Development and Characterization of Biphasic Hydroxyapatite/β‐TCP Cements

Biphasic calcium phosphate bioceramics composed of hydroxyapatite (HA) and β‐tricalcium phosphate (β‐TCP) have relevant 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/β‐TCP ratios were obtained from self‐setting α‐TCP/β‐TCP pastes. The strategy used allowed synthesizing BCPCs with modulated composition, compressive strength, and specific surface area. Due to its higher solubility, α‐TCP was fully hydrolyzed to a calcium‐deficient HA (CDHA), whereas β‐TCP remained unreacted and completely embedded in the CDHA matrix. Increasing amounts of the non‐reacting β‐TCP phase resulted in a linear decrease of the compressive strength, in association to the decreasing amount of precipitated HA crystals, which are responsible for the mechanical consolidation of apatitic cements. Ca²⁺ release and degradation in acidic medium was similar in all the BCPCs within the timeframe studied, although differences might be expected in longer term studies once β‐TCP, the more soluble phase was exposed to the surrounding media.