Bone‐bonding ability of P2O5‐Free CaO · SiO2 glasses

Abstract

An apatite- and wollastonite-containing glass-ceramic (A · W-GC) has been reported to form a tight bond with living bone through an apatite layer formed on its surface. This layer is considered to be formed by dissolution of Ca²⁺ and HSiO₃⁻ ions from the glass-ceramic into the surrounding body fluids. In order to confirm this proposed mechanism for the surface reaction of A · W-GC, three kinds of glass in the systems CaOSiO₂, CaOSiO₂CaF₂, and CaOSiO₂P₂O₅ were implanted into the tibiae of rabbits for 3 or 8 weeks. Contact microradiography and SEM-EPMA showed that all three kinds of glass formed a Ca, P-rich layer in combination with a Si-rich layer on their surfaces within 3 weeks and formed a direct bond with bone via these layers. The detaching test, performed 8 weeks after implantation, showed that the loads required to detach the implants from the bone were almost equal for the phosphorus-free and the phosphorus-containing glasses. It was concluded that even P₂O₅-free CaO · SiO₂ glass formed a Ca,P-rich layer on its surface and bonded tightly with living bone. If glasses and glass-ceramics release at least Ca²⁺ and HSiO₃⁻ ions, this would be sufficient for them to form the Ca,P-rich layer on their surfaces in vivo, enabling them to bond directly with bone.