Ceramics-Silikáty 46, (1) 9 - 14 (2002)

The materials for bone and dental implants are tested in vitro using simulated body fluid (SBF). The composition of most used SBF differs from that of blood plasma by high content of Cl⁻ ions and lower content of HCO₃⁻ ions. Considering the composition of bone-like apatite, which contains carbonate ions, the test results could be influenced by this difference. The glass of system Na₂O-CaO-SiO₂-P₂O₅ was leached in fluids of composition (in mmol/l): 142 Na⁺, 5 K⁺, 2.5 Ca²⁺, 1 Mg²⁺,1 SO₄ ²⁻, 1 HPO₄ ²⁻, 136 (Cl⁻ +HCO₃ ⁻ ). The content of HCO₃ ⁻ ranged between 5 and 27 mmol/l. The decrease of phosphorus concentration was observed after 2 days in all solutions indicating the creation of phosphate layer on the glass surface. X-ray diffraction (XRD) confirmed the various extent of apatite layer creation in different solutions. The intensity of XRD peaks seems to be more influenced by the initial solution supersaturation than by the supersaturation values during the interaction. This fact indicates that the nucleation could be the control mechanism of apatite precipitation. Both experimental and supersaturation results indicate that the SBF with increased amount of HCO₃ ⁻ ions is more appropriate and sensible to in vitro testing of bioactive materials.