Periapical inflammatory responses and their modulation

Cytokine expression of IL-8 before and after root canal treatment in patients with symptomatic apical periodontitis: A clinical trial

This study's objective was to compare the cytokine expression of IL-8 in periapical tissues of single-rooted teeth with symptomatic apical periodontitis (SAP) before and after root canal treatments. As well as, comparing IL-8 levels in peri-apical tissues between vital and necrotic teeth with SAP.

METHODOLOGY

Thirty-six patients were allocated according to their pulp status into two experimental groups (n = 18) receiving the same treatment protocol; group 1: Vital pulps with SAP, and group 2: non-vital pulps with SAP. Conventional endodontic treatment was done on two visits; isolation and disinfection of the operative field were undertaken, and two-stage access cavity preparation was implemented. The first pre-instrumentation peri-apical sample (S1) was collected prior to cleaning and shaping procedures. A 2.5% NaOCl irrigation was used to thoroughly irrigate the canal after performing root canal preparation utilising the ProTaper Next (PTN) rotary system. After 1 week, the second post-instrumentation peri-apical sample (S2) was collected. Using an ELISA kit, the quantity of IL-8 was evaluated following the collection of all samples.

RESULTS

In all pre-instrumentation samples, IL-8 was detected (100%). The level of IL-8 expression was significantly decreased from the S1 to S2 of all samples (p < 0.001). The intra-group comparison showed a statistically significant reduction in the level of IL-8 expression between S1 and S2 in both vital and non-vital groups where p < 0.001* in both groups. The inter-group comparison of levels of IL-8 expression (vital and non-vital) revealed a significant difference between both groups regarding the pretreatment sample with the higher levels of IL-8 shown in the non-vital group (p < 0.001). While in the post-treatment sample, both groups showed a significant reduction in the level of IL-8 expression but the difference between them was not statistically significant (p = 0.226).

CONCLUSION

Root canal instrumentation seems to be efficient in decreasing the levels of anti-inflammatory cytokines, namely IL-8. Further research should clarify how intra-canal medicaments affect inflammatory mediator levels.

TLR2 agonist prevents the progression of periapical lesions in mice by reducing osteoclast activity and regulating the frequency of Tregs

AIM

To evaluate the role of regulatory T lymphocytes (Tregs) in the presence or absence of the synthetic ligand Pam3Cys during the progression of periapical lesion in wild-type (WT) and toll-like receptor 2 knockout (TLR2KO) mice.

METHODOLOGY

A total of 130 C57BL/6 male WT and TLR2KO mice were allocated into control (n = 5) and experimental (periapical lesion induction) (n = 10) groups. In specific groups (WT+Pam3cys and TLR2KO+Pam3cys), the synthetic ligand Pam3cys was administered intraperitoneally every 7 days, according to the experimental period (14, 21 and 42 days). At the end of those periods, the animals were euthanized, and the mandible and the spleen were submitted to histotechnical processing. Mandible histological sections were analysed by haematoxylin and eosin, TRAP histoenzymology and immunohistochemistry (FOXP3, RANK, RANKL and OPG). Spleen sections were analysed by immunohistochemistry (FOXP3).

RESULTS

The inflammatory infiltrate and bone resorption were more intense in the TLR2KO group compared to the WT group. The animals that received the Pam3cys had smaller periapical lesions when compared to the animals that did not receive the ligand (p < .05). TLR2KO animals showed a significant increase in the number of osteoclasts when compared to TLR2KO+Pam3cys group (p < .05). At 21 days, the WT+Pam3cys group had a lower number of osteoclasts when compared to the WT animals (p = .02). FOXP3 expression was more intense in the WT+Pam3cys groups when compared to the WT animals in the 42 days (p = .03). In the spleen analysis, the WT+Pam3cys group also had a higher expression of FOXP3 when compared to the WT animals at 14 and 42 days (p = .02). Concerning RANKL, there was a reduction in staining in the KOTLR2+Pam3cys groups at 21 and 42 days (p = .03) and a higher binding ratio between RANK/RANKL in animals that did not receive the ligand.

CONCLUSION

Administration of the Pam3cys increased the proliferation of Tregs, showed by FOXP3 expression and prevented the progression of the periapical lesion in WT mice. On the other hand, in the TLR2KO animals, Treg expression was lower with larger areas of periapical lesions. Finally, systemic administration of the Pam3cys in KO animals was able to limit the deleterious effects of the absence of the TLR2 receptor.

Effects of mineral trioxide aggregate and methyl sulfonyl methane on pulp exposure via RUNX2 and RANKL pathways

The aim of this study was to determine the therapeutic effects of mineral trioxide aggregate (MTA) and methyl sulfonyl methane (MSM) on pulp damage due to pulp exposure through the RUNX2 and RANKL pathways. Seventy-two male Sprague-Dawley rats aged 4-6 months and weighing 250-300 g were divided into healthy, control, MTA, and MSM groups. After experimental applications, all rats at 2, 4, and 8 weeks were killed anesthetically with xylazine hydrochloride (Rompun, Bayer) 30 mg/kg and ketamine hydrochloride (Ketalar, Pfizer) 50 mg/kg injections (i.p.). We observed that necrotic odontoblasts, edema, inflammation, and vascular congestion findings were reduced from week 2 to week 8 in the MSM treatment group after pulp capping compared to the control group and MTA group. Similarly, we found a decrease in RUNX2 and RANKL levels in the MSM application group compared to the control and MTA groups (p < 0.05). MSM material has shown therapeutic effects on pulp capping treatment-induced pulp injury via increased RUNX2 ve RANKL expression.

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.

Pathogenesis of non-infection related inflammatory root resorption in permanent teeth: A narrative review

BACKGROUND

The mechanism of action of root resorption in a permanent tooth can be classified as infection-related (e.g., microbial infection) or non-infection-related (e.g., sterile damage). Infection induced root resorption occurs due to bacterial invasion. Non-infection-related root resorption stimulates the immune system through a different mechanism.

OBJECTIVES

The aim of this narrative review is to describe the pathophysiologic process of non-infection-related inflammatory processes involved in root resorption of permanent teeth.

METHODS

A literature search on root resorption was conducted using Scopus (PubMed and Medline) and Google Scholar databases to highlight the pathophysiology of bone and root resorption in non-infection-related situations. The search included key words covering the relevant category. It included in vitro and in vivo studies, systematic reviews, case series, reviews, and textbooks in English. Conference proceedings, lectures and letters to the editor were excluded.

RESULTS

Three types of root resorption are related to the non-infection mechanism of action, which includes surface resorption due to either trauma or excessive orthodontic forces, external replacement resorption and external cervical resorption. The triggers are usually damage associated molecular patterns and hypoxia conditions. During this phase macrophages and clastic cells act to eliminate the damaged tissue and bone, eventually enabling root resorption and bone repair as part of wound healing.

DISCUSSION

The resorption of the root occurs during the inflammatory phase of wound healing. In this phase, damaged tissues are recognized by macrophages and neutrophiles that secrete interlaukines such as TNF-α, IL-1, IL-6, IL-8. Together with the hypoxia condition that accelarates the secretion of growth factors, the repair of the damaged perioduntiom, including damaged bone, is initiated. If the precementum and cementoblast are injured, root resorption can occur.

CONCLUSIONS

Wound healing exhibits different patterns of action that involves immune stimulation in a bio-physiological activity, that occurs in the proper sequence, with overlapping phases. Two pathologic conditions, DAMPs and hypoxia, can activate the immune cells including clastic cells, eliminating damaged tissue and bone. Under certain conditions, root resorption occurs as a side effect.

Human Periapical Odontogenic Granulomas: Aspects of Microvessel Density (MVD), Heterogeneity of Blood Vessels and Mast Cells Density (MCD)

Periapical odontogenic granulomas are among the most encountered pathology that involve the alveolar bone, with severe consequences such as bone resorption, the presence of inflammatory infiltrate and the formation of abnormal vascularization. The present study aimed to quantify the existence of the microvessel density (MVD), mast cell density (MCD) and heterogeneity of the encountered blood vessels. A total of 37 patients diagnosed with odontogenic periapical granulomas were included, and the gender distribution, age and localization of the pathological lesions was assessed. After the surgical removal of the periapical odontogenic granuloma, the collected tissue was fixed in 10% buffered formalin. Primary processing, morphological analysis and immunohistochemical staining was performed in order to characterize the altered tissue. The results outlined the presence of a high number of mast cells, especially in the area of the inflamed tissue; the high heterogeneity of the blood vessels; and increased MVD with positive CD34. The conclusions of the study focus on the key role of the mast cells and their implication in the initiation and development of the angiogenesis process, triggering the inflammatory response of the host. Nevertheless, periapical odontogenic granulomas develop as an inflammatory response to the interaction between the host's immune system and microbial invasion.

Efficacy of imaging techniques for the diagnosis of apical periodontitis: A systematic review

BACKGROUND

Apical periodontitis (AP) is a chronic inflammatory response of microbial aetiology. Pathological changes associated with AP may not be visible on radiographic images and may linger without causing any symptoms. Clinicians rely mostly on clinical examination and imaging techniques to establish a diagnosis.

OBJECTIVES

The aim of this review was to answer the following question using the PICO format: In the adult human permanent dentition (P), what is the efficacy of diagnostic imaging of the periapical tissues (I) using histopathology as a reference standard (C) in the diagnosis of apical periodontitis, in terms of diagnostic accuracy (O).

METHODS

MEDLINE, EMBASE, Scopus and Cochrane Library were searched for English articles published through October 2021. At least two independent reviewers evaluated the study design, imaging modality used, histopathological assessment, outcome measures, results and conclusions for each article. The risk of bias was assessed using the Quality Assessment Tool for Diagnostic Accuracy Studies-2.

RESULTS

The initial search strategy identified 544 articles. Seven articles were included for analysis in the final review, all of which involved tissue samples obtained from cadavers. No clinical studies were identified that met the eligibility criteria. A consistently low sensitivity score and negative predictive value were reported for periapical radiography, especially in comparison to CBCT, which scored highly. Both modalities achieved high scores for specificity and positive predictive value. Diagnostic accuracy of CBCT was lower for root-filled teeth in comparison to non-root-filled teeth.

DISCUSSION

Assessment of the periapical tissues using periapical radiographs was shown to have a low to moderate agreement with the histopathological assessment. CBCT was reported to be more accurate than PR and demonstrated a good agreement with histopathology, especially for non-root-filled teeth.

CONCLUSIONS

This review identified a need for greater standardization in methodology and reporting, and as the findings are based on cadaver studies, their clinical relevance must be interpreted with caution.

REGISTRATION

PROSPERO (CRD42021272147).

Modulation of blood redox status by the progression of induced apical periodontitis in rats

This study aimed to investigate if apical periodontitis in different periods changes systemic levels of the antioxidant and pro-oxidant parameters in Wistar rats. Twenty-four rats were randomly allocated into healthy animals, apical periodontitis at 14 days (AP14) and apical periodontitis at 28 days (AP28). The first mandibular molars were accessed in the AP groups, and the pulp chamber was exposed to the oral environment, inducing the apical lesion. After 14 and 28 days, the animals were anesthetized, euthanized, and hemimandibles were collected for micro-computed tomography (micro-CT) analysis to measure lesion volume, bone volume (BV), percent of bone to total tissue volume (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), and trabecular space (Tb.Sp). A histological examination of the remaining bone was also performed. Finally, blood samples were collected for oxidative biochemistry analysis, investigating glutathione (GSH), Trolox equivalent antioxidant capacity (TEAC), and lipid peroxidation (TBARS). The lesion volume was greater at 28 than at 14 days, as shown by micro-CT. AP14 and AP28 had decreased BV and Tb.Th, but only AP28 showed a reduction in BV/TV. Tb.N and Tb. Sp were increased in apical periodontitis at 28 days. In the histopathological analysis, AP14 had focal regions of moderate mononuclear inflammatory infiltrate, and AP28 had an intense inflammatory infiltrate with bacterial colonies. In the biochemical evaluation, GSH, TEAC, and TBARS were increased after 14 days. However, GSH returned to control levels, TEAC was similar to AP14, and TBARS increased significantly after 28 days. Therefore, the oxidative biochemistry response was modulated according to the progression of periapical damage. After 14 days, the organism could still react to the injury. However, at 28 days, the antioxidant response decreased, associated with an increase in TBARS.

Nociceptor-Macrophage Interactions in Apical Periodontitis: How Biomolecules Link Inflammation with Pain

Periradicular tissues have a rich supply of peripheral afferent neurons, also known as nociceptive neurons, originating from the trigeminal nerve. While their primary function is to relay pain signals to the brain, these are known to be involved in modulating innate and adaptive immunity by initiating neurogenic inflammation (NI). Studies have investigated neuroanatomy and measured the levels of biomolecules such as cytokines and neuropeptides in human saliva, gingival crevicular fluid, or blood/serum samples in apical periodontitis (AP) to validate the possible role of trigeminal nociceptors in inflammation and tissue regeneration. However, the contributions of nociceptors and the mechanisms involved in the neuro-immune interactions in AP are not fully understood. This narrative review addresses the complex biomolecular interactions of trigeminal nociceptors with macrophages, the effector cells of the innate immune system, in the clinical manifestations of AP.

Vital pulp therapy for permanent teeth with diagnosis of irreversible pulpitis: biological basis and outcome

Root canal treatment (RCT) has been considered the conventional standard for the management of teeth with carious pulp exposure, particularly in mature teeth presenting with symptoms. Following a better understanding of the histopathology of deep carious lesions, the histology of the cariously exposed pulp and the healing potential of the inflamed pulp, vital pulp therapy (VPT) is increasingly adopted around the world for the management of permanent teeth with clinical signs and symptoms indicative of irreversible pulpitis. Furthermore, VPT became a recognized treatment modality by the European Society of Endodontology (ESE) and the American Association of Endodontists (AAE) by virtue of its high success rates reported in outcome studies using contemporary hydraulic calcium silicate-based cements. However, proper case selection, strict asepsis, capping materials and good coronal seal are mandatory for success. The aim of this paper is to review the biological basis for VPT in symptomatic teeth with carious pulp exposure and to report on the outcome of pulpotomy in teeth with clinical diagnosis of irreversible pulpitis.

3D Organoids for Regenerative Endodontics

Apical periodontitis is the inflammation and destruction of periradicular tissues, mediated by microbial factors originating from the infected pulp space. This bacteria-mediated inflammatory disease is known to interfere with root development in immature permanent teeth. Current research on interventions in immature teeth has been dedicated to facilitating the continuation of root development as well as regenerating the dentin-pulp complex, but the fundamental knowledge on the cellular interactions and the role of periapical mediators in apical periodontitis in immature roots that govern the disease process and post-treatment healing is limited. The limitations in 2D monolayer cell culture have a substantial role in the existing limitations of understanding cell-to-cell interactions in the pulpal and periapical tissues. Three-dimensional (3D) tissue constructs with two or more different cell populations are a better physiological representation of in vivo environment. These systems allow the high-throughput testing of multi-cell interactions and can be applied to study the interactions between stem cells and immune cells, including the role of mediators/cytokines in simulated environments. Well-designed 3D models are critical for understanding cellular functions and interactions in disease and healing processes for future therapeutic optimization in regenerative endodontics. This narrative review covers the fundamentals of (1) the disease process of apical periodontitis; (2) the influence and challenges of regeneration in immature roots; (3) the introduction of and crosstalk between mesenchymal stem cells and macrophages; (4) 3D cell culture techniques and their applications for studying cellular interactions in the pulpal and periapical tissues; (5) current investigations on cellular interactions in regenerative endodontics; and, lastly, (6) the dental-pulp organoid developed for regenerative endodontics.

Lithium carbonate accelerates the healing of apical periodontitis

Apical periodontitis is a disease caused by bacterial invasions through the root canals. Our previous study reported that lithium chloride (LiCl) had a healing effect on apical periodontitis. The aim of this report is to investigate the healing properties and mechanism of lithium ion (Li⁺) for apical periodontitis using rat root canal treatment model. 10-week-old male Wistar rat's mandibular first molars with experimentally induced apical periodontitis underwent root canal treatment and were applied lithium carbonate (Li₂CO₃) containing intracanal medicament. Base material of the medicament was used as a control. Subject teeth were scanned by micro-CT every week and the periapical lesion volume was evaluated. The lesion volume of Li₂CO₃ group was significantly smaller than that of the control group. Histological analysis showed that in Li₂CO₃ group, M2 macrophages and regulatory T cells were induced in the periapical lesion. In situ hybridization experiments revealed a greater expression of Col1a1 in Li₂CO₃ group compared with the control group. At 24 h after application of intracanal medicament, Axin2-positive cells were distributed in Li₂CO₃ group. In conclusion, Li₂CO₃ stimulates Wnt/β-catenin signaling pathway and accelerate the healing process of apical periodontitis, modulating the immune system and the bone metabolism.

Visualization of clinically silent, odontogenic maxillary sinus mucositis originating from periapical inflammation using MRI: a feasibility study

OBJECTIVES

Maxillary sinus mucositis is frequently associated with odontogenic foci. Periapical inflammation of maxillary molars and premolars cannot be visualized directly using radiation-based imaging. The purpose of this study was to answer the following clinical question: among patients with periapical inflammatory processes in the maxilla, does the use of magnetic resonance imaging (MRI), as compared to conventional periapical (AP) and panoramic radiography (OPT), improve diagnostic accuracy?

METHODS

Forty-two subjects with generalized periodontitis were scanned on a 3 T MRI. Sixteen asymptomatic subjects with mucosal swelling of the maxillary sinus were enrolled in the study. Periapical edema was assessed using short tau inversion recovery (STIR) sequence. Apical osteolysis and mucosal swelling were assessed by MRI, AP, and OPT imaging using the periapical index score (PAI). Comparisons between groups were performed with chi-squared tests with Yates' correction. Significance was set at p < 0.05.

RESULTS

Periapical lesions of maxillary premolars and molars were identified in 16 subjects, 21 sinuses, and 58 teeth. Bone edema and PAI scores were significantly higher using MRI as compared to OPT and AP (p < 0.05). Using the STIR sequence, a significant association of PAI score > 1 and the presence of mucosal swelling in the maxillary sinus was detected (p = 0.03).

CONCLUSION

Periapical inflammation and maxillary mucositis could be visualized using STIR imaging. The use of MRI may help detect early, subtle inflammatory changes in the periapical tissues surrounding maxillary dentition. Early detection could guide diagnostic criteria, as well as treatment and prevention.

Root canal microbiota as an augmented reservoir of antimicrobial resistance genes in type 2 diabetes mellitus patients

BACKGROUND

Antimicrobial resistance is a global public health problem. Root canal microbiota associated with apical periodontitis represents a well-known reservoir of antimicrobial resistance genes (ARGs). However, the effect of type 2 diabetes mellitus (T2DM) in this reservoir is unknown. This study aimed to establish if root canal microbiota associated with apical periodontitis in T2DM patients is an augmented reservoir by identifying the prevalence of nine common ARGs and comparing it with the prevalence in nondiabetic patients.

METHODOLOGY

This cross-sectional study included two groups: A T2DM group conformed of 20 patients with at least ten years of living with T2DM and a control group of 30 nondiabetic participants. Premolar or molar teeth with pulp necrosis and apical periodontitis were included. A sample was collected from each root canal before endodontic treatment. DNA was extracted, and ARGs were identified by polymerase chain reaction.

RESULTS

tetW and tetM genes were the most frequent (93.3 and 91.6%, respectively), while ermA was the least frequent (8.3%) in the total population. The distribution of the ARGs was similar in both groups, but a significant difference (p<0.005) was present in ermB, ermC, cfxA, and tetQ genes, being more frequent in the T2DM group. A total of eighty percent of the T2DM patients presented a minimum of four ARGs, while 76.6% of the control group presented a maximum of three.

CONCLUSIONS

Root canal microbiota associated with apical periodontitis in T2DM patients carries more ARGs. Therefore, this pathological niche could be considered an augmented reservoir.

Ex vivo Detection of Amyloid-β in Naturally Formed Oral Biofilm

Background

Oral infection has been implicated in the possible etiology of Alzheimer's disease.

Objective

To detect amyloid-β (Aβ) within microbial biofilms.

Methods

Freshly extracted teeth (N = 87) with periodontal disease were separated into Group A (N = 11), with primary root canal infection and Group B (N = 21) with failed endodontic treatment identified by the presence of, gutta percha root filling. Biofilm characteristics were observed by scanning electron microscopy (SEM). Demineralized paraffin wax embedded tooth sections and mineralized calculus biofilm were immunostained with the anti-Aβ antibody. The gutta perchas were processed either for on-section acrylic resin tissue immunocolloidal gold silver staining (IGSS) using the anti-Aβ antibody or in Araldite resin for ultrastructure.

Results

SEM demonstrated calculus and gutta percha in situ harboring a polymicrobial biofilm featuring extracellular polymeric substance (EPS) and water channels. Immunohistochemistry on rehydrated paraffin wax tooth sections from Group A, demonstrated Aβ staining on external (calculus and plaque) and all intracanal infected regions. In Group B, the gutta percha biofilm IGSS gave an inconclusive result for Aβ. Transmission electron microscopy of selected teeth with infected intra-canals (Group A) and 20% of gutta percha biofilm (Group B) EPS contained electron dense fibrils of variable sizes, some of which were typical of human Aβ fibrils.

Conclusion

This study detected both soluble and insoluble Aβ fibrils within the EPS of periodontal and endodontic natural biofilm, strongly suggesting its role as an antimicrobial peptide in combatting local infection, with potential risk for cross-seeding into the brain for AD development.

Revisiting the role of IL-1 signaling in the development of apical periodontitis

Apical periodontitis (AP) develops as a result of an immune response to pulpal bacterial infection, and various cytokines are involved in the pathogenesis of AP, with Interleukin (IL)-1 being considered a key cytokine. The role of IL-1 in the pathogenesis of AP has been well studied. It is known that IL-1 expression in periapical lesions correlates closely with the development of AP. IL-1 is a potent bone-resorptive cytokine that induces osteoclast formation and activation. Hence, inhibiting its signaling with IL-1 receptor antagonist (IL-1RA) results in a reduction in periapical lesion size. On the other hand, IL-1 is also a central cytokine that combats bacterial infection by activating innate immune responses. Therefore, a complete loss of IL-1 signaling leads to a failure to limit bacterial dissemination and consequently exacerbates AP. In vivo, IL-1 expression is tightly regulated and its signaling is modulated to optimize the immune response. Obesity causes systemic low-grade chronic inflammation and increases the risk of cardiovascular, renal, and other disorders. In experimentally induced AP, obesity significantly increases periapical bone loss, albeit the underlying mechanism remains unclear. Recent technological innovations have enabled more comprehensive and detailed analyses than previously, leading to new insights into the role of IL-1RA in regulating IL-1 signaling, and modulating apical lesion progression in obesity. In this review, we provide a brief overview of the function of IL-1 in AP development, with special emphasis on the latest findings in normal weight and obese states.

Association between Endodontic Infection, Its Treatment and Systemic Health: A Narrative Review

The ‘Focal Infection Era in Dentistry’ in the late 19th and early 20th century resulted in widespread implementation of tooth extraction and limited the progress of endodontics. The theory proposed that bacteria and toxins entrapped in dentinal tubules could disseminate systemically to remote body parts, resulting in many types of degenerative systemic diseases. This theory was eventually refuted due to anecdotal evidence. However, lately there has been increased interest in investigating whether endodontic disease could have an impact on general health. There are reviews that have previously been carried out on this subject, but as new data have emerged since then, this review aims to appraise the available literature investigating the dynamic associations between apical periodontitis, endodontic treatment, and systemic health. The available evidence regarding focal infection theory, bacteraemia and inflammatory markers was appraised. The review also collated the available research arguing the associations of apical periodontitis with cardiovascular diseases, diabetes mellitus, adverse pregnancy outcome and autoimmune disorders, along with the effect of statins and immunomodulators on apical periodontitis prevalence and endodontic treatment prognosis. There is emerging evidence that bacteraemia and low-grade systemic inflammation associated with apical periodontitis may negatively impact systemic health, e.g., development of cardiovascular diseases, adverse pregnancy outcomes, and diabetic metabolic dyscontrol. However, there is limited information supporting the effect of diabetes mellitus or autoimmune disorders on the prevalence and prognosis post endodontic treatment. Furthermore, convincing evidence supports that successful root canal treatment has a beneficial impact on systemic health by reducing the inflammatory burden, thereby dismissing the misconceptions of focal infection theory. Although compelling evidence regarding the association between apical periodontitis and systemic health is present, further high-quality research is required to support and establish the benefits of endodontic treatment on systemic health.

Trigeminal neurons control immune-bone cell interaction and metabolism in apical periodontitis

Abstract

Apical periodontitis (AP) is an inflammatory disease occurring following tooth infection with distinct osteolytic activity. Despite increasing evidence that sensory neurons participate in regulation of non-neuronal cells, their role in the development of AP is largely unknown. We hypothesized that trigeminal ganglia (TG) Nav1.8⁺ nociceptors regulate bone metabolism changes in response to AP. A selective ablation of nociceptive neurons in Nav1.8^Cre/Diphtheria toxin A (DTA)^Lox mouse line was used to evaluate the development and progression of AP using murine model of infection-induced AP. Ablation of Nav1.8⁺ nociceptors had earlier progression of AP with larger osteolytic lesions. Immunohistochemical and RNAscope analyses demonstrated greater number of macrophages, T-cells, osteoclast and osteoblast precursors and an increased RANKL:OPG ratio at earlier time points among Nav1.8^Cre/ DTA^Lox mice. There was an increased expression of IL-1α and IL-6 within lesions of nociceptor-ablated mice. Further, co-culture experiments demonstrated that TG neurons promoted osteoblast mineralization and inhibited osteoclastic function. The findings suggest that TG Nav1.8⁺ neurons contribute to modulation of the AP development by delaying the influx of immune cells, promoting osteoblastic differentiation, and decreasing osteoclastic activities. This newly uncovered mechanism could become a therapeutic strategy for the treatment of AP and minimize the persistence of osteolytic lesions in refractory cases.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s00018-022-04335-w.

Deciphering Stem Cell from Apical Papilla - Macrophage Choreography using a Novel 3D Organoid System

INTRODUCTION

Immune cell - mesenchymal stem cell crosstalk modulates the process of repair and regeneration. In this study, a novel heterogenous cell containing matrix based three-dimensional (3D) tissue-construct was employed to study the interactions between stem cells from apical papilla (SCAP) and macrophage for a comprehensive understanding on the cellular signalling mechanisms guiding inflammation and repair.

METHODS

SCAP and macrophages were seeded with collagen in 3D printed molds to generate self-assembled tissue-constructs, which were exposed to three conditions: no stimulation, lipopolysaccharide (LPS), and interleukin-4 (IL-4) from 0 to 14 days. Specimens from each group were evaluated for cellular interactions, inflammatory mediators (IL-1β, TNF-α, MDC, MIP-1β, MCP-1, IL-6, IL-8, TGF-β1, IL-1RA, IL-10), expression of surface markers (CD80, 206), transcription factors (pSTAT1, pSTAT6) and SCAP differentiation markers (DSPP, DMP-1, and alizarin red) using confocal laser scanning microscopy and multiplex cytokine profiling from 2 to 14 days.

RESULTS

SCAP and macrophages displayed a cytokine-mediated interaction and differentiation characteristics. The increased pro-inflammatory cytokines/chemokines: IL-1β, TNF-α, MDC and MIP-1β in the earlier phase followed by the higher ratio of pSTAT6/pSTAT1 and decreased CD206 (p<0.05), indicated a distinct polarization behavior in macrophages during repair in LPS group. Conversely, the equal ratio of pSTAT6/pSTAT1, late increase in CD206 and amplified secretion of IL-1RA, IL-10 and TGF-β1 (p<0.05) in the anti-inflammatory environment, directed alternative macrophage polarization, promoting SCAP differentiation and tissue modeling in IL-4 group.

CONCLUSIONS

The novel 3D organoid system developed in this study allowed a comprehensive analysis of the SCAP-macrophage interactions during inflammation and healing, providing a deeper insight on the periapical dynamics of immature tooth.

Effects of calcium hydroxide intracanal medications on T helper (Th1, Th2, Th9, Th17, and Tfh) and regulatory T (Treg) cell cytokines in apical periodontitis: a CONSORT RCT

INTRODUCTION

This CONSORT RCT investigated T helper (Th1, Th2, Th9, Th17, and Tfh), regulatory T (Treg) cell-type cytokines, and their networks in apical periodontitis (AP). We also assessed the effects of calcium hydroxide [Ca(OH)2] intracanal medications (ICMs) on helper T and Treg cell-type cytokines.

METHODS

Twenty teeth with primary endodontic infection and apical periodontitis (PEIAP) were randomly divided into two groups: Ca(OH)2 + saline solution (SSL; n = 10) and Ca (OH)2 + 2% Chlorhexidine-gel (2% CHX-gel; n = 10). Samples were collected from the periradicular tissue fluid (PTF) before (PTFs1) and after 14 days of ICMs (PTFs2). The Human High Sensitivity T Cell Panel was used to quantify target T-helper (Th)1: IL-2, 12, and IFN-γ; Th2: IL-4, -5, -13; Th9: IL-9; Th17: IL-17; T follicular helper cells (Tfh): IL-21; and Treg-cell-type cytokine: IL-10.

RESULTS

Th1-type cytokines were higher, compared to Th2-type, at PTFs1. Positive (+) associations were found among all Th1-type cytokines and all Th2-type cytokines. There were negative (-) correlations between all Th1- and Th2-type cytokines. Size of radiolucent lesions (SRL) and symptoms (TTP and/or POP) were positively correlated with Th1-type cytokines, IL-17, and IL-21 but negatively correlated with Th2-type cytokines and IL-10 (all, p < 0.001). Both ICMs increased Th2-type cytokines and IL-10 (P < 0.05) and decreased Th1- type cytokines, IL-17, and IL-21 (P < 0.05), with no differences among them (P > 0.05).

CONCLUSIONS

Complex T-cell cytokine networks are involved in AP. Both Ca(OH)2 ICMs effectively increased IL-4, IL-5, IL-10, and IL-13 and lowered IL-2, IL-12, IL-17, IL-21, and IFN-γ.

Indigenous microbiota protects development of medication-related osteonecrosis induced by periapical disease in mice

Bacterial infection is a common finding in patients, who develop medication-related osteonecrosis of the jaw (MRONJ) by the long-term and/or high-dose use of anti-resorptive agents such as bisphosphonate (BPs). However, pathological role of bacteria in MRONJ development at the early stage remains controversial. Here, we demonstrated that commensal microbiota protects against MRONJ development in the pulp-exposed periapical periodontitis mouse model. C57/BL6 female mice were treated with intragastric broad-spectrum antibiotics for 1 week. Zoledronic acid (ZOL) through intravenous injection and antibiotics in drinking water were administered for throughout the experiment. Pulp was exposed on the left maxillary first molar, then the mice were left for 5 weeks after which bilateral maxillary first molar was extracted and mice were left for additional 3 weeks to heal. All mice were harvested, and cecum, maxilla, and femurs were collected. ONJ development was assessed using μCT and histologic analyses. When antibiotic was treated in mice, these mice had no weight changes, but developed significantly enlarged ceca compared to the control group (CTL mice). Periapical bone resorption prior to the tooth extraction was similarly prevented when treated with antibiotics, which was confirmed by decreased osteoclasts and inflammation. ZOL treatment with pulp exposure significantly increased bone necrosis as determined by empty lacunae and necrotic bone amount. Furthermore, antibiotics treatment could further exacerbate bone necrosis, with increased osteoclast number. Our findings suggest that the commensal microbiome may play protective role, rather than pathological role, in the early stages of MRONJ development.

Local immunomodulatory effects of intracanal medications in apical periodontitis

The immune system is an extremely complex biological network that plays a crucial role in the hemostasis of periapical tissue, pathogenesis of apical periodontitis (AP) as well as periapical tissue healing. The successful elimination of microbial infections remains a significant challenge, mostly due to the ever-growing development of antimicrobial-resistant pathogens. The bacterial endurance in the root canal system contributes to features ranging from altered post-treatment healing to exacerbation of chronic periradicular immune response, that compromise the outcome of endodontic treatment. A highly effective strategy for combating infectious diseases and the associated inflammation-mediated tissue damage is to modulate the host immune response in conjunction with antimicrobial therapy. There are several medications currently used in endodontic treatment, however, they suffer various levels of microbial resistance and do not deliver all the required characteristics to simultaneously address both intracanal bacteria and periapical inflammation. Interaction of antimicrobial agents with the immune system can impact its function, leading to immune-suppressive or immune-stimulatory effects. The group of non-conventional antimicrobial medications, such as antimicrobial peptides, propolis, and nanomaterials, are agents that provide strong antimicrobial effectiveness and concomitant immunomodulatory and/or reparative effect, without any host tissue damages. Herein, we provide an overview of local immune modulation in AP and a comprehensive review of the immunomodulatory effect of antimicrobials intracanal medications applied in endodontics with specific emphasis on the antimicrobial nanomaterial-based approaches that provide immunomodulatory potential for successful clinical deployment in endodontics.

Apical periodontitis promotes insulin resistance and alters adaptive immunity markers in rats

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Periapical lesions promotes higher T-bet expression and lower GATA3 and FOXP3 expression.

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Periapical lesion promotes increased GATA3 and decreased FOXP3 expression in the group with 4 periapical lesions (4PL)

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The adaptive immune system, with a predominance of the Th1 polarization, may be involved in the development of insulin resistance in rats with Periapical lesions.

Objective

Apical periodontitis (AP) is a chronic or acute inflammatory disease usually developed from endodontic infections, predominantly due to gram-negative anaerobic bacteria invading the dental pulp. This study aimed to evaluate lymphocyte markers to assess the involvement of adaptive immunity in insulin resistance (IR) in a rat model of AP.

Design.

Forty-five male Wistar albino rats were divided into 3 groups (control, 1AP and 4AP). AP was induced in the upper right first molar (1AP), and in the first and second upper and lower right molars (4AP). The spleen was collected to evaluate the expression of transcription factors involved in lymphocyte polarization, including T-bet (Th1), GATA3 (Th2), and FOXP3 (Treg). Blood samples were assessed for serum cytokine levels transcribed by the respective lymphocyte polarizations, INF-γ (Th1), IL-4 (Th2) and TGF-β (Treg). In addition, glucose and insulin levels were measured to evaluate IR by the HOMA-IR method.

Results

The results showed higher T-bet expression on AP groups, along with lower GATA3 and FOXP3 expression in the 1AP, in addition to increased GATA3 and decreased FOXP3 expression in the 4AP group compared to the CN group. There was no difference in the INF-γ levels, while IL-4 was decreased in the AP groups. Taken together, these results suggest that the adaptive immune system, with a predominance of the Th1 polarization, may be involved in the development of IR in rats with AP.

Conclusions

AP promotes increase in the expression of T-bet (4AP) and decrease of FOXP3 expressions and IL-4 levels (1AP and 4AP). However, depending on the number of lesions (1 or 4 lesions), the expression of GATA3 appears differently. Thus, innate immunity and adaptive immunity may contribute to the IR observed in rats with AP.

Vital Pulp Therapy in Permanent Teeth with Irreversible Pulpitis Caused by Caries: A Prospective Cohort Study

Background: When a tooth is diagnosed with irreversible pulpitis, root canal therapy (RCT) is generally performed to completely remove pulp tissue, which might lead to a higher risk of loss of vascularity, and teeth being more prone to fracture. Vital pulp therapy (VPT) is a personalized method of treating irreversible pulpitis, which conforms to the trend of minimally invasive endodontics. The remaining vital pulp could promote the physiological development of the roots of young permanent teeth with incomplete apical foramen. However, clear guidelines for VPT indication are still missing. Objective: This prospective cohort study evaluated the outcomes of vital pulp therapy (VPT) using iRoot BP Plus (Innovative Bioceramix Inc, Vancouver, BC, Canada) in permanent teeth of 6- to 20-year-old patients with irreversible pulpitis caused by caries and analyzed the preoperative factors affecting VPT prognosis. Methods: Fifty-nine permanent teeth in 59 patients with irreversible pulpitis caused by caries were treated with VPT using iRoot BP Plus. All patients received VPT under a standardized protocol. After informed consent, teeth were isolated with a dental dam, then operators performed VPT with iRoot BP Plus and restored the teeth with composite resin or stainless steel crown. Patients were postoperatively recalled after 3, 6 and 12 months and then recalled annually. Successful cases were defined as successful in both clinical and radiographic evaluations. A statistical analysis was performed using the Fisher exact test, and the level of significant difference was p < 0.05. Results: After 6–36 months of follow-up, a total of 57 teeth from 57 patients were accessible for evaluation. The mean age of subjects was 11.75 ± 3.81 years. The overall clinical and radiographic success rate of VPT was 91.2% (52/57). With an observation time of one year or more, the success rate was 90.5% (38/42). All the symptoms and physical examination findings showed no significant effect on VPT prognosis (p > 0.05) using a binary logistic regression model. Conclusions: Permanent teeth in 6- to 20-year-old patients diagnosed as irreversible pulpitis caused by caries can be successfully treated with VPT using iRoot BP Plus.

The Antimicrobial, Antioxidative, and Anti-Inflammatory Effects of Polycaprolactone/Gelatin Scaffolds Containing Chrysin for Regenerative Endodontic Purposes

The appropriate endodontic material should eliminate the infection and inflammation to provide a situation for regeneration and healing of pulp tissue besides biomineralization. Chrysin is one of the active ingredients of plant flavonoids, which has significant anti-inflammatory and antimicrobial properties. In the present study, this natural substance was evaluated for antioxidant, anti-inflammatory, and mineralization properties on dental pulp stem cells (DPSCs). SEM, FTIR, and TGA tests were used to determine the successful synthesize of chrysin-loaded scaffolds. The antimicrobial effects of the synthesized scaffold against Acinetobacter baumannii, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis were assessed by the agar diffusion test and live/dead assay. The proliferation of DPSCs on these scaffolds was determined by the MTT assay, DAPI staining, and DNA extraction. Moreover, the antioxidant and anti-inflammation activity of chrysin-loaded scaffolds on inflamed DPSCs was evaluated. Alkaline phosphatase activity and Alizarin Red S Stain tests were done to evaluate the mineralization of DPSCs seeded on these scaffolds. The chrysin-loaded scaffolds reported antimicrobial effects against evaluated bacterial strains. The proliferation of DPSCs seeded on these scaffolds was increased significantly (p < 0.05). The TNFα and DCF levels in inflamed DPSCs showed a significant decrease in the presence of chrysin-loaded scaffolds (p < 0.05). The ALP activity and formation of mineralized nodules of DPSCs on these scaffolds were significantly increased compared with the control group (p < 0.05). These results indicated that chrysin as an ancient therapeutic agent can accelerate the healing and regeneration of damaged pulp tissue, and this active ingredient can be a potential natural substance for regenerative endodontic procedures.

The Wnt/β-catenin signaling pathway has a healing ability for periapical periodontitis

Various disease-related genes have recently been identified using single nucleotide polymorphisms (SNPs). This study identified disease-related genes by analyzing SNP using genomic DNA isolated from Japanese patients with periapical periodontitis. Results showed that the SNP in LRP5 demonstrated a significant genotypic association with periapical lesions (Fisher’s exact test, P < 0.05). We constructed an in vivo murine periapical periodontitis model to confirm the Wnt/β-catenin signaling pathway’s role in developing and healing periapical periodontitis. We observed that administration of the Wnt/β-catenin signaling pathway inhibitor enlarged the periapical lesion. Moreover, applying lithium chloride (LiCl) to root canals accelerated periapical periodontitis healing. Histological analysis demonstrated that the expression levels of Col1a1 and Runx2 increased in the LiCl application group compared to that in the control group. Furthermore, many CD45R-positive cells appeared in the periapical lesions in the LiCl application group. These results indicated that LiCl promoted the healing of periapical periodontitis by inducing bone formation and immune responses. Our findings suggest that the Wnt/β-catenin signaling pathway regulates the development of periapical periodontitis. We propose a bioactive next-generation root canal treatment agent for this dental lesion.

Scanning Electron Microscopic and Dye Penetration Evaluation of Hand Instrumentation Techniques on Formation of Smear Layer in Root Canal Preparation: An In vitro Study

Aims and Objectives:

The present study was undertaken for evaluating various hand instrumentation techniques with different instruments in the formation of smear layer.

Materials and Methods:

One hundred and seventy-five extracted mandibular molars were collected and were cut at cementoenamel junction. Afterward, the distal roots were separated. Working length was determined, and roots were divided into five equal groups with 35 roots in each group as follows: Group A: K-type files with conventional step-back technique, Group B: Canal Master U instrument with clockwise–counterclockwise rotation, Group C: Flex-R^® files with clockwise–counterclockwise rotation, Group D: FlexoFiles^® with conventional step-back technique, and Group E: Nickel titanium files with conventional step-back technique. Biomechanical preparation was done according to their respective groups. The teeth in various groups were scanned under scanning electron microscope and scoring was done. All the results were analyzed by SPSS software version 17.0.

Results:

Scanning electron microscopic results indicated that apparently there seems to be a significant difference in the scoring of the smear layer between each group at all the three levels, but the difference was statistically nonsignificant. Microleakage was present in all the samples. Nonsignificant results were obtained while comparing the microleakage in between different the groups. However, microleakage was highest in Group D.

Conclusion:

The amount of smear layer is maximum at the apical third and lesser in the middle third followed by the coronal third in all the groups. All the samples showed microleakage to a varying extent.

Systemic burden and cardiovascular risk to Porphyromonas species in apical periodontitis

OBJECTIVE

Porphyromonas (P.) species (spp.) are a major etiological agent of apical periodontitis (AP), which in turn represents a risk factor for cardiovascular diseases. This study explored the associations between endodontic infection with Porphyromonas species, the systemic bacterial burden, and cardiovascular risk, based on high-sensitivity C-reactive protein (hsCRP), in young adults with AP.

MATERIALS AND METHODS

Cross-sectional study. Otherwise, healthy individuals with AP and controls (n = 80, ≤ 40 years) were recruited at the University Dental Clinic. Oral parameters and classic cardiovascular risk factors were registered. Endodontic Porphyromonas endodontalis and Porphyromonas gingivalis were identified using conventional PCR. Serum concentrations of anti-P. endodontalis and anti-P. gingivalis antibodies, and endotoxins were determined through ELISA and Limulus-amebocyte assays. Serum hsCRP was determined for cardiovascular risk stratification.

RESULTS

Intracanal detection of P. endodontalis and P. gingivalis in AP were 33.3% and 22.9%, respectively. Serum anti-P. endodontalis and anti-P. gingivalis IgG was higher in AP than controls (p < 0.05 and p = 0.057, respectively). Intracanal P. endodontalis associated with higher endotoxemia (p < 0.05). Among endodontic factors, the presence (OR 4.2-5.5, p < 0.05) and the number of apical lesions (OR 2.3, p < 0.05) associated with moderate-severe cardiovascular risk, whereas anti-P. endodontalis IgG were protective (OR 0.3, p > 0.05).

CONCLUSIONS

AP and infection with P. endodontalis positively associated with cardiovascular risk based on hsCRP levels and endotoxemia, respectively, whereas anti-P. endodontalis IgG response seems to be protective against low-grade systemic inflammation.

CLINICAL RELEVANCE

Apical periodontitis and endodontic P. endodontalis can influence the systemic burden with impact on the surrogate cardiovascular risk marker hsCRP, providing mechanistic links.

Non-coding RNAs in endodontic disease

The immunocompetence and regeneration potential of the dental pulp and its surrounding apical tissues have been investigated extensively in the field of endodontics. While research on the role of non-coding RNAs in these tissues is still in its infancy, it is envisioned that improved understanding of the regulatory function of ncRNAs in pulpal and periapical immune response will help prevent or treat endodontic disease. Of particular importance is the role of these RNAs in regenerating the dentin-pulp complex. In this review, we highlight recent progress on the role of non-coding RNAs in the immune response to endodontic infection as well as the repair and regenerative response to injury.

BiodentineTM Full Pulpotomy in Mature Permanent Teeth with Irreversible Pulpitis and Apical Periodontitis

Vital pulp therapy, including direct pulp capping and partial and full pulpotomy, is primarily indicated for immature or mature permanent teeth with reversible pulpitis. Mature permanent teeth with irreversible pulpitis are frequently treated with root canal therapy. This report presents two cases of full pulpotomy using Biodentine^TM in mature permanent teeth with irreversible pulpitis and acute apical periodontitis. The periapical radiograph illustrated a deep carious lesion extended to the pulp with apical radiolucency lesion or widened periodontal ligament space. Full pulpotomy with a tricalcium silicate-based cement was chosen as the definitive treatment. After decayed tissue excavation under a rubber dam, the exposed pulp tissue was amputated to the level of the canal orifice with a new sterile bur. Biodentine^TM was applied as the pulp capping agent after hemostasis was obtained and for temporary restoration. The clinical signs disappeared quickly after the treatment. After one month, the coronal part of the temporary restoration was removed, and a composite resin was placed over the capping agent as a final restoration. At two-year follow-ups, the teeth were asymptomatic. Radiographs showed healing of the periapical lesion and periodontal ligament. Biodentine^TM full pulpotomy of mature permanent teeth with irreversible pulpitis and apical periodontitis can be an alternative option to root canal therapy.

Vital Pulp Therapy in Permanent Mature Posterior Teeth with Symptomatic Irreversible Pulpitis: A Systematic Review of Treatment Outcomes

Background and Objectives: Symptomatic irreversible pulpitis in permanent mature teeth is a common indication for nonsurgical root canal treatment (NSRCT), but contemporary studies have reported on vital pulp therapy (VPT) applied in such teeth as a less invasive treatment. This systematic review assessed the outcomes of VPT, including partial and full pulpotomy performed with hydraulic calcium silicate cements (HCSCs) in permanent mature posterior teeth diagnosed with symptomatic irreversible pulpitis. Materials and Methods: The PRISMA guidelines were followed. The search strategy included PubMed^®, EMBASE, Cochrane library and grey literature electronic databases. The quality assessment of the identified studies followed the Cochrane Collaboration Risk of Bias, ROBINS-I and Newcastle–Ottawa Scale tools. Results: The search of primary databases identified 142 articles, of which 9 randomized controlled trials and 3 prospective cohort studies were selected for review. The risk-of-bias was assessed as ‘high’ or ‘serious’, ‘fair’, and ‘low’ for three, seven and two articles, respectively. One to five years after VPT using HCSCs, the success rates mostly ranged from 78 to 90%. Based on two articles, the outcomes of the VPT and NSRCT were comparable at one and five years. Despite the necessity for the intra-operative pulp assessment in VPT procedures, the majority of the studies did not fully report on this step or on the time needed to achieve hemostasis. Small sample sizes, of under 23 teeth, were reported in three studies. Conclusions: The reviewed 12 articles reported favorable outcomes of the VPT performed with HCSCs in permanent mature posterior teeth with symptomatic irreversible pulpitis, with radiographic success in the range of 81 to 90%. Two articles suggested comparable outcomes of the VPT and root canal treatment. Universal case selection and outcome criteria needs to be established for VPT when considered as an alternative to NSRCT. This evidence supports the need for further research comparing longer-term outcomes of both of the treatment modalities.

Study of the ultrastructure of Enterococcus faecalis and Streptococcus mutans incubated with salivary antimicrobial peptides

OBJECTIVES

Enterococcus faecalis has been associated with root canal infections, while Streptococcus mutans has a central role in the etiology of dental caries. One of the main reasons of endodontic failure has been associated to the presence of E. faecalis and the formation of biofilms. S. mutans inhabits the oral cavity, specifically the dental plaque, which is a multispecies biofilm formed on the hard surfaces of the tooth. The biofilm formation is the main factor determining the pathogenicity of numerous bacteria. Natural antimicrobial peptides in the saliva protect against pathogenic bacteria and biofilms. The aim of this study was to assess the ultrastructural damage induced by salivary peptides in bacteria involved in biofilms has not been previously studied.

MATERIAL AND METHODS

Enterococcus faecalis and S. mutans incubated with cystatin C, chromogranin A, or histatin 5 were morphologically analyzed and counted. The ultrastructural damage was evaluated by transmission electron microscopy (TEM).

RESULTS

A decrease in bacterial numbers was observed after incubation with cystatin C, chromogranin A, or histatin 5, compared to the control group (P <  0.001). Ultrastructural damage in E. faecalis and S. mutans incubated with salivary peptides was found in the cell wall, plasma membrane with a decreased distance between the bilayers, a granular pattern in the cytoplasm, and pyknotic nucleoids.

CONCLUSIONS

This study demonstrated that salivary peptides exert antibacterial activity and induce morphological damage on E. faecalis and S. mutans. Knowledge on the ultrastructural damage inflicted by salivary antimicrobial peptides on two important bacteria causing dental caries and root canal infections could aid the design of new therapeutic approaches to facilitate the elimination of these bacteria.

VEGF and FGF-2 Released In Palatal Suture after Rapid Maxillary Expansion (RME)

Vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (FGF-2) have the ability to increase vascular proliferation and permeability. The aim of this study was to quantify the release of two diffusible angiogenic growth factors (VEGF and FGF-2) after rapid maxillary expansion (RME). Thirty animals were randomly assigned to two groups. Control group (5 rats - intact suture) and Experimental groups (25 rats with RME) which were evaluated in different periods of treatment. Five animals were euthanized in different periods of healing at 0, 1, 2, 3, 5 and 7 days after RME. RT-PCR was used to evaluate the gene expression of angiogenic growth factors released on different periods of study. Data were submitted to statistical analysis using ANOVA followed by Tukey test and significance was assumed at a=0.05. RT-PCR showed that mRNAs of VEGF and FGF-2 were expressed in intact palatal suture tissue. mRNAs of VEGF and FGF-2 was upregulated in early periods (24 h) after RME (p<0.001 and p<0.01, respectively). The molecular levels of VEGF never returned to its original baseline values, and FGF-2 expression decreased up to day 5 (p<0.001) and suddenly increased at day 7, returning to its original level. RME increased VEGF secretion, but decreased FGF-2 secretion when compared to intact tissue. The results showed that these angiogenic growth factors are released and regulated in the palatal suture tissue after RME and could make an important contribution to the knowledge of overall reparative response of the suture tissue during the bone remodeling process.

MicroRNAs: emerging players in apical periodontitis

Apical periodontitis is an inflammatory disorder of periradicular tissues developed from endodontic infections. Understanding its pathophysiology and the underlying molecular mechanisms is key to the advancement of endodontics. MicroRNAs (miRNAs), a group of evolutionarily conserved small non-coding RNAs, may be phenotypically and functionally associated with the pathogenesis of apical periodontitis. Several studies have focused on the role of miRNAs in the pulp and periradicular biology, and they have demonstrated their essential functions, such as initiating odontogenic differentiation and promoting pro- or anti-inflammatory responses in pulpitis. Up to date, over 2,000 miRNAs have been discovered in humans; however, only few have been reported to associate with apical periodontitis. Therefore, identifying miRNAs involved in diseased apical tissues and conducting functional studies are important in expanding our current knowledge of pulp and periradicular biology and exploring novel therapeutic avenues. In this review, we revisit current models of apical periodontitis and miRNA biogenesis, analyze existing evidence of the involvement of miRNAs in diseased apical tissues, and discuss their diverse functions and potential values. Based on their sheer abundance, prolonged stability in biofluid, and relative ease of sampling, miRNAs may be a useful tool to be developed as diagnostic biomarkers for apical periodontitis. Furthermore, it can be used as therapeutic targets in conjunction with conventional endodontic therapies.

Photobiomodulation effect of red LED (630 nm) on the free radical levels produced by pulp cells under stress conditions

The aim of this study was to assess the ability of red light emitting diodes (LED) to modulate oxidative stress in human dental pulp fibroblasts (HDPFs) when different irradiation parameters are employed. Cells from primary teeth were seeded (100,000 cells/well) in 24-well plates in culture medium (DMEM). At 24 h after incubation, the culture medium was replaced with DMEM containing 10 μg/mL lipopolysaccharide (LPS). Thereafter, the cells were irradiated (LED 630 nm, 0.04 W/cm² and 0.08 W/cm²) at 0 J/cm² (control group), 4 J/cm², 15 J/cm², and 30 J/cm²; and their viability (MTT assay), number (Trypan Blue), synthesis of nitric oxide (NO) (Griess reagent), and reactive oxygen species (ROS) (fluorescence probe, DCFH-DA) were assessed. The Kruskal-Wallis and Mann-Whitney statistical tests using Bonferroni correction were employed (significance level of 5%). Compared to that in control fibroblasts, increased viability was observed in HDPFs exposed to LPS and irradiated with 15 J/cm² and 30 J/cm² at 0.04 W/cm² and 4 J/cm² and 15 J/cm² at 0.08 W/cm² (p < 0.05). Exposure to 4 J/cm² at 0.04 W/cm² and 15 J/cm² and 30 J/cm² at 0.08 W/cm² modulated the oxidative stress in cells relative to that observed in non-irradiated LPS-treated pulp cells (p < 0.05). It was concluded that the irradiation strategies of using red LED with radiant exposures of 15 J/cm² and 30 J/cm² at 0.04 W/cm² and 15 J/cm² at 0.08 W/cm² were the best parameters to decrease NO and ROS concentration and to stimulate viability of HDPFs exposed to LPS challenge.

Inflammatory Response Mechanisms of the Dentine-Pulp Complex and the Periapical Tissues

The macroscopic and microscopic anatomy of the oral cavity is complex and unique in the human body. Soft-tissue structures are in close interaction with mineralized bone, but also dentine, cementum and enamel of our teeth. These are exposed to intense mechanical and chemical stress as well as to dense microbiologic colonization. Teeth are susceptible to damage, most commonly to caries, where microorganisms from the oral cavity degrade the mineralized tissues of enamel and dentine and invade the soft connective tissue at the core, the dental pulp. However, the pulp is well-equipped to sense and fend off bacteria and their products and mounts various and intricate defense mechanisms. The front rank is formed by a layer of odontoblasts, which line the pulp chamber towards the dentine. These highly specialized cells not only form mineralized tissue but exert important functions as barrier cells. They recognize pathogens early in the process, secrete antibacterial compounds and neutralize bacterial toxins, initiate the immune response and alert other key players of the host defense. As bacteria get closer to the pulp, additional cell types of the pulp, including fibroblasts, stem and immune cells, but also vascular and neuronal networks, contribute with a variety of distinct defense mechanisms, and inflammatory response mechanisms are critical for tissue homeostasis. Still, without therapeutic intervention, a deep carious lesion may lead to tissue necrosis, which allows bacteria to populate the root canal system and invade the periradicular bone via the apical foramen at the root tip. The periodontal tissues and alveolar bone react to the insult with an inflammatory response, most commonly by the formation of an apical granuloma. Healing can occur after pathogen removal, which is achieved by disinfection and obturation of the pulp space by root canal treatment. This review highlights the various mechanisms of pathogen recognition and defense of dental pulp cells and periradicular tissues, explains the different cell types involved in the immune response and discusses the mechanisms of healing and repair, pointing out the close links between inflammation and regeneration as well as between inflammation and potential malignant transformation.

Vascular Endothelial Growth Factor: A Translational View in Oral Non-Communicable Diseases

Vascular endothelial growth factors (VEGFs) are vital regulators of angiogenesis that are expressed in response to soluble mediators, such as cytokines and growth factors. Their physiologic functions include blood vessel formation, regulation of vascular permeability, stem cell and monocyte/macrophage recruitment and maintenance of bone homeostasis and repair. In addition, angiogenesis plays a pivotal role in chronic pathologic conditions, such as tumorigenesis, inflammatory immune diseases and bone loss. According to their prevalence, morbidity and mortality, inflammatory diseases affecting periodontal tissues and oral cancer are relevant non-communicable diseases. Whereas oral squamous cell carcinoma (OSCC) is considered one of the most common cancers worldwide, destructive inflammatory periodontal diseases, on the other hand, are amongst the most prevalent chronic inflammatory conditions affecting humans and also represent the main cause of tooth loss in adults. In the recent years, while knowledge regarding the role of VEGF signaling in common oral diseases is expanding, new potential translational applications emerge. In the present narrative review we aim to explore the role of VEGF signaling in oral cancer and destructive periodontal inflammatory diseases, with emphasis in its translational applications as potential biomarkers and therapeutic targets.

Neutrophils defending the defenders

Neutrophils are the most abundant granulocytes which are involved in defense mechanism. As innate immune cells, they are first-line defenders and can perform different functions in the human body to maintain equilibrium. Neutrophils are the main leukocyte and their role in healthy oral cavity is to face pathological changes within oral environment. With regard to these, it has been observed that neutrophils are highly heterogeneous in their behavior. The aim of this review is to give an overview of the role of neutrophils in context of various physiological and pathological conditions.

Expression Profiling and Functional Characterization of MicroRNAs in Apical Periodontitis

INTRODUCTION

MicroRNAs (miRNAs) are evolutionarily conserved small noncoding RNAs that may orchestrate the pathogenesis of apical periodontitis (AP). This study aimed to identify differentially expressed miRNAs and investigate their target gene pathways in AP.

METHODS

Total RNA was extracted from 10 human AP and 2 healthy apical tissues (controls) and subjected to miRNA sequencing for the identification of differentially expressed miRNAs (>1.5-fold changes). The function of the most up-regulated miRNA was further studied in vitro. miR-10a-5p mimics and inhibitors were introduced to human stem cells from the apical papilla and K-562 cells challenged with lipopolysaccharide, and expressions of predicted target genes were examined via quantitative reverse-transcription polymerase chain reaction and RNA sequencing.

RESULTS

A total of 852 miRNAs were identified, of which 12 were significantly up-regulated (1.54- to 8.44-fold) and 94 were significantly down-regulated (0.14- to 0.67-fold) in AP. Predicted target genes of these miRNAs are involved in inflammation, pain, and related pathways. miR-10a-5p showed the highest expression levels in AP. Overexpression of miR-10a-5p in LPS-challenged stem cells from the apical papilla resulted in down-regulation of messenger RNA levels of TNFA and up-regulation of interleukin IL10. RNA sequencing of K-562 cells treated with miR-10a-5p mimics and inhibitors identified miR-10a-5p target genes associated with multiple pathways, including macrophage-mediated inflammation and coagulation pathways.

CONCLUSIONS

Over 100 miRNAs were differentially expressed in AP and appeared to be involved with modulation of genes in inflammatory and immune pathways. MiR-10a-5p was the most significantly up-regulated miRNA in AP and may play a critical role in suppressing inflammation and promoting healing.

Expression of Inflammatory Markers RANK, MMP-9 and PTHrP in Chronic Apical Periodontitis from People Living with HIV Undergoing Antiretroviral Therapy

To compare the expression of the receptor activator of nuclear factor-kappa B (RANK), matrix metalloproteinase 9 (MMP-9) and parathyroid hormone-related protein (PTHrP) in primary chronic apical periodontitis lesions (CAPLs) between people living with HIV (PLWHIV) undergoing antiretroviral therapy (ART) and HIV- individuals, 32 CAPLs (16 lesions from each group) were submitted to histopathological and immunohistochemical analyses and compared between groups. The majority of the PLWHIV group had undetectable plasma viral loads (n = 13; 81.3%). The means of TCD4+ lymphocytes, exposure to HIV-1 and the time of the use of ART were 542.1 cells/mm³ (SD = 256.4), 6.3 years (SD = 2.9) and 5.0 years (SD = 2.5), respectively. Of all variables studied, only histopathological diagnosis showed a significant difference between groups (LWHIV: granuloma n = 11 (68.0%); cyst n = 5 (31.2%); HIV-: granuloma n = 15 (93.8%); cyst n = 1 (6.2%); p = 0.015). When comparing the expressions of the three inflammatory markers between the groups, no significant differences were seen. There was no difference in the expression of RANK, PTHrP and MMP-9 in primary chronic apical periodontitis lesions between PLWHIV under ART and HIV- individuals.

Proteomic analysis of human dental pulp in different clinical diagnosis

OBJECTIVES

The present study aimed to identify proteins obtained from pulp tissue and correlate with each clinical diagnosis (healthy pulp, inflamed pulp, and necrotic pulp).

MATERIALS AND METHODS

A total of forty-five molars were used. Three biological replicas were evaluated. Lysis and sonication were used for protein extraction. Protein quantification was assessed by using the Bradford technique, and shotgun proteome analysis was performed by nanoUPLC-MS^E using a Synapt G2 mass spectrometer. Mass spectra data were processed using the Waters PLGS software, and protein identification was done using the human Uniprot database appended to the PLGS search engine.

RESULTS

A total of 123 different proteins were identified in all evaluated pulp conditions. Among these, 66 proteins were observed for healthy pulp, 66 for inflamed pulp, and 91 for necrotic pulp. Most protein identification was related to immune response, multi-organism process, platelet activation, and stress in inflamed pulp samples compared to healthy pulp. Proteins related to cellular component organization or biogenesis, developmental process, growth, immune response, multi-organism process, response to stimulus, signaling, stress, and transport were identified in cases of apical periodontitis compared to inflamed pulp.

CONCLUSIONS

The progression of the disease to inflamed pulp promoted a high abundance of proteins related to the immune system and stress. Comparing the necrotic pulp with inflamed pulp conditions, a high abundance of proteins was noticed related to metabolism, transport, and response between organisms.

CLINICAL RELEVANCE

This finding may assist in future studies of new markers, understanding of tissue engineering, and development of future products.

Mineral trioxide aggregate (MTA) inhibits osteoclastogenesis and osteoclast activation through calcium and aluminum activities

OBJECTIVE

To evaluate the effect(s) of mineral trioxide aggregate (MTA) on in vitro RANKL-mediated osteoclast-dependent bone resorption events and the influence of Ca²⁺ and Al³⁺ on the osteoclastogenesis inhibition by MTA.

MATERIALS AND METHODS

Two types of osteoclast precursors, RAW 264.7 (RAW) cell line or bone marrow cells (obtained from BALB/c mice and stimulated with recombinant (r) macrophage colony stimulation factor (M-CSF), were stimulated with or without recombinant (r) activator of nuclear kappa B ligand (RANKL), in the presence or absence of MTA for 6 to 8 days. White Angelus MTA and Bios MTA (Angelus, Londrina, Paraná, Brazil) were prepared and inserted into capillary tubes (direct contact surface = 0.50 mm² and 0.01 mm²). Influence of MTA on these types of osteoclast precursors was measured by the number of differentiated tartrate-resistant acid phosphatase (TRAP)-positive multinuclear cells (RAW and bone marrow cells), TRAP enzyme activity (RAW cells), cathepsin K gene expression (RAW cells), and resorptive pit formation (RAW cells) by mature osteoclasts. Besides, RAW cells were also stimulated with Ca²⁺ and Al³⁺ to evaluate the influence of these ions on MTA anti-osteoclastogenic potential.

RESULTS

In bone marrow and RAW cells, the number of TRAP-positive mature osteoclast cells induced by rRANKL was significantly inhibited by the presence of MTA compared with control rRANKL stimulation without MTA (p < 0.05), along with the reduction of TRAP enzyme activity (p < 0.05) and the low expression of cathepsin K gene (p < 0.05). In contrast, to control mature osteoclasts, the resorption area on dentin was significantly decreased for mature osteoclasts incubated with MTA (p < 0.05). rRANKL-stimulated RAW cells treated with Ca²⁺ and Al³⁺ decreased the number of osteoclasts cells. Besides, the aluminum oxide was the dominant suppressor of the osteoclastogenesis process.

CONCLUSIONS

MTA significantly suppressed RANKL-mediated osteoclastogenesis and osteoclast activity and, therefore, appears able to suppress bone resorption events in periapical lesions. This process might be related to Ca²⁺ and Al³⁺ activities.

CLINICAL RELEVANCE

MTA is an important worldwidely acknowleged biomaterial. The knowledge about its molecular activities on osteoclasts might contribute to improving the understanding of its clinical efficacy.

Clinical Study of Sodium Hypochlorite, Polymyxin B And Limewater Effect on MMP-3,-8,-9 In Apical Periodontitis

This study aimed to evaluate sodium hypochlorite (NaOCl), limewater (LW), and Polymyxin B (PMB) as irrigants over MMP-3, MMP-8 and MMP-9. Thirty-three patients with apical periodontitis of single-rooted teeth were treated according to three-experimental groups (n=11): group-1: 2.5% NaOCl was used as irrigant; group-2: 2.5% NaOCl for the first two files and LW: [0.14% Ca(OH)2] for the last two files; group-3: 2.5% NaOCl for the first two files and PMB for the last two files. The association of Ca(OH)2 and CHX was used as an intracanal medication in all groups. Four root canal samplings (S) were collected: S1) immediately after access cavity; S2) after biomechanical preparation; S3) after EDTA application; and S4) after removal of the intracanal medication. After quantification of MMP-3, MMP-8, and MMP-9, the data were analyzed by Friedman and Kruskal-Wallis tests and completed by Dunn test (5%). Regardless the used irrigant, there was no difference in reducing MMP-3 or MMP-8 (P=0,5273, P=0,7048 respectively). However, in reducing MMP-9 (P=0,0246) the NaOCl group was the most effective followed by NaOCl+LW group and NaOCl+PMB group respectively. The intracanal medication [Ca(OH)2 + CHX] with the NaOCl and NaOCl+LW was effective in reducing MMP-8 (P<0,0001, P=0,0025) and MMP-9 (P=0,0007, P=0,0047) respectively, but not for the group of NaOCl+PMB which was not effective in reducing MMP-8 or MMP-9 (P=0,1718, P=0,1953) respectively. NaOCl and NaOCl+LW were effective in reducing MMP-9 levels, and this effectivity could be improved by the use of the intracanal medication [Ca(OH)2 + CHX] in reducing MMP-8 and MMP-9 levels.

Association of DNA sequence-independent genetic regulatory mechanisms with apical periodontitis: A scoping review

OBJECTIVE

Different studies in the last decade have proposed that gene expression alterations that are independent of the DNA sequence may also play an important role in periapical disease. The present study aimed to assess the available evidence supporting a relationship between these alterations and apical periodontitis through a scoping review.

DESIGN

Specific strategies were developed for different databases (MEDLINE via PubMed, Cochrane Library, Scopus, Web of Science, and Virtual Health Library) and a search performed by March 1st, 2019. The evidence sources were selected according to the eligibility criteria and underwent a critical appraisal of methodological quality.

RESULTS

The initial search retrieved 212 references, with eight eligible articles after the removal of replicates and application of exclusion criteria. Five studies identified altered DNA methylation on inflammatory response genes (FOXP3, CXCL3, FADD, MMP2, MMP9, IFNG, IL4, IL12) on AP patients. Three others identified the alterations on the expression of several microRNAs (miR-29b, 106b, 125b, 143, 146a, 155, 198) during AP. No evidence was identified regarding mechanisms of histone methylation, or of epigenetic heritability or stability.

CONCLUSIONS

There is available evidence for the involvement of different genetic regulatory mechanisms independent of changes in DNA sequence in the development or severity of apical periodontitis. However, due to methodological limitations, further research must be performed before novel therapies and diagnostic tools for AP may arise from these data.

Aggregatibacter, A Low Abundance Pathobiont That Influences Biogeography, Microbial Dysbiosis, and Host Defense Capabilities in Periodontitis: The History of A Bug, And Localization of Disease

Aggregatibacter actinomycetemcomitans, the focus of this review, was initially proposed as a microbe directly related to a phenotypically distinct form of periodontitis called localized juvenile periodontitis. At the time, it seemed as if specific microbes were implicated as the cause of distinct forms of disease. Over the years, much has changed. The sense that specific microbes relate to distinct forms of disease has been challenged, as has the sense that distinct forms of periodontitis exist. This review consists of two components. The first part is presented as a detective story where we attempt to determine what role, if any, Aggregatibacter plays as a participant in disease. The second part describes landscape ecology in the context of how the host environment shapes the framework of local microbial dysbiosis. We then conjecture as to how the local host response may limit the damage caused by pathobionts. We propose that the host may overcome the constant barrage of a dysbiotic microbiota by confining it to a local tooth site. We conclude speculating that the host response can confine local damage by restricting bacteremic translocation of members of the oral microbiota to distant organs thus constraining morbidity and mortality of the host.