Non-destructive evaluation of crystallinity and chemical composition by Raman spectroscopy in hydroxyapatite-coated implants

MicroRaman measurements have been performed on a commercially available plasma, sprayed hydroxyapatite-coated titanium implant. A double-band structure in the v(1) vibration mode was clearly identified and attributed to the presence of beta-tricalcium phosphate at the metal substrate-hydroxyapatite interface. beta-tricalcium phosphate probably results from the specific crystallization mode of the molten hydroxyapatite particles due to rapid cooling during the plasma spray process. The presence of beta-tricalcium phosphate can explain the dissolution of the hydroxyapatite coating when exposed to the body fluid for a long period of time due to the high solubility of beta-tricalcium phosphate in acidic medium. (C) 2003 Elsevier B.V. All rights reserved.