Comparative Analysis of Enterococcus faecalis Biofilm Formation on Different Substrates

Antibacterial Effects of Silica Nanoparticles Loading Nano-silver and Chlorhexidine in Root Canals Infected by Enterococcus faecalis

INTRODUCTION

The persistence of microbial infection can lead to endodontic failure. Enterococcus faecalis (E. faecalis) is acknowledged to be a closely associated bacterium. This study investigated the antimicrobial effects of mesoporous silica nanoparticles (nMS) carrying nano-silver and chlorhexidine (nMS-nAg-Chx) on E. faecalis.

METHODS

Analyses were conducted to assess the antimicrobial efficacy of nMS-nAg-Chx toward planktonic E. faecalis, including the zone of inhibition, minimal inhibitory concentration, and growth curves. The measurement of lactic acid, scanning electron microscopy, live-dead bacteria staining, and quantitative real-time PCR were done to further investigate its anti-biofilm effect. Colony forming unit and scanning electron microscopy were used to assess its efficacy in infected root canals.

RESULTS

The growth of planktonic E. faecalis was suppressed with a minimal inhibitory concentration value of 25 μg/mL (P＜.05). nMS-nAg-Chx concentration-dependently inhibited biofilm formation of E. faecalis with the reduction of lactic acid (P < .05), sparse biofilm structure, reduced percentage of viable bacteria (P < .05), and suppressed expression of ebpR, gelE, ace, and efa genes (P < .05). The 7-day sealing of nMS-nAg-Chx resulted in a notable reduction in bacterial counts compared to the saline control group in the E. faecalis infected root canals (P < .05).

CONCLUSIONS

nMS-nAg-Chx effectively inhibits E. faecalis and removes its biofilm from infected human root canals. It may be used for endodontic treatments in the control of E. faecalis bacteria as an intracanal medication.

Antimicrobial action and cytotoxicity of hypochlorous acid obtained from an innovative electrolytic device - An in vitro study

OBJECTIVE

This study evaluated the antimicrobial effect and cytotoxicity of hypochlorous acid(HClO) obtained from an innovative electrolytic device.

DESIGN

The root canals of fifty extracted human teeth were inoculated with Enterococcus faecalis and divided into 5 groups (n = 10): DW (control); 2% chlorhexidine gel(CHX); 2.5% sodium hypochlorite(NaOCl); 250 ppm HClO and 500 ppm HClO. The counting of colony forming units evaluated the decontamination potential of each group. Cytotoxicity was evaluated after inoculation of tested protocols in fibroblastic cells for 3 min, calculating the cell viability. Specific statistical analysis was performed (α = 5%).

RESULTS

The highest bacterial reduction was observed in experimental groups, with no statistical differences from each other (p > 0.05). The highest number of viable cells was observed in control group, followed by 250 ppm HClO and 500 ppm HClO groups, with statistical differences from each other (p < 0.05).

CONCLUSIONS

It could be concluded that HClO presented high antimicrobial activity and low cytotoxicity at both tested concentrations.

Evaluation of the pH and Antibacterial Efficacy of Mineral Trioxide Aggregate With and Without the Incorporation of Titanium Tetrafluoride

Introduction Microorganisms play an important role in causing inflammation in the pulp and periapical regions. Even after undergoing chemo-mechanical procedures during root canal treatment, bacteria may persist within dentinal tubules, posing a risk of disease recurrence. Mineral trioxide aggregate (MTA), introduced as a dental material, has been investigated as a potential antibacterial agent since its early use. Calcium and phosphorus are the primary ions in MTA, and their antibacterial characteristics are attributed to the release of calcium hydroxide through surface hydrolysis of calcium silicate components. Previous studies have shown that MTA has limited antimicrobial properties. Several alterations have been made to enhance the biological properties of MTA, such as incorporating nanoparticles made from silver, zinc, gold, and titanium. Therefore, in this study, titanium tetrafluoride (TiF4) was added to MTA in an effort to enhance its antimicrobial properties. Aim To compare and evaluate the antibacterial efficacy of MTA after the incorporation of TiF4. Materials and methods A total of 56 samples were made by mixing MTA with different weight proportions of TiF4 (1 wt%, 2 wt%, and 3 wt%). Out of these, 28 samples were taken to test each of the following properties: antibacterial efficacy and pH. The specimens were prepared using stainless steel molds of recommended dimensions for testing the pH. The pH was evaluated using a pH meter, and the antibacterial efficacy was assessed using the direct contact test. Data regarding the antibacterial efficacy and pH of MTA with various proportions of TiF4 were investigated for normality using the Kolmogorov-Smirnov test and assessed for normal distribution. The antibacterial properties among the four groups were analyzed using one-way analysis of variance (ANOVA), followed by pairwise multiple comparisons using Tukey's Honest Significant Difference test. The level of statistical significance was determined at p ≤ 0.05. MTA, when incorporated with TiF4, showed enhanced antibacterial properties. Results On day 1, the group treated with MTA containing 3% TiF4 demonstrated the strongest antibacterial effectiveness, with a mean of 4.67 ± 0.04 colony-forming units (CFU)/mL × 10^8. However, the group treated with plain MTA had the lowest mean values, at 5.67 ± 0.25 CFU/mL × 10^8. On day 1, the MTA group with 3% TiF4 also had the highest mean pH values (11.90 ± 0.05), while the plain MTA group had the lowest mean pH values (11.64 ± 0.78). On day 7, the MTA group with 3% TiF4 had the highest pH value (12.85 ± 0.08), whereas the plain MTA group had the lowest pH value (11.92 ± 0.09). Conclusion The inclusion of TiF4 resulted in an augmentation of the antibacterial efficacy of MTA against Enterococcus faecalis (E. faecalis). Hence, the integration of TiF4 into MTA can be considered a promising development against E. faecalis during endodontic procedures.

Antimicrobial action, cytotoxicity and erosive potential of hypochlorous acid obtained from an electrolytic device compared with sodium hypochlorite

OBJECTIVES

This study aimed to compare the antimicrobial action, cytotoxicity, cleaning ability, and erosion of dentine of hypochlorous acid (HClO) obtained from an electrolytic device at two different concentrations (Dentaqua) and three concentrations of sodium hypochlorite (NaOCl).

METHODS

Microbiological test-The root canals of sixty single-rooted extracted human teeth were inoculated with Enterococcus faecalis and divided into 6 groups (n = 10), according to decontamination protocol: DW (control); 1% NaOCl; 2.5% NaOCl; 5.25% NaOCl; 250 ppm HClO and 500 ppm HClO. The colony-forming units were counted to evaluate the decontamination potential of each group, calculating the reduction in bacterial percentage. Cytotoxicity test-Cytotoxicity was evaluated after inoculation of the same tested protocols in fibroblastic cells for 3 min, calculating the cell viability percentages. Specifical statistical analysis was performed (α = 5%). Cleaning ability and erosion-Fifty-six single-rooted bovine lower incisors were divided into seven groups of 8 roots each, being the test groups 1% NaOCl; 2.5% NaOCl; 5,25% NaOCl; 250 ppm HClO and 500 ppm HClO, and a negative and positive control. Negative control was not contaminated, and the other groups were inoculated with Enterococcus faecalis. SEM images were ranked as from the cleanest to the least clean. Erosion was also assessed, being ranked from the least to the most eroded dentine.

RESULTS

The highest bacterial reduction was observed in experimental groups, with no statistical differences between them (p > 0.05). The highest number of viable cells was observed in control group, followed by 250 ppm HClO and 500 ppm HClO groups, with statistical differences between them (p < 0.05). 1% NaOCl; 2.5% NaOCl; 5.25% NaOCl and 500 ppm HClO displayed the cleanest areas. All sodium hypochlorite groups displayed erosion with higher ranks with greater concentration, while hypochlorous acid did not display any erosion regardless the concentration.

CONCLUSIONS

It is possible to conclude that HClO obtained from an electrolytic device presented high antimicrobial activity and low cytotoxicity in both tested concentrations. 500 ppm HClO did not display erosion and showed great cleaning ability.

CLINICAL RELEVANCE

The use of 500 ppm hypochlorous acid may reduce unfavorable behavior of sodium hypochlorite whilst maintaining its antimicrobial action.

Rational design of EDTA-incorporated nanoflowers as novel and effective endodontic disinfection against biofilms

The ethylenediaminetetradiacetic acid (EDTA) is one of the most commonly used irrigation solutions. Although EDTA has a very low antimicrobial property, it is used to remove inorganic part of smear layer in areas of root canal system. Herein, we developed EDTA-incorporated nanoflowers (EDTA NFs), for the first time, as novel and effective irrigation solution with quite high antimicrobial property to provide complete disinfection in root canal system. We both systematically elucidated the formation of the EDTA NFs with various techniques, and their catalytic and antimicrobial activities in the presence of hydrogen peroxide (H2O2) were documented through intrinsic EDTA property and peroxidase-like activities.

Advances in Material Modification with Smart Functional Polymers for Combating Biofilms in Biomedical Applications

Biofilms as living microorganism communities are found anywhere, and for the healthcare sector, these constitute a threat and allied mechanism for health-associated or nosocomial infections. This review states the basis of biofilms and their formation. It focuses on their relevance for the biomedical sector, generalities, and the major advances in modified or new synthesized materials to prevent or control biofilm formation in biomedicine. Biofilm is conceptualized as an aggregate of cells highly communicated in an extracellular matrix, which the formation obeys to molecular and genetic basis. The biofilm offers protection to microorganisms from unfavorable environmental conditions. The most frequent genera of microorganisms forming biofilms and reported in infections are Staphylococcus spp., Escherichia spp., and Candida spp. in implants, heart valves, catheters, medical devices, and prostheses. During the last decade, biofilms have been most commonly related to health-associated infections and deaths in Europe, the United States, and Mexico. Smart, functional polymers are materials capable of responding to diverse stimuli. These represent a strategy to fight against biofilms through the modification or synthesis of new materials. Polypropylene and poly-N-isopropyl acrylamide were used enough in the literature analysis performed. Even smart polymers serve as delivery systems for other substances, such as antibiotics, for biofilm control.

Analysis of antimicrobial efficacy of sodium hypochlorite and ozonated water against biofilm in oval canals

This in vitro study compared the antimicrobial efficacy of 2.5% sodium hypochlorite (NaOCl) and 8 µg/mL ozonated water agitated by passive ultrasonic irrigation (PUI) or PUI combined with EndoActivator (EA) against mature multispecies biofilm. One hundred and five oval-shaped mandibular premolars were instrumented, sterilized, and inoculated with Enterococcus faecalis, Candida albicans, and Staphylococcus aureus, divided into: control group - saline; O3 group - ozonated water; O3 PUI group - ozonated water with PUI agitation; O3 PUI+EA group - ozonated water with PUI+EA agitation; NaOCl group - NaOCl; NaOCl PUI group - NaOCl with PUI agitation; and NaOCl PUI+EA group - NaOCl with PUI+EA agitation. Microbiological samples were collected before (S1) and after (S2) the disinfection procedures and the data were statistically analyzed using the Kruskal-Wallis test. In the culture method, there was significant disinfection in the O3 PUI+EA, NaOCl, NaOCl PUI, and NaOCl PUI+EA groups (p˂0.05). The combination of NaOCl with PUI+EA reduced microbial counts to zero (p˂0.05). In the qPCR method, there was a significant reduction in the total count of viable microorganisms in the O3 PUI, O3 PUI+EA, NaOCl, NaOCl PUI, and NaOCl PUI+EA groups (p˂0.05). It can be concluded that 2.5% NaOCl with and without agitation, as well as 8 µg/mL ozonated water with its action enhanced by the agitation techniques, were effective in root canal disinfection, and their antimicrobial efficacy is related to the microorganisms present in the biofilm.

The presence of Enterococcus faecalis in saliva as a risk factor for endodontic infection

Aim

The aim of the present study was to investigate and correlate the prevalence of Enterococcus faecalis in saliva and in root canals with different pulpal and periapical conditions.

Methodology

Sixty-seven patients were divided into five groups based on pulpal and periapical tissue status: healthy vital teeth (HVT, n=7), healthy treated teeth without lesion (HTT, n=9), irreversible pulpitis (IP, n=13), necrosis (N, n=18), and post-treatment apical periodontitis (PTAP, n=20). Saliva, rubber dam, sterility control and pre-treatment root canal samples were collected and microbiologically processed by culture method. The phylogenetic relationship of E. faecalis isolates collected from root canals and saliva were investigated by whole genome sequencing. Fisher’s exact test was used to correlate the presence of E. faecalis in root canals or saliva with clinical and/or radiographic findings. Linear/logistic regression analyses were performed to establish the relationship between the presence of E. faecalis in root canals, saliva, and the status of periapical tissues.

Results

E. faecalis was found in 18 root canal and saliva samples. E. faecalis root canal isolates were recovered with the highest frequency from post-treatment apical periodontitis. The occurrence of E. faecalis in saliva was strongly associated with its detection in the root canals (P &lt; 0.001). The pretreatment presence of E. faecalis in root canals was associated with significantly higher odds of having periapical lesions (OR=11.03; 95% CI, 1.27-95.70; p &lt; 0.05). Saliva and root canal isolates from the same patient were highly correlated at the phylogenetic level (Jaccard index &gt;0.95).

Conclusion

This pilot study confirms the role of E. faecalis in developing peri-radicular lesions in secondary endodontic infections and suggests that saliva could be the main source of infection. Further studies are needed to investigate the exact origin of this bacteria and its true role in the pathogenesis of secondary/persistent endodontic infections.

Evaluation of the antibacterial activity of trans-anethole against Enterococcus cloacae and Enterococcus faecalis strains of food origin

The present study sought to evaluate the antibacterial activity of trans-anethole against food-borne strains of Enterobacter cloacae and Enterococcus faecalis. The study was performed using Minimum Inhibitory Concentration (MIC), and Minimum Bactericidal Concentration (MBC) methods, in addition, disc diffusion technique was used to evaluate the association of trans-anethole with synthetic antimicrobials. Minimum Inhibitory Concentration for Adherence (MICA) testing was also performed. The results revealed that trans-anethole presents no antibacterial activity at any of the concentrations used against the E. cloacae strains tested. However, trans-anethole presented antibacterial effect against five of the six E. faecalis bacterial strains tested, with MIC values ranging from 500 μg/mL to 1000 μg/mL. Further, when analyzing the MBC results against E. faecalis, it was observed that the compound presented values ranging from 500 μg/mL to 1000 μg/mL. As for the associations, it was observed that trans-anethole when combined with the antimicrobials ampicillin, gentamicin, ciprofloxacin, and ceftriaxone presented synergistic effect against most strains of E. faecalis. However, both trans-anethole and the control chlorhexidine (0.12%) presented no antibiofilm effects against strains of E. faecalis. In short, trans-anethole presented potential antibacterial against E. faecalis strains of food origin, and may upon further study, it may be used alone or in association with synthetic antimicrobials to combat infections caused by this bacterium.

Antibacterial Efficacy of Cold Atmospheric Plasma, Photodynamic Therapy with Two Photosensitizers, and Diode Laser on Primary Mandibular Second Molar Root Canals Infected with Enterococcus faecalis: An In Vitro Study

Objectives

This study aimed to compare the antibacterial efficacy of cold atmospheric plasma (CAP), photodynamic therapy (PDT) with two photosensitizers (PSs), and diode laser for disinfection of primary mandibular second molar root canals infected with Enterococcus faecalis (E. faecalis).

Materials and Methods

In this in vitro experimental study, 50 primary second primary molars underwent chemomechanical preparation of root canals. The root canals were then inoculated with E. faecalis. After 3 weeks of incubation, the teeth were randomly assigned to five groups of CAP, 940 nm diode laser, PDT with 445 nm laser and curcumin PS, PDT with 660 nm laser and methylene blue (MB) PS, and 2.5% sodium hypochlorite (NaOCl). Samples were collected from the vortexed root canals and cultured on agar, and the number of colonies was counted. Data were analyzed by one-way analysis of variance.

Results

The percentage of reduction in bacterial count was significantly different among the study groups (P < 0.001). The highest reduction in bacterial count was noted in 2.5% NaOCl and the lowest in 940 nm diode laser group. The difference in bacterial count reduction between 445 nm laser + curcumin and 660 nm laser + MB (P = 0.989), and CAP and NaOCl (P = 1.000) groups was not significant.

Conclusion

CAP was found to be more effective than PDT and diode laser as an adjunct to mechanical root canal disinfection of primary molars for elimination of E. faecalis and can serve as an alternative to 2.5% NaOCl irrigation.

Efficacy of chitosan paste as intracanal medication against Enterococcus faecalis and Candida albicans biofilm compared with calcium hydroxide in an in vitro root canal infection model

Background

Enterococcus faecalis and Candida albicans are frequently found in persistent endodontic infection and could remain in dentinal tubules despite intracanal medication with calcium hydroxide (Ca(OH)₂), a commonly used medication. Thus, an effective and safe antimicrobial medication against such refractory infection is necessary in endodontic retreatment, so we aimed to test the efficacy of chitosan paste against these microorganisms compared with Ca(OH)₂ in root canals of extracted human teeth.

Methods

Thirty-six sterilized human root samples prepared from extracted premolars and upper maxillary incisors were infected with E. faecalis for 14 days, while 32 were infected with C. albicans for 48 h, for mature biofilm formation. The samples were assigned to 6 groups of intracanal medications: Group 1: no medication (negative control); Group 2: 20% Polyethylene glycol (PEG); Group 3: 20% Propylene glycol (PG); Group 4: Ca(OH)₂; Group 5: Chitosan + PEG; and Group 6: Chitosan + PG. After 7 days, intracanal surface dentin was harvested using Protaper next, resuspended, serially diluted and spread on Brain–Heart-Infusion agar (for E. faecalis) and Yeast Extract-Peptone-Dextrose agar (for C. albicans) for colony count. Antimicrobial efficacy was determined as percentage of remaining colony forming unit (CFUs) relative to negative control and analyzed using One-way ANOVA and post-hoc Games-Howell test. The significance level was set at 0.05.

Results

For E. faecalis, chitosan + PG had significantly higher antibacterial activity than Ca(OH)₂ (P = 0.039). Chitosan + PEG and chitosan + PG medication significantly reduced viable bacteria compared with negative control, PEG and PG (P = 0.001, 0.003, 0.024, respectively for chitosan + PEG; P = 0.002, 0.003, 0.014, respectively for chitosan + PG). For C.albicans, chitosan + PEG and chitosan + PG were not significantly different from Ca(OH)₂. However, Chitosan + PEG and chitosan + PG, but not Ca(OH)₂, showed a significantly lower level of remaining CFUs compared with negative control (P = 0.013 and 0.005, respectively).

Conclusion

Chitosan paste showed better efficacy in reducing viable E. faecalis biofilm when compared to Ca(OH)₂ after 7-day intracanal medication in this in vitro root canal model. It could also significantly reduce viable C. albicans, but was not significantly different from Ca(OH)₂.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-022-02385-x.

Antimicrobial action of ozonated water and photodynamic therapy with sonic activation in root canals infected with Enterococcus faecalis

Background

New protocols are constantly being tested in the search for complete disinfection of root canals without the undesirable effects of sodium hypochlorite. This study evaluated the antimicrobial effect of ozonated water and photodynamic therapy (PDT) with sonic activation in root canals infected with Enterococcus faecalis.

Material and Methods

Seventy single-rooted canals of human teeth were prepared and contaminated with E. faecalis for 21 days. The teeth were divided into six experimental groups (n=10): ozonized water without (O + S-) and with sonic activation (O + S +); PDT without (PDT + S-) and with sonic activation (PDT + S +); PDT + ozonized water without (PDT + O + S-) and with sonic activation (PDT + O + S +); and two control groups, one positive (n = 5) and one negative (n = 5). Microbial collections were performed before and shortly after treatment, counted in the log of colony-forming units and tested for significant difference between these counts, if any (Student's t-test). The ANOVA two-way test was applied to evaluate whether the Treatment factor (Ozone, PDT and Ozone + PDT) and the Sonic factor (With and without sonic activation) had any effect on microbial reduction.

Results

In all protocols, there was a significant microbial reduction (p=0.025), whereas in the groups in which sonic activation was used, the microbial reduction was significantly greater (p=0.001).

Conclusions

The treatments significantly reduced the number of microorganisms in the root canals. Sonic activation helped to increase the microbial reduction in infected root canals. Key words:Endodontics, ozone, photodynamic therapy, enterococcus faecalis.

Antimicrobial potential and osteoblastic cell growth on electrochemically modified titanium surfaces with nanotubes and selenium or silver incorporation

Titanium nanotube surfaces containing silver, zinc, and copper have shown antimicrobial effects without decreasing osteoblastic cell growth. In this in-vitro study we present first results on the biological evaluation of surface modifications by incorporating selenium and silver compounds into titanium-dioxide (TiO₂) nanotubes by electrochemical deposition. TiO₂-nanotubes (TNT) and Phosphate-doped TNT (pTNT) were grown on the surface of Ti6Al4V discs by anodization. Hydroxyapatite (HA), selenium (Se) and silver (Ag) compounds were incorporated by electrochemical deposition. Colony forming units of Staphylococcus epidermidis (DSM 3269) were significantly decreased in SepTNT (0.97 ± 0.18 × 10⁶ CFU/mL), SepTNT-HA (1.2 ± 0.39 × 10⁶ CFU/mL), AgpTNT (1.36 ± 0.42 × 10⁶ CFU/mL) and Ag₂SepTNT (0.999 ± 0.12 × 10⁶ CFU/mL) compared to the non-modified control (2.2 ± 0.21 × 10⁶ CFU/mL). Bacterial adhesion was calculated by measuring the covered area after fluorescence staining. Adhesion was lower in SepTNT (37.93 ± 12%; P = 0.004), pTNT (47.3 ± 6.3%, P = 0.04), AgpTNT (24.9 ± 1.8%; P < 0.001) and Ag₂SepTNT (14.9 ± 4.9%; P < 0.001) compared to the non-modified control (73.7 ± 11%). Biofilm formation and the growth of osteoblastic cells (MG-63) was observed by using Crystal Violet staining. Biofilm formation was reduced in SepTNT (22 ± 3%, P = 0.02) and Ag₂SepTNT discs (23 ± 11%, P = 0.02) compared to the non-modified control (54 ± 8%). In comparison with the non-modified control the modified SepTNT-HA and pTNT surfaces showed a significant higher covered area with osteoblastic MG-63-cells. Scanning electron microscope (SEM) images confirmed findings regarding bacterial and osteoblastic cell growth. These findings show a potential synergistic effect by combining selenium and silver with titanium nanotubes.

The dentine-sealer interface: modulation of antimicrobial effects by irrigation

AIM

Assess whether sodium hypochlorite (NaOCl) or chlorhexidine (CHX) and two irrigation protocols may alter the antibacterial properties of dentine and three endodontic sealers using a novel ex vivo tooth model.

METHODOLOGY

Prior to antibacterial testing, the tooth model was validated by means of scanning electron microscopy (SEM) to evaluate the separation between dentine and sealer surfaces. Root blocks prepared from extracted human roots were pretreated with 17% EDTA + 0.9% saline and subsequently treated with 1% NaOCl (G1), 2% CHX (G2) or no irrigant (G3). Two irrigation protocols were further investigated, "1% NaOCl + 17% EDTA" (P1) and "1% NaOCl + 17% EDTA + 2% CHX" (P2). Following irrigation, the root blocks were either filled with AH Plus, BioRoot RCS and Pulp Canal Sealer (PCS), or left empty. All groups were incubated for 1, 7 and 28 days. Direct contact tests for planktonic E. faecalis and 48 hours E. faecalis biofilms were performed at the level of dentine and sealer surfaces. Statistical analysis was performed on the bacterial survival between irrigants (G1, G2 and G3) and between irrigation protocols (P1 and P2) (p<0.05).

RESULTS

The model was considered reproducible as SEM examination of dentine samples indicated consistent separation between dentine and sealer surfaces. Irrigation with CHX (G2) and irrigation protocol (P2) enhanced the antibacterial properties of dentine without sealer application as well as dentine in contact with all three sealers tested, especially against planktonic E. faecalis. G2 and P2 also improved the antibacterial effect of AH Plus surfaces for all three incubation times. No irrigation groups (G1, G2) or irrigation protocols (P1, P2) altered the antibacterial properties of BioRoot RCS surfaces against planktonic bacteria or biofilms. Only BioRoot RCS surfaces eliminated the planktonic E. faecalis in all irrigation groups (G1, G2, G3) and protocols (P1, P2) investigated while PCS surfaces eliminated E. faecalis in biofilms in all groups up to 7 days.

CONCLUSIONS

The tooth model was reproducible. CHX improved the antibacterial activity upon both sealer and dentine surfaces. Among sealers, BioRoot RCS was less affected by NaOCl and CHX, and exhibited high antibacterial properties regardless the irrigation applied.

An in vitro study on the effects of serum proteins on Enterococcus faecalis adhesion to three types of root sealers and gutta-percha

BACKGROUND

The extrusion of overfilled materials that extend beyond the apical foramina into the periradicular tissue may serve as a reservoir for bacterial adhesion and further affect recovery from periapical diseases. The aim of this study was to evaluate the effects of serum proteins on Enterococcus faecalis adhesion and survival on the surface of a calcium hydroxide-based root canal sealer (Apexit Plus), an epoxy resin sealer (AH-Plus) and a bioceramic sealer (iRoot SP).

METHODS

Apexit Plus, AH-Plus and iRoot SP were evenly coated on gutta-percha, using gutta-percha alone as the control. After root canal sealer setting, the number of E. faecalis adhering to the root canal sealers and gutta-percha was counted in fetal bovine serum (FBS) or tryptic soy broth supplemented with 1% glucose (TSBG) by viable cell plate counts. The morphology of 7-day-old E. faecalis biofilms in FSB and TSBG was observed by scanning electron microscopy (SEM). Furthermore, E. faecalis biofilms on the three root canal sealers were labeled with a LIVE/DEAD BacLight™ Bacterial Viability Kit, and the ratios of viable to dead cells were analyzed using laser scanning microscopy operative software (Zen software).

RESULTS

In the assays, after 1 and 7 days, the number of E. faecalis adhering to the root canal sealers or gutta-percha in FBS were significantly lower than those in TSBG (P < 0.05). In FBS, E. faecalis adhesion to iRoot SP and gutta-percha was reduced to a greater extent than that adhered to Apexit Plus and AH-Plus. Few E. faecalis accumulated on iRoot SP in FBS, whereas many bacteria assembled on iRoot SP and formed biofilms in TSBG. The ratio of viable cells in the E. faecalis biofilm on iRoot SP was the lowest.

CONCLUSIONS

Calcium hydroxide-based root canal sealers, epoxy resin sealers and bioceramic sealers may provide a substrate for E. faecalis adhesion, and the bioceramic sealer in this study showed the least E. faecalis adhesion in the presence of serum proteins compared to the other two sealers.

A new model for the formation of an Enterococcus faecalis endodontic biofilm with nutritional restriction

An in vitro model for the formation of an Enterococcus faecalis endodontic biofilm under nutritional restriction was established, simulating clinical conditions for the evaluation of antimicrobial substances. Biofilm formation in dentin was standardized using root quarters incubated with E. faecalis ATCC 29212 at 37°C without nutritional changes. Biofilms were evaluated at 7, 14, and 30 days, counting bacterial colony-forming units using conventional culture and verified scanning electron microscopy. Bacterial viability and biovolume were determined with confocal laser microscopy. Colonization of E. faecalis and biofilm formation on the dentinal surface was confirmed after 7 and 14 days, respectively. Microorganism colonization was homogeneous over the entire root surface at each time point, without significant differences in the viability percentage and biovolume. On the contrary, a decrease in viability and an increase in biovolume were observed when the time was increased. Compared with other incubation times, 14 days was found to be the best time for the establishment of the biofilm in terms of biovolume and bacterial viability. This in vitro model for the formation of endodontic biofilm will allow future evaluation of the efficacy of antimicrobial substances with a more adequate clinical approach.

Model system parameters influence the sodium hypochlorite susceptibility of endodontic biofilms

AIM

To evaluate in a laboratory setting the influence of several model system parameters on the sodium hypochlorite (NaOCl) susceptibility of endodontic biofilms. Based on these findings, a relevant in vitro endodontic biofilm model is proposed.

METHODOLOGY

In vitro biofilms were cultured, varying the following experimental model parameters: biofilm composition (monospecies Enterococcus faecalis and a multispecies biofilm including E. faecalis, Fusobacterium nucleatum, Prevotella intermedia and Porphyromonas gingivalis), incubation time (24 h or 11 days), incubation atmosphere (aerobically or anaerobically) and biofilm substrate (polystyrene microtiter plate wells, hydroxyapatite or dentine). Biofilms were subjected to treatment with NaOCl (0.025%, 0.1%, 0.5%, 2.5%) for 1 min, control groups included treatment with purified water. Biofilms were harvested and the number of surviving cells was determined by plate counting using general (monospecies biofilms) or selective (multispecies biofilms) media. A two-way ANOVA was used to explore the effect of the model parameters on biofilm eradication. Finally, the most physiologically relevant biofilm model (11-day-old multispecies biofilm grown anaerobically on dentine discs) was characterized by selective media plate counting, NaOCl susceptibility testing, scanning and transmission electron microscopy.

RESULTS

There was no difference in NaOCl eradication between the anaerobically and aerobically grown E. faecalis biofilms. One-day-old biofilms of E. faecalis were more susceptible to most tested NaOCl concentrations than 11-day-old biofilms (p < .05). When grown in a multispecies biofilm, E. faecalis was significantly less susceptible to NaOCl treatment than in a monospecies biofilm (p < .05). E. faecalis in a multispecies biofilm grown in a MTP was more susceptible to NaOCl (0.025% and 0.1%) than when grown on hydroxyapatite or dentine. No difference in biofilm NaOCl susceptibility was seen between hydroxyapatite and dentine. The multispecies biofilm proved to be a reproducible model with high NaOCl resistance, complex structure and organization.

CONCLUSION

The parameters biofilm age, biofilm composition and substrate had a significant influence on the NaOCl susceptibility of E. faecalis biofilms. Older biofilms, multispecies biofilms and biofilms grown on dentine and hydroxyapatite had reduced NaOCl susceptibility. These findings emphasize the importance of selecting relevant parameters when designing a laboratory biofilm model system for the evaluation of antimicrobial treatments.

Antibacterial effect of silver nanoparticles mixed with calcium hydroxide or chlorhexidine on multispecies biofilms

The purpose is to evaluate the antibacterial effects of the silver nanoparticles (AgNPs) (Nanografi, METU Teknokent, Ankara, Turkey) mixed with calcium hydroxide (Ca(OH)₂) (Ultracal XS, Ultradent, St Louis, US) or chlorhexidine gel (CHX) (Gluco-Chex, Cerkamed, Stalowa Wola, Poland) against a multispecies biofilm, by confocal laser scanning microscopy (CLSM) and culture-based analysis. Dentine blocks were inoculated with Enterococcus faecalis, Streptococcus mutans, Lactobacillus acidophilus and Actinomyces naeslundii for 1 week. Infected dentine blocks were randomly divided into groups according to medication; saline solution (SS), Ca(OH)₂, Ca(OH)₂ + AgNP, 2%CHX gel and 2%CHX gel + AgNP and time of application: 1 and 7 days (all groups, n = 5). Bacterial samples were collected before and after medication to quantify the bacterial load. Biofilm elimination was quantitatively analyzed by Live/Dead BacLight Bacterial Viability staining and CLSM. The addition of AgNPs to Ca(OH)₂ increased the effectiveness of medicament in terms of bacterial reduction in both application times (1 and 7 days) (p < 0.05: ANOVA, Tukey's test) according to culture-based analysis. The CLSM images revealed that mixture of AgNP with CHX killed significantly more bacteria when compared with all other medicaments at 1- and 7-day application times (p < 0.05 and p > 0.05, respectively: Kruskal-Wallis, Dunn post hoc tests). The efficacy of Ca(OH)₂ mixed with AgNPs was superior to Ca(OH)₂ used alone in both application times (p < 0.05) according to CLSM analysis. The present study put forth the potential use of AgNPs mixed with Ca(OH)₂ or CHX on multispecies (Enterococcus faecalis, Streptococcus mutans, Lactobacillus acidophilus and Actinomyces naeslundii) biofilm in 1 and 7day application periods.

Dosimetry of pulsed magnetic field towards attaining bacteriostatic effect on Enterococcus faecalis: Implications for endodontic therapy

AIM

To examine in a laboratory setting the efficacy of moderate to high strength magnetic fields, as a potential bacteriostatic stimulus, against Enterococcus faecalis, one of the causative agents for infection during root canal treatments.

METHODOLOGY

Four different strengths (1, 2, 3 and 4 T) of the pulsed magnetic field (PMF) were applied in thirty repetitions to bacterial suspension. A pickup coil setup was used to measure the electromotive force induced inside the bacterial suspensions. The optical density (OD) was monitored over time (for 16 h 40 min) during the post-treatment period to assess bacterial growth. Along with the change in OD values, live/dead assay, membrane depolarization study, atomic force microscopy (AFM), scanning electron microscopy (SEM) and reactive oxygen species (ROS) assay on selected samples were studied to evaluate the effect of PMFs. All results were analysed using one-way ANOVA followed by post hoc Tukey test and considered significant at p < .05. Regression analysis (at a confidence of 95%, α = 0.05) was performed on the bacterial growth and membrane depolarization studies to determine progressive changes of the outcomes.

RESULTS

The peak value of the induced electromotive force was recorded as 0.25 V, for the 4 T magnetic field pulse with a pulse width of 16 ms. There was a significant arrest of bacterial cell growth after an exposure to PMFs of 1 T, 3 T and 4 T (ANOVA score: F (4, 495) =395.180 at p = .05). The image-based qualitative results of the live/dead assay using fluorescence microscopy techniques indicated that an exposure to higher PMFs (3 T/ 4 T) induced a bacteriostatic effect in a longer post-exposure timescale. Evidence of altered membrane potential within the 2 h of exposure to 4 T PMF was supported by the incidence of elevated ROS. For the ROS assay, a significant difference occurred for 4 T exposed samples (ANOVA score: calculated F (1, 3) =20.2749 at p = .05). SEM and AFM observations corroborated with the outcomes, by portraying significant membrane damage.

CONCLUSION

In a laboratory setting, PMFs with higher magnitudes (3 T and 4 T) were capable of inducing bacteriostatic effects on E. faecalis.

Influence of ultrasonic activation on antimicrobial activity of a new final irrigant containing glycolic acid: An in vitro study

This study evaluated the influence of ultrasonic activation (US) on the antimicrobial activity of a new final irrigant containing glycolic acid (GA). Extracted teeth were used, being 70 to counting of colony-forming units (CFUs) and 35 to confocal laser scanning microscopy. Samples were inoculated with Enterococcus faecalis and divided into 7 groups: distilled water + US; 17% EDTA; Qmix; 17% GA; 17% EDTA + US; QMix + US; and 17% GA + US and kept in contact with test solution for 1 min in the groups with or no US. In the CFUs, the highest bacterial reduction was observed in QMix + US group, followed by QMix and GA + US. In the confocal evaluation, the lowest number of viable cells was observed in EDTA + US, with no statistical difference from QMix, QMix + US and GA + US (P > 0.05). The use of US improves the antimicrobial activity of EDTA and GA, being statistically different from the isolated use of these final irrigants in both evaluation tests.

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.

Pathogenic potential of Enterococcus faecalis strains isolated from root canals after unsuccessful endodontic treatment

OBJECTIVES

To evaluate strains of Enterococcus faecalis isolated from endodontic failures cases for (a) presence of virulence genes, namely, gelatinase production (gelE), surface protein (esp), collagen-binding adhesin (ace), cytolysin activator (cylA), E. faecalis antigen A (efaA) and aggregation substance (asa), all by using PCR; (b) biofilm formation capacity; and (c) activity of gelatinase and β-lactamase.

MATERIALS AND METHODS

Twenty-five strains of E. faecalis were tested. The DNA extracted from these strains was used for identification of virulence genes by PCR and 1% agarose gel. Biofilm formation was performed on polystyrene microplates by using the violet crystal staining method. For assessment of the gelatinase activity, inoculum of pure cultures was deposited in tubes containing gelatin and a nutrient broth, whereas nitrocefin disks were used to assess the β-lactamase action.

RESULTS

The virulence genes efaA and cylA were detected in 100% of the strains, whereas gelE was present in 84%, ace in 68%, esp in 56% and asa in 48%. Four strains had no biofilm formation, 17 had poor formation and four had moderate formation. Gelatinase production was observed in three strains and β-lactamase resistance in five strains of E. faecalis.

TOPIC

Diverse patterns of virulence gene detection were observed among the E. faecalis strains, with predominance of those capable of forming biofilm. A few strains have been found to hydrolyze gelatin proteins, whereas β-lactamase resistance was detected in different isolates.

CLINICAL RELEVANCE

To understand the influence of virulence factors in E. faecalis on the host heath status.

Antimicrobial activities of natural plant compounds against endodontic pathogens and biocompatibility with human gingival fibroblasts

OBJECTIVES

The aim of the present study was to investigate three licorice-derived polyphenols (glabridin, licochalcone A, licoricidin) as well as cinnamon oil for their antimicrobial activities against major endodontic pathogens: Enterococcus faecalis, Streptococcus mutans, Actinomyces israelii, Fusobacterium nucleatum, Prevotella intermedia, Porphyromonas endodontalis, and Candida albicans. The synergistic interactions between the four compounds and chlorhexidine were assessed on E. faecalis. Lastly, the biocompatibility of the tested compounds was assessed using human gingival fibroblasts.

DESIGN

Minimal inhibitory concentrations (MIC) and minimal microbicidal concentrations (MMC) were determined using a microplate dilution assay. A luminescence assay monitoring adenosine triphosphate was used to assess the antimicrobial activity of the tested compounds against E. faecalis biofilm. The synergistic effects of the tested compounds in association with chlorhexidine were evaluated using the checkerboard technique. Cytotoxicity toward human gingival fibroblasts was assessed by determination of cell metabolic activity using a colorimetric assay.

RESULTS

Cinnamon oil showed the strongest microbicidal activity. Licochalcone A, licoricidin, and glabridin had MIC values ranging from 1.56 to 25 μg/mL against the six endodontic bacterial pathogens. The natural plant compounds were active to various extents against E. faecalis embedded in a biofilm. Synergistic antibacterial effects between chlorhexidine and the compounds, mainly glabridin, were observed against E. faecalis. Following a 2-h exposure, licochalcone A, licoricidin, and glabridin demonstrated no cytotoxicity toward gingival fibroblasts at concentrations up to 50 μg/mL, while cinnamon oil and, to a lesser extent, chlorhexidine displayed some cytotoxicity.

CONCLUSIONS

The present study provides evidence that the natural plant compounds tested show promise as root canal disinfection agents.

Physico-chemical and antimicrobial properties and the shelf life of experimental endodontic sealers containing metal methacrylates

The objective of this study was to evaluate the physico-chemical and antimicrobial properties of a dual polymerization experimental endodontic sealer (E) and experimental sealers containing dibutyltin methacrylate (Sn²⁺) (ETs) or calcium methacrylate (Ca²⁺) (ECs). The pH and ion release levels of the sealers were measured. The dimensional stability was evaluated in accordance with ISO 6876. Biofilm growth inhibition was evaluated using confocal laser scanning microscopy (CLSM). Biofilm viability analysis was performed using the SYTO 9 technique. The shelf life was evaluated through the degree of conversion and film thickness tests after the sealers had been stored for different periods of time. For statistical analysis, ANOVA and Tukey's post hoc test were used, with a significance level of 5%. ETs revealed better anti-biofilm potential after 15 days than that of the controls. The degree of conversion was reduced after the shelf-life period. The addition of calcium and dibutyltin methacrylate improved the anti-biofilm properties of the experimental endodontic sealer without impairing their physico-chemical properties.

Influence of Endodontic Procedure on the Adherence of Enterococcus faecalis

INTRODUCTION

The purpose of this study was to investigate the effects of instrumentation and irrigation on the initial adherence of Enterococcus faecalis to root canal dentin and to explore initial microbial adhesion to root filling materials.

METHODS

The following specimens were prepared: instrumented and uninstrumented dentin, dentin treated with different irrigation protocols, and root filling materials. The number of E. faecalis cells adhered on dentin was measured. The adhesion force of E. faecalis cells on different materials and the roughness of different surfaces were measured. The contact angle of the surfaces was recorded. The results were analyzed using the t test.

RESULTS

Instrumented dentin specimens had a significantly higher amount of E. faecalis adherence than uninstrumented dentin. There were higher numbers of adhering bacteria on the dentin when EDTA was used alone (P < .05) compared with other irrigants alone. The use of chlorhexidine (CHX) as the last irrigant for a certain time resulted in a reduced number of adhering bacteria when the specimens were first exposed to sodium hypochlorite (NaOCl) followed by EDTA. EDTA used alone had the highest adhesion force followed by NaOCl alone and CHX alone (P < .05). Dentin treated with EDTA alone had the highest roughness and contact angle followed by NaOCl alone and CHX alone (P < .05). CHX added as the final irrigant after NaOCl with EDTA irrigation reduced the contact angle (P < .05). Larger amounts of adhering bacteria and higher adhesion force were detected on the surface of gutta-percha and sealer than on the dentin surface (P < .05).

CONCLUSIONS

Instrumentation and irrigation alter the initial adherence of E. faecalis to root canal dentin and the surface properties of the dentin as well.

Effectiveness of calcium and sodium hypochlorite in association with reciprocating instrumentation on decontamination of root canals infected with Enterococcus faecalis

The aim of this study was to evaluate the antimicrobial activity of sodium and calcium hypochlorite utilising reciprocating instrumentation. Sixty root canals were inoculated with E. faecalis for 14 days. Samples were divided into six groups according to decontamination protocol: G1: no treatment, G2: distilled water, G3: 2.5% sodium hypochlorite, G4: 2.5% calcium hypochlorite, G5: 5.25% sodium hypochlorite and G6: 5.25% calcium hypochlorite. Instrumentation was performed with Wave One reciprocating system (Dentsply Sirona Endodontics, York, PA, USA) in groups G2 to G6. Colony-forming units (CFUs) counting was performed and the data were subjected to Anova and Tukey (α  =  0.05). Group 1 and 2 showed the highest mean contamination, with a significant difference between them (P < 0.05). Groups 3, 4, 5 and 6 showed the lowest contamination means with no significant difference between them (P < 0.05). Sodium and calcium hypochlorite, in association with reciprocating instrumentation, can be an effective decontamination protocol in root canals infected with E. faecalis.

Analysis of Demineralized Chemical Substances for Disinfecting Gutta-percha Cones

Introduction:

The aim of the present research was to evaluate the effectiveness of 5% malic acid, 17% EDTA and 10% citric acid solutions used to disinfect gutta-percha cones contaminated by Enterococcusfaecalis (ATCC 29212).

Methods and Materials:

Two hundred and ten previously sterilized gutta-percha cones were contaminated with E. faecalis at concentration of 1.5×10⁸ CFU/mL. The cones were immersed in 5% malic acid, 17% EDTA, 10% citric acid, 1% NaOCl and 2.5% NaOCl for 1, 5 and 10 min. Then each cone was kept in Eppendorf tubes containing BHI sterile solution at 37^°C for 48 h. The presence of turbidity in BHI solution was analyzed. The results were statistically analyzed by Kruskal-Wallis test and 5% Dunn comparisons. P-value was considered statistically significant when P<0.05.

Results:

Regardless of exposure time, 1% NaOCl and 2.5% NaOCl were the most effective agents for rapid disinfection of gutta-percha cones (P<0.001). All specimens immersed in experimental demineralized solutions presented bacterial growth (P>0.05).

Conclusion:

Demineralized solutions tested were not effective for elimination of Enterococcus faecalis on the surface of gutta-percha cones.

The evaluation of E. faecalis colonies dissolution ability of sodium hypochlorite in microenvironment by a novel device

Enterococcus faecalis(E. faecalis) is a common microorganism could be isolated from the infected canals, especially in the case of refractory apical periodontitis. Due to its ability to invade the dentinal tubules and highly resistant to antimicrobial strategies, the thorough debridement of E.faecalis is hard to achieve. And that may be one of the reasons to cause reinfection and therapeutic failure. According to the anatomy of dentinal tubules published before and the results of our team previous work, we designed six types of microtubes with different sizes. By using the method of centrifugation and incubation, a standard infected model mimicking dentinal tubules was established. Sodium hypochlorite (NaClO) is the most popular irrigant applied in root canal treatment. We used three different concentrations with four distinct irrigation duration to observe the antibacterial process of E. faecalis colonies within microtubes dynamically. We concluded that the role of NaClO in the microtubes is concentration dependent and duration dependent. And the interpretation of the results has a certain reference value for clinicians.

Evaluation of antimicrobial activity of association of chlorhexidine to photosensitizer used in photodynamic therapy in root canals infected by Enterococcus faecalis

INTRODUCTION

The aim of the present study was to evaluate, in vitro, the influence of the addition of chlorhexidine to photosensitiser in the antimicrobial activity of photodynamic therapy in root canals infected by Enterococcus faecalis.

METHODS

The root canals of 50 single-rooted human extracted teeth were enlarged up to a file F3 of Pro-Taper system, autoclaved, inoculated with Enterococcus faecalis and incubated for 14days. The samples were divided into five groups (n=10) according to the protocol of decontamination: G1 (control group) - no procedure was performed; G2-photosensitiser (0.01% methylene blue); G3-2% chlorhexidine gel; G4-photodynamic therapy; and G5-photodynamic therapy with photosensitiser modified by chlorhexidine. Microbiological test (CFU counting) was performed to evaluate the effectiveness of proposed treatments. Data were subjected to one-way ANOVA followed by post-hoc Tukey test (α=0.05).

RESULTS

Group 3 (CHX) showed the lowest mean contamination (2.03 log₁₀ CFU/mL), being statistically different from all other all groups (p<0.05). There was no statistically significant difference between groups 4 (PDT) and 5 (PDT+CHX) (p<0.05), being more effectives against E. faecalis when compared to groups 1 (NT) and 2 (MB), and less effective when compared to group 2 (CHX).

CONCLUSIONS

The addition of chlorhexidine to photosensitiser did not result in a better decontamination potential of photodynamic therapy alone over root canals infected by E. faecalis.

Effect of Silver Nanoparticles on Physicochemical and Antibacterial Properties of Calcium Silicate Cements

Mineral trioxide aggregate (MTA) and Portland cement (PC) are calcium silicate cements. They have similar physicochemical, mechanical and biological properties. The addition of zirconium oxide (ZrO2) to PC provides radiopacity. Silver nanoparticles (AgNPs) may improve some properties of cements. The aim of this study was to evaluate the effect of AgNPs on physicochemical/mechanical properties and antibacterial activity of white MTA (WMTA) and PC associated with ZrO2. The following materials were evaluated: WMTA; PC 70% + ZrO2 30%; WMTA+ AgNPs; and PC 70% + ZrO2 30% + AgNPs. The study evaluated radiopacity, setting time, pH, compressive strength and solubility. For radiopacity analysis, radiographs were made alongside an aluminum (Al) step wedge. To evaluate the antibacterial activity, direct contact test was performed on planktonic cells and Enterococcus faecalis biofilm induced on bovine root dentin for 14 days. The experimental periods were 5 and 15 h. Data were obtained as CFU mL-1. The obtained data were submitted to ANOVA and Tukey tests (p<0.05). The addition of AgNPs to WMTA increased the pH, lowered the solubility and the initial and final setting times. The addition of AgNPs to PC/ZrO2 maintained the pH, lowered the solubility, and increased the setting time and compressive strength. The radiopacity of all materials was higher than 4 mmAl. The addition of AgNPs promoted an increase in antibacterial activity for calcium silicate cements and favored the physicochemical and mechanical properties of the materials.

Antibacterial active open-porous hydroxyapatite/lysozyme scaffolds suitable as bone graft and depot for localised drug delivery

An engineered synthetic scaffold for bone regeneration should provide temporary structural support and a medium for controlled and localised release of bioavailable medical drugs. In this work, a method is proposed to incorporate biologically active agents without impairing agent activity into open-porous resorbable hydroxyapatite scaffolds. Scaffolds are obtained by a one-pot freeze gelation process and loaded with different amounts of lysozyme, a model macromolecular drug with antibacterial activity. The antibacterial activity is tested by submerging hydroxyapatite scaffolds with 0.5 to 2.5 wt.% lysozyme into two different bacteria stock solutions. A complete dieback of M. luteus bacteria when in contact with the scaffolds is observed. Higher lysozyme amount in the scaffold leads to faster dieback. In contact with scaffolds containing 2.5 wt.% lysozyme after 30 min, no viable bacteria can be observed. An amount of 0.5 wt.% lysozyme in the scaffolds is sufficient to kill all bacteria after a contact time of 24 h. For L. innocua, a bacteriostatic effect is observed. The scaffolds have spongiosa-like stability and are suitable bone implant substitutes. As agents are released from the scaffolds by degrees over a time period of at least 9 days, they are particularly attractive as depot for localised drug delivery of bioactive macromolecular drugs.

Effect of addition of nano-hydroxyapatite on physico-chemical and antibiofilm properties of calcium silicate cements

Objective

Mineral Trioxide Aggregate (MTA) is a calcium silicate cement composed of Portland cement (PC) and bismuth oxide. Hydroxyapatite has been incorporated to enhance mechanical and biological properties of dental materials. This study evaluated physicochemical and mechanical properties and antibiofilm activity of MTA and PC associated with zirconium oxide (ZrO₂) and hydroxyapatite nanoparticles (HAn).

Material and Methods

White MTA (Angelus, Brazil); PC (70%)+ZrO₂ (30%); PC (60%)+ZrO₂ (30%)+HAn (10%); PC (50%)+ZrO₂ (30%)+HAn (20%) were evaluated. The pH was assessed by a digital pH-meter and solubility by mass loss. Setting time was evaluated by using Gilmore needles. Compressive strength was analyzed by mechanical test. Samples were radiographed alongside an aluminum step wedge to evaluate radiopacity. For the antibiofilm evaluation, materials were placed in direct contact with E. faecalis biofilm induced on dentine blocks. The number of colony-forming units (CFU mL-1) in the remaining biolfilm was evaluated. The results were submitted to ANOVA and the Tukey test, with 5% significance.

Results

There was no difference in pH levels of PC+ZrO₂, PC+ZrO₂+HAn (10%) and PC+ZrO₂+HAn (20%) (p>0.05) and these cements presented higher pH levels than MTA (p<0.05). The highest solubility was observed in PC+ZrO₂+HAn (10%) and PC+ZrO₂+HAn (20%) (p<0.05). MTA had the shortest initial setting time (p<0.05). All the materials showed radiopacity higher than 3 mmAl. PC+ZrO₂ and MTA had the highest compressive strength (p<0.05). Materials did not completely neutralize the bacterial biofilm, but the association with HAn provided greater bacterial reduction than MTA and PC+ZrO₂ (p<0.05) after the post-manipulation period of 2 days.

Conclusions

The addition of HAn to PC associated with ZrO₂ harmed the compressive strength and solubility. On the other hand, HAn did not change the pH and the initial setting time, but improved the radiopacity (HAn 10%), the final setting time and the E. faecalis antibiofilm activity of the cement.

Antimicrobial Activity and Physicochemical Properties of Calcium Hydroxide Pastes Used as Intracanal Medication

INTRODUCTION

The aim of the present study was to evaluate the pH, calcium release, solubility, and antimicrobial action against biofilms of calcium hydroxide + saline solution, Calen (SS White Artigos Dentários Ltd, Rio de Janeiro, Brazil) (CH/P), Calen camphorated paramonochlorophenol (CMCP) (CH/CMPC), and calcium hydroxide + chlorhexidine (CH/CHX) pastes.

METHODS

The pH of the pastes was determined with a calibrated pH meter placed in direct contact with each paste. The root canals of acrylic teeth (N = 10) were filled with the previously mentioned intracanal dressings and immersed in ultrapure water to measure hydroxyl (pH meter) and calcium ion release (atomic absorption spectrophotometer) at time intervals of 3, 7, 15, and 30 days. To assess solubility, the root canals of acrylic teeth (N = 10) were filled with the previously mentioned pastes and scanned by micro-computed tomographic imaging before (initial) and after 7, 15, and 30 days of immersion in ultrapure water. The solubility of each specimen was the difference between the initial and final volume scanning. For antimicrobial analysis, monospecies and dual-species biofilms were in vitro induced on dentin blocks (N = 20). Afterward, they were treated with the pastes for 7 days. Live/dead dye and a confocal microscope were used to measure the percentage of living cells. Data were statistically compared (P < .05).

RESULTS

The highest OH^- ion release values were found in 3 and 30 days. Ca²⁺ releases were greater in CH/CMCP. CH/P and CH/CMCP showed a higher percentage of volume loss values. CH/CHX presented the greatest antimicrobial action.

CONCLUSIONS

CH/P and CH/CMPC showed higher solubility values in the period analyzed. Seven days of contact may be insufficient for calcium hydroxide + saline solution, CH/P, and CH/CMCP pastes to kill bacterial cells in the biofilms studied. Chlorhexidine added to CH favored greater effectiveness against the previously mentioned bacterial biofilms.

Antifungal effects of synthetic human β-defensin 3-C15 peptide

OBJECTIVES

The purpose of this ex vivo study was to compare the antifungal activity of a synthetic peptide consisting of 15 amino acids at the C-terminus of human β-defensin 3 (HBD3-C15) with calcium hydroxide (CH) and Nystatin (Nys) against Candida albicans (C. albicans) biofilm.

MATERIALS AND METHODS

C. albicans were grown on cover glass bottom dishes or human dentin disks for 48 hr, and then treated with HBD3-C15 (0, 12.5, 25, 50, 100, 150, 200, and 300 µg/mL), CH (100 µg/mL), and Nys (20 µg/mL) for 7 days at 37℃. On cover glass, live and dead cells in the biomass were measured by the FilmTracer Biofilm viability assay, and observed by confocal laser scanning microscopy (CLSM). On dentin, normal, diminished and ruptured cells were observed by field-emission scanning electron microscopy (FE-SEM). The results were subjected to a two-tailed t-test, a one way analysis variance and a post hoc test at a significance level of p = 0.05.

RESULTS

C. albicans survival on dentin was inhibited by HBD3-C15 in a dose-dependent manner. There were fewer aggregations of C. albicans in the groups of Nys and HBD3-C15 (≥ 100 µg/mL). CLSM showed C. albicans survival was reduced by HBD3-C15 in a dose dependent manner. Nys and HBD3-C15 (≥ 100 µg/mL) showed significant fungicidal activity compared to CH group (p < 0.05).

CONCLUSIONS

Synthetic HBD3-C15 peptide (≥ 100 µg/mL) and Nys exhibited significantly higher antifungal activity than CH against C. albicans by inhibiting cell survival and biofilm.

Antimicrobial action of calcium hydroxide-based endodontic sealers after setting, against E. faecalis biofilm

Enterococcus faecalis are gram positive bacteria that can mostly resist endodontic therapy, inducing persistent infection in the root canal system. Endodontic sealers with antimicrobial activity may help eliminate residual microorganisms that survive endodontic treatment. The present study aimed at comparing the antimicrobial activity of Acroseal, Sealapex and AH Plus endodontic sealers in an in vitro biofilm model. Bovine dentin specimens (144) were prepared, and twelve blocks for each sealer and each experimental time point (2, 7 and 14 days) were placed and left in contact with plates containing inoculum of E. faecalis (ATCC 51299), to induce biofilm formation. After 14 days, the samples were transferred to another plate with test sealers and kept at 37°C and 5% CO2 for 2, 7 and 14 days. The specimens without sealers were used as a control for each period. The samples were agitated in a sonicator after each experiment. The suspensions were agitated in a vortex mixer, serially diluted in saline, and triple plated onto m-Enterococcus agar. Colonyforming units were counted, and the data were statistically analyzed using ANOVA, Shapiro-Wilk and Kruskal-Wallis one-way tests (p < 0.05) to determine antimicrobial potential. Sealapex showed significant differences at all the experimental time points, in comparison with all the other groups. AH Plus and Acroseal showed antimicrobial activity only on the 14th experimental day. Neither of the sealers tested were able to completely eliminate the biofilm. Sealapex showed the highest antimicrobial activity in all the experimental periods. The antimicrobial activity of all the sealers analyzed increased over time.

Effects of ciprofloxacin-containing scaffolds on enterococcus faecalis biofilms

INTRODUCTION

Antibiotic-containing polymer-based nanofibers (hereafter referred to as scaffolds) have demonstrated great potential for their use in regenerative endodontics from both an antimicrobial and cytocompatibility perspective. This study sought to evaluate in vitro the effects of ciprofloxacin (CIP)-containing polymer scaffolds against Enterococcus faecalis biofilms.

METHODS

Human mandibular incisors were longitudinally sectioned to prepare radicular dentin specimens. Sterile dentin specimens were distributed in 24-well plates and inoculated with E. faecalis for biofilm formation. Infected dentin specimens were exposed to 3 groups of scaffolds, namely polydioxanone (PDS) (control), PDS + 5 wt% CIP, and PDS + 25 wt% CIP for 2 days. Colony-forming units (CFU/mL) (n = 10) and scanning electron microscopy (SEM) (n = 2) were performed to quantitatively and qualitatively assess the antimicrobial effectiveness, respectively.

RESULTS

PDS scaffold containing CIP at 25 wt% showed maximum bacteria elimination with no microbial growth, differing statistically (P < .05) from the control (PDS) and from PDS scaffold containing CIP at 5 wt%. Statistical differences (P < .05) were also seen for the CFU/mL data between pure PDS (5.92-6.02 log CFU/mL) and the PDS scaffold containing CIP at 5 wt% (5.39-5.87 log CFU/mL). SEM images revealed a greater concentration of bacteria on the middle third of the dentin specimen after 5 days of biofilm formation. On scaffold exposures, SEM images showed similar results when compared with the CFU/mL data. Dentin specimens exposed to PDS + 25 wt% CIP scaffolds displayed a practically bacteria-free surface.

CONCLUSIONS

On the basis of the data presented, newly developed antibiotic-containing electrospun scaffolds hold promise as an intracanal medicament to eliminate biofilm/infection before regenerative procedures.

Antimicrobial activity of root canal irrigants associated with cetrimide against biofilm and planktonic Enterococcus faecalis

AIM

To evaluate the antibacterial activity of sodium hypochlorite (NaOCl) and chlorhexidine (CHX) alone or associated with cetrimide (CTR), and QMiX against biofilm and planktonic Enterococcus faecalis (E. faecalis) [American type culture collection (ATCC) 29212].

MATERIALS AND METHODS

The solutions 2.5% NaOCl, 2.5% NaOCl + 0.2% CTR, 2% CHX, 2% CHX + 0.2% CTR, 0.2% CTR, and QMiX were evaluated. E. faecalis biofilms were induced for 14 days on bovine dentin blocks. The irrigants were evaluated after contact with E. faecalis suspension and biofilm for 1 and 3 minutes. After that, serial decimal dilutions were made and plated on tryptic soy agar (TSA) medium. Plates were incubated for 24 hours at 37°C and the colony-forming unit (CFU) 1 ml was determined. Data were subjected to ANOVA and Tukey's tests at 5% significance.

RESULTS

All microorganisms were eliminated by direct contact of the irrigants with planktonic cells. Only NaOCl and NaOCl + CTR were able to completely eliminate the microorganisms by direct contact with E. faecalis biofilm. CHX presented effectiveness similar to CHX + CTR CTR, and QMiX after 1 minute of contact and similar to NaOCl and NaOCl + CTR after 3 minutes (p > 0.05), but was unable to completely eliminate the microorganisms. CTR and QMiX did not differ from each other.

CONCLUSION

CTR addition to CHX and NaOCl solutions did not improve the antimicrobial activity against biofilm. All evaluated irrigants and associations presented activity against planktonic E. faecalis. Only NaOCl and NaOCl + CTR eliminated biofilm after 1 and 3 minutes of direct contact.