The aim of this study was to improve the diversified working conditions of dental hygienists in ChibaPrefecture municipalities. The working conditions of dental hygienists, and their lack of professional information and skills were assessed by analyzing the answers to a questionnaire. The responses were summarized as follows. The working duties of dental hygienists were maternal and child oral health services, adult oral health services, home visit oral health services, elderly oral health services, school oral health services, oral health services for handicapped persons, planning and budgeting, collecting and analyzing oral health information, and coordination between organizations related to oral health services. New dental hygienists were inclined to have difficulties with their working conditions because of their lack of professional knowledge and skills. However, after gaining some experience, few dental hygienists appeared to think that the difficulties in oral health services for maternal and child care were due to their lack of knowlege and skills. But many veteran dental hygienists thought that the difficulties in the management of the council on health promotion, collecting and analyzing oral health information, oral health services for handicapped persons and home visit oral health service were due to their lack of knowledge and skills. The solutions for the improvement of their knowledge and skill included participating in oral health training programs, reading professional magazines, becoming a member of the dental hygienist association, studying among other colleagues (public health nurses, dental hygienists and so on), and studying under the guidance of dental hygienists who were working in other municipalities. The results suggest that dental hygienists in public health offices should be encouraged to enter various training programs and information exchanges with other colleagues and other relevant facilities.

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A dental examination as an isolated dental health service and a total health examination, including dental and medical checkups as a total health service, were provided for the same age groups of residents in a local community. The oral health status of the subjects of these examinations was compared, and the following results were obtained. 1. An overall comparison of dental conditions in the subjects of the two examinations revealed that the number of decayed teeth, reated teeth and missing teeth, the DFT index, and the DMFT index were tended to be higher for the total examination than for the isolated dental examination. Among the male subjects, the number of decayed teeth, treated teeth and missing teeth, the DFT index, and the DMFT index also tended to be higher for the total examination. In the female subjects, however, there was no consistent difference between the two examinations. 2. With regard to dental treatment, the percentage of subjects with decayed teeth, the percentage of those requiring prostheses treatment, and the number of teeth requiring prostheses treatment were slightly higher for the total examination. Among the male subjects, all these indices were higher for the total examination.In the female subjects, there was no consistent difference between the two examinations. 3. The overall distribution of the individual maximum CPITN code exhibited higher codes for the total examination, showing a significant difference between the two examinations. The results were also significantly higher for the total examination than for the isolated dental examination, when the male and female subjects were analyzed separately. 4. The mean number of sextants for each CPITN code was significantly lower for the isolated dental examination as a whole. The same tendency was observed when male and female subjects were analyzed separately.

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Three hundred and twenty seven kindergarten children aged 5 years from four kindergartens (three urban, one rural) in Miyagi prefecture were examined for dental caries of the deciduous teeth. Parents were asked to complete a questionnaire on daily dietary and toothbrushing habits and the results were compared with their childrens caries prevalence and dental needs. The rate of caries-free children in each kindergarten was 21.4% to 57.6% and the mean dft ranged from 2.93 to 7.06. There was a significant difference in the above figures between the kindergarten with the highest caries occurence and the others. ln the kindergarten with the highest dental caries, the children with after dinner snacking habits before bedtime were found to have statistically less caries occurence than those who didn't snack. The group which experienced toothaches resulting in a dental office visit had higher caries prevalence than those without toothaches. Eighty eight parents (26.9%) checked the item, "no dental needs" in the questionnaire and their kindergarten children had a 3.31 mean dft, which was a statistically lower caries occurence than the other groups. The health and preventive items such as "want to know how to prevent decay", "want to know how to brush teeth" and "want to have fluoride topical application", predominated over the items of restorative treatments. Summarizing these findings, dental caries prevalence in 5 year old kindergarden children depends on their previous life style in kindergardens and at home, and the dental needs and concerns toward prevention of caries. Therefore, besides the practice of periodic oral health examinations and preventive care once a year in the kindergarten, it is important to educate parents frequently, especially those in rural areas, with the appropriate knowledge for the prevention of dental caries prevalence in deciduous teeth.

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The purpose of this study was to evaluate longitudinally the retention of fissure sealants applied to first permanent molars with sticky fissures in order to grasp the appropriate period for maintenance of sealants. 0ne hundred sixty seven schoolchildren aged between 11 and 14 years were investigated in this study. These subjects participated in a school-based fluoride mouthrinse program, combined with a targeted fissure sealant for 5 to 6 years. In the sealant program, they received a light-cured sealant on only the surfaces whose fissures could be detected as "sticky" using an explorer. Two hundred seventy three sealed teeth, which were done in subjects between the ages of 6-9 years, and which had gone more than 4 years since the initial treatment, were analyzed. Teeth and sealant conditions were assessed regularly twice a year in elementary school and once a year in junior high school by calibrated examiners. Sealant replacements, if needed, were done only for elementary schoolchildren. The total retention rate of sealants was 88.6% during the survey periods, which included completely intact sealant (69.6%) and replaced intact sealant (19.0%). The failure rate of sealants, which were revealed because of occurring dental decay or restoration due to decay, was 9.9%. Using survival analysis (Kaplan-Meier survivor functions), the cumulative retention rates for initial and replacement sealants were found to be 68.3±3.2 (SE)% after 8 years and 67.2±7.9 (SE)% after 6 years, respectively. Statistically significant difference was not found (generalized Wilcoxon analysis) between the cumulative retention rate of the initial sealant and replacement. In both initial and replacement sealants, the cumulative retention rates gradually decreased up to 3 years. After that, there was a charge from a slight decrease to a stable condition according to follow-up periods. 0f all the cases in which initial sealants dropped out, 77.1% were observed in under 4 years. All the decayed or restored (because of caries) teeth, except one, were found within 4 years of the fissures being sealed. These results indicate that the probability of resealing needs and of occurring caries reduces in sealants more than 4 years old. Therefore, the results suggest that the period of 4 years should be addressed as the appropriate period for maintenance of sealants.

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Several cases of contact allergy due to dental metals have been reported, and the allergenic chemicals were generally assessed by patch test. But it was not easy to distinguish irritant reactions from true allergic reactions with patch testing. In this paper, the skin irritation and contact sensitization of dental metals were evaluated with animal tests using guinea pigs. The following results were obtained. 1. Skin irritation due to 10 metals was compared via an intradermal injection method, in which mercury showed the strongest irritation. The skin irritation due to platinum, copper and chromium was stronger than that caused by silver and nickel. 2. Comparing two sensitization methods, the Maximization test, which is the most widely used test and is accepted as being very sensitive, was more sensitive than the Buehler method in the detection of silver, tin, chromium and DNCB (1-chloro 2, 4-dinitrobenzene) as a positive sensitization control. However, mercury did not give a positive sensitive reaction with the Maximization method, because of the severe local damage caused by the combination of an adjuvant and the intradermal induction of mercury. 3. When an Aluminium Finn Chamber patch test for human was used for epidermal occlusive application in guinea Pigs, the irritation of mercury or platinum was enhanced by the chemical reaction between aluminium and mercury or platinum. 4. There were cross sensitivity responses for reactions between silver and palladium, chromium and nickel. However, as for the cross reactions between tin and palladium, mercury and gold, mercury and platinum did not generate a response. 5. The repeat epidermal application of mercury raised the positive ratio, but it came down after long intervals of repeat challenges. There were large differences among individual animals in the skin irritation and contact dermatitis response. Acoording to the five grade classification of allergenic potency, we assigned DNCB as extreme (V) sensitizer, mercury and chromium as moderate (III), and silver and tin as mild (II).

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The purpose of the present study was to examine the effect of NaF and NH₄F solutions on intact human enamel using two different reacting times. Fifty four intact human enamel blocks were immersed or stirred in three kinds of solutions at 37℃ for 5 minutes and 60 minutes respectively. The solutions were as follows : (1)sodium fluoride solution-NaF group, 900 ppmF^-, pH 5.0 ; (2)ammmonium fluoride solution-NH₄F group, 900 ppm^-, pH 5.0 ; (3)deionized water-control group. The phosphoric acid was used for pH adjusting of each solution. Morphological observation was done with SEM. Distribution of calcium, phosphorus, and fluoride in the enamel were determined by electron probe micro analysis (EPMA), and with an energy dispersive X-ray spectrometer (EDX). They were also used to identify the reaction products in fluoride treated enamel surfaces. In SEM preparations, spherical crystals were deposited on the enamel surfaces after both fluoride treatments. In the spherical crystals, the concentrations of Ca and F were higher, but P was lower than in the control group. Therefore, it appeared that the spherical crystals were CaF₂. In parts of the enamel surfaces, without deposition of spherical crystals, a slightly higher F concentration was observed. This would seem to form fluorapatite (FAp). In the 60 min. groups, more CaF₂ and FAp were formed in the treated enamel compared with the 5 min. groups. In addition, more CaF₂ formed in the NH₄F group than the NaF group after both of the reacting times. In the NH₄F group (for 5 min.), the formation of CaF₂ was significantly higher than in the NaF group (for 5 min), although it was lower than in the 60 min. groups. Therefore, the treatment of NaF and NH₄F solutions resulted in production of CaF₂ and FAp on the enamel surface (for both 5 min. and 60 min.). Thus, CaF₂ would be effective in preventing caries as a source of dilute fluoride supply. NaF and NH₄F solutions (for 5 min.) would be expected to have a cariostatic effect.

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This investigation was carried out to clarify the opinions and attitudes of parents of primary school children on the use of fluoride and discuss the application of fluoride in Kanagawa prefecture. The subjects were drawn from separate schools within three different areas of the prefecture, and a total of 663 parents completed self-administered questionnaires. The questionnaire was made up of questions relating to a hypothetical model concerning the use of fluoride. The results of the analyses were as follows. 1. There were few differences among the three areas. A small number of parents had positive opinions on water fluoridation, but many parents supported topical application of fluoride and 73% of parents approved fluoride mouth-rinsing at home. However, it is suggested that accurate knowledge and information was insufficient, because many parents answered "neither" to most of the questions. 2. 70% of all sample children experienced professional topical application of fluoride, although children treated regularly made up less than 10%. 3. The results of LISREL analyses indicated that "positive attitudes toward prevention" related to "support for topical application" but not to "acceptance of water fluoridation". Moreover, the relationship between "experience of professional topical application" and "support for topical application" was very strong.

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The effects of bicarbonate ions on remineralization of enamel and dentin lesions (total 68 samples) were studied in vitro. Extracted healthy premolars from subjects aged 50-57 years (the mean age was 54.1 years) were used in this study. The lesions were produced by a 7 days exposure to demineralizing solution of 0.1 mol lactic acid containing 3.0 mmol Ca, 1.8 mmol P at pH 5.0 and 37℃. The lesions were exposed to a remineralizing solution containing the same amount of Ca and P and 2 ppm F at pH 7.0 and 37℃ for 7 days. During 7 days remineralization, the lesions were immersed in 4 different concentrations of sodium bicarbonate solutions (0.0, 0.5, 5.0, and 50.0 mmol/l) for 30 min. at an interval of 8 hours. Two kinds of bicarbonate solutions such as 5.0 mmol/l and 50.0 mmol/l were corresponding concentrations of bicarbonate ions in resting whole saliva and stimulated whole saliva, respectively. Then, thin sections were prepared, the changes in minerals were assessed by microradiography for lesion depth (Ld, μm), mineral loss value (ΔZ, in vol%・μm), maximal mineral value at the surface (vmax, in vol %), and minimal mineral value in the lesion body (Vmin, in vol %). Microradiographic analysis showed remineralization in the lesion body on enamel. In enamel, the change in mineral accumulation of Vmin was proportional to the concentrations of bicarbonate but not significantly different (p=0.09). In the 5.0 mmol/l groups of dentine, significant remineralization was restricted in the surface region, but did not significantly differ (p=0.08). This study shows that the difference in bicarbonate penetration between enamel and dentin can be attributed to different patterns of remineralization.

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The prevalence of caries among 1.5- and 3-year-old children in Hamamatsu city was surveyed for the fiscal years between 1989 and 1996. Annual changes were compared with those in the whole of Japan, in the government ordinance cities and special wards in Tokyo. Thirty-five administration districts in Hamamatsu were divided into 4 areas according to the union of the districts. Geographical distribution of caries prevalence was also investigated among 35 districts and 4 areas. Caries prevalence among 1.5- and 3-year-old children has been decreasing in Hamamatsu, and this trend corresponded with the changes in the whole of Japan, the government ordinance cities and the special wards in Tokyo. Among 35 administration districts, caries prevalence in the inner city areas was lower than in the suburbs in the early 1990's. However, caries prevalence in the suburbs has been declining annually When observed from the perspective of the 4 areas divided according to the union of the districts, regional characteristics can be seen. These differences have been reducing annually.

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We studied the health behavior and oral health conditions in women who were given a citizens' health examination. The subjects were surveyed with a questionnaire on Breslow's 7 health habits, and oral health examination by dentists. The rating of health behavior increased in accordance with age. In low DMFT groups, women with moderate leisure-time, physical activity and moderate weight for height rated higher than those without those characteristics. But periodontal disease, chewing ability and tooth brushing habits were not significantly associated with the rating of health behavior. A multivariate analysis of the results suggested that the health factor which affects both dental caries and periodontal disease has a specific construction, and the major factor relating to oral health conditions was not health behavior, but age.

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