Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “RESINS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,279 records · Page 71Linked to original sources
PubMed1997

Bond strength and interface micromorphology of an improved resin-modified glass ionomer cement.

PURPOSE: To evaluate the influence of surface treatment with 20% polyacrylic acid containing 3% aluminum chloride (AlCl3) on the shear bond strength of an improved resin-modified glass ionomer cement to enamel and dentin, and to analyze the micromorphology of the cement-tooth interface. MATERIALS AND METHODS: Flat enamel and dentin surfaces of bovine incisors were ground up with sequentially finer abrasives to 1000-grit silicon carbide paper. Each surface was treated with 10% polyacrylic acid (Dentin Conditioner: DC) for 20 seconds or with 20% polyacrylic acid containing 3% aluminum chloride (Cavity Conditioner: CC) for 10 seconds, rinsed, and gently air-dried. A resin-modified glass ionomer cement (Fuji II LC) and its improved version (Fuji II LC-I) were applied to the tooth substrate, and bond strengths measured at periods of 5 minutes, 1 day, and 1 week after light curing. As a control, the resin-modified glass ionomer cements were applied to untreated surfaces and were tested at 1 day. To evaluate the interface micromorphology, specimens were prepared following the adhesive-sandwich technique, cut in equal halves, and observed under a scanning electron microscope (SEM). Additionally, in order to observe the effect of surface pre-treatment of each conditioner on dentin, pre-treated dentin disks were freeze-dried, fractured, and the morphology of the treated and fractured surfaces were observed. RESULTS: Shear bond strength of CC+ Fuji II LC-I to enamel was significantly higher than that of DC+ Fuji II LC at 1 day and 1 week (P < 0.0001). As for dentin, the improved system showed significantly higher bond strength at 5 minutes after light curing (P < 0.001), but bond strengths were not statistically different at 1 day and 1 week. Fracture patterns, examined with a stereomicroscope, were mixed adhesive/cohesive within the cement for all groups. Interface micromorphology, observed with an SEM, suggested the formation of a resin-rich layer and an indistinct zone between the resin-modified glass ionomer cements and the underlying dentin.

Acid Etching, Dental↗
PubMedDate not supplied

Resin-infiltrated dentin layer formation of new bonding systems.

The purpose of this study was to evaluate the resin-dentin interfacial morphology and shear bond strength of several new and experimental dentin bonding systems classified as single-bottle/total etch, multi-step/total etch, and self-etching. Class 1 and 5 cavities were prepared from freshly extracted permanent molars and restored with composite resin. Each bonded sample was cross sectioned and one-half was completely demineralized and deproteinized, while the other half was polished along the cut surface to permit measurement of the thickness of resin-infiltrated dentin layer (RIDL) within intertubular dentin (iRIDL) and around the peritubular walls (pRIDL) of resin tags by SEM. Shear bond strength was measured for all the systems 2 minutes after photocuring. SEM showed iRIDL and resin tags of different morphology depending on material and dentin location. The iRIDL was thinner in superficial dentin and thicker in deep dentin. Peritubular RIDL (pRIDL) was thinner than intertubular RIDL. Bond strength measurements varied from 12 to 21 MPa, depending on the materials used. Self-etching primer systems exhibited the highest bond strength, although one of the one-step/total etch systems also yielded very high values. The contribution of pRIDL to adhesion onto superficial dentin is limited by the small number of tubules. Single-component bonding agents produced SEM morphology and bond strengths similar to those of multi-step systems. Self-etching systems, despite their limited RIDL thickness, produced the highest immediate bond strengths. Bond strength did not correlate well with the thickness and morphology of RIDL.

Adult↗
PubMed2006

Use of dipicolinate-based complexes for producing ion-imprinted polystyrene resins for the extraction of yttrium-90 and heavy lanthanide cations.

Highly selective separation of yttrium (and lanthanides) is of interest for the design of radiopharmaceuticals, and an efficient method based on the ion-imprinting concept is proposed here. The synthesis and structural, thermodynamic and photophysical characterization of complexes of trivalent yttrium and lanthanides with two new vinyl derivatives of dipicolinic acid, HL1 and L2, are described. The feasibility of using ion-imprinted resins for yttrium and lanthanide separation is demonstrated. The resins were obtained by copolymerization with styrene and divinylbenzene and subsequent acid treatment to remove the metal ion. High-resolution Eu luminescence experiments revealed that the geometry of the complexation sites is well preserved in the imprinted polymers. The ion-imprinted polymer based on HL1 proved to be particularly well adapted for yttrium extraction, having a sizeable capacity (8.9+/-0.2 mg g(-1) resin) and a fast rate of extraction (t(1/2)=1.7 min). In addition, lighter and heavier lanthanide ions are separated. Finally, the resin displays high selectivity for yttrium and lanthanide cations against alkali and alkaline earth metals. For instance, in a typical experiment, 10 mg of yttrium was extracted from 5 g of milk ash sample by 2 g of the resin. The good separation properties displayed by the resin based on HL1 open interesting perspectives for the production of highly pure (90)Y and radiolanthanides for medical applications, and for trace analysis of these radiochemicals in food and in the environment.

Cations↗
PubMed2004

Deproteinizing effects on resin-tooth bond structures.

This study investigated the effects of NaOCl on resin-tooth bonds to simulate the situations of long-term durability and caries invasion. Resin-tooth bonded specimens were produced with the use of two resin adhesives (Excite and One-Bond). Resin-tooth bonded beams (adhesive area; 0.9 mm2) were serially sectioned and the specimens were immersed in 10% NaOCl medium for 0 (control), 2, 4, and 6 h after being stored in water for 24 h. After immersion, microtensile bond tests were performed. SEM fractography was conducted to calculate each failure mode by image analysis. In addition, the adhesive interface was examined with the use of TEM. In the control specimens, enamel bond strengths had no difference between Excite (45.6 +/- 15.0) and One-Bond (56.9 +/- 12.9). On the other hand, dentin bond strengths had significant difference between Excite (80.6 +/- 21.2) and One-Bond (50.7 +/- 11.2). The bond strengths decreased with increased storage time for both systems with enamel and dentin bonds. The deteriorated mineralized dentin of beams resulted in bond-strength reduction for resin-enamel bonds. For dentin bonding, the adhesive interface was gradually dissolved from the outer to the center portion of the beam. The depletion of collagen fibrils within the demineralized dentin or hybrid layer deformation was found under SEM and TEM examinations. These morphological changes are responsible for bond strength reduction of resin-dentin bonds.

Dental Materials↗
PubMed2002

A quartz crystal microbalance study of the adsorption of asphaltenes and resins onto a hydrophilic surface.

The adsorption of extracted and purified samples of asphaltenes and resins onto gold surfaces has been studied as a function of bulk concentration using a quartz crystal microbalance with dissipation measurements (QCM-D). With this device, which works equally well in transparent, opaque, and nontransparent samples, the adsorbed amount is measured through a change in resonant frequency of the quartz oscillator. The measured change in dissipation reports on changes in layer viscoelasticity and slip of the solvent at the surface. The results show that the adsorbed amount for resins from heptane corresponds to a rigidly attached monolayer. The adsorbed amount decreases with increasing amount of toluene in the solvent and is virtually zero in pure toluene. Asphaltenes, on the other hand, adsorb in large quantities and the mass and dissipation data demonstrate the presence of aggregates on the surface. The aggregates are firmly attached and cannot be removed by addition of resins. On the other hand, resins and asphaltenes associate in bulk liquid and the adsorption from mixtures containing both resins and asphaltenes is markedly different from that obtained from the pure components. Hence, we conclude that preformed resin aggregates adsorb to the surface. These results are compared and discussed in relation to adsorption from crude oil diluted in heptane/toluene mixtures.

Journal Article↗
PubMed2002

Chemiluminescent investigation of tris(2,2'-bipyridyl)ruthenium(II) immobilized on a cationic ion-exchange resin and its application to analysis.

Tris-(2, 2'-bipyridyl)ruthenium(II) complex, Ru(bpy)(3)(2+), was immobilized on the Dowex-50 W cationic ion-exchange resin. The chemiluminescent characteristics of Ru(bpy)(3)(2+) in solution and in resin form were compared by using batch and flow injection methods. A strong chemiluminescence was observed during the reaction of Ru(bpy)(3)(2+) both in solution and in resin with KMnO(4) or Ce(SO(4))(2) under acidic or basic conditions. The Ru(bpy)(3)(2+) immobilized resin is stable, which can be used at least for 6 months when it reacts with the dilute KMnO(4) solution. Based on this property, Ru(bpy)(3)(2+) immobilized in the resin phase was developed as a flow-through chemiluminescent sensor that could be used to determine oxalate, sulfite and ethanol chemically or electronically with Ru(bpy)(3)(3+) generation on the surface of resin. The limits of detection were 1 x 10(-6) M for oxalate, 0.5% (v/v) for ethanol and 1 x 10(-7) M for sulfite. The method has been successfully applied to determine sulfite in sugar.

Journal Article↗
PubMed2003

Characterization of the sorption of uranium(VI) on different complexing resins.

The sorption of uranium(VI) on two cationic resins containing different complexing groups, the iminodiacetic resin Chelex 100 and the weak carboxylic resin Amberlite CG-50, was investigated. The Gibbs-Donnan model was used to describe and to predict the sorption through the determination of the intrinsic complexation constants. These quantities, even though non-thermodynamic, characterize the sorption as being independent of experimental conditions. The sorption mechanism of the metal on the complexing resins was also studied by adding a competitive soluble ligand that shifts the sorption curves to higher pH values. The ligand competes with the resin for the complexation with the metal ion. Uranium is also strongly sorbed on Chelex 100 at very acid pH, through formation of two complexes in the resin phase: ML with log beta(110i)=-1.16, in more acidic solution, and ML(2 )with log beta(120i)=-5.72. Only the presence of the competitive ligand in solution makes the determination of the second complex possible. Also on Amberlite CG-50 the sorption is strong and involves the formation of the complex ML(2), in more acidic solution, with log beta(120i)=-3.16. In the presence of the ligand EDTA, the complex ML(2)(OH)(2 )was characterized with log beta(12-2i)=-5.15. In all the experiments the hydrolysis reaction in the aqueous phase was quantitatively considered.

Journal Article↗
PubMed1996

Determination of resin acids in pulp mill EOP bleaching process effluent.

Resin acids are tricyclic diterpenoids which are natural constituents of the wood from conifers. They are released from the wood during the manufacture of pulp and paper. These acids are very resistant to chemical degradation and survive the pulping and also the EOP bleaching process (EOP=alkaline extraction, oxygen and peroxide, the chemicals used in the bleaching process). Resin acids were extracted from alkaline medium using liquid-liquid extraction with t-butyl methyl ether and solid phase extraction with RP C18 adsorbent and a highly porous polystyrene-divinylbenzene polymer. After conversion of the acids to their pentafluorobenzyl esters, the extracts were analysed by GC/MS using a 25 m OV17 capillary column. Recovery values for single resin acids were determined by all three extraction methods. The solid phase extraction methods were applied to the analysis of the EOP effluent from a pulp mill bleaching process. 14 different resin acids and one resin acid methyl ester have been identified in the effluent. One of these was an oxo resin acid which might well be a product of the bleaching process.

Journal Article↗
PubMed1995

Exposure to acid anhydrides in three resin and one cushioned flooring manufacturing plants.

Acid anhydrides are reactive organic chemicals of low molecular weight which cause occupational asthma. No previous research on the relationship between exposure to these chemicals and respiratory sensitization and development of occupational asthma has been reported. A retrospective cohort study was carried out in four factories (three alkyd resin factories and one cushioned flooring factory) to investigate the nature of exposure-response relationships for sensitization to phthalic anhydride (PA), trimellitic anhydride (TMA) and maleic anhydride (MA). This paper describes the results of full-shift and task-specific exposure measurements. Exposure to PA was low in relation to the Occupational Exposure Standard (OES). The highest full-shift PA exposures occurred among resin operators in the resin factory that used solid PA as compared to other resin factories where liquid PA was used. Arithmetic mean exposure levels to TMA and MA in the resin factories were well below their respective OESs. Short-term high exposures occurred during loading of acid anhydrides into the reactors and sampling and testing of the resin. Relatively high full-shift exposure to TMA occurred in the cushioned flooring factory, although no high peak exposures were detected.

Anhydrides↗
PubMed1994

Leaching and cytotoxicity of formaldehyde and methyl methacrylate from acrylic resin denture base materials.

Acrylic resin dentures have the potential to elicit irritation, inflammation, and an allergic response of the oral mucosa. Studies of substances leachable from acrylic resins, their cytotoxicity to cultured cells, and means of reducing their leaching were systematically conducted. Under in vivo and in vitro conditions, formaldehyde and methyl methacrylate were significantly leached into human saliva and saliva-substitute buffer, especially from autopolymerized resins. Both leachable substances showed cytotoxic potentials in the range of their leaching concentrations. Formaldehyde was cytotoxic at lower concentrations than methyl methacrylate. Preleaching in water reduced subsequent leaching of both formaldehyde and methyl methacrylate, and the amount of reduction depended on an increase in the preleaching temperatures. Immersion of acrylic resin dentures in hot water (50 degrees C) before insertion is recommended, especially for autopolymerized resins used either for rebasing or as denture base materials, to minimize the risk of adverse reactions in patients who wear acrylic resin dentures.

Cell Count↗
PubMed1987

Sorption studies of heavy metal ions on a novel chelating resin and its application in the stripping of mercury (II).

A chelating resin containing a stable thiol group was synthesised, using polystyrene as the starting material. The resin is stable towards conc. HCl, 0.1M HNO(3) and 0.1M NaOH. The resin shows affinity towards Ag(+), Hg(2+), Bi(3+), Pb(2+), Cu(2+), Zn(2+) and Cd(2+). Extraction of these metal ions as a function of pH, kinetics of exchange and breakthrough capacities is evaluated. The selectivity of the resin for the metal ions is in the order Ag(+) > Hg2+ > Cu2+ > Pb2+ > Cd2+ > Zn2+. The equilibrium constants for exchange and kinetics of exchange are favourable for the recovery of mercury from lean sources. Application of the resin in the stripping of mercury from chlor-alkali plant affluent, and in the enrichment of mercury from seawater, have been investigated. Mercury sorbed resin can be regenerated using 5% thiourea in 0.1M HCl.

Journal Article↗
PubMed2005

Study of Burseraceae resins used in binding media and varnishes from artworks by gas chromatography-mass spectrometry and pyrolysis-gas chromatography-mass spectrometry.

In the present work, a study attempting to characterize the Manila elemi and Mexican copal resins from the Burseraceae family, which are used as components of varnishes and binding media of artworks, has been carried out. A new GC-MS method involving the use of methyl chloroformate as derivatisation reagent has been proposed. A second method which uses pyrolysis-GC-MS and hexamethyldisilazane as derivatization reagent has also been applied. Characterization of the main components of the mono-, sesqui- and triterpenoid fractions occurring in the raw materials has been achieved. Both alpha- and beta-amyrin have been established as the major triterpenoid compounds occurring in these resins together with hop-22(29)-en-3beta-ol, found only in the Mexican copal. Artificially aged samples of Manila elemi and Mexican copal have also been analysed in order to study the stability of the triterpenoid components of the resins and their possible use as marker molecules. The results obtained indicate that these molecules, in particular, alpha- and beta-amyrin undergo oxidation processes during both artificial and natural ageing. Nevertheless, hop-22(29)-en-3beta-ol could be selected as marker compound for Mexican copal. The proposed methods of analysis have been applied to real paint samples extracted from paintings in which Mexican copal was present as the main component of an "oleoresin" binding medium to assess their ability for identifying this product when used in artworks. Satisfactory identification of this resin is obtained by means of GC-MS whereas Py-GC-MS provides, in general, weaker signals for the components of the resin. Additionally, the influence of the pigments present in real samples on the resin ageing process has been considered.

Burseraceae↗
PubMed2004

Effects of mastic resin and its essential oil on the growth of proteolytic Clostridium botulinum.

Studies were done to determine the effect of mastic resin and its essential oil, alone and in conjunction with ethanol, on the growth of proteolytic strains of Clostridium botulinum in media, and on neurotoxin production in challenge studies with English-style crumpets. Preliminary studies, using a spot-on-the-lawn method, indicated that high levels of mastic resin in ethanol ( approximately 8% w/w) were required for complete inhibition of all strains of C. botulinum tested, but mastic resin in ethanol had a greater anti-botulinal effect than ethanol alone. However, only low levels of mastic oil ( approximately 0.3% v/v) were required for inhibition of proteolytic strains of C. botulinum. Both studies showed a strain specific inhibition, with C. botulinum type A strains being more sensitive to mastic resin and its essential oil than type B strains. However, mastic resin in ethanol proved to be more effective when used as a vapor phase inhibitor applied to cotton pads and placed inside inoculated plates than when added directly to media. While both mastic resin and its essential oil inhibited the growth of proteolytic strains of C. botulinum in vitro, they failed to inhibit neurotoxin production in challenge studies with C. botulinum in English-style crumpets.

Botulinum Toxins↗
PubMed2005

Solid-state storage of Ag nanoparticles in anion exchange resin beads and their recovery.

This paper reports the idea and describes a method of reversible storage and recovery of silver nanoparticles (NPs) in anion exchange resin beads based on the principle of ion exchange. We also report that similar exchange of NPs was not possible with cation exchange resins. The Ag NPs were stored by simple exchange of anions of the resins, which were activated with OH- and NO3- ions. FTIR spectroscopic measurements support that the Ag NPs were exchanged with NO3- ions in the resins. The so-stored NPs could be regenerated by addition of NaBH4 solution to the resins. These NPs were recovered and subsequently utilized for catalytic reduction of an organic dye (eosin). Powder X-ray diffraction (XRD) pattern indicated storage of the NPs in the form of various oxides of silver in the resin, with the peak value of intensity corresponding to XRD of the NPs not changing with time. Scanning electron microscopic measurements show that the NPs in the beads were stable for over a month without the formation of any apparent agglomeration.

Journal Article↗
PubMed1999

In vitro cytotoxicity of orthodontic bonding resins on human oral fibroblasts.

Polymerization of bonding resins is compromised by atmospheric oxygen, giving rise to a layer of low molecular weight chemical species commonly known as the oxygen inhibited layer. The aim of this study was to evaluate the cytotoxic effect of this layer on primary cultures of human oral fibroblast. The cytotoxic effect related to the modes of polymerization of seven commercially available orthodontic bonding resins was also evaluated statistically. Each material was polymerized into 12 resin disks of standardized dimensions. Half of them were washed with 99% acetone to remove the oxygen inhibited layer. In duplicates, human oral fibroblasts were exposed to the intact and washed resin disks in tissue culture inserts. Cell viability was assessed by tetrazolium bromide reduction assay (MTT) 1, 3, and 6 days after exposure. Glass disks served as controls. ANOVA was used to test for statistical significance. Overall, the presence of an oxygen inhibited layer renders bonding resins 33% more cytotoxic (P <.01, F = 11.83, DF = 1). Light-cured and chemically cured 2-pastes materials had their mean cytotoxicities approximating their inert controls over 6 days. In chemically cured liquid-paste materials, the viability of human oral fibroblasts was only 37% (P <.001, F = 26.4, DF = 2) comparing to the control, 64% on day 1, 30% on day 3 and 14% on day 6. This suggested that the oxygen inhibited layer formed on the surface of bonding resins is an important cytotoxic source in vitro. Chemically cured liquid-paste materials were more cytotoxic than light-cured and chemically cured 2-paste materials. Further investigation into the influence of the modes of polymerization on materials' toxicodynamic effect is warranted to verify its clinical implication.

Analysis of Variance↗
PubMed2001

Water structures in ion-exchange resin particles: solvation dynamics of Nile Blue A.

The structures of water, partitioned in cation-exchange resin particles, were studied on the basis of fluorescence dynamics of Nile Blue A (NB). The fluorescence lifetime of NB in the resin was longer than that in water and increased with increasing cross-linking density of the resin (rho). The results demonstrated that the water structures in the resin were significantly different from those in water and dependent on rho. A study on solvation dynamics of NB in the resin, reflecting structured water around the ion-exchange group, revealed the roles of "bound water" molecules in the water structures, since the solvent relaxation time (tauS) in the resin was much longer than that in water and depended on p; tauS increased from 34 to 55 ps with increasing rho from 2 to 8%. The origin of the rho dependence of tauS was discussed in terms of the separation distance between the ion-exchange groups, and the effects of the counterion of the ion-exchange group on the solvation processes were also discussed.

Journal Article↗
PubMed2000

Rasta silanes: new silyl resins with novel macromolecular architecture via living free radical polymerization

Heating TEMPO-methyl resin with dialkylsilane styrenes affords larger resin beads via living free radical polymerization. The new silyl resins prepared by this solvent-free suspension polymerization protocol have been coined "Rasta silanes". Rasta silanes have a novel macromolecular architecture typified by long straight chain polymers bearing the silanes which emanate from the phenyl rings of a cross-linked polystyrene core. By careful selection of comonomers during the polymerization step, loading capacity, silane spacing, and the relative distance of the silane moieties from the resin core can be controlled. The consistently high-loading Rasta silane resins produced can be easily converted into either a reactive silyl chloride or triflate to subsequently anchor alcohols and phenols to the solid phase. Cleavage from the resin can be mediated by treatment with HF.pyridine, TFA solutions, or TBAF.

Journal Article↗
PubMed1998

High Catalytic Activity of Chiral Amino Alcohol Ligands Anchored to Polystyrene Resins.

Enantiomerically pure (2S,3S)-2,3-epoxy-3-phenylpropanol (3) has been anchored to Merrifield resins with different degrees of cross-linking and functionalization. The resulting epoxy-functionalized resins 4 have been submitted to completely regioselective (C-3 attack) and stereospecific ring-opening with secondary amines [piperidine (a), N-methylpiperazine (b), and cis-2,6-dimethylpiperidine (c)] in the presence of lithium perchlorate to afford (2R,3R)-3-(dialkylamino)-2-hydroxy-3-phenylpropoxy resin ethers 5a-c. The progress of these two processes has been monitored by (13)C gel-phase NMR spectroscopy. Polymer-supported amino alcohols 5a-c have been evaluated as catalytic ligands in the enantioselective addition of diethylzinc to benzaldehyde, best results being obtained with the cis-2,6-dimethylpiperidine containing ligand 5c. Analogously, (2R,3R)-3-(cis-2,6-dimethylpiperidino)-3-phenyl-1,2-propanediol (11) has been anchored to a 2-chlorotrityl chloride resin (Barlos resin) in dichloromethane in the presence of diisopropylethylamine, and the anchoring process has been also monitored by (13)C gel-phase NMR spectroscopy. The resulting resin 12 has subsequently been used as a chiral ligand in the catalytic addition at 0 degrees C of diethylzinc to a family of fourteen representative aromatic and aliphatic aldehydes 8a-n, to afford the corresponding (S)-1-substituted 1-propanols 10a-n with a mean enantiomeric excess of 92%.

Journal Article↗