Comparative assessment of the corrosion process of orthodontic archwires made of stainless steel, titanium-molybdenum and nickel-titanium alloys

The phenomenon of corrosion of orthodontic appliances is of interest to both clinicians and researchers dealing with the issue of biocompatibility of medical materials. The oral cavity, due to its temperature fluctuations, changing pH, high humidity, action of mechanical forces and the presence of microorganisms is a favorable environment for degradation of dental materials. This article presents the comparative assessment of the intensity of corrosion of orthodontic archwires made of alloy steel, nickel-titanium and titanium-molybdenum alloys in laboratory conditions. Corrosion resistance examinations were carried out by means of the impedance and the potentiodynamic methods using an Autolab PGSTAT100 potentiostat/galwanostat (Eco Chemie B.V., Holand) with FRA2 module, in non-deaerated artificial saliva solution at 37 °C. An analysis of the impendence method's data showing that the highest corrosion resistance is observed for NiTi arches (3M, USA), while the lowest resistance for SS arches (3M, USA). These observations were confirmed by the data obtained from potentiodynamic tests; it was observed that the average corrosion current density [Icor] was the lowest for nickel-titanium archwires (3M, USA) and averaged 2.50 × 10−3 μA/cm2. The highest Icor corrosion current was observed in the case of steel wires from the same manufacturer and averaged 4.96 × 10−2 μA/cm2.