RESUMO
BACKGROUND: Photodynamic therapy (PDT) has demonstrated promising results in the treatment of several clinical pathologies through the photochemical reaction caused by the combination of a photosensitizer and a light source. The objective of this study was to evaluate the antimicrobial effect of the combination of the photosensitizers (PSs) erythrosine/methylene blue activated by a white halogen light device on Streptococcus mutans biofilm. METHODS: Two separate experiments were conducted, the first using the PSs at the concentration of 100⯵M, and the second 250⯵M. The PSs were tested on S. mutans biofilms cultured for 24â¯h in isolation, in combination, with and without light activation for 2â¯min fractionated in 4 periods of 30â¯s. After treatment, biofilms were diluted and plated on BHI medium and incubated for 24â¯h for colony forming units (CFU) counting. The results (log10) were analyzed with ANOVA followed by Tukey test (pâ¯<â¯0.05). RESULTS: The erythrosine/methylene blue combination activated by white halogen light at 100 and 250⯵M, and erythrosine at 250⯵M, methylene blue at 250⯵M presented significantly reduced cell counts (3.2 log10, 5.3 log10, 4.5 log10, 4.3 log10, respectively) when compared to controls (pâ¯<â¯0.05). CONCLUSION: PDT with the combination of erythrosine/methylene blue demonstrated better results that the PSs in isolation regardless of the concentration. The use of this combination at the concentration of 250⯵M shows promise as an antibacterial treatment for carious lesions and should be further assessed.