Strength Enhancement of β‐TCP Consolidated Bodies Through Hydrothermal Dissolution–Reprecipitation

ABSTRACT

Beta‐tricalcium phosphate (β‐TCP) possesses excellent bioresorbability; however, achieving sufficient mechanical strength for load‐bearing applications remains a major challenge. This study aimed to fabricate hydroxyapatite (HA)/β‐tricalcium phosphate (β‐TCP) biphasic calcium phosphate (BCP) consolidated bodies by hydrothermal treatment and to identify factors contributing to strength enhancement. Consolidated β‐TCP bodies were hydrothermally treated at 200°C–290°C and characterized by compressive strength testing, x‐ray diffraction (XRD), scanning electron microscopy, and potentiometric titration. The relationship between the Equi‐Acid‐Base‐Point (EABP) and compressive strength was also examined. Hydrothermal treatment promoted the transformation of β‐TCP to HA with increasing temperature, resulting in a maximum compressive strength of 57 MPa. In contrast, the amount of water used during treatment had little effect on strength. Potentiometric titration revealed that the EABP shifted toward lower pH values with increasing treatment temperature, and this shift correlated with enhanced compressive strength. The observed EABP changes could not be explained solely by HA formation and suggested the formation of calcium phosphate phases with lower Ca/P ratios. These results indicate that strengthening of β‐TCP consolidated bodies is governed not only by β‐TCP‐to‐HA phase transformation but also by compositional and microstructural changes associated with dissolution–reprecipitation.