Comparative evaluation of photosensitizers nitrogen-doped graphene quantum dots and indocyanine green against Enterococcus faecalis - An in vitro microbiological study

Background: The persistent endodontic infections are commonly allied with Enterococcus faecalis , a microorganism capable of forming resistant biofilms that compromise root canal disinfection. Nitrogen-doped graphene quantum dots (N-GQDs) have recently arose as promising photosensitizers for antimicrobial photodynamic therapy (aPDT). The present study equated the antibacterial efficacy of N-GQD-mediated aPDT, indocyanine green (ICG)-mediated aPDT, and diode laser-activated sodium hypochlorite (NaOCl) in contrast to mature E. faecalis biofilms. Materials and Methods: Thirty extracted human lower arch premolars were prepared and inoculated with E. faecalis for 14 days. Specimens were arbitrarily allocated to three groups ( n = 10): Group I, N-GQDs (100 µg/mL) activated with a 670 nm diode laser; Group II, 0.05% ICG activated with an 810 nm diode laser; and Group III, 3% NaOCl activated with an 810 nm diode laser. Bacterial samples were collected before the treatment and after the treatment, cultured, and quantified by the colony-forming unit (CFU) analysis. Statistical assessments were executed using one-way ANOVA and Bonferroni post hoc tests. Results: All the treatment modalities reduced the bacterial counts; however, N-GQD-mediated aPDT demonstrated the greatest antibacterial effect. It showed a 99.27% reduction in CFUs, which was significantly higher than ICG-mediated aPDT (82.05%) and laser-activated NaOCl (62.03%) ( P < 0.001). Conclusion: N-GQD-mediated aPDT showed superior antibacterial activity against mature E. faecalis biofilms and can serve as an effective adjunctive approach for enhanced root canal disinfection.