Comparative Evaluation of Photosensitizers Nitrogen-Doped Graphene Quantum Dots And Indocyanine Green Against E. Faecalis- An In vitro Microbiological Study

Background Persistent endodontic infections are frequently associated with Enterococcus faecalis , whose biofilm resistance limits the effectiveness of conventional irrigants. Nitrogen-doped graphene quantum dots (N-GQDs) have emerged as advanced photosensitizers with enhanced photodynamic potential. This study compared the antibacterial efficacy of N-GQD–mediated antimicrobial photodynamic therapy (aPDT), indocyanine green (ICG)–mediated aPDT, and diode laser–activated sodium hypochlorite (NaOCl) against mature E. faecalis biofilms. Materials and Methods Forty-five prepared human mandibular premolars were inoculated with E. faecalis for 14 days. Samples were randomly assigned to three groups (n = 15): Group I, N-GQDs (100 µg/mL) + 670 nm diode laser; Group II, ICG (0.05%) + 810 nm diode laser; Group III, 3% NaOCl + 810 nm diode laser. Microbial samples were collected before and after treatment, serially diluted, plated, and incubated for CFU quantification. Data were analyzed using one-way ANOVA and Bonferroni post hoc testing. Results N-GQD aPDT produced the highest bacterial reduction, with post-treatment CFU values approaching sterilization and significantly lower than ICG and NaOCl groups (p < 0.001). ICG aPDT demonstrated moderate reduction, while laser-assisted NaOCl showed the least CFU decrease. Percentage reduction analysis confirmed the superior efficacy of N-GQDs (99.27%) compared with ICG (82.05%) and NaOCl (62.03%). Conclusion N-GQD–mediated aPDT exhibited the most effective antibacterial activity against E. faecalis biofilms under the tested parameters. These findings suggest that N-GQDs may serve as a promising adjunct for enhanced root canal disinfection, warranting further preclinical and clinical evaluation.