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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It has been reported that the tensile bond strength between the 4-META/MMA-TBB resin and dentin pretreated with 10% citric/3% ferric chloride solution decreased after immersion in water for 2 years. The current study investigated the effect of an experimental dentin conditioner on the bonding of 4-META/MMA-TBB resin to dentin after thermocycling. The experimental conditioner was an aqueous solution of 10% ascorbic acid and 5% ferric chloride (Exp). Human teeth were prepared to expose flat dentin surfaces. These were treated sequentially with 40% phosphoric acid, 10% sodium hypochlorite, and the experimental conditioner. A commercially available dentin conditioner, an aqueous solution of 10% citric/3% ferric chloride (10-3) was used for a control group. Stainless steel rods were bonded to the pretreated dentin surfaces with the use of the 4-META/MMA-TBB resin. Tensile bond strengths were determined after 0, 5,000, 10,000, 20,000 themocycles. All data were analyzed by ANOVA, and differences among groups were analyzed by Duncan's new multiple range test (n = 10, p < 0.05). The experimental group showed no significant decrease in bond strength through 20,000 thermocycles, while the control group exhibited significant decrease after 10,000 thermocycles. Mean bond strength of the experimental groups were significantly higher than those of the control group at both 10,000 and 20,000 thermocycles. A hybrid layer could not be identified in SEM micrographs of the experimental groups. 10-3-conditioned specimen SEMs displayed crack formation between the adhesive resin and a hybrid layer. The experimental dentin pretreatment improved the bond strength of a 4-META/MMA-TBB resin to human dentin compared to 10-3 treatment after thermocycling.
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PMID:Improvement of the bond strength of 4-META/MMA-TBB resin to collagen-depleted dentin. 1562 72

Although 4-META/MMA-TBB resin has adhesive properties to dentin, and has been clinically used for the bonding treatment of vertically fractured roots and apicoectomy, there has not been any investigation on the adhesion of 4-META/MMA-TBB resin to cementum. The purpose of this in vitro study was to evaluate the bonding and the sealing ability of 4-META/MMA-TBB resin to cementum. Bovine root cementum and dentin surfaces were treated with a citric acid and ferric chloride solution, and the 4-META/MMA-TBB resin was applied on the treated surfaces before testing. The microtensile bond strength and the leakage levels obtained for the cementum were almost equal to those for the dentin. In SEM and TEM observations, a hybrid layer approximately 2-3 microm in thickness was observed at the interface between the resin and the cementum. It is concluded that 4-META/MMA-TBB resin adhered to cementum via a hybrid layer on cementum, as previously reported for dentin.
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PMID:Hybrid layer seals the cementum/4-META/MMA-TBB resin interface. 1668 Jun 94

Nano-sized TiO(2) or SiO(2)/TiO(2) particles were prepared by hydrolysis and condensation reactions in aqueous media, followed by mixing with poly(AA-co-MMA) latex to form different composites, then blending with poly(ethylene terephthalate), PET. The TGA results of composites indicated that negative charged latexes had greater interaction with TiO(2)/ or SiO(2)/TiO(2) particles through strong electrostatic forces, while cationic latexes incorporated with TiO(2) or SiO(2)/TiO(2) particles by pH induced coagulation, carbonyl group chelation and hydrogen bonding. The soapless latex polymer particles showed lower ability of adsorption to TiO(2) particles due to the decrease of total surface area of these larger particles. If SiO(2)/TiO(2) particles were used instead of TiO(2) particles, unexpected high adsorption result was observed. Morphology results observed by SEM showed that PET blended with positive charged composites was more homogeneous than PET blended with negative charged composites. DSC results also indicated that the T(g) of PET was increased, melting temperatures (T(m) or T(m)(')) were increased, and the temperature range of crystallization was narrowed after blending with the composites. The presence of composites affected the mobility and packing of PET molecular chains therefore changing the thermal properties of PET.
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PMID:Synthesis of nano-sized TiO(2)/poly(AA-co-MMA) composites by heterocoagulation and blending with PET. 1725 Aug 47

The purposes of this study were twofold, namely to evaluate: (1) the effect of hybridization on microtensile bond strength (microTBS) to dentin, and (2) the ultrastructure of the dentin-adhesive interface with 4-META/MMA-TBB resin after acid-base challenge. Dentin surfaces, which received no treatment (NT), 65% phosphoric acid (PA), or 10% citric acid-3% ferric chloride (10-3), were bonded with a 4-META/MMA-TBB resin. To evaluate dentin bond strength, microTBS test was performed at a crosshead speed of 1 mm/min. For ultrastructural evaluation of the adhesive interfaces, SEM was used to examine the interfaces of the bonded specimens after acid-base challenge. The microTBS of NT was not determined, while that of 10-3 was significantly higher than that of PA (p < 0.05). With PA and 10-3, the hybrid layer was clearly observed, but no so for the acid-base resistant zone. Wall lesion was found in NT only. In conclusion, hybridization is vital to improving microTBS to dentin and enhancing resistance at the adhesive interface against acid-base challenge.
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PMID:Effect of hybridization on bond strength and adhesive interface after acid-base challenge using 4-META/MMA-TBB resin. 1949 98

In the present paper, Eu0.5 Tb0.5 (TTA)3 Phen was synthesized and Eu0.5 Tb0.5 (TTA)3 Phen/PMMA was prepared by in-situ polymerization. The structure of Eu0.5 Tb0.5 (TTA)3 Phen/PMMA was characterized by FTIR spectra. Microscopic morphology and photoluminescence properties were investigated by SEM photographs and fluorescence spectra. The results indicated that polymer parts were attached with the rare-earth molecular parts in the composite luminescent materials. And Eu0.5 Tb0.5 (TTA)3 Phen/PMMA could emit mostly characteristic fluorescence of europium ion and intense red fluorescence with a peak wavelength at 611.8 nm and a bandwidth of 10.4 nm (Purity: 0.9905) under UV excitation at 365 nm. Its fluorescence intensity was found to be influenced with the content of MMA. It w as demonstrated that Eu0.5 Tb0.5 (TTA)3 Phen/PMMA was an excellent red photoluminescent rare-earth polymer material.
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PMID:[Spectral analysis and photoluminescence properties of Eu-Tb codoped polymer]. 1962 66

In this study, poly(acrylic)/SiO2/EuL3 x 2H2O hybrid thin films were prepared from various acrylic monomers (MMA and EDMA/TMPTA), lanthanide metal complexs (EuL3 x 2H2O, L = pyridine carboxylic acid), and monodispersed colloidal silica with a coupling agent, 3-(trimethoxysilyl)propyl methacrylate (MSMA). It was a combination of the sol-gel reaction, thermal polymerization, and spin coating. The EuL3 x 2H2O content in the hybrid thin films was fixed at 0.05 g and silica content was varied from 10 to 50 wt%. TEM results showed that both SiO2 and EuL3 x 2H2O were well dispersed in the hybrid thin films without aggregation. PL spectra showed the unique emission of Eu3+. The addition of SiO2 made the compounds of Eu3+ disperse better and diminished the effect of concentration quenching. UV-Vis spectra and n&k analysis showed that the hybrid thin films had good transparency in visible light. Besides, the refractive index of hybrid thin films could be effectively controlled through the different ratio of SiO2 to EuL3 x 2H2O. TGA and DSC analysis indicated that the temperature of pyrolysis and T(g) increased with the increase in the SiO2 content. The results of SEM, SCMS, and AFM also showed that the hybrid thin films which prepared from the poly-functional acrylate had a flatter surface than those obtained from the single functional acrylate.
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PMID:Hybrid thin films derived from poly(acrylic)/ colloidal silica/lanthanide metal complex. 1991 6

This article describes the preparation and characterization of fluorescent and magnetic composite particles of poly(styrene-co-methacrylic acid-co-2-naphthyl methacrylate) (poly(St/MAA/NMA)). First, monodisperse (D(w)/D(n)<1.1) and fluorescent poly(St/MAA/NMA) submicron particles were prepared using emulsifier-free emulsion polymerization by varying the concentration of the fluorescent comonomer, i.e., NMA. Composition of the particles was characterized by (1)H NMR, FT-IR, GPC, and DSC analyses. The molecular weights and particle size of the particles were dependent on the NMA concentration. Second, Fe(3)O(4) nanoparticles were immobilized onto the poly(St/MAA/NMA) submicron particles to give rise to multifunctional properties. The morphology and particles size were characterized by FE-SEM and CHDF. These poly(St/MAA/NMA)/Fe(3)O(4) composite particles exhibited both fluorescent properties under UV irradiation at 365 nm and magnetic properties. Photo-luminescent (PL) intensity of the particles showed linear dependence with NMA concentration.
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PMID:Monodisperse and fluorescent poly(styrene-co-methacrylic acid-co-2-naphthyl methacrylate)/Fe3O4 composite particles. 2003 48

The combination of gelatin (Gel) with a bioactive component hydroxyapatite (HA) and cartilage powder (CP) to form biocomposites takes advantage of the osteoconductivity and osteoinductivity properties. The studies on bionanocomposites containing HA, CP fillers and Gel are still being conducted. In this present study, the bioactive fillers were loaded onto poly(hydroxylethylmethacrylate) and poly(hydroxylethylmethacrylate-co-methyl methacrylate) grafted gelatin copolymers to produce novel bionanocomposites having osteoconductive and osteoinductive properties. The resulting bionanocomposites were assessed by ATR-IR and SEM-EDX techniques to prove the interaction between different matrices. In vitro behavior of these bionanocomposites was performed in SBF for 21 days at pH 7.4 to verify formation of the apatite layer on the surfaces and its enhancement. The results confirmed the formation of thick plentiful aggregated (hexagonal or spherical) nanoparticles with a bright color (apatite layer) containing carbonate ions onto the surface of composites especially these containing CP and P(HEMA-co-MMA) having bone cement formation in their structure. These novel bionanocomposites have unique bioactivity that can be applied in bone implants as scaffolds and tissue engineering in future.
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PMID:Synthesis and in vitro evaluation of gelatin/hydroxyapatite graft copolymers to form bionanocomposites. 2008 33

The photochemical method is a convenient and simple way to synthesize the polymer brush on surface. We presented here a facile approach to fabricate PMMA brush on silica particles (SPs) by combination of self-assembly monolayer of hyperbranched polymeric thioxanthone (HPTX) and surface-initiated photopolymerization (SIPP). HPTX was immobilized on the surface of silica particles (SPs) through nucleophilic addition between amine and epoxy groups, and then initiated photopolymerization of MMA to generate PMMA brush on SPs at room temperature. The whole process was well-traced by FT-IR, TGA, SEM, and TEM. The results show that it is easy to create PMMA brushes of tunable thickness under UV irradiation. Especially, TEM images reveal the obvious formation of well-defined hybrid particles with SPs as the core and PMMA layers as the shell. The obtained hybrid particles can be implanted into PMMA matrix to produce PMMA composite with enhanced thermal and mechanical properties.
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PMID:Well-defined PMMA brush on silica particles fabricated by surface-initiated photopolymerization (SIPP). 2042 23

A novel pH-sensitive amphiphilic copolymer brush poly(methyl methacrylate-co-methacrylic acid)-b-poly(poly(ethylene glycol) methyl ether monomethacrylate) [P(MMA-co-MAA)-b-PPEGMA] was defined and synthesized by atom transfer radical polymerization (ATRP) technique. The molecular structures and characteristics of this copolymer and its precursors were confirmed by (1)H NMR, FT-IR, and GPC. The CMC of P(MMA-co-MAA)-b-PPEGMA in aqueous medium was determined to be 1-4 mg/L. This copolymer could self-assemble into micelles in aqueous solution with an average size of 120-250 nm determined by DLS. The morphologies of the micelles were found to be spherical by SEM and TEM. Ibuprofen (IBU), a poorly water-soluble drug, was selected as the model drug and wrapped into the core of micelles via dialysis method. Drug entrapment efficiency reached to 90%. The in vitro release behavior of IBU from these micelles was pH-dependent. The cumulative release percent of IBU was less than 20% of the initial drug content in simulated gastric fluid (SGF, pH 1.2) over 12 h, but 90% was released in simulated intestinal fluid (SIF, pH 7.4) within 6 h. The release profiles showed that the P(MMA-co-MAA)-b-PPEGMA micelles could inhibit the premature burst drug release under the intestinal conditions. All the results indicate that the P(MMA-co-MAA)-b-PPEGMA micelle may be a potential oral drug delivery carrier for poorly water-soluble drugs.
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PMID:pH-Sensitive micelles self-assembled from amphiphilic copolymer brush for delivery of poorly water-soluble drugs. 2112


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