Susceptibilities of Enterococcus faecalis biofilms to some antimicrobial medications

Current insights into the effects of cationic biocides exposure on Enterococcus spp

Cationic biocides (CBs), such as quaternary ammonium compounds and biguanides, are critical for controlling the spread of bacterial pathogens like Enterococcus spp., a leading cause of multidrug-resistant healthcare-associated infections. The widespread use of CBs in recent decades has prompted concerns about the potential emergence of Enterococcus spp. populations exhibiting resistance to both biocides and antibiotics. Such concerns arise from their frequent exposure to subinhibitory concentrations of CBs in clinical, food chain and diverse environmental settings. This comprehensive narrative review aimed to explore the complexity of the Enterococcus' response to CBs and of their possible evolution toward resistance. To that end, CBs' activity against diverse Enterococcus spp. collections, the prevalence and roles of genes associated with decreased susceptibility to CBs, and the potential for co- and cross-resistance between CBs and antibiotics are reviewed. Significant methodological and knowledge gaps are identified, highlighting areas that future studies should address to enhance our comprehension of the impact of exposure to CBs on Enterococcus spp. populations' epidemiology. This knowledge is essential for developing effective One Health strategies that ensure the continued efficacy of these critical agents in safeguarding Public Health.

Prevalence of Enterococcus faecalis and Candida albicans in endodontic retreatment Cases: A comprehensive study

Introduction

Endodontic treatment failures often stem from the presence of microbial pathogens, particularly Enterococcus faecalis and Candida albicans. This study systematically assesses the prevalence of E. faecalis and C. albicans in endodontic retreatment cases, aiming to explore their impact on treatment outcomes.

Methods

Employing a systematic sampling approach, 30 patients with a history of previous endodontic treatment were selected. Rigorous clinical and radiographic assessments were conducted, following standardized protocols for root canal sample collection. Microbiological analysis, utilizing selective culture media, was employed to identify and quantify E. faecalis and C. albicans. Statistical analyses, including chi-square and logistic regression tests, were performed.

Results

The study involved 30 patients undergoing endodontic retreatment, with comprehensive clinical and radiographic evaluations for cases with and without periradicular lesions. Microbiological analysis unveiled a significant prevalence of E. faecalis and C. albicans, establishing a robust association between these pathogens and retreatment failure. These findings underscore the critical need for targeted antimicrobial interventions to enhance the overall success rates of endodontic retreatment procedures.

Conclusion

This study highlights the substantial prevalence of E. faecalis and C. albicans in endodontic retreatment cases, emphasizing the importance of identifying and effectively managing these pathogens for successful treatment outcomes. The notable association between these microbial agents and retreatment failure underscores the imperative for tailored antimicrobial strategies to enhance the efficacy of endodontic retreatment procedures.

Expert consensus on irrigation and intracanal medication in root canal therapy

Chemical cleaning and disinfection are crucial steps for eliminating infection in root canal treatment. However, irrigant selection or irrigation procedures are far from clear. The vapor lock effect in the apical region has yet to be solved, impeding irrigation efficacy and resulting in residual infections and compromised treatment outcomes. Additionally, ambiguous clinical indications for root canal medication and non-standardized dressing protocols must be clarified. Inappropriate intracanal medication may present side effects and jeopardize the therapeutic outcomes. Indeed, clinicians have been aware of these concerns for years. Based on the current evidence of studies, this article reviews the properties of various irrigants and intracanal medicaments and elucidates their effectiveness and interactions. The evolution of different kinetic irrigation methods, their effects, limitations, the paradigm shift, current indications, and effective operational procedures regarding intracanal medication are also discussed. This expert consensus aims to establish the clinical operation guidelines for root canal irrigation and a position statement on intracanal medication, thus facilitating a better understanding of infection control, standardizing clinical practice, and ultimately improving the success of endodontic therapy.

Comparative Evaluation of Platelet-rich Fibrin and Concentrated Growth Factor as Scaffolds in Regenerative Endodontic Procedure: A Randomized Controlled Clinical Trial

AIM

This randomized controlled trial evaluated the efficacy of platelet-rich fibrin (PRF) and concentrated growth factor (CGF) as scaffolds in the regenerative endodontic procedure (REP) using clinical and radiographic parameters along with cone-beam computed tomographic (CBCT) analysis.

MATERIALS AND METHODS

The apexogenesis procedure was performed in 16 teeth. They were randomly divided into two groups of eight teeth each: group I and group II. In group I PRF was used as the scaffold and in group II CGF was used as the scaffold. They were evaluated for pain, pulpal vitality, tenderness on percussion, and mobility, and also evaluated using digital radiographs at 3, 6, 12, and 18 months interval. The response of the teeth was graded using Chen and Chen criteria. Increase in root length, reduction in the apical foramen dimension, and reduction in periapical lesion volume were evaluated using CBCT scans taken preoperatively and at 18 months.

RESULTS

At the end of 3 months, 50% of teeth without periapical pathology were found to be vital in both groups. At the end of 18 months, 60% of the teeth in both groups showed increase in root length, all teeth showed closure of apical foramen, and reduction in the volume of periapical lesion. However, there was no statistically significant difference between the groups (p < 0.05).

CONCLUSION

The clinical and radiographic features reported in this study revealed that both PRF and CGF act as effective scaffolds in REP for regeneration of pulp-dentin complex with promising results.

CLINICAL SIGNIFICANCE

Apexogenesis by revascularization has not been used regularly for the treatment of nonvital teeth with open apex because the results are not reliable. Since platelet concentrates like PRF and CGF are rich in growth factors; when apexogenesis is performed by REP using these platelet concentrates, desirable results can be achieved in a short duration of time. They also accelerate the healing of periapical lesions present in such cases. With the increased success rate of apexogenesis with REP, many clinicians would prefer to use REPs as a treatment option for teeth with open apex.

Comparing the Antifungal Effect of Sodium Hypochlorite Gel versus Different Types of Root Canal Medicaments at Different Time Intervals Using the Agar Diffusion Test: An In Vitro Study

Aims

The purpose of this study was to compare the antifungal activity of sodium hypochlorite gel to those of four intracanal medicaments at various time intervals.

Materials and Methods

The agar well diffusion technique was utilized to test the antifungal activity of the following medicaments against Candida albinans (C. albicans): sodium hypochlorite gel, chlorhexidine gel, calcium hydroxide paste, Ledermix, and Diapex Plus. The inhibition zone related to each medicine was measured in millimeter after 24, 48, and 72 hours of incubation at 37°C. The data were analyzed using one-way ANOVA and Games–Howell tests, at a significance level of P < 0.05.

Results

Except for Ledermix and Diapex Plus, which had no antifungal action, all of the medicaments showed varied inhibitory zones for C. albicans. At all periods, the NaOCl gel had the most significant inhibition zones, followed by the CHX gel and calcium hydroxide. At all time intervals, the NaOCl gel demonstrated comparable antifungal efficacy. When compared to a 24-hour time interval, the CHX gel showed an increased antifungal activity at the 48-hour and 72-hour intervals. Calcium hydroxide, on the other hand, showed a decrease in its antifungal activity at the 72-hour interval.

Conclusion

The antifungal activity of sodium hypochlorite gel was the highest among the investigated medicaments. Chlorhexidine gel's antifungal activity improved over time, whereas calcium hydroxide's antifungal activity declined. Diapex Plus and Ledermix did not have any antifungal properties.

Characterization of Enterococcus faecalis in different culture conditions

The aim of this study was to investigate how carbohydrates (glucose or sucrose) affect the characteristics of Enterococcus faecalis (E. faecalis) planktonic and biofilm in vitro. For this study, E. faecalis was cultured in tryptone-yeast extract broth with 0% glucose + 0% sucrose, 0.5% glucose, 1% glucose, 0.5% sucrose, or 1% sucrose. Viability of E. faecalis was examined by colony forming unit counting assays. Biofilm formation was assessed by measuring extracellular DNA (eDNA), a component of the biofilm matrix. Quantitative real-time PCR (qRT-PCR) was performed to investigate the expression of virulence-associated genes. Field emission scanning electron microscopy analysis, confocal laser scanning microscopy analysis, and crystal violet colorimetric assay were conducted to study E. faecalis biofilms. E. faecalis showed the highest viability and eDNA levels in 1% sucrose medium in biofilms. The result of qRT-PCR showed that the virulence-associated genes expressed highest in 1% sucrose-grown biofilms and in 1% glucose-grown planktonic cultures. E. faecalis showed highly aggregated biofilms and higher bacteria and exopolysaccharide (EPS) bio-volume in sucrose than in 0% glucose + 0% sucrose or glucose. The results indicate that the production of eDNA and EPS and expression of virulence-associated genes in E. faecalis are affected by the concentration of carbohydrates in biofilm or planktonic culture.

Chlorhexidine rinsing inhibits biofilm formation and causes biofilm disruption on dental enamel in situ

OBJECTIVES

This in situ study aims to evaluate the effects of chlorhexidine (CHX) mouth rinsing on biofilm formation and moreover on the disruption of existing mature dental biofilms.

METHODS

Biofilms were formed in situ by five volunteers on bovine enamel specimens fixed to individual acrylic splints. For biofilm formation analysis, the volunteers intraorally exposed the splint for 48 h. Mouth rinsing using 10 ml of 0.2% CHX or water as control was performed for 30 s every 12 h. For analysis of biofilm disruption, the biofilm was formed on enamel specimens for 48 h. Then, the first CHX rinse was carried out. A second rinse followed after an additional 12 h, again for 30 s using 10 ml of 0.2% CHX. Biofilm vitality was imaged by fluorescence microscopy after vital fluorescence staining. Additionally, the ultrastructure of the biofilm was examined by transmission electron microscopy.

RESULTS

Rinses with 0.2% CHX significantly reduced biofilm formation on enamel. Both biofilm colonization and vitality were dramatically impaired. Moreover, a considerable biofilm disruption induced by the CHX rinses was observed. Remarkably, a single application of CHX to a 48-h mature biofilm causes biofilm ultrastructure alterations and induces a substantial reduction in biofilm thickness and bacterial vitality.

CONCLUSIONS

CHX mouth rinses induced a significant inhibition of biofilm formation on native enamel. Furthermore, an important biofilm disrupting effect under in situ conditions was detected.

CLINICAL RELEVANCE

CHX rinses could be used as a short-term treatment protocol for biofilm management focused on patients unable to reach adequate oral hygiene.

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.

Evaluating the Bioactivity of a Novel Antimicrobial and Anticancer Peptide, Dermaseptin-PS4(Der-PS4), from the Skin Secretion of Phyllomedusa sauvagii

Dermaseptins belonging to a large family of cationic membrane-disruption antimicrobial peptides display extensive antibacterial and antiproliferative activities depending on a coil-to-helix transition and the specific structural parameters. Herein, a novel dermaseptin peptide named Der-PS4 was discovered from the skin secretion of the waxy monkey tree frog, Phyllomedusa sauvagii. The complementary DNA (cDNA)-encoding precursor was obtained relying on "shotgun" cloning, and afterwards, a mature peptide amino acid sequence was identified by reverse-phase high performance liquid chromatography (RP-HPLC) and MS/MS. Specimens were chemically synthesized and applied for further functional studies. Structural analysis demonstrated a higher α-helical content in the membrane-mimetic environment compared with that in the ammonium acetate/water circumstance. Der-PS4 displayed a broad spectrum of antimicrobial activities against tested pathogenic microorganisms, however, exhibiting slight membrane-damaging effectiveness towards horse red blood cells. Coincident with the inhibitory activities on pathogens, Der-PS4 also showed considerable biofilm eradicating impact. Also, Der-PS4 penetrated cell membrane in a relative short period under each minimum bactericidal concentration. In addition, Der-PS4 possessed antiproliferative capacity against five cancer cell lines, while presenting slight suppressing effect on human microvascular endothelial, HMEC-1. These findings provide a promising insight for the discovery and development of novel drugs from a natural source.

Update of the therapeutic planning of irrigation and intracanal medication in root canal treatment. A literature review

Background

The success of endodontic treatment derives from the complete elimination of microorganisms capable of causing an intraradicular or extraradicular infection. To achieve a more effective eradication of these microorganisms, endodontic instrumentation must always be implemented with abundant irrigation, which has to achieve chemical, mechanical and biological effects. The irrigators most used today are NaOCl, CHX and EDTA, released into the ducts through different techniques such as syringe, manual agitation, positive or negative apical pressure, sonic or ultrasonic activation, PIPS and PDT. The objective of this review is to update the different irrigating solutions and intracanal disinfection drugs, as well as to establish an irrigation protocol in the endodontic treatment.

Material and Methods

Systematic search of scientific articles in the databases PubMed, Medline and Google Scholar, with the following keywords Endodontic, Infection, Failure, Irrigation, Retreatment and Irrigation protocol. The exclusion criteria were “case report” articles and articles with a publication date prior to 2000.

Results

48 articles that met the inclusion criteria were analyzed. Comparing the different articles it can be seen that the NaOCl is the “gold standard” in terms of immediate antimicrobial efficacy, followed by the CHX that has a long-term antibacterial effect. As an intra-conductive drug it is advisable to use the combination of Ca(OH)2 with CPMC.

Conclusions

The most adequate irrigation protocol consists of using 2.5% NaOCl activated with ultrasound followed by a final wash with 7% MA or 0.2% CTR combined with 2% CHX.

Key words:Endodontic failure, endodontic infection, enterococcus faecalis, endodontic retreatment, irrigation, sodium hipoclorite, irrigation protocol.

Antibiofilm efficacy of biosynthesized silver nanoparticles against endodontic-periodontal pathogens: An in vitro study

Background:

Endodontic-periodontal pathogens exist as biofilms which are difficult to eliminate. Biosynthesized silver nanoparticles (AgNPs) emerged as newer antimicrobial agents with potential benefits.

Aim:

The aim of this study is to determine the minimum inhibitory concentration (MIC); evaluate the antibiofilm efficacy of fungal-derived AgNPs against Porphyromonas gingivalis, Bacillus pumilus, and Enterococcus faecalis.

Materials and Methods:

MIC of AgNPs against test pathogens was determined using micro broth dilution method. Serial dilutions of AgNPs ranging from 80 to 1 μg/ml concentration were added to wells containing 10 μl of bacterial inoculum in culture media and control group without AgNPs. For biofilm models, 120 dentin blocks were prepared, sterilized, and contaminated for 2 weeks with (n = 40 each). Group 1: B. pumilus, Group 2: E. faecalis, and Group 3: P. gingivalis and each group is divided into four subgroups (n = 10 each) and treated with distilled water, AgNPs, 2% and 0.2% chlorhexidine (CHX). Colonies counted after 24 h of incubation and statistically analyzed using one-way ANOVA and post hoc Tukey tests.

Results:

MIC for B. pumilus was determined as 20 μg/ml and 30 μg/ml for E. faecalis and P. gingivalis. AgNPs were effective as 2% CHX against all biofilms compared to control group. Post hoc Tukey test (P < 0.0001) shows no significant difference between groups.

Conclusion:

Fungal-derived AgNPs are effective against endo-perio pathogens.

Rapid Bacterial Detection during Endodontic Treatment

Bacteria present in the root canal (RC) space following an RC treatment (RCT) can lead to persistent infections, resulting in treatment failure and the need for reintervention or extraction. Currently, there are no standardized methods in use to clinically detect bacterial presence within RC spaces. The use of paper point sampling and fluorescence staining was shown to be a rapid method, able to detect residual bacteria following treatment. The study demonstrated that Calcein acetoxymethyl (AM) proved to be a suitable dye for detecting vital bacteria within mature endodontic biofilms, with an improved sensitivity over colony-forming unit counting in a stressed biofilm model. Furthermore, in a clinical trial with primary RCTs, 53 infected teeth were sampled in vivo, and increased detection of vital cells was found when compared with colony-forming unit counting, highlighting the sensitivity of the technique in detecting low cell numbers. By combining fluorescent staining and microspectroscopy with software-based spectral analysis, successful detection of vital cells from RCs was possible after 5 min of Calcein AM incubation. Application of this technology during RCT has the potential to reduce persistent infections through vital cell detection and additional treatment. Furthermore, this technique could be applied to antimicrobial research and disinfection control in clinical settings ( ClinicalTrials.gov NCT03055975).

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.

Effect of Nanosilver Gel, Chlorhexidine Gluconate, and Camphorated Phenol on Enterococcus faecalis Biofilm

Aim. To assess the effectiveness of nanosilver gel (NSG) in comparison to chlorhexidine gluconate (CHX) and camphorated phenol (CP) against Enterococcus faecalis (E.f) biofilm. Methods and Materials. Two tests were done, methyl thiazolyl tetrazolium (MTT) assay and confocal laser scanning microscopy (CLSM) analysis, to determine the effectiveness of NSG, CHX, and CP on E.f biofilm. Polystyrene microtiter 96- and 6-well plates were used for MTT and CLSM, respectively. Nanosilver gel was in three concentrations (0.05%, 0.1%, and 0.2%), chlorhexidine gluconate used was 2%, and camphorated phenol and normal saline were as control. Analysis was done using one-way ANOVA; the post hoc test was run for multiple comparisons. The level of statistical significance was set at P < 0.05. Results. One-way ANOVA showed significant differences among groups (0.05% NSG and CP, 0.1% NSG and CP, 0.2% NSG and CP, 0.1% NSG and 2% CHX, 0.2% and NSG and 2% CHX) (P < 0.001) and also showed significant difference between groups (P < 0.001), f-ratio 87.823. A post hoc Tukey's test revealed no significant difference between chlorhexidine gluconate and 0.05% nanosilver gel (P > 0.05). Conclusions. 0.1% and 0.2% nanosilver gel is more effective on Enterococcus faecalis biofilm as compared to chlorhexidine gluconate and camphorated phenol.

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.

Detection of Enterococcus faecalis and Candida albicans in previously root-filled teeth in a population of Gujarat with polymerase chain reaction

BACKGROUND

Micro-organisms are the primary causative agents of endodontic infections. Phenotype based procedures for bacterial identification has certain drawbacks especially, when investigating the microbiota of root-filled teeth. Thus, more sensitive methods like Polymerase chain reaction (PCR) can provide results that are more accurate and reliable for the microbial prevalence in the root filled teeth.

AIM

In this study, we have investigated twenty symptomatic root-filled teeth with chronic apical periodontitis for the prevalence of Enterococcus faecalis and Candida albicans in the root filled teeth associated with symptomatic cases with or without periradicular lesions.

MATERIALS AND METHODS

Microbiological samples were taken from the canals immediately after removal of previous gutta percha cones using aseptic techniques. After removal of root canal filling, samples were obtained with paper points placed in the canal. Paper points were transferred to a cryotube containing "Tris EDTA" buffer and immediately frozen at -20°C.

RESULTS

By PCR amplification of the samples using taxon specific primers, E. faecalis was found to be prevalent species, detected in 65% of the cases and C. albicans was detected in 35% of cases.

CONCLUSION

The results of the study shows that geographical influence and dietary factors might have some role to play in the prevalence of the species like C. albicans and presence of E. faecalis confirming the assertion of previous culture-dependent and independent approaches for the microbiological survey of root filled teeth.

Suitability of Biomorphic Silicon Carbide Ceramics as Drug Delivery Systems against Bacterial Biofilms

The present work is aimed at getting a new insight into biomorphic silicon carbides (bioSiCs) as bone replacement materials. BioSiCs from a variety of precursors were produced, characterized, and loaded with a broad-spectrum antibiotic. The capacity of loaded bioSiCs for preventing and/or treating preformed S. aureus biofilms has been studied. The differences in precursor characteristics are maintained after the ceramic production process. All bioSiCs allow the loading process by capillarity, giving loaded materials with drug release profiles dependent on their microstructure. The amount of antibiotic released in liquid medium during the first six hours depends on bioSiC porosity, but it could exceed the minimum inhibitory concentration of Staphylococcus aureus, for all the materials studied, thus preventing the proliferation of bacteria. Differences in the external surface and the number and size of open external pores of bioSiCs contribute towards the variations in the effect against bacteria when experiments are carried out using solid media. The internal structure and surface properties of all the systems seem to facilitate the therapeutic activity of the antibiotic on the preformed biofilms, reducing the number of viable bacteria present in the biofilm compared to controls.

In vitro efficacy of different irrigating solutions against polymicrobial human root canal bacterial biofilms

The purpose of this in vitro study was to compare the antimicrobial efficacy of five different irrigating solutions against complex polymicrobial bacterial biofilms harvested from root canals to model actual endodontic irrigation as closely as possible, and to test the efficacy of these irrigants in these conditions. Two multi-species in vitro biofilms were generated from bacterial samples taken from patients presenting with acute pulpitis. The microbial composition of these samples was characteristic of the disease. The biofilms were incubated with 1000 p.p.m. Solumium Dental (ClO(2)), 0.2% chlorhexidine (CHX), 5.25% sodium-hypochlorite (NaOCl), 5.25% Neomagnol, 10% iodine and phosphate buffered saline (PBS) as control. After the microbiological preparation of the samples, colony forming units (CFU) were counted. NaOCl, iodine and Neomagnol were the most effective, whilst CHXand Solumium appeared to be less effective against these specific biofilms. The efficacy of the most effective agents differed according to biofilm and application time. All irrigants were efficient to some extent, but NaOCl proved to be the most efficient, while chlorine dioxide (ClO(2)) yielded the poorest results in these circumstances. The efficacy of NaOCl was already well-known, but our results also point out that iodine could have an important role in endodontic irrigation.

The effect of calcium hydroxide on the antibiotic component of Odontopaste and Ledermix paste

AIM

To investigate the chemical interaction of calcium hydroxide with the antibiotics demeclocycline calcium in Ledermix Paste and clindamycin hydrochloride in Odontopaste.

METHODOLOGY

Validated methods were developed to analyse the interaction of calcium hydroxide in two forms, Pulpdent and calcium hydroxide powder, with the two antibiotics. High-performance liquid chromatography (HPLC) was used to analyse the mixed samples of the pastes and calcium hydroxide. The concentration of demeclocycline calcium over 0-, 1-, 18-, 24-, 72-h and 7-day time-points was determined. The concentration of clindamycin hydrochloride over 1-, 6-, 24-, 72-h and 7-day time-points was determined. All tests with HPLC involved testing of the standard in duplicate alongside the samples. Linearity, precision and specificity of the testing procedures and apparatus were validated. Descriptive statistics are provided.

RESULTS

The antibiotics in both Odontopaste and Ledermix Paste were affected by the addition of calcium hydroxide. When mixed with calcium hydroxide powder, Odontopaste had a 2% loss of clindamycin hydrochloride over 7 days, but when mixed with Pulpdent, there was a 36% loss over 7 days. Ledermix Paste showed an 80% loss of demeclocycline calcium over 7 days when mixed with calcium hydroxide powder and a 19% loss when mixed with Pulpdent over the 7-day period.

CONCLUSION

The addition of calcium hydroxide to Odontopaste or Ledermix Paste results in reductions of the respective antibiotic over a 7-day time period.

Antimicrobial effect of alexidine and chlorhexidine against Enterococcus faecalis infection

A previous study demonstrated that alexidine has greater affinity for the major virulence factors of bacteria than chlorhexidine. The aim of this study was to compare the antimicrobial activity of 1% alexidine with that of 2% chlorhexidine using Enterococcus faecalis-infected dentin blocks. Sixty bovine dentin blocks were prepared and randomly divided into six groups of 10 each. E. faecalis was inoculated on 60 dentin blocks using the Luppens apparatus for 24 h and then the dentin blocks were soaked in 2% chlorhexidine or 1% alexidine solutions for 5 and 10 min, respectively. Sterile saline was used as a control. The antimicrobial efficacy was assessed by counting the number of bacteria adhering to the dentin surface and observing the degradation of bacterial shape or membrane rupture under a scanning electron microscope. Significantly fewer bacteria were observed in the 2% chlorhexidine- or 1% alexidine-soaked groups than in the control group (P<0.05). However, there was no significant difference in the number of bacteria adhering to the dentinal surface between the two experimental groups or between the two soaking time groups (P>0.05). Ruptured or antiseptic-attached bacteria were more frequently observed in the 10-min-soaked chlorhexidine and alexidine groups than in the 5-min-soaked chlorhexidine and alexidine groups. In conclusion, 10-min soaking with 1% alexidine or 2% chlorhexidine can be effective against E. faecalis infection.

Antimicrobial effect of alexidine and chlorhexidine against Enterococcus faecalis infection

A previous study demonstrated that alexidine has greater affinity for the major virulence factors of bacteria than chlorhexidine. The aim of this study was to compare the antimicrobial activity of 1% alexidine with that of 2% chlorhexidine using Enterococcus faecalis-infected dentin blocks. Sixty bovine dentin blocks were prepared and randomly divided into six groups of 10 each. E. faecalis was inoculated on 60 dentin blocks using the Luppens apparatus for 24 h and then the dentin blocks were soaked in 2% chlorhexidine or 1% alexidine solutions for 5 and 10 min, respectively. Sterile saline was used as a control. The antimicrobial efficacy was assessed by counting the number of bacteria adhering to the dentin surface and observing the degradation of bacterial shape or membrane rupture under a scanning electron microscope. Significantly fewer bacteria were observed in the 2% chlorhexidine- or 1% alexidine-soaked groups than in the control group (P<0.05). However, there was no significant difference in the number of bacteria adhering to the dentinal surface between the two experimental groups or between the two soaking time groups (P>0.05). Ruptured or antiseptic-attached bacteria were more frequently observed in the 10-min-soaked chlorhexidine and alexidine groups than in the 5-min-soaked chlorhexidine and alexidine groups. In conclusion, 10-min soaking with 1% alexidine or 2% chlorhexidine can be effective against E. faecalis infection.

In vitro Enterococcus faecalis biofilm formation on five adhesive systems

Objective: To determine the E. faecalis biofilm formation on the surface of five adhesive systems (AS) and its relationship with roughness. Study Design: The formation of E. faecalis biofilms was tested on the surface of four dual-cure AS: AdheSE DC, Clearfil DC Bond, Futurabond DC and Excite DSC and one light-cure antimicrobial AS, Clearfil Protect Bond, after 24 hours of incubation, using the MBEC high-throughput device. Results: E. faecalis biofilms grew on all the adhesives. The least growth of biofilm was on Excite DSC, Clearfil Protect Bond, and the control. Futurabond DC resulted in the greatest roughness and biofilm amount. There was a close relationship between the quantity of biofilm and roughness, except for Clearfil Protect Bond, which showed little biofilm but high roughness. Conclusion: None of the tested AS prevented E. faecalis biofilm formation, although the least quantity was found on the surface of Clearfil Protect Bond.

Key words:Adhesive systems, biofilm, Enterococcus faecalis, roughness.

Antibacterial activity of calcium hydroxide combined with chitosan solutions and the outcomes on the bond strength of RealSeal sealer to radicular dentin

The purpose of this study was to investigate the antibacterial activity of calcium hydroxide [Ca(OH)₂] combined with chitosan solutions against Enterococcus faecalis-infected root canal dentin and the effect of this new intracanal medicament on the bond strength of RealSeal sealer to radicular dentin. An experimental intracanal medicament was prepared by mixing different concentrations of chitosan solution (25%, 50%, and 100%, W/V) to Ca(OH)₂ powder. Antibacterial activity was evaluated and the total numbers of colony forming units were determined. Bonding ability of RealSeal sealer to radicular dentin was evaluated using push-out bond strength test. Data were analyzed using one-way analysis of variance (ANOVA) and Tukey's multiple comparison tests. We found that Ca(OH)₂ combined with different concentrations of chitosan solutions showed better antibacterial activity than Ca(OH)₂ mixed with saline, without significantly affecting the bond strength of RealSeal sealer to radicular dentin (P > 0.05). The findings suggest that Ca(OH)₂ combined with chitosan is a promising intracanal medicament and may be effective in endodontic therapy.

Development of a multispecies biofilm community by four root canal bacteria

INTRODUCTION

The development of multispecies biofilm models are needed to explain the interactions that take place in root canal biofilms during apical periodontitis. The aim of this study was to investigate the ability of 4 root canal bacteria to establish a multispecies biofilm community and to characterize the main structural, compositional, and physiological features of this community.

METHODS

Four clinical isolates isolated from infected root canals, Actinomyces naeslundii, Lactobacillus salivarius, Streptococcus gordonii, and Enterococcus faecalis, were grown together in a miniflow cell system. Simultaneous detection of the 4 species in the biofilm communities was achieved by fluorescence in situ hybridization in combination with confocal microscopy at different time points. The LIVE/DEAD BacLight technique (Molecular Probes, Carlsbad, CA) was used to assess cell viability and to calculate 3-dimensional architectural parameters such as biovolume (μm(3)). Redox fluorescence dye 5-cyano-2,3-ditolyl tetrazolium chloride was used to assess the metabolic activity of biofilm bacteria.

RESULTS

The 4 species tested were able to form stable and reproducible biofilm communities. The biofilms formed in rich medium generally showed continuous growth over time, however, in the absence of glucose biofilms showed significantly smaller biovolumes. A high proportion of viable cells (>90%) were generally observed, and biofilm growth was correlated with high metabolic activity of cells. The community structure of biofilms formed in rich medium did not change considerably over the 120-hour period, during which E. faecalis, L. salivarius, and S. gordonii were most abundant.

CONCLUSIONS

The ability of 4 root canal bacteria to form multispecies biofilm communities shown in this study give insights into assessing the community lifestyle of these microorganisms in vivo. This multispecies model could be useful for further research simulating stresses representative of in vivo conditions.

A direct comparison between extracted tooth and filter-membrane biofilm models of endodontic irrigation using Enterococcus faecalis

Endodontic restorations often fail due to inadequate disinfection of the root canal even though the antimicrobial irrigants used have been shown to be capable of killing the bacterium frequently implicated in this complication, Enterococcus faecalis (Ef). Extracted human teeth were root-prepared and filled with a liquid culture of Ef. Following incubation, the root canals were irrigated with 1% sodium hypochlorite (NaOCl), electrochemically activated water or saline control. Irrigation was modelled using an electronic pipette to deliver the solutions at a reproducible flow velocity. A series of parallel experiments employed a membrane biofilm model that was directly immersed into irrigant. Experimental conditions where contiguous between the extracted tooth model and biofilm model wherever possible. After 60 s of exposure, 1% NaOCl effectively sterilised the biofilm model, whereas log 3.36 viable Ef where recoverable from the analogous extracted tooth model, the other irrigants proved ineffective. Biofilms of Ef were susceptible to concentrations of irrigant that proved ineffective in the tooth model. NaOCl was the most effective biocide in either case. This suggests that the biofilm modality of bacterial growth may not be the most important factor for the recalcitrance of root canal infections during endodontic irrigation; it is more likely due to the inability of the irrigant to access the infection.

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.

Antibacterial efficacy of intracanal medicaments on bacterial biofilm: a critical review

The purpose of this paper is to discuss critically the antibacterial efficacy of intracanal medicaments on bacterial biofilm. Longitudinal studies were evaluated by a systematic review of English-language articles retrieved from electronic biomedical journal databases (MEDLINE, EMBASE, CENTRAL) and handsearching records, using different matches of keywords for root canal biofilm, between 1966 and August 1st, 2007. The selected articles were identified from titles, abstracts and full-text articles by two independent reviewers, considering the tabulated inclusion and exclusion criteria. Disagreements were resolved by consensus. The search retrieved 91 related articles, of which 8.8% referred to in vivo studies demonstrating the lack of efficacy of endodontic therapy on bacterial biofilm. Intracanal medicaments were found to have a limited action against bacterial biofilm.

Chlorhexidine gluconate in endodontics: an update review

The major objective in root canal therapy is to disinfect the entire root canal system. This requires that the pulpal contents be eliminated as sources of infection. This goal may be accomplished using mechanical instrumentation and chemical irrigation, in conjunction with medication of the root canal between treatment sessions. Microorganisms and their by-products are considered to be the major cause of pulpal and periradicular pathosis. In order to reduce or eliminate bacteria, various irrigation solutions have been used during treatment. Chlorhexidine is a cationic molecule which can be used during treatment. It has a wide range antimicrobial activity. Furthermore, because of its cationic structure, chlorhexidine has a unique property named substantivity. The purpose of this paper is to review different aspects of the use of chlorhexidine gluconate in endodontics.

Determination of the minimum inhibitory concentration of four medicaments used as intracanal medication

The aim of this study was to determine the minimum inhibitory concentration (MIC) of iodoform, calcium hydroxide, IKI (iodine potassium iodine) and CFC (ciprofloxacin, Flagyl (metronidazole) and calcium hydroxide) required to kill S. aureus, Pseudomonas aeruginosa, Enterococcus faecalis and B. fragilis. In the experiment, medicaments were added to bacterial species into test tubes, in 10 different concentrations. The MIC was the lowest concentration of the drug at which bacterial growth could not be observed. In this investigation, CFC was the most effective medicament against all bacteria. All drugs were able to eliminate E. faecalis and B. fragilis, while IKI was not effective against S. aureus. IKI and calcium hydroxide were not able to eliminate P. aeruginosa as well.

The use of calcium hydroxide, antibiotics and biocides as antimicrobial medicaments in endodontics

Bacteria have been implicated in the pathogenesis and progression of pulp and periapical diseases. The primary aim of endodontic treatment is to remove as many bacteria as possible from the root canal system and then to create an environment in which any remaining organisms cannot survive. This can only be achieved through the use of a combination of aseptic treatment techniques, chemomechanical preparation of the root canal, antimicrobial irrigating solutions and intracanal medicaments. The choice of which intracanal medicament to use is dependent on having an accurate diagnosis of the condition being treated, as well as a thorough knowledge of the type of organisms likely to be involved and their mechanisms of growth and survival. Since the disease is likely to have been caused by the presence of bacteria within the root canal, the use of an antimicrobial agent is essential. Many medicaments have been used in an attempt to achieve the above aims but no single preparation has been found to be completely predictable or effective. Commonly used medicaments include calcium hydroxide, antibiotics, non-phenolic biocides, phenolic biocides and iodine compounds. Each has advantages and disadvantages, and further research is required to determine which is best suited for root canal infections.

Susceptibility of Enterococcus faecalis biofilm to antibiotics and calcium hydroxide

The purpose of this study was to investigate the antimicrobial efficacy of six groups of antibiotics and calcium hydroxide against Enterococcus faecalis biofilm in a membrane filter model. Two-day-old E. faecalis (ATCC 29212) biofilm was exposed to ampicillin, co-trimoxazole, erythr omycin, oxytetracycline, vancomycin, vancomycin followed by gentamicin, Ca(OH)(2), and phosphate-buffered saline (control). After 1 h of exposure, the antimicrobial activity was neutralized by washing each disc five times in PBS, and then the colony-forming units of the remaining viable bacteria on each disc were counted. The results revealed that only erythromycin, oxytetracycline and Ca(OH)2 showed 100% biofilm kill. An ANOVA with a Bonferroni post hoc test (P < 0.05) detected significant differences among the test agents, except in the ampicillin group versus the co-trimoxazole group. It is concluded that erythromycin, oxytetracycline and Ca(OH)2 are 100% effective in eliminating E. faecalis biofilm, whereas ampicillin, co-trimoxazole, vancomycin, and vancomycin followed by gentamicin are ineffective.

Chlorhexidine Gluconate

The aim of root canal treatment is to eliminate bacteria from the infected root canal and to prevent reinfection. Biomechanical cleaning and shaping greatly reduces the number of bacteria. Nevertheless, due to anatomical complexity of the root canal system, residues and bacteria cannot be removed completely. Therefore, various substances have been used during canal preparation to remove debris, necrotic tissue, bacteria and smear layer. The most common irrigant of choice is sodium hypochlorite (NaOCI): it is an effective antimicrobial agent and tissue solvent. However, NaOCI can be toxic. Chlorhexidine gluconate (CHX) is a broad-spectrum antimicrobial agent. As a root canal irrigant and intracanal medicament, CHX has an antibacterial efficacy comparable to that of NaOCI, and is effective against resistant bacterial strains. CHX may result in residual antimicrobial activity of the dentine surface after prolonged exposure of the root canal to CHX. CHX also has a low grade of toxicity. In this review CHX will be discussed in detail.

Susceptibilties of Two Enterococcus faecalis Phenotypes to Root Canal Medications

This study aimed to investigate and compare the efficacy of selected root canal irrigants and a medicament on a clinical isolate of Enterococcus faecalis grown as biofilm or planktonic suspension phenotype. A cell-dense pellet "presentation" prepared from planktonic phenotype was also tested. Each bacterial presentation was exposed to calcium hydroxide (pH 12.3), 0.2% chlorhexidine gluconate, 17% ethylene-diamine-tetra-acetic acid, 10% povidone iodine, or 3.0% sodium hypochlorite (NaOCl) for a range of time periods (1, 2, 4, 8, 15, 30, and 60 min). Phosphate buffered saline was used as a control agent. The difference in gradients of bacterial killing among the biofilm, planktonic suspension or pellet presentation was significant (p < 0.05) and dependent upon the test agent except in the case of NaOCl and calcium hydroxide where no difference could be detected. NaOCl was the most effective agent and achieved 100% kills for all presentations of E. faecalis after a 2 min contact time.

Effect of 2% Chlorhexidine Gel as an Intracanal Medication on the Apical Seal of the Root-Canal System

The purpose of this study was to determine what effect intracanal medications might have on the apical seal of the root-canal system. Forty-two teeth were cleaned and shaped in a crown-down manner to a size #50 K-file. The teeth were divided into three groups: (A) immediate obturation; (B) intracanal placement of calcium hydroxide placed for 14 days; and (C) 2% chlorhexidine gel placed for 14 days. After 14 days, these materials were removed using copious irrigation and obturation was completed on groups B and C. Obturation was performed using the continuous wave of condensation technique using AH Plus sealer in all groups. Leakage was evaluated 60 days after obturation by using a fluid-filtration device. Using the one-way ANOVA test, there was no statistically significant difference in leakage between the three groups. Under the conditions of this study, 2% chlorhexidine gel and calcium hydroxide paste did not adversely affect the apical seal of the root-canal system.

Lysostaphin disrupts Staphylococcus aureus and Staphylococcus epidermidis biofilms on artificial surfaces

Staphylococci often form biofilms, sessile communities of microcolonies encased in an extracellular matrix that adhere to biomedical implants or damaged tissue. Infections associated with biofilms are difficult to treat, and it is estimated that sessile bacteria in biofilms are 1,000 to 1,500 times more resistant to antibiotics than their planktonic counterparts. This antibiotic resistance of biofilms often leads to the failure of conventional antibiotic therapy and necessitates the removal of infected devices. Lysostaphin is a glycylglycine endopeptidase which specifically cleaves the pentaglycine cross bridges found in the staphylococcal peptidoglycan. Lysostaphin kills Staphylococcus aureus within minutes (MIC at which 90% of the strains are inhibited [MIC(90)], 0.001 to 0.064 microg/ml) and is also effective against Staphylococcus epidermidis at higher concentrations (MIC(90), 12.5 to 64 microg/ml). The activity of lysostaphin against staphylococci present in biofilms compared to those of other antibiotics was, however, never explored. Surprisingly, lysostaphin not only killed S. aureus in biofilms but also disrupted the extracellular matrix of S. aureus biofilms in vitro on plastic and glass surfaces at concentrations as low as 1 microg/ml. Scanning electron microscopy confirmed that lysostaphin eradicated both the sessile cells and the extracellular matrix of the biofilm. This disruption of S. aureus biofilms was specific for lysostaphin-sensitive S. aureus, as biofilms of lysostaphin-resistant S. aureus were not affected. High concentrations of oxacillin (400 microg/ml), vancomycin (800 microg/ml), and clindamycin (800 microg/ml) had no effect on the established S. aureus biofilms in this system, even after 24 h. Higher concentrations of lysostaphin also disrupted S. epidermidis biofilms.