DISSOLUTION BEHAVIOR OF CALCIUM-PHOSPHATE COATINGS OBTAINED BY LASER-ABLATION

Pulsed laser deposited calcium phosphate coatings on titanium alloy ha ve been tested under simulated physiological conditions in order to ev aluate the changes in morphology, composition and structure. The coati ngs were deposited under different conditions to obtain different crys talline structures, ranging from amorphous and mixed crystalline phase s to pure crystalline hydroxyapatite (HA). The coated samples were imm ersed in a Ca-free Hank's balanced salt solution for up to 5 days. Cha racterization of the coatings was performed by X-ray diffraction, scan ning electron microscopy and Fourier-transform Raman spectroscopy befo re and after immersion. Their dissolution behaviour was also monitored through their mass loss and calcium release. Coatings of pure HA pres erve their morphology and structure during the exposure time in soluti on. In multiphasic coatings, consisting of HA with tetracalcium phosph ate (TetraCP) or beta-tricalcium phosphate (beta-TCP) with a-tricalciu m phosphate (alpha-TCP), microporosity is induced by the complete diss olution of TetraCP or alpha-TCP. Amorphous calcium phosphate coatings totally dissolve. (C) 1998 Elsevier Science Ltd. All rights reserved.