Photoinactivation of Candida albicans on simulated complete dentures

Objectives: The aim of this study was to evaluate the effectiveness of Photodynamic Therapy (PDT) on the inactivation of Candida albicans on dentures. Methods: Forty dentures were fabricated in a standardized procedure and subjected to ethylene oxide sterilization. Photogem^®, a hematoporphyrin derivate, was used as a photosensitizer (PS). A blue light-emitting diode (LED) device (~455nm, 24mW/cm²) was specially designed to irradiate the dentures. The samples were individually inoculated with Tryptic Soy Broth media containing 10⁷cfu/mL of C. albicans ATCC2327. After 48h at 37ºC, dentures were immersed in sterile saline and divided into four groups (n=10 each): 1-control, 2-PS, 3-LED and 4-PDT. In the PS group, dentures were sprayed with 50mg/L of PS and left in the dark for 10min. In the LED group, each sample was illuminated for 26min (37.5J/cm²). PDT dentures were individually sprayed with the same concentration of PS (50mg/L) and, after 10min in the dark, illuminated with the same fluence (37.5J/cm²). Control dentures were not exposed to neither PS nor LED. For all groups, dentures were immersed in sterile saline and replicate aliquots (25 µL) of suspensions were plated at dilutions of 10⁰ to 10^-3 on Sabouraud Dextrose Agar plates. After 48h at 37°C, colonies on plates were counted and the data [log(cfu/mL)] were statistically analyzed by Kruskal-Wallis and Dunn tests (p<0.05). Results: Compared to control, PS and LED, PDT promoted significant reduction of cfu/mL of C. albicans from dentures (80%, 77% and 79% of inactivation, respectively). PS alone reduced significantly cfu/mL values compared to control (12% killing). LED alone was not able to kill yeast. Conclusion: The association of Photogem^® with LED light (PDT) may be an alternative procedure to inactivate C. albicans on dentures.