Does microwave and hydrogen peroxide disinfection reduce Candida albicans biofilm on polymethyl methacrylate denture surfaces?

Abstract

Statement of problemWhether the disinfection of polymethyl methacrylate (PMMA) dentures eliminates Candida albicans biofilm is unclear. PurposeThe purpose of this in vitro study was to determine the antimicrobial effect of immersion in hydrogen peroxide (H2O2) and subsequent application of microwaves on the formation of C albicans biofilm on the surface of polished and unpolished PMMA disks. Material and methodsPolished and unpolished PMMA disks (n=40) were mounted in a Center for Disease Control (CDC) biofilm reactor by adding yeast-dextrose-peptone (YPD) broth inoculated with C albicans in a cell suspension for 24 hours. After this period, the PMMA disks (n=8) were disinfected with 5 different solutions: saline solution, 1% sodium hypochlorite (NaOCl), H2O2, H2O2 microwaved at 650 W for 3 minutes (H2O2/μw), and distilled water microwaved at 650 W for 3 minutes (H2O/μw). On the polished and unpolished surface of each disk, arbitrary fluorescence units (AFU) were quantified with the live/dead bacterial viability kit (Invitrogen) by using confocal laser scanning microscopy (CLSM) to evaluate 10 different areas of each surface; these were counted as the colony-forming units (CFUs). The mean values were compared by using the Mann–Whitney U test (α=.05). ResultsPolished surfaces disinfected with H2O2/μw obtained the lowest viable cells (9.76 AFU) and nonviable cells (12.46 AFU) compared with H2O/μw and H2O2. In the unpolished surface the lowest mean values of viable cells (14.64 AFU) and nonviable cells (12.46 AFU) were obtained for the PMMA disks disinfected with H2O/μw compared with H2O2/μw and H2O2. Both polished and unpolished disks showed significant difference (P<.05) compared with the group of PMMA disks immersed in saline solution. No CFUs were detected in the polished or unpolished PMMA disks immersed in H2O2/μw or in NaOCl. ConclusionsH2O2 alone did not eliminate the formation of the biofilm of C albicans; however, in combination with the use of the microwave at 650 W for 3 minutes, the biofilm formation of C albicans on polished surfaces was reduced. The number of AFUs of viable-nonviable cells and CFUs depended on whether the surfaces are polished or unpolished.