The Role of Environmental Changes on Monospecies Biofilm Formation on Root Canal Wall by Enterococcus faecalis

Antibiofilm effect of different concentrations of silver nanoparticles combined with calcium hydroxide against Enterococcus faecalis biofilm: An ex vivo study

This study aimed to evaluate the antibiofilm activity of different concentrations of silver nanoparticles (AgNPs) in combination with calcium hydroxide [Ca(OH)2] against Enterococcus faecalis biofilm. On an E. faecalis biofilm on dentin discs, the following medicaments were applied for 7 days (n = 13/group): 0.005% AgNPs+Ca(OH)2, 0.01% AgNPs+Ca(OH)2, 0.02% AgNPs + Ca(OH)2, Ca(OH)2 and saline/control. Specimens were stained with LIVE/DEAD® BacLight™ dye and analysed with confocal laser scanning microscopy. Proportion of dead bacteria was calculated and analysed. There was a significant reduction in E. faecalis biofilm in all medicament groups (43.5%, 49.1%, 69.1%, 48.7%) respectively, compared with control group (2.54%) (p < 0.001). The 0.02% AgNPs + Ca(OH)2 group demonstrated the most significantly superior antibiofilm effect, with no significant difference between remaining groups. In conclusion, combining 0.02% AgNPs enhanced the antibiofilm effect of Ca(OH)2 on E. faecalis biofilm compared with lower AgNPs concentrations.

Comparative Evaluation of Sodium Hypochlorite Gel Penetration Using Er,Cr:YSGG Laser and Passive Ultrasonic Activation After Apicoectomy: An In Vitro Study with Confocal Laser Scanning Microscopy

Background: Lasers from the erbium family have been investigated to activate irrigation with sodium hypochlorite (NaOCl), improving the disinfection depth of the dentinal tubules of the root canal walls during root canal treatment. However, the possibility of laser-activated irrigation (LAI) in retro-cavity preparation has not been investigated to the date. The aim of our experimental study is to evaluate the efficacy of NaOCl gel penetration inside the dentinal tubules when activated during retro-cavity preparation, comparing passive ultrasonic activation (PUI) and Er,Cr:YSGG LAI. Materials and Methods: Fifty extracted mature single-root human teeth were divided into four groups (control, PUI, and two LAI groups with different NaOCl concentrations). After conventional endodontic treatment and root end resection, NaOCl gel (impregnated with rhodamine dye for confocal laser scanning microscopy (CLSM) analysis) was applied and activated according to the study group. The penetration index and mean penetration length were measured using computer software. Results: Both penetration index and mean penetration length were found to have increased in the PUI group compared to the control samples. However, LAI had a better penetration that was statistically significant compared to both the PUI and control groups. The difference in NaOCl concentration in the laser groups did not affect the penetration values. Conclusions: Within the limitations of our in vitro study using NaOCl gel activation in the retro-cavity after apicectomy, Er,Cr:YSGG LAI significantly enhanced NaOCl gel penetration capacity compared to PUI, regardless of its concentration. LAI can enhance its penetration in a safe way, avoiding its extrusion to the surrounding periapical tissues.

Unveiling SmearOFF Efficacy in Smear Layer Removal through Ultrasonic Activation Examined by Scanning Electron Microscopy

A layer of smear that coats the walls of root canals is produced by root canal instrumentation, which could be unfavorable to endodontic therapy. The endodontic irrigant SmearOFF is designed to effectively remove both the smear layer and bacteria concurrently. The objective of this study was to evaluate and compare the efficacy of SmearOFF and 17% EDTA in removing the smear layer across the coronal, middle, and apical thirds of root canals. Sixty-four single-canal mandibular premolar roots were chosen. Two irrigant protocols were separated into two sets of thirty-two teeth, respectively, Group 1 (6% NaOCL/SmearOFF) and Group 2 (6% NaOCl/17% EDTA.) Until X2, the ProtaperNext rotary system (Dentsply, Maillefer, Switzerland), with a COXO C-SMART Endomotor (Foshan COXO Medical instrument Co., Ltd., China) was utilized for the shaping of all teeth, the equipment settings were tuned to 300 revolutions per minute (rpm) and a torque of 3 Newton-centimeters (Ncm). Before applying the final irrigants, an initial irrigation with 6% sodium hypochlorite (NaOCl) was performed using a 27-G side-vented needle. An ultrasonic gadget, EndoUltra, was utilized to activate the irrigation. After that, the determination of how well the proposed solutions worked on the prepared teeth was conducted by scanning electron microscopy. The mean smear layer scores were lower in all three regions (coronal, middle, and apical) using 17% EDTA in comparison with the samples treated with SmearOFF. Despite that, there were no significant differences between G1, 6% NaOCL/SmearOFF and G2, 6% NaOCL/17% EDTA in smear layer removal according to Kruskal-Wallis tests and Mann-Whitney U-tests (p < 0.05). Considering the findings of this investigation, both 17% EDTA and SmearOFF serve as chelating agents, demonstrating the capability to effectively remove the smear layer. This process is facilitated with the assistance of passive ultrasonic irrigation at intervals of every third of the root canal.

Effect of Herbal Extract of Spilanthes acmella and Cinnamon Oil on Enterococcus faecalis Biofilm Eradication: An In Vitro Study

Introduction

Enterococcus faecalis has a pathogenic role in failed endodontic treatments. The study aimed to assess the efficiency of Spilanthes acmella (SA) and cinnamon oil (CO) extract on E. faecalis biofilm eradication.

Materials and methods

The antibacterial efficacy of SA and CO against E. faecalis was assessed by the tests of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), and further, the interaction with agents was evaluated at different time intervals by a time-kill assay. The inhibition efficacy of both agents was determined by biofilm adhesion reduction crystal violet assay.

Results

The MIC of SA was 25 μg/mL, and for CO, it was 12.5 μg/mL. The time-kill assay revealed that antibacterial efficacy was identified till 36 hours by both the test materials. The mean biofilm reduction at 25 µg/mL of calcium hydroxide [Ca(OH)2], SA, and CO was 1.53 ± 0.05, 1.83 ± 1.57, and 2.06 ± 0.05, respectively.

Conclusion

SA and CO demonstrated promising antibacterial efficacy against E. faecalis and CO presented significant eradication of biofilms compared to SA.

How to cite this article

Bhamare SA, Dahake PT, Kale YJ, et al. Effect of Herbal Extract of Spilanthes acmella and Cinnamon Oil on Enterococcus faecalis Biofilm Eradication: An In Vitro Study. Int J Clin Pediatr Dent 2024;17(9):1004-1013.

Triton X-100 enhanced antibacterial effect of photodynamic therapy against Enterococcus faecalis infection: an in vitro study

Photodynamic therapy (PDT) is an effective method for bacterial infection control in root canals of teeth with a broad-spectrum antibacterial activity. However, its application in root canal treatment is limited due to its inefficiency under hypoxic conditions and dentin staining. Triton X-100 (TX) shows great potential in enhancing the efficiency of antimicrobial agents through improving bacterial membrane permeability. The present study employed a combination of toluidine blue O (TB)-mediated PDT with TX to target the Enterococcus faecalis (E. faecalis), a bacterium with strong resistance to various antibacterial agents and mostly detected in infected root canals. PDT combined with TX showed enhanced antibacterial efficiency against both planktonic cells and biofilms of E. faecalis. At the same time, TX enhanced the antibacterial effect in dentinal tubules and reduced the incubation time. Mechanism studies revealed that TX improved reactive oxygen species (ROS) production through increasing the proportion of TB monomers. Additionally, increased membrane permeability and wettability were also observed. The findings demonstrated the PDT combined with TX could be used as a highly effective method for the root canal disinfection of teeth.

Nanoarchitectonics-Based Materials as a Promising Strategy in the Treatment of Endodontic Infections

Endodontic infections arise from the interactive activities of microbial communities colonizing in the intricate root canal system. The present study aims to update the latest knowledge of nanomaterials, their antimicrobial mechanisms, and their applications in endodontics. A detailed literature review of the current knowledge of nanomaterials used in endodontic applications was performed using the PubMed database. Antimicrobial nanomaterials with a small size, large specific surface area, and high chemical activity are introduced to act as irrigants, photosensitizer delivery systems, and medicaments, or to modify sealers. The application of nanomaterials in the endodontic field could enhance antimicrobial efficiency, increase dentin tubule penetration, and improve treatment outcomes. This study supports the potential of nanomaterials as a promising strategy in treating endodontic infections.

Oxygen Self-Supplied Nanoplatform for Enhanced Photodynamic Therapy against Enterococcus Faecalis within Root Canals

The successful treatment of persistent and recurrent endodontic infections hinges upon the eradication of residual microorganisms within the root canal system, which urgently needs novel drugs to deliver potent yet gentle antimicrobial effects. Antibacterial photodynamic therapy (aPDT) is a promising tool for root canal infection management. Nevertheless, the hypoxic microenvironment within the root canal system significantly limits the efficacy of this treatment. Herein, a nanohybrid drug, Ce6/CaO2/ZIF-8@polyethylenimine (PEI), is developed using a bottom-up strategy to self-supply oxygen for enhanced aPDT. PEI provides a positively charged surface, which enables precise targeting of bacteria. CaO2 reacts with H2O to generate O2, which alleviates the hypoxia in the root canal and serves as a substrate for Ce6 under 660 nm laser irradiation, leading to the successful eradication of planktonic Enterococcus faecalis (E. faecalis) and biofilm in vitro and, moreover, the effective elimination of mature E. faecalis biofilm in situ within the root canal system. This smart design offers a viable alternative for mitigating hypoxia within the root canal system to overcome the restricted efficacy of photosensitizers, providing an exciting prospect for the clinical management of persistent endodontic infection.

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.

Comparative evaluation of antimicrobial efficacy of different combinations of calcium hydroxide against Enterococcus faecalis

BACKGROUND

The study aims to compare the synergistic antibacterial efficacy of different combinations of calcium hydroxide as an intracanal medicament against E. faecalis.

MATERIAL AND METHODS

The current study included four hundred extracted human permanent mandibular premolar teeth. After complete chemo-mechanical preparation, the middle third of the root was sectioned using a rotary diamond disc and a total of 400 samples were obtained. The specimens were inoculated with E. faecalis for 21 days. After that, specimens were divided into five groups (n = 80) based on materials used for the disinfection of samples: Group I, calcium hydroxide alone; Group II, calcium hydroxide + 2% chlorhexidine gel; Group III, calcium hydroxide + 2% chitosan gel; Group IV, calcium hydroxide + 0.02% silver nanoparticle gel; Group V, calcium hydroxide + Bioactive glass S53P4. Dentin shavings from the apical third were obtained from the inner third of dentin were obtained using gates glidden no.1 to the apical depth, followed by no.2, 3, 4 and 5 analyzed for E. faecalis using the culture method. One-way analysis of variance (ANOVA) was used for data analysis, followed by post-hoc Tukey's test for multiple comparisons of means to check the difference in bacterial inhibition between the groups.

RESULTS

ANOVA results revealed a significant reduction of bacterial counts in all the groups compared (p < 0.001). Intergroup comparison showed maximum bacterial reduction (p < 0.001) with calcium hydroxide + bioactive glass S53P4 compared with other groups.

CONCLUSION

Synergistic effect of calcium hydroxide showed better bacterial reduction compared to calcium hydroxide alone. Among the combinations evaluated, calcium hydroxide with bioactive glass, found to be most effective compared to other groups.

Scanning Electron Microscopy Analysis of Smear Layer Removal Ability of Conventional Endodontic Irrigation Regimen, MTAD, and QMix™ Versus a Mixture of Azadirachta indica and Citrus limon: An In Vitro Study

INTRODUCTION

Smear layer removal from root canals aid in the penetration of both irrigants and endodontic sealer into the dentinal tubules, thereby improving the efficacy of endodontic treatment. The aim of this in vitro study was to compare the smear layer removal ability of a conventional endodontic irrigation regimen, MTAD (mixture of tetracycline, acid, and detergent), and QMix™ (Dentsply Sirona, Charlotte, North Carolina, United States) with that of a mixture of herbal irrigants, namely, aqueous extracts of Azadirachta indica (neem) and Citrus limon (lemon), evaluated using scanning electron microscopy (SEM).

MATERIALS AND METHODS

We selected 40 extracted human premolar teeth for the study, which we randomly divided into five groups (eight samples each) according to irrigation solution: (i) Group A (normal saline); (ii) Group B (conventional endodontic regimen, 3% sodium hypochlorite (NaOCl) + 17% ethylenediamine tetraacetic acid (EDTA) + 2% chlorhexidine (CHX)); (iii) Group C (MTAD); (iv) Group D (QMix 2-in-1); and (v) Group E (aqueous extracts of Azadirachta indica and Citrus limon). After we prepared the canals with ProTaper Universal nickel-titanium (Ni-Ti) rotary files (Dentsply Sirona) and the respective irrigants, we split the teeth longitudinally to evaluate the amount of remnant smear layer in the coronal, middle, and apical thirds using SEM photomicrographs. We performed statistical analyses of the data using the Kruskal-Wallis and Mann-Whitney U tests, where the level of significance was set at 0.05.

RESULTS

The SEM analysis of the coronal third showed mean values of 3.83 in Group A, 3.67 in Group B, 2.79 in Group C, 3.63 in Group D, and 4.00 in Group E. The SEM analysis of the middle third showed mean values of 4.00 in Group A, 3.88 in Group B, 3.75 in Group C, 3.50 in Group D, and 3.50 in Group E. The SEM analysis of the apical third showed mean values of 3.92 in Group A, 3.63 in Group B, 3.71 in Group C, 3.88 in Group D, and 3.17 in Group E. Therefore, we found that there were significant statistical differences between the groups when an overall comparison was done for the coronal, middle, and apical third, with a p-value of 0.001. On multiple comparisons across the different tooth-section thirds. Groups A and B showed statistically significant differences in the apical third (p-value=0.017). Groups A and C showed statistically significant differences in the coronal third and middle third (p-values=0.001 and 0.010, respectively). Groups A and D showed statistically significant differences in the middle third (p-value=0.001). Groups A and E showed statistically significant differences in all thirds (p-values=0.039, 0.001, and 0.001, respectively) Conclusion: The conventional needle irrigation with MTAD showed the highest level of smear layer removal ability on the root canal surface, followed by QMix 2-in-1, the Azadirachta indica leaf and Citrus limon extract mixture, and the conventional endodontic regimen. Normal saline showed the lowest smear layer removal effect.

A Novel Endodontic Approach in Removing Smear Layer Using Nano and Submicron Diamonds with Intracanal Oscillation Irrigation

Sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) are commonly recommended for effectively removing organic and inorganic components in the smear layer. This layer is found on root canal walls after root canal instrumentation. However, high-concentration EDTA reduces the strength of dentin and the dissolution efficacy of organic substances in NaOCl solution. The objective of this study was to investigate the efficacy of applying nano and submicron diamonds in irrigation solutions with sonic and ultrasonic oscillation for removing the smear layer during endodontic treatment. Extracted single-rooted human teeth were instrumented with ProTaper^® Gold (Dentsply Sirona) nickel-titanium rotary instruments. Subsequently, each canal was irrigated with 3% NaOCl, 17% EDTA, distilled water, and 10-1000 nm-sized nano and submicron diamond irrigation solutions, respectively. Sonic and ultrasonic instruments were compared for oscillating the irrigation solutions. The teeth were processed for scanning electron microscopy to observe the efficiency of smear layer removal on the canal walls. Our results indicated that diamond sizes of 50 nm and above irrigation solutions showed significant effectiveness in removing the smear layer following the oscillation of sonic instruments for 10 s. Ultrasonic assisted 500 nm and 1000 nm diamond solutions significantly differed from the other diamond-sized solution in their ability to remove the smear layer. These results suggest that sonic and ultrasonic oscillation with specific sizes of nano and submicron diamond irrigation solution can be used as an alternative approach to removing the smear layer during endodontic treatment. The potential clinical application of root canal treatments can be expected.

Effect of photon-induced photoacoustic streaming and shock-wave enhanced emission photoacoustic streaming technique on the removal of the smear layer after root canal preparation in curved root canals

Background/purpose

The efficiency of root canal irrigation has an important impact on the prognosis of root canal treatment. Photon-induced photoacoustic streaming (PIPS) and shock wave enhanced emission photoacoustic streaming (SWEEPS) are the special modality of Er: YAG laser, whether can they improve the efficiency of root canal irrigation remains to be studied.

Materials and methods

Fifty human teeth with curved root canals were collected and stored in the thymol solution until used in the study. After traditional endodontic cavities preparation, root canals were prepared to size #35 with a 0.04 taper. The final irrigating techniques were as follows: (I) manual dynamic activation (MDA), (II) ultrasonically activated irrigation (UAI), (III) sonically activated irrigation (SAI), (IV) PIPS, and (V) SWEEPS. Fifty teeth were randomly divided into five groups mentioned above. After root canal preparation, the roots were cleaved longitudinally. The dentine surfaces were photographed from the coronal, middle, and apical third of the root by scanning electron microscopy operated at a low vacuum. Two examiners separately graded each image according to the remained smear layer situations.

Results

PIPS and SWEEPS groups showed fewer smear layers remaining than the others in the middle and the apical third (P < 0.05) of the root canal. In contrast, in the coronal third, five groups showed no significant difference (P > 0.05).

Conclusion

PIPS and SWEEPS showed superior smear layer clearing efficiency than traditional irrigating techniques in curved root canals.

Update on citric acid use in endodontic treatment: a systematic review

This systematic review aims to analyse the available evidence concerning the use of citric acid (CA) in endodontics treatment and to assess its results in terms of different considerations: effect on smear layer removal, influence on sealer bond strength, activation effect by means of sonic or ultrasonic devices, effects on dentine surface, antibacterial activity, and effectiveness boost for regenerative procedures, releasing growth factors from dentin. To evaluate the results of CA as a final irrigant and compare them to other chelating agents. This review followed the PRISMA checklist. An electronic search was conducted in MEDLINE (OVID), Scopus (Elsevier) and the Web of Science (Thomson Reuters) databases. Risk of bias of included studies was evaluated using the modified CONSORT checklist and the PRIRATE checklist 2020 guidelines. 39 studies fulfilled the eligibility criteria to be included in this review: 27 in vitro studies using extracted human teeth, 10 in vitro studies using human dentin disks, and 2 RCT. Citric acid has proven to be effective in smear layer removal, showing better results in coronal and middle root thirds, improving its effect when combined with manual dynamic activation. There is no agreement regarding citric acid effect on sealer adhesion and adaptation to root canal walls due to heterogeneity within studies. Citric acid irrigation can decrease dentine microhardness and cause decalcification and erosion, especially when used before NaOCl. Citric acid has proven to be beneficial in regenerative endodontic procedures due to higher TGF-β1 release.Trial registration: Prospero database CRD42021267055.

Disinfection of dentinal tubules with diclofenac sodium and N-Acetylcysteine compared with calcium hydroxide as intracanal medicaments against Enterococcus faecalis

The purpose of this study was to evaluate the disinfection of dentinal tubules with diclofenac sodium (DS), N-acetylcysteine (NAC) and calcium hydroxide (CH). Contaminated dentinal blocks were divided into two control and seven experimental groups (n = 15): CH, DS, NAC, CH + 5% DS, 50% CH + 50% DS, CH + 5% NAC and 50% CH + 50% NAC. After seven days, dentine debris was obtained from two depths of 100 and 200 µm. The bacterial load was assessed by counting the number of colony-forming units (CFUs). Pure DS exhibited maximum antibacterial activity at both depths. At 200 µm, it showed statistically significant differences with all the other groups (P < 0.05). Mixing CH with either 5% or 50% of DS and NAC did not increase the antibacterial efficacy (P > 0.05). Pure DS was most effective in disinfecting dentinal tubules, and mixing CH with DS or NAC is not recommended.

Insights Into the Dynamics and Composition of Biofilm Formed by Environmental Isolate of Enterobacter cloacae

Bacterial biofilms are clinically admissible and illustrate an influential role in infections, particularly those related to the implant of medical devices. The characterization of biofilms is important to understand the etiology of the diseases. Enterobacter cloacae are known for causing infections by forming biofilms on various abiotic surfaces, such as medical devices. However, a detailed characterization in terms of morphology and the molecular composition of the formed biofilms by this bacterium is sparse. The present study provides insights into the biofilm formation of E. cloacae SBP-8, an environmental isolate, on various surfaces. We performed assays to understand the biofilm-forming capability of the SBP-8 strain and characterized the adhering potential of the bacteria on the surface of different medical devices (foley latex catheter, enteral feeding tube, and glass) at different temperatures. We found that medical devices exhibited strong colonization by E. cloacae SBP-8. Using field emission-scanning electron microscopy (FE-SEM) studies, we characterized the biofilms as a function of time. It indicated stronger biofilm formation in terms of cellular density and EPS production on the surfaces. Further, we characterized the biofilm employing surface-enhanced Raman spectroscopy (SERS) and identified the vast heterogenic nature of the biofilm-forming molecules. Interestingly, we also found that this heterogeneity varies from the initial stages of biofilm formation until the maturation and dispersion. Our studies provide insights into biofilm composition over a period of time, which might aid in understanding the biofilm dispersion phases, to enhance the presently available treatment strategies.

Bactericidal Efficacy of Photon-Induced Photoacoustic Streaming-Erbium:Yttrium-Aluminum-Garnet Laser Combined with Irrigation Solution on Enterococcus faecalis in Curved Root Canals: An In Vitro Study

Objective: This experiment aimed to study the bactericidal effect of photon-induced photoacoustic streaming (PIPS)-erbium:yttrium-aluminum-garnet (Er:YAG) laser on Enterococcus faecalis in curved root canals. Materials and methods: Sixty-two molars with moderately curved roots (10°-20°) and 62 molars with severely curved roots (25°-40°; one root was selected in each tooth) were assigned to group A and group B, respectively. A curved root canal model with E. faecalis infection was established. Four samples were used for sterility test, and 20 samples were used for testing if the modeling was valid. The remaining 100 samples were randomly divided into 5 subgroups (A1/A2/A3/A4/A5 and B1/B2/B3/B4/B5, n = 10) and treated as follows: A1/B1: PIPS-Er:YAG laser +5.25% sodium hypochlorite (NaOCl); A2/B2: passive ultrasonic irrigation +5.25% NaOCl; A3/B3: PIPS-Er:YAG laser+normal saline (NS); A4/B4: two-hole root canal irrigator +5.25% NaOCl; A5/B5: two-hole root canal irrigator+NS. After treatment, bacterial culture counts and scanning electron microscopic (SEM) observations were carried out for each subgroup, and the bacterial clearance rate of each subgroup was calculated. SPSS 23 software package was used for statistical analysis of the data, and a single-factor analysis of variance was used to compare the subgroups. Results: The bacterial clearance rate in group A was higher than that in group B; however, in each group, A or B, there were significant differences between the subgroups (p < 0.001) except for subgroups 1 and 2 (p > 0.05). SEM revealed that the antibacterial and smear layer removal effect of root canal in subgroups 1 and 2 was better than that in subgroups 3, 4, and 5. Conclusions: PIPS-Er:YAG can significantly enhance the bactericidal effect of NaOCl on E. faecalis in moderately and severely curved root canals.

Formulation and Antibacterial Potential of Sarang Semut (Myrmecodia pendans) against Oral Pathogenic Bacteria: An In Vitro Study

Background:

Dental diseases are generally caused by oral bacteria such as Enterococcus faecalis, Streptococcus mutans, and Streptococcus sanguinis. These bacteria have resistance to synthetic drugs; thus, it is required to discover new antibacterial agents. Sarang Semut (Myrmecodia pendans) has been empirically used as a medicinal plant to treat various conditions, including those caused by pathogenic bacteria.

Objective:

The present study was aimed to investigate the antibacterial activity of Sarang Semut extracts against E. faecalis, S. mutans, and S. sanguinis.

Materials and Methods:

Sarang Semut was extracted with several solvents to yield n-hexane, ethyl acetate, methanol, and water extracts. Each extract and combination were adjusted for assay with chlorhexidine, fosfomycin, and quercetin and used as positive controls.

Results:

The n-hexane extract showed activity with inhibition zone values of 7.15 and 10.45 ppm against E. faecalis and S. mutans at 1%, respectively. All combination extracts could inhibit the growth of E. faecalis and S. sanguinis. The synergistic effects resulting from the combination of extract-fosfomycin were also presented in this evaluation, with the strongest shown by water-fosfomycin against S. mutans, with inhibition zones of 28.5 mm at 1%.

Conclusion:

Sarang Semut extracts demonstrated antibacterial activity against oral pathogenic bacteria. These results offer alternative natural sources for the new antibacterial drug candidate.

Anti-Acid Biomimetic Dentine Remineralization Using Inorganic Silica Stabilized Nanoparticles Distributed Electronspun Nanofibrous Mats

Background

To manage the sharp pain of dentine hypersensitivity, various materials are utilized to conduct dentine remineralization. However, many prior materials are limited with their single function and complicated operations. In this study, silica and calcium (strontium) carbonates mineralized nano cellulose fibrous (Si/Ca(Sr)-NCF) mat with the ability to release acid resistant and biomimetic mineralizational silica/calcium (strontium) carbonate co-precipitation nanoparticles (Si/Ca(Sr) NPs) were fabricated. The dentine occluding effects, antibacterial activity and cytocompatibility of the Si/Ca(Sr)-NCF mats were evaluated.

Methods

The Si/Ca(Sr)-NCF mats were fabricated by dipping the electrospun nano cellulose fiber (NCF) into silica and calcium (strontium) carbonate liquid. Physicochemical characterizations and ion release were confirmed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), ion release assays and transmission electron microscopy (TEM). Sixty dentine discs were randomly divided into five groups: 1, blank NCF; 2, Si/Ca(Sr 0)-NCF; 3, Si/Ca(Sr 0.01)-NCF; 4, Si/Ca(Sr 0.05)-NCF; 5, Si/Ca(Sr 0.1)-NCF. Dentine discs were mineralized by the mats and observed with SEM immediately, after acid challenge and remineralized in artificial saliva. The releasing liquid was investigated by TEM and type I collagen model. Then, antibacterial property and cytocompatibility were evaluated.

Results

SEM and TEM results confirmed that the experiment mats continuously released amorphous Si/Ca(Sr) NPs and consequently realized anti-acid dentine biomimetic remineralization. Homogeneous surface coverage and collagen intrafibrillar mineralization in strontium adding groups illustrated the mineralization effect was not only by in site precipitation, but also collagen heterogeneous nucleation. Additionally, acceptable antibacterial and cytocompatibility properties were illustrated in low and middle Sr²⁺ containing mats.

Conclusion

In vitro studies on human dentine discs and type I collagen demonstrated that Si/Ca(Sr)–NCF system was a multifunction system inducing anti-acid, biomimetic, antibacterial and cytocompatible dentine remineralization. This multifunction mat would be a promising DH treatment candidate for complicated exposed dentine surfaces.

An in vitro investigation of the sealing ability of biodentine and mineral trioxide aggregate as retrofilling materials after the use of various irrigating solutions

Aim:

Materials and Methods:

Statistical Analysis:

Results:

Conclusion:

Present status and future directions - microbiology of endodontic infections

Apical periodontitis has a microbial aetiology and is one of the most common inflammatory diseases that affect humans. Fungi, archaea and viruses have been found in association with apical periodontitis, but bacteria are by far the most prevalent and dominant microorganisms in endodontic infections. Bacterial infection of the root canal system only occurs when the pulp is necrotic or was removed for previous treatment. In some specific cases, including acute and chronic abscesses, the bacterial infection may reach the periradicular tissues. Intracanal bacteria are usually observed as sessile multispecies communities (biofilms) attached to the dentinal root canal walls. Infection in the main root canal lumen can spread to other areas of the root canal system. Although more than 500 bacterial species have been detected in endodontic infections, a selected group of 20 to 30 species are most frequently detected and may be considered as the core microbiome. There is a high interindividual variability in the endodontic microbiome in terms of species composition and relative abundance. Obligate anaerobic species are more abundant in the intraradicular bacterial communities of teeth with primary apical periodontitis, while both anaerobes and facultatives dominate the communities in post-treatment apical periodontitis. Bacterial interactions play an essential role in determining the overall virulence of the community, which has been regarded as the unit of pathogenicity of apical periodontitis. This article reviews the microbiologic aspects of endodontic infections and provides perspectives for future research and directions in the field.

The Photobiomodulation Effect of 940nm Laser Irradiation on Enterococcus faecalis in Human Root Dentin Slices of Varying Thicknesses

Introduction: An increase in dentine thickness could result in an inadequate depth of laser energy penetration. This study aimed to evaluate the effect of a 940 nm laser on Enterococcus faecalis through varying thicknesses of human root dentin slices. Methods: Thirty-five dentin slices of root dentin with thicknesses ranging between 500 and 3000 µm were produced. Six experimental groups (500, 1000, 1500, 2000, 2500, and 3000 µm (n=5 each) were lased and the seventh, non-lased group served as the positive control with a dentine thickness of 2000 µm. The slices were inoculated with 2 µL of E. faecalis suspension of 1.5 × 10⁸ E. faecalis cells/mL. All the lased slices were lased from the opposing side of the inoculation. A non-initiated 200 μm bare end fibre at the power of 1 W, in a continuous wave was used. Four doses of laser irradiation of 5 seconds with a side to side movement with the tip held at a 5º angle to the dentine slice were performed. The colony-forming units of E. faecalis were determined and the bacterial photobiomodulation effect analysed using one-way ANOVA with a Bonferroni and Holm post hoc test at a significance level of P > 0.05. Results: There were statistical differences between the dentin slices of 500, 1000, and 1500 μm treated with the laser compared to the positive control (P < 0.01). However, there were no statistical differences between the lased 2000 and 2500 μm slices compared to the positive control. There was significantly more photobiomodulation of the E. faecalis for the dentine slices of 3000 μm than the positive control (P < 0.01). Conclusion: Laser treatment through dentine slices of 2000 μm and thinner significantly reduced bacterial growth. The photobiomodulation effects started to occur in dentine slices thicker than 2500 μm compared to the positive control.

The Application of Chitosan Nanostructures in Stomatology

Chitosan (CS) is a natural polymer with a positive charge, a deacetylated derivative of chitin. Chitosan nanostructures (nano-CS) have received increasing interest due to their potential applications and remarkable properties. They offer advantages in stomatology due to their excellent biocompatibility, their antibacterial properties, and their biodegradability. Nano-CSs can be applied as drug carriers for soft tissue diseases, bone tissue engineering and dental hard tissue remineralization; furthermore, they have been used in endodontics due to their antibacterial properties; and, finally, nano-CS can improve the adhesion and mechanical properties of dental-restorative materials due to their physical blend and chemical combinations. In this review, recent developments in the application of nano-CS for stomatology are summarized, with an emphasis on nano-CS’s performance characteristics in different application fields. Moreover, the challenges posed by and the future trends in its application are assessed.

Synergistic effects of silver ions and metformin against enterococcus faecalis under high-glucose conditions in vitro

Background

This study aimed to evaluate the synergistic antibacterial activities of silver ions (Ag⁺) and metformin hydrochloride (Met) against Enterococcus faecalis (E. faecalis) under normal or high-glucose conditions.

Results

The minimum inhibitory concentration, minimum bactericidal concentration, growth curves, and colony-forming units were used to evaluate the antibacterial effects of Ag⁺ and Met on planktonic E. faecalis in Brain Heart Infusion broth with or without additional glucose. The influences of Ag⁺ and Met on four weeks E. faecalis biofilm on human dentin slices was also tested. Cytotoxicity was tested on MC3T3-E1 osteoblastic cells using CCK-8 assays. The results indicated that E. faecalis showed higher resistance to drug treatment under high-glucose conditions. Ag⁺ (40 μg/mL) plus Met (3.2% or 6.4%) showed enhanced antibacterial activities against both planktonic E. faecalis and biofilm on dentin slices, with low cytotoxicity.

Conclusions

Met enhanced the bactericidal effects of Ag⁺ against both planktonic and biofilm E. faecalis under normal or high-glucose conditions with low cytotoxicity. Further molecular studies are needed to be conducted to understand the mechanisms underlying the synergistic activity between Met and Ag⁺.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02291-2.

Effectiveness of D,L-2-hydroxyisocaproic acid (HICA) and alpha-mangostin against endodontopathogenic microorganisms in a multispecies bacterial-fungal biofilm in an ex vivo tooth model

AIM

To develop a defined multispecies root canal biofilm model ex vivo, and to perform viable compositional analysis following D,L-2-hydroxyisocaproic acid (HICA), alpha-mangostin, Calcicur^® , and Odontopaste^® exposure.

METHODOLOGY

Time-kill assays were conducted in vitro using HICA, alpha-mangostin, Calcicur^® , Odontopaste^® , and saline solution on the planktonic cultures of C. albicans, E. faecalis, L. rhamnosus, and S. gordonii. Human root dentine blocks were prepared (n = 100) ex vivo, and multispecies suspensions containing each of 1.5 × 10⁸  CFU/mL C. albicans, E. faecalis, L. rhamnosus, and S. gordonii in brain heart infusion (BHI) were incubated within the root canals for 21 days. Canals (n = 20/group) were then exposed to medicaments for 7 days. Samples taken from the inner (first 0.1 mm) and deeper (second 0.1 mm) dentine by drilling with Ash Steel Burs No. 5 and No. 6, and residual roots were cultured in broth for 24 h. Cell growth was detected by spectrophotometry and confirmed by culture on agar. The other set of inner dentine, deeper dentine, and residual root samples were sonicated, and then exposed with 50 μM PMA before DNA was extracted using the QIAamp DNA mini kit. Real-time quantitative PCR was performed to determine the biofilm composition as well as the number of live and total cells remaining in the biofilm following each treatment. The OD data were analysed with Kruskal-Wallis and Friedman with Wilcoxon signed-rank test between and within groups, respectively, agar culture and qPCR data with Pearson chi-square with Mann-Whitney and Cochran with McNemar tests, respectively (p < .0001).

RESULTS

Time-kill assays revealed that HICA and Calcicur^® killed all planktonic organisms within 24 h, whilst alpha-mangostin killed the organisms within 72 h. However, Odontopaste^® was a slow-killing agent: 10 cells of planktonic organisms survived after exposure to the agent for 7 days. The ex vivo tooth model demonstrated that HICA and alpha-mangostin significantly inhibited the cell growth in all sampling depths (p < .0001). All species-specific data revealed the effectiveness of each medicament on the biofilm composition.

CONCLUSIONS

D,L-2-hydroxyisocaproic acid and alpha-mangostin had antimicrobial activity against multispecies bacterial-fungal biofilms.

[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.

Radiographic and antimicrobial evaluation of enterococcus Faecalis and Actinomyces Israelii micro-organisms after photodynamic therapy (aPDT)

This study evaluated the action of Antimicrobial Photodynamic Therapy (aPDT) on Enterococcus faecalis and Actinomyces israelii. Samples were taken from the root canal system, at different stages of treatment and bacteria were identified through qPCR. Fifty teeth (incisors, canines, and premolars) with pulp necrosis and periapical lesion diagnosis were randomly selected and divided into 2 groups: Group 1 (G1) - Endodontic Therapy with Mechanical Chemical Preparation (MPQ) and intracanal medication; Group 2 (G2) - Endodontic therapy with MPQ, intracanal medication, and 2 applications of aPDT. APDT was performed with application of 0.005% methylene blue, wavelength of 660 nm, and 90 seconds. Follow-up was performed with an initial x-ray and an x-ray 60 days after the end of treatment. The radiographs were scored evaluated by two examiners to classify periapical repair: total repair, partial repair, doubtful repair, or no repair. Enterococcus faecalis was found more frequently in G1 than G2. Actinomyces israelii was found equally in G1 and G2. Evaluation of the two bacteria between collections 1, 2 and 3, showed that there was no difference, both in G1 and in G2. There was association between the variables group and repair classification in radiographs evaluation. APDT did not promote better results in endodontic treatment, being similar to conventional treatment. However, this study pointed out that molecular methods may not be efficient in detecting bacteria after treatment, and colony-forming units may complement, being an effective quantifying method. Therefore, new studies must be carried out to show the possible effectiveness of aPDT.

Induction of proteome changes involved in biofilm formation of Enterococcus faecalis in response to gentamicin

BACKGROUND

Enterococcus faecalis is a significant cause of nosocomial infections and other diseases, including endocarditis, bacteremia, and urinary tract infections. This microorganism forms biofilms to overcome difficult environmental conditions, such as lack of oxygen, lack of water, and the presence of antimicrobials. These biofilms make diseases difficult by changing their proteome contents, protecting the bacterium, and increasing their pathogenicity. This study aimed to evaluate gentamicin's effect on proteome changes and biofilm formation in E. faecalis.

METHOD

Twenty-five clinical isolates and one standard isolate were selected for the experiments. A label-free/gel-free proteomic and microtiter plate techniques were used to study proteome changes and biofilm formation, respectively.

RESULTS

Gentamicin significantly increased the biofilm formation in 62% of isolates and the rest of the isolates; no significant change was observed. The abundance of lactate utilization protein C, ribosomal RNA small subunit methyltransferase H, and protein translocase subunit SecA were increased. However, the abundances of proteins effective in cell division and metabolism, such as replication initiation protein and segregation and condensation protein A, were decreased.

CONCLUSION

The present study's findings exhibited that antibiotics might have adverse effects on treatment and increase microorganisms' pathogenicity. It was observed in gentamicin as induction of biofilm formation through different mechanisms, particularly changes in the expression of specific proteins in E. faecalis.

Fluorescence characteristics of E. faecalis in dentine following treatment with oxidizing endodontic irrigants

INTRODUCTION

This study aimed to assess changes in the fluorescence characteristics of Enterococcus faecalis in human dentine over a period of 24 h following treatment with endodontic irrigants.

METHOD

Sterilised, non-functional extracted third molars were embedded in acrylic resin and uniformly sectioned into 2 mm thick dentine sections. After the removal of smear layer, the dentine sections were inoculated with E. faecalis and cultured for 7 days. The infected dentine sections were subsequently treated with different concentrations of sodium hypochlorite (NaOCl) and hydrogen peroxide (H₂O₂). Bacterial fluorescence readings were assessed at different time points using a calibrated laser device. All data were assessed for normality (Kolmogorov Smirnoff test) and analysed using ANOVA with Bonferroni post-hoc tests.

RESULTS

Fluorescence readings were quenched when E. faecalis infected human dentine sections were treated with oxidizing irrigants in vitro. Throughout a 24-hour period, fluorescence recovered in part but did not return to baseline level.

CONCLUSION

The fluorescence quenching effect of these oxidizing agents needs to be considered when using laser fluorescence in assessing the quality of root canal debridement or disinfection.

Quaternary ammonium silane (k21) based intracanal medicament triggers biofilm destruction

BACKGROUND

Compare antimicrobial efficacy of a quarternary ammonium silane (QAS)/k21 as an intracanal medicament against E. faecalis and C. albicans biofilms formed on root dentin.

METHODOLOGY

Dentin blocks were sterilized and E. faecalis and C. albicans microbial colonies were counted for colony-forming-units against 2%k21, 2%CHX and Ca(OH)2 medicaments. Biofilm colonies after 7 days on dentin were analysed using confocal laser scanning microscopy with live/dead bacterial viability staining. TEM was done to study dentin collagen matrix. Dentin discs from 3rd day and 7th day well plate was used for Raman spectra and observed under fluorescent-microscope. Docking studies were carried out on MMP-2 S1 binding-domain with k21.

RESULTS

There was reduction of E. faecalis/C. albicans when k21, chlorhexidine and calcium hydroxide were used with highest percentage in 2%k21 treated specimens. 2%k21 showed dense and regular collagen network with intact cross-banding and decreased Raman intensity for 2%k21 on 3rd day. NaOCl + k21 showed least adherence, whereas saline groups showed highest adherence of E. faecalis and C. albicans to root-canal dentin. Alizarin red staining of hDPSCs revealed calcium deposition in all groups with significant difference seen amongst 2%k21 groups. MMP-2 ligand binding was seen accurately indicating possible target sites for k21 intervention.

CONCLUSION

2%k21 can be considered as alternative intracanal medicament.

Effect of Propolis Nanoparticles against Enterococcus faecalis Biofilm in the Root Canal

To determine the antibacterial effect of propolis nanoparticles (PNs) as an endodontic irrigant against Enterococcus faecalis biofilm inside the endodontic root canal system. Two-hundred-ten extracted human teeth were sectioned to obtain 6 mm of the middle third of the root. The root canal was enlarged to an internal diameter of 0.9 mm. The specimens were inoculated with E. faecalis for 21 days. Following this, specimens were randomly divided into seven groups, with 30 dentinal blocks in each group including: group I-saline; group II-propolis 100 µg/mL; group III-propolis 300 µg/mL; group IV-propolis nanoparticle 100 µg/mL; group V-propolis nanoparticle 300µg/mL; group VI-6% sodium hypochlorite; group VII-2% chlorhexidine. Dentin shavings were collected at 200 and 400 μm depths, and total numbers of CFUs were determined at the end of one, five, and ten minutes. The non-parametric Kruskal-Wallis and Mann-Whitney tests were used to compare the differences in reduction in CFUs between all groups, and probability values of p < 0.05 were set as the reference for statistically significant results. The antibacterial effect of PNs as an endodontic irrigant was also assessed against E. faecalis isolates from patients with failed root canal treatment. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were also performed after exposure to PNs. A Raman spectroscope, equipped with a Leica microscope and lenses with curve-fitting Raman software, was used for analysis. The molecular interactions between bioactive compounds of propolis (Pinocembrin, Kaempferol, and Quercetin) and the proteins Sortase A and β-galactosidase were also understood by computational molecular docking studies. PN300 was significantly more effective in reducing CFUs compared to all other groups (p < 0.05) except 6% NaOCl and 2% CHX (p > 0.05) at all time intervals and both depths. At five minutes, 6% NaOCl and 2% CHX were the most effective in reducing CFUs (p < 0.05). However, no significant difference was found between PN300, 6% NaOCl, and 2% CHX at 10 min (p > 0.05). SEM images also showed the maximum reduction in E. faecalis with PN300, 6% NaOCl, and 2% CHX at five and ten minutes. CLSM images showed the number of dead cells in dentin were highest with PN300 compared to PN100 and saline. There was a reduction in the 484 cm^-1 band and an increase in the 870 cm^-1 band in the PN300 group. The detailed observations of the docking poses of bioactive compounds and their interactions with key residues of the binding site in all the three docking protocols revealed that the interactions were consistent with reasonable docking and IFD docking scores. PN300 was equally as effective as 6% NaOCl and 2% CHX in reducing the E. faecalis biofilms.

Antibacterial Activity of Sodium Hypochlorite Gel versus Different Types of Root Canal Medicaments Using Agar Diffusion Test: An In Vitro Comparative Study

Aim

This study aimed to evaluate the antibacterial effect of sodium hypochlorite gel and four types of intracanal medicaments.

Materials and Methods

The agar diffusion method was used to evaluate the antibacterial effect of five medicaments (sodium hypochlorite gel (NaOCl), chlorhexidine gel (CHX), calcium hydroxide paste (CH), Ledermix, and Diapex plus) against Enterococcus faecalis (E. faecalis), Staphylococcus aureus (S. aureus), and Escherichia coli (E. coli). The zone of inhibition around each medicament was measured in millimeters, after 48 hours of incubation at 37°C. The antibacterial effects of medicaments against each microbial strain and the sensitivity of microorganisms towards each medicament were compared using the one-way ANOVA and Games–Howell post hoc tests. The level of significance was set to p < 0.05.

Results

All medicaments showed variable inhibition zones for all bacterial strains except Diapex Plus which showed no antibacterial activity. NaOCl gel exhibited the most significant inhibition zones for all bacterial strains followed by CHX gel, Ledermix, and CH. However, the effect of CHX and CH paste against S. aureus was statistically similar, while the effect of CH against E. faecalis was significantly higher than the Ledermix.

Conclusion

Sodium hypochlorite gel displayed the highest antibacterial activity among tested medicaments and can be recommended as a potent intracanal medicament. Chlorhexidine gel showed a significantly higher antibacterial effect when compared with Ledermix and calcium hydroxide. Calcium hydroxide demonstrated stronger antibacterial activity against E. faecalis than Ledermix. Diapex Plus exhibited no antibacterial effect.

Preparation of PLGA-chitosan based nanocarriers for enhancing antibacterial effect of ciprofloxacin in root canal infection

The aim of this study is to prepare and evaluate the antibacterial and antibiofilm activity of ciprofloxacin (CIP) loaded PLGA nanoparticles (F2) and CIP-PLGA nanoparticles coated with chitosan (F3) versus ciprofloxacin solution (Fl) as a control on Enterococcus faecalis. F2 was prepared using double emulsion evaporation technique then coated with chitosan (F3). The prepared F2 and F3 were evaluated for size, surface charge, encapsulation efficiency, morphology and in vitro release. F1, F2, F3, and Chitosan (CS) were assessed in vitro using agar diffusion technique and biofilm inhibition assay. Finally, biofilm inhibition on teeth using Colony Forming Unit (CFU) was implemented with different concentrations of the three formulae. The results revealed that F2 is 202.9 nm with a negative charge -0.0254 mv, while F3 is 339.6 nm with a positive charge +28.5 mv. The encapsulation efficiency of F2, and F3 was 64% and 78% respectively. The amount released was 92.62% and 78.3% for F2 and F3, respectively, after 72 h, while F1 showed 100% released in the first hour. CS, F1, F2, and F3, showed antibacterial effect with inhibition zone of 12 mm, 22 mm, 20 mm, and 32 mm respectively. Biofilm inhibition of F1, F2, and F3 were 60%, 74%, and 91.8%, respectively. F3 colony count was less than F2, and F1 in all concentrations. It can be concluded that F3 had proven to exhibit potential antibacterial and antibiofilm activity in a controlled release pattern consequently, they can be used as an intra-canal medication.

A comparative evaluation of smear layer removal by using ethylenediamine tetraacetic acid, citric acid, and maleic acid as root canal irrigants: An in vitro scanning electron microscopic study

Introduction:

Irrigants remove or dissolve smear layer formed during instrumentation. Thus it is important to study the effect of different irrigant solutions on smear layer removal.

Objectives:

The aim of this study is to determine which irrigant effectively removes the smear layer from the coronal, middle, and apical third of the root canal.

Materials and Methodology:

One hundred and twenty single-rooted mandibular premolars were decoronated and biomechanical preparation was done through hand instrumentation up to size 40 k file with 2.5% NaOCl irrigation between each successive filing, followed by irrigation with 5 ml of saline. The teeth were divided into Groups I, II, III, and IV containing 30 samples each and irrigated with 5 ml of 17% ethylenediamine tetraacetic acid (EDTA), 10% Citric acid, 7% Maleic acid and normal saline respectively for 1 min and final irrigation was done with 5 ml of distilled water of each sample. The canals were dried with 2% absorbent paper points. The roots were then split with a chisel and mallet. One-half of each tooth was selected and then was analyzed using a scanning electron microscope. The dentinal surfaces were observed at the cervical, middle, and apical third with ×2000 for the smear layer. The scores were attributed, according to Torabinejad et al. rating system.

Results:

7% maleic acid and 10% citric acid both are equally effective in smear layer removal from coronal and middle third, but in apical third 7% maleic acid is more effective than 10% citric acid. Between citric acid and EDTA, both are equally effective in smear layer removal from coronal and middle third, but in apical third, 10% citric acid is more efficacious than 17% EDTA.

Conclusion:

Within the limitations of the study, it can be concluded that all three tested irrigants removed the smear layer from coronal, middle, and apical third. However, in apical third 7% maleic acid is the most efficacious irrigant in smear layer removal.

Metabolome responses of Enterococcus faecium to acid shock and nitrite stress

Enterococcus faecium is gaining increasing interest due to its virulence and tolerance to a range of stresses (e.g., acid shock and nitrite stress in human stomach). The chemical taxonomy and basic structural features of cellular metabolite can provide us a deeper understanding of bacterial tolerance at molecular level. Here, we used hierarchical classification and molecular composition analysis to investigate the metabolome responses of E. faecium to acid shock and nitrite stress. Our results showed that considerable high biodegradable compounds (e.g., dipeptides) were produced by E. faecium under acid shock, while nitrite stress induced the accumulations of some low biodegradable compounds (e.g., organoheterocyclic compounds and benzenoids). Complete genome analysis and metabolic pathway profiling suggested that E. faecium produced high biodegradable metabolites responsible for the proton-translocation and biofilm formation, which increase its tolerance to acid shock. Yet, the presence of low biodegradable metabolites due to the nitrite exposure could disturb the bacterial productions of surface proteins, and thus inhibiting biofilm formation. Our approach uncovered the hidden interactions between intracellular metabolites and exogenous stress, and will improve the understanding of host-microbe interactions.

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.

Quaternary ammonium silane, calcium and phosphorus-loaded PLGA submicron particles against Enterococcus faecalis infection of teeth: An in vitro and in vivo study

Refractory root canal infection of human teeth is the primary cause of dental treatment failure. Enterococcus faecalis is the major cause of refractory root canal infection. In the present study, poly(D,L-lactic-co-glycolide) (PLGA) submicron particles were used as carriers to deliver an antimicrobial quaternary ammonium silane (code-named K21) as well as calcium and phosphorus elements. The release profiles, antibacterial ability against E. faecalis, extent of infiltration into dentinal tubules, biocompatibility and in vitro mineralization potential of the particles were investigated. In addition, the antimicrobial effects of the particles against E. faecalis infection were evaluated in vivo in the teeth of beagle dogs. The encapsulated components were released from the PLGA particles in a sustained-release manner. The particles also displayed good biocompatibility, in vitro mineralization ability and antibacterial activity against E. faecalis. The particles could be driven into dentinal tubules of dentin slices by ultrasonic activation and inhibited E. faecalis colonization. In the root canals of beagle dogs, PLGA submicron particles loaded with K21, calcium and phosphorus demonstrated strong preventive effects against E. faecalis infection. The system may be developed into a new intracanal disinfectant for root canal treatment.

Comparison of Five Different Irrigation Techniques on Smear Layer Removal in Apical Thirds of Root Canals of Mandibular First Premolar: A Scanning Electron Microscopic Study

Aim:

This study was conducted to compare smear layer removal by five different irrigation techniques—conventional needle irrigation (CI), manual dynamic activation (MDA), passive ultrasonic irrigation (PUI), sonic irrigation (SI), and negative apical pressure (NAP).

Materials and Methods:

Fifty freshly extracted mandibular first premolars were cleaned and shaped by One Curve rotary files and 3% sodium hypochlorite and 17% ethylenediaminetetraacetic acid. The samples were divided into five equal groups (n = 10), according to the final irrigation activation technique: Group I, CI; Group II, MDA; Group III, PUI; Group IV, SI; and Group V, NAP. The samples were prepared and observed under a scanning electron microscope. The photomicrographs were recorded and evaluated with a scoring system.

Results:

Group I and Group II had the highest scores, which showed a statistically significant difference between the other groups (P < 0.05). This was followed by PUI, NAP, and SI.

Conclusion:

Final irrigation activation with SI and NAP resulted in the better removal of smear layer when compared to that with other groups.

Ex vivo comparison of antibacterial efficacy of conventional chemomechanical debridement alone and in combination with light-activated disinfection and laser irradiation against Enterococcus faecalis biofilm

BACKGROUND AND OBJECTIVES

Intracanal disinfection plays an important role in endodontic treatment success. Enterococcus faecalis (E. faecalis) is a resistant microorganism responsible for endodontic infections. We aimed to assess the bactericidal effects of three disinfection methods on E. faecalis biofilm.

MATERIALS AND METHODS

Fifty-five freshly extracted single-rooted human teeth were evaluated. A barbed broach was used to extract the pulp tissue. No further root canal preparation was performed. Specimens were sterilized with gamma radiation, and inoculated with E. faecalis suspension. They were then incubated for 4 days and 4 weeks. Biofilm formation was confirmed using a scanning electron microscope (SEM). The teeth were randomly assigned to three subgroups (n = 7) to assess the antimicrobial efficacy of the following three disinfection methods against immature (4-day) and mature (4-week) biofilms: the conventional chemomechanical debridement (CCMD), CCMD + light-activated disinfection (LAD; 810 nm, 0.3 W, 120 J/cm²) with indocyanine Green (EmunDo) as photosensitizer and CCMD + diode laser irradiation (810 nm, 2 W). The teeth were then longitudinally split into two halves and the colony count was reported as colony forming units (CFUs) to assess bacterial viability after each disinfection protocol.

RESULTS

None of the disinfection methods could completely remove the biofilm. CCMD + LAD caused the highest and CCMD + diode laser caused the lowest reduction in biofilm. Antibacterial efficacy was significantly lower against the mature (4-week) biofilm compared with immature (4-day) biofilm in all groups (P < 0.05).

CONCLUSION

All three disinfection methods were effective for partial elimination of E. faecalis biofilm. But CCMD + LAD was significantly more efficacious in decreasing both mature and immature biofilms.

Effectiveness of different disinfection techniques of the root canal in the elimination of a multi-species biofilm

Background

The purpose of the study was to evaluate the effectiveness of different root canal disinfection techniques in the elimination of a multi-species biofilm from inside the root canal.

Material and Methods

Fifty mandibular first premolars were used in the present study, standardized to 11mm of root length, and instrumented with a reciprocation system Reciproc, (VDW GmbH, Munich, Germany) to a #50. Longitudinally sectioned halves of the roots were obtained and washed with NaOCl 4%, EDTA 17% and 5% sodium thiosulfate, and sterilized by autoclaving for 15 minutes at 121°C. A multi-species biofilm broth was developed with three strains of bacteria under laboratory conditions: Enterococcus faecalis ATTC 29212, Eikenella corrodens ATTC 23834, Streptococcus anginosus ATTC 33397. Roots were autoclaved and transferred to the broth for 4 days and then were subjected to either disinfection with sodium hypochlorite 4% and XP-endo Finisher (FKG Dentaire, La Chaux-de-Fonds, Switzerland) or chlorhexidine 2% with and without activation with XP-endo Finisher (FKG Dentaire, La Chaux-de-Fonds, Switzerland).

Results

The evaluations of the biofilm elimination showed results that indicate that the 4% sodium hypochlorite group with positive pressure irrigation presented significant differences with the group that had irrigation with sodium hypochlorite activated with XP-endo Finisher and the chlorhexidine groups to 2% (P<0.05).

Conclusions

Chlorhexidine 2% activated with the XP-endo Finisher does not exert elimination or improved cleaning effect on the multi-species biofilm. Activation of sodium hypochlorite 4% improved the elimination of the multi-species biofilm.

Key words:Biofilm, multispecies, chlorhexidine, sodium hypochlorite.

Antibacterial efficacy of silver diamine fluoride as a root canal irrigant

Objectives

Conventional disinfectants and medicaments have not been able to achieve and maintain sterilization of root canals. The purpose of the study was to evaluate the antibacterial efficacy of 3.8% silver diamine fluoride (SDF) in comparison with 2% chlorhexidine (CHX) against Enterococcus faecalis biofilm.

Materials and methods

Extracted human teeth were used to make 70 dentin discs that were then inoculated with E. faecalis to generate a 3‐week‐old biofilm model. The discs were subjected to treatment with 3.8% SDF, 2% CHX, sodium hypochlorite (NaOCl), or saline for 10 min. After exposure, the dentin discs were examined with a confocal laser scanning microscope to verify the percentage of live versus dead cells within the biofilm. Univariate one‐way analysis of variance and Tukey‐honestly significant difference post hoc analysis (p < .05) were performed to detect significant differences.

Results and conclusion

The NaOCl group showed the greatest percentage of dead cells (62.26%) among all groups (p < .05). The SDF group showed a significantly higher percentage of dead cells (57.39%) than the 2% CHX and saline groups (p < .05). SDF possessed higher antimicrobial activity than 2% CHX against E. faecalis biofilms.

Incorporating N-acetylcysteine and tricalcium phosphate into epoxy resin-based sealer improved its biocompatibility and adhesiveness to radicular dentine

OBJECTIVE

This in vitro study was designed to evaluate the biocompatibility, adhesiveness, and antimicrobial activity of epoxy resin-based sealer associated with N-Acetylcysteine (NAC) or beta-tricalcium phosphate nanoparticles (β-TCP) as an experimental retro-filling material.

METHODS

Cytotoxicity was assessed using 2,3-Bis-(Methoxy-4-Nitro-5-Sulphophenyl)-2H-Tetrazolium-5-Carboxanilide (XTT) and Sulforhodamine B (SRB) assays after exposing human periodontal ligament fibroblasts to extracts of the materials for 1, 3, or 7 days. For the adhesive resistance test, root canals (48 single-root teeth) were instrumented with Reciproc #40 files (VDW GmbH, Germany) and obturated. After 7 days, the apices were sectioned and a retrograde cavity prepared and filled with the experimental materials (Mineral trioxide aggregate, Epoxy sealer, Epoxy sealer+NAC, and Epoxy sealer+β-TCP). For the push-out test, one 2-mm thick slice was obtained from the apical third of each specimen. Antimicrobial activity was performed using agar diffusion method. Biofilms were grown in microplates and exposed to the extracts of retro-filled materials, followed by analysis of growth inhibition on agar plates.

RESULTS

Epoxy sealer in association with β-TCP or NAC showed better bond strength while Mineral trioxide aggregate allowed for the lowest adhesion. Mineral trioxide aggregate, Epoxy sealer+β-TCP, and Epoxy sealer+NAC showed low cytotoxicity. Epoxy sealer was the most cytotoxic. In antimicrobial activity assays, all materials had no effect on Candida albicans. Addition of NAC improved the antimicrobial property of Epoxy sealer against Enterococcus faecalis compared to unmodified Epoxy sealer (P<0.05).

SIGNIFICANCE

Incorporating β-TCP or NAC with Epoxy sealer could improve the adhesiveness and biocompatibility for better use in endodontic therapy.

Formulation and characterization of chlorhexidine HCl nanoemulsion as a promising antibacterial root canal irrigant: in-vitro and ex-vivo studies

Introduction and aim: Chlorhexidine Hydrochloride [Chx.HCl] has a broad-spectrum antibacterial effect, sustained action and low toxicity so it has been recommended as a potential root canal irrigant. The aim of this study was to improve the penetration ability, cleansing and antibacterial effect of Chx.HCl using a newly formulated Chx.HCl nanoemulsion and use it as root canal irrigant.

Methods: Chx.HCl nanoemulsions were prepared using two different oils; Oleic acid and Labrafil M1944CS, two surfactants; Tween 20 and Tween 80 and co-surfactant; Propylene Glycol. Pseudoternary phase diagrams were constructed to designate the optimum systems. The prepared nanoemulsion formulae were evaluated for their drug content, emulsification time, dispersibility, droplet size, in-vitro drug release, thermodynamic stability, In-vitro antibacterial activity and ex-vivo study for the selected formula. Comparisons were made of Chx.HCl nanoemulsion with two different concentrations 0.75% and 1.6% vs Chx.HCl normal particle size as root canal irrigant for their penetration ability, cleansing effect and antibacterial effect.

Results: The selected formula was F6 with composition of 2% Labrafil, 12% Tween 80 and 6% Propylene glycol. It has small particle size (12.18 nm), short emulsification time (1.67 seconds), and fast dissolution rate after 2 minutes. It was found to be a thermodynamically/physically stable system. The higher concentration of Chx.HClnanoemulsion1.6% shows the best penetration ability compared to Chx.HCl normal particle size due to the smaller particle size. Chx.HCl nanoemulsion 1.6% has the lowest mean value of the remaining debris surface area (2001.47 µm²) when compared to normal particle size material (2609.56 µm²).

Conclusion: Chx.HCl nanoemulsion preparation has better cleansing ability and antibacterial effect with high efficacy on Enterococcus faecalis, where high reduction rate or complete eradication of bacterial cells has been achieved.

Antimicrobial Effect of Different Sizes of Nano Zinc Oxide on Oral Microorganisms

Objectives:

The purpose of the present study was to evaluate the antimicrobial effect of various sizes and concentrations of zinc oxide (ZnO) nanoparticles on Streptococcus mutans (S. mutans), Enterococcus faecalis (E. faecalis), Lactobacillus fermentum (L. fermentum), and Candida albicans (C. albicans).

Materials and Methods:

Solutions at the concentration of 10 μg/ml were prepared using 20-nm, 40-nm, and 140-nm nano ZnO (nZnO) powder. The antimicrobial effect of nZnO was determined using the disk diffusion method. The inhibition zone (mm) was measured using a ruler. Data were analyzed by analysis of variance (ANOVA) and the Bonferroni correction. The minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of nZnO were determined using the broth microdilution method in Mueller-Hinton Agar (MHA) for S. mutans and E. faecalis, De Man, Rogosa, and Sharpe (MRS) agar, and Sabouraud Dextrose Agar (SDA).

Results:

The greatest inhibition zones were observed against S. mutans with 20-nm and 40-nm nZnO, while 140-nm nZnO formed the greatest inhibition zones against S. mutans and E. faecalis. The smallest inhibition zones were observed against C. albicans with the three nZnO particle sizes. The MICs for C. albicans with 40-nm and 140-nm particles and for L. fermentum with 140-nm particles were higher than 10 μg/ml. A significant correlation was found between the particle size and the antibacterial activity against S. mutans (P=0.00), L. fermentum, and E. faecalis (P<0.02).

Conclusion:

The antimicrobial activity of nZnO increases with decreasing the particle size. The greatest antimicrobial effect was observed against S. mutans and E. faecalis. S. mutans is more sensitive to the changes in the particle size compared to other bacteria.