The supplies of two elementary schools', one in Tokyo (School N) and the other in Saitama (School F) were investigated to predict the caries incidence in the 6th grade from the data of 1st graders and to identify the children at high risk for caries. The results were as follows. 1. The two schools showed almost no gender difference. In comparison between the two schools, all 14 indices except ft of the molar region at the age of 6(6-M-ft), the ft of the front region at the age of 6(6-F-ft), FT at the age of 6(6-FT), DT at the age of 11(11-DT) and &lrtri;DMFT from 6 to 11 years of age (6-11&lrtri;DMFT) had significant difference at p<0.01. 2. The ROC curve of 11-DMFT, in which fewer than 3 DMFT was fixed as negative, had the least estimative probability of all three curves. 3. The estimative probability of school N was higher than that of school F. 4. To predict caries in the 6th grade, more than 5 dmft at 6-M-dmft was judged as a high risk when the cut-off point was set at 4. The same result was seen at 6-dft. 5. To evaluate the increase of caries in permanent teeth in the 6th grade, more than 5 dmft at both 6-M-dmft and 6-dft was judged as a high risk when the cut-off point was set at 4. 6. To predict the children who would have more than 4 DMFT at 11-DMFT, more than 6 dmft at both 6-M-dmft and 6-dft was judged as a high risk when the cut-off point was set at 5. 7. When 11-DMFT was set as an objective value, a significant multiple regression equation : 11-DMFT = 0.37(6-M-dt) + 0.30(6-M-ft) + 0.65(6-M-mt) + 0.59(6-M-mt)+0.30(6-FT), 1.04 was obtained at P <0.01. 8. When 6-11 &lrtri;DMFT was set as an objective value, a significant multiple regression equation : 6-11-DMFT = 0.34(6-M-dt) + 0.29(6-M-ft) + 0.59(6-M-mt) + 0.30(6-FT) + 1.03 was obtained at P<0.01. Therefore, the prediction of the number and increase of caries in the 6th grade can be detected from children in the 1st grade. This should be applied in actual dental health care of schools.

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A questionnaire survey on the tooth-brushing habits, the use of fluoride dentifrice, and the user's consciousnesses of it was conducted in seven different age groups to promote the spread of fluoride dentifrice in Japan. In four groups of one-and-a-half-year olds to elementary school children, the rate of children using dentifrice to brush their teeth was 1.7〜49.2%, and users of fluoride dentifrice among them were 50〜90%. In three adult groups, the rate of users of fluoride dentifrice was comparatively small (34〜47%). There were some (8〜43%) dentifrice users who selected their dentifrices for fluoride medicinal properties. This trend was observed more strongly in groups of adults than in children. In addition, there was also a small percentage (13〜45%) of fluoride dentifrice users who selected their dentifrices for the fluoride. It is strange that there were very small part of non-fluoride dentifrice users who selected their dentifrices for the fluoride. It is concluded that the following strategies are necessary for the promotion of fluoride dentifrices. 1. Education on the usefulness of fluoride dentifrice is necessary for everyone including adults. 2. Dentifrice manufacturers should clearly label their products "fluoride dentifrice" and fluoridate more dentifrices for adults. 3. Japanese dental health organizations should recomend fluoride dentifrices.

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The effect of tea catechins, which are major components in green tea infusion, on the acid resistance with respect to the dissolution of synthetic hydroxyapatite together with fluoride and Al (III) was investigated. Dissolution rates of hydroxyapatites pretreated with a sodium fluoride (NaF) solution (1.49μmol F/ml), an aluminium nitrate (Al (NO_2)_3) solution (1.85μmol Al/ml), or a mixture of NaF and Al (NO_3)_3 in water (pH 5.6) were 39.2±1.2, 42.5±0.4, and 33.7±0.4 nmol/min, respectively, whereas those with polyphenon-100 (5.0mg/ml, pH 5.6) were 39.8±1.4, 42.8±0.7, and 28.1±0.9 nmol/min, respectively. Only the mixture of catechins-Al (III)-fluoride showed a synergistic effect on the acid resistance, though polyphenon-100 itself did not show any effect at all. The synergism of fluoride, Al (III), and tea catechnis in green tea infusion may be an important factor for the retardation of acid dissolution rate of hydroxyapatite.

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The purpose of this study was to assess the effect of professional tooth cleaning on prolongation of tooth life. A group of 407 subjects participated in a 6-year follow-up study. After a baseline examination, they were subjected to professional tooth cleaning. During the subsequent 6 years, they were recalled for preventive measures once every 2-3 months. The professional tooth cleaning was based on tooth brushing aiming at removal of interdental plaque and gingival mechanical stimulation. After the final examination, tooth loss over a 6-year period was calculated. The data of the National Survey of Dental Disease were used as control. More teeth in the middle age or older groups were preserved compared to those in the corresponding control groups. The ratio of mobile teeth and the number of untreated carious teeth at the baseline examination were most significant to predict tooth loss. We suggest that regularly repeated professional tooth cleaning conducted in a middle-aged population will prolong overall tooth life effectively.

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The purpose of this study was to examine the relationship between oral health and nutrition. A survey of food intake frequency, dietary habits, life style and oral health conditions were conducted on 282 women aged from 20 to 91 years, living in Siroyama (a suburb of Tokyo). The oral investigations included evaluation of the periodontium, caries, and prostheses. The periodontium was identified according to Russell and caries according to WHO. The questionnaires were a survey of the frequency of various kinds of foods (rice, breads, noodles, nuts, potatoes, sugars, sweets, fats and oils, beans, fruits, green and yellow vegetables, other vegetables, mushrooms, seaweed, seafood, meat, eggs, milk, and prepared foods), dietary habits, life style (hieght, weight, sleep, sports, smorking, alcohol, breakfast, snacks) and chewing ability according to Yamamoto's classification. Body measurements were evaluated with the Body Mass Index (kg/m^2). Results were as follows, 1. The number of missing teeth and periodontal Index (PI) were closely correlated with age. 2. Subjects of 20 to 39 years of age tended to skip breakfast and to eat fats, meat, and prepared foods more often. The intake of rice in subjects of 70 years and above was higher than in the other age groups. 3. Subjects were divied into 2 groups according to chewing ability as rated by Yamamoto's classification questionnaire: score 1-5 as "unsatisfactory", and score 6-7 as "satisfactory". In subjects of 50 years and above, the satisfactory group had fewer missing teeth than the unsatisfactory group with statistically significant differrence. Chewing ability was highly correlated to the number of missing teeth in the groups of 50-59, 60-69 and 70 years and above. A proper weight was estimated from the Body Mass Index (kg/m^2) : a BMI of 20-25 was regarded as "appropriate weight" and BMI<20 or BMI>25 as "inappropriate weight". In the groups aged 50-59 and 60-69 years both the number of missing teeth and the Periodontal Index were lower in the group with appropriate weight than in the groups with inappopriate weight. 4. In a factor analysis, age was correlated with oral health conditions and frequency of intake of fats, green and yellow vegetables, meats. 5. In a multiple regression analysis, chewing ability and frequency of intake of rice, fats, and green and yellow vegetables was significantly associated with the number of missing teeth. Thus, oral health can be maintained and promoted by a suitable life style and desirable food intake and dietary habits.

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Plaque removal efficacy of toothbrushes of various shapes was evaluated. Although many studies on adult toothbrushes have been reported, there are few on children's toothbrushes. In this study, plaque removal efficacy of a newly designed toothbrush (PC toothbrush) having a straight handle, a compact head and a slim neck for mixed dentition, designed so as to enhance its handling in the oral cavity, was compared with an angled neck toothbrush on the market (R toothbrush). Fifty school children, 7 to 12 years old, 17 males and 33 females, were assigned one of the test brushes. They were instructed to brush their teeth by the scrubbing method. Plaque scores were measured before and after a single brushing. The results showed that the PC toothbrush was significantly more effective overall (p<0.01) than the R toothbrush for removing plaque. The PC toothbrush removed significantly (p<0.01) more plaque than the R toothbrush on the first molars and on the lingual and distal surfaces. The PC toothbrush was also significantly more effective (p<0.01) than the R toothbrush on the central incisors. This suggests that the PC toothbrush is superior for use on mixed dentition. It also suggests that a straight-handled toothbrush is suitable for children at various stages of growth and dexterity of hand and arm.

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The effects of lactic acid, which has often been invoked as a major plaque metabolite, the effects of formic acid, whose pKa is lower and supplies hydrogen ions at a high rate, and the effects of a mixture of both acids at different ratios on early enamel caries lesions was studied using a sandwitch technique. Enamel samples of a thickness of 100μm were prepared and exposed to five types of solutions containing lactic acid alone, lactic acid and formic acid mixed at the ratios of 3 : 1, 1 : 1, and 1 : 3, and formic acid alone. These solutions were adjusted to pH 4.5 and final acid concentration was adjusted to 0.1M. Every 3 to 24hours, microradiographs of each sample were taken. The change of mineral content with the passage of time showed that there was a decreasing tendency towared maximum mineral content of the surface layer(Max.) and minimum mineral content of the lesion (Min.). There was a increasing tendency toward lesion depth (Ld) and mineral loss(&lrtri;Z). These findings suggest that the demineralization of enamel was affected by the mixture of organic acids.

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In order for people to be able to enjoy eating throughout their life-time, keeping their mouth and teeth always clean is of basic importance. In the present study, aimed at working out a program for providing oral health education effectively to adults with few missing teeth, we examined the effects of oral conditions on food intake in a total of 1,407 company employees of both sexes under 60 years of age after conducting a dental examination and a food intake survey. A multivariate analysis of the results was performed using Hayashi's quantification method II . A summary of the findings is as follows : 1. The main results of the food intake survey showed that the ratio of the difficult-to-chew food (-) group was about 85% in both sexes and that this ratio tended to decrease among the subjects aged 40 and above. 2. In the difficult-to-chew food (+) group, only one food item was cited as being hard to chew by the 60% of the men and 71% of the women. 3. A screening level was determined in accordance with the index for the intraoral condition : 3 for the number of decayed teeth ; 2 for the number of missing teeth ; 3 for CPITN code ; and 80-90% for the masticatory index. 4. Hayashi's quantification II analysis revealed that, from the size of the range, food intake was affected most when the CPITN code reached the maximum. Thus, in the subjects with relatively few missing teeth, it can be said that periodontal tissue conditions affect food intake to the greatest extent, suggesting the importance of oral health education and the prevention of periodontal disease.

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In order to identify the distribution of air pollution in dental hospitals, airborne bac teria, airflow, and number of persons were measured in orthodontics, pedodontics, restoration, and prosthetics clinics at Asahi University dental hospital for 2 years. Airborne bacteria were detected at five spots in each dental clinic with an SY type pinhole sampler method (SY method) and Koch's dropping method (Koch method). Chronological changes in number of airborne bacterial colonies and distribution in number of airborne bacterial colonies at the five measuring spots in the clinics were evaluated by two-way analysis of variance. Cluster analysis was performed to classify the five measuring spots in the clinics according to factors of airborne bacterial colonies estimated with the SY method and the Koch method. Correlation between the personal movement factor and the number of airborne bacterial colonies were also evaluated. The following results were obtained ; 1. The airborne bacterial count was from 0,02 to 1.42 colony-forming units (CPU) per liter with the SY method and 0.08 to 6.83 with the Koch method in the clinics, and it was found that the distribution of the airborne bacterial count varied with the seasons. 2. According to the two-way analysis of variance, the measuring spots showed difference of airborne bacterial count in each clinic. Thus, a number of measuring spots are necessary to obtain a realistic bacterial count. 3. The five measuring spots were classified into two groups by cluster analysis. Cluster analysis is a useful method to identify the distribution of the number of airborne bacterial colonies and to select measuring spots in dental clinics. 4. The correlation between the personal movement factor and the number of airborne bacterial colonies in dental clinic was highly significant (P <0.01).

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In 1992 we investigated the tooth brushing habits and the use of toothpaste, especially fluoride toothpaste, by questionnaire. The subjects were 349 infants aged 1.5 years and their 348 parents and 167 kindergartners aged 3-6 years and their 164 parents in Fukuoka city. The results were as follows. 1. Fifty four percent of the infants and more than 85% of the kindergartners brushed their teeth every day and more than 90% of the parents brushed their teeth every day. 2. Few infants used toothpaste. Sixty to eighty five percent of the kindergartners and more than 80% of parents used toothpaste. It is not common to use the toothpaste for infants in Japan. 3. Five percent of the infants and 32-56% of the kindergartners used fluoride toothpaste and 36% of the parents used fluoride toothpaste. 4. The main reasons for using toothpaste were the prevention of dental caries and the fluoride in the toothpaste. There were few subjects that used fluoride toothpaste on the recommendation of dentists or dental hygienists. We found that most dental personnel gave instructions not to use toothpaste. 5. In this investigation, the percentage o? the use of fluoride toothpaste was 76% in children and 39% in adults. In theory, fluoride toothpaste is supposed to reduce the incidence of dental caries by 20-25%. In Japan, the use of fluoride toophpaste is lower than in other industrialized countries. Dentists and dental hygienists and other dental personnel in Japan need to give to information on fluoride toothpaste and recommend to people the use of fluoride toothpaste.

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We investigated the electrochemical characteristics of oral streptococci by using cyclic voltammetry. S. cricetus HS-6, S. rattus BHT, S. mutans NCTC 10449 and S. mutans OMZ 175 showed irreversible oxidation potential (Epa) 0.5V vs Ag/AgCl in an aqueous neutral buffer solution, but S. sobrinus K1-R showed 0.9V. The oxidation current (Ipa) of these bacteria were classified into three groups (S. scbrinus K1-R, 3μA ; S. cricetus HS-6 and S. rattus BHT, 2μA; S. mutans NCTC 10449 and S. mutans OMZ 175, 0.5/μA). The oxidation potentials and currents depended on the pH value of the electrolytic solution. Specific adsorption behavior of the bacteria on the surface of the In-Sn oxide electrode (ITO) was observed by scanning electron microscopy. These results suggested that the method of cyclic voltammetry can be useful for examining the potential of adsorption of oral bacterium, since the Epa and Ipa for oral bacterium were different in each species.

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The attachment of bacteria to a dental enamel surface is affected by various interactions consisting of long range and short range forces. In this study we studied the theoretical attachment due to electrostatic (Vel) and van der Walls (V_A) interactions, long range forces, between fluoridated hydroxyapatite and bacterium. Hydroxyapatite (HAp) was treated with NaF, APF and SnF_2. Zeta potentials of HAp and bacterium, a dominant parameter in the Vel, was measured in 0.03M phosphate buffer at different pHs. In the Vel calculation Hogg-Healy's theory, of dissymmetrical double layer interactions was applied. Hamaker (van der Walls) constants for the VA were taken from the literature. We obtained a maximum (Vmax) and minimum (Vmin) in the total interaction potential energy as a function of distance between fluoridated HAp and bacterium. In general Vmax tended to slightly decrease for APF and faintly increase for SnF_2 in comparison with untreated HAp. These effects in the degree of Vmax depended on bacterial species. We concluded that the fluoridation of HAp has effect on the surface potential energy, only for bacterium that have a high zeta potential, but the potential energy is markedly influenced by a bacterial surface feature which comes from surface charges.

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The high efficiency in discriminating between periodontally sound and affected subjects with the aid of our self-administered questionnaire (self-check of periodontal disease) was confirmed in a previous report (J. Dent. Hlth., 41 : 667, 1991). This study examines the association between selfcheck scores of lower anterior gingival health and periodontal conditions assessed uisng the CPITN. A total of 231 subjects aged 19-70 yr was given the questionnaire to check their gingival conditions in accordance with the colour-illustrated figures of health and affected gingiva. Statistically significant association (p<0.05, p<0.01) was found between the self-check scores of interdental papilla, marginal and attached gingiva and subgroups by CPITN score. Subjects with low counts of self-check score (less than 1.8 : quivalent to 25 %-ile) were designated as a periodontally sound group, and those with high scores over 2.5 (equivalent to 75 %-ile) as a periodontally affected group. These figures are statistically highly significant (p<0.01). The results of the present study suggest that the self-check of lower anterior gingiva was useful in enhancing awareness of periodontal disease in the population.

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