What question did this study set out to answer?

To assess the effectiveness of Nd:YAG laser, aPDT, and PUI against Enterococcus faecalis biofilms compared to NaOCl.

May 28, 2026Open Access

Antimicrobial activity of Nd: YAG irradiation, laser activated photodynamic therapy and passive ultrasonic irrigation on enterococcus faecalis biofilms (an ex vivo study)

SGSalma M. El GazarAlexandria University RBRania N. El BacklyAlexandria University WLWalid A. LotfyPharos University in Alexandria

Key Points

To assess the effectiveness of Nd:YAG laser, aPDT, and PUI against Enterococcus faecalis biofilms compared to NaOCl.
Sixty-nine single-rooted mandibular premolars were infected with E. faecalis for 3 weeks.
Teeth were randomly divided into five groups, each receiving different disinfection methods.
Bacterial counts were evaluated via CFU measurement and SEM analysis for biofilm assessment.
Bacterial counts in the NaOCl needle irrigation, PUI, and Nd:YAG laser groups were significantly lower than untreated and distilled water groups.
The aPDT group showed no significant bacterial reduction compared to the positive control or distilled water groups.
Nd:YAG laser and PUI enhanced bacterial reduction, but did not significantly improve NaOCl's antibacterial effects.

Abstract

Abstract Aim To evaluate the antimicrobial effects of Nd: YAG laser irradiation, antimicrobial photodynamic therapy (aPDT), and passive ultrasonic irrigation (PUI) in comparison with conventional irrigation with Sodium hypochlorite (NaOCl) in root canals infected with Enterococcus faecalis biofilms. Materials and methods Sixty-nine single rooted mandibular premolars were accessed and instrumented till master apical file #40/04. After sterilization of the teeth, the root canals were infected with E. faecalis for 3 weeks. The teeth were randomly divided into five groups according to the method of disinfection (n=13 each): group I: irrigation with distilled water; group II: irrigation with 2.5% sodium hypochlorite (NaOCl) with side vented needle; group III: PUI activation for 2.5% NaOCl; group IV: Nd:YAG laser activation for 2.5% NaOCl , group V: aPDT with 0.01% methylene blue as the photosensitizer and laser irradiation (λ635nm, power 400mW, 5min). The four remaining teeth were used as control groups (n=2 each): negative control (without bacteria) and positive control (without treatment). Colony forming units (CFU) were then counted and Scanning Electron Microscope (SEM) analysis was performed to evaluate Enterococcus faecalis biofilm reduction. Results were analyzed using the Kruskal–Wallis test followed by Bonferroni‑adjusted pairwise comparisons. Results The bacterial counts in the NaOCl needle irrigation, PUI, and Nd: YAG laser groups were significantly lower than those of the untreated positive control and distilled water groups. Furthermore, they were also significantly lower than those of the aPDT group which did not show any significant reduction in bacterial count compared to the positive control nor the distilled water groups. Conclusion Adjunctive irrigation using Nd:YAG laser and PUI increased bacterial reduction, however, they did not significantly enhance the antibacterial effects of NaOCl when used alone in this specific tooth model. Furthermore, antimicrobial photodynamic therapy with methylene blue failed to show any noticeable antimicrobial effects.

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