Effect of Combining Erythrosine with a High-Power Dental Curing Light Appliance on the Viability of a Planktonic Culture of Streptococcus mutans

Objective: The aim of this in vitro study was to evaluate the effectiveness of antimicrobial photodynamic therapy (aPDT) composed of the association of the photosensitizer (PS) erythrosine irradiated by a high-intensity dental light source against a culture of Streptococcus mutans , comparing this effect with that of a 0.12% chlorhexidine solution. Materials and methods: For this purpose, planktonic suspensions of S. mutans were subjected to experimental conditions in which three different concentrations of erythrosine (E) (2, 4, and 8 μM) associated with three different doses emitted by the light source (L) (48, 96, and 144 J/cm 2 ) were crossed, corresponding to the exposure times of 40, 80, and 120 sec, respectively, delivered in pulsed mode. The following experimental conditions were evaluated: G1—treatment with dye and light source (E+L+); G2—treatment with the dye only (E+L−); G3—treatment with the light source only (E−L+); G4—absence of dye and light (negative control); and G5—0.12% chlorhexidine (positive control). After treatment, aliquots of each group were plated on blood agar, then the colony forming units per milliliter (CFU/mL) later counted. The results were subjected to ANOVA and Tukey tests, considering the level of significance of 5%. Results: Group aPDT showed complete eradication of microorganisms as from the concentration of 4 μM irradiated for 40 sec, demonstrating statistically significant difference in comparison with the negative control group ( p ≤ 0.05) and efficacy similar to that of the 0.12% chlorhexidine group ( p ≥ 0.05). Conclusions: The authors concluded that the light-polymerizing appliance used in pulsed mode, associated with the PS erythrosine, was efficient for the control of S. mutans in a planktonic suspension in a short period of irradiation time.