In Situ Formation of Hydroxyapatite - Αlpha Tricalcium Phosphate Biphasic Ceramics with Higher Strength and Bioactivity

Synthetic bone grafts based on hydroxyapatite–alpha tricalcium phosphate (HA/α‐TCP) biphasic system are preferred for their higher resorbability and bioactivity. In this work, a viable method is suggested to produce HA/α‐TCP systems with enhanced bioactivity and mechanical strength, through the in situ conversion of calcium‐deficient apatite precursor. A homogeneous precipitation technique was used to produce the precursor powder. It was heat‐treated to study the phase conversion using XRD and FTIR. The precursor got converted HA/β‐TCP system above 762°C, which further transformed to HA/α‐TCP system after 1165°C. The sintering temperature was optimized at 1175°C. It is the net Ca/P ratio of the precursor which decides the ratio of the phases in the final ceramic. The precursor with Ca/P = 1.585 gave a biphasic ceramic containing 47% α‐TCP. The flexural strength of this sample was more than 2.5 times higher compared to the biphasic ceramic made by sintering HA/α‐TCP powder mix. The internal microstructure of the ceramic revealed the formation of α‐TCP in sheet‐like morphology. Preferential dissolution of the α‐TCP from the sample surface in aqueous and acidic environment was confirmed quantitatively. Biomimetic growth technique in simulated body fluid has been used to assess the bioactivity in vitro.