Osteoblastic cell attachment to hydroxyapatite-coated implant surfaces in vitro

Hydroxyapatite (HA) used as a coating for implants can exhibit varying leve ls of interaction with the biologic environment. The crystallinity of the H A-based coating has been shown to control the rate of dissolution and appea rs to play a role in the initial cellular interaction with the implant surf aces. An osteoblastic cell attachment assay was employed to examine the cel l attachment to untreated and pretreated (pH 5.2, 24 hours) titanium and HA coatings of low (50%), medium (75%), and high (90%) crystallinity. A sligh tly higher percentage of cell attachment (%CA) was found on untreated and p retreated HA surfaces as compared to the titanium surface. No significant d ifference could be found in the %CA between the 3 levels of crystallinity. However, higher levels of %CA were observed on pretreated HA surfaces than on untreated HA surfaces (t test, P < .05). Elevated calcium and phosphate levels in culture medium did not have any effect on cell attachment. Scanni ng electron microscopic examinations revealed surface degradation of the HA coating following pretreatment in the simulated inflammatory media (pH 5.2 , 24 hours). The results suggest that the altered surface topography may in fluence the initial cell attachment to HA surfaces.