Depositions of nitrogen on NiTi instruments.

This study was designed to obtain nitrogen-rich layers on the surfaces of endodontic files made of nickel-titanium (NiTi) alloy by chemical vapor deposition. Experimental samples (GT rotary instruments) were deposited by using two different methods. The first one was based on the reaction of wet NH3 with NiTi under high temperatures (300 degrees C). The second technique is a typical MOCVD (metal organic chemical vapor deposition) procedure that uses Ti(Et2N)4 as a titanium and nitrogen precursor. Control samples were not exposed to any process. The chemical composition of the surface layers of each sample was determined by means of X-ray photoelectron spectroscopy and X-ray diffraction measurements. The experimental instruments showed surface chemical composition that was different from that seen in the control group; samples treated with gaseous NH3 showed a surface nitrogen/titanium (N/Ti) ratio = 0.9; MOCVD instruments showed a surface N/Ti ratio of 2; control samples showed a N/Ti ratio = 0.2; MOCVD of nitrogen ion of nickel-titanium files produced a higher concentration of nitrogen on the surface.