Green synthesis of nanohydroxyapatite with Elaeagnus angustifolia L. extract as a metronidazole nanocarrier for in vitro pulpitis model treatment.

The aim of this study is to introduce a dental capping agent for the treatment of pulp inflammation (pulpitis). Nanohydroxyapatite with Elaeagnus angustifolia L. extract (nHAEA) loaded with metronidazole (nHAEA@MTZ) was synthesized and evaluated using a lipopolysaccharide (LPS) in vitro model of pulpitis. nHAEA was synthesized through sol-gel method and analyzed using Scanning Electron Microscopy, Transmission Electron Microscopy, and Brunauer Emmett Teller. Inflammation in human dental pulp stem cells (HDPSCs) induced by LPS. A scratch test assessed cell migration, RT PCR measured cytokines levels, and Alizarin red staining quantified odontogenesis. The nHAEA nanorods were 17-23 nm wide and 93-146 nm length, with an average pore diameter of 27/312 nm, and a surface area of 210.89 m2/g. MTZ loading content with controlled release, suggesting suitability for therapeutic applications. nHAEA@MTZ did not affect the odontogenic abilities of HDPSCs more than nHAEA. However, it was observed that nHAEA@MTZ demonstrated a more pronounced anti-inflammatory effect. HDPSCs treated with nanoparticles exhibited improved migration compared to other groups. These findings demonstrated that nHAEA@MTZ could be an effective material for pulp capping and may be more effective than nHAEA in reducing inflammation and activating HDPSCs to enhance pulp repair after pulp damage.

Inhibiting Nav1.7 channels in pulpitis: An in vivo study on neuronal hyperexcitability.

Pulpitis constitutes a significant challenge in clinical management due to its impact on peripheral nerve tissue and the persistence of chronic pain. Despite its clinical importance, the correlation between neuronal activity and the expression of voltage-gated sodium channel 1.7 (Nav1.7) in the trigeminal ganglion (TG) during pulpitis is less investigated. The aim of this study was to examine the relationship between experimentally induced pulpitis and Nav1.7 expression in the TG and to investigate the potential of selective Nav1.7 modulation to attenuate TG abnormal activity associated with pulpitis. Acute pulpitis was induced at the maxillary molar (M1) using allyl isothiocyanate (AITC). The mice were divided into three groups: control, pulpitis model, and pulpitis model treated with ProTx-II, a selective Nav1.7 channel inhibitor. After three days following the surgery, we conducted a recording and comparative analysis of the neural activity of the TG utilizing in vivo optical imaging. Then immunohistochemistry and Western blot were performed to assess changes in the expression levels of extracellular signal-regulated kinase (ERK), c-Fos, collapsin response mediator protein-2 (CRMP2), and Nav1.7 channels. The optical imaging result showed significant neurological excitation in pulpitis TGs. Nav1.7 expressions exhibited upregulation, accompanied by signaling molecular changes suggestive of inflammation and neuroplasticity. In addition, inhibition of Nav1.7 led to reduced neural activity and subsequent decreases in ERK, c-Fos, and CRMP2 levels. These findings suggest the potential for targeting overexpressed Nav1.7 channels to alleviate pain associated with pulpitis, providing practical pain management strategies.

Macrophage M2 polarization promotes pulpal inflammation resolution during orthodontic tooth movement.

Mechanical force induces hypoxia in the pulpal area by compressing the apical blood vessels of the pulp, triggering pulpal inflammation during orthodontic tooth movement. However, this inflammation tends to be restorable. Macrophages are recognized as pivotal immunoreactive cells in the dental pulp. Whether they are involved in the resolution of pulpal inflammation in orthodontic teeth remains unclear. In this study, we investigated macrophage polarization and its effects during orthodontic tooth movement. It was demonstrated that macrophages within the dental pulp polarized to M2 type and actively participated in the process of pulpal inflammation resolution. Inflammatory reactions were generated and vascularization occurred in the pulp during orthodontic tooth movement. Macrophages in orthodontic pulp show a tendency to polarize towards M2 type as a result of pulpal hypoxia. Furthermore, by blocking M2 polarization, we found that macrophage M2 polarization inhibits dental pulp-secreting inflammatory factors and enhances VEGF production. In conclusion, our findings suggest that macrophages promote pulpal inflammation resolution by enhancing M2 polarization and maintaining dental health during orthodontic tooth movement.

Influence of IgA nephropathy on the progression of pulpitis and apical periodontitis in HIGA mice.

OBJECTIVES: Immunoglobulin (Ig)A nephropathy has been associated with oral infections such as periodontitis, but its pathogenesis is not fully understood; no treatments exist. This study analyzes the influence of IgA nephropathy, an autoimmune disease, on the pathogenesis of pulpitis and apical periodontitis. METHODS: Two groups of mice were used in pulp infection experiments: high serum IgA nephropathy model mice (HIGA) and control mice (BALB/c). Histologic analyses of the pulp and apical periodontal tissues were performed on days 3, 5, 7, 14, and 28 following oral bacterial infection. The dynamics of odontoblasts, apoptotic cells, and IgA expression were analyzed using anti-Nestin, TUNEL, and anti-IgA staining, respectively. RESULTS: Inflammatory cells infiltrated the exposed pulp at day three in both groups and by 14 days, these cells had infiltrated from the pulp to the apical periodontal tissue. The area of necrotic pulp tissue increased significantly in the control group at seven days. Odontoblasts decreased from day three onwards and disappeared by 28 days in both groups. The number of apoptotic cells in the pulp and apical periodontal tissues was significantly higher in the experimental group at day 28. The experimental group exhibited a significant increase in IgA production in the pulp after 14 days. Bone resorption in the apical periodontal tissue was significantly decreased in the experimental group at day 28. CONCLUSIONS: The results of this study suggest that IgA nephropathy may modulate the inflammatory response and sustain long-term biological defense responses in pulpitis and apical periodontitis in HIGA mice.

Cell-Based Regenerative Endodontics for the Treatment of Irreversible Pulpitis: AnIn VivoInvestigation.

INTRODUCTION: This study aims to investigate the ability of umbilical cord mesenchymal stem cells (UC-MSC) to enhance the regeneration of pulp-dentin complex in immature permanent teeth with irreversible pulpitis. METHODS: A total of 32 mandibular premolar teeth with immature apices in 5 dogs were used in this in-vivo randomized controlled trial (RCT). Eight healthy teeth without pre-existing pathosis served as the positive control samples and received no treatment, while in another 8 teeth, the pulp was completely extirpated (negative control). Class V cavities were prepared to induce inflammation in the remaining 16 teeth (groups 3 and 4) and the pulp was extirpated 2-4 mm short of the radiographic apex. Of the 16, the 8 teeth in group 4 received 1 mL of cord blood stem cells with a hydrogel scaffold. Blood clots were covered with mineral trioxide aggregates at the cementoenamel junction in the experimental groups, and teeth were filled with RMGI and composite. Three months later, block sections were removed for histologic evaluations for the evaluation of postoperative apical closure, degree of inflammation, and presence of normal pulp tissue. The data were statistically analyzed with the chi-square test (P < .05). RESULTS: All teeth with complete pulp extirpation demonstrated pulpal necrosis with no postoperative closure of their apices, while apical closure was seen in all the teeth in the remaining groups. There was a statistically significant (P < .001) difference in the presence of inflammation and normal pulp tissue between the experimental groups. The teeth in group 3 showed normal pulp tissue extending to the level of MTA, but there was inflammation within the canal space. In contrast, the teeth in the UC-MSC group demonstrated organized, normal pulp tissue with no inflammation. CONCLUSION: Based on these results, the regeneration of the pulp-dentin complex is possible with no inflammation when UC-MSCs are used and 2-4 mm of the apical pulp remains intact in immature teeth with irreversible pulpitis.

Establishment of a Murine Pulp Exposure Model with a Novel Mouth-Gag for Pulpitis Research.

Pulpitis, a common cause of natural tooth loss, leads to necrosis and loss of bioactivity in the inflamed dental pulp. Unraveling the mechanisms underlying pulpitis and its efficient treatment is an ongoing focus of endodontic research. Therefore, understanding the inflammatory process within the dental pulp is vital for improving pulp preservation. Compared to other in vitro experiments, a murine pulpitis model offers a more authentic and genetically diverse context to observe the pathological progression of pulpitis. However, using mice, despite their cost-effectiveness and accessibility, poses difficulties due to their small size, poor coordination, and low tolerance, complicating intraoral and dental procedures. This protocol introduces a novel design and application of a mouth-gag to expose mouse pulp, facilitating more efficient intraoral procedures. The mouth-gag, comprised of a dental arch readily available to most dentists and can significantly expedite surgical preparation, even for first-time procedures. Micro-CT, hematoxylin-eosin (HE) staining, and immunofluorescence staining were used to identify changes in morphology and cell expression. The aim of this article is to help researchers establish a more reproducible and less demanding procedure for creating a pulp inflammation model using this novel mouth-gag.

Vital Pulp Therapy of Young First Permanent Molars: A Retrospective Study on Radiographic Findings 24 Months Post-treatment.

PURPOSE: With success rates comparable to that of root canal treatment, vital pulp therapy (VPT) has gained clinical interest and has been used in the management of young permanent teeth with inflamed pulps. The aim of the present study was to retrospectively evaluate the radiographic success of VPT in young first permanent molars 24 months post-treatment and correlate findings with tooth and treatment-related characteristics. MATERIALS AND METHODS: Dental records of all patients with first permanent molars which received VPT in the Department of Paediatric Dentistry (National and Kapodistrian University of Athens) were retrieved. Demographic characteristics and data regarding the treatment performed were recorded. Patients' radiographs were evaluated at 6, 12 and 24 months post-treatment by two qualified paediatric dentists blinded regarding the treatment performed. Radiographic success, reasons for failure and continuation of root development were evaluated. Differences were tested using the Χ2 and Student's t-test, and possible correlations were determined by calculating the odds ratio. RESULTS: Overall radiographic success rate at 24 months was 77%, ranging between 50% for direct pulp capping and 92% for full pulpotomy. Differences were not statistically significant. Continuation of root development was recorded in almost 1/3 of the teeth and completion in almost 1/5. No statistically significant association was recorded between the outcome and any tooth and treatment-related variables. CONCLUSION: VPT seems to be a reliable option in the long term for the treatment of deep carious lesions in young permanent molars.

Microscopic Alterations of the Dental Pulp in Surgically Extracted Teeth of Dogs.

Microscopic alterations in the dental pulp of dogs have not been extensively studied. The aim of this study was to investigate microscopic alterations of the dental pulp in dogs' teeth. One hundred and ten surgically extracted teeth (20 incisors, 23 canines, 28 premolars, and 39 molars) from 74 dogs, of different ages, with a history of chronic periodontitis (66 dogs), periapical abscesses (2 dogs), pulpitis (2 dogs), oral cavity neoplasms (2 dogs), dens invaginatus (1 dog), and dental fractures (1 dog) were included. Eight-one maxillary and 29 mandibular teeth were included. Coronal, radicular, and coronal plus radicular calculus were present in 28.2%, 17.3%, and 54.5% of the teeth, respectively. In total 78 teeth (71%) had pulp alterations, including fibrosis (26%), calcification (14%), necrosis associated with the absence of odontoblasts (14%), presence of predentin and dentin inside the cavity (8%), odontoblastic hyperplasia (3%), pigmentation (3%), pulpitis (2%), and pulp stones (1%). Forty-nine (60.5%) of the maxillary teeth and all of the mandibular teeth had pulp alterations. The premolars were most affected, and the molars least affected, by pulp alterations. Pulp fibrosis, calcification, and necrosis were observed in teeth irrespective of the distribution of dental calculus.

Determination of the Severity of Pulpitis by Immunohistological Analysis and Comparison with the Clinical Picture.

INTRODUCTION: Inflammation of the dental pulp due to caries is a highly prevalent pathology which causes intense pain. Here, we sought to correlate the clinical picture with the histopathology of the affected tissue. The interaction between nociceptive neurons and immune cells is fundamental to regulate the inflammatory response, but little is known about the glial network involved in this process, and its impact on caries pathogenesis. METHODS: This study characterized Schwann cells and other neuroimmune components in human dental pulps with reversible and symptomatic irreversible pulpitis (IP). Twenty eight human teeth were extracted for reasons beyond the scope of this study. Twelve were diagnosed as reversible and symptomatic IP respectively, and 4 as controls. The teeth were decalcified, processed for immunolabeling and analyzed with confocal microscopy. RESULTS: Symptomatic IP was characterized by a significantly higher density of neutrophils, and the release of neutrophil extracellular traps. Between IP and healthy controls, there were significant differences in the density of Schwann cells, macrophages, and neutrophils, in addition to morphological alterations. In IP, Schwann cell arborization extended toward the pulpodentinal interface along with more spindle-shaped cell bodies, while some macrophages displayed a distinct fusiform phenotype. CONCLUSIONS: The dental pulp has a complex multicellular organization and its pulpodentinal interface acts as a barrier in which Schwann and immune cells are distributed strategically to stop the progress of pathogens. A synergistic interaction of Schwann cells with immune cells creates a novel perspective to better understand the role of these glial cells and their active participation in pulpal inflammation.

Highly targeted electrochemical disruption of microbes with minimal disruption to pulp cells.

INTRODUCTION: Pulpitis results from the infiltration of mixed populations of bacteria which trigger inflammation in the dental pulp, causing significant disruption to these tissues. Clinically, pulpitis frequently leads to devitalization or extraction, as disinfection of the dental pulp while maintaining its vitality is extremely difficult. Here we describe the use of an electrocatalytic titanium dioxide (TiO2)-based apparatus adapted from water purification technology, which can efficiently deliver anti-microbial oxidants (e.g., hydroxyl radicals) when low voltages are applied. As these oxidants are also potentially harmful to pulp cells, oxidant exposure protocols that disrupt oral bacteria, yet are innocuous to dental pulp cells must be established. METHODS: Stem cells from Human Exfoliated Deciduous teeth (SHEDs) and mixed salivary bacteria were exposed to apparatus generated oxidants for time points of 15, 100 or 300 s. SHED apoptosis, necrosis, and vitality post exposure were analyzed by florescent marker staining and flow cytometry. Destruction of mixed salivary bacteria was analyzed by post exposure counts of adherent bacterial cells. RESULTS: When applied to SHEDs the apparatus generated oxidants do not significantly induce apoptosis or necrosis at any exposure time. SHED cell vitality is not decreased with apparatus exposure. Exposure to apparatus generated oxidants destroys mixed salivary bacteria, with significant destruction seen at 15 s and maximal destruction achieved at 100 s. CONCLUSIONS: This technology has the potential to be useful in the disinfection of deep lesions and pulp tissues, efficiently producing oxidants which eliminate bacteria but do not harm native pulp cells after relatively brief exposures. CLINICAL SIGNIFICANCE: Incomplete disinfection of inflamed dental pulp is a significant cause of pulp destruction, leading to devitalization or extraction. Novel technology which enhances the disinfection of the pulp may provide clinicians with treatments options that preserve pulp vitality and tooth structure.

Wnt signalling in oral and maxillofacial diseases.

Wnts include more than 19 types of secreted glycoproteins that are involved in a wide range of pathological processes in oral and maxillofacial diseases. The transmission of Wnt signalling from the extracellular matrix into the nucleus includes canonical pathways and noncanonical pathways, which play an important role in tooth development, alveolar bone regeneration, and related diseases. In recent years, with the in-depth study of Wnt signalling in oral and maxillofacial-related diseases, many new conclusions and perspectives have been reached, and there are also some controversies. This article aims to summarise the roles of Wnt signalling in various oral diseases, including periodontitis, dental pulp disease, jaw disease, cleft palate, and abnormal tooth development, to provide researchers with a better and more comprehensive understanding of Wnts in oral and maxillofacial diseases.

Analysis and Assessment of Pulp Vitality of 102 Intrinsically Stained Teeth in Dogs.

Our prospective study analyzed clinical, radiographic, and histological characteristics of 102 intrinsically stained teeth. Sixty-nine dogs ranging from one to fifteen years of age were included in this study. Little more than half of the intrinsically stained teeth had no evidence of coronal injury (53.9%, 55/102). We found that most intrinsically stained teeth were histologically nonvital (87.6%, 85/97) and approximately 2/3 of these (57.7%, 56/97) had no histological endodontic or periodontal inflammation at the time of evaluation. Radiographic evidence of endodontic disease was present in 57% (58/102) of the intrinsically stained teeth. Radiographic evidence of periodontal disease was present in 48% (49/102) of intrinsically stained teeth and 28% (29/102) had radiographic evidence of tooth resorption. 18.6% (19/102) of intrinsically stained teeth were radiographically normal. Evidence of pulp necrosis was common in these intrinsically stained teeth, while only occasional teeth (12.4%, 12/97) had histologically confirmed pulpitis. All teeth with radiographic evidence of periapical lucency had pulp necrosis. Based on our histological findings, the majority of intrinsically stained teeth 87.6% are truly nonvital.

3D Visualization of Dynamic Cellular Reaction of Pulpal CD11c+ Dendritic Cells against Pulpitis in Whole Murine Tooth.

In dental pulp, diverse types of cells mediate the dental pulp immunity in a highly complex and dynamic manner. Yet, 3D spatiotemporal changes of various pulpal immune cells dynamically reacting against foreign pathogens during immune response have not been well characterized. It is partly due to the technical difficulty in detailed 3D comprehensive cellular-level observation of dental pulp in whole intact tooth beyond the conventional histological analysis using thin tooth slices. In this work, we validated the optical clearing technique based on modified Murray's clear as a valuable tool for a comprehensive cellular-level analysis of dental pulp. Utilizing the optical clearing, we successfully achieved a 3D visualization of CD11c+ dendritic cells in the dentin-pulp complex of a whole intact murine tooth. Notably, a small population of unique CD11c+ dendritic cells extending long cytoplasmic processes into the dentinal tubule while located at the dentin-pulp interface like odontoblasts were clearly visualized. 3D visualization of whole murine tooth enabled a reliable observation of these rarely existing cells with a total number less than a couple of tens in one tooth. These CD11c+ dendritic cells with processes in the dentinal tubule were significantly increased in the dental pulpitis model induced by mechanical and chemical irritation. Additionally, the 3D visualization revealed a distinct spatial 3D arrangement of pulpal CD11c+ cells in the pulp into a front-line barrier-like formation in the pulp within 12 h after the irritation. Collectively, these observations demonstrated the unique capability of optical clearing-based comprehensive 3D cellular-level visualization of the whole tooth as an efficient method to analyze 3D spatiotemporal changes of various pulpal cells in normal and pathological conditions.

Mitochondrial DNA leakage induces odontoblast inflammation via the cGAS-STING pathway.

BACKGROUND: Mitochondrial DNA (mtDNA) is a vital driver of inflammation when it leaks from damaged mitochondria into the cytosol. mtDNA stress may contribute to cyclic GMP-AMP synthase (cGAS) stimulator of interferon genes (STING) pathway activation in infectious diseases. Odontoblasts are the first cells challenged by cariogenic bacteria and involved in maintenance of the pulp immune and inflammatory responses to dentine-invading pathogens. In this study, we investigated that mtDNA as an important inflammatory driver participated in defending against bacterial invasion via cGAS-STING pathway in odontoblasts. METHODS: The normal tissues, caries tissues and pulpitis tissues were measured by western blotting and immunohistochemical staining. Pulpitis model was built in vitro to evaluated the effect of the cGAS-STING pathway in odontoblast-like cell line (mDPC6T) under inflammation. Western blot and real-time PCR were performed to detect the expression of cGAS-STING pathway and pro-inflammatory cytokines. The mitochondrial function was evaluated reactive oxygen species (ROS) generated by mitochondria using MitoSOX Red dye staining. Cytosolic DNA was assessed by immunofluorescent staining and real-time PCR in mDPC6T cells after LPS stimulation. Furthermore, mDPC6T cells were treated with ethidium bromide (EtBr) to deplete mtDNA or transfected with isolated mtDNA. The expression of cGAS-STING pathway and pro-inflammatory cytokines were measured. RESULTS: The high expression of cGAS and STING in caries and pulpitis tissues in patients, which was associated with inflammatory progression. The cGAS-STING pathway was activated in inflamed mDPC6T. STING knockdown inhibited the nuclear import of p65 and IRF3 and restricted the secretion of the inflammatory cytokines CXCL10 and IL-6 induced by LPS. LPS caused mitochondrial damage in mDPC6T, which promoted mtDNA leakage into the cytosol. Depletion of mtDNA inhibited the cGAS-STING pathway and nuclear translocation of p65 and IRF3. Moreover, repletion of mtDNA rescued the inflammatory response, which was inhibited by STING knockdown. CONCLUSION: Our study systematically identified a novel mechanism of LPS-induced odontoblast inflammation, which involved mtDNA leakage from damaged mitochondria into the cytosol stimulating the cGAS-STING pathway and the inflammatory cytokines IL-6 and CXCL10 secretion. The mtDNA-cGAS-STING axis could be a potent therapeutic target to prevent severe bacterial inflammation in pulpitis. Video Abstract.

Autophagy in tooth: Physiology, disease and therapeutic implication.

Autophagy is an evolutionarily conserved cellular process, in which damaged organelles and proteins are engulfed in autophagic vesicles and subsequently fuse with lysosomes for degradation. Autophagy is widely involved in different physiologic or pathologic processes in human. Accumulating evidence indicates that autophagy operates as a critical quality control mechanism to maintain pulp homeostasis and structural integrity of the dentin-pulp complex. Autophagy is activated during stresses and is involved in the pathogenesis of pulpitis and periapical infection. Recent discoveries have also provided intriguing insights into the roles of autophagy in tooth development, pulp aging and stress adaptation. In this review, we provide an update on the multifaceted functions of autophagy in physiology and pathophysiology of tooth. We also discuss the therapeutic implications of autophagy modulation in diseases and the regeneration of dentin-pulp complex.

The Genetic and Epigenetic Mechanisms Involved in Irreversible Pulp Neural Inflammation.

AIM: To identify the critical genetic and epigenetic biomarkers by constructing the long noncoding RNA- (lncRNA-) related competing endogenous RNA (ceRNA) network involved in irreversible pulp neural inflammation (pulpitis). MATERIALS AND METHODS: The public datasets regarding irreversible pulpitis were downloaded from the gene expression omnibus (GEO) database. The differential expression analysis was performed to identify the differentially expressed genes (DEGs) and DElncRNAs. Functional enrichment analysis was performed to explore the biological processes and signaling pathways enriched by DEGs. By performing a weighted gene coexpression network analysis (WGCNA), the significant gene modules in each dataset were identified. Most importantly, DElncRNA-DEmRNA regulatory network and DElncRNA-associated ceRNA network were constructed. A transcription factor- (TF-) DEmRNA network was built to identify the critical TFs involved in pulpitis. RESULT: Two datasets (GSE92681 and GSE77459) were selected for analysis. DEGs involved in pulpitis were significantly enriched in seven signaling pathways (i.e., NOD-like receptor (NLR), Toll-like receptor (TLR), NF-kappa B, tumor necrosis factor (TNF), cell adhesion molecules (CAMs), chemokine, and cytokine-cytokine receptor interaction pathways). The ceRNA regulatory relationships were established consisting of three genes (i.e., LCP1, EZH2, and NR4A1), five miRNAs (i.e., miR-340-5p, miR-4731-5p, miR-27a-3p, miR-34a-5p, and miR-766-5p), and three lncRNAs (i.e., XIST, MIR155HG, and LINC00630). Six transcription factors (i.e., GATA2, ETS1, FOXP3, STAT1, FOS, and JUN) were identified to play pivotal roles in pulpitis. CONCLUSION: This paper demonstrates the genetic and epigenetic mechanisms of irreversible pulpitis by revealing the ceRNA network. The biomarkers identified could provide research direction for the application of genetically modified stem cells in endodontic regeneration.

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.

Anti-Inflammatory Effects of Melatonin and 5-Methoxytryptophol on Lipopolysaccharide-Induced Acute Pulpitis in Rats.

AIM: The aim of this study was to investigate the possible therapeutic impacts of two pineal hormones, melatonin and 5-methoxytryptophol (5-MTX), in a rat model of acute pulpitis by analyzing biochemical and histopathological parameters. METHODS: This research was done using 32 male and female Wistar albino rats with weight between 200 and 250 g. The rats were randomly divided into four groups: a control group (rats without any treatment), acute pulpitis (AP) group, AP+melatonin group, and AP+5-MTX group. In the AP-induced groups, the crowns of the upper left incisors were removed horizontally. Lipopolysaccharide solution was applied to the exposed pulp tissue before the canal orifices were sealed with a temporary filling material. Melatonin (10 mg/kg) and 5-MTX (5 mg/kg) were administered intraperitoneally. The rats were sacrificed 24 hours after pulp injury, and trunk blood and pulp samples were collected. The concentrations of TNF-α, IL-1ß, MMP-1, and MMP-2 in sera and pulp samples were determined using ELISA assay kits. RESULTS: TNF-α, IL-1ß, MMP-1, and MMP-2 levels in the serum and pulp tissues were considerably higher in the AP group than the control group (p < 0.01-0.001). In the AP+melatonin and AP+5-MTX groups, TNF-α, IL-1ß, MMP-1, and MMP-2 levels in the serum and pulp tissues were significantly lower than in the AP group (p < 0.05-0.001). CONCLUSIONS: Both melatonin and 5-MTX provided protective effects on acute pulpitis, which indicates they may be promising as a therapeutic strategy for oral disease.

Long noncoding RNA MEG3 expressed in human dental pulp regulates LPS-Induced inflammation and odontogenic differentiation in pulpitis.

Pulpitis refers to inflammation of the inner pulp by invading microbes, and tissue repair occurs due to odontogenic differentiation of human dental pulp cells (hDPCs) with multidifferentiation potential. Long noncoding RNAs (lncRNAs) can modulate numerous pathological and biological processes; however, the role of lncRNAs in the inflammation and regeneration of the dentin-pulp complex in pulpitis is unclear. Here, we performed high-throughput sequencing to identify differentially expressed lncRNAs between human normal and inflamed pulp and concluded that lncMEG3 (lncRNA maternally expressed gene 3, MEG3) was significantly upregulated in both inflamed pulp and LPS-treated hDPCs. MEG3 expression in the pulp tissue was detected using the RNAscope® technique. RNA pulldown assays identified the MEG3-interacting proteins and the potential mechanisms. With MEG3 knockdown, we investigated the role of MEG3 in the secretion of inflammatory cytokines in LPS-treated hDPCs and odontogenic differentiation of hDPCs. MEG3 downregulation inhibited the secretion of TNF-α, IL-1ß and IL-6 in LPS-treated hDPCs, and the p38/MAPK signaling pathway may be related to this effect. MEG3 knockdown promoted odontogenic differentiation of hDPCs by regulating the Wnt/ß-catenin signaling pathway. Our study suggested that MEG3 has a negative effect on inflammation and regeneration of the dentin-pulp complex in pulpitis.

Role of macrophage-mediated Toll-like receptor 4-interleukin-1R signaling in ectopic tongue pain associated with tooth pulp inflammation.

BACKGROUND: The existence of referred pain and ectopic paresthesia caused by tooth pulp inflammation may make definitive diagnosis difficult and cause misdiagnosis or mistreatment; thus, elucidation of that molecular mechanism is urgent. In the present study, we investigated the mechanisms underlying ectopic pain, especially tongue hyperalgesia, after tooth pulp inflammation. METHODS: A rat model with mandibular first molar tooth pulp exposure was employed. Tooth pulp exposure-induced heat and mechanical-evoked tongue hypersensitivity was measured, and immunohistochemical staining for Iba1, a marker of active macrophages, IL-1ß, IL-1 type I receptor (IL-1RΙ), and toll-like receptor 4 in the trigeminal ganglion was performed. In addition, we investigated the effects of injections of liposomal clodronate Clophosome-A (LCCA), a selective macrophage depletion agent, lipopolysaccharide from Rhodobacter sphaeroides (LPS-RS, a toll-like receptor 4 antagonist), IL-1ß, or heat shock protein 70 (Hsp70, a selective agonist of toll-like receptor 4), to examine changes in tongue hypersensitivity and in the regulation of IL-1RΙ, toll-like receptor 4, and transient receptor potential vanilloid 1 (TRPV1) biosynthesis. RESULTS: At day 1 after tooth pulp exposure, obvious tooth pulp inflammation was observed. Tooth pulp exposure-induced heat and mechanical tongue hypersensitivity was observed from days 1 to 3 after tooth pulp exposure. The production of IL-1ß in activated macrophages and toll-like receptor 4 and IL-1RΙ expression were significantly increased in trigeminal ganglion neurons innervating the tongue following tooth pulp exposure. Intra-trigeminal ganglion injection of LCCA significantly suppressed tongue hypersensitivity; however, toll-like receptor 4 and IL-1RΙ expression in trigeminal ganglion neurons innervating the tongue was not significantly altered. Intra-trigeminal ganglion injection of LPS-RS significantly suppressed tongue hypersensitivity and reduced IL-1RΙ expression in the trigeminal ganglion neurons innervating the tongue following tooth pulp exposure. Intra-trigeminal ganglion injection of recombinant Hsp70 significantly promoted tongue hypersensitivity and increased IL-1RI expression in trigeminal ganglion neurons innervating the tongue in naive rats. Furthermore, intra-trigeminal ganglion injection of recombinant IL-1ß led to tongue hypersensitivity and enhanced TRPV1 expression in trigeminal ganglion neurons innervating the tongue in naive rats. CONCLUSIONS: The present findings suggest that the neuron-macrophage interaction mediated by toll-like receptor 4 and IL-1RI activation in trigeminal ganglion neurons affects the pathogenesis of abnormal tongue pain following tooth pulp inflammation via IL-1RI and TRPV1 signaling in the trigeminal ganglion. Further research may contribute to the establishment of new therapeutic and diagnostic methods.