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Although implants are becoming increasingly common in dental practice, before implantation strict patient selection criteria have to be implemented since the implants should have a good chance of osseointegration into the maxillary bone. Moreover, the implanted sites can become severely infected and, consequently, the implant might have to be removed. To avoid implant-related infections and to promote the osseointegration of commercial Titanium implants, different silica-chitosan matrices were synthesized using the sol-gel process. Three different alkoxysilanes were used, methyltrimethoxysilane (MTMOS), 3glycidoxypropyltrimethoxysilane (GPTMS), and tetraethoxysilane (TEOS). The network formed during the matrix synthesis gradually degrades in aqueous media, and during this hydrolytic degradation, silicon is released, inducing bone formation. Chitosan, with its high biocompatibility and strong antibacterial activity, was selected to confer antibacterial properties to the coatings. The synthesized hybrids were characterized using 29 Si-and 13 C-NMR to verify the correct formation of the network. The technique was also used to confirm the covalent union between chitosan and the silicon network. Hydrolytic degradation and silicon release studies in the aqueous media were examined, showing the effective silicon release from the hybrids. The analysis of cell cultures in vitro demonstrated that the hybrid coatings were not cytotoxic and promoted cell proliferation on their surfaces. The coatings containing 5%-10% chitosan had substantial antibacterial properties. The introduction of different amounts of chitosan and TEOS modulated the degradation of the coatings and, consequently, the Si release.

For use in vertebroplasty and kyphoplasty, an acrylic bone cement should possess many characteristics, such as high radiopacity, low and constant viscosity during its application, low value of the maximum temperature reached during the polymerization process (T(max)), a setting time (t(set)) that is neither too low nor too high, and high compressive strength. The objective of this study was to investigate the influence of the powder particle distribution on various properties of one acrylic bone cement; namely, residual monomer content, T(max), t(set), complex viscosity, storage and loss moduli, injectability, and quasi-static compressive strength and modulus. It was found that the formulations that possessed the most suitable complex viscosity-versus-mixing time characteristics are those in which the ratio of the large poly(methyl methacrylate) beads (of mean diameter 118.4 microm) to the small ones (of mean diameter 69.7 microm) was at least 90% w/w. For these formulations, the values of the other properties determined were acceptable.

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