HEATING OF CALCIUM-PHOSPHATE CRYSTALS - MORPHOLOGICAL CONSEQUENCES AND BIOLOGICAL IMPLICATIONS

Sintering hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP) affects the chemical composition, the crystallinity, and the morpholo gical features as demonstrated by means of X-ray diffraction (XRD), in frared spectroscopy (IR), and scanning electron microscopy (SEM). When heated to 1230 degrees C, 16.7% of HA had de composed to beta-TCP. SE M investigations showed homogeneous, sharp angular polyhedric blocks o f 30 to 50 mu m with rare surface pores. On heating at 1230 degrees C, beta-TCP had entirely transformed to alpha-TCP. During sintering, the size of the powder grains increased and progressive bridging between the grains was observed. At 1230 degrees C, a network within round-sha ped polyhedric blocks of 50 to 90 mu m was formed. In both, HA and bet a-TCP, surfaces were smooth. The chemical composition and the crystall inity of calcium phosphate ceramics determine their dissolution behavi or and osteogenic properties. Nevertheless, their temperature dependen t morphological features, such as, particle shape and size, surface te xture, and porosity, as demonstrated in the present study, also influe nce the resorption rates, tissue responses, and wound healing duration . This should be emphasized more by clinicians in choosing an appropri ate material for bone substitution.