Total fluoride (F) concentrations in dental plaque obtained from children aged 4-5yr and 14-15yr in F area (0.3-1.8ppm F in natural drinking water) and non F area (under 0.1ppm F) were determined by the AlF molecular absorption spectrometry. The logarithmic normal distribution was showed in F concentration of dental plapue. The geometric means of F concentration in plaque obtained from the non F area were 25.7ppm (4-5yr) and 18.1ppm (14-15yr) as dry weight. The contents of plaque in F area, contrary, were significantly higher than those in non F area (4-5yr: 54.4ppm, 14-15yr: 24.3ppm).
The plapue F from 4-5yr group was significantly higher than that from 14-15yr group in both areas. A possible explanation for the different levels of F in dental plaque from two age groups might be due to the difference of plaque quality such as plapue age.
The present experiments confirmed the higher levels of F in dental plaque were acquired from naturaly fluoridated drinking water.

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[in Japanese]

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This study was undertaken to learn what kind of components in mouth air are the main source of halitosis and what kind of symptoms or clinical examination have a relation to halitosis.
In 26 patients complaining of bad breath, we examined the subjective or objective consciousness of their bad breath, the evaluation of halitosis by olfactory panel, the analysis of volatile sulfur compounds in mouth air by gas chromatography, some oral conditions (decayed teeth, pus discharge from gingival pockets, gingival bleeding, food impaction, tongue coating, PI, DI, CI and OHI), olfactometry, and questionnaire findings (Y-G and C.M.I.). The interrelationships between these data were investigated statistically.
The results obtained were as follows:
1. Three kinds of volatile sulfur compounds, i. e., hydrogen sulfide (H₂S), methyl mercaptan (CH₃SH) and dimethyl sulfide ( (CH₃) ₂S), were detected from the mouth air, and significant positive correlations between the evaluation of halitosis and the concentration of these three volatile sulfur compounds were found. CH₃SH was always detected in the patients with halitosis and a highly significant correlation (r=0.743) with the evaluation of halitosis by olfactory panel was obtained (Fig. 5). It therefore seemed that CH₃SH is a main source of halitosis.
2. Significant positive correlations between the score of tongue coating and the evaluation of halitosis, and the concentration of CH₃SH were found (Fig. 6, 7).
3. The mean concentration of (CH₃) ₂S in mouth air in the patients with gingival bleeding was statistically less than that in the patients without bleeding (Table 6).
4. Complaints of patients about bad breath were divided into three types, i. e., self-awareness, indication by others or presumption from the attitude of other persons, and investigated in relation to the diagnosis of halitosis by olfactory panel. No relation was found between them (Table 3, 4).
5. A relatively high concentration of (CH₃) ₂S was detected in the patients whose threshold value of iso-valeric acid was increased (Fig. 8).
6. There was no relation between the area of C.M.I. and the presence or absence of halitosis (Table 9).
7. From Y-G personality inventory, no relation between the types of personality and presence or absence of halitosis was found (Table 11). But some complaints of their bad breath still remained after objective halitosis disappeared. Further study is needed to clarify the relation between the personality of the patients and halitosis.

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Differences in fluoride concentration might be related to analogous variations in caries prevalence, but unconfirmed suggestion that fluoride concentration in the surface enamel of males is higher than in females seemed potentially important in this respect. No subsequent data having been published, the present study was undertaken in order to make a similar comparison between fluoride concentrations in the surface enamel of young male vs. female subjects.
The material consisted of premolar teeth extracted for orthodontic purposes from 9 and 10-year-old children. Twenty-four of the teeth were from males (13 unerupted and 11 erupted) and 32 from females (19 unerupted and 13 erupted). Windows on the enamel surface were exposed to acid and F and P concentrations were determined using microsampling and analytical techniques (previousely described by Weatherellet al., 1973).
Three sites on the buccal surface and one site in the centre of the lingual surface were examined and fluoride gradients were calculated. Sex differences were observed at the buccal occulusal site at the depth of 10-20μm from the enamel surface and fluoride concentrations in females were high compared with males.

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Epidemiological analyses were performed on dental caries prevalence of 1107 mentally retarded individuals at entrance, who were registered with the Niigata prefectural institute of total training for the mentally retarded, Colony Niigata Shiroiwa-no-Sato, during 1971-1988. The subjects represented 9-14% of the severely and profoundly retarded, and 8-12% of the moderately retarded in Niigata prefecture. Dental examination was performed adopting the four-graded diagnostic standard for dental caries using plane mouth mirrors and sickle-shaped explorers under artificial lighting. Data base was constructed from the examination records and statistical analyses were performed.
(1) The personal DMF rate in 15 year olds and over was 90-100% in general and the tooth DMF rate showed a tendency to gradually increase with age, and was calculated to reach more than 50% at the end of the 40s from 22-32% in 15-19-year-olds, in three terms, 1971-1975, 1976-1981, 1982-1988, categorized by the subjects' entrance year.
(2) The DMFT index showed a tendency to gradually increase with age. The DT index was up to 5.26 in all the age groups but showed no increasing tendency with age. Also there was no increasing tendency with age in the FT index, but there was a long-term increase of 1.20-2.96 in 1971-1975 and 1.67-6.06 in 1982-1988 (over 15 years of age). An increasing tendency of 0.92-2.05 in the MT index with age was remarkable in 15-19-year-olds in all of the three terms, which would make it 11.82 in 40-year-old males and 8.27 in females of the same age in 1982-1988.
(3) Yearly variation of DMFT index and average number of examined teeth per person by age and sex was not significant statistically.
(4) There was no statistical difference of DMFT index in comparison with the Survey of Dental Disease by Ministry of Health and Welfare Japan. A tendency of lower FT index and higher MT index was recognized, when refered to each DMFT component. However, in 1982-1988, the difference in the MT index faded and the difference in the FT index tended to be improved.

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Caries incidence for 2 years after discontinuation of school-based fluoride mouthrinsing (5 times/week, 500ppm F), which was practiced at an elementary school for 6 years, was evaluated by tooth types of permanent dentition and duration of fluoride exposure.
Incremental DMFT rates of the fluoride group (N=100) were lower than those of the control group (N=105) for all tooth types. Statistically significant differences between the two groups were observed in lower first and second molars (p<0.01, p<0.001) and all upper teeth except canines (p<0.05, p<0.01, p<0.001). In the fluoride group, caries increments were different for each tooth type and incremental DMFT rates of molars (11-49%) were much higher than those of the other tooth types (0-5%) in both upper and lower dentition. For all tooth types, however, no significant relationship between caries increments and previous duration of fluoride exposure in the elementary school was observed.
The results of our study suggest that the cariostatic effects of fluoride mouthrinsing are not likely to be accumulated with the passage of time and it is necessary to continue the program until the eruption of second molars is completed.

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The purpose of this study was to investigate in vivo the effect of topical fluoride application on deciduous tooth enamel. Experimental materials were physiologically dropped deciduous teeth of school children who recieved the topical fluoride application once a year and fluoride mouth rinsing 5 times a week for four years. The cariostatic effect was already confirmed in these children. Electron probe X-ray microanalysis, acid solubility test, and X-ray crystallographic analysis were performed.
Fluoride determination were performed on the smooth surface, fissures and caries lesions of enamel and dentin by electron probe X-ray microanalysis. An acid solubility test was done to determine the released calcium content from intact enamel surface of milk cuspid into 0.4 M acetate-sodium acetate buffer (pH 4.0) during three hours every thirty minutes. Microfocus X-ray diffraction was performed on the smooth surface, fissures, cusps and caries lesions of enamel. The (310), (002) reflections of microfocus Laue photographs were charted by microphotometer and, the crystallinity of enamel apatite were evaluated by estimating these half maximun breadth.
Electron probe X-ray microanalysis showed that the fluorine concentration of surface enamel was increased not only in smooth surfaces but also in fissure areas by fluoride application and repeated fluoride mouth rinsing for four years. Caries lesions also revealed fluoride uptake. An acid solubility test proved that the acid resistance was increased about 1.5 times more in the fluoride group than in the control group. In the X-ray diffraction analysis, no reaction products were detected, and all specimens showed almost the same pattern of hydroxyapatite. The crystallinity of the deciduous teeth was different in different tooth areas, especially in c-axis directions. The crystallinity of enamel apatite was increased in both the a- and c-axis directions in the smooth surface areas, and in the c-axis in the inner layer of fissures, and in the outer and inner layer of caries lesions.
As a result, it could be seen that topical fluoride application was effective in the portions of high caries incidence in deciduous teeth.

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We examined changes in S. mutans, lactobacilli, total streptococci, and total anaerobic bacteria counts in plaque and saliva, when college student volunteers used toothpaste containing semiconductor TiO₂, having bactericidal activity for S. mutans in vitro. S. mutans counts of plaque in subjects using toothpaste containing semiconductor TiO₂ (TiO₂ subjects) decreased and more significantly with time decreased than those of subjects using control paste (control subjects) after 2 weeks (p<0.01). Comparison of S. mutans counts between subjects using toothpaste contained TiO₂ without semiconductor effect and control subjects were not significant. Lactobacilli counts of plaque in TiO₂ subjects was also more sxgnificantly decreased than those in control subjects after 2 weeks (p<0.05). Salivary cariogenic bacterial counts were not changed by using toothpaste containing semiconductor TiO₂.
We suggest that toothpaste containg semiconductor TiO₂ effective by to decreases S. mutans in plaque and contributes to the prevention of dental caries.

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A dental health examination of 1, 243 inhabitants, 40 years of age and over, of Irabu-cho, Okinawa, was carried out in concurrence with a general health examination.
The rate of carious teeth, the rate of untreated teeth, and the rate of missing teeth increased with advancing age, and the rate of intact teeth and rate of treated teeth decreased. This tendency was particularly marked in those aged 80 years and over.
The prevalence of dental caries was 67.5%, and the prevalence of untreated dental caries was 34.2%, which was lower than the nation-wide average, and also indicated the influence of the high rate of missing teeth in inhabitants of this area.
Some general diseases were present in 45.6% of the inhabitants examined, 25% of which were suffering from two diseases or more. Particularly in subjects aged 60 years and over, the prevalence was as high as 57.1%, 62.8% of which were evaluated as requiring treatment. Cardiovascular diseases were present in 58.6% of the subjects with general diseases; the incidence of hypertension was the highest, and 32.3% of the subjects with carious teeth requiring treatment were also suffering from general diseases for which treatment was necessary. The incidence of general complications in the subjects aged 60 years and over was particularly high, 41.8%.

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[in Japanese]

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[in Japanese]

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Processing the data from dental health examinations requires detailed procedures for many items. In order to use the computed data to the best advantage for regional health programs and for personal health guidance, the arrangement of our work environment to enable precise data processing is an urgent need. For this, we used to process examination data on the main computer system of the Computer Center, at the University of Tokyo. However, preparing a file for the data processing on a computer is always annoying and time consuming. Therefore, we designed here an input software to directly prepare a data file on a personal computer, and put it to trial in an actual dental health examination. We were able to file and process the examination data very quickly. The application of a computer to dental health examinations is thus very useful and helpful for further development of dental health science

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In Niigata Prefecture as of 1986, 536 educational institutions composed of kindergardens, primary schools, and junior high schools in 71 municipalities had adopted the school-based fluoride mouth rinsing (FMR) program and good results in the improvement of the dental caries situation have been obtained. The percentage of primary schoolchildren in the FMR program is 22%.
However, it will be impossible to attain the goal of the WHO in the year 2000 (DMFT 3.0 at 12 years of age), if only 22% of chldren participate in the FMR program.
The purpose of this study was to develop a prediction model to estimate the caries prevalence at 12 years of age in the year 2000 and to analyze conditions in order to attain the goal of the WHO.
Five parameters were designed to predict the caries prevalence for the future.
The parameters were as follows:
a. Percentage of children participating in the FMR program in 1992. (a) 22%: no increase from 1986, b) 41%: all towns and villages perform FMR in addition to the present cities' prevalence in 1992, c) 50%: reach 50% in 1992, d) 100%: reach 100% in 1992)
b. Effectiveness of dental caries reduction by FMR.
a) Clinical effectiveness; Effectiveness of dental caries reduction by FMR in ideal conditions.
b) Community effectiveness; Effectiveness of dental caries reduction in all schoolchildren participating in the FMR program in Niigata Prefecture.
c. Natural reduction of dental caries without FMR.
d. Annual increment of dental caries between 11 (6th grade of primary school) and 12 (1st grade of junior high school) years of age.
e. Annual change in children's population in municipalities in Niigata prefecture
Twenty-eight cases were assumed from these parameters.
Estimated values were calculated in these 28 cases.
The maximum DMFTindex in the year 2000 will be 4.05 if the percentage of children performing FMR by community effectiveness is 22% and there is no natural reduction of dental caries without FMR. The minimum will be 1.73 if the percentage of children in the FMR program because of clinical effectiveness is 100% continually from preschools and there is natural reduction of dental caries without FMR. Although there are 9 cases which attain the goal of the WHO, 6 of these suppose 100% participation in 1992. However, it seems impractical to expect 100% participation. The remaining 3 cases suppose participation of 41% or 50%, and the effectiveness of dental caries reduction by FMR is clinical effectiveness. And there are 2 cases which approach the goal of the WHO under the condition of 41%. One case is 3.26 (No. 8) based on the condition that there is natural reduction of dental caries without FMR, and another is 3.12 (No. 11) based on the condition that primary school-chidren perform FMR continually from preschools. Therefore, we suggest that in order to attain the 12-year-old children's goal of the WHO in Niigata Prefecture, the percentage of children performing FMR should be more than 41% (all towns and villages performing FMR in addition to the present cities' prevalence) in the year 1992, the schoolchildren should perform FMR continually from preschools, FMR program should be performed properly under the supervision of the people who are concerned with health and education to get more effective caries prevention, and the use of fluoride-containing dentifrices should be encouraged to get natural reduction of dental caries without FMR.

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[in Japanese]

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For determining the total fluorine (F) level in biological samples containing organofluorine (organic F) compounds, we used pyrohydrolytic F separation and gas chromatography for the determination of F in the resulting aqueous HF solution (PyH-GC method).
We investigated the operating conditions of the apparatus for PyH which was developed by Itai et al. and the recovery of F using calf serum. In order to examine the suitability of the PyH-GC method for determining various organic F compounds, we applied four analytical methods including the PyH-GC method to test the recovery rates of six organic F compounds and then compared the F values obtained from each method.
Furthermore, for confirming the applicability of the PyH-GC method to determine low level F in biological samples, we applied both the PyH-GC method and the low temperature plasma ashing method followed by GC (LTA-GC method) to determine the total F in the blood plasma of rats which had been given 6-fluoro-tryptophan (6-FT).
The results were as follows:
(1) Concerning pyrohydrolysis, the best results were obtained when the temperature of the steam generator was 95°C, sample quantities were 300μl or 0.3-0.4g, and highly purified oxygen was used. When NaF, NH₄F, 6-FT or CaF₂ was added to calf serum, good reproducibility and recovery rates were obtained without addition of any acid flux for total F determination. The detection limits in this method were 4ng/ml for serum and 3ng/g for soft tissue.
(2) In comparing the four determining methods, the diffusion method using a strong acid proved to be deficient and the AlF molecular absorption method showed low recovery rates for half of the organic F compounds examined. Although the PyH-GC method showed a low recovery rate for 4-fluorobenzophenone which has a low melting point, it showed fairly good recovery rates for the other organic F compounds; the LTA-GC method showed the best recovery rate.
(3) The total F values in the plasma of the rats resulted in an excellent agreement between the samples pretreated with LTA and those with PyH. This result indicates that both methods are suitable for determining F in 6-FT and its metabolite in the plasma.
However, it is better to use the PyH-GC method for determination of total F in biological samples becausè it is more rapid and simpler than the LTA-GC method.

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