Objective: The objective of this study was to compare the effect of wire type, pH and immersion time upon mean corrosion rates of four orthodontic wires. Materials and Methods : Four types of orthodontic wires, a. Nickel-titanium (NiTi) b. Regular stainless steel (SS) c. Australian stainless steel (Aus) and d. Titanium-molybdenum alloy (TMA) were immersed in artificial saliva, either at pH 6 or pH 2.5. The time of test was either as-received or 90 days immersion time. Corrosion analysis was

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... ormed using linear sweep voltammetry. Results: 3-way ANOVA statistical analysis showed that wire type, pH, immersion time and combination of these factors, both second order and third order interactions, accounted for significant differences of the mean corrosion rates. At baseline status, (as-received wires, at pH 6) post hoc multiple comparison test showed that the mean corrosion rates of NiTi > Aus >SS>TMA (P < 0.05). Interaction plots revealed that the corrosion susceptibility of these wires could be modulated by pH 2.5 and 90 days immersion time, with different extent across wire types. Under pH 2.5 and 90 days immersion time condition, SS showed statistically greatest increase of mean corrosion rates. However, TMA, Aus and NiTi mean corrosion rates were not different from each other (P<0.05). Therefore, interaction of pH and immersion time upon wire types could deviate the pattern of relative mean corrosion rates from the as-received status. Conclusion: Corrosion behavior was dependent on the interactions of alloy type and the environment factors (pH and immersion time).