Influence of dental biofilm on release of mercury from amalgam exposed to carbamide peroxide

Abstract

Tooth bleaching is a popular procedure in modern aesthetic dentistry. Bleaching agents may affect amalgam restorations by altering the release of mercury. The aim of this study was to explore the effect of biofilm-coated amalgam restorations on the release of mercury in the presence of carbamide peroxide. Samples of SDI and Valliant amalgams were submerged for either 14 days or 7 months in buffered KCl after which they were coated with saliva, bacteria, and polysaccharides. The samples were exposed to 10% carbamide peroxide (CP) for 24 h. The amount of mercury released was examined for 120 h. Results showed that most of mercury release occurred within the first 24 h, after which the release rate decreased sharply. After 120 h the release of mercury from the tested samples was minimal and similar to the control group. The presence of biofilm coating on the amalgam samples did not induce the release of mercury but tended to reduce mercury release into the surrounding environment. CP induces the release of mercury from amalgam samples. However, the presence of biofilm did not prevent large amounts of mercury release from amalgam coated with biofilms and exposed to CP. This study indicates that dental biofilm may retard the release of mercury from amalgam restorations.

Surface Change of Dental Amalgam after Treatment with 10% Carbamide Peroxide

“…Carbamide peroxide is synonymous with urea peroxide, hydrogen peroxide carbamide, and perhydrol urea. The usual tray bleaching method uses 10 to 15％ carbamide peroxide decomposing into 3 to 5％ hydrogen peroxide and 7 to 10％ urea once the solution comes into contact with moisture 4,5) . Hydrogen peroxide is the active ingredient contained in the bleaching agent.…”

“…Popular commercial preparations contain about 10％ CP and have an average pH of 5 to 6.5. The bleaching procedure takes place with CP decomposed into 6.4％ urea, ammonia, carbon dioxide, and approximately 3.6％ hydrogen peroxide 4,5) . Against this background, controlled mouthguard bleaching procedures are considered relatively safe with regard to systemic effects.…”

Effect of Bleaching on Mercury Release from Amalgam Fillings and Antioxidant Enzyme Activities: A Pilot Study

“…The inorganic portion may be from food, medicaments, and amalgam restorations. Mercury ions are much less readily absorbed in the gastrointestinal tract …”

“…Mercury ions are much less readily absorbed in the gastrointestinal tract. [26][27][28][29] Mercury ion release is also augmented under bleaching conditions. 2,5,6,27 It may then be absorbed by the oral mucosa as well as by the respiratory and gastrointestinal tract with a potential risk of toxic systemic effects.…”

“…[26][27][28][29] Mercury ion release is also augmented under bleaching conditions. 2,5,6,27 It may then be absorbed by the oral mucosa as well as by the respiratory and gastrointestinal tract with a potential risk of toxic systemic effects. The raised mercury levels in bleaching-treated amalgam can interact and be absorbed by the oral tissues and contribute to increased mercury concentrations in blood, saliva, and urine.…”