Different Concentrations Of Fluoride Research Articles

Regulating effect of miR-132–3p on the changes of MAPK pathway in rat brains and SH-SY5Y cells exposed to excessive fluoride by targeting expression of MAPK1

BackgroundAlthough the changes of mitogen-activated protein kinase (MAPK) pathway in the central nervous system (CNS) induced by excessive fluoride has been confirmed by our previous findings, the underlying mechanism(s) of the action remains unclear. Here, we investigate the possibility that microRNAs (miRNAs) are involved in the aspect. MethodsAs a model of chronic fluorosis, SD rats received different concentrations of fluoride in their drinking water for 3 or 6 months and SH-SY5Y cells were exposed to fluoride. Literature reviews and bioinformatics analyses were used to predict and real-time PCR to measure the expression of 12 miRNAs; an algorithm-based approach was applied to identify multiply potential target-genes and pathways; the dual-luciferase reporter system to detect the association of miR-132–3p with MAPK1; and fluorescence in situ hybridization to detect miR-132–3p localization. The miR-132–3p inhibitor or mimics or MAPK1 silencing RNA were transfected into cultured cells. Expression of protein components of the MAPK pathway was assessed by immunofluorescence or Western blotting. ResultsIn the rat hippocampus exposed with high fluoride, ten miRNAs were down-regulated and two up-regulated. Among these, miR-132–3p expression was down-regulated to the greatest extent and MAPK1 level (selected from the 220 genes predicted) was corelated with the alteration of miR-132–3p. Furthermore, miR-132–3p level was declined, whereas the protein levels MAPK pathway components were increased in the rat brains and SH-SY5Y cells exposed to high fluoride. MiR-132–3p up-regulated MAPK1 by binding directly to its 3′-untranslated region. Obviously, miR-132–3p mimics or MAPK1 silencing RNA attenuated the elevated expressions of the proteins components of the MAPK pathway induced by fluorosis in SH-SY5Y cells, whereas an inhibitor of miR-132–3p just played the opposite effect. ConclusionMiR-132–3p appears to modulate the changes of MAPK signaling pathway in the CNS associated with chronic fluorosis.

Concentration of some macronutrients of tooth enamel in patients living in areas with different concentrations of fluoride in drinking water

BACKGROUND: This article examines the effect of fluoride concentration in drinking water on the concentration of certain macronutrients of tooth enamel in patients living in areas with different levels of fluoride. AIM: To determine the relationship between the concentration of fluoride in drinking water and the content of macronutrients in tooth enamel. MATERIALS AND METHODS: Information was collected on the concentration of fluoride in drinking water in various areas. Then a sample of patients living in these areas was collected and the content of trace elements in the enamel of their teeth was analyzed. RESULTS: The data obtained demonstrate the presence of a significant correlation between the concentration of fluoride in drinking water and the content of certain macronutrients in the enamel of patients’ teeth. A high concentration of fluoride in drinking water was associated with an increased content of certain trace elements, while a low concentration of fluoride was associated with their low levels. CONCLUSIONS: These results highlight the importance of fluoride content in drinking water for dental health. They also provide additional data for the development of recommendations on the optimal level of fluoride in drinking water, which can help in maintaining dental health of the population in various areas. Further research in this area may help refine these results and advance our understanding of the relationship between fluoride and macronutrients in tooth enamel.

Mineralization of Dentinal Lesions with Different Concentrations of Fluoride.

The present study aimed to investigate the relationship between fluoride concentration and mineral distribution within the dentinal lesion body. Remineralization of artificial deep dentinal lesions with various levels of fluoride was studied using a scanning electron microscope, microhardness tests, and polarized light microscope. Human molars were exposed to demineralization at pH 5.0 for 2 weeks. Then, they were divided into different groups for remineralization with different fluoride concentrations (0.1-10.0 ppm) for 1, 2, 3, and 4 weeks. The results indicated a proportional relationship between fluoride concentration and dentinal lesion remineralization from 0.1 to 10.0 ppm. In the present study, the formation of a well-remineralized surface layer inhibited remineralization at the lesion front. On the other hand, the lesion front remineralization was found to be independent of fluoride concentration. Our results stated that for effective remineralization of dentinal lesions to the innermost part, fluoride levels from 1.0 to 5.0 ppm have the highest efficiency.

Comparative Gas chromatography-mass spectrometry (GC-MS) analysis of two cultivars of Hordeum vulgare L.

Hordeum vulgare L. is a multi-nutritional food grain crop of the Poaceae family. It is a significant staple crop in Asia with significant nutritional and commercial importance. It is possible to grow this plant under a number of abiotic conditions of stress, such as fluoride stress. The objective of the current study was to determine whether two chosen cultivars of Hordeum vulgare could endure or tolerate fluoride stress conditions by using gas chromatography-mass spectrometry (GC-MS) analysis. The two H. vulgare cultivars’ seeds that were chosen, RD2786 and RD2794, were planted in pH-5 soil and allowed to mature for a month in clay pots. Different concentrations of fluoride (0, 5, 10, 15, 20 ppm) were added to the soil as supplements. Moreover, GC-MS was used to assess factors such as protein content and nitric oxide. Additional TLC analysis was carried out using a TLC sheet. As a result of free radical production, the cultivar RD2786 had higher total protein and nitric oxide scavenging enzyme (NOSA) activity than RD2794. Because of its osmoprotectant properties and ability to tolerate fluoride stress conditions, cultivar RD2786 of H. vulgare is therefore advised for farmers in fluoride-affected regions based on the results of this study.

Effect of different fluoride pretreatments on adhesion to enamel and dentin using a universal adhesive

Objectives To evaluate and compare the bond strength of bulk fill composite when bonded to enamel or dentin pretreated with different concentrations of fluoride (F) compounds using a universal adhesive. Methods A total of 120 teeth were used, including 40 enamel specimens and 80 dentin specimens. Enamel specimens were ground flat, while dentin specimens were prepared by cutting until mid-coronal dentin. The teeth were divided into four groups (n = 30) to test the F-based agents: 1.23% acidulated phosphate fluoride (APF), 1.1% neutral sodium fluoride (NSF), 0.4% stannous fluoride (SF), and a control group without F pretreatment. Each agent was applied for 30 s and rinsed before bonding. Enamel specimens underwent phosphoric acid etching (ER), while dentin specimens were bonded using either ER or self-etch (SE) protocols. Microtensile bond strength testing (μTBS) was performed after 24 h or 10,000 thermal cycles, and failure patterns were assessed. Results The study variables did not significantly affect μTBS values of enamel specimens. However, all study variables had a significant effect on μTBS values of dentin specimens. The ER protocol, after both control and SF pretreatment, exhibited the highest μTBS values. Conclusions Pretreatment of enamel with different concentrations of F prior to bonding appears to be safe in terms of bond durability. However, pretreatment with F concentrations higher than 1000 ppm adversely affected bonding to dentin. Clinical significance Pretreating tooth structure with F-based agents at concentrations below 1000 ppm prior to bonding shows promise as a viable option without compromising bond durability.

Applicability of the equilibrium adsorption isotherms and the statistical tools on to them: a case study for the adsorption of fluoride onto Mg-Fe-CO3 LDH

The demand for a low-cost, easy-to-use, low-maintenance system of adsorbents for detoxifying wastewater effluents is growing. A proper understanding of adsorption mechanisms, their controls, and adsorbate-adsorbent behavior is essential. Thus, the current study deals with the required understanding of linear equilibrium adsorption isotherm models. The adsorption data of different concentrations of fluoride onto Mg-Fe-CO3 LDH is fitted to isotherm models. The two-parameter models discussed are Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich, whereas the three-parameter model cited is Redlich-Peterson. To identify the best-fitting model(s) in an equilibrium isotherm study to quantitatively represent the relevant sorption system, various error functions and statistical tools, such as average relative error deviation (ARED), sum of square errors (ERRSQ or SSE), hybrid relative error function (HYBRID), Marquardt’s percent standard error deviation (MPSD), sum of absolute errors (EABS), sum of normalized errors (SNE), correlation coefficient of Pearson (r), coefficient of determination (r2), chi-square test (χ2), student’s T-test and F-test were applied. It is found that the Temkin model best fits the isotherm data, and the sorption process occurs over multiple layers as per the Freundlich isotherm and was found to be more promising than Langmuir’s monolayer sorption process. The exothermic physisorption course for the adsorbate-absorbent interactions is deduced from the isotherm parameters.

Effects of prolonged fluoride exposure on innate immunity, intestinal mechanical, and immune barriers in mice

The aim of this study is to explore the effects of fluoride on the innate immunity, intestinal mechanical barrier, and immune barrier of C57BL/6 mice, as well as to analyze the degree of structural and tissue damage, providing reference data for related research. Mice were randomly divided into four groups and then treated with 0 mg/L (control), 50 mg/L, 100 mg/L, 125 mg/L sodium fluoride solution, respectively, for 120 days. Histological technique, ELISA, MTT colorimetry methods were used to detect and analyze the effects of different concentrations of fluoride on the intestinal morphology, mechanical barrier and the immune functions and innate immunity of mice. The results showed that compared with the control group, the villi were injured in different degrees of the three fluoride groups, the number of goblet cells, the protein expression levels of connexin ZO-1, Claudin-1 and Occludin, the content of Diamine Oxidase (DAO), endotoxin (ET) and D-lactic acid (D-LA), the activity of natural killer cell (NK cells), the number and percentage of neutrophils and erythrocytes, the phagocytic rate of neutrophils, and the rate of C3bR rosette (which is formed by the adhesion of C3b receptors on the red blood cell membrane to complement sensitized yeast) and IC rosette (which is formed by the adhesion of C3b molecules in the immunecomplex adhered to the red blood cell membrane to non sensitized yeast) of red blood cells, the content of interlenkin 1 beta (IL-1β) and interlenkin 8 (IL-8), the number and percentage of lymphocytes decreased with the increasing of fluoride concentration. In addition, the content of the Immunoglobulin A (sIgA) showed a trend of increase at first and then decrease in salivary gland and jejunum. It is concluded that excessive intake of fluoride for a long time has a certain damage effect on the intestinal tract, leading to an increase in the permeability of the intestinal tract, thereby destroying the mechanical and immune barrier function of the intestinal tract.

Fluoride induces osteoblast autophagy by inhibiting the PI3K/AKT/mTOR signaling pathway in vivo and in vitro.

Fluorosis primarily manifests as bone damage in the form of dental fluorosis and skeletal fluorosis and represents a critical global public health challenge. However, few studies have examined autophagy-related signaling pathways in skeletal fluorosis. This study aimed to investigate the effect of fluoride on autophagy in osteoblasts using comprehensive methods and to explore the role of the PI3K/AKT/mTOR signaling pathway in regulating fluoride-induced autophagy in osteoblasts. Sprague-Dawley (SD) rats were exposed to different concentrations of fluoride (NaF: 5, 50, and 100 mg/L) for six months. Primary osteoblasts were treated with 0.5, 1.0, or 3.0 mM NaF. Hematoxylin and eosin (H&E) staining, transmission electron microscopy (TEM), immunohistochemistry (IHC), immunofluorescence staining, and western blotting were performed to evaluate morphological changes in bone tissues and autophagosomes and to detect the protein expression of autophagy-related markers and PI3K/AKT/mTOR signaling pathway-related molecules both in vivo and in vitro. The bone tissues of fluoride-exposed rats showed osteosclerosis, autophagosomes and autolysosomes. LC3B immunofluorescence staining revealed an increase in autophagosomes in the primary osteoblasts treated with fluoride. The LC3Ⅱ/Ⅰ ratio and levels of autophagy-related markers (Beclin 1 and Atg7) were increased, whereas P62 levels were decreased in bone tissues and primary osteoblasts in the fluoride groups. Simultaneously, p-AKT and p-mTOR levels were reduced in bone tissues and primary osteoblasts in the fluoride groups. Moreover, a PI3K inhibitor (LY294002) further downregulated p-AKT and p-mTOR protein expression but slightly increased the LC3Ⅱ/Ⅰ ratio in primary osteoblasts. These results demonstrate that fluoride induces autophagy in osteoblasts by inhibiting the PI3K/AKT/mTOR signaling pathway, which deepens our understanding of the molecular mechanisms underlying fluoride-induced bone damage and provides a theoretical basis for the prevention and treatment of skeletal fluorosis.

The effect of different concentrations of fluoride in toothpastes with or without bioactive glass on artificial root caries

ObjectiveTo investigate the effect of different toothpastes either containing 5,000ppm-F, 1,450ppm-F or bioactive glass (BG) with 540ppm-F on artificial root carious lesions (ARCLs). MethodThe crowns of 23 extracted sound teeth were removed leaving their roots only. Subsequently, each root was divided into four parts. A total of 15 sound root dentine (SRD) was left untreated as baseline. The ARCLs were developed for the remaining roots using demineralisation solution (pH-4.8). 15-ARCLs samples were then left untreated. The rest of samples were divided into four groups (n = 15 each) and treated with Group-1(BG with 540ppm-F); Group-2(5000ppm-F); Group-3(1450ppm-F) and Group-4(deionised water). 13-day pH-cycling included using demineralisation solution for 6 h, then placing samples into remineralisation solution (pH-7) for 16 h. Each sample was brushed with the assigned toothpaste twice a day during pH-cycling. Fluoride concentrations at each time point were measured using F-ISE, whilst calcium (Ca2+) and phosphorus (P) ion release was determined using ICP-OES, KHN, XRD, 19F-MAS-NMR analyses. ResultsKHN showed significant surface changes for each group (p<0.001). The uptake of Ca2+ occurred at days 1–2, phosphorus ion loss was high when compared to the uptake in all groups. XRD showed presence of sharp diffraction lines evidencing apatite formation for Groups 1–3. 19F-MAS-NMR confirmed fluorapatite presence in Groups 1–3. ConclusionAll toothpastes were promising in fluorapatite formation. BG with 540ppm-F toothpaste released more ions (Ca2+and P) and reharden the artificial root carious lesions when compared to other groups. However, 1450ppm-F toothpaste showed more fluoride-substituted apatite formation whilst 5000ppm-F toothpaste had more fluorapatite formation. Clinical significanceToothpaste containing BG with 540ppm-F, 5000ppm-F and 1450ppm-F toothpastes are likely to have a significant impact in reversing and arresting root caries. However, randomised controlled double-blinded clinical trials are required to translate these results into clinical practice.

Коррозионная усталость меди в водных средах

The failure of the cooling systems of engines and propellers of the ship poses the serious hazard to passengers and crew. Damage to these units is often caused by corrosion, with localized corrosion being the most dangerous. In the case under consideration, when the metal is simultaneously affected by a corrosive environment and alternating mechanical loads, conditions arise for the behaviour (occurrence) of corrosion fatigue. The prospects of cathodic electrochemical protection of these units are considered in the paper. Since the cooling systems and propellers are made of copper alloys, the effect was studied concerning the potential and composition of the solution on the corrosion of the main component of the structural material — copper. Copper samples with a smooth mechanical pressure concentrator cantilevered in a fluoroplastic electrochemical cell were tested. Alternating bending loads were applied to them, and the number of load cycles before the destruction of the sample (durability) was determined. The experiments were carried out in deaerated solutions of the surfactantly inactive electrolyte NaF, as well as fluoride solutions with additives of surfactants and organic surfactants - benzotriazole. At the same time, an interval of potentials was set, in which the only Faraday process is possible — the reduction of traces of dissolved oxygen. It was found that at potentials less than the zero charge potential, the durability of copper increases significantly. And the introduction of chloride ions and benzotriazole into the solution, on the contrary, leads to a strong decrease in its durability. The potential of zero charge of copper was determined from the measurement data of the differential capacitance of the metal in sodium fluoride solutions with different concentrations of fluoride. The increase in the durability of the metal is explained by the occurrence of hydrogen bonds between the water molecules adsorbed by the hydrogen atoms. This manifests the so-called negative Rebinder effect. For electrochemical protection, the potential range is recommended below the potential of zero charge of the metal, but above the potential of water decomposition. For cooling systems, it is recommended to use deionized water as a coolant.

The influence of NQO2 on the dysfunctional autophagy and oxidative stress induced in the hippocampus of rats and in SH-SY5Y cells by fluoride.

For investigating the mechanism of brain injury caused by chronic fluorosis, this study was designed to determine whether NRH:quinone oxidoreductase 2 (NQO2) can influence autophagic disruption and oxidative stress induced in the central nervous system exposed to a high level of fluoride. Sprague-Dawley rats drank tap water containing different concentrations of fluoride for 3 or 6months. SH-SY5Y cells were either transfected with NQO2 RNA interference or treated with NQO2 inhibitor or activator and at the same time exposed to fluoride. The enrichment of gene signaling pathways related to autophagy was evaluated by Gene Set Enrichment Analysis; expressions of NQO2 and autophagy-related protein 5 (ATG5), LC3-II and p62, and mammalian target of rapamycin (mTOR) were quantified by Western-blotting or fluorescent staining; and the levels of malondialdehyde (MDA) and superoxide dismutase (SOD) assayed biochemically and reactive oxygen species (ROS) detected by flow cytometry. In the hippocampal CA3 region of rats exposed to high fluoride, the morphological characteristics of neurons were altered; the numbers of autophagosomes in the cytoplasm and the levels of NQO2 increased; the level of p-mTOR was decreased, and the levels of ATG5, LC3-II and p62 were elevated; and genes related to autophagy enriched. In vitro, in addition to similar changes in NQO2, p-mTOR, ATG5, LC3 II, and p62, exposure of SH-SY5Y cells to fluoride enhanced MDA and ROS contents and reduced SOD activity. Inhibition of NQO2 with RNAi or an inhibitor attenuated the disturbance of the autophagic flux and enhanced oxidative stress in these cells exposed to high fluoride. Our findings indicate that NQO2 may be involved in regulating autophagy and oxidative stress and thereby exerts an impact on brain injury caused by chronic fluorosis.

Association between Level of Parental Oral Health Literacy and the Rational Use of Fluoride for Children from 0 to 4 Years of Age after Instruction: An Intervention Trial

An inadequate level of oral health literacy (OHL) can hinder the understanding of dental information, which can have a negative impact on health promotion actions, such as the rational use of fluoride. The aims of the present study were (1) to look for association between parents/guardians’ OHL and the amount of fluoride toothpaste used for children from zero to four years of age; (2) to compare the effect of different modes of educational interventions on the amount of fluoride toothpaste used for children from zero to four years of age; and (3) to assess the ability of parents/guardians to choose a toothpaste with adequate fluoride concentration, after the educational intervention. A randomized intervention study was conducted with parents/guardians of children from zero to four years of age (n = 145). The participants answered the Oral Health Literacy Adults Questionnaire and a questionnaire addressing sociodemographic characteristics. The participants were allocated to four intervention groups based on type of counseling (written, oral, written + photograph, and oral + photograph), with randomization stratified by level of OHL. The participants were instructed to place the adequate amount of toothpaste on a toothbrush for children from zero to four years of age (smear of 0.125 mg) before and after the intervention. The correct choice of toothpaste was also evaluated by the interpretation of the labels of four toothpastes of different brands and with different concentrations of fluoride. Associations between variables were tested using the Student’s t test and one-way ANOVA. Level of OHL was associated with the amount of fluoride toothpaste deposited prior to the educational intervention (p = 0.021) and the percentage of approximation to the appropriate amount of fluoride toothpaste (p < 0.05). The choice of toothpaste was associated with schooling (p = 0.031). In conclusion, parents/guardians with adequate OHL better quantified fluoride toothpaste before and after the educational intervention and also came closer to the appropriate amount of toothpaste after the educational intervention. No significant differences in the final amount of toothpaste placed on the toothbrush were found among the intervention groups. The choice of the correct toothpaste was associated with a higher level of schooling.

Germination and morphological responses of Triticum aestivum L. to different concentrations of fluoride

A laboratory experiment was conducted on germination papers to study the effect of fluoride (F) at 0 (T1), 50 (T2), 100 (T3), 200 (T4), 250 (T5) and 300 (T6) ppm on germination and morphological parameters in wheat (Triticum aestivum L.) variety, HUW-234 at 2, 4 and 6 days after initiation of germination process. Fluoride toxicity caused reduction in germination per cent, germination index, coefficient of velocity of germination and germination energy (%) while mean germination time increased with fluoride concentration. Root and shoot lengths and dry matters decreased with increased concentrations of fluoride. Ratio of root: shoot weight increased with increased concentration of fluoride. Elongation of seminal roots was adversely affected by increased fluoride level. Increased fluoride level in the germination medium decreased RGR of seedlings progressively. Present study revealed that enhanced fluoride concentration in germination medium caused reduction in germination and germination related parameters.

Effects of brief sodium fluoride treatments on the growth of early and mature cariogenic biofilms

Although fluoride has been widely used as a preventive agent for dental caries, the effects of fluoride on the activities of biofilms in different stages of cariogenic biofilm formation are less studied. This study was designed to investigate the antibiofilm activity of sodium fluoride during the early and mature stages of Streptococcus mutans (S. mutans) biofilm formation. S. mutans biofilms were formed on saliva-coated hydroxyapatite disks. In the early (0–46 h) and mature (46–94 h) biofilm stages, the biofilms were treated with different concentrations of fluoride (250, 500, 1000, 2000 ppm; 5 times in total, 1 min/treatment). Acidogenicity, dry weight, colony-forming units (CFUs), water-soluble/insoluble extracellular polysaccharides (EPSs), and intracellular polysaccharides were analysed, and confocal laser scanning microscopy images were obtained of the two stages of biofilms to determine antibiofilm activities of fluoride at varying concentrations during the formation of early and mature biofilms. In the early stages of cariogenic biofilm formation, test groups with all fluoride concentrations significantly inhibited the growth of S. mutans biofilms. The antibiofilm and anti-EPS formation activities of the brief fluoride treatments increased with a concentration-dependent pattern. At the mature biofilm stage, only the 2000 ppm fluoride treatment group significantly inhibited biofilm accumulation, activity, and intracellular/extracellular polysaccharide content compared with those of the control and other fluoride treatment groups. The antimicrobial effect of fluoride treatment on the growth of S. mutans biofilms was linked with the stage of cariogenic biofilm formation. The inhibition of S. mutans biofilm growth by fluoride treatment was easier in the early formation stage than in the mature stage. Fluoride treatment in the early stage of cariogenic biofilm formation may be an effective approach to controlling cariogenic biofilm development and preventing dental caries.

The effects of strontium-doped bioactive glass and fluoride on hydroxyapatite crystallization

ObjectivesThis study investigated the effects of a new strontium-doped bioactive glass and fluoride on hydroxyapatite crystallization. MethodsWe designed an in vitro experiment with calcium phosphate (CaCl2·2H2O + K2HPO4 in buffer solution) with different concentrations of strontium-doped bioactive glass (1 mg/mL or 5 mg/mL), and different concentrations of fluoride (0 ppm, 1 ppm or 5 ppm). Tris-buffered saline served as negative control. After incubation at 37 ℃ for 48 h, the shape and organization of crystals were examined by transmission electron microscopy (TEM) and electron diffraction. Structure of the crystals was assessed by powder X-ray diffraction (P-XRD) and unit cell parameters were calculated. Characterization of the crystals were performed by Raman spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR). ResultsTEM and selected-area electron diffraction revealed that the precipitates in all experimental groups were crystalline apatite. There was an interaction between strontium and fluoride with different concentrations on crystal thickness (p = 0.008). P-XRD indicated the formation of strontium-substituted-fluorohydroxyapatite and strontium-substituted-hydroxyapatite in the groups with both bioactive glass and fluoride. Expansion or contraction of crystal unit cell was influenced by the concentrations of strontium and fluoride. Raman spectra showed strong phosphate band at 960 cm−1 in all experimental groups and displayed no obvious shift. FTIR results confirmed the formation of apatite. ConclusionsThe results of this study suggest that strontium-doped bioactive glass and fluoride have synergistic effects on hydroxyapatite crystallization. Clinical SignificanceStrontium-doped bioactive glass and fluoride have synergistic effects on hydroxyapatite crystallization by producing strontium-substituted-hydroxyapatite and strontium-substituted-fluorohydroxyapatite with enhanced bioactivity and reduced solubility which could be beneficial for caries management.

Silicon-regulated antioxidant and osmolyte defense and methylglyoxal detoxification functions co-ordinately in attenuating fluoride toxicity and conferring protection to rice seedlings

The objective of this manuscript was to demonstrate the efficacy of silicon supplementation in relieving the fluoride-induced damages in rice cultivar, Khitish. The exposure of seedlings to two different concentrations of fluoride, viz., 25 and 50 mg L−1 NaF caused increase in fluoride accumulation, as a result of which the seedlings suffered severe oxidative stress, as evident from growth inhibition, reduction in seed germination, tissue biomass, root and shoot length, decline in chlorophyll content, increases in electrolyte leakage, H2O2 content, lipid peroxidation (malondialdehyde content and lipoxygenase activity), protein carbonylation and protease activity. The extent of damage was more at higher fluoride concentration. Silicon amendment, irrespective of fluoride concentrations, led to large build-up of endogenous silicon level and brought considerable improvement in all the parameters examined with respect to fluoride stress. The fluoride-mediated enhancement in methylglyoxal level was lowered by silicon, because of the prominent activation of glyoxalase I and glyoxalase II. While the stress-mediated induction in antioxidative enzymes like GPOX, APX, SOD, GPX and GR was lowered by silicon, the inhibition in CAT activity was relieved. The antioxidative defense mechanism was also boosted up via enhanced content of total phenolics and carotenoids. However, the fluoride-mediated increase in anthocyanins, flavonoids, xanthophyll, ascorbate and reduced glutathione, and osmolytes like total amino acids, proline and glycine-betaine, were all lowered in presence of silicon, together with reduced PAL and P5CS activity. Overall, silicon reduced oxidative damages to develop fluoride-tolerant rice plants through augmentation of different antioxidant and osmolyte defense and methylglyoxal detoxification system.

ENAM Gene Variation in Students Exposed to Different Fluoride Concentrations.

The ENAM gene is important in the formation of tooth enamel; an alteration can affect the lengthening of the crystals, and the thickness in enamel. The objective was to determine the presence of the single nucleotide variant (SNV) rs12640848 of the ENAM gene in students exposed to different concentrations of fluoride. Methods: A cross-sectional study was conducted on students exposed to high concentrations of fluoride in the city of Durango which were divided according to the severity of fluorosis and dental caries. Genotype determination was performed by DNA sequencing. The relationship between the severity of dental fluorosis and the allele distribution was determined by the Fisher’s exact and Kruskal–Wallis tests. Results: Seventy-one students were included for the sequencing. In the different allelic variations, for the normal genotype AA/TT, the control group presented 75%, for the AG/TC variation, 70.8% in the TF ≤ 4 group, 65% in TF ≥ 5, and 16.7% in TF = 0; with respect to GG/CC variation, 12.5% in TF ≤ 4, 22% in TF ≥ 5, and 8.3% in TF = 0 group (p = 0.000). Conclusion: The ENAM gene showed an association in the population exposed to different concentrations of fluoride.

Fluoride toothpastes of different concentrations for preventing dental caries.

Fluoride toothpastes of different concentrations for preventing dental caries.

Effect of fluoride mouthrinse on adhesion to bovine root dentin.

The purpose of this study was to evaluate the effect of fluoride mouthrinses on dentin bonding performance of a two-step selfetch adhesive; Clearfil SE Bond. Bovine root dentin surface was treated with either 450, 900, or 9,000 ppm F solutions for 30 s (immediate), and continually treated for one month (one month) before the bonding procedures. Microtensile bond strength (µTBS) test and scanning electron microscopic (SEM) observation of the acid-base resistance zone (ABRZ) were performed. Chemical state of fluorine on dentin surface was analyzed by X-ray absorption fine structure (XAFS). The 450 and 900 ppm F fluoride mouthrinses did not influence the µTBS to dentin, while the 9,000 ppm F fluoride solution adversely affected the µTBSs. The fluoride application to dentin significantly enhanced acid resistance at the adhesive/dentin interface including the ABRZ. The XAFS analysis indicated different concentrations of fluoride might create different chemical compounds on the dentin surface, influencing the µTBS results.

Investigation of Fluoride Tolerance in&lt;i&gt; Acidithiobacillus ferrooxidans&lt;/i&gt;

Anionic ion species occur in gangue minerals and impact the bioleaching efficiency even at low concentrations. Recently, the detrimental influence of fluoride ions on bioleaching microorganisms has caused great attention in research. However, the tolerance mechanisms of bioleaching microorganisms for fluoride are still unclear. In order to reveal fluoride tolerance, culture experiments with different concentrations of fluoride and ferrous iron-grown Acidithiobacillus ferrooxidans were carried out. The results showed that oxidation-reduction potential, oxidation capacity of iron and cell density were all negatively correlated to the fluoride concentration. The growth of A. ferrooxidans showed a longer delayed time and a slower growth rate when fluoride concentration increased. The fluoride tolerance for A. ferrooxidans could be attributed to the generated ferric ions from ferrous oxidation. Ferric ions reacted with HF to decrease the concentration of F- and finally reduced the toxicity of fluoride on A. ferrooxidans.