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Query: UMLS:C0268596 (EMA)
 2,520 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The objective of this study was to synthesize a hybrid type filler composed of an organic component with inorganic component at the molecular level and to examine the properties of the filler. The composite resin was prepared by mixing synthesized filler with monomer and its physical properties were also examined. An organic-inorganic hybrid filler was synthesized by using 3-methacryloxypropyltrimethoxysilane (3-MPTS), methyltriethyoxysilane (MTES) and methanol silica sol. Firstly, poly3-methacryloxypropyltrimethoxysilane (poly3-MPTS) was synthesized by polymerization of 3-MPTS. A gelation product was obtained by graft-polymerization of poly3-MPTS with condensed organopolysiloxane after the hydrolysis of 3-MPTS, MTES and methanol silica sol. The gelation product was dried and ground to a filler. From the results of thermogravimetry-differential thermal analysis (TG-DTA), the organic-inorganic hybrid filler was found to be composed of 16.5 wt% organic component, 83.1 wt% inorganic component and 0.4 wt% residual water. A trial composite resin was prepared by mixing 55 wt% dimethacryloxyethyl 2,2,4-trimethylhexamethylene diurethane (UDMA), 15 wt% triethyleneglycol dimethacrylate (TEGDMA), 30 wt% 1-fluoro-1,3,3,5,5-penta (methacryloxyethyleneoxy) cyclotriphosphazene [P3N3(F)1 (EMA)5] as a base monomer and then 32.0 wt% of this monomer was mixed with 68.0 wt % of synthesized filler and a photo initiator, comphorquinone (CQ), was added. Compressive strength of the trial visible-light cured composite resin showed 397.0 MPa, and flexural strength and elastic modulus showed 142.5 MPa and 11.5 GPa, respectively. From the results, it was demonstrated that the present organic-inorganic hybrid filler at the molecular level can be used as a composite resin filler.
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PMID:Synthesis of organic-inorganic hybrid fillers at the molecular level and their application to composite resin. 1261 4

The thermal expansion characteristics of dental resins prepared by light-curing of Bis-GMA, TEGDMA, UDMA, Bis-EMA(4) or PCDMA dimethacrylate monomers and of commercial light-cured resin composites (Z-100 MP, Filtek Z-250, Sculpt-It and Alert), the organic matrix resin of which is based on different combinations of the above monomers, were studied by thermomechanical analysis (TMA). This study showed the existence of a glass transition temperature at around 35-47 degrees C for the resins and 40-45 degrees C for the composites; then the coefficient of linear thermal expansion (CLTE) was calculated at the temperature intervals 0-60 degrees C, 0-T(g) and T(g)-60 degrees C. The CLTE values of Bis-GMA, TEGDMA and UDMA resins are similar and lower than those of Bis-EMA (4) and PCDMA resins. The CLTE values of the composites indicated that the major factor that affects the CLTE of a composite is the filler content, but it also seems to be affected by the chemical structure of the matrix resin. TMA on water-saturated samples showed that water desorption takes place during the measurement and that the residual water acts as a plasticizer decreasing the T(g) and increasing the CLTE values. Furthermore, TMA on post-heated samples for 1, 3 or 6h showed, only for the resins, an initial decrease of CLTE and increase of the T(g) after 1h that was not significantly changed after 6h of heating.
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PMID:Thermal expansion characteristics of light-cured dental resins and resin composites. 1496 43

In the present work the elution of residual monomers from light-cured dental resins and resin composites into a 75% ethanol:water solution was studied using High-Performance Liquid Chromatography (HPLC). The resins studied were made by light-curing of bisphenol A glycol dimethacrylate (Bis-GMA), triethylene glycol dimethacrylate (TEGDMA), urethane dimethacrylate (UDMA), ethoxylated bisphenol A glycol dimethacrylate [Bis-EMA(4)] and mixtures of these monomers. The resin composites were made from two commercial light-cured restorative materials (Z100 MP and Filtek Z250), the resin matrix of which is based on copolymers of these monomers. The effect of the curing time on the amount of monomers eluted was investigated. The concentration of the extractable monomers was determined at several immersion periods from 3 h to 30 days. For all the materials studied, it was observed that the chemical structure of the monomers used for the preparation of the resins, which defines the chemical and physical structure of the corresponding resin, directly affects the amount of eluted monomers, as well as the time needed for the elution of this amount. In the case of composites, it seems that the elution process it is not influenced by the presence of filler.
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PMID:Elution study of unreacted Bis-GMA, TEGDMA, UDMA, and Bis-EMA from light-cured dental resins and resin composites using HPLC. 1588 33

Poly(ethylene-co-methyl acrylate) (EMA) membranes with different amounts of methyl acrylate (MA) content were studied in terms of the thermal and mechanical properties, swelling and drug permeation. The increase in MA content in the copolymer significantly increased the percentage of elongation and decreased the tensile strength and modulus of elasticity of the membranes. The degree of swelling of the EMA membranes increased with the ethanol composition and MA content. The contact angle of a sessile drop (10 microL of ethanol/water solution) decreased with an increase in the ethanol fraction suggesting that the membrane wettibility increased with the ethanol content. The flux of diltiazem hydrochloride increased from 0.012 to 0.018 mg cm(-2)h(-1) with an increase in the MA content from 16.5 to 29.0%. By increasing the ethanol fraction from 0.4 to 1.0, the flux of diltiazem hydrochloride into the membranes with 29.0% MA, increased from 2.56 (+/-0.09) x 10(-3) to 18.38 (+/-0.62) x 10(-3) mg cm(-2)h(-1). The permeability coefficient increased from 5.85 x 10(-6) to 3.53 x 10(-4) cm h(-1) with an increase in the ethanol fraction. The flux can also be correlated with the drug solubility in the membrane and ethanol. For example, the solubilities of diltiazem hydrochloride, paracetamol and ibuprofen were 0.64, 6.68 and 504.48 mg cm(-3) in the membrane, respectively. Under the same conditions, the flux for the above mentioned drugs was 0.08 (+/-0.01), 0.53 (+/-0.01) and 45.11 (+/-2.00) mg cm(-2)h(-1).
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PMID:Poly(ethylene-co-methyl acrylate) membranes as rate-controlling barriers for drug delivery systems: characterization, mechanical properties and permeability. 1599 79

A visible light-curing calcium hydroxide cement is presented here and the effects of its resin matrix on the Ca2+ releasing, compressive strength of set material and the pH value of water in which set materials immersed are evaluated. Experimental results show that the effects of the selected resin matrix on Ca2+ releasing, compressive strength and pH value are significant. The calcium hydroxide cement containing BEMA or EMA and HEMA as resin matrix has good properties. The pulp capping test showed that an excellent dentin bridge appeared in dogs capped teeth at 70 days. pulp, pulp capping, calcium hydroxide, visible light-curing, dental materials
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PMID:[Development of a visible light-curing calcium hydroxide cement]. 1612 23

Elution of organic compounds from resin-based dental fillings during their application in the human mouth environment may have a potential impact on the human health. Ethanol, water and other solvents very often present in the human mouth have the ability to penetrate dental fillings placed in the human tooth. Penetration of liquids into the tooth may lead to the liberation of unreacted dental filling ingredients or their degradation products. Determination of these compounds is necessary for better knowledge from possible harmful effects caused by dental fillings. The aim of this study was the isolation and identification of compounds released from resin-modified glass-ionomer cements (RMGICs), resin-based dental materials applied in dentistry. Compounds were extracted from fillings by using four solvents (40% ethanol, water, 1% acetic acid and artificial saliva). Liquid samples containing eluted compounds were then extracted, evaporated and analyzed by using of HPLC-MS (high-performance liquid chromatography-mass spectrometry) and HPLC-DAD (high-performance liquid chromatography-diode array detection) techniques. Almost thirty components (monomers and additives) of RMGICs were identified. The main identified extractables were: Bis-GMA (bisphenol A glycidyl dimethacrylate), Bis-EMA (ethoxylated bisphenol A dimethacrylate), UDMA (urethane dimethacrylate), TEGDMA (triethylene glycol dimethacrylate), HEMA (2-hydroxyethyl methacrylate) as monomers and diphenyliodonium chloride, camphorquinone (initiators), BHA (inhibitor), 4-(dimethylamino) ethyl benzoate (co-initiator) as additives.
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PMID:Identification of organic extractables from commercial resin-modified glass-ionomers using HPLC-MS. 1682 88

This work was aimed at the study of the viscoelastic properties of two current light-cured dental resin composites, Rok (hybrid) and Ice (nanohybrid), by dynamic mechanical analysis, under the influence of variable temperatures and frequencies 1 h after curing or after storage at 37 degrees C either in air or distilled water for 1, 7 or 30 days. They both contain about the same amount of filler, which is strontium aluminosilicate particles, but they have different size distribution, 40 nm-2.5 microm for Rok and 10 nm-1 microm for Ice. The resin matrix of Rok consists of UDMA, while that of Ice consists of UDMA, Bis-EMA and TEGDMA. During dynamic testing elastic modulus (E'), viscous modulus (E'') and loss tangent (tan delta) were determined over a temperature range from 25 to 185 degrees C at a frequency of 0.1, 1.0 or 10.0 Hz. The elastic modulus (8.40 +/- 0.61 GPa) and tan delta (0.114) of Rok at 37 degrees C and 1 Hz was slightly higher than that of Ice (E' = 7.58 +/- 0.50 GPa and tan delta = 0.110) which, however, were not statistically different (P < or = 0.05). Both the light-cured composites showed two T(g) values, at 58 and 121 degrees C for Rok and at 63 and 117.0 degrees C for Ice. The first T(g) has an apparent value, since inside the glass transition region an additional curing reaction occurred of the unreacted C=C methacrylate groups; the second T(g) is due to the new material formed during the DMA scan. During the storage of composites in air or water also an additional curing reaction took place. The nanohybrid Ice showed a slight lower elastic modulus and tan delta than the hybrid Rok at 25-50 degrees C, which, however, were not statistically different (P < or = 0.05).
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PMID:Dynamic mechanical analysis of a hybrid and a nanohybrid light-cured dental resin composite. 1972 42

This work was aimed at the study of some physical properties of two current light-cured dental resin composites, Rok (hybrid) and Ice (nanohydrid). As filler they both contain strontium aluminosilicate particles, however, with different size distribution, 40 nm-2.5 mum for Rok and 10 nm-1 mum for Ice. The resin matrix of Rok consists of UDMA, that of Ice of UDMA, Bis-EMA and TEGDMA. Degree of conversion was determined by FT-IR analysis. The flexural strength and modulus were measured using a three-point bending set-up according to the ISO-4049 specification. Sorption, solubility and volumetric change were measured after storage of composites in water or ethanol/water (75 vol%) for 1 day, 7 or 30 days. Thermogravimetric analysis was performed in air and nitrogen atmosphere from 30 to 700 degrees C. Surface roughness and morphology of the composites was studied by atomic force microscopy (AFM). The degree of conversion was found to be 56.9% for Rok and 61.0% for Ice. The flexural strength of Rok does not significantly differ from that of Ice, while the flexural modulus of Rok is higher than that of Ice. The flexural strengths of Rok and Ice did not show any significant change after immersion in water or ethanol solution for 30 days. The flexural modulus of Rok and Ice did not show any significant change either after immersion in water for 30 days, while it decreased significantly, even after 1 day immersion, in ethanol solution. Ice sorbed a higher amount of water and ethanol solution than Rok and showed a higher volume increase. Thermogravimetric analysis showed that Rok contains about 80 wt% inorganic filler and Ice about 75 wt%.
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PMID:Physical properties of a hybrid and a nanohybrid dental light-cured resin composite. 1979 42

The interactions between an acrylic copolymer, poly ethylmethacrylate/methylacrylate (70:30) (Poly(EMA/MA), and Ca(OH)2 nanoparticles were investigated in order to establish the reciprocal influence of these two compounds on their peculiar properties. The carbonation kinetics of Ca(OH)2 nanoparticles by atmospheric CO2 was investigated by FTIR and SEM measurements and compared to that of a nanocomposite film. CaCO3 formation occurred even in the presence of the copolymer, but only after an induction period of ca. 200 h and with a lower reaction rate. Some implications in cultural heritage conservation dealing with application of nanolime on artifacts previously treated with acrylic copolymers were discussed. Contact angle measurements, mechanical cohesion properties, and water vapor permeability allowed us to conclude that the optimum behavior of nanolime with respect to transpiration was not compromised by the presence of the copolymer, and the behavior in terms of mechanical properties recovery by the application of Ca(OH)2 nanoparticles remained excellent even in the presence of poly(EMA/MA).
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PMID:Interactions between nanostructured calcium hydroxide and acrylate copolymers: implications in cultural heritage conservation. 2388 58

Biodegradable poly(lactic-co-glycolic acid) (PLGA) porous films are developed to support mammary cell growth and function. Such porous polymer matrices of PLGA are generated using the easily implemented water-templating "breath-figure" technique that allows water droplets to penetrate the nascent polymer films to create a rough porous polymer film. Such breath figure-based micropatterned porous films show higher epithelial differentiation and growth than the corresponding flat 2D films, and represent the first instance of using them for tissue culture. Specifically, the breath figure morphology supports robust acinar growth with almost double the number of lobular-alveolar units compared to the 2D cultures. Gene profile analysis indicates that the cells grown on porous polymer films show enhanced expressions of mammary differentiation genes (GATA3, EMA, and INTEGB4) but lower the expression of mesenchymal gene (CALLA). Hormonal stimulation of these cultures dramatically increases expression of progenitor marker gene Notch1. Importantly, cells grown on porous PLGA films exhibit an enhanced resistance to doxorubicin treatment in comparison to 2D cultures. Breath-figure PLGA films show promise in mimicking in vivo mammary functions and can potentially be used to screen chemotherapeutic drugs. The simplicity and ease of fabrication of these polymer films is especially appealing to the development of effective biomaterials to support cell culture and differentiation.
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PMID:Novel "breath figure"-based synthetic PLGA matrices for in vitro modeling of mammary morphogenesis and assessing chemotherapeutic response. 2413 33


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