Microscopical analysis of Candida albicans biofilms on heat-polymerised acrylic resin after chlorhexidine gluconate and sodium hypochlorite treatments.

The ability of Candida albicans to form biofilms on denture surfaces is a significant cofactor in the pathogenesis of denture stomatitis. In this study, we applied a differential staining approach and scanning electron microscopy (SEM) to analyse the effect of sodium hypochlorite and chlorhexidine gluconate on the viability, removal and morphology of C. albicans forming biofilms on denture acrylic using an in vitro model. Immediately after treatment, to distinguish live from dead C. albicans cells in the remaining biofilms, the specimens were stained differentially and analysed by confocal scanning laser microscopy. Moreover, morphological alterations of fungal cells were investigated using scanning electron microscopy. All disinfectant solutions killed all remaining fungal cells on the specimens. Interestingly, 4% chlorhexidine did not remove these cells from the acrylic resin surface whereas sodium hypochlorite solutions (1% and 2%) provided almost complete biofilm removal. Furthermore, treating the specimens with sodium hypochlorite induced cell morphology alterations, as seen in the residual fungal cells. Finally, according to our findings, it can be suggested that sodium hypochlorite solutions are the first choice as denture cleanser when compared with 4% chlorhexidine because those solutions not only killed C. albicans biofilms but also removed them from the heat-polymerised acrylic resin.

Effect of repeated cycles of chemical disinfection on the roughness and hardness of hard reline acrylic resins.

OBJECTIVE: The aim of this study was to assess the effect of repeated cycles of five chemical disinfectant solutions on the roughness and hardness of three hard chairside reliners. METHODS: A total of 180 circular specimens (30 mm x 6 mm) were fabricated using three hard chairside reliners (Jet; n = 60, Kooliner; n = 60, Tokuyama Rebase II Fast; n = 60), which were immersed in deionised water (control), and five disinfectant solutions (1%, 2%, 5.25% sodium hypochlorite; 2% glutaraldehyde; 4% chlorhexidine gluconate). They were tested for Knoop hardness (KHN) and surface roughness (microm), before and after 30 simulated disinfecting cycles. Data was analysed by the factorial scheme (6 x 2), two-way analysis of variance (anova), followed by Tukey's test. RESULTS: For Jet (from 18.74 to 13.86 KHN), Kooliner (from 14.09 to 8.72 KHN), Tokuyama (from 12.57 to 8.28 KHN) a significant decrease in hardness was observed irrespective of the solution used on all materials. For Jet (from 0.09 to 0.11 microm) there was a statistically significant increase in roughness. Kooliner (from 0.36 to 0.26 microm) presented a statistically significant decrease in roughness and Tokuyama (from 0.15 to 0.11 microm) presented no statistically significant difference after 30 days. CONCLUSIONS: This study showed that all disinfectant solutions promoted a statistically significant decrease in hardness, whereas with roughness, the materials tested showed a statistically significant increase, except for Tokuyama. Although statistically significant values were registered, these results could not be considered clinically significant.