Antimicrobial effects of carbamide peroxide against a polymicrobial biofilm model.

PURPOSE: To investigate the in vitro antimicrobial effects of carbamide peroxide (CP) and CP-based home bleaching agents against polymicrobial (PM) biofilms. METHODS: Using a high-throughput active attachment model, PM biofilms were cultured on glass coverslips by diluting the stimulated saliva of one healthy adult. All experiments were performed anaerobically in McBain medium, which was refreshed twice daily. After biofilm formation for 24 or 72 hours, the biofilms were treated with 0.5%, 2.5%, 5%, or 10% CP, 20-fold dilutions of HiLite Shade Up (HS) or Opalescence Regular (OR), 0.2% chlorhexidine digluconate (CHX), 0.2% NaF, or deionized water (n = 10 each). Biofilms were dispersed and the number of colony forming units (CFU) was measured on tryptic soy agar blood plates. Coverslips containing 72-hour biofilms treated with 0.5% and 10% CP and deionized water were stained and scanned by confocal laser scanning microscopy (CLSM). RESULTS: Treatment of 24- and 72-hour biofilms with HS, OR and CH yielded significantly fewer colonies than treatment with water or 0.2% NaF. No growing colonies were observed after treatment with 10% CP. CLSM showed that the percentage of dead bacteria increased as the concentration of CP increased.