A model system to study antimicrobial strategies in endodontic biofilms

Bio-inspired synthesis of silver nanoparticles usingSalsola imbricataand its application as antibacterial additive in glass ionomer cement

Nanotechnology has gained immense popularity and observed rapid development due to the remarkable physio-chemical properties of nanoparticles (NPs) and related nanomaterials. The green production of NPs has many benefits over traditional techniques because the current procedures are expensive, time-consuming, and involve harmful substances that limit their applicability. This study aimed to use a novel green source, theSalsola imbricata(SI) plant, which is commonly found in Central Asia and known for its medicinal properties as a reducing and stabilizing agent for the synthesis of AgNPs. The current study also utilized efficient statistical design, the Plackett-Burman Design (PBD) of Experiment method to synthesize the NPs. The characterization of NPs was carried out using UV-Vis spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy (SEM). The PBD results showed that only two out of four factorsi.e.AgNO3concentration and incubation time, were significant for the synthesis of SI-AgNPs. While remaining factors, incubation temperature and plant extract: AgNO3ratio were non-significant. The SEM analysis result showed that SI-AgNPs had a size of 20-50 nm. The SI-AgNPs demonstrated strong antibacterial activity against oral pathogens such asS. mutans and Lactobacillus acidophilus, with the highest efficacy observed at a concentration of 2 mg ml-1. The addition of SI-AgNPs in glass ionomer cement significantly increased the antibacterial activity of GIC againstS. mutans. Based on the results of the current study, the plant based AgNPs can be further evaluated in detail as alternate antimicrobial agent either alone or in combination with other antimicrobial agents for different dental applications.

Comparative evaluation of antimicrobial efficacy of triple antibiotic paste and amoxicillin clavulanate paste as an intracanal medicament against Enterococcus faecalis: An in vitro study

Background

Triple antibiotic paste (TAP) is the commonly used intracanal medicament against Enterococcus faecalis. Amoxicillin clavulanate paste (ACP) is recommended as a "fall-back" antibiotic when traditional dental antibiotics fail. Literature comparing the antimicrobial efficacy of TAP and ACP in eradicating E. faecalis from the root canal system is sparse; hence, this in vitro study was conducted to evaluate and compare the antimicrobial efficacy of TAP and ACP as an intracanal medicament for endodontic treatment of single-rooted permanent teeth against E. faecalis.

Materials and Methods

This in vitro, experimental study evaluated 60 root samples obtained from extracted single-rooted human permanent teeth. The canal diameter was enlarged and subsequently infected with E. faecalis for 21 days. Four groups of the contaminated samples were treated with TAP, ACP, calcium hydroxide (positive control), and saline (negative control), respectively. Dentinal shavings were collected at the end of the 1st, 7th, and 10th day and inoculated in agar plates. The number of colony-forming units was determined, and the data were statistically analyzed using the Kolmogorov-Smirnov and Shapiro-Wilks test. P <0.05 was considered statistically significant.

Results

The mean number of E. faecalis colony counts across all 3 test days demonstrated that TAP exhibited the highest inhibition of bacterial growth, followed by ACP which is not statistically significant (P = 1.00).

Conclusion

Considering the limitations of this in vitro study, the findings suggest that ACP could be an effective alternative intracanal medicament to TAP for endodontic therapy.

Efficacy of Endodontic Disinfection Protocols in an E. faecalis Biofilm Model-Using DAPI Staining and SEM

The aim of this study was to investigate the antimicrobial efficacy of different disinfection protocols in a novel Enterococcus faecalis biofilm model based on a visualization method and to evaluate the potential alteration of dentinal surface. A total of 120 extracted human premolars were allocated to 6 groups with different irrigation protocols. The assessment of the effectiveness of each protocol and the alteration of dentinal surface were visualized by using SEM and fluorescence microscopy (DAPI). A dense E. faecalis biofilm with a penetration depth of 289 μm (medial part of the root canal) and 93 μm (apical part) validated that the biofilm model had been successfully implemented. A significant difference between the 3% NaOCl groups and all the other groups in both observed parts of the root canal (p < 0.05) was detected. However, the SEM analysis revealed that the dentinal surface in the 3% NaOCl groups was severely altered. The established biofilm model and the visualization method based on DAPI are appropriate for bacterial quantification and evaluation of the depth effect of different disinfection protocols in the root canal system. The combination of 3% NaOCl with 20% EDTA or MTAD with PUI allows the decontamination of deeper dentine zones within the root canal but simultaneously alters the dentinal surface.

Benefits and Challenges of the Use of Two Novel vB_Efa29212_2e and vB_Efa29212_3e Bacteriophages in Biocontrol of the Root Canal Enterococcus faecalis Infections

Bacteriophage therapy has emerged as a strategy supplementing traditional disinfection protocols to fight biofilms. The aim of the study was to isolate the phages against E. faecalis and to characterize its biological features, morphology, and lytic activity in a formed biofilm model.

METHODS

E. faecalis ATCC 29212 strain was used for the trial. Two novel vB_Efa29212_2e and vB_Efa29212_3e virulent phages were isolated from urban wastewater and characterized. The E. faecalis biofilm was established in 15 bovine teeth for 21 days. Transmission (TEM) and scanning electron (SEM) microscopes with the colony-forming unit (CFU) counting were used for assessment.

RESULTS

Isolated phages differed in morphology. Taxonomy for vB_Efa29212_2e (Siphoviridae, Efquatovirus) and for vB_Efa29212_3e (Herelleviridae, Kochikohdavirus) was confirmed. Both phages were stable at a temperature range of 4-50 °C and showed a different tolerance to chemicals: 15% EDTA, 1-3% sodium hypochlorite, and chlorhexidine. SEM analysis showed distortion of bacteria cells after phage inoculation, which proved the lytic activity against E. faecalis. A 54.6% reduction in the E. faecalis biofilm confirmed bacteriophage efficacy against isolates in the ex vivo model.

CONCLUSIONS

Results strongly support the concept that phage therapy has a real therapeutic potential for the prevention and treatment of E. faecalis-associated infections.

Influence of different agitation techniques on bacterial reduction in curved root canals

The aim of this study was to evaluate the influence of agitation techniques on bacterial reduction in curved root canals. Eighty human mandibular molars were prepared, inoculated with Enterococcus faecalis and incubated at 37°C for 60 days. Then, specimens were randomly separated into two test groups (n = 36) and two control groups (n = 04) according to agitation technique: Passive ultrasonic irrigation (PUI, Irrisonic) and XP-endo Finisher (XPF). Microbial samples were collected before and after instrumentation and after final agitation using sterile paper points. Bacterial growth was analysed by turbidity of culture medium and UV spectrophotometry. The Wilcoxon rank test was used for the paired analysis, while the Mann-Whitney U-test was used for the non-paired analysis. The samples collected after final agitation were significantly different between test groups (p < 0.05). Bacterial reduction was greater in the PUI than in the XPF (p < 0.05) group. The irrigant agitation provided significant bacterial reduction. The use of the PUI showed better results.

Ex Vivo Effect of Novel Lipophosphonoxins on Root Canal Biofilm Produced by Enterococcus faecalis: Pilot Study

(1) Background: The root canal system has complex anatomical and histological features that make it impossible to completely remove all bacteria by mechanical means only; they must be supplemented with disinfectant irrigation. Current disinfectants are unable to eliminate certain microorganisms that persist in the root canal, resulting in treatment failure. At the Institute of Organic Chemistry and Biochemistry, Prague, novel substances with the bactericidal effect, termed lipophosphonoxins (LPPOs), have been discovered. The aim of this pilot study was to investigate the ex vivo effects of second- and third-generation LPPOs on Enterococcus faecalis and compare them with 5% sodium hypochlorite (NaOCl), 0.12% chlorhexidine digluconate, and 17% ethylenediaminetetraacetic acid (EDTA). (2) Methods: The root canal’s dentin was used as a carrier for biofilm formation in the extracted human mature mandibular premolars. The samples were filled with cultivation broth and 0.25% glucose with tested solutions. In control samples, only fresh cultivation broth (negative control) and cultivation broth with bacterial suspension (growth control) were used. Each sample was inoculated with E. faecalis CCM4224 except for the negative control, and cultivation was performed. To determine the number of planktonic cells, the sample content was inoculated on blood agar. To evaluate biofilm formation inhibition, samples were placed in tubes with BHI. (3) Results: LPPOs exhibited a reduction in biofilm growth and bacteria comparable to NaOCl, and they were superior to other tested disinfectants. (4) Conclusions: The study results suggest the effect of lipophosphonoxins on E. faecalis CCM 4224 reduces planktonic bacterial cells and inhibits formation of biofilm in root canal samples.

Cold atmospheric plasma coupled with air abrasion in liquid medium for the treatment of peri-implantitis model grown with a complex human biofilm: an in vitro study

OBJECTIVE

Treatment of implants with peri-implantitis is often unsuccessful due to residual microbial biofilm hindering re-osseointegration. The aim of this study was to treat biofilm-grown titanium (Ti) implants with different modalities involving air abrasion (AA) and cold atmospheric plasma (CAP) to compare the effectiveness in surface decontamination and the alteration/preservation of surface topography.

MATERIALS AND METHODS

Saliva collected from a peri-implantitis patient was used to in vitro develop human biofilm over 35 implants with moderately rough surface. The implants were then mounted onto standardized acrylic blocks simulating peri-implantitis defects and treated with AA (erythritol powder), CAP in a liquid medium, or a combination (COM) of both modalities. The remaining biofilm was measured by crystal violet (CV). Surface features and roughness before and after treatment were assessed by scanning electron microscope (SEM). The data were statistically analyzed using Kruskal-Wallis followed by Tukey's multiple comparison test.

RESULTS

In the present peri-implantitis model, the human complex biofilm growth was successful as indicated by the statistical significance between the negative and positive controls. All the treatment groups resulted in a remarkable implant surface decontamination, with values very close to the negative control for AA and COM. Indeed, statistically significant differences in the comparison between the positive control vs. all the treatment groups were found. SEM analysis showed no post-treatment alterations on the implant surface in all the groups.

CONCLUSIONS

Decontamination with AA delivering erythritol with or without CAP in liquid medium demonstrated compelling efficacy in the removal of biofilm from implants. All the tested treatments did not cause qualitative alterations to the Ti surface features. No specific effects of the CAP were observed, although further studies are necessary to assess its potential as monotherapy with different settings or in combination with other decontamination procedures.

CLINICAL RELEVANCE

CAP is a promising option in the treatment of peri-implantitis because it has potential to improve the elimination of bacterial plaque from implant surfaces, in inaccessible pockets or during open-flap debridement, and should stimulate the process of the re-osseointegration of affected dental implants by not altering surface features and roughness.

Biofilm models in endodontics-A narrative review

The knowledge of biofilm and its eradication from the root canal system are of utmost importance in the clinical practice of an endodontist. Various treatment strategies and protocols have been demonstrated and discussed by numerous clinicians and researchers, on these models, that play an important role in the treatment outcome . Once a biofilm model is developed by considering various factors, several methods can be used to assess the biofilms formed on these models. This review discusses the importance of biofilm models in endodontics, types of biofilm models and factors associated with developing and the methods to evaluate these models.

Use of electromagnetic stimulation on an Enterococcus faecalis biofilm on root canal treated teeth in vitro

Root canal disinfection is of utmost importance in the success of the treatment, thus, a novel method for achieving root canal disinfection by electromagnetic waves, creating a synergistic reaction via electric and thermal energy, was created. To study electromagnetic stimulation (EMS) for the disinfection of root canal in vitro, single rooted teeth were instrumented with a 45.05 Wave One Gold reciprocating file. Specimens were sterilized and inoculated with Enterococcus faecalis ATCC 29,212, which grew for 15 days to form an established biofilm. Samples were treated with 6% sodium hypochlorite (NaOCl), 1.5% NaOCl 1.5% NaOCl with EMS, 0.9% saline with EMS or 0.9% saline. After treatments, the colony forming units (CFU) was determined. Data was analyzed by Wilcoxon Rank Sums Test (α = 0.05). One sample per group was scored and split for confocal laser scanning microscopy imaging. There was a significant effect with the use of NaOCl with or without EMS versus 0.9% saline with or without EMS (p = 0.012 and 0.003, respectively). CFUs were lower when using 0.9% saline with EMS versus 0.9% saline alone (p = 0.002). Confocal imaging confirmed CFU findings. EMS with saline has an antibiofilm effect against E. faecalis and can potentially be applied for endodontic disinfection.

Novel technique using cold atmospheric plasma coupled with air-polishing for the treatment of titanium discs grown with biofilm: An in-vitro study

OBJECTIVES

The aim of the present study was to assess the decontamination efficacy and titanium surface alterations of erythritol based air abrasion (AA) and cold atmospheric plasma (CAP) targeting a human complex biofilm.

METHODS

Saliva collected from a peri-implantitis patient was used to develop in vitro human biofilm over titanium discs with machined (group A) and moderately rough (group B) surface. The discs were treated with AA, experimental CAP or a combination of both treatments (COM). The amount of biofilm on the discs was measured by crystal violet (CV). Surface features and roughness before and after treatment were assessed by SEM and laser profilometry, respectively. The data were statistically analyzed using Kruskal Wallis followed by Dunn's multiple comparison test after being checked for normality by Shapiro-Wilk test.

RESULTS

All the discs in group A performed better to treatments compared to group B. In both groups, CV data showed significantly lower amount of biofilm after AA treatment compared to CAP (p<0.05). Cleaning efficacy revealed relevant decontamination of both the surfaces following AA and COM treatments and almost complete biofilm removal after AA application on group A (99.92%). SEM analysis demonstrated no post-treatment alterations on the discs and laser profilometry did not show statistically significant changes in S_a and S_dr values.

SIGNIFICANCE

Decontamination with AA delivering erythritol with or without CAP is highly effective in biofilm removal from different titanium surfaces. All the tested treatments, including CAP showed no noticeable alterations of the titanium discs surface features. Further in vivo studies are necessary to understand the potential of CAP technology in implant surface decontamination.

Mini-review: from in vitro to ex vivo studies: an overview of alternative methods for the study of medical biofilms

Microbial biofilms are a natural adaptation of microorganisms, typically composed of multiple microbial species, exhibiting complex community organization and cooperation. Biofilm dynamics and their complex architecture are challenging for basic analyses, including the number of viable cells, biomass accumulation, biofilm morphology, among others. The methods used to study biofilms range from in vitro techniques to complex in vivo models. However, animal welfare has become a major concern, not only in society, but also in the academic and scientific field. Thus, the pursuit for alternatives to in vivo biofilm analyses presenting characteristics that mimic in vivo conditions has become essential. In this context, the present review proposes to provide an overview of strategies to study biofilms of medical interest, with emphasis on alternatives that approximate experimental conditions to host-associated environments, such as the use of medical devices as substrata for biofilm formation, microcosm and ex vivo models.

Electrochemical Disinfection of Experimentally Infected Teeth by Boron-Doped Diamond Electrode Treatment

Disinfection and prevention of re-infection are the decisive treatment steps in endodontic therapy. In this study, boron-doped diamond (BDD) electrodes have been fabricated and used for disinfecting the root canals of extracted human teeth, which had been covered with bacterial biofilms formed by Bacillus subtilis and Staphylococcus epidermidis. The growth of B. subtilis could be successfully impaired, achieving a complete disinfection after 8.5 min treatment time with the success of disinfection depending on the insertion depth of the electrode in the root canal. S. epidermidis could completely be removed after 3.5 min treatment time. A clinically applicable electrode array led to complete disinfection after treatment times of 10 min for S. epidermidis and 25 min for B. subtilis. BDD electrode application allowed for the improved disinfection of root canals and dentin tubules based on a continuous production of reactive oxygen species and their enhanced penetration of dentin tubules most likely due the formation of a continuous stream of small gas bubbles. The treatment times that are required here will be shortened in clinical application, as mechanical shaping of the canal system would precede the disinfection process.

Virgicin, a novel lanthipeptide from Virgibacillus sp. strain AK90 exhibits inhibitory activity against Gram-positive bacteria

There is a significant increase in the discovery of new antimicrobial compounds in recent past to combat drug resistant pathogens. Members of the genus Bacillus and related genera have been screened extensively due to their ability to produce wide range of antimicrobial compounds. In this study, we have isolated and characterized a new antimicrobial peptide from a marine bacterium identified as Virgibacillus species. The low molecular mass and stability of the antimicrobial substance pointed towards the bacteriocinogenic nature of the compound. The RAST analysis of genome sequence showed presence of a putative bacteriocin biosynthetic cluster containing genes necessary for synthesis of a lanthipeptide. Translated amino acid sequence of mature C-terminal propeptide showed identity with salivaricin A (52.2%) and lacticin A (33.3%). Accordingly, the mass (2417 Da) obtained by MALDI analysis was in agreement with posttranslational modifications of the leader peptide to yield three methyl lanthionine rings and a disulfide bond between two free cysteine residues. The lanthipeptide was named as virgicin, which selectively inhibited the growth of Gram-positive bacteria and biofilm formation by Enterococcus faecalis. Inhibition of biofilm formation by E. faecalis was also observed in in vitro model experiments using hydroxyapatite discs. Thus, virgicin appears to be a promising new bacteriocin to control oral biofilm formation by selective pathogens.

Antibacterial Activity of Phytochemical Extracts and Endophytic Fungi of Carapa Guianensis Against Enterococcus Faecalis in Endodontic Infections An In Vitro Study

Objective:

The objective of this study was to evaluate the antibacterial activity of phytochemical extracts and endophytic fungi of Carapa guianensis against Enterococcus faecalis. Carapa guianensis leaves and stems were collected to obtain phytochemical extracts and fungal metabolites and evaluated for in vitro antibacterial activity against E. faecalis using the disc diffusion method and dentin blocks with bacterial biofilm.

Methods:

Thirty dentin blocks were prepared and contaminated for 60 days with E. faecalis. The specimens were randomly divided into 6 experimental groups according to the test solution used: G1 – hexane stem extract of Carapa guianensis; G2 – methanol stem extract of Carapa guianensis; G3 – methanol leaf extract of Carapa guianensis; G4 – ethyl acetate extract of the endophytic fungus Penicillium isolated from Carapa guianensis; G5 – negative control, with no addition of bacterial inoculum; G6 – positive control.

Results:

Bacterial growth was analyzed by spectrophotometry after 14 days of direct contact between the extracts and dentin blocks. The hexane-stem, methanol-stem, methanol-leaf, and ethyl-acetate endophytic fungus Penicillium extracts inhibited bacterial growth in 100% of the samples.

Conclusion:

The present study demonstrated the antibacterial potential of phytochemical extracts and endophytic fungi of Carapa guianensis against E. faecalis.

Influence of the EndoActivator Irrigation System on Dentinal Tubule Penetration of a Novel Tricalcium Silicate-Based Sealer

This study compared the effects of a conventional endodontic needle with an agitation system on a novel tricalcium silicate-based sealer (NTS) in terms of dentinal tubule penetration and interfacial adaptation to a root canal. Fifty single-rooted, recently-extracted human maxillary central incisors were randomly distributed into two homogeneous groups characterized by two different final cleansing systems: Conventional endodontic needle, or EndoActivator^®. After instrumentation, all the teeth were filled with the gutta-percha single cone technique in conjunction with the novel tricalcium silicate-based sealer. Teeth were horizontally sectioned at 1 and 5 mm from the apex and were observed under a confocal laser scanning microscope (CLSM) at five magnifications. The maximum, mean, and the circumferential percentage of the sealer penetration inside the tubules were measured. Moreover, the gap width was evaluated using Image J software (National Institutes of Health, Bethesda, MD). EndoActivator^® did not result in a significantly higher circumferential percentage of sealer penetration than conventional irrigation (p > 0.05). However, the gap width was significantly lower with EndoActivator^®, compared to conventional needles at both 1 mm (p = 0.035) and 5 mm (p = 0.038). The EndoActivator^® irrigation system did not significantly improve the NTS penetration, as compared to the conventional endodontic needle irrigation. Activation of the irrigation reduced the gap width significantly.

Enhancing antibacterial effect of sodium hypochlorite by low electric current-assisted sonic agitation

Background

This research focused on the effects of low electric current (μE)-assisted sonic agitation of sodium hypochlorite on Enterococcus faecalis infected human root dentin.

Methods

Extracted human canine roots were instrumented, sterilized, and experimentally contaminated with E. faecalis. After incubation for 21 days, the presence of the biofilm was confirmed by scanning electron microscopy (n = 3). Roots were randomly divided into seven groups according to decontamination procedures: G1: no treatment; G2: sterile saline; G3: 5.25% sodium hypochlorite; G4: passive ultrasonic irrigation; G5: EndoActivator (Dentsply Tulsa Dental Specialties, Tulsa, OK) agitation (EA); G6: μE agitation; and G7: μE-assisted sonic agitation. Fixed μE amperage and intensities were applied in G6 and G7. Following microbial sampling, bacterial colonies were counted using the direct plating method.

Results

Biofilm was not eradicated in any sample. The μE-assisted sonic agitation of sodium hypochlorite revealed the lowest cfu values (p<0.05), whereas there were no significant differences among the passive ultrasonic irrigation, EndoActivator and μE agitation alone (p>0.05).

Conclusions

Based on available evidence, the following conclusions were drawn: The μE-assisted sonic agitation increased the antibiofilm efficiency of sodium hypochlorite than passive ultrasonic irrigation and EndoActivator. The μE-assisted sonic agitation on 5.25% sodium hypochlorite is not capable to eradicate biofilms at 10mA energy level in 60s.

Experimental Models of Oral Biofilms Developed on Inert Substrates: A Review of the Literature

The oral ecosystem is a very complex environment where more than 700 different bacterial species can be found. Most of them are organized in biofilm on dental and mucosal surfaces. Studying this community is important because a rupture in stability can lead to the preeminence of pathogenic microorganisms, causing dental decay, gingivitis, or periodontitis. The multitude of species complicates biofilm analysis so its reproduction, collection, and counting are very delicate. The development of experimental models of dental biofilms was therefore essential and multiple in vitro designs have emerged, each of them especially adapted to observing biofilm formation of specific bacteria within specific environments. The aim of this review is to analyze oral biofilm models.

[Development of an Enterococcus faecalis periapical biofilm model for in vitro morphological study]

OBJECTIVE

This study aims to develop and observe a model system of the periapical biofilm structure of Enterococcus faecalis (E. faecalis).

METHODS

A total of 24 intact human single-rooted premolars extracted for orthodontic reasons were collected and randomly divided into eight groups (n = 3). The specimens were subjected to ultraviolet disinfection, inoculated with E. faecalis (ATCC 29212) suspension adjusted to 1 x 10(8) CFU x mL(-1), and incubated at 37 degrees C for 1, 2, and 7 d. Specimen groups were prepared for scanning electron microscope to examine the biofilm formation. The specimens in the confocal laser scanning microscope (CLSM) groups were stained with propidium iodide (PI) and ConA-fluorescein isothiocyanate (ConA-FITC) to examine the biofilm formation. The images were randomized, and biofilm coverage (%) was assessed using Photoshop CS5.

RESULTS

The biofilm coverage (%) on the cementum increased with increasing incubation period. The biofilm coverage of the 7 d group was significantly higher than those of the 1 and 2 d groups (P < 0.05). The values of the latter two groups were not significantly different (P > 0.05). Dense aggregations composed of E. faecalis and the amorphous matrix were observed on the root cementum surfaces of the specimens in the 7 d group. The bacteria were stained red by PI, and the matrix was stained green by ConA-FITC under CLSM observation. The biofilm coverage (%) on the samples in the 7 d group was 17.23% +/- 1.52%, showing multi-level space structure and water channels.

CONCLUSION

E. faecalis forms bacterial biofilms on the root cementum surface in 7 d. The biofilms were composed of E. faecalis and the amorphous matrix.

The disinfecting efficacy of root canals with laser photodynamic therapy

INTRODUCTION

Infecting microorganisms of the root canals are difficult to eliminate during endodontic treatment. In this study the effect of root canal disinfection with photodynamic therapy (PDT) at different time intervals in comparison to 2.5% sodium hypochlorite (NaOCl) irrigation and passive ultrasonic irrigation (PUI) in extracted teeth colonized with Enterococcus faecalis and Candida albicans was tested to assess which treatment reaches the best disinfection rate.

METHODS

One hundred and fifty-six extracted single-rooted teeth were collected, sterilized, and incubated with Enterococcus faecalis (ATCC 29212) and Candida albicans (ATCC 60193). The two groups were further divided into 6 groups depending on the treatment mode; HELBO(®)Endo Blue photosensitizer dye application followed by HELBO laser irradiation, with the output power 100 mW and emission of 660 nm, for a 1, 3 and 5 minutes, irrigation with 2.5% NaOCl, 10 second PUI with 2.5% NaOCl and control group. Flow cytometry and scanning electron microscopic (SEM) analysis were used to determine the effectiveness of the different disinfecting methods.

RESULTS

The different disinfecting methods had a significantly different effect on the percent of dead cells (p<0.001). A statistical significance of dead cells between organisms (p<0.001) was observed. Interaction between the disinfecting method and both of organisms had shown the statistical significance (p=0.045). Percent of dead cells in treatment groups were significantly higher compared to control group for both organisms (p<0.001).

CONCLUSIONS

PUI still remains the most effective method for disinfection of infected root canals in endodontics compared to hand instrumentation for both microorganisms. SEM analysis only confirmed the results. Other results ex vivo suggested that prolonging the time from 1 to 5 minutes of PDT increased the number of killed microorganisms significantly, therefore longer times of photodynamic therapy were recommended. Irrigation with 2.5% NaOCl showed similar results to 5 min irradiation.

Nanosilver Application in Dental Cements

Streptococcus mutans is the microorganism mostly responsible for initiation of tooth decay and also for the progression of an established lesion. Silver has been used for its antibacterial properties for many years, in different forms: ionised and elementary forms, as silver zeolites or as nanoparticles. The purpose of this study was to evaluate the antibacterial activity of three dental cements modified by nanosilver. Three cements were used: Sealapex, RelyX ARC, and Vitrebond. The cements were incorporated with 0.05 mL of silver nanoparticles solution. Control groups were prepared without silver. Six Petri plates with BHI were inoculated with S. mutans using sterile swabs. Three cavities were made in each agar plate (total = 18) and filled with the manipulated cements. They were incubated at 37°C for 48 h, and the inhibition halos were measured. The paired t-Test was used for statistical analysis (P<0.05). No inhibition halos were obtained for Sealapex and Rely X, but Vitrebond showed bactericidal activity without silver and enhanced effect with silver incorporation.

Microbial biofilm proliferation within sealer-root dentin interfaces is affected by sealer type and aging period

INTRODUCTION

Root canal fillings are intended to prevent microbial proliferation over time in the canal after treatment. The objective of this study was to assess biofilm proliferation within the sealer-dentin interfaces of 2 methacrylate resin-based systems, self-etch (SE) and total-etch (TE), and an epoxy resin-based sealer (EP), aged for up to 6 months.

METHODS

Standardized specimens (n = 45) comprising the coronal 5 mm of human roots were filled with the test materials and gutta-percha. Specimens were either not preincubated (control, n = 9) or were incubated in sterile saline for 1 week, 1 month, 3 months, or 6 months (n = 3/group). Monospecies biofilms of Enterococcus faecalis were grown on the specimens for 7 days in a chemostat-based biofilm fermentor mimicking pathogenic oral conditions. The extent of E. faecalis proliferation within the sealer-dentin interface for each material and incubation period group was assessed by using fluorescence microscopy of dihydroethidium-stained specimens.

RESULTS

TE had less biofilm proliferation than both EP and SE (P < .01). Deeper biofilm proliferation was detected in SE and EP specimens aged for 1 and 3 months than those aged for 1 week or 6 months (P < .05). Maximum depth of biofilm penetration was recorded for SE at 1 month (P < .05).

CONCLUSIONS

Within the test model used, the SE and EP sealers were more susceptible to interfacial biofilm proliferation than the TE restorative material. This susceptibility diminished after aging the materials' interfaces for 6 months.

Development of an intracanal mature Enterococcus faecalis biofilm and its susceptibility to some antimicrobial intracanal medications; an in vitro study

OBJECTIVES

To develop a mature biofilm of Enterococcus faecalis inside the root canal system and to test its susceptibility to some antimicrobial medications in vitro.

METHODS

Single rooted premolars were mechanically enlarged, sterilized, and then infected with a clinical isolate of E. faecalis. Biofilm formation and maturation was monitored using SEM. Biofilm bacteria were exposed to Amoxicillin+clavulanate, Ciprofloxacin, Clindamycin, Doxycycline, and calcium hydroxide as intracanal medications for 1 week. Finally bacterial samples were collected, and colony-forming units were enumerated.

RESULTS

SEM examination confirmed the formation of a mature biofilm at the end of the incubation period. All the chemotherapeutic agents used were significantly better than Calcium hydroxide in elimination of biofilm bacteria. The antimicrobial effect of Amoxicillin + clavulanate, Ciprofloxacin and Clindamycin was significantly better than Doxycycline (P=.05). However the difference in the antimicrobial effectiveness among them was statistically non-significant (P=.05).

CONCLUSIONS

The method used for bacterial biofilm development and maturation is reliable and can be used to assess the anti bacterial potential of endodontic materials. Also, the local application of antibacterial agents can be beneficial in resistant cases of apical periodontitis but only after careful culture and sensitivity testing to choose the appropriate agent for the existing flora.

The biofilm architecture of sixty opportunistic pathogens deciphered using a high throughput CLSM method

This study proposes a high throughput method based on Confocal Laser Scanning Microscopy (CLSM) combined with the use of 96-wells microtiter plates compatible with high resolution imaging for the study of biofilm formation and structure. As an illustration, the three-dimensional structures of biofilms formed by 60 opportunistic pathogens were thus observed and quantified. The results revealed the diversity of biofilm architectures. Specific spatial arrangement such as the mushroom-like structures already described for Pseudomonas aeruginosa was observed. Other features, such as hollow voids in microcolonies of Salmonella enterica strain Agona, were identified for the first time. The combined use of microplates and confocal imaging proved to be a good alternative to the other high throughput methods commonly used as it enables the direct, insitu, qualitative and quantitative characterization of biofilm architecture. This high content method should lead to a clearer understanding of the structure-function relationships implicated in biofilms traits.

In vitro scanning electron microscopic study on the effect of doxycycline and vancomycin on enterococcal induced biofilm

INTRODUCTION

Enterococcus (E) faecalis bacteria adhere to dentine of teeth root canals to form the biofilm. E. faecalis has been shown to be resistant to antibiotics. This in vitro study aimed to investigate the efficacy of vancomycin and doxycycline in inhibiting E. faecalis biofilm formation.

MATERIALS AND METHODS

A total of 60 extracted human teeth were incubated with E. faecalis (ATCC 35550 strain) for 45 days to allow biofilm formation. The teeth were equally divided into six groups (n=10): 1) positive control, 2) negative control, 3) doxycycline alone 4) doxycycline with filing, 5) vancomycin alone, 6) vancomycin with filing. The relevant canals were irrigated with 4µg/mL of either vancomycin or doxycycline antibiotic. Teeth were processed for scanning electron microscopy (SEM). Areas of biofilm remaining in the canals after antibiotic treatment were measured with Scion image analysis software using the SEM images.

RESULTS

Vancomycin is more effective in reducing the overall biofilm area compared with doxycycline; moreover filing after antibiotic administration increased this effect.

CONCLUSION

We can conclude that vancomycin had greater efficacy than doxycycline for inhibiting and reducing E. faecalis biofilms growth in root canals. However, it failed to completely eliminate biofilm formation.