Effect of Immersion in 0.12% Chlorhexidine Solution on Corrosion and Unloading Force of Rhodium-Coated NiTi Archwires

The types of orthodontic archwires commonly used in orthodontic treatment are NiTi non-coated and rhodium-coated. Corrosivity and unloading force on the wires may undergo changes due to the use of mouthwash, specifically chlorhexidine 0.12%. The aim of this study was to investigate the effect of immersing NiTi non-coated and rhodium-coated with a diameter of 0.014” in chlorhexidine 0.12% solution on their corrosivity and unloading force after immersion for 1, 7, and 14 days. A total of 48 NiTi non-coated and rhodium-coated archwires were divided into 12 groups (n = 4 each) cut to a length of 30 mm. They were grouped based on immersion media (chlorhexidine 0.12% and artificial saliva) and immersion time (1, 7, 14 days). In the chlorhexidine immersion group, the wires were immersed and shaken for one minute twice a day, then rinsed and immersed in artificial saliva. Samples were tested using atomic absorption spectrophotometry (AAS) and a three-point bending test. Statistical analysis was performed using two-way ANOVA, DMRT 5%, and linear regression. The NiTi non-coated archwires immersed in chlorhexidine exhibited high corrosivity of 0.0083 ppm and unloading force of 2.0275 N after 14 days. SEM analysis of NiTi non-coated archwires revealed a rougher surface with larger porosities, while rhodium-coated archwires showed peeling of the coating and pitting. The immersion of non-coated NiTi archwire and rhodium-coated archwire in chlorhexidine solution on the 14th day has the highest corrosivity and unloading force compared to immersion durations on days 1 and 7.