The deciduous teeth that play a great part in the growth and development of children during the infantile and preschool periods are very susceptible to dental caries, and therefore can become carious before completion of the deciduous dentition. When dentists teach caries prevention from the point of view of personal health, the instruction does not have sufficient effect. Therefore it is important that caries of the deciduous teeth should be studied epidemiologically and that caries prevention should be taught from the point of view of public health.
Though many studies on caries of the deciduous teeth have been reported, studies on children under 3 years of age are few, and most of them are based on cross-sectional data.
In this study I tried to evaluate the oral conditions not by studying single teeth but by studying the mouth as a whole, observing children from 1 to 3 years of age, and classfying the dental ages (I-VII) and the caries attack patterns (a-d).
A follow-up study was carried out using 205 children, 100 boys and 105 girls, living in Yokosuka-city, Kanagawa prefecture.
The rersults were as follows:
1) The caries prevalence rate increased with increasing age, especially at 2 years of age.
2) The upper deciduous central incisors were attacked the most caries between dental ages I and VI. The lower deciduous second molars were attacked the most at dental age VII.
3) At 1 year of age, the caries prevalence rate in the labial surface of the upper deciduous central incisor was highest, at 2 years of age the rate in the mesial surface of the upper deciduous central incisor was highest, and at 3 years of age the rate in the occlusal surface of the lower deciduous second molar was highest.
4) Dft and dfs in most of the children who suffered from dental caries at 1 and 2 years of age increased after 1 and 2 years, but decreased in a few of the children after 1 and 2 years.
5) At 1 year of age caries attack patterns of the b type (the dental caries was located in upper and/or lower deciduous anterior teeth) were the most prevalent at 2 years of age patterns of the a type (the dental caries was located in upper and/or lower deciduous molars) were the most prevalent, and at 3 years of age patterns of the c type (the dental caries was distributed in the upper or lower deciduous anterior teeth, and in the upper and/or lower deciduous molars) were the most prevalent.
6) The patterns of the b type at 1 year of age did not belong to the b type but to c or d type (the dental caries was distributed in the upper and lower deciduous anterior teeth and molars) at 3 years of age.

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In vitro adsorption of dextranase by dental plaque and buccal mucosa was determined, and clinical oral retention of dextranase was also confirmed.
Additions of 1320, 6600 and 13200 units of dextranase to dental plaque samples resulted in adsorptions of 2.9, 10.8 and 15.1 enzyme units per 1 milligram dry weight of dental plaque, respectively. Moreover, buccal mucosa adsorbed about 6 units of dextranase per milligram dry weight of buccal mucosa when treated with 16800 units enzyme. The adsorption by buccal mucosa was considered to be weaker than that by dental plaque.
After rinsing the mouth for 30 sec. with 13200 units of dextranase, the enzyme activity in the whole saliva was reduced rapidly and disappeared completely after 90min. In spite of this, however, a significant amount of the enzyme activity was found in, the dental plaque of each subject.

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In orcer to examine the feasibility of the use of tea drinking for caries prevention in public health, the fluoride content of tea leaf infusions was analysed in 190 samples obtained from inside and outside Japan.
Fluoride content in the tea infusion showed wide variation ranging from 15mg/kg to 1800mg/kg dry weight of the sample. For the purpose of the caries prevention, selection of the type of tea is the most important prerequisite.
The content of fluoride in tea leaf infusions depends on at least three factors: location of the plantation, probably a nature of the soil containing fluoride; the tea bush, and the age of the leaves.
For this reason high quality commercially processed tea would not be appropriate, but cheap Bancha prepared from the aged leaves may be more suitable, Chewing pickled tea leaves may be a better preventive against pit and fissure caries for the people in Burma and Thailand.
Acknowledgement: We express our appreciasion to Dr. R. Noor, professor Mustopo, and Dr. Soelaiman of Indonesia for their kind assistance in collecting tea samples, and to professor Isra Yuktanandana and Mr. Chit Khin Way for collecting pickled tea leaves in Thailand and Burma.

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The purpose of this study is to describe process of acquiring the toothbrushing habit by the Japanese children who are not under continuous instruction by dentists or dental hygienists.
The field science methodology adopted for this study was that developed by Jiro KAWAKITA, who is a Japanese anthropologist. 48 mothers were interviewed by the author concerning the toothbrushing habits of their 85 children. The data were organized by the KJ method of KAWAKITA.
The process of acquiring the toothbrushing habit was divided into 5 stages: 1) beginning stage 2) play stage 3) habit formation stage 4) habit fixation stage 5) fixed habit stage with avoidance.
The beginning stage was when the children first had contact with toothbrushing or toothbrushes. About 90% of the 3-year-old children experienced this stage in this survey. The play stage was when they handled toothbrushes the same as their toys, and their mothers also realized it. The stage of habit formation was when their mothers began instructing their children in toothbrushing.
The habit fixation stage was when the children came to use their toothbrushes with their own hands daily, the frequency becoming fixed. About 50% of the 4-year-old children experienced this stage and almost all used their toothbrush once a day in this survey. The habit stage with avoidance was when they sometimes avoided brushing their teeth.
The manner of avoidance is like that of adults. This stage began gradually after the entrance to elementary school. Toothbrushes were given at the beginning stage, and dentifrices were given at the habit formation stage in general. Some anxiety was found in mothers, this was found typically during the habit formation stage.
The habit changing process should be considered in dental health education. Help for mothers with some anxiety is needed, and the author thinks an important aid is education. The field scicnce methodology is effective for this study, because it is effective for description of the daily life circumstances in which various complex factors are involved.

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The sharpness of the dental explorer will influence the detection rate of dental caries. In order to estimate the variation of point form, the explorers manufactured by four Japanese dental factories were measured with a profile projector. Considerable variation in the sharpness of the explorers were found. Then, to find the difference in caries detection ability between sharp and blunt explorers which were selected from the instruments studied, thirty-seven children of tweleve years of age were examined by the blind recording method performed once with each explorer on each individual. The result showed that the sharp explorer detected more carious lesions than the blunt one at 0.22 DMFT or 0.19 DMFS per child examined. Within the limits of the detection of early lesions, the sharp explorer found 30% more carious cavities than the blunt one. There was a statistically significant difference at a probability less than 0.01. A standardized explorer was suggested and the wear on the point when used for from one to six children was also determined. From this evidence, it becomes clear that point uniformity in dental explorers is essential in epidemiological caries studies. To maintain uniformity, the explorer should be resharpened to a standard point once every three examinaitons.

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For the purpose of studying the correlation between the amount of occlusal plaque and the prevalence of dental caries, 829 school-children of Aji Island and Ichinoseki aged 6 to 15 years were examined. The occlusal surfaces of their permanent premolar and molar teeth which had erupted completely and were not decayed nor filled were scored 0 to 3 according to the extent of the area covered with dental plaque. The criteria of scoring were as follows:
Score 0-No clinical plaque. Linear staining only of the contents of pits and fissures.
1-Less than one-third of the occlual surface covered with stained palaque.
2-Less than two-thirds of the occlusal surface covered with stained plaque.
3-More than two-thirds of the occlusal surface covered with stained plaque.
The mean score per kind of tooth in one individual was called the individual Occlusal Plaque Index (O.P.I.), and the mean of the individual values was called the population O.P.I. of each kind of tooth. The O.P.I. was calculated for the following kinds of teeth; first molars, the second molars, whole molars, premolars, and premolar-and-molars.
The values of all kinds of population O.P.I. were already high immediately after complete eruption and declined with age for some years. While the declination was slight in the first molars, it was very marked in premolars. The means of molar O.P.I. were constantly higher in females, but the means of premolars were not so.
The coefficients of correlation between the various O.P.I. 's and the numbers of DMFT and DMFS were calculated and investigated statistically. All the correlations seemed to be basically a positive relationship, and statistically significant correlations were frequently found in the several kinds of O.P.I. except for the period just after eruption. High significant correlations were very often present in the O.P.I. of molars but were rarely present in the premolars. The highest coefficients were obtained between the number of DMFS and the O.P.I. of the first molars and whole molars in the 5th and 6th grade elementary schoolchildren because almost all of the children with a high value of the O.P.I. had suffered from more carious lesions than average.
From these findings it was concluded that the O.P.I. of the permanent first molars and whole molars had a highly significant correlation with the prevalence of dental caries in schoolchildren.

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Forty-five volunteers were divided into three groups depending upon the degree of staining of their anterior teeth after an oral hygiene check-up by hygienists.
Each group used one of three test dentifrices with different polishing ability, and the cleaning effect of each dentifrice on their anterior teeth was photographically evaluated at the beginning, 13, 26, 42, and 62 days.
In order to study the relationship between the cleaning effect of each dentifice In Vivo and the In Vitro polishing ability the weight loss of an antimony plate was measured after 10000 strokes of a brush with each dentifrice on it.
The group which used the dentifrice with low polishing ability showed a significant amount of stains on their teeth, but these stains were not observed in the remaning gorups, which used common dentifrice and the dentifrice with a high polishing ability.
The relationship between the cleaning effect in a clinical study and the polishing ability of the three dentifrices showed good agreement with Kitchin's study.
These results suggest that the dentifrice should have a certain level of polishing ability and that brushing with this dentifrice should be recommended to keep the teeth clean.

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Otaka engyme (O.E.) is a campound of various enzymes extracted from the vegetables which are arbitraily chosen and there have been published reports on its curative effect of an inflammation of the oral mucosa as well as its bactericidal action. From these effects, its beneficial actions on inhibiting the deposition of plaque and preventing the cases of gingivitis can be reasonably expected.
In the present study, the authors used high school girls by way of experimental subjects. A group of 39 girls, who had been given a previous training in a toothbrushing method, were instructed to use O.E. containing dentifrice and another group of 43 girls were instructed to use a placebo for a period of one week.
The degrees of dental surface cleanliness and PMA indices before and after the experiments were examined and compared. There was observed a tendency of improvement in both of these areas in common with the experimental and control groups. But the experimental group was found to reveal a statistical difference. This fact is thought to have bearings on the O.E. dentifrice.

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With a view to determining the maximum no-effect level of NaF on the rabbit bloodin vivo, different doses of NaF were applied to the oral cavity isolated by ligating the esophagus or subcutaneously. Then the F, Ca, glucose and lactate levels of the rabbit blood were determined. The morphological changes of the erythrocytes were also observed with an electron microscope.
The maximum plasma F level was reached 1 hr. after a 15min. topical treatment with 12.5mg/kg NaF (F: 2800ppm) and this was 1.69ppm more than that of the control. But the treatment had no effect on the Ca level and erythrocytes.
A remarkably high level of blood glucose and a great variation of blood lactate appeared to the same degree in both NaF treated and untreated animals at the oral cavity administration because of the stress caused by immobilization, general narcosis and operation. Accordingly, the effect of NaF on blood glucose was studied by means of subcutaneous administration in which F level of plasma was the same as that of the topical application. We could not find any effect of NaF on blood glucose.
When a clinically used concentration (F: 500ppm) was applied to the oral cavity of a rabbit for 1 min., the maximum plasma F level was observed after 30 min. and it was only 0.06ppm more that than of the control. As this level is remarkably low in comparison with that of the 15min. topical treatment with 12.5 mg/kg NaF (F: 2800ppm), it probably has no effect on the blood glycolysis.

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The present study was concerned with the measurement of lead contained in a dental alginate impression material. The lead is included in the impression material for the purpose of enhancing its surface smoothness, ease of manipulation and higher viscosisity.
For measuring the lead, use was made of an atomic extinction meter and, at the same time, the number of air-borne particles at the time of trituration were measured with a Royco 202 particle counter. The weight of the material was meosured before and after and after trituration, and the difference between the two was used to indicate the number of air-borne lead particles.
As a result, the following findings were obtained:
1. With the exception of one product (domestic), the usual amount of lead was 5-35μg/g. Two paste-like products (domestic) were found to contain the least amount, 7μg/g.
The four foreign products (U.S.A.), on the other hand, containnd an average amount of 16.2μg/g. The three domestic products had an average value of 26.2μg/g, one of them containing as much as 9.7μg/g.
2. In terms of the size of air-borne lead particles at trituration, there was no product ir. which the size was less than 0.6μ.
The number of air-borne particles was anywhere from 14.7×10³ to 44.9×10³ pieces/1.
The products in which the particles were less than 0.8-10.0μ accounted for 52.9-72.7% whereas in the rest the particles were more than 10.0μ.
3. The weight of air-borne lead particles at trituration was 146.13-343.12mg for one-time use, which accounted for 0.81-1.55% of the total under examination. The amount of lead contained in these particles was anywhere from 5.11 to 8.23μg.
Care should be taken in the use of alginate impression material in a clinical environment.

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It is a well known fact that the influence of age factor is very great in the susceptibility to lead poisoning. However, the reason for this phenomenon has not yet been proven. Further, there has been few studies conducted on the differences in the susceptibility, using experimental animals. The experiments were conducted to determine the relationship between the distribution of lead in the teeth and the femur of rats and their age by using 210-Pb tracer. The animals which were used in the experiments were Wistar male rats of 3 weeks, 3 months, and 22 months of age. A single intraperitoneal injection of lead nitrate solution of 210-Pb 10μCi/kg, and solutions of other densities were administered to the rats and after a lapse of 3 days, the percentages of lead intake in the femur and the teeth were measured, with results as follows.
1) Whereas the excretion of lead decreased exponentially when a small amount of lead (210-Pb 10 μCi/kg only) was administered to the control group, the excretion decreased linearly when 1 mg/kg of lead was administered. It was found that 21 days after the administration, the excretion of lead was 39.8% in the former case and 24.3% in the latter. The percetage of excretion in the feces was constantly higher than that in the urine.
2) With the increase in the dosage of lead, it was noted that the percentages of lead in the hard tissue decreased. The decrease in the percentage of lead intake was remarkable when 10 mg/kg and 100 mg/kg were administered. This tendency became predominant in the aged rats.
3) The average percentage of lead intake measured in the femur, incisor and molar of the 3 weeks old rats in the control group were 6.25%, 0.81% and 0.55%, respectively. Those of the rats of 3 months old were 2.52%, 0.76% and 0.10%, and the rats of 22 months old, 2.28, 0.97 and 0.21%, respectively.
4) In the groups of rats to which 1 mg/kg lead were administered, the average intakes of lead in the femur, incisor and molar were 2.50%, 0.37% and 0.19% respectively, in the age group of 3 weeks, 0.80%, 0.17% and 0.05% in the age group of 3 months, 0.22%, 0.07% and 0.02% in the age group of 22 months.
5) It was observed that in the suckling rats of the control group, the amount of lead was largest in the femur, but in the adult and aged rats the largest amount of lead was found in the incisor.

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