In Vitro Adherence of Candida albicans to Zirconia Surfaces

Objectives: This in vitro study aimed to characterize surface properties such as roughness (Ra) and surface free energy (SFE) of glazed and polished yttria-stabilized zirconia polycrystal ceramics and to evaluate the ability of C. albicans and salivary bacteria, Staphylococcus epidermidis, mixed with C. albicans, respectively, to adhere to these substrata. Additionally, the influence of salivary proteins (albumin, mucin and α– amylase) on quantity of yeast adhesion was studied.
Methods: Glazed (series A) and polished (series B) zirconia discs were used as test specimens. Ra and SFE of series were measured and morphological surface characteristics were observed by SEM. To simulate pellicle formation, specimens were wetted with human whole saliva, albumin, mucin or α– amylase for 2h. Pellicle-coated or uncoated zirconia discs were incubated with C.albicans and mixed suspension of C.albicans and Staphylococcus epidermidis for 24h, respectively. Microbial adhesion was quantified by counting colony forming units (CFU). Differences in physicochemical properties were proved by t-test. The effects of material surface property and the influence of salivary proteins were estimated by Friedman test and Wilcoxon signed-rank test (p<0.05).
Results: SFE and Ra average values of glazed specimens were significantly higher than corresponding values of polished ones. In contrast to glazed, polished zirconia appeared completely smooth with no micro-retentive properties (SEM). Fungal adhesion to uncoated zirconia was greater in series A (glazed). When coated, more Candida cells adhered to polished discs (series B). Saliva-coated specimens showed significantly less susceptibility to Candida than protein-coated samples. Significantly higher quantities of adhering fungi were found after mucin incubation compared to α-amylase and saliva. In mixed suspension, growth of Candida was completely prevented.
Conclusions: Glazed and polished zirconia differs in terms of physicochemical surface properties. These differences appear to be modulated by pellicle coating affecting the biomass of adhered Candida. Coating with different salivary proteins yields fungal binding differences.