Fluoride Absorption Research Articles

Comparative Evaluation of Ion Release and Uptake of Fluoride Varnish Containing Dicalcium Phosphate Dihydrate and Casein Phosphopeptide-Amorphous Calcium Phosphate – An Experimental Approach.

The effectiveness of fluoride varnish may be restricted due to inadequate bioavailability of phosphate and calcium ions in the oral cavity. Dicalcium phosphate dihydrate and Casein phosphopeptide–amorphous calcium phosphate have exhibited ability to enhance absorption of calcium and fluoride. The present study aims to compare the remineralization potential of fluoride varnishes containing DCPD and CPP-ACP. Materials and Method: The ion release, precipitation and surface microhardness of enamel blocks were compared following topical application of various Floride varnishes. Thirty enamel blocks were divided into 3 groups following randomization that included: NaF varnish (Group A), CPP-ACP NaF varnish (Group B) and DCPD- NaF varnish (Group C). Pre- and post-treatment microhardness was evaluated using Vickers Microhardness Tester. UV-Vis Spectroscopy assessed the fluoride release at 2 hrs, 4 hrs and 6 hrs. The uptake of fluoride, calcium and phosphates were determined using SEM-EDX. The statistical significance was tested with One-way ANOVA variance for normality followed by post-hoc tests (p ≤ 0.05). Results: All the groups showed statistically significant increase in microhardness post-treatment (Group A: p=0.03, Group B, C: p=0.00). The mean increase in VHN was Group B (53.67) > Group C (34.75) > Group A (27.40). No significant difference in the F release was noted over time (p=0.00). The fluoride release over all three time intervals was Group C > Group B > Group C. Fluoride, Calcium and Phosphates showed highly significant differences between groups (p=0.00) with Group C > Group A> Group B. Conclusion: The novel NaF-DCPD Varnish displayed a promising remineralization potential, however it cannot be conclusively considered to be superior to the commercially available NaF-CPP ACP Varnish. Further in-vivo investigations need to be undertaken to determine the efficacy of NaF-DCPD varnish to determine its feasibility in clinical practice.

Kinetics of fluoride after brushing with the no-rinse method

BackgroundFluoride plays a vital role in preventing dental caries, with its addition to oral care products significantly promoting oral hygiene. A no-rinse brushing method aims to increase fluoride retention in the oral cavity, as rinsing with water decreases fluoride levels in saliva, which could affect remineralization. While the no-rinse brushing method holds promise for improving fluoride retention in the oral cavity, critical inquiries persist regarding its safety. This study investigated the kinetics of oral fluoride and potential risks to fully assess its effectiveness and implications for oral health.MethodsTen healthy adults participated in a crossover study comparing the no-rinse with the rinse method. All subjects followed American Dental Association (ADA) brushing guidelines. Levels of fluoride in saliva (supernatant and sediment) and urine were measured over time, and plasma fluoride was measured one hour after brushing. Pharmacokinetic parameters were also calculated from the data.ResultsParticipants using the no-rinse method had higher fluoride levels in supernatant immediately and up to 30 min post-brushing compared to the rinse method. Fluoride levels in sediment were higher only immediately after brushing. The total fluoride concentration in saliva remained elevated for up to 5 min with the no-rinse method. Systemic fluoride absorption showed no significant difference between the two methods based on blood and urine analysis.ConclusionThis research indicates that the no-rinse method can enhance fluoride retention in the oral cavity for up to 30 min after a single brushing. In addition, our findings suggest that this method does not significantly influence systemic fluoride levels or toxicity.RegistryThai Clinical Trials Registry, TCTR (http://thaiclinicaltrials.org). Clinical trial registration number: TCTR20231104001 (4/11/2023).

Effects of topical fluoride on primary tooth enamel microhardness after diode laser treatment

ObjectivesTooth decay is controlled and prevented using fluorides. Specifically, a combination of laser irradiation and topical fluoride application can improve fluoride absorption. Although laser irradiation is recommended in traditional technology for caries prevention, little is known about the efficacy of caries-inhibiting laser diodes. Further, most studies have focused on permanent teeth. The objective of this study was to explore the effect of laser diode radiation mixed with topical fluoride on the enamel surface microhardness of primary teeth. Material and methodThe 60 primary teeth were divided into 60 plates. Baseline Vickers microhardness was established for each enamel surface. The samples were then divided into three groups. 4 % NaF varnish (group A) and 4 % NaF varnish using diode 2 and 3 W lasers (groups B and C, respectively). The final microhardness was measured and statistically evaluated using SPSS version 16. ANOVA was used to compare the means of the tested groups, which had a P-value of 0.05, indicating significance. ResultThe mean and standard deviation of microhardness for the different groups was tested. Group C (4 % NaF with a diode laser at 3 W) showed a higher average Vickers hardness (VHN) than Group B (4 % NaF with a diode laser at 2 W), whereas group A showed the lowest average VHN. There was a significant difference in microhardness between groups (P 0.05). ConclusionThis study explored the effect of laser mixed with topical fluoride on enamel surface microhardness of primary teeth. The use of a diode laser (Quanta System, Italy) with a fluoride varnish applied to the enamel surface has a greater effect on the resistance of the enamel to caries.

Fluoride removal from aqueous solution using Ce-modified red mud as adsorbent

Fluorine pollution has become an urgent global public health concern due to its adverse effects on aquatic organisms and human life, which raises the imperative demand for the development of economical and efficient fluoride adsorbents. In this study, we demonstrate that solid waste of red mud (RM) originating from the aluminum industry can be converted into fluoride adsorbents by the integration of cerium-based compounds. Besides the adsorption kinetics and isotherm, the effects of adsorbent dosage, contact time, pH of solution, initial concentration, temperature, and competitive ions on the defluoridation performance of the absorbents have been systematically investigated. Benefiting from the strong affinity between cerium species and F-ions as well as the structure advantage, the optimized RM-derived fluoride absorbents show a maximal adsorption capacity above 14.74 mg/g at 298 K at pH = 7. More importantly, our RM-derived fluoride absorbents can be applied towaste water with heavy fluorine pollution (up to 60 mg/L), multiple interference ions (NO3−, SO42−, and Cl−), and a wide pH range (2–8), which outperforms most RM-based defluorination materials ever reported. The present work gives a full understanding of fluoride absorption behavior and mechanism and also offers potential practical applications of the RM-derived functional materials for wastewater treatment.

Fluoride contamination in ground-drinking water and urine from rural population of Uttar Pradesh, India

This study was carried out to assess the fluoride concentration in ground-drinking water, vegetable juice and urine samples of the five villages in Lakhimpur (Kheri) of Uttar Pradesh, India. The experimental site retains a few agro-based industries like sugarcane processing units due to it enriched cultivation by the local farmers. Hence, the availability of fluoride in ground-drinking water is natural, and its excess intake through drinking water over a period caused irreversible serious illness affecting the nervous system and osteo-dental fluorosis. The fluoride level in ground-drinking water found from 0.5 to 4.3 mg L−1 with average of 3.42 mg L−1. Total number of residents involved in the study for analyzing their urine samples were 548 (277 males and 271 females). The absorption of fluoride was high among the youngsters (13–44 yrs). The positive correlation observed between fluoride content in ground drinking water intake and urine.

Enhanced fluoride removal from groundwater using red and white kaolinite lithomarge to develop a low cost eco-friendly defluoridation unit in rural areas of Shilabati river basin, West Bengal

Fluoride is an anionic pollutant found in high concentrations (>2 mg/l) in the Shilabati river basin of West Bengal, India, which has reported numerous serious cases of skeletal fluorosis and bone deformation in recent years. This study investigated fluoride adsorption on kaolinite lithomarge (red and white laterite) from Paschim Medinapore (West Bengal, India), exploring both kinetic and equilibrium facets with a series of batch tests and a fixed bed column study using natural water. Based on the X-ray Powder Diffraction analysis, Alpha SiO2 with trigonal structure and Alpha Al2O3 with hexagonal structure of this natural adsorbent played a critical role in fluoride absorption mechanism. Experimental results showed that based on pH values relevant to the fluoride enriched groundwater, kaolinite lithomarge of red type was the most efficient having an effective removal efficiency (98.32 %) at pH 6.58 whereas the white type demonstrated the highest removal efficacy of 95.31 % at pH 6.51. The modelled breakthrough curves were obtained, and they were in good accordance with the corresponding experimental data. Finally, water samples were collected from 11 sites from the fluoride contaminated zone within the river basin and natural groundwater was filtered using kaolinite lithomarge of red type obtaining a removal capacity of 97.13 % within 30 min, for the initial concentration of 2.37 mg/l. The prototype tested in the laboratory showed promising contaminant removal as a low-cost, time saving, natural filtration option supplying a liter of fluoride free water for 0.0015 USD.

Analysis and Visualization of the Fluoride Hazard Quotient in the Groundwater of Rural Areas in Northwestern Region of Ajmer District, Rajasthan, India

Abstract: Groundwater contamination by fluoride is a major concern in many regions of India. Fluoride in excess is one of the most harmful pollutants to human health. Water contains about 80% of the total fluoride acquired in the human body (mg/kg/day). The health risks connected with fluoride-rich ground water must be evaluated. Ajmer district (25°38'-26°58' N: 73°54'-75°22' E) covers an area of 8481 km2. The district's principal geomorphic characteristics include alluvial plains, linear ridges, pediment, denudation hill, buried pediment, and structural valleys. During this study, 15 villages in the northwestern district of Ajmer were sampled. The fluoride exposure dose, which is an individual's chronic daily absorption of fluoride by eating, was determined for infants, children, and adults; a hazard quotient greater than one suggests the possibility of detrimental health effects. The Hazard Quotient for fluoride in the research region was mapped using Inverse Distance Weighting (IDW) interpolation. The HQ analysis showed that all readings above the permissible limit of one, with values ranging from 1.01 for Pushkar to 4.38 for nearby Hokhra. The average fluoride value for the whole research region was 2.73, with a standard deviation of 0.950. Fluorosis appears to be caused mostly by fluoride-rich waterways in the region. Decomposition, dissociation, and dissolution are the primary chemical events responsible for fluoride mobility and transit into groundwater. Low-cost fluoride control strategies include mixing, artificial recharge, effective irrigation systems, and well construction.

Estimation of fluoride ion concentration in urine after application of silver diamine fluoride in patients with severe early childhood caries.

Despite the University of California San Francisco, the American Academy of Pediatric Dentistry (AAPD), and the Food and Drug Administration having approved the use of silver diamine fluoride (SDF) in arresting dentinal caries, literature available on its systemic absorption is limited. This study aimed to assess any systemic absorption of fluoride ion following the topical application of SDF in young children. Children aged between 3 and 6 years who were diagnosed with severe early childhood caries and required rehabilitation were recruited for the study. Before the onset of treatment for the arrest and control of caries, a baseline urine sample as a control was collected from the patient. In accordance with the manufacturer's instructions and AAPD guidelines, SDF was topically applied on a minimum of five carious teeth, following which additional urine samples were collected after 2 h and after 24 h, respectively, of application of SDF. The urine samples were stored at -20°C, and the estimation of fluoride ion concentrations in urine was then ascertained using a fluoride ion selective electrode. The results revealed that the fluoride concentration in urine before application of SDF was 0.66 mg/L ± 0.25 mg/L, and following 2 h of application, it was 1.13 mg/L ± 0.23. However, 24 h postapplication, the urinary fluoride concentration was reduced to 0.63 mg/L ± 0.20, which is close to the baseline value of the control sample. There was no significant systemic absorption of fluoride following the application of SDF, and it could be adopted as an effective and safe agent in the armamentarium for managing caries in young children.

Acidic Microenvironment-Sensitive Core-Shell Microcubes: The Self-assembled and the Therapeutic Effects for Caries Prevention.

The aim of this study was to develop a new material with integrated interface design that could achieve the purpose of environmental-sensing controlled release against cariogenic bacteria. Furthermore, this material can rebalance oral flora and serve as a preventive and reparative measure of dental caries. NaF@PAA@HA@polyelectrolytes@HA@PAA particles were synthesized using the method of two-solution phases precipitation followed by biocompatible polymers coating layer by layer. The structure of the particles was confirmed by transmission electron microscope. The fluoride release profile was measured by fluoride ion electrode. Antimicrobial activity against the cariogenic microorganisms was analyzed by scanning electron microscopy and energy dispersive spectrum. The efficacy experiments were conducted on tooth enamel slides to evaluated fluoride absorption and antibacterial activity of the prototype toothpaste containing microcube particles RESULTS: The structure of NaF@PAA@HA@polyelectrolytes@HA@PAA particles showed a core surrounded by tooth-adhesion polymer layers in thin fin or filament structure. The loaded concentration of fluoride in the particles' core was 148,996 ± 28,484 ppm. NaF@PAA@HA@polyelectrolytes@HA@PAA particles showed selective inhibition of cariogenic microorganisms over probiotic strains and stronger fluoride adhesion on tooth enamel. A burst release (over 80%) of fluoride from the particle-containing toothpaste was observed under cariogenic acidic environment (pH < 5), while it remained extremely low under neutral environment. Compared with the best results of commercial toothpastes, our prototype toothpaste increased enamel fluoride uptake by 8-fold in normal enamel slides and by 11-fold in the slides with induced white spot lesions after either 1- or 7-day treatment. The prototype toothpaste also showed better inhibition of cariogenic microorganisms than the commercial brands. The coverage area of cariogenic bacteria under our toothpaste treatment was 73% on normal enamel slides compared with the commercial brands, while it was 69% in the induced white spot lesions. In our study, an intelligent toothpaste was developed that selectively inhibits cariogenic bacteria by microenvironment proton-triggered fluoride release. Such novel design would accomplish a favorable flora balance for optimal long-term oral health.

Calcium bioavailability in leafy vegetables and medicinal plants

Large quantities of fluoride intake are the primary reason for the prevalence of dental and skeletal fluorosis. Absorption of fluoride is 100% when it is administered through drinking water without food. But the fluoride absorption reduced from 50% to 80% when it is administered along with diet. Mostly diets with high calcium with rich in bioavailability reduce the fluoride absorption from the gastrointestinal tract by forming calcium fluoride insoluble complex. Apart from drinking water, milk and milk products; commonly available leafy vegetables and medicinal plants are the good sources for dietary calcium. Hence this study is proposed to account the total and bioavailable calcium level in various leafy vegetables and medicinal plants. For this purpose, eighteen leafy vegetables and five medicinal plants are collected and analyzed for total and bio-available calcium levels. Total and bio-available calcium levels are determined through wet digestion and in-vitro miller method respectively by the use of atomic absorption spectrophotometer. Among the selected leafy vegetables dwarf-copper, block-nightshade, curry, cabbage, drumstick and mint leaves contain high total calcium with rich in bioavailability.

Fluoride Metabolism in Pregnant Women: A Narrative Review of the Literature.

Epidemiological studies use biomarkers of fluoride exposure in pregnant women as surrogate measures of fetal fluoride exposure; however, there is little understanding of how pregnancy affects fluoride metabolism and its biomarkers. This narrative review summarizes the changes of pregnancy that have the potential to impact fluoride’s absorption, distribution and excretion, and highlights the limited body of evidence on the topic. The physiologic systems that experience pregnancy-associated changes relevant to fluoride’s metabolism are the cardiovascular, renal, metabolic and gastrointestinal, as well bone and calcium metabolism and the body’s acid-base balance. The available evidence indicates that fluoride is found in the maternal plasma and urine, placenta, amniotic fluid and fetus. Although plasma and urinary fluoride vary across gestation, there is insufficient quality evidence to determine the direction or extent of such variation. Furthermore, there is no doubt that fluoride from maternal blood crosses the placenta and is absorbed and excreted by the fetus; however, the biological mechanisms behind this placental passage are unknown. Research on maternal and prenatal biomarkers of fluoride exposure would benefit from studies on how pregnancy-associated changes affect the metabolism of fluoride across gestation, the mechanisms for the intestinal absorption of fluoride in pregnant women, and the placental passage of fluoride.

Recent Innovations of Organo-fluorine Synthesis and Pharmacokinetics

The fluorinated compounds have significance in medicinal chemistry and pharmaceutical research. The introduction of fluorine atom in the heterocyclic compounds increases biological activity by favourable physiochemical interactions. The combination of heterocycles with fluorine substituents has a wide range of applications in the study of various pharmacological research. The compounds not only exhibit biological activity but have also shown unique physical and chemical characteristics features that open the new avenues for multidisciplinary research. Fluorine atom tolerance to maximal functional groups, simplicity in operation, replacing hydrogen with fluorine of bioactive molecules are more efficient for the synthesis of fluorinated compounds at the commercial level. The fluorine substitution also increases the binding affinity to the targeted protein. Furthermore, the incorporation of fluorine on the drug molecules helps in enhancing the polarity, increasing the rate of drug metabolism and improving metabolic stability. The pharmacokinetic study plays an important role in clinical research. In 1996, researcher Whitford found that the pharmacokinetics of fluorine is affected by pH and quantity in the bone study. The pH of organofluoride influences fluoride absorption, distribution, and excretion. It also increases the stability when bound to carbon atom, resulting in increased bioactivity. This is the primary reason that fluoride is a key component of around 25% of currently available active drugs for various diseases, including cancer, diabetes, HIV etc. Not only the pharmacokinetic properties but also the physical properties of the drug can be enhanced or altered by selective insertion at the key place of the fluorine atom in the drug candidate. In this report, we have studied and referred to the interesting research articles reported since 2000 for the synthesis of low fluorine substituted organic compounds for medicinal research and pharmacokinetic use, example neurological diseases, cancer, and tuberculosis research.

Cimento de ionômero de vidro e sua aplicabilidade na Odontologia: Uma revisão narrativa com ênfase em suas propriedades

O presente trabalho trata-se de uma revisão narrativa da literatura com o objetivo de discutir acerca das propriedades físicas, mecânicas e biológicas dos cimentos de ionômero de vidro (CIVs). Para reabilitar unidades dentais com cavidades patológias o cirurgião-dentista pode lançar mão de diversos materias, dentre eles podemos destacar os cimentos de ionômero de vidro, sendo esse um dos materiais mais utilizados para reabilitação oral, principalmente na dentição decídua. Sua ampla utilização está associada as excelentes propriedades desse material, como: liberação e absorção de flúor, garantindo redução da progressão e início de lesões cariosas; coeficiente de expansão térmico linear semelhante a estrutura dental, reduzindo draticamente os casos de infiltração marginal; adesividade nos tecidos; biocompatibilidade, para assim não agredir os tecidos biológicos do dente; resistência e estética aceitáveis, quando comparado a outros materiais como óxido de zinco e eugenol . Para realização desse estudo foi realizada uma busca completa nas bases de dados: PubMed, Scielo, Lilacs e Google Scholar, utilizando as palavras-chave “glass ionomer cements, dental materials and dentistry”, inseridas nas buscas de maneira cruzada adotando a expressão boolena "and”. Afim de selecionar os artigos a serem analisados foram elencados critérios de inclusão e exclusão. Para garantir sucesso restaurador e longevidade das restaurações com ionômero o profissional necessita realizar um diagnóstico e técnica correta, para que dessa forma haja um melhor aproveitamento e desempenho das propriedades desse material.

Evaluation and DFT analysis of 3D porous rhombohedral Fe-modified MgO for removing fluoride efficiently

Three-dimensional porous rhombohedral Fe-modified MgO mixed metal oxide (CMF) adsorbent was successfully prepared via a one-step hydrothermal method without the use of a template and surfactant. This material can be used to remove excess fluoride from water. Because of the integration of Fe, it efficiently responds to low concentrations of fluoride in water, and the resulting adsorbent exhibits lamellar peeling and reorganization; it also captures a large amount of fluoride. The adsorption behavior of fluoride on the surface of CMF conforms to the Freundlich isothermal model and to the pseudo-second-order kinetics model. The maximum adsorption capacity of CMF for fluoride was as high as 126.79 mg/g. Electrostatic attraction, ion exchange, and bonding of fluoride and metal were the adsorption mechanism of CMF. DFT analysis showed that Fe-modified MgO with a low doping rate is more beneficial for the adsorption of fluoride, and the adsorption energy is −1.139 eV. F bonds to metal via orbital hybridization. Moreover, cycling experiments indicated that the material has good reusability and can be used for long-term absorption of fluoride. This task may contribute to the task of developing sustainable water resources, which is beneficial to human life and natural environment.

Health risk assessment due to fluoride exposure from groundwater in rural areas of Agra, India: Monte Carlo simulation

The present study deals with the assessment of the fluoride concentration from 60 different spatially distributed well locations and associated health risks to rural residents in the Achhnera block of Agra, Western Uttar Pradesh, India. Monte Carlo simulation and sensitivity analysis were applied to quantify uncertainties in risk estimation. Assessment of the human health risk was carried out using computations based on fluoride ingestion (EDIing), dermal absorption of fluoride (EDIder) and hazard quotient (HQ) in all three categorized groups, i.e., infants, children, and adults. Fluoride concentration analyzed was found to be ranging between 0.15 and 2.50 mg/L with an average value of 1.51 mg/L. More than 58% of samples analyzed surpassed the permissible level as per drinking water specifications. From the model obtained for non-carcinogenic risk due to water ingestion, values of IRw range between 55.4% and 62.5% in all the three exposure groups, while that of Cw ranges between 37% and 42.8%. Based on the HQ investigation it was found that infants were at maximum risk followed by children and the least affected were adults. Results showed that based on the sensitivity analysis, a definition of the probability distributions of CW, IRw, EF and SA is presented as the main factor to improve the accuracy of the result.

Comparing groundwater fluoride level with WHO guidelines and classifying at-risk age groups; based on health risk assessment

ABSTRACT The main route of fluoride uptake is drinking water. Fluoride absorption in the acceptable range (0.5–1.5 mg L−1) is suitable for the body, but its too much consumption can have irreversible health effects. To compare fluoride concentration with the WHO guidelines, 112 water samples were taken from groundwater aquifers in 22 villages of Garmsar County, the central part of Iran, during 2018 to 2019. Fluoride concentration was measured by the SPANDS method and its non-carcinogenic impacts were calculated using EDI and HQ. The statistical population was divided into four categories of infant, children, teenagers, and adults. Linear regression and Spearman rank correlation coefficient tests were used to investigate the relationships between the well’s depth and fluoride concentration in the water samples. The annual mean concentrations of fluoride in 2018 and 2019 were 0.75 and 0.64 mg L−1and, the fluoride mean concentration in the samples classifying the cold and hot seasons of the studied years was 0.709 and 0.689 mg L−1, respectively. The amount of fluoride in 27% of the samples in both years was less than the acceptable minimum (0.5 mg L−1). Also, 11% of the samples in 2018 (6 samples) had fluoride levels higher than 1.5 mg L−1. The HQ showed that the children were vulnerable; teenagers and adults were in the next ranks, respectively. Statistical tests showed a reverse and significant correlation (R2 = – 0.02, β < 0.0001) between well depth and fluoride content. The border between the usefulness/harmfulness of fluoride is very narrow and requires extensive studies.

Calcium, magnesium and aluminium ions as decontaminating agents against dermal fluoride absorption following hydrofluoric acid exposure

The fluoride ions of the industrially largely irreplaceable, locally corrosive hydrofluoric acid (HF) can scavenge cations in biological tissues, which explains their high toxic potential, and also leads to local acidification through proton release. The influence of three complexing agents, calcium (Ca2+) gluconate (as 2.5% Ca2+gel and individually (2.84%) or commercially (10%) formulated Ca2+solution), magnesium (Mg2+) gluconate (2.84%) solution and aluminium (Al3+) solution (Hexafluorine®, pure and diluted) on the absorption of fluoride following HF exposure (1–3 min, 100 μl, 30%/0.64 cm2) through human skin was investigated in an ex-vivo diffusion cell model. Fluoride absorption was assessed over 6–24 h and analysed with a fluoride electrode. Decreasing the contamination time reduced the fluoride absorption distinctly which was further reduced by the application of fluoride-binding decontamination agents (Ca2+, Mg2+, Al3+) or water alone without being significantly different. Ca2+ appeared slightly more effective than Mg2+ in reducing fluoride absorption. Moreover, the addition of pH adjusting buffer promoted the decontamination efficacy. Fluoride-binding agents can facilitate the decontamination of dermal HF exposure. However, prompt decontamination appeared to be the key to successful limitation of fluoride absorption and pushes the choice of decontamination agent almost into the background.

Fluoride absorption, transportation and tolerance mechanism in Camellia sinensis, and its bioavailability and health risk assessment: a systematic review.

Tea is the one of the most popular non-alcoholic caffeinated beverages in the world. Tea is produced from the tea plant (Camellia sinensis (L.) O. Kuntze), which is known to accumulate fluoride. This article systematically analyzes the literature concerning fluoride absorption, transportation and fluoride tolerance mechanisms in tea plants. Fluoride bioavailability and exposure levels in tea infusions are also reviewed. The circulation of fluoride within the tea plantation ecosystems is in a positive equilibrium, with greater amounts of fluoride introduced to tea orchards than removed. Water extractable fluoride and magnesium chloride (MgCl2 ) extractable fluoride in plantation soil are the main sources of absorption by tea plant root via active trans-membrane transport and anion channels. Most fluoride is readily transported through the xylem as F- /F-Al complexes to leaf cell walls and vacuole. The findings indicate that tea plants employ cell wall accumulation, vacuole compartmentalization, and F-Al complexes to co-detoxify fluoride and aluminum, a possible tolerance mechanism through which tea tolerates higher levels of fluoride than most plants. Furthermore, dietary and endogenous factors influence fluoride bioavailability and should be considered when exposure levels of fluoride in commercially available dried tea leaves are interpreted. The relevant current challenges and future perspectives are also discussed. © 2020 Society of Chemical Industry.

Novel fluoride rechargeable dental composites containing MgAl and CaAl layered double hydroxide (LDH)

ObjectiveThis study aims to incorporate 2:1 MgAl and 2:1 CaAl layered double hydroxides (LDHs) in experimental dental-composites to render them fluoride rechargeable. The effect of LDH on fluoride absorption and release, and their physico-mechanical properties are investigated. Methods2:1 CaAl and 2:1 MgAl LDH-composite discs prepared with 0, 10 and 30wt% LDH were charged with fluoride (48h) and transferred to deionized water (DW)/artificial saliva (AS). Fluoride release/re-release was measured every 24h (ion-selective electrodes) with DW/AS replaced daily, and samples re-charged (5min) with fluoride every 2 days. Five absorption-release cycles were conducted over 10 days. CaAl and MgAl LDH rod-shaped specimens (dry and hydrated; 0, 10 and 30wt%) were studied for flexural strength and modulus. CaAl and MgAl LDH-composite discs (0, 10, 30 and 45wt% LDH) were prepared to study water uptake (over 7 weeks), water desorption (3 weeks), diffusion coefficients, solubility and cation release (ICP-OES). ResultsCaAl LDH and MgAl LDH-composites significantly increased the amount of fluoride released in both media (P<0.05). In AS, the mean release after every recharge was greater for MgAl LDH-composites compared to CaAl LDH-composites (P<0.05). After every recharge, the fluoride release was greater than the previous release cycle (P<0.05) for all LDH-composites. Physico-mechanical properties of the LDH-composites demonstrated similar values to those reported in literature. The solubility and cation release showed a linear increase with LDH loading. SignificanceLDH-composites repeatedly absorbed/released fluoride and maintained desired physico-mechanical properties. A sustained low-level fluoride release with LDH-composites could lead to a potential breakthrough in preventing early stage carious-lesions.

A study on bioremediation of fluoride-contaminated water via a novel bacterium Acinetobacter sp. (GU566361) isolated from potable water

Fluorosis is an agonizing and crippling disease caused by fluoride intake. In the present study, fluorinated aqueous solution was treated with three novel bacterial strains viz., Bacillus sp. (GU566359), Rheinheimera sp. (GU566360) and Acinetobacter sp. (GU566361) isolated from potable waters of Mahabubnagar, Telangana State, India to screen the competence of potential bacteria for the removal of fluoride. SPADNS colorimetric method was adapted to measure fluoride concentration in broth media. Among the three bacteria studied Acinetobacter sp., showed 57.3% fluoride absorption efficacy after 10 h of incubation. Batch optimization studies revealed that the fluoride removal was optimum at pH 7.5, 35 °C and biosorbent dose of 40 mg/100 mL. Further the physicochemical characterization studies were confirmed that, morphology and functional groups of Acinetobacter sp. is suitable for removal of fluoride and therefore be used as a potential microbial species for endemic fluoride defluoridation applications in water.