Development and Characterization of Biphasic Hydroxyapatite/ b-TCP Cements

Biphasic calcium phosphate bioceramics composed of hydroxy-apatite (HA) and b-tricalcium phosphate (b-TCP) have rele-vant properties as synthetic bone grafts, such as tunable resorption, bioactivity, and intrinsic osteoinduction. However, they have some limitations associated to their condition of high-temperature ceramics. In this work self-setting Biphasic Calcium Phosphate Cements (BCPCs) with different HA/b-TCP ratios were obtained from self-setting a-TCP/b-TCP pastes. The strategy used allowed synthesizing BCPCs with modulated composition, compressive strength, and specific sur-face area. Due to its higher solubility, a-TCP was fully hydro-lyzed to a calcium-deficient HA (CDHA), whereas b-TCP remained unreacted and completely embedded in the CDHA matrix. Increasing amounts of the non-reacting b-TCP phase resulted in a linear decrease of the compressive strength, in association to the decreasing amount of precipitated HA crys-tals, which are responsible for the mechanical consolidation of apatitic cements. Ca2+ release and degradation in acidic med-ium was similar in all the BCPCs within the timeframe studied, although differences might be expected in longer term studies once b-TCP, the more soluble phase was exposed to the sur-rounding media. I