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

PURPOSE: 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). MATERIALS AND METHODS: 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. RESULTS: 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.

The effects of peroxide bleaching on composite to enamel bond strength.

OBJECTIVES: The objective of this in vitro study was to evaluate the effects of an in-office type of bleaching regimen on the composite to enamel bond. METHODS: The enamel on forty extracted human teeth was subjected to a 25% hydrogen peroxide bleaching treatment. Ten additional unbleached specimens served as controls (Group A). The 40 bleached specimens were divided into four equal groups (Groups B-E). Composite cylinders were bonded to the prepared surfaces at various time intervals following bleaching. Group B was bonded immediately, Group C at 1 d, Group D at 1 wk, and Group E at 1 mon post-bleaching. RESULTS: Mean shear bond strength values showed a significant decrease in bond strength for Group B. However, the bond strength returned to normal values after 1 d and remained normal for at least 1 mon. Scanning electron microscope examination showed an apparent decrease in the number of resin tags present in the enamel/composite interface for Group B compared with the other groups including controls. SIGNIFICANCE: Polymerization inhibition of the resin bonding agent is the likely mechanism for the effects of the bleaching on bond strength.