The Department of Hygiene Kyushu Dental College The average numbers of existed deciduous teeth, permanent teeth eruption and average ages for permanent teeth eruption was investigated and population of school children and pupils in Hagi city consisting of 1186 males and 1200 females from 6 to 15 years old. Comparison was made with the data obtained respectively from groups of 2071 males and 1947 females from 6 to 15 years old and living in Tokuyama city as examined in 1956 by Shindo, and also from groups of 989 males and 909 females, 6 to 14 years old and living in Saga city as examined in 1958 by Shigyo. The results were summarized as follows. 1. The average numbers of existing deciduous teeth Hagi city: Male>Female Male. Female: Tokuyama city>Hagi city≈Saga city 2. The average numbers of erupted permanent teeth Hagi city: Male<Female Male: Tokuyama city≈Hagi city≈Saga city Female: Tokuyama city<Hagi city≈Saga city 3. The average ages for permanent teeth eruption was expressed as follows. Hagi city: Male>Female Male: Tokuyama city>Hagi city≈Saga city Female: Tokuyama city≈Hagi city≈Saga city
Since the end of the War, dental hygiene for mothers and children has been taken up in the government policies, its significance is growing steadily along with their sanitary problems in general. Accordingly, the Contest has been yearly held throughout the country, under the joint auspieces of the Welfare Ministry, the Japan Dentists Association and the Yomiuri Press. Lucky enough, however, the author was able to carry out the oral cavity examination of the contest winners, Mrs. _??_ and her children who live in the same locality as the author's, (namely, the city of Yokkaichi, Mie Prefecture). The same mother and her eldest son _??_ won the second best prize for the 1937 National Contest, while for the 1958 National Contest, she and her eldest daughter _??_ gained the best prize. The author also availed himself of this opportunity to report on their healthy mouth cavities, hygienic mouth conditions and the hereditary factors there of in quite a different way from that of making a routine report on clinical researches. May the author here conclude hurriedly that the strong anticaries nature of the healthy teeth of the winning mother and children is largely due to their hereditary factors, besides an evidently favorable condition of their constantly taking in calcium from the sea weed?
From 1955 in the Industrial Hygiene Week of October in every year, “the Tokyo Dental Association” has been performing the dental hygiene functions in the factories and works here in Tokyo City the objects of our studies 51, 063 sheets of mass clinical examination tables which had been filled up by the members of “the Association” from 1955 to 1957 and 5, 244 sheets of mass clinical examination tables by the Department of Hygiene of Nippon Dental College where they examined at their at certain times, of course in succession, and then the following results were obtained. (I). D.M.F. in an average number of teeth per person in each year had showed an decreasing tendency from 1955 forward yearly. (II). The common caries in an average number of teeth per person in each year showed an decreasing tendency from 1956 downward, showed especially low value in 1957, as for missing teeth, however, we observed no remarkable tendency going downward with years, while in the cases of treated teeth, an increasing tendency had been visible from 1956 onward yearly. The above-mentioned desirable tendencies were considerably observed from the rate of common caries, missing teeth and treated teeth in proportion to D.M.F. (III). Surface caries showed a yearly decrease from 1956 forward, showed especially low value in 1957 while deep seated caries increased, to some extent high in 1957 but no tendency a yearly increase perceived in root stump caries. (IV). Since the dental hygiene function performed in the factories and works here by “the Tokyo Dental Association” from 1955 forward yearly, common caries, cases have very much decreased, especially so in surface caries ones while evil cases of deep seated caries have largely gone away and treated ones increased considerably. These matter-of-facts, to be sure, owe, it was supporsed, to the functions performed by mass medical examinations when they discovered slight caries unknown to themselves as well as, so-called hopeful early treatment; both of these did bring this desirable results on the domain of dental hygienical applications in Tokyo City.
The statistical operation of multiple classification is very important for the analysis of the oral examination results. However, the calculation of data in multiple classification by sex, age, location and degree of diseases is very complicated in performance. because the combination of the items is numerous. The author indicated a plan of applying the Remington Rand accounting system for the statistical analysis of the dental examinations. The caries rate, DMF rate, case rate of dental calculus, gingivitis, alveolar pyorrhoea and prodthetic appliance: crown, inlay, plate denture, dummy and abutment teeth were classified in raw materials. Graphs, based on those data, were drawn for understanding the general tendency.
Sugar consumption of the individual Japanese during the war period between 1943 and 1945 was extremely reduced, and during the worst year, it was less than 1kg. a year. The author carried on a statistical study, using a method contrived by Prof. Mitsuharu Takeuchi with the opinion that, in order to take a statistics of the rate of caries incidence, it should be compiled from the new carious incidence in one single kind of tooth during a year. For the material, the records of the dental examinations on 7, 894 primary school children in Tokyo, who were born between 1929 and 1951, were employed. The results were as follows: 1. The interrelative ratio between the amount of total sugar consumption of a child during the maturation period of the tooth (0-5 years old) and the rate of new caries incidence in the first moler during 6-11 years of age, indicates that there is an extremely little co-relation between them. 2. On the other hand, the interrelative ratios of the new caries incidence in the first moler to sugar consumption are: the year of the new caries incidence, the year before and the year before last are respectively 0.8, 0.7 and 0.6. Therefore, caries incidence is statistically clear to have a close relation with sugar consumption of the same year or the previous year. 3. Moreover, it was presumed that on the semilog graph, the rate of new caries incidence during a yeaa and the sugar consumption during the same year will show a straight line, and when the element other than sugar which may cause incidental caries was subduced, they will make a slow curve on it. 4. The first molers of the upper and lower jaws are naturally have different tendencies of caries infection (It is different in each tooth.); whereas effect of sugar appears to be equally strong for them.
Recently, being encouraged by “Campaign for reduction of decayed teeth”, it is required to evaluate the status of dental health program in school. Although considerable epidemiological surveys on the dental condition of japanese school children have been taken, the actual status of dental health program in school is not estimated from the surveys of this type. Therefore, the author would like to propose a new method of quantitative evaluation for the status of dental health program in school, which is refered as “Dental Health Index” (D.H.I.). Author's Dental Health Index is ratio obtained by dividing standardized rate of high grade carious teeth by standardized rate of filled teeth. In order to estimate the dental condition of school children involving various age groups, it is necessary to standardize the figures using the factor calculated form data of whole community. Because the rate of dental caries incidence seems to alter regardless of endeavor on children's side, the incipient carious teeth are not taken into consideration. For this reason, numbers of untreated carious teeth with high grade carious lesion and numbers of filled teeth are adopted as object of the evaluation for the status of dental health program in school; the numbers of untreated carious teeth with high grade carious lesion are useful as the indicator of negligence for oral hygiene, and the numbers of filled teeth as the indicator of results of dental health education in school. It is believed that this index excels any other means in evaluating the status of the dental health program in school.
As to the blackish-brown deposit on the teeth, th- author investigated not only the frequency of the type of its occurrence but also the relations between that deposit and the decay of teeth, and seeking after the nature of that deposit, carried out various experiments with following results. 1. The author named the sole object of his study, i. e. the deposit on the teeth blackishbrown dental deposit. 2. The frequency of occurrence of blackishbrown dental deposit. Investigating the occurrence of the deposit about 7191 persons of both sexes from 6 to 14 Years of age, the author obtained the following results: 1) As to the age and sex, that deposit occurs most frequently at the epoch when the teething of deciduous teeth or the eruption of permanent teeth is completed in both sexes. 2) As to the position, the deposit occurs most frequently at the front teeth of lower jaw in both sexes. 3. The type of occurrence of the blackishbrown dental deposit. The author divided the types into 4 types and 8 kinds according to the states of occurrence of the deposit, that is Type I: one having the deposit on the whole set of teeth of both jaws, Type II a: one having it on the whole row of teeth of upper jaw only, Type II b: one having it on the whole dentition of upper jaw and on a limited part of lower jaw, Type III a: one having it on the whole dentition of lower only, Type III b: one having it on the whole row of lower jaw and on a limited part of upper jaw, Type IV a: one having it on a limited part of upper jaw. Type IV b: one having it on a limited part of lower jaw, Type IV c: one having it on a limited part of both jaws. 4. As to the age and sex of the same age, the deposit occurs most frequently on the whole set of teeth of both jaws (type 1) independent to the age and sex, 5. Relation between the blackish-brown dental deposit and the tendency to suffer the decay of teeth. Searching for the ratio, of the decaying of teeth about 1601 persons having this deposit and 1225 persons having no such deposit, it was found that the one having that deposit is less disposed to the decay of teeth than the one having no such deposit, independent to sex and age. 6. The author could not find any difference between the hydrogen ion concentration of the saliva of the one having blakish-brown dental deposit and that of the one having no such deposit. 7. Comparing the amylase value of saliva of the one having blackish-brown dental deposit and that of the one having no such deposit, the acthor could not find any difference between the two. 8. When compared the result of spectroscopic analysis of the saliva and serum of the one possessing blackish-black deposit to that of the one having no such deposit, the saliva of the former was found to contain Mn in addition to the constituents of saliva of the latter, but no difference could be found as of their sera. 9. Analysis of blackish-brown dental deposit, 1) Results of the analysis of blackish-brown dental deposit showed clearly that it consists of Ca, Sr, Ag, Zn, Cu, Al, Fe, Mg, Mn, (Au), P, Si, Hg, and B. 2) Analysis by X-ray diffraction method showed that blakish-black dental deposit was Ca3 (PO4) 2. H2O. 3) According to the results of quantitative analysis of b-b. dental deposit, it contains 18.9% P and 36.6% of Ca. 10. From the results of the colour dissolution test of b-b. dental deposit, it was clear that the pigment black colour was organic and soluble in antiformine.