This study was made on the comparison between the deciduous dental caries at five years old and the dental caries of permanent dentition at eighteen years old by the follow-up examination in the same persons, who were residented in Suginami-ku, Tokyo. The subjects of this study were born in 1943, 1947 and 1948, and those numbers were 46, 66 and 41 respectively.
Conclusion were as follow: -
1. It appeared that the significant correlation was existed between the number of def teeth at the age of five and the number of DMF teeth at the age of eighteen in subjects born in 1947 and 1948. (r=0.55 in 1947 case and r=0.44 in 1948 case.) But there was no significant relationship in 1943 case, (r=0.23) probably because of the changes of food conditions during the Second World War.
2. According to the extention pattern of deciduous dental caries, subjects were divided into four groups, and the relationship in each group was studied. There was found the tendency that the group with the more extensive conditions in deciduous caries had the more DMF teeth in their permanent dentition.
3. With regard to the intensity and extension on the caries conditions of deciduous molars, they were divided into four groups. There were also the tendency that the severer group in deciduous molars had the more DMF teeth in their permanent dentition.

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The author has previously reported the marked difference of the morbidity from gingivitis classified by PMA index of Massler and Schour between the school pupils age ranging from 7, 11 and 14 years of the inland farm and of the Pacific coast fishing areas in northeastern Japan. The results thus encouraged the author to study the oral conditions of 551 adult inhabitants 40 years and over from the inland farm and the coastal fishing villages.
In this examination the pyorrhea findings were expressed using a new periodontal disease index “Score 6, 8”of the author. And the mean index value of each age class was compared between the two areas among male and female.
Periodontal index (S. 6, 8) values were higher in the inland farm area than in the coastal fishing area for both sexes with the significance level of P<0.01 in all the age classes.
Since nutritional studies in an inland farm and a Pacific coastal areas have revealed that the intake of protein, calcium and vitamins of B complex was superior in the coastal area, and the acid-base balance, indicated by both serum CO₂ content and serum total calcium level gave higher values, the significant difference in the morbidity of periodontal disease between both areas infers that the nutritional condition in early life might influence the development of gingivitis and pyorrhoea in later life.

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A few follow-up studies have been published to determine the advancing speed of early carious lesion by some investigators. However, since they are only concerned with two types of incipient caries, the sticky fissure and the caries of 1st degree, the results obtained are not exhausive or conclusive. This study was therefore performed.
The permanent teeth of elementary school children, 181 boys and 180 girls of six to ten years of age in Asaka of Saitama Prefecture, were thoroughly inspected in April of 1965. At this examination, 42 cases of white spots, 6 cases of brown spots, 163 cases of the browned pits or fissures, 98 cases of the sticky fissures, 261 cases of visible carious cavities restricted within the tooth enamel, 124 cases of carious cavities reached to the dentine, and 40 cases of more advanced cavities suspected the presence of pulpitis were detected. The lesions were re-examined six-monthly for two-years by the same examiner. In case of any alteration was observed, it was noted in a chart as Fig. 1. From counting the cases altered or not, Tables 1 and 2 were made. A number of the cases were treated in every six-months because they were not supervised through the observation period. By the computing method except that the cases were treated, each supposed progressing rates of four six-months were obtained. The cumulative progressing rates for 12 to 24 months were calculated from these four estimates. The results were presented in Tables 3 and 4 or Figures 2 to 8.
1. About ten percent of the withe spots, just one-third of the brown spots, approximate one-third of the browned pits or fissures, and 60 percent of the sticky fissures were progressed into discernible carious cavities in a year. But they did not become the more advanced cavity suspected a diseased pulp in the same period.
2. One year after, 50 percent of the visible cavities resticted within the tooth enamel were become definite dentine caries and 4 percent of them were advanced to the large cavities suspected pulpitis.
3. Approximate one-fourth of the carious cavities reached the dentine were progressed into the large cavities presumed pulpitis and 3 percent were indicated for tooth extraction after a year.
4. More than one-third of the carious cavities suspected pulpitis were become indication for tooth extraction in a year.
5. The supposed progressing rates of four six-months periods vary considerably in every carious lesions. By using chi-square distribution-test, the variations of the white spots, the sticky fissures, and of the large cavities suspected pulpitis showed statistically significant difference at 1 or 5 percent level. The others also had some tendency, however they did not present a significant difference (Tables 5 and 6). Then, it was assumed that the initial caries of school children had a trend to progress in the first year but the clinical cavity did not.
From the consideration of these results, it seems to be apparent that the visible surface breakdown and the sticky fissure in young permanent teeth should be accepted as a clinical caries in order to avoid a serious damage by caries, but the white or brown spot and the browned pit or fissure should not.

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Basically, this research project was planned with Takeuchi's conception of epidemiological principles on dental caries attack. The standard of diagnosis of dental caries was in accordance with those decided by WHO, while attention was paid to those points which were reported by ADA as being necessary in such a conduct.
The subjects employed in this field work were third and fourth grades in 1964 in primary schools in urban and rural environments, and the investigation was made on two kinds of caries attacked tooth surface, one was the presence of tooth surfaces showing only the clinical caries by WHO standard, and in the other, tooth surfaces having spots such as white and/or chalky spots, rough spots or tiny discoloured spots were included, as well as the above-mentioned tooth surfaces showing clinical caries.
By stratified random sampling in various degrees of caries, the subjects were divided into experimental group and control group. A dentifrice containing 0.7% sodium monofluorophosphate (Na₂PO₃F) was given to the experimental group, while a dentifrice containing no fluoride component was given to the control group. Both were instructed to brush their teeth properly twice a day, and were supervised to continue it for one year.
The numbers of subjects who could cooperate throughout the year were 611 in the experimental group, and 619 in the control group.
The judgment of the effect of caries prevention was done merely in the limited range of the mesial and distal surfaces of the upper central incisors and the mesial surfaces of the upper lateral incisors. The result was as follows:
The caries incidence rates under the diagnosis of the clinical caries alone were the experimental group 4.27%, and the control group 5.64%, that is, the percent reduction was 24.3. On the other hand, the caries incidence rates under the diagnosis of the above-mentioned spots in addition to the clinical caries were the experimental group 9.30%, and the control group 11.88%, showing 21.7% of reduction. These differences in the caries incidence rates were statistically significant. The reversal of diagnosis of clinical caries and spots were 5.0% in the experimental group, and 2.7% in the control group.
From these results of field work, the dentifrice containing sodium monofluorophosphate was recognized to be effective in the prevention of dental caries.

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In succession with the previous report, more detailed observation on two lesions, absent Pb-mark and infected tubulus in the fissure caries of rats, was reported in the present paper. Chronological observation of these lesions showed that the absent Pb-mark appeared earlier, being called the early lesion, and the infectious lesion was found at later stage of experiment in highest incidence, being called the late lesion, a successor of the early lesion.
The early lesion often accompanied with half-moon shaped hematoxylin-phobe dentin matrix, brown pigmentation of dentin, bacterial crowd at the dentinoenamel junction, bacterial plaque in the fissure and bacterial invasion in the enamel binding above two bacterial settlements. The findings concluded that the once marked Pb-line in dentin did not remove spontaneously during 110 days after marking, but in vitro examination proved that removal of Pb-mark was easily resulted after action of decalcification agents, either acid or chelator. Therefore, the half moon shaped discoloration of the early lesion may probably be a track of decalcification. And decalcifying agents may sent from the bacterial crowd existing in the dentinoenamel junction. In dentin caries, however, the early lesion may follow the pre-early lesion characterized by the intact Pb-mark, the bacterial crowd and brown pigmentation.
Instead of the early lesion, progress of infectious process in the late lesion may need action of neither acids nor chelators as bacterial products. The late lesion was often found under the cavity, exposing dentinal lesion toward the bottom of the fissure. In additional findings, at the summit caries, only the late type of lesion was found from the first. The differences between the early and late lesion in the mechanism of their production could be assumed from point of view on the different growth environment of bacteria existing, i-e. beneath the thick enamel layer and in dentinal tubulus under the open cavity where oxygen supply to bacteria may be much better than the dentinoenamel junction. Now carious progress in rat dentin may assume that in the early stage, after some lag phase of pre-early pictures, it proceeds exclusively decalcification by acid or chelator produced from bacterial crowd in the dentinoenamel junction, which in the later stage, invades into dentinal tubulus under the environment of better supply of oxygen and organic nutrient.

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