The purpose of this study was to clarify the mechanism responsible for the different sensitivity of cells to fluoride (F) using four normal human diploid fibroblasts derived from the fetal lung and adult gingiva.
The following results were obtained:
1. The activity of cell growth in decreasing order was NDU-1 cells (fetal lung) >GF-12-Y cells [adult gingiva, population doubling level (PDL): 10-15] >FR 30 cells (F-resistant cells produced from NDU-1 cells) >GF-12-E cells (PDL; 30-35).
2. The doubling time of cells in decreasing order was GF-12-E>FR 30>GF-12-Y>NDU-1 cells.
3. In nonsynchronized cultures, the F sensitivity of cells estimated by measuring the F concentration necessary to inhibit the DNA synthesis and/or the growth of cells in decreasing order was NDU-1>GF-12-Y>GF-12-E, FR 30 cells.
4. The time of S phase and pre-DNA phase was measured using synchronized cultures. The time of S phase was about 7 to 8 hrs in all four cell types. The time of pre-DNA phase was about 10 hrs in NDU-1 cells, about 20 hrs in GF-12-Y cells, about 32 hrs in FR 30 cells, and about 34 hrs in GF-12-E cells.
5. The DNA synthesis of synchronized cells at the S phase was depressed to about 50% of control cells for all four cell types when cultured with 0.79mM F for 8 hrs (time of S phase). A lethal F concentration was not observed in the cells in the pre-DNA phase.
These results indicate that the F sensitivity of cells was dependent on the phase of the cell cycle. The different sensitivities to F that have been observed between cells (nonsynchronized) is probably releated to the fact the cells were in different phases of the cell cycle.

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The aim of the present study was to examine the long-term effect of low concentration of sodium fluoride in drinking water on bone metabolism in growing senesence-accelerated mice (SAM-P/6) as a spontaneous experimental model of senile osteoporosis.
SAM-P/6 mice were given 1 and 5mg of sodium fluoride per one liter of drinking water for 11 months. All aminals were fed a commercial diet ad libitum. The concentration of calcium in serum and bone was evaluated by atomic absorption spectrophotometry. The concentration of serum phosphorus and alkaline phosphatase was determined colorimetrically. Fluoride was determined with a fluoride-specific ion electrode.
During the 11 months after beginning treatment, there were almost no differences in body weightserum calcium-fluoride and alkaline phosphatase-levels between control and fluoride-treated groups, although serum levels of phosphorus were higher in the fluoride-treated groups than in controls. Calcium and fluoride content per dry weight of femoral bone were higher in fluoride-treated groups than in controls. Bone magnesium and phosphorus contents did not differ between controls and fluoride-treated groups.
Histologic studies of femoral bone revealed that bone formation in the fluoride-treated groups trended to increase.
In this study, it appeared that in growing SAM-P/6 mice, intake of low-concentration of sodium fluoride for a long-term affected the bone matabolism.

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The purpose of this study was to explore the association of melanin pigmentation in attached gingiva and cigrarette smoking. Oral examinations and a questionnaire concerning smoking habits were administered to 317 male employees of two companies. Among them, 48% of subjects were current smokers, 11% were former smokers, and 41% had never smoked. Melanin pigmentation was assessed in the labial aspects of attached gingiva in the frontal region, and was found in 57% of the subjects. The presence of the pigmentation was 82% among current smokers, 51% among former smokers, and 29% among those who had never smoked. The odds ratio of the pigmentation between current smokers and those who had never smoked was 11.6 (P<0.001). This trend was similar in both companies. The melanin index, which is an indicator of the degree of pigmentation in the labial aspect of the frontal region, was positively correlated to daily number of cigarettes smoked, and the number of years of smoking, and lifetime exposure to smoking (P<0.001). The index was also correlated closely to the number of sextants having gingival melanin pigmentation (r=0.922. N=163). These result indicate that gingival melanin pigmentation is strongly associated with cigarette smoking habits.

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酢酸緩衝液 (pH 4.0) に対するヒドロキシアパタイトの耐酸性に及ぼす緑茶抽出液の効果を解析する目的で, 緑茶抽出液中に存在する種々の無機および有機化合物の効果を検討した。ヒドロキシアパタイトへのフッ化物イオンの吸着量は液中のフッ化物イオン濃度に比例し, 緑茶抽出液とNaF水溶液に差異は認められなかった。すなわち, 緑茶抽出液中のフッ化物イオンは, 同じpH 5.6においてNaF水溶液中のフッ化物イオンと同じ挙動を示すことが明らかとなった。一方, ヒドロキシアパタイトの耐酸性もまた処理溶液中のフッ化物イオン濃度に比例して強化されたが, フッ化物イオンの吸着量が同じであっても, 緑茶抽出液の方がNaF水溶液よりも効果が大きかった。その原因の一部は, 緑茶抽出液中に含まれるアルミニウムイオンによることが明らかとなったが, 緑茶抽出液中に存在するその他の物質は, ヒドロキシアパタイトの耐酸性強化に寄与しなかった。以上の結果より, ヒドロキシアパタイトの耐酸性向上に及ぼす緑茶抽出液の効果は, 主としてフッ化物イオンとアルミニウムイオンによることが明らかとなったものの, それらのみでは緑茶抽出液の効果は理解できず, 緑茶抽出液中に存在する極微量成分あるいはそれらと他の成分との相乗作用の寄与があることが示唆された。

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To elucidate the structural changes caused in human dental enamel by laser irradiation, the optical properties and permeability of heated human enamel and lased enamel after treatment with various solutions were investigated. Heated enamel at 400°C for 24 hours acquired the highest resistance to acid decalcification and showed a high positive birefringence which was similar to that of lased enamel. Carbolic fuchsin, acidulated phosphate fluoride (APF), and calcifying fluid did not penetrate the heated enamel, though those solutions penetrated the lased enamel well. Changes in birefringence after treatment with lactate buffer was not observed in the heated enamel, but was observed in the lased enamel.
APF penetrated the lased enamel well and the affected area had an optically isotropic appearance (R region). Carbolic fuchsin could not penetrate the APF-treated area of lased enamel. However, the high positive birefringence in the layer below the R region changed to a low negative one after treatment with lactate buffer for 3 hours. Slight surface decalcification was also observed on the surface of the R region at this time.
These results suggested that the structural changes in lased enamel are different from those of heated enamel. It appears that lased enamel has micropathways through which solutions can penetrate into the enamel, and also microspaces which could act as sites of deposition for ions released by acid decalcification.

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The delayed achievements regarding mental health in the dental health field have prevented the possibility of social adjustment by mental patients. To promote mental health more effectively, dental health measures are needed that are based on the characteristics of a mental patient's condition. We conducted a follow-up investigation of the state of dental health since the last oral hygiene instruction. The subjects were patients of A mental hospital in Shizuoka. We surveyed the dental diseases: the caries experience was examined by DMF, the periodontal condition was examined by CPITN, the state of oral hygiene was examined by PHP, and caries activity was examined by S·T MEDIA®. The names of the recipients of past dental care were extracted from the examination data and comparison material for a total of 71 persons (34 men and 37 women) was obtained. The follow-up investigation of the state of dental health revealed that the caries experience, state of periodontal disease, state of oral hygiene, and caries activity had all improved. Improvement in the introduction of dental health care and dental remedial treatment was taken as a factor of this improvement. Dental health control program is necessary for mental patient's, in addition to dental treatment for them.

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The aim of this study was to find the optimal remineralizing solution under various remineralizing conditions. To evaluate the combined effect of elements in remineralizing solution, a factorial experiment (3 factors, 3 levels) was performed. The optimal remineralizing solution was determined as that which produced the highest fluoride incorporation in the remineralized enamel.
Demineralized lesions were produced on human enamel (N=54; Area=15mm²) by a 2-day immersion in 0.1mol/l lactic acid solution (pH 4.0, 37°C). The remineralizing solutions (pH 7.0, 37°C) containing various concentrations of carboxymethylcellulose (CMC), Ca/P and fluoride were changed every 2 days during the 10-day remineralizing period. The concentrations of CMC, Ca/P, and fluoride consisted of the following three levels, respectively: 0.5, 1.0 and 1.5% for CMC; 1.0/0.6, 2.0/1.2 and 3.0/1.8 mmol for Ca/P and 1.0, 2.0 and 3.0ppm for fluoride.
The lowest concentration of CMC (0.5%) showed the highest fluoride incorporation in remineralized enamel. The highest concentration of fluoride (3ppm) showed the highest fluoride incorporation throughout the entire remineralized enamel. The highest concentration of Ca/P (3.0/1.8mmol) showed the highest fluoride incorporation but was limited to the first layer. The middle concentration of Ca/P (2.0/1.2mmol) showed rather higher fluoride incorporation in inner part of the remineralized enamel than the highest concentration of Ca/P (3.0/1.8mmol). Interaction between CMC and Ca/P was found from the second to the forth layers. Interaction between CMC and fluoride was found at the third layer only.
Judging from the highest fluoride incorporation at the first layer, the remineralizing solution containing 1.0% CMC, 3.0/1.8mmol Ca/P and 2.0ppm fluoride seemed to be an optimal remineralizing solution. On the other hand, considering the high fluoride incorporation in the inner layers, the remineralizing solution containing 0.5% CMC, 2.0/1.2mmol Ca/P and 3.0ppm fluoride also seemed to be an optimal remineralizing solution. Remineralized enamel derived from the optimal remineralizing solutions showed acid resistance against acid challenge.

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Epidemiological analyses, with respect to periodontal disease severity according to signs and symptoms using the Ramfjord Calculus Index (CI) and Periodontal Disease Index (PDI), were performed on 881 mental retardates possessing one or more subject teeth at 15-48 years of age. They were among a group of 1107 subjects who were admitted to the Niigata Prefectural Institute of Total Training for the Mentally Retarded, Colony Niigata Shiroiwa-no-Sato, during the years 1971-1988. The average number of sextants without signs and symptoms of disease decreased, and that of gingivitis, calculus accummulation, and periodontitis increased with age in 3 periods of admission, 1971-1975, 1976-1981 and 1982-1988. After the mid 1970's, the time and sex appeared to have no influence, but these two factors did seem to have some influence in the first half of the 1970's. IQ and the experience of institutionalization had no influence. Average number of sextants with gingivitis and periodontitis were considered similar and higher, respectively, than those of the standard Japanese population.

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A study was conducted to assess the attitudes of dentists toward the fluoride mouth rinsing (FMR) program. The responses were obtained by administering a questionnaire to 299 dentists. The factors which influence the attitude toward the FMR program were analayzed by stepwised multiple regression analysis. The attitudes of the subjects toward the FMR program were not very positive since only two-thirds of the subject wanted their children or grandchildren to participate in the FMR program. The factor influencing the attitude was the knowledge of fluorides for caries prevention. It was concluded that the negative attitudes of the subjects toward the FMR program in this study was caused by poor knowledge about fluorides.

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In dietary fiber (DF), there are water-soluble fibers (SDF) and water-insoluble fibers (IDF). They have different properties. The purpose of this study was to examine the influence of different types of DF on plaque formation and dental caries occurrence. Three-week-old male golden hamsters were fed a cariogenic diet (powder), AIN-76 purified diet modified for hamsters, containing 5 types of DF for 59 days. Each diet contained 10-20% of DF. For a control group, diet containing 20% of α-starch was given.
The results were as follows:
1) In the hamsters fed a diet containing pectin (SDF), more plaque formation and tooth destruction by caries were observed compared to the control group. The higher the content of pectin, the more plaque accumulation and the more tooth destruction by caries were observed.
2) Tooth destruction by caries was higher in the group fed hydroxypropylmethylcellulose (HPMC) 60 SH-4000 (SDF of high viscosity) compared to the HPMC60SH-50 (SDF of low viscosity) diet group.
To investigate the reason why the diet containing pectin was more cariogenic, Streptococcus mutans NCTC 10449 was administered to cultures containing 7 types of DF and pH values were measured after 24 hours incubation at 37°C. Only the cultures with pectin showed pH values about 5.5. S. mutans NCTC 10449 fermented pectin and produced acid.
From these results, it was concluded that the diet containing pectin had a high level of cariogenicity.

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The gtf genes coding for glucosyltransferase (GTF), which produces water-soluble glucan, were cloned from Streptococcus sobrinus SL1 (ATCC 33478).
Chromosomal DNA of S. sobrinus SL1 was digested with Pst I and ligated into Pst I-cleaved plasmid vector pUC19. After transformation, a clone library was generated.
Through the screening of the clone library, two sucrase-positive transformed cells were selected from 213 transformants. One sucrase-positive clone carried plasmid pYTK 100, consisting of an insert of a 6.1kb Pst I-Pst I fragment containing the gene which expressed a glucosyltransferase synthesizing a water-soluble glucan. The gene inserted in pYTK 100 was very similar to gtfT gene of S. sobrinus OMZ176 previously isolated. Another sucrase-positive clone carried plasmid pYTK 104, consisting of an insert of a 4.5kb Pst I-Pst I fragment, which contained a part of a fourth gtf gene (gtfU) of S. sobrinus.

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