• The korean journal of orthodontics
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• v.49 no.4
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• pp.246-253
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• 2019

Objective: To evaluate the effectiveness of three different caries-preventing agents on artificial caries in a Streptococcus mutans-based caries model. Methods: Sixty-five caries-free human molar enamel blocks were treated with a demineralization solution and a remineralization solution. The specimens were assigned to the following groups according to the caries-protective product applied: group A, chlorhexidine varnish; group B, fluoride-releasing chemically cured sealant; group C, fluoride-releasing lightcured sealant; group D, positive control (specimens that were subjected to de- and remineralization cycles without treatment with any caries-protective agents); and group E, negative control (specimens that were not subjected to de- and remineralization cycles). Samples in groups A-D were stored in demineralization solution with S. mutans and thereafter in artificial saliva. This procedure was performed for 30 days. Average fluorescence loss (${\Delta}F$) and surface size of the lesions were measured using quantitative light-induced fluorescence at baseline and on the 7th, 14th, and 30th days. Results: After 30 days, group A demonstrated a significant increase in ΔF and the surface size of the lesions, no significant difference in comparison with the positive control group, and a significant difference in comparison with the negative control group. Group B showed no significant changes in both parameters at any of the measurement points. While group C showed increased ${\Delta}F$ after 14 days, no significant fluorescence change was observed after 30 days. Conclusions: Both fluoride-releasing sealants (chemically or light-cured) show anti-cariogenic effects, but the use of chlorhexidine varnish for the purpose of caries protection needs to be reconsidered.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.7
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• pp.714-721
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• 2010

This research was undertaken to evaluate the feasibility of lanthanum hydroxide for fluoride removal from aqueous solutions. A batch sorption experiments were conducted to study the influence of various factors such as pH, contact time, initial fluoride concentration and temperature on the sorption of fluoride on lanthanum hydroxide. The optimum fluoride removal was observed in the $pH_{eq}{\leq}8.8$. Sorption equilibrium of fluoride on lanthanum hydroxide was better described by the Freundlish isotherm model than by the Langmuir isotherm model. The adsorption energy obtained from D-R model was 9.21 kJ/mol indicating an ion-exchange process as primary adsorption mechanism. The pseudo-second-order kinetic model described well the experimental kinetic data. Thermodynamic parameters such as ${\Delta}Go^{\circ}$, ${\Delta}H^{\circ}$ and ${\Delta}S^{\circ}$ indicated that the nature of fluoride sorption is spontaneous and endothermic. The used lanthanum hydroxide could be regenerated by washing with NaOH solution. Also, the results applied to real ground water indicate that fluoride selectivity and removal capacity of lanthanum hydroxide were superior to those of PA anion-exchange resin.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.4
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• pp.662-670
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• 2008

The purpose of this in vitro study was to evaluate the effect of fluoride containing adhesive film on prevention of enamel demineralization. Eighty bovine enamel blocks were divided randomly into 4 groups of 25: (1) APF gel applied ; (2) CavityShield$^{TM}$ applied; (3) 3% fluoride film applied; (4) 5% fluoride film applied; Early caries lesions were produced by placing each specimen into demineralization solution at pH 4.0 for 72 hours. Then lesion of the surface microhardness were measured by the Vicke's hardness test and the lesions depth were measured by polarizing light microscope. The results of the present study are as follows: 1. Difference of microhardness value ($M{\pm}SD$) between control and experimental side was the highest in group II, followed by group IV, III, I but, no significant difference was between group II, III and IV. 2. Difference of mean lesion depth ($M{\pm}SD$) between control and experimental side was the highest in group II, followed by group III, IV and I but no significant difference was between group III and IV. The results of the present study indicate that the fluoride film application is more effective than APF gel and is similar to fluoride varnish application for prevention of dental caries.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.10
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• pp.986-993
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• 2010

In this study, sorption characteristics of thermally treated activated alumina (AA) for fluoride were investigated. Sorption experiments have been conducted in equilibrium and kinetic batch conditions. Also, effects of solution pH and anions on fluoride removal have been observed. The properties of thermally treated ( $700^{\circ}C$) activated alumina (AA700) and untreated activated alumina (UAA) were compared using field-emission scanning electron microscope, energy-dispersive spectrometry, X-ray diffractometer (XRD) analysis, and Brunauer-Emmett-Teller (BET) analysis. From the experiments using AA thermally treated at different temperatures (100, 300, 500, $700^{\circ}C$), it was found that at high fluoride concentrations (50, 100, 200 mg/L) the sorption capacity of thermally treated AA increased with increasing thermal treatment temperature. At an initial fluoride concentration of 200 mg/L, the sorption capacity of AA700 was 3.67 times greater than that of UAA. The BET analysis showed that the specific surface area of UAA was about 2 times larger than that of AA700. The XRD analysis indicated that UAA was composed of both boehmite (AlOOH) and bayerite ($Al(OH)_3$) while AA700 was $Al_2O_3$. The reason that fluoride sorption capacity of AA700 increased despite of decrease in specific surface area compared to UAA could be attributed to the change of crystal structure. The kinetic sorption test showed that fluoride sorption to AA700 arrived at equilibrium after 24 h. The equilibrium test demonstrated that the maximum sorption capacity of AA700 was 5.70 mg/g. Additional batch experiments indicated that fluoride sorption to AA700 was the highest at pH 7, decreasing at both acidic and basic solution pHs. Also, fluoride sorption to AA700 decreased in the presence of anions such as phosphate, nitrate, and carbonate. This study demonstrated that thermal treatment of AA at high temperature could increase its sorption capacity for fluoride.

• Economic and Environmental Geology
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• v.54 no.6
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• pp.709-716
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• 2021

In this study, an adsorbent prepared by natural drying of iron hydroxide-based sludge collected from settling basin at a mine drainage treatment facility located in Gangneung, Gangwon-do was used to remove fluoride in an artificial fluoride solution and mine drainage, and the adsorption characteristics of the adsorbent were investigated. As a result of analyzing the chemical composition, mineralogical properties, and specific surface area of the adsorbent used in the experiment, iron oxide (Fe₂O₃) occupies 79.2 wt.% as the main constituent, and a peak related to calcite (CaCO₃) in the crystal structure analysis was analyzed. It was also identified that an irregular surface and a specific surface area of 216.78 m²·g^-1. In the indoor batch-type experiment, the effect of changes in reaction time, pH, initial fluoride concentration and temperature on the change in adsorption amount was analyzed. The adsorption of fluoride showed an adsorption amount of 3.85 mg·g^-1 16 hours after the start of the reaction, and the increase rate of the adsorption amount gradually decreased. Also, as the pH increased, the amount of fluoride adsorption decreased, and in particular, the amount of fluoride adsorption decreased rapidly around pH 5.5, the point of zero charge at which the surface charge of the adsorbent changes. Meanwhile, the results of the isotherm adsorption experiment were applied to the Langmuir and Freundlich isotherm adsorption models to infer the fluoride adsorption mechanism of the used adsorbent. To understand the thermodynamic properties of the adsorbent using the Van't Hoff equation, thermodynamic constants 𝚫H° and 𝚫G° were calculated using the adsorption amount information obtained by increasing the temperature from 25℃ to 65℃ to determine the adsorption characteristics of the adsorbent. Finally, the adsorbent was applied to the mine drainage having a fluoride concentration of about 12.8 mg·L^-1, and the fluoride removal rate was about 50%.

• Bulletin of the Korean Chemical Society
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• v.25 no.12
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• pp.1822-1828
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• 2004

Electrochemical, in situ electrochemical scanning tunneling microscope (EC-STM), and attenuated total reflectance-FTIR (ATR-FTIR) spectroscopic methods were employed to investigate the preparation of atomically flat Si(111)-H surface in ammonium fluoride solutions. Electrochemical properties of atomically flat Si(111)-H surface were characterized by anodic oxidation and cathodic hydrogen evolution with the open circuit potential (OCP) of ca. -0.4 V in concentrated ammonium fluoride solutions. As soon as the natural oxide-covered Si(111) electrode was immersed in fluoride solutions, OCP quickly shifted to near -1 V, which was more negative than the flat band potential of silicon surface, indicating that the surface silicon oxide had to be dissolved into the solution. OCP changed to become less negative as the oxide layer was being removed from the silicon surface. In situ EC-STM data showed that the surface was changed from the initial oxidecovered silicon to atomically rough hydrogen-terminated surface and then to atomically flat hydrogenterminated surface as the OCP moved toward less negative potentials. The atomically flat Si(111)-H structure was confirmed by in situ EC-STM and ATR-FTIR data. The dependence of atomically flat Si(111)-H terrace on mis-cut angle was investigated by STM, and the results agreed with those anticipated by calculation. Further, the stability of Si(111)-H was checked by STM in ambient laboratory conditions.

• The Journal of the Korean dental association
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• v.15 no.7
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• pp.521-526
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• 1977

• Journal of dental hygiene science
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• v.11 no.5
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• pp.445-453
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• 2011

Objectives : The purpose of this study was to determine of fluoride-releasing of orthodontic resin cements containing fluoride and compare decalcification of tooth attached fluoride and non-fluoride resin cements. Methods : Total eighty premolar tooth were used in this study. Forty tooth were used for fluoride releasing measurement and forty tooth were used for decalcification measurement. Each forty tooth were randomly divided into four groups, and brackets were attached on tooth surface with Blugloo, Light Bond, Orthofolw(experimental groups) and Transbond cement(control group). After brackets were attached on tooth surface, forty tooth were immersed in artificial salival and then the quantity of fluoride releasing was measured ever day for 8days and then three-days intervals for 3 weeks. Forty tooth were immersed in decalcification solution for 48hours and then degree of decalcification was measured as lesion area, ${\Delta}F$, and ${\Delta}Q$ using QLF. The data were analysed by one-way ANOVA and Pearson's correlation coefficient using SPSS 12.0 program. Results : Fluoride release of experimental groups was higher than control group(p<0.05). Cumulative fluoride release of experimental groups was also higher than control group(p<0.05). There were the highest release during first day. ${\Delta}F$, and ${\Delta}Q$ was high TB > BG > OF > LB (p<0.05). Change of ${\Delta}F$, and ${\Delta}Q$ was also high TB > BG > OF > LB (p<0.05). As for correlation between fluoride release and lesion area, ${\Delta}F$, and ${\Delta}Q$ showed negative correlation but there was no significant difference. Conclusions : This study shows that orthodontic reins cements containing fluoride release fluoride and prevent initial enamel decalcification caused by orthodontic treatment.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.150.2-150.2
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• 2017

This research was conducted to investigate in detail the effect of $PO_4{^{3-}}$, $CO_3{^{2-}}$ and $F^-$ anions on the electrochemical properties of the thin air-formed oxide film-covered AZ31 Mg alloy. In this work, native air-formed oxide films on AZ31 Mg alloy samples were prepared by knife-abrading method and the changes in the electrochemical properties of the air-formed oxide film were investigated in electrolytes containing 0.01 M, 0.05 M and 0.1 M of $PO_4{^{3-}}$, $CO_3{^{2-}}$ and $F^-$ anions. It was observed that the trend of open circuit potential (OCP) transients changed only in the solution containing $PO_4{^{3-}}$ ions. The Nyquist plots obtained from electrochemical impedance spectroscopy (EIS) showed that the resistance of the new surface films formed in fluoride ion containing bath increased with the increase in concentration of fluoride ions but the resistance of surface films formed in carbonate ion containing bath decreased with the increase in concentration of carbonate ions. The potentiodynamic polarization curves illustrated that under anodic polarization, there was growth of porous passive layer only in fluoride ion containing solution while the surface layer formed in phosphate and carbonate ion containing solutions lost its passivity at high anodic potential of $2.5V_{Ag/AgCl}$.

• Journal of Korean society of Dental Hygiene
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• v.8 no.3
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• pp.139-148
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• 2008

A fluorine solution was used to measure the growth of S.mutans and the pH changes were also measured in order to find an effective and preventative dentistry lab within a limited time for the dental hygiene department curriculum and the following results were obtained. 1. In the growth comparison of S.mutans, the culture medium of the experiment group with fluorine weighed 0.3g and the culture medium with no fluorine weighed 0.5g, which shows that the growth rate of S.mutans is significantly decreased in the culture medium with the fluorine. 2. The pH7.8 of the culture medium was not nearly changed; it became 7.0 after culturing with fluoride, however the pH was significantly decreased to 3 in the culture medium that had no fluorine. 3. Since it has been proven that the fluorine can control the growth of germs, it is believed that the effect of fluorine as a cavity preventative should be emphasized to students and in addition, it will help students transmit the effect of fluoride to their patients since this knowledge has been acquired through practice. 4. It is considered that this is a simple test protocol providing effective results in the microorganism and preventive dentistry lab within a limited time and furthermore, it will furnish the students of dental hygiene with comprehensive accessibility to dental hygiene curriculum.