The purpose of this study was to assess the fluoride concentrations in surface enamel using a biopsy procedure, in relation to fluoride contens of drinking water in a fluoride area (Kitatsugaru, 0.3-3.2 F^- ppm occuring naturally) and a fluoride-free area (Matsuo, 0.07 F^- ppm in drinking water). Dental fluorosis was found in 12.9 percent (including moderate and severe cases) of 404 school children aged 6 to 11 years old (79 percent including questionable enamel mottling) in this fluoride area, which was reported in our previous paper (1975). This study also aims to investigate a parameter for distinguishing between dental fluorosis and nonfluoride opacities based on fluoride concentration in surface enamel in vivo. The subjects for biopsy samples were 39 school children aged 9 and 10 in the fluoride area and 11 subjects aged 9 and 10 from the fluoride-free area.
A round filter paper disc (φ5mm) was put onto the labial surface of the maxillary central incisor. The disc was then impregnated with 10μl of 0.5 M perchloric acid using a micropipet. Exposure time of the tooth surface was 60 seconds. Fluoride was determined by means of a fluoride ion activity combination electrode (ORION, 69-09) and calcium by atomic absorption spectrophotometry.
The results were as follows:
The fluoride concentrations of the central incisors at the depth of approximate 4μm were 1490±549 ppm (Mean±S.D.) in the fluoride area and 939±432 ppm in the fluoride-free area. A significant difference of fluoride concentration in surface enamel was found between the fluoride ares and the fluoride-free area. Furthermore, a significant correlation was established between the fluoride concentration of surface enamel and both the actual concentrations of drinking water at present (r=+0.55, P<0.001) and the degree of dental fluorosis biopsyed (r=+0.35, p<0.05).
These results suggest that a high concentration of fluoride in surface enamel seems to be mostly caused by the actual amount of fluoride in drinking water due to incorporation into surface enamel, rather than by an increase in the amount of fluoride ions present during enamel formation or pre-eruption. Regarding caries experience in these two areas, the DMFT Index was 1.34±1.69 in the fluoride area and 2.54±2.49 in the fluoride-free. area. It is suggested that the low caries incidence in the fluoride area resulted from an increase of fluoride content in surface enamel due to water-born fluoride after eruption.

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A widespread dental fluorosis has been found recently in two primary school districts, Soekawadaiichi and Umezawa, in the Kitatsugaru area (northern part of Japan), which was reported in our previous paper (1976). The fluorine concentrations in drinking water were determined monthly by fluoride electrode with samples from 23 deep wells (100-300 meters in depth) during eight months in 1975.
The fluorine concentrations of these samples ranged from 0.31 to 3.18ppm. The waters containing fluorine over 0.8ppm are supplied to 734 houses, which shows 85.4 percent of the total number of houses in these districts. The value of 0.8ppm is the maximum allowable amount of fluorine in communal water established by the communal water administration in Japan. The drinking waters with fluorine concentrations of more than 2.0ppm are supplied to 190 houses (44.4%) in Soekawadaiichi district and 55 houses (12.8%) in Umezawa district.
On the whole, relatively high pH values (pH 7.2-8.7), high sodium (41-265ppm) and chlorine (19-460ppm) concentrations, and low values in total hardness were observed in these samples. It was also noticed that the concentrations of fluorine showed a positive correlation with sodium and chlorine in these samples.
The source of the fluorine detected in the water of these districts has not yet been ascertained. However, the possibilities that result from a mixing of mineral and hot spring waters, an influence of oceanic factors, or elution from fluorine-rich rocks were discussed.

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The fucosyl and sialyl residues are located at the end positions of the carbohydrate chain in various glycoproteins such as salivary glycoproteins, serum glycoproteins and glycoproteins from cellular membranes. Bacterial fucosidase and neuraminidose that split the period linkages from oral glycoproteins may be important in pathological conditions. The purpose of this study was to search for the presence of a-L-fucosidase and/or neuraminidase activity in some oral streptococci.
The streptococcal strains were grown in trypticase soy broth at 37°C for 24hr. The resulting cultures were separated into the culture supernatant and whole cells by centrifugation. The enzyme proteins in the culture supernatant were precipitat the addition of 80% saturation of ammonium sulfate and dissolved in phosphate buffer. This mixture was termed the extracellular fraction. Bacterial cells were resuspended in phosphate buffer and disintegrated in a sonicator. This fraction was celled the intracellular fraction for convenience. As substrate for the assay or α-L-fucosidase, porcine submaxillary glycoprotein (PSG) and/or p-nitrophenyl-α-L-fucoside (p-NPF) were used. Neuraminidase activity was determined using human plasma glycoprotein Fr. VI as substrate.
Extracellular fucosidase activity was found only in S. sanguis ATCC 10557 and S. mitis ATCC 9811 using PSG, but not p-NPF. The intracellular fractions of several strains possessed fucosidase activity against the PSG and/or p-NPF. Neuraminidase activity was found only in extracellular fractions of S. sanguis ATCC 10557 and S. mitis ATCC 9811. a-L-Fucosidase in the intracellular fraction appeared late in the growth phase, increased to a maximum and then disappered gradually. On the other hand, the activity of extracellular α-L-fucosidase increased quite late in the growth phase and continued to increase quite late in the growth phase and continued to increase during the entire experiment. The qehaviour of the appearance of neuraminidase activity was quite, similar to that of fucosidase. The optimal pH for these enzymes was between 5.5 and 6.5.
This study has clearly demonstrated that bacterial fucosidase and neuraminidase were produced by oral streptococci.

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The frequency and the position of congenitally missing teeth (excluding third molars) were examined in 3, 435 students in Hokkaido. X-ray photographs were taken of suspected cases with occlusal film. Among the subjects, 296 cases (8.6 percent) had congenitally missing teeth. Cases with one tooth missing were most frequent, followed by cases with two missing. In the present samples, the premolars were most frequently missing followed by the incisors. Among 172 cases with missing premolars, 81 cases were in the mandible, 64 cases in the maxilla and 27 cases in both jaws, whereas of the cases with missing incisors, 86 were in the mandible, 36 in the maxilla and 3 cases in both jaws.

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