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The purpose of this study was to evaluate the effects of a fluoride mouth-rinsing program (FMR) on dental health after the FMR program was completed. The state of dental health, including caries prevalence, was examined under blind recording conditions concerning participation in the FMR for 11th grade students in 10 public high schools, from 11 municipalities in Niigata Prefecture. The procedures of the FMR were carried out in these areas weekly, with 0.2% NaF, or daily, with 0.05% NaF, supervised by the classroom teachers in each school. The subjects, 321 in total, were classified into 3 rinse groups, each of which participated in the FMR for different periods of time, and a control group. The results of the statistical analysis showed increasing benefits in relation to increasing periods of participation. The reduction rate of caries prevention was the highest in the F11-group, subjects who participated in the program for 11 years from 4 to 14years of age. The F11-group was 56.0% lower in the mean DMFT and 81.8% lower in the mean number of highly progressed carious teeth than the control group, with statistical significance in both cases. The percentage of students who had toothaches or who were absent from school in order to visit a dentist was lower in the rinse groups than in the control group. We conclude that, in countries such as in Japan where caries prevalence is relatively high, a school-based FMR program throughout the school years is profoundly effective in preventing the occurrence and the progression of caries, and it could be the foundation of lifelong dental health care.

a comparative study was made in Karakoram (Goma village, 1974), northwest Nepal (Simikot village, 1983) and Yunnan province (Sinong village, 1989). Japanese data (1987) was used for comparison.1) In Goma and Simikot, the number of cases of permanent tooth caries was extremely small. On the other hand, it was very great in Sinong and Japan.2) The patterns of DFT can be divided into two groups: one group includes Sinong and Japan, the other Goma and Simikot.3) The DFT rate according to the location of teeth. The patterns can be divided into two groups, Sinong and Japan, Goma and Simikot.4) Caries surfaces: in Simikot, there was not a great difference between the number of cases of occlusal, proximal or distal and labiolingual surface caries. In Sinong, both upper and lower jaws had a great number of cases of occlusal surface caries, but the difference between the surfaces decreased according to age.5) The transition of caries grade: in the three Tibetan areas, the ratio of C4 to all carious teeth was quite similar.6) Missing teeth: in Goma, where the number of caries cases was extremely small, the number of missing teeth was the greatest after 35 years of age, probably because of severe attrition.7) Caries ratio of three molar teeth:Second and third molars: caries increase patterns were similar in the three Tibetan areas and in Japan.First molar: in Sinong, caries increased rapidly after eruption, Goma and Japan followed Sinong and in Simikot, caries increased very slowly.

Five thousand eight hundred elderly persons (2, 212 males and 3, 588 females) aged 40 years or above, who lived in Miyako district, Okinawa, were examined for the occuccence of dental caries, periodontal diseases, and tooth loss with reference to systemic conditions of the examinees.The Average number per person of present, intact, and carious teeth decreased with increase of age, and the rate of carious teeth (the total, untreated and heavy) and tooth loss increased. However, the relative number of persons who suffered from dental diseases, namely dental caries. periodontal diseases, or untreated tooth defects, decreased with higher age. Compared to ambulatory (non-bed-ridden) persons aged 60 years or higher, the bed-ridden had fewer present and intact teeth and the rate of untreated and severe carious teeth was higher. The Majority of the bed-ridden also had multiple and severe dental diseases, mainly dental caries and tooth loss, at higher rate. The tooth defects were mostly untreated but no other dental diseases coexisted in most of the cases.A significant number (41.3%) of the examinees had systemic disorders, mainly cardiovascular diseases. Most of the patients suffered from multiple diseases (40.2%) and required medical treatment (51.9%). Approximately two-thirds (63.4%) of the examinees required dental treatment. The bed-ridlen had generally a multiple number of systemic diseases, of which more than half (55.3%), compared to onefourth (28.1%) for the healthy, required prompt medical examination and treatment. The neccessity of dental treatment was higher (61.9%) for the bed-ridden than for the ambulatoy (53.9%), and in most cases prompt treatment was desirable.

A dental health examination of 908 inhabitants, 40 years of age and over, of Ueno, Okinawa, was carried out in concurrence with a general health examination.This study is deals especially with dental caries and general diseases. The prevalence of dental caries was 81.8%, and the prevalence of untreated dental caries was 42.6%, and these decreased with advancing age. This tendency was particularly marked in those aged 70 years and over, and also indicated the influence of the high rate of missing teeth in inhabitants of this age. The ratio of carious teeth, the ratio of untreated teeth, and the ratio of missing teeth increased with advancing age. This tendency was particularly marked in those aged 80 years and over.Some general diseases were present in 55.5% of the inhabitants examined, 36.4% of whom were suffering from two diseases or more. Particularly in subjects aged 60 years and over, the prevalence was as high as 67.6%, 58.9% of which were evaluated as requiring treatment. The incidence of locomotorial, connective tissue and cardiovascular diseases, and nervous, sensory diseases was high, and 28.1% of the sujects with carious teeth requiring treatment were also suffering from gneral diseases for which treatment was necessary. The incidence of general complications in the subjects aged 60 years and over was particularly high, 37.7%. These results suggest that it is necessary to formulate a new medical examination system that will be able to accomodate general conditions in the aged for the establishment of dental science and treatment in this group.

The aim of this study was to develop a new classification of carious incidence patterns in children. The subjects were 702 children aged 18/19 months and 378 aged 24/25 months. The children's teeth were examined and they were grouped by their carious tooth types at 40/41 months of age the mean dmft and mean dmfs were compared between groups. The following results were obtained.The children with caries at the age of 18/19 months could be divided into two classes, i. e., children who had carious teeth in only upper anteriors (class 1-A) and those who had carious teeth in molars or lower anteriors (class 1-B). The children with caries at the age of 24/25 months could be divided into four classes, i. e., children who had carious teeth in only the upper incisors or lower molars (class 2-A), those who had carious teeth in the upper cuspids or upper molars but not in the lower anteriors (class 2-B), those who had carious teeth in the lower incisors but not in the lower cuspids (class 2-C), and those who had carious teeth in the lower cuspids (class 2-D).When the classifications were applied and the carious scores compared between classes at the age of 40/41 months, the children of class 1-A had statistically lower carious scores than those of class 1-B. The children of class 2-A had the lowest carious scores, and those of class 2-B, class 2-C, and class 2-D had significantly more carious teeth in ascending order.From these results, we suggest that the newly proposed carious incidence patterns of children aged 18/19 months or 24/25 months is useful for predisting the caries prevalence at the age of 40/41 months.

Thirteen hundred and nineteen children aged 3 years living in Higashi-ku of Fukuoka City were examined for dental caries. To their mothers were given questionnaires concerning feeding methods, between-meal eating habits, using period of feeding bottles, use of feeding bottles at bedtime, kinds of between-meal snacks, drinking of acidophilus beverages, and so on. The percentage of the children with carious teeth was 75.5 and the mean deft was 4.5, and these were both samaller than the percentage of children with caious teeth and the mean deft of the whole nation, respectively. The percent of children with carious teeth was significantly larger in the following groups: breast-fed children, children using feeding bottles for more than 24 months, children using feeding bottles often at bedtime, children eating between meals irregularly, and children drinking acidophilus beverages every day or 2-3 times per week. The groups that took between-meal snacks irregularly had the largest percentage of children with carious teeth (83.5%) and the largest mean deft (5.5) throughout this study. Regarding the use of feeding bottles at bedtime, and between-meal eating habits including drinking of acidophilus beverages, breast-fed children did not have so strong a tendency toward dental caries as mixedand bottle-fed children. This study indicated that some circumstances such as breast feeding, long-term use of feeding bottles, frequent use of feeding bottles at bedtime, and irregular eating between-meal snacks might be harmful to the dental health of 3-year-old children.

In order to control permanent tooth caries among school children in a nonfluoridated community, a dental health administration was conducted in Saku City, Nagano Prefecture, for six years, from April 1971. This health administration consisted of two parts: (1) daily mouth rinsing for one minute with 0.05% sodium fluoride solution and (2) detection and immediate filling of initial caries, extending the treatment from the children in lower grades to those in higher grades. At the beginning of the study, the subjects numbered 872 in the administration group (two primary schools and one middle school) and 1, 047 in the control group (also two and one). The latter group, however, was disqualified for the control group after 1976, because children in those schools have been administered the fluoride mouth rinsing from April 1975.After the start of the administration, the percentage of children with DMF teeth in the administration group reduced gradually from 72.8% in 1971 to 56.2% in 1975 and 52.2% in 1977, while those in the control group were 79.1% in 1971 and 73.5% in 1975. In comparison between mean DMF teeth per child of both groups in 1975, a mean caries reduction by the dental health administration for four years was 63.4%, and it was greatly significant statistically. As a peculiarity of caries preventive effects in this work, it was observed that the lower the grade of the children was in initiating the treatment, and the longer the administration term, the greater were the effects derived from it. As to the preventive effects to the tooth surface type after four years, the effects on the smooth surface (69.8%) were a little greater than those on pits and fissures (64.1%). Among the children in the administration group, smooth surface caries were observed in one tenth of those among in the control group; especially, the effects seemed to be remarkable in the case of the children who were respectively in the 1st or 2nd grade when they got the initial administration and received the administration for more than four years. As a result of using the primary and secondary caries preventive methods over a six-year period, no subject with advanced dental caries (C3and C4) was observed in the administration group.The chair time required for the treatment was about 15 minutes per tooth in initial caries, while about 1 hour in advanced caries. Assuming that a dental team consisting of one dentist and one dental hygienist spends one day a week for caries treatment to the school children from May to December after the annual dental examination in April, it is estimated that 800 carious teeth can be treated during the period. Therefore, even if we underestimate the caries preventive effects of the fluoride mouth rinsing at 50%, it is estimated that one dental team is able to control about 2, 000 school children.

Dental caries in school children has not decreased to a level corresponding to the efforts made to prevent it. As the caries prevalence in permanent teeth is very high during the period of compulsory education, the effective caries prevention should be promoted during this period. Therefore, it is considered valuable to survey the real state of caries prevention and provide school dental health service according to the results of survey. Yearly observation of the changes in oral conditions of same subject gives reliable results. In this study, I made a survey of dental caries prevalence on permanent teeth of school children for 9 years from the age of 6 years until they graduated from middle high school, and I preformed cumulative analysis of variance of multiple-way layout of the results. The decomposition of factors was also followed to exhibit the difference in caries prevalence between different kinds of teeth or tooth groups which have not completely analyzed been so far.I obtained the following results.Caries prevalence during the period of compulsory education increased by 2.85 carious teeth per year and its regression equation was as follows;Y (DMF) =2.85X (school year) -0.78The tendency of caries prevalence in different kinds of teeth or tooth groups was varied and the dental health care for younger and older primary school children and middle high school children should be focused on the first molar, incisor of upper jaw and premolar, and second molar, respectively. Moreover, the comparison of these results with those of commonly used cross sectional studies showed much similarity. I also suggest that the caries prevalence of the first molar could represent the tendency of the whole dentition.The statistic analysis used for the first time in this kind of survey was useful to analyze yearly data or the data from different kinds of teeth or tooth groups.

The incidence of dental diseases would be expected to rise as frequency of tooth to denture base discrepancy becomes higher, because the discrepancy seems to have pathogenetic influence on malocclusion, dental caries, and other related disorders. By studying incidence and seriousness of dental diseases in each historic age, therefore, it may be possible to obtain pathogenetic information on dental caries, to estimate the degree and extent of reduction of human dentition, and even to discuss evolution and civilization.From this point of view, we have already reported on dental caries and some other diseases in Japanese remains from the Kamakura era, and conclusively pointed out that the degree of the discrepancy was not so dominant in that era as in the modern age, but it seemed firmly to exsist, with pathogenetic influence on dental caries. In the present paper, incidence and specificity of dental caries, and occlusal and proximal attritions observed in Japanese remains from the later Jomon period are reported. We also discuss the degree and extent of the discrepancy, its pathogenetic role in dental caries, and the food and eating behavior in comparison with those in the Kamakura and modern ages.The materials used were 89 maxillae and 102 mandibles with permanent or mixed dentition, selected from 327 Japanese skulls mostly from the later Jomon period, stored in the University Museum, The University of Tokyo.The frequency of dental caries in the Jomon period was almost the same as in the Kamakura era, but much lower than in the modern age. However, its seriousness was much worse than in the Kamakura era, and almost the same as in the modern age, as indicated from the fact that the carious teeth are distributed more frequently in C3 and C4 than in C1 and C2.The pathogenetic pattern of dental caries in the Jomon period is different from that in the Kamakura era and in the modern age in the following points. 1. The distribution of carious teeth is biased towards the posterior teeth, but not so dominantly as in the Kamakura era. 2. Carious teeth are distributed even in the anterior region. 3. The rate of carious teeth for the third molar does not exceed that for the first molar in both maxilla and mandible. From these facts, the dental caries in the later Jomon period seems to be of environmental pollution type, while it is of the discrepancy type in the Kamakura era and of a combination type in the modern age.

A community dental health program was conducted in Maki Village (population was about 5, 000), Niigata Prefecture, for 10 years from 1974.This community dental health program consists of two parts: (1) fluoride mouth rinsing in nursery, elementary and junior high school and (2) detection and immediate treatment of initial caries extending the treatment from the children in low grades to those in high grades.In 1975, the Association of Dental Health for Children was organized for promoting this program in Maki Village.A comparison of caries prevalence was carried out among school children at baseline (1974), 5 years after (1979) and 10 years after (1984) in Maki Village, and the caries prevalence of school children in Maki Village (1984) was compared with that in Village S (1984). The school children in Village S had not used fluoride mouth rinsing.The results were as follows.1) In Maki Village, mean DMF teeth per children of the elementary and junior high school children was 3.67 (SE=0.11) in 1974, 1.93 (0.10) in 1979, and 0.93 (0.06) in 1984. Caries reduction rate was 75 % for 10 years, and this was highly significant statistically.The percentage of school children without carious teeth increased from 13 % in 1974 to 56% in 1984, and the percentage of school children with some decayed teeth was only 6% in 1984.2) The caries prevalence of the school children in Maki Village was lower than that in Village S. The difference of the percentage of children with DMF teeth and of mean DMF teeth was 35% and 69%, respectively.The good dental health in Maki Village was the result of the 10-year community dental health program of school-based fluoride mouth rinsing, and detection and immediate treatment of caries.The continuation of this program was supported by the Association of Dental Health for Children.

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).

This study was undertaken to find the relationship between the morphological characteristics of fissures and the prevalence and the extent of initial caries and to deduce the site of caries attack in the fissures of premolars extracted from orthodontic patients. The teeth were 124 premolars which appeared clinically sound, extracted from 61 children aged 8 to 15 years, and having electrical resistance values of above 600KΩ. Vertical bucco-lingual serial ground sections were prepared from each tooth and 835 sections were obtained.The sections were observed by light and polarizing microscopy and by microradiography, and the size of fissures was measured using a profile projector.The following results were obtained.1. In the frequency of morphological characteristics, IK-type of fissures were 55, I-type 40, U-type 19, V-type 14, and other types 13 (Table 3).2. In the prevalence of carious lesions, carious teeth were 54 out of 124 (43.5%), and carious fissures were 56 out of 141 (39.7%) (Table 5).3. Regardless of morphological characteristics, all sites of carious lesions showed the same tendency: 56 (100%) were found at the outer third of the fissure, 55 (98.2%) at the fissure entrance, 47 (83.9%) at the middle third of the fissure, 34 (60.7%) at the inner third of the fissure, and 14 (25%) at the bottom of the fissure (Fig. 2, Table 6). From these findings, it was assumed that the main site of caries attack was probably at the outer third of the fissures.

As an index for the estimation of oral environmental condition in a population, the annual sugar consumption per head (p) has been used by Takeuchi and his group. They observed that the curve of Cx (number of teeth newly attacked by caries during the post-eruptive tooth age x-year per initial 100 teeth) in the cohort survey on one kind of tooth at the time when p was roughly constant represented the most fundamental pattern of dental caries incidence. Furthermore, ΣCx (cumulative number of carious teeth up to the post-eruptive tooth age x-year per initial 100 teeth) at the time when p has been constant at 10, 20, or 30kg, could be profitable to evaluate the condition of caries prevalence with reference to the different level of p.The present survey aimed at obtaining caries indexes for low sugar consuming population in order to make such a graph, at the same time assisting a public dental health program in the Republic of China.The survey was conducted in some mountain farming villages, about 500m above the sealevel, where high quality tea and bamboo are producted, in Loo-Ku Song, Nantou Hsien, at 60-70km south-south-east of Taichung, Taiwan.Oral examinations were made once a year in September from 1971 through 1977. The project was composed of three kinds of surveys: I: cross-sectional surveys of the 1st-6th grade pupils of primary school and 1st-3rd year pupils of junior high school in 1971 and 1972: II: cohort survey of the children who entered primary school in 1971 and 1972, continuing untill 1977; and III: cross-sectional surveys of 1st-6th grade pupils of primary school and 1st-2nd year pupils of junior high school in 1976 and 1st-6th grade pupils of primary school and 1st-3rd year pupils of junior high school in 1977 (Fig. 6).The judgement of dental caries was made by WHO criteria for dental caries. Practically insignificant level fluoride was found in the drinking water of district. A survey on snacks taken between meals was conducted in the first year and 7th year.The results of the surveys which were done in 1971 and 1972 were as follows.1) The total number of the examinees in 1971 and 1972 was 6, 080.2) Caries frequency of these children was shown in Table 2.3) Average DMF score of these children was shown in Table 3.4) The sugar intake through snacks was tabulated in Table 5. The average annual sugar intake per child was estimated to be approximately 7kg.

Kikuchi City has been said to have the largest number of pupils having carious teeth. The following investigation was made by the Research Group of the Association in order to clarify their actual condition.Material was the records of oral examinations in a total of 3774 pupils in all the eleven primary schools in Kikuchi City, and soley the so-called 6-year-old molars were investigated, counting both treated and untreated teeth, and a child having either one molar or even four (upper, lower, left and right) molars affected by caries as a head.1. The caries incidence rate per head of the 6-year-old molars in the pupils of oll the primary schools in Kikuchi City in 1965 was 71.11% (_??_67.51, _??_74.93). Also the per-head-percentage of the carious 6-year-old molars which had been treated on was 40.99%, while its per-tooth-percentage was 52.33%. It is rather good, but is far from an idealistic dental service.2. In this study the city was divided into four parts, the mountain, the mountain with some paddyfields, the business area, and the level area mostly paddy-field. The highest rates of caries incidence in the 6-year-old molars at different age levels always were those in the business area, the part of the mountain with paddy-fields closely following. Then the mountain, and the lowest rates always were those in the level area.3. The caries incidence percentages of the 6-year-old molars per head and per year of entrance to school were: the 1st graders in 1960 was 16.00%, while those in 1965 was 38.39%, the latter being approximately 2.6 times as much as the former.

A total of 487 pupils ranging from 4 to 6 years of age, selected from 5 kindergarten in Tokyo City were investigated. Dental examination was conducted together with the nutrition investigation based on the Nutrition Survey in Japan. The investigation was conducted for three days from October 2, 1963.As for the nutrition, the amount taken was investigated for each item of investigation. As for the teeth, the number of caries was compared and observed for each kindergarten and each age group. The results were as follows.1. In case of the total number of boys and girls, the carious teeth prevalence rate was 88% for 4 year old children, and 96% for 5 and 6 year old children. When these figures were compared with the national average shown in the Report of the Survey of Dental Diseases (1957) conducted by the Medical Affairs Bureau, Ministry of Health and Welfare, the number was low for 4 year old children, high for 5 year old children, and the same for 6 year old children. As for the average number of carious teeth per person, it was 5.4 for 4 year old pupils, 8.1 for 5 year old pupils, and 8.1 for 6 year old pupils. They were all less than the national average.2. As for 5 and 6 year old children, when the average number of carious teeth and the amount of the nutrition investigation items taken by each pupil were compared for each kindergarten and age group, the number of caries increased when the amount of candy taken was increased, and those taking sufficient amount of nutrition for all items of the investigation showed less caries.In case the average number of carious teeth is obtained for the 3, 5, and 6 year old pupils according to the month of birth, those born in August and September had the greatest number of carious teeth. Contrary to this, those born in January and June had less number of carious teeth.3. The difference in this average number of carious teeth per person was assumed to be caused by the changes in the mother body owing to climatic changes and especially the nutrition, since infants born in August and September have the period of mineralization in the bad season of summer when it is high temperature and high humidity whereas, infants born in January and June have the period of mineralization in spring or autumn when the climate is very good.

Though Takeuchi and his group have clarified epidemiological phenomena of caries attack in parmanent teeth, no study of this sort has been done in deciduous teeth. Therefore, this study was made to obtain basic epidemiological patterns of caries attack in the deciduous teeth for each type of tooth when the annual sugar consumption per head (represented as p) was constant.For this purpose, the central part of Kameoka City near Kyoto (Fig, 1), was chosen as the place of investigation. The standard of living in this place was about the average of Japan (Table 1) and the flouride content in the drinking water was insignificant in relation to caries attack (Table 6) . Considering all of the infants aged 0, 1 and 2 years in 1965 in this area as population, a semi-annual oral examination for longitudinal study was carried out in the same individuals for 3.5 years (Table 2) . During this period (p) was 19-22 kg. Examination was performed by a dentist (the author) with an explorer and a dental mirror, considering as carious the pits and fissures that were clearly sticky or worse and the surfaces that were rough or had worse changes.Only the teeth observed from their post-eruptive tooth age 0 were calculated at every half-year, putting the teeth of the same denomination of both sexes and left and right sides together, and separating those of different types, using a tooth or a surface as the unit of caries attack (Table 3) . Three kinds of indexes were calculated by the following methodCaries incidence rate during post-eruptive tooth age x (Mx) = Number of teeth newly attacked by caries during post-eruptive tooth age (x-0.5 yr. ) to x-yr. / Number of sound teeth at the post-eruptive tooth age (x-0.5 yr. ) ×100 The number of teeth newly attacked by caries during the post-eruptive tooth age x (per six monthes) per initial 1, 000 teeth (Cx) was calculated with Mx as follows: Tooth age Number of sound teeth (Sx) Cx 0 S0 = 1, 000 S0×1O M0=C0 0.5 (S0-C0) = S0.5 S0.5×1O M0.5 = C0.51.0 (S0.5-C0.5) = S1.0 S1.0×1O M1.0=C1.0The cumulative number of carious teeth up to the post-eruptive tooth age x-year (per six monthes) per initial 1, 000 teeth (ΣCx) is the accumulation of Cx. The same methods were used in the calculations of the tooth surface. Furthemore, the e-kx line was drawn by the method shown in Fig. 2, and from the polygonal lines of Cx and ΣCx, their trend lines were plotted.The three indexes of caries (Mx, Cx and ΣCx) were shown in Table 4. In graphs the polygonal lines of Mx are shown in Figs. 3 and 4. The polygonal line of Cx is shown in Fig. 5 and the polygonal line of Cx in Figs. 7 and 8. The trend lines of Cx and ΣCx, and the e-kx line are as shown in Fig. 9. The angle between the e-kx line and the 1-line and the post-eruptive tooth age at which Cx trend line reached its summit are shown in Table 9.It was conceivable that Fig. 9 shows a typical pattern of caries attack on the deciduous teeth in Japanese infants when (p) is around 20 kg. It was noticed that the Cx trend line of this figure coincides with integrals of exponential probability and that the e-kx line is a straight line. From these facts it was deduced that at least in the case of deciduous teeth and when (p) is constant, caries occurs as a phenomenon in which the resistance of the tooth makes the normal distribution as a process in the first stage, then as the second stage, an initial carious change appears in accordance with the chance of caries which is constant (Fig. 10).Patterns of proximal surface caries were also discussed (Figs. 6, 11, 12).

It is generally believed that the lactobacillus count in a measure of susceptibility for tooth decay of the public as well as the acidogenic potency in a mouth. However, numerous facilities and materiales which can be available in only civilized countries should be equipped on its practice.Sputocrit estimation of Lactobacillus count was originally found by Kondo and Onisi in their findings that bulk of oral desquamates obtainable in a gargled water is parallel with populations of organisms belonging to the glycolytic layer in the mouth, such as Streptococci, Veillonella, Lactobacilli, and Micrococci. Their findings, however, based on the results that were obtained from bulk of desquamate which was sedimented under 10000 rpm centrifugation. In the present work, a 800 rpm very popularhand centrifuge was used.The obtained bulks of desquamates in such way, significantly correlated to the intraoral. populations of Str. salivarius, Str. mitis, and Veillonella, but not to Lactobacilli and Fusobacteria at 1% level of significance.Thus, use of hand centrifuge seems to be simple substitude of sputocrit estimation of latent glycolytic potency in the mouth of the school children.For the sake of caries susceptibility, number of DF cavities and carious teeth were also counted, but results insignificantly correlated to the bulk of desquamates. Another possibility of neutral correlation between actual cavities and desquamation was discussed to be an inexisting relation.

In primary school, the prevention of dental caries with the use of fluoride offers various difficulties regarding equipment, the means of actual administration, time and expense. Using tablets for oral washing containing 1 mg of sodium fluoride per tablet, 116 school children between the second and fourth year were made to chew 2 tablets daily after their lunch for 1 year, after which the mouth was rinsed with water, as a measure for preventing caries.Using 206 children in the same school year as controls, children of both groups were examined as to the state of carious invasion of the permanent teeth with DF (treated and untreated teeth) in comparison.As a result, in children of each school year, the percent with DF in the upper and lower jaw, the average number of carious teeth per person, and the number of involved molar tooth surfaces per person increased in both the treated and control groups after 1 year. However, the increase was smaller in the treated group. In the ratio of DF teeth in the upper and lower jaw, an increase was noted in control children but a decrease was seen in treated children.The ratio of caries inhibition in the DF teeth of treated children was calculated. In the average number of teeth per person in the upper and lower jaw, the ratio was 57.67% in the second school year, 55.63% in the third school year, and 34.62% in the fourth school year, giving a higher rate in the lower school years. However, in the average number of involved molar tooth surfaces per person, the ratio was 35.38% in the second school year, 52.83% in the third school year, and 53.33% in the fourth school year, giving a higher rate in the higher school years.The present trial using tablets containing sodium fluoride for oral washing can apparently reduce expenses and omit the complex procedure of dissolving tablets in water. Moreover, an effect of caries prevention is obtained. This then appears to represent an effective method for preventing dental caries in children.

As yet few observations had been reported concerning the prevalance of carious lesions in preschool children in Japan, authors examined the dental caries incidence of 2, 123 children in City of Kawasaki under the purpose to obtain the more conclusive data. The results are as follows:1. In the deciduous dentition, caries started prior to the first birthday, and the percentage of dental caries contraction was 85% at 3 years and 98.5% at 6 years of age.2. The number of carious teeth per person were 6.25 teeth at 3 years and 10.25 teeth at 6 years of age.3. In the upper jaw, the susceptibility to carious lesions were central incisor, second- and first-molars, lateral incisor and canine in descending order. In the lower, both molars had equivalent high susceptibility, but all frontal teeth had extremely resistance to carious lesions.4. The rate of caries contraction on each surface of teeth in transition of age were studied.In addition, 1, 884 extracted deciduous teeth were also examined, and proximal surface has more susceptibility to carious lesion than the result attained by clinical examination.

Statistical observations conducted on the relationship between the prevalence of caries in deciduous teeth and bodily physical development in 1065 children between 3 years and 3 years and 1 month of age living in Tokyo between June 1963 and August 1964 revealed the following results.1. Relationship between the prevalence of caries in deciduous teeth and the Kaup index.The relationship between types of caries experience A, B and C in 3-year-old children according to the guide for dental health by the Ministry of Health and Welfare of the Japanese Government and the Kaup index classified into 5 groups, from 13 to 17 failed to show a significant difference among the groups. The ratio of types A, B and C was 2: 3: 0.5.No significant difference was noted in each group according to the author's classification based on the number of carious teeth, type a (free carious teeth), type b (1-4 carious teeth), type c (5-8 carious teeth), type d (9-12 carious teeth), type e (more than 13 carious teeth). However, those with a low index or under poor nutritional conditions had numerous caries. The ratio of types b, c, d and e was 3: 4: 2: 0.5 except in groups 13 and 17.The caries prevalence rate, the average number of carious teeth per child and the rate of carious teeth per total teeth present were calculated for each of the groups of caries classified according to the symptoms such as untreated teeth, caries 1st degree, caries 2nd degree and caries 3rd degree. In untreated teeth, C2 and C3, the group with a low index gave a significantly higher rate than the group with a high index.2. Relationship between the prevalence of caries and body length at birth and growth of body length from birth until the present.No relationship was found between the type of prevalence of caries and body length at birth and subsequent growth in body length. In the group with a short body length at birth, types a and e were frequently found in the number of carious teeth, but there was no significant difference in the degree of growth.In untreated caries and caries separated according to symptoms, the group with large body length at the time of birth showed a somewhat higher rate of prevalence. In the degree of growth, as in the number of caries, no significant difference was found.3. Relationship between the prevalence of carious teeth and body weight at birth and growth of body weight from birth until the present.No positive correlation was noted between the type of prevalence of caries and body weight at birth and growth of body weight. In the type of caries number, types d and e appeared less frequently in children with good development of body weight.In the untreated carious teeth and carious teeth according to symptoms, the ratio of caries was high in those with high body weight at birth. Regardless of the body weight at birth, the ratio of carious teeth was high in those with current poor development. The appearance of severe caries was especially high. Such a relationship was more pronounced in body weight than in body length.

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.

The relationship between the dental caries and the physical constitution together with the incidence of absence to school, which might be connected with learning, was investigated by making use of individual records of both physical and dental states at the time of the periodical health examination in 1963 on 259 pupils, the second- to the 6th-year graded, of a certain elementary school at a central part of Tokyo City.As for the classification of caries proceeding grades, deciduous teeth and permanent teeth were separately divided into either the treatment teeth or the carious teeth. In particular, carious teeth among permanent teeth were subdivided into the dental caries of the first grade (C1), of the second grade (C2), of the third grade (C3) and of the fourth grade (C4). Concerning to each grade, the average number of carious teeth per person was calculated and checked in relation to the physical constitution such as the height, the weight and the girth of the chest and to the incidence of absence to school, obtaining the following results.1. In the height, as compared with those who showed higher values than the national average value, those who showed lower values had more carious teeth. In deciduous teeth, the number of carious teeth was larger equally in pupils of all the year grades, while in permanent teeth the number of carious teeth of C2 and C3 was larger in them except for the 5th year grade.2. In the weight, those pupils who showed lower values than the national value of average, as compared with those who showed higher values, had more carious teeth in deciduous teeth throughout the year grades. Meanwhile, in case of their permanent teeth, the number of treatment teeth were smaller in the 2nd, 4th and 6th year grades. However, the 6th-year graded pupils showed a little larger number of C2, C3 and C4 carious teeth.3. In the girth of the chest, those pupils who showed lower values than the national average value, when they were compared with those who showed higher values, had generally more carious teeth in deciduous teeth throughout the year grades. In permanent teeth they exhibited a small number of treatment teeth except for pupils of the 3rd year grade. At the same time, it may be said that C1 was rare except for the 5th-year graded pupils, while C2, C3 and C4 occurred in general frequently.4. As described above, it was observed that carious teeth appeared rather often in case of the poor physical constitution at the time of the examination, that means, in pupils showing a poor bodily development, suggesting the importance in the protection of deciduous teeth during the elementary school period.5. During one year before the physical examination, those pupils who were never absent to school showed, in comparison with those who made as many as more than 10 times of absence, more numerous carious teeth of deciduous teeth in the 2nd, 3rd and 4th year grades and C1, C2 and C3 of permanent teeth in the 5th and 6th year grades. Therefore, it is assumed that the absence to school may be connected with the caries of the deciduous tooth in pupils of the low and middle year grades and of the permanent tooth in those of the high year grade.6. Similarly, if the R.I.D. Index (1961) of pupils making no absence was compared with that of pupils showing many times of absence, the former exhibited lower values throughout the year grades. Consequently, those who showed high caries proceeding grades of both deciduous and permanent teeth, showed also frequent absence to school.

This study was the result of three successive experiments that started from 1959, 1960 and 1962. Only first grade children of the primary schools in Tokyo and Yokohama city were used for the experiment.Experiment 1959: -The children who had lower first permanent molars free from carious lesions were selected from 16 schools. These children totalling 1.221 were divided into three groups, i. e., 2% NaF group, 4% SnF2 group and the control group independently in Tokyo and Yokohama area. All children were recieved dental prophylaxis and the children of experimental group were applied with respective fluoride solution for three minutes according to Knutson's method. The control group was similarly treated with distilled water. The treatment of all groups were carried out four times within one month.After two years, the 23 per cent (Tokyo) reduction and the 33 per cent (Yokohama) reduction were shown in children who were treated with 2% NaF as compared with the control group being evaluated by DMFT. In 4% SnF2 group, there were 20 per cent reduction in Yokohama, area, but no reduction in Tokyo area. These reduction were considered statistically significant at 1% level by Chi-square test.Experiment 1960: -The children totalling 994 were selected from 24 schools similarly as in 1959, and were divided into four groups that were 2% NaF, 2% SnF2, 8% SnF2 and the control group. All children were recieved dental prophylaxis and topical application of respective fluoride solution or distilled water (in the control group) according to Muhler's method. Two per cent NaF group and 2% SnF2 group were recieved four treatment during one month, but the control group and 8% SnF2 group were recieved a single treatment.After two years, the reduction of new carious teeth in 2% NaF group were indicated as 39 per cent (Tokyo) and 23 per cent (Yokohama) when compared with the control group. Per cent reduction of the SnF2 group versus the control group were indicated as follows, 2% SnF2 group was 16 per cent (Tokyo) and 6 per cent (Yokohama); 8% SnF2 group was 27 per cent (Tokyo) and 15 per cent (Yokohama). Two per cent NaF group in Tokyo and Yokohama and 8% SnF2 group in Tokyo were considered to show the significant reduction, but in other groups it was not significant (at 1% level).Experiment 1962: -The children in a school totalling 132 in Yokohama city were divided into two groups. The experimental group were recieved a single application of 2% NaF solution followed by a single application of 8% SnF2 solution on all the teeth after the dental prophylaxis. The latter treatment was applied in the following seven days. The other group served as the control without treatment.After one year, 57 per cent reduction (a significant difference at 10% level) was shown in this group evaluated by DMFT incidence, but after two years, there was indicated only 13 per cent reduction which was not statistically significant.In Yokohama city the children of six schools totalling 819 were divided into two groups. The experimental group was recieved a single application of 8% SnF2 solution on all the teeth after the dental prophylaxis, and control group was not treated. After one year, the 4 per cent or 7 per cent reduction was shown according to the DMFT incidence per capita or the DMFT percentage. After two years, there was no reduction being evaluated by DMFT incidence. These reduction were not considered to be significant.One of the reasons of apparently lower percentage reduction in SnF2 group might be attributed to the pigmentation on the fissures and pits after the stannous fluoride treatment, which were wrogly diagnosed as carious lesions and filled by the dentists in practice. To support this assumption, the filling teeth ratio in the SnF2 group was actually increased.