Fluoride has an inhibitory effect on cholinesterase (ChE) in vitro, so the effects of sodium fluoride administration on activities of ChE in serum, brain and salivary glands were studied in female rats. ChE activies in them were measured by the colorimetric method of Ellman et al. two percent NaF solution was administered orally to female Wister rats and the animals were sacrificed by heart puncture 1, 3, 24 and 48 hours after a single dose to remove the various organs and the blood.
Fluoride analysis was performed for all the serum, brains, kidneys, and salivary glands and ChE activity in serum, brains and salivary glands. In fluoride administrated animals the fluoride concentration in the serum, kidney, and salivary glands was about one hundred times higher than control rats at one hour after a single dose of NaF.
Peak inhibition of ChE occurred a few hours after administration of NaF per os. The ChE inhibition caused NaF elevated acetylcholine concetration, so that acute intoxication resulted in signs of parasympathetic stimulation such as salivation and nausea.

View full abstract

The effect of dextranase in vitro on the release of reducing sugars from the dental plaque of schoolchildren and adults was evaluated and the effect of mouth-rinsing with dextranase was confirmed. Dextranase was effective for the release of reducing sugars from the dental plaque of both schoolchildren and adults. When 10000 units of dextranase was added to dental plaque suspension in vitro, reducing sugars corresponding to 59.0 and 20.3μg of glucose were released during incubation for 10 minutes. The ratio of these reducing sugars to the dry weight of dental plaque samples were 0.3 and 0.15%, respectively.
Mouth-rinsing with 10000 units of dextranase showed a more statistically significant effect on the release of reducing sugars from the oral cavity than inactivated dextranase (p<0.01). In the experiments, 37 subjects out of 48 (who had not brushed their teeth for a day before examination) showed evident effects of dextranase. The mean values of released reducing sugars of the dextranase (I) and heat inactivated dextranase (II) groups were 112.7 and 99.9μg, respectively.

View full abstract

Sucrose taste thresholds were determined for 98 children, five to six years old, and 213 young adults (average age 23 years). The children displayed higher mean sucrose taste threshold (47.9±19.4) mM) than young adults (13.7±6.2 mM). Significant difference was found between these two groups (p<0.001). The high thresold of the children was considered to be due to two causes: recognition as threshould of sensation (higher than threshold of judgement) and immature or dull taste sensitivity of the growing children.
The relationship between the sucrose taste threshold and the sweet food intake, or between the sucrose taste threshold and the liking of sweet was unclear. Moreover, it was thought that the sucrose taste threshold was not implicated in the dental caries experiences.
Females showed lower sucrose taste threshold than males, especially significant in adults. This is presumably caused by some physiological factors.

View full abstract

In 1, 134 children 3 years of age in the metropolitan Tokyo area, the relationship between the prevalence of carious teeth and food intake was statistically analyzed.
Food intake was studied after classification of intake into main meals and between-meal food. The frequency of between-meal food intake was classified into“once”, “twice”and“three or more times”a day groups, and the mode of eating into“regular”, “somewhat regular”and“irregular”. The preference for sweets was classified into“liking sweets”, “liking both sweets and non-sweets”and“not liking sweets. ”The prevalence of carious teeth tended to be higher as the frequency of intake became higher, the mode of eating irregular and the preference for sweets more pronounced.
The most profound influence on the prevalence of carious teeth was exerted by the frequency of intake, followed by the preference for sweets and mode of eating.
The influence of the frequency of intake, mode of eating and sweet preference was most distinctly reflected on the prevalence of carious teeth on the occlusal surface of the molars and the neighboring and labial surface of the anterior teeth. This tendency was especially pronounced on the occlusal surface of the molars.
As to the relationship between the sweet preference and frequency of intake between-meal food, the prevalence of carious teeth tended to be higher as the tendency of“liking sweets”and the tendency of“liking both kinds of foods”plus the frequency of the intake became higher. In the group of“not liking sweets”, the caries rate did not increase very much even if the frequency of intake was increased.
As to the relationship between the tendency to like between-meal food and the mode of eating, the caries rate tended to be higher in the group of“liking sweets”and that of an“irregular feeding”In the groups of“liking both sweets and non-sweets”and“not liking sweets”, no difference was noted in the caries rate regardless of the mode of eating.
Among the various factors affecting food intake, however, the expense for between-meal food, the amount of intake at the main meals, appetite, and biased intake failed to show significant relation to the caries rate.
These results indicate an especially intimate relationship between the frequency of betweenmeal food intake, mode of eating or tendency to like sweets and the prevalence of carious deciduous teeth.

View full abstract

It has recently been reported in our laboratory that a bacterilytic enzyme derived from Streptomyces globisporus strain 1829 significantly inhibited experimental dental caries in hamsters when added to the diet at 0.1% (w/w).
The purpose of the present investigation was to determine the effects of starting time to the enzyme administration on experimental caries.
A NIH (U.S.A.) strain of male golden hamsters weighing around 41 gr. at 30 days of age were inoculated orally with Brain Heart Infusion broth cultures of streptomycinr-esistant strain of S. mutansAHT-R and fed cariogenic diet #2000. The bacteriolytic enzyme was added to the diet at a 0.2% (w/w) level.
Enzyme administration started two days before 1st inoculation with strain AHT-R, and on the 5th and the 12th day after the inoculation. After rearing under these conditions for 35 days, the animals were sacrificed and the extent of dental plaque, caries and alveolar bone loss of the molar dentition were estimated.
When the hamsters were fed the diet #2000 without the enzyme, dental plaque and caries of the molars developed without the loss of alveolar bone. By addition of the bacteriolytic enzyme to the diet at 0.2%, the plaque formation was reduced, and the caries development was naturally inhibited with statistical significance. The earlier the starting of enzyme administration, the greater the inhibition of dental caries. The intake of diet and gain of body weight of the animals during the experimental period were not influenced by the enzyme in the diet.

View full abstract

The children at the Minamihata, Asaka 3rd and Osato elementary schools were instructed in their diaries their tooth-brushing habits for one year. Careful analyses of the diaries revealed that, as compared with other months of June, August, October and December, the number of their tooth-brushings decreased per day in August.
At the same time, it was confirmed that on Sundays the number of tooth-brushings was less than on week days.
When analyzed in terms of different schools, at the Minamihata elementary school 35% accounted for the tooth-brushing after lunch, whereas at the Asaka 3rd and Osato elementary school more than half of the children brushed their teeth at getting up in the morning or before retiring for the night.
This kind of differences may be ascribed to the teaching policy of the schools concerned.
Those children who brushed their teeth more than once a day were observed to be unstable in their habit than those who regularly brushed their once a day.
It has been difficult to infer their habit of tooth-brushing of a day for that of one month or the whole year.
Although the taste and flavor of a tooth-paste liked by the children were factors to be considered in the formation of tooth-brushing habit, it seemed that a dental paste or dental powder could be easily changed. Therefore, it is necessary that, in the instruction of tooth-brushing in schools, many factors involved in the picture should be given a sufficient consideration.

View full abstract

The problem of the“distance radlus”of dental clinics has been nearly completely neglected to date. Therefore, in the present study the author was concerned with several observations concerning this subject.
A. As to the relationship between local social environments and the number of dentists and dental clinics, there was observed a high correlation between the population composition of prefectures under study and the number of dental clinics, with r=0.94. In terms of the age groups versus the number of dental clinics, the finding was that r=-0.65 in a group of family dependents, all indices showing negative values. In the relation between local economic activities and the dentist and dental clinic, the number of dentists and dental clinics was compared with the rate of road construction or improvement in the prefectures, the actual working hours of a local inhabitant on the average and the number of automobiles registered, suits possessed and piano possessors in a given prefecture. The findings were a positive correlation. But, when the number of library books and of high school graduates desiring to go into higher educational institutions or universities were compared with the number of dentists, the findings did not give correlation. In terms of the average monetary expenditure of a local inhabitant in a given prefecture versus the number of dentists, r=0.86, and, moreover, high correlations were observed between the purely disposable income and the number of dental clinics as r=0.98.
B. In four different dental clinics consiting of (1) a dental clinic in a commercial area, (2) a dental clinic in a residential district, (3) a dental clinic in medium-sized city, and (4) the dental department of a general hospital, the distance approximately 90% of the number of patients traveled was 0.75km in groups (1), 1.7km in group (2), 1.38km in group (3), and 5.5km in group (4). In the composition of national health insurance holders vs. distance, 90% of the patients in groups (1) and (2), the distance was more convenient for the family dependents, where the nearest was in group (3). In the number of treaement days vs. distance, the majority of patients amounting to 90% came from 0.8km in (1), 2.0km in (2) and as far as 12.5km in (3). As for group (4), the average distance was 9.3km. The number of those patients who were regular in their clinic attendance until they were fully cured was 69.6% in group (2), followed in order by (4), (1) and (3). 95% of the patients in group (2) came from 2.8km, followed in order by (1), (4) and (3), where the longest distance was 15.5km. A correlation of r=-0.55 was obtained between the number of dental clinics available within a radius of 1km and the number of patients living in it.

View full abstract