Action Of Fluoride Research Articles

CF Bond Activation of Unactivated Aliphatic Fluorides: Synthesis of Fluoromethyl‐3,5‐diaryl‐2‐oxazolidinones by Desymmetrization of 2‐Aryl‐1,3‐difluoropropan‐2‐ols

How to lose fluorine: Biologically relevant oxazolidinones 1 were synthesized through the desymmetrization of unactivated aliphatic difluorides by Si-induced catalytic CF bond-cleavage using BSA/CsF (BSA=bis(trimethylsilyl)acetamide). The direct transformation of 2 with isocyanates into 1 by cascade carbamoylation/cyclization, in which cyclization is induced by Na-assisted CF bond activation, was also achieved.

Fluoride plus functionalized β-TCP: a promising combination for robust remineralization.

With more than 50 years of clinical success, fluoride serves as the gold standard agent for preventing tooth decay. In particular, the action of fluoride facilitates saliva-driven remineralization of demineralized enamel and alters solubility beneficially. Still, tooth decay remains problematic, and one way to address it may be through the development of new mineralizing agents. Laboratory and clinical studies have demonstrated that the combination of fluoride and functionalized β-tricalcium phosphate (fTCP) produces stronger, more acid-resistant mineral relative to fluoride, native β-TCP, or fTCP alone. In contrast to other calcium-based approaches that seem to rely on high levels of calcium and phosphate to drive remineralization, fTCP is a low-dose system designed to fit within existing topical fluoride preparations. The functionalization of β-TCP with organic and/or inorganic molecules provides a barrier that prevents premature fluoride-calcium interactions and aids in mineralization when applied via common preparations and procedures. While additional clinical studies are warranted, supplementing with fTCP to enhance fluoride-based nucleation activity, with subsequent remineralization driven by dietary and salivary calcium and phosphate, appears to be a promising approach.

Effect of Fluoride on Insulin Level of Rats and Insulin Receptor Expression in the MC3T3-E1 Cells

Studies on the role of insulin and insulin receptor (InsR) in the process of skeletal fluorosis, especially in osteogenic function, are rare. We evaluated the effect of increasing F⁻ doses on the marker of bone formation, serum insulin level and pancreatic secretion changes in vivo and mRNA expression of InsR and osteocalcin (OCN) in vitro. Wistar rats (n = 50) were divided into two groups, i.e. a control group and fluoride group. The fluoride groups were treated with fluoride by drinking tap water containing 100 mg F⁻/L. The fluoride ion-selective electrode measured the fluoride concentrations of femurs. The alkaline phosphatase (ALP), OCN, insulin and glucagon of serum were tested to observe the effect of fluoride action on them. Meantime, the pancreas pathological morphometry analysis via β cells stained by aldehyde fuchsin showed the action of fluoride on pancreas secretion. MC3T3-E1 cells (derived from newborn mouse calvaria) were exposed to varying concentrations and periods of fluoride. The mRNA expression of InsR and OCN was quantified with real-time PCR. Results showed that 1-year fluoride treatment obviously stimulated ALP activity and OCN level along with increase of bone fluoride concentration of rats, which indicated that fluoride obviously stimulated osteogenic action of rats. In vitro study, the dual effect of fluoride on osteoblast function is shown. On the other hand, there was a significant increase of serum insulin level and a general decrease of glucagon level, and the histomorphometry analysis indicated an elevated insulin-positive area and increase in islet size in rats treated with fluoride for 1 year. In addition, fluoride obviously facilitated the mRNA expression of InsR in vitro. To sum up, there existed a close relationship between insulin secretion and fluoride treatment. The insulin signal pathway might be involved in the underlying occurrence or development of skeletal fluorosis.

Fluoride decreased osteoclastic bone resorption through the inhibition of NFATc1 gene expression

Over the past two decades, fluoride effects on osteoclasts have been evaluated; however, its molecular mechanisms remain unclear. In this study, we investigated the effect of fluoride on osteoclast formation, function, and regulation using osteoclasts formed from mice bone marrow macrophages treated with the receptor activator of NF-κB ligand and macrophage colony-stimulating factor. Our data showed that fluoride levels ≤ 8 mg/L had no effect on osteoclast formation; however, it significantly reduced osteoclast resorption at 0.5 mg/L. Fluoride activity on bone resorption occurred through the inhibition of nuclear factor of active T cells (NFAT) c1 expression. Furthermore, the expression of its downstream genes, including the dendritic cell-specific transmembrane protein, c-Src, the d2 isoform of vacuolar (H+) ATPase v0 domain, matrix metalloproteinase 9, and cathepsin K were decreased, leading to impaired osteoclast acidification, reduced secretion of proteolytic enzymes, and decreased bone resorption. In summary, our results suggested that fluoride has different roles in osteoclast formation and function. Fluoride ≤ 8 mg/L did not impact osteoclast formation; however, it significantly decreased the resorption activity of newly formed osteoclasts. The molecular mechanism of fluoride action may involve inhibition of NFATc1 and its downstream genes.

Enhancement of fluoride activity against Streptococcus mutans biofilms by a substance separated from Polygonum cuspidatum

Polygonum cuspidatum is a plant with spreading rhizomes and numerous reddish-brown stems that has been used in Korean folk medicine to improve oral hygiene. Nevertheless, there are no reports related to its possible effect on the virulence of dental biofilms. In this study, the ability of a fraction (F1) separated from P. cuspidatum, alone or in combination with fluoride, to disrupt virulence factors and the composition of Streptococcus mutans biofilms was examined. F1 was mainly composed of resveratrol, emodin and physcion (approximately 16.2%, 18.9% and 2.07% of the weight of F1, respectively). F1 showed inhibitory effects on acid production and F-ATPase activity of S. mutans in biofilms, and could enhance fluoride activity against acid production and acid tolerance of S. mutans in biofilms. When S. mutans biofilms were briefly treated with F1 (10 min, a total of five times), the biomass accumulation, water-insoluble polysaccharides and intracellular iodophilic polysaccharides were reduced. Furthermore, the fluoride activity against biomass accumulation was enhanced by F1. These results suggest that F1 may be useful in the control of dental biofilms and in improving the cariostatic properties of fluoride without increasing its exposure.

ChemInform Abstract: Direct Hiyama Cross‐Coupling of Enaminones with Triethoxy(aryl)silanes and Dimethylphenylsilanol.

AbstractOrganosilanol (IV) can also be used in a direct C—H cross‐coupling, even without fluoride activation [cf.

Catalytic effect of fluoride on silica polymerization at neutral pH

The catalytic effect of fluoride on the polymerization of sodium silicate and phosphoric acid solutions at pH 7.15 was studied through a simple and inexpensive method: the observation of the meniscus of the resulting sol in a test tube. Reaction was found to be second-order regarding silicate concentration as reported previously. Novel results show that the reaction also follows a pseudo-second-order kinetics with respect to fluoride. A rate law for the catalyzed polymerization of the form r = K v[Si(OH)4][HF]2 was established. A mechanism for fluoride action on silica polymerization, where silicon increases its coordination number to five, is proposed.

Fluoride

Fluoride is a naturally occurring element with multiple implications for human health. This review discusses its metabolism and toxicity, along with the current understanding of the mechanism of action of fluoride and its role as a safe and effective agent in the prevention of dental caries. The relationship between excessive fluoride intake during periods of dental enamel formation and the development of dental fluorosis is also reviewed.

New role of chromium fluoride: Its catalytic action on the synthesis of hydroxymethylfurfural in ionic liquid using raw plant biomass and characterization of biomass hydrolysis

A simple two-step process was conducted to scrutinize new catalytic action of chromium fluoride (CrF 3) by evaluating its effect on the yield of hydroxylmethylfurfural (HMF) in ionic liquid (1-octyl-3-methylimidazolium chloride) using raw tapioca root biomass with high starch, and hydrolysis efficiency of the biomass extract was characterized by FT-IR spectrometry and FESEM image analysis. The FT-IR absorbance bands confirmed the presence of starch and other soluble sugars in the acidic biomass extract by presenting its frequency signals in the 950–1200 cm −1 regions. FESEM image showed that the efficiency of the biomass hydrolysis is time-dependent. The concentration of CrF 3 significantly affected the yield of HMF. Its highest yield (52.6 ± 4.8 dwt%) was achieved at 1% CrF 3, but over 1% CrF 3 its yields began to decline. The combined addition of CrF 3 and CrBr 3 showed ca. 1.3-fold higher yield than CrF 3 alone. The reaction rates of HMF synthesis were considerably influenced by the stoichiometry ratio of CrF 3 to biomass. The highest reaction rate (0.41 g/g biomass/h) occurred at 0.2 ratio value.

The Benzyne Fischer Indole Reaction

A new approach to the Fischer-indole synthesis is reported that uses the reactive intermediate benzyne. The addition of N-tosyl hydrazones to arynes, generated through fluoride activation of 2-(trimethylsilyl)phenyl triflate precursors, leads to efficient N-arylation. Addition of a Lewis acid to the same reaction pot then affords N-tosylindole products via Fischer cyclization.

Sodium fluoride inhibits HSP synthesis in heat-stressed cultured cells of Arabidopsis thaliana

Fluorine is a component of atmospheric emissions in industrial areas. It negatively affects plant development and weakens the defense systems, thus making plants vulnerable to extreme environmental conditions. The heat shock proteins (HSP) are known to promote the plant resistance to various biotic and abiotic stresses. We studied the action of sodium fluoride (NaF) on growth, viability, respiration, transmembrane electric potential at the inner mitochondrial membrane (mtΔΨ), the development of induced thermotolerance, and HSP synthesis in the cell culture of Arabidopsis thaliana (L) Heynh (accession Columbia). The treatment with 20 mM NaF (for 120 min) had no negative influence on viability of the cell culture but inhibited the development of induced thermotolerance and suppressed the induction of HSP (Hsp101 and Hsp17.6) synthesis during mild heat stress (37°C). At the same time, the treatment with NaF inhibited respiration and suppressed the increase in mtΔΨ induced by mild heat stress. Hence, the negative impact of NaF on plants might arise from its ability to inhibit synthesis of stress proteins indispensible for plant adaptation to changing environmental conditions.

The Benzyne Fischer-Indole Reaction

A new approach to the Fischer-indole synthesis is reported that uses the reactive intermediate benzyne. The addition of N-tosyl hydrazones to arynes, generated through fluoride activation of 2-(trimethylsilyl)phenyl triflate precursors, leads to efficient N-arylation. Addition of a Lewis acid to the same reaction pot then affords N-tosylindole products via Fischer cyclization.

Fluoride geochemistry of thermal waters in Yellowstone National Park: I. Aqueous fluoride speciation

Thermal water samples from Yellowstone National Park (YNP) have a wide range of pH (1–10), temperature, and high concentrations of fluoride (up to 50 mg/l). High fluoride concentrations are found in waters with field pH higher than 6 (except those in Crater Hills) and temperatures higher than 50 °C based on data from more than 750 water samples covering most thermal areas in YNP from 1975 to 2008. In this study, more than 140 water samples from YNP collected in 2006–2009 were analyzed for free-fluoride activity by ion-selective electrode (ISE) method as an independent check on the reliability of fluoride speciation calculations. The free to total fluoride concentration ratio ranged from <1% at low pH values to >99% at high pH. The wide range in fluoride activity can be explained by strong complexing with H + and Al 3+ under acidic conditions and lack of complexing under basic conditions. Differences between the free-fluoride activities calculated with the WATEQ4F code and those measured by ISE were within 0.3–30% for more than 90% of samples at or above 10 −6 molar, providing corroboration for chemical speciation models for a wide range of pH and chemistry of YNP thermal waters. Calculated speciation results show that free fluoride, F −, and major complexes ( HF ( aq ) 0 , AlF 2+, AlF 2 + and AlF 3 0 ) account for more than 95% of total fluoride. Occasionally, some complex species like AlF 4 - , FeF 2+, FeF 2 + , MgF + and BF 2 ( OH ) 2 - may comprise 1–10% when the concentrations of the appropriate components are high. According to the simulation results by PHREEQC and calculated results, the ratio of main fluoride species to total fluoride varies as a function of pH and the concentrations and ratios of F and Al.

Ulcerogenic Mechanism of Ethanol and the Action of Sulphanilyl Fluoride on the Rat Stomach In-vivo

The effects of ethanol alone and in combination with sulphanilyl fluoride on some of the antioxidant defences in the stomach of rats have been examined. These effects were correlated with lesion formation in the gastric mucosa. Oral administration of ethanol induced gastric lesions which were prevented by sulphanilyl fluoride pre-treatment. N-Ethylmaleimide antagonized the anti-lesion action of sulphanilyl fluoride. Ethanol administration lowered the glucose-6-phosphate dehydrogenase activity in the gastric mucosa, an effect potentiated by N-ethylmaleimide pre-treatment. The total superoxide dismutase activity was unaffected by the drugs used in the present study. Ethanol, however, markedly increased mucosal catalase activity which was reduced by sulphanilyl fluoride pretreatment and reversed by N-ethylmaleimide. It is concluded that the ulcerogenic mechanism of ethanol is mediated at least in part by the depression of the hexose monophosphate shunt and the production of active oxygen species, whereas the anti-lesion action of sulphanilyl fluoride is probably not mediated through these mechanisms.

The determination of aluminium in antacid formulations by Gran's Plot titration with sodium fluoride.

The aluminium content of a number of proprietary antacid formulations has been determined by titration with sodium fluoride, using the fluoride activity electrode as an end-point detector. Results compared favourably with the official method. The fluoride titration, however, involved less sample manipulation and was more rapid to carry out. End-point detection was made easier by treating titration data by the Gran's Plot method.

Synthesis of fluorine-18-labelled TSPO ligands for imaging neuroinflammation with Positron Emission Tomography

Fluorine-18 radiochemistry is an essential tool in Positron Emission Tomography, providing the bridge between the cyclotron-produced raw radioisotope and the biomedical image of an in vivo radioactivity distribution. From the fluorine-18 labelled radioligands for the translocator protein 18 kDa that are produced in our laboratory, namely [ 18F]FEDAA1106, 6-[ 18F]F-PBR28, [ 18F]PBR111 and [ 18F]DPA-714, we address various aspects of fluorine-18 radiochemistry, such as rationales of radiotracer design, radioisotope production and [ 18F]fluoride activation, and procedures of radiofluorination, purification and formulation. Automation of the radiochemistry process has become indispensable in order to assure a constant radiopharmaceutical quality and reproducible radiochemical yields as well as to meet the required radiation protection aspects.

Thiophilic nucleophilic trifluoromethylation of α-substituted dithioesters. Access to S-trifluoromethyl ketene dithioacetals and their reactivity with electrophilic species

The nucleophilic trifluoromethylation of dithioesters bearing a nucleofugal group in α-position, using CF 3TMS under fluoride activation, afforded unprecedented S-CF 3 ketene dithioacetals via a domino process thiophilic trifluoromethylation–β-elimination. The best results were obtained with non-enolisable α-carbamoyloxydithioesters. The higher homologues S-C 2F 5 ketene dithioacetals were prepared by a similar way. These new dithioacetals react with methylating reagents quantitatively and chemoselectively at sulfur to give stable dimethylsulfonium type salts. They react more classically with triflic acid, protonation taking place at the β-carbon to give a dithiolium salt, characterized in solution but non-isolable.

AZ91 Magnesium Alloys: Anodizing of Using Environmental Friendly Electrolytes

An anodizing process, based on environmental friendly electrolyte solutions has been studied on AZ 91 magnesium alloys by using three types of electrolytes: the first is based on sodium silicate, the second on sodium hydroxide-boric acid-borax and the third on sodium silicate- potassium hydroxide-sodium carbonate-sodium tetra borate. A pretreatment including fluoride activation was applied before the anodizing process. It was found that the anodic film thickness increases as current density or anodizing voltage increases. It is also increased with deposition time until the deposition stops due to the formation of a thick anodic film. Optimization of the anodizing conditions - current density and deposition time- was made for each electrolyte. Characterization of anodizing layer was achieved by determination of surface morphology, microstructure, phase analysis, coat thickness, adhesion and corrosion resistance. In all cases, excellent adhesion and corrosion resistance was obtained. A corrosion efficiency ranging from 94% to 97% was reached; the highest value corresponding to the third electrolyte.

Fluoride-Containing Materials and the Prevention of Demineralization During Orthodontic Treatment—Which Research Method Should We Now Use?

With time, cariologists have changed their understanding of the effects of fluoride on the caries process. These findings have been discovered predominantly through work carried out in laboratories. Although cariologists perform laboratory studies to explain the mechanisms of action of fluoride and material scientists to test the properties and biocompatibility of materials, as orthodontists we are more interested in determining how useful a product is in clinical practice. In this article, I will outline the advantages and disadvantages of laboratory methods designed to determine whether a fluoride-containing material is effective in reducing demineralization during orthodontic treatment. I will argue that the only way to test a material is to undertake a randomized clinical trial, with a parallel group design, over the full-length of orthodontic treatment. With time, cariologists have changed their understanding of the effects of fluoride on the caries process. These findings have been discovered predominantly through work carried out in laboratories. Although cariologists perform laboratory studies to explain the mechanisms of action of fluoride and material scientists to test the properties and biocompatibility of materials, as orthodontists we are more interested in determining how useful a product is in clinical practice. In this article, I will outline the advantages and disadvantages of laboratory methods designed to determine whether a fluoride-containing material is effective in reducing demineralization during orthodontic treatment. I will argue that the only way to test a material is to undertake a randomized clinical trial, with a parallel group design, over the full-length of orthodontic treatment.

Knowledge and practices of caries prevention among Taiwanese dentists attending a national conference

Background/purpose This study was carried out to evaluate Taiwanese dentists’ knowledge and practice towards preventive dental care. Materials and methods A questionnaire survey was conducted at the nationwide annual dental congress in 2008 in Taipei, Taiwan. Dentists’ knowledge about preventive dentistry was assessed based on their responses to 19 statements. Dentists’ attitudes towards preventive dentistry were assessed based on responses to the effectiveness of 16 preventive procedures. The dentists were also asked about their experience with the use of sealants and fluoride. Results More than 80% could not distinguish between new and old theories of the mechanism of action of fluoride. The correct answer was “remineralization of incipient decay”, not “incorporation of fluoride into developing teeth”. Also 68% incorrectly answered that “lactobacilli play a more-significant role in the initiation of smooth surface carious lesions than do mutans streptococci”, an older theory. Over 80% perceived the effectiveness of “pit and fissure sealants”, “professional prophylaxis”, and “flossing” for preventing caries in children, and the last 2 procedures for adults. “Community water fluoridation” and sealants were selected as the most effective procedures for caries prevention in children, and “professional prophylaxis” and “flossing” for adults. Although sealants were perceived as being effective, 44% of dentists reported that they only applied sealants to ≤10% of their [children/pediatric?] patients. The reasons were that patients had difficulty understanding the value (67%) and were unwilling to pay (63%). Nearly 55% of dentists provided topical fluoride treatments to children more than 2 times per year. However, the frequency decreased to less than once per year for teenagers and adults. Most of the dentists finished a fluoride application in 1 min for in-office treatments. Conclusions A portion of Taiwanese dentists seemed to have limited up-to-date information about certain topics related to caries prevention. The frequency of treatments for caries prevention, such as topical fluoride and sealants, did not match the perceived effectiveness of these treatments by participants.