Nickel and chromium ion release from coated and uncoated orthodontic archwires under different pH levels and exposure times

OBJECTIVES The purpose of this study was to determine and compare nickel and chromium ion release from traditional stainless steel and nickel titanium wires and newer esthetic archwires under different pH conditions, for different time intervals. METHODS Ten pieces of 10-mm segments of five different orthodontic archwires were submerged in buffer solutions of pH 4.0, 5.5, and 7.0, for 4 and 13 weeks. The sample solutions were analyzed using ICP-MS. First, the results were analyzed by three-way ANOVA to determine any significant differences in metal concentration (ppb) between the different groups. Then, a post-hoc multiple pairwise comparison by Tukey's Studentized Range (HSD) Test was conducted to further compare the different materials and pH conditions. RESULTS For nickel, uncoated NiTi had the highest nickel ion release (ppb), while AO Iconix had the lowest average nickel ion release, with a significant difference (p