Hydroxyapatite activation analysis using X-ray diffraction, FT-IR spectroscopy and SEM

Hydroxyapatite (HAp) can be used as a bone substitute or as a pulp capping material in dentistry. As a bioactive material it binds to live tissue, inducing biological response. HAp with undersized particles, as well as high crystalline content might have very low biological activity. Treating of bioactive materials by various methods changes their characteristics. Surrounding condition, such as saliva presence, could influence the bioactivity of HAp. Aim of the study was to determine the bioactivation - structural, morphological and chemical changes of HAp, induced by artificial saliva using XRD, FT-IR and SEM. Ten HAp samples (crystallographicaly pure phase), each of 0.5 g, were exposed to artificial saliva for 35 days (i.e. activated) and observed. At regular intervals of 7 days XRD, FT-IR spectra and SEM micrographs were obtained from the samples. XRD of an untreated HAp sample showed cristaline structure. After the exposition to the artificial saliva it showed the amorphisation - bioactivation. The amorphisation progressed in time. Combined XRD and FT-IR showed changes in concentration of Ca an P ions in HAp, as well as the ions interchange with the surrounding solution. SEM analysis of untreated HAp showed small crystal particles of the initial powder. After 35-day treatment the material structure was changed to a sponge-like structure, with a lot of unoccupied space. By combining the methods of XRD, FT-IR and SEM bioactivation of HAp with artificial saliva was detected and determined.