Adhesion of Hydroxyapatite Plasma Coatings.

Hydroxyapatite (HA) coatings were sprayed by an arc plasma gun with argon-nitrogen plasma at the power of 25 kW from the powder with particle size of 25–63 μm at the distance of 95 mm. Before spraying of the coatings, the samples were preheated in a resistance furnace in air to the temperatures within the range from 20 to 600°C. Adhesion of the HA plasma coating to a titanium substrate was determined on pin samples. The maximum mean value of adhesion was observed when the titanium substrate was preheated to the temperature of 550°C. The results of the study were discussed by reference to the way of increase in activity of the titanium substrate at its preheating for increase in the HA coating adhesion and formation of an equilibrium phase state in the HA coating necessary for long-term usage of the implants. The obtained results will be used for formation of the optimal structure of the bioactive coating consisting of a three-dimensional capillary-porous titanium coating (3D CP Ti) in the form of crests and hollows with porosity of 50% and HA coating sprayed on its surface at the temperature of 550°C. Such mode of the spraying provides formation of a dense, strong, and stable HA coating on endosseous implants. [ABSTRACT FROM AUTHOR]