Effect of Ultraviolet Irradiation on Candida Albicans Biofilm on Poly-methyl Methacrylate Resin

Objectives: Oral mucositis and systemic co-morbidities have been associated with Candida albicans attachment to Polymethyl Methacrylate (PMMA) dentures. Chemical cleansing has been used to reduce the microbial presence on PMMA with the disadvantage of increasing the PMMA surface roughness, and incomplete disinfection of the surface. Ultraviolet light (UV, 254 nm) is a promising, minimally invasive approach to disinfect PMMA. The objective of this study was to investigate the effect of UV-C light on the viability of Candida albicans biofilm on PMMA. The fungicidal effect was compared to chemical disinfection with 3.8% sodium perborate. Methods: Forty-four PMMA specimens (1cm x 1cm x 1mm) were placed in 6-well culture plates. Each well contained 8ml of 104 CFU/ml of C. albicans ATCC90028 and Sabouraud dextrose broth. Plates were incubated at 37°C for 24hr. Specimens were then divided into 11 groups (n=4): no treatment control groups, 3.8% sodium perborate immersion for 5 minutes (PP5m) and for 12 hours (PO12h), and 6 groups exposed to UV for 5, 15, 30, 60, 120 or 300 seconds separately using UVP XX-15S series lamps. After sonication, cell suspensions were plated and colony-forming units were counted. The relationship between survival of C. albicans and UV irradiation energy exposure was analyzed and compared to the survival of sodium perborate groups with confidence interval at 95%. The effect of disinfection treatments and UV energy exposure on C. albicans survival was analyzed with ANOVA (alpha=0.05). Results: Energy analysis of experimental groups showed a significant decrease in C. albicans survival with increasing UV energy exposure (p<0.05). Survival vs. immersion exposure time analysis of chemical disinfection showed no survival of C. albicans in groups PP5m and PO12h (p0.01). The survival fraction of C. albicans in the UV 300s group with energy of 0.21 J/cm2 (71 CFU/ml) showed a statistical difference from that of two chemical immersion groups (0 CFU/ml) (PP5m, PO12h) (p< 0.05). Conclusion: Within the limitation of this study, UV light (254 nm) irradiation demonstrated a significant inhibition of C. albicans survival on PMMA samples. No difference in survival of C. albicans between UV exposure of 300 seconds and 3.8% sodium perborate groups.