Ceramics-Silikáty 58, (1) 70 - 78 (2014)

Hydroxyapatite materials prepared by two methods: synthetic (HA-S) and bovine (HA-B) granules were exposed to a longterm in vitro test under dynamic conditions. Testing cells, filled up to one fourth (¼V) of their volume with the tested material, were exposed to continuous flow of simulated body fluid (SBF) for 56 days. The objective of the experiment was to determine whether reactivity of the biomaterials (hydroxyapatites), prepared by different methods but identical in terms of their chemical and phase composition, in SBF were comparable. Analyses of the solutions proved that both materials were highly reactive from the very beginning of interaction with SBF (significant decrease of Ca²⁺ and (PO₄)^3- concentrations in the leachate). SEM/EDS images have shown that the surface of bovine HA-B was covered with a new hydroxyapatite (HAp) phase in the first two weeks of the test while synthetic HA-S was covered after two weeks of the immersion in SBF. At the end of the test, day 56, both materials were completely covered with well developed porous HAp phase in form of nano-plates. A calculation of the rate of HAp formation from the concentration of (PO₄)^3- ions in SBF leachates confirmed that all removed ions were consumed for the formation of the HAp phase throughout the entire testing time for bovine HA-B and only during the second half of the testing time for synthetic HA-S.