Hydroxyapatite induced microstructure by cooling rate modification of cancellous bone thermal treatment

Hydroxyapatite was studied because of its wide set of applications in biocompatible materials. Natural hydroxyapatite obtained by heat treatment technique preserves the structure and the chemical composition of the raw material. The present work investigates the effects of the thermal treatment and the influence of the cooling conditions on crystallinity, morphology and porosity of the cancellous bovine bone using the scanning electron microscopy (SEM) and the Fourier transform infrared (FT-IR) spectroscopy techniques. After deproteinisation, the bovine bone samples were subsequently subjected to different calcination temperatures (ranging from 1000 degrees C to 1300 degrees C), being quenched in two different environments (air and frozen water). The SEM analysis showed that the trabecular bone matrix and its basic microstructure were preserved after calcination. The size of the apatite crystals has increased leading to an increased crystallinity with temperature. Additionally, an apparently increased apatite crystal size was observed in air-quenched samples, resulting a higher degree of compaction for the air-quenched samples than for frozen water-quenched ones. The FT-IR analysis identified bands of hydroxyapatite (500 - 700 cm(-1)) and some bands (around 870cm(-1) and 1400 - 1450 cm(-1)) that are assimilated with the carbonate substitutions in the hydroxyapatite crystal lattice and no collagen or protein traces.