Abstract
The aim of this study was to evaluate the effect of varying calcination temperature and duration (500°C -1h, 600°C-1h, 600°C-6h, and 900°C-3h) on the bioactivity property of crystalline hydroxyapatite pellets immersed in a physiological solution (simulated body fluid) for 7 days. The microstructural properties and composition of the powders−such as the degree of crystallinity, crystallite size, additional thermal phases of -tricalcium phosphate (β-TCP) and CaO, and functional groups (hydroxyl and carbonate)−vary depending on the calcination parameter and immersion process. X-ray diffraction (XRD) and infrared spectroscopy (IR) analyses showed significant microstructural changes for the HAP calcined at 900°C for 3 hours. Moreover, atomic absorption spectroscopy (AAS) analysis and pH measurements indicated variations in calcium ion concentration (42.2 ± 0.70 mg/L after 3 days, and 34.2 ± 0.48 mg/L after 7 days of immersion time) and pH of the medium-which decreased from 7.440 ± 0.02 to 7.305 ± 0.03-for the HAP pellet calcined at 900°C. These results were confirmed by X-ray fluorescence (XRF) and electron microscopy, which indicated an increase in the Ca content from 55.06 ± 0.156% to 55.85±0.148%, and in the P content from 24.64±0.155% to 27.59±0.158%, as well as the deposition of dispersed particles and large agglomerates, suggesting the formation of a non-uniform layer of calcium phosphate (CaP) on the surface of the powder pellet calcined at 900°C.
Highlights
Variations in the calcination parameters of hydroxyapatite affect its biological response.
CaP deposit formation after 7 days of immersion on the surface of HAp calcined at 900°C.
The thermal decomposition of HAp can promote the formation of CaP deposits.