• Molecules and Cells
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• v.27 no.2
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• pp.191-198
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• 2009

The present study was undertaken to determine whether treatment with genistein, the plant-derived estrogen-like compound influences agonist-induced vascular smooth muscle contraction and, if so, to investigate related mechanisms. The measurement of isometric contractions using a computerized data acquisition system was combined with molecular experiments. Genistein completely inhibited KCl-, phorbol ester-, phenylephrine-, fluoride- and thromboxane $A_2$-induced contractions. An inactive analogue, daidzein, completely inhibited only fluoride-induced contraction regardless of endothelial function, suggesting some difference between the mechanisms of RhoA/Rho-kinase activators such as fluoride and thromboxane $A_2$. Furthermore, genistein and daidzein each significantly decreased phosphorylation of MYPT1 at Thr855 had been induced by a thromboxane $A_2$ mimetic. Interestingly, iberiotoxin, a blocker of large-conductance calcium-activated potassium channels, did not inhibit the relaxation response to genistein or daidzein in denuded aortic rings precontracted with fluoride. In conclusion, genistein or daidzein elicit similar relaxing responses in fluoride-induced contractions, regardless of tyrosine kinase inhibition or endothelial function, and the relaxation caused by genistein or daidzein was not antagonized by large conductance $K_{Ca}$-channel inhibitors in the denuded muscle. This suggests that the RhoA/Rho-kinase pathway rather than $K^+$- channels are involved in the genistein-induced vasodilation. In addition, based on molecular and physiological results, only one vasoconstrictor fluoride seems to be a full RhoA/Rho-kinase activator; the others are partial activators.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.4
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• pp.257-262
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• 2013

The fluorine-containing waste water tends to show a higher removal efficiency through the coagulative precipitation process with calcium. However the tetrafluoroborate produced from the etching process is difficult to remaval due to it's low reactivity with calcium. The objective of this study is improving the efficiency of fluoride ion removal in tetrafluoroborate through decomposing. Research on tetrafluoroborate decomposition depending on reaction pH, temperature, and aluminum dosage were conducted, using a laboratory-scale reactor. The result shows that the reaction of tetrafluoroborate with aluminum is faster with lower pH, higher water temperature, and higher Al/T-F (Aluminum/Total Fluoride) mole ratio. It is found that there was no big change in concentration after over 120 minutes of reaction. This study is to be able to improve the efficiency of tetrafluoroborate and fluoride wastewater treatment by using aluminum.

• Advances in environmental research
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• v.2 no.1
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• pp.35-49
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• 2013

Research work on removal of fluoride from water, referred to as water defluoridation, has resulted into the development of a number of technologies over the years but they suffer from either cost or efficiency drawbacks. In this work, enhancement effects of phosphate and silicate on defluoridation of water by low-cost Plaster of Paris (calcined gypsum) were studied. To our knowledge, the influence of silicate on defluoridation was not reported. It was claimed, that the presence of some ions in the treated water samples, was decreasing the fluoride removal since these ions compete the fluoride ions on occupying the available adsorption sites, however, phosphate and silicate ions, from its sodium slats, have enhanced the fluoride % removal, hence, precipitation of calcium-fluoro compounds of these ions can be suggested. Percentage removal of $F^-$ by neat Plaster is 48%, the electrical conductance (EC) curve shows the typical curve of Plaster setting which begins at 20 min and finished at 30 min. The addition of phosphate and silicate ions enhances the removal of fluoride to high extent > 90%. Thermodynamics parameters showed spontaneous fluoride removal by neat Plaster and Plaster-silicate system. The percentage removal with time showed second-order reaction kinetics.

• Environmental Analysis Health and Toxicology
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• v.13 no.1_2
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• pp.19-26
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• 1998

In Korea, fluoride was first introduced into the drinking water of residents of Jinhae, KyungNam in 1981 for the prevention of dental caries. Ever since, growing numbers of communities favor fluoridation. The mechanism of F prevention of tooth decay is well known: fluoride ions substitute for hydroxyl ions in hydroxyapatite of hard tissues, which result in crystal perfection, with consequent reduction in dental caries. Soluble fluorides such as sodium fluoride are almost completely absorbed from the gastrointestinal tract. However, the presence of divalent or trivalent cations such as aluminum, magnesium, and calcium that can complex with F can reduce the degree of absorption. In U.S.A., over 7000 communities are now adding F to their drinking water. However, some portion of population oppose fluoridation, voicing both concern about the safety of fluoridation as well as for personal choice. Thus, This paper reviews the interaction of fluoride and cations as well as fluoride and suggests possible problems associated with fluoridation, a controversial issue.

• Nuclear Engineering and Technology
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• v.53 no.6
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• pp.1931-1938
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• 2021

Uranium ingot is produced by metallothermic reduction of uranium tetrafluoride using magnesium or calcium as reductant. Presence of oxygen containing compounds viz. uranyl fluoride and uranium oxide in the starting uranium fluoride has a significant effect on the firing time, final temperature of the charge, slag-metal separation and hence the metal recovery. As reported in the literature, the maximum tolerable limit for uranyl fluoride in the UF₄ is 2.5 wt% and limit for uranium oxide content is in the range 2-3 wt%. No theoretical or experimental basis is available till date for these limits. Analyses have been carried out in this study to understand the effect of UO₂F₂ concentration in the starting fluoride on the final temperature of the products and thus the reduction characteristics. UF₄ having uranyl fluoride concentration, less than as well as more than 2.5 wt%, have been investigated. Thermodynamic calculations have been carried out to arrive at a general expression for the final temperature attained by the products during calciothermic reduction of UF₄. Finally, an upper limit for the oxygen containing impurities has been estimated using the CaO-CaF₂ phase diagram.

• Restorative Dentistry and Endodontics
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• v.44 no.3
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• pp.24.1-24.1
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• 2019

• Restorative Dentistry and Endodontics
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• v.37 no.1
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• pp.16-23
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• 2012

Objectives: Present study was undertaken to investigate the crystal growth onto synthetic hydroxyapatite (HA) seeds in pH 4.3 and pH 7.0 supersaturated solutions with different fluoride concentrations. Materials and Methods: 8 groups of pH 4.3 and 7.0 calcium phosphate supersaturated solutions were prepared with different fluoride concentrations (0, 1, 2 and 4 ppm). Calcium phosphate precipitates yield crystal growth onto the HA seed surface while solutions flow. For evaluation of crystallizing process, the changes of $Ca^{2+}$, $PO{_4}^{3-}$, $F^-$ concentrations of the inlet and outlet solutions were determined. The recovered solid samples were weighed to assess the amount of minerals precipitated, and finally determined their composition to deduce characteristics of crystals. Results: During the seeded crystal growth, there were significantly more consumption of $Ca^{2+}$, $PO{_4}^{3-}$, $F^-$ in pH 4.3 solutions than pH 7.0 (p < 0.05). As fluoride concentration increased in pH 4.3 solution, $Ca^{2+}$, $PO{_4}^{3-}$, $F^-$ consumption in experimental solutions, weight increment of HA seed, and fluoride ratio in crystallized samples were increased. There were significant differences among the groups (p < 0.05). But in pH 7.0 solution, these phenomena were not significant. In pH 7.0 solutions, analyses of crystallized samples showed higher Ca/P ratio in higher fluoride concentration. There were significant differences among the groups (p < 0.05). But in pH 4.3 solution, there were not significant differences in Ca/P ratio. Conclusions: Crystal growth in pH 4.3 solutions was superior to that in pH 7.0 solutions. In pH 4.3 solutions, crystal growth increased with showed in higher fluoride concentration up to 4 ppm.

• Journal of Korean Academy of Oral Health
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• v.42 no.4
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• pp.199-203
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• 2018

Objectives: The market for bottled water is increasing steadily in South Korea. Bottled water contains several naturally occuring minerals, such as calcium, magnesium, sodium, and fluoride. Fluoride is proven to be effective in preventing dental caries. In South Korea, the maximum permissible concentration of fluoride is 2 ppm for bottled water and 1.5 ppm for tap water. The aim of this study was to investigate the fluoride content of different commercially available brands of bottled water in South Korea, and compare the measured fluoride concentration to the concentration written on the label of each brand of bottled water. Methods: Twenty-seven of the 59 different brands of bottled water produced in South Korea were investigated in this study. Three bottles of each brand were purchased from supermarkets, marts, and convenience stores in each region of Korea in August 2016. For each bottled water brand, the fluoride content was measured three times using a fluoride-ion selective electrode (Orion ionplus Fluoride Electrode 9609, Orion Research, USA). The calibration curve was generated using 0.2 and 2 ppm standard solutions, and confirmed using a 1 ppm standard solution. Results: The mean fluoride content of the 27 brands of bottled water was $0.374{\pm}0.332mg/L$ (range=0.040 to 1.172 mg/L). The fluoride content was labeled by the manufacturer, on each of the tested brands of bottled water. In eight brands, the labeled fluoride content differed from the experimental data. The minimum to maximum fluoride content measured from 10 brands showed a variation of 0.3 mg/L or more when compared to the labeled fluoride content. Conclusions: This study investigated the fluoride content of various brands of bottled water produced in South Korea and compared the measured fluoride levels with fluoride information on the bottle labels. To ensure that consumers are suitably informed regarding their exposure to fluoride, correct labelling of fluoride content in bottled water is important.

• Journal of the Korean Applied Science and Technology
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• v.38 no.5
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• pp.1282-1291
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• 2021

The aim of this study was to investigate the hematology and serum chemistry values on Sprague-Dawley rats, used sodium fluoride (NaF) for 5 weeks. Seven-week-old male rats were divided into nine groups and fed experimental diets with oral NaF treatment, basal diet group (BG), basal diet plus oral NaF groups (NF3~NF50). Concentrations of non-esterified fatty acid (NEFA), blood urea nitrogen (BUN), creatinine, uric acid in serum were significantly higher in the oral NaF groups than BG (𝛼=0.05). Total calcium (T-Ca) and phosphorus (Pi) concentrations was observed to be significant difference, it was decreased with an increase in the NaF levels (𝛼=0.05). Accordingly, sodium fluoride exposures and dose-response relationship, which was found on the bad influences in hematology. Such association is considered that the long-term fluoride exposure caused nephrotoxicity.

• The korean journal of orthodontics
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• v.40 no.4
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• pp.212-226
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• 2010

Objective: The aim of this study was to evaluate the effect of remineralization and inhibition to demineralization after fluoride gel (acidulated phosphate fluoride, APF) or hydroxyapatite (HAp) paste application on interdentally stripped teeth. Methods: After interdental stripping, 1.23% APF or 5%, 10% HAp paste were applied for 7 days for remineralization. Afterwards, teeth were exposed to lactate carbopol buffer solution for demineralization. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were used to compare change in surface contents and crystal structures after remineralization, and then after demineralization. Results: EDS analysis indicated that calcium (p < 0.001) and phosphate (p < 0.01) contents were increased after 10% HAp paste application on stripped enamel, calcium (p < 0.05) and phosphate (p < 0.01) contents were increased after 5% HAp paste application, and fluoride (p < 0.01) contents were increased after 1.23% APF application. SEM image showed that enamel surfaces became smoother and crystal structures became small and compact after APF or HAp application. After demineralization, calcium (p < 0.05) and phosphate (p < 0.05) contents remained increased on the enamel remineralized with 10% HAp paste, and phosphate (p < 0.05) contents remained increased on the enamel remineralized with 5% HAp paste. After demineralization, surfaces looked less destroyed in the enamel remineralized beforehand than those of the control, and small pores between crystal structures, formed by remineralization were remained. Conclusions: Hydroxyapatite paste and fluoride gel were helpful to remineralize and inhibit deminerlization on stripped enamel.