Comparative evaluation of metal ion release and corrosion resistance of orthodontic archwires in different mouthwashes : From rinse to reactivity.

OBJECTIVE: To quantitatively compare nickel and chromium ion release and corrosion resistance of copper-nickel-titanium (Cu-NiTi), stainless steel (SS), and beta-titanium (β-Ti) archwires following immersion in povidone-iodine (Betadine), chlorhexidine, amine fluoride (Amflor) mouthwashes, and distilled water. MATERIALS AND METHODS: An in vitro study was performed using 60 rectangular archwire specimens (20 each of Cu-NiTi, SS, and β‑Ti), divided into four subgroups according to the immersion medium (chlorhexidine, Betadine, Amflor, distilled water; n = 5 per subgroup). Wires were immersed in each solution at 37 °C for 1.5 h to simulate approximately 3 months of daily mouthwash exposure. Metal ion release was analyzed by atomic absorption spectrophotometer (AAS), while corrosion behavior was assessed using potentiodynamic polarization via a Zive SP1 potentiostat. Two-way analysis of variance (ANOVA) with Tukey's post hoc test was used to determine statistically significant effects of wire and solution type (p < 0.05). RESULTS: Significant differences were observed among wire and solution types (p < 0.001). β‑Ti wires showed no detectable metal ion release and the lowest corrosion rates. Cu-NiTi and SS wires exhibited measurable nickel release, highest in chlorhexidine (46.91 ppm for Cu-NiTi, 42.93 ppm for SS). Chromium release was exclusive to SS (maximum 23.62 ppm). The corrosion hierarchy was chlorhexidine > Betadine > Amflor > distilled water, with β‑Ti demonstrating superior resistance. CONCLUSION: Both material composition and mouthwash formulation critically affect corrosion and ion release. β‑Ti exhibits optimal biocompatibility, whereas chlorhexidine significantly accelerates corrosion.