VIBRATIONAL-SPECTRA OF CONTROLLED-STRUCTURE HYDROXYAPATITE COATINGS OBTAINED BY THE POLYMERIC ROUTE

This work illustrates the role of HPO42- ions, contained in the major precursors of hydroxyapatite (HAP), in both the in vitro and in vivo f ormation of HAP. In fact this ion, through strong OHO H-bonding, can s tabilize the structure of the different calcium phosphates (amorphous tricalcium phosphate, amorphous and crystalline octacalcium phosphate, non-stoichiometric apatites, etc.) involved in the professes of HAP f ormation. Therefore, the planning of bioceramic coatings which induce the osteogenesis process should be aimed at obtaining HAP surfaces con taining HPO42- ions with variable and determinate PO43-/HPO42- molar r atios. On the basis of vibrational spectroscopic results, this work in dicates that instead of the plasma flame spray (PFS) method, which ind uces deep modifications of composition and structure of the coating, t he polymeric route wet-way method coupled with a surface treatment sim ilar to that used in dentistry for the 'smear layer' is able to yield a surface containing HAP and also HPO42- ions.