Effect of home bleaching products on mercury release from an admixed amalgam

To test the effect of three carbamide peroxide bleaching products, Opalescence (O), Nite White (N), and Platinum (P) on mercury release from amalgam (Valiant PhD).

Sixty uniform amalgam specimens were prepared in Acrylite clear acrylic blocks. After aging for 1 week at 37 degrees C, the specimens were placed in individual polystyrene jars containing 20 mL of sterile saline, and divided into three groups A, B, and C. Specimens were bleached in cycles by removing them from the jars, blotting to remove excess moisture, and covering with either O, N, P, or saline control (SC). After 8 hours, the specimens were cleaned with a toothbrush, rinsed with deionized water, and returned to the saline. Group A was tested for mercury release after 8 hours of bleaching, Group B after 40 total hours of bleaching, and Group C after 80 total hours of bleaching. Mercury testing was performed by first reducing the mercury in solution in each jar with 1 mL of SnCl2, and then testing the remaining headspace with a Gold Film Mercury Vapor Analyzer.

ANOVA indicated there was no significant difference between the bleaches and controls at 8 and 40 hours, however at 80 hours, O caused significantly more mercury release (P < 0.05). Means at 80 hours in mg/m3 were: O = 0.98 +/- 0.36; N = 0.58 +/- 0.20; P = 0.47 +/- 0.11; SC = 0.52 +/- 0.14.