Functionalization of orthodontic alloys with DLC coatings

Abstract

Biometals stand out in orthodontics due to the excellent combination of mechanical-chemical-physical properties. However, intraoral corrosion leads to metallic ions release with an inevitable harmful effect on human health and wellness. In fact, the cytotoxicity of Ni, Cr and Fe has been highlighted, and both metallic Ni and its compounds are considered carcinogenic according to IARC. Therefore, it is imperative to develop and implement new strategies in order to minimize those effects without losing biocompatibility of the metallic alloys. The present work is devoted to Diamond-Like Carbon (DLC) coatings, by magnetron sputtering, as a functional barrier to metal release from biomedical metallic alloys. The corrosion resistance of DLC films with Cr interlayer for adhesion improvement was studied. The static immersion tests were performed in artificial saliva solution by selecting two pH values and two bathing times. Chemical and morphological characterization of the samples were performed by SEM/EDS and AFM, and static contact angles were also measured. The quantification of metallic ions released into the immersion solution baths was obtained by ICP-AES. The results were very satisfactory, showing that pitting corrosion, which was detected on austenitic stainless-steel substrates, could be avoided by using a DLC-based coating, especially in highly acidic environment.