Antimicrobial Susceptibility of Monoculture Biofilms of a Clinical Isolate of Enterococcus faecalis

A Comparative Evaluation of Contact Angle and Depth of Penetration of Sodium Hypochlorite With Various Surfactants: An In Vitro Study

OBJECTIVE

Sodium hypochlorite (NaOCl) is regarded as the most frequently used root canal irrigant. Its high surface tension prevents its penetration into complex canal anatomies. The present study assesses the contact angle and penetration depth of 2.5% NaOCl with 0.2% cetrimide and propylene glycol.

MATERIAL AND METHODS

Sixty recently extracted mandibular premolars with a single root were obtained. Thirty were sectioned longitudinally, and the remaining 30 teeth were sectioned transversely. Acrylic blocks were used to mount the parts, and 5 µL of each of the following solutions was placed on the dentin surface: Group 1: 2.5% NaOCl (control), Group 2: 0.2% cetrimide + 2.5% NaOCl, and Group 3: propylene glycol + 2.5% NaOCl. Following this, contact angle analysis was made using a contact angle goniometer. We prepared and instrumented access cavities in 30 teeth to work up to the size of the ProTaper Gold F2 (Dentsply Tulsa Dental Specialties, Tulsa, OK). Samples were allocated to the three groups, and irrigation was done accordingly. They were sectioned at the coronal, middle, and apical thirds and then subjected to confocal laser scanning microscopy. The data were analyzed using a one-way ANOVA and a Tukey multiple comparison test.

RESULTS

Group 2 had the least contact angle (35.20°) and the highest depth of penetration (DOP; 752.409 µm) when compared to Groups 1 and 3. The DOP decreased significantly from the coronal, middle, and apical thirds. No discernible variation in the contact angle was found between the radicular and coronal portions.

CONCLUSION

0.2% cetrimide improved the efficiency of 2.5% NaOCl as an irrigant by lowering its contact angle and increasing its DOP.

Traditional and Recent Root Canal Irrigation Methods and Their Effectiveness: A Review

According to contemporary dental standards, the primary goal of endodontic therapy is the chemo-mechanical cleaning of the complex root canal system. Watering root canals with approved solutions and activating them are essential parts of this operation. This review outlines various irrigant activation methods for root canal therapy. Specifically, a comparison among the methods of manual dynamic activation, sonics (subsonic, sonic, and ultrasonic), internal heating, and lasers, was conducted. The results in this work were gathered using Scopus, Web of Science, Google Scholar, and PubMed databases by searching the following keywords: sodium hypochlorite, cleaning, activation, and irrigation methods. The present work concluded that the use of irrigant activation has a greater benefit than its absence. Regardless, it is impossible to point to a single effective activation method.

Evaluating the Efficacy of Certain Intermediate Irrigants in Preventing Precipitate Formed Due to Sodium Hypochlorite and Chlorhexidine Within the Root Canal System: An In Vitro Study

AIM

Root canal irrigation using a mixture of sodium hypochlorite (NaOCL) and chlorhexidine gluconate (CHX) might cause a precipitate to develop. This study aims to check the efficacy of sodium thiosulfate and normal saline as irrigating solutions.

MATERIALS AND METHODS

Roots of 45 teeth were biomechanically prepared, and the teeth were then tested. A size 15k file was introduced to the point where the apical foramen could be visible in order to provide an accurate reading of the working length. As a precaution against irrigating solutions leaking out, the specimens' tips were sealed with modeling wax before being instrumented. Each group's root canals were instrumented with #F4 hand Protaper (Dentsply Sirona, USA) as recommended by the manufacturer. Between instrumentation, The canals were lubricated with ethylenediamine tetraacetic acid (EDTA) and irrigated with 2.5% sodium hypochlorite (RC Help, Prime Dental, Mumbai, India). Fifteen samples were randomly assigned to one of three experimental categories based on the middle watering arrangement used: Group 1 (control), Group 2 (saline irrigant), and Group 3 (3.86% sodium thiosulfate). The jewel plate was submerged in water to cool it down, while two longitudinal scores were made on the root's buccal and lingual surfaces. We used a stereomicroscope to examine the exposed surfaces of the root trench in the coronal, middle, and apical thirds for the orange-earthy colored material (Stereozoom Nikon magnifying lens under 20X amplification), and we used the Mann-Whitney U test and the Kruskal Wallis test during our thorough analysis.

RESULTS

The precipitation generated in the coronal, middle, and apical thirds had significantly different thicknesses. While precipitation did occur in all three regions, it was at a much lower rate in the apical third compared to the coronal and middle regions. In Group 1, the control group, the precipitate was thicker than in Groups 2 (saline irrigant) and 3 (3.86% sodium thiosulfate).

CONCLUSION

Sodium thiosulfate, which is a biocompatible solution, can be used as an intermediate irrigant as it shows less precipitate as compared to saline.

Biofilm elimination from infected root canals using four different single files

INTRODUCTION

Enterococcus faecalis (E. faecalis) is the most commonly isolated bacterium from infected root canals. It is found in the form of a biofilm, which makes it more resistant to antimicrobials, and requires optimal chemomechanical strategies to maximize root canal disinfection.

AIM

To evaluate the efficacy of 4 different endodontic file systems against E. faecalis biofilm growth in root canals using colony-forming units per milliliter (CFU/mL) and scanning electron microscope (SEM).

METHODS

Eighty-five extracted human mandibular premolars with straight root canals and apical diameters not larger than the #15 K-file were randomly selected. After performing a pilot study (n = 15) to determine the ideal incubation period for E. faecalis biofilm development, sixty-five root canals were infected with E. faecalis, incubated for 3 weeks, and then mechanically prepared using one of four single files (XP-endo Shaper, Hyflex EDM, One Curve, and Fanta. AFTM F One) (n = 15). Five infected root canals were excluded for the positive control. Five non-contaminated root canals were included for the negative control. Samples were collected using sterile paper points pre- and post-instrumentation to determine the bacterial load (CFU/mL). Root canals from each group were topographically evaluated at the coronal, middle, and apical segments using scanning electron microscope (SEM). Bacterial reduction data were estimated and statistically analyzed by Kruskal-Wallis and Mann-Whitney U tests (post hoc test) (P ≤ .05).

RESULTS

XP-endo Shaper, Hyflex DEM, and One Curve significantly could eradicate E. faecalis biofilms in infected root canals with no significant difference among them compared to Fanta. AF™ F One.

CONCLUSION

None of the systems were capable of completely eliminating biofilms. XP-endo Shaper, Hyflex EDM, and One Curve mechanically eliminated E. faecalis biofilms compared to Fanta. AF™ F One from infected root canals.

Current Trends in Irrigation Solution and Adjunct Use During Endodontic Therapy Among Dental Professionals in Jeddah, Saudi Arabia: A Cross-Sectional Study

Introduction  Chemical irrigation is a crucial component of endodontic therapy, and irrigation adjuncts increase the efficiency of non-surgical root canal system disinfection, reduce microbial loads, and enhance the penetration of irrigants throughout the root canal system. This study aimed to determine the current trends in chemical irrigation and its adjunct use during root canal therapy by general dental practitioners (GDPs) and endodontic specialists in both government and private sectors in the city of Jeddah, Saudi Arabia. Methods This cross-sectional study used a self-administered survey sent to GDPs and endodontic specialists in both government and private sectors in the city of Jeddah, Saudi Arabia. Responses were accepted from November 2019 till May 2020. The survey was randomly distributed to consenting participants. The results are presented using descriptive statistics. Results A total of 302 participants responded to the survey, with a 44% response rate. The majority of responses were from GDPs (54%), while 46% were from endodontic specialists. Regarding the workplace, 59% of respondents were public sector professionals, 25% were private sector professionals, and 16% were both public and private sector professionals. Around 30% of the respondents used sodium hypochlorite (NaOCI) as their primary irrigation solution during root canal treatment, with 52% using it at its full-strength concentration and 18% and 17% preferring to use it in combination with Ethylenediaminetetraacetic acid (EDTA) only or EDTA and saline, respectively. When asked to rank the reasons for choosing their irrigant of choice during therapy; antibacterial capability and tissue dissolution were the most crucial factors to 80% and 57% of participants, respectively. Half of the respondents irrigated the canal to 2 mm from the apex and 21% irrigated to 1 mm from the apex. Three-quarters of participants aimed to remove the smear layer during root canal treatment. Only 47% of respondents used adjuncts to irrigation, and 71% reported that their choice of irrigation solution would differ depending on whether the apex is open or closed. Conclusion Most respondents used full-strength NaOCI concentration as the main irrigation solution and routinely removed the smear layer during root canal treatment. Only 47% of respondents used irrigation adjuncts such as ultrasonics.

Antibacterial Efficacy of the Grape Seed Extract as an Irrigant for Root Canal Preparation

Objective:

The purpose of this research was to compare relative effectiveness of sodium hypochlorite 5.25% (NaOCl), 2% chlorhexidine gel (CHX) and 6.5 % grape seed extract (GSE) against Enterococcus faecalis using instrument Reciproc R25 in root canal preparation.

Methods:

Forty-five mesiobuccal root canals from extracted human maxillary molars were collected and infected with Enterococcus faecalis. The samples were divided into five groups according to the different types of irrigants: saline (positive control) (n=5); in the other groups were used 10 root canals for each group: NaOCl+EDTA; CHX gel+EDTA; GSE solution+EDTA; GSE gel+EDTA. All the groups were prepared with reciprocating instruments Reciproc R25. Bacterial reduction was measured by two-way ANOVA (P<0.001) followed by Tukey HSD post-hoc tests, from the counting of colony forming units (CFUs) from samples collected before instrumentation and after. The significance level established at 5% (P<0.05).

Results:

The group prepared with the NaOCl resulted in highest antimicrobial capacity among of all (P>0.05), followed by CHX and GSE gel (P<0.05). Control and GSE solution showed similar results (P<0.05) and resulted in the lowest percentage of the reduction of the microorganism into the root canals.

Conclusion:

NaOCl had the higher elimination capacity of Enterococcus faecalis than GSE and CHX.

Effects of Endodontic Irrigants on Material and Surface Properties of Biocompatible Thermoplastics

Passive irrigation is an efficient method for a successful endodontic treatment. During sonic activation biocompatible polymer tips are used to activate irrigants. Compared to ultrasonic activation with metallic tips, polymer tips have the advantage of a reduced risk of fracture and minimise dentine damage. Hence, two polymers, polyether ether ketones (PEEK) and polyamide (PA6), were identified for the manufacturing of novel irrigation tips. The chemical resistance against the irrigants ethylenediaminetetraacetic acid (EDTA) 20%, chlorhexidine gluconate (CHX) 2% and sodium hypochlorite (NaOCl) 5.25% was analysed. Using microindentation, the change of hardness, elasticity, surface roughness and appearance of the polymers was determined. PA6 had a high absorption of irrigant compared to PEEK. PEEK was resistant to the investigated irrigants and showed no significant alteration of surface and mechanical properties, whereas PA6 slightly increased its hardness, elastic modulus and surface roughness during long-term exposure at 37 °C. However, PA6 tips seem to be a promising disposable product due to the material’s high deformability and low manufacturing costs. Particularly with regard to structural-dynamic properties and high chemical resistance, PEEK can be considered as a material for reusable irrigation tips.

A Review Over Benefits and Drawbacks of Combining Sodium Hypochlorite with Other Endodontic Materials

INTRODUCTION

As the root canal system considered to be complex and unpredictable, using root canal irrigants and medicaments are essential in order to enhance the disinfection of the canal. Sodium hypochlorite is the most common irrigant in endodontics. Despite its excellent antimicrobial activity and tissue solubility, sodium hypochlorite lacks some important properties such as substantivity and smear layer removing ability.

OBJECTIVE

The aim of this review was to address benefits and drawbacks of combining sodium hypochlorite with other root canal irrigants and medicaments.

DISCUSSION

According to the reviewed articles, NaOCl is the most common irrigation solution in endodontics. However, it has some drawbacks such as inability to remove smear layer. One of the drawbacks of NaOCl is its inability to remove the smear layer and lack of substantivity.

CONCLUSION

The adjunctive use of other materials has been suggested to improve NaOCl efficacy. Nevertheless, further studies are required in this field.

Bactericidal Effect of Different Anti-Microbial Agents on Fusobacterium Nucleatum Biofilm

INTRODUCTION

The root canal anatomy of the teeth is very complex. Complete debridement of the root canals is a challenge and is very important for the success of the root canal treatment. Hence, this study was done to find an effective irrigant which can be used during root canal treatment.

OBJECTIVE

The bactericidal effect of a potential root canal irrigant was compared with two commonly used root canal irrigants against monoculture biofilm of a commercially available isolate of Fusobacterium nucleatum.

METHODS

A monoculture biofilm of Fusobacterium nucleatum was grown on glass slides. The glass slides containing the biofilm were immersed in centrifuge tubes containing 5% sodium hypochlorite, 2% Chlorhexidine, 6% turmeric solution, 9% turmeric solution and distilled water for a time span of one minute. A wire loop was used to scrape off the biofilms onto sterile brain heart infusion agar plates. This was further subjected to an incubation period of 96 hours at 37° C. Colony forming units were quantified by statistical analysis and results were obtained.

RESULTS

The anti-bacterial activity of 6% and 9% turmeric solution was statistically significant against Fusobacterium nucleatum when compared to 2% Chlorhexidine and 5% sodium hypochlorite.

CONCLUSION

In endodontic treatment, turmeric solution may be considered as an effective irrigant.

Confocal laser scanning, scanning electron, and transmission electron microscopy investigation of Enterococcus faecalis biofilm degradation using passive and active sodium hypochlorite irrigation within a simulated root canal model

Root canal irrigation is an important adjunct to control microbial infection. The aim of this study was to investigate the effect of 2.5% (wt/vol) sodium hypochlorite (NaOCl) agitation on the removal, killing, and degradation of Enterococcus faecalis biofilm. A total of 45 root canal models were manufactured using 3D printing with each model comprising an 18 mm length simulated root canal of apical size 30 and taper 0.06. E. faecalis biofilms were grown on the apical 3 mm of the models for 10 days. A total of 60 s of 9 ml of 2.5% NaOCl irrigation using syringe and needle was performed, the irrigant was either left stagnant in the canal or agitated using manual (Gutta-percha), sonic, and ultrasonic methods for 30 s. Following irrigation, the residual biofilms were observed using confocal laser scanning, scanning electron, and transmission electron microscopy. The data were analyzed using one-way ANOVA with Dunnett post hoc tests at a level of significance p ≤ .05. Consequence of root canal irrigation indicate that the reduction in the amount of biofilm achieved with the active irrigation groups (manual, sonic, and ultrasonic) was significantly greater when compared with the passive and untreated groups (p < .05). Collectively, finding indicate that passive irrigation exhibited more residual biofilm on the model surface than irrigant agitated by manual or automated (sonic, ultrasonic) methods. Total biofilm degradation and nonviable cells were associated with the ultrasonic group.

Cleaning Effectiveness of a Reciprocating Single-file and a Conventional Rotary Instrumentation System

Objective:

To compare cleaning effectiveness by histological analysis of a reciprocating single-file system with ProTaper rotary instruments during the preparation of curved root canals in extracted teeth.

Methods:

A total of 40 root canals with curvatures ranging between 20 - 40 degrees were divided into two groups of 20 canals. Canals were prepared to the following apical sizes: Reciproc size 25 (n=20); ProTaper: F2 (n=20). The normal distribution of data was tested by the Kolmogorov-Smirnov test and the values obtained for the test (Mann-Whitney U test, P < .05) were statistically analyzed using the GraphPad InStat for the Mac OS software (GraphPad Software, La Jolla, CA, USA).

Results:

There were no significant differences in remaining debris (P > .05) between the two groups.

Conclusion:

The application of reciprocating motion during instrumentation did not result in increased debris when compared with continuous rotation motion, even in the apical part of curved canals. Both instruments resulted in debris in the canal lumen, irrespective of the movement kinematics applied.

Root Canal Irrigation: Chemical Agents and Plant Extracts Against Enterococcus faecalis

BACKGROUND

There are various microorganisms related to intra and extra-radicular infections and many of these are involved in persistent infections. Bacterial elimination from the root canal is achieved by means of the mechanical action of instruments and irrigation as well as the antibacterial effects of the irrigating solutions. Enterococcus faecalis can frequently be isolated from root canals in cases of failed root canal treatments. Antimicrobial agents have often been developed and optimized for their activity against endodontic bacteria. An ideal root canal irrigant should be biocompatible, because of its close contact with the periodontal tissues during endodontic treatment. Sodium hypoclorite (NaOCl) is one of the most widely recommended and used endodontic irrigants but it is highly toxic to periapical tissues.

OBJECTIVES

To analyze the literature on the chemotherapeutic agent and plant extracts studied as root canal irrigants. In particularly, the study is focused on their effect on Enterococcus faecalis.

METHOD

Literature search was performed electronically in PubMed (PubMed Central, MEDLINE) for articles published in English from 1982 to April 2015. The searched keywords were "endodontic irrigants" and "Enterococcus faecalis" and "essential oil" and "plant extracts".

RESULTS

Many of the studied chemotherapeutic agents and plant extracts have shown promising results in vitro.

CONCLUSION

Some of the considered phytotherapic substances, could be a potential alternative to NaOCl for the biomechanical treatment of the endodontic space.

Antimicrobial efficacy of chlorhexidine as a root canal irrigant: a literature review

Use of an appropriate root canal irrigant is essential during endodontic treatment, due to the complex and unpredictable anatomy of the root canal system and limitations in the mechanical instrumentation techniques used to obtain a clean, bacteria-free canal. Several irrigants, such as sodium hypochlorite, chlorhexidine, hydrogen peroxide, and normal saline, have been proposed as canal system irrigants in endodontic treatment. The widely used endodontic irrigant chlorhexidine is a positively charged lipophilic/hydrophobic molecule that interacts with phospholipids and lipopolysaccharides on the bacterial cell membrane. In endodontics, its mode of antibacterial activity is determined by its concentration (0.2% or 2%). This article reviews findings from available endodontic studies on the antibacterial, antifungal, and antibiofilm activities of chlorhexidine.

Penetration of Sodium Hypochlorite Modified with Surfactants into Root Canal Dentin

Abstract The aim of this study was to evaluate the effect of concentration, exposure time and temperature of sodium hypochlorite (NaOCl) added with surfactants on its penetration into dentinal tubules. Sixty-five extracted human permanent maxillary anterior teeth with single canals were prepared by ProTaper SX hand-operated instruments. The teeth were then sectioned perpendicular to the long axis. The crowns and apical thirds of all the teeth were removed. The remaining roots were processed into 4-mm-long blocks and stained overnight in crystal violet. One hundred and thirty stained blocks were further split into halves and treated by nine different types of NaOCl-based solutions. Three solutions were added with surfactants (Hypoclean, H6, Chlor-Xtra) and the others were regular hypochlorites at increasing concentrations (1%, 2%, 4%, 5.25%, <6%, 6% NaOCl) from different brands. The dentin blocks were exposed to the solutions for 2, 5, and 20 min at 20 °C, 37 °C and 45 °C, respectively. The depth of NaOCl penetration was determined by bleaching of the stain and measured by light microscopy at 20 and 40. Statistical comparisons were made by using a generalized linear model with Bonferroni's post-hoc correction. The shortest penetration (81±6.6 μm) was obtained after incubation in 1% NaOCl for 2 min at 20 °C; the highest penetration (376.3±3.8 μm) was obtained with Chlor-Xtra for 20 min at 45 °C. Varying NaOCl concentration produced a minimal effect while temperature and exposure time had a significant direct relationship with NaOCl penetration into dentinal tubules, especially those with lowered surface tension. The exposure time and temperature of sodium hypochlorite as well as the addition of surfactants may influence the penetration depth of irrigants into dentinal tubules.

Comparison of Different Irrigants in the Removal of Endotoxins and Cultivable Microorganisms from Infected Root Canals

This study was conducted to compare the effectiveness of different irrigants used to remove endotoxins and cultivable microorganisms during endodontic therapy. Forty root canals were contaminated and divided into groups according to the irrigant: 2% NaOCl + surfactant, 2% CHX, 2.5% NaOCl, and pyrogen-free saline solution (control). Samples were collected after root canal contamination (S1), after instrumentation (S2), and 7 days after instrumentation (S3). Microorganisms and endotoxins were recovered from 100% of the contaminated root canals (S1). At S2, 2% NaOCl + surfactant, 2% CHX, and 2.5% NaOCl were able to completely eliminate cultivable microorganisms. At S3, both 2% CHX and 2.5% NaOCl were effective in preventing C. albicans and E. coli regrowth, but E. faecalis was still detected. No microorganism species was recovered from root canals instrumented with 2% NaOCl + surfactant. At S2, a higher percentage value of endotoxin reduction was found for 2% NaOCl + surfactant (99.3%) compared to 2% CHX (98.9%) and 2.5% NaOCl (97.18%) (p < 0.05). Moreover, at S3, 2% NaOCl + surfactant (100%) was the most effective irrigant against endotoxins. All irrigants tested were effective in reducing microorganisms and endotoxins from root canals. Moreover, 2% NaOCl + surfactant was the most effective irrigant against endotoxins and regrowth of microorganisms.

Antibacterial and residual antimicrobial activities against Enterococcus faecalis biofilm: A comparison between EDTA, chlorhexidine, cetrimide, MTAD and QMix

We compared the antibacterial and residual antimicrobial activities of five root canal irrigants (17% EDTA,2% chlorhexidine,0.2% cetrimide, MTAD, and QMix) in a model of Enterococcus faecalis biofilm formation. Sixty dentin blocks with 3-week E. faecalis biofilm were divided into six equal groups and flushed with irrigant for 2 min or left untreated. A blank control group was also established. Antibacterial activities of the irrigants were evaluated by counting colony forming units. To test residual antimicrobial activities, 280 dentin blocks were divided into seven equal groups and flushed with irrigant for 2 min or left untreated and then incubated with E. faecalis suspension for 48 h, or used as a blank. No bacteria were observed in the blank control group. The number of viable E. faecalis was significantly fewer in the irrigant-treated groups compared with the untreated control (P < 0.05). Among the five irrigants, QMix had the strongest antibacterial activity. Residual antimicrobial activities of CHX were significantly higher at 12 h, 24 h and 36 h compared to untreated control (P < 0.05). All five root canal irrigants were effective to some extent against E. faecalis, but QMix and CHX had the strongest, and CHX the longest (up to 36 h), antimicrobial activity.

Chemical composition of Enterococcus faecalis in biofilm cells initiated from different physiologic states

Enterococcus faecalis is a ubiquitous bacterium of the gut that is observed in persistent periradicular infections. Its pathogenicity is associated with biofilm formation and the ability to survive under nutrient-poor (starvation) conditions. However, characteristics of chemical composition of biofilm cells developed by starved E. faecalis cells remain poorly understood. In this study, E. faecalis cells in exponential, stationary, and starvation phases were prepared and separately cultured to form biofilms. Confocal laser scanning microscopy was performed to verify biofilm formation. Raman microscopy was used to investigate the chemical composition of cells within the biofilms. Compared to cells in exponential or stationary phase, starved cells developed biofilms with fewer culturable cells (P < 0.05). Raman analysis revealed that cells produced in the biofilms from starved planktonic cells contained more protein and less nucleic acids than either the corresponding planktonic cells or the cells in biofilms from planktonic cells in exponential or stationary phases, suggesting that biofilm-grown cells from the starvation phase were characterized by increased synthesis of proteins and decreased nucleic acids. This study provides an insight into the chemical composition of biofilm cells developed by starved E. faecalis.

Effect of culture media and nutrients on biofilm growth kinetics of laboratory and clinical strains of Enterococcus faecalis

OBJECTIVE

Enterococcus faecalis is a bacterial pathogen that is often associated with endodontic infections. Biofilm formation is a key virulence attribute in the pathogenicity of E. faecalis. In the present study, we comprehensively examined the effect of various culture media and nutrients on the development of E. faecalis biofilms.

DESIGN

A reference strain and a clinical isolate of E. faecalis were used in all experiments for comparison. Commonly used liquid culture media with different nutrient compositions were used to support the development of E. faecalis biofilms in a time-dependent assay. E. faecalis biofilms were quantified by colony forming unit (CFU) and crystal violet (CV) assays. Biofilm architecture and cellular viability were evaluated by scanning electron microscopy and confocal laser scanning microscopy.

RESULTS

Growth kinetics evaluated by CFU and CV assays and by microscopy showed that E. faecalis biofilms reached maturity at 72h. "Pg broth" (Tryptic Soy Broth with yeast extract, hemen and vitamin K) promoted E. faecalis biofilm formation more than Brain Heart Infusion broth or Tryptic Soy Broth. Addition of 2% glucose enhanced biofilm formation. Thus, it seems that nutrients such as hemen, vitamin K and glucose are important for E. faecalis for the formation of biofilms.

CONCLUSION

The present study demonstrated that nutrient-rich media containing glucose enhances the formation of E. faecalis biofilms, which exhibit maturation at 72h.

The antibacterial activity of sodium hypochlorite and chlorhexidine against Enterococcus faecalis: A review on agar diffusion and direct contact methods

Complete debridement and disinfection of the root canal system are fundamental requirements for successful endodontic treatment. Despite the morphological challenges of the internal root anatomy, root canal irrigants play an important role in the optimization of the root canal preparation, which is essentially a chemo-mechanical procedure. Enterococcus faecalis is one of the most resistant microorganisms that dominants the microbial ecosystem of persistent periradicular lesions in retreatment cases. For that reason, many in vitro and in vivo studies evaluated and compared the antibacterial activity of sodium hypochlorite and chlorhexidine at varying concentrations using different experimental models against this microorganism. However, many controversies with regard to the ideal irrigant and concentration do in fact exist. Hence, this review aims to discuss the antibacterial activity of these two main root canal irrigants against Enterococcus faecalis using the agar diffusion and direct contact methods and the possible modulating factors responsible for inconsistent findings among different studies. In addition, the disinfection potential of both chemical agents on gutta percha and Resilon cones are also discussed. The source of this review was conducted through an electronic literature search using PubMed database from December 1997 until December 2011, which analyze the related laboratory investigations of both irrigants, published in major endodontic journals.

A comparative study of biofilm removal with hand, rotary nickel-titanium, and self-adjusting file instrumentation using a novel in vitro biofilm model

INTRODUCTION

This study sought to present a standardized biofilm model in extracted teeth with an artificial apical groove to quantify the efficacy of hand, rotary nickel-titanium, and self-adjusting file (SAF) instrumentation in biofilm bacteria removal.

METHODS

Thirty-six extracted single-rooted teeth with oblong canals were selected. Each tooth was split longitudinally, and a 0.2-mm-wide groove was placed in the apical 2 to 5 mm of the canal. After growing mixed bacteria biofilm inside the canal under an anaerobic condition, the split halves were reassembled in a custom block, creating an apical vapor lock. Teeth were randomly divided into 3 treatment groups (n = 10 per group) using the K-file, ProFile (Dentsply Tulsa Dental Products, Tulsa, OK), and the SAF (ReDent-Nova, Ra'anana, Israel). Irrigation consisted of 10 mL 3% NaOCl and 4 mL 17% EDTA. Six teeth received no treatment. Areas inside and outside the groove were examined using a scanning electron microscope.

RESULTS

The scanning electron microscope showed a consistently thick layer of biofilm grown in the canals of the control group after 4 weeks. Within the groove, a smaller area remained occupied by bacteria after the use of the SAF compared with the ProFile and the K-file (3.25%, 19.25%, and 26.98%, respectively; P < .05). For all groups, significantly more bacteria were removed outside the groove than inside (P < .05). No statistical differences were found outside the groove (P > .05).

CONCLUSIONS

Although all techniques equally removed bacteria outside the groove, the SAF reduced significantly more bacteria within the apical groove. No technique was able to remove all bacteria. This biofilm model represents a potentially useful tool for the future study of root canal disinfection.

Residual and antimicrobial activity of final irrigation protocols on Enterococcus faecalis biofilm in dentin

INTRODUCTION

The use of root canal irrigating solutions exerting antimicrobial activity and prolonged residual activity is desirable in order to control dentin infection and delay reinfection of the root canal. The aim of this study was to evaluate the residual antimicrobial activity and the capacity to eradicate Enterococcus faecalis biofilm of different irrigating solutions, alone and in combination, in a dentin-volumetric test.

METHODS

Solutions of 2.5% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), 0.2% cetrimide (CTR), 17% ethylendiaminetetraacetic (EDTA), 7% maleic acid (MA), and regimens of 2.5% NaOCl followed by 17% EDTA or 7% MA and 0.2% CTR or 2% CHX were used to determine their residual activity by exposing treated dentin blocks to E. faecalis for 24 hours. Antimicrobial activity was assayed on 3-week biofilm formed on dentin blocks. Results of residual activity and antimicrobial activity were respectively expressed as the inhibition percentage of biofilm formation and the kill percentage of biofilm.

RESULTS

A 2% CHX and 0.2% CTR solution showed 100% biofilm inhibition; 2.5% NaOCl showed the lowest residual activity (18.10%). The kill percentage of 2.5% NaOCl and 0.2% CTR was 100% followed by 7% MA and 2% CHX, whereas 17% EDTA was the least effective (44%). Solutions of 7% MA or 17% EDTA followed by 0.2% CTR or 2% CHX showed 100% residual and antimicrobial activity.

CONCLUSIONS

A 0.2% CTR solution alone and the combinations in which 2% CHX or 0.2% CTR was the final irrigating solution achieved the maximum residual and antimicrobial activity.

A selenium-dependent xanthine dehydrogenase triggers biofilm proliferation in Enterococcus faecalis through oxidant production

Selenium has been shown to be present as a labile cofactor in a small class of molybdenum hydroxylase enzymes in several species of clostridia that specialize in the fermentation of purines and pyrimidines. This labile cofactor is poorly understood, yet recent bioinformatic studies have suggested that Enterococcus faecalis could serve as a model system to better understand the way in which this enzyme cofactor is built and the role of these metalloenzymes in the physiology of the organism. An mRNA that encodes a predicted selenium-dependent molybdenum hydroxylase (SDMH) has also been shown to be specifically increased during the transition from planktonic growth to biofilm growth. Based on these studies, we examined whether this organism produces an SDMH and probed whether selenoproteins may play a role in biofilm physiology. We observed a substantial increase in biofilm density upon the addition of uric acid to cells grown in a defined culture medium, but only when molybdate (Mo) and selenite (Se) were also added. We also observed a significant increase in biofilm density in cells cultured in tryptic soy broth with 1% glucose (TSBG) when selenite was added. In-frame deletion of selD, which encodes selenophosphate synthetase, also blocked biofilm formation that occurred upon addition of selenium. Moreover, mutation in the gene encoding the molybdoenzyme (xdh) prevented the induction of biofilm proliferation upon supplementation with selenium. Tungstate or auranofin addition also blocked this enhanced biofilm density, likely through inhibition of molybdenum or selenium cofactor synthesis. A large protein complex labeled with (75)Se is present in higher concentrations in biofilms than in planktonic cells, and the same complex is formed in TSBG. Xanthine dehydrogenase activity correlates with the presence of this labile selenoprotein complex and is absent in a selD or an xdh mutant. Enhanced biofilm density correlates strongly with higher levels of extracellular peroxide, which is produced upon the addition of selenite to TSBG. Peroxide levels are not increased in either the selD or the xdh mutant upon addition of selenite. Extracellular superoxide production, a phenomenon well established to be linked to clinical isolates, is abolished in both mutant strains. Taken together, these data provide evidence that an SDMH is involved in biofilm formation in Enterococcus faecalis, contributing to oxidant production either directly or alternatively through its involvement in redox-dependent processes linked to oxidant production.

Irrigation in endodontics

The success of endodontic treatment depends on the eradication of microbes from the root-canal system and prevention of reinfection. The root canal is shaped with hand and rotary instruments under constant irrigation to remove the inflamed and necrotic tissue, microbes/biofilms, and other debris from the root-canal space. Irrigants have traditionally been delivered into the root-canal space using syringes and metal needles of different size and tip design. Clinical experience and research have shown, however, that this classic approach typically results in ineffective irrigation. Many of the compounds used for irrigation have been chemically modified and several mechanical devices have been developed to improve the penetration and effectiveness of irrigation. This article summarizes the chemistry, biology, and procedures for safe and efficient irrigation and provides cutting-edge information on the most recent developments.

Enterococcus faecalis biofilms eradication by root canal irrigants

The aim of this study was to evaluate the minimal biofilm eradication concentration (MBEC) of sodium hypochlorite (NaOCl), chlorhexidine (CHX), EDTA, and citric and phosphoric acids after 1, 5, and 10 minutes of exposure to biofilms of Enterococcus faecalis. The biofilms grew in the MBEC high-throughput device for 24 hours at 37 degrees C and were exposed to 10 serial two-fold dilutions of each irrigating solution. The viable cell counts were log(10) transformed, and a concentration of an irrigant was considered to eradicate the biofilms when it produced a reduction of > or = 5 logarithmic units. NaOCl was the most effective agent, capable of eradicating the biofilms after 1 minute at a concentration of 0.00625%. CHX eradicated biofilm after 5 minutes at 2%. EDTA and citric and phosphoric acid solutions were not effective against the biofilms at any concentration or time tested.