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Dental biofilms are produced by bacterial communities. During the first 24 h of colonization, oral streptococci compose 60% to 90% of the supragingival plaque biomass. Mutans streptococci are biofilm-forming bacteria and are considered to be the primary etiologic agents of human dental caries. They possess a variety of abilities to colonize tooth surfaces and under certain conditions are present in large quantities in cariogenic biofilms and also form biofilms with other organisms, including other streptococci and bacteria. To reduce microbial, like biofilm, can be performed by using photodynamic therapy. Successful of this kind of therapy is induced by penetration of light and photosensitizer into target cells. The sonodynamic therapy offers greater penetrating capability into tissues. Then, the purpose of this study was to evaluate the antibacterial effect of photodynamic inactivation (PDI) associated with ultrasound (U) using curcumin solution irradiated by LED light source over Streptococcus mutans biofilm. Initially, minimum inhibitory (MIC) and minimum bactericidal (MBC) concentrations were performed, The concentrations of 40 and 80 μM were selected for the next experiments. Streptococcus mutans biofilm were induced using a 96-well plates for 7 days according to Groups G1 (negative control, L0D0), G2 (L + U +), G3 (L + D0), G4 (L0D40-80), G5 (chlorhexidine, positive control), G6 (L + D40-80 U +), G7 (L + D40-80) and G8 (D40-80 U +). For the dark cytotoxicity, curcumin was incubated for 5 minutes. For PDI, the groups were incubated in the dark for 5minutes (pre-irradiation time) and irradiated by blue LED at 15J/cm2 (36mW/cm2) for 7minutes and 55seconds. Ultrasound was used for 5min under 0.16KW of power output and 1.5A (pre-irradiation). After treatment, the strains were seeded on BHI agar and incubated at 37°C for 48 hours to determine the number of CFU/mL. The results were transformed into log10 and submitted to analysis of variance (ANOVA) and Tukey test at the 5% level. Significant reductions in the number of viable cells of S. mutans were observed in groups G6 (6log10) providing 4log10 of bacterial reduction when compared to group G1 (2log10) (p <0.05). The association of PDI and ultrasound can be an effective method to control microorganisms in the oral cavity, especially S. mutans, which causes dental caries.
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