Corrosion of orthodontic archwires in artificial saliva in the presence of Lactobacillus reuteri

The aim of this work was to examine the influence of probiotic supplements, recommended for use in orthodontic patients, on the corrosion stability of stainless steel and three types of NiTi orthodontic wires. Electrochemical studies, polarization measurements and electrochemical impedance spectroscopy, were conducted in artificial saliva with oral probiotic supplement as well as in saliva containing the probiotic bacteria L. reuteri alone. Obtained results show that probiotic bacteria L. reuteri and probiotic supplement influence on a general corrosion rate as well as on likelihood of pitting corrosion occurrence, and their effect is dependent on the type of alloy and coating. In general the probiotic supplement has more corrosive influence than bacteria alone as it increases the probability of localized corrosion of studied orthodontic wires. On the other hand probiotic bacteria do not increase the possibility of localized corrosion occurrence in any of studied wires than rather decrease the general corrosion rate of stainless steel wires. Based on the obtained results it is concluded that the additional substances from probiotic supplement are responsible for the localized corrosion of studied wires rather than probiotic bacteria L. reuteri alone.