Abstract
Glass-ceramics of Na2O-R2O3-P2O5-SiO2 (Narpsio) consist of a skeleton structure of 12-tetrahedra-membered rings and exhibit a super Na+ conductivity. Glass-ceramic Narpsio was proved to be electrically polarized through highly mobile sodium ions. Narpsio also shows relatively higher solubility in water. Taking into account of the water solubility and the chemical composition, the reactivity of polarized and non-polarized glass-ceramic Narpsio in the stimulated body fluid (SBF) were investigated in relation to bioactivity. After the 6 days' immersion of SBF, hydroxyapatite microcrystals aggregated semispherically were grown on the glass-ceramic Narpsio surfaces. Although the acceleration effects were under study, the growth rate was recognized to be higher in both of the negatively and positively charged surfaces. In analogy with polarized bioglasses, we confirmed the chemico-vector effects of glass-ceramic Narpsio for biomedical purpose. Additionally, glass-ceramic Narpsio, prepared by the locally biasing crystallization method, showed unreported microstructural changes of surfaces during chemical polishing with water, depending upon the direction of a biasing field. The phenomenon was interpreted as a mechanochemico-vector effect.
