Evaluation of the presence of microorganisms from root canal of teeth submitted to retreatment due to prosthetic reasons and without evidence of apical periodontitis

Non-faecium non-faecalis enterococci: a review of clinical manifestations, virulence factors, and antimicrobial resistance

SUMMARYEnterococci are a diverse group of Gram-positive bacteria that are typically found as commensals in humans, animals, and the environment. Occasionally, they may cause clinically relevant diseases such as endocarditis, septicemia, urinary tract infections, and wound infections. The majority of clinical infections in humans are caused by two species: Enterococcus faecium and Enterococcus faecalis. However, there is an increasing number of clinical infections caused by non-faecium non-faecalis (NFF) enterococci. Although NFF enterococcal species are often overlooked, studies have shown that they may harbor antimicrobial resistance (AMR) genes and virulence factors that are found in E. faecium and E. faecalis. In this review, we present an overview of the NFF enterococci with a particular focus on human clinical manifestations, epidemiology, virulence genes, and AMR genes.

Enterococcus faecalis Extracellular Vesicles Promote Apical Periodontitis

Enterococcus faecalis is an important contributor to the persistence of chronic apical periodontitis. However, the mechanism by which E. faecalis infection in the root canals and dentinal tubules affects periapical tissue remains unclear. Bacterial extracellular vesicles (EVs) act as natural carriers of microbe-associated molecular patterns (MAMPs) and have recently attracted considerable attention. In this study, we investigated the role of EVs derived from E. faecalis in the pathogenesis of apical periodontitis. We observed that E. faecalis EVs can induce inflammatory bone destruction in the periapical areas of mice. Double-labeling immunofluorescence indicated that M1 macrophage infiltration was increased by E. faecalis EVs in apical lesions. Moreover, in vitro experiments demonstrated the internalization of E. faecalis EVs into macrophages. Macrophages tended to polarize toward the M1 profile after treatment with E. faecalis EVs. Pattern recognition receptors (PRRs) can recognize MAMPs of bacterial EVs and, in turn, trigger inflammatory responses. Thus, we performed further mechanistic exploration, which showed that E. faecalis EVs considerably increased the expression of NOD2, a cytoplasmic PRR, and that inhibition of NOD2 markedly reduced macrophage M1 polarization induced by E. faecalis EVs. RIPK2 ubiquitination is a major downstream of NOD2. We also observed increased RIPK2 ubiquitination in macrophages treated with E. faecalis EVs, and E. faecalis EV-induced macrophage M1 polarization was notably alleviated by the RIPK2 ubiquitination inhibitor. Our study revealed the potential for EVs to be considered a virulence factor of E. faecalis and found that E. faecalis EVs can promote macrophage M1 polarization via NOD2/RIPK2 signaling. To our knowledge, this is the first report to investigate apical periodontitis development from the perspective of bacterial vesicles and demonstrate the role and mechanism of E. faecalis EVs in macrophage polarization. This study expands our understanding of the pathogenic mechanism of E. faecalis and provides novel insights into the pathogenesis of apical periodontitis.

The Safety of Removing Fractured Nickel-Titanium Files in Root Canals Using a Nd: YAP Laser

The fracture of nickel-titanium (Ni-Ti) instruments during root canal instrumentation leads to compromised outcomes in endodontic treatments. Despite the significant impact of instrument facture during a root canal treatment, there is still no universally accepted method to address this complication. Several previous studies have shown the ability of a Neodymium: Yttrium-Aluminum-Perovskite (Nd: YAP) laser to cut endodontic files. This study aims to determine safe irradiation conditions for a clinical procedure involving the use of a Neodymium: Yttrium-Aluminum-Perovskite (Nd: YAP) laser for removing fractured nickel-titanium files in root canals. A total of 54 extracted permanent human teeth (n = 54) were used. This study involved nine distinct groups, each employing different irradiation conditions. Groups 1 s, 3 s, 5 s, 10 s, and 15 s simply consist of irradiation for 1, 3, 5, 10, and 15 s, respectively. After identifying the longest and safest duration time, four additional groups were proposed (labeled A, B, C, and D). Group A was composed of three series of irradiations of 5 s each separated by a rest time of 30 s (L5s + 30 s RT). Group B consisted of three series of irradiations of 5 s each separated by a rest time of 60 s (L5s + 60 s RT). Group C consisted of two series of irradiations of 5 s each separated by a rest time of 30 s (L5s + 30 s RT), and group D consisted of two series of irradiations of 5 s each separated by a rest time of 5 s (L5s + 5 s RT). In all groups, during the rest time, continuous irrigation with 2.5 mL of sodium hypochlorite (3% NaOCl) was carried out. The variation in temperature during irradiation was registered with a thermocouple during irradiation with different protocols. The mean and standard deviation of the temperature increase was noted. The calculation of the temperature was made as the Δ of the highest recorded temperature at the root surface minus (-) that recorded at baseline (37°). Additionally, scanning electron microscopy (SEM) was used after irradiation in all groups in order to assess the morphological changes in the root dentinal walls. The Nd: YAP laser irradiation parameters were a power of 3W, an energy of 300 mJ per pulse, a fiber diameter of 200 µm, a pulsed mode of irradiation with a frequency of 10 Hz, a pulse duration of 150 µs, and an energy density of 955.41 J/cm2. Our results show that the safest protocol for bypassing and/or removing broken instruments involves three series of irradiation of 5 s each with a rest time of 30 s between each series. Furthermore, our results suggest that continuous irradiation for 10 s or more may be harmful for periodontal tissue.

Antibiotic Resistance Profile of Clinical Strains of Enterococci from Secondary/Persistent Endodontic Infections: What do We Know? A Systematic Review of Clinical Studies

INTRODUCTION

Enterococcus faecalis is the most common enterococcal species associated with infective endocarditis and 1 of the most commonly detected bacteria in cases of secondary/persistent endodontic infection (SPEI). Antimicrobial resistance is a global public health concern. This review aimed to answer the following research question: "Is there a change in the antibiotic resistance profile in clinical strains of E. faecalis over the years?". P (population) - patients with SPEI, I (intervention) -endodontic retreatment, C (comparison) -not included, O (outcome) - profile of Enterococci resistance and susceptibility to systemic antibiotics used.

METHODS

Two authors independently performed study selection, data extraction, and risk of bias assessment. The literature search was conducted using the following electronic databases: PubMed, Scopus, EMBASE, Web of Science, and Medline. Clinical studies in which Enterococci strains were isolated to assess their antimicrobial resistance were included.

RESULTS

Eleven clinical trials were included. Overall, E. faecalis isolated from teeth with SPEI presented an intermediate resistance to 16 antibiotics. In recent years, E. faecalis showed a little resistance to amoxicillin (without clavulanate) and benzylpenicillin. Erythromycin and rifampicin presented an increase in the intermediate-resistance status between the first and the last studies. E. faecium presented intermediate-resistance results.

CONCLUSION

The most effective drugs remain the combination of amoxicillin and clavulanate, followed by amoxicillin and benzylpenicillin. In patients allergic to penicillin derivatives, moxifloxacin and azithromycin may be indicated with caution. The antibiotics with the highest pattern of resistance against E. faecalis are clindamycin, gentamicin, metronidazole, and rifampicin and are therefore, contraindicated in cases of SPEI. Very few clinical studies using a microbiological approach in teeth with endodontic failure have been carried out to improve the efficacy of prophylactic regimens. However, as bacteria periodically develop resistance to the main drugs used, regular studies should be carried out on the action of these drugs in infection control.

Microbiological profile of root canals indicated for endodontic retreatment due to secondary endodontic infections or for prosthetic reasons

OBJECTIVE

The objective of this study was to evaluate the microbiological profile of root canals indicated for endodontic retreatment due to secondary endodontic infections evidenced by the presence of chronic apical periodontitis (G1) or for prosthetic reasons, without clinical and radiographic signs of endodontic reinfection (G2).

METHODS

Microbiological samples were collected from thirty teeth (N=30) out of which 15 were indicated for retreatment due to the presence of chronic apical periodontitis (G1) and 15 were indicated exclusively for prosthetic reasons (G2). Samples were collected from root canals before (S1), after chemomechanical preparation (S2), and after 30 days of intracanal medication composed of calcium hydroxide and 2% chlorhexidine gel (S3). The molecular analysis was performed using Nested-PCR for the detection of 17 bacterial species. The efficacy of each stage of the retreatment in reducing the microbial load was verified by counting colony-forming units (CFU). The statistical analysis considered a significance level of 5%.

RESULTS

The results showed that bacteria were detected in 100% of the cases in S1, in both groups, by Nested PCR. The most frequently found species in S1 in both groups were Enterococcus faecalis, Fusobacterium nucleatum, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, and Parvimonas micra. The microbial load of G1 was higher than G2 in the initial samples (S1). Endodontic retreatment was effective in reducing the microbial load in G1 and G2. Statistically significant associations were found between specific bacteria and clinical signs and symptoms.

CONCLUSION

It was concluded that the microbial community present in the root canal of teeth indicated for endodontic retreatment is mixed and heterogeneous. G1 and G2 differ in the number of species per case and microbial load.

CLINICAL RELEVANCE

Endodontic retreatment was effective in reducing the microbial load. Statistically significant associations were found between specific bacteria and clinical signs and symptoms.

Efficacy of 6% Sodium Hypochlorite on Infectious Content of Teeth with Symptomatic Irreversible Pulpitis

INTRODUCTION

The objective of this study was to monitor the effects of chemomechanical preparation (CMP) performed with 6% sodium hypochlorite and calcium hydroxide-based intracanal medication (ICM) on the levels and diversity of bacteria, endotoxins (LPS) and lipoteichoic acid (LTA) in root canals of teeth with symptomatic irreversible pulpitis.

METHODS

Samples were collected from ten teeth with symptomatic irreversible pulpitis before CMP (S1), after CMP (S2) and after ICM (S3). The levels of bacteria, LPS and LTA were assessed by using checkerboard DNA-DNA hybridisation, LAL Pyrogent 5000 and enzyme linked immunosorbent assay (ELISA), respectively. Wilcoxon's test, repeated measures ANOVA and Tukey's post-hoc test were used for statistical analysis at a significance level of 5%.

RESULTS

Forty species were detected at S1. Two species were eliminated after CMP and five after ICM. Resistant and pain-related species were detected in the root canals. Higher levels of culturable bacteria were detected at S1. However, CMP and ICM effectively reduced the microbial load in the root canals. Higher levels of LPS and LTA were detected at S1. CMP was effective in reducing both LPS and LTA (P < 0.05). ICM produced additional reduction in the levels of LPS (P > 0.05) and LTA (P < 0.05).

CONCLUSION

Chemomechanical preparation using 6% sodium hypochlorite and calcium hydroxide-based intracanal medication were effective in reducing the levels of bacteria, endotoxins and lipoteichoic acid in teeth with vital pulp and irreversibly inflamed pulp.

Residual antibacterial effects of a mixture of silver nanoparticles/calcium hydroxide and other root canal medicaments against Enterococcus faecalis

Background/purpose

Intracanal medicaments with high residual inhibition effects are used to achieve successful endodontic treatment and prevent reinfection. This in vitro study aimed to assess antimicrobial residual effects of different intracanal medicaments against Enterococcus faecalis (E. faecalis) in root dentin one week after drug therapy.

Materials and methods

Seventy human teeth were standardized to have 15 mm of length and were prepared by ProTaper rotary system. The teeth were randomly divided into six experimental (n = 10) and two control (n = 5) groups and subjected to drug therapy as follows; group CHX: 2% chlorhexidine gel, group CH: calcium hydroxide paste, group CH/CHX: mixture of calcium hydroxide and 2% CHX, group TAP: triple antibiotic paste, group DAP: double antibiotic paste, group CH/AgNPs: mixture of CH paste and silver nanoparticle suspension. After one week, the medicaments were removed from the root canals and E. faecalis was inoculated into the canals. The teeth were incubated at 37 °C for 24 h. Using a size 40 hedstrom file, dentin chips were collected and number of colony forming units were counted.

Results

The difference between all experimental groups was statistically significant in this regard (P < 0.05) except for DAP and TAP groups, in which, no bacterial colony was noted after culture. After DAP and TAP, the lowest colony count was noted in CH/AgNPs, CH/CHX and CHX groups. The highest colony count was noted in CH group.

Conclusion

Our results showed favorable residual antibacterial effects of TAP, DAP and CH/AgNP medicaments after one week of application.

Critical analysis of research methods and experimental models to study removal of root filling materials

Despite enjoying high favourable outcome rates, root canal treatment is not always successful. Root canal retreatment is a widely practised option for managing a non-healing root treated tooth. A basic distinction between retreatment and initial treatment is the requirement to remove the existing root filling material occupying the root canal space. Only then, can the technical deficiencies and possible causes of failure be addressed. Hence, the successful removal of the root filling material is critical to achieving the objectives of retreatment. Many different materials and techniques have been used for root canal filling, which have been documented in a plethora of studies; these are mainly laboratory studies investigating the removal of root filling materials. To help guide future research, which may then better inform clinical practice in relation to retreatment procedures, the focus of this narrative review is on the research methods and experimental models employed to study the removal of root filling materials. The current available literature demonstrates great variation in the research methodologies used to study the removal of root filling material, including direct visualization by splitting tooth samples or clearing, three-dimensional radiographic imaging including using microcomputed tomography or cone-beam computed tomography, and a combination of these techniques. Depending on the research method employed, variation also exists in quantification of root filling material removal; these include measurements of surface area, volume or weight, and criteria-based (semi-quantitative) assessment. Experimental models, using human teeth or resin models, differ with respect to standardization techniques and replication of the clinical scenario including initial sample preparation, canal filling, allocation and technical aspects of retreatment procedures. Future models should replicate, as closely as possible, the clinical scenario. Currently, microcomputed tomography provides a highly detailed, non-invasive and non-destructive method of objectively assessing and quantifying root filling removal.

Preparation and characterisation of a gellan gum-based hydrogel enabling osteogenesis and inhibiting Enterococcus faecalis

Infections are the leading cause of failure of osteogenic material implantation. Antibiotic treatment, treatment with bone cement, or collagen sponge placement can result in drug resistance and difficulties in operation. To address this, gellan gum (GG) was selected in this study and prepared as an injectable hydrogel containing chlorhexidine (CHX) and nanohydroxyapatite (nHA) that overcomes these intractable problems. Scanning electron microscopy and micro-computed tomography revealed a three-dimensional polymeric network of the hydrogel. The hydrogel had excellent biocompatibility, as detected by cell counting kit-8 and Live/Dead assay. Bone marrow mesenchymal stem cells could be encapsulated into the network, showing that the structure was suitable for cell growth. Additionally, loading the hydrogel with nHA improved its mechanical, biodegradable, and osteogenic properties. Quantitative alkaline phosphatase and Alizarin Red S staining validated its osteogenic ability. Furthermore, antibacterial activity assessment showed that the hydrogel loaded with 50 μg/mL CHX inhibited Enterococcus faecalis in a concentration-dependent manner. Thus, we report an injectable GG-based hydrogel with superior antibacterial effect against E. faecalis and osteogenesis, which holds promise for treating infectious bone defects caused by refractory periradicular periodontitis.