Nitriding of titanium disks and industrial dental implants using hollow cathode discharge

Faster osseointegration of dental implants made of commercially pure Ti or various Ti alloys can be achieved by modifying the surface properties of the original implants. Apart from the possibility of creating different surface topographies, changing surface roughness, cleaning/sterilizing contaminated surface and modifying surface wettability, plasma treatment can be used to change the local chemical properties by formation of different phases, e.g., by creation of a nitrided surface layer. In this work, titanium disk samples were nitrided using a hollow cathode discharge (HCD) configuration of a standard plasma nitriding system in a 80% H2–N2 atmosphere at pressures of 150 and 250 Pa, and temperatures of 400, 450 and 500 °C for 1 and 2 h. The surface topography and the nitrided layer thickness of the samples were ascertained from optical and electron microscopy. Phases were determined by X-ray diffraction. The surface roughness and wettability were also quantified. Stable nitrided layers with increased surface roughness and higher wettability have been observed for samples treated at 450 and 500 °C, and at a pressure of 150 Pa. Industrially fabricated dental implants were then nitrided at 500 °C/150 Pa for 2 h. The results show the capability of HCD for nitriding dental implants without geometrical distortion, with a significant improvement in the surface texture and superior wettability over untreated dental implants.