Effect of Carbamide Peroxide Treatments on the Metal-ion Release and Microstructure of Different Dental Amalgams

Abstract

A variety of methods have been used to model the effects of bleaching agents on tooth tissue and dental materials. Although several studies have evaluated the effects of bleaching agents on restorative materials, little attention has been directed to metal ion release from dental amalgam following exposure to bleaching agents. This in vitro study investigated the effects of two carbamide-peroxide-based bleaching gels on metal ion release from different dental amalgams. Thirteen discs (10x2 mm) prepared from tgloy (non-gamma 2, admix amalgam), Septalloy NG 50 (single composition, non-spherical, non-gamma 2, ternary amalgam), Dispersalloy (dispersed phase, admix amalgam) and Permite C (high-copper, non-gamma 2, admix alloy), according to the manufacturers' instructions and polished after 24 hours, were aged for seven days at 37 degrees C in air. The discs were then immersed in 10 ml of distilled water for 24 hours at 37 degrees C. The amount of metal ion (Hg, Ag, Sn and Cu) release was determined using inductively coupled plasma mass spectrometry. The discs were treated with either 16% or 30% carbamide peroxide gel and ion release analysis was repeated. The specimens were also evaluated for surface changes using scanning electron microscopy (SEM). The data were analyzed using the MannWhitney U, Wilcoxon Signed Ranks and Kruskal Wallis tests. Statistical analysis showed that treatment with either 16% or 30% carbamide peroxide resulted in a significant release of Hg from all tested amalgams (p < 0.05). There was no significant difference between 16% and 30% carbamide peroxide treatments (p > 0.05). The use of carbamide peroxide gels did not make any difference in Ag levels (p > 0.05). The release of Sn after treatment with 16% or 30% carbamide peroxide was increased (p < 0.05). The release of Cu release was decreased with tgloy and Septaloy NG 50, but increased with Dispersalloy. Additionally, Permite C (p < 0.05) SEM images revealed slight differences after treatment with 30% carbamide peroxide. Changes in the surface levels of ions were also in accordance with the ion release analysis. The release of metal ions and the microstructure of dental amalgams could be changed by treatment with 16% or 30% carbamide peroxide.