Bioactivity of MgO-CaO-SiO₂ Porous Glass-Ceramics

Abstract

Porous glass-ceramics with bone-bonding ability, i.e. bioactivity, have been attractive as scaffold materials for bone regeneration, since their bioactivity and bioresorbability can be easily controlled by varying their composition. The prerequisite for artificial materials to show bioactivity is formation of a bone-like apatite layer on their surfaces in the body environment. This type of apatite formation can be observed in a simulated body fluid (Kokubo solution) which mimics the composition of human extracellular fluid. Previous studies revealed that the CaO-SiO₂ system is quite effective for the deposition of apatite in the body environment. Magnesium is one of the major inorganic elements existing in body fluid, and has already been used in bioactive glass-ceramics. Dissolution of glasses in the system CaO-SiO₂ could be controlled by addition of MgO. In this study, we synthesized porous glass-ceramics by heat treatment of glass powder with composition of 10MgO•40CaO•50SiO₂ mol% at various temperatures. Porous bodies with continuous pores about 500 μm in diameter were obtained after sintering and crystallization. Precipitation of para-wollastonite and diopside appeared after heat treatment at 900°C and more. The amount of precipitated diopside increased with increasing temperature of the heat treatment. The synthesized specimens formed apatite on their surfaces after soaking in Kokubo solution. Consequently, glasses in the system MgO-CaO-SiO₂ give easy production of porous glass-ceramics with bioactivity and bioresorption by a conventional sintering process.