Effect of TiN/TiO2 multilayer coatings on the properties of stainless steel for biomedical applications

A large number of research studies have been focused recently on possible methods for surface modification of metals and alloys. Titanium nitride (TiN) and titanium dioxide (TiO2) films deposited on different substrates have found many applications because of their good mechanical properties, resistance to corrosion, and biocompatibility. The substrates for coating can consist of various kinds of metals and alloys used for manufacturing implants, and endodontic or rotary dental instruments. In this study, stainless steel 304L substrates and endodontic files were coated by a DC-magnetron-sputtered TiN/TiO2 multilayer; the mechanical and biocompatible properties of the newly deposited films were explored. The structure of the coatings was examined by X-ray diffraction (XRD), whereas the hardness was investigated by nanoindentation. The corrosion resistance was evaluated by potentiodynamic polarization tests in Ringer solution. Each endodontic file coated with TiN/TiO2 was used for mechanical preparation of five root canals and, afterwards, their surface morphology was studied by scanning electron microscopy (SEM). Our results confirmed that the TiN/TiO2 multilayer coatings prepared had good stoichiometry and corrosion resistance. Moreover, the pre-coated instruments had a smoother surface and less debris and defects after mechanical preparation of five root canals compared to the non-coated ones. This indicated the usefulness of the coating formed in dental applications.