The comparison of powder characteristics and physicochemical, mechanical and biological properties between nanostructure ceramics of hydroxyapatite and fluoridated hydroxyapatite

In this study, several fluorine-substituted hydroxyapatite ceramics with the general chemical formula Ca5(PO4)3(OH)1 − xFx (0 ≤ x ≤ 1), where x = 0.0 (hydroxyapatite; HA), x = 0.68 (fluorhydroxyapatite; FHA) and x = 0.97 (fluorapatite; FA) were prepared. The powders were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infra-red (FTIR), X-ray diffraction (XRD), F-selective electrode, atomic absorption spectroscopy (AAS) and EDTA titration analyses. The powders were uniaxially pressed and were formed as a disc shape. Subsequently, sinterability and thermal stability of synthesized powders were compared together. Also the effect simultaneously of fluoride content and temperature were examined on the lattice parameters and crystallites size of the obtained powders. Mechanical properties including hardness, elastic modulus and fracture toughness were measured using indentation. The in vitro dissolution studies of the samples were carried out at osteoclastic resorption conditions. Finally, the biocompatibility and cytotoxicity of the samples were carried out using osteoblast-like cells and L929 cell line, respectively. The obtained results showed that the thermal stability substantially is increased with increase incorporated fluoride into HA structure. Also it was found that the fluoride reduced the lattice parameters and crystallites size of HA. Finally, the in vitro dissolution studies results suggest that the fluoride substitutions in HA offer the ability to prepare HAs with different degrees of solubility.