Effect of sodium oxide and magnesia on structure, in vitro bioactivity and degradability of wollastonite

Wollastonite CaSiO3 (W-0) and CaSiO3 doped with Na2O (W-Na) or MgO (W-Mg) were synthesized by sintering sol-gel derived powders and compacts. The effects of Na2O and MgO on structure, in vitro bioactivity, degradability and mechanical properties of wollastonite were studied. The main crystal phases of these ceramic powders were β-CaSiO3. In addition, Na2Ca2Si3O9 appeared in sample W-Na and Ca3Mg(SiO4)2 appeared in W-Mg. For ceramic block W-Mg, CaMgSi2O6 appeared. After soaking in simulated body fluid (SBF) for 7 days, the apatite layer was formed on the surface of these ceramics. The addition of Na2O increased the degradation rate of wollastonite and MgO decreased the degradation rate. Na2O and MgO improved the bending strength of wollastonite. The elastic moduli of ceramics accorded with that of dense bone of human body.