Of 211 rural of randum sampling cases, 99 men and 112 women aged above 15, from 100 families of two communities in Ibaragi Prefecture, the relations in quality and quantity of dental caries with sex, age, teeth and jaws, was statistically studied out, but as there is no difference of significance between those communities, they are regarded as one enlarged community we could obtain the following results:
I. The relations in quality of each dental caries, in surface, deep seated and root stump caries, all caries with those and women sampled, anterior and posterior teeth, upper and lower jaws, no difference of significance were perceived, but in the cases of missing teeth and prosthetic teeth, we could perceive the difference of significance, in women's lower jaws posterior teeth; -that is, P=0.001.
II. On the relations quantity of each dental caries, the number of surface caries in anterior teeth 25, and in posterior ones, 96, the total being 121, while deep seated caries in anterior teeth were 61 in number, in posterior 119, the total being 180. Root stump caries in anterior teeth were 57, in posterior teeth they were 256 the total being 313. Missing teeth in anterior teeth were numbered 106, in posterior teeth, they are 541, the total being 647. Prosthetic teeth required treatments in anterior teeth were 161, and further in posterior teeth, 739, the total being 900. All the teeth that should be treated amounted to 2, 161, therefore, it was 36.58±0.62% among the total 5, 908 teeth.

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Based on the data of a certain quality and quantity of dental caries already won in the farm-village adults that were surveyed in the 1st Report, we examined the necessary the relations between expenses and the time reserve-hours of cases for medical treatment of dental caries keeping the assortments cases in view, the following results were obtained:
1. By the data of books and magazines, that is, all of those which were quoted in the first rank form, through dental statistics, from 19 assortments of books and magazines previously published, we examined each deliberately.
2. In 100 houses in the farm-village districts, among 211 adults of those men and women, -aged above 15-, 200 persons demanded our dental treatments.
3. We presume that the total medical treatment expense amounted to ¥ 759, 520 and an average expense for one treatment was ¥ 183±8 and theyshowed 95% confident degree in them.
4. It is resumed that the total hours examined. by us for medical treatments, -in the case under one unit of a dentist, a dental sanitarian and a dental craftman, -was 2, 615.64 hours in all and an average hour for a medical treatment was 36±1 minutes and they showed 95% confident degree on their parts.
5. The relations among the medical treatment assortments between the necessary expense and hours, concerned were indicated by “Lorenz curved line” and were calculated, the coefficient of concentration degree resulting in the value of 2λ=56% in the former while 2λ=54% in the latter.

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In 1949, the Dental Surveys on 376 school boys and girls of a certain primary school in Tokyo, aged from 7 to 10, who were dispersed and who were non-dispersed during the time from 1944 to 1946 on account terribleness of the World War II. The dispersed ones were divided, according to districts, into such as cities, towns and rural regions, fishing villages, and according to ages, and then did observe minutely caries of permanent teeth, (surface caries, deep seated caries and root stump caries) DMF, first general conditions of 1949 and 1950, and secondly increase and decrease of caries for one year, and got the following results:
I. The dispersed ones compared with non-dispersed through all childrens, ages showed in general low in caries and DMF, especially remarkably low in deep seated caries of 1949. In 1950 surface caries and DMF showed almost the similar degree, while deep seated and root stump caries of non-dispersed showed a considerably low degree, however tendency of increasing throughout the year showed similarity in each age except aged 10 in 1949 among those children.
II. Among those dispersed ones who were on farms and fishing villages in comparison with those children who were from cities and towns, aged above 8, showed generally low degree in caries and DMF in 1949, and especially, they were the remarkable cases in deep seated and root stump caries with aged 8 and 9 ones. In 1950, in aged from 8 to 10, we observed almost the similar contraction cases in both urban children, and rural and fishing ones. Accordingly, increasing inclination of one year showed rather a greater degree in farming regions and fishing villages in 1949 with those aged 7, but in other ages almost the similar inclination was observed. And the very inclination became lower as ages advanced in both urban communities and rural, fishing settlements.
III. The quality of nourishment during the War had effect on caries contraction cases of permanent teeth of those children, so we can easily guess that the dispersed ones were far better circumstanced than the those non-dispersed, and at the same time, we recognized that in the same circumstance contraction cases showed similarity after all.

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In October, 1958, “Tokyo Dental Association” executed the task of the public health dentistry about the people engaged in works and factories in Tokyo. On that occasion, the people who were medically and clinically examined in mass by the members of “Tokyo Dental Association” and perfectly registered the results on 6, 200 sheets of personal oral examination table at 130 works and factories here, all of which were the objects of the our studies. And then, the works and factories of the objects in view were concerned divided and by each industrial phase further subdivided into business servants, laborers and in each work and factory examined. And as for teeth examinations they were divided such as Decayed, Missing, Filled teeth and DMF, as for the gum of teeth such as deposition of dental calculus, gingivitis and pyorrhoea alveolaris, each contraction and the rate contraction were sought for, compared at once, with the relation of each tooth to each gingiva, using the table of correlation as well as the coefficient of correlation between and came to the following conclusion:
1. In comparison of each industrial phase division with one another, the public servants, generally speaking, compared with other industrial laborers showed high tendency in healthy teeth and low in gingiva sufferings and dental hygiene condition seemed to be improving.
2. As for business servants and laborers, the business servants at large compared with laborers showed lower tendency in Decayed and Missing teeth, but higher in Filled ones and lower suffering from gingivitis and pyorrhoea alveolaris and the dental hygiene condition seemed, in general, better.
3. As to the comparison with sexes, men, compared with women, showed higher tendency in pyorrhoea alveolaris in the cases of business servants, but lower in gingiva cases on the part of laborers.
4. As for the correlation between teeth and gingiva, in the total of business servants and laborers, in the total of men and women, that of filled teeth and deposition of dental culculus, showed negative correlation; while on the part of business servants, Decayed teeth and deposition of dental culculus, proved active correlation; we found negative correlation in men laborers, and in women active one respectively, however, especially in the case of DMF, the relation between teeth and gingiva in business servants being active, while negative correlation was shown in laborers.
5. The laborers, generally speaking, compared with business servants show worse condition of dental hygiene, therefore, the plan of promoting dental hygiene in laborers and in women should especially, be taken more care of, hereafter.

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It has been known from the former times that some kind of metal has had an evil effect upon the living condition of lower class of microbes. The present author and collaborators have made studies on methods and sensitive strains for this experiment as well as analyses of their functional factors, while they have proceeded with experiments on more or less different line from the hitherto. Results thus obtained are as belows.
Experimental methods and materials.
In the present experiment, the pure silver plate is mainly used, and two kinds of gram-positive bacilli and gram-positive cocci highly sensitive to the oligodynamic action are separated from the oral cavity. On the other hand, two methods are used for experiment. The one involves plate culture medium, on the surface, and in the depth of which metals are placed. By the other method liquid culture medium is used, and strains and metals put into the medium are measured by the resultant turbidity.
Conclusion
It is concluded from researches on factors of the metallic oligodynamie that those factors are attributable to the action of metallic ion ensuing from free dissolution of fusible metrllic salt formed on the surface of metal.

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With the method to observe the caries incidence during the limited period by “one tooth as unit”, they found out extremely close timely and quantitative relation between an average sugar consumption of a Japanese during the year and the caries incidence during the year on first molar after the dentition of them. The author carried out an epidemiological study on both upper central and lateral incisors as a different crown type tooth from the first molars, by Takeuchi, Takahashi and Koike.
Namely, employing as material, the dental examination records of 10, 288 primary school children in Tokyo and Kyoto range over pre-war, mid-war and post-war time and six years continued dental examination records on 8, 393 students of junior and senior high school in Tokyo.
He made an epidemiological study on relation between an average sugar consumption of a Japanese during a year and a caries incidence during a year pursue it after the dentition on the Cohorts which are divided by their dentition by “one tooth as unit” about upper central and lateral incisors and obtained a following results.
1. On upper central and lateral incisors period of the average sugar consumption of a Japanese during a year shows 15kg, when the “odont-age” -amount of years after the dentition-shows 5-9 years caries incidence during a year is 3-5 %, but when the average sugar consumption are reduced from 10 kg to 0.2kg caries incidence during a year reduce with timely agreement taking 2-3 years lateness comparatively closely and when the average sugar consumption increases caries incidence increases too.
2. Coefficients of correlation between the caries incidence and the sugar consumption on the year of new caries incidence-year before of new caries incidence on upper central and lateral incisors are about 0.5 and the coefficients of correlation between caries incidence and the sugar consumption on 2-3 years before the new caries incidence shows higher result than it on the year of new caries incidence.
That ratio to the cumulative sugar consumption during the year of tooth formation is low.
3. The pattern of the caries incidence per year in pre-war period while the sugar consumption shows a constant quantity to compare with the pattern of the first molars, on upper central and lateral incisors, the period which has a biggest incidence after the dentition is delayed 3-4 years to the first molars'.
4. Increasement of the rate of an incidence per year of 1 year 3 years before the new caries incidence on upper central and lateral incisor in 5-9 odont-age and the increasement of the sugar consumption in a year of new caries incidence show a almost streight line on semi-log graph, and the proportion of the inclination shows almost parallel with the first molars'.
5. According to the above mentioned result he recognized, the relation between average sugar consumption of a Japanese during a year and the caries incidence on upper central and lateral incisors are close after the dentition than the period of tooth formation and also he presumed the reason of the fact that a relation to the sugar consumption during a year is not close timely like a case of the first molar.

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