Persistent Endodontic Infections Research Articles

The Impact of Azadirachta Indica Extract on the Expression Profile of Esp Gene in Treated Enterococcus faecalis

Background and Objectives Enterococcus faecalis is a bacterium often associated with persistent endodontic infections, posing challenges for effective root canal disinfection and treatment outcomes due to its resilience in adverse root canal conditions and resistance to antimicrobial therapies. This study aimed to investigate the effects of Azadirachtaindica's active plant compounds at subinhibitory concentrations on the expression of the virulence gene (esp) in Enterococcus faecalis strains (ATCC 29212). Materials and Methods Azadirachta indica (neem) specimens were obtained in Erbil, Northern Iraq, and the active compounds from the dried plant samples were extracted. Dry extracts were dissolved in Dimethylsulphoxide (DMSO) until reaching 100 mg/ml. Bacterial samples were treated with the extracted plant material and incubated. The assessment of relative esp gene expression in treated Enterococcus faecalis strains (ATCC 29212) began with total RNA extraction using the RNXplus kit, followed by a Quantitative RT-PCR assay. Results The minimum concentration of Azadirachta indica's ethyl acetate fraction 3 (30 mg/ml) inhibited the growth of the targeted bacteria. In contrast, the highest concentration inhibiting the target bacteria was 50 mg/ml of fraction 6 (Azadirachta indica-water). All fractions of Azadirachta indica decreased the expression of the target gene, with fraction 5 (ethyl alcohol) showing the highest fold change. Conclusion The ethyl alcohol extraction of Azadirachta indica inhibited the expression of the virulence gene (esp) by 2.84-fold, suggesting a potential decrease in (esp) gene expression, which could be considered as an alternative to classical irrigants.

Factors Influencing Non-Surgical Root Canal Treatment Outcomes in Mandibular Second Molars: A Retrospective Cone-Beam Computed Tomography Analysis.

Background/Objectives: This study aimed to investigate the influence of the root canal morphology and various treatment variables on the outcomes of root canal treatments (RCTs) in mandibular second molars, assessed through cone-beam computed tomography (CBCT) imaging. Methods: A total of 150 CBCT images were examined, comprising 100 cases of persistent endodontic infections and 50 of previously treated root canals with normal apices in the mandibular second molars. CBCT was utilized to evaluate the root canal configuration, the radiographic quality of coronal restorations and treated canal systems, and the presence of periapical lesions. Statistical analyses were performed to explore the correlations between these factors. Results: The presence of a C-shaped root canal configuration did not demonstrate a significant correlation with periapical lesions (p = 0.05). Factors influencing endodontic treatment outcomes included missing canals (p = 0.018), underfilling or overfilling (p = 0.045), and inadequate coronal restoration (p = 0.006). Missing a canal was identified as the variable most significantly associated with periapical lesions (OR = 3.103). Inhomogeneous root canal obturation was more commonly observed in C-shaped root canals (p < 0.001). Conclusions: Regardless of the root canal morphology of mandibular second molars, successful RCT depends on thorough disinfection to eliminate any untreated canals, precise three-dimensional filling of the canals at the correct working length, and a securely sealed coronal restoration to prevent leakage.

The impact of administration of Annona muricata leaf on estrogen and progesterone functions following mercury-induced toxicity in adult female Wistar rats

Environmental toxicants have been linked to female reproductive dysfunction resulting from oxidative stress. The study assesses the impact of ethanolic leaf extract of Annona muricata (EAM) on ovarian and uterine function following mercury-induced toxicity in female Wistar rats. The study involved 40 female Wistar rats, each weighing 114–156g, divided into eight groups of five animals each. Group A received feed and water only; group B received 500 mg/kg of EAM only; and group C received 25 mg/kg of mercury chloride (HgCl2). Groups D and E received 100 mg/kg and 500 mg/kg of EAM for 4 weeks and were treated with 25 mg/kg of HgCl2, respectively. Group F received 500 mg/kg of EAM for 4 weeks and treated immediately with co-administrstion of 25 mg/kg of HgCl2 and 500 mg/kg of EAM for 4 weeks. Groups G and H received 25 mg/kg of HgCl2 and received 100 mg/kg and 500 mg/kg of EAM for 4 weeks, respectively. Progesterone amd Estrogen levels were measured at the end of the administration. The data was analysed using SPSS version 25, with inferential statistics performed, and significant values were set at p≤0.05. Administration of mercury resulted in a decreased level of oestrogen, and progesterone. EAM treatments resulted in statistically significant increased levels of progesteron in groups E, F, G and H; group D also showed an increase, though not statistically significant. Estrogen levels were increased in groups F, G and H, but groups D and E showed a decrease in estrogen levels, though not statistically significant. The study reveals that EAM enhances female reproductive hormonal levels and may turn out into a potential capable of reversing or preventing female infertility linked to mercury chloride toxicity.

Oxygen Self-Supplied Nanoplatform for Enhanced Photodynamic Therapy against Enterococcus Faecalis within Root Canals.

The successful treatment of persistent and recurrent endodontic infections hinges upon the eradication of residual microorganisms within the root canal system, which urgently needs novel drugs to deliver potent yet gentle antimicrobial effects.Antibacterial photodynamic therapy (aPDT) is a promising tool for root canal infection management. Nevertheless, the hypoxic microenvironment within the root canal system significantly limits the efficacy of this treatment. Herein, a nanohybrid drug, Ce6/CaO2/ZIF-8@polyethylenimine (PEI), is developed using a bottom-up strategy to self-supply oxygen for enhanced aPDT. PEI provides a positively charged surface, which enables precise targeting of bacteria. CaO2 reacts with H2O to generate O2, which alleviates the hypoxia in the root canal and serves as a substrate for Ce6 under 660nm laser irradiation, leading to the successful eradication of planktonic Enterococcus faecalis (E. faecalis) and biofilm in vitro and, moreover, the effective elimination of mature E. faecalis biofilm in situ within the root canal system. This smart design offers a viable alternative for mitigating hypoxia within the root canal system to overcome the restricted efficacy of photosensitizers, providing an exciting prospect for the clinical management of persistent endodontic infection.

Poly(Lysine)-Derived Carbon Quantum Dots Conquer Enterococcus faecalis Biofilm-Induced Persistent Endodontic Infections.

Persistent endodontic infections (PEIs) mediated by bacterial biofilm mainly cause persistent periapical inflammation, resulting in recurrent periapical abscesses and progressive bone destruction. However, conventional root canal disinfectants are highly damaging to the tooth and periodontal tissue and ineffective in treating persistent root canal infections. Antimicrobial materials that are biocompatible with apical tissues and can eliminate PEIs-associated bacteria are urgently needed. Here, ε-poly (L-lysine) derived carbon quantum dots (PL-CQDs) are fabricated using pyrolysis to remove PEIs-associated bacterial biofilms. Due to their ultra-small size, high positive charge, and active reactive oxygen species (ROS) generation capacity, PL-CQDs exhibit highly effective antibacterial activity against Enterococcus faecalis (E. faecalis), which is greatly dependent on PL-CQDs concentrations. 100 µg/mL PL-CQDs could kill E. faecalis in 5 min. Importantly, PL-CQDs effectively achieved a reduction of biofilms in the isolated teeth model, disrupting the dense structure of biofilms. PL-CQDs have acceptable cytocompatibility and hemocompatibility in vitro and good biosafety in vivo. Thus, PL-CQDs provide a new strategy for treating E. faecalis-associated PEIs.

Genotypic Identification of Endodontic Bacteria Isolated from Berhampur, Odisha, India: First Insights

ABSTRACT Background: Endodontic infections caused by many bacterial species including Staphylococcus aureus, Klebsiella pneumonia and Salmonella enterica present a significant challenge in dental health. Accurate identification of these pathogens is crucial for effective treatment strategies. Aims and Objectives: The aim of the study was to utilize 16S rRNA genotypic analysis for the precise identification of certain bacterial strains isolated from endodontic infected tissues. Materials and Methods: Tissue samples were collected from patients with persistent endodontic infections and microbial cultures were prepared. Strains were isolated, purified. DNA extraction was performed and 16S rRNA gene amplification was carried out using polymerase chain reaction. Subsequently, the amplicons were sequenced and the sequences were compared with known reference sequences using bioinformatics programs. Phylogenetic analysis was conducted to ascertain the evolutionary relationships between the identified isolates and known strains. Results: To our knowledge, this is the first report focusing on genotypic identification of endodontic bacteria from Berhampur, Odisha, India. This study holds implications for species specific microbial ecology in dental infections facilitating quicker identification. Conclusion: Management strategies for endodontic infections may involve a systematic approach to identify, analyze and address the specific challenges such as diagnosis and endodontic emergencies, presented by each case. Focused and individualized treatment plans shall contribute to better clinical outcomes. Further detailed records can be maintained with genotype based treatment plan followed by post treatment outcomes to guide future decisions and research.

Strategies and mechanisms targeting Enterococcus faecalis biofilms associated with endodontic infections: a comprehensive review.

Enterococcus faecalis is one of the main microorganisms that infects root canals, ranking among the most prevalent microorganisms associated with endodontic treatment failure. Given its pervasive presence in persistent endodontic infections, the successful elimination of Enterococcus faecalis is crucial for effective endodontic treatment and retreatment. Furthermore, Enterococcus faecalis can form biofilms - defense structures that microbes use to fight environmental threats. These biofilms confer resistance against host immune system attacks and antibiotic interventions. Consequently, the presence of biofilms poses a significant challenge in the complete eradication of Enterococcus faecalis and its associated disease. In response, numerous scholars have discovered promising outcomes in addressing Enterococcus faecalis biofilms within root canals and undertaken endeavors to explore more efficacious approaches in combating these biofilms. This study provides a comprehensive review of strategies and mechanisms for the removal of Enterococcus faecalis biofilms.

Highly effective DPA-SCP sonosensitizers for biofilm removal in infected root canals via sonodynamic therapy

This article explores AIE sonosensitizers' efficiency in eradicating biofilms, demonstrating its potential as an alternative therapy for persistent endodontic infections.

Evaluation of the Antimicrobial Potential of Cashew Nut Shell Liquid Extract (Anacardium occidentale) against Enterococcus faecalis Strains

The resistance of microorganisms present in the root canal system is a problem associated with the failure of endodontic treatments. Therefore, the search for treatments based on herbal extracts has been an alternative to prevent persistent endodontic infections. The aim of this in vitro study was to evaluate the antimicrobial potential of cashew nut shell liquid extract (E-CNSL) against Enterococcus faecalis strains. The antimicrobial activity was evaluated using the agar well diffusion method. Petri dishes containing Mueller Hinton agar were inoculated on the surface by the microorganism using a swab, then 20 μL of the E-CNSL solution at concentrations of 500 μg/mL and 1000 μg/mL was aseptically deposited in the wells of the inoculated media. The plates were incubated at 37 °C for 24 hours. All the strains studied showed an inhibition halo ≥6 mm at both concentrations of the extract. Therefore, the extract of cashew nut shell liquid (A. occidentale) showed a potential antimicrobial effect against E. faecalis strains.

Antibacterial activity of root canal sealers against established monospecies biofilm: An in vitro study.

Endodontic treatment is primarily a combination of chemical as well as mechanical preparation of canal space which helps in the placement of a biocompatible material. The main purpose of endodontic treatment is to eradicate microorganisms from the infected root canal system and prevent recontamination. The principle constituents of an endodontic filling are core material "Gutta Percha" and "Endodontic Sealers." Endodontic sealers should ideally eliminate residual bacteria and prevent reinfection after chemomechanical treatment and obturation of the root canal. The aim of this study is to investigate the antimicrobial effect of four endodontic sealers against bacteria in biofilms commonly detected from persistent and secondary endodontic infections.

Clinical applications of antimicrobial photodynamic therapy in dentistry.

Given the emergence of resistant bacterial strains and novel microorganisms that globally threaten human life, moving toward new treatment modalities for microbial infections has become a priority more than ever. Antimicrobial photodynamic therapy (aPDT) has been introduced as a promising and non-invasive local and adjuvant treatment in several oral infectious diseases. Its efficacy for elimination of bacterial, fungal, and viral infections and key pathogens such as Streptococcus mutans, Porphyromonas gingivalis, Candida albicans, and Enterococcus faecalis have been investigated by many invitro and clinical studies. Researchers have also investigated methods of increasing the efficacy of such treatment modalities by amazing developments in the production of natural, nano based, and targeted photosensitizers. As clinical studies have an important role in paving the way towards evidence-based applications in oral infection treatment by this method, the current review aimed to provide an overall view of potential clinical applications in this field and summarize the data of available randomized controlled clinical studies conducted on the applications of aPDT in dentistry and investigate its future horizons in the dental practice. Four databases including PubMed (Medline), Web of Science, Scopus and Embase were searched up to September 2022 to retrieve related clinical studies. There are several clinical studies reporting aPDT as an effective adjunctive treatment modality capable of reducing pathogenic bacterial loads in periodontal and peri-implant, and persistent endodontic infections. Clinical evidence also reveals a therapeutic potential for aPDT in prevention and reduction of cariogenic organisms and treatment of infections with fungal or viral origins, however, the number of randomized clinical studies in these groups are much less. Altogether, various photosensitizers have been used and it is still not possible to recommend specific irradiation parameters due to heterogenicity among studies. Reaching effective clinical protocols and parameters of this treatment is difficult and requires further high quality randomized controlled trials focusing on specific PS and irradiation parameters that have shown to have clinical efficacy and are able to reduce pathogenic bacterial loads with sufficient follow-up periods.

Antimicrobial Effectiveness of Different Root Canal Irrigants on Viablility of Root Canal Flora

Introduction: Cleaning and shaping of sophisticated root canal system plays an important role in the success of endodontic treatment. In addition to root canal instrumentation, irrigation also becomes a crucial aspect in the effective disinfection of root canal system. The chemical substances like acids, chelating agents, alkaline solutions, Sodium Hypochlorite (NaOCl), oxidative agents, and normal saline are used as root canal irrigants. But each irrigant has its own limitations. With the advent of novel materials and techniques, the search for the optimal root canal irrigant still continues. Aim: To evaluate and compare the antimicrobial effectiveness of various root canal irrigant solutions such as combination of 5.25% NaOCl and 2% Chlorhexidine gluconate, 2% Chlorhexidine gluconate, Miswak extract and normal saline for root canal irrigation. Materials and Methods: In this prospective observational study was conducted from February 2021 to April 2021, on 10 patients with persistent endodontic infection on single rooted teeth. After obtaining access to the root canals, paper points were inserted and the soaked paper points were placed immediately in a microtube with two mL of Reduced Transport Fluid (RTF) to obtain the bacterial suspension. The sensitivity of gram negative anerobic bacteria and E.faecalis to different irrigants was assessed with disc diffusion test and bacterial load was evaluated with Colony Forming Unit (CFU) assay. The study was analysed statistically using Kruskal-Wallis test and Dunn test (post-hoc test). Result: The results of disk diffusion method showed that the zone of inhibition for 2% chlorhexidine gluconate was 29 mm for gram negative anerobic bacteria and 22 mm for E.faecalis, and the zone of inhibition for Miswak extract was 8 mm for gram negative anerobic bacteria and 10 mm for E.faecalis. Gram negative anerobic bacteria on the culture plates treated with Miswak extract had 6.41 CFU/mL, and E.faecalis had 5.21 CFU/mL. Gram negative anerobic bacteria on the culture plates treated with normal saline had a CFU/mL of 6.77, and E.faecalis had a CFU/mL of 5.77. The antibacterial activity of miswak extract was lower than that of other irrigants. The normal saline lacked any antimicrobial qualities. Conclusion: The antibacterial effectiveness of the combination of 5.25% NaOCl and 2% Chlorhexidine gluconate was found to be higher than, 2% Chlorhexidine gluconate, Miswak extract and normal saline for root canal irrigation. A combination of 5.25% NaOCl and 2% Chlorhexidine gluconate can be used as a better choice over the other three irrigants.

The microbial community of persistent endodontic infection and the use of root canal disinfectants against E. faecalis: In vitro and in vivo review

In cases of unsuccessful endodontic treatment, E. faecalis is commonly detected and remains popular among the scientific community for in vitro and in vivo research. The nature of the bacteria's predominance is dependent on the difficulty in cleaning the apical portion of the tooth and E. faecalis' capacity to grow deep into the dentinal tubules. The purpose of this review is to gather current research on root canal disinfection against E. faecalis. In this literature review, four databases were searched: PubMed, EBSCOhost, ScienceDirect, and Google Scholar, with explicit inclusion and exclusion criteria. The compiled review shows that a predominant multi-microbial community within a persistent root canal infection include Porphyromonas gingivalis, Fusobacterium nucleatum, and Enterococcus faecalis. E. faecalis produces moderate biofilms and causes infection through its virulence factors such as esp, cylA, ace, gelE, asa, and efaA. Several disinfecting agents and approaches have been explored for their capacity to eradicate E. faecalis and penetrate the dentinal tubules. Sodium hypochlorite (NaOCl) and chlorhexidine (CHX) gel eliminate E. faecalis and other resistant microbes such as Staphylococcus aureus, and Escherichia coli. Combing NaOCl irrigation with the following: Photon-induced photoacoustic streaming, passive ultrasonic irrigation, and diode laser irradiation, eradicates E. faecalis. The current research has shifted towards nanoparticles against E. faecalis because of its dissolution capacity, size, and antimicrobial efficacy. E. faecalis resists calcium hydroxide through its proton pump mechanism, but it is susceptible to Ca(OH)2 when applying a proton pump inhibitor or chlorhexidine.

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

BackgroundEnterococcus 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.MethodsThirty-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.ResultsFor 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).ConclusionChitosan 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.

Fucoidan-derived carbon dots against Enterococcus faecalis biofilm and infected dentinal tubules for the treatment of persistent endodontic infections

Enterococcus faecalis (E. faecalis) biofilm-associated persistent endodontic infections (PEIs) are one of the most common tooth lesions, causing chronic periapical periodontitis, root resorption, and even tooth loss. Clinical root canal disinfectants have the risk of damaging soft tissues (e.g., mucosa and tongue) and teeth in the oral cavity, unsatisfactory to the therapy of PEIs. Nanomaterials with remarkable antibacterial properties and good biocompatibility have been developed as a promising strategy for removing pathogenic bacteria and related biofilm. Herein, carbon dots (CDs) derived from fucoidan (FD) are prepared through a one-pot hydrothermal method for the treatment of PEIs. The prepared FDCDs (7.15 nm) with sulfate groups and fluorescence property are well dispersed and stable in water. Further, it is found that in vitro FDCDs display excellent inhibiting effects on E. faecalis and its biofilm by inducing the formation of intracellular and extracellular reactive oxygen species and altering bacterial permeability. Importantly, the FDCDs penetrated the root canals and dentinal tubules, removing located E. faecalis biofilm. Moreover, the cellular assays show that the developed FDCDs have satisfactory cytocompatibility and promote macrophage recruitment. Thus, the developed FDCDs hold great potential for the management of PEIs.Graphical

Enhanced Eradication of Enterococcus faecalis Biofilms by Quaternized Chitosan-Coated Upconversion Nanoparticles for Photodynamic Therapy in Persistent Endodontic Infections.

Due to the persistent presence of Enterococcus faecalis biofilms in apical root canals, persistent endodontic infections (PEIs) have always been an intractable disease to solve. The conventional root canal disinfectants (e.g., calcium hydroxide, chlorhexidine) are arduous to scavenge the stubborn infection. With the progress of nanomedicine in the biomedical field, antimicrobial photodynamic therapy (aPDT) is emerging as a prospective anti-infective therapy for PEIs. Herein, quaternized chitosan (QCh) modified upconversion nanoparticles (UCNP)@SiO2/methylene blue (MB) are developed with enhanced antibacterial/biofilm performance for aPDT in PEIs. QCh is coated on the UCNP@SiO2/MB by testing the changes in diameter, chemical functional group, and charge. Interestingly, QCh also increases the conversion efficiency of UCNP to generate more reactive oxygen species (ROS). Furthermore, the prepared UCNP@SiO2/MB@QCh exhibits highly effective antibacterial activity against free E. faecalis and related biofilm in vitro and extracted teeth. Importantly, the additional QCh with positive charges enhance UCNP@SiO2/MB@QCh contact with E. faecalis (negative charges) through electrostatic interaction. Then, UCNP@SiO2/MB@QCh could stick close to the E. faecalis and generate ROS under the irradiation by a 980 nm laser. The in vitro cellular test shows that UCNP@SiO2/MB@QCh has acceptable cytocompatibility. Thus, UCNP@SiO2/MB@QCh could offer a novel strategy for the potential aPDT clinical applications in the treatment of PEIs.

The Products of Probiotic Bacteria Effectively Treat Persistent Enterococcus faecalis Biofilms.

Objectives: Enterococcus faecalis is a Gram-positive commensal bacterium that possesses various survival and virulence factors, including the ability to compete with other microorganisms, invade dentinal tubules, and resist nutritional deprivation. E. faecalis is associated with persistent endodontic infections where biofilms formed by this bacterium in the root canal frequently resist dental therapies. Aseptic techniques, such as the inclusion of sodium hypochlorite, are the most commonly used methods to treat E. faecalis infections within the root canal system. In this work, we assess the effectiveness of probiotic strains to prevent the regrowth of E. faecalis biofilm cells treated by sodium hypochlorite irrigation. Methods: First, methods are presented that evaluate the effects of short-term exposure to sodium-hypochlorite on established E. faecalis. Next, we evaluate the effects of the secreted products of probiotic strains on biofilm cells and planktonic cells. Results: Sodium hypochlorite, the treatment conventionally used to decontaminate infected root canal systems, was extremely toxic to planktonic bacteria but did not fully eradicate biofilm cells. Furthermore, low concentrations of sodium hypochlorite induced eDNA dependent biofilms. Strikingly, conditioned medium from the probiotic bacteria Lactobacillus plantarum and Lactobacillus casei was sufficient to fully prevent the regrowth of treated biofilms while showing reduced potency towards planktonic cells. Conclusion: Sodium hypochlorite irrigations may contribute to the persistence of biofilm cells if used at concentrations lower than 3%. Probiotic strains and their products represent a new reservoir of biofilm therapies for E. faecalis infections formed in the root canal system.

Single‐cell Raman microspectroscopy‐based assessment of three intracanal disinfectants' effect on Enterococcus faecalis

AbstractEnterococcus faecalis (E. faecalis) is frequently encountered in asymptomatic, persistent endodontic infections; thus, its control and eradication via disinfectants are important. To explore a disinfectant formulation that is effective yet with minimal side effects, here, we evaluated the susceptibility of E. faecalis to three intracanal disinfectants. We quantitatively assessed and compared the growth‐ or metabolism‐inhibiting effects of intracanal disinfectants via minimum inhibitory concentration (MIC) and minimum inhibitory concentration based on metabolic activity (MIC‐MA), based on the broth dilution test and D2O‐probed single‐cell Raman spectra (SCRS), respectively. For sodium hypochlorite (NaClO), hydrogen peroxide (H2O2), and chlorhexidine gluconate (CHX), the corresponding MIC was 0.45 g/L, 110 mg/L, and 6 mg/L, respectively. Under their respective MIC doses, metabolic activity of bacterial cells was reduced to 2%, 4%, and 2% remained at 8 h, yet recovered to a retention level of 90%, 97%, and 2% at 24 h. Despite the halting of growth, the remained metabolic activity suggests a “nongrowing but metabolically active” (NGMA) state that may lead to potential recurring infections. In contrast, at their respective MIC‐MA doses of 0.9 g/L, 220 mg/L, and 12 mg/L, metabolic activities of all cells were completely inhibited throughout 24‐h exposure. Furthermore, lower combined concentration of above three intracanal disinfectants can elicit equivalent metabolism‐inhibiting effect with that of solo use of each one at the MIC‐MA dose. Thus, binary combined use of disinfectants can outperform their solo use in controlling infection of E. faecalis and reducing side effects. In conclusion, the MIC‐MA derived from D2O‐probed single‐cell Raman microspectroscopy is a promising approach in quantitatively assessing disinfectants' antimicrobial efficacy via metabolic activity.

Investigating the Antibacterial Effect of Passive Ultrasonic Irrigation, Photodynamic Therapy and Their Combination on Root Canal Disinfection.

Introduction: Enterococcus faecalis is a gram-positive, facultative anaerobic bacterium associated with persistent endodontic infections. Conventional disinfection methods may not completely eradicate the bacteria within the root canal system. Therefore, novel modalities have been suggested to optimize root canal disinfection. The aim of this study was to evaluate and compare the antibacterial effect of photodynamic therapy (PDT), passive ultrasonic irrigation (PUI) and their combination in addition to conventional endodontic irrigation against E. faecalis biofilms in root canals. Methods: Root canals of 50 single-rooted extracted human teeth were prepared and incubated with E. faecalis for 21 days. They were then divided into 4 treatment groups and a control group as follows: (1) NaOCl-Syringe irrigation with 2.5% NaOCl, (2) PUI-Passive ultrasonic irrigation with NaOCl, (3) NaOCl+PDT-Photodynamic therapy following syringe irrigation with NaOCl, (4) PUI+PDT, (5) Control-Syringe irrigation with saline. Colony-forming units were counted and bacterial reduction was calculated for each treatment group. Results: All treatments led to significant reductions in the bacterial load compared to the control group. PUI and PUI+PDT led to the complete elimination of the bacteria from the root canals. NaOCl and NaOCl+PDT treatments reduced the bacteria by 99.9% and 99.5% respectively. NaOCl+PDT was significantly less effective in reducing the bacteria compared to other treatment groups. There were no significant differences between the NaOCl, PUI, and PUI+PDT groups. Conclusion: Passive ultrasonic irrigation with or without the combination of Photodynamic therapy completely eradicated the bacteria. The use of PDT as an adjunction to NaOCl syringe irrigation and PUI did not enhance their antibacterial effect.

Influence of silver-containing filler on antibacterial properties of experimental resin composites against Enterococcus faecalis

Purpose: The aim of the presented work was to investigate the impact of the S-P introduction into resin-based composites on their effectiveness against Enterococcus faecalis (E. faecalis). Design/methodology/approach: Seven experimental composites based on typical matrix were developed. Six of them contained a filler with antimicrobial properties (silver sodium hydrogen zirconium phosphate, S-P), while the control material contained only common reinforcement fillers. The materials were characterized in terms of the dispersion of the extender in the matrix and then subjected to microbiological tests. The efficiency in the reduction of E. faecalis in the microenvironment was tested. Findings: The composites show a satisfactory distribution of fillers and a high initial reduction of bacteria colonies for the tested strain of E. faecalis. The reduction in bacteria colonies achieved for S-P concentrations from 7% to 13% was similar (median value from 99.8 to 99.9%, when for control material and compound with 1% S-P the number of colonies increased compared to positive control. Research limitations/implications: Laboratory test results may differ from in vivo test performance. In addition, there are many models for conducting laboratory antimicrobial efficacy studies, the results of which are also varied. The cytotoxic tests, long-term investigations and in vivo experiments need to be performed in future experiments. Practical implications: E. faecalis is a Gram-positive bacterium that is commonly detected in persistent endodontic infections and may enter the root canal through the coronal part. Development of composites with antimicrobial properties against this bacterium is as important as obtaining efficacy against cariogenic bacteria. Originality/value: The antimicrobial effectiveness against E. faecalis of experimental composites with submicrometer-sized particles of S-P was not investigated until now.