Ceramics-Silikáty 54 (1) 8-13 (2010)

DISSOLUTION BEHAVIOR OF BIOACTIVE GLASS CERAMICS WITH DIFFERENT CaO/MgO RATIOS

M. U. Hashmi , S. A. Shah , S. Alam, A. Shamim

In this work, powders of three different compositions, each having 34 SiO₂-14.5 P₂O₅-1 CaF₂-0.5 MgF (% wt) and ratio of CaO/MgO varying from 11.5:1 to 1:11.5 were thoroughly mixed and melted under oxy-acetylene flame in a fire clay crucible that made the glass formation cheaper in time and cost. The melt of each composition was quenched in water to form three different glasses. Every glass was sintered at 950°C to form three glass ceramics named G1, G2 and G3 respectively. To study the dissolution behavior, each sample was immersed in a simulated body fluid (SBF) for 2, 5, 10, 20 and 25 days at room temperature. Thin film XRD analysis revealed that the samples with larger CaO/MgO ratio exhibited better bioactivity. pH of SBF increased efficiently in case of G1 whereas in case of G2 and G3, this increase was slower due to greater amount of MgO. The concentrations of Ca, P, Mg and Si ions were measured by Atomic Absorption Spectroscopy. EDS analysis showed the increase in P and Ca ions and presence of C in G1 after 5 days immersion and after 10 days, in case of G2 indicating the higher formation rate of hydroxycarbonate Apatite layer in G1 as compared to G2 due to greater CaO/MgO ratio whereas in G3 Mg-hydroxycarbonate apatite (Ca(Mg)₅(CO₃)(PO₄)₃(OH)) (heneuite) layer was recognized after 20 days showing the least bioactivity due to very large amount of Mg and the least CaO/MgO ratio.

Keywords: Oxyacetylene Flame, Dissolution behavior, Atomic Absorption Spectroscopy, MgHydroxycarbonate apatite (Heneuite)