Variation in structure and properties of a non-dispersive TTCP/DCPA-derived CPC immersed in Hanks' solution

The present work is to characterize a non-dispersive, fast-setting and high-strength tetra calcium phosphate (TTCP)/dicalcium phosphate anhydrous (DCPA)-based calcium phosphate cement (nd-CPC) recently developed in the authors' laboratory. Comparison between this CPC and a conventional TTCP/DCPA-based CPC (c-CPC) is made. The results show that, during setting c-CPC reaches its pH plateau after 10 min, while nd-CPC approaches plateau after 20 min. During immersion in Hanks' solution the pH values of both cements reach their maxima after immersion for a few days, then decline eventually to near neutrality. With immersion time TTCP and DCPA phases gradually dissolve and apatite phase precipitates. The nd-CPC has a higher apatite formation rate and denser structure than c-CPC under similar conditions, especially at early stage. The nd-CPC also demonstrates higher strength both during setting and after immersion.