Characterization of calcium phosphate cements modified by addition of amorphous calcium phosphate

In this study the influence of amorphous calcium phosphate (ACP) on the setting of, and the formed apatite crystallite size in, a calcium phosphate cement (CPC) based on α-tricalcium phosphate (α-TCP) or tetracalcium phosphate (TTCP)/monocalcium phosphate monohydrate (MCPM) was investigated. Setting times at 22 °C were measured in air atmosphere; those at 37 °C were measured at 100% relative humidity. The phase composition of the set cements was investigated after 1 week using X-ray diffractometry and infrared spectroscopy and the morphology was investigated using scanning electron microscopy. The compressive strength (CS) of the set CPCs was measured after 1 day. Viability of MC3T3-E1 cells on the CPCs was analyzed after 7, 14 and 21 days of incubation using the CellTiter 96® Aqueous Non-Radioactive Cell Proliferation Assay. The α-TCP-based cement exhibited long setting times, a high CS and was converted to a calcium-deficient hydroxyapatite (CDHAp). The TTCP/MCPM-based CPC was only partly converted to CDHAp, produced acceptable setting times and had a low CS. Addition of ACP to these two CPCs resulted in cements that exhibited good setting times, CS suitable for non-load-bearing applications and a full conversion to nanocrystalline CDHAp. Moreover, the ACP containing CPCs demonstrated good cell viability, making them suitable candidates for bone substitute materials.