Antimicrobial photodynamic therapy in dentistry using an oil-in-water microemulsion with curcumin as a mouthwash

Background: Antimicrobial photodynamic therapy (PDT) has emerged as an alternative therapeutic strategy to conventional procedures using antibiotics. A mouthwash based on a microemulsion with curcumin for disinfecting the oral cavity in combination with PDT was developed. Methods: A pseudo-ternary phase diagram was constructed to select the microemulsion, and a physicochemical characterization of the selected formulation was performed. Curcumin was quantified using spectrophotometry. The stability of the formulation with curcumin was evaluated after storage for 60 days at 40 degrees C, and the in vitro effectiveness of the formulation associated with PDT was evaluated using a light-emitting diode at 430 nm (blue) with two irradiation times (10 and 30 min) on biofilms of Candida albicans, methicillin-resistant Staphylococcus aureus (MRSA), and Escherichia coli. Results: The formulation registered a pH of 6.24, apparent viscosity of 1.64 cP, Newtonian rheological behavior, droplet size of 14 +/- 1 nm, polydispersity index of 0.151, and zeta potential of -7.7 mV. The preparation remained stable after storage for 60 days. There was a significant CFU. mL(-1) reduction in all tested microorganisms after treatment combining PDT and curcumin microemulsion (30 or 60 mu g.mL(-1)), and the largest reductions were 5.6175 log10 CFU. mL(-1) in E. coli (10 ' and 30 ', both with 30 mu g.mL(-1)); 5.181 log10 CFU.mL(-1) in MRSA (30 ' and 30 mu g.mL(-1)); and 3.497 log10 CFU. mL(-1) in C. albicans (30 ' and 60 mu g.mL(-1)). Conclusions: The formulation containing curcumin in combination with antimicrobial PDT showed promising results in vitro, and this potential formulation awaits further evaluation in clinical trials.