No abstract

While titanium has been successful as an orthopaedic or dental implant material, performance problems still persist concerning implant-bone interfacial strength and mechanical modulus mismatch between metal and tissue. Porous structures are an advantageous alternative because the elastic modulus can be adjusted to match that of bone, thereby preventing bone resorption. Furthermore, to achieve early and strong stabilization theses structures may be coated with bioactive deposits, as hydroxyapatite. In the present work, titanium porous scaffolds were produced from TiH(2) slurry by a replication sponge reactive sintering method, and coated with hydroxyapatite by the sol-gel process. The obtained structures were microstructurally and mechanically characterized. Their in vitro bioactivity was investigated by soaking in a simulated body fluid (SBF). Electrochemical characterization was also performed in order to evaluate the effect of coating on corrosion resistance. The scaffolds exhibit a three-dimensionally interconnected porous structure that can be mechanically and morphologically compared to trabecular bone. Their in vitro bioactivity suggests potential for osseous integration. Coating also improves corrosion resistance in physiologically saline environment.

No abstract

Composite bone cements were prepared with bioactive glasses (MgO-SiO(2)-3CaO.P(2)O(5)) of different reactivities. The matrix of these so-called hydrophilic, partially degradable and bioactive cements was composed of a starch/cellulose acetate blend and poly(2-hydroxyethyl methacrylate). The addition of 30 wt.% of glasses to this system made them bioactive in acellular medium: a dense apatite layer formed on the surface after 7 days of immersion in simulated body fluid. This was demonstrated both by microscopic and infrared spectroscopic techniques. The composition of the glass and, consequently, its structure was found to have important effects on the rate of the apatite formation. The combination of reactivity obtained by one formulation with the hydrophilic and degradable character of these cements makes them a very promising alternative to conventional acrylic bone cements, by allowing a better stabilization of the implant and a stronger adhesion to the bone.

A carbonated simulated inorganic plasma (CSIP) physiologically buffered with carbonate-hydrogencarbonate, where a flow of CO 2 at controlled partial pressure enables pH control between 7.3-7.4 while maintaining a constant HCO 2 3 concentration within the plasmatic range (24 to 27 mmol dm 23 ), was previously developed and reported 1 by the authors. The present work represents a step forward, by introducing albumin in this solution, to produce albumin-containing CSIP (CSIPA). Mineralisation studies were performed on three materials (two calcium phosphate ceramics and a glass of the Si-Ca-Mg-P system) in CSIPA, and compared with those performed in traditional Tris-buffered Kokubo's SBF containing albumin (SBFA). It was found that the formation of apatite deposits in CSIPA is favoured when compared not only with SBFA, but also with albumin-free CSIP. The results indicate that the presence of HCO 2 3 in physiological concentration and/or the absence of Tris/HCl buffer may alter the role of albumin in the mineralising medium. The results also suggest that CSIPA-simulated plasma not only mimics in vivo biomineralisation more closely than traditional SBF, but may also be a suitable medium for biomimetic deposition of apatite.