Investigation of the effect of different bleaching agents on ion release from metal brackets

This in-vitro experimental study aimed to evaluate the amount of metal ion release from stainless steel orthodontic brackets produced by different manufacturers after exposure to in-office bleaching agents. A total of 90 MBT prescription (0.022" slot) stainless steel brackets from three different manufacturers were divided into three groups: 40% hydrogen peroxide (HP), 45% carbamide peroxide (CP), and artificial saliva (control). Brackets were immersed in 0.5 mL of bleaching solution for 40 minutes, then transferred to 10 mL of artificial saliva and incubated at 37 °C for 28 days. The release of nine metal ions (nickel, chromium, cobalt, strontium, copper, zinc, titanium, lead, cadmium) was quantitatively analyzed using Inductively Coupled Plasma–Optical Emission Spectrometry (ICP-OES). Data were statistically analyzed using non-parametric tests. The amount of ion release varied depending on both the type of bleaching agent used and the bracket brand. Hydrogen peroxide (HP) and carbamide peroxide (CP) solutions caused higher ion release compared to artificial saliva. American Orthodontics™ Mini Master brackets exhibited the highest release of cobalt, chromium, copper, strontium, titanium, lead, and cadmium, while showing the lowest release for zinc. Dentaurum™ Discovery Smart brackets did not exhibit the highest release for any ion and showed the lowest release of nickel, chromium, copper, strontium, titanium, lead, and cadmium. 3M Unitek™ Solventum brackets showed the highest release of nickel and zinc, and the lowest release of cobalt. Significant differences were observed in ion release depending on bracket type and bleaching solution (p<0.005). The findings indicate that the interaction between material and bleaching agent should be clinically considered.