Degradation of the resin-dentin bonds after simulated and inhibited cariogenic challenge in an in situ model

The aim of this study was to evaluate the resindentin bonds of two simplified etch-and-rinse adhesive after simulated cariogenic and inhibited cariogenic challenge in situ. Dental cavities (4 mm wide, 4 mm long, and 1.5 mm deep) were prepared in 60 bovine teeth with enamel margins. Restorations were bonded with either adhesive Adper Single Bond 2 (3MESPE) or Optibond Solo Plus (Kerr). Forty restorations were included in an intra-oral palatal appliance that was used for 10 adult volunteers while the remaining 20 dental blocks were not submitted to any cariogenic challenge [NC group] and tested immediately. For the simulated cariogenic challenge [C+DA], each volunteer dropped 20% sucrose solution onto all blocks four times a day during 14 days and distilled water twice a day. In the inhibited cariogenic challenge group [C + FA], the same procedure was done, but slurry of fluoride dentifrice (1.100 ppm) was applied instead of water. The restored bovine blocks were sectioned to obtain a slice for cross-sectional Vickers microhardness evaluation and resindentin bonded sticks (0.8 mm2) for resindentin microtensile evaluation. Data were evaluated by two-way ANOVA and Tukey's tests (a = 0.05). Statistically lower microhardness values and degradation of the resindentin bonds were only found in the C + DW group for both adhesives. The in situ model seems to be a suitable short-term methodology to investigate the degradation of the resindentin bonds under a more realistic condition. (c) 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 100B: 14661471, 2012.

Toward supramolecular architectures of the anti-HIV drug lamivudine: understanding the effect of the inclusion of water in a hydrochloride form

Two salts of the anti-HIV drug lamivudine, namely, lamivudine hydrochloride and lamivudine hydrochloride monohydrate, were prepared for the first time. Structural relationships and the role of water in crystal assembly and lamivudine conformation were established and allowed for a rational approach to understand how solid state properties could be changed by engineering new salts of the drug.

CeO2 nanoparticles synthesized by a microwave-assisted hydrothermal method: evolution from nanospheres to nanorods

Ceria (CeO2) plays a vital role in emerging technologies for environmental and energy-related applications. The catalytic efficiency of ceria nanoparticles depends on its morphology. In this study, CeO2 nanoparticles were synthesized by a microwave-assisted hydrothermal method under different synthesis temperatures. The samples were characterized by X-ray diffraction, transmission electron microscopy, Raman scattering spectroscopy, electron paramagnetic resonance spectroscopy and by the Brunauer-Emmett-Teller method. The X-ray diffraction and Raman scattering results indicated that all the synthesized samples had a pure cubic CeO2 structure. Rietveld analysis and Raman scattering also revealed the presence of structural defects due to an associated reduction in the valence of the Ce4+ ions to Ce3+ ions caused by an increasing molar fraction of oxygen vacancies. The morphology of the samples was controlled by varying the synthesis temperature. The TEM images show that samples synthesized at 80 degrees C consisted of spherical particles of about 5 nm, while those synthesized at 120 degrees C presented a mix of spherical and rod-like nanoparticles and the sample synthesized at 160 degrees C consisted of nanorods with 10 nm average diameter and 70 nm length. The microwave-assisted method proved to be highly efficient for the synthesis of CeO2 nanoparticles with different morphologies.

Characteristics of WWTP sludge after drying in greenhouse for agricultural purposes

The sludge generated by sewage treatment which meets regulatory standards can be used in agriculture. With this understanding, the focus of this study is the evaluation of the agricultural characteristics and inorganic substances in excess activated sludge, which was subjected to drying in a greenhouse. The variables (factor) evaluated during the drying process were: type of sludge (digested or not digested), addition of lime to the sludge, and the physical layout and rotation of sludge in the greenhouse. The parameters monitored for this assessment were moisture, volatile solids and pH. The greenhouse cover and sides were made of translucent plastic to allow the penetration of solar radiation and prevent water from entering. A impermeable floor was used. The sludge was generated in sewage treatment plants located in the metropolitan region of Grande Vitoria, Espirito Santo, Brazil. The solar drying of wastewater sludge in a greenhouse presented satisfactory results.

Photoluminescence of core-shell nanoparticles made from yttrium stabilized zirconia powder grain coated with alumina

A YSZ@Al2O3 nanocomposite was obtained by Al2O3 coating on the surface of yttrium stabilized zirconia via a polymeric precursor method. The resulting core–shell structures were characterized by X-ray diffraction, scanning electron microscopy, transmission electronic microscopy and PL spectra. The TEM micrographs clearly show a homogeneous Al2O3 shell around the ZrO2 core. The observed PL is related to surface–interface defects. Such novel technologies can, in principle, explore materials which are not available in the bulk single crystal form but their figure-of-merit is dramatically dependent on the surface–interface defect states.