMFT-index of sixth grade children who rinsed from first grade or preschool was compared to the baseline score. The mean of caries reduction rate was 29.0% (SD=17.8) and 41.4% (SD=20.3), respectively.
2) Analysis based on municipalities: In each municipality in Niigata Prefecture, the DMFT index of sixth grade children in 1985 was caluculated. The mean of these scores was 3.35. Minimum and maximum were 0.83 and 5.37, respectively. There was much variation among these scores of municipalities.
The relationship between each score of DMFT-index in 1985 and each rate of carrying out the fluoride mouth rinsing program in 1980 when sixth grade children in 1985 had entered school was also investigated. It was confirmed that municipalities which had a high ratio of carrying out the fluoride mouth rinsing program tended to show a lower DMFT-index.

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An analysis of the incidence of dental caries of one-and-a-half year-old children (n=656) was performed at Hakone, Japan, during the period from 1978 to 1982. Most caries was found at the maxillary 1st or 2nd deciduous incisors, and 100 (15.2%) had at least one df (decayed or filled) teeth at these sites. The df person rate (the rate of those who had at least one df tooth) varied by several factors: the rate was high among those who had heavier body weight than average, those who had been raised by grandparents, or those who had experienced eczema. The effects of these factors, except for the experience of eczema, could be partly explained by longer exposure of teeth to the oral environment because of an early eruption of the teeth, and partly by caries-prone environments related with sugar-rich and/or low pH conditions. However, the season of the subjects' birth also affected the df person rate. Those born in July-September had a higher rate and those born in October-December had a lower rate among both boys and girls. Only among girls, those born in January-March showed the highest df person rate (25.8%). The rate of those who had been raised by grandparents was high among the girls born in January-March, but the July-September peak was not correlated significantly with other confounding factors. When the subjects with the eczema experience were selected, those born in July-September showed a higher df person rate (40.0%). To explain the results, one could propose that some seasonal factors which affected the subjects at a particular stage of development during a pre-or perinatal period may have left some defects not only on the characteristics of teeth but also on other immunological characteristics.

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[in Japanese]

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In our previous study, we demonstrated that supervised daily mouth-rinsing program with a weak fluoride solution (F: 100ppm) based on a six-year school dental health service (in an elementary school) had a significant cariostatic effect. When the participants in this program left school, however, they had to discontinue the fluoride mouth-rinsing. It is, therefore, necessary to assess the durability of the cariostatic effect obtained through this program. As the subjects for present study, the children who took part in this program (the fluoride group) and others who were given the same school dental care without the fluoride mouth-rinsing (the control group) were chosen. Three years after they left their elementary schools, they were given a dental examination. During this three-year period, no organized prophylaxis had been given to them. The routine dental examination was the same as that used by us in previous reports.
The results may be summarized as follows:
1. The new DMFT increment during the three years after the discontinuing of the fluoride mouth-rinsing was 1.76 in the fluoride group and 2.58 in the control group, showing a caries reduction of 31.8%.
2. The new DMFS increments on different tooth surfaces during this three years were analyzed, showing a caries reduction of 71.9% on smooth surfaces and 20.6% on other surfaces with pits and fissures.
3. No cariostatic effect was found on the second molars, especially in the newly erupted teeth.
4. This means that there was no cariostatic effect on teeth with little exposure to fluoride.
It is evident from this investigation that there was a prolonged cariostatic effect during the three years after discontinuing of the weak fluoride mouth-rinsing. Therefore, we suggested that the fluoride mouth-rinsing program should be continued longer, to protect the second molars from dental caries.

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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.

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[in Japanese]

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The relationship between fluoride distribution and histological structure of human cementum was studied.
The materials used were cementum of of the root apex of thirty canine teeth which were extracted from nine subjects averaging 55.9 years of age.
Distribution of fluoride in cementum was obtained from ground cementum specimens through the abrasive micro-sampling method (Weatherell, et al., 1985). Histological findings were obtained from microscopic observation of specimens without stain and with hematoxylin stain.
X-ray micro-analysis on the specimens indicated that the phosphorus concentration was constant at approximately 12.2% in all specimens, regardless of depth or structure of the cementum. This phosphorus concentration was used to calculate the mass of each specimen.
The graphs of fluoride distribution were superimposed on the photographs of the magnified image of histological structure of cementum.
The results and conclusion were as follows:
1. Each individual had approximately the same distribution of fluoride concentration in all his canines, which means that each subject has his own characteristic pattern of fluoride distribution.
2. Fluoride concentration was high in the acellular cementum and was low in the cellular cementum.
3. Fluoride concentration was relatively high on“the incremental lines”but it was relatively low between the lines.
4. There was a close relationship between the pattern of fluoride distribution and histological stiucture of the cementum within each individual.

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[in Japanese]

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The effects of fluoride (F) on the growth, protein synthesis, alkaline phosphatase (ALP) activity, cyclic adenosine 3', 5'-monophosphate (cAMP) levels and ultrastructure were examined in normal human diploid cells (NDU-1 cells, fibroblasts) derived from fetal lung tissue.
Concentrations of F between 0.026mM-0.53mM had no effect on the growth of NDU-1 cells. However, 0.79mM F depressed the growth of the cells and 1.05mM F led to complete inhibition of growth. Reduced protein synthesis (incorporation of ¹⁴C-leucine) was observed with 0.79mM F, but, 0.026mM F and 0.53mM F slightly enhanced protein synthesis to 109% and 108% of the control, respectively.
After 24 hours of exposure to concentrations of 0.026mM-1.05mM F, ALP activity in the cells was increased in a manner similar to that of control cells. However, ALP activity in cells treated with 2.63mM F seemed to be strongly depressed.
The cAMP values increased rapidly after the addition of 2.63mM F.
Cells cultured for 24 hours with 0.026mM F or 0.53mM F contained a well-developed, roughsurfaced endoplasmic reticulum (rER) when compared with control cultures. In cells treated with 0.79mM F or 1.05mM F, numerous lysosomes and a less-developed rER were observed. Many vacuoles were also observed in the 2.63mM F treated cells.
In conclusion, the higher concentrations of F tested inhibited cell growth and protein synthesis, but the lower concentrations of F accelerated protein synthesis. These findings are supported by morphological investigation. Finally, F had a stimulatory effect on cAMP, but a depressant effect on ALP activity.

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Dental health control and health education are often difficult in severely multi-handicapped children because of their intellectual and physical disabilities. This study surveyed 57 male and 61 female children institutionalized in an institution for the severely multi-handicapped in order to study the relationship between their oral condition and the systemic evaluation. The results are summarized below.
1. The following mean values were obtained: dft, 5.5; DMFT, 9.4; f ratio, 2 percent; F ratio, 3 percent; OHI-S, 1.86; and PMA-I, 18.69.
2. When examined by age group, the dft increased until the age of 8 years and then decreased thereafter. The DMF was found to increase with age. The PMA-I value increased until the ages of 15 to 19 years and continued to be high thereafter. The OHI-S value increased with age. This was shown to be attributable to the increase in the CI-S value.
3. Compared to the values obtained in the survey of dental diseases conducted in 1981, the incidence of caries was low for the molar teeth but high for the lower anterior teeth among the deciduous teeth, and low for the lower molar teeth among the permanent teeth.
4. When the children were classified by Ohshima's classification for the severely multi-handicapped, the dft, DMFT, PMA-I, and OHI-S values tended to be higher in groups 5 to 9 than in the other groups.
5. With regard to the relationship between IQ, degree of behavioral disturbance, and the oral condition, the DMFT, unlike the dft, tended to be higher in the children with higher IQs and only slight behavioral disturbances. The PMA-I and OHI-S values were higher in the group with IQs of 0 to 25 than in the other groups, but they were lower than in the patients classified as“able to walk”by degree of behavioral disturbance.
6. With regard to the relationship between the classification of growth and function and the oral condition, it was found that the DMFT tended to be higher in the children who showed higher levels of growth and function with regard to tooth brushing, eating, and type of diet. The PMA-I value was high in the children who showed poor growth and function with regard to tooth brushing and those who required partial help when eating. The OHI-S value was high in those patients who showed poor growth and function.
From these results, this study suggests that it is inadequate to evaluate dental caries and gingivitis in severely multi-handicapped children by examining the oral condition only, and that it is necessary to take into consideration such systemic factors as the patient's daily activities, intellectual disability, and motor function disorders.

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