The present study was undertaken to clarify the effect of restricting the intake of sweetened foodstuffs on caries prevalence in deciduous teeth. 1961 nursery school children aged 1 to 5 years old in Sendai were given a dental examination and dietary data were obtained from parents by the use of a questionnaire (Fig. 1) in 1984. The correlation between data was statistically analyzed and the results were as follows.
The children who had restricted intake of sweetened foodstuffs had less caries than those who did not, but the difference was not statistically significant except in the 4-year-group (Table 2). However, the children who had commenced sweet restriction earlier showed less caries prevalence than those who had commenced late, and the differences were significant in the 2 to 5 year-age groups (Table 3).
With regard to the relation between the reason for the restriction of sweetened foodstuffs and caries prevalence, the mean deft in the group which had restricted sweets because of tooth decay was higher than in other groups or in the groups with no restriction and significant differences were observed between these groups in the children 2 to 5 years of age (Table 5).
These findings suggest that the caries preventive effect of sweet restriction in cross-sectional surveys will be masked by highly caries-susceptible children who have recently commenced sweet restriction because of dental caries.

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The aim of the present study was to investigate the effect of fluoridated drinking water on the fluoride content of the enamel and on the development of dental caries in the rat. Twenty-one-dayold Sprague-Dawly rats were subjected to a 4-week pre-caries test period during which they were fed a non cariogenic diet and given distilled water containing 0 ppm, 10 ppm, or 50 ppm fluoride concentration as sodium fluoride. After this period, each group was fed a cariogenic diet and given distilled water for a further 4 weeks. The fluoride concentrations in enamel of the first or second mandibular molar after the fluoride treatment were determined weekly. The fluoride content in enamel of the molar was also determined after the end of the cariogenic period. The fissure and proximal surface carious lesions in the first and second mandibular molar were observed and scored for caries prevalence and severity following the method of König.
The fluoride concentrations of the first molar treated with 10 ppm and with 50 ppm fluoride for 4 weeks were both significantly higher than those of the first molar treated for 1 week (P<0.05). Likewise, the fluoride contents of the second molar treated with both fluoride concentrations showed significantly higher values at 3 weeks than those at 1 week (P<0.05-0.01).
The amount of fluoride uptake into the enamel of first and second molars was shown to be directly related to the level of fluoride in the drinking water with the latter being significantly higher than the former (P<0.05-0.01). The fluoride treated groups showed less caries than the control group on the sulcal surfaces of the first and second molar; especially, caries was significantly inhibited in the 50 ppm fluoride group (P<0.001). The groups receiving 10 ppm or 50 ppm fluoride developed significantly less caries than the control group on the proximal surfaces of the second molar (P<0.05). The fluoride incorporated into enamel by fluoride treatment seemed to be almost entirely retained even after the 4 week cariogenic period.
The results of this study strongly suggest that enamel-bound fluorides provided prior to a cariogenic challenge conferred protection from caries, especially, from sulcal lesions.

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The purpose of this study was to investigate fluoride distribution patterns in different teeth from the same mouth. Fluoride distribution in the cementum was determined in 27 noncarious teeth from a single male cadaver aged 54 years, using the abrasive micro-sampling technique.
The following results were obtained.
1) The distribution pattern: the fluoride concentration was maximal at or near the external surface layer of the cementum and tended to decrease towards the deep layer and this was roughly consistent in all teeth except numbers (FDI) 15 and 45.
2) There was very little difference in the distribution pattern between apical and cervical cementum.
3) The distribution patterns of the same tooth types tended to be similar to each other.
4) The distribution patterns tended to be roughly similar between right and left homologous teeth and between upper and lower homologous teeth. The patterns appeared to be more similar between upper and lower homologous teeth than between left and right homologous teeth.
5) Although the total fluoride values in the cervical cementum were lower than those in the apical cementum, the average and maximum fluoride concentrations in the cervical cementum tended to be higher than those in the apical cementum.

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In the previous paper, I reported that fluoride distribution patterns in the cementum of 27 different teeth from a single male subject aged 54 years were roughly consistent. These results suggested that each subject would have its own characteristic fluoride distribution pattern influenced by personal history in relation to the fluoride environment.
In the present work therefore, I studied fluoride distribution patterns in the apical cemeneum of 8 different tooth types (21, 23, 24, 26, 31, 33, 34, 36) from 5 male subjects aged 30-70 years, using the abrasive micro-sampling technique.
The results were as follows:
1) Although distribution patterns of fluoride in the cementum varied with subjects, those obtained rom the same subject were roughly similar. I concluded that each subject had its own characteristic fluoride distribution pattern in the cementum.
2) The subject itself was more significantly related to the fluoride content than the tooth type or the upper or lower jaw.

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The Distribution of fluoride in different dental tissues such as enamel, dentine, and cementum, of the same tooth could be important in evaluating the fluoride uptake during the life of tooth. However, there have been few studies reporting the complete distribution profiles of fluoride in three different hard tissues of the same tooth.
In the present study, the distribution of fluoride was examined across the entire width of enamel, dentine, and cementum of the same tooth section. Sections about 300gμm thick were prepared on the bucco-lingual aspect of 20 mandibular premolars from male individuals of different ages. Parallel blocks of tissues, about 1mm wide, extending from the surface of enamel or cementum across the dentine, were removed under a dissecting microscope using a thin diamond disk.
The specimems were then mounted vertically on brass rods. Using a Mikrokator, the layers of known thickness were serially removed by abrasion with a lapping film. The material was extracted from the abrasive surface with perchloric acid. Fluoride and phosphorous concentrations were determined as previously described (Weatherell et al. Caries Res 19: 97-102, 1985).
The results are summarized as follows:
1) Concentration of fluoride was the highest in the outermost layer of the enamel, and there was a marked decrease in concentration from the surface to a distance of 100-200μm. In the middle and inner third of the enamel, concentration tended to level off with a small increase at a distance of 50μm adjacent to the enamel dentine junction (EDJ).
2) A higher level of fluoride in the coronal dentine than in the enamel was observed at the enameldentine junction (EDJ), and it continued to a distance of about 300μm from the pulpal surface of the coronal dentine. There was a great increase of fluoride concentration in the coronal dentine near the pulp. The level of fluoride increased with age.
3) Fluoride concentration was maximal at or near the surface of the cementum and decreased toward the interior of the cementum. There were different types of fluoride distribution in the cementum. The level of fluoride concentration increased with age.
4) Concentration of fluoride decreased after cementum-dentine junction (CDJ), reached the lowest value in the middle of the root dentine, and rose again toward the surface of the pulpal dentine.
5) Although Total Fluoride, Average Fluoride, and Maximum Fluoride in the enamel showed no clear tendency of increase with age, those of the coronal dentine increased with age until a plateau was reached at about 50 years.
6) Increases in Total Fluoride, Average Fluoride, and Maximum Fluoride in both root dentine and cementum continued to a higher age of the tooth than in the coronal dentine. Particularly, Total Fluoride increased in the cementum more than in any other tissues examined.
7) It was concluded that, although the fluoride concentration in the enamel could have been changed due to its post-eruptive environment, the coronal dentine takes up fluoride from the pulp until about the age of 50 and the root dentine and the cementum take up fluoride from both the pulp and the periodontal ligament all during the life of the tooth.

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A nationwide survey of dental diseases in Japan has been performed five times, i. e., in 1957, 1963, 1969, 1975 and 1981. The survival rate curve and life span of the respective teeth were published in the report on the survey of dental diseases in 1981. Two rises were seen on the survival rate curve of the lower first molars, the first in the 10 to 14 years age group and second between 35 and 49 years of age. The pepole who were born between 1932 to 1946 and grew up during the second world war or immediately after constituted this second rise in 1981.
The second rise was seen on the survival curve of the lower first molars in last five surveys (see Table 1). We believe that the second rise was caused by the lower consumption of sugar.
If the influence of lower consumption of sugar were removed from consideration, the second rise would be flattened and the life span of the lower first molars would be shortened 1.6 to 1.7 years (Fig. 3). If the influence of lower consumption of sugar were continued and the survival rate of the 15 to 39 year olds shifted to the highest past value, the life span of the lower first molars would be prolonged 1.1 to 2.2 years (Fig. 4 and 5).
The average age of 14 present teeth was calculated. In 1981, this was 63.59 years in males and 59.00 years in females. The variation of thease ages was 0.96 years in males and 1.12 years in females during the past 25 years.
We considered that the life span of the lower first molars of Japanese was based on middle aged groups in 1981, so it is important to provide comprehensive dental care for middle-aged persons to prolong the life of their teeth.

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The prevention of occupational dental disease has been regarded as a serious thing for a long time in industrial dental health. In recent years, however, the understanding of dental health control has become a very important matter, and dental health care in industry has become popular. The aim of this study was to conduct an epidemiological survey on periodontal status and treatment needs in an industrial population.
A CPITN (Community Periodontal Index of Treatment Needs proposed by WHO) was evaluated using a WHO periodontal examination probe on 149 males who were divided into four groups (below 19, 20-29, 30-44, and 45-64 years of age) and analysed for severity and localization, of periodontal disease.
At the same time, caries incidence and modified VPI (Visible Plaque Index of Ainomo) were evaluated. A questionaire about subjective periodontal symptoms was given to all subjects. Correlation between the results of the CPITN and these data were evaluated for each age group.
From the results of the CPITN code, subjects requiring periodontal treatment needs increased with age, being about 80% below 29 years of age, and about 95% above 30 years of age. The severity of periodontal disease went up rapidly in the age group above 30 years of age.
In the distribution of CPITN code, it seemed that the progression of periodontal disease was different in each tooth group. There was no relationship between the CPITN and the VPI, but between the CPITN and subjective symptoms, there was a remarkable correlation.
As a result, it is recognized that the periodontal disease in industrial workers may be controled by oral hygiene instruction and scaling in younger age groups and by a combination of professional and personal care in age groups above 30. The CPITN is a simple and valuable method to evaluate the periodontal status in industrial workers, it is especially valuable to survey for the primary screening of periodontal diseases.

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A previous report has shown the anticariogenic effects of combined topical fluoride application in school dental health programs (Isozaki, 1984). The aim of the present study was to evaluate the cariostatic effects on each tooth surface in school children given topical fluoride treatments by using Cohort analysis.
The subjects of this study were 827 school children (437 boys and 390 girls) who were in the 1-6 grade in 1975. Topical fluoride application was given once a year using an acidulated phosphate fluoride solution (0.9% F^-, pH 3.6), and fluoride mouthrinsing was practiced 5 times a week after every school lunch with a phosphoric acid-acidfied sodium fluoride solution (0.05% F^- pH 5.0). Cohort observations on each tooth surface were carried out for anticariogenic effects from 1976 to 1980 according to the school grade levels of the subjects.
Cohort analysis on the DMFS of each tooth type showed a statistically significant anticariogenic effect in the groups which started these programs from the lower grade levels. The results were as follows: The proximal- and lingal-surface of central and lateral incisor, and occlusal surface of first and second premolar of maxilla, and occlusal surface of second premolar of mandibula showed a decrease in the DMFS rate. Especially, the group which started from the first grade showed high anticariogenic effect on the occlusal surface of the maxillar and mandibular first molar.
These results study indicate that combined topical fluoride treatments have a high anticariogenic effect on each tooth surface.
Regarding the measures of caries prevention applied to school dental health program, it is suggested that combined topical fluoride treatments are usefull, and that it is necessary to start from the lower school grade and to carry out this program continuously through the primary school years.

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The purpose of this study was to investigate the contribution of fluoride and titanium uptake in powdered enamel to the acquisition of acid resistance.
Experiments were made in vitro by treatment with solution of (NH₄) ₂ TiF₆ (9000 ppm of F, pH 3.4) or APF (acidulated phosphate fluoride solution) for 3 minutes at 37°C with powdered enamel (particle size 70-140 μm), and 24-hour washing with synthetic saliva or 1M KOH solution was used to distinguish the soluble and permanently bound fluoride. Chemical analyses were performed to determine fluoride, titanium, calcium, and phosphorus. Acid solubility of enamel was evaluated to determine the calcium released from powdered enamel into acetate buffer (pH 4.5). The reaction products were identified by X-ray diffractometry.
A large amount of fluoride uptake, most of it in the form of CaF₂, was found after application of APF. Synthetic saliva or KOH washing removed most of the fluoride from APF treated enamel, but (NH₄) ₂ TiF ₆-treated enamel had lower levels of fluoride uptake and higher retention after both washings. These facts indicated that a higher level of more permanently bound fluoride formed in (NH₄) ₂ TiF₆-treated enamel.
Titanium in (NH₄) ₂ TiF₆-treated enamel was resistant to synthetic saliva washing, but the KOH wash caused a partial release of titanium.
The acid solubility test of fluoride-treated enamel showed the same degree of acid resistance before and after synthetic saliva wash. However, the KOH wash decreased an acid resistance of both types of fluoride-treated enamel. A decrease of acid resistance in APF-treated enamel may contribute to the release of alkali-soluble fluoride such as CaF₂. In the case of (NH₄) ₂ TiF₆, a decrease of acid resistance might be related to the titanium concentration in enamel. The release of fluoride and titanium from (NH₄) ₂ TiF₆-treated enamel into 1MKOH solution suggests a hydrolysis of titaniumfluoride compound, which forms an organometallic bond with the enamel protein called“glaze”, rather than a release of CaF₂.
As the results, it is suggested that glaze-like substance is soluble in strong alkali such as 1MKOH soluion but stable in acid circumstances, and controls acquisition of acid resistance of powdered enamel.

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