Abstract
Denture stomatitis is common among denture wearers. Candida species are common etiological agents because they have the ability to adhere and form biofilms on poly(methyl methacrylate) (PMMA) denture base resin. The aim of this study is to evaluate the effect of different concentrations of methanol and chloroform extracts of Nigella sativa on Candida sp. adhesion to PMMA denture base, as well as estimate the nanomechanical properties of PMMA. Cylindrical shaped PMMA base resin specimens containing 1%, 3%, and 5% of N. sativa extracts were prepared. Yeast suspensions were applied to the surface of each specimen, the cells were allowed to adhere and were analyzed. The number of adherent yeast cells was evaluated by counting colony-forming units (CFUs). The adherence of Candida cells to the surface of PMMA specimens was also evaluated using fluorescence microscopy after staining with acridine orange (AO). PMMA elastic modulus and hardness were measured using nanoindentation techniques. PMMA containing different N. sativa extract concentrations showed decreased adhesion of Candida cells. Compared with control PMMA, addition of 1% methanol extract reduced the adhesion of C. albicans, C. tropicalis, and C. parapsilosis by 29%, 29.4%, and 19.1%, respectively. At 3% and 5%, the adhesion of C. albicans was inhibited by 60% and 67.5%, respectively. Inhibition of yeast adhesion was also seen with a chloroform extract but it was lower than that with the methanol extract. PMMA nanohardness and nanomodulus increased after the addition of extract. Our results demonstrated the potential use of N. sativa extracts to control the adhesion of Candida sp. to PMMA and yeast biofilm formation on PMMA.