Investigation of Nickel and Chromium Ion Release from Simulated Fixed Orthodontic Appliances in Artificial Saliva Containing Fluoride

Abstract

Fluoride is found in many oral hygiene products due to its anti-cariogenic effect. However, fluoride has a corrosive effect that begins at the time of application and continues with the fluoride remaining in the residual saliva. This study aimed to investigate the effect of different fluoride concentrations on the release of nickel and chromium ions from simulated fixed orthodontic appliances made of copper-nickel-titanium (Cu-NiTi), nickel-titanium (NiTi) and stainless steel (SS) archwires. Simulated orthodontic appliances in the experimental groups were immersed in Klimek artificial saliva containing 125, 500, or 900 ppm fluoride (NaF) for one hour and 0.1 ppm fluoride for eleven hours. The process was repeated in subsequent periods. Control groups were exposed to only Klimek artificial saliva. The amounts of nickel and chromium ions released into Klimek artificial saliva were measured using inductively coupled plasma mass spectroscopy (ICP-MS). The morphological characteristics of the archwires were examined using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The average roughness value of SS archwires before and after immersion was lower than that of Cu-NiTi or NiTi archwires (p<0.05). Simulated orthodontic appliances with SS archwires released more chromium ions than simulated orthodontic appliances with Cu-NiTi and NiTi archwires in experimental groups with 125 ppm fluoride (p<0.05). Simulated fixed orthodontic appliances with SS archwires released fewer nickel ions than simulated fixed orthodontic appliances with Cu-NiTi archwires in both control and experimental groups (p<0.05). Additionally, simulated fixed orthodontic appliances with SS archwires released fewer nickel ions than those with NiTi archwires in control and experimental groups with 500 ppm fluoride (p<0.05).