Investigation of the effects of titanium oxide concentration on the sinterability, microstructural characteristics, mechanical properties, in vitro bioactivity, and cell culture behavior of chicken-derived hydroxyapatite

This study focuses on how titanium oxide (TiO₂) in concentrations ranging from 0.5 to 4% by weight added the hydroxyapatite (CHA) made from chicken femur bones’, affects sinterability, microstructural, mechanical, and in vitro bioactivity properties. According to the results of the experiments, it was determined that CHA decomposed into whitlockite, alpha tricalcium phosphate (α-TCP), tetracalcium phosphate (TTCP), and calcium oxide (CaO) phases at different temperatures. Rutile and perovskite (CaTiO₃) phases were also found in TiO₂ added CHAs in addition to these phases. With increasing sintering temperature of CHA, the diameters and the heights of the samples decreased. Density increased up to 1250 °C and decreased at 1300 °C respectively. while the partial density value showed similar behavior with density and hardness, At 1200 °C, the maximum values of fracture toughness (1.071 MPam^1/2) and compressive strength (145.417 MPa) were attained; however, as sintering temperatures increased, these values shifted downward to 0.882 MPam^1/2 and 111.096 MPa, respectively. It has been determined that grain growth and decomposition are the underlying factors in obtaining the highest density, hardness, fracture toughness and compressive strength values for CHA at different temperatures. Among the TiO₂ added CHAs, the best properties are obtained for CHA-0.5TiO₂ sintered at 1300 °C (Density: 3.0057 g/cm3, Hardness: 3.973 GPa, Fracture toughness: 1.583 MPam^1/2 and Compressive strength: 170.045 MPa) and the properties of the CHA-TiO₂ composite decreased with increasing TiO₂ ratio. This is due to the fact that increasing TiO₂ has a detrimental impact on CHA’s sinterability behavior and causes it to become more porous and degrade more quickly. It was discovered through in vitro bioactivity and cell culture assays that the addition of TiO₂ had a detrimental impact on the proliferation of bone tissues.