Three-step procedure for the deposition of hydroxyapatite coatings

Dental implants made of titanium covered with hydroxyapatite (Ti-HA) offer several advantages regarding mechanical, physicochemical, and biochemical aspects but lack stability in time, quality bone-bonding capabilities, or anticorrosion resistance in physiological media. In order to improve the characteristics of dental Ti-HA implants, we propose a new strategy for obtaining the deposited layer, consisting of the electrodeposition of the ceramic (HA) onto Ti metal followed by sintering of the ensemble at 600°C and then the electrodeposition of a second HA layer on top of the first one. The goal was to obtain a coating made up of two HA layers with a porosity gradient (one dense inner layer and one porous outer layer), and the results confirmed the formation of preferentially oriented, low-crystallinity double HA coatings. The base layer was made up of feathery crystals, and the top layer consisted of stellate clusters of crystals. Electrochemical tests, performed in artificial saliva solution at 37°C, showed that some HA coatings could moderately decrease the corrosion rate of Ti.