Public dental health activities are important factors for maintaining good dental health among residents in a community. To fulfill the needs of the community, sufficient dental manpower is essential and also public-health-minded students should be educated at the undergraduate level in dental schools.
In this context, we conducted a questionnaire survey of the opinions of senior dental students from five dental schools in the Tokyo area with the support of the Tokyo Metropolitan Government's Bureau of Public Health.
On the basis of the survey, this paper deals with the students' attitudes to public dental health activities, specifically focusing on how prior experience in the observation and practice of the activities in health centers affects these attitudes.
Willingness to participate in public dental health activities after graduation was found at a significantly higher level in those students who had had experience in observing and practicing the activities in health centers. They also selected a wider variety of professional dental careers for their future.

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The purpose of this study was to simplify the glucose clearance test as a clinical test for caries activity in dental practice. Dental caries is commonly recognized as a multi-factorial disease, and the incidence and progress of dental caries are thought to be influenced by various oral environmental factors. There are many caries activity tests that evaluate these oral environmental factors. The best way to evaluate caries activity is to consider the results of a number of caries activity tests.
Glucose clearance time is considered to be the factor which affects the acid production of plaque. Therefore, it is important to evaluate both glucose clearance time and the acid productivity of plaque. I performed two studies, one was to clarify the ability of the glucose clearance test to evaluate the oral environment, and the other was to simplify this test for clinical use.
The results obtained were as follows.
1) There was a positive correlation between glucose clearance test and DMF tooth number (p<0.05).
2) The values of pH, buffer capacity of stimulated whole saliva, and pH of resting whole saliva in a low caries prevalent group were significantly higher than in a high caries prevalent group (p<0.05).
3) The high caries prevalent group showed significantly higher positive values of Caricstat® than the low caries prevalent group (p<0.05).
4) There were multi-collinearities among the oral environmental factors.
5) The eigen value of each factor was calculated by principal component analysis. There was negative correlation between glucose clearance time and buffer capacity of stimulated whole saliva.
6) Decreasing glucose concentration in saliva was found to be a two-step process, especially when rinsing the mouth with 10% (G10) and 20% glucose (G20).
7) In rinsing with 5% glucose (G5), the two-step process was not clear.
8) According to the principal component analysis, there were differences among G5, G10, and G20 in the first component. In G5, the eigen value of buffer capacity of stimulated whole saliva was the most negative value in first principal component. For G10, the eigen value of flow rate of stimulated whole saliva was the most negative value against glucose concentration of saliva.
9) 5% gluccse solution was thought to be better than the other concentrations for clinical use.
10) For clinical effectiveness, I recommend that the glucose concentration in resting whole saliva be measured 4-6 minutes after the rinsing the mouth with 5% glucose solution.

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The purpose of this study was to evaluate the oral health of Iranian workers in Japan and their general life conditions, 125 Iranian subjects aged 20-43 yr congregating in Yoyogi and Ueno Parks in Tokyo were examined. The mean decayed, missing, and filled teeth (DMFT=7.8) and filled teeth (FT=2.3) scores were lower than the Japanese national average. The mean decayed teeth (DT=3.4) and missing teeth (MT=2.2) scores were higher than the Japanese national average. Calculus was the predominant periodontal problem, and shallow pockets prevailed in persons aged 30-34 yr. 39.7% of the subjects had complaints about their oral health, but only 16.8% desired dental treatment in Japan. Most of the subjects could not undergo dental treatment because of the high cost. Analysis of the results showed poor dental health in this survey group and emphasizes the necessity of improving the (dental) health service programs for foreigners.

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In China, water fluoridation was begun in Guangdong province in Guangzhou in 1965 and in Dongguan in 1974, and was stopped in 1983 and 1986, respectively. There is at present no fluoridation being practiced in China. Both cities are located north of Hong Kong and belong to the subtropical zone (mean temperature=71.1°F). According to Minoguchi's formula, an optimal fluoride concentration is 0.6-0.7ppm. The fluoride concentration was unstable for the first 10 years, when annual fluoride concentrations ranged from 0.8ppm to 0.9ppm, higher than the optimal fluoride concentration. After that the concentration was about 0.7ppm. The fluoride concentration of drinking water in Guangzhou may have been sometimes higher than the optimal fluoride concentration. In December 1990, seven years after fluoridation was discontinued, a dental survey of schoolchildren aged 15 was made in Guangzhou, and also in Fushan (0.2ppm) as a control area. Two dentists examined dental caries and one dentist examined dental fluorosis with Dean's Index, and other enamel defects were also recorded. Subjects were 62 students in Guangzhou and 71 students in Fushan. The mean DMFT was 0.44 (SE=0.10) in Guangzhou and 2.20 (0.33) in Fushan. The percent difference was 80% (p<0.001). The prevalence rate of dental fluorosis was 21% in Guangzhou and 2.8% in Fushan and the CFI was 0.42 and 0.08, respectively. Many dark brown teeth, not caused by fluoride, were found. They may have been caused by tetracycline or exanthematous fevers. The present study proved that water fluoridation produced high caries-preventive effects and the favorable effects remained for seven years after discontinuation of water fluoridation without serious dental fluorosis in Guangzhou.

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Epidemiological analyses, with respect to periodontal disease prevalence according to signs and symptoms using the Ramfjord Calculus Index (CI) and Periodontal Disease Index (PDI), were performed on 881 mental retardates aged 15-48 who had one or more subject teeth. They were among a group of 1107 subjects admitted to the Niigata Prefectural Institute of Total Training for the Mentally Retarded, Colony Niigata Shiroiwa-no-Sato, during the years 1971-1988. It was found that the prevalence rate of disease increased, that of gingivitis and of calculus accummulation did not fluctuate, and the prevalence rate of periodontitis increased with age in 3 periods of admission, 1971-1975, 1976-1981 and 1982-1988. The admission periods, gender, IQ and the institutionalization did not appear to influence these rates. The prevalence rates of gingivitis and periodontitis were considered to be higher than in the standard Japanese population.

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The aim of this sutudy was to identify dental hospital environmental problems. Temperature, humidity, air flow, and number of persons were measured for a year in the orthodontics clinic and the oral surgery clinic at Asahi University dental hospital. Airborne bacteria were detected with an SY type pinhole sampler (SY method) and Koch's dropping method (Koch method).
The following conclusions were obtained,
1. The room temperature was 13.3-27.4°C, humidity was 23.3-64.7%, and the air flow was 0.03-0.50m/sec.
2. The number of persons in the clinic varied from 2 to 40 people.
3. The bacterial count was from 0.01 to 0.68 colonies per liter with the SY method and 0.07 to 2.60 with the Koch method.
4. The correlation between the number of airborne bacteria detected with the SY method and those detected with the Koch method had the high coefficient of 0.544. We believe that Koch's dropping method can be used to monitor airborne bacteria pollution in dental hospitals.
5. A high statistical correlation was obtained between the number of colonies and the number of people in the clinic, with a coefficient of 0.371 in the SY method and a coefficient of 0.281 in the Koch method.
6. A high statistical correlation was obtained between the number of colonies and the number of times the air-conditioning was turned on in the clinic, with a coefficient of -0.480 in the SY method and a coefficient of -0.274 in the Koch method.
7. Statistical by significant difference was recognized between months when air-conditioning was used and months when it wes not in the number of airborne colonies, and this indicated efficient air-cleaning action by the air-conditioner.

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The purpose of this study was to investigate the effect of dentifrices containing low concentrations of fluoride on hydroxyapatite powder and human enamel powder.
Fluoride solutions were prepared containing 100ppm F^- in (1) NaF, (2) NaF+20% glycerine (NaF+G), and (3) K-100, and 1, 000ppm F^- in (4) MFP, (5) SnF₂, and (6) SnF₂+50% glycerine (SnF₂+G). Some powder was treated with distilled water as the control.
Before treatment, the pH and free fluoride concentration in each solution were measured. Powders were treated with these solutions for 6 min. In all groups, a part of the sample was washed with 1M KOH solution for 24hr, in order to remove CaF₂ in the powder and to measure the permanently bound fluoride concentration.
Fluoride uptake was measured, and an acid resistance test and IR analysis were performed.
The pH of SnF₂ solution and SnF₂+G solution was 2.6, and the other solutions were slightly acidic.
Free fluoride concentration was 7% in MFP solution and 90% in other fluoride solutions.
The fluoride concentration in powder was increased by the application of fluoride solution. NaF, NaF+G, and K-100 caused fluoride uptake similar to that of the MFP group. After washing with 1 M KOH solution, fluoride concentration was decreased in all groups in hydroxyapatite powder, but in NaF, NaF+G, and K-100 groups, fluoride remained above 90%.
The acid resistance test proved that calcium release was inhibited in fluoride groups both after treatment and after washing with 1 M KOH solution. After treatment, acid resistance was more than doubled in SnF₂ and SnF₂+G groups as compared to the other fluoride groups, but the other groups were similar to each other. After washing with 1 M KOH solution, all fluoride groups had the same acid resistance.
IR analysis showed no clear difference in all the experimental groups.
These findings showed that the effect of NaF solution (100ppmF) was similar to that of MFP solution (1, 000ppmF) on the fluoride uptake and acquisition of acid resistance, and that NaF solution (100 ppmF) for dentifrice use was a useful agent for caries prevention.

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The aim of this study was to examine the change in acid resistance of lased-remineralized enamel. Sixty-six enamel slabs were prepared from thirty-three human premolars. These enamel slabs were demineralized artificially. They were irradiated with a Q-switch Nd-YAG laser and remineralized with two remineralizing solutions, one with and the other without fluoride. To evaluate acid resistance, the enamel slabs were subsequently immersed in 0.1M lactic acid solution (pH 4.5) while stirring (139r.p.m. ±12; Mean±S.D.), and dissolved Ca²⁺ was measured as a function of time from 15min to 180min.
The results were as follows:
1) Laser irradiation increased acid resistance of demineralized enamel during short periods (up to 60min).
2) Remineralization without fluoride increased acid resistance of demintralized enamel during short periods (up to 60min) regardless of laser irradiation.
3) Remineralization with fluoride increased acid resistance of demineralized enamel during long periods (up to 180min) regardless of laser irradiation.

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The purpose of this study was to evaluate the plaque removal effect of a dentifrice containing granulated zeolite. Fifteen volunteers, who were nurses, dental hygienists and dentists between the ages of 21 and 42 years participated in the experiments. Following professional toothbrushing, the subjects refrained from toothbrushing for 3 days. Then daily professional toothbrushing was performed by trained dental hygienists with the experimental dentifrice for 5 days. No oral hygiene procedure was performed for 3 days after the first clinical trial. The second trial with the control dentifrice was done for 5 days. During each trial, the subjects stopped all personal oral hygiene procedures. The plaque removal effect was evaluated using plaque scores before and after toothbrushing. At 24 and 72 hours after toothbrushing, the inhibitory effect on plaque formation was calculated. The results showed that the experimental dentifrice was significantly more effective in removing plaque on the lingual surfaces and gingival margins and the interproximal gingival margins of the teeth than the control dentifrice. Significant difference was also found between the two dentifrices in removing plaque in pits on the occlusal surfaces. There was no significant difference in the inhibitory effect of the two dentifrices on plaque formation. This suggests that the dentifrice containing granulated zeolite improved the effect of toothbrushing. A questionnaire survey indicated that many subjects preferred the dentifrice containing granulated zeolite. No clinical side effects were observed in the two dentifrices.

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[in Japanese]

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Wearing oral appliances like dentures has some demerits, such as deterioration of the oral environment and difficulty in masticating of adhesive foodstuffs. We developed a new coating material for acrylic appliances to relieve these demerits.
In this study, by applying an acrylic palatal base to 10 adult subjects, we evaluated the effect of coating by fluoro-plastic material on plaque accumulation and on the mastication of some adhesive foodstuffs. And the results were as follows.
1. The Area of plaque accumulation on the mucous side was smaller on the coated side than on the uncoated side. Statistical significance was found between the two sides after the 2nd day of observation.
2. Experimental mastication by the 10 adult subjects and the answers to the questionnaire indicated that the coating has an alleviative effect on the difficulty in masticating some adhesive foodstuffs.

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We studied the inhibitory effects of passive immunization with antibody against Streptococcus mutans surface protein antigen I/II (SAI/II) on experimental dental caries in rats and humans was investigated. The results obtained were as follows. Two groups of rats were infected with S. mutans (c) and fed a modified diet 2000 which contained 50% sucrose and 6% lyophilized normal rabbit serum or 6% lyophilized anti-SAI/II rabbit serum. A significantly lower caries score was observed in rats fed the modified diet 2000 containing anti-SAI/II serum powder as compared with the control rats. In the intraoral cariogenicity test experiment in humans, the enamel slabs set on both sides of the device were immersed in 3% sucrose solution for 10min. outside the mouth. One side of the enamel was treated with normal rabbit serum and the other side was treated with anti-SAI/II rabbit serum, 3 times daily for 2 weeks. The enamel treated with sucrose plus anti-SAI/II serum showed statistically significant lower demineralization, than the enamel treated with sucrose plus normal serum.

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