Fabrication of silica-substituted octacalcium phosphate blocks based on the setting reaction of the CaCO₃–H₃PO₄–Na₂SiO₃ cementing process

Abstract

Although silica-substituted octacalcium phosphate (OCP–silica) blocks have demonstrated outstanding biocompatibility and bone-regeneration capacity, their mechanical strength is insufficient for further applications. Therefore, in this study, we introduce a novel process for fabricating OCP–silica based on the cement-setting reactions of CaCO₃, H₃PO₄, and Na₂SiO₃. Despite having the same basic composition as the acidic calcium phosphate powder used in the initial components, the mechanical strength of the fabricated OCP–silica blocks [diametral tensile strength (DTS) of ∼1.0 MPa] was approximately threefold greater than that of the legacy blocks (DTS of ∼0.3 MPa). The fabricated OCP–silica blocks exhibited a fine structure consisting of closely interlocked, well-developed, plate-like crystals. The high mechanical strength of the fabricated blocks is attributed to the close interlocking of the OCP crystals. The fabricated OCP–silica (CaCO₃) blocks exhibited sufficient mechanical strength to be used as a bone substitute; thus, the fabrication process reported herein provides a valuable tool for advancing clinical applications.