The challenge of combating caries disease seeks, in addition to reducing sucrose consumption, to achieve efficient biofilm control. Among antimicrobial therapies, photodynamic antimicrobial chemotherapy (PACT) stands out for reducing microorganisms and, at the same time, not developing bacterial resistance. This treatment uses photosensitizing agents, such as methylene blue, which are activated by visible light of specific wavelength to generate oxygen free radicals that are capable of promoting cell death. Studies have shown that inorganic potassium iodide salt enhances microbial reduction in gram positive and negative but not in oral bacteria. In the present work, we will analyze the effect of potassium iodide addition on antimicrobial photodynamic therapy in biofilms formed on dentin caries lesions developed in microcosm environment in vitro, using the methylene blue photosensitizer and low power laser (» = 660nm). A pilot study will be conducted to obtain appropriate parameters for the use of the PACT associative protocol. The groups will be divided into (n = 4), in triplicate: C (negative control, 0.9% NaCl), CX (positive control, 0.2% chlorhexidine), P (photosensitizer, 0.01% methylene blue) , KI (inorganic salt, potassium iodide), PKI (photosensitizer + inorganic salt), L (laser), LP (laser + photosensitizer), LKI (laser + inorganic salt) and LPKI (laser + photosensitizer + inorganic salt). The cariogenic biofilm will be formed on bovine dentin from microbial growth in an oral microcosm model supplemented with 1% sucrose. Response variables will be cell viability by determination of colony forming units (CFU / mL) of total Streptococci, S. mutans and Lactobacillus, biomass analysis of the formed biofilm, as well as a quali-quantitative evaluation by confocal laser scanning microscopy. Data normality and homoscedasticity will be evaluated by the Shapiro-Wilks and Levene tests, respectively, and the results will be subjected to appropriate analyzes, with a significance level of 5%.
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