A critical analysis of research methods and experimental models to study pulpitis

Construction of dental pulp decellularized matrix by cyclic lavation combined with mechanical stirring and its proteomic analysis

The decellularized matrix has a great potential for tissue remodeling and regeneration; however, decellularization could induce host immune rejection due to incomplete cell removal or detergent residues, thereby posing significant challenges for its clinical application. Therefore, the selection of an appropriate detergent concentration, further optimization of tissue decellularization technique, increased of biosafety in decellularized tissues, and reduction of tissue damage during the decellularization procedures are pivotal issues that need to be investigated. In this study, we tested several conditions and determined that 0.1% Sodium dodecyl sulfate and three decellularization cycles were the optimal conditions for decellularization of pulp tissue. Decellularization efficiency was calculated and the preparation protocol for dental pulp decellularization matrix (DPDM) was further optimized. To characterize the optimized DPDM, the microstructure, odontogenesis-related protein and fiber content were evaluated. Our results showed that the properties of optimized DPDM were superior to those of the non-optimized matrix. We also performed the 4D-Label-free quantitative proteomic analysis of DPDM and demonstrated the preservation of proteins from the natural pulp. This study provides a optimized protocol for the potential application of DPDM in pulp regeneration.

The role of Semaphorin 3A in oral diseases

Semaphorin 3A (SEMA3A), also referred to as H-Sema III, is a molecule with significant biological importance in regulating physiological and pathological processes. However, its role in oral diseases, particularly its association with inflammatory immunity and alveolar bone remodeling defects, remains poorly understood. This comprehensive review article aims to elucidate the recent advances in understanding SEMA3A in the oral system, encompassing nerve formation, periodontitis, pulpitis, apical periodontitis, and oral squamous cell carcinoma. Notably, we explore its novel function in inflammatory immunomodulation and alveolar bone formation during oral infectious diseases. By doing so, this review enhances our comprehension of SEMA3A's role in oral biology and opens up possibilities for modulatory approaches and potential treatments in oral diseases.

Comparation of the effectiveness of conventional needle irrigation and photon-induced photoacoustic streaming with sodium hypochorite in the treatment of teeth with apical periodontitis: a randomized clinical trial

Photon-initiated photoacoustic streaming (PIPS) with an Er: YAG laser has been introduced in root canal treatment to improve irrigation and facilitate the removal of bacteria in the root canal system. This study aimed to compare the antibacterial effectiveness of two different root canal irrigation techniques, conventional needle irrigation (CNI) and PIPS, using 1% sodium hypochlorite (NaOCl), in the treatment of teeth with apical periodontitis. Sixty patients with a total of sixty teeth affected by apical periodontitis were included in this study. The teeth underwent root canal therapy, and after mechanical instrumentation, they were randomly assigned to two groups (n = 30) based on the final irrigation protocol: CNI or PIPS with 1% NaOCl. Bacterial suspensions in the root canals were evaluated using Adenosine 5'-triphosphate (ATP) assay kit after mechanical instrumentation and after final irrigation. Then, a follow-up was conducted after 7 days. The results revealed that final irrigation significantly reduced ATP values in both the CNI and PIPS groups (P < 0.001). The ATP values after final irrigation was greater in the CNI group compared to the PIPS group (P < 0.001). After a 7-day follow-up, percussion tenderness and fistula were significantly resolved in both groups (P < 0.05). A multivariate linear regression model was used to identify the factors that influence post irrigation ATP values. The analysis demonstrated that pre-operative percussion tenderness (P = 0.006), the presence of a fistula (P < 0.001) and the method used in the final irrigation (P < 0.001) had a significant impact on the ATP value after final irrigation. These results indicate that employing PIPS with 1% NaOCl as the final irrigation protocol exhibited superior antibacterial effectiveness and has the potential to enhance clinical outcomes in the treatment of teeth afflicted with apical periodontitis.

Antimicrobial Peptide- and Dentin Matrix-Functionalized Hydrogel for Vital Pulp Therapy via Synergistic Bacteriostasis, Immunomodulation, and Dentinogenesis

The preservation of vital pulps is crucial for maintaining the physiological functions of teeth; however, vital pulp therapy (VPT) of pulpitis teeth remains a substantial challenge due to uncontrolled infection, excessive inflammation, and limited regenerative potential. Current pulp capping agents have restricted effects in the infectious and inflammatory microenvironment. To address this, a multifunctional hydrogel (TGH/DM) with antibacterial, immunomodulatory, and mineralization-promoting effects is designed. The antimicrobial peptide (AMP) and demineralized dentin matrix are incorporated into the hydrogel, achieving sustainable delivery of AMP and a cocktail of growth factors. In vitro results show that TGH/DM could kill endodontic microbiota, ameliorate inflammatory responses of human dental pulp stem cells (hDPSCs), and prompt odontogenic differentiation of inflammatory hDPSCs via activation of peroxisome proliferator-activated receptor gamma. In vivo results suggest that TGH/DM is capable of inducing M2 phenotype transformation of macrophages in mice and fostering the regeneration of the dentin-pulp complex in inflamed pulps of beagle dogs. Overall, this study first proposes the synergistic regulation of AMP and tissue-specific extracellular matrix for the treatment of pulpitis, and the advanced hydrogel provides a facile and effective way for VPT.

Dual-Fuel Propelled Nanomotors with Two-Stage Permeation for Deep Bacterial Infection in the Treatment of Pulpitis

Bacterial infection-induced inflammatory response could cause irreversible death of pulp tissue in the absence of timely and effective therapy. Given that, the narrow structure of root canal limits the therapeutic effects of passive diffusion-drugs, considerable attention has been drawn to the development of nanomotors, which have high tissue penetration abilities but generally face the problem of insufficient fuel concentration. To address this drawback, dual-fuel propelled nanomotors (DPNMs) by encapsulating L-arginine (L-Arg), calcium peroxide (CaO2 ) in metal-organic framework is developed. Under pathological environment, L-Arg could release nitric oxide (NO) by reacting with reactive oxygen species (ROS) to provide the driving force for movement. Remarkably, the depleted ROS could be supplemented through the reaction between CaO2 with acids abundant in the inflammatory microenvironment. Owing to high diffusivity, NO achieves further tissue penetration based on the first-stage propulsion of nanomotors, thereby removing deep-seated bacterial infection. Results indicate that the nanomotors effectively eliminate bacterial infection based on antibacterial activity of NO, thereby blocking inflammatory response and oxidative damage, forming reparative dentine layer to avoid further exposure and infection. Thus, this work provides a propagable strategy to overcome fuel shortage and facilitates the therapy of deep lesions.

Injectable CNPs/DMP1-loaded self-assembly hydrogel regulating inflammation of dental pulp stem cells for dentin regeneration

Vital pulp preservation, which is a clinical challenge of aseptic or iatrogenic accidental exposure of the pulp, in cases direct pulp capping is the main technology. Human dental pulp stem cells (hDPSCs) play a critical role in pulp tissue repair, but their differentiative ability could be inhibited by the potential infection and inflammatory response of the exposed pulp. Therefore, inflammatory regulation and differentiated promotion of hDPSCs are both essential for preserving living pulp teeth. In this study, we constructed a functional dental pulp-capping hydrogel by loading cerium oxide nanoparticles (CNPs) and dentin matrix protein-1 (DMP1) into an injectable Fmoc-triphenylalanine hydrogel (Fmoc-phe3 hydrogel) as CNPs/DMP1/Hydrogel for in situ drugs delivery. With a view to long-term storage and release of CNPs (anti-inflammatory and antioxidant) to regulate the local inflammatory environment and DMP1 to promote the regeneration of dentin. Results of CCK-8, LDH release, hemolysis, and Live/Dead assessment of cells demonstrated the good biocompatibility of CNPs/DMP1/Hydrogel. The levels of alkaline phosphatase activity, quantification of the mineralized nodules, expressions of osteogenic genes and proteins demonstrated CNPs/DMP1/Hydrogel could protect the activity of hDPSCs' osteogenic/dentinogenic differentiation by reducing the inflammation response via releasing CNPs. The therapy effects were further confirmed in rat models, CNPs/DMP1/Hydrogel reduced the necrosis rate of damaged pulp and promoted injured pulp repair and reparative dentin formation with preserved vital pulps. In summary, the CNPs/DMP1/Hydrogel composite is an up-and-coming pulp-capping material candidate to induce reparative dentin formation, as well as provide a theoretical and experimental basis for developing pulp-capping materials.

Icariin negatively regulated lipopolysaccharide-induced inflammation and ameliorated the odontogenic activity of human dental pulp cells in vitro

Alleviating inflammation and promoting dentine regeneration is critical for the healing of pulpitis. In this study, we investigated the anti-inflammatory, angiogenesis and odontogenesis function of icariin on Human dental pulp cells (HDPCs) under inflammatory state. Furthermore, the underlying mechanisms was also evaluated. Icariin attenuated the LPS-induced pro-inflammatory marker expression, such as interleukin-1β (IL-1β), IL-6 and IL-8. The immunoblotting and immunofluorescence staining results showed that icariin suppressed the inflammatory responses mediated by the protein kinase B (Akt) and nuclear factor kappa-B (NF-κB) signaling cascades. Additionally, icariin also upregulated the expression of odontogenic and angiogenic genes and proteins (namely dentin sialophosphoprotein (DSPP), dentin matrix protein 1 (DMP1), anti-collagen Ⅰ (COL-Ⅰ), and vascular endothelial growth factor (VEGF) and fibroblast growth factor-1 (FGF-1)), alkaline phosphatase activity, and calcium nodule deposition in LPS-exposed HDPCs. In a word, our findings indicated that icariin attenuated pulp inflammation and promoted odontogenic and angiogenic differentiation in the inflammatory state. Icariin may be a promising vital pulp therapy agent for the regenerative treatment of the inflamed dental pulp.

Approaches to vital pulp therapies

Tooth decay, which leads to pulpal inflammation due to the pulp's response to bacterial components and byproducts is the most common infectious disease. The main goals of clinical management are to eliminate sources of infection, to facilitate healing by regulating inflammation indental tissue, and to replace lost tissues. A variety of novel approaches from tissue engineering based on stem cells, bioactive molecules, and extracellular matrix-like scaffold structures to therapeutic applications, or a combination of all these are present in the literature. Shortcomings of existing conventional materials for pulp capping and the novel approches aiming to preserve pulp vitality highligted the need for developing new targeted dental materials. This review looks at the novel approches for vital pulp treatments after briefly addresing the conventional vital pulp treatment as well as the regenerative and self defense capabilities of the pulp. A narrative review focusing on the current and future approaches for pulp preservation was performed after surveying the relevant papers on vital pulp therapies including pulp capping, pulpotomy, and potential approaches for facilitating dentin-pulp complex regeneration in PubMed, Medline, and Scopus databases.

The influence of anxiety on pain perception and its repercussion on endodontic treatment: a systematic review

OBJECTIVE

To evaluate the influence of dental anxiety on the perception of pain before and during endodontic treatments.

MATERIALS AND METHODS

The PRISMA checklist was followed. A search was conducted in Scopus, Medline/PubMed, The Cochrane Library, and Web of Science databases. Based on PECOS criteria, the first outcome was a possible association between pre-operative pain and anxiety. The second outcome was a possible association between intraoperative pain and anxiety. The type of studies was observational. The JBI Critical Appraisal Checklist was used to evaluate the methodological quality of articles. The certainty of the evidence was analyzed using the GRADE approach.

RESULTS

Four articles were included with a total of 471 patients. Two studies found a positive association between pain and pre-endodontic treatment anxiety. Three studies investigated the relationship between anxiety and intraoperative pain; two identified an extremely significant positive association. One article noted that anxiety influences pain expectancy. The studies were of good quality as assessed by the JBI Critical Appraisal Checklist for cross-sectional studies. However, the certainty of the evidence was considered low and very low.

CONCLUSIONS

Dental anxiety can be directly associated with pre- and intraoperative pain during endodontic procedures.

CLINICAL RELEVANCE

It is necessary to identify patients with dental anxiety to employ therapies to bring their anxiety under control, avoiding the increase of endodontic infections, and the postponement and evasion of endodontic treatments.

Effectiveness of diagnosing pulpitis: A systematic review

BACKGROUND

The diagnosis of the status of the inflamed pulp is essential in clinical diagnosis and treatment provision. There are a limited number of well-designed and well-executed clinical trials on the diagnosis of the true status of the pulp.

OBJECTIVES

Three PICO questions were formulated and agreed a priori by the European Society of Endodontology to evaluate the clinical tests for sensibility testing, determination of biomarkers and pulp bleeding with regard to their suitability to correctly diagnose the condition of the pulp tissue for the development of S3-Level guidelines.

METHODS

A literature search was conducted using PubMed, Clarivate Analytics' Web of Science, Scopus, Google Scholar and Cochrane Central Register of Controlled Trials from inception to 21 January 2022. Additionally, a hand search was performed, and the contents of the major subject journals were also examined. Eligibility criteria followed the proposed PICO questions. Two independent reviewers were involved in study selection, data extraction and appraising the included studies; disagreements were resolved by a third reviewer. The risk of bias was assessed by the QUADAS-2 tool for diagnostic accuracy studies, the Newcastle-Ottawa scale for noncomparative, nonrandomized studies and the Newcastle-Ottawa Quality Assessment scale adapted for cross-sectional studies.

RESULTS

In total, 28 studies out of 29 publications were considered eligible and were included in the review. Twelve studies were identified to investigate the diagnostic accuracy of the pulp vitality. Ten studies fulfilled the criteria to evaluate the diagnostic accuracy of the pulpal conditions, while 6 studies investigating the expression of biomarkers were eligible. Three studies addressing the prognostic factors and therapeutic interventions relating to pulpal status were included.

DISCUSSION

The core problem in pulp diagnostics is that a reliable reference standard is lacking under clinical conditions. Based on limited evidence, the most promising current approach seems to define a combination of different clinical tests and symptoms, probably in future including molecular diagnosis ("diagnostic package") will be required to ascertain the best possible strategy to clinically diagnose true pulpal conditions.

CONCLUSIONS

The effectiveness of diagnosing pulpitis is low due to limited scientific evidence regarding the accuracy and reproducibility of diagnostic tests. There is a lack of evidence to determine the true status of the pulp or to identify prognostic indicators allowing for a reliable pre-operative estimation of the outcome of vital pulp treatment.

REGISTRATION

PROSPERO database (CRD42021265366).

Bioactive Endodontic Hydrogels: From Parameters to Personalized Medicine

Regenerative endodontic procedures (REPs) aim at recreating dental pulp tissue using biomaterials such as hydrogels. Their bioactivity is mostly related to the nature of biomolecules or chemical compounds that compose the endodontic hydrogel. However, many other parameters, such as hydrogel concentration, bioactive molecules solubility, and apex size, were reported to influence the reciprocal host-biomaterial relationship and hydrogel behavior. The lack of knowledge regarding these various parameters, which should be considered, leads to the inability to predict the clinical outcome and suggests that the biological activity of endodontic hydrogel is impossible to anticipate and could hinder the bench-to-bedside transition. We describe, in this review, that most of these parameters could be identified, described, and studied. A second part of the review lists some challenges and perspectives, including development of future mathematical models that are able to explain, and eventually predict, the bioactivity of endodontic hydrogel used in a clinical setting.

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.

Chronic exposure to lipopolysaccharides as an in vitro model to simulate the impaired odontogenic potential of dental pulp cells under pulpitis conditions

BACKGROUND

Simulating a bacterial-induced pulpitis environment in vitro may contribute to exploring mechanisms and bioactive molecules to counteract these adverse effects.

OBJECTIVE

To investigate the chronic exposure of human dental pulp cells (HDPCs) to lipopolysaccharides (LPS) aiming to establish a cell culture protocol to simulate the impaired odontogenic potential under pulpitis conditions.

METHODOLOGY

HDPCs were isolated from four healthy molars of different donors and seeded in culture plates in a growth medium. After 24 h, the medium was changed to an odontogenic differentiation medium (DM) supplemented or not with E. coli LPS (0 - control, 0.1, 1, or 10 µg/mL) (n=8). The medium was renewed every two days for up to seven days, then replaced with LPS-free DM for up to 21 days. The activation of NF-κB and F-actin expression were assessed (immunofluorescence) after one and seven days. On day 7, cells were evaluated for both the gene expression (RT-qPCR) of odontogenic markers (COL1A1, ALPL, DSPP, and DMP1) and cytokines (TNF, IL1B, IL8, and IL6) and the production of reactive nitrogen (Griess) and oxygen species (Carboxy-H2DCFDA). Cell viability (alamarBlue) was evaluated weekly, and mineralization was assessed (Alizarin Red) at 14 and 21 days. Data were analyzed with ANOVA and post-hoc tests (α=5%).

RESULTS

After one and seven days of exposure to LPS, NF-κB was activated in a dose-dependent fashion. LPS at 1 and 10 µg/mL concentrations down-regulated the gene expression of odontogenic markers and up-regulated cytokines. LPS at 10 µg/mL increased both the production of reactive nitrogen and oxygen species. LPS decreased cell viability seven days after the end of exposure. LPS at 1 and 10 µg/mL decreased hDPCs mineralization in a dose-dependent fashion.

CONCLUSION

The exposure to 10 µg/mL LPS for seven days creates an inflammatory environment that is able to impair by more than half the odontogenic potential of HDPCs in vitro, simulating a pulpitis-like condition.

Assessment of correlation between clinical, radiographic, microbiological, and histopathological examinations in identification of pulpal diseases - a single-centre study

Aim

This study aimed to analyse the presence of pulpitis using different techniques and compare the findings of the various examination methods.

Methods

A total of 108 patients were enrolled and randomly divided into two groups: 56 patients whose pulp samples were sent for histopathological analysis and 52 patients whose samples were sent for microbiological analysis. All participants underwent endodontic procedures, with clinical evaluation and assessment using periapical radiography. Bacteria were isolated and identified using agar culture and VITEK 2 identification cards.

Results

Histopathology confirmed chronic pulpitis in 33 samples (58.9%) and acute pulpitis in 23 samples (41.1 %). For chronic pulpitis, the histopathological diagnosis agreed with the clinical evaluation diagnosis in 65.2% of cases, and a similar percentage of agreement was observed for acute pulpitis. Chronic pulpitis was observed in 34.8% of patients on clinical examination; however, according to histopathology, these cases were acute. Dilated blood vessels were detected in 56.5% of patients with acute pulpitis and 15.2% of patients with chronic pulpitis. Neutrophilic leucocytes were observed in 43.5% of patients with acute pulpitis and 69.7% of patients with chronic pulpitis. Lymphocytes were observed in 17.4% of acute pulpitis samples but zero chronic pulpitis samples. Microbiological analysis identified gram-positive bacilli in 22 samples, gram-positive cocci in 51 samples, and fungi in 2 samples. Acute pulpitis was typically found to be associated with anaerobic Clostridium bifermentans, aerobic Streptococcus mitis, and Granulicatella elegans, whereas chronic pulpitis was more often associated with two facultative anaerobes, Streptococcus oralis and Streptococcus mitis.

Conclusion

Comparison of clinical, radiographic, and histological examination techniquesrevealed several notable discrepancies. Radiographic imaging only suggested the presence of pulpal pathologies; therefore, histopathological analysis of the pulp material was still ultimately required to verify the clinical diagnosis and exclude other pathologies. Although histopathology remains the gold standard for assessing pulpal disease, performing additional examinations may provide the most comprehensive, and perhaps the most effective, approach.

Association between short-term exposure to ambient air pollution and outpatient visits for pulpitis in Hefei, China: a time series study

Evidence suggests a possible association between ambient air pollutants and oral diseases. Nevertheless, information regarding the relationship between air pollutants and pulpitis is scarce and inconclusive. In view of this, the present study aimed to investigate the relationship between short-term exposure to air pollution and outpatient visits for pulpitis. Daily data on outpatient visits for pulpitis, air pollutants, and meteorological data in Hefei, China, was collected from January 1, 2015 to December 31, 2021. The association between exposure to air pollutants and pulpitis outpatient visits was evaluated using distributed lag non-linear model (DLNM) and a generalized linear model (GLM). Furthermore, stratified analyses were performed by gender, age and season. A total of 93,324 records of outpatient visits for pulpitis were included in this study. The results showed that exposure to NO₂, PM_2.5, and CO were positively correlated with an increased risk of pulpitis outpatient visits. Each 10 μg/m³ increase in NO₂ and PM_2.5 concentration, at lag 0-2 day, was associated with a 2.4% (relative risk (RR) = 1.024, 95% confidence interval (CI): 1.014-1.035) and 0.5% (RR = 1.005, 95% CI: 1.000-1.010) increase in pulpitis outpatient visits, respectively. With a 1 mg/m³ increase in CO concentration, the risk of pulpitis outpatient visits increased by 9.1% (RR = 1.091, 95% CI: 1.031-1.154, lag 0-1 day). Intriguingly, exposure to O₃ was associated with a decreased risk of pulpitis outpatient visits (RR = 0.990, 95% CI: 0.984-0.995, lag 0-5 day). Subgroup analysis revealed that in the warm season, exposure to PM_2.5, O₃, and CO was related with a significantly higher outpatient risk of pulpitis than in the cold season. Additionally, the influence of PM_2.5 and CO exposure at age < 65 years was significantly stronger than at age ≥ 65 years. In conclusion, exposure to ambient NO₂, PM_2.5, and CO is associated with an increase in pulpitis outpatient visits in Hefei, China. Conversely, exposure to O₃ reduces the risk of outpatient visits for pulpitis. Age and season are effect modifiers of these associations.

DDIT3 aggravates pulpitis by modulating M1 polarization through EGR1 in macrophages

DNA damage-inducible transcript 3 (DDIT3), a stress response gene, engages in the physiological and pathological processes of organisms, whereas its impact on pulpitis has not been defined yet. It has been demonstrated that macrophage polarization has a significant impact on inflammation. This research intends to investigate the effect of DDIT3 on the inflammation of pulpitis and macrophage polarization. C57BL/6J mice were used to model experimental pulpitis at 6, 12, 24, and 72 h after pulp exposure, with untreated mice as the control. The progression of pulpitis was visible histologically, and DDIT3 showed a trend of initially upward and downward later. Compared with wild-type mice, inflammatory cytokines and M1 macrophages were reduced, while M2 macrophages were increased in DDIT3 knockout mice. In RAW264.7 cells and bone borrow-derived macrophages, DDIT3 was found to enhance M1 polarization while impair M2 polarization. Targeted knockdown of early growth response 1 (EGR1) could rescue the blocking effect of DDIT3 deletion on M1 polarization. In conclusion, our results indicated that DDIT3 could exacerbate inflammation of pulpitis through the regulation of macrophage polarization, and DDIT3 could promote M1 polarization by inhibiting EGR1. It provides a new target for pulpitis treatment and tissue regeneration in the future.

In vitro, ex vivo, and in vivo models for dental pulp regeneration

Based on the concept of tissue engineering (Cells-Scaffold-Bioactive molecules), regenerative endodontics appeared as a new notion for dental endodontic treatment. Its approaches aim to preserve dental pulp vitality (pulp capping) or to regenerate a vascularized pulp-like tissue inside necrotic root canals by cell homing. To improve the methods of tissue engineering for pulp regeneration, numerous studies using in vitro, ex vivo, and in vivo models have been performed. This review explores the evolution of laboratory models used in such studies and classifies them according to different criteria. It starts from the initial two-dimensional in vitro models that allowed characterization of stem cell behavior, through 3D culture matrices combined with dental tissue and finally arrives at the more challenging ex vivo and in vivo models. The travel which follows the elaboration of such models reveals the difficulty in establishing reproducible laboratory models for dental pulp regeneration. The development of well-established protocols and new laboratory ex vivo and in vivo models in the field of pulp regeneration would lead to consistent results, reduction of animal experimentation, and facilitation of the translation to clinical practice.

Development of Rat Caries-Induced Pulpitis Model for Vital Pulp Therapy

Rodent animal models for vital pulp therapy are commonly used in dental research because their tooth anatomy and cellular processes are similar to the anatomy and processes in humans. However, most studies have been conducted using uninfected sound teeth, which makes it difficult to adequately assess the inflammatory shift after vital pulp therapy. In the present study, we aimed to establish a caries-induced pulpitis model based on the conventional rat caries model and then evaluate inflammatory changes during the wound-healing process after pulp capping in a model of reversible pulpitis induced by carious infection. To establish the caries-induced pulpitis model, the pulpal inflammatory status was investigated at different stages of caries progression by immunostaining targeted to specific inflammatory biomarkers. Immunohistochemical staining revealed that both Toll-like receptor 2 and proliferating cell nuclear antigen were expressed in moderate and severe caries-stimulated pulp, indicating that an immune reaction occurred at both stages of caries progression. M2 macrophages were predominant in moderate caries-stimulated pulp, whereas M1 macrophages were predominant in the severe caries-stimulated pulp. Pulp capping in teeth with moderate caries (i.e., teeth with reversible pulpitis) led to complete tertiary dentin formation within 28 d after treatment. Impaired wound healing was observed in teeth with severe caries (i.e., teeth with irreversible pulpitis). During the wound-healing process in reversible pulpitis after pulp capping, M2 macrophages were predominant at all time points; their proliferative capacity was upregulated in the early stage of wound healing compared with healthy pulp. In conclusion, we successfully established a caries-induced pulpitis model for studies of vital pulp therapy. M2 macrophages have an important role in the early stages of the wound-healing process in reversible pulpitis.

Upregulation of TACAN in the trigeminal ganglion affects pain transduction in acute pulpitis

OBJECTIVE

Acute pulpitis is one of the common causes of tooth pain. TACAN (Tmem120a) is a newly identified ion channel that senses mechanical pain. In this experiment, we studied the expression of the TACAN ion channel in the trigeminal ganglia in a rat model of pulpitis to explore the correlation between the expression of this ion channel and inflammatory pain.

DESIGN

Lipopolysaccharide was used to induce acute pulpitis in rats, and pulpitis was assessed histologically. The facial pain threshold of the rats was measured by the von Frey test. TACAN mRNA expression in rat dental pulp and the trigeminal nerve was measured by qPCR, and TACAN protein expression in the trigeminal ganglia was evaluated by western blot analysis and immunofluorescence. Antisense oligonucleotides were used to reduce TACAN protein expression in the trigeminal ganglia, and the change in the pain threshold in the rats with acute pulpitis was determined.

RESULTS

The results showed that the TACAN transcript level in rat pulp tissue increased under inflammatory conditions, and we proved that pulpitis increased TACAN protein expression in the rat ipsilateral trigeminal ganglia. The facial pain threshold was decreased in rats with pulpitis. A short-term decrease in TACAN protein expression could improve the pain threshold.

CONCLUSIONS

With the development of pulpitis after bacterial infection, the upregulation of TACAN expression in the trigeminal ganglia promoted pain sensitivity. A short-term reduction in TACAN expression relieved pain. Therefore, this study indicated that TACAN is a potential target channel for new analgesics.

Where Is the Artificial Intelligence Applied in Dentistry? Systematic Review and Literature Analysis

This literature research had two main objectives. The first objective was to quantify how frequently artificial intelligence (AI) was utilized in dental literature from 2011 until 2021. The second objective was to distinguish the focus of such publications; in particular, dental field and topic. The main inclusion criterium was an original article or review in English focused on dental utilization of AI. All other types of publications or non-dental or non-AI-focused were excluded. The information sources were Web of Science, PubMed, Scopus, and Google Scholar, queried on 19 April 2022. The search string was “artificial intelligence” AND (dental OR dentistry OR tooth OR teeth OR dentofacial OR maxillofacial OR orofacial OR orthodontics OR endodontics OR periodontics OR prosthodontics). Following the removal of duplicates, all remaining publications were returned by searches and were screened by three independent operators to minimize the risk of bias. The analysis of 2011–2021 publications identified 4413 records, from which 1497 were finally selected and calculated according to the year of publication. The results confirmed a historically unprecedented boom in AI dental publications, with an average increase of 21.6% per year over the last decade and a 34.9% increase per year over the last 5 years. In the achievement of the second objective, qualitative assessment of dental AI publications since 2021 identified 1717 records, with 497 papers finally selected. The results of this assessment indicated the relative proportions of focal topics, as follows: radiology 26.36%, orthodontics 18.31%, general scope 17.10%, restorative 12.09%, surgery 11.87% and education 5.63%. The review confirms that the current use of artificial intelligence in dentistry is concentrated mainly around the evaluation of digital diagnostic methods, especially radiology; however, its implementation is expected to gradually penetrate all parts of the profession.