Qualitative comparison of sonic or laser energisation of 4% sodium hypochlorite on anEnterococcus faecalisbiofilm grownin vitro

Principle and antimicrobial efficacy of laser-activated irrigation: A narrative review

In the last two decades, the activation of root canal irrigants with pulsed lasers as an adjunct in root canal treatment has become increasingly popular. This narrative review explains the physical basics and the working mechanism of laser-activated irrigation (LAI), explores the parameters influencing LAI efficacy, considers historical evolutions in the field and summarizes laboratory and clinical evidence with emphasis on the antimicrobial action of LAI. Cavitation is the driving force behind LAI, with growing and imploding vapour bubbles around the laser tip causing various secondary phenomena in the irrigant, leading to intense liquid dynamics throughout the underlying root canal. High-speed imaging research has shown that laser wavelength, pulse energy, pulse length and fibre tip geometry are parameters that influence this cavitation process. Nevertheless, this has not resulted in standardized settings for LAI. Consequently, there is significant variability in studies assessing LAI efficacy, complicating the synthesis of results. Laboratory studies in extracted teeth suggest that, with regard to canal disinfection, LAI is superior to conventional irrigation and there is a trend of higher antimicrobial efficacy of LAI compared to ultrasonic activation. Clinical evidence is limited to trials demonstrating similar postoperative pain levels after LAI versus no activation or ultrasonic activation. Clinical evidence concerning the effect of LAI on healing of apical periodontitis as yet is scarce.

Effect of ultrasonic and Er,Cr:YSGG laser-activated irrigation protocol on dual-species root canal biofilm removal: An in vitro study

Aim

The aim of the study was to investigate the disinfecting efficacy of a standardized irrigating solution activated by ultrasonics or laser irradiation on mature dual-species biofilms at different root levels in vitro.

Materials and Methods

Conventional access cavity preparations were done on 160 single-rooted mandibular premolar teeth with single canals. Freshly extracted oral microbial strains of Staphylococcus aureus, Streptococcus mutans, Enterococcus faecalis, and Candida albicans after biochemical confirmation were used to generate two discrete dual-species microbial inoculums. The sterilized tooth samples were randomly segregated into two groups (n = 80) and inoculated with a mixed inoculum of S. aureus + E. faecalis strains (Group 1) and S. mutans + C. albicans strains (Group 2), respectively. Following the 21-day incubation period under aerobic conditions, the infected specimens in each group were divided into four subgroups (n = 20) and subjected to experimental treatment protocols. This included a positive control (no treatment of biofilms), syringe irrigation alone with TruNatomy needle, passive ultrasonically activated irrigation with 20# Irrisafe tip, and laser agitation of irrigant with Er,Cr:YSGG laser using RFT 2 laser tip. Root canals of experimental specimens (except the control samples) are instrumented with TruNatomy rotary file system using 1:1 mixture of 3% NaOCl and 18% etidronic acid as irrigants. The quantitative assessment of reduction in viable biofilm microbes after treatment was done using colony-forming unit counts and confocal laser scanning microscopy image analysis. The obtained data were analyzed statistically with a significant level set at 0.05.

Results

Laser-assisted irrigation has shown a considerably higher mean percentage reduction of microbes compared to ultrasonic agitation and the syringe irrigation showed the least microbial reduction (P = 0.001). No significant difference was noted between the three root regions of ultrasonic and laser groups (P > 0.05), whereas in the syringe groups, apical portions showed higher microbial counts compared to cervical and mid-root regions (P = 0.001).

Conclusion

Erbium laser-assisted irrigation has performed superior to ultrasonic agitation against both the experimental dual-species biofilms, while the syringe irrigation showed the least microbial reduction specifically at apical root portions.

Efficacy of Three Irrigation Methods in Removing Calcium Hydroxide from Curved Root Canals: An In Vitro Micro-CT Study

Aims and Objectives

This in vitro study aimed to compare the efficacy of three different irrigation methods in removing calcium hydroxide from curved root canals and to estimate the amount of residual medicament using microcomputed tomography.

Materials and Methods

Thirty extracted molars with curved mesial root canals, ranging from 25° to 30°, were prepared with ProTaper Next using X2 to full working length and were filled with calcium hydroxide. Teeth also were randomly divided into four groups: group 1 (n = 8)- Erbium: Yttrium-Aluminum-Garnet (Er:YAG) laser; group 2 (n = 8)-EndoActivator; group 3 (n = 8)-EndoVac; and a control group (n = 6)-negative control with no calcium hydroxide. Microcomputed tomography was used to evaluate the residual amount of filling material. Statistical analysis was performed using IBM SPSS Statistics 26, with a significance level of 0.05. Descriptive statistics, student t test, and Chi-square test were applied for data analysis.

Results

The greatest amount of residual calcium hydroxide was observed in the samples with EndoVac irrigation (0.515 mm3), followed by EndoActivator (0.381 mm3) and Er:YAG laser (0.121 mm3). However, no statistically significant difference was observed between the groups. The greatest residual amount was observed in the apical third (0.419 mm3), followed by the middle (0.050 mm3) and the coronal (0.015 mm3).

Conclusions

No statistically significant differences were observed in the efficacy of the tested techniques for removing calcium hydroxide from curved root canals, whereas a significant difference was observed in the distribution of residual material depending on the technique used. The removal of the calcium hydroxide was more effective in the coronal and middle third of the canal. The greatest residual material was found in the apical portion of the root canal.

Efficacy of Endodontic Disinfection Protocols in an E. faecalis Biofilm Model-Using DAPI Staining and SEM

The aim of this study was to investigate the antimicrobial efficacy of different disinfection protocols in a novel Enterococcus faecalis biofilm model based on a visualization method and to evaluate the potential alteration of dentinal surface. A total of 120 extracted human premolars were allocated to 6 groups with different irrigation protocols. The assessment of the effectiveness of each protocol and the alteration of dentinal surface were visualized by using SEM and fluorescence microscopy (DAPI). A dense E. faecalis biofilm with a penetration depth of 289 μm (medial part of the root canal) and 93 μm (apical part) validated that the biofilm model had been successfully implemented. A significant difference between the 3% NaOCl groups and all the other groups in both observed parts of the root canal (p < 0.05) was detected. However, the SEM analysis revealed that the dentinal surface in the 3% NaOCl groups was severely altered. The established biofilm model and the visualization method based on DAPI are appropriate for bacterial quantification and evaluation of the depth effect of different disinfection protocols in the root canal system. The combination of 3% NaOCl with 20% EDTA or MTAD with PUI allows the decontamination of deeper dentine zones within the root canal but simultaneously alters the dentinal surface.

Biofilm in Endodontics: In Vitro Cultivation Possibilities, Sonic-, Ultrasonic- and Laser-Assisted Removal Techniques and Evaluation of the Cleaning Efficacy

Incomplete and inadequate removal of endodontic biofilm during root canal treatment often leads to the clinical failure. Over the past decade, biofilm eradication techniques, such as sonication of irrigant solutions, ultrasonic and laser devices have been investigated in laboratory settings. This review aimed to give an overview of endodontic biofilm cultivation methods described in papers which investigated sonic-, ultrasonic- and Er:Yag laser-assisted biofilm removal techniques. Furthermore, the effectiveness of these removal techniques was discussed, as well as methods used for the evaluation of the cleaning efficacy. In general, laser assisted agitation, as well as ultrasonic and sonic activation of the irrigants provide a more efficient biofilm removal compared to conventional irrigation conducted by syringe/needle. The choice of irrigant is an important factor for reducing the bacterial contamination inside the root canal, with water and saline being the least effective. Due to heterogeneity in methods among the reviewed studies, it is difficult to compare sonic-, ultrasonic- and Er:Yag laser-assisted techniques among each other and give recommendations for the most efficient method in biofilm removal. Future studies should standardize the methodology regarding biofilm cultivation and cleaning methods, root canals with complex morphology should be introduced in research, with the aim of simulating the clinical scenario more closely.

Multispecies biofilm removal by XP-endo Finisher and passive ultrasonic irrigation: A scanning electron microscopy study

The aim was to assess the effect of XP-endo Finisher (XPF) on multispecies biofilm removal, in comparison with passive ultrasonic irrigation (PUI) and conventional syringe irrigation (CSI), by scanning electron microscope (SEM). Fifty mandibular first premolars were instrumented, longitudinally sectioned. The split halves were incubated for 4 days with a broth obtained from three bacteria strains: Enterococcus faecalis, Eikenella corrodens and Streptococcus anginosus. Subsequently, the re-approximated split halves were irrigated with 4% sodium hypochlorite (NaOCl) or water using CSI, and the final irrigation protocols were CSI with 4% NaOCl (CSI+4%NaOCl), PUI+4%NaOCl, XPF+4%NaOCl and CSI+water. The analysis of biofilm removal was performed using SEM images. There were no differences between PUI and XPF (P > 0.05), and both groups promoted higher biofilm removal than CSI+4%NaOCl and CSI+water groups (P < 0.05). It can be concluded the multispecies biofilm removal was significantly improved using XPF and PUI when compared to CSI.

Multiple assessment methodologies in determining the antibiofilm actions of sodium hypochlorite mixed with clodronate or etidronate in endodontic irrigation

This study aimed to use multiple methodologies, including a novel usage of scanning electron microscopy (SEM), to evaluate the antimicrobial actions of sodium hypochlorite (NaOCl) admixed with clodronate or etidronate in root canal irrigation. The study also examined the usefulness of colony counting as a biofilm assessment methodology. Seven day Enterococcus faecalis biofilms were grown on hydroxyapatite discs. The discs were disinfected with 0.26 M clodronate-5% NaOCl, 0.26 M etidronate-5% NaOCl, 5% NaOCl, or treated with phosphate buffered saline (PBS). Assessments were performed using colony counting, SEM and the XTT reduction assay. The XTT assessment used the same groups but with 2.5% NaOCl. For colony counting, bacteria were removed from the discs by vortex mixing, followed by plating. The discs were subsequently fixed for SEM imagining and evaluators scored the SEM micrographs for remaining bacteria. Antibiofilm actions were assessed with the Kruskal-Wallis and Dunn's multiple comparison tests. SEM micrographs and the XTT assay revealed no differences between the NaOCl controls and the clodronate or etidronate mixtures with NaOCl (P > 0.05). It was concluded that the chelator mixtures with NaOCl had antibiofilm actions comparable to NaOCl. Furthermore, vortex mixing incompletely removed biofilm from HA discs in the PBS controls and hence colony counting using E. faecalis biofilms on hydroxyapatite discs could not be used for intergroup comparisons involving PBS. Additionally, colony counting could not be used for comparisons between the NaOCl treatment groups because the removal of bacteria from the substrate by vortex mixing was affected by the irrigant type.

Efficacy of laser and ultrasonic-activated irrigation on eradicating a mixed-species biofilm in human mesial roots

This study investigated the efficacy of Er,Cr:YSGG laser and ultrasonic activated irrigation on eradicating a mixed-species biofilm grown in root canals with complex anatomy. The biofilm was grown over 4-weeks in the root canals of decoronated human mandibular molar teeth. Control roots received no further treatment. The remaining roots were chemomechanically prepared using different irrigating protocols: 4% NaOCl and 15% EDTAC with ultrasonic activated irrigation and laser activated irrigation using power settings of 0.5 W and 0.75 W. Cellular viability was determined using serial plating. One tooth from each group was subjected to qualitative SEM analysis. Quantification by culturing revealed significant differences between control group and all other treatment groups. This study demonstrated that chemomechanical irrigation with laser and ultrasonic activated irrigation significantly reduced the bacterial load from complex root canal systems; however, there were no significant differences found between the experimental groups.

Effectiveness of low concentration of sodium hypochlorite activated by Er,Cr:YSGG laser against Enterococcus faecalis biofilm

Bacteria living in biofilms exhibit altered growth phenotypes, while the biofilm provides benefits, the foremost of which is a certain protection against both immune system and killing effect by antimicrobials. Laser-activated irrigation (LAI) and passive ultrasonic irrigation (PUI) have been proposed as alternative methods for cleaning and disinfecting the root canal, as an adjuvant to conventional chemo-mechanical preparation in order to improve debridement and disinfection. Nevertheless, the potential antibacterial effect of LAI using 0.5% of sodium hypochlorite (NaOCl) has received little attention. Glass Pasteur pipettes were used to mimic single-tooth root canal and to build Enterococcus faecalis biofilm. Several irrigants and treatments were assayed for 60 s including (I) Saline, (II) NaOCl 0.5%, (III) NaOCl 5%, (IV) Er,Cr:YSGG, (V) Saline + LAI, (VI) NaOCl 0.5% + LAI, (VII) Saline + PUI, and (VIII) NaOCl 0.5% + PUI. Bacterial reduction was measured by counting the colony-forming units (CFUs). Additionally, AFM visualization and measurement of nano-roughness parameters were used to evaluate LAI effect on bacteria. NaOCl 5% unpowered and NaOCl 0.5% + LAI were capable of eliminating all bacteria, whereas non-activated saline solution and NaOCl 0.5% failed to eliminate E. faecalis. Lower efficiencies were achieved by PUI. Surface analysis by AFM revealed apparent alterations in NaOCl + LAI-treated cells. The Er,Cr:YSGG laser-activated irrigation (LAI) increased the bactericidal efficiency of 0.5% NaOCl against E. faecalis biofilm.

Investigation of the effect of rapid and slow external pH increases on Enterococcus faecalis biofilm grown on dentine

BACKGROUND

Calcium hydroxide is a common endodontic medicament and has an antimicrobial effect by increasing the localized pH within the root canal. However, Enterococcus faecalis has shown some resistance to calcium hydroxide.

METHODS

A flow cell apparatus was used to grow an E. faecalis biofilm on dentine discs. Following 4 weeks growth in Todd Hewitt Broth, flow cells were exposed to either a rapid or slow increase to pH 11.5 or 12.5. Cellular viability was determined using serial plating and the number of colony-forming units was normalized against the cellular protein content. Scanning electron microscopy was carried out to qualitatively observe the effects of the different rates of pH increase.

RESULTS

A significant difference in viability between the pH rapid and slow groups was not shown in this study. Compared with pH 11.5 solutions, pH 12.5 solutions were more effective at killing bacteria although some E. faecalis still survived.

CONCLUSIONS

Enterococcus faecalis did not adapt and develop a greater resistance to high pH following a slow rise in pH compared with a rapid rise in pH. As expected, pH 12.5 was more effective in reducing bacterial numbers compared with pH 11.5 although E. faecalis was not completely eliminated.

Association between Extracellular Material and Biofilm Formation in Response to Sodium Hypochlorite by Clinical Isolates of Enterococcus faecalis

INTRODUCTION

Extracellular material (ECM) surrounding Enterococcus faecalis may play a role in increasing resistance to environmental stresses. Our aim was to determine ECM levels in response to subminimal inhibitory concentrations of sodium hypochlorite (sub-MIC/NaOCl) or anaerobic growth and determine the impact on biofilm development.

METHODS

From 37 E. faecalis clinical strains, 19 were selected according to their biofilm-producing ability by using a crystal violet biofilm assay: 10 strong, 4 intermediate, and 5 non-biofilm producers. Biofilm assays were subsequently performed on all strains when subjected to sub-MIC/NaOCl. All strains were evaluated for ECM production under aerobic and anaerobic conditions and with sub-MIC/NaOCl. ECM production was assessed by using scanning electron microscopy. Double-blinded independent assessors were used to score levels of ECM production. The esp gene was detected by using polymerase chain reaction. Gelatinase activity was determined by using Todd-Hewitt and gelatin agar.

RESULTS

In aerobic conditions, ECM was expressed in all strains. In the presence of sub-MIC/NaOCl, of the 10 strong biofilm producers, 5 increased their ECM production, and 4 showed increased biofilm growth. Two strains had less ECM production and showed decreased biofilm growth. One isolate demonstrated no observable changes. Most non-biofilm producers demonstrated no observable differences in ECM production, although 1 strain increased biofilm growth. ECM production in anaerobic conditions was highly variable. The esp gene (n = 15) and gelatinase activity (n = 7) were evident among the isolates.

CONCLUSIONS

Clonal diversity among strains of E. faecalis suggests that some strong biofilm producers can upregulate ECM production and increase biofilm growth in response to sub-MIC/NaOCl.

Antibacterial Efficacy of Calcium Hypochlorite with Vibringe Sonic Irrigation System on Enterococcus faecalis: An In Vitro Study

Aim. The purpose of this study was to compare the in vitro efficacy of calcium hypochlorite (Ca[OCl]₂) and sodium hypochlorite (NaOCl) associated with sonic (Vibringe) irrigation system in root canals which were contaminated with Enterococcus faecalis. Material and Methods. The root canals of 84 single-rooted premolars were enlarged up to a file 40, autoclaved, inoculated with Enterococcus faecalis, and incubated for 21 days. The samples were divided into 7 groups according to the irrigation protocol: G0: no treatment; G1: distilled water; G2: 2.5% NaOCl; G3: 2.5% Ca(OCl)₂; G4: distilled water with sonic activation; G5: 2.5% NaOCl with sonic activation; and G6: 2.5% Ca(OCl)₂ with sonic activation. Before and after decontamination procedures microbiological samples were collected and the colony-forming units were counted and the percentages of reduction were calculated. Results. Distilled water with syringe irrigation and sonic activation groups demonstrated poor antibacterial effect on Enterococcus faecalis compared to other experimental groups (p < 0.05). There was no statistically significant difference between syringe and sonic irrigation systems with Ca(OCl)₂ and NaOCl. Conclusion. The antimicrobial property of Ca(OCl)₂ has been investigated and compared with that of NaOCl. Both conventional syringe irrigation and sonic irrigation were found effective at removing E. faecalis from the root canal of extracted human teeth.

Efficacy of low concentrations of sodium hypochlorite and low-powered Er,Cr:YSGG laser activated irrigation against an Enterococcus faecalis biofilm

AIM

To establish the antibacterial efficacy of low concentrations of sodium hypochlorite with and without Er,Cr:YSGG laser activation on Enterococcus faecalis biofilms in extracted teeth.

METHODOLOGY

The root canals of 96 decoronated single-rooted extracted human teeth were prepared to a size 40, 0.06 taper 1 mm beyond the apex. They were mounted within a flow cell, which was sterilized before pumping a nutrient media through the root canals. The flow cell was inoculated with E. faecalis (ATCC 700802) and cultivated for 4 weeks. The root-ends were sealed, and the roots were then subjected to one of six treatment groups: group 1: syringe irrigation (SI) with saline (control) using a 27 -gauge Monoject needle 1 mm from the apex for 2 min; group 2: as for group 1 but with 1% NaOCl; group 3: as for group 1 but with 4% NaOCl; group 4: 0.5% NaOCl irrigation for 15 s followed by laser-activated irrigation (LAI) with four 15-s cycles replenishing the irrigant between cycles; group 5: as for group 4 but with 1% NaOCl as the irrigant; group 6: as for group 4 but with 4% NaOCl as the irrigant. Following treatment, teeth were crushed and viable bacteria were quantitated by serial dilution and plating. The colony-forming unit values were compared between groups using one-way anova and Tukey-adjusted post hoc tests. A two-tailed P value of <0.05 was considered statistically significant.

RESULTS

The mean number of cells recovered from the 1% NaOCl SI group was significantly higher than that from the 4% NaOCl LAI group (P = 0.02).

CONCLUSION

Within the limitations of this laboratory study, low-powered (0.5 W) Er,Cr:YSGG laser activation did not improve the antibacterial effect of low concentrations of sodium hypochlorite.

Radiographic evaluation of root canal cleaning, main and laterals, using different methods of final irrigation

OBJECTIVE: To evaluate the efficacy of passive ultrasonic irrigation (PUI) using intermittent or continuous flushing and conventional manual irrigation (CMI) on the cleaning of main and simulated lateral root canals.MATERIAL AND METHOD: The root canals of 24 artificial teeth were prepared and simulated lateral canals were made in the medium and apical thirds of the root. The specimens were divided into three groups: G1- CMI, G2- PUI 1 (intermittent flushing) and G3- PUI 2 (continuous flushing). Root canals were filled with contrast solution and the roots were radiographed pre- and post-irrigation. The digital images were transferred to Image Tool 3.0 software and the areas of root canal completely filled with contrast, and after irrigation with contrast remnant, were measured to obtain percentage data. Statistical analysis between groups was performed by ANOVA and Tukey tests.RESULT: In the apical third, G2 and G3 (PUI) groups showed higher percentage of cleaning than G1 (CMI) (p<0.05).CONCLUSION: Passive ultrasonic irrigation using intermittent flushing promoted a higher cleaning of simulated lateral canals than conventional manual irrigation in the apical third. There were no differences between groups in the main root canal and the middle third.

Enhanced removal of Enterococcus faecalis biofilms in the root canal using sodium hypochlorite plus photon-induced photoacoustic streaming: an in vitro study

OBJECTIVE

The purpose of this study was to determine the effectiveness of laser-activated irrigation by photon-induced photoacoustic streaming (PIPS) using Er:YAG laser energy in decontaminating heavily colonized root canal systems in vitro.

MATERIALS AND METHODS

Extracted single-rooted human teeth (n=60) were mechanically and chemically prepared, sterilized, inoculated with Enterococcus faecalis for 3 weeks, and randomly assigned to four groups (n=15): Group I (control, no decontamination), Group II (PIPS+6% NaOCl), Group III (PIPS+saline), and Group IV (6% NaOCl). PIPS settings were all preset to 50 μsec pulse, 20 mJ, 15 Hz, for an average power of 0.3 W. After decontamination, the remaining live microbes from all specimens were collected and recovered via plate counting of the colony-forming units (CFUs). Randomized root canal surfaces were examined with scanning electron microscopy and confocal laser microscopy. Mean variance and Dunnett's t test (post-hoc test) comparisons were used to compare mean scores for the three groups with the control group.

RESULTS

The CFU analysis showed the following measurements (mean±SE): Group I (control), 336.8±1.8; Group II (PIPS+NaOCl), 0.27±0.21; Group III (PIPS+saline), 225.0±21; and Group IV (NaOCl), 46.9±20.29. Group II had significantly lower CFUs than any other groups (p<0.05). Both imaging analyses confirmed levels of remaining bacteria on examined root surfaces.

CONCLUSIONS

The use of the PIPS system along with NaOCl showed the most efficient eradication of the bacterial biofilm. It appears that laser-activated irrigation (LAI) utilizing PIPS may enhance the disinfection of the root canal system.