In vitro corrosion behavior of lingual orthodontic archwires

Abstract

To investigate the in vitro electrochemical corrosive behavior of archwires used in lingual orthodontics and the effects on the phase transition temperatures. Materials and Methods. Six different types of archwires of stainless steel, titanium-molybdenum, nickel-titanium and nickel-titanium-copper were used. Corrosion tests were performed following ISO-standard 10993-15:2000. Differential scanning calorimetry and scanning electron microscopy were used. Results. The stainless steel archwires showed an Epit around −600mV, and those of titanium alloys showed Epit values around 1000mV. Differential scanning calorimetry detected a rhombohedral phase in nickel-titanium archwires, while it was not detected in nickel-titanium-copper wires. A difference of 2◦C to 3.5◦C from the manufacturer’s claim was found in the as-received and polarized samples, respectively. Conclusions. The 0.016 stainless steel archwires were found to be the less resistant to corrosion. A rhombohedral phase was detected on the nickel-titanium archwires. No major differences were observed among groups concerning phase transformation temperatures.