Ep. Paschalis et al., DEGRADATION POTENTIAL OF PLASMA-SPRAYED HYDROXYAPATITE-COATED TITANIUM IMPLANTS, Journal of biomedical materials research, 29(12), 1995, pp. 1499-1505
The purpose of this study was to develop an analytical method for eval
uating the dissolution behavior of plasma-sprayed hydroxyapatite (HAP)
coatings. Six commercially available and clinically used coatings app
lied to nonporous titanium coupons according to their respective speci
fications for orthopedic devices were used in this study. Dissolution
behavior was monitored by first preconditioning the implant in 0.15 mo
l L(-1) sodium chloride solution at 37 degrees C until either equilibr
ium or the desired change in solution hydrogen and calcium ion concent
rations had been reached. In the second step, the implants were subjec
ted to dual constant composition (DCC) dissolution under conditions of
controlled undersaturation. Results indicate that the dissolution rat
es of the HAP coatings may differ by as much as a factor of 5 despite
the fact that analytical techniques, including X-ray diffraction and F
TIR, indicate no change in crystallinity or composition of the coating
s before and after the solution treatment. These results indicate that
HAP coatings from different sources react very differently when place
d in the same local aqueous environment. However, more work will be ne
cessary before these in vitro results can be used to predict in vivo b
ehavior. (C) 1995 John Wiley & Sons, Inc.