Dissolution of Hydroxyapatite Powder in Simulated Body Fluid

Commercial hydroxyapatite (HA) powders were calcined at the temperature range of 1000-1350 °C in air and the calcined powders were immersed in simulated body fluid (SBF) at 37 °C for 3 or 7 days. At 1200°C, HA gradually releases its OH' ions and transforms into oxyhydroxyapatite (Ca 10 (PO 4 ) 6 O x (OH)2-2x, OHAP). HA initiated to decompose to a-tricalcium phosphate (a-TCP) and tetracalcium phosphate (TTCP) phase at 1350°C. The surface dissolution of HA powders was accelerated by non-stoichiometric composition such as a-TCP, TTCP and the powders with smooth surface appeared to be dissolved on the edge showing fiber-like particles, followed by separation of the large particle to small one with the immersion time. The fiber-like particles consisted of new phases such as, carbonated-apatite (CHA) and octacalcium phosphate (OCP).