Fluoride supplements (tablets, drops, lozenges or chewing gums) for preventing dental caries in children.

BACKGROUND: Dietary fluoride supplements were first introduced to provide systemic fluoride in areas where water fluoridation is not available. Since 1990, the use of fluoride supplements in caries prevention has been re-evaluated in several countries. OBJECTIVES: To evaluate the efficacy of fluoride supplements for preventing dental caries in children. SEARCH METHODS: We searched the Cochrane Oral Health Group's Trials Register (to 12 October 2011), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 3), MEDLINE via OVID (1950 to 12 October 2011), EMBASE via OVID (1980 to 12 October 2011), WHOLIS/PAHO/MEDCARIB/LILACS/BBO via BIREME (1982 to 12 October 2011), and Current Controlled Trials (to 12 October 2011). We handsearched reference lists of articles and contacted selected authors. SELECTION CRITERIA: We included randomised or quasi-randomised controlled trials comparing, with minimum follow-up of 2 years, fluoride supplements (tablets, drops, lozenges) with no fluoride supplement or with other preventive measures such as topical fluorides in children less than 16 years of age at the start. The main outcome was caries increment measured by the change in decayed, missing and filled tooth surfaces (DMFS). DATA COLLECTION AND ANALYSIS: Two review authors, independently and in duplicate, assessed the eligibility of studies for inclusion, and carried out risk of bias assessment and data extraction. In the event of disagreement, we sought consensus and consulted a third review author. We contacted trial authors for missing information. We used the prevented fraction (PF) as a metric for evaluating the efficacy of the intervention. The PF is defined as the mean caries increment in controls minus mean caries increment in the treated group divided by mean caries increment in controls. We conducted random-effects meta-analyses when data could be pooled. We assessed heterogeneity in the results of the studies by examining forest plots and by using formal tests for homogeneity. We recorded adverse effects (fluorosis) when the studies provided relevant data. MAIN RESULTS: We included 11 studies in the review involving 7196 children.In permanent teeth, when fluoride supplements were compared with no fluoride supplement (three studies), the use of fluoride supplements was associated with a 24% (95% confidence interval (CI) 16 to 33%) reduction in decayed, missing and filled surfaces (D(M)FS). The effect of fluoride supplements was unclear on deciduous or primary teeth. In one study, no caries-inhibiting effect was observed on deciduous teeth while in another study, the use of fluoride supplements was associated with a substantial reduction in caries increment.When fluoride supplements were compared with topical fluorides or with other preventive measures, there was no differential effect on permanent or deciduous teeth.The review found limited information on the adverse effects associated with the use of fluoride supplements. AUTHORS' CONCLUSIONS: This review suggests that the use of fluoride supplements is associated with a reduction in caries increment when compared with no fluoride supplement in permanent teeth. The effect of fluoride supplements was unclear on deciduous teeth. When compared with the administration of topical fluorides, no differential effect was observed. We rated 10 trials as being at unclear risk of bias and one at high risk of bias, and therefore the trials provide weak evidence about the efficacy of fluoride supplements.

Roughness and light scattering of ion-beam-sputtered fluoride coatings for 193 nm

Scattering characteristics of multilayer fluoride coatings for 193 nm deposited by ion beam sputtering and the related interfacial roughnesses are investigated. Quarter- and half-wave stacks of MgF2 and LaF3 with increasing thickness are deposited onto CaF2 and fused silica and are systematically characterized. Roughness measurements carried out by atomic force microscopy reveal the evolution of the power spectral densities of the interfaces with coating thickness. Backward-scattering measurements are presented, and the results are compared with theoretical predictions that use different models for the statistical correlation of interfacial roughnesses.

Remaining phosphorus and sodium fluoride pH in soils with different clay contents and clay mineralogies

The remaining phosphorus (Prem) has been used for estimating the phosphorus buffer capacity (PBC) of soils of some Brazilian regions. Furthermore, the remaining phosphorus can also be used for estimating P, S and Zn soil critical levels determined with PBC-sensible extractants and for defining P and S levels to be used not only in P and S adsorption studies but also for the establishment of P and S response curves. The objective of this work was to evaluate the effects of soil clay content and clay mineralogy on Prem and its relationship with pH values measured in saturated NaF solution (pH NaF). Ammonium-oxalate-extractable aluminum exerts the major impacts on both Prem and pH NaF, which, in turn, are less dependent on soil clay content. Although Prem and pH NaF have consistent correlation, the former has a soil-PBC discriminatory capacity much greater than pH NaF.

Stabilization of fluoroindate glasses by magnesium fluoride and other heavy metal fluorides

Their extended transparency in the IR makes them attractive for use as optical fibers for CO laser power delivery and optical amplification. This paper firstly describes the spectacular stabilizing effect of MgF2 on the binary system InF3-BaF2. The investigation of the InF3-BaF2-MgF2 system led to samples up to 5mm in thickness. Further optimization of this system was achieved by incorporation of limited amounts of other fluorides and resulted in increased resistence to devitrification. The second approach of this work was concerned to the investigation of the pseudo-ternary system InF3-GdF3-GaF3 at constant concentrations of ZnF2-SrF2-BaF2-NaF. Several compositions were studied in this system. The samples presented a better thermal stability when compared to other families of fluoride glasses. Therefore, these glasses seem to be very promising for the fabrication of special optical fibers. Thermal data are reported.

Selective detection of fluoride based on a pyridinium n-phenolate-calix[4]pyrrole displacement assay: an undergraduate laboratory experiment

A two-step experiment is proposed for a third year class in experimental organic chemistry. Over a period of five weeks, the students synthesized calix[4]pyrrole, a receptor that is highly selective for fluoride, and a pyridinium N-phenolate dye. Subsequently, the students used the synthesized compounds to investigate a displacement assay on the basis of the competition in acetonitrile between fluoride and the dye for calix[4]pyrrole. The experiment increased the students' skills in organic synthesis and in the characterization of organic compounds, provided a very attractive and accessible illustration of important supramolecular phenomena, and allowed the study of a chromogenic chemosensor.

Protection of plasmid DNA by a Ginkgo biloba extract from the effects of stannous chloride and the action on the labeling of blood elements with technetium-99m

Ginkgo biloba extract (EGb) is a phytotherapeutic agent used for the treatment of ischemic and neurological disorders. Because the action of this important extract is not fully known, assays using different biological systems need to be performed. Red blood cells (RBC) are labeled with technetium-99m (Tc-99m) and used in nuclear medicine. The labeling depends on a reducing agent, usually stannous chloride (SnCl2). We assessed the effect of different concentrations of EGb on the labeling of blood constituents with Tc-99m, as sodium pertechnetate (3.7 MBq), and on the mobility of a plasmid DNA treated with SnCl2 (1.2 µg/ml) at room temperature. Blood was incubated with EGb before the addition of SnCl2 and Tc-99m. Plasma (P) and RBC were separated and precipitated with trichloroacetic acid, and soluble (SF-P and SF-RBC) and insoluble (IF-P and IF-RBC) fractions were isolated. The plasmid was incubated with Egb, SnCl2 or EGb plus SnCl2 and agarose gel electrophoresis was performed. The gel was stained with ethidium bromide and the DNA bands were visualized by fluorescence in an ultraviolet transilluminator system. EGb decreased the labeling of RBC, IF-P and IF-RBC. The supercoiled form of the plasmid was modified by treatment with SnCl2 and protected by 40 mg/ml EGb. The effect of EGb on the tested systems may be due to its chelating action with the stannous ions and/or pertechnetate or to the capability to generate reactive oxygen species that could oxidize the stannous ion.

NMR studies of strong hydrogen bond to fluoride ion

Systems such as MF/diol (M = alkali metal) and }1F/carboxylic acid were subjected to IH, I9F and 13C nmr study to investigate the nature of the very strong H-bonding of fluoride ions with these systems. Evidence indicates a strong H-bond in diol-fluoride systems (~H ~ -(56) kJ mol-I) which is stronger than most 'typical' H-bonds (~H = -(12-40) kJ mol-I), but weaker than that reported for carboxylic acid-fluoride systems (~H ~ -(120) kJ mol-I). Approximate fluoride H-bonded shifts (o(OH)OHF) were evaluated for MF/diol systems from IH chemical shift measurements. No direct correlation was observed between I9F chemical shift and H-bond strength. Thermodynamic parameters were calculated from temperature dependent IH and 19F shifts. Preliminary studies of BUn 4NF-acetylacetone by I9F nmr were conducted at low temperatures and a possible Jmax (ca. 400 Hz) is reported for the fluoride ion H-bonded to acetylacetone. Highfield shift for non-protonated carbons and downfield shift for protonated carbons were observed in carboxylic acid/KF systems. Significant decreas$in I3C TI due to strong H-bonding to fluoride ions were also detected in both diol and carboxylic acid systems. Anomalous results were obtained, such as increasing NOE with increasing temperature in neat 1,2-ethanediol (values above the theoretical maximum of 1.988) and in 1,2-ethanediol/KF. The large 13C NOE's for carboxy carbons in neat carboxylic acids which are. further enhanced by the addition of KF are also unusual.

The calculation of force constants and normal co-ordinates II: methyl fluoride

The mathematical difficulties which can arise in the force constant refinement procedure for calculating force constants and normal co-ordinates are described and discussed. The method has been applied to the methyl fluoride molecule, using an electronic computer. The best values of the twelve force constants in the most general harmonic potential field were obtained to fit twenty-two independently observed experimental data, these being the six vibration frequencies, three Coriolis zeta constants and two centrifugal stretching constants DJ and DJK, for both CH3F and CD3F. The calculations have been repeated both with and without anharmonicity corrections to the vibration frequencies. All the experimental data were weighted according to the reliability of the observations, and the corresponding standard errors and correlation coefficients of the force constants have been deduced. The final force constants are discussed briefly, and compared with previous treatments, particularly with a recent Urey-Bradley treatment for this molecule.

The infra-red spectra of silyl fluoride and silyl fluoride-d3

Infra-red spectra have been recorded for silyl fluoride and silyl fluoride-d3 at a resolution of circa 0·3 cm-1. Rotational structure has been observed for parallel fundamentals in both molecules, and for all perpendicular fundamentals. In both SiH3F and SiD3F the A1 and E species deformation modes interact strongly via a Coriolis perturbation; this has been analysed, and the band origin of v5 for SiH3F is reassigned. A hybrid-orbital force field based on the experimental data is also reported.

The general harmonic force field of methyl fluoride

The complete general harmonic force field of methyl flouride was recalculated using the most recent literature frequency, Coriolis ζ, and centrifugal distortion data for 12CH3F, 13CH3F, 12CD3F, 12CHD2F and 12CH2DF. The anharmonic corrections applied to the observed frequency data and the adopted molecular geometry are considered to be more realistic than those used hitherto. There is excellent overall agreement between the fitted force constants and the highest quality ab initio force field currently available.

Comparative study of Barium Fluoride thin films produced by ion-beam sputtering and thermal evaporation

Coatings and filters for spaceflight far-infrared components require a robust, non-absorptive low-index thin film material to contrast with the typically higher refractive index infrared materials. Barium fluoride is one such material for the 10 to 20µm wavelength infrared region, however its optical and mechanical properties vary depending on the process used to deposit it in thin film form. Thin films of dielectric produced by thermal evaporation are well documented as having a lower packing density and refractive index than bulk material. The porous and columnar micro structure of these films causes possible deterioration of their performance in varied environmental conditions, primarily because of the moisture absorption. Dielectric thin films produced by the more novel technique of ion-beam sputtering are denser with no columnar micro structure and have a packing density and refractive index similar to the bulk material. A comparative study of Barium Fluoride (BaF2) thin films made by conventional thermal evaporation and ion-beam sputtering is reported. Films of similar thicknesses are deposited on Cadmium Telluride and Germanium substrates. The optical and mechanical properties of these films are then examined. The refractive index n of the films is obtained from applying the modified Manifacier's evvelope method to the spectral measurements made on a Perkin Elmer 580 spectrophotometer. An estimate is also made of the value of the extinction coefficient k in the infrared wavelength transparent region of the thin film. In order to study the mechanical properties of the BaF2 films, and evaluate their usefulness in spaceflight infrared filters and coatings, the thin film samples are subjected to MIL-F-48616 environmental tests. Comparisons are made of their performance under these tests.

Electronic properties of liquid hydrogen fluoride: A sequential quantum mechanical/Born-Oppenheimer molecular dynamics approach

The electronic properties of liquid hydrogen fluoride (HF) were investigated by carrying out sequential quantum mechanics/Born-Oppenheimer molecular dynamics. The structure of the liquid is in good agreement with recent experimental information. Emphasis was placed on the analysis of polarisation effects, dynamic polarisability and electronic excitations in liquid HF. Our results indicate an increase in liquid phase of the dipole moment (similar to 0.5 D) and isotropic polarisability (5%) relative to their gas-phase values. Our best estimate for the first vertical excitation energy in liquid HF indicates a blue-shift of 0.4 +/- 0.2 eV relative to that of the gas-phase monomer (10.4 eV). (C) 2010 Elsevier B.V. All rights reserved.