Fabrication of a Hard Tissue Replacement Using Natural Hydroxyapatite Derived from Bovine Bones by Thermal Decomposition Method

BACKGROUND For the treatment of bone defects that exceed the critical size of the injury, several therapies have been investigated. Thermal decomposition method is suggested for extraction of natural hydroxyapatite bioceramic (HA). This technique in comparison with other methods of producing HA, has less complexity and greater economic efficiency. OBJECTIVE In the present study, a thermal decomposition method is suggested for extraction of natural HA from bovine femur bones. METHODS In this experiment, to extract the ceramic material, the bone samples were first de-fatted and ground to particles less than 420 μm, and also 420-500 μm, respectively. Prepared powders were heated at 170 °C for 24 h, and then divided into two groups for 6 h. The first group was heated at 750 °C; the second group was heated at 850 °C. The calcium phosphate compounds were obtained with complete elimination of the organic phase of the bone. These bioceramic compounds were characterized physiochemically by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray (EDX), and scanning electron microscopy (SEM). RESULTS We found that the powder heated at 750 °C in two dimensional scales was rich in carbonated hydroxyapatite, and therefore, eminently suitable for using in hard tissue replacements. However, increasing the temperature up to 850 °C reduced the Ca/P ratio to 1.5 in the powder sample sizes less than 420 μm. Consequently, the obtained composition became rather similar to the chemical formula of tricalcium phosphate (TCP) that is appropriate in tissue engineering and drug delivery applications. CONCLUSION The observations affirmed that by eliminating the collagen and other organic materials existing in the bovine bones, the mineral phase of the bone had the potential of transformation to nano-particles. To investigate the repair of critical-size bone defects and bone augmentation, cylindrical blocks were fabricated by applying different pressures of 150, 160 and 170 MPa. The structure and compressive strength of the pressed samples after sintering at 1200 °C were characterized by SEM and compressive strength test.