Bacterial species associated with persistent apical periodontitis exert differential effects on osteogenic differentiation

The influence of microorganisms on bone homeostasis in apical periodontitis

OBJECTIVE

This review aims to provide an overview of the role of microorganisms in the onset and progression of periapical diseases, particularly regarding their effects on bone homeostasis.

DESIGN

The search for this narrative review was conducted in PubMed, Web of Science and Google Scholar using relevant keywords, including checking reference lists of journal articles by hand searching.

RESULTS

Microorganisms directly promote osteoclasts through pathways such as nuclear factor-κB (NF-κB) and extracellular regulated protein kinases (ERK), while inhibiting osteoblasts function by interfering with the wingless-related integration site (Wnt)/β-catenin pathway in the periapical area. Moreover, microorganisms indirectly regulate periapical bone homeostasis by inducing programmed cell death and modulating the immune microenvironment through the activation of innate immunity via pattern-recognition receptors (PRRs) and subsequent cascades of responses. Among these microorganisms, Enterococcus faecalis, Porphyromonas gingivalis and Fusobacterium nucleatum play significant roles.

CONCLUSION

Microorganisms regulate pathways such as NF-ĸB and Wnt/β-catenin, as well as programmed cell death and the immune microenvironment in the periapical area, thereby disrupting bone homeostasis.

Extracellular vesicle production by oral bacteria related to dental caries and periodontal disease: role in microbe-host and interspecies interactions

Extracellular vesicles (EVs) are cell membrane-derived structures between 20-400 nm in size. In bacteria, EVs play a crucial role in molecule secretion, cell wall biogenesis, cell-cell communication, biofilm development, and host-pathogen interactions. Despite these increasing reports of bacterial-derived vesicles, there remains a limited number of studies that summarize oral bacterial EVs, their cargo, and their main biological functions. Therefore, the aim of this review is to present the latest research on oral bacteria-derived EVs and how they can modulate various physiological and pathological processes in the oral cavity, including the pathogenesis of highly relevant diseases such as dental caries and periodontitis and their systemic complications. Overall, caries-associated bacteria (such as Streptococcus mutans) as well as periodontal pathogens (including the red complex pathogens Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola) have all been shown to produce EVs that carry an array of virulent factors and molecules involved in biofilm and immune modulation, bacterial adhesion, and extracellular matrix degradation. As bacterial EV production is strongly impacted by genotypic and environmental variations, the inhibition of EV genesis and secretion remains a key potential future approach against oral diseases.

The immune landscape in apical periodontitis: From mechanism to therapy

Apical periodontitis (AP) is featured by a persistent inflammatory response and alveolar bone resorption initiated by microorganisms, posing risks to both dental and systemic health. Nonsurgical endodontic treatment is the recommended treatment plan for AP with a high success rate, but in some cases, periapical lesions may persist despite standard endodontic treatment. Better comprehension of the AP inflammatory microenvironment can help develop adjunct therapies to improve the outcome of endodontic treatment. This review presents an overview of the immune landscape in AP, elucidating how microbial invasion triggers host immune activation and shapes the inflammatory microenvironment, ultimately impacting bone homeostasis. The destructive effect of excessive immune activation on periapical tissues is emphasized. This review aimed to systematically discuss the immunological basis of AP, the inflammatory bone resorption and the immune cell network in AP, thereby providing insights into potential immunotherapeutic strategies such as targeted therapy, antioxidant therapy, adoptive cell therapy and cytokine therapy to mitigate AP-associated tissue destruction.

Prognostic Impact of Microbiome Dysbiosis: A Prospective Study

AIMS

To determine the relationship between microbiome dysbiosis indices and biofilm immunogenicity and their prognostic implications on periodontal treatment response.

MATERIALS AND METHODS

Thirty periodontally healthy controls and 30 periodontitis cases (stage III) were recruited. Cases received non-surgical periodontal therapy (NSPT), and their treatment response at 6 months was evaluated using a treat-to-target endpoint (≤ 4 sites with probing depths ≥ 5 mm). Pooled subgingival biofilm samples were obtained from controls and cases. The V3-4 hypervariable region of the 16S rRNA gene was sequenced and two compositional indices (subgingival microbiome dysbiosis index, SMDI, and dysbiosis ratio, DR) were calculated. Nuclear factor kappa-B (NF-κB) activation elicited by biofilm samples in monocytic reporter cells was quantified to assess biofilm immunogenicity.

RESULTS

SMDI, DR and biofilm immunogenicity were highly diagnostic for periodontitis (area under curves [AUC] > 0.90, p < 0.001). Among periodontitis cases, all three microbial parameters were significantly reduced after NSPT (p < 0.001). Cases achieving the treat-to-target endpoint had lower pre-treatment SMDI and biofilm immunogenicity (p < 0.05) and different microbial recolonization patterns from poor responders. Both measures predicted treatment response (AUC of 0.767 and 0.835, respectively, p < 0.05).

CONCLUSION

Subgingival biofilm dysbiosis quantified using SMDI and biofilm immunogenicity was diagnostic of periodontitis and predictive of NSPT outcomes.

PANoptosis: a new insight for oral diseases

PANoptosis, a burgeoning area of research, is a unique type of programmed cell death typified by pyroptosis, apoptosis, and necroptosis, yet it defies singular classification by any one mode of death. The assembly and activation of PANoptosomes are pivotal processes in PANoptosis, with several PANoptosomes already identified. Linkages between PANoptosis and the pathophysiology of various systemic illnesses are established, with increasing recognition of its association with oral ailments. This paper aims to deepen understanding by conducting a comprehensive analysis of the molecular pathways driving PANoptosis and exploring its potential implications in oral diseases.

Primary apical periodontitis correlates to elevated levels of interleukin-8 in a Swedish population: A report from the PAROKRANK study

AIM

To explore associations between root filled teeth, primary and secondary apical periodontitis, and levels of inflammatory markers in blood from patients with a first myocardial infarction and matched controls.

METHODOLOGY

Between May 2010 and February 2014, 805 patients with a first myocardial infarction and 805 controls, matched for sex, age, and postal code area, were recruited to the multicentre case-control study PAROKRANK (periodontitis and its relation to coronary artery disease). All participants underwent a physical and oral examination, as well as blood sampling. Using panoramic radiography, root filled teeth, primary apical periodontitis, and secondary apical periodontitis were assessed by three independent observers. Blood samples were analysed with enzyme-linked immunosorbent assay method for the following inflammatory markers: interleukin-1β (IL-1β), IL-2, IL-6, IL-8, IL-12p70, tumour necrosis factor-α, and high-sensitivity C-reactive protein (hsCRP). Additionally, white blood cell count and plasma-fibrinogen were analysed. Associations between endodontic variables and the levels of inflammatory markers were statistically analysed with Mann-Whitney U-test and Spearman correlation, adjusted for confounding effects of baseline factors (sex, age, myocardial infarction, current smoking, diabetes, family history of cardiovascular disease, education, marital status, and periodontal disease).

RESULTS

Mean age of the cohort was 62 years, and 81% were males. Root fillings were present in 8.4% of the 39 978 examined teeth and were associated with higher levels of hsCRP, fibrinogen, and leukocyte count, but lower levels of IL-2 and IL-12p70. After adjusting for confounders, root filled teeth remained associated with higher levels of fibrinogen, but lower levels of IL-1β, IL-2, IL-6, and IL-12p70. Primary apical periodontitis was found in 1.2% of non-root filled teeth and associated with higher levels of IL-8 (correlation 0.06, p = .025). Secondary apical periodontitis was found in 29.6% of root filled teeth but did not relate to the levels of any of the inflammatory markers.

CONCLUSIONS

This study supports the notion that inflammation at the periapex is more than a local process and that systemic influences cannot be disregarded. Whether the observed alterations in plasma levels of inflammatory markers have any dismal effects on systemic health is presently unknown but, considering the present results, in demand of further investigation.

Comparative Evaluation of Microhardness, Smear Layer Removal Efficacy and Depth of Penetration Using Punica granatum, Emblica officinalis and Sodium Hypochlorite As Endodontic Irrigants: An In Vitro Study

Introduction Root canal morphology tends to be complicated by nature and dealing with this intricacy can be challenging because it makes it difficult to completely disinfect the root canal space. The success of root canal therapy is also determined by the biomechanical preparation of the canal with the application of instruments and irrigating solutions. Due to the fact that the root dentin surface continues to interact with the irrigating solution during preparation, it's critical to evaluate the mechanical characteristics and smear layer removal. Though sodium hypochlorite (NaOCl) is the most commonly used irrigant due to its tissue-dissolving abilities, it has certain drawbacks which include the inability to remove the smear layer and also affects the mechanical properties of root dentin. To overcome these limitations, a variety of herbal substitutes like Punica granatum and Emblica officinalis which possess anti-bacterial and anti-fungal properties can be used as endodontic irrigants. Several studies on the anti-bacterial properties of natural irrigants of pomegranate and amla were reported. However, the mechanical properties and smear layer removal of Punica granatum and Emblica officinalis have not been explored in the field of endodontics. Aim The main aim of this in vitro study is to compare and evaluate microhardness, smear layer removal efficacy and depth of penetration of herbal and conventional irrigants. Materials and methods Thirty-six palatal roots of maxillary molars were decoronated and instrumented up to F3. These roots were sectioned longitudinally and divided into three test groups: Group 1: 12.5% Punica granatum; Group 2: 6.25% Emblica officinalis; control: Group 3: 2.5% NaOCl. All specimens were irrigated with 5ml of each irrigant for 5 minutes. Microhardness of root dentin was measured using a Vickers diamond intender, smear layer removal using a scanning electron microscope (SEM) and depth of penetration using a stereomicroscope. The data was analyzed using one-way ANOVA and the inter-group comparison using Tukey's post hoc test. Results Statistical analysis was done using one-way analysis of variance (ANOVA) and Tukey's post hoc test using SPSS software version 17.0 (SPSS Inc., Chicago ). The highest microhardness was seen in Group 1 (cervical: 53.8375 ± 1.35956, middle: 53.9875 ± 1.01761, apical: 53.6875 ± 1.63133) while Group 2 (cervical: 43.2750 ± 1.73596, middle: 43.3125 ± 1.17648, apical: 43.8000 ± ​​​​​​​1.32665) and Group 3 (cervical: 42.7250 ±​​​​​​​ 2.93391, middle: 41.9625 ±​​​​​​​ 1.66985, apical: 42.0250 ±​​​​​​​ 2.21085) showed significant reduction in root dentin hardness. Regarding smear layer removal Group 1 (1.3750 ±​​​​​​​ 0.51755), and Group 2 (1.2500 ±​​​​​​​ 0.46291) reveals greater smear removal in the middle third of the root dentin compared with Group 3 (2.3750 ±​​​​​​​ 0.51755), which showed the least smear layer removal. A greater depth of penetration was seen in Group 1 (0.5488 ± 0.05222) and Group 2 (0.5263 ±​​​​​​​ 0.05181) than in Group 3 (0.3087 ±​​​​​​​ 0.05743). Conclusion The present study reveals that the least reduction of microhardness was seen in Punica granatum followed by Emblica officinalis and NaOCl. The smear layer removal efficacy and depth of penetration were greater in Punica granatum and Emblica officinalis than in NaOCl. It was concluded that as these herbal irrigants are biocompatible agents, they can be considered for future use in root canal treatment.

Fusobacterium nucleatum triggers proinflammatory cell death via Z-DNA binding protein 1 in apical periodontitis

BACKGROUND

Z-DNA binding protein 1 (ZBP1) is a vital innate immune sensor that regulates inflammation during pathogen invasion. ZBP1 may contribute to pyroptosis, apoptosis and necroptosis in infectious diseases. In this study, Fusobacterium nucleatum (F. nucleatum) infection caused periapical inflammation through proinflammatory cell death and ZBP1 was involved in regulating the inflammatory activities caused by F. nucleatum infection in apical periodontitis (AP).

METHODS

Human periapical tissues were tested by fluorescent in situ hybridization, immunohistochemical staining, immunofluorescence staining, quantitative real-time PCR (qRT‒PCR) and western blotting. F. nucleatum-infected and F. nucleatum extracellular vesicles (F. nucleatum-EVs)-treated RAW264.7 cells were used to detect the expression of inflammatory cytokines and different cell death mechanisms by qRT‒PCR and western blotting. ZBP1 expression in F. nucleatum-infected tissues and RAW264.7 cells was detected by qRT‒PCR, western blotting, and immunohistochemical and immunofluorescence staining. Furthermore, the expression of ZBP1 was inhibited by siRNA and different cell death pathways, including pyroptosis, apoptosis, and necroptosis, and inflammatory cytokines were measured in F. nucleatum-infected RAW264.7 cells.

RESULTS

F. nucleatum was detected in AP tissues. F. nucleatum-infected RAW264.7 cells polarized to the M1 phenotype, and this was accompanied by inflammatory cytokine production. High levels of ZBP1 and GSDME (gasdermin E)-mediated pyroptosis, caspase-3-mediated apoptosis and MLKL-mediated necroptosis (PANoptosis) were identified in F. nucleatum-infected tissues and RAW264.7 cells. ZBP1 inhibition reduced inflammatory cytokine secretion and the occurrence of PANoptosis.

CONCLUSION

The present study identified a previously unknown role of ZBP1 in regulating F. nucleatum-induced proinflammatory cell death and inflammatory activation. Video abstract.

Effect of Antibacterial Root Canal Sealer on Persistent Apical Periodontitis

The infection of Enterococcus faecalis and its interacting microorganisms in the root canal could cause persistent apical periodontitis (AP). Antibacterial root canal sealer has favorable prospects to inhibit biofilms. The purpose of this study was to investigated the antibacterial effect of root canal sealer containing dimethylaminododecyl methacrylate (DMADDM) on persistent AP in beagle dogs for the first time. Persistent AP was established by a two-step infection with Enterococcus faecalis and multi-bacteria (Enterococcus faecalis, Lactobacillus acidophilus, Actinomycesnaeslundii, Streptococcus gordonii). Root canal sealer containing DMADDM (0%, 1.25%, 2.5%) was used to complete root canal filling. The volume of lesions and inflammatory grade in the apical area were evaluated by cone beam computer tomography (CBCT) and hematoxylin-eosin staining. Both Enterococcus-faecalis- and multi-bacteria-induced persistent AP caused severe apical destruction, and there were no significant differences in pathogenicity between them. DMADDM-modified sealer significantly reduced the volume of periapical lesion and inflammatory grade compared with the control group, among them, the therapeutic effect of the 2.5% group was better than the 1.25% group. In addition, E.faecalis-induced reinfection was more sensitive to the 2.5% group than multi-bacteria reinfection. This study shows that root canal sealer containing DMADDM had a remarkable therapeutic effect on persistent AP, especially on E. faecalis-induced reinfection.

Drug Carriers Based on Graphene Oxide and Hydrogel: Opportunities and Challenges in Infection Control Tested by Amoxicillin Release

Graphene oxide (GO) was proposed as an efficient carrier of antibiotics. The model drug, amoxicillin (AMOX), was attached to GO using a peptide linker (Leu-Leu-Gly). GO-AMOX was dispersed in a hydrogel to which the enzyme responsible for releasing AMOX from GO was also added. The drug molecules were released by enzymatic hydrolysis of the peptide bond in the linker. As the selected enzyme, bromelain, a plant enzyme, was used. The antibacterial nature of the carrier was determined by its ability to inhibit the growth of the Enterococcus faecalis strain, which is one of the bacterial species responsible for periodontal and root canal diseases. The prepared carrier contained only biocompatible substances, and the confirmation of its lack of cytotoxicity was verified based on the mouse fibrosarcoma cell line WEHI 164. The proposed type of preparation, as a universal carrier of many different antibiotic molecules, can be considered as a suitable solution in the treatment of inflammation in dentistry.

Can Probiotics Emerge as Effective Therapeutic Agents in Apical Periodontitis? A Review

Apical periodontitis (AP) is a biofilm-associated disease initiated by the invasion of dental pulp by microorganisms from the oral cavity. Eradication of intracanal microbial infection is an important goal of endodontic treatment, and this is typically accomplished by mechanical instrumentation and application of sodium hypochlorite and chlorhexidine. However, these agents are tissue-irritating at higher concentrations and cytotoxic. Certain probiotics have been found effective in controlling marginal periodontitis, as evidenced by reduction of pathogenic bacterial loads, gains in clinical attachment levels, and reduced bleeding on probing. In vitro studies have shown inhibitory activity of some probiotics against endodontic pathogens. Similarly, in vivo studies in rats have demonstrated a positive immuno-modulatory role of probiotics in AP, as manifested by decreased levels of proinflammatory markers and increased levels of anti-inflammatory markers. A role for probiotics in effecting a reduction of bone resorption has also been reported. This review provides an outline of current research into the probiotic management of AP, with a focus on understanding the mechanisms of their direct antagonistic activity against target pathogens and of their beneficial modulation of the immune system.