SUMMARYSUMMARY Highly ®lled composites, Ormocers (organically modi®ed ceramics) and`smart' materials have been developed to overcome the polymerization shrinkage problems of conventional composite materials. The purpose of the current study was to investigate the effect of longer-term (up to 8 weeks) ageing of these resin-based dental restorative materials and determine the effect of post-curing on cytotoxicity. Twelve discs of each material (Colombus/IDR, De®nite/Degussa, Ariston pHc/Vivadent) were either light-cured (Lc) or light-cured and postcured (Pc). For cytotoxicity testing, the discs were placed in contact with cell culture medium (DMEM) and incubated at 37°C. Extracts from composite materials were collected after 24 h and weekly over a time period of 8 weeks. Cytotoxicity of the eluates to cultured ®broblasts (Balb/c3T3) were measured by the succinic dehydrogenase (SDH) activity (MTT assay) and the results expressed in percentage of negative controls (Te¯on discs). The results showed that ageing signi®cantly in¯uenced the cytotoxicity of the materials. Except for Ariston pHc, materials were less cytotoxic after 8 weeks of ageing than they were in early intervals and post-curing was not generally useful in reducing cytotoxicity. The Ariston pHc was initially moderately toxic, but then become highly cytotoxic for 5 weeks before returning to initial levels. The current study demonstrated the importance of assessing the cytotoxicity of resin composite materials at multiple times.

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Binary diffusion coefficients of anisole, 2,4-dimethylphenol, and nitrobenzene in supercritical carbon dioxide have been determined at 313, 323, and 333 K and at pressures between 15.0 and 35.0 MPa. Measurements have been obtained using the Taylor−Aris dispersion technique. The data have been correlated with temperature, pressure, density, and viscosity, and some general trends have been established. The applicability of several correlations to the experimental data was examined, and some correlations have shown that they are satisfactory for predicting diffusion coefficients.

in Wiley InterScience (www.interscience.wiley.com).Binary diffusion coefficients at infinite dilution in supercritical carbon dioxide, D AB , have been measured for the four monohalogenated benzenes (fluorobenzene, chlorobenzene, bromobenzene, and iodobenzene) with the Taylor-Aris technique in a chromatographic apparatus as a function of temperature and pressure. The ranges covered for these two variables were 313-333 K and 15.0-35.0 MPa, respectively. As the four solutes are similar molecules, the corresponding states principle (CSP) has been tested, together with the results of several predictive equations.

In this work was evaluated the efficiency of an antishrinkage additive in a dental resin. This additive was a mixture 1:1 of five and six-membered ring spiroorthocarbonates functionalized with allylic groups (SOC DA). The aim of this study was to reduce the shrinkage of a typical dental resin composed of a blend of the dimethacrylates, Glycerolate bisphenol A dimethacrylate (Bis-GMA)/2-[(3,5,5-trimethyl-6-[2-(2-methyl prop-2-enoyloxy) ethoxycarbonylamino] hexyl) carbamoyloxy] ethyl, 2-methyl prop-2-enoate, (UDMA)/triethyleneglycol dimethacrylate (TEGDMA) in a 50:30.20 molar ratio, and silicon dioxide as filler. SOC DA was added at 5, 10 and 20 mol% to the already mentioned formulation. It was found that the addition of 20 mol% of SOC DA decreased 53 % the shrinkage of the cured composite material, in comparison with a formulation where it was not added the antishrinkage additive. Besides, the kinetics of photopolymerization determined by Real-Time infrared spectroscopy, demonstrated that the addition of increasing concentration of SOC DA improved the conversion of double bonds of dimethacrylates. Additionally, the presence of SOC DA at 10 % mol, helped to increase the flexural strength and the compressive strength of the composite, as a consequence of the augment of the crosslink density, induced by the ring opening polymerization of SOC DA.

Measurements of binary diffusion coefficients of aniline, styrene, and mesitylene have been carried out by means of the Taylor-Aris chromatographic method. The diffusivities of mesitylene are consistent with those of Sua ´rez et al.

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