Calcium phosphate cements modified with pore expanded SBA-15 materials

Abstract

The effects of adding a mesoporous ordered silica to a calcium phosphate cement (CPC) based on α-tricalcium phosphate (α-TCP) are described in this study. The influence of this mesoporous seed material and of the phosphate concentrations in the cement liquid on the physico-chemical, mechanical and microstructural properties of the CPC was investigated. SBA-15 and ultra-large pore (ULP) SBA-15 were used as seed materials. For the latter, a novel reproducible synthesis procedure was developed. When using a 4 wt% Na₂HPO₄ solution, the α-TCP based cement exhibited setting times convenient for clinical applications, but the material was very weak and no conversion to a calcium-deficient hydroxyapatite (CDHAp) occurred. Adding either SBA-15 or ULP SBA-15 to the CPC stimulated the nucleation and growth of apatite crystals and influenced the microstructure of the set cement. The ratio between the concentration of silica in the cement powder and the phosphate concentration in the cement liquid was crucial for tailoring the properties of the CPC. Cements with 5 wt% ULP SBA-15 as seed material could be used in a clinical setting for load-bearing applications.