Antibiofilm activity of irrigating solutions associated with cetrimide. Confocal laser scanning microscopy

The effect of the enzymes trypsin and DNase I on the antimicrobial efficiency of root canal irrigation solutions

The purpose of this study was to evaluate the antibacterial efficacy of using 2.5% NaOCl, 2% chlorhexidine (CHX), Irritrol, and chitosan-coated silver nanoparticles (AgCNPs) alone or in combination with deoxyribonuclease I (DNase I) and trypsin pre-enzyme applications in dentin samples contaminated with Enterococcus faecalis (E. faecalis) by CLSM. 144 dentin blocks with confirmed E. faecalis biofilm formation were divided randomly according to the irrigation protocol (n = 12): NaOCl, CHX, Irritrol, AgCNPs, trypsin before NaOCl, CHX, Irritrol, AgCNPs, and DNase I before NaOCl, CHX, Irritrol, AgCNPs. Dentin blocks were stained with the Live/Dead BacLight Bacterial Viability Kit and viewed with CLSM after irrigation applications. The percentage of dead and viable bacteria was calculated using ImageJ software on CLSM images. At a significance level of p < 0.05, the obtained data were analyzed using one-way Anova and post-hoc Tukey tests. In comparison with NaOCl, CHX had a higher percentage of dead bacteria, both when no pre-enzyme was applied and when DNase I was applied as a pre-enzyme (p < 0.05). There was no difference in the percentage of dead bacteria between the irrigation solutions when trypsin was applied as a pre-enzyme (p > 0.05). AgCNPs showed a higher percentage of dead bacteria when trypsin was applied as a pre-enzyme compared to other irrigation solutions (p < 0.05), while the pre-enzyme application did not affect the percentage of dead bacteria in NaOCl, CHX, and Irritrol (p > 0.05). No irrigation protocol tested was able to eliminate the E. faecalis biofilm. While the application of trypsin as a pre-enzyme improved the antimicrobial effect of AgCNPs, it did not make any difference over other irrigation solutions.

Effectiveness of continuous chelation irrigation protocol in endodontics: a scoping review of laboratory studies

This scoping review aimed to synthesize and explore the current boundaries and limitations of laboratory research on the effectiveness of continuous chelation irrigation protocol in endodontics. This scoping review was reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Extension for Scoping Reviews. Literature search was conducted on Pubmed and Scopus to identify all laboratory studies evaluating smear layer and hard-tissue debris removal or, antimicrobial efficacy, or dentine erosion induced by continuous chelation. Two independent reviewers performed the all review steps and the relevant items were recorded. Seventy-seven potentially relevant studies were identified. Finally, 23 laboratory studies met the eligibility criteria for qualitative synthesis. Seven studies focused on the smear layer/debris removal outcome, 10 on antimicrobial activity, and 10 on dentine erosion. In general, the continuous chelation protocol was equally or more effective in the cleanliness of root canals and antimicrobial activity compared with traditional sequential protocol. In addition, etidronate solutions seemed to be milder chelating agents compared to those with EDTA, thus resulting in reduced or no dentine erosion and roughness modification. Yet, the methodological differences among the included studies limit the results' generalizability. The continuous chelation seems to be equally or more effective in all investigated outcomes when compared with the traditional sequential protocol. The methodological variability among the studies and shortcomings in the methods employed limit the generalizability and clinical relevance of the results. Standardized laboratory conditions combined with reliable three-dimensional investigation approaches are necessary to obtain clinically informative findings.

An In Vitro Study: Does Adding Iodine Potassium Iodide and Cetrimide to Calcium Hydroxide Paste Enhance Its Antimicrobial Effect Against Oral Biofilms?

Objectives This study aimed to evaluate the antibiofilm effect of calcium hydroxide (CH), 0.5% iodine potassium iodide (IKI), and 0.5% cetrimide (CTR), alone and in combinations on one-week and three-week-old biofilms. Materials and methods Gingival plaque was collected, and biofilms were grown in vitro anaerobically. Biofilms were exposed to each of the three medicaments and their combinations for one day, one week, and two weeks. Proportions of dead and live bacteria in the biofilms were evaluated. Results The killing of bacteria by different medicaments in the three-week-old biofilm was lower than in the one-week-old biofilm (p<0.05). The efficacy of IKI and CTR in killing bacteria was weaker than that of CH, but the highest efficacy in killing was achieved when all three were combined (p<0.05). There was no significant difference in the antibiofilm effect between a day's exposure to the mixture of the three medicaments and one or two weeks of treatment with CH alone (p>0.05). Conclusions Three-week-old biofilms are more resistant to medicaments than one-week-old biofilms. Combining IKI and CTR with CH resulted in a stronger antibiofilm effect than using CH alone. Mixing the three medicaments may enable obtaining the desired clinical effect in a shorter exposure time.

Periodontal effects of two innovative oral rinsing substances in oncologic patients

Chemotherapy often presents side effects, including oral adverse effects that may interfere with the completion of the oncology treatment, threatening the outcome of the treatment and significantly affecting the quality of life of the patient. The aim of the present study was to evaluate two antiseptic, antimicrobial and antifungal substances that may be used in order to achieve improved oral hygiene and to lower the prevalence of side effects during chemotherapy. Patients were randomly divided into three groups: Placebo, oral rinse with cetrimide and mouth coating with a pharmacy-made compound (nystatin, neomycin and metronidazole). Their oral hygiene and periodontal parameters were determined at baseline and 14 days of use. It was revealed that the most effective clinical results were achieved in the group that used cetrimide mouth rinse that highlighted the best improvements of parameter values, whereas the control and coating-using group did not obtain statistically significant improvements. Cetrimide oral rinse was demonstrated to be an efficient adjunct method in achieving better oral hygiene and improved periodontal parameters in chemotherapy patients. The present study offers an alternative to the commonly used compounds that may present unwanted side effects in patients during chemotherapy, it promotes the importance of good oral hygiene in the prevention of chemotherapy-induced oral adverse effects and improves the quality of life of the patient.

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

AIM

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

METHODOLOGY

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

RESULTS

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

CONCLUSION

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

Disruption and bactericidal indices depicted in polygonal graphs to show multiple outcome effects of root canal irrigant supplements on single- and dual-species biofilms

OBJECTIVES

The aims of this study were to (1) investigate the relative time-dependent disruption and bactericidal effects of detergent-type surfactants on single- or dual-species biofilms of root canal isolates and (2) to examine the utility of polygonal graphs for depiction of biofilm disruption and cell killing.

MATERIALS AND METHODS

Single-species biofilms of Streptococcus sanguinis, Enterococcus faecalis, Fusobacterium nucleatum and Porphyromonas gingivalis were grown on nitro-cellulose membranes for 72 h and immersed in Tween®80, cetyltrimethylammoniumbromide (CTAB), and sodium dodecyl sulphate (SDS) for 1-, 5- or 10-min (n = 3 per test). The number of viable and non-viable bacteria "disrupted" from the biofilm and those "remaining-attached" was determined using a viability stain in conjunction with fluorescence microscopy. The data were analysed using non-parametric Kruskal-Wallis test with 5% significance level.

RESULTS

Gram-negative obligate anaerobes were more susceptible to cell removal than gram-positive facultative anaerobes. The majority of cells were disrupted after 1-min of exposure; however, the extent varied according to the agent and species. CTAB and SDS were more effective than Tween 80™ at disrupting biofilms and killing cells but all agents failed to achieve 100% disruption/kill.

CONCLUSIONS

Biofilm disruption and cell viability were influenced by the species, the test agent and the duration of exposure. CTAB and SDS were more effective in biofilm disruption than Tween 80™. Graphical depiction of biofilm disruption- and viability-outcomes provides an alternative means of simultaneously visualising and analysing relative efficacy in different domains.

CLINICAL RELEVANCE

Surfactants were not as effective at biofilm disruption as NaOCl but may be added to other non-disruptive antibacterial agents to enhance this property.

Influence of surfactants addition on the properties of calcium hypochlorite solutions

Objectives

The aim of this study was to evaluate the influence of surfactants 0.2% or 0.1% cetrimide (Cet) or 0.008% benzalkonium chloride (BAK) on 2.5% calcium hypochlorite (Ca(OCl)₂), and compare to sodium hypochlorite (NaOCl), regarding the properties of pH, free chlorine content, surface tension, contact angle, pulp dissolution and antimicrobial activity.

Material and Methods

The pH and free chlorine content were evaluated by digital pHmeter and by titration, respectively. Surface tension was measured by the platinum ring technique with a Du Noüy tensiometer. The solution's contact angle in human dentin surfaces was checked by Drop Shape Analyzer software. Bovine pulps were used for pulp dissolution analysis and the dissolving capacity was expressed by percent weight loss. Antimicrobial activity over Enterococcus faecalis was evaluated by the agar diffusion method.

Results

Surfactants addition to Ca(OCl)₂ and NaOCl did not alter the pH, free chlorine content and pulp dissolution properties. Ca(OCl)₂ had the highest surface tension among all tested solutions. When surfactants were added to Ca(OCl)₂ and NaOCl, there was a significant reduction of surface tension and contact angle values. The addition of 0.2% or 0.1% Cet enhanced antimicrobial activity of both Ca(OCl)² and NaOCl.

Conclusion

Surfactant addition to 2.5% Ca(OCl)² has shown acceptable outcomes for pH, free chlorine content, surface tension, contact angle, pulp dissolution and antimicrobial activity. Furthermore, the addition of 0.2% Cet showed better results for all tested properties.

Penetration of sodium hypochlorite into root canal dentine: effect of surfactants, gel form and passive ultrasonic irrigation

AIM

To assess the penetration of sodium hypochlorite (NaOCl) gel or NaOCl solutions with surfactants, and the effect of passive ultrasonic irrigation (PUI) on penetration into dentinal tubules.

METHODOLOGY

Bovine incisor root canals were instrumented, the roots sectioned and the dentine blocks obtained were stained with crystal violet. Dentine blocks (n = 10 per group) were exposed to 3% NaOCl gel or 3% NaOCl solution for 10 and 20 min. Other dentine blocks (n = 10 per group) were exposed to Chlor-Extra (6% NaOCl + surfactant), 6% NaOCl, 2.5% NaOCl with 0.2% cetrimide and 2.5% NaOCl for 10 and 20 min. The penetration depth of irrigants into dentinal tubules was measured in micrometres by viewing the bleached crystal violet under a stereomicroscope. Additionally, bovine incisor root canals, instrumented and stained with crystal violet, were distributed into two groups (n = 10) and irrigated with 2.5% NaOCl with PUI or conventional syringe irrigation (CSI). The penetration depth of irrigants into dentinal tubules was assessed 3 and 7 mm from the apex. Statistical analysis was performed by ANOVA and Tukey tests (α = 0.05).

RESULTS

There was significantly greater penetration of 3% NaOCl solution into dentinal tubules compared with the gel form (P < 0.05). There was no difference (P > 0.05) between 6% NaOCl and Chlor-Extra, and between 2.5% NaOCl and 2.5% NaOCl + cetrimide. PUI significantly increased the penetration depth of NaOCl into dentinal tubules when compared with CSI (P < 0.05).

CONCLUSIONS

In extracted bovine incisors, NaOCl gel penetrated less into dentinal tubules than NaOCl solution. The addition of surfactants did not increase the penetration depth. The use of PUI significantly increased NaOCl penetration into dentinal tubules.

The effect of gelatinase production of Enterococcus faecalis on adhesion to dentin after irrigation with various endodontic irrigants

Objectives: The aim of this study was to evaluate whether the gelatinase production ability of Enterococcus faecalis provides any advantage on adhesion of this bacterium to dentin treated with various irrigants and their combinations.

Materials and methods: Standardized dentin discs were randomly divided into five groups (n = 20): group 1: 2.5% sodium hypochlorite (NaOCl), group 2: 2% chlorhexidine (CHX), group 3: NaOCl + Saline + CHX, group 4: NaOCl + EDTA + NaOCl, group 5: QMix. After incubation of dentin discs with irrigants, each group was divided into two subgroups (n = 10) according to the bacterial strains used; a gelatinase-producing and a gelatinase-deficient strain of E. faecalis. After incubation of the discs with the bacterial suspensions aerobically for 48 h, XTT assay was conducted for bacterial adherence evaluation. Data were statistically analyzed by ANOVA and Tukey’s HSD tests (p = .05).

Results: Gelatinase-producing E. faecalis adhered to dentin was significantly more than gelatinase-deficient E. faecalis in all test groups (p < .05). Adherence to CHX-treated dentin was lower than to the surfaces treated with other irrigants, alone or in combination (p < .05). These differences were significant except for comparisons with QMix for gelatinase-producing bacteria (p < .05).

Conclusions: Gelatinase production of E. faecalis may be an important factor for bacterial adhesion. The addition of CHX to the irrigation regimen resulted in fewer adhered bacteria to dentin. QMix was not as effective as CHX in terms of bacterial adhesion prevention.

Evaluation of antimicrobial efficacy of cetrimide and Glycyrrhiza glabra L. extract against Enterococcus faecalis biofilm grown on dentin discs in comparison with NaOCl

This study aimed to determine the antimicrobial efficacy of NaOCl, cetrimide, and Glycyrrhiza glabra L. extract against Enterococcus faecalis biofilms on dentine discs. Broth microdilution method was used to determine minimal bactericidal concentrations (MBCs) of the agents. A biofilm susceptibility assay was performed using E. faecalis biofilms grown on dentine discs. Minimal bactericidal concentrations (MBCs) of NaOCl (0.5%), cetrimide (0.015%), and G. glabra L. extract (0.25%) were applied for 1, 3, and 5 min, and the mean viable cell counts were recorded and statistically analyzed. There was no significant difference between cetrimide and NaOCl at 1 min (p>0.05). NaOCl was the most effective agent at 3 and 5 min (p<0.05) while G. glabra L. extract was the least (p<0.05). The MBCs of NaOCl, cetrimide, and G. glabra that eliminated the planktonic E. faecalis did not eradicate the biofilms grown on dentin discs.

QMix® irrigant reduces lipopolysacharide (LPS) levels in an in vitro model

The presence of endotoxin inside the root canal has been associated with periapical inflammation, bone resorption and symptomatic conditions.Objectives To determine, in vitro, the effect of QMix® and other three root canal irrigants in reducing the endotoxin content in root canals.Material and Methods Root canals of single-rooted teeth were prepared. Samples were detoxified with Co-60 irradiation and inoculated with E. coli LPS (24 h, at 37°C). After that period, samples were divided into 4 groups, according to the irrigation solution tested: QMix®, 17% EDTA, 2% chlorhexidine solution (CHX), and 3% sodium hypochlorite (NaOCl). LPS quantification was determined by Limulus Amebocyte Lysate (LAL) assay. The initial counting of endotoxins for all samples, and the determination of LPS levels in non-contaminated teeth and in contaminated teeth exposed only to non-pyrogenic water, were used as controls.Results QMix® reduced LPS levels, with a median value of 1.11 endotoxins units (EU)/mL (p<0.001). NaOCl (25.50 EU/mL), chlorhexidine (44.10 EU/mL) and positive control group (26.80 EU/mL) samples had similar results. Higher levels were found with EDTA (176.00 EU/mL) when compared to positive control (p<0.001). There was no significant difference among EDTA, NaOCl and CHX groups. Negative control group (0.005 EU/mL) had statistically significant lower levels of endotoxins when compared to all test groups (p<0.001).Conclusion QMix® decreased LPS levels when compared to the other groups (p<0.001). 3% NaOCl, 2% CHX and 17% EDTA were not able to significantly reduce the root canal endotoxins load.

Confocal microscopy evaluation of the effect of irrigants on Enterococcus faecalis biofilm: An in vitro study

The purpose of this study was to evaluate in vitro the effectiveness of two endodontic irrigants and their association against Enterococcus faecalis (E. faecalis) by confocal laser scanning microscope (CLSM). Twenty-four bovine incisors were inoculated in a monoculture of E. faecalis for 21 days. After this period, the teeth were divided into three test groups (n = 5) according to the chemical used. Group 1: 2.5% sodium hypochlorite (NaOCl), group 2: 2% chlorhexidine gel (CHX), group 3: 2.5% NaOCl + 2% CHX gel, and two control groups (n = 3): negative control group (NCG)-sterile and without root canals preparation and positive control group (PCG)-saline. Then, the samples were stained with SYTO9 and propidium iodide and subjected to analysis by CLSM. Bacterial viability was quantitatively analyzed by the proportions of dead and live bacteria in the biofilm remnants. Statistical analysis was performed by the One-way ANOVA test (p = 0.05). No statistical differences were observed to bacterial viability. According to CLSM analysis, none of the tested substances could completely eliminate E. faecalis from the root canal space. Until now, there are no irrigant solutions able to completely eliminate E. faecalis from the root canal. In this regard, the search for irrigants able to intensify the antimicrobial action is of paramount importance.

Antimicrobial efficacy of photodynamic therapy, Nd:YAG laser and QMiX solution against Enterococcus faecalis biofilm

BACKGROUND

Lasers have been recommended in final root canal disinfection protocol, however, there is no clear evidence about their efficacy against bacteria in biofilms. The aim of the study was to evaluate and compare the disinfection effect of antimicrobial photodynamic therapy (aPDT), Nd:YAG laser and QMiX solution against Enterococcus faecalis biofilm.

METHODS

The study sample consisted of 65 dentine slices, which were inoculated with E. faecalis and incubated anaerobically for three weeks. The dentine discs were randomly allocated to one of the following experimental groups: aPDT (100 mW, 10 mg/ml phenothiazinium chloride, 1 min), Nd:YAG laser (2 W, 15 Hz, 4×5 s), QMiX solution (1 min). Positive controls did not receive any treatment and negative controls were treated with 5.25% NaOCl. To harvest surviving adherent cells, each dentine sample was transffered to a test tube containing of TSB, serial ten-fold dilutions were made and aliquot of 1 ml was plated onto blood agar plates and incubated for 48 h. Colony forming units grown were counted and transformed into actual counts based on the dilution factor. The remaining viable cells after each protocol were analysed by FISH.

RESULTS

The aPDT and the QMiX solution were equally effective, with the reduction rate of E. faecalis CFUs of 98.8% and 99.3% respectively (p=1.107). The Nd:YAG laser caused 96% reduction of E. faecalis (P<0.001).

CONCLUSION

The aPDT and the QMiX solution showed similar antibacterial efficacy against old E. faecalis biofilm, followed by Nd:YAG irradiation.

Atomic force microscopy visualization of injuries in Enterococcus faecalis surface caused by Er,Cr:YSGG and diode lasers

Aim: To visualize by Atomic Force Microscopy the alterations induced on Enterococcus. faecalis surface after treatment with 2 types of laser: Erbium chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser and Diode laser. Material and Methods: Bacterial suspensions from overnight cultures of E. faecalis were irradiated during 30 seconds with the laser-lights at 1 W and 2 W of power, leaving one untreated sample as control. Surface alterations on treated E. faecalis were visualized by Atomic Force Microscopy (AFM) and its surface roughness determined. Results: AFM imaging showed that at high potency of laser both cell morphology and surface roughness resulted altered, and that several cell lysis signs were easily visualized. Surface roughness clearly increase after the treatment with Er,Cr:YSGG at 2W of power, while the other treatments gave similar values of surface roughness. The effect of lasers on bacterial surfaces visualized by AFM revealed drastic alterations. Conclusions: AFM is a good tool to evaluate surface injuries after laser treatment; and could constitute a measure of antimicrobial effect that can complete data obtained by determination of microbial viability.

Key words:Atomic force microscopy, Er,Cr:YSGG laser, diode laser, Enterococcus faecalis, surface roughness.