Enhanced Removal of E. faecalis Biofilms in the Root Canal Using NaOCl Plus PIPS

Discover the groundbreaking effectiveness of using Sodium Hypochlorite combined with Photon-Induced Photoacoustic Streaming (PIPS) in eradicating stubborn E. faecalis biofilms from root canals.

Authors: Mohammed Al Shahrani, Enrico DiVito, Christopher V. Hughes, Dan Nathanson, George T-J Huang

Journal: Photomedicine and Laser Surgery (2014)

Objective

To determine the effectiveness of photon-induced photoacoustic streaming (PIPS) using Er:YAG laser energy, in combination with sodium hypochlorite (NaOCl), for decontaminating root canal systems heavily colonized with Enterococcus faecalis biofilms, in vitro.

Materials and Methods

• Sample:
  60 extracted single-rooted human teeth, mechanically and chemically prepared, sterilized, and inoculated with E. faecalis for 3 weeks to establish biofilms.

• Groups (n=15 each):

  • Group I: Control (no decontamination)

  • Group II: PIPS + 6% NaOCl

  • Group III: PIPS + saline

  • Group IV: 6% NaOCl (needle irrigation, no PIPS)

• Irrigation Protocol:

  • PIPS settings: 50 μsec pulse, 20 mJ, 15 Hz (0.3 W), applied in three 30-second intervals (90 sec total), with the PIPS tip positioned in the coronal pulp chamber.

  • NaOCl (6%) and saline used as irrigants, with a total volume of 21 mL NaOCl per sample for relevant groups.

• Assessment:

  • Remaining live bacteria quantified by colony-forming unit (CFU) counts.

  • Root canal surfaces examined by scanning electron microscopy (SEM) and confocal laser microscopy (CLM) to visualize biofilm presence and viability.

Key Results

• CFU Counts (Mean ± SE):

  • Group I (Control): 336.8 ± 1.8

  • Group II (PIPS + NaOCl): 0.27 ± 0.21

  • Group III (PIPS + Saline): 225.0 ± 21

  • Group IV (NaOCl only): 46.9 ± 20.3

• Statistical Analysis:

  • Group II (PIPS + NaOCl) had significantly fewer CFUs than all other groups (p < 0.05).

  • PIPS + NaOCl was significantly more effective than NaOCl alone or PIPS with saline.

• Imaging:

  • SEM and CLM confirmed the near-complete removal of biofilm in the PIPS + NaOCl group, with minimal remaining bacteria, while other groups showed more residual biofilm.

Conclusions

• The combination of PIPS and 6% NaOCl resulted in the most efficient eradication of E. faecalis biofilms from the root canal system.

• PIPS alone (with saline) was not as effective, highlighting the importance of NaOCl as the irrigant.

• Laser-activated irrigation with PIPS greatly enhances the disinfection potential of NaOCl, compared to conventional needle irrigation.

• These findings support the use of PIPS with NaOCl for improved root canal disinfection, especially in cases of persistent biofilm.

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1 A close-up view of the photon-induced photoacoustic streaming (PIPS) tip and its composition, with stripped sheath that helps to propagate the shockwaves in the root canal system (A). Illustration shows how the PIPS is placed in the coronal aspect of access only, not in the canal, and how it delivers the shock waves (B).

2 Scanning electron microscope analysis of root canal surface. (A and B) Group I shows E. faecalis colonies attached to the root canal surface. (C and D) Group II (PIPS+ NaOCl) shows a clean root canal surface. (E and F) Group III (PIPS+saline) shows colonies attached to the root canal surface. (G–I) Group IV (irrigation with NaOCl) shows some colonies and the other image shows no colonies.

3 Confocal scanning laser microscopy analysis of live/dead bacteria on root canal surface. (A) Example of a split-opened tooth sample showing the exposed root canal surface. The box at the mid-root area of the root canal system indicates where the imaging analysis was performed. (B) Negative control sterile tooth samples showing no detectable autofluorescence background. (C–F) Experimental samples with live bacterial biofilms are shown in green fluorescence and the dead bacterial biofilm in red fluorescence. (C) Group I, a control sample with no treatment, the green fluorescence (arrows) indicate live bacteria. (D) A representative sample from Group II (PIPS+NaOCl) showing red fluorescence (arrow) in dentinal tubules indicative of dead bacteria. (E) Group III, (PIPS+saline), the green indicates still live bacteria (marked with arrows) with some red dead bacteria. (F) Group IV, NaOCl with no PIPS, shows the red fluorescence (upper vertical arrow) on the superficial layer with green florescence deeper in dentin tubules (lower horizontal arrow) where NaOCl was unable to penetrate without laser activation.