In vitro bioactivity and biocompatibility of a Co–Cr–Mo alloy after heat treatment in contact with different bioactive systems

As-cast samples of a cobalt base alloy (ASTM F-75) were heat treated in contact with different bioactive materials: (a) powder mixtures of β-tricalcium phosphate (TCP)–bioactive glass (BG) in different proportions (TCP–BG: 60–40, 70–30 and 80–20 wt%) and (b) mineral and synthetic wollastonite. Samples were packed with each bioactive material and heat treated for 1 h at 1220 °C. To characterize the in vitro bioactivity, heat treated samples were immersed in a simulated body fluid. After immersion, a ceramic layer containing Ca and P was formed on all samples. The thicker and more homogeneous layers, identified as apatite, were formed more rapidly on the heat treated samples in contact with 80TCP–20BG and synthetic wollastonite. The more bioactive coatings were selected for MC3T3 cell adhesion, proliferation and differentiation assays. Cell proliferation and alkaline phosphatase activity were not affected by the different coatings. Additionally, samples packed with 80TCP–20BG presented a higher cell adhesion than those packed with synthetic wollastonite. On the samples previously packed with synthetic wollastonite, a denser homogeneous Ca- and P-rich layer was formed 21 days after cell seeding and incubation in differentiative conditions.