• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.2
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• pp.377-398
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• 1999

Calcium fluoride, created by topical fluoride application, is the reservoir for fluoride ion regulated by pH in the oral environment. Therefore, the amount and the maintenance of calcium fluoride have an important role in preventing dental caries. The aim of this study is to evaluate the effect of Nd:YAG laser irradiation on the generation of calcium fluoride and the acid resistance of tooth enamel. The bovine anterior permanent teeth were prepared (n=276), and divided into following groups : no treatment (control) fluoride application alone, laser irradiation alone, laser irradiation after fluoride application, and fluoride application after laser irradiation. And each group was subdivided based on the application time of 1.23% acidulated phosphate fluoride (APF) (5 min and 30 min) and the irradiation energy of Nd:YAG laser ($20J/cm^2\;and\;40J/cm^2$). In case of fluoride application, each group was divided according to KOH treatment. Twenty three treatment conditions were made for this experiment and twelve specimens were assigned to each treatment condition. In each treatment condition, ten specimens were used for chemical analysis and two specimens were observed under SEM. In groups without treating KOH, fluoride content and the depth of enamel dissolved were measured using enamel biopsy technique. In groups with treating KOH, the amount of calcium fluoride was measured by the treatment with 1 M KOH for 24 hours and enamel biopsy was performed after KOH treatment. The results were analyzed by the fluoride content and the depth of enamel dissolved by enamel biopsy, amount and thickness of calcium fluoride, and the surface structures of enamel. The results are as follows: 1. In groups without treating KOH, the fluoride content of removed enamel showed a positive relationship with the energy density of laser when the laser irradiated before fluoride application 2. In groups without treating KOH, the depth of enamel dissolved decreased more with the combined laser and fluoride treatment than with laser or fluoride treatment, except for the case of $20J/cm^2$ laser irradiation after 5 minute fluoride application (p<0.05). 3. The amount of calcium fluoride did not increased by laser treatment with no statistical significance(p>0.05). 4. The particle size of calcium fluoride increased in case of fluoride treatment after laser irradiation, compared with fluoride application alone. In case of laser treatment after fluoride application, the particle size of calcium fluoride increased and some of the particles fused as well. 5. There were no significant differences in the fluoride content of dissolved enamel between groups without treating KOH and control group, except for the case of laser irradiation after treatment of APF for 30 minutes (p>0.05). 6. In groups with treating KOH, depth of removed enamel in the groups of combined treatment with laser and fluoride was shallower than that in fluoride application groups (p<0.05). 7. In groups without treating KOH, the relationship between fluoride content and the depth of enamel dissolved showed more negative (Spearman correlation coefficient: -0.6281) than in groups with treating KOH (Spearman correlation coefficient: -0.3792). The greater amount of calcium fluoride could be found in case where there was a significant differences of the depth of enamel dissolved between groups with and without treating KOH. From these results, it can be concluded that laser seems to be a little effects on the amount of calcium fluoride formation, but has some effect on the lowering the solubility of calcium fluoride. As the combined treatment of laser and fluoride application showed more effective acid-resistant property, more extended recall period for fluoride application can be achieved with this combined treatment in the clinic.

• Journal of Korean Society of Water and Wastewater
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• v.14 no.2
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• pp.164-173
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• 2000

Fluoridation of drinking water to a level of about 0.8mg/l (below 1.5mg/l) for reducing the incidence of tooth decay is recommended. However, concerns about potential problems of unknown effects and overdosing hinders the fluoridation. This study describes the work performed to obtain information on the behavior of fluoride under various conditions in the process of water fluoridation. Effects of water treatment chemicals, water treatment unit, and water distribution on water fluoridation were investigated at both lab and an actual water treatment plant. Residual fluoride concentration was not affected by lime and chlorine dosage up to 20mg/l. Flocculation with PAC slightly decreased the residual fluoride concentration as PAC dosage increased. Average fluoride concentration of 0.87mg/l at an intake basin was decreased to 0.83mg/l by sedimentation, 0.81mg/l by dual media(sand+anthracite) filtration, and 0.79mg/l by granular activated carbon filtration in the water treatment plant.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.6
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• pp.682-688
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• 2013

In this study, we investigated about cell toxicity and oxidative stress of HepG2 cell by treatment of sodium fluoride (NaF) and fluoride extracts from krill Euphausia superba meat, shell, whole body and krill meal. The cell toxicity showed significant at 300 and $500{\mu}g/mL$ NaF treatment group. But krill (Euphausia superba) fluoride extract (KFE) treatment in all groups were not toxic. The superoxide radical production increased significantly in NaF treated group, but there was no significant change in KFE treated group. The superoxide dismutase activity was a significant increase 21.5% at $100{\mu}g/mL$ and 24.7% at $300{\mu}g/mL$ treatment group of fluoride extracts from krill meat, and 8.7% at $300{\mu}g/mL$ in krill meals, compared to the control group. However, hydroxy radical flux and catalase and glutathione peroxidase activity of fluoride extracts from krill meat did not change. As a result, for a short period of time, NaF treatment in HepG2 cells affect the cell toxicity and oxidative stress, but in the case of KFE, these were not recognized. Thus, depending on the type of food ingested with fluoride, cell toxicity and oxidative stress was found to be different.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.2
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• pp.125-134
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• 2005

Waste concrete powder was used to remove fluoride ions in highly concentrated fluoride wastewater. 92.6% of fluoride in 100 mg F/L wastewater was removed by 1% dose of the cement paste powder that represents characteristics of waste concrete powder, whereas the removal efficiencies of raw cement and lime were 47.3% and 96.4%, respectively. The cement paste powder was competitive to lime, common fluoride removal agent. Various Ca-bearing hydrates such as portlandite, calcium silicate hydrate, and ettringite in cement paste slurry can remove fluoride by precipitating $CaF_2$ and absorbing $F^-$ ions. In the experiments using both cement paste and lime, 50~67% of lime can be substituted by cement paste to satisfy fluoride effluent limitation of 15 mg/L. Since cement paste has higher acid neutralization capacity than lime, it can be recycled to neutralize more acid and to remove more fluoride. Therefore waste concrete powder can be more economical and viable alternative for lime in fluoride wastewater treatment.

• Journal of Korean society of Dental Hygiene
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• v.10 no.3
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• pp.473-481
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• 2010

Objectives : To evaluate the effect of fluoride application on the color and microhardness of bleached enamel and compare it to that of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) application. Methods : Twenty freshly extracted human adult molar were each sectioned into halves, the specimens divided and treated according to five experimental groups: Group 1, treatment with 10% carbamide peroxide (CP) bleaching agent; Group 2, treatment with 10% CP followed by a 1.23% fluoride gel application; Group 3, treatment with 10% CP followed by a 2.23% sodium fluoride varnish application; Group 4, treatment with 10% CP followed by a 0.11% sodium fluoride gel application; Group 5, treatment with 10% CP followed by a CPP-ACP gel application. All groups were treated 6 h per day for 14 days then immersed in distilled water for 2 weeks. Changes in enamel color were evaluated on Baseline and Day 14. Microhardness were evaluated on Baseline, Days 7 and 14. Statistical analysis was performed using one-way ANOVA and post-hoc Tukey tests. Results : All the bleached enamel specimens revealed increased whiteness and overall color value. Group 1 showed the lowest microhardness values than that of Groups 2, 3, 4 and 5. In all groups, the hardness of tooth after bleaching showed a significant decrease in the microhardness as compared with the one prior to tooth bleaching. The specimens treated with remineralizing agents showed relatively less reduction in enamel microhardness than control group. Conclusions : The addition of fluoride and CPP-ACP did not impede the whitening effect. The use of remineralizing agents during bleaching treatment can significantly enhance the microhardness of bleached enamel.

• Journal of Korean society of Dental Hygiene
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• v.9 no.4
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• pp.740-752
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• 2009

Objectives : This study was carried out to examine the effect of varnish fluoride and APF gel on the acid resistance and the remineralization of the enamel. Methods : At first, the microhardness changes of enamel surface were measured after demineralizing the fluoride treated tooth surface. Next, the changes were measured after fluoride application to the demineralized enamel surface. Results : 1. Acid resistance was higher in varnish fluoride groups than APF gel groups and the difference was significant(p<0.001). 1) Varnish fluoride groups Microhardness of enamel surface showed $297.76{\pm}9.89$ after fluoride treatment and $260.90{\pm}28.67$ after drmineralization. The changes of Vickers hardness number(VHN) were $-36.86{\pm}27.30$. 2) APF gel groups Microhardness of enamel surface showed $298.79{\pm}17.28$ after fluoride treatment and $43.75{\pm}18.58$ after demineralization The changes of VHN were $-255.04{\pm}21.31$. 2. No significant changes were surveyed in both varnish fluoride groups and APF gel groups as for remineralization of enamel(p>0.05). 1) Varnish fluoride groups Microhardness of enamel surface showed $46.58{\pm}15.42$ after demineralization and $46.61{\pm}15.70$ after fluoride treatment. The changes of VHN were $0.02{\pm}3.75$. 2) APF gel groups Microhardness of enamel surface showed $47.13{\pm}19.31$ after demineralization and $42.59{\pm}16.12$ after fluoride treatment. The changes of VHN were $-4.54{\pm}5.06$. Conclusions : Varnish fluoride showed higher acid resistance than APF gel, however both of them were observed to have no effect on the remineralization of the enamel.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.5
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• pp.767-775
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• 2011

In this study we verified if the electro-coagulation process can treat properly the nitrate and fluoride that are not removed well in the conventional small water treatment plants which usually employ chlorination and filtration only. As we gave a change of electrode material and gap-distance between electrodes, removal efficiency of the nitrate and fluoride was determined by electro-coagulation process which were equipped with aluminum and stainless steel (SUS304) electrodes. In addition, electrode durability was investigated by determination of electrodes mass change during the repetitive experiments. Removal efficiency was great when aluminum was used as an anode material. Nitrate removals increased as electric density and number of electrodes increased, but fluoride removal was less sensitive to both parameters than nitrate. After 10 minutes of contact time with the current density from $1{\times}10^{-3}$ to $3{\times}10^{-3}A/cm^{2}$, nitrate and fluoride concentration ranged from 9.2 to 1.2mg/L and from 0.02 to 0.01mg/L, which satisfied the regulation limits. Regardless of the repeating number of experiments, removal efficiency of both ions were almost similar and the change of electrode mass ranged within ${\pm}$0.5%, indicating that the loss of the electrode mass is not so much great under the limited circumstances.

• Environmental Analysis Health and Toxicology
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• v.14 no.3
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• pp.113-120
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• 1999

Fluorination of drinking water has been used world widely to reduce the incidence of caries. Recently, contradictory results on the cytotoxicity of fluoride compounds are reported. In addition, there are attempts to use fluorosilicate for fluorination of drinking water in Korea, therefore, we tried to analyze the cytotoxicity of fluoride compounds on oral epidermoid carcinoma (KB and A253) and osteosarcoma (HOS and MG-63) cells in this study. We treated cells with 0, 10, 50 and 250 ppm of fluorosilicic acid (domestic or from Fluka, F$\_$6/H$_2$Si), sodium fluorosilicate (F$\_$6/Na$_2$Si), sodium fluoroacetate (FCH$_2$CO$_2$Na), sodium fluoride (NaF) or potassium fluoride(KF) and measured the relative cell survival by MTT assay. At the concentration of < 10ppm, no significant cytotoxicity was observed. At 50 ppm, each cells revealed different response to fluoride treatment. Among cells used in this study, MG-63 was the most resistant to fluoride treatment. Comparable toxicity data from domestic and imported fluorosilicic acids were obtained. When we compared the relative cytotoxicity of fluoride compounds against their fluoride contents, the differences in relative cell survival were smaller. Most of cells showed < 20% of survival at 250 ppm. In order to analyze the pH dependence of the cytotoxicity of fluorosilicates, the pH of cell culture media containing fluorosilicate was adjusted to 7.4 or 6.5 and the relative cytotoxicity was measured. At lower pH, about 10% higher cytotoxicity was obtained. Thus, our data suggested that the toxicity of domestic fluorosilicic acid was similar to that of fluorosilicic acid from Fluka, and the cytotoxicity of fluoride compounds was dependent on the relative content of fluoride and pH.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.2
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• pp.212-222
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• 2004

The application of acidulated phosphate fluoride gel(APF) and fluoride varnishes are the most common topical fluoride therapy. The purpose of this in vitro study was to compare the remineralization effects of two topical fluoride agents, APF gel and fluoride varnish with microtomograph and 3D image analyzer without sample preparation and chemical fixation. For the purpose of the study, the artificial caries lesion was caused on the caries-free permanent pre molar and 48 specimens were divided into three groups each containing 16 specimens No application was performed on group 1, which acted as control group. Group 2 was treated with APF gel and was removed after a minute. Group 3 was treated with the topical application of fluoride varnish and removed after 45 minutes. Each specimen was placed into a closed container with 50ml of a artificial saliva during three months and the 3D images of the remineralization area were taken using the SkyScan each month. Using the density-measuring program in V $works^{TM}$, the density value of the remineralization area was measured. The following results were obtained: 1. All groups demonstrated an increase in the density of artificial caries lesion with time. 2. The density was significantly higher in APF gel and fluoride varnish group than control group at 1 month, 2 months, 3 months after the treatment(P<0.05). 3. The difference of the density between that "prior to treatment" and that "1 month after treatment" in Group 2 and Group 3 was significantly higher than that of Group 1 and, the difference of the density between that "1 month after treatmen" and that "2 month after treatment" in Group 3 was significantly higher than that of Group 1 and 2(P<0.05). 4. The fluoride varnish was more effective after 2 and 3 months and continuous than the APF gel.

• Advances in environmental research
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• v.12 no.2
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• pp.77-93
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• 2023

The water can be contaminated by natural sources or by industrial effluents. One such contaminant is fluoride. Fluoride contamination in the water environment due to natural and artificial activities has been recognized as one of the major problems worldwide. Among the commonly used treatment technologies applied for fluoride removal, the adsorption technique has been explored widely and offers a highly efficient simple and low-cost process for fluoride removal from water. This review paper the recent developments in fluoride removal from surface water by adsorption methods. Studies on fluoride removal from aqueous solutions using various carbon materials are reviewed. Various adsorbents with high fluoride removal capacity have been developed, however, there is still an urgent need to transfer the removal process to an industrial scale. Regeneration studies need to be performed to more extent to recover the adsorbent in field conditions, enhancing the economic feasibility of the process. Based on the review, technical strategies of the adsorption method including the Nano-surface effect, structural memory effect, anti-competitive adsorption and ionic sieve effect can be proposed. The design of adsorbents through these strategies can greatly improve the removal efficiency of fluoride in water and guide the development of new efficient methods for fluoride removal in the future. This paper describes brief discussions on various low-cost adsorbents used for the effective removal of fluoride from water.