A new improved protocol for in vitro intratubular dentinal bacterial contamination for antimicrobial endodontic tests: standardization and validation by confocal laser scanning microscopy

Influence of different presentation forms of chlorhexidine on contaminated root canals during agitation

This in vitro study aimed to verify the influence of chlorhexidine (CHX) (gel and solution) in association with different activation protocols on disinfection of root canals contaminated with Enterococcus faecalis. In total, 120 lower premolar roots were selected, contaminated and divided into 12 groups according to irrigation technique and substance. Samples were collected before and after each irrigation technique and analysed for colony-forming units (CFU). Three dentin discs were obtained for quantification of viable intratubular cells by using confocal laser scanning microscopy (CLSM). CFU results showed that sonic and ultrasonic were more effective than conventional irrigation. Ultrasonic activation was more effective than sonic for CHX gel (p < 0.05). CLSM showed that either activation was better than conventional in all groups and root canal thirds (p < 0.05). It was concluded that ultrasonic/sonic activation was more effective than conventional techniques and CHX enhanced intratubular dentin decontamination across all irrigation methods.

Bactericidal Effect of Triple Antibiotic Paste against Enterococcus faecalis in Dentinal Tubules: An Ex Vivo Study

OBJECTIVE

The aim of this study was to investigate the bactericidal effect of various concentrations of triple antibiotic paste (TAP) against Enterococcus faecalis (E. faecalis) in dentinal tubules using a bacterial culture assay and confocal laser scanning microscope (CLSM).

METHODS

Ninety human teeth were contaminated with E. faecalis (ATCC 29212) and randomly allocated into 5 groups; the negative control (without TAP), 1 mg/ml, 5 mg/ml, 7.5 mg/ml and 10 mg/ml TAP (n=18). After a 3-week TAP treatment, samples were collected from the root canal space, root dentin at 100-μm and 200-μm depth. The collected samples were subjected to a bacterial culture assay (n=10). Eight roots from each group underwent CLSM analysis to determine the live/dead bacterial cells.

RESULTS

The bacterial culture assay results indicated that the negative control samples were all culturable. The number of culture-positive samples decreased after TAP treatment at 1, 5, 7.5 and 10 mg/ml, with 2, 2, 1 and 0 culturable samples, respectively. However, there was no significant difference among the TAP treatments. Surprisingly, the CLSM analysis demonstrated live bacteria in the dentinal tubules in all samples. The negative control had 52.36%+-3.24 live bacteria. TAP treatment at 10 mg/ml had the lowest percentage of live bacterial cells (40.58%+-5.40), followed by 7.5 mg/ml (44.14%+-6.03), 5 mg/ml (46.31%+-5.32) and 1 mg/ml (52.55%+-8.82). The percentage of live cells in the 10 mg/ml, 7.5 mg/ml and 5 mg/ml TAP groups were significantly lower than the 1 mg/ml TAP and negative control groups.

CONCLUSION

TAP treatment significantly decreased the percentage of viable E. faecalis cells in the dentinal tubules and its bactericidal effect was dose-dependent.

Sonic-assisted antibacterial photodynamic therapy: a strategy for enhancing lateral canal disinfection

BACKGROUND

Bacterial infections in lateral canals pose challenges for root canal treatment. This in vitro study aims to evaluate the antibacterial efficacy of sonic-assisted methylene blue mediated antimicrobial photodynamic therapy (MB-aPDT) against Enterococcus faecalis (E. faecalis) in infected lateral canals.

METHODS

Sixty-five premolars infected with E. faecalis in lateral canals were randomly divided into five groups (n = 13) and treated with : (1) 5.25% NaOCl (positive control); (2) Saline (negative control); (3) Sonic-assisted MB-aPDT; (4) 3% NaOCl + MB-aPDT; (5) 3% NaOCl + sonic-assisted MB-aPDT, respectively. The antibacterial efficacy was evaluated by the colony- counting method (CCM) and scanning electronic microscope (SEM).

RESULTS

Both 5.25% NaOCl and the 3% NaOCl + sonic-assisted MB-aPDT exhibited the most effective while comparable antibacterial effects without significant statistical difference (P > 0.05). Furthermore, the antibacterial effect of the 3% NaOCl + MB-aPDT group was significantly higher compared to that of the sonic-assisted MB-aPDT group (P < 0.05). The SEM results demonstrated notable morphological alterations in E. faecalis across all experimental groups, except for the negative control group.

CONCLUSION

The concentration of NaOCl can be reduced to a safe level while preserving its antibacterial efficacy through the synergism with the sonic-assisted MB-aPDT in this study.

Reducing Apical Bacterial Extrusion: The Impact of Reciproc File Size and Irrigation Technique

Introduction

This study used different irrigation techniques to compare the levels of apical bacterial extrusion during the preparation of root canals with a reciprocating instrument widely used in endodontics, the Reciproc files 25/0.08 and 40/0.06.

Materials and Methods

The irrigation techniques employed were conventional syringe irrigation and passive ultrasonic irrigation (PUI); the latter, with one or two activation cycles. Seventy extracted mandibular human premolars were contaminated with Enterococcus faecalis for 5 days and were distributed into 6 experimental groups (n=10), and the remaining specimens were used as positive and negative control groups (n=5). Group 1: instrumentation performed with Reciproc 25/0.08 and conventional syringe irrigation; Group 2: instrumentation performed with Reciproc 25/0.08 along with PUI for one minute after instrumentation (PUI-1); and Group 3: instrumentation performed with Reciproc 25/0.08 along with PUI for one minute before and after instrumentation (PUI-2). Groups 4, 5 and 6 were instrumented with Reciproc 40/0.06, and irrigation was performed similar to the previous groups, in the aforementioned order. Each root canal was irrigated with saline solution. Extruded debris was collected in microtubes. The contents of the microtubes were homogenized, diluted, and spread on Brain Heart Infusion agar. After 48 hours, the number of colony-forming units was determined for each sample. For statistical analysis, the Kruskal-Wallis test followed by the Dunn's tests were used (α=0.05).

Results

The CFU/mL count indicated that the instrumentation with Reciproc 25/0.08 was associated with the highest bacterial extrusion, mainly when PUI was performed (P<0.05).

Conclusion

All the instrumentation techniques caused bacterial extrusion through the apical foramen; however, the largest file size of the Reciproc 40/0.06 groups was associated with less apical bacterial extrusion.

Antimicrobial efficacy of sodium hypochlorite and hyper-pure chlorine dioxide in the depth of dentin tubules in vitro

OBJECTIVES

The study aimed to compare the antibacterial effect of a novel disinfectant, hyper-pure chlorine dioxide (hClO2) to sodium hypochlorite (NaOCl) in various depths of dentin tubules.

MATERIALS AND METHODS

The distal root of the extracted lower molars was infected artificially with Enterococcus faecalis. The control group was rinsed with saline, and the test groups were irrigated with either 5% NaOCl or 0.12% hClO2. The longitudinally split teeth were stained by viability stain. The coronal third of the root was scanned with a confocal laser scanning microscope. The fluorescent intensities were measured, and the percentage of dead bacteria was calculated at depths up to 950 μm along the dentin tubules. The effect of penetration depth, irrigants, and their interaction on antimicrobial efficacy was determined by the linear mixed model.

RESULTS

The percentage of dead bacteria was higher both in the NaOCl (45.1 ± 2.3%, p < 0.01) and in the hClO2 (44.6 ± 3.8%, p < 0.01) irrigant groups compared to saline (23 ± 4.5%); however, there was no difference between them. The percentage of killed bacteria was not correlated with the depths in any group (p = 0.633).

CONCLUSIONS

Our results suggest that the functional penetration depth of NaOCl is at least 2-3 times more than published to date. There is no difference in disinfection effectiveness along the dentin tubules between NaOCl and hClO2 until at least the measured 950 μm. However, both were only able to eradicate the intratubular bacteria partially.

CLINICAL RELEVANCE

Hyper-pure ClO2 could be used as an alternative or final adjuvant irrigant in endodontic treatment.

Antimicrobial effect of Pentaclethra Macroloba plant extract against Enterococcus Faecalis

This study evaluated the antimicrobial efficacy of a new intracanal drug based on Pentaclethra macroloba extract, a plant of Amazonian origin, against Enterococcus faecalis using macrodilution test and intratubular evaluation with Confocal Laser Scanning Microscopy (CLSM). The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of the pure extract of Pentaclethra macroloba andits association with calcium hydroxide and ultracall were determined. Then, thirty-three dentin cylinders were prepared and inoculated with E. faecalis, to evaluate the antimicrobial effect of the medications on the dentinal tubules with CLSM. The data was analyzed using the Kruskal-Wallis and Dunn tests. The extract in association with calcium hydroxide showed a lower CBM, and in the intratubular test all tested medications were effective against E. faecalis (P >0.05). The new intracanal drug based on P. macroloba extract has an antimicrobial effect against E. faecalis and further studies are needed for its clinical use.

Antimicrobial efficacy of Kerr pulp canal sealer (EWT) in combination with 10% amoxicillin on Enterococcus faecalis: A confocal laser scanning microscopic study

Background: Sealers with antimicrobial properties play an important role in endodontic therapy success especially against Enterococcus faecalis infection found in failed root canal therapy. Addition of antibiotic agents to endodontic sealers may show significant increase in their antibacterial properties both against anaerobic and aerobic microbes. The purpose of the present study was to evaluate antimicrobial efficacy of Kerr pulp canal sealer (EWT) in combination with 10% amoxicillin against E. faecalis and post-root canal treatment viability of Enterococcus faecalis on the first and seventh day. Methods: A total of 60 extracted human mandibular premolar teeth were decoronated after initial decontamination with 1% NaOCl. Root length standardized to 12 mm. Canal instrumentation was done using ProTaper Universal file system till size F2 using 5.25% NaOCl. It was then infected with a pure strain of E. faecalis for a period of four days. Obturation was done using plain sealer, (n=30) and sealer-antibiotic combination, (n=30). Half of the teeth were sectioned at 24 hours (S, SA) and other half were sectioned seven days after obturation (S7, SA7). All samples were stained with SYTO9 and propidium iodide for imaging under Confocal Laser Scanning microscope. Statistical analysis was performed with the statistical software SPSS v. 17.0 (SPSS for Windows; SPSS Inc, Chicago, IL). Data was analysed using One Way ANOVA and post hoc Tukey test to determine statistical significance with p value < 0.01 considered significant. Results: Statistically significant differences were observed in green to red ratio between group S (9.561976) and S7 (0.435418) (p < 0.01). There was no difference found between SA (mean of green to red ratio, (0.70431) and SA7 (mean of green to red ratio, 0.85184). Conclusions: Antibiotics added to the sealer effectively eradicated of E. faecalis 24 hours post-obturation. However, after seven days, plain sealer was as effective as sealer-antibiotic combination.

Antimicrobial efficacy of Kerr pulp canal sealer (EWT) in combination with 10% amoxicillin on Enterococcus faecalis: A confocal laser scanning microscopic study

Background: Sealers with antimicrobial properties play an important role in endodontic therapy success especially against Enterococcus faecalis infection found in failed root canal therapy. Addition of antibiotic agents to endodontic sealers may show significant increase in their antibacterial properties both against anaerobic and aerobic microbes. The purpose of the present study was to evaluate antimicrobial efficacy of Kerr pulp canal sealer (EWT) in combination with 10% amoxicillin against E. faecalis and post-root canal treatment viability of Enterococcus faecalis on the first and seventh day. Methods: A total of 60 extracted human mandibular premolar teeth were decoronated after initial decontamination with 1% NaOCl. Root length standardized to 12 mm. Canal instrumentation was done using ProTaper Universal file system till size F2 using 5.25% NaOCl. It was then infected with a pure strain of E. faecalis for a period of four days. Obturation was done using plain sealer, (n=30) and sealer-antibiotic combination, (n=30). Half of the teeth were sectioned at 24 hours (S, SA) and other half were sectioned seven days after obturation (S7, SA7). All samples were stained with SYTO9 and propidium iodide for imaging under Confocal Laser Scanning microscope. Statistical analysis was performed with the statistical software SPSS v. 17.0 (SPSS for Windows; SPSS Inc, Chicago, IL). Data was analysed using One Way ANOVA and post hoc Tukey test to determine statistical significance with p value < 0.01 considered significant. Results: Statistically significant differences were observed in green to red ratio between group S (9.561976) and S7 (0.435418) (p < 0.01). There was no difference found between SA (mean of green to red ratio, (0.70431) and SA7 (mean of green to red ratio, 0.85184). Conclusions: Antibiotics added to the sealer effectively eradicated of E. faecalis 24 hours post-obturation. However, after seven days, plain sealer was as effective as sealer-antibiotic combination.

A new model of in vitro dentin intratubular contamination for Fusobacterium nucleatum: Validation by confocal laser scanning microscopy

Objectives

To test and validate a new protocol for in vitro contamination of dentinal tubules using Fusobacterium nucleatum (F. nucleatum) by confocal laser scanning microscopy (CLSM), in addition to evaluating the effectiveness of conventional endodontic irrigants such as sodium hypochlorite (NaOCl) and chlorhexidine (CLX) on this biofilm.

Material and methods

Thirty lower premolars were contaminated with F. nucleatum (ATCC 51190) for 7 days under anaerobic conditions using the proposed new model. The specimens were divided into a control group and experimental groups, according to the irrigants: NaOCl 2.5% and CLX 2%. Then, the samples were submitted for analysis by CLSM and the LIVE/DEAD technique to quantify bacterial viability. Data normality was verified by the Shapiro-Wilk test. Intragroup and intergroup comparisons were performed using the Kruskal-Wallis test, followed by Dunn's post-test.

Results

The CLSM images obtained demonstrated the effectiveness of the proposed new contamination protocol, with a high percentage of viable bacteria in relation to the treated groups (p < 0.05). Lower viability values were observed for the 2.5% NaOCl group.

Conclusion

The new contamination protocol resulted in a high and homogeneous percentage of viable bacteria in the dentinal tubules in all specimens evaluated. Both irrigating solutions proved to be effective in reducing the intratubular microbiota, especially 2.5% NaOCl.

The Vehicles of Calcium Hydroxide Pastes Interfere with Antimicrobial Effect, Biofilm Polysaccharidic Matrix, and Pastes' Physicochemical Properties

The objective of the present study was to investigate the pH, volumetric alteration, antimicrobial action, and effect on biofilm matrix polysaccharides of calcium hydroxide (CH) pastes with different vehicles available in endodontics: CH + propylene glycol (CHP), UltraCal XS^®, Metapaste^®, and Metapex^®. The pH was analyzed at different time intervals using a pH meter. For volumetric alteration, a microtomographic assay was performed before and after immersion in water. Enterococcus faecalis was chosen for microbiological tests. The bacterial viability and extracellular matrix were quantified with direct contact evaluation (dentin blocks) and at the intratubular level (dentin cylinders) using LIVE/DEAD BacLight and Calcofluor White dyes via confocal laser scanning microscopy (CLSM). Kruskal-Wallis and Dunn's tests were used to analyze pH and direct contact assays, while one-way ANOVA and Tukey tests were used to analyze volumetric alteration and intratubular decontamination (α = 0.05). Higher pH values were obtained during the initial days. Volumetric alterations were similar in all groups. Lower bacterial viability was obtained for dentin blocks and cylinders when CH pastes were used. UltraCal XS and Metapex had lower values for the extracellular matrix. The pH of all CH pastes decreased with time and did not promote medium alkalization for up to 30 days. CH paste can reduce bacterial viability through direct contact and at an intratubular level; however, UltraCal XS and Metapex are involved with lower volumes of extracellular matrices.

Can the Concentration of Citric Acid Affect Its Cytotoxicity and Antimicrobial Activity?

Background: There has been no unanimity concerning the ideal concentration of citric acid for safe use in clinical practice. This study evaluated the cytotoxicity and the antibacterial activity in infected dentinal tubules of 10% and 1% citric acid (CA) solutions. Methods: The cytotoxicity of CA solutions in DMEM (diluted 1/10, 1/100) was assessed in L-929 fibroblasts. A broth macrodilution method (MIC and MBC) was used to assess CA antibacterial concentration. The antimicrobial activity of CA solutions was also evaluated after their final rinse inside root canals in previously Enterococcus faecalis-contaminated dentinal tubules. Ten infected dentine samples were rinsed for 5 min with 5% NaOCl and subsequently with 1% citric acid for 3 min. Another 10 were rinsed with 5% NaOCl and 10% citric acid for 3 min; the remaining four specimens were utilized as positive controls. Two uncontaminated specimens were used as negative controls. After LIVE/DEAD BacLight staining, the samples were assessed using CLSM to analyze the percentage of residual live and dead cells. Results: Both undiluted and diluted CA solutions showed severe toxicity; no changes from normal morphology were displayed when diluted 1/100. The MIC and MBC of CA were 6.25 mg/mL and 12.50 mg/mL, respectively. CA solutions demonstrated significantly low levels of bacterial counts than the positive control group, reporting a value of 9.3% for the 10% solution versus the 1% solution (35.2%). Conclusions: Despite its valuable antimicrobial properties, the cytotoxic effects of citric acid should be considered during endodontic treatment.

Electrospun Nanofiber Films Suppress Inflammation In Vitro and Eradicate Endodontic Bacterial Infection in an E. faecalis-Infected Ex Vivo Human Tooth Culture Model

Treatment failure of endodontic infections and their concurrent inflammations is commonly associated with microbial persistence and reinfection, also stemming from the anatomical restrictions of the root canal system. Aiming to address the shortcomings of current treatment options, a fast-disintegrating nanofibrous film was developed for the intracanal coadministration of an antimicrobial (ZnO nanoparticles) and an anti-inflammatory (ketoprofen) agent. The electrospun films were fabricated based on polymers that dissolve rapidly to constitute the actives readily available at the site of action, aiming to eliminate both microbial infection and inflammation. The anti-inflammatory potency of the nanofiber films was assessed in an in vitro model of lipopolysaccharide (LPS)-stimulated RAW 264.7 cells after confirming their biocompatibility in the same cell line. The nanofiber films were found effective against Enterococcus faecalis, one of the most prominent pathogens inside the root canal space, both in vitro and ex vivo using a human tooth model experimentally infected with E. faecalis. The physical properties and antibacterial and anti-inflammatory potency of the proposed electrospun nanofiber films constitute a promising therapeutic module in the endodontic therapy of nonvital infected teeth. All manuscripts must be accompanied by an abstract. The abstract should briefly state the problem or purpose of the research, indicate the theoretical or experimental plan used, summarize the principal findings, and point out major conclusions.

Impact of irrigation protocols with some chelators and mechanical agitation on intratubular decontamination

This study evaluated main canal and intratubular decontamination using different irrigation solutions followed by adjunctive agitation steps for infected root canals. Sixty-eight lower incisors were contaminated with Enterococcus faecalis and allocated to groups according to canal treatment (n = 10): G1, NaOCl followed by ethylenediaminetetraacetic acid (EDTA); G2, a mixture of NaOCl with hydroxyethylidene bisphosphonate (HEBP); and G3, NaOCl followed by EDTA-T (EDTA with sodium lauryl ether sulfate). All three groups of teeth were agitated with passive ultrasonic irrigation (PUI) using saline solution, whereby G4, G5, and G6 were prepared as above, and agitation was performed using an XP-Endo Finisher instrument. Microbiological samples were collected from the root canals with paper points at three times: before and after chemomechanical preparation and after agitation. The colony-forming units (CFU)/mL count was determined, and bacterial intratubular viability was analyzed via confocal laser scanning microscopy using Live/Dead staining. Statistical analysis was performed using a Kruskal-Wallis test followed by Dunn tests. A Friedman test was applied for colony-counting data (α = 0.05). CFU/mL counting indicated equally effective decontamination in the experimental groups (p > 0.05). According to microscopy images, the use of irrigation solutions followed by agitation with the XP-Endo Finisher yielded better results. Moreover, NaOCl+EDTA-T followed by XP-Endo Finisher resulted in significantly lower viability than in the PUI-activated groups (p < 0.05). The cervical and medium thirds of the specimens presented similar results. Overall, NaOCl+EDTA-T exhibited the best intratubular antibacterial activity, mainly for canals that were subsequently agitated using XP-Endo Finisher.

Ultrasonic agitation reduces the time of calcium hydroxide antimicrobial effect and enhances its penetrability

OBJECTIVES

The objective of the present work was to evaluate the ultrasonic agitation, time and vehicle (propylene glycol or distilled water) on the antimicrobial potential and penetrability of calcium hydroxide pastes on infected dentin by means of Confocal Laser Scanning Microscopy (CLSM) and microbiological culture (MC).

MATERIALS AND METHODS

Dentin specimens were infected with Enterococcus faecalis using a new contamination protocol of 5 days. The specimens were divided into eight groups and dressed with the pastes for 7 or 15 days: G1) calcium hydroxide (CH) + propylene glycol (prop)/7 days (d), G2) CH + prop/7d + ultrasonic agitation (U), G3) CH + distilled water (dw)/7d, G4) CH + dw/7d + U, G5) CH + prop/15d, G6) CH + prop/15d + U, G7) CH + dw/15d, G8) CH + dw/15d + U. The ultrasonic activation was made for 1 min in both directions with a plain point insert. After medications removal, the images obtained by CLSM showed the viable (green) and dead (red) bacteria with Live and Dead dye. By the MC, the dentinal wall debris obtained by burs were collected for colony counts. For the penetration test, the Rodamine B dye was added to the CH pastes and analyzed by CLSM.

RESULTS

The 7 and 15-days CH + prop+U pastes performed better antimicrobial efficacy, followed by the CH + dw+U/15d paste.

CONCLUSIONS

All pastes demonstrated better penetration and antimicrobial activity against E. faecalis when agitated with ultrasound, even in periods of up to seven days. The propylene glycol vehicle showed better results.

CLINICAL RELEVANCE

Agitation of the dressing that remains for less time inside the root canal can optimize the decontamination of endodontic treatment.

Antibacterial Efficacy of Triple Antibiotic Medication With Macrogol (3Mix-MP), Traditional Triple Antibiotic Paste, Calcium Hydroxide, and Ethanol Extract of Propolis: An Intratubular Dentin Ex Vivo Confocal Laser Scanning Microscopic Study

INTRODUCTION

This study aimed to assess the effectiveness of antibacterial activity of medications used in regenerative endodontic treatment.

METHODS

Sixty-seven dentin cylinders of single-rooted teeth were contaminated with a culture of Enterococcus faecalis (ATCC 29212; American Type Culture Collection, Manassas, VA) for 5 days. Samples were divided into 1 control group and the following experimental groups according to the medication applied: traditional triple antibiotic paste (TAP), clindamycin-modified TAP (mTAP), triple antibiotic medication with macrogol (3Mix-MP), clindamycin-modified 3Mix-MP (m3Mix-MP), calcium hydroxide (CH), and ethanol extract of propolis (EEP). After 14 days, the medications were removed, and the samples were submitted to confocal laser scanning microscopic analysis to quantify the percentage of viable bacteria. The distribution of data was confirmed by the Shapiro-Wilk test. The Kruskal-Wallis and Dunn tests were used for intergroup comparisons, and the Wilcoxon test was used for comparison between superficial and deep antibacterial efficacy for the same medication. The level of significance was set at P < .05.

RESULTS

3Mix-MP and m3Mix-MP presented significantly higher antibacterial efficacy compared with the other tested medications (P < .05), except for mTAP. mTAP was more effective than TAP (P < .05). The antibacterial efficacy of EEP and CH did not differ significantly from TAP and mTAP (P > .05). All medications showed effective antibacterial action compared with the control group (P < .05).

CONCLUSIONS

3Mix-MP and m3Mix-MP, which present extremely high concentrations of antibiotics (1500 mg/mL), were not more effective than mTAP at the concentration recommended by the American Association of Endodontists (5 mg/mL). Moreover, CH and EEP were as effective as TAP and mTAP.

Antibacterial efficacy of copper-added chitosan nanoparticles: a confocal laser scanning microscopy analysis

The aim of this study was to evaluate the antibacterial efficacy of copper added chitosan nanoparticles (CU-CNPs) as an irrigation solution with different irrigants in terms of eliminating Enterococcus Faecalis (E. faecalis) from the root canals. Fifty mandibular premolar teeth were prepared and infected with E. faecalis for 21 days. After the incubation period, samples were randomly divided into a control group irrigated with distilled water and 4 experimental groups (n = 10) irrigated with as follows, %6 NaOCl, %6 NaOCl + %9 editronate (HEBP), Chitosan nanoparticles (CNPs), and CU-CNPs. To calculate the proportion of dead E. faecalis cell volume, stained using LIVE/DEAD BacLight Bacterial Viability Kit and were scanned using confocal laser scanning microscope (CLSM). All the irrigation solutions significantly (P < .05) killed the bacteria in the canal, except for the control group. CU-CNPs solution killed the highest (P < .05) number of bacteria compared with the other experimental groups. No significant difference was found between CNPs, NaOCl + HEBP, and NaOCl in terms of antibacterial activity. CU-CNPs solution was exhibited higher antibacterial efficacy against E. faecalis.

The presence of smear layer affects the antimicrobial action of root canal sealers

AIM

To assess the chemical and microstructural characteristics of dentine after the use of two irrigation protocols and correlate this with the antimicrobial properties of hydraulic calcium silicate cement (HCSC) sealers and changes to the dentine structure/chemistry after sealer placement.

METHODOLOGY

Two irrigation protocols - Protocol A using 2% NaOCl used 5 mL/5 min and Protocol B with 2% NaOCl (5 mL/5 min) followed by 17% EDTA (5 mL/3 min) - were used to prepare dentine. The chemical and microstructural changes following irrigation were assessed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared (FT-IR) spectroscopy (n = 5) on dentine obtained from the mid-root and coronal parts of extracted human teeth. Four sealers (AH Plus, BioRoot, MTA Fillapex, TotalFill) were characterized by SEM/EDS (n = 3). The ability of the sealers to eradicate intratubular Enterococcus faecalis biofilms was assessed by live/dead dye and confocal laser scanning microscopy to measure the percentage of living cells. The effect of combined irrigation and root filling on dentine was assessed by SEM and EDS analysis (n = 5). Statistical analysis was undertaken using one-way anova and a number of post hoc tests to detect intergroup differences. The F-test was used for comparison of variances in the microbiology testing.

RESULTS

The use of NaOCl alone left the smear layer intact, with traces of chlorine remaining on dentine. The use of BioRoot sealer restored the calcium levels of dentine which had been depleted by the irrigation with EDTA. BioRoot exhibited antimicrobial properties against intratubular bacteria even in the presence of smear layer (Protocol A). Smear layer removal improved the bactericidal effect of all sealers and Ca²⁺ leaching. The use of a chelating agent was important for the intratubular sealer penetration for AH Plus but not the other sealers.

CONCLUSION

The removal of smear layer was necessary for penetration of AH Plus into the dentinal tubules. BioRoot was a more effective sealer in reducing the bacterial load in the dentinal tubules than the other materials tested and the presence of smear layer did not affect its activity.

Can kinematics, file diameter, and PUI influence the intracanal decontamination and apical bacterial extrusion?

The present study investigated the intracanal decontamination and apical extrusion of bacteria and debris from root canals instrumented with rotary and reciprocating systems (ProDesign Logic or ProDesign R), with different file diameters and using conventional syringe irrigation (CSI) or passive ultrasonic irrigation (PUI). Eighty extracted mandibular premolars were contaminated with Enterococcus faecalis and randomly assigned to eight experimental groups according to the root canal instrumentation and irrigation technique employed (n = 10): G1: Prodesign Logic 25.06; G2: Prodesign R 25.06; G3 and G4 were instrumented with the same single-file systems, respectively, using 35.05 diameters and CSI. G5, G6, G7, and G8 were instrumented like the previous groups, but with PUI. Apically extruded debris during instrumentation was collected into pre-weighed microtubes. The weight of the empty microtube was subtracted from the final weight to establish the amount of extruded debris. Bacteria from root canals and extruded debris were collected for a microbiological evaluation of colony forming units (CFU/mL). For statistical analyses, the Mann-Whitney and Kruskal-Wallis followed by the Dunn's tests were used (α = 0.05). All instruments caused extrusion of debris. For irrigation techniques, PUI promoted greater debris and bacterial extrusion (p < 0.05). The CFU/mL count indicated that the instrumentation of the experimental groups were equally effective in the decontamination of the root canal (p > 0.05). The systems tested (regarding file diameter and kinematics) were associated with similar amounts of apically extruded debris and root canal decontamination. PUI was associated with greater debris and bacterial extrusion.

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

Aim

To 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.

Methodology

Biofilm 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.

Results

US 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.

Conclusions

The 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.

The influence of centrifugation and inoculation time on the number, distribution, and viability of intratubular bacteria and surface biofilm in deciduous and permanent bovine dentin

The present study aimed to assess the influence of centrifugation and inoculation time on the number, distribution, and viability of intratubular bacteria and surface monospecies E. faecalis biofilm.

MATERIALS AND METHODS

Forty-four semicylindrical specimens cut from primary (n = 22) and permanent (n = 22) bovine teeth were randomly assigned to the experimental groups. Teeth of each type were inoculated with E. faecalis with and without centrifugation for 1 and 14 days. The number, localization, viability of bacteria and depth of their penetration were assessed with bacterial culturing of dentin shavings, scanning electron microscopy (SEM) and confocal laser electron microscopy (CLSM). Three-way ANOVA with post-hoc Tukey test were used to assess the influence of different experimental setups on dentin infection.

RESULTS

Severe dentin infection was observed in permanent and deciduous teeth after centrifugation and 1-day incubation: bacteria reached the full length of dentinal tubules and colony-forming units were too numerous to count. The volume of green fluorescence didn't differ significantly in permanent teeth compared with deciduous (p = 1.0). After 1-day stationary inoculation, small number of cultivable bacteria and few viable bacteria in dentinal tubules were found in both groups. After 14-day stationary inoculation, the dentin infection according to CLSM was deeper in deciduous teeth compared with permanent (p = 0.006 and p = 0.019 for centrifugation and stationary inoculation, respectively).

CONCLUSION

The most even and dense dentin infection was observed in primary and permanent bovine teeth after centrifugation and 1-day inoculation, and in deciduous teeth after 14-day stationary inoculation.

Antimicrobial peptide GH12 as root canal irrigant inhibits biofilm and virulence of Enterococcus faecalis

AIM

The objectives of this laboratory-based study were to investigate the effects of GH12 on Enterococcus faecalis biofilm and virulence.

METHODOLOGY

Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of GH12 against E. faecalis were first determined. A time-kill assay was further conducted. The effects of GH12 on the expression of virulence and stress genes in E. faecalis were evaluated by RT-qPCR. Crystal violet stain was used to investigate the effects of GH12 on E. faecalis biofilm formation and 1-day-old biofilm. Finally, an ex vivo tooth model contaminated with E. faecalis was used to evaluate the antimicrobial activity of GH12 as an irrigant by CFU counting, SEM and CLSM. One-way anova and Tukey's multiple comparisons test were used to compare the differences amongst groups (α = 0.05).

RESULTS

The MICs and MBCs of GH12 against E. faecalis were 8.0 ± 0.0 and 16.0 ± 0.0 mg L^-1 , respectively, and GH12 at 32.0 mg L^-1 reduced the bacterial numbers by more than 99.9% within 1 min. Various virulence genes (efaA, esp and gelE) and stress genes (dnaK, groEL, ctsR and clpPBCEX) in E. faecalis were significantly downregulated by GH12 at sub-MIC levels (P < 0.05). Additionally, both E. faecalis biofilm formation and the biomass of 1-day-old E. faecalis biofilm were significantly reduced by GH12 (P < 0.05). Elimination of E. faecalis in biofilms from root canal walls was achieved through irrigation with 64.0 mg L^-1 GH12 for 30 min. CLSM analysis revealed that GH12 at 64.0 mg L^-1 was most effective in eliminating bacteria within dentinal tubules (P < 0.05).

CONCLUSION

In a laboratory setting, and when used as an irrigant, GH12 suppressed E. faecalis, downregulated specific virulence and stress-associated genes, eliminated intracanal E. faecalis protected by biofilms and killed bacteria in dentinal tubules. These results emphasize the need for preclinical and clinical studies to explore the potential of GH12 as an antimicrobial agent during root canal treatment.

Quantitative Assessment of Dentinal Tubule Disinfection in Absence of Biofilm on Root Canal Walls: An in vitro Study

Introduction

This study aimed at assessing the quantitative effect of calcium hydroxide, 2% chlorhexidine gel, and 1.5% chlorhexidine linked to xanthan gel specifically against intratubular bacteria.

Methods and Materials

Fifty-two semi-cylindrical bovine dentin specimens were infected with Enterococcus (E.) faecalis by centrifugation with subsequent 7-days incubation. The surface of specimens was disinfected with 3% H₂O₂. Scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and the count of bacterial colony-forming units (CFU/mg) were used to assess dentin infection. A total of 40 specimens were incubated for 2 weeks with one of the intracanal medication applied (10 samples for each group): 1) calcium hydroxide, 2) 2% chlorhexidine gel, 3) 1.5% chlorhexidine linked to xanthan gel and 4) sterile saline. Final passive ultrasonic irrigation with 3% sodium hypochlorite was performed in half of the total specimens. The effect of intracanal medications and irrigation against intratubular bacteria was assessed by bacterial culturing of dentin shavings. Two-Way ANOVA model was applied followed by post-hoc Tukey's test for multiple pair-wise comparisons of mean CFU/mg values.

Results

SEM, CLSM, and bacterial culturing confirmed the absence of the surface biofilm on the root canal wall and showed vital intratubular bacteria at the depth up to 700  m. Two-week application of 1.5% chlorhexidine with xanthan gel and 2% chlorhexidine gel significantly decreased intratubular bacterial counts compared with saline (P=0.0003 and P=0.0005, respectively). Subsequent passive ultrasonic irrigation with 3% sodium hypochlorite significantly reduced the number of intratubular bacteria in all groups except for the group with 1.5% chlorhexidine-xanthan gel (P=0.0054).

Conclusion

This modified ex vivo model study showed ultrasonically activated irrigation with sodium hypochlorite had greater effect on intratubular bacteria counts compared with 2-week application of intracanal medications.

Antibacterial Effect of Photodynamic Therapy on Root Canal Disinfection Combined with Different Irrigation Protocols

Introduction

Photodynamic therapy (PDT) is an emerging alternative therapy to conventional endodontic treatment to optimize bacterial elimination. The aim of this study was to evaluate the in vitro antibacterial effect of PDT combined with different irrigation protocols on root canals inoculated with Enterococcus (E.) faecalis.

Methods and Materials

Ninety uni-radicular human premolars were prepared and contaminated with E. faecalis for 4 days. Teeth were randomly divided into six groups: positive control group (C+) consisted of conventional needle irrigation with 2.5% sodium hypochlorite (NaOCl); negative control group (C-) consisted of no treatment after contamination; PDT group as treated with 0.005% methylene blue and diode laser irradiation for 90 sec at wavelength of 660 nm, energy of 9 Joules, power of 100 mW; the fourth group consisted of NaOCl+PDT, the fifth group were treated with passive ultrasonic irrigation (PUI) with NaOCl+PDT (PUI+PDT); and the final group were treated with XP Endo Finisher with NaOCl+PDT (XP Endo+PDT). The contents of the root canals were collected with sterile absorbent paper points at two times: before and 24 h after decontamination protocols. The number of colony-forming units (CFU) was determined for each root canal. ANOVA and the Tukey test were used, with significance set at 5% (P<0.05).

Results

The inhibition percentage ranged from 10.72 (C-) to 100% (XP Endo+PDT), with CFU/mL counts differing among all protocols tested (P<0.05). The different protocols significantly influenced bacterial inhibition (P<0.05). However, the XP Endo+PDT protocol resulted in the highest inhibition percentage (100%), followed by NaOCl+PDT (65.85%).

Conclusions

PDT combined with different final irrigation protocols was more effective in inhibiting E. faecalis growth than photodynamic therapy alone. XP Endo was the best irrigation protocol to eradicate this microorganism.

In vitro Evaluation of the Antimicrobial Effect of N-acetylcysteine and Photodynamic Therapy on Root Canals Infected with Enterococcus faecalis

Introduction

This study aimed to evaluate the in vitro effectiveness of N-acetylcysteine (NAC), photodynamic therapy (PDT) and NAC with supplemental PDT in optimizing the removal of bacteria from infected dentinal tubules of root canals infected with Enterococcus (E.) faecalis biofilm.

Methods and Materials

Eighty human teeth were randomly divided into 5 groups (n=16) according to the intracanal medication used: saline solution (control); calcium hydroxide (CH); NAC; PDT; NAC+PDT. Ten samples from each group were prepared for microbiological culture analysis (CFU/mL) and were inoculated with E. faecalis suspension for 21 days for biofilm development; the other six samples from each group were prepared for scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) and submitted to a 5-days contamination protocol including eight centrifugation cycles on every other day for dentinal tubules infection. For antimicrobial activity analysis by microbiological culture (CFU/mL), the root canals were contaminated with E. faecalis biofilm, instrumented and then medicated according to the experimental groups. Three samples were collected from the root canals: after 21-days of contamination, immediately after the instrumentation and 14-days after the medication according to the experimental groups. The morphology of E. faecalis biofilm on the root canal walls and bacterial cells viability were assessed by means of SEM and CLSM, respectively. One-way ANOVA and Repeated Measures ANOVA tests were used to analyze the obtained data statistically.

Results

CFU/mL analysis showed that CH, NAC and NAC+PDT promoted greater antibacterial activity with statistically significant difference compared to saline solution and PDT (P<0.0001). However, saline solution and PDT were statistically similar (P>0.07). Illustrative images by SEM confirmed partially the CFU/mL results. CLSM showed that all groups were effective eliminating E. faecalis except for the saline solution group.

Conclusions

Based on this in vitro study NAC was bactericidal against E. faecalis biofilms regardless PDT stimulation, presenting similar antimicrobial activity to CH.

Antimicrobial action of photodynamic therapy in root canals using LED curing light, curcumin and carbopol gel

AIM

To evaluate the capacity of carbopol gel to maintain the intensity of a LED curing light (blueLED) along the length of prepared root canals in bovine teeth, and to assess the antimicrobial capacity of curcumin photoactivated by a LED curing light in the presence of carbopol gel.

METHODOLOGY

Experiment 1: Eight straight roots of bovine incisors were standardized to a length of 15 mm, and the root canals instrumented up to a size 120 K-file. The LED curing light was irradiated inside the root canals using an aluminium collimator (1.5 mm in diameter) placed at the orifice (n = 8). Initially, the irradiation was performed in empty root canals and then repeated with the root canals filled with carbopol gel. Simple standardized photographs of the roots were taken with a digital camera in the mesial perspective during the irradiation procedure and the images analysed in OriginLab software to verify the light intensity along the length of the root. Experiment 2: Twenty dentine blocks were obtained from the cervical third of bovine incisors using a trephine bur. Biofilms were induced for 21 days on the blocks using Enterococcus faecalis (ATCC 4083) at 10⁹ cells mL^-1 . The blocks were treated according to the groups (n = 5): positive control; standard PDT (methylene blue + diode Laser); curcumin; LED curing light; and curcumin + LED curing light. After the treatment, the samples were dyed with Live/Dead BacLight Bacterial Viability solution and fluorescence images were obtained by Confocal Scanning Laser Microscopy (CSLM). Experiment 3: Thirty-two roots of bovine incisors were prepared as described in experiment 1. Their dentinal tubules were contaminated and the root canals treated according to the groups (n = 8): positive control; standard PDT; curcumin + LED curing light; curcumin + carbopol gel + LED curing light. The specimens were sectioned longitudinally and the split roots were treated with the Live/Dead dye to obtain fluorescence images by CSLM. All images were processed using BioImageL software to measure the percentage of viable bacteria and the data analysed statistically using the nonparametric Kruskal-Wallis test (α < 0.05).

RESULTS

In Experiment 1, carbopol gel did not improve the intensity of LED light transmission along the root canal. In Experiment 2, a significant decrease (P < 0.05) in bacterial viability occurred in the following order: positive control < only LED curing light < only curcumin < curcumin + LED curing light = standard PDT; and in Experiment 3 positive control = curcumin + LED curing light ≤ curcumin + gel + LED curing light ≤ standard PDT.

CONCLUSION

Similar disinfection effectiveness was obtained using curcumin + LED curing light and methylene blue + 660 nm LASER (standard PDT). The use of carbopol gel did not favour a greater transmission of LED light along the root canal and also resulted in less bacterial killing when used in endodontic PDT.

Intradentinal antimicrobial action and filling quality promoted by ultrasonic agitation of epoxy resin-based sealer in endodontic obturation

The aim of this study was evaluate the influence of ultrasonic activation (UA) of AH Plus to improve canal and isthmus filing, and analyse the antimicrobial effect against Enterococcus faecalis within dentinal tubules.

Demetallization of Enterococcus faecalis biofilm: a preliminary study

Objectives To determine the concentration of calcium, iron, manganese and zinc ions after the application of chelator to Enterococcus faecalis biofilms. Material and Methods Fifty bovine maxillary central incisors were prepared and inoculated with E. faecalis for 60 days. The following were used as irrigation solutions: 17% EDTA (pH 3, 7 and 10), 2.5% sodium hypochlorite (NaOCl) combined with 17% EDTA (pH 3, 7 and 10), distilled water (pH 3, 7 and 10), and 2.5% NaOCl. Each solution was kept in the root canal for five minutes. Fifteen uncontaminated root canals were irrigated with 17% EDTA (pH 3, 7 and 10). Six teeth were used as bacterial control. The number of calcium, iron, manganese and zinc ions was determined using flame atomic absorption spectrometry. Mean ± standard deviation (SD) values were used for descriptive statistics. Results Calcium chelation using 17% EDTA at pH 7 was higher than at pH 3 and 10, regardless of whether bacterial biofilm was present. The highest concentration of iron occurred at pH 3 in the presence of bacterial biofilm. The highest concentration of manganese found was 2.5% NaOCl and 17% EDTA at pH 7 in the presence of bacterial biofilm. Zinc levels were not detectable. Conclusions The pH of chelating agents affected the removal of calcium, iron, and manganese ions. The concentration of iron ions in root canals with bacterial biofilm was higher after the use of 17% EDTA at pH 3 than after the use of the other solutions at all pH levels.

Effect of ultrasound streaming on the disinfection of flattened root canals prepared by rotary and reciprocating systems

New technical and scientific developments have been advocated to promote the success of the endodontic treatment. In addition to rotary and reciprocating systems, irrigating solution agitation has been suggested and passive ultrasonic irrigation (PUI) is the most used. Objective: To evaluate, in vitro, the effect of ultrasound streaming (US) in the disinfection of flattened root canal systems prepared by the ProTaper, BioRaCe and Reciproc systems, utilizing the microbiological culture. Methodology: Extracted human mandibular incisors (n=84) were used. Suspensions of Enterococcus faecalis (ATCC 29212) were standardized and inserted along with the teeth immersed in brain-heart infusion (BHI) broth. The contamination was made following a protocol during 5 days. The teeth were randomly divided into six groups: G1, ProTaper Universal; G2, ProTaper Universal with US; G3, BioRaCe; G4, BioRaCe with US; G5, Reciproc; and G6, Reciproc with US. Irrigation was performed with saline solution. After biomechanical preparation, microbiological samples were performed with sterilized paper points, which were diluted and spread on BHI agar; after 48 h, the colony forming units (CFU/mL) were counted for each sample. Results: Groups using ultrasonic agitation presented a greater antibacterial effect than the other ones, even using saline solution as irrigant. The ProTaper Universal system showed the best antibacterial activity of the tested systems (median of 0 CFU/mL with and without surfactant or ultrasonic activation [PUI]). Even with PUI, Reciproc (median of 2.5 CFU/mL with PUI and 5 without it) could not reduce as many colonies as ProTaper Universal without US. The BioRaCe system had greater bacterial reduction when using US (median of 0 CFU/mL with PUI and 30 without it). Conclusions: US promoted greater reduction in the number of bacteria in the flattened root canals prepared with nickel-titanium mechanized systems. Regarding the instruments used, the ProTaper Universal system was the most effective in reducing the bacterial number.

Effect of ultrasonic streaming on intra-dentinal disinfection and penetration of calcium hydroxide paste in endodontic treatment

Objective

The antimicrobial effect of ultrasonic agitation of calcium hydroxide (CH) pastes in infected bovine dentin and their penetrability were evaluated using confocal laser scanning microscopy (CLSM) and microbiological culture.

Material and Methods

Fifty-two bovine teeth were infected with Enterococcus faecalis using a new contamination protocol; then they received CH paste and were divided into groups with or without ultrasound. Ultrasonic agitation was conducted for 1 min with a plain point insert. After 15 d, the CLSM analyzed the viable and dead bacteria with Live and Dead assay. The dentinal wall debris was collected by burs, and the colony forming units (CFU/mL) were counted. The penetrability of the paste inside dentinal tubules was tested using the B-rodamine dye.

Results

The calcium hydroxide paste showed better results with the use of ultrasonic agitation (p<0.05).

Conclusion

The ultrasonic agitation of CH paste increased its antimicrobial action and was responsible for intradentinal penetration with the fulfilment of the tubules.

Intratubular disinfection with tri-antibiotic and calcium hydroxide pastes

OBJECTIVE

The aim of this study was to compare the in vitro intradentinal antimicrobial ability of the calcium hydroxide and tri-antibiotic pastes.

MATERIALS AND METHODS

Standard bovine dentin tubes were sterilized and then infected with Enterococcus faecalis by a new contamination protocol of great depths of dentin. The specimens were filled with the medications, divided into two test-groups: calcium hydroxide (Group 1) and tri-antibiotic (Group 2) pastes. After 15 days, the teeth were evaluated by microbiological culture and confocal laser scanning microscopy (CLSM) with viability dye assay LIVE/DEAD inside dentinal tubules. In experiment of culture, the bacterial collection of the dentin fragments was done for counting the colony-forming units.

RESULTS

The tri-antibiotic paste had a slightly greater antimicrobial effect; however, there was no statistical difference between the groups.

CONCLUSIONS

It was concluded that the tri-antibiotic paste and the calcium hydroxide paste exercise the same effect on intra-tubular decontamination against E. faecalis. So, due the multiples advantages, the calcium hydroxide paste can be the choice for dentinal decontamination in regenerative procedures.

Exopolysaccharide dispelled by calcium hydroxide with volatile vehicles related to bactericidal effect for root canal medication

Objective:

Enterococcus faecalis is the dominant microbial species responsible for persistent apical periodontitis with ability to deeply penetrate into the dentin. Exopolysaccharides (EPS) contribute to the pathogenicity and antibiotic resistance of E. faecalis. Our aim was to investigate the antimicrobial activity of calcium hydroxide (CH), camphorated parachlorophenol (CMCP), and chlorhexidine (CHX) against E. faecalis in dentinal tubules.

Material and Methods:

Decoronated single-canal human teeth and semicylindrical dentin blocks were incubated with E. faecalis for 3 weeks. Samples were randomly assigned to six medication groups for 1 week (n=10 per group): CH + 40% glycerin-water solution (1:1, wt/vol); CMCP; 2% CHX; CH + CMCP (1:1, wt/vol); CH + CMCP (2:3, wt/vol); and saline. Bacterial samples were collected and assayed for colony-forming units. After dentin blocks were split longitudinally, confocal laser scanning microscopy was used to assess the proportion of viable bacteria and EPS production in dentin.

Results:

CMCP exhibited the best antimicrobial activity, while CH was the least sensitive against E. faecalis (p<0.05). CHX showed similar antimicrobial properties to CH + CMCP (1:1, wt/vol) (p>0.05). CH combined with CMCP inhibited EPS synthesis by E. faecalis, which sensitized biofilms to antibacterial substances. Moreover, increasing concentrations of CMCP decreased EPS matrix formation, which effectively sensitized biofilms to disinfection agents.

Conclusion:

The EPS matrix dispelled by CH paste with CMCP may be related to its bactericidal effect; the visualization and analysis of EPS formation and microbial colonization in dentin may be a useful approach to verify medicaments for antimicrobial therapy.