Potassium iodide enhances inactivation of Streptococcus mutans biofilm in antimicrobial photodynamic therapy with red laser.

OBJECTIVE To evaluate the effect of potassium iodide (KI) addition on antimicrobial photodynamic therapy (aPDT) mediated by red laser (λ = 660 nm) and methylene blue in Streptococcus mutans biofilm model. METHODS S. mutans biofilms were cultured in 96-well plates containing BHI broth with 1% sucrose for 18 h, 10% CO2 and 37°C and divided in groups (n = 3, in triplicate): C (NaCl 0.9%); CX (0.2% chlorhexidine); P (photosensitizer); KI (10, 25 and 50 mM); PKI (10, 25 and 50 mM); L (L 1: : 100 J/cm2, 9 J; L2: 200 J/cm2, 18 J); PL (photosensitizer + L1 or L2); KIL (KI at 10, 25 and 50 mM + L1 or L2); and PKIL (photosensitizer + 10, 25 and 50 mM KI + L1 or L2). Biofilms were submitted to three pre-irradiation (PI) times (5, 10, and 15 min). After the treatments, microbial counting's reduction was analyzed by Kruskal-Wallis and post-hoc Dunn's tests, respectively, and the interaction between light parameters and the PI times by two-way ANOVA (p 0.05). CONCLUSION Addition KI to TFDA mediated by methylene blue and red laser promoted an additional effect in reducing the microbial viability of S. mutans biofilm.