Preparation of porous glass-ceramics containing whitlockite and diopside for bone repair

Control of the surface reactivity of bioactive materials to surrounding body fluids is essential in the design of novel bone-repairing materials, because apatite formation on bioactive materials is governed by the dissolution of constituents from the materials and the nucleation of hydroxyapatite on the resultant surface. These bioactive materials are therefore recognized as "chemicovector ceramics", as described by Yamashita et al. Glass-based bioactive materials have the benefit of easy control of their bioactivity and bioresorbability, as their surface reactivity in body environments can be easily controlled by varying their composition. Consequently, glass-derived biomaterials are attractive for use in the fabrication of porous glass-ceramics as bone substitute and scaffold materials for bone regeneration. We anticipated that a glass-ceramic containing tricalcium phosphate (TCP; 3CaO · P₂O₅) and diopside (CaO · MgO · 2SiO₂) would show high bioactivity and high mechanical strength, as well as bioresorbability. In this study, glass-ceramics were prepared with compositions of x(3CaO · P ₂O₅) · (100 - x) (CaO · MgO · 2SiO₂), where x = 0, 38, 50, or 60 mass%, and their bioactivity evaluated by examining in vitro apatite formation in a simulated body fluid (SBF). Pulverized glasses of each composition were compacted and heated to obtain the bulk glass-ceramics. When the compacted materials were sintered at 1200°C, whitlockite (β-TCP) and diopside precipitated from the glasses with compositions where x = 38, 50, 60 mass%, and diopside alone precipitated when x = 0. The prepared glass-ceramics containing β-TCP and diopside formed apatite on their surfaces within 7 d in SBF. This result indicates that these glass-ceramics have the potential to show bioactivity. Porous glass-ceramics with continuous pores of about 500 μm were successfully prepared with the above compositions. These porous glass-ceramics containing β-TCP and diopside are expected to be useful as scaffold materials for bone repair.