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At least 1,081 records · Page 60Linked to original sources
PubMed1996

The effects of pulsed Nd:YAG laser irradiation with fluoride on root surface.

This study evaluated the effects of pulsed Nd:YAG laser treatment on root surface in vitro with or without fluoride. Fifty specimens of human teeth were randomly assigned to five different treatment groups: (1) untreated group; (2) laser-treated only; (3) laser-treated after applying black ink; (4) laser-treated after applying 38% Ag(NH3)2F for 1 min; (5) laser-treated followed by applying 2% NaF for 4 min. Following their respective treatments, all specimens were prepared for evaluation by light microscopy, scanning electron microscopy, and EDX (Energy dispersive x-ray spectroscopy). Specimens from group 2 to 4 exhibited gross alterations of root surface not observed in controls such as pitting, crater formation, cracking, and porous globules. The specimens of group 5 had rough surfaces with some particles of approximately 1-micron diameter on the root surface. The fluoride uptake into the root measured by EDX was higher in groups 4 and 5. The depth of penetration of fluoride and silver was approximately 20 microns. Under light microscopy, the specimens of group 2, 3, 4, and 5 revealed some melted cementum, with no changes of underlying dentin. The results of this in vitro study suggested that the laser irradiation with or without fluoride, altered the morphology of the root surface and improved the fluoride uptake into the root surface. Whether the laser-induced surface changes with or without fluoride are beneficial to prevention of root surface caries needs to be studied further.

Cariostatic Agents↗
PubMed2001

Effect of desensitizers on bond strength of adhesive luting agents to dentin.

The current study investigates the influence of three dentin hypersensitivity treating agents (Gluma CPS, MS Coat and Saforide) on bond strength to dentin of two luting agents (Panavia Fluoro Cement and Super-Bond C & B). Sixty bovine dentin substrates were divided into 12 combinations of four treatment conditions (Gluma CPS, MS Coat, Saforide and control) and three adhesive systems (AD Gel sodium hypochlorite + Panavia Fluoro Cement, Panavia Fluoro Cement without AD Gel and Super-Bond C & B). After bonding the treated teeth to steel rods, 24-h tensile bond strengths were determined, and average values (n=5) were compared by analysis of variance (ANOVA). Without application of the desensitizers, bond strengths of the two groups (Super-Bond C & B, 10.2 MPa; AD Gel + Panavia, 11.5 MPa) were comparable, and they were greater than the group bonded with the Panavia material with no AD Gel conditioning (7.1 MPa). Application of the Saforide ammoniated silver fluoride desensitizer reduced bond strength of both the Super-Bond and Panavia luting agents, whereas the MS Coat polymeric agent negatively affected bond strength of the Panavia cement only. The use of the Gluma desensitizer did not affect bond strength of any of the three adhesive systems, and the bond strength of the Panavia cement with the AD Gel conditioning was not reduced by application of any of the three desensitizers. The four combinations of two desensitizers (MS Coat and Gluma CPS) and two adhesive systems (Super-Bond C & B and AD Gel + Panavia) are deemed to be applicable to fixed prosthodontic treatment.

Acid Etching, Dental↗
PubMed2001

Reaction of metallotetraphenylporphyrins on hydroxyl-modified silver colloid and Ag2O colloid by surface-enhanced Raman scattering.

This paper reports a novel reaction of metallotetraphenylporphyrins on hydroxyl-modified silver colloid and Ag2O colloid. Surface-enhanced Raman spectra of Ag(II) and Cu(II) complexes of tetraphenylporphyrin (TPP) adsorbed on the hydroxyl-modified Ag colloid and Ag2O colloid have been studied. The time-dependent SERS spectra of MTPP (M = Ag, Cu) on hydroxyl-modified Ag colloid were recorded and dramatic change on SERS spectra was observed. The final spectra were found to be strikingly different from the corresponding normal Raman spectra (NRS), with the appearance of new Raman bands at 1614. 1417, 947, 674 and 292 cm(-1). The UV-visible absorption spectrum of MTPP on hydroxyl-modified Ag colloid exhibits a broad shoulder near 460 nm. Similar spectral phenomena were also observed for AgTPP and CuTPP adsorbed on Ag2O colloid. The observed spectral alterations were ascribed to new species formation due to the irreducible oxidation of MTPP on the colloids.

Colloids↗
PubMed1996

Fluoridation of hydroxyapatite powder by ammonium hexafluorosilicate.

Diamine silver fluoride [AgF: (NH3)2AgF] is a unique fluoride solution used clinically in Japan for primary teeth. AgF has been shown to reduce dental caries and dentine hypersensitivity. However, AgF also stains teeth black due to sulfide precipitation and thus is unacceptable for permanent teeth. In the present study, the potential value of ammonium hexafluorosilicate [SiF: (NH4)2SiF6], which has a formula similar to that of AgF but contains no Ag, was studied with respect to its ability to fluoridate apatite. Hydroxyapatite [HAP: Ca10(PO4)6(OH)2] powder was treated with several topical fluoride solutions, i.e. neutral sodium fluoride, acidulated phosphate fluoride (APF) along with AgF and SiF. Following treatment, the HAP powders were analyzed for their fluorine content, crystallinity changes, and solubility in acidic solution. The highest level of fluoridated HAP [FAP: Ca10(PO4)6(OH)xF2-x] was observed in HAP powder treated with SiF, even though more total fluorine in the form of FAP and CaF2 was observed in HAP powder samples treated with APF. Presumably as a consequence of this higher level of FAP formation after SiF treatment, the highest level of crystallinity along with the lowest solubility in acidic solution were observed in HAP powder treated with SiF solution. We concluded, therefore, that SiF may have potential value for use as a topical fluoride solution.

Acidulated Phosphate Fluoride↗
PubMed2004

Part II: surface-enhanced Raman spectroscopy investigation of methionine containing heterodipeptides adsorbed on colloidal silver.

Surface-enhanced Raman scattering (SERS) spectra of methionine (Met) containing dipeptides: Met-X and X-Met, where X is: L-glycine (Gly), L-leucine (Leu), L-proline (Pro), and L-phenylalanine (Phe) are reported. Using pre-aggregated Ag colloid we obtained high-quality SERS spectra of these compounds spontaneously adsorbed on colloidal silver. Additionally, we measured Raman spectra (RS) of these heterodipeptides in a solid state as well as in acidic and basic solutions. The RS and SERS spectra of Met-X and X-Met presented in this work appear to be different. One of the most prominent and common features in the SERS spectra of all these dipeptides is a band in the 660-690 cm(-1) range that is due to the C-S stretching, v(CS), vibration of Met. This suggests that all the abovementioned compounds adsorb on the silver surface through a thioether atom. On the other hand, the SERS spectra of X-Met show clearly that not only the S atom but also the carboxylate group interact with the colloid surface as manifested by the enhancement of bands in the 920-930 and 1380-1396 cm(-1) regions. These bands are ascribed to the v(C-COO(-)) and v(sym)(COO(-)) vibrations, respectively. Additionally, a SERS spectrum of Phe-Met indicates that the interaction of the thioether atom, amine group, and aromatic side chain with the silver surface is favorable and may dictate the orientation and conformation of adsorbed peptide.

Adsorption↗
PubMed2004

Syntheses, structures and antimicrobial activities of water-soluble silver(I)-oxygen bonding complexes with chiral and racemic camphanic acid (Hca) ligands.

Water-soluble, relatively light-stable, chiral and achiral silver(I) complexes [[Ag(2)(ca)(2)]](n) and [[Ag(2)(ca)(2)(Hca)(2)]](n)(R- and S-Hca =(1R,4S)- and (1S,4R)-4,7,7-trimethyl-3-oxo-2-oxabicyclo[2.2.1]heptane-1-carboxylic acid, respectively) prepared from the reaction of Ag(2)O with chiral and racemic Hca in 1:2 and 1:4 molar ratios were characterized by elemental analysis, TG/DTA, FTIR, and solution ((1)H, (13)C and (109)Ag) and solid-state ((13)C) NMR spectroscopy. Crystallography revealed that unique 2(1) helical polymer and zigzag structures were formed on self-assembly of the dimeric units in the crystals of [[Ag(2)(S-ca)(2)]](n) and three [[Ag(2)(ca)(2)(Hca)(2)]](n). In the crystal of [[Ag(2)(S-ca)(2)]](n) two 2(1) helices and a loop were observed in the stair-like polymer structure, whereas zigzag and a loop were seen in the crystals of three [[Ag(2)(ca)(2)(Hca)(2)]](n). Carbon NMR spectra in the solid state and in D(2)O indicated that these polymeric structures were loosely bound and fast ligand-exchange reactions took place in aqueous solution. The complexes, [[Ag(2)(ca)(2)]](n) and [[Ag(2)(ca)(2)(Hca)(2)]](n), showed a wide spectrum of effective antimicrobial activity as anticipated for weak silver(i)-O bonding complexes. Similar antimicrobial activity of [[Ag(2)(ca)(2)]](n) and [[Ag(2)(ca)(2)(Hca)(2)]](n) against selected microorganisms suggested that ligand exchangeability played an important role as well as the coordination geometry of the silver(i) ion.

Anti-Bacterial Agents↗
PubMed1983

Acute toxicity of some silver salts of sulfonamides in mice and the efficacy of penicillamine in silver.

The silver salt of 2-metanilamido-5-chloropyrimidine (AgMCP) and the sodium, amminosilver and trimethylphosphite-silver salts of 3',5'-dichlorobenzenesulfonanilide (NaDBS, AgNH3DBS and AgP(OCH3)3DBS were synthesized as possible antibiotic of antiparasitic drugs. All the organosilver compounds were extremely water-insoluble. For animal studies these, and other reference compounds, were given as fine suspensions in an Emulphor-safflower oil mixture. The ip LD50's in mice in mmol/kg were: 1.67 for NaDBS, 0.22 for silver acetate (AgAc), 0.15 for AgP(OCH3)3DBS, 0.13 for AgMCP and 0.10 for AgNH3DBS. When given by mouth, 15 mmol AgAc/kg produced a high mortality, but none of the organosilver compounds caused death in maximal doses (1.9 to 2.6 mmol/kg) that could be given based on considerations of total volume and stability of the suspension. All the silver compounds, including AgAc, produced a similar toxic syndrome with initial hyperexcitability, ataxia, central nervous depression, labored breathing, loss of righting reflex and death. Most deaths occurred between 12 and 24 hours after dosing. In contrast, animals given NaDBS often died within 3 hours although the major signs were very similar to those produced by the silver compounds. When given ip as a single dose 30 minutes after AgAc, D-penicillamine was effective in reducing mortality, but it had no effect on the mortality of the organosilver compounds. Histological studies revealed similar patterns of silver deposition, especially in the liver and kidneys, at 6, 18 and 24 hours after the organosilver compounds and after AgAc. We conclude that the presence of silver contributes significantly to the acute toxicity of these sulfonamides although they may dissociate free silver less readily than does AgAc.

Animals↗
PubMed2004

Silver-catalyzed [2 + 2] cycloadditions of siloxy alkynes.

We have described the first [2 + 2] cycloadditions of siloxy alkynes with a range of unsaturated carbonyl compounds. The reactions are efficiently promoted by substoichiometric amount of silver trifluoromethanesulfonimide and display excellent regio- and diastereoselectivity combined with a broad substrate scope. Our studies have established unambiguously the stepwise mechanism of this process and provided evidence for a novel role of silver in the catalytic cycle of the reaction, which involves silver-based complexation and activation of siloxy alkyne toward the subsequent 1,4-addition.

Alkynes↗
PubMed2005

Self-assembly of a series of extended architectures based on polyoxometalate clusters and silver coordination complexes.

Three unusual compounds based on polyoxometalate building blocks, [(H2O)5Na2(C6NO2H4)(C6NO2H5)3Ag2][Ag2IMo6O24(H2O)4] x 6.25H2O (1), [(H2O)4Na2(C6NO2H5)6Ag3][IMo6O24] x 6H2O (2), and (C6NO2H6)2[(C6NO2H5)2Ag][Cr(OH)6Mo6O18] x 4H2O (3), have been synthesized and characterized by elemental analysis; IR, XPS, and ESR spectroscopy; TG analysis; and single-crystal X-ray diffraction. Compound 1 is constructed from the cationic two-dimensional (2D) coordination polymer sheets which are constituted of [(H2O)5Na2(C6NO2H4)(C6NO2H5)3Ag2]3+ and anionic [Ag2IMo6O24(H2O)4]3- chains as pillars, forming a three-dimensional (3D) supramolecular framework via weak Ag-O interactions. Compound 2 is composed of the well-defined [IMo6O24]5- building blocks, which are linked through trinuclear Ag-pyridine-3-carboxylic acid, [(C6NO2H5)6Ag3]3+, fragments into a one-dimensional (1D) hybrid chain; adjacent chains are further connected by sodium cations to yield a novel 2D network. Compound 3 has a 1D chainlike structure constructed from [Cr(OH)6Mo6O18]3- building blocks and Ag-pyridine-4-carboxylic acid coordination units. The crystal data for these compounds are the following: 1, triclinic, P1, a = 13.280(3) A, b = 13.641(3) A, c = 16.356(3) A, alpha = 89.68(3) degrees, beta = 88.31(3) degrees, gamma = 75.87(3) degrees, Z = 2; 2, triclinic, P1, a = 11.978(2) A, b = 12.008(2) A, c = 13.607(3) A, alpha = 116.14(3) degrees, beta = 108.85(3) degrees, gamma = 93.86(3) degrees, Z = 1; 3, triclinic, P1, a = 10.458(2) A, b = 10.644(2) A, c = 12.295(3) A, alpha = 97.40(3) degrees, beta = 112.38(3) degrees, gamma = 113.59(3) degrees, Z = 1.

Journal Article↗
PubMed2001

Calcium dicaesium silver thiocyanate dihydrate.

The title compound, CaCs2[Ag2(SCN)6]*2H2O, forms a continuous structure where the Ag atoms form chains with S atoms in the c-axis direction. The chains are bonded together through Cs and Ca atoms. The crystal water of the structure is bonded to the Ca atoms, which lie on centers of symmetry.

Journal Article↗
PubMed2006

Design of nevirapine derivatives insensitive to the K103N and Y181C HIV-1 reverse transcriptase mutants.

Nevirapine (Viramune) belongs to the first generation of non-nucleoside reverse transcriptase inhibitors (NNRTIs). Its efficiency is limited by drug resistant mutations, such as K103N and Y181C, so, the aim of this work was to design novel nevirapine analogues insensitive to the K103N and Y181C HIV-1 RT. 360 Nevirapine derivatives were designed using a combinatorial library design approach and these compounds were docked into the binding pocket of mutant HIV-1 RT enzyme structures, using the GOLD program. 124 Compounds having a GoldScore higher than that of nevirapine (55.00 and 52.00 for K103N and Y181C mutants, respectively) were first retrieved and submitted to a topological analysis with the SILVER program. Consequently, 31 compounds presenting a significant percentage of the surfaces buried upon binding (>80%) and exhibiting hydrogen bonds to either N103 or C181 residues of the HIV-RT were selected. To ensure that these compounds had hydrogen bonding interaction to either N103 or C181 residues, their interaction energies were estimated by quantum chemical calculations (QCCs). Finally, QCCs represent an alternative method for performing post docking procedure.

Anti-HIV Agents↗
PubMed1999

The formation of explosive compounds in bitumen/nitrate mixtures

Ignition of various bitumen/nitrate mixtures was examined using a new method of thermal analysis, developed in the present study, in order to determine the self-ignition temperatures (SIT) of the sample materials. The effects on the SIT of transition elements, particularly silver, and the heating rates were examined. The same bitumen/nitrate mixtures were prepared by mixing bitumen, NaNO(3), Ni(NO(3))(2) and either AgNO(3) or AgI. The sample heating rates were in the range from 0.5 to 4.0 degrees C/min. In the present work, SIT was found to be independent on the heating rate when AgI is added, while SIT was found to depend on the heating rate when AgNO(3) was added. The activation energy E(a) for the ignition of bitumen/nitrate mixtures has been calculated to be 30 kJ/mol. The suspected initiator of the ignition is thought to be silver fulminates or related compounds.

Journal Article↗