The Effect of Sodium Hypochlorite and Chlorhexidine as Irrigant Solutions for Root Canal Disinfection: A Systematic Review of Clinical Trials

Sodium Hypochlorite Concentration and Post-Endodontic Pain - Unveiling the Optimal Balance: A Systematic Review and Meta-analysis

INTRODUCTION

This study systematically reviewed literature regarding the effect of different concentrations of sodium hypochlorite (NaOCl) used during root canal treatment (RCT) on post-endodontic pain (PEP) and rescue analgesia.

METHODS

Following registration with PROSPERO (CRD42023388916), a search was conducted using PubMed, Scopus, Web of Science, and Embase databases. Randomized controlled trials (RaCTs) of patients receiving RCT which assessed PEP at different time intervals were included. Following data extraction and Cochrane risk of bias assessment 2, meta-analyses were performed to evaluate PEP during the first 48h along with rescue analgesic intake. The certainty of the evidence was evaluated using the Grading of Recommendations, Assessment, Development and Evaluation approach.

RESULTS

Five RaCTs with 674 patients were included. One study exhibited a low risk of bias, while four raised some concerns. Patients treated with low concentrations of NaOCl (≤3%) were significantly less likely to report PEP at 24h (OR=2.32; [95%CI, 1.63-3.31]; P<0.05) and 48h (OR=2.49; [95% CI,1.73-3.59]; P<0.05) as compared with high concentrations of NaOCl (≥5%). Furthermore, with low concentrations of NaOCl, significantly lesser moderate-severe PEP was reported at 24h (OR=2.32; [95%CI, 1.47-3.62]; P<0.05) and 48h (OR=2.35; [95%CI, 1.32-4.16]; P<0.05) and lesser analgesia was needed (OR=2.43; [95%CI, 1.48-4.00]; P<0.05).

CONCLUSIONS

While PEP can be influenced by several factors, low certainty evidence suggests that when NaOCl is used as an irrigant during RCT, PEP may be less likely with lower concentrations of NaOCl. Moderate certainty evidence indicates that lesser analgesia may be required with lower concentrations of NaOCl. These results should be cautiously interpreted.

Elimination of E. faecalis with NaOCl versus chlorhexidine gluconate from primary molar root canal systems: an ex vivo model study

OBJECTIVES

This ex vivo human study aimed to evaluate the efficacy of NaOCl and chlorhexidine gluconate (CHG) irrigations in eliminating Enterococcus faecalis from the RCS of primary molars.

MATERIALS AND METHODS

Disinfected extracted primary molars were inoculated with E. faecalis for 24 h. Then, the RCS samples were then irrigated with either 2.5% NaOCl, 0.2% and 2% CHG, or sham saline. The samples were collected immediately after irrigation; and 24 h later, the bacterial viability and counts were measured using blood agar and qRT-PCR, respectively. Histological sections were used to measure E. faecalis penetration and viability in dentin tubules using fluorescence microscopy.

RESULTS

The recovery of viable E. faecalis after the irrigation of the primary molars showed more significant bactericidal effects of NaOCl and 0.2% and 2% CHG than of saline. Immediately after the irrigation, the NaOCl group showed the greatest reduction in E. faecalis; and 24 h later, all the groups had lower viable E. faecalis than the saline control. The bacterial penetration was also lowest in the NaOCl group, although there was no difference in bacterial viability in the tubules between the groups.

CONCLUSION

In primary teeth, NaOCl and CHG showed similar degrees of bacterial elimination efficacy in terms of E.faecalis.

CLINICAL RELEVANCE

Within the limitations of this study, NaOCl and CHG have the similar ability to perform endodontic irrigation of primary ex vivo teeth regarding the elimination of E.faecalis, but NaOCl penetrates dentin tubules better.

Differences of protein expression in enterococcus faecalis biofilm during resistance to environmental pressures

BACKGROUND

Enterococcus faecalis biofilm was frequently found on the failed treated root canal wall, which survived by resisting disinfectant during endodontic treatment.Many researches have been conducted to explore the mechanisms of persistence of this pathogen in unfavorable conditions. However, no comprehensive proteomics studies have been conducted to investigate stress response in Enterococcus faecalis caused by alkali and NaOCl.

OBJECTIVE

Enterococcus faecalis (E.f) has been recognized as a main pathogen of refractory apical periodontitis, its ability to withstand environmental pressure is the key to grow in the environment of high alkaline and anti-bacterial drug that causes chronic infection in the root canal. This study aims to focus on the protein expression patterns of E.f biofilm under extreme pressure environment".

METHODS

Enterococcus faecalis biofilm model was established in vitro. Liquid Chromatograph-Mass Spectrometer (LC-MS/MS)-based label free quantitative proteomics approach was applied to compare differential protein expression under different environmental pressures (pH 10 and 5% sodium hypochlorite (NaOCl)). And then qPCR and Parallel Reaction Monitoring Verification (PRM) were utilized to verify the consequence of proteomics.

RESULTS

The number of taxa in this study was higher than those in previous studies, demonstrating the presence of a remarkable number of proteins in the groups of high alkaline and NaOCl. Proteins involved in ATP-binding cassette (ABC) transporter were significantly enriched in experimental samples. We identified a total of 15 highly expressed ABC transporters in the high alkaline environment pressure group, with 7 proteins greater than 1.5 times.

CONCLUSIONS

This study revealed considerable changes in expression of proteins in E.f biofilm during resistance to environmental pressures. The findings enriched our understanding of association between the differential expression proteins and environmental pressures.

Temporary Root Canal Obturation with a Calcium Hydroxide-Based Dressing: A Randomized Controlled Clinical Trial

Successful bacterial inactivation or elimination is essential for successful outcomes in endodontics. This study investigated the efficacy of a calcium hydroxide paste (Ca(OH)2) as a temporary medical dressing for 1 week after chemomechanical root canal treatment (CMRCT). Microbiological samples from 26 patients were collected after endodontic emergency treatment as follows: (1) removal of the provisional filling material; (2) CMRCT; (3) irrigation with sodium hypochlorite I (3%); (4) medicinal insertion of Ca(OH)2; and (5) irrigation with sodium hypochlorite II (3%). A microbiological examination was carried out after the specimens had been taken from the root canals via saline and sterile paper points. CMRCT resulted in a significant reduction in total bacterial load (TBL) in the root canal (p < 0.05). Additional irrigation (3) resulted in a further significant reduction in TBL (p < 0.05). In contrast, Ca(OH)2 medication did not prevent the bacterial load from returning to the previous level immediately after CMRCT, but did not increase above that level either (p < 0.05). However, the increase in TBL was significant (p < 0.05) in comparison with the disinfection groups (I/II). Administration of Ca(OH)2 for 1 week shows that in combination with an additional disinfection procedure, an increase in TBL must be expected, but not above the level of conditions after CMRCT.

Disinfectant effectiveness of chlorhexidine gel compared to sodium hypochlorite: a systematic review with meta-analysis

This study aimed to compare the disinfectant ability of chlorhexidine (CHX) gel and sodium hypochlorite (NaOCl). Systematic searches were conducted from inception until December 8th, 2022 (MEDLINE/PubMed, Cochrane Library, Web of Science, Scopus, Embase, and Grey Literature databases). Only randomized clinical trials were included. The revised Cochrane risk of bias tools for randomized trials were used to assess the quality of studies. Meta-analyses were performed. The overall quality of evidence was assessed through the Grading of Recommendations Assessment, Development, and Evaluation tool. Six studies were included. Five had a low risk of bias and 1 had some concerns. Three studies assessed bacterial reduction. Two were included in the meta-analysis for bacterial reduction (mean difference, 75.03 [confidence interval, CI, -271.15, 421.22], p = 0.67; I2 = 74%); and 3 in the meta-analysis for cultivable bacteria after chemomechanical preparation (odds ratio, 1.03 [CI, 0.20, 5.31], P = 0.98; I2 = 49%). Five studies assessed endotoxin reduction. Three were included in a meta-analysis (mean difference, 20.59 [CI, -36.41, 77.59], p = 0.48; I2 = 74%). There seems to be no difference in the disinfectant ability of CHX gel and NaOCl, but further research is necessary.

Effectiveness of root canal irrigation and dressing for the treatment of apical periodontitis: A systematic review and meta-analysis of clinical trials

BACKGROUND

Sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) and/or calcium hydroxide (Ca(OH)2 ) are commonly used during root canal treatment. Evaluation of their effectiveness regarding clinical and patient-related outcomes requires further understanding.

OBJECTIVES

To assess the effectiveness of root canal irrigation and dressing for the treatment of teeth with apical periodontitis (AP).

METHODS

A search was conducted in the PubMed-MEDLINE, Scopus, EMBASE, Google scholar databases and available repositories, followed by hand searches, until July 2021. Eligibility criteria followed the a priori formulated Population, Intervention, Comparator, Outcomes, Timing, and Study design (PICOTS) framework. Clinical studies restricted to English language were included. The revised Cochrane risk-of-bias tool for randomised trials (RoB 2) was used to assess the quality of included studies. Meta-analyses were performed using the fixed-effect model to obtain Risk Ratio (RR) and 95% Confidence Interval (CI), with sensitivity analysis. Overall quality of evidence of meta-analyses was assessed through the Grading of Recommendations Assessment, Development, and Evaluation tool.

RESULTS

The search identified 1357 records of which six fulfilled the inclusion criteria, providing data for 'irrigation' from 212 teeth and for 'dressings' from 438 teeth. Two studies reported no significant difference regarding the outcome 'pain at 7 days' using 2% chlorhexidine vs. 5.25% NaOCl and EDTA or after using different concentrations of NaOCl (1% vs. 5%). No significant difference was detected between different NaOCl concentrations regarding the reduction of AP. A meta-analysis was possible for the comparison of single-visit (SV) versus multiple-visits including the use of Ca(OH)2 demonstrating a significant effect in favour of SV (RR: 1.10; 95% CI: 1.03-1.19; p = .007; I2  = 0). RoB of included studies was moderate to low.

DISCUSSION

The use of Ca(OH)2 for the treatment of AP may not be beneficial. There is scarce or no evidence fulfilling the proposed PICOTS regarding irrigants and dressings.

CONCLUSIONS

There is moderate certainty that SV treatment is associated with better radiographic evidence of normal periodontal ligament space (strict criteria) compared with the use of Ca(OH)2. Reduction of AP is comparable after irrigation with 1% and 5% NaOCl, whereas postoperative pain at 7 days for the irrigants assessed is similar.

REGISTRATION

PROSPERO database CRD42021260271.

Antimicrobial efficacy of chlorine agents against selected oral pathogens

OBJECTIVES

Method-dependent comparison of antimicrobial agents' efficacy against oral pathogens.

MATERIALS AND METHODS

Several sodium hypochlorite solutions (NaOCl)-Perisolv®, Carisolv® and Dakin's solution-were equated with chlorhexidine (CHX) and hydrogen peroxide (H2O2) against ten oral micro-organisms related to caries and periodontitis using different minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) techniques. Agents were adjusted to the final 70 mmol/L concentration of active chlorine molecule.

RESULTS

Apart from H2O2 and the amino acids of Perisolv®, all the agents revealed an antimicrobial effect. Agar diffusion test ranked CHX (p < 0.05) as the most effective against all ten specimens, followed by the NaOCl of Perisolv® and Dakin's solution. Correspondingly, in broth microdilution on agar, CHX was the most effective in eradicating micro-organisms at 0.03 mmol/L compared with 2.2 mmol/L of Dakin's solution. In contrast, the bactericidal concentration of Dakin's solution was the most effective at 0.2 mmol/L, (p < 0.001), followed by Perisolv® (2.14 mmol/L), CHX (2.38 mmol/L) and Carisolv® (3.33 mmol/L) after 5 and 10 min in broth dilution test. In live/dead analysis, 60-min exposure to a 2-fold concentration of agents resulted in two-log Aggregatibacter actinomycetemcomitans inhibition by CHX (35 mmol/L) whilst Streptococcus mutans was more susceptible, in 0.8 and 8.8 mmol/L, after 10 min to CHX and Dakin's respectively.

CONCLUSION

Replacement of CHX with tested hypochlorite agents showed evident potential and promoted rapid antimicrobial effect.

CLINICAL RELEVANCE

Effective antimicrobial agents are crucial in controlling pathogen-induced oral infections increasing clinical possibilities to combat oral biofilms. Additionally, CHX substitution with hypochlorite agents could eliminate CHX's adverse effects.

Antimicrobial and Antibiofilm Activity of Synthetic Peptide [W7]KR12-KAEK Against Enterococcus faecalis Strains

The emergence of infections caused by microorganisms in the oral cavity and increasing concerns regarding the use of antibiotics have resulted in the development of novel antimicrobial molecules, such as antimicrobial synthetic peptides. The purpose of this study was to evaluate the antimicrobial and antibiofilm activities of the native peptide KR-12 and its derivative, the synthetic peptide [W7]KR12-KAEK, against planktonic and biofilms Enterococcus faecalis strains. The methods used to evaluate the antimicrobial activity in planktonic cultures include minimum inhibitory concentration and minimum bactericidal concentration assays. The effects of [W7]KR12-KAEK on biofilm formation and mature biofilms were evaluated by quantifying biomass (crystal violet staining) and counting colony-forming units. Structural assessments of the biofilms and cellular morphological changes were performed using scanning electron microscopy. Peptide [W7]KR12-KAEK showed potential antimicrobial activity against planktonic cells. Interestingly, the native peptide KR-12 showed no antimicrobial activity. Moreover, it inhibited biofilm formation and disrupted the mature biofilms of E. faecalis strains. These results suggest that [W7]KR12-KAEK may be a potential molecule for the development of auxiliary antimicrobial therapies against oral infections.

The effect of nanobased irrigants on the root canal dentin microhardness: an ex-vivo study

BACKGROUND

Given the favorable antimicrobial properties of zinc oxide (ZnONPs), standard silver (AgNPs), and imidazolium-based silver (Im-AgNPs) nanoparticles, this study aimed to evaluate their influence on the microhardness of root canal dentin.

METHODS

In this experimental study, 40 mandibular premolars were decoronated at the cementoenamel junction and longitudinally sectioned into halves to create 80 specimens. They were randomly allocated to 5 groups (n = 16) and irrigated with ZnONPs, AgNPs, Im-AgNPs, NaOCl, or normal saline (as the negative control) for 15 min. The Vickers Hardness Number (VHN) was measured on each root canal third before and after being soaked in irrigants. Statistical analysis was performed using paired t-test, one-way ANOVA, and post hoc Tukey's test (α = 0.05).

RESULTS

Im-AgNPs and ZnONPs irrigants improved the microhardness of root dentin, whereas, AgNPs and NaOCl decreased it. ZnONPs yielded the highest VHN at the coronal third (P˂0.001), while the Im-AgNPs provided the highest VHN at the middle and apical thirds (P˂0.001). The AgNPs group showed the lowest VHN at the apical third.

CONCLUSIONS

The irrigants containing Im-AgNPs and ZnONPs significantly enhanced the root dentin microhardness. However, the use of AgNPs resulted in decreased microhardness.

Evaluation of Antibacterial Efficacy of High-Intensity Focused Ultrasound Versus Photodynamic Therapy Against Enterococcus faecalis-Infected Root Canals

OBJECTIVE

The high incidence of endodontic failure is associated with the remnants of Enterococcus faecalis present within the intricate anatomies of the root canal system (RCS), often inaccessible by the current endodontic practices. This study was aimed at evaluating the effect of high-intensity focused ultrasound (HIFU) and photodynamic therapy (PDT) on E. faecalis biofilms in artificially infected root canals for the potential application in current endodontic practices.

METHODS

Forty-five single-rooted extracted teeth were instrumented using hand files, sterilized in an autoclave, infected with E. faecalis and incubated for 4 wk. The specimens were treated and identified as follows: Control, 4% sodium hypochlorite (NaOCl); riboflavin (1 mg/mL); light only; HIFU (250 kHz, 20 W, 60s); PDT; riboflavin/HIFU; light/HIFU; and riboflavin/HIFU/light. Bactericidal efficacy was determined by colony-forming units (CFU), (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) (MTT) assay, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM).

RESULTS

Enterococcus faecalis biofilm exhibited significantly lower metabolic activity when treated with HIFU (250 kHz, 20 W, 60 s) compared with the control (4% NaOCl) and PDT groups. A similar phenomenon was observed with the CFU assay. HIFU remained the most effective treatment modality, with consistent results in CLSM and SEM.

CONCLUSION

This study highlighted the potential application of HIFU as an adjunct drug-free, non-destructive root canal disinfection method for endodontic treatment, suggesting an alternative to the current gold standard of 4% NaOCl and PDT.

Antimicrobial FiteBac® K21 promotes antimicrobial Potency and wound healing

Objectives

Successful root canal therapy is dependent on the efficacy of complete instrumentation and adequate use of chemical irrigant to eliminate the biofilm from dentin surface. The aim of the study was to examine antibiofilm and antimicrobial effectiveness of newly formulated Quaternary ammonium silane (QAS/also codenamed K21; against Fusobacterium nucleatum (F. nucleatum) and Enterococcus faecalis (E. faecalis) biofilm on radicular dentin with evaluation of the anti-inflammatory consequence in vivo.

Methods

Fourier Transform Infrared Spectroscopy (FTIR) was performed after complete hydrolysis of K21 solution. Human teeth were inoculated with biofilms for 7-days followed by treatment with various irrigants. The irrigant groups were Sodium hypochlorite [NaOCl (6%)], Chlorhexidine [CHX (2%)], K21 (0.5%), K21 (1%) and Saline. Scanning electron microscopy (SEM) was performed for biofilm and resin-dentin penetration. Transmission Electron Microscopy (TEM) of biofilms was done to evaluate application of K21. For in vivo evaluation, Albino wistar rats were injected subcutaneously and sections were stained with haematoxylin/eosin. Macrophage, M1/M2 expression were evaluated along with molecular simulation. Raman measurements were done on dried biofilms.

Results

FTIR K21 specimens demonstrated presence of ethanol/silanol groups. Raman band at 1359 cm-1 resemble to -CH2- wagging displaying 29Si atoms in Nuclear Magnetic Resonance (NMR). 0.5%K21 showed cells exhibiting folded membranes. SEM showed staggering amount of resin tags with 0.5% K21 group. TEM showed membrane disruption in K21-groups. K21 groups were initially irritant, which subsided completely afterwards showing increased CD68. K21 and MMP/collagen complex was thermodynamically favourable.

Conclusion

K21 root canal irrigant was able to penetrate bacterial wall and can serve as a potential irrigant for therapeutic benefits. Expression of M2 polarized subsets showed K21 can serve in resolving inflammation and potentiate tissue repair.

Irrigants and irrigation activation systems in Endodontics

Root canal infections are typically polymicrobial and involve strong bacterial interactions. The goal of endodontic treatment is to remove infected content from the root canal system to allow the healing of a pre-existing periapical lesion or to prevent infection of the periradicular tissues. Instrumentation alone is not capable of touching all of the root canal walls. Therefore, the irrigation process is an essential step in the endodontic treatment. However, due to the complex anatomy of the root canal system, this cleaning is very challenging. Although syringe and needle irrigation associated with the use of chemical substances is still the most used method, it does not guarantee optimal cleaning of the root canals. As a result, not only alternative irrigating substances but also numerous activation systems - which are technologies that aim to optimize the action of irrigating substances, both chemically and physically - have been developed. This work aimed to review the characteristics of both classic and current alternatives of irrigating substances and irrigation activation systems.

Pretreatment of Root Dentin Using Photon-Induced Photoacoustic Streaming, Photodynamic Therapy, and Riboflavin with EDTA as a Final Irrigant to Improve Bond Integrity of Glass Fiber Post

Objective: To evaluate the outcome of post space disinfection using Er,Cr:YSGG laser (ECYL), riboflavin photosensitizer (RFP), and photon-induced photoacoustic streaming (PIPS) along with ethylene diamine tetra acetic acid (EDTA) as final irrigant on the bond values of glass fiber post (GFP) to the canal wall. Materials and methods: Forty human mandibular premolars were subjected to root canal treatment after decoronation till the cementoenamel junction. Post space was prepared using a Gates-Glidden drill leaving 4 mm of gutta perch at the apical third of the root section. Random allocation of samples was performed into four groups based on the post space disinfection (n = 10 each): Group 1: 1% RFP and 17% EDTA, group 2: 5.25% sodium hypochlorite (NaOCl) and 17% EDTA (control), group 3: PIPS and 17% EDTA, and group 4: ECYL and 17% EDTA. GFP was luted using Rely X Unicem. A universal testing machine and stereomicroscope were used to assess the push-out bond strength (PBS) and failure mode, respectively. Analysis of variance determined the PBS amid different experimental groups at three root levels. Multiple group comparison using means of tested groups was identified using post hoc Tukey. Results: The coronal third of group 2 (5.25% NaOCl +17% EDTA) demonstrated the highest PBS (8.83 ± 0.11 MPa). However, the lowest bond integrity (4.15 ± 0.52 MPa) was displayed in an apical third of group 1 (RFP +17% EDTA). The intergroup comparison revealed that 5.25% NaOCl +17% EDTA at all three levels demonstrated comparable outcomes of PBS with PIPS +17% EDTA and ECYL +17% EDTA specimens (p > 0.05). However, riboflavin +17% EDTA demonstrated the lowest bond strength (p < 0.05). Conclusions: Er,Cr: YSGG and PIPS in combination with 17% EDTA demonstrated comparable outcomes of bond score with those of conventional gold standard irrigation regime 5.25% NaOCl.

The effect of different acidic irrigation solutions on the pushout bond strength of root canal filling

Background

This study investigated the effects of different acidic solutions used as the final irrigation on the push-out bond strength (PBS) of resin-based and bioceramic-based root canal sealers.

Methods

100 single root and canal human incisors were selected and decorated. Root canal shaping was done with ProTaper Next rotary files up to X4 and rinsed with 5 mL of 5.25% NaOCl between each file. Then, teeth were divided into five main groups according to the final irrigation (n=20). Group 1: glycolic acid; Group 2: phosphoric acid; Group 3: citric acid; Group 4: EDTA and group 5: saline. Then, each group was divided into two subgroups according to the canal sealer used (n=10). The groups filled with bioceramic-based sealer (bioserra) were named A, and the groups filled with resin-based sealer (AH Plus) were called B. PBS test was applied to one of the two samples obtained from the coronal third of each root. The data were statistically analyzed using a two-way analysis of variance and Tukey's HSD test (α=0.05).

Results

Statistically, the highest PBS value was obtained in group 2A (4.81±0.03 MPa), which was irrigated with phosphoric acid and filled with bioserra, and the lowest PBS value was obtained in group 5B (1.10±0,03), which was irrigated with saline and filled with AH Plus (P<0.05). There was a statistical difference between all groups except group 1A and group 3A (P<0.05).

Conclusion

The bioceramic-based root canal sealer (bioserra) bond strength is superior to resin-based (AH Plus). Phosphoric acid, glycolic acid, and citric acid can be an alternative to EDTA.

Antimicrobial and cleaning effects of ultrasonic-mediated plasma-loaded microbubbles on Enterococcus faecalis biofilm: an in vitro study

BACKGROUND

Enterococcus faecalis (E. faecalis) is the most frequently isolated bacteria from teeth with root canal treatment failure. This study aims to evaluate the disinfection effect of ultrasonic-mediated cold plasma-loaded microbubbles (PMBs) on 7d E. faecalis biofilm, the mechanical safety and the mechanisms.

METHODS

The PMBs were fabricated by a modified emulsification process and the key reactive species, nitric oxide (NO) and hydrogen peroxide (H₂O₂) were evaluated. The 7d E. faecalis biofilm on human tooth disk was constructed and divided into the following groups: PBS, 2.5%NaOCl, 2%CHX, and different concentrations of PMBs (10⁸ mL^-1, 10⁷ mL^-1). The disinfection effects and elimination effects were verified with confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Microhardness and roughness change of dentin after PMBs treatment were verified respectively.

RESULTS

The concentration of NO and H₂O₂ in PMBs increased by 39.99% and 50.97% after ultrasound treatment (p < 0.05) respectively. The CLSM and SEM results indicate that PMBs with ultrasound treatment could remove the bacteria and biofilm components effectively, especially those living in dentin tubules. The 2.5% NaOCl presented an excellent effect against biofilm on dishes, but the elimination effect on dentin tubules is limited. The 2% CHX group exhibits significant disinfection effect. The biosafety tests indicated that there is no significant changes on microhardness and roughness after PMBs with ultrasound treatment (p > 0.05).

CONCLUSION

PMBs combined with ultrasound treatment exhibited significant disinfection effect and biofilm removal effect, the mechanical safety is acceptable.

Effect of EDDY and manual dynamic activation techniques on postoperative pain in non-surgical retreatment: a randomized controlled trial

BACKGROUND

During non-surgical retreatment process, the products such as dentin debris, root canal fillings, irrigation solutions, microorganisms and remaining pulp tissues can extrude to the apical area and can cause the postoperative pain and flare-up. Thus, the aim of this study was to evaluatethe effect of EDDY and manual dynamic activation (MDA) techniques on postoperative pain (PP) associated with retreatment.

METHODS

Ninety patients scheduled for retreatment were treated at a single visit. Non-vital mandibular premolar teeth diagnosed with asymptomatic apical periodontitis were included in this study. The patients were divided into two groups (n = 45) on the basis of the need for additional irrigation activation procedures (EDDY and MDA). The patients' post-treatment pain levels were asked to rate the intensity of their pain on a 10-point numerical rating scale (NRS) at the 12th, 24th, 48th, and 72nd h and 7 days.The data were analyzed using the chi-square and Wilcoxon signed-rank test was used for within-group comparisons and Mann Whitney U test was used to compare the groups by time period.

RESULTS

The difference in postoperative pain intensity between two groups was statistically significant at 12, 24, 48, and 72 h (p < 0.05). There was no significant difference at 7 days. Moreover, no statistically significant difference was found between the two groups in terms of gender and analgesic medication intake (p > 0.05). Pain intensity after the treatment was lesser in the MDA groupthanin the EDDY group at 12, 24, 48, and 72 h.

CONCLUSION

This study could lead us to conclude that the two activation systems can be used during endodontic retreatment with no difference at PP 7 days later. However, a comparison of the groups indicated that the EDDY resulted in significantly more PP at 12, 24, 48, and 72 h. Trial registration ClinicalTrials.gov Identifier: NCT04726670.

To evaluate and compare the effect of 17% EDTA, 10% citric acid, 7% maleic acid on the dentinal tubule penetration depth of bio ceramic root canal sealer using confocal laser scanning microscopy: an in vitro study

Background: The main factors that affect the success of an endodontic infection are effective cleaning and shaping of the root canal system including complete disinfection by using chemical irrigating solutions and obturation with an endodontic sealer to provide a fluid-tight seal. Using rotary and hand instruments for shaping and cleaning the root canal along with irrigants produces a smear layer on the surface of the root dentin affecting the penetration of the endodontic sealer into the dentinal tubules. This smear is difficult to remove with the use of only endodontic irrigants, hence, chelating agents were introduced in adjunct with irrigating solutions for irrigation protocol for effective removal of smear layer which affect the penetration of endodontic sealers into the dentinal tubules. Methods: 32 mandibular premolar teeth were used. The biomechanical preparation was done till Protaper F3 size. Irrigation was done with 2.5 mL sodium hypochlorite (NaOCl) solution after each instrumentation change for 1 min. Samples were then divided into 4 groups according to the irrigating solution used as the final rinse used with passive ultrasonic agitation. The groups were: Group I: 5 ml of saline, Group II: 5ml of 17% ethylenediaminetetraacetic acid, Group III: 5 ml of 10% citric acid, Group IV: 5 ml of 7% maleic acid each for one minute. All the canals were obturated with BioRoot tmRCS with gutta-percha using the ultrasonic condensation technique. For staining the samples for Confocal LASER microscopy, BioRoot tmRCS was mixed with Rhodamine B dye. Results: The maximum penetration of bio-ceramic sealer was observed in the coronal region. At the apical third, the maximum sealer penetration was seen with 7% maleic acid. Conclusions: Maximum sealer penetration was seen in the coronal section followed by the middle and apical section. Maximum sealer penetration was seen with 7 % maleic acid at the apical third.

To evaluate and compare the effect of 17% EDTA, 10% citric acid, 7% maleic acid on the dentinal tubule penetration depth of bio ceramic root canal sealer using confocal laser scanning microscopy: an in vitro study

Background: The main factors that affect the success of an endodontic infection are effective cleaning and shaping of the root canal system including complete disinfection by using chemical irrigating solutions and obturation with an endodontic sealer to provide a fluid-tight seal. Using rotary and hand instruments for shaping and cleaning the root canal along with irrigants produces a smear layer on the surface of root dentin affecting the penetration of the endodontic sealer into the dentinal tubules. This smear is difficult to remove with the use of only endodontic irrigants, hence, chelating agents were introduced in adjunct with irrigating solutions for irrigation protocol for effective removal of smear layer which effect the penetration of endodontic sealers into the dentinal tubules. Methods: 32 mandibular premolar teeth were used. The biomechanical preparation was done till Protaper F3 size. Irrigation was done with 2.5 mL sodium hypochlorite (NaOCl) solution after each instrumentation change for 1 min. Samples were then divided into 4 groups according to the irrigating solution used as the final rinse used with passive ultrasonic agitation. The groups were: Group I: 5 ml of saline, Group II: 5ml of 17% ethylenediaminetetraacetic acid, Group III: 5 ml of 10% citric acid, Group IV: 5 ml of 7% maleic acid each for one minute. All the canals were obturated with BioRoot tmRCS with gutta-percha using the ultrasonic condensation technique. For staining the samples for Confocal LASER microscopy, BioRoot tmRCS was mixed with Rhodamine B dye. Results: The maximum penetration of bio-ceramic sealer was observed in the coronal region. At the apical third, the maximum sealer penetration was seen with 7% maleic acid. Conclusions: Maximum sealer penetration was seen in the coronal section followed by the middle and apical section. Maximum sealer penetration was seen with 7 % maleic acid at the apical third.

An overview of systematic reviews on endotoxins in endodontic infections and the effectiveness of root canal therapy in its removal

Background The objective of this overview was to synthesise the current evidence on the role of endotoxins in endodontics infections and to evaluate the effectiveness of endodontic procedures in its removal using information from published systematic reviews.Methods Electronic databases Medline, Scopus, Embase, Cochrane Library and Google Scholar were searched for reviews published up to July 2021. Systematic reviews on endotoxins based on clinical and/or observational studies were included. The quality of systematic reviews was assessed with the AMSTAR2 tool.Results A total of five systematic reviews were selected, of which two reviews were of high quality. A significantly higher level of endotoxins were found in teeth with exudation, teeth with a previous episode of pain and pain on percussion. Chemomechanical preparation of root canals significantly reduce endotoxin levels. Calcium hydroxide intracanal medication in symptomatic teeth was significantly effective in endotoxin reduction (standardised mean difference -1.051 [95% confidence interval -2.039 to -0.063]; p <0.05; I2 = 83.3%; certainty of evidence = very low). Multiple session root canal treatment in teeth with symptomatic apical periodontitis was significantly more effective in endotoxins/lipopolysaccharides removal than single-session treatment.Conclusion Limited quality of evidence showed a significant association of endotoxins in infected teeth with clinical symptoms. Conventional chemomechanical preparation of root canals and intracanal medication were unable to eliminate endotoxins from the root canal system. Future evolution of effective disinfection therapies is warranted.

Efficacy of the Adjunct Use of Povidone-Iodine or Sodium Hypochlorite with Non-Surgical Management of Periodontitis: A Systematic Review and Meta-Analysis

This systematic review sought to assess the efficacy of combining either sodium hypochlorite or povidone-iodine as disinfection solutions with non-surgical treatment of periodontitis. An electronic search was conducted through PubMed, Scopus, Web of Science, CENTRAL, and Google Scholar from inception until 10 September 2022. Outcomes included clinical outcomes (probing pocket depth, plaque index, clinical attachment level, relative-horizontal attachment level, bleeding on probing, gingival recession, the position of gingival margin) and biochemical (BAPNA level) properties. A subgroup analysis was conducted according to the assessment timepoint. Ten studies reporting the use of povidone-iodine and five studies reporting the use of sodium hypochlorite were included in this review. Overall, in the meta-analysis of povidone-iodine, no significant changes were noted in any of the assessed outcomes; however, minor changes were noted in probing pocket depth and clinical attachment level at a specific timepoint. Regarding sodium hypochlorite, a significant reduction in all clinical outcomes, except for bleeding on probing, was noted. In conclusion, the use of povidone-iodine does not result in an improvement in clinical outcomes, whereas sodium hypochlorite has promising properties that result in significant improvement in probing pocket depth and clinical attachment level. However, more studies are needed to confirm these observations.

Comparative evaluation of the antifungal efficacy of sodium hypochlorite, chlorhexidine, and silver nanoparticles against Candida albicans

Candida albicans is a microorganism that causes root canal infections. However, it cannot be eliminated with conventional irrigation solutions. Recently, silver nanoparticles (AgNPs) have become popular for their superior antimicrobial effects. The purpose of this study was to evaluate the antifungal effect of AgNPs to C. albicans comparing with 5.25% sodium hypochlorite (NaOCl) and 2% chlorhexidine (CHX). Silver nanoparticles were synthesized by chemical reduction method. Minimum inhibitory concentration and minimum fungicidal concentration of AgNPs against C. albicans strain were determined according to microdilution method reported by Clinical Laboratory Standards Institute. C. albicans biofilm layer was formed on the dentin blocks for 10 days. The biofilm structure was observed by scanning electron microscopy. Statistical analysis was performed with one way analysis of variance analysis and group comparisons were performed with Tukey test. AgNPs showed the highest antifungal effect among the groups. 5.25% NaOCl showed the lowest antifungal effect among the groups. While the 2% CHX solution had a statistically lower antifungal effect than AgNPs, it was found to have a higher effect than NaOCl (p < .016). Nanoparticles present a wide research field as an alternative irrigation solution in root canal treatment. The antifungal effect of AgNPs against C. albicans was confirmed in this study. Further in vivo studies should evaluate the conditions of use and long-term prognosis of AgNPs.

Photocrosslinkable methacrylated gelatin hydrogel as a cell-friendly injectable delivery system for chlorhexidine in regenerative endodontics

OBJECTIVES

This work sought to formulate photocrosslinkable chlorhexidine (CHX)-laden methacrylated gelatin (CHX/GelMA) hydrogels with broad spectrum of action against endodontic pathogens as a clinically viable cell-friendly disinfection therapy prior to regenerative endodontics procedures.

METHODS

CHX/GelMA hydrogel formulations were successfully synthesized using CHX concentrations between 0.12 % and 5 % w/v. Hydrogel microstructure was evaluated by scanning electron microscopy (SEM). Swelling and enzymatic degradation were assessed to determine microenvironmental effects. Compression test was performed to investigate the influence of CHX incorporation on the hydrogels' biomechanics. The antimicrobial and anti-biofilm potential of the formulated hydrogels were assessed using agar diffusion assays and a microcosms biofilm model, respectively. The cytocompatibility was evaluated by exposing stem cells from human exfoliated deciduous teeth (SHEDs) to hydrogel extracts (i.e., leachable byproducts obtained from overtime hydrogel incubation in phosphate buffer saline). The data were analyzed using One- and Two-way ANOVA and Tukey's test (α = 0.05).

RESULTS

CHX/GelMA hydrogels were effectively prepared. NMR spectroscopy confirmed the incorporation of CHX into GelMA. The addition of CHX did not change the micromorphology (pore size) nor the swelling profile (p > 0.05). CHX incorporation reduced the degradation rate of the hydrogels (p < 0.001); whereas, it contributed to increased compressive modulus (p < 0.05). Regarding the antimicrobial properties, the incorporation of CHX showed a statistically significant decrease in the number of bacteria colonies at 0.12 % and 0.5 % concentration (p < 0.001) and completely inhibited the growth of biofilm at concentration levels 1 %, 2 %, and 5 %. Meanwhile, the addition of CHX, regardless of the concentration, did not lead to cell toxicity, as cell viability values were above 70 %.

SIGNIFICANCE

The addition of CHX into GelMA showed significant antimicrobial action against the pathogens tested, even at low concentrations, with the potential to be used as a cell-friendly injectable drug delivery system for root canal disinfection prior to regenerative endodontics.

Collagen-depletion strategies in dentin as alternatives to the hybrid layer concept and their effect on bond strength: a systematic review

Strategies aiming to improve the longevity of resin-dentin adhesive interface developed so far have only been able to retard the problem. Different approaches are thus needed. The objective of this review was to determine whether the use of collagen-depletion strategies after acid-etching procedures may improve the bond strength of resin-based materials to dentin. A systematic review was planned following 2021 PRISMA statement guidelines, with a search strategy performed in five electronic databases: PubMed/Medline, Scopus, EMBASE, SciELO and IADR Abstract Archive (last search: 17/01/2022). Inclusion criteria encompassed studies which evaluated a collagen-depletion strategy in acid-etched human dentin and tensile/shear bond strength tests. Risk of bias assessment was carried out by two reviewers, working independently on an adapted five-domain risk of bias (RoB) checklist for laboratory studies. Results were synthesized qualitatively, as a meta-analysis was not possible due to limited number of studies and their RoB. A total of eight studies were eligible for inclusion in the systematic review after inclusion/exclusion criteria application. Out of these, two evaluated the effect of using NaOCl followed by an antioxidant, and the remaining six evaluated different enzymatic treatments (bromelain, chondroitinase ABC, papain, and trypsin). None of the studies reported a decrease of bond strength when a collagen-depletion strategy was used, in comparison to traditional hybrid layers (control). All enzymatic treatment studies which respected the inclusion criteria improved the bond strength to dentin. Some specific collagen-depletion strategies seem to play a favorable role in improving immediate bond strengths to dentin. Further research with sound methodology is required to consolidate these findings, since limitations in RoB and a low number of studies were found. The assessment of further proteolytic agents and long-term outcomes is also required.

Antimicrobial photodynamic therapy in endodontic reintervention: A systematic review and meta-analysis

BACKGROUND

To evaluate the effectiveness of the use of antimicrobial photodynamic therapy (aPDT) in root canals disinfection in cases of endodontic retreatments.

METHODS

This Systematic Review was registered in PROSPERO (CRD42021260013) and followed the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). Searches were performed in the electronic databases PubMeb, Scopus, Web of Science, Embase, Web of Science, Clinical Trials and Cochrane Library. Methodological quality and risk of bias were assessed by the Cochrane Risk of Bias tool for randomized clinical trials (RCT) and by the Newcastle-Ottawa (NOS) qualifier for non-RCT (prospective) studies. Meta-analysis was performed using R software, version 3.6.3 with the "META" package assistant by the RStudio platform. The odds ratio (OR) measure of effect was calculated and the random effect model was applied with a 95% confidence interval, and heterogeneity tested by the I2 index. The certainty of evidence was rated using GRADE.

RESULTS

Regarding the 1513 studies screened, 10 met the eligibility criteria and were included, and 8 used in the quantitative synthesis. Meta-analysis showed that all of studies data presented a significant difference before and after of antimicrobial photodynamic therapy in the microbial load reduction in secondary endondontic infections (OR 0.15 [0.07; 0.32], p < 0.0001). Overall, the studies had a low risk of bias and, the analysis of evidence by GRADE assessment was rated as moderate.

CONCLUSION

It is suggested that aPDT is a beneficial and promising tool, showing efficacy in reducing the microbial load in cases of endodontic retreatment.

Recent Advances in Direct Adhesive Restoration Resin-Based Dental Materials With Remineralizing Agents

Resin-based dental materials are popular restorative materials especially in direct adhesive restoration because of the excellent mechanical and esthetic properties. Toward the realization of minimally invasive dental procedures, direct composite resin adhesive restoration has become the main treatment for dental defects. In addition, for caries-affected dentin close to the pulp, conservation remineralization has been advocated to save the living pulp. However, the resin–dentin interface can be destabilized by various factors, especially the enzymatic degradation of collagen fibrils within the hybrid layer and polymer hydrolysis. Furthermore, for resin-based restorative materials, the marginal gap remains a major problem that can lead to the occurrence of secondary caries. To address these issues, research efforts have focused on the remineralization of mineral-depleted dental hard tissues using remineralizing bioactive substances. In this review, we first described various bioactive agents with remineralizing properties. Furthermore, we discussed recent advances in resin-based dental materials for enamel or dentin remineralization. Finally, we examined the current challenges and prospects of these emerging materials. This work aims to provide a theoretical foundation for the future development of resin-based dental materials in direct adhesive restoration with remineralizing agents.

CBCT Evaluation and Conservative Management of a Large Periapical Lesion Associated with Dens Invaginatus Type II

This case report illustrated the conservative management of an invaginated type II tooth with a large periapical lesion. This dental malformation is characterized by the complexity of root canal anatomy, which when associated with a periapical lesion complicates the performance of conventional endodontic treatment, hence resulting to the difficulty of obtaining the optimal disinfection of the root canal system, which is an essential element for the success of any endodontic treatment. In the present case report, clinical and radiographic examinations were supplemented by CBCT examination to identify the root canal configuration and the extension of the periapical lesion. Conservative orthograde endodontic treatment was performed by combining mechanical and chemical action. Additionally, active nonsurgical decompression was performed and the follow-up visits revealed a favorable outcome.

Irrigating Solutions and Activation Methods Used in Clinical Endodontics: A Systematic Review

Background

Ex vivo and in vitro studies have demonstrated the effectiveness of some irrigation protocols in reducing the bacterial load in the root canal system. However, standardized protocols have not yet been defined for the real clinical context due to many irrigation procedures available.

Objective

To evaluate the clinical endodontic protocols and limitations of irrigating solutions in the disinfection of the root canal system in patients with apical periodontitis.

Methods

PubMed, Scopus, Embase, Web of Science, and Cochrane databases were searched for randomized controlled trials (RCT) published until January 2021. Hand searching was also performed. Studies focused on evaluating the effectiveness of irrigating solutions and/or irrigation activation methods in reducing the bacterial load in the root canal system were considered. The Cochrane risk-of-bias tool for randomized trials (RoB2) was used to assess the quality of the studies.

Results

Four hundred and twenty eight published articles were identified. After removing the duplicate studies and analyzing full texts, seven RCTs were selected. Two studies compared pure NaOCl with some combination of NaOCl with HEDP and MTAD. Two studies analyzed the antibacterial efficacy of NaOCl and chlorhexidine (CHX). Three studies compared conventional needle irrigation with different irrigation activation methods (PUI, XP-endo finisher, F-file activator, EndoVac activator). The review attained a satisfactory methodology. The main results of each included study were described.

Discussion

Activation methods provide significantly higher biofilm reduction than conventional needle irrigation methods. Combinations of NaOCl with different chelating agents were ineffective in terms of antimicrobial, but it could potentially increase the risk of irrigant extrusion. However, the irrigating protocols were not carefully detailed, especially those regarding the irrigants application time or total volume. The existing literature lacks high-quality studies. The level of evidence is moderate.

Conclusions

The available data is too heterogeneous to compare and identify the superiority of specific valuable irrigation protocols in each clinical context. Application time, volume, and activation methods should be standardized to determine the optimal irrigating procedures to reduce the bacterial load and ensure higher predictability of the endodontic treatment.

Systematic Review Registration

(https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=218555), PROSPERO registration: CRD42020218555.

In vitro Characterization of Biofilm Formation in Prevotella Species

Background: Periodontitis, a chronic inflammatory oral infection is the outcome of disturbances in the homeostasis of the oral biofilm microbiota. A number of studies have found the occurrence of Prevotella species in elevated levels in periodontitis compared to healthy subjects. Even though different aspects of Prevotella as part of oral biofilm have been studied, in vitro biofilms formed by these species have not been characterized systematically. The objective of this study was to characterize biofilms formed by several Prevotella species and further to assess biofilm inhibition and detachment of preformed biofilms.

Methods: Biofilms were grown in 24-well plates containing brucella broth in anaerobic conditions for 3 days, and were quantified using crystal violet staining. Images of SYTO 9 Green fluorescent stained biofilms were captured using confocal microscopy. Biofilm inhibition and detachment by proteinase and DNase I was tested. The biochemical characterization included quantification of proteins and DNA in the biofilms and biofilm-supernatants.

Results:Prevotella loescheii, Prevotella oralis and Prevotella nigrescens showed highest biofilm formation. P. nigrescens formed significantly higher amounts of biofilms than P. loescheii (P = 0.005) and P. oralis (P = 0.0013). Inhibition of biofilm formation was significant only in the case of P. oralis when treated with proteinase (P = 0.037), whereas with DNase I treatment, the inhibition was not significant (P = 0.531). Overall, proteinase was more effective in biofilm detachment than DNase I. Protein and DNA content were higher in biofilm than the supernatant with the highest amounts found in P. nigrescens biofilm and supernatants. P. oralis biofilms appeared to secrete large amounts of proteins extracellularly into the biofilm-supernatants.

Conclusion: Significant differences among Prevotella species to form biofilms may imply their variable abilities to get integrated into oral biofilm communities. Of the species that were able to grow as biofilms, DNase I and proteinase inhibited the biofilm growth or were able to cause biofilm detachment.

Functional screening of a human saliva metagenomic DNA reveal novel resistance genes against sodium hypochlorite and chlorhexidine

Objective

Many sections of the health care system are facing a major challenge making infectious disease problematic to treat; antimicrobial resistance (AMR). Identification and surveillance of the resistome have been highlighted as one of the strategies to overcome the problem. This study aimed to screen for AMR genes in an oral microbiota, a complex microbial system continuously exposed to antimicrobial agents commonly used in dental practice.

Materials and methods

As a significant part of the oral microbiome cannot be conventionally cultured, a functional metagenomic approach was chosen. The human oral metagenomic DNA was extracted from saliva samples collected from 50 healthy volunteers in Norway. The oral metagenomic library was then constructed by ligating partially digested oral metagenome into pSMART BAC vector and introducing into Escherichia coli. The library was screened against antimicrobials in dental practices. All resistant clones were selected and analyzed.

Results

Screening of the oral metagenomic library against different antimicrobials detected multiple clones with resistance against chlorhexidine, triclosan, erythromycin, tetracycline, and sodium hypochlorite. Bioinformatic analysis revealed both already known resistance genes, including msr, mef(A), tetAB(46), and fabK, and genes that were not previously described to confer resistance, including recA and accB conferring resistance to sodium hypochlorite and chlorhexidine, respectively.

Conclusion

Multiple clones conferring resistance to antimicrobials commonly used in dental practices were detected, containing known and novel resistant genes by functional-based metagenomics. There is a need for more studies to increase our knowledge in the field.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-021-02000-5.

Effects of methylene blue and curcumin photosensitizers on the color stability of endodontically treated intraradicular dentin

BACKGROUND

Photodynamic therapy with photosensitizers can reduce the microbial load. However, few studies have evaluated the effects of photosensitizers on the color stability of endodontically treated intraradicular dentin. This in vitro study investigated the effects of methylene blue and curcumin photosensitizers used in photodynamic therapy on the color stability of intraradicular dentin.

METHODS

Sixty human incisors were divided into three experimental groups according to the photosensitizer solutions used and their concentrations: methylene blue (25 mg/L), curcumin (1000 mg/L), and curcumin (1500 mg/L). The color stability of endodontically treated intraradicular dentin was evaluated using a portable reflectance spectrophotometer before and after the samples been storage in 2 mL of the photosensitizer solutions during 5 min (n = 20). Color stability data were subjected to a normality test, and statistical analysis was performed using the one-way analysis of variance and Tukey least significant difference test (α = 0.05).

RESULTS

Samples treated with 25 mg/L methylene blue photosensitizer showed a higher level of color alteration than those stored in 1000 mg/L curcumin (p = .03322). However, there was no significant difference in the color alteration profiles between the samples treated with 25 mg/L methylene blue and 1500 mg/L curcumin (p = .36428). Furthermore, there was no difference in the color alteration profiles between the dentin samples immersed in 1000 mg/L and 1500 mg/L curcumin photosensitizer solutions (p = .45321).

CONCLUSIONS

Methylene blue and curcumin photosensitizers influenced the color stability of endodontically treated intraradicular dentin, and this color alteration exceeded the clinical acceptability threshold. Samples treated with 25 mg/L methylene blue showed the highest level of color alteration.

Enhanced antibacterial effect against Enterococcus faecalis by silver ions plus Triton X-100 with low concentrations and cytotoxicity

Enterococcus faecalis (E. faecalis) is commonly considered to be one of chief culprits of secondary and persistent root canal infections. As antibiotic resistance has become a global issue, in order to reduce the use of antibiotics, metal ions have recently been widely used as an alternative. Silver ions (Ag⁺) have been proved to be a strong bactericide but with high cytotoxicity and discoloration property. Triton X-100 (TX-100) and Ag⁺ were co-used for the first time as a clinical intracanal medication to obtain both enhanced antibacterial effect and low cytotoxicity. The synergistic antibacterial effect of TX-100 + Ag⁺ was tested on both planktonic and biofilm-resident E. faecalis on dentine. And the cytotoxicity was tested on MC3T3-E1 cells. Results confirmed the antibacterial activity against both planktonic and biofilm-resident E. faecalis was dramatically improved after TX-100 incorporation. TX-100 and Ag⁺ mixture demonstrated a similar inhibitory effect as the 2% chlorhexidine (CHX), while the cytotoxicity was much lower than 2% CHX (p < 0.05). In conclusion, TX-100 + Ag⁺ mixture might be developed into a new effective intracanal medication as the 2% CHX.

Influence of photodynamic therapy and intracanal medication on Martens hardness, elastic modulus and bond strength of glass-fiber posts to endodontically treated root dentin

BACKGROUND

The purpose of this in vitro study was to evaluate the influence of photodynamic therapy (PDT) with methylene blue photosensitizer (PS) and calcium hydroxide intracanal medication on Martens hardness (MH), elastic modulus (Eit) and adhesive bond strength of glass-fiber posts in different thirds of intraradicular dentin.

METHODS

Ninety-six bovine teeth were distributed into the following 6 experimental groups: a negative control irrigated with deionized water; a positive control irrigated with deionized water and filled with calcium hydroxide intracanal medication (Ca[OH]₂); Ca[OH]₂ + methylene blue 50 mg/L without activation; Ca[OH]₂ + methylene blue 100 mg/L without activation; Ca[OH]₂ + methylene blue 50 mg/L activated by red laser; and Ca[OH]₂ + methylene blue 100 mg/L activated by red laser (n = 16). MH and Eit were measured using an ultramicrodurometer under load action of 3 mN (n = 8). Adhesive bond strength was measured using the push-out test in a universal testing machine (n = 8), and representative samples underwent scanning electron microscopy. Data on MH, Eit, and bond strength were subjected to normality tests and analyzed by ANOVA and Tukey's test (α = 0.05).

RESULTS

Methylene blue PS, activated or not by red laser, associated with calcium hydroxide medication did not promote significant difference as compared to the control groups irrigated with deionized water, associated or not with the use of intracanal medication, regarding mechanical properties and bond strength (p > 0.05). Experimental groups showed no difference between the thirds regarding root canal depth (p > 0.05), except for the positive control group, in which the apical third showed higher Eit values than the middle third (p = 0.0324). There was a predominance of mixed failure in all experimental groups, excepted the red laser-activated group treated with the highest concentration of methylene blue, which showed predominance of adhesive failure.

CONCLUSIONS

PDT with methylene blue PS at 50 mg/L, associated with intracanal calcium hydroxide medication is a satisfactory alternative for endodontic treatment as there is no interference in the mechanical properties and bond strength among glass-fiber posts to intraradicular dentin at any depth of the root canal.

Stability Evaluation of Lyotropic Liquid Crystalline Precursor for the Co-delivery of Chlorhexidine and Silver Nanoparticles

Sealing the therapeutic agents in the root canal is considered to be an essential step in root canal therapy. The lyotropic liquid crystalline precursor (LLCP) incorporated with chlorhexidine (CHX) and silver nanoparticles (Ag-NPs) has been confirmed as a promising candidate for root canal therapy in the previous study. Importantly, the stability of the LLCP system was a significant determinant for its therapeutic effect and further application. The objective of this study was to comprehensively investigate the stability of the LLCP incorporated with CHX and Ag-NPs. The oil-water partition coefficient of CHX and Ag-NPs was measured. The water absorption and the physical stability of drug-loaded LLCP solution were studied. Stability under high temperature, high humidity, and strong light irradiation was also investigated. The results demonstrated that CHX and Ag-NPs could be entrapped in the water channel of LLCP, indicating the low tendency of drugs leakage. The drug-loaded LLCP was a pseudoplastic fluid and it showed an excellent physical stability with a sedimentation rate of 0.981 and a settling time of 26~28 h. The payload of LLCP was confirmed to weaken the water absorption behavior, which facilitated its transformation to cubic liquid crystal. The stress testing under high temperature, high humidity, and strong light irradiation also manifested that the LLCP was stable when stored under moisture-proof condition. In conclusion, the developed LLCP incorporated with CHX and Ag-NPs was highly stable during storage and qualified for further application.

Antibacterial and antibiofilm efficacy of k21-E in root canal disinfection

OBJECTIVES

The aim of the current project was to study the antimicrobial efficacy of a newly developed irrigant, k21/E against E. faecalis biofilm.

METHODS

Root canals were instrumented and randomly divided into the following groups: irrigation with saline, 6% NaOCl (sodium hypochlorite), 6% NaOCl+2% CHX (Chlorhexidine), 2% CHX, 0.5% k21/E (k21 - quaternary ammonium silane) and 1% k21/E. E. faecalis were grown (3-days) (1×10⁷CFU mL^-1), treated, and further cultured for 11-days. Specimens were subjected to SEM, confocal and Raman analysis and macrophage vesicles characterized along with effect of lipopolysaccharide treatment. 3T3 mouse-fibroblasts were cultured for alizarin-red with Sortase-A active sites and Schrödinger docking was performed. TEM analysis of root dentin substrate with matrix metalloproteinases profilometry was also included. A cytotoxic test analysis for cell viability was measured by absorbance of human dental pulp cells after exposure to different irrigant solutions for 24h. The test percentages have been highlighted in Table 1.

RESULTS

Among experimental groups, irrigation with 0.5% k21/E showed phase separation revealing significant bacterial reduction and lower phenylalanine 1003cm^-1 and Amide III 1245cm^-1 intensities. Damage was observed on bacterial cell membrane after use of k21/E. No difference in exosomes distribution between control and 0.5%k21/E was observed with less TNFα (*p<0.05) and preferential binding of SrtA. TEM images demonstrated integrated collagen fibers in control and 0.5%k21/E specimens and inner bacterial membrane damage after k21/E treatment. The k21 groups appeared to be biocompatible to the dental pulpal cells grown for 24h.

SIGNIFICANCE

Current investigations highlight potential advantages of 0.5% k21/E as irrigation solution for root canal disinfection.

[Comparison of three rotary file systems for removal of Enterococcus faecalis from infected root canals]

OBJECTIVE

To compare the efficacy of a novel rotary file system (EZ Pass) with two well-established rotary file systems(ProTaper Gold and ProTaper Next)for removal of Enterococcus faecalis from infected root canals in extracted maxillary central incisors.

METHODS

Models of root canal infection with Enterococcus faecalis were constructed in 51 extracted singlerooted maxillary central incisors.One of the incisor model with infected root canal was demineralized, sectioned, and stained with Brown & Brenn technique for microscopic observation; The remaining 50 models were randomly divided into 5 groups(n=10) for treatment with EZ Pass, ProTaper Gold, ProTaper Next, 0.9% NaCl or 2% NaOCl.Samples were collected from the infected root canals before and after the treatments to assess the percent reduction and logarithmic reduction value of CFU in the root canals.

RESULTS

The incisors with root canal infection by Enterococcus faecalis showed obvious biofilms on the surface of the root canals and massive bacterial invasion deep into the dentinal tubules, with a maximum invasion depth of about 475 μm.The percent reduction of the CFU did not differ significantly after treatments with EZ Pass, ProTaper Gold, ProTaper Next and 2% NaOCl (P > 0.05), but all these treatments resulted in significantly greater reduction than 0.9% NaCl (P < 0.01).The logarithmic reduction of CFU were comparable after treatments with EZ Pass (1.47±0.12), ProTaper Gold (1.74±0.14) and ProTaper Next (1.63±0.17;P > 0.05).

CONCLUSION

EZ Pass can significantly reduce the bacterial load in infected root canals with an equivalent bacterial elimination capacity to ProTaper Gold and ProTaper Next.

Influence of occlusal reduction on pain after endodontic treatment: a systematic review and meta-analysis

The purpose of this systematic review was to analyze the influence of occlusal reduction on the postoperative pain levels after endodontic treatment (instrumentation and obturation of the root canal system). This review followed the PRISMA statement and was registered at PROSPERO (CRD42018107918). Two independent reviewers searched the Lilacs, Cochrane Library, PubMed (Medline), Web of Science, Scopus, Scielo, and ScienceDirect for articles published until April 2021. The research question was, "Does occlusal reduction decrease postoperative pain in endodontically treated teeth?". Only randomized clinical trials were included. The RevMan 5 program was used for meta-analysis, calculating the relative risk (RR) and 95% confidence interval (CI) of the dichotomous outcome (presence or absence of pain). The search strategies retrieved 4114 studies. Twelve studies were included for qualitative analysis and nine for quantitative analysis. The meta-analysis results did not reveal a significant difference in the reduction of postoperative pain levels for endodontic instrumentation at 6, 12, 24, 48 h and for endodontic obturation at 6 or 12 h after occlusal reduction. According to the GRADE tool, the analyzed outcome was classified as having a moderate level of certainty. It is concluded that occlusal reduction does not interfere with postoperative pain levels after endodontic treatment.

In Vitro Development of a New Sponge-Based Delivery System for Intracanal Antimicrobial Administration in Endodontic Treatment

This study aimed to evaluate the in vitro performance of collagen-based sponges as a drug delivery system for intracanal antimicrobial administration. Four groups of loaded collagen-based sponges (A, 0.3% w/v amoxicillin trihydrate: potassium clavulanate (4:1); B, 0.03% w/v chlorhexidine gluconate [CHX]; C, 0.3% w/v amoxicillin trihydrate: potassium clavulanate (4:1) and 0.03% w/v CHX; D, 1% w/v amoxicillin trihydrate: potassium clavulanate (4:1) and 0.03% w/v CHX) were designed. Release kinetics were tested in vitro on cultures in Petri dishes, and the effect on bacterial biofilms was studied ex vivo on 114 extracted human single-rooted teeth. Biofilm formation was tested by scanning electron microscopy (SEM). Collagen sponges containing amoxicillin and chlorhexidine showed a time-sustained antimicrobial effect in vitro and were also able to destroy mature biofilms ex vivo. This datum was validated by means of SEM-based study of E. faecalis and S. aureus biofilms.

Influence of adjunctive photodynamic therapy (curcumin) on the extrusion bond strength of radicular dentin to contemporary root canal sealers

OBJECTIVE

The aim was to compare Photodynamic therapy (PDT) as an adjunct to NaOCl and EDTA on the extrusion bond strength (EBS) of AH Plus (AH), Sealapex (SA) and MTA Fillapex (MF) root canal sealers.

MATERIALS AND METHOD

Root canal treatment for human teeth (n = 60) using protaper universal system was performed followed by irrigation with NaOCl/ EDTA. Samples were divided (n = 30) based on disinfection technique, NaOCl/EDTA and NaOCl/EDTA with PDT (Curcumin-PS-CP) as an adjunct. Specimens were divided in three subgroups (n = 10) based on sealers used (Gp 1-Na-E-AH, Gp 2-Na-E-PDT-AH, Gp 3-Na-E-SA, Gp 4-Na-E-PDT-SA, Gp 5-Na-E-MF & Gp 6-Na-E-PDT-MF). Canals were dried and obturated followed by sectioning at coronal and middle third. EBS testing was performed using a universal testing machine (UTM) and modes of failure were assessed. Analysis of variance (ANOVA) and Tukey multiple comparison tests were used to compare the means of EBS. (p < 0.05).

RESULTS

Sealers showed a significant influence on EBS, as Gp 1 (Co: 9.21 ± 0.62, Mid: 8.54 ± 0.55) and Gp 2 (Co: 7.11 ± 0.68, Mid: 7.30 ± 0.37) showed higher EBS than Gp 3 (Co: 5.21 ± 0.63, Mid: 4.36 ± 0.83) and Gp 4 (Co: 5.39 ± 0.72, Mid: 4.46 ± 0.74). Gp 5 (Co: 9.04 ± 0.13, Mid: 8.14 ± 0.91) and Gp 6 (Co: 8.67 ± 0.42, Mid: 8.07 ± 0.07) exhibited higher EBS than Gp 3 and Gp 4 specimens. Adjunctive use of PDT for AH sealer (Gp 2) showed decreased EBS compared to Gp 1 specimens. EBS remained comparable for both MTA-Fillapex and Sealapex with and without PDT.

CONCLUSION

AH Plus (Gp 1 and 2) and MTA-Fillapex (Gp 5 and 6) sealers displayed better EBS compared to Sealapex (Group 3 and 4). Adjunctive Application of PDT (CP) did not show a significant improvement in bond strength of sealers to root dentin.

Influence of two photodynamic therapy sessions and different photosensitizers on the bond strength of glass-fiber posts in different regions of intraradicular dentin

BACKGROUND

Although photodynamic therapy associated with photosensitizers can promote microbial reduction, studies evaluating the consequences of two photodynamic therapy sessions associated with different photosensitizers on the bond strength of glass-fiber posts to endodontically treated intraradicular dentin are scarce. This in vitro study aimed to investigate the influence of two photodynamic therapy sessions using methylene blue or curcumin photosensitizers on the bond strength of glass-fiber posts to intraradicular dentin in different root thirds.

METHODS

Seventy-two teeth were divided into 9 experimental groups according to photosensitizer type, concentration and light-activation: Control - deionized water; Methylene blue 50 mg/L; Methylene blue 50 mg/L + laser; Methylene blue 100 mg/L; Methylene blue 100 mg/L + laser; Curcumin 500 mg/L; Curcumin 500 mg/L + LED; Curcumin 1000 mg/L; and Curcumin 1000 mg/L + LED. Push-out bond strength of the fiber posts to endodontically treated dentin was evaluated using a universal test machine (n = 8). Bond strength data underwent Kruskal-Wallis test, followed by Dunn test for comparison between treatments, and Friedman test for comparison between thirds (α = 0.05). Illustrative scanning electron microscopy images were obtained to qualify the failure mode.

RESULTS

Curcumin at higher concentration, activated or not by blue LED, decreased the bond strength values in the apical region when compared with the control group (P < 0.05). There was no difference between two photodynamic therapy sessions using methylene blue photosensitizer (activated or not) and the control group regardless of concentrations and root canal depth evaluated (P > 0.05). Regarding intraradicular depth, the different thirds showed no statistical difference on bond strength values (P > 0.05). All experimental groups presented predominance of mixed-type failure, excepting the methylene blue group at higher concentration activated by red laser, and the curcumin photosensitizer at both concentrations activated by blue LED.

CONCLUSIONS

Methylene blue at a 50 mg/L concentration can be applied in two PDT sessions, after biomechanical preparation and before glass-fiber post luting, as it presents no influence on root dentin bond strength in in vitro conditions.

Starvation Survival and Biofilm Formation under Subminimum Inhibitory Concentration of QAMs

Quaternary ammonium methacrylates (QAMs) are useful antimicrobial compounds against oral bacteria. Here, we investigated the effects of two QAMs, dimethylaminododecyl methacrylate (DMADDM) and dimethylaminohexadecyl methacrylate (DMAHDM), on biofilm formation, survival and development of tolerance by biofilm, and survival and development of tolerance against QAMs after prolonged starvation. Enterococcus faecalis (E. faecalis), Streptococcus gordonii (S. gordonii), Lactobacillus acidophilus (L. acidophilus), and Actinomyces naeslundii (A. naeslundii) were used. Minimum inhibitory concentration (MIC) of QAMs against multispecies biofilm was determined. Biofilm formed under sub-MIC was observed by crystal violet staining and confocal laser scanning microscopy (CLSM). Metabolic activity was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and lactic acid production measurement. Development of tolerance was determined by MIC values before and after exposure to QAMs or after prolonged starvation. It was found that E. faecalis and S. gordonii could survive and form biofilm under sub-MIC of QAMs. Lactic acid production from biofilms formed under sub-MIC was significantly higher than control specimens (p < 0.05). The exposure to sub-MIC of QAMs promoted biofilm formation, and prolonged starvation or prolonged contact with sub-MIC helped bacteria develop tolerance against killing by QAMs.

The Influence of Sodium Hypochlorite and Chlorhexidine on Postoperative Pain in Necrotic Teeth: A Systematic Review

Objective:

The purpose of this systematic review was to provide the answer to the question: Can sodium hypochlorite and chlorhexidine influence postoperative pain after the endodontic treatment in necrotic teeth?

Methods:

The PROSPERO registration number is CRD42018096433 and was conducted following the PRISMA statements. The MeSH and free terms were used to search for articles published in the electronic databases (PubMed, Web of Science, Scopus, Cochrane Library, and Virtual Health Library), in the gray literature, and by a manual search. The reviewers selected the studies considering predetermined eligibility criteria, performed data extraction, and evaluated the risk of bias. Only clinical trials comparing the effect of sodium hypochlorite and chlorhexidine on postoperative pain in teeth of adult patients with necrotic pulps were included.

Results:

Five studies were qualified for the systematic review. Two studies were considered a low risk of bias. The results showed no statistically significant difference regarding postoperative pain in the groups. Only 1 study reported a statistically significant difference in the sixth postoperative hour, and the pain was associated with the sodium hypochlorite group.

Conclusion:

There was no influence of auxiliary chemical substance (NaOCl and CHX) on postoperative pain used in endodontic treatment in the teeth with pulp necrosis. However, one study observed a significant difference in the sixth postoperative hour, associated with the sodium hypochlorite group.

Current uses of chlorhexidine for management of oral disease: a narrative review

Objectives

Chlorhexidine (CHX) is a commonly used antiseptic mouthwash, used by dental practitioners and the public, due to its antimicrobial effects. The aim of this article was to provide a narrative review of current antimicrobial uses of CHX relevant to dentistry in the context of oral diseases, highlighting need for further studies to support its safe and appropriate use.

Study selection, data and sources

Randomised controlled trials, systematic reviews and national (UK and US) guidelines were consulted where available, with search terms for each subject category entered into MEDLINE, PubMed, Google Scholar and the Cochrane database.

Results

Some evidence existed to support adjunctive short-term use of CHX to manage dental plaque, and reduce clinical symptoms of gingivitis, dry socket, as well as reduce aerosolisation of bacteria. However, use must be weighed alongside the less desirable effects of CHX, including extrinsic staining of teeth, antimicrobial resistance to antiseptic agents and the rare, but fatal, allergic reactions to CHX. Conversely, evidence for the effectiveness of chlorhexidine to manage or prevent periodontitis, dental caries, necrotising periodontal diseases, peri-implantitis, and infections associated with extraction and aerosolised viruses remains less certain.

Conclusions

The use of CHX in dentistry and oral healthcare continues to be widespread and thus it is important that dental practitioners understand that, based on its differential mechanisms of action on different microbes, appropriate clinical and dental use of CHX should be oral disease specific. However, further scientific and clinical research is required before full recommendations can be made.

Properties of a modified quaternary ammonium silane formulation as a potential root canal irrigant in endodontics

OBJECTIVES

Evaluate a new modified quaternary ammonium silane irrigant solution for its antimicrobial, cytotoxic and mechanical properties of dentine substrate.

METHODS

Root canal preparation was performed using stainless steel K-files™ and F4 size protaper with irrigation protocols of 6% NaOCl + 2% CHX; 3.5% QIS; 2% QIS and sterile saline. Biofilms were prepared using E. faecalis adjusted and allowed to grow for 3 days, treated with irrigants, and allowed to grow for 7 days. AFM was performed and surface free energy calculated. MC3T3 cells were infected with endo irrigant treated E. faecalis biofilms. Raman spectroscopy of biofilms were performed after bacterial re-growth on root dentine and exposed to different irrigation protocols and collagen fibers analysed collagen fibers using TEM. Antimicrobial potency against E. faecalis biofilms and cytoxicity against 3T3 NIH cells were also. Resin penetration and MitoTracker green were also evaluated for sealer penetration and mitochondrial viability. Data were analysed using One-way ANOVA, principal component analysis and post-hoc Fisher's least-significant difference.

RESULTS

Elastic moduli were maintained amongst control (5.5 ± 0.9) and 3.5% QIS (4.4 ± 1.1) specimens with surface free energy higher in QIS specimens. MC3T3 cells showed reduced viability in 6%NaOCl+2%CHX specimens compared to QIS specimens. DNA/purine were expressed in increased intensities in control and 6% NaOCl + 2% CHX specimens with bands around 480-490 cm^-1 reduced in QIS specimens. 3.5% QIS specimens showed intact collagen fibrillar network and predominantly dead bacterial cells in confocal microscopy. 3.5% QIS irrigant formed a thin crust-type surface layer with cytoplasmic extensions of 3T3NIH spread over root dentine. Experiments confirmed MitoTracker accumulation in 3.5% treated cells.

SIGNIFICANCE

Novel QIS root canal irrigant achieved optimum antimicrobial protection inside the root canals facilitating a toxic effect against the Enterococcus faecalis biofilm. Root dentine substrates exhibited optimum mechanical properties and there was viability of fibroblastic mitochondria.

Effect of Silver Antibacterial Agents on Bond Strength of Fiber Posts to Root Dentin

This study was conducted to evaluate whether antibacterial pretreatment irrigation with silver nanoparticles (SNPs) and silver diamine fluoride (SDF) has any effect on bond strength of fiber posts cemented with three types of resin cements in root canal space. Fifty-four endodontically treated maxillary central incisor roots were prepared for fiber post (FRC Postec Plus NO.3, Ivoclar Vivadent) cementation and divided into nine groups in terms of three cement types and two pretreatments with silver antibacterial agents. The cements were as follows: an etch-and-rinse cement (ER, Excite DSC/Variolink N), a self-etch cement (SE, ED Primer/Panavia F2.0), and a self-adhesive cement (SA, Panavia SA Luting Plus). For each cement, the control group was with no treatment and two experimental groups were with SNPs and SDF treatments that were used after acid-etching for ER cement and after EDTA treatment for SE and SA cements. After fiber post cementation, each bonded root was horizontally sectioned into 1-mm thickness microslices to create two slices for each root region (apical, middle and coronal) and underwent push-out bond strength (PBS) test. Data in MPa were analyzed with two-way ANOVA and Tukey test (p=0.05). The interaction of the pretreatment type and cement type was significant (p<0.001). SNPs and SDF significantly increased PBS with ER cement (p≤0.04). This positive effect was also marginally significant for SDF with SE cement (p=0.049). For SA cement, SNPs showed a significant positive effect, but SDF had a significant adverse effect on PBS (p<0.001). The effect of pretreatment with silver antibacterial agents prior to adhesive cementation of fiber posts depends on the resin cement used. Contrary to SNPs with beneficial or no significant effect on bonding for all cements, SDF exhibited a deleterious effect with self-adhesive cement.

Endodontic approach in a replanted tooth with an immature root apex and chronic apical periodontitis: a case report

This study describes the clinical steps taken in the treatment of a patient who had an avulsed right upper central incisor that presented with incomplete root development and chronic apical periodontitis. A 7-year-old boy was referred from a private dentist to a dental office specializing in endodontics. The tooth had remained in a dry environment for 20 minutes, and tooth replantation was performed at an emergency appointment. After clinical and radiographic examinations, root canal decontamination was performed, followed by several changes in intracanal calcium hydroxide medication. Blood clot formation was attempted, but bleeding within the root canal was insufficient; therefore, we opted for an intracanal medication change to stimulate mineralized tissue formation in the apical region. Root obturation was performed 45 days after the last change of intracanal medication, and clinical, radiographic, and tomographic follow-up examinations were performed at 3, 6, 18, and 40 months after the endodontic intervention. The increase in thickness and length of the root structure and the absence of root resorption were verified through follow-up examinations. Therefore, it was concluded that the procedures used were successful for tooth replantation.

Mucosal Fenestration After 2% Chlorhexidine Extrusion Used in Substitution of Sodium Hypochlorite: A Case Report

This report describes a case of sodium hypochlorite (NaOCl) and chlorhexidine (CHX) extrusion through the apical foramen, causing acute pain, swelling and mucosal fenestration. A 62-year-old woman was referred for endodontic treatment in the first left maxillary premolar with a diagnosis of necrotic pulp. After the root canal irrigation with 2.5% NaOCl, the patient felt a burning sensation and pain. Discrete swelling and redness were noted in the patient’s face at the end of the session. Antibiotic and corticosteroids were prescribed. In the next appointment, 2% CHX was used, but another episode of extrusion occurred, with a sudden acute pain and intense swelling within a few minutes after the injection. After 2 weeks, the patient exhibited a left-side facial swelling extending anterior and inferior to the left zygomatic arch and superior to the body of the mandible. Oral antibiotic and anti-inflammatory drugs were administered. After 10 days, the swelling had completely diminished, but a mucosal fenestration and tooth mobility were verified. A cone beam CT was requested and showed a periapical lesion involving both buccal and palatal roots. After a prosthetic evaluation, the tooth extraction was indicated. One week after tooth removal, the mucosa was completely healed.

Biocompatible combinations of nisin and licorice polyphenols exert synergistic bactericidal effects against Enterococcus faecalis and inhibit NF-κB activation in monocytes

Enterococcus faecalis is one of the bacterial species most frequently isolated from persistent endodontic and apical periodontal infections. The aim of the present study was to evaluate the synergistic antibacterial effects of nisin and selected licorice polyphenols (glabridin, licoricidin, licochalcone A) against planktonic and biofilm-embedded E. faecalis cells. The biocompatibility and anti-inflammatory properties of the nisin/licorice polyphenol combinations were also investigated. The lantibiotic bacteriocin (nisin), the two isoflavonoids (glabridin, licoricidin), and the chalcone (licochalcone A) efficiently inhibited the growth of E. faecalis, with MICs ranging from 6.25 to 25 µg/mL. Combining nisin with each licorice polyphenol individually resulted in a significant synergistic antibacterial effect. Following a 30-min contact, nisin in combination with either glabridin, licoricidin, or licochalcone A caused significant biofilm killing. The nisin/licorice polyphenol combinations had no cytotoxic effects (oral epithelial cells, gingival fibroblasts, and stem cells of the apical papilla), with the exception of nisin/glabridin, when used at their MICs. Lastly, we showed that nisin/glabridin, nisin/licoricidin, and nisin/licochalcone A inhibit NF-κB activation induced by E. faecalis in a monocyte model, suggesting that these combinations possess anti-inflammatory properties. The present study provides evidence that combinations of nisin and glabridin, licoricidin, or licochalcone A show promise as root canal disinfection agents.