Effect of surface-charged poly(methyl methacrylate) on the adhesion of Candida albicans

The aim of this study was to investigate the ability of a new surface-modified denture resin to reduce adhesion of Candida albicans to the denture surface. This material has a negative charge incorporated by copolymerization of methacrylic acid to methyl methacrylate. An in vitro system was designed to assess the adhesion of C. albicans to surface-charged poly(methyl methacrylate) (PMMA) surfaces.

Four experimental groups consisted of a control (pure PMMA) and 3 groups of modified PMMA (mPMMA) (95:5, 90:10, and 80:20 MMA:methacrylic acid). Four resin samples (11 x 5 mm) for each experimental group were made to enable the adhesion assay. Resin samples of varying ratios of methacrylic acid were placed in C. albicans suspensions, and the adherent cells were stained with Gram's crystal violet. The surface area of adherent C. albicans was examined for the entire sample using the computer image at a magnification of x 25. Percentage of surface area of adherent C. albicans colonies was averaged and compared between the control and each experimental group. Analysis of variance and Bonferroni's multiple-comparisons test were performed on the data.

As the ratio of incorporated methacrylic acid to PMMA increased, the surface area of adherent C. albicans decreased. Analysis of data revealed a significant decrease in C. albicans adhesion to the resin blocks (p < 0.0001) when the methacrylic acid was present at 10% of the PMMA. There also existed a correlation between the surface area of adherent C. albicans and the contact angle measurement as the ratio of methacrylic acid changed. Surface contact angle analysis of resin surfaces revealed that as the amount of methacrylic acid increased, the surface energy of the resins increased.

The present results support the role of electrostatic interaction in adhesion, and introduce an effective method of reducing adhesion of C. albicans to PMMA surfaces through modification of the surface charge of polymeric biomaterials.