Photodynamic therapy and simultaneous use of two wavelengths for disinfection of carious tissue

Abstract Purpose To evaluate the combined use of photobiomodulation with antimicrobial photodynamic therapy (aPDT) and the simultaneous use of laser at two different wavelengths for disinfection of carious tissue. Methods Ninety permanent molars were selected and their coronal dentin was exposed. A cariogenic challenge was performed using brain heart infusion (BHI) supplemented with 0.5% yeast extract, 1% glucose, 1% sucrose, and Streptococcus mutans ATCC 25,175 standardized to 0.5 McFarland turbidity. Specimens were randomly allocated across 6 groups ( n = 15/each): C (control), no disinfection; MB, 0.005% methylene blue; LSR, red laser irradiation; MB + LSR, aPDT with methylene blue and red laser; PBM + MB+LSR, photobiomodulation with red laser and aPDT with MB + LSR; MB + LS (R + IR), MB and simultaneous irradiation with red and infrared lasers. S. mutans counts were obtained before and after the cavity disinfection procedures. Results were analyzed by the Kruskal–Wallis test followed by the Student–Newman–Keuls procedure, at a significance level of 5%. Results The greatest reduction in S. mutans counts in carious dentin was seen in the PBM + MB+LSR group (99.81%), with statistically significant differences compared to all experimental groups. The MB + LS (R + IR) (99.42%) and MB + LSR (97.14%) groups showed similar microbial reductions, with significant decreases in S. mutans counts compared to groups C, MB, and LSR. Conclusion Within the limitations of an in vitro study using standardized strains, it was possible to conclude photobiomodulation prior to aPDT and the simultaneous use of red and infrared lasers enhanced disinfection of carious tissue as measured by reduction in S. mutans counts, providing a rapid alternative method for this purpose.