Preclinical study of a cost-effective photodynamic therapy protocol for treating oral candidoses

Photodynamic therapy (PDT) is a promising treatment for oral candidoses. Its use as an alternative to antifungals prevents several adverse effects, including microbial resistance. However, most PDT protocols do not employ devices and consumables commonly available in dental practice, thus influencing treatment affordability. This study aimed to determine the efficacy of a PDT method based on light curing units' blue LEDs combined to a plaque-disclosing composition (5% erythrosine) against C. albicans in culture and in a murine model of oral candidosis. Standard and resistant fungal strains were tested in vitro in planktonic and biofilm forms. PDT (pre-irradiation time periods: 30 and 60 s; irradiation time: 3 min) was compared to control conditions without light and/or erythrosine. Mice with induced oral candidosis (n = 40) randomly received PDT or similar control conditions with subsequent C. albicans count. These mice underwent histological analysis, as well as 12 healthy mice submitted to experimental treatments. PDT completely inactivated C. albicans planktonic cells and biofilm. Control conditions presented minor differences (ANOVA, p < 0.05), with mean values ranging from 5.2 to 6.8 log10 (UFC/mL). Infected mice presented no significant difference in C. albicans counts consequent to treatments (ANOVA, p = 0.721), although the PDT protocol was able to enhance the inflammatory infiltrate in healthy mice. It can be concluded that the tested PDT protocol can inactivate C. albicans but still needs further investigation in order to achieve efficacy and safety. (AU)