Evaluation of the Breakdown Potential of Orthodontic Archwires in Acidic Soft Drinks

Abstract

Objective: To investigate the effect of acidic soft drinks on the breakdown potential of orthodontic archwires in comparison with artificial saliva using the electrochemical technique of anodic polarization. Materials and methods: Five specimens each of 0.019 × 0.025 inch stainless steel, 0.018 inch Australian Special Plus and Premium Plus, 0.018 inch Nickel-Titanium (NiTi), 0.016 inch Elgiloy® and 0.017 × 0.025 inch beta-titanium, in as received form, were subjected to accelerated corrosion by the electrochemical technique of anodic polarization in an electrochemical cell containing 250 ml of artificial saliva (pH-6.7), a phosphoric acid-based beverage [Pepsi® (pH-2.46)] and a citric acid-based beverage [Limca® (pH-2.69)] at room temperature, followed by examination of wire surface under scanning electron microscope. Results: The polarization currents and breakdown potential were seen to rise in the manner; in artificial saliva: Premium Plus > Special Plus (90 mv) > NiTi (180 mv) > stainless steel (560 mv) > Elgiloy® (8-40 mv) > beta-Titanium; in Pepsi®: Premium Plus > NiTi (310 mv) > Special Plus (410 mv) > Elgiloy® (820 mv) > stainless steel (1440 mv) > beta-titanium; in Limca®: Premium Plus > Special Plus (260 mv) > stainless steel (380 mv) > NiTi (410 mv) > Elgiloy® (710 mv) >beta-titanium. Between solutions, artificial saliva was significantly more corrosive than the beverages except with stainless steel wherein Limca® was more corrosive. Between artificial saliva and Limca®, significant differences were noted between all wires except beta-Titanium and Elgiloy®. Between Pepsi® and artificial saliva, significant differences were noted between all wires except in case of beta-Titanium. Between the two beverages, no significant differences were noted in the current densities curves except in case of stainless steel and Elgiloy®. SEM analysis revealed pitting and greater surface changes in Australian wires in all solutions and NiTi in artificial saliva. Conclusion: Under the parameters tested, acidic beverages per se were observed to have a lesser corrosive effect over artificial saliva on orthodontic archwires.