Luminescent properties of hybrid materials prepared by the polymeric precursor method

Rare earth complexes (RE) can be incorporated in silica matrixes, originating organic/inorganic hybrid materials with good thermal stability and high rare earth emission lines. In this work, the hybrid material was obtained by the polymeric precursor method and ultrasonic dispersed with spherical silica particles prepared by the Stöber Method. The Raman spectra indicated that the Eu3+ ions are involved in a polymeric structure formed as consequence of the chelation and polyesterification reactions of this ion with citric acid and ethylene glycol. After the ultrasonic stirring, 2-hydroxynicotinic ligand will also compose this polymeric rigid structure. The TGA/DTA analysis showed that this polymeric material was thermal decomposed at 300 °C. Moreover, this process allows the chelating process of the 2-hydroxynicotinic acid ligand to the Eu3+ ions. The 29Si NMR showed that the ultrasonic dispersion of the reactants was not able to promote the functionalization of the silica particles with the 2-hydroxynicotinic acid ligand. Moreover, heat treatment promotes the [Eu(HnicO2)3] complex particles incorporation into silica pores. At this temperature, the TGA curve showed that only the thermal degradation of ethylene glycol and citric acid used during the experimental procedure occurs. The silica and hybrid materials are composed by spherical and aggregated particles with particle size of approximately 450 nm, which can be influenced by the heat treatment. These materials also present an absorption band located at 337 nm. The photoluminescent study showed that when the hybrid samples were excited at 337 nm wavelength, the ligand absorbs the excitation light. Part of this energy is transferred to the Eu3+ ion, which main emission, 5D0→ 7F2, is observed in the emission spectrum at 612 nm. As the heating temperature increases to 300 C, the energy transfer is more favorable. The lifetime values showed that the Eu3+ emission is enhanced due to the energy transfer process in the powders. © 2013 Elsevier B.V. All rights reserved.

Volumetric microleakage assessment of glass-ionomer-resin composite hybrid materials

Objective: This study was intended to quantify the marginal leakage of three glass-ionomer-resin composite hybrid materials and compare it with the leakage exhibited by a glass-ionomer cement and a bonded resin composite system. Method and materials: Standardized Class V cavities were prepared on root surfaces of 105 extracted human teeth, randomly assigned to five groups of 21 each, and restored with either Ketac-Fil Aplicap, Z100/Scotchbond Multi-Purpose Plus, Vitremer, Photac-Fil Aplicap, or Dyract. The teeth were thermally stressed for 500 cycles and stained with methylene blue. The microleakage was quantified spectrophotometrically, and the data were statistically analyzed with Friedman's test. Results: There were no significant differences in microleakage among the five groups. Restorations of all tested materials showed some marginal leakage in Class V cavities. Conclusion: The microleakage performance of glass-ionomer-resin composite hybrid materials was similar to those of a conventional glass-ionomer and a bonded resin composite system.

COLOR STABILITY of SEALED COMPOSITE RESIN RESTORATIVE MATERIALS AFTER ULTRAVIOLET ARTIFICIAL AGING and IMMERSION IN STAINING SOLUTIONS

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evaluation of the Cohesive Strength Between Resin Composite and Light-curing Characterizing Materials

Purpose: To evaluate the cohesive strength between composite and different light-curing characterizing materials (LCCM), which were prepared using the intrinsic technique.Materials and Methods: One hundred composite specimens were made by using a prefabricated Teflon device, and a layer of LCCM was applied at the interface. The specimens were divided into 5 groups (n = 20): group 1 (control), no LCCM was used; group 2: application of White Kolor Plus Pigment (Kerr) LCCM; group 3: White Tetric Color Pigment (Ivoclar/Vivadent) LCCM; group 4: Brown Kolor Plus Pigment (Kerr) LCCM; group 5: Black Tetric Color Pigment (Ivoclar/Vivadent) LCCM. All materials were used according to the manufacturers' instructions. Specimens were submitted to a tensile test in a universal testing machine (EMIC DL-200MF) to evaluate the cohesive strength at the composite interface. Data were subjected to one-way ANOVA and Tukey's test (alpha = 5%).Results: ANOVA showed a p-value = 0.0001, indicating that there were significant differences among the groups. The mean values in MPa (+/- standard deviation) obtained for the groups were: G1: 28.5 (+/-2.74)a; G2: 23.5 (+/-2.47)b; G3: 20.3 (+/-2.49)b; G4: 10.5 (+/-2.40)c; G5: 9.66 (+/-3.06)c. The groups with the same letters presented no significant differences. The control group presented statistically significantly higher cohesive strengths when compared to the other groups. The groups in which Brown Kolor Plus Pigment and Black Tetric Color Pigment LCCM were used showed significantly lower cohesive strengths when compared to the groups in which White Kolor Plus Pigment and White Tetric Color Pigment LCMM were used.Conclusion: The use of LCCM produced with the intrinsic technique reduced the cohesive strength of composite.

Small-angle X-ray scattering study of sol-gel-derived siloxane-PEG and siloxane-PPG hybrid materials

Hybrid organic-inorganic two-phase nanocomposites of siloxane-poly(ethylene glycol) (SiO3/2-PEG) and siloxane-poly(propylene glycol) (SiO3/2-PPG) have been obtained by the sol-gel process. In these composites, nanometric siloxane heterogeneities are embedded in a polymeric matrix with covalent bonds in the interfaces. The structure of these materials was investigated in samples with different molecular weights of the polymer using the smalt-angle X-ray scattering (SAXS) technique. The SAXS spectra exhibit a well-defined peak that was attributed to the existence of a strong spatial correlation of siloxane clusters. LiClO4-doped siloxane-PEG and siloxane-PPG hybrids, which exhibit good ionic conduction properties, have also been studied as a function of the lithium concentration [O]/[Li], O being the oxygens of ether type. SAXS results allowed us to establish a structural model for these materials for different basic compositions and a varying [Li] content. The conclusion is consistent with that deduced from ionic conductivity measurements that exhibit a maximum for [O]/[Li] =15.

Evolution of rheological properties and local structure during gelation of siloxane-polymethylmethacrylate hybrid materials

Hybrid siloxane-polymethylmethacrylate (PMMA) nanocomposites with covalent bonds between the inorganic (siloxane) and organic (polymer) phases were prepared by the sot gel process through hydrolysis and polycondensation of 3-(trimethoxysilyl)propylmethacrylate (TMSM) and polymerization of methylmethacrylate (MMA) using benzoyl peroxide (BPO) as initiator. The effect of MMA, BPO and water contents on the viscoelastic behaviour of these materials was analysed during gelation by dynamic rheological measurements. The changes in storage (G') and loss moduli (G), complex viscosity (eta*) and phase angle (6) were measured as a function of the reaction time showing the viscous character of the sot in the initial step of gelation and its progressive transformation to an elastic gel. This study was complemented by Si-29 and C-13 solid-state nuclear magnetic resonance (NMR/MAS) measurements of dried gel. The analysis of the experimental results shows that linear chains are formed in the initial step of the gelation followed by a growth of branched structures and formation of a three-dimensional network. Near the gel point this hybrid material demonstrates the typical scaling behaviour expected from percolation theory.

Montmorillonite (MMT) effect on the structure of poly(oxyethylene) (PEO)-MMT nanocomposites and silica-PEO-MMT hybrid materials

In this work we report the effects of incorporation of variable amounts (0.5-25%w/w) of montmorillonite in poly(oxyethylene) based materials in order to decrease the polymer crystallinity. Two different classes of materials were studied: silica-poly(oxyethylene)-montmorillonite hybrids prepared by the sol-gel route and poly(oxyethylene)-montmorillonite nanocomposites prepared by mixing the dry clay or the clay aqueous suspension into the melt poly(oxyethylene). The effects of monternorillonite loading on the poly(oxyethylene) crystallization control and on the nanostructural features were investigated by X-ray powder diffraction, small-angle X-ray scattering and differential scanning calorimetry. Experimental results show that free montmorillonite layers coexist with open aggregates and tactoids in the poly(oxyethylene)-montmorillonite nanocomposites, with different features depending on the filler proportion and preparation route. The intercalation of polymer chains in montmorillonite galleries markedly hinders the crystallization of the poly(oxyethylene) matrix. For hybrids materials the silica phase favors the exfoliation of montmorillonite tactoids, so that samples are predominantly constituted by dispersed platelets. (c) 2006 Elsevier B.V. All rights reserved.

SAXS study of gelation, aging and drying of silica-polypropyleneglycol hybrid materials

New silica-polypropyleneglycol ormosils (organically modified silicates) with covalent bends between the organic (polymer) and inorganic (silica) phases have been prepared by the sol-gel process. Their structural evolution during sol formation, sol-gel transition, gel aging and drying has been studied in situ by small-angle X-ray scattering (SAXS). The experimental SAXS curves corresponding to sols and gels exhibit features expected from fractal objects. Clusters of size around 55 Angstrom with an initial fractal dimension D = 2.4 are formed in the sol. They are constituted of small primary silica particles chemically crosslinked at the end of the polymer chains. A strong liquid-like spatial correlation between the silica particles develops during drying due to the shrinkage of the polymeric network induced by water and ethanol evaporation. The continuous increase in SAXS intensity during drying, while the interparticle distance remains constant, is a consequence of the progressive growth of the dry fraction of the total volume. After drying, the gel structure consists of a rather compact arrangement of silica particles embedded in the polypropyleneglycol matrix.

Influence of bleaching treatment on flexural resistance of hybrid materials.

The aim of this study is to evaluate the flexural resistance of three types of restorative materials: compomer (Freedom), resin-modified glass-ionomer (Vitremer) and composite resin (Esthet-X), observing whether the application of bleaching agent can cause alterations of their flexural properties. Sixty samples were made using a 10 x 1 x 1 mm brass mold, and divided into three groups: G1- Freedom (SDI); G2- Vitremer (3M ESPE); G3- Esthet-X (Dentsply). On half of the samples of each group (10 samples) the bleaching treatment was applied and the other half used as control, was stored in distilled water at a temperature of 37 degrees C. Whiteness HP Maxx bleaching system was applied on the sample surface following the manufacturer's recommendations, simulating the bleaching treatment at the clinic. After this period, a flexural strength (three-point bending) test was conducted using (EMIC DL 1000) machine until the samples fractured. The data were submitted to ANOVA and Tukey tests. Of the restorative materials studied, G3-(87.24 +/- 31.40 MPa) presented the highest flexural strength, followed by G1-(61.67 +/- 21.32 MPa) and G2-(61.67 +/- 21.32 MPa). There was a statistical difference in flexural strength after the bleaching treatment. It was concluded that the use of a beaching agent can promote significant alteration of the flexural strength of these restorative materials.

Controlled Drug Release from Ureasil-Polyether Hybrid Materials

Flexible, transparent, and insoluble urea-cross-linked polyether-siloxane hybrids presenting a tunable drug delivery pattern were prepared using the sol-gel method from PEO (poly(ethylene oxide)) and PPO (poly(propylene oxide)) functionalized at both chain ends with triethoxysilane. Different polyether chain lengths were used to control the urea/siloxane (named ureasil) node density, flexibility, and swellability of the hybrid network. We herein demonstrate that the drug release from swellable hydrophilic ureasil-PEO hybrids can be sustained for some days, whereas that from the unswellable ureasil-PPO hybrids can be sustained for some weeks. This outstanding feature conjugated with the biomedically safe formulation of the ureasil cross-linked polyether-siloxane hybrid widens their scope of application to include the domain of soft and implantable drug delivery devices.

Evaluation of the Smear Layer and Hybrid Layer in Noncarious and Carious Dentin Prepared by Air Abrasion System and Diamond Tips

Purpose: To analyze the smear layer and the hybrid layer in noncarious and carious dentin prepared by different cutting instruments and restored with composite resin. Study design: Cavities were randomly prepared in 160 specimens (noncarious and artificial carious dentin) by high-speed diamond tips (KG Sorensen 1013), air abrasion system (Prepstart, Danville Engineering), ultrasonic tip (CVDentus 8.3231-1), and ultrasonic tip associated with ultrasonic cavitation by water for 10 s. Half of the cavities in each group were conditioned with 37% phosphoric acid for 15 s. The amount of smear layer and dentinal tubules present were analyzed using scanning electron microscopy and graded from 0 to 3. Cavities were prepared in another 20 noncarious specimens and 20 carious specimens and restored with adhesive composite resin system. The restorations were hemisected longitudinally and analyzed using scanning electron microscopy to evaluate the hybrid layer and resinous prolongation characteristics, using scores ranging from 1 to 6. Results: The data were statistically analyzed using Kruskal-Wallis and Dunn tests at 5% of significance level. There was evidence that the most efficient smear layer removal was the acid etching in the noncarious dentin and the water ultrasonic cavitation in the carious dentin. The hybrid layer formed on the noncarious and carious dentin prepared by the ultrasonic tip was more regular than in the specimens prepared by high-speed diamond tip, with many resinous prolongations. Conclusion: The ultrasonic tip seems to be a promising tool for carious dentin cavity preparation. Microsc. Res. Tech. 73:597-605, 2010. (C) 2009 Wiley-Liss, Inc.

A retrospective look at esthetic resin composite and glass-ionomer Class III restorations: A 2-year clinical evaluation

Objective: A restorative material for Class III cavities must, besides being functional, be esthetically satisfactory, providing good working conditions and several shade and color options. A clinical evaluation was initiated to compare the suitability of resin composite and glass-ionomer cement materials for such restorations.Method and materials: Forty-two Class III conservative cavities, esthetically important because of facial extensions, were selected. Resin composite restorations were placed in 21 cavities, and the remaining 21 were restored with glass-ionomer cement. The following characteristics were studied: color or-esthetics, anatomic shape, surface texture, staining, marginal infiltration, dental plaque retention, and occurrence of fracture. After 24 months, the restorations were evaluated.Results: the only statistically significant difference between the resin composite and glass-ionomer cement restorations in the experimental period involved color or esthetics.Conclusion: Resin composites and glass-ionomer materials provide excellent functional and esthetic results in Class III cavities when properly indicated.

Drug-matrix interaction of sodium diclofenac incorporated into ureasilpoly(ethylene oxide) hybrid materials

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)