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At least 757 records · Page 42Linked to original sources
PubMed1999

Macroporous poly(glycidyl methacrylate-triallyl isocyanurate-divinylbenzene) matrix as an anion-exchange resin for protein adsorption.

A novel macroporous poly(glycidyl methacrylate-triallyl isocyanurate-divinylbenzene) matrix was prepared by a radical suspension copolymerization. The matrix contained epoxy groups, so diethylaminohydroxypropyl groups were coupled to the matrix, leading to an anion-exchange resin. We studied the components, surface and pore structures of the anion-exchange resin by Fourier transform infared spectroscopy and scanning electron microscopy (SEM). SEM observations showed that the resin abounded in macropores as large as 3 to 8 microns both in the surface and the interior. The back-pressure of the column packed with the resin was modest even at a high flow-rate (60.2 cm/min). Then, bovine serum albumin (BSA) was used as a model protein to examine the adsorption properties of the anion-exchange resin. The results showed that under optimum conditions the resin had a capacity as high as 22.8 mg BSA/g wet resin, or 68.7 mg/g dry resin. The adsorbed protein could be desorbed by increasing the liquid phase ionic strength. Most importantly, the matrix had little nonspecific adsorption for BSA before introducing the ion-exchange groups.

Adsorption↗
PubMed2002

Simultaneous uptake of anionic surfactants and micellar-solubilized contaminants using anion-exchange resins.

This research studied simultaneous uptake of anionic surfactants and micellar-solubilized organic contaminants by anion-exchange resins. Anionic surfactant molecules adsorbed onto the positively charged resin mainly through electrostatic attraction, while the micellar-solubilized contaminants were excluded from aqueous solutions once the remaining micelles could no longer solubilize them. Data suggest that the excess contaminants adsorbed onto the resin skeleton and admicelle layer formed on the resin surface through hydrophobic interactions and eventually partitioned into the resin gel phase matrix. In batch adsorption, the contaminant solubilization capacity did not decrease linearly with respect to surfactant concentration decrease due to the increased solution counterion activity during anion exchange, and caused "delayed" contaminant uptake relative to that of the surfactant. No such effect occurred in continuous column adsorption, where the surfactant and contaminant breakthrough occurred simultaneously. Surfactant head and tail group properties, along with resin structure and particle size significantly affected surfactant and contaminant uptake rates. Relative to recovering the surfactant, the high exchange potential of the anionic surfactant prevented effective surfactant desorption, even at high electrolyte concentration and in the presence of a cosolvent. The resin matrix also had high affinity for the partitioned contaminant, and the contaminant elution from the resin seemed to be controlled by equilibrium partitioning.

Adsorption↗
PubMed1995

Scanning electron microscopic evaluation of two compaction techniques using a composite resin as a root canal filling material.

The canals of 20 human dental roots were instrumented using a a step- back technique. The smear layer was removed, and the canals were obturated with composite resin. Two different techniques of compaction were used: either vertical or lateral motions were used to condense composite resin inside the root canal that was then photopolymerized layer by layer using the argon laser (488 nm). The beam was delivered into the root canal by means of an optical fiber 320 micrometers in diameter. Longitudinal and cross-sections of the samples and resin replicas of the root canals were examined using a light and scanning electron microscope. Scanning electron microscopic examination revealed that laterally compacted resin fillings showed fewer voids than those obtained by vertical compaction. In both experimental groups, adhesion of the resin to the dentin walls, pulled-out resin tags, microfailure, and resin fracture, leaving a layer of resin associated with the wall surface were observed.

Argon↗
PubMed1991

Scanning electron microscopy observations on the penetration and structure of resin tags in bleached and unbleached bovine enamel.

The purpose of this study was to determine the effect of hydrogen peroxide on the ability of composite resin to penetrate bovine enamel etched with phosphoric acid. In a previous investigation, the flattened enamel surfaces of extracted bovine incisors were immersed in either saline (control) or 35% hydrogen peroxide (experimental) for 5 or 30 min before or after acid etching with 37% phosphoric acid gel for 60 s. A standard-sized light-cured resin cylinder was then bonded to the enamel surface. The specimens were stored in a water bath at 37 degrees C for 1 day or 7 days, after which the enamel-resin bond was tensile tested to failure. Sixteen of the failed specimens (eight control and eight experimental) were randomly selected for the present scanning electron microscopic study to evaluate the appearance of the resin tags at the resin-enamel interface. In the control specimens, the tags were well defined and contiguous with resin which was uniformly adherent to the enamel surface. In the experimental specimens, large areas of the enamel surface were free of resin. When tags were present, they were fragmented, poorly defined, and penetrated to a lesser depth than in the saline controls. The changes observed suggest that there may be interaction between resin and residual peroxide at or near the enamel surface.

Acid Etching, Dental↗
PubMed2003

Marginal integrity of ceramic inlays luted with a self-curing resin system.

OBJECTIVE: Aim of this study was to observe the efficacy of two different composite cements on the prevention of marginal deterioration around adhesive ceramic inlay restorations, under laboratory conditions, and to test the null hypothesis that different luting procedures cannot affect sealing ability of luted inlays. METHODS: Twenty-six standardized mesio-occlusal Class II cavities were prepared in extracted posterior teeth. Class II inlays were fabricated with IPS Empress II system following the manufacturer's instructions. The samples were divided into two groups of 13 teeth each at random. Group 1: The ceramic inlays of Group 1 were luted using Excite DSC and an experimental self-curing resin cement (Multilink, Vivadent); in this group, Excite DSC was self-activated and not light-cured. Group 2: Excite DSC in combination with a dual-curing resin cement (Variolink II, Vivadent) was used (as control). In this group Excite DSC was light-cured for 20s separately, before resin cement application. The 'wet' bonding technique was followed. Three samples of each group were selected at random for SEM observations, while the other 10 samples were processed for marginal leakage. The bonding mechanism to dentin and resin cement thickness was evaluated. RESULTS: Samples of both groups showed resin tag and adhesive lateral branch formation. In Group 1 the hybrid layer was mainly uniform along the interface between dental substrates and adhesive material, and resin cement thickness was between 20 and 85 microm. At the cervical margin no gap was detected. In Group 2 the cement thickness was between 30 and 110 microm and hybrid layer formation was observed along the interface but at the cervical margin it was not always uniform and continuous. Resin tag formation was uniform in both groups. At cervical margins, 80% of Group 1 samples showed a perfect seal at the dentin-cementum margins, and 90% at enamel margins. Group 2 samples showed only 50% of cervical margins free from leakage and 80% at the occlusal enamel margins. Statistically significant differences were found at cervical margins between the two groups, while no significant differences were found at enamel site. CONCLUSIONS: It can be concluded that the self-curing adhesive-resin cement combination can properly seal Class II porcelain inlays.

Dental Bonding↗
PubMed1997

On the adsorption of hyaluronan and ICAM-1 to modified hydrophobic resins.

Hyaluronan is a negatively charged glycosaminoglycan that occurs in connective tissue and has a wide range of mechanical and cell biological functions. The purpose of this study was to utilize affinity chromatography resins for purification of detergent (Triton X-100) solubilized hyaluronan binding proteins from liver, the major organ of hyaluronan clearance from the blood. However, during these studies we made the unexpected finding that hyaluronan binds to Sepharose substituted with a hexamethylene chain, a commonly used spacer arm in affinity chromatography resins, capped with either a terminal primary amine or a terminal acetoamido group. Hyaluronan did not bind the hydrophobic resins hexyl- or octyl-Sepharose under the same conditions. It was also found that rat liver intercellular adhesion molecule-1 binds to resins containing the hexamethylene spacer arm, an interaction which could be inhibited with free hyaluronan oligosaccharides. Finally, we have determined that resins with ethylene spacer arms show no affinity for hyaluronan and can therefore be used to immobilize hyaluronan for chromatography of hyaluronan binding proteins. By using this resin we have purified two proteins of approximately 200 and 400 kDa from rat liver endothelial cells. In summary, this study demonstrates the efficacy of certain "capped-hydrophobic" resins for binding hyaluronan; these resins may provide a novel means for the study and/or purification of this glycosaminoglycan. This study further demonstrates the importance of the careful design of appropriate affinity columns for the specific purification of hyaluronan binding proteins.

Adsorption↗
PubMed2001

Influence of hyperbranched multi-methacrylates for dental neat resins on proliferation of human gingival fibroblasts.

We have previously shown that hyperbranched multi-methacrylate (H-MMA)-modified dental resins have VLC activities, lower polymerization shrinkage, and improved mechanical properties, compared to the 2,2-bis[4-(2-hydroxy-3-methacryloyolxypropoxy)phenyl]propane/triethyleneglycol dimethacrylate (BisGMA/TEGDMA) neat resin. The results are due to the unique molecular structure and high molecular weight of H-MMA intermediates. The purpose of this study was to evaluate the biocompatibility of H-MMA-modified dental neat resins. The cell proliferation of three human gingival fibroblast strains on either H-MMA, BisGMA/TEGDMA, or a polystyrene disk was examined. Following 10 days of cell proliferation, there was no statistical difference in cell number between H-MMA-modified and unmodified resin disks. H-MMA-modified resins had less free monomer leaching than the unmodified resin but showed similar properties in water sorption and contact angle values. All these results suggest that the biocompatibility of H-MMA-modified dental neat resins is as good as that of commercially used BisGMA/TEGDMA resin and H-MMA has potential applications in dental composites.

Adult↗
PubMedDate not supplied

The adsorption of lead and copper from aqueous solution on modified peat-resin particles.

Raw peat was modified with sulfuric acid, then mixed modified with resin to prepare the modified peat-resin particles. Using the batch experimental systems, the removal of heavy metals (copper and lead) on the modified peat-resin particles was investigated. The data of the adsorption isotherm could be fitted by the Langmuir equation well. The adsorption rate of heavy metals on modified peat-resin particles was very swift. The removal processes of heavy metals on modified peat-resin particles could be well described by pseudo-second order model. The adsorption rate of lead was affected by the initial heavy metal concentration, initial pH, particle size, agitation speed and particle mass. In the adsorption of heavy metals (lead and copper) on the modified peat-resin particles, ion exchange was the major reaction mechanism. Desorption data showed that the lead adsorbed by modified peat-resin particle could be desorbed by 0.5 N or 1.0 N HNO3. The desorption rate was swift. The experiments indicated that the modified peat-resin particles have great potential for the removal of heavy metals from wastewater.

Adsorption↗
PubMed2006

Comparison of some newly synthesized chemically modified Amberlite XAD-4 resins for the preconcentration and determination of trace elements by flow injection inductively coupled plasma-mass spectrometry (ICP-MS).

XAD copolymer resins may be functionalized with heavy metal ion-selective ligands either by covalent linkage to the polymer backbone or by impregnation. These resins may be tailored to be specific for certain heavy metals by adjusting the retention and elution parameters. For the synthesis of immobilized Amberlite XAD-4 copolymer resins that are expected to preconcentrate a number of transition and heavy metals, the Schiff base method was chosen. For this purpose the copolymer was nitrated, reduced to the corresponding amine and converted to the imine compounds via a Schiff base reaction using different organic aldehyde compounds. The interactions of 8 elements (Cd, Co, Cu, Mn, Ni, Pb, U and Zn) with the resins were qualitatively investigated. Optimal pH for retention was typically 6-8 for most resins although one could be used at pH 5 and elution was achieved using 0.1 M HNO3. The resins were characterized by FTIR, SEM and elemental analysis. It was demonstrated that the resins could be used to preconcentrate ultra-trace analytes from natural waters, and analysis of environmental certified reference materials using FI-ICP-MS showed good agreement with the certified values. Metal retention capacities were also calculated using a batch system and were found to compare favorably with other resins reported in the literature.

Absorption↗
PubMed2003

The effect of the addition of poly(methyl methacrylate) fibres on some properties of high strength heat-cured acrylic resin denture base material.

The self-reinforcement of acrylic resin with butadiene styrene surface treated poly(methyl methacrylate) fibres has been reported to have the potential to substantially improve the transverse bend strength of conventional heat-cured acrylic resin. The aim of this study was to investigate the effect of the addition of butadiene styrene surface treated poly(methyl methacrylate) fibres in cross-ply arrangement to high impact acrylic resin on the transverse and impact strength. Specimens were prepared as specified in the International Standard Organization and British Standards for the Testing of Denture Base Resins (ISO 1567, 1988; BS 2487, 1989) and the British Standard Specification for Orthodontic resins (BS 6747, 1987) for transverse bend and impact testing. The impact strength was measured using a Zwick pendulum impact tester and the transverse bend strength measured using a Lloyds Instruments testing machine. The results showed that the impact strength was not improved with the addition of fibres, high impact acrylic resin with fibres (LF) 11.1 kJ m-2 and high impact acrylic resin (L) (12.5 kJ m-2). The modulus of rupture was decreased with the addition of fibres (57.8 MPa) for (LF) compared with (60.4 MPa) for (L). The modulus of elasticity was also reduced with the addition of fibres (1834.9 MPa) (LF) and 2086.2 MPa (L) as was the peak load (LF) (50.8 N) and (L) (55.8 N). It was concluded that the addition of surface treated poly(methyl methacrylate) fibres in cross-ply arrangement to high strength acrylic resin did not produce an improvement in the impact or transverse strength and cannot be recommended as a method of reinforcement.

Acrylic Resins↗
PubMed1999

Occupational allergic contact dermatitis from unsaturated polyester resin in a car repair putty.

BACKGROUND: Unsaturated polyester (UP) resins are widely used as cements in car repair painting to produce a smooth surface before the final painting. We report two car painters with hand and face dermatitis who were sensitized to a UP resin used for car repair cements. METHODS: Patch testing with commercial substances and ingredients and extracts from UP resins was used to verify the sensitivity. RESULTS: Both patients showed an allergic patch test reaction to a UP resin. They also had an allergic patch test reaction to diethyleneglycol maleate (DEGM), an extract of a UP resin. CONCLUSIONS: Both patients had been patch tested elsewhere with negative results because UP resins had not been used for patch testing. Accordingly, patients with dermatitis who have been exposed to UP resins need to be patch tested with UP resins. The specific chemical causing allergic contact dermatitis in our patients was DEGM.

Automobiles↗
PubMed1999

Conjugation of 7-oxodehydroabietic acid to lysine, a haptenation mechanism for an oxidized resin acid with dermal sensitizing properties.

This article explores protein conjugation of 7-oxodehydroabietic acid, a resin acid found in both aerosol from soldering with rosin flux and in rosin solids. In a murine model, conjugation (haptenation) of resin acids to proteins is required to generate antibodies against rosin. Hydroperoxy resin acids are dermal sensitizers, with haptenation thought to occur via radical mechanisms. Dermal sensitization to 7-oxodehydroabietic acid has been observed, although no radical haptenation mechanism has been proposed to explain the sensitizing properties of this compound. Conjugation of L-lysine to 7-oxodehydroabietic acid was predicted, with a Schiff base (or imine) linkage formed between C-7 of the resin acid and a free amino group of lysine. Fast atom bombardment mass spectrometry provided evidence of the conjugate; a small peak was seen for the conjugate (M+H)+ ion in aqueous ethanol with 20 mM concentrations of the free resin and amino acids. A larger conjugate peak was observed with addition of tertiary amine as a mild basic catalyst, and the intensity of the conjugate peak exceeded that of the precursors upon replacement of the ethanol with benzene. Resin acids accumulate in the plasma membrane, a non-aqueous environment apparently conducive to conjugation of 7-oxodehydroabietic acid with lysine side chains of membrane proteins. The result would be dehydroabietic acid covalently bound to protein, which could lead to interaction with immune cells having resin acid specificity. The haptenation mechanism presented may be involved in allergic contact dermatitis and occupational asthma observed from exposure to resin acid solids and aerosols. As sampling and analytical methods have been previously demonstrated for 7-oxodehydroabietic acid, this compound may be a useful exposure marker with relevance to negative health effects such as occupational asthma.

Abietanes↗
PubMed2005

Pyrolysis of foundry sand resins: a determination of organic products by mass spectrometry.

Pyrolysis-gas chromatography-mass spectrometry (MS) was used to identify the major organic products produced by pyrolysis of three foundry sand resins: (i) Novolac and (ii) phenolic urethane (PU) (both phenol-formaldehyde based resins) and (iii) furan (furfuryl alcohol based resin). These resins are used in the metal casting industry as a "sand binder" for making cores (used to produce cavities in molds) and molds for nonferrous castings. During the casting process, the cores and molds are subjected to intense heat from the molten metal. As a result, the organic resins undergo thermal decomposition and produce a number of complex organic compounds. In this study, the organics were tentatively identified by MS after pyrolysis of the resins at 750 degrees C. The major thermal decomposition products from the Novolac, PU, and furan resins were derivatives of phenol, benzene, and furan, respectively. Compounds identified that are of potential environmental concern were benzene, toluene, phenol, o- and p-xylene, o- and m-cresol, and polycyclic aromatic hydrocarbons. Pyrolysis of the Novolac resin resulted in the generation of the most compounds of environmental concern. Because there is interest in beneficially using foundry molding sands in manufactured soils and other agricultural products, it is necessary that organic thermal decomposition products be identified to ensure environmental protection.

Conservation of Natural Resources↗
PubMed1999

Removal of orthodontic bonding resin residues by CO2 laser radiation: surface effects.

OBJECTIVE: The purpose of this in vitro study was to evaluate the potential use of pulsed CO2 laser radiation to remove selectivity residues of orthodontic bonding resin that remain after debonding of fixed orthodontic appliances. SUMMARY BACKGROUND DATA: Current techniques used for removal of orthodontic bonding resin after removal of fixed appliances include rotary instruments, debonding pliers, and ultrasonic scalers. These techniques, however, are time-consuming and inefficient, and may damage tooth enamel. METHODS: A standardized cylinder of orthodontic bonding resin was bonded to the buccal surfaces of 100 extracted premolar teeth, which were then divided into 10 groups of 10 specimens each. In 9 groups, the resin was ablated using 1 of 9 different laser parameters, while in the remaining control group, the resin was removed with a slow speed tungsten carbide bur. Specimens were evaluated by light microscopy and scanning electron microscopy (SEM) to assess the amount of resin remaining and the extent of the damage to the underlying enamel. RESULTS: The 2 W/100 ms combination was optimal, with a high efficiency of resin removal and the least enamel damage. Higher laser powers increased the extent of enamel damage without enhancing resin removal. CONCLUSIONS: This laser technique appears promising, however, further studies of the extent of thermal changes at the level of the dental pulp are necessary to establish more fully the risk-benefit ratio.

Analysis of Variance↗
PubMed2004

Enamel surface roughness following debonding using two resin grinding methods.

The purpose of this study was to assess quantitatively the roughness of the enamel surface following debonding using two resin removal methods. The enamel surface of 30 premolar crowns was covered with black tape with a 3 mm window on the middle buccal third to standardize the area of analysis. The initial enamel surfaces were subjected to profilometry, registering four roughness parameters (Ra, Rq, Rt and Rz). The brackets were bonded to the plaster-embedded enamel surfaces with a chemically cured, no-mix adhesive, and debonded after 1 week. Resin removal in half of the specimens was performed with an eight-bladed carbide bur, and in the other half with an ultra-fine diamond bur, both attached to a high speed hand piece; a second profilometric measurement was made after resin removal. Finishing of all surfaces was achieved with Soflex discs and a third registration of roughness followed. The duration of each resin removal protocol was also recorded. The results were analysed with two-way ANOVA and the Newman-Keuls test with the two resin grinding modes and the three intervals serving as discriminating variables (n = 15). For the duration results, a one-way ANOVA was used. Significant differences (P < 0.05) were observed with respect to enamel roughness parameters between the two resin grinding methods used, while there was no consistent roughness-reducing effect of finishing with Soflex discs. Resin removal with a diamond bur was achieved in approximately half the time compared with the eight-bladed bur. The increase in most roughness variables induced by the debonding procedures was not reversed at the end of the finishing stage, regardless of the resin removal protocol used, suggesting an irreversible effect on enamel texture.

Analysis of Variance↗
PubMed2000

Changes in volatile terpene and diterpene resin acid composition of resistant and susceptible white spruce leaders exposed to simulated white pine weevil damage.

Induced (traumatic) resin in white spruce (Picea glauca (Moench) Voss) leaders resistant or susceptible to the white pine weevil (Pissodes strobi Peck) was analyzed for volatile terpenes and diterpene resin acids after simulated white pine weevil damage. Leaders from 331 trees were wounded just below the apical bud with a 1-mm diameter drill, coinciding with the natural time of weevil oviposition in the spring. Leaders were removed in the fall, and the bark and xylem from the upper and lower regions of the leader extracted and analyzed by gas chromatography. Unwounded trees had low amounts of resin in xylem compared with bark. In response to wounding, volatile terpenes and diterpene resin acids increased in the upper xylem (area of wounding), with resistant trees showing a greater increase than susceptible trees. Wounding caused monoterpenes in particular to decrease in the lower region of the leader (away from the drilled area) in greater amounts in susceptible trees than in resistant trees. In response to wounding, the proportion of monoterpene to resin acid increased in the upper and lower xylem of resistant trees, and slightly increased in the upper xylem of susceptible trees. Monoterpene-enriched resin is more fluid than constitutive resin, and probably flows more readily into oviposition cavities and larval mines, where it may kill immature weevils. Loss of resin components in the lower xylem suggested catabolism and transport of these materials to the site of wounding; however, energetic and regulatory data are necessary to confirm this hypothesis. This study provides a basis for measuring the ability of a tree to undergo traumatic resinosis that could be used to screen for resistance to white pine weevil.

Animals↗
PubMed1998

Effect of resin monomer composition on toothbrush wear resistance.

The purpose of this study was to compare the toothbrush abrasion resistance of seven different experimental resins which were made by changing the composition of resin monomers. The experimental resins were made by mixing four kinds of dental resin monomers (Bis-GMA, UDMA, TMPT and TEGDMA), camphorquinone (1 wt%), dimethylaminoethyl methacrylate (2 wt%) and 2,6-di-tert-butyl-p-cresol (0.05 wt%). The resin specimens were stored in air for 2 weeks, and then put on a toothbrush abrasion testing machine. After 100000 strokes, the wear loss of each specimen was determined by weight change during the wear test. TMPT-TEGDMA resin showed the most wear resistance, while Bis-GMA- and UDMA-based resins showed increased wear resistance with an increased content of TEGDMA. Also, a inverse relationship between the microhardness number and the amount of wear of the respective resins was confirmed.

Analysis of Variance↗
PubMed2004

Comparison of the tensile bond strengths of cast metal crowns luted with resin cements.

The limitation of photoactivation of dual-polymerized resin cements along the margins of metal restorations may adversely affect the mechanical properties of these cements, thus impairing the retention of restorations. The aim of this study was to assess the bond strength of cast metal crowns cemented with three dual-polymerized resin cements, using a chemically-activated resin cement and zinc phosphate as controls. Fifty nickel-chromium alloy crowns were cast and randomly assigned to five groups of equal size. Castings were cemented on their corresponding metal dies with one of the tested luting agents: Scotchbond Resin Cement, Enforce and Panavia F (dual-polymerized resin cements), Cement-It (chemically-activated resin cement) and Zinc Phosphate Cement (zinc phosphate cement). Specimens were stored in distilled water at 37 degrees C for 24 h and then loaded in tension until failure. Panavia F and Zinc Phosphate Cement provided the highest and lowest bond strength means, respectively. Scotchbond Resin Cement, Enforce and Cement-It cements exhibited similar intermediate values, but with statistically significant difference compared to the other materials (P < 0.05). Even with the restriction or absence of light activation, all tested dual-polymerized resin cements produced significantly higher bond strength than did the zinc phosphate cement and yielded similar or better results than the chemically activated cement. It should be pointed out that the findings of this study relate to a test scenario which does not mimic clinical circumstances and that further work is required to identify the clinical significance of the reported tensile bond strength differences between the different luting materials.

Chromium Alloys↗