Potential Novel Strategies for the Treatment of Dental Pulp-Derived Pain: Pharmacological Approaches and Beyond

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.

Identification of the Ideal Reference Site and Pain Threshold Values for the Placement of Electric Pulp Testers in Permanent Upper and Lower Anterior Teeth: A Cross-Sectional Study

INTRODUCTION

Electric pulp testers (EPTs) are widely used diagnostic tools for diagnosing traumatized teeth. Several factors can affect the result of an electric pulp test. One such factor that will affect the diagnosis is the electrode tip placement. Hence, the current study aims to identify the most painful site and response time threshold in healthy anterior teeth.

METHODS

A total of 90 individuals, 48 male and 42 female, aged 19 to 25 years, were recruited. An EPT was placed on three different sites: the cervical, middle, and incisal third of the labial surface of both upper and lower anterior teeth (central incisor, lateral incisor, and canine) with an appropriate electrolyte as a conducting medium. Later, the threshold values were recorded, and pain assessment was done using the Memojis pain scale (MPS). Finally, the data was analyzed statistically using the Mann-Whitney U test.

RESULTS

Mean and standard deviation values of reaction time were collected from 540 EPT readings (three sites from 180 teeth). Among the three sites tested, the difference between the upper and lower central incisors was statistically insignificant (p > 0.05). Similarly, when upper and lower lateral incisors and canines were compared, a statistically significant difference was observed among the three sites (p<0.05). There was a significant difference (p<0.05) in the pain scores only on the incisal and cervical thirds of the upper and lower central incisors. Only the incisal third showed a statistically significant difference (p<0.05) between the pain scores in the upper and lateral incisors. At the same time, a statistically significant difference in the pain scores was observed among the three tested sites between the upper and lower canines (p<0.05).  Conclusion: Lower threshold values were appreciated at the incisal third of all the upper and lower anterior teeth for placing the EPT. Most individuals have experienced a score of 2 (hurts little bit) for the perceived pain using EPTs for both the upper and lower anterior teeth.

Comprehensive Strategies in Endodontic Pain Management: An Integrative Narrative Review

This narrative review comprehensively examines the current and emerging strategies for pain management in endodontics, encompassing a wide range of pharmacological and non-pharmacological approaches. Through an extensive exploration of 20 distinct parts, the review discusses traditional analgesics, antibiotics, the use of corticosteroids, and the role of novel treatments such as platelet-rich fibrin (PRF) and cryotherapy. The review also delves into the intricacies of clinical methods, such as trephination and occlusal reduction, and discusses the potential of advanced techniques such as GABAergic signaling, acupuncture, in silico modulation, and low-level laser therapy (LLLT) for the effective management of endodontic pain. The analysis reveals a trend toward integrative methods that combine established practices with cutting-edge research, highlighting the importance of a tailored approach in endodontic pain management. The findings underscore the significance of understanding the complex nature of dental pain and the need for multifaceted treatment strategies. The review emphasizes that while traditional pharmacological methods remain foundational, emerging therapies offer promising adjuncts or alternatives, especially in cases where conventional treatments may be inadequate or unsuitable. This review aims to serve as a comprehensive resource for endodontic practitioners and researchers, offering insights into the multifarious aspects of pain management in endodontics. It underscores the ongoing evolution in the field and suggests directions for future research, particularly in refining and validating new pain management techniques.

A novel rapidly mineralized biphasic calcium phosphate with high acid-resistance stability for long-term treatment of dentin hypersensitivity

OBJECTIVES

Treating dental hypersensitivity (DH) rapidly and maintaining long-term effectiveness remains challenging. We aimed to address this problem by fabricating a novel rapidly mineralized biphasic calcium phosphate (RMBCP), which could rapidly elicit mineralization to form hydroxyapatite (HA) and perform excellent acid-resistant stability, thus effectively blocking the exposed dental tubules and protecting them from acid attack.

METHODS

RMBCP was firstly synthesized by precisely adjusting the molar ratio of acetic acid and calcium hydroxide and characterized by X-ray diffraction (XRD), X-ray fluorescence microprobe (XRF), Fourier-transform infrared (FTIR) spectrometer, scanning electron microscope (SEM), and transmission electron microscope (TEM). Subsequently, using a commercialized desensitizing agent, 45S5 bioglass (BG), as the control group, the mineralization performance of RMBCP was investigated in simulated body fluid (SBF), Dulbecco's modified eagle medium (DMEM), and even slightly acidic artificial saliva (pH=6.6). Moreover, the biocompatibility of RMBCP was studied. Finally, the tubule occlusion effect and acid-resistant stability of RMBCP were evaluated in vitro and in vivo.

RESULTS

The rapid mineralization behavior of RMBCP could easily adhere to the dentin surface and block the dentinal tubules completely in vitro and in vivo within 7days. RMBCP performed high acid-resistant stability to maintain the long-term therapeutic effect of DH treatment.

SIGNIFICANCE

Developing novel bioactive calcium phosphate materials with the ability to trigger mineralization for HA formation rapidly will be an effective strategy for the long-term treatment of dentin hypersensitivity.

Evaluation of the transdentinal capability of the intrinsic antibacterial cetylpyridinium chloride/cholesterol sterosomes in vitro and in vivo

AIM

Dentinal tubules serve as disease-causing channels for infiltration and penetration of bacteria and their by-products; which are regarded as the major driver of pathogenesis in pulpal inflammation and infection. In this study, we aimed to evaluate the transdentinal potential of nanoscale cetylpyridinium chloride/cholesterol (CPC/Chol) sterosomes, which are a recently developed type of cationic non-phospholipid liposomal nanocarrier; as well as their intrinsic and universal antibacterial activity.

METHODOLOGY

Cetylpyridinium chloride/cholesterol sterosomes were formulated, with a hydrodynamic diameter of 134 ± 4 nm, a low polydisperse index of 0.161 ± 0.007, and a positive zeta potential of 41 ± 3 mV at pH 7.4. Transdentinal diffusion ability of sterosomes was evaluated using human dentine blocks in vitro, and Wistar rat molar teeth in vivo. The intrinsic antibacterial activities of CPC/Chol sterosomes against Enterococcus faecalis, Streptococcus mutans, Fusobacterium nucleatum, and Porphyromonas gingivalis were further examined.

RESULTS

Cetylpyridinium chloride/cholesterol sterosomes successfully penetrated through the dentinal tubules, and diffused into the pulp, which could be internalized by dental pulp cells with a high efficiency. In addition, they exhibited substantial levels of intrinsic antibacterial activity against these Gram-positive and Gram-negative endodontic bacteria and their biofilms.

CONCLUSIONS

Given its high penetration and diffusion ability through the dentine and pulp, great potential for multi-drug delivery, and distinct intrinsic antibacterial activity; sterosome-based nanocarriers might serve as a promising therapeutic strategy aimed at targeting various specific pathways associated with pulpal diseases. This will help determine and characterize the most appropriate prophylactic and therapeutic targets for early intervention in our future dentistry practice.

Maintaining Tooth Vitality With Super Minimally Invasive Pulp Therapy

In aging humans, tooth loss is a predictor of decreased longevity. Tooth loss is mainly caused by dental caries and periodontal disease. Pulpitis refers to inflammation of the dental pulp caused by bacterial infection secondary to dental caries. It is accompanied by severe toothache and has infectious disease-associated pathophysiology. Pulpitis is mainly treated by pulpectomy, which is aimed at removing the infected dental pulp and controlling pain by removing nociceptive nerve fibers. However, teeth without dental pulp have a poor prognosis. In this report, we proposed a novel “super minimally invasive pulp” therapy for treating pulpitis without pulpectomy, which combines antibiotics, steroids, and ultrasound-guided trigeminal nerve block (UGTNB) to protect the dental pulp. UGTNB is used as an analgesic for severe pain, antibiotics for pulp infections, and steroids as antiinflammatory drugs. This novel therapy could improve the longevity of the tooth and thereby oral health.

Histopathological Analysis and Comparison between Experimentally Fabricated Hydroxyapatite from Nile Tilapia Bone and Mineral Trioxide Aggregate as A Direct Pulp Capping Agents on Dog Pulp (In Vivo Study)

AIM: The aim of this study was to study response of exposed dental dog pulp to the HP from Nile Tilapia bone and MTA on induction of reparative dentin formation and to inflammatory response in pulp tissue. MATERIALS AND METHODS: Four male mongrel dogs 1 year old with total of 20 teeth from each dog were selected and divided into two groups that each group has 40 teeth according to the material used as pulp capping agents. The maxillary teeth and the mandibular teeth for each dog were capped by both materials alternatively; the cavities were then sealed by glass-ionomer cement. Each group divided in two groups according to 2-time intervals (4 weeks and 8 weeks). Animals were sacrificed and teeth were collected for histopathological analysis. RESULTS: Specimens capped by fish bone powder after 4 weeks, which showed non-significantly higher of inflammatory cell scores than that capped by MTA. It showed thin (score 1) to moderate (score 2) thickness of dentine bridge formation, mostly a-tubular dentin, in all specimens. After 8 weeks, significant decrease in inflammatory cell infiltration scores for both groups were found, but it was significant in case of fish bone powder. Furthermore, dentine bridge became more significant for both materials with slight histological change in the group capped by fish bone powder. CONCLUSIONS: HA from Nile Tilapia bone could be considered as a direct pulp capping material. Furthermore, more studies needed on the fabrication of this material to give better result in shape and the pattern of reparative dentine formed.

Exosome‑derived lncRNA‑Ankrd26 promotes dental pulp restoration by regulating miR‑150‑TLR4 signaling

At present, retaining the biological function of dental pulp is an urgent requirement in the treatment of pulp disease; it has been recognized that application of dental pulp stem cells (DPSCs) in regenerating dental pulp and dentin complexes is expected to become a safe and effective treatment of pulp disease; meanwhile the role of DPSC‑derived exosomes in dental pulp regeneration and repair is gaining attention. However, the underlying mechanism of DPSCs in dental pulp regeneration and repair is still unclear. In the present study, a variety of in vitro biological experiments and an animal model, as well as next‑generation sequencing and bioinformatics analysis, demonstrated that DPSCs promoted migration and osteoblastic differentiation of mesenchymal stem cells (MSCs) via exosomes; this was induced by DPSC‑derived exosomal long non‑coding (lnc)RNA‑ankyrin repeat domain (Ankrd)26. Mechanistically, the effect of exosomal lncRNA‑Ankrd26 on migration and osteoblastic differentiation of MSCs was dependent on microRNA (miR)‑150/Toll‑like receptor (TLR)4 signaling; this was regulated by lncRNA‑Ankrd26. The present study demonstrated that exosomes‑derived lncRNA‑Ankrd26 from DPSCs promoted dental pulp restoration via regulating miR‑150‑TLR4 signaling in MSCs; these findings help to understand the mechanism of dental pulp repair, identify therapeutic targets in the development of pulpitis and develop clinical treatments.

Immunohistochemistry as a detection tool for ion channels involved in dental pain signaling

Background

Despite advances in pain detection, diagnosis, and management, the prevalence of dental pain is still on the rise. Although dental pain is not directly related to fatal outcomes, the two most common types of dental pain—dental caries and dentin hypersensitivity—have a significant impact on an individual’s quality of life. Understanding the mechanism of the pain pathway is one of the crucial steps in providing better treatment for these patients. Ion channels are critical biomolecules that have been the subject of dental study owing to their roles in the transmission and transduction of external stimuli, as well as in the control and perception of pain. Numerous immunohistochemical (IHC) staining approaches have also been used to identify the many ion channels implicated in peripheral pain signaling in dental pulp.

Highlight

This review highlights the critical steps in IHC and its role in the detection of ion channels involved in the dental pain signaling pathway.

Conclusion

The key ion channels identified using IHC and whose functions have been widely researched in dental tissues are addressed in this review article.

Inhibition of the Nav1.7 Channel in the Trigeminal Ganglion Relieves Pulpitis Inflammatory Pain

Pulpitis causes significant changes in the peripheral nervous system, which induce hyperalgesia. However, the relationship between neuronal activity and Nav1.7 expression following pulpal noxious pain has not yet been investigated in the trigeminal ganglion (TG). The aim of our study was to verify whether experimentally induced pulpitis activates the expression of Nav1.7 peripherally and the neuronal activities of the TGs can be affected by Nav1.7 channel inhibition. Acute pulpitis was induced through allyl isothiocyanate (AITC) application to the rat maxillary molar tooth pulp. Three days after AITC application, abnormal pain behaviors were recorded, and the rats were euthanized to allow for immunohistochemical, optical imaging, and western blot analyses of the Nav1.7 expression in the TG. A significant increase in AITC-induced pain-like behaviors and histological evidence of pulpitis were observed. In addition, histological and western blot data showed that Nav1.7 expressions in the TGs were significantly higher in the AITC group than in the naive and saline group rats. Optical imaging showed that the AITC group showed higher neuronal activity after electrical stimulation of the TGs. Additionally, treatment of ProTxII, selective Nav1.7 blocker, on to the TGs in the AITC group effectively suppressed the hyperpolarized activity after electrical stimulation. These findings indicate that the inhibition of the Nav1.7 channel could modulate nociceptive signal processing in the TG following pulp inflammation.

Challenges and strategy in treatment with exosomes for cell-free-based tissue engineering in dentistry

In dentistry, problems of craniofacial, osteochondral, periodontal tissue, nerve, pulp or endodontics injuries, and osteoarthritis need regenerative therapy. The use of stem cells in dental tissue engineering pays a lot of increased attention, but there are challenges for its clinical applications. Therefore, cell-free-based tissue engineering using exosomes isolated from stem cells is regarded an alternative approach in regenerative dentistry. However, practical use of exosome is restricted by limited secretion capability of cells. For future regenerative treatment with exosomes, efficient strategies for large-scale clinical applications are being studied, including the use of ceramics-based scaffold to enhance exosome production and secretion which can resolve limited exosome secretory from the cells when compared with the existing methods available. Indeed, more research needs to be done on these strategies going forward.

Pharmacological Approaches and Regeneration of Bone Defects with Dental Pulp Stem Cells

Bone defects in the craniomaxillofacial skeleton vary from small periodontal defects to extensive bone loss, which are difficult to restore and can lead to extensive damage of the surrounding structures, deformities, and limited functions. Plenty of surgical regenerative procedures have been developed to reconstruct or prevent alveolar defects, based on guided bone regeneration involving the use of autogenous bone grafts or bone substituents. However, these techniques have limitations in the restoration of morphological and functional reconstruction, thus stopping disease progression but not regenerating lost tissue. Most promising candidates for regenerative therapy of maxillofacial bone defects represent postnatal stem cells, because of their replication potential in the undifferentiated state and their ability to differentiate as well. There is an increased need for using various orofacial sources of stem cells with comparable properties to mesenchymal stem cells because they are more easily available with minimally invasive procedures. In addition to the source of MSCs, another aspect affects the regeneration outcomes. Thermal, mechanical, and chemical stimuli after surgical procedures have the ability to generate pain, usually managed with pharmacological agents, mostly nonsteroidal anti-inflammatory drugs (NSAIDs). Some studies revealed that NSAIDs have no significant cytotoxic effect on bone marrow stem cells from mice, while other studies showed regulation of osteogenic and chondrogenic marker genes in MSC cells by NSAIDs and paracetamol, but no effect was observed in connection with diclofenac use. Therefore, there is a need to focus on such pharmacotherapy, capable of affecting the characteristics and properties of implanted MSCs.

Pivotal role of Transient Receptor Potential Channels in oral physiology

BACKGROUND

Transient Receptor Potential (TRP) Channels constitute a large family of non-selective permeable ion channels involved in the perception of environmental stimuli with a central and continuously expanding role in oral tissue homeostasis. Recent studies indicate the regulatory role of TRPs in pulp physiology, oral mucosa sensation, dental pain nociception and salivary gland secretion. This review provides an update on the diverse functions of TRP channels in the physiology of oral cavity, with emphasis on their cellular location, the underlying molecular mechanisms and clinical significance.

METHODS

A structured search of bibliographic databases (PubMed and MEDLINE) was performed for peer reviewed studies on TRP channels function on oral cavity physiology the last ten years. A qualitative content analysis was performed in screened papers and a critical discussion of main findings is provided.

RESULTS

TRPs expression has been detected in major cell types of the oral cavity, including odontoblasts, periodontal ligament, oral epithelial, salivary gland cells, and chondrocytes of temporomandibular joints, where they mediate signal perception and transduction of mechanical, thermal, and osmotic stimuli. They contribute to pulp physiology through dentin formation, mineralization, and periodontal ligament formation along with alveolar bone remodeling in dental pulp and periodontal ligament cells. TRPs are also involved in oral mucosa sensation, dental pain nociception, saliva secretion, swallowing reflex and temporomandibular joints' development.

CONCLUSION

Various TRP channels regulate oral cavity homeostasis, playing an important role in the transduction of external stimuli to intracellular signals in a cell type-specific manner and presenting promising drug targets for the development of pharmacological strategies to manage oral diseases.

The functions of mechanosensitive ion channels in tooth and bone tissues

Tooth and bone are independent tissues with a close relationship. Both are composed of a highly calcified outer structure and soft inner tissue, and both are constantly under mechanical stress. In particular, the alveolar bone and tooth constitute an occlusion system and suffer from masticatory and occlusal force. Thus, mechanotransduction is a key process in many developmental, physiological and pathological processes in tooth and bone. Mechanosensitive ion channels such as Piezo1 and Piezo2 are important participants in mechanotransduction, but their functions in tooth and bone are poorly understood. This review summarizes our current understanding of mechanosensitive ion channels and their roles in tooth and bone tissues. Research in these areas may shed new light on the regulation of tooth and bone tissues and potential treatments for diseases affecting these tissues.

Dental care management during the COVID-19 outbreak

Aim

The level of preparedness of the healthcare system plays an important role in management of coronavirus disease 2019 (COVID‐19). This study attempted to devise a comprehensive protocol regarding dental care during the COVID‐19 outbreak.

Methods and result

Embase, PubMed, and Google Scholar were searched until March 2020 for relevant papers. Sixteen English papers were enrolled to answer questions about procedures that are allowed to perform during the COVID‐19 outbreak, patients who are in priority to receive dental care services, the conditions and necessities for patient admission, waiting room and operatory room, and personal protective equipment (PPE) that is necessary for dental clinicians and the office staff.

Conclusion

Dental treatment should be limited to patients with urgent or emergency situation. By screening questionnaires for COVID‐19, patients are divided into three groups of (a) apparently healthy, (b) suspected for COVID‐19, and (c) confirmed for COVID‐19. Separate waiting and operating rooms should be assigned to each group of patients to minimize the risk of disease transmission. All groups should be treated with the same protective measures with regard to PPE for the dental clinicians and staff.