Filler Content, Surface Microhardness, and Rheological Properties of Various Flowable Resin Composites.

OBJECTIVES: The objectives of this study were to determine the filler content, the surface microhardness (at baseline and after immersion in water for 2 years), and the rheological properties of various flowable resin composites. METHODS: Three flowable resin composites (Grandioso Heavy Flow [GHF], Grandio Flow [GRF], Filtek Supreme XTE Flow [XTE]), one pit and fissure sealant resin composite (ClinPro [CLI]), and three experimental flowable resin composites with the same matrix and a variable filler content (EXPA, EXPB, EXPC) were tested. The filler content was determined by calcination. The Vickers surface microhardness was determined after polymerization and then after immersion in distilled water at 37°C for 7, 60, 180, 360, and 720 days. The rheological measurements were performed using a dynamic shear rheometer. RESULTS: The determined filler contents differed from the manufacturers' data for all the materials. The materials with the highest filler content presented the highest microhardness, but filler content did not appear to be the only influencing parameter. With respect to the values recorded after photopolymerization, the values were maintained or increased after 720 days compared with the initial microhardness values, except for GHF. For the values measured after immersion for 7 days, an increase in microhardness was observed for all the materials over time. All the materials were non-Newtonian, with shear-thinning behavior. At all the shear speeds, GRF presented a lower viscosity to GHF and XTE. CONCLUSIONS: GRF presented a low viscosity before photopolymerization, associated with high filler content, thereby providing a good compromise between spreadability and mechanical properties after photopolymerization.

High-resolution tomography study of the porosity of three restorative resin composites.

OBJECTIVES: The aim of this study was to analyze the porosity of three photopolymerizable resin composites: one high-viscous resin composite (Filtek™ P60®, 3 M™ ESPE™), one moderate-viscosity resin composite (Grandio®, VOCO™), and one low-viscous resin composite (Filtek™ Supreme XTE®, 3 M™ ESPE™). MATERIALS AND METHODS: A total of 36 cylindrical samples with a height of 2 mm and a diameter of 2 mm were prepared using PTFE molds. Eighteen cylinders were prepared by two incremental applications of 1 mm into the molds, then polymerized (group 1). For the other 18 samples (group 2), the first increment was polymerized before the second addition was made. The average porosity percentage and the average porosity volume were evaluated by high-resolution tomography (Nanotom M® - Phoenix X-Ray(TM), Wunstorf, Germany). The impact of incremental applications in terms of porosity was also evaluated. RESULTS: Irrespective of the protocol used, the low viscous material presented an average porosity percentage and an average porosity volume significantly greater than those of the other materials. Incremental application (group 2 samples) led to an increase in the average porosity percentage and volume irrespective of the material compared to the group 1 samples. CONCLUSIONS: High-resolution tomography appeared to be a particularly suitable tool for studying the porosity of resin composites. The viscosity and the handling of these materials seemed to be influential factors on their porosity. CLINICAL RELEVANCE: The presence of porosities in dental resin composites remains an objective reality, especially with low-viscous resin composites. Since the intrinsic porosity of the materials can be neither controlled nor modified by the operator, rigorous and iterative clinical protocols still remain the best way to limit inclusion of porosities in the resin composites.

Effects of Ar-H2-N2 microwave plasma on chitosan and its nanoliposomes blend thin films designed for tissue engineering applications.

This work addresses the functionalization of chitosan thin films and its nanoliposomes blend films by a microwave-excited Ar/N2/H2 surface-wave plasma treatment which was found an effective tool to modify surface properties. Changes in the film properties (wettability, chemical composition, morphology) induced by the plasma treatment are studied using water contact angle measurements, X-ray photoelectron spectroscopy and scanning probe microscopy. The results suggest that hydrophilicity of the films is improved by plasma treatment in a plasma condition dependency manner. Water contact angle of chitosan films before and after plasma treatment are, respectively, 101° and 27°. Besides chemical changes on the surface, the nanoliposomes incorporation and plasma treatment also induce morphological modifications. Moreover, a correlation is found between the nanoliposomes composition and size, and the effects of plasma treatment. It is shown that the plasma treatment significantly improves the chitosan film functionalization. The effect of N2 content (88% and 100%) in the plasma gas mixture on the film etching is also pointed out.

The beta-spherulite morphology of isotactic polypropylene investigated by Raman spectroscopy.

Raman spectroscopy is used to investigate the alpha- and beta-crystalline polymorphs of isotactic polypropylene. Raman spectra of the polymorphs show some minor differences, in particular the wavenumber shifting of certain scattering bands, which reflect the environment of an isolated macromolecular chain within the packing unit cell of the different crystal forms. For example, the shifting of the 842 cm(-1) scattering band, which is the most susceptible band to cause intermolecular interactions, is used to generate a structural map of one beta-spherulite among alpha-spherulites with a well-defined resolution. Anisotropy of the crystalline phase orientation within a beta-spherulite is also investigated by performing polarized Raman spectroscopy measurements. Differences in the polarized spectra are then finely exploited to map the radial lamellae orientation distribution within one beta-spherulite.

Computed tomography of the brain in eclampsia.

Computed tomography (CT) of the brain was performed on 44 women with eclampsia, 31 during pregnancy and 13 postpartum. All CT scans were done within 24 hours of eclampsia, including 12 within 1 hour of the convulsions and eight before the repetition of additional seizures, 2 minutes to 14 hours later. Control scans were performed on 15 hypertensive pregnant patients and on ten normotensive pregnant women after fetal death or just after delivery. Among the women with eclampsia, 26 CT scans were considered normal with no evidence of cerebral edema, three displayed signs of cerebral hemorrhage or thrombosis, six showed areas of focalized hypodensity located in the cortical lobes and the subcortical white matter, and nine were classified as cerebral atrophy with enlarged cerebral ventricles. We conclude that radiologic evidence of diffuse brain edema is probably not a common feature in eclampsia.