Chemical and mechanical influence of root canal irrigation on biofilm removal from lateral morphological features of simulated root canals, dentine discs and dentinal tubules.

T C Pereira,W J Van De Meer,R J B Dijkstra,P.K Sharma,L W M Van Der Sluis,X Petridis,F B De Andrade

doi:10.1111/iej.13399

Abstract

AimTo investigate the anti‐biofilm efficacy of irrigation using a simulated root canal model, the chemical effect of irrigants against biofilms grown on dentine discs and their impact on biofilm viscoelasticity, the efficacy of the irrigants in decontaminating infected dentinal tubules and the capacity of bacteria to regrow.MethodologyBiofilm removal, viscoelastic analysis of remaining biofilms and bacterial viability were evaluated using a simulated root canal model with lateral morphological features, dentine discs and a dentinal tubule model, respectively. Experiments were conducted using a two‐phase irrigation protocol. Phase 1: a modified salt solution (RISA) and sodium hypochlorite (NaOCl) were used at a low flow rate to evaluate the chemical action of the irrigants. Ultrasonic activation (US) of a chemically inert solution (buffer) was used to evaluate the mechanical efficacy of irrigation. Phase 2: a final irrigation with buffer at a high flow rate was performed for all groups. Optical coherence tomography (OCT), low load compression testing (LLCT) and confocal scanning laser microscopy analysis were used in the different models. One‐way analysis of variance (anova) was performed for the OCT and LLCT analysis, whilst Kruskal–Wallis and Wilcoxon ranked tests for the dentinal tubule model.ResultsUS and high flow rate removed significantly more biofilm from the artificial lateral canal. For biofilm removal from the artificial isthmus, no significant differences were found between the groups. Within‐group analysis revealed significant differences between the steps of the experiment, with the exception of NaOCl. For the dentine discs, no significant differences regarding biofilm removal and viscoelasticity were detected. In the dentinal tubule model, NaOCl exhibited the greatest anti‐biofilm efficacy.ConclusionsThe mechanical effect of irrigation is important for biofilm removal. An extra high flow irrigation rate resulted in greater biofilm removal than US in the artificial isthmus. The mechanical effect of US seemed to be more effective when the surface contact biofilm–irrigant was small. After the irrigation procedures, the remaining biofilm could survive after a 5‐day period. RISA and NaOCl seemed to alter post‐treatment remaining biofilms.

Highlights

Bacteria tend to grow in biofilms, adhering to a surface or liquid interface and co-adhering to each other (Kolenbrander et al 2010)
In the root canal model with lateral morphological features, the outcome measure was biofilm removal evaluated by Optical coherence tomography (OCT)
Within the limitations of the present study, the mechanical effect of syringe irrigation at low and high flow rate was important for biofilm removal

Summary

Introduction

Bacteria tend to grow in biofilms, adhering to a surface or liquid interface and co-adhering to each other (Kolenbrander et al 2010). If the root canal is infected, biofilm will be present in lateral morphological features such as lateral canals, fins, isthmuses and the dentinal tubules (Peters et al 2001, Ricucci et al 2013). To eradicate biofilms from these areas is a challenge These lateral morphological features are not reached by instrumentation (Peters et al 2001, Ricucci et al 2013). In this respect, getting more insight into the fate of the remaining biofilm after mechanical or chemical challenges during root canal irrigation is warranted (remaining biofilm)

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Discussion

Conclusion