Microbial community in persistent apical periodontitis: a 16S rRNA gene clone library analysis

Association between endodontic symptoms and root canal microbiota: a systematic review and meta-analysis of bacteroidetes, spirochaetes and fusobacteriales

OBJECTIVES

This systematic review and meta-analysis aimed to assess the prevalence of Bacteroidetes, Spirochaetes, and Fusobacteriales in symptomatic versus asymptomatic apical periodontitis as a primary objective. The secondary objective was to evaluate the prevalence of these species independently in symptomatic and asymptomatic apical periodontitis.

MATERIALS AND METHODS

An electronic search of the PubMed, Scopus, and Open-Grey databases was carried out from November 2022 to February 2023 and was later updated through July 2024..The risk of bias was assessed using the New Castle Ottawa scale. The quality of evidence was assessed using the Grading of Recommendations. Assessment, Development, and Evaluation.

RESULTS

The initial search resulted in 968 records. Following the removal of duplicates and a review of titles and abstracts, 66 studies underwent full-texts analysis. Twenty studies were deemed eligible for inclusion. For the first outcome, a fixed-effects model was used. In a total of 7 studies with 193 participants, Spirochaetes were more prevalent in symptomatic apical periodontitis (p < .05) with a risk ratio of 1.91 [ 95% CI 1.25-2.92]. No significant difference was observed (p˃.05) in the prevalence of Bacteroidetes (12 studies with 451 participants) and Fusobacteriales (7 studies with 205 participants) in symptomatic vs asymptomatic apical periodontitis with a risk ratio of (.96), and (1.1), [95% CI, .78-1.19], and [95% CI, 0.84.1.44], respectively. The overall quality of evidence was low.

CONCLUSIONS

The confirmation of the prevalence of Bacteroidetes and Fusobacteriales in symptomatic vs asymptomatic apical periodontitis remains uncertain. However, there is an association between Spirochetes and symptomatic apical periodontitis. Additional research is required to address the limitations of the current body of evidence.

CLINICAL RELEVANCE

Identifying key pathogens in symptomatic apical periodontitis can help develop targeted interventions that address the underlying microbial causes.

Lipopeptide biosurfactant as a potential root canal irrigation agent: Antimicrobial and anti-biofilm evaluation

OBJECTIVES

Lipopeptide Biosurfactant (LB) is a bacteria derived compound able to reduce surface tension between water and hydrophobic substances and exhibit antimicrobial and anti-biofilm properties. This study aimed to investigate the antimicrobial and anti-biofilm effect of a Lipopeptide Biosurfactant (LB) on Enterococcus faecalis, and its potential use in root canal treatment, either as a standalone irrigation solution or in conjunction with sodium hypochlorite (NaOCl).

METHODS

LB was extracted from Bacillus clausii isolate and the dry extract was diluted in deionized water. The antimicrobial effect of LB against planktonic E. faecalis was evaluated by determining the Minimal Inhibitory Concentration (MIC50). The anti-biofilm effect was evaluated by Minimal Biofilm Inhibitory Concentration (MBIC50) and Minimal Biofilm Eradication Concentration (MBEC50) assays on biofilm grown on dentin specimen surface. To evaluate the effectiveness of LB as a single irrigation solution and as a pre-irrigation prior to NaOCl, live and dead bacterial cells were quantified using Confocal Laser Scanning Microscopy (CLSM), and cell biomass was assessed.

RESULTS

LB exhibited an MIC50 and MBIC50 of 100 ppm, with an MBEC50 of 1000 ppm, resulting in 52.94 % biofilm inhibition and 60.95 % biofilm eradication on dentin specimens. The effectiveness was concentration-dependent, at 500 ppm, LB demonstrated comparable antimicrobial efficacy to 2.5 % NaOCl. Pre-irrigation with LB resulted in lower biofilm biomass compared to NaOCl alone.

CONCLUSION

Pre-irrigation with LB enhanced the antimicrobial effect when followed by NaOCl irrigation. Consequently, LB shows promise as both a standalone root canal irrigation solution and as an adjunct to NaOCl in root canal treatment.

CLINICAL SIGNIFICANCE

The study highlights the potential of Lipopeptide Biosurfactant (LB) as an environmentally friendly irrigation solution for root canal treatment, demonstrating potent antimicrobial and anti-biofilm properties against Enterococcus faecalis. LB exhibits concentration-dependent efficacy comparable to 2.5 % NaOCl and can be used as a standalone irrigation solution or in conjunction with NaOCl.

"Magnet" Based on Activated Silver Nanoparticles Adsorbed Bacteria to Predict Refractory Apical Periodontitis Via Surface-Enhanced Raman Scattering

Refractory apical periodontitis (RAP) is an endodontic apical inflammatory disease caused by Enterococcus faecalis (E. faecalis). Bacterial detection using surface-enhanced Raman scattering (SERS) technology is a hot research topic, but the specific and direct detection of oral bacteria is a challenge, especially in real clinical samples. In this paper, we develop a novel SERS-based green platform for label-free detection of oral bacteria. The platform was built on silver nanoparticles with a two-step enhancement way using NaBH4 and sodium (Na+) to form "hot spots," which resulted in an enhanced SERS fingerprint of E. faecalis with fast, quantitative, lower-limit, reproducibility, and stability. In combination with machine learning, four different oral bacteria (E. faecalis, Porphyromonas gingivalis, Streptococcus mutans, and Escherichia coli) could be intelligently distinguished. The unlabeled detection method emphasized the specificity of E. faecalis in simulated saliva, serum, and even real samples from patients with clinical root periapical disease. In addition, the assay has been shown to be environmentally friendly and without secondary contamination through antimicrobial assays. The proposed label-free, rapid, safe, and green SERS detection strategy for oral bacteria provided an innovative solution for the early diagnosis and prevention of RAP and other perioral diseases.

Single-cell atlas of dental pulp stem cells exposed to the oral bacteria Porphyromonas gingivalis and Enterococcus faecalis

Introduction: Porphyromonas gingivalis and Enterococcus faecalis promote the development of pulpitis and periapical periodontitis. These bacteria are difficult to eliminate from the root canal systems, leading to persistent infection and poor treatment outcomes. We explored the response of human dental pulp stem cells (hDPSCs) to bacterial invasion and the mechanisms underlying the impact of residual bacteria on dental pulp regeneration. Methods: Single-cell sequencing was used to categorize the hDPSCs into clusters based on their response to P. gingivalis and E. faecalis. We depicted a single-cell transcriptome atlas of hDPSCs stimulated by P. gingivalis or E. faecalis. Results: The most differentially expressed genes in the Pg samples were THBS1, COL1A2, CRIM1, and STC1, which are related to matrix formation and mineralization, and HILPDA and PLIN2, which are related to the cellular response to hypoxia. A cell cluster characterized by high expression levels of THBS1 and PTGS2 was increased after P. gingivalis stimulation. Further signaling pathway analysis showed that hDPSCs prevented P. gingivalis infection by regulating the TGF-β/SMAD, NF-κB, and MAPK/ERK signaling pathways. Differentiation potency and pseudotime trajectory analyses showed that hDPSCs infected by P. gingivalis undergo multidirectional differentiation, particularly to the mineralization-related cell lineage. Furthermore, P. gingivalis can create a hypoxia environment to effect cell differentiation. The Ef samples were characterized by the expression of CCL2, which is related to leukocyte chemotaxis, and ACTA2, which is related to actin. There was an increased proportion of a cell cluster that was similar to myofibroblasts and exhibited significant ACTA2 expression. The presence of E. faecalis promoted the differentiation of hDPSCs into fibroblast-like cells, which highlights the role of fibroblast-like cells and myofibroblasts in tissue repair. Discussion: hDPSCs do not maintain their stem cell status in the presence of P. gingivalis and E. faecalis. They differentiate into mineralization-related cells in the presence of P. gingivalis and into fibroblast-like cells in the presence of E. faecalis. We identified the mechanism underlying the infection of hDPSCs by P. gingivalis and E. faecalis. Our results will improve understanding of the pathogenesis of pulpitis and periapical periodontitis. Furthermore, the presence of residual bacteria can have adverse effects on the outcomes of regenerative endodontic treatment.

Prevalence of Oral Pathogen Slackia exigua among Clinical Orthodontic and Non-Orthodontic Saliva Samples

Slackia exigua (SE) is a recently identified intestinal microbe, which recent oral surveys suggest may be associated with oral diseases including caries and periodontal disease. Based upon the lack of information regarding this organism, the primary objective of this study was to determine the oral prevalence of this microbe and any potential associations with patient characteristics such as age, sex, or the presence of orthodontic appliances. This retrospective study involved the screening of an existing saliva repository composed of previously collected unstimulated clinical saliva samples. More specifically, N = 266 were identified and screened using a spectrophotometer at absorbances of A260 and A280 nm to determine their DNA purity and concentration. qPCR screening of these samples revealed a higher prevalence of Slackia exigua positive samples among pediatric patients (63.1%) compared with adults (36.9%) in this clinic population, p = 0.0007. In addition, higher percentages of Slackia exigua were observed among orthodontic patients (71.2%) compared with non-orthodontic patients (28.8%), p = 0.0001. These results did not vary by sex with nearly equal percentages of Slackia exigua positive males and females among adult and pediatric patients, as well as orthodontic and non-orthodontic samples. These results suggest a strong potential for association between the prevalence of this organism with age as well as orthodontic status, given that younger patients and those with orthodontic brackets (regardless of age) were most likely to harbor this pathogen in sufficient levels to be detected in saliva. More research will be needed to determine any associations with specific outcomes, such as caries or periodontal disease, among Slackia exigua positive patients within these specific populations.

Antibacterial efficacy of antibiotic pastes versus calcium hydroxide intracanal dressing: A systematic review and meta-analysis of ex vivo studies

Background

Conflicting findings on the potency of antibiotic pastes versus calcium hydroxide (CH) have been evident in the literature.

Aims

To compare the antibacterial efficacy of single antibiotic paste (SAP), double antibiotic paste (DAP), triple antibiotic paste (TAP), and modified TAP (mTAP) with CH on bacterial biofilms.

Methods

PubMed, Scopus, and Embase were comprehensively searched until August 23, 2021. The study protocol was registered in the PROSPERO. Ex vivo studies performed on Enterococcus faecalis or polymicrobial biofilms incubated on human/bovine dentin were selected. The quality of the studies was assessed using a customized quality assessment tool. Standardized mean difference (SMD) with a 95% confidence interval (CI) was calculated for the meta-analysis. Meta-regression models were used to identify the sources of heterogeneity and to compare the efficacy of pastes.

Results

The qualitative and quantitative synthesis included 40 and 23 papers, respectively, out of 1421 search results. TAP (SMD = -3.82; CI, -5.44 to -2.21; P < 0.001) and SAPs (SMD = -2.38; CI, -2.81 to - 1.94; P < 0.001) had significantly higher antibacterial efficacy compared to the CH on E. faecalis biofilm. However, no significant difference was found between the efficacy of DAP (SMD = -2.74; CI, -5.56-0.07; P = 0.06) or mTAP (SMD = -0.28; CI, -0.82-0.26; P = 0.31) and CH. Meta-regression model on E. faecalis showed that SAPs have similar efficacy compared to TAP and significantly better efficacy than DAP. On dual-species (SMD = 0.15; CI, -1.00-1.29; P = 0.80) or multi-species (SMD = 0.23; CI, -0.08-0.55; P = 0.15) biofilms, DAP and CH had similar efficacy.

Conclusions

Ex vivo evidence showed that antibiotic pastes were either superior or equal to CH. The studied SAPs had considerably higher or similar antibacterial effectiveness compared to DAP, CH, and TAP. Hence, combined antibiotic therapy was not necessarily required for root canal disinfection ex vivo.

Microbial Communities in the Extraradicular and Intraradicular Infections Associated With Persistent Apical Periodontitis

Microorganisms in the complex root canal system and the extraradicular regions, including the periapical lesions and extraradicular biofilm may cause root canal treatment failures. However, few studies described the difference between the intraradicular and extraradicular infections from the same tooth associated with persistent apical periodontitis. This study aimed to characterize the microbiome present in the root canal, extraradicular biofilm, and periapical lesions associated with persistent apical periodontitis. The microbial communities in the root canal, extraradicular biofilm, and periapical lesions were investigated by Illumina high-throughput sequencing using Illumina Hiseq 2500 platform. The dominant phyla in the extraradicular and intraradicular infections associated with persistent apical periodontitis were Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria, and the genera Fusobacterium, Morganella, Porphyromonas, Streptococcus, and Bifidobacterium dominated across all samples. Although extraradicular infection sites showed higher OTU richness and β-diversity compared to intraradicular samples, the occurrence of sinus tract rather than the sampling sites demarcated the microbial communities in the infections associated with persistent apical periodontitis. PERMANOVA analysis confirmed that the samples with or without sinus tracts contained significantly different microbial communities. Porphyromonas, Eubacterium, Treponema, and Phocaeicola were found in significantly higher levels with sinus tracts, whilst Microbacterium and Enterococcus were more abundant in samples without sinus tracts. In conclusion, diverse bacteria were detected in both intraradicular and extraradicular infections associated with persistent apical periodontitis, which might be influenced by the occurrence of the sinus tract. The results may provide new insight into the pathogenesis of persistent apical periodontitis.

Present status and future directions - microbiology of endodontic infections

Apical periodontitis has a microbial aetiology and is one of the most common inflammatory diseases that affect humans. Fungi, archaea and viruses have been found in association with apical periodontitis, but bacteria are by far the most prevalent and dominant microorganisms in endodontic infections. Bacterial infection of the root canal system only occurs when the pulp is necrotic or was removed for previous treatment. In some specific cases, including acute and chronic abscesses, the bacterial infection may reach the periradicular tissues. Intracanal bacteria are usually observed as sessile multispecies communities (biofilms) attached to the dentinal root canal walls. Infection in the main root canal lumen can spread to other areas of the root canal system. Although more than 500 bacterial species have been detected in endodontic infections, a selected group of 20 to 30 species are most frequently detected and may be considered as the core microbiome. There is a high interindividual variability in the endodontic microbiome in terms of species composition and relative abundance. Obligate anaerobic species are more abundant in the intraradicular bacterial communities of teeth with primary apical periodontitis, while both anaerobes and facultatives dominate the communities in post-treatment apical periodontitis. Bacterial interactions play an essential role in determining the overall virulence of the community, which has been regarded as the unit of pathogenicity of apical periodontitis. This article reviews the microbiologic aspects of endodontic infections and provides perspectives for future research and directions in the field.

Ckip-1 Mediates P. gingivalis-Suppressed Cementoblast Mineralization

Porphyromonas gingivalis is responsible for the destruction of cementum in patients with periodontitis and periapical periodontitis. However, research about the effects of P. gingivalis on cementoblast mineralization and the underlying mechanism is still lacking. Casein kinase 2 interacting protein 1 (Ckip-1) is a scaffold protein that interacts with various proteins and signals to regulate different cell functions, such as cell morphology, apoptosis, and differentiation. In this study, we verified the suppressive effects of P. gingivalis and lipopolysaccharide (Pg-LPS) on OCCM-30 mineralization. We also showed that Ckip-1 gradually decreased during OCCM-30 mineralization but increased with the aggravation of Pg-induced inflammation. However, it remained unchanged when cells were stimulated with Pg-LPS, regardless of the concentration and incubation time. Then, more cellular cementum and enhanced Osterix expression were observed in Ckip-1 knockout mice when compared with the wild-type mice. Meanwhile, Ckip-1 silencing significantly enhanced cementoblast mineralization with or without P. gingivalis-associated inflammation. The trend was opposite when Ckip-1 was overexpressed. Finally, we found that the p38, Akt, and Wnt pathways were activated, while the Erk1/2 pathway was inhibited when Ckip-1 was silenced. The opposite results were also observed in the Ckip-1 overexpression group. Furthermore, we proved that cell mineralization was weakened when p38, Akt inhibitors were applied and strengthened when the Erk1/2 pathway was inhibited. In summary, Ckip-1 is upregulated underP. gingivalis-induced inflammation and negatively regulates cementoblast mineralization partially through mitogen-activated protein kinases and Akt signaling pathways, which may contribute to the restoration of cementum destroyed by P. gingivalis.

Coexistence of Candida albicans and Enterococcus faecalis increases biofilm virulence and periapical lesions in rats

The present study utilized an in vitro dual-species biofilm model and an in vivo rat post-treatment endodontic disease (PTED) model to investigate whether co-infection of Candida albicans and Enterococcus faecalis would aggravate periapical lesions. The results showed that co-culturing yielded a thicker and denser biofilm more tolerant to detrimental stresses compared with the mono-species biofilm, such as a starvation-alkalinity environment, mechanical shear force and bactericidal chemicals. Consistently, co-inoculation of E. faecalis and C. albicans significantly increased the extent of in vivo periapical lesions compared with mono-species infection. Specifically, coexistence of both microorganisms increased osteoclastic bone resorption and suppressed osteoblastic bone formation. The synergistic effects also up-regulated inflammatory cytokines including TNF-α and IL-6. In summary, coexistence of C. albicans and E. faecalis increased periapical lesions by enhanced biofilm virulence.

The Microbiota Profile Analysis of Combined Periodontal-Endodontic Lesions Using 16S rRNA Next-Generation Sequencing

OBJECTIVE

The primary aim of this investigation was to analyze the microbiome in patients with combined periodontal-endodontic lesions.

METHOD

Patients with loose and/or painful teeth referred for treatment from March 2020 to December 2020 in the First People's Hospital of Jinzhong were recruited. Samples were collected from teeth diagnosed as chronic periodontics (PE), ulcerative pulpitis (PU), and retrograde pulpitis (RE). Genomic DNA was extracted. The quantitative polymerase chain reaction, targeting the 16S ribosomal RNA (rRNA), was adopted for the quantification of bacteria. Then, the V3-V4 hypervariable regions of the 16S rRNA gene were amplified and subjected to next-generation sequencing. The statistical analysis was performed by R software (V3.5.1).

RESULTS

A total of 57 qualified samples were collected from 48 patients and analyzed (7 PE, 21 PU, and 19 RE). By linear discriminant analysis effect size, Kingella and Barnesiella were significantly increased in the periodontal pocket of retrograde pulpitis (RE-PE), compared with PE. The relative abundance of Clostridiales Incertae Sedis XI, Fusobacteriaceae, Fusobacterium, Parvimonas, Micrococcaceae, and Rothia was significantly increased in the pulp of retrograde pulpitis (RE-PU) than PU and RE-PE. Prevotella, Leptotrichia, Porphyromonas, Streptococcus, and Fusobacterium are consistently at a high abundance, across PU, RE-PE, and RE-PU.

CONCLUSION

The current study highlighted the evidence that a specific microbial community is associated with the occurrence of retrograde pulpitis. The microenvironment of the root canal and pulp chamber will select microbiota. This study offered insights into the pathogenesis of retrograde pulpitis.

Diverse bacterial profile in extraradicular biofilms and periradicular lesions associated with persistent apical periodontitis

AIM

To characterize the bacterial community present in the extraradicular biofilm and periradicular lesions associated with persistent apical periodontitis.

METHODOLOGY

Eighteen adult patients who presented with persistent periradicular lesions after root canal treatment and scheduled for endodontic surgery were selected. During surgery, extraradicular samples of biofilms and periradicular lesions were collected. Ten pairs of periradicular lesions and extraradicular biofilm samples were randomly selected for ribosomal 16S rRNA cloning and sequencing. A Wilcoxon's rank-sum test was used to compare total bacterial counts and the levels of individual genera and species between the two groups (P < 0.05).

RESULTS

Overall, seventy-three phylotypes belonging to six different phyla were identified from 1000 sequenced clones. Mogibacterium timidum, Streptococcus intermedius and Enterococcus faecalis predominated in both extraradicular biofilm and periapical lesions. Propionibacterium propionicus, Abiotrophia adiacens, Peptostreptococcus prevotii, Campylobacter gracilis and Pseudomonas aeruginosa were found in significantly higher levels in the extraradicular biofilm than periapical lesions, whilst Parvimonas micra and Atopobium rimae were more abundant in periapical lesions (P < 0.05).

CONCLUSIONS

The microbial profile of extraradicular biofilms differed from periapical lesions, indicating the presence of diverse bacterial populations in these regions. Several genera and species were significantly associated with the formation of extraradicular biofilms.

Identification of Fusobacterium nucleatum in primary and secondary endodontic infections and its association with clinical features by using two different methods

OBJECTIVE

Fusobacterium nucleatum is an important oral pathogen involved in endodontic infections. This study aimed to assess the frequency of Fusobacterium nucleatum in primary and secondary endodontic infections and its associations with the clinical features in a Brazilian population by using both culture and nested PCR methods.

METHODS

A total of 100 microbial samples from patients with primary (n=50) and secondary endodontic infections (n=50) were analyzed by using culture and nested PCR methods. Strict anaerobic techniques were used for culture and identification of F. nucleatum. The DNA extracted from the samples was analyzed for the presence of target species by using species-specific primers.

RESULTS

Culture and nested PCR methods detected F. nucleatum, respectively, in 11/100 and 82/100 root canals. F. nucleatum was isolated by culture from 10/50 (20%) root canals with primary infections and from 1/50 (2%) root canal with secondary/persistent infections. Nested PCR detected F. nucleatum in 42/50 (84%) root canals with primary infections and in 40/50 (80%) root canals with secondary/persistent endodontic infections. F. nucleatum was associated with spontaneous pain, tenderness to percussion, pain on palpation, swelling, tooth mobility, wet root canals, hemorrhagic exudate, tooth decay, inadequate restoration, and poor endodontic filling.

CONCLUSION

F. nucleatum was found in more cases of primary endodontic infections than in cases of secondary/persistent ones. A higher prevalence of F. nucleatum was detected by using the nested PCR method than by using culture. The presence of F. nucleatum in the root canals was associated with several clinical features.

CLINICAL RELEVANCE

The high prevalence of F. nucleatum in the root canals detected by molecular methods, and its association with several clinical features reveals the importance of these species in the development of apical pathologies and reinforces the need of an endodontic treatment directed to bacterial elimination.

In vitro and in vivo research of atmosphere pressure nonequilibrium plasmas on root canal disinfection: implication for alternative strategy for irrigation

OBJECTIVE

To investigate an intracanal disinfection methodology of APNPs (atmosphere pressure nonequilibrium plasmas) or modified APNPs in root canal treatment and evaluate the antimicrobial efficiency against in vitro infected dentinal tubules and in vivo experimental apical periodontitis.

MATERIALS AND METHODS

Dentine specimens were centrifugated with Enterococcus faecalis to generate 1-day-old and 3-week-old biofilms, and were treated with 2% chlorhexidine (Chx), APNP or modified APNP for 3 and 10 min (n=4). LIVE/DEAD staining was employed to analyze the ratio of deactivated bacteria. Experimental apical periodontitis in beagles was induced. Root canal therapy with APNPs or modified APNPs was performed and the antimicrobial effect was evaluated by histological and radiographical analyses.

RESULTS

APNP deactivated 1-day-old and 3-week-old E. feacalis in dentinal tubules as much as 2% Chx irrigating. Modified APNP significantly deactivated more E. faecalis biofilms in dentinal tubules for 3-min and 10-min treatments, without thermal damage or dentinal destruction being observed. In beagles' apical periodontitis, significantly increased BV/TV and decreased lesion volume of apical bone were found in modified APNP group than 2% Chx irrigation group according to μCT. Fewer inflammatory cells and bacterial residual in dentine were observed in modified APNP-treated apical tissue by histology staining compared with those in the 2% Chx irrigation group.

CONCLUSION

The antimicrobial effect of APNP jet irradiation was comparable to that of 2% Chx irrigation. No structural damage in dentine or tissue necrosis at the periapical region was induced upon treatment. The modified APNP demonstrated an increased antimicrobial efficacy compared with 2% Chx irrigation both in vitro and in vivo.

CLINICAL RELEVANCE

The modified APNPs can be used as an alternative intracanal disinfection strategy.

Antimicrobial Effectiveness of Calcium Silicate Sealers against a Nutrient-Stressed Multispecies Biofilm

Purpose: This study compared the antimicrobial efficacy of calcium silicate sealers (BioRoot RCS and Total Fill BC) and conventional sealers (AH Plus and Tubli-seal) against planktonic bacteria and a nutrient-stressed multispecies biofilm. Methods: Antimicrobial properties of freshly mixed sealers were investigated using the direct contact test (DCT) and a nutrient-stressed multispecies biofilm comprised of five endodontic strains. Antimicrobial activity was determined using quantitative viable counts and confocal laser scanning microscopy (CLSM) analysis with live/dead staining. The pH of the sealers was analysed over a period of 28 days in Hanks Balanced Salt Solution (HBSS). Analysis of variance (ANOVA) with Tukey tests and the Kruskal–Wallis test were used for data analysis with a significance of 5%. Results: All endodontic sealers exhibited significant antimicrobial activity against planktonic bacteria (p < 0.05). BioRoot RCS caused a significant reduction in viable counts of the biofilms compared to AH Plus and the control (p < 0.05), while no significant difference could be observed compared to TotalFill BC and Tubli-seal (p > 0.05). CLSM analysis showed that BioRoot RCS and TotalFill BC exhibited significant biofilm inhibition compared to Tubli-seal, AH Plus and the control (p < 0.05). BioRoot RCS presented with the highest microbial killing, followed by TotalFill BC and Tubli-seal. Alkalizing activity was seen from the onset by BioRoot RCS, TotalFill BC and AH Plus. After 28 days, BioRoot RCS demonstrated the highest pH in HBSS (pH > 12). Conclusions: Calcium silicate sealers exhibited effective antimicrobial properties. This was demonstrated by superior biofilm inhibition capacity and microbial killing, with strong alkalizing activity compared to epoxy-based and zinc oxide-eugenol-based sealers.

Microbial Association with Genus Actinomyces in Primary and Secondary Endodontic Lesions, Review

The main reason for root canal treatment failure is the persistence of microorganisms after therapy, or the recontamination of the root canal system due to an inadequate seal. In the mouth, Actinomyces spp. constitute a significant part of the normal flora, which is indicative of their ability to adhere to oral tissue and resist cleansing mechanisms, such as salivary flow. This review, performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA), aims to clarify the prevalence of microbial genera that are associated with the genus Actinomyces in primary and secondary endodontic infections (primary outcome), and to identify the most prevalent species of the Actinomyces genus in endodontic lesions (secondary outcome). A total of 11 studies were included in the qualitative and quantitative analysis, and a total of 331 samples were analyzed. Bacteria of the genus Actinomyces were found in 58 samples, and 46 bacterial genera were detected in association with bacteria of the genus Actinomyces. Bacteria of the genus Streptococcus and Propionibacterium were those most frequently associated with Actinomyces in the endodontic lesions considered, and Actinomyces israelii was the most frequently involved species.

Gut microbiome variation is associated to Multiple Sclerosis phenotypic subtypes

Objective

Multiple sclerosis (MS) is a heterogenous, inflammatory disease of the central nervous system. Microbiota alterations in MS versus healthy controls (HC) are observed, but results are inconsistent. We studied diversity, enterotypes, and specific gut microbial taxa variation between MS and HC, and between MS subgroups.

Methods

Amplicon sequencing of the 16S ribosomal RNA V4 region (Illumina MiSeq) was used to evaluate alpha and beta diversity, enterotypes, and relative taxa abundances on stool samples. MS subgroups were based on phenotype, disease course modifiers, and treatment status. Results were controlled for recently identified confounders of microbiota composition.

Results

Ninety‐eight MS patients and 120 HC were included. Microbial richness was lower in interferon‐treated (RRMS_I, N = 24) and untreated relapsing–remitting MS during relapse (RRMS_R, N = 4) when compared to benign (BMS, N = 20; Z = −3.07, Pcorr = 0.032 and Z = −2.68, Pcorr = 0.055) and primary progressive MS (PPMS, N = 26; Z = −2.39, Pcorr = 0.062 and Z = −2.26, Pcorr = 0.071). HC (N = 120) and active untreated MS (RRMS_U, N = 24) showed intermediate microbial richness. Enterotypes were associated with clinical subgroups (N = 218, χ² = 36.10, P = 0.002), with Bacteroides 2 enterotype being more prevalent in RRMS_I. Butyricicoccus abundance was lower in PPMS than in RRMS_U (Z = −3.00, Pcorr = 0.014) and BMS (Z = −2.56, Pcorr = 0.031), lower in RRMS_I than in BMS (Z = −2.50, Pcorr = 0.034) and RRMS_U (Z = −2.91, Pcorr = 0.013), and inversely correlated with self‐reported physical symptoms (rho = −0.400, Pcorr = 0.001) and disease severity (rho = −0.223, P = 0.027).

Interpretation

These results emphasize the importance of phenotypic subcategorization in MS‐microbiome research, possibly explaining previous result heterogeneity, while showing the potential for specific microbiome‐based biomarkers for disease activity and severity.

Mucosal-associated invariant T cells and oral microbiome in persistent apical periodontitis

Opportunistic bacteria in apical periodontitis (AP) may pose a risk for systemic dissemination. Mucosal-associated invariant T (MAIT) cells are innate-like T cells with a broad and potent antimicrobial activity important for gut mucosal integrity. It was recently shown that MAIT cells are present in the oral mucosal tissue, but the involvement of MAIT cells in AP is unknown. Here, comparison of surgically resected AP and gingival tissues demonstrated that AP tissues express significantly higher levels of Vα7.2-Jα33, Vα7.2-Jα20, Vα7.2-Jα12, Cα and tumour necrosis factor (TNF), interferon (IFN)-γ and interleukin (IL)-17A transcripts, resembling a MAIT cell signature. Moreover, in AP tissues the MR1-restricted MAIT cells positive for MR1–5-OP-RU tetramer staining appeared to be of similar levels as in peripheral blood but consisted mainly of CD4⁺ subset. Unlike gingival tissues, the AP microbiome was quantitatively impacted by factors like fistula and high patient age and had a prominent riboflavin-expressing bacterial feature. When merged in an integrated view, the examined immune and microbiome data in the sparse partial least squares discriminant analysis could identify bacterial relative abundances that negatively correlated with Vα7.2-Jα33, Cα, and IL-17A transcript expressions in AP, implying that MAIT cells could play a role in the local defence at the oral tissue barrier. In conclusion, we describe the presence of MAIT cells at the oral site where translocation of oral microbiota could take place. These findings have implications for understanding the immune sensing of polymicrobial-related oral diseases.

Prevalence of Candida Species in Endodontic Infections: Systematic Review and Meta-analysis

INTRODUCTION

Candida in endodontic infections has been investigated in a large number of studies, but its role as an endodontic pathogen is still debatable. The aim of this study was to systematically review the literature on the prevalence of Candida species in root canal infections.

METHODS

Extensive literature research was performed in the most important electronic biomedical databases, and additional studies have been identified from references from relevant articles. Studies were critically appraised using a modified version of the Joanna Briggs Institute Critical Appraisal Checklist.

RESULTS

From 2225 unique records, 2118 were excluded on the basis of title and abstract. Of the remaining 107 studies, 50 were excluded after full-text review, and 57 were included for qualitative and quantitative analysis. The overall prevalence of Candida spp. in root canal infections was 8.20% (95% confidence interval, 5.56%-11.21%). Candida albicans was the most frequently isolated species. Significant heterogeneity among studies was observed (P < .001, I² = 86.07%). Subgroup analyses revealed a higher prevalence of Candida spp. from African samples. All studies considered, a high or unclear risk of bias was prevalent regarding 6 out of the 8 items considered in the critical appraisal.

CONCLUSIONS

Candida spp. occurred in a small proportion of root canal infections. Further and better designed research is needed to investigate the real contribution of Candida spp. to the microbial ecology in infected root canals.

Whole-Cell Detection of C-P Bonds in Bacteria

Naturally produced molecules possessing a C-P bond, such as phosphonates and phosphinates, remain vastly underexplored. Although success stories like fosfomycin have reinvigorated small molecule phosphonate discovery efforts, bioinformatic analyses predict an enormous unexplored biological reservoir of C-P bond-containing molecules, including those attached to complex macromolecules. However, high polarity, a lack of chromophores, and complex macromolecular association impede phosphonate discovery and characterization. Here we detect widespread transcriptional activation of phosphonate biosynthetic machinery across diverse bacterial phyla and describe the use of solid-state nuclear magnetic resonance to detect C-P bonds in whole cells of representative Gram-negative and Gram-positive bacterial species. These results suggest that phosphonate tailoring is more prevalent than previously recognized and set the stage for elucidating the fascinating chemistry and biology of these modifications.

5-Lipoxygenase Knockout Aggravated Apical Periodontitis in a Murine Model

5-Lipoxygenase (5-LO) plays a vital role in the host innate immune response, including bacteria-induced inflammation. Apical periodontitis (AP) is due to immune disorders caused by imbalances between bacterial invasion and subsequent host defense response. In this work, we investigated the role of 5-lipoxygenase in AP by using 5- lo knockout mice (5- lo-/- mice). Results showed that 5- lo-/- mice had greater periapical bone loss and more osteoclasts positive for tartrate-resistant acid phosphatase staining than did wild-type mice, as determined by micro-computed tomography and histologic staining. The inflammation- and osteoclastogenesis-related factors IL-1β, TNF-α, RANK, and RANKL were also significantly elevated in 5- lo-/- mice, whereas osteoprotegerin was reduced. Furthermore, peritoneal macrophages from 5- lo-/- mice revealed an obviously impaired ability to phagocytose the AP pathogenic bacteria Fusobacterium nucleatum. In vivo experiments confirmed that 5- lo knockout led to decreased macrophage recruitment and increased F. nucleatum infection around the periapical area due to decreased leukotriene B₄ and LXA4 production. All these results showed that 5- lo knockout impaired the host innate immune system to promote the release of bone resorption-related factors. Therefore, 5- lo deficiency aggravated AP in an experimental murine AP model.

Simplified Method of Detection of Dialister invisus and Olsenella uli in Oral Cavity Samples by Polymerase Chain Reaction

Aims and Objectives:

The oral microbial flora is highly complex and diverse with obligate anaerobic bacteria as the predominant component. Most of these are not yet cultivated/difficult to cultivate due to technical limitations. In this study, we aim to detect two novel oral bacterial species Dialister invisus and Olsenella uli by simplified and economical procedure of polymerase chain reaction (PCR) and study their association with primary and persistent endodontic infections.

Material and Methods:

The study involved 60 patients that included 30 patients of primary endodontic infections and 30 with persistent endodontic infections. The sample collection from the root canal was performed by universally accepted protocol by using sterile paper points. The deoxyribonucleic acid (DNA) extraction was done, followed by PCR with species specific primers. We made several changes to the protocol mentioned by original authors. We adopted a one-step protocol for amplification of bacterial DNA, omitting the 16SrDNA amplification step with universal primers.

Results:

It was seen that 7 (23.3 %) samples in primary endodontic infection group and 24 (80 %) samples in persistent endodontic infection group were positive for D. invisus. On the other hand, 11 (36.6 %) patients of primary endodontic infection showed positivity for O. uli in comparison to 9 (30 %) of persistent endodontic infection.

Conclusion:

The results from the present study showed efficient amplification of both O. uli and D. invisus in a single-step PCR. Hence, we conclude that the modified protocol used here with taq polymerase enzyme offers a faster and cheaper alternative to nested PCR without compromising the quality of amplification process.

Orofacial granulomatosis: A case report of three cases may be caused by apical periodontitis

RATIONALE

Orofacial granulomatosis (OFG) is a rare disease characterized by noncaseating granulomatous inflammation. The most common clinical presentation is persistent swelling of the soft tissues in the oral and maxillofacial regions. The precise cause of OFG is unknown. Corticosteroids are the first-line and best treatment, but there is lack of uniform treatment prescription and standard. It is important to identify the pathogen in order to improve treatment specificity.

PATIENT CONCERNS

Three patients presented with recurring lip swelling and cobblestone formation on buccal mucosa, complained of toothache or dental caries for many years. They had very similar and characteristic clinical signs, especially the corresponding location with infected teeth, which suffered from apical periodontitis.

DIAGNOSES

The three patients were all diagnosed with typical clinical signs and non-caseating epithelioid cell granulomas histologically.

INTERVENTIONS

The teeth with apical periodontitis were extracted or treated and corticosteroids were prescribed locally or/and systematically.

OUTCOMES

A complete resolution of lip swelling and cobblestone formation were shown after treatment.

LESSONS

This is the first report to highlight that apical periodontitis may intrigue the pathogenesis of OFG, which suggested that dental infection may be the direct and initial etiology of OFG. Removal of infected teeth should be performed as soon as possible in order to reduce the dosage of corticosteroids and occcurence rate of OFG.

Bacterial communities associated with apical periodontitis and dental implant failure

Background

Previously, we demonstrated that bacteria reside in apparently healed alveolar bone, using culture and Sanger sequencing techniques. Bacteria in apparently healed alveolar bone may have a role in peri-implantitis and dental implant failure.

Objective

To compare bacterial communities associated with apical periodontitis, those colonising a failed implant and alveolar bone with reference biofilm samples from healthy teeth.

Methods and results

The study consisted of 196 samples collected from 40 patients undergoing routine dental implant insertion or rehabilitation. The bacterial 16S ribosomal DNA sequences were amplified. Samples yielding sufficient polymerase chain reaction product for further molecular analyses were subjected to terminal restriction fragment length polymorphism (T-RFLP; 31 samples) and next generation DNA sequencing (454 GS FLX Titanium; 8 samples). T-RFLP analysis revealed that the bacterial communities in diseased tissues were more similar to each other (p<0.049) than those from the healthy reference samples. Next generation sequencing detected 13 bacterial phyla and 373 putative bacterial species, revealing an increased abundance of Gram-negative [Prevotella, Fusobacterium (p<0.004), Treponema, Veillonellaceae, TG5 (Synergistetes)] bacteria and a decreased abundance of Gram-positive [(Actinomyces, Corynebacterium (p<0.008)] bacteria in the diseased tissue samples (n=5) relative to reference supragingival healthy samples (n=3).

Conclusion

Increased abundances of Prevotella, Fusobacterium and TG5 (Synergistetes) were associated with apical periodontitis and a failed implant. A larger sample set is needed to confirm these trends and to better define the processes of bacterial pathogenesis in implant failure and apical periodontitis. The application of combined culture-based, microscopic and molecular technique-based approaches is suggested for future studies.

Nanoparticles for antimicrobial purposes in Endodontics: A systematic review of in vitro studies

INTRODUCTION

Antimicrobial nanoparticles with enhanced physiochemical properties have attracted attention as modern antimicrobials, especially in the complicated oral cavity environment. The goal of the present article is to review the current state of nanoparticles used for antimicrobial purposes in root canal infections.

METHODS

A review was conducted in electronic databases using MeSH keywords to identify relevant published literature in English. The analysis and eligibility criteria were documented according to the Preferred Reporting Items for Systematic Reviews and Meta Analysis (PRISMA-guidelines). No restrictions on publication date were imposed. Data regarding root canal disinfections, general antimicrobial mechanisms of nanoparticles, type of nanoparticles as antimicrobial agent and antimicrobial effect of nanoparticles in endodontics were collected and subjected to descriptive data analysis.

RESULTS

The literature search in electronic databases according to the inclusion criteria provided 83 titles and abstracts. Among them 15 papers were related to antimicrobial effect of nanoparticles in Endodontics. Silver nanoparticles with sustainable activity were the most studied agent for its antimicrobial behavior in root canal infection. Aided polymeric nanoparticles with photo or ultrasound, glass bioactive nanoparticles as well as Calcium derivative based nanoparticles, with improved activity in comparison with the non-nano counterparts, are of importance in infection control of dental root canal. Bioactive Non-organic nanoparticles with structural capabilities present enhanced antimicrobial activity in root canal infections.

DISCUSSION

All included studies showed an enhanced or at least equal effect of nanoparticulate systems to combat dental root canal infections compared to conventional antimicrobial procedures. However, it is crucial to understand their shortcomings and their probable cellular effects and toxicity as well as environmental effects.

Comparison of Bacterial Community Composition of Primary and Persistent Endodontic Infections Using Pyrosequencing

INTRODUCTION

Elucidating the microbial ecology of endodontic infections (EIs) is a necessary step in developing effective intracanal antimicrobials. The aim of the present study was to investigate the bacterial composition of symptomatic and asymptomatic primary and persistent infections in a Greek population using high-throughput sequencing methods.

METHODS

16S amplicon pyrosequencing of 48 root canal bacterial samples was conducted, and sequencing data were analyzed using an oral microbiome-specific and a generic (Greengenes) database. Bacterial abundance and diversity were examined by EI type (primary or persistent), and statistical analysis was performed by using non-parametric and parametric tests accounting for clustered data.

RESULTS

Bacteroidetes was the most abundant phylum in both infection groups. Significant, albeit weak associations of bacterial diversity were found, as measured by UniFrac distances with infection type (analyses of similarity, R = 0.087, P = .005) and symptoms (analyses of similarity, R = 0.055, P = .047). Persistent infections were significantly enriched for Proteobacteria and Tenericutes compared with primary ones; at the genus level, significant differences were noted for 14 taxa, including increased enrichment of persistent infections for Lactobacillus, Streptococcus, and Sphingomonas. More but less abundant phyla were identified using the Greengenes database; among those, Cyanobacteria (0.018%) and Acidobacteria (0.007%) were significantly enriched among persistent infections. Persistent infections showed higher phylogenetic diversity (PD) (asymptomatic: PD = 9.2, standard error [SE] = 1.3; symptomatic: PD = 8.2, SE = 0.7) compared with primary infections (asymptomatic: PD = 5.9, SE = 0.8; symptomatic: PD = 7.4, SE = 1.0).

CONCLUSIONS

The present study revealed a high bacterial diversity of EI and suggests that persistent infections may have more diverse bacterial communities than primary infections.