Fluoride Ion-selective Electrode Research Articles

Fluoride Concentration in Drinking water in The Libyan City of Zliten: Dental Perspective

Background: Having optimally fluoridated drinkable water supply is important to reduce the prevalence of both dental decay and dental fluorosis. This research aimed to report all possible drinking water sources and their fluoride content in the Libyan city of Zliten.
 Methods: This descriptive study used a convenient sampling strategy to collect 68 samples from different drinking water sources across the city. The fluoride concentration was identified using potentiometric method by means of fluoride selective ion electrode.
 Results: 31 source of desalinated water and 37 ground water source have been identified as drinking water. Moreover, the fluoride content was found to be much lower than recommended by the national and international standards for the desalinated water (0.047 ppm±0.062) while that of ground source was found to range from 0.9 to 2.23 ppm with a mean of (1.43 ppm±0.38).
 Conclusion: People in the city have many choices for drinkable water, however, those who drink from the desalinated water consume less water-dissolved fluoride than those who rely on the ground water as a source of drinking. This reflects the fact that the residents have no equal chances to get the sufficient amounts of fluoride necessary for healthy teeth. Accordingly, more research is needed to evaluate the actual effect of this discrepancy in fluoride consumption on the population and consequently to implement the required strategies essential to assure optimum oral health for the whole population.

Thermodynamic and Kinetic Studies on the Conversion of Solvent-Shared to Contact Ion Pairs in Sparingly Soluble MF2 (M = Mg2+ and Ca2+) Aqueous Solutions: Implications for Understanding Supersaturated Behavior and Association Constant Determination.

The thermodynamic and kinetic behaviors of Mg2+-F- ion pairing in aqueous solution are investigated theoretically and experimentally and are contrasted to those of Ca2+-F-. Thermodynamically, similar to CaFx(H2O)142-x (x = 1 and 2), MgF(H2O)y+ (y = 14-20) contact ion pairs (CIPs) are more stable than their solvent-shared ion pairs (SSIPs), whereas the CIPs and SSIPs of MF2(H2O)y are almost isoenergetic. However, in kinetics, the conversion of SSIPs to CIPs for M2+-F- (M = Mg2+ and Ca2+) ion pairing must overcome a high energy barrier due to the strong hydration of Mg2+ and F-. The kinetics dominate after the thermodynamics and kinetics are balanced, which hinders the formation of M2+-F- CIPs in practical MF2 aqueous solutions (less than or equal to saturated concentrations). This result is also supported by the 19F nuclear magnetic resonance spectra of saturated MF2 solutions. Although the interaction between Mg2+ and F- is slightly stronger than that between Ca2+ and F- due to the smaller radius of Mg2+, the formation of Mg2+-F- CIPs needs to go through two rate-limiting steps, the dehydration and entrance of F- (i.e., via exchange mode) with a higher energy barrier, due to the ability of strongly bound water molecules and rigorous octahedral coordinated configuration of Mg2+, while the formation of Ca2+-F- CIPs only goes through a single rate-limiting step, the entrance of F- (i.e., via swinging mode) with a lower energy barrier, due to the flexible coordination configuration of Ca2+. This is responsible for precipitation in MgF2 aqueous solution requiring a larger supersaturation degree and a lower precipitation rate than in CaF2. These kinetic factors lead to the association constants previously reported for MF+ determined by a fluoride ion-selective electrode (ISE) combined with the titration method, where the MF2 solutions were always unsaturated at the titration end point, which actually corresponds to those of the ligand process going from completely free M2+ and F- to their SSIPs. A possible strategy to accurately determine the association constants of MF+ and MF2(aq) CIPs by fluoride ISEs is proposed. The present results suggest that judging the formation of M2+-F- CIPs in practical solutions from a theoretical calculation perspective requires significant consideration of the kinetic factors, except for the thermodynamic factors.

High energy radiation – Induced cooperative reductive/oxidative mechanism of perfluorooctanoate anion (PFOA) decomposition in aqueous solution

The mechanism of high-energy radiation induced degradation of perfluorooctanoate anion (PFOA, C7F15COO−) was investigated in aqueous solutions. Identification and quantification of transient species was performed by pulse radiolysis and of final products by gas and ion chromatography, electrochemical method using fluoride ion-selective electrode and ESI-MS after γ-radiolysis. Experimental data were further supported by kinetic simulations and quantum mechanical calculations. Radiation induced degradation of PFOA includes as a primary step one-electron reduction of PFOA by hydrated electrons (e−aq) resulting in formation of [C7F15COO−]●−. The rate constants of this reaction were found to be in the range 7.7 × 107−1.3 × 108 M−1s−1 for ionic strength of the solutions in the range 0.01–0.1 M and were independent of pH of the solutions. At pH > 11 [C7F15COO−]●− tends to defluorination whereas at lower pH undergoes protonation forming [C7F15COOH]•−. A sequence of consecutive reactions involving [C7F15COOH]•− leads to PFOA regeneration what explains a high radiation resistance of PFOA at moderately acidic solutions. A simultaneous presence of oxidizing transient species (●OH) in the irradiated system enhanced decomposition of (C7F14)·COO− as well as [C7F15COOH]•−. The key steps in this complex radical mechanism are the reactions of both these radical anions with ●OH leading to semi-stable products which further undergo consecutive thermal reactions. On the other hand, direct reactions of PFOA with ●OH and ●H were found to be relatively slow (7 × 103 and <4 × 107 M−1s−1, respectively) and do not play relevant role in PFOA degradation. Collected for the first time results, such as dependence of selected reaction rate constants and selected products radiation chemical yields on pH as well as finding of several semi-stable products, missing in previous studies, indicate incompleteness of published earlier reaction pathways of PFOA degradation. The presented overall mechanism explains experimental results and verifies previously suggested mechanisms found in the literature.

Simultaneous determination of H2SiF6, HF and total fluoride in fluorosilicic acid recovered from wet phosphoric acid production by potentiometric titration

Fluorosilicic acid is generally obtained unintentionally in phosphate fertilizer manufacturers, particularly during wet phosphoric acid and triple superphosphate (TSP) production from fluorapatite. Since sustainability is a major environmental concern, phosphoric acid production factories have a fluorine recovery process as fluorinated products, mainly consisting of fluorosilicic acid (H2SiF6). In other words, to optimize the control of the fluorine recovery during the phosphate chemical process and to investigate the valorization alternatives of the concomitantly produced fluorosilicic acid, the main fluorine-based by-products have to be analyzed.The present work describes the development of a potentiometric analytical method for the major constituents of fluorosilicic acid produced during the chemical phosphate process, i.e., H2SiF6, HF and total fluoride. Therefore, a preliminary speciation study was investigated on industrial and synthetic fluorosilicic acid samples using fluorine-19 (19F) and silicon-29 (29Si) nuclear magnetic resonance (NMR) spectroscopies. Interestingly, we observed the presence of two forms of fluoride in a highly acidic medium (pH = 1.80) ascribed to HF and H2SiF6, as well asasingleformofsiliconwhichis assigned toH2SiF6. Moreover, a potentiometric titration of fluorosilicic acid with known H3PO4 content, using a 0.5 mol.L−1 NaOH solution as a titrant, allowed us to determine the H2SiF6 concentration as well as the amount of total acid content. Then, the amount of hydrofluoric acid is calculated from the difference between total acid, phosphoric acid and fluorosilicic acid contents. The total fluoride content is deduced from H2SiF6 and HF contents. The results obtained with this method are compared to other standard methods, e.g., silicon determination by flame atomic absorption spectroscopy and total fluoride determination by fluoride ion selective electrode (F-ISE). It is worth noting that, based on this comparison study, the developed method provides consistent results. Furthermore, the analysis is fast and accurate, and is therefore applicable to the control of recovery process as well as to the characterization of industrial fluorosilicic acid.

Seasonal Variations in the Groundwater Fluoride of Swarna River Basin in Southern India: A GIS-based Study.

ABSTRACTObjectives:The study aimed (1) to assess fluoride concentration of groundwater along the Swarna river basin in Udupi District; (2) to investigate variations in fluoride concentration with respect to rainfall status in Udupi district; and (3) to develop a spatial distribution map for the groundwater fluoride concentration in Udupi district.Materials and Methods:Water samples were procured from 30 different sampling points across three time zones in a year: pre-monsoon, monsoon, and post-monsoon. The samples thus collected were analyzed for fluoride ion concentration using fluoride ion selective electrodes (Orion™). Mean determination readings at each time zone were calculated. Repeated-measures analysis of variance was done to analyze whether there was a difference in the concentration of fluoride over different time zones.Results:The mean (SD) pre-monsoon concentration was 0.25 (± 0.07) ppm, whereas the mean monsoon and post-monsoon concentrations were 0.26 (± 0.09) and 0.57 (± 0.23) ppm, respectively. There was a significant increase in post-monsoon fluoride levels when compared with the pre-monsoon and monsoon levels.Conclusion:The groundwater fluoride concentration in the Swarna river basin was found acceptable for human consumption at all the sampled sites and across all time zones. As the fluoride concentration was found to be lower than the recommended values for dental caries prevention at most of the sampling sites, use of topical fluorides needs to be encouraged.

Comparison of antibacterial activity and fluoride release in tooth-colored restorative materials: Resin-modified glass ionomer, zirconomer, giomer, and cention N

Considering the important role of fluoride in preventing caries by reducing the number and activity of cariogenic bacteria and introducing new fluoride-releasing tooth-colored restorative materials, this study was performed to compare and evaluate fluoride ion release and antibacterial activity of resin-modified GI, zirconomer, giomer (Beautifil), and Cention N.In this experimental in vitro study, eighty samples (20 samples in each group) were prepared, 10 samples for fluoride testing and 10 samples for antibacterial activity. To evaluate the release of fluoride (PPM), fluoride ion-selective electrode was used on days 1st, 3rd, 7th, 14th, and 21st; and antibacterial activities against Streptococcus mutans were examined using direct contact test by absorption of light hourly once every 5 h and days 1st, 2nd, and 7th using an ELISA reader with a microplate reader of 800 TS at a wavelength of 630 nm. The results were analyzed using one-way ANOVA, Tamhane post hoc test, and paired t-test in SPSS software (IBM, Somers, NJ, USA) at a significant level of (P < 0.05).The release of fluoride from materials showed a statistically significant difference (P < 0.001). The maximum mean of fluoride released during the 1st, 3rd and 7th days belonged to the zirconomer group and the minimum for the giomer group. During the measurement period of light absorption from 0 to 24 h after planting, light absorption of foursubstances together was found to be statistically significant (P <.001). Zirconomer light absorption increased on the 7th day, unlike other substances, but still, the minimum light absorption was related to zirconomer.The highest fluoride release was in zirconomer, Cention N, fuji II LC, and giomer, sequentially. Zirconomer showed maximum and giomer showed minimum antibacterial activities.

Assessment of Fluoride and pH Levels in a Range of Ready-to-Drink Children’s Beverages Marketed in Malaysia

This study aimed to determine the fluoride and pH levels of beverages likely to be consumed by children in Malaysia and to estimate daily fluoride intake from consumption of these beverages. A convenience sampling of 120 ready-to-drink beverages were purchased and categorised into 11 groups (UHT recombined milk, fresh milk [pasteurised], cultured milk [probiotic], yogurt beverages, fresh fruit juices, fruit flavoured beverages, soy-based beverages, malt-based beverages, tea, carbonated beverages and bottled waters). Fluoride concentration was measured using a fluoride ion-selective electrode while the pH level was measured using a pH meter. The fluoride concentration in the beverages ranged from 0.02±0.00 mg/L to 2.77±0.06 mg/L. Tea was found to have the highest fluoride concentration. The intake of fluoride from consumption of other types of beverages is below the lowest-observed-adverseeffect level (except tea). The pH of the beverages included in the study ranged from 2.20±0.01 to 7.76±0.00. Carbonated beverages (mean pH: 2.98±0.50) were found to be extremely acidic followed by fresh fruit juices (mean pH: 3.38±0.34) and fruit flavoured beverages (mean pH: 3.90±0.92). The correlation between fluoride and pH levels was weak, τ = 0.058 and not statistically significant (p

The Potentiometric determination of fluoride in various brands of toothpaste

The potentiometric analysis of the fluoride content (as F-ion) in toothpaste suspension with an ion-selective fluoride electrode is simple, reliable and inexpensive. Very low fluoride ion concentrations (up to 10–5 mol / l) can be determined with a fluoride-selective electrode, whereby the ionic strength of a solution is regulated and the concentration of hydroxide ions and interfering metal ions is controlled. The influence of the pH value and the complex ions of metals can be successfully regulated by the Total ionic strength adjustment buffer (TISAB) solution and by maintaining the pH value in the range from 5.00 to 8.00. The fluoride concentrations of 34 different toothpaste samples of different brands are determined using an ion-selective electrode. The highest value is 1285.85 ppm from Germany (Blend a. Med) and the lowest value is 18.15 ppm from Indonesia (Formula junior). Most of the low values are from Asian countries between (18.15-514.84) ppm, which are less than 600 ppm and this concentration is insufficient for Iraqi prescriptions and World Health Organization (WHO) specifications, the highest Values are between (940.66-1285.85) ppm, from Japan, USA and Germany References Abramowitz, A. (1967) ‘Principles, current practice, and applications of potentiometers based on Poggendorff’s second method’, Review of Scientific Instruments, 38(7), pp. 898–904. doi: 10.1063/1.1720918. Barmes, D. E. (1996) ‘Fluorides and oral health’, Community Dental Health, pp. 3–4. Bereczki, R. et al. (2006) ‘How to assess the limits of ion-selective electrodes: Method for the determination of the ultimate span, response range, and selectivity coefficients of neutral carrier-based cation selective electrodes’, Analytical Chemistry, 78(3), pp. 942–950. doi: 10.1021/ac050614s. Bralić, M. et al. (2001) ‘Fluoride electrode with LaF3-membrane and simple disjoining solid-state internal contact’, Talanta, 55(3), pp. 581–586. doi: 10.1016/S0039-9140(01)00448-9. Chakraborty, M., Pandey, M. and Pandey, P. (2017) ‘Spectrophotometric method vs ion selective electrode for field determination of fluoride in water and complex samples’, Reserch Journal of Chemical Sciences, 7(5)(5), pp. 31–37. Available at: http://www.isca.in/rjcs/Archives/v7/i5/5.ISCA-RJCS-2017-022.pdf. Gao, W., Xie, X. and Bakker, E. (2020) ‘Direct Potentiometric Sensing of Anion Concentration (Not Activity)’, ACS Sensors, 5(2), pp. 313–318. doi: 10.1021/acssensors.9b02523. J, U. (2019) ‘a Review on Effect of Fluoride Concentration in Drinking Water.’, International Journal of Advanced Research, 7(3), pp. 475–478. doi: 10.21474/ijar01/8659. Jasielec, J. (no date) Modelling of potentiometric ion sensors. Julie, L. (1967) ‘A Universal Potentiometer’, IEEE Trans Instr. Meas., IM(3), pp. 187–191. Lennon, M. A. et al. (2004) ‘Rolling Revision of the WHO Guidelines for Drinking-Water Quality’, World Health Organization, (September), pp. 105–116. Available at: http://www.who.int/water_sanitation_health/dwq/chemicals/en/nitratesfull.pdf. Light, T. S. and Cappuccino, C. C. (1975) ‘Determination of fluoride in toothpaste using an lon-selective electrode.’, Journal of chemical education, 52(4), pp. 247–250. doi: 10.1021/ed052p247. Michalski, R. and Mathews, B. (2006) ‘Simultaneous determination of fluoride and monofluorophosphate in toothpastes by supressed ion chromatography’, Central European Journal of Chemistry, 4(4), pp. 798–807. doi: 10.2478/s11532-006-0042-0. Midgley, D. (1987) ‘Limits of detection of ion-selective electrodes: Theory and practice’, Transactions of the Institute of Measurement &amp; Control, 9(1), pp. 25–36. doi: 10.1177/014233128700900105. Radić, J. et al. (2020) ‘Development of the New Fluoride Ion-Selective Electrode Modified with FexOy Nanoparticles’, Molecules (Basel, Switzerland), 25(21). doi: 10.3390/molecules25215213. Seguí Femenias, Y. et al. (2016) ‘Ag/AgCl ion-selective electrodes in neutral and alkaline environments containing interfering ions’, Materials and Structures/Materiaux et Constructions, pp. 2637–2651. doi: 10.1617/s11527-015-0673-8. TOKALIOGLU, Š., KARTAL, S. and SAHIN, U. (2004) ‘Determination of Fluoride in Various Samples and’, Turk J Chem, 28(2), pp. 203–211. Tzimou-Tsitouridou, R., Kabasakalis, B. and Alexiades, C. A. (1985) ‘A new TISAB with Aluminon for fluoride determination in water with ion-selective electrode’, Microchemical Journal, 32(3), pp. 373–382. doi: 10.1016/0026-265X(85)90104-3. Yildiz, Y. et al. (2018) ‘Analytical Chemistry : An Indian Journal Potentiometric Determination of % Fluoride Ion Content ( w / v ) in Toothpastes by Ion Selective Electrode’, 18(August), pp. 0–8. Zohoori, F. V. et al. (2015) ‘Effect of exercise on fluoride metabolism in adult humans: A pilot study’, Scientific Reports, 5, pp. 1–9. doi: 10.1038/srep16905.

An In Vitro Evaluation of the Mechanical Properties and Fluoride-releasing Ability of a New Self-cure Filling Material

The aim of this study was to examine and compare the flexural strength, shear bond strength, and fluoride-releasing ability of glass ionomer cement (GIC), Fuji IX GIC®, and a new alkasite filling material, Cention N®. The materials were divided into two groups, Fuji IX GIC® (n = 30) and Cention N® (n = 30) and further divided (n = 10) to test three parameters, the fluoride releasing ability, flexural strength, and shear bond strength. Fluoride release was checked using fluoride ion-selective electrode, and flexural strength and shear bond strength were tested using universal testing machine (Intron 3366, UK). Fluoride release of Fuji IX GIC® was significantly higher compared to that of control Cention N® over a period of 21 days. Flexural strength of Cention N® was significantly higher compared to Fuji IX GIC® and there were no significant differences in shear bond strength of both the materials. From the results of the study, it can be concluded that Cention N® is an alkasite filling material for the complete and permanent replacement of tooth structure in posterior teeth and can be a good alternative when compared to GICs on the basis of their superior mechanical properties. Cention N® is an innovative filling material for the complete and permanent replacement of tooth structure in posterior teeth and can be a good alternative when compared to GICs on the basis of their superior mechanical properties.

The effect of layered double hydroxide on fluoride release and recharge from a commercial and an experimental resin varnish

ObjectivesLayered Double Hydroxide (LDH) is capable of fluoride anion exchange and release. This study investigated the effects of incorporating ZnAl-LDH in commercial and experimental dental varnishes, on fluoride release and re-release after charging in NaF. MethodsFive discs of each material (commercial ClinproXT varnish and experimental light cured resin varnish), with and without 9%ZnAl-LDH were immersed and agitated in deionised water (DW) at 37 °C. A fluoride ion selective electrode measured fluoride release in DW daily over two-weeks. At 3, 6, 9 and 12 days the discs were recharged in 15 ml 0.05 M NaF solution (37 °C) for five minutes followed by immersion in DW. Energy dispersive X-ray spectra (EDS), weight changes and SEMs were performed on discs, before and after each cycle. ResultsEvidence of ZnAl-LDH was confirmed by the presence of peaks for zinc and aluminium in EDS spectra. Cumulative fluoride and mean fluoride released between Clinpro, Clinpro + LDH and resin were significantly different (ANOVA, Tukey’s HSD post-hoc test, p < 0.001) except between the resin and resin + LDH. Mean fluoride concentrations differed significantly after every recharge between Clinpro, Clinpro + LDH and resin, but not between the resin and resin + LDH (p < 0.01). The weights and SEMs of the experimental resins +/-LDH, appeared to be stable whilst the weights of Clinpro samples +/−LDH, fluctuated and fragmented. SignificanceClinproXT and experimental resin containing ZnAl-LDH recharged with fluoride did not significantly increase fluoride release compared to the unmodified materials. However, all LDH-F incorporated materials demonstrated fluoride recharging properties which appear beneficial to dentistry and thus further work is required to improve these properties.

Fluoride Ion-Selective Electrode for Organic Solutions.

Fluoride ions are used in battery electrolytes in fluoride shuttle batteries. Since organic solvents are used in battery electrolytes, there is a growing demand to develop appropriate methods for quantifying fluoride ion concentration in organic solvents. In this study, a fluoride ion-selective electrode (ISE) for organic solutions is proposed as an electrode of the second kind. A Ag|AgF electrode was made via the anodization of a silver wire in propylene carbonate (PC) containing dissolved fluoride ions. The resultant electrode exhibits a stable linear response of the open circuit potential to the logarithm of the fluoride ion concentration in PC solutions over a range of 10-4-10-2 mol dm-3. The lower and upper limits of the linear response were interpreted in terms of the solubility and the formation of a silver fluoride complex. The use of this electrode of the second kind is suitable for the analysis of fluoride ions in organic solutions and is a promising concept for the development of ISEs for the detection of ions in organic solutions under highly restrictive conditions.

A Hydroxypropyl Methylcellulose Film Loaded with AFCP Nanoparticles for Inhibiting Formation of Enamel White Spot Lesions.

ObjectiveThis study investigated the effects of mineralizing film consisting of hydroxypropyl methylcellulose (HPMC) and amorphous fluorinated calcium phosphate (AFCP) nanoparticles on enamel white spot lesions (WSLs).Material and MethodsThe AFCP nanoparticles and mineralizing film were prepared via nanoprecipitation and solvent evaporation, respectively. They were characterized with Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), inductively coupled plasma atomic emission spectrometry (ICP-AES), and fluoride ion selective electrode. Thirty-two human enamel slices (4 mm × 4 mm × 1.5 mm) were highly polished and randomly assigned to four groups: negative control (no treatment); pure HPMC film; mineralizing film; GC Tooth Mousse Plus® (contains 10% CPP-ACP and 0.2% NaF). Subsequently, samples were challenged by a modified pH-cycling and characterized by color measurement, Micro-CT, SEM/EDX, and nanoindentation.ResultsThe mineralizing film could sustain release of Ca, P and F ions over 24 h and maintain AFCP nanoparticles in metastable state over 8~12 h. During 4 weeks of pH cycling, the mineralizing film group exhibited least color change (∆E), mineral loss and lesion depth (120 ± 10 µm) among four groups (p < 0.05). SEM findings revealed that the porosities among enamel crystals increased in negative control and pure HPMC film groups after pH cycling, whereas in mineralizing film group, the original microstructure of enamel was well conserved and mineral deposits were detected between enamel prisms. Mineralizing film group demonstrated a least reduction of nanomechanical properties such as elastic modulus of 77.02 ± 6.84 GPa and hardness of 3.62 ± 0.57 GPa (p < 0.05).ConclusionThe mineralizing film might be a promising strategy for prevention and management of WSLs via inhibiting enamel demineralization and promoting enamel remineralization.

Green MIP-202(Zr) Catalyst: Degradation and Thermally Robust Biomimetic Sensing of Nerve Agents.

Rapid and robust sensing of nerve agent (NA) threats is necessary for real-time field detection to facilitate timely countermeasures. Unlike conventional phosphotriesterases employed for biocatalytic NA detection, this work describes the use of a new, green, thermally stable, and biocompatible zirconium metal-organic framework (Zr-MOF) catalyst, MIP-202(Zr). The biomimetic Zr-MOF-based catalytic NA recognition layer was coupled with a solid-contact fluoride ion-selective electrode (F-ISE) transducer, for potentiometric detection of diisopropylfluorophosphate (DFP), a F-containing G-type NA simulant. Catalytic DFP degradation by MIP-202(Zr) was evaluated and compared to the established UiO-66-NH2 catalyst. The efficient catalytic DFP degradation with MIP-202(Zr) at near-neutral pH was validated by 31P NMR and FT-IR spectroscopy and potentiometric F-ISE and pH-ISE measurements. Activation of MIP-202(Zr) using Soxhlet extraction improved the DFP conversion rate and afforded a 2.64-fold improvement in total percent conversion over UiO-66-NH2. The exceptional thermal and storage stability of the MIP-202/F-ISE sensor paves the way toward remote/wearable field detection of G-type NAs in real-world environments. Overall, the green, sustainable, highly scalable, and biocompatible nature of MIP-202(Zr) suggests the unexploited scope of such MOF catalysts for on-body sensing applications toward rapid on-site detection and detoxification of NA threats.

Capacitive Deionization with Titania and Amine Modified Activated Biochar

Capacitive deionization based on electrosorption has become a viable process for brackish water desalination. In this study, activated biochar was employed as a low-cost carbon-based electrode material with comparable adsorption capacity to activated carbon and other biomass derived materials. Modification of the activated biochar was done by amine functional group grafting and metal oxide incorporation to improve ionic transport, and cation/anion selectivity, reducing the co-ion effect. Cation and anion selective electrodes were prepared by using titanium dioxide, and 3-aminopropyltriethoxysilane (3-APTES) via diazonium salt activation. These modified biochar electrodes were physically characterized by SEM-EDX, TEM, XPS, and XRD. Cyclic voltammetry, galvanostatic charge/discharge measurements, and impedance spectroscopy were performed to analyze the electrochemical property of both types of electrodes. This study investigated salt removal capacity of NaCl and NaF solutions using chloride and fluoride ion-selective electrode. Three different asymmetrical CDI cell designs (TB cathode – AmB anode, TB cathode – AcB anode, and AcB cathode – AmB anode) and two symmetrical cell designs AcB anode – AcB cathode and TB anode – TB cathode) were tested. Titania, amine, and activated biochar electrodes are denoted as TB, AmB, and AcB, respectively. It was found that a symmetric cell design with titania modified biochar electrodes show a 30% better removal capacity than the other cell designs. This work shows that biochar can be modified and explored broadly as an inexpensive alternative electrode material for capacitive deionization.

Geochemical characterization and assessment of fluoride sources in groundwater of Siloam area, Limpopo Province, South Africa

Siloam’s groundwater is reportedly characterized by high fluoride. In response to the reported high incidence of dental fluorosis in the area, sources of elevated fluoride in the groundwater were investigated. Total fluoride (TF) was determined using Ion Chromatograph and Fluoride Ion Selective Electrode. The mineral composition of rocks and soils were determined using X-ray Fluorescence and X-ray diffraction, respectively. Results revealed that groundwater fluoride concentration ranged from 3.92 to 4.95 mg/L. Na-Cl water type was found to be dominant in the water samples. TF content of the rocks and soils ranged from 10 to 2000 mg/L. Leachates were obtained by making a slurry from the samples at a predetermined temperature and time. TF in leachates ranged between 0.27 and 14.88 mg/L and 0.05 to 10.40 mg/L at induced, and non-induced temperatures, respectively. The possible source of fluoride has been previously inferred to be caused by fluorite minerals occurring at greater depth. However, this study proves that fluoride decreases with depth and the elevated fluoride in the groundwater is caused by smectite-kaolinite clay, muscovite and chlorite minerals abundant in the area. Geothermal temperature exhibited by the groundwater in the area is a major factor enhancing the release of fluoride from the clay materials.

Comparative assessment of antibacterial activity and fluoride release potential of Cention-N and different bioactive restorative materials: An in vitro study

Aim: This study was directed to assess the antibacterial activity and fluoride release potential of Alkasite material (Cention N) in comparison to two different bioactive materials (Activa BioACTIVE restorative and Zirconomer) at various time intervals Materials and methods: Total 75 disc-shaped specimens of three different restorative materials (Zirconomer, Activa BioACTIVE, and Cention N) were made. 45 specimens for fluoride release (n =15) and 30 specimens for antibacterial activity (n=10). For Antibacterial activity specimens divided into 3 groups (n=10) Group1: Zirconomer, Group2: Cention N and Group 3: Activea bioactive. For fluoride release the specimens divided into 3 groups (n =15) Group1: Zirconomer, Group2: Cention N and Group 3: Activea bioactive. Each fluoride release group was further subdivided into three equal subgroups (n=5) according to the storage time (one day, 7days and 14days). Antibacterial Activity and diameters of inhibition zone were recorded after 48 hours also Fluoride release was evaluated at the end of Day 1, 7and Day 14, using fluoride ion-selective electrode. Data analysis was performed using ANOVA and post-hoctest. Results: Zirconomer group revealed significantly the highest mean fluoride release value than in Cention N and Activea bioactive. Also, Cention N significantly higher fluoride release than Activa BioACTIVE. Cention N group showed statistically significant largest zone of inhibition against Streptococcus mutans at 48 hours followed by Zirconomer group, the smallest zone of inhibition observed with Activa bioactive group. Conclusion: Cention N and Zirconomer had better antibacterial activity and fluoride release while Activea bioactive had limited antibacterial activity and fluoride release.

Dietary Fluoride Intake by Children: When to Use a Fluoride Toothpaste?

Fluoride is recommended for its cariostatic effect, but excessive fluoride intake may have health risks. Increased prevalence of dental fluorosis in areas with low fluoride content in drinking water has been attributed to the inappropriate excessive intake of fluoride supplements (tablets and drops) and toothpaste ingestion. The aim of the present study was to estimate the fluoride intake and the risk of fluorosis in children (6 months–6 years) in the Castelli Romani area (province of Rome, Italy), which is volcanic, therefore with a higher concentration of fluorine. Measurements of the fluoride content in drinking water, mineral waters, vegetables and commercial toothpaste for children were performed. The fluoride concentrations of all samples were determined using a Fluoride Ion Selective Electrode (GLP 22, Crison, Esp). Data were analyzed by descriptive statistics. Differences between samples were determined by Student’s t-test. The fluoride content in tap water samples collected from public sources averaged from 0.35 to 1.11 ppm. The Pavona area showed the highest content of fluoride with respect to the others (p ≤ 0.05). The fluoride content in mineral water samples averaged from 0.07 to 1.50 ppm. The fluoride content of some vegetables showed increased mean values when compared to control vegetables (p ≤ 0.05). Within the limitations of the present study, considerations should be made when prescribing fluoride toothpaste for infants (6 months–4 years) in the areas with high fluoride content, because involuntary ingestion is consistent.

Determination of chemical species of fluoride during uptake mechanism of glass-ionomer cements with NMR spectroscopy

ObjectiveThe aim of the present study was to determine the chemical species formed inside glass-ionomer cements after fluoride uptake and to investigate the depth of penetration of fluoride ions within the cement matrix. MethodsAn experimental fluoride-free glass with composition 2SiO2–AlO3–CaO was produced. The glass powder was mixed with aqueous poly(acrylic acid) (PAA), and allowed to set. The resulting specimens were stored in 20ml KF solution with 1000ppm fluorine for 24h and then placed into the same amount of water as for 24h. A fluoride selective electrode was used to give the F concentration of the respective solutions. 19F MAS-NMR spectra were recorded on powdered cement specimens using a Bruker AVANCE-NEO 600 spectrometer. In addition, SEM observation and EDX chemical analysis were conducted on the cross-section of a carefully fractured specimen. ResultsFluoride was shown to be mainly present in the surface layers of the specimen after placement in the KF solution, and only a small fraction was re-released into water. 19F NMR spectroscopy showed that AlF complexes were formed within the cement. SignificanceThe fluoride taken up by a free-fluoride glass ionomer cement mostly occupies surface layers and is retained because it bonds to aluminum within the matrix. This finding explains why the majority of fluoride taken up by conventional glass ionomer cements is retained.

No Association was Detected between Polymorphism of COL1A2 Genes and Occurrence of Dental Fluorosis Among the Subjects Living in a Fluorosis-Endemic Area of India

Objective: To determine any genetic association of COL1A2 polymorphism and the occurrence of dental fluorosis within an Indian human dental fluorosis population. Material and Methods: Fifty-six (56) subjects from two groups i.e. cases with dental fluorosis from the Pavagada population (n=29) and a control group (n=27) without fluorosis, were explored. The ages ranged between 15 and 76 years (mean 50.8 years) were included, and the male to female ratio was 70:30. The severity of dental fluorosis was graded using WHO’s Thylstrup-Fejerskov index (TF), and the concentration of fluoride was determined by a fluoride ion selective electrode (ISE). Genomic DNA was extracted using the standard phenol-chloroform method. The rs412777 and rs414408 polymorphism in COL1A2 were genotyped using the Sanger sequence method. Results: Genotype distributions for rs412777 within each group were: AA 41%, AC 51%, and CC 7% for dental fluorosis participants, and AA 56%, AC 46%, and CC 0% for the control participants. Conclusions: The rs412777 and rs414408 polymorphisms in the COL1A2gene showed no significant association between COL1A2 and the occurrence of dental fluorosis amongst this Indian population.

Comparison of the Fluoride Release of Silver Diamine Fluoride, Fluoride Varnish, Acidulated Phosphate Fluoride Gel on Extracted Teeth over Various Time Intervals in Artificial Saliva

Silver Diamine Fluoride (SDF) has been documented to effectively arrest dental caries and reduce dental hypersensitivity. SDF promotes remineralization and harden the carious lesion. SDF increases fluoride concentration in saliva and increase the bioavailability of fluoride in saliva. After SDF application, fluoride ion promotes remineralization and silver ion is available for antimicrobial action.&#x0D; Aim: The study aims to determine and compare the amount of fluoride released from various fluoride releasing materials in artificial saliva after 24 hours, 7th day and 14th day of the study.&#x0D; Materials and Methods: 96 premolars free of any caries, fractures, or any other defects were sterilized in 10% formalin for 2 weeks. Then they were rinsed in tap water to remove any fixative from its surface and then stored in deionised distilled water for a period of 30 days prior to testing. Tooth samples were divided into four groups- Group 1: 38% SDF, Group 2: 1.23% APF gel, Group 3: Fluoride varnish and Group 4: Control. All the teeth specimens were blot dried and subjected to their respective material. Fluoride release was analysed using a Fluoride ion-selective electrode after 24 hours, 7days and 14 days of suspension in artificial saliva.&#x0D; Results: Mann-Whitney U Test for inter-group comparison was used for statistical evaluation. 24 Hours fluoride release: The maximum amount of fluoride was released from Fluoride Varnish followed by SDF then APF Gel and least by artificial saliva alone (control) (p&lt;0.001). 7th Day fluoride release: The maximum amount of fluoride was released from SDF followed by Fluoride Varnish then APF Gel and least by artificial saliva alone (control) (p&lt;0.001). 14th Day fluoride release: The maximum amount of fluoride was released from Fluoride Varnish followed by SDF then APF Gel and least by artificial saliva alone (control) (p&lt;0.001).