Formation and Biomimetic Deposition of Bone-like Hydroxyapatite on Wollastonite-gypsum Composites

Bone cements are often used for bone repair and fixation. The main objective of formulating a bone cement is to achieve structure and properties similarity to bone. In addition, bioactivity of a bone cement provides a major advantage that helps achieving better binding and interaction with the surrounding tissues. In the current study, gypsum was used as a matrix for a composite that comprises highly crystalline prestine and acid-treated wollastonite (CaSiO₃) fibers. Composites made by mixing their powder precursors with deionized water at room temperature, were investigated for their composition using X-ray diffraction (XRD) and Thermogravimetric Analysis (TGA), for their microstructure using Scanning Electron Microscopy (SEM), for their compressive strengths and modulus of elasticity, and for setting time measurements. In addition, cement composites were evaluated for their preliminary bioactivity in a protein-free Simulated Body Fluid (SBF) for up to 14 days. Results show the improvement of mechanical properties and bioactivity of the composites using acid-treated wollastonite fibers. This was attributed to the formation of hydrated silica layer on the surface of the acid-treated fibers which improved the binding with the gypsum matrix and provided nucleating sites for the deposition of bone-like apatite spherolites from SBF media.