Clinical examination of enamel white flecks and urinanalysis were carried out on 1678 schoolchidren, aged from 6 to 11 years, who grew up in a city which supplied city water containing low fluoride (less than 0.24ppm).
Findings were as follows: -
1) Individuals with one or more teeth in“Very mild”or higher grade condition were found to be about 25.6% of the sample. On the contrary, according to the criterion for dental fluorosis rating as the two teeth showing the most severe grade developed by Dean (1934), “Very mild or mild” was about 11.1%; however, according to the criterion as the two teeth showing the most severe rating among the several teeth (four or more teeth) distributed symmetrically developed by the authors (1973), “Very mild or mild”was about 4.5% only. Thus, the authors considered that it is important to take into accout the symmetrical distribution of several mottled teeth and to examine children aged about ten or more years for the assessment of dental fluorosis in specific areas.
2) Fluoride concentration, as well as protein, glucose and pH of urine samples collected immediately after arising in the morning were analysed. A relatively higher level of fluoride concentration was found in the higher school years than in the lower school years.
Fluoride concentration in samples was ranged widely (2.5-0.10 ppm), a little variation, however, was observed at the level of minimum urinary fluoride level fraction (about 0.1ppm-0.15ppm). Thus, the increasing of minimum urinary fluoride level of residents would be recommended for the assessment of pollution by fluoride. Besides, a positive correlation between slight (or questionable) albuminuria and urinary fluoride concentration was observed.

View full abstract

In order to find a base for assesment of fluoride in urine, an experimental study was conducted, mainly on male adults aged 20-30 years, who lived in a low-fluoride area (less than 0.1ppm fluoride).
Both in individuals and between individuals, a relatively narrow and stable variation range (0.1-1.1ppm) of urinary fluoride level was shown.
In this range, the urinary fluoride concentration is estimated to fluctuate ±60% of the mean value in individuals and ±110% between individuals. Moreover, a negative correlation was found between urinary volume and fluoride concentration in a urine retained for a definite time.
This correlation was lost after ingestion of fluoride, and a trend of urinary fluoride excretion proportionate to the ingested amount was visible; however, urinary fluoride concentration did not always change in proportion. After the ingestion of fluoride, about 30% was excreted within 3 hours, and 50% in 24 hours.
Consequently, urinary fluoride may be evaluated roughly by its concentration in spot samples, by considering the variations above mentioned, but a more accurate assesment will be obtained by considering the amount of urinary fluoride over a time course.

View full abstract

In order to figure out quantitatively the susceptibility to caries common to all types of teeth, which is indicated by the factor“r”in the epidemiological principles of dental caries attack proposed by Takeuchi, it is necessary to elucidate the distribution of the acid resistance of the surface enamel of each type of tooth. In this study, the Kameoka community was chosen for the investigation on the basis of its representing the average condition of Japan as regards socio-economical situation for epidemiological surveys. Furthermore, the influence of fluoride concentration in the drinking water on caries incidence in this area was negligible, and the annual sugar consumption per person in Japan was. approximately 20kg at the time of this investigation. Subjects for this study were divided into two groups. Group“A”consisted of the children of Kameoka Primary School who. entered the first grade in 1965, and Group“B”was the children of Kameoka and Oi Primary Schools who entered the fourth grade in 1965 (Table 1 and Fig. 1).
The acid resistance of the enamel in the individual was inferred from the phosphorus biopsied from the upper central incisors using spectrophotometric determination with molybdatesafranin.
Results were as follows:
1. After polishing with tooth paste prepared with a calcium carbonate base, an agar plate (AP), impregnated with 0.1 M lactate buffer solution of pH 4.0, of 2mm in thickness and 6.5mm in diameter was placed on the surface of the enamel for 3 minutes for pre-etching, and then a second agar plate was applied for 3 minutes. The phosphorus dissolved in the second agar plate was determined. The pattern of its distribution in 166 fourth-grade children of Group“A”corresponded to the normal distribution (Fig. 4), and those of 177 children in the fourth grade of Group“B”and 164 first-year students of junior high school of Group“B”showed a slightly normal distribution (Figs. 2 and 3). The average phosphorus determined were 1.2-1.3μg (Table 3).
2. After polishing with tooth paste prepared with a calcium carbonate base, a non-woven, paper plate (NP) impregnated with 0.1 M lactate buffer solution of pH2.5 was placed on the surface of the enamel for 20 seconds for pre-etching, and then a second plate was applied for 3 minutes. Phosphorus dissolved in this plate was determined. The pattern of its distribution in 197 sixth grade children of Group“A”revealed a normal distribution significantly at the 95 per cent confidence limits (Fig. 6 and Table 3). The average phosphorus value and the standard deviation were 3.00μg and 0.73μg, respectively.
3. It was observed that the application of a non-woven paper plate impregnated with 0.1 M lactate buffer solution of pH2.5 is an appropriate method for revealing the distribution of the acid resistance of the enamel if its distribution in the tooth population is normal curve. Moreover, this method can be applied without difficulty and the acid agent used was ascertained to be harmless.
4. A slightly significant positive relationship was observed between the caries prevalance curve of the upper first molars of children whose upper central incisors had been classified as weak group and that classified strong and medium group with regard to the acid resistance determined by the above-mentioned method (Fig. 12).

View full abstract

A model to show the condition of caries attack was constructed by Takeuchi with the post-eruptive tooth age as the X-axis, the annual caries incidence rate (Mx) or the cumulative number of carious teeth per initial 1, 000 healthy teeth (ΣCx) as the Y-axis, and the annual sugar consumption per person after the eruption of the tooth (p) as the Z-axis. In this model the values at the times when p was 0-15kg were the results of the physical examinations at schools in Japan, while those for 30kg were plotted from data in New Zealand. Therefore, additional data, especially concerning cohort studies in periods when p in Japan was greater than the above are desired.
The material of this study consists of a part of the materials used for the author's study on the epidemiological distribution pattern of the acid resistance of the surface enamel by means of phosphorus determined by enamel biopsy, and in relation to caries incidence.
The subjects for this study were children in two primary schools and a junior high school in Kameoka City, Kyoto Prefecture. The fluoride contents in the drinking water of this area had little influence on caries attack, and the living standards of the inhabitants were more or less the Japanese average. Group“A”consisted of the children in the first grade and Group“B”those in the fourth grade of the primary schools in 1965. From this year oral examinations were performed on the same individuals once a year for three years, totaling four times, and the results of these examinations were summed up to be used as data. p was 16.8kg in 1962, 18.9kg in 1965, and 21.2kg in 1967.
The diagnostic standards of caries used here were more severe than the usual standards of a sticky feeling in pits and fissures and a soft feeling on smooth surfaces.
In collecting, the calculations were done by the post-eruptive tooth age and by types of teeth. The results are summarized in Table 1 and Fig. 1. They show the appearance of greater influence of p compared to the cases under p=12-15kg reported by Shimizu (Fig. 2).

View full abstract

Sealing of the pit and fissure for the purpose of caries prevention should be done on healthy molars at the earliest chance after the complete emergence of the occlusal surface from the alveolar mucosa. On the other hand, caries attack on the first molar seems to occur, not to a small extent, even in the course of eruption in recent years in Japan.
In order to analyse the caries status in the erupting molar especially before its occlusal surface is sufficiently exposed to receive sealing, an investigation was made in the first molars in a total of 1, 069 subjects, of which 379 children of the 1 st grade of a primary school (mostly 6 years of age with a few 7 years-old) and 255 children of a kindergarten (mostly 5 years of age) were chosen from an urban area in June, 1971, and 352 children of the 1st grade of a primary school in an urban area and 83 children of the 1 st grade of a primary school in a rural area were chosen in June, 1972. The annual sugar consumption per capita at the time of the investigation was about 27.5kg in 1971, and about 28.8kg in 1972.
The examinations were performed in accordance with the classification of the partially exposed occlusal surfaces shown in Fig. 1. The synthetic standard judgment of clinical caries defined in WHO Oral Health Survey (1971) was used. The first molars of the right and left sides, and males and females were put together in calculation.
The percentages of caries attacks on the erupting first molars were 4.5% in the maxilla and 22.5% in the mandible. In addition, the percentages of D and F teeth in the newly erupted first molars were 27.9% in the maxilla and 59.8% in the mandible, indicating a high percentage of the teeth in which the caries preventive sealing is not feasible.

View full abstract

The authors studied the possibility of adverse effects of chlorhexidine digluconate as applied to the oral area and the possible development of resistant Streptococcus mutans as a result of prolonged application.
Different groups of experimental rats were respectively treated with 0.2% and 2.0% aquous solutions of chlorhexidine digluconate for 35 days. However, there were not observed any abnormal findings on the dental surfaces, gingivae and oral mucosa.
In another series of tests with mice to which chlorhexidine digluconate was orally administerea in 5 different dosages of 12mg/Kg, 120mg/Kg, 180mg/Kg, 240mg/Kg, and 300mg/Kg, the 12mg/Kg group was found to show a normal healthy growth without abnormal findings.
Five Streptococcus mutans strains were subjected to the dilution method in an effort to study the possibility of the development of resistant strains as a result of prolonged use of chlorhexidine digluconate. The result indicated that it would be difficult for resistant strains to develop.
An experiment with primary school pupils, in which 3rd grade pupils were either treated with 2.0% solution or rinse of chlorhexidine digluconate in conjunction with instruction in the proper use of the toothbrush for a year, showed no abnormalcy on the dental surfaces, gingivae and oral mucosa. An application of chlorhexidine digluconate on a weekly basis proved successful in inhibiting the formation of dental plaques, and findings of this part of our studies will be given in a later report.

View full abstract

Dental plaque plays a decisive role in the initation and development of dental caries and marginal periodontal disease. Inhibition and control of the microbial deposition onto tooth surface is a prerequisite for preventing these oral diseases.
A new bacteriolytic enzyme derived from Streptomyces globisporus strain 1829 has been shown to be active against various strains of pathogenic plaque microorganisms. The purpose of the present report was to study the effect of the lytic enzyme preparation on the formation of dental plaque in humans and to determine the capability of the enzyme for preventing plaque growth under conditions similar to daily life but without tooth brushing.
Eleven male volunteers, 23 to 28 years old, who had clinically healthy gingiva and no carious lesions were instructed to withdraw active oral hygiene procedures. The enzyme was administered into their oral cavity by inserting a chewable tablet (troche) in the mucobuccal fold of upper molar or by vigorous rinsing for one minute with mouthwash after each meals for 3 days. Bacterial plaques deposited on the buccal surfaces of the maxillary second premolar and first and second molars were collected and weighed, and plaques onto the labial surfacees of maxillary and mandibular anterior teeth were stained, photographed and evaluated.
With the troche method, a relatively high level of the enzyme activity in the oral cavity persisted for a certain period, and the plaque deposition was apparently inhibited by the administration of the lytic enzyme at a dose of 23, 000 to 46, 000 units per day, which was statistically significant. With the mouth-rinsing method, on the other hand, the majority of the lytic enzyme activity disappeared from the oral cavity shortly after rinsing, but plaque accumulation was apt to be inhibited by the rinse with the enzyme of 18, 000 units per day. Rinsing with the placebo mouthwash was also effective to some extent in retarding microbial deposition on the tooth surface.
The plaque samples obtained from the lytic enzyme-treated group and the placebo group were analysed both chemically and microbiologically, and the results did not show any significant differences between the groups in total hexosamine, total reducing power, protein and calcium content and in viable cell numbers of streptococci.
It is concluded from the results that this bacteriolytic enzyme may contribute to the prevention and control of plaque formation.

View full abstract