Effect of whitening agents containing carbamide peroxide on cariogenic bacteria

PURPOSE: The purpose of this study was to investigate the in vitro antibacterial effects of three different carbamide peroxide products (Nitewhite, Opalescence, and Proxigel) on cariogenic microorganisms (mutans streptococci [MS] and lactobacilli), and to evaluate the effects of a 10% carbamide peroxide solution (Proxigel) on salivary levels of MS and lactobacilli clinically. MATERIALS AND METHODS: Growth inhibition studies were performed to determine the concentration and exposure time of carbamide peroxide to give total inhibition of recoverable growth of MS and lactobacilli. Paraffin-stimulated saliva samples were collected from subjects before and after 6 weeks of treatment with 10% carbamide peroxide in bleaching trays, and levels of MS and lactobacilli were determined. RESULTS: The growth inhibition studies showed no visible growth of MS or lactobacilli at 24-, 48-, or 72-hour incubation, after a 2-hour exposure to 1% carbamide peroxide. Identical results were obtained with all three carbamide peroxide products. In the clinical study, the mean salivary MS levels, expressed as logarithm colony-forming units per milliliter (CFU/mL), were 5.38 for the pretreatment samples and 5.23 for the post-treatment samples. The differences were not statistically significant (p > .05). However, there was a reduction in logarithm lactobacilli counts from a mean of 4.12 pretreatment to a mean of 2.74 post-treatment. This was statistically significant (p < .05).