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The effect of the composition and bonding configuration of the bioactive silica-based glasses on the initial stage in vitro bioactivity is presented. Information of the IR active Si-O groups of glass in the system SiO(2)-P(2)O(5)-CaO-Na(2)O-K(2)O-MgO-B(2)O(3) was obtained by fourier transform Infrared (FTIR) spectroscopy. Two different bands associated to non-bridging oxygen stretching vibrations (Si-O-1NBO and Si-O-2NBO) and a gradual shifting of the bridging oxygen stretching vibration (Si-O) have been observed and evaluated. Both effects are attributed to a decrease of the local symmetry originating from the incorporation of alkali ions into the vitreous silica network. The Si-O-NBO(s)/Si-O(s) absorbance intensity ratio increases with a gradual incorporation of the alkali ions (diminution of SiO(2) content) following a linear dependence up to values close to 50 wt % of SiO(2). In vitro test analysis by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA) showed a correlation between the amount and type of the non-bridging oxygen functional groups and the growth of the silica-rich and CaP layers. It was found that a minimum concentration of Si-O-NBO bonds in the glass network is required in order to have an efficient ion exchange and dissolution of the silica network. Finally, the bioactivity of the glass is favored by the presence of the Si-O-2NBO groups in the glassy network. The role of these functional groups in the dissolution of the silica network through the formation of silanol groups and the adsorption of water is discussed.

Abstract. Biomorphic silicon carbide ceramics are light, tough and high-strength materials with interesting biomedical applications. The fabrication method of the biomorphic SiC is based in the infiltration of molten-Si in carbon preforms with open porosity. The final product is a biostructure formed by a tangle of SiC fibers. This innovative process allows the fabrication of complex shapes and the tailoring of SiC ceramics with optimised properties and controllable microstructures that will match the biomechanical requirements of the natural host tissue. An interdisciplinary approach of the biomorphic SiC fabricated from beech, sapelly and eucalyptus is presented. Their mechanical properties, microstructure and chemical composition were evaluated. The biocompatible behaviour of these materials has been tested in vitro.