Pulp development, repair, and regeneration: challenges of the transition from traditional dentistry to biologically based therapies

Chitosan-Calcium Aluminate as a Cell-homing Scaffold: Its Bioactivity Testing in a Microphysiological Dental Pulp Platform

In vitro models of the dental pulp microenvironment have been proposed for the assessment of biomaterials, to minimise animal use in operative dentistry. In this study, a scaffold/3-D dental pulp cell culture interface was created in a microchip, under simulated dental pulp pressure, to evaluate the cell-homing potential of a chitosan (CH) scaffold functionalised with calcium aluminate (the 'CHAlCa scaffold'). This microphysiological platform was cultured at a pressure of 15 cm H2O for up to 14 days; cell viability, migration and odontoblastic differentiation were then assessed. The CHAlCa scaffold exhibited intense chemotactic potential, causing cells to migrate from the 3-D culture to its surface, followed by infiltration into the macroporous structure of the scaffold. By contrast, the cells in the presence of the non-functionalised chitosan scaffold showed low cell migration and no cell infiltration. CHAlCa scaffold bioactivity was confirmed in dentin sialophosphoprotein-positive migrating cells, and odontoblastic markers were upregulated in 3-D culture. Finally, in situ mineralised matrix deposition by the cells was confirmed in an Alizarin Red-based assay, in which the CHAlCa and CH scaffolds were adapted to fit within dentin discs. More intense deposition of matrix was observed with the CHAlCa scaffold, as compared to the CH scaffold. In summary, we present an in vitro platform that provides a simple and reproducible model for selecting and developing innovative biomaterials through the assessment of their cell-homing potential. By using this platform, it was shown that the combination of calcium aluminate and chitosan has potential as an inductive biomaterial that can mediate dentin tissue regeneration during cell-homing therapies.

Effects of histone acetyltransferase (HAT) and histone deacetylase (HDAC) inhibitors on proliferative, differentiative, and regenerative functions of Toll-like receptor 2 (TLR-2)-stimulated human dental pulp cells (hDPCs)

OBJECTIVES

This in vitro study aimed to modify TLR-2-mediated effects on the paracrine, proliferative, and differentiation potentials of human dental pulp-derived cells using histone acetyltransferase (HAT) and histone deacetylase (HDAC) inhibitors.

MATERIALS AND METHODS

Cell viability was assessed using the XTT assay. Cells were either treated with 10 μg/ml Pam3CSK4 only, or pre-treated with valproic acid (VPA) (3 mM), trichostatin A (TSA) (3 μM), and MG-149 (3 μM) for a total of 4 h and 24 h. Control groups included unstimulated cells and cells incubated with inhibitors solvents only. Transcript levels for NANOG, OCT3-4, FGF-1 and 2, NGF, VEGF, COL-1A1, TLR-2, hβD-2 and 3, BMP-2, DSPP, and ALP were assessed through qPCR.

RESULTS

After 24 h, TSA pre-treatment significantly upregulated the defensins and maintained the elevated pro-inflammatory cytokines, but significantly reduced healing and differentiation genes. VPA significantly upregulated the pro-inflammatory cytokine levels, while MG-149 significantly downregulated them. Pluripotency genes were not significantly affected by any regimen.

CONCLUSIONS

At the attempted concentrations, TSA upregulated the defensins gene expression levels, and MG-149 exerted a remarkable anti-inflammatory effect; therefore, they could favorably impact the immunological profile of hDPCs.

CLINICAL RELEVANCE

Targeting hDPC nuclear function could be a promising option in the scope of the biological management of inflammatory pulp diseases.

Potential applications of medicinal herbs and phytochemicals in oral and dental health: Status quo and future perspectives

OBJECTIVE

Herbal therapies are utilized to treat a broad diversity of diseases all over the globe. Although no clinical studies have been conducted to demonstrate the antibacterial, antimicrobial, and antiplaque characteristics of these plants, this does not imply that they are ineffectual as periodontal treatments or anti-cariogenic drugs. However, there is a scarcity of research confirming their efficacy and worth.

SUBJECT

Herbs are utilized in dentistry as antimicrobial, antineoplastic, antiseptic, antioxidant, and analgesics agents as well as for the elimination of bad breath. In addition, the application of herbal agents in tissue engineering improved the regeneration of oral and dental tissues. This study reviews the application of medicinal herbs for the treatment of dental and oral diseases in different aspects.

METHODS

This article focuses on current developments in the use of medicinal herbs and phytochemicals in oral and dental health. An extensive literature review was conducted via an Internet database, mostly PubMed. The articles included full-text publications written in English without any restrictions on a date.

CONCLUSION

Plants have been suggested, as an alternate remedy for oral-dental problems, and this vocation needs long-term dependability. More research on herbal medicine potential as pharmaceutical sources and/or therapies is needed.

Tideglusib-incorporated nanofibrous scaffolds potently induce odontogenic differentiation

Pulp-Dentin regeneration is a key aspect of maintain tooth vitality and enabling good oral-systemic health. This study aimed to investigate a nanofibrous scaffold loaded with a small molecule i.e. Tideglusib to promote odontogenic differentiation. Tideglusib (GSK-3β inhibitor) interaction with GSK-3β was determined using molecular docking and stabilization of β-catenin was examined by confocal microscopy. 3D nanofibrous scaffolds were fabricated through electrospinning and their physicochemical characterizations were performed. Scaffolds were seeded with mesenchymal stem cells or pre-odontoblast cells to determine the cells proliferation and odontogenic differentiation. Our results showed that Tideglusib (TG) binds with GSK-3β at Cys199 residue. Stabilization and nuclear translocation of β-catenin was increased in the odontoblast cells treated with TG. SEM analysis revealed that nanofibers exhibited controlled architectural features that effectively mimicked the natural ECM. UV-Vis spectroscopy demonstrated that TG was incorporated successfully and released in a controlled manner. Both kinds of biomimetic nanofibrous matrices (PCLF-TG100, PCLF-TG1000) significantly stimulated cells proliferation. Furthermore, these scaffolds significantly induced dentinogenic markers (ALP, and DSPP) expression and biomineralization. In contrast to current pulp capping material driving dentin repair, the sophisticated, polymeric scaffold systems with soluble and insoluble spatiotemporal cues described here can direct stem cell differentiation and dentin regeneration. Hence, bioactive small molecule-incorporated nanofibrous scaffold suggests an innovative clinical tool for dentin tissue engineering.

Enhancing effects of immobilized chondroitin sulfate on odontogenic differentiation of dental pulp stem cells and reparative dentin formation

OBJECTIVES

Chondroitin sulfate (CS) is a major proteoglycan involved in the mineralization of the organic matrix of dentin. In this study, the roles of CS immobilized in crosslinked collagen I hydrogels (CS-Col I) on odontogenic differentiation of dental pulp stem cells (DPSCs) and reparative dentin formation were investigated.

METHODS

Different concentrations of CS were incorporated into the genipin- crosslinked Col I hydrogels (CS-0.05, CS-0.1, and CS-0.2 respectively). The influences of CS on proliferation and odontogenic differentiation of DPSCs were investigated. Finally, the effect of the functionalized hydrogel on the formation of reparative dentin was analyzed in a rat pulp capping model in vivo.

RESULTS

CS improved the proliferation of DPSCs seeded on the hydrogels (p<0.05). CS also enhanced the mineralization activities and increased the expression levels of the odontogenic related proteins of DPSCs on day 7 and day 14 (p<0.05). In vivo, CS-0.1 hydrogel induced reparative dentin formation with higher quality compared to mineral trioxide aggregate (MTA).

CONCLUSION

CS immobilized in Col I hydrogels could induce odontogenic differentiation of DPSCs in vitro and promote homogeneous mineralized barrier formation in vivo. CS-Col I hydrogel has the potential for reparative dentin formation of high quality in direct pulp capping.

Next-generation biomaterials for dental pulp tissue immunomodulation

OBJECTIVES

The current standard for treating irreversibly damaged dental pulp is root canal therapy, which involves complete removal and debridement of the pulp space and filling with an inert biomaterial. A regenerative approach to treating diseased dental pulp may allow for complete healing of the native tooth structure and enhance the long-term outcome of once-necrotic teeth. The aim of this paper is, therefore, to highlight the current state of dental pulp tissue engineering and immunomodulatory biomaterials properties, identifying exciting opportunities for their synergy in developing next-generation biomaterials-driven technologies.

METHODS

An overview of the inflammatory process focusing on immune responses of the dental pulp, followed by periapical and periodontal tissue inflammation are elaborated. Then, the most recent advances in treating infection-induced inflammatory oral diseases, focusing on biocompatible materials with immunomodulatory properties are discussed. Of note, we highlight some of the most used modifications in biomaterials' surface, or content/drug incorporation focused on immunomodulation based on an extensive literature search over the last decade.

RESULTS

We provide the readers with a critical summary of recent advances in immunomodulation related to pulpal, periapical, and periodontal diseases while bringing light to tissue engineering strategies focusing on healing and regenerating multiple tissue types.

SIGNIFICANCE

Significant advances have been made in developing biomaterials that take advantage of the host's immune system to guide a specific regenerative outcome. Biomaterials that efficiently and predictably modulate cells in the dental pulp complex hold significant clinical promise for improving standards of care compared to endodontic root canal therapy.

Bioactivity of Dental Restorative Materials: FDI Policy Statement

The term bioactivity is being increasingly used in medicine and dentistry. Due to its positive connotation, it is frequently utilised for advertising dental restorative materials. However, there is confusion about what the term means, and concerns have been raised about its potential overuse. Therefore, FDI decided to publish a Policy Statement about the bioactivity of dental restorative materials to clarify the term and provide some caveats for its use in advertising. Background information for this Policy Statement was taken from the current literature, mainly from the PubMed database and the internet. Bioactive restorative materials should have beneficial/desired effects. These effects should be local, intended, and nontoxic and should not interfere with a material's principal purpose, namely dental tissue replacement. Three mechanisms for the bioactivity of such materials have been identified: purely biological, mixed biological/chemical, or strictly chemical. Therefore, when the term bioactivity is used in an advertisement or in a description of a dental restorative material, scientific evidence (in vitro or in situ, and preferably in clinical studies) should be provided describing the mechanism of action, the duration of the effect (especially for materials releasing antibacterial substances), and the lack of significant adverse biological side effects (including the development and spread of antimicrobial resistance). Finally, it should be documented that the prime purpose, for instance, to be used to rebuild the form and function of lost tooth substance or lost teeth, is not impaired, as demonstrated by data from in vitro and clinical studies. The use of the term bioactive dental restorative material in material advertisement/information should be restricted to materials that fulfil all the requirements as described in the FDI Policy Statement.

Tissue Engineering with Stem Cell from Human Exfoliated Deciduous Teeth (SHED) and Collagen Matrix, Regulated by Growth Factor in Regenerating the Dental Pulp

Maintaining dental pulp vitality and preventing tooth loss are two challenges in endodontic treatment. A tooth lacking a viable pulp loses its defense mechanism and regenerative ability, making it more vulnerable to severe damage and eventually necessitating extraction. The tissue engineering approach has drawn attention as an alternative therapy as it can regenerate dentin-pulp complex structures and functions. Stem cells or progenitor cells, extracellular matrix, and signaling molecules are triad components of this approach. Stem cells from human exfoliated deciduous teeth (SHED) are a promising, noninvasive source of stem cells for tissue regeneration. Not only can SHEDs regenerate dentin-pulp tissues (comprised of fibroblasts, odontoblasts, endothelial cells, and nerve cells), but SHEDs also possess immunomodulatory and immunosuppressive properties. The collagen matrix is a material of choice to provide structural and microenvironmental support for SHED-to-dentin pulp tissue differentiation. Growth factors regulate cell proliferation, migration, and differentiation into specific phenotypes via signal-transduction pathways. This review provides current concepts and applications of the tissue engineering approach, especially SHEDs, in endodontic treatment.

Outcome of full pulpotomy in mature permanent molars using 3 calcium silicate-based materials: A parallel, double blind, randomized controlled trial

AIM

The aim of the study was to compare the outcome of full pulpotomy using 2 calcium silicate-based materials compared with mineral trioxide aggregate (MTA) in symptomatic mature permanent teeth with carious pulp exposure.

METHODOLOGY

This study was designed as a parallel, double blind, randomized controlled trial where symptomatic mature permanent teeth with carious pulp exposure meeting the inclusion criteria were randomly treated with full pulpotomy using one of 3 calcium silicate-based materials (ProRoot MTA, Biodentine and TotalFill). Full pulpotomy was performed, and haemostasis was achieved via a cotton pellet moistened with 2.5% NaOCl. A 3-mm layer of the calcium silicate-based material was randomly placed as the pulpotomy agent through a block randomization process followed by a resin-based composite restoration. Postoperative periapical radiograph was taken. Clinical and radiographic evaluation were completed after 6 months and 1 year. The patient and evaluator were blinded to the type of materials used. Pain levels were scored preoperatively and 7 days after treatment. Effect of potential prognosis factors including gender, age, diagnosis, bleeding time and type of caries were also analysed.

RESULTS

One hundred and sixty-four teeth in 146 patients received full pulpotomy and were randomly assigned to either the tested or control material through block randomization technique (50 MTA, 50 Biodentine and 64 TotalFill). The age ranged from 10 to 70 years. The diagnosis was irreversible pulpitis in 112 teeth (72%) and reversible pulpitis in 28 teeth (28%). The majority of patients presented with severe pain, during the first week 96.9% reported complete relief of pain or mild pain. Four cases had immediate failure. At 6 months the overall success rate was 92.2%, over 1 year 156/164 teeth attended follow-up with 12 failures (2 restorative failures and 10 endodontic failures), the overall success of pulpotomy at 1 year was 92.3% (144/156); 91.8% in MTA, 93.3% in Biodentine and 91.9% in TotalFill with no significant difference amongst the groups and no side effects observed. No significant association was evident between outcome and the investigated variables.

CONCLUSIONS

The 1-year success rate of full pulpotomy did not differ significantly between Biodentine pulpotomy, TotalFill pulpotomy, and MTA pulpotomy. The study was registered with clinical trials; registration number (NCT04345263).

Towards Induction of Angiogenesis in Dental Pulp Stem Cells Using Chitosan-Based Hydrogels Releasing Basic Fibroblast Growth Factor

Introduction. Chitosan is a natural biopolymer that attracted enormous attention in biomedical fields. The main components of regenerative endodontic procedures (REPs), as well as tissue engineering, are scaffolds, stem cells, and growth factors. As one of the basic factors in the REPs is maintaining vascularization, this study was aimed at developing basic fibroblast growth factor- (bFGF-) loaded scaffolds and investigating their effects on the angiogenic induction in human dental pulp stem cells (hDPSCs). Methods. Poly (ε-caprolactone) (PCL)/chitosan- (CS-) based highly porous scaffold (PCL/CS) was prepared and evaluated by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analyses. The adhesion and survival potency of seeded cells were assessed by SEM and MTT assays, respectively. The amount of angiogenic markers was investigated in gene and protein levels by real-time PCR and western blotting assays, respectively. Results. Based on our findings, the SEM and FTIR tests confirmed the appropriate structure of synthesized scaffolds. Besides, the adhesion and survival rate of cells and the levels of VEGFR-2, Tie2, and Angiopoietin-1 genes were increased significantly in the PCL/CS/bFGF group. Also, the western blotting results showed the upregulation of these markers at protein levels, which were considerably higher at the PCL/CS/bFGF group ( $P<0.05$ ). Conclusions. On a more general note, this study demonstrates that the bFGF-loaded PCL/CS scaffolds have the potential to promote angiogenesis of hDPSCs, which could provide vitality of dentin-pulp complex as the initial required factor for regenerative endodontic procedures.

Evaluation of Injectable Hyaluronic Acid-Based Hydrogels for Endodontic Tissue Regeneration

Dental pulp tissue engineering (TE) endeavors to regenerate dentin/pulp complex by combining a suitable supporting matrix, stem cells, and biochemical stimuli. Such procedures foresee a matrix that can be easily introduced into the root canal system (RCS) and tightly adhere to dentin walls to assure the dentin surface’s proper colonization with progenitor cells capable of restoring the dentin/pulp complex. Herein was investigated an injectable self-setting hyaluronic acid-based (HA) hydrogel system, formed by aldehyde-modified (a-HA) with hydrazide-modified (ADH), enriched with platelet lysate (PL), for endodontic regeneration. The hydrogels’ working (wT) and setting (sT) times, the adhesion to the dentine walls, the hydrogel’s microstructure, and the delivery of human dental pulp cells (DPCs) were studied in vitro. Hydrogels incorporating PL showed a suitable wT and sT and a porous microstructure. The tensile tests showed that the breaking point occurs after 4.3106 ± 1.8677 mm deformation, while in the indentation test after 1.4056 ± 0.3065 mm deformation. Both breaking points occur in the hydrogel extension. The HA/PL hydrogels exhibited supportive properties and promoted cell migration toward dentin surfaces in vitro. Overall, these results support using PL-laden HA injectable hydrogels (HA/PL) as a biomaterial for DPCs encapsulation, thereby displaying great clinical potential towards endodontic regenerative therapies.

Effect of Magnesium on Dentinogenesis of Human Dental Pulp Cells

Introducing therapeutic ions into pulp capping materials has been considered a new approach for enhancing regeneration of dental tissues. However, no studies have been reported on its dentinogenic effects on human dental pulp cells (HDPCs). This study was designed to investigate the effects of magnesium (Mg²⁺) on cell attachment efficiency, proliferation, differentiation, and mineralization of HDPCs. HDPCs were cultured with 0.5 mM, 1 mM, 2 mM, 4 mM, and 8 mM concentrations of supplemental Mg²⁺ and 0 mM (control). Cell attachment was measured at 4, 8, 12, 16, and 20 hours. Cell proliferation rate was evaluated at 3, 7, 10, 14, and 21 days. Crystal violet staining was used to determine cell attachment and proliferation rate. Alkaline phosphatase (ALP) activity was assessed using the fluorometric assay at 7, 10, and 14 days. Mineralization of cultures was measured by Alizarin red staining. Statistical analysis was done using multiway analysis of variance (multiway ANOVA) with Wilks' lambda test. Higher cell attachment was shown with 0.5 mM and 1 mM at 16 hours compared to control (P < 0.0001). Cells with 0.5 mM and 1 mM supplemental Mg²⁺ showed significantly higher proliferation rates than control at 7, 10, 14, and 21 days (P < 0.0001). However, cell proliferation rates decreased significantly with 4 mM and 8 mM supplemental Mg²⁺ at 14 and 21 days (P < 0.0001). Significantly higher levels of ALP activity and mineralization were observed in 0.5 mM, 1 mM, and 2 mM supplemental Mg²⁺ at 10 and 14 days (P < 0.0001). However, 8 mM supplemental Mg²⁺ showed lower ALP activity compared to control at 14 days (P < 0.0001), while 4 mM and 8 mM supplemental Mg²⁺showed less mineralization compared to control (P < 0.0001). The study indicated that the optimal (0.5–2 mM) supplemental Mg²⁺ concentrations significantly upregulated HDPCs by enhancing cell attachment, proliferation rate, ALP activity, and mineralization. Magnesium-containing biomaterials could be considered for a future novel dental pulp-capping additive in regenerative endodontics.

Local Drug Delivery Systems for Vital Pulp Therapy: A New Hope

Vital pulp therapy (VPT) is deliberated as an ultraconservative/minimally invasive approach for the conservation of vital pulpal tissues, preservation of dental structure, and maintenance of tooth function in the oral cavity. In VPT, following the exposure of the dental pulp, the environment is prepared for the possible healing and probable refunctionalisation of pulpal connective tissue. However, to succeed in VPT, specific biomaterials are used to cover and/or dress the exposed pulp, lower the inflammation, heal the dental pulp, provoke the remaining odontoblastic cells, and induce the formation of a hard tissue, i.e., the dentinal bridge. It can be assumed that if the employed biomaterial is transferred to the target site using a specially designed micro-/nanosized local drug delivery system (LDDS), the biomaterial would be placed in closer proximity to the connective tissue, may be released in a controlled and sustained pattern, could properly conserve the remaining dental pulp and might appropriately enhance hard-tissue formation. Furthermore, the loaded LDDS could help VPT modalities to be more ultraconservative and may minimise the manipulation of the tooth structure as well as pulpal tissue, which could, in turn, result in better VPT outcomes.

In Vivo Evaluation of Decellularized Human Tooth Scaffold for Dental Tissue Regeneration

Conventional root canal treatment may result in loss of tooth vitality, which can lead to unfavorable treatment outcomes. Notably, a ceased tooth development of immature permanent teeth with open apices, regeneration of periodontal ligaments (PDL), and pulp is highly expected healing process. For regeneration, the scaffold is one of the critical components that carry biological benefits. Therefore, this study evaluated a decellularized human tooth as a scaffold for the PDL and pulp tissue regeneration. A tooth scaffold was fabricated using an effective decellularization method as reported in previous studies. PDL stem cells (PDLSCs) and dental pulp stem cells (DPSCs) obtained from human permanent teeth were inoculated onto decellularized scaffolds, then cultured to transplant into immunosuppressed mouse. After 9 weeks, PDLSCs and DPSCs that were inoculated onto decellularized tooth scaffolds and cultured in an in vivo demonstrated successful differentiation. In PDLSCs, a regeneration of the cementum/PDL complex could be expected. In DPSCs, the expression of genes related to revascularization and the hard tissue regeneration showed the possibility of pulp regeneration. This study suggested that the potential possible application of decellularized human tooth could be a scaffold in regeneration PDL and pulp tissue along with PDLSCs and DPSCs, respectively, as a novel treatment method.

Preserving the vitality of teeth adjacent to a large radicular cyst in periapical microsurgery: a case report with 4-year follow-up

Background

Radicular cysts may enlarge considerably, cause extensive bone destruction, and jeopardize the integrity of the associated vital teeth. The different treatment approaches are aimed mainly at eliminating the cystic epithelial membrane while reducing the risk of injury to vital structures. Contrary to other treatment modalities, preapical surgery offers an unequivocal single occasion resolution for the patient. However, it has been associated with higher risk of collateral damages.

Case presentation

A patient presented with a large radicular cyst originating from a maxillary lateral incisor. The adjacent central and canine teeth initially failed to exhibit responses to sensibility tests but showed signs of vitality. Microsurgical management was aimed at enucleating the cystic membrane while maintaining adjacent teeth vitality. Upon careful and controlled cyst enucleation under the dental operating microscope, the neurovascular bundle of one of the involved teeth was visualized and its integrity was maintained throughout the procedure.

Results

The procedure was successful and follow up recalls revealed recovery of normal sensibility of tooth 11 and 13 with complete bone regeneration around their apices.

Conclusion

Within the limitation of the present case report, we demonstrated that complete excision of large periapical cyst can be performed without sacrificing the vitality of the adjacent teeth, by preserving the integrity of their neurovascular supply through controlled microsurgical enucleation, and by a potential apical vascular repair ensuing unintended injury. Diagnosing the pulp vitality of non-offending teeth whose apices protrude into the cystic lumen is a complex process and can be misleading. Pressure from the growing cyst can inhibit vital teeth responses to neural-based sensibility tests leading to false negative results. Thus, in such cases, the use of blood perfusion-based vitality testing is recommended for correct initial diagnosis.

Platform technologies for regenerative endodontics from multifunctional biomaterials to tooth-on-a-chip strategies

OBJECTIVES

The aim of this review is to highlight recent progress in the field of biomaterials-mediated dental pulp tissue engineering. Specifically, we aim to underscore the critical design criteria of biomaterial platforms that are advantageous for pulp tissue engineering, discuss models for preclinical evaluation, and present new and innovative multifunctional strategies that hold promise for clinical translation.

MATERIALS AND METHODS

The current article is a comprehensive overview of recent progress over the last 5 years. In detail, we surveyed the literature in regenerative pulp biology, including novel biologic and biomaterials approaches, and those that combined multiple strategies, towards more clinically relevant models. PubMed searches were performed using the keywords: "regenerative dentistry," "dental pulp regeneration," "regenerative endodontics," and "dental pulp therapy."

RESULTS

Significant contributions to the field of regenerative dentistry have been made in the last 5 years, as evidenced by a significant body of publications. We chose exemplary studies that we believe are progressive towards clinically translatable solutions. We close this review with an outlook towards the future of pulp regeneration strategies and their clinical translation.

CONCLUSIONS

Current clinical treatments lack functional and predictable pulp regeneration and are more focused on the treatment of the consequences of pulp exposure, rather than the restoration of healthy dental pulp.

CLINICAL RELEVANCE

Clinically, there is great demand for bioinspired biomaterial strategies that are safe, efficacious, and easy to use, and clinicians are eager for their clinical translation. In particular, we place emphasis on strategies that combine favorable angiogenesis, mineralization, and functional tissue formation, while limiting immune reaction, risk of microbial infection, and pulp necrosis.

Immunomodulatory Expression of Cathelicidins Peptides in Pulp Inflammation and Regeneration: An Update

The role of inflammatory mediators in dental pulp is unique. The local environment of pulp responds to any changes in the physiology that are highly fundamental, like odontoblast cell differentiation and other secretory activity. The aim of this review is to assess the role of cathelicidins based on their capacity to heal wounds, their immunomodulatory potential, and their ability to stimulate cytokine production and stimulate immune-inflammatory response in pulp and periapex. Accessible electronic databases were searched to find studies reporting the role of cathelicidins in pulpal inflammation and regeneration published between September 2010 and September 2020. The search was performed using the following databases: Medline, Scopus, Web of Science, SciELO and PubMed. The electronic search was performed using the combination of keywords "cathelicidins" and "dental pulp inflammation". On the basis of previous studies, it can be inferred that LL-37 plays an important role in odontoblastic cell differentiation and stimulation of antimicrobial peptides. Furthermore, based on these outcomes, it can be concluded that LL-37 plays an important role in reparative dentin formation and provides signaling for defense by activating the innate immune system.

Vital pulp therapy in carious pulp-exposed permanent teeth: an umbrella review

OBJECTIVE

There has been increasing evidence indicating rather high success rates of vital pulp therapies. This umbrella review aimed to provide an overview of existing systematic reviews regarding the outcomes of vital pulp therapy, specifically direct pulp capping, partial pulpotomy and full pulpotomy, in carious pulp-exposed permanent human teeth.

MATERIALS AND METHODS

The specific PICO questions were as follows: Population - permanent human teeth with carious pulp exposure; Intervention - direct pulp capping with pulp capping materials; Comparators - partial pulpotomy and full pulpotomy; Outcomes - success rate and prognostic factors. PubMed, Ovid and Cochrane databases were searched in conjunction with hand searching. Grey literature was searched too. Study selection, data extraction and study appraisal were performed independently by two authors. A consensus was reached through discussion when disagreements arose.

RESULTS

Six articles fulfilled the inclusion criteria. Higher and more predictable success rates of ≥ 2 years were observed for partial pulpotomy and full pulpotomy in carious pulp-exposed permanent human teeth as compared to direct pulp capping. Possible prognostic factors (pre-operative pulp status, pulp capping material and apex closure) yielded conflicting results. Restorative material, periapical status at baseline, final irrigation solution, age and study type did not seem to affect the treatment outcome.

CONCLUSIONS

Vital pulp therapy is a reliable treatment option for permanent teeth with carious pulp exposure. However, more high-quality studies are required to corroborate this finding.

CLINICAL RELEVANCE

Vital pulp therapy could be considered as an alternative for root canal treatment for carious pulp-exposed permanent teeth.

Histology-based profile of inflammatory mediators in experimentally induced pulpitis in a rat model: screening for possible biomarkers

Aim

To profile molecular changes in lipopolysaccharide (LPS)‐induced experimental pulpitis in a rat model and explore the feasibility of a molecular‐based diagnostic strategy for pulpitis.

Methodology

Seventy‐three maxillary incisors of Sprague‐Dawley rats were used to establish pulpitis models with LPS. Inflammatory grading was performed in four equal sections of the pulp divided from the injured site to the root apex. An antibody array was used to compare the expression of 67 molecules between control pulp and inflamed pulp 12 and 72 h after LPS application. The levels of differentially expressed molecules in the control and inflamed pulp (collected at 3, 6, 9, 12, 24 and 72 h after LPS treatment) were examined via ELISA, and correlations between inflammatory scores and molecule expression were assessed. The molecule distributions in the pulp were investigated by immunofluorescence staining. Data were analysed with paired t‐test, one‐way anova, Kruskal–Wallis tests, and Spearman’s and Pearson’s correlations with significance set at P < 0.05.

Results

Polymorphonuclear neutrophils were observed in the injured site 3 h after LPS stimulation. Inflammatory infiltration peaked at 12 h and was limited to the injured site with osteodentine deposition at 72 h. Thirteen molecules were significantly differentially expressed between the control and LPS‐injured pulp. ELISA validated that tissue inhibitor of metalloproteinase‐1 (TIMP‐1) expression dramatically peaked at 12 h (compared with other time points, P < 0.05) and returned to baseline at 72 h. The TIMP‐1 concentration was strongly correlated with inflammation severity in the apical three‐quarters of the pulp, and the strongest correlation was found in the lower‐middle quarter (r = 0.786, P < 0.001). Immunofluorescence staining revealed that in the apical three‐quarters of the pulp, TIMP‐1 expression was significantly higher in the 12 h group than in the control and 3, 6, 24 and 72 h groups (P < 0.01).

Conclusion

This study provides a molecular profile of LPS‐induced pulpitis in a rat model. TIMP‐1 had a strong positive correlation with the severity of dental pulp inflammation, verifying the feasibility of applying biomarkers to identify specific pathological conditions in pulpitis.

N-Cadherin Regulates the Odontogenic Differentiation of Dental Pulp Stem Cells via β-Catenin Activity

Dental pulp stem cell (DPSC) transplantation has shown new prospects in dental pulp regeneration, and is of great significance in the treatment of pulpitis and pulp necrosis. The fate and regenerative potential of stem cells are dependent, to a great extent, on their microenvironment, which is composed of various tissue components, cell populations, and soluble factors. N-cadherin-mediated cell–cell interaction has been implicated as an important factor in controlling the cell-fate commitment of mesenchymal stem cells. In this study, the effect of N-cadherin on odontogenic differentiation of DPSCs and the potential underlying mechanisms, both in vitro and in vivo, was investigated using a cell culture model and a subcutaneous transplantation mouse model. It was found that the expression of N-cadherin was reversely related to the expression of odontogenic markers (dentin sialophosphoprotein, DSPP, and runt-related transcription factor 2, Runx2) during the differentiation process of DPSCs. Specific shRNA-mediated knockdown of N-cadherin expression in DPSCs significantly increased the expression of DSPP and Runx2, alkaline phosphatase (ALP) activity, and the formation of mineralized nodules. Notably, N-cadherin silencing promoted nucleus translocation and accumulation of β-catenin. Inhibition of β-catenin by a specific inhibitor XAV939, reversed the facilitating effects of N-cadherin downregulation on odontogenic differentiation of DPSCs. In addition, knockdown of N-cadherin promoted the formation of odontoblast-like cells and collagenous matrix in β-tricalcium phosphate/DPSCs composites transplanted into mice. In conclusion, N-cadherin acted as a negative regulator via regulating β-catenin activity during odontogenic differentiation of DPSCs. These data may help to guide DPSC behavior by tuning the N-cadherin-mediated cell–cell interactions, with implications for pulp regeneration.

Response of pulp cells to resin infiltration of enamel white spot-like lesions

OBJECTIVES

To investigate the trans-enamel and trans-dentinal biological effects of treating enamel white spot-like lesions (EWSLs) with resin infiltration components (RICs) on odontoblast-like cells (MDPC-23) and human dental pulp cells (HDPCs).

METHODS

EWSLs were induced in 60 enamel/dentin discs (4.0 ± 0.2 mm thick) using S. mutans. The discs were adapted into artificial pulp chambers and MDPC-23 were seeded on the dentin surface. The components of a resin infiltration system (Icon) were applied individually or in combination on the enamel surface as following (n = 10/treatment): Etch, Infiltrant, Etch+Infiltrant, or Etch+Dry+Infiltrant. The application of water or hydrogen peroxide served as negative and positive controls, respectively. After 72 h, MDPC-23 viability was evaluated. The extracts were exposed for 72 h to pre-cultured MDPC-23 and HDPCs in 96-well plates to evaluate cell viability, alkaline phosphatase activity (ALP), mineralized nodule formation (MN), and the expression of inflammatory cytokines (ICs) and mineralization-related genes (MRs). Data were analyzed by ANOVA complemented with Tukey or Games-Howell post-hocs (α = 5%).

RESULTS

Cell viability, ALP activity, and MN formation were significantly reduced in response to the RICs, presenting intermediate values compared to positive and negative controls. Likewise, ICs were upregulated, whereas MRs were downregulated. Among the RICs, the Etch component caused the most notorious detrimental effects.

SIGNIFICANCE

Resin infiltration of EWSLs negatively affected the metabolism of pulp cells in vitro. Therefore, even though resin infiltration is a micro-invasive therapy for non-cavitated caries in enamel, it should be closely followed up seen that components may diffuse and unbalance pulp homeostasis.

Cytotoxicity assessment of different doses of ozonated water on dental pulp cells

Background

The purpose of this study was to assess the cytotoxicity of various concentrations of ozonated water (OW) on human primary dental pulp cells.

Methods

Human primary dental pulp cells were isolated from exfoliated primary canine teeth of an 11-year-old patient with good systemic and oral health. Afterwards, cells were divided into 6 experimental groups; four groups of OW in concentrations of 2 mg/L, 4 mg/L, 8 mg/L, and 16 mg/L, untreated control group, and cell culture without cells. Cytotoxicity was evaluated after exposure for 5-min exposure using Mosmann’s Tetrazolium Toxicity (MTT) assay at 0 h and 48 h time points. Data were analyzed using a repeated measures analysis of variance and Post-hoc tests were performed using Bonferroni correction for multiple comparisons.

Results

All experimental groups showed proliferation at 0 h time point. However, all groups also experienced a decrease in overtime at 48 h time point (p < 0.05). At both time points 2 mg/L OW showed the highest cell viability as well as proliferation. At 0 h time point, the increase in cell viability for all experimental groups was found statistically significant when compared to positive control group (p < 0.05). At 48 h time point, although 8 mg/L and 16 mg/L OW showed statistically significant reduction in compare to 0 h time point, 2 mg/L and 4 mg/L OW groups didn’t experience any statistically significant difference (p < 0.05).

Conclusion

Considering our findings, due to ozonated water's induced a higher proliferation rate of dental pulp cells, indicating their biocompatibility and a possible adjuvant on irrigating agent in regenerative endodontic procedures.

Success of pulpotomy in mature permanent teeth with irreversible pulpitis: A systematic review

The objective of the present systematic review is to evaluate the success of pulpotomy in mature permanent teeth presented with irreversible pulpitis. The following databases were searched: PubMed, Oral and Dentistry Database, Cochrane, and CINAHL plus. We included studies published in the English language only. However, narrative reviews and case reports/series were excluded. The first electronic and hand search yielded a total of 2851 articles. After going through extensive screening and eligibility process, only six articles were finally selected for the review. The follow-up period ranged from 1 to 10 years. Randomized controlled trial compared pulpotomy with the root canal treatment and reported comparable and even better success of the pulpotomy (78% success). All the other studies have also shown better clinical and radiographic success of pulpotomy (68%–100%). Pulpotomy can be considered an alternative option for mature permanent teeth with irreversible pulpitis.

Microscopic and elemental characterization of hydrated dental pulp capping agents

Context:

Characteristics of dental pulp capping agents may influence its interaction with the pulpal cells and can impact the treatment outcome.

Aims:

This study aims to microscopically characterize various pulp capping agents following hydration.

Settings and Design:

Original research.

Materials and Methods:

Disk-shaped specimens of five calcium silicate-based materials, i.e., mineral trioxide aggregate (MTA) Angelus, Biodentine, TheraCal LC, ApaCal ART, and Endocem MTA were prepared. After final set, the materials were immersed in 10 mL of deionized water for 14 days at 37°C. The set materials were characterized by scanning electron microscopy (SEM), X-ray energy dispersive analysis (EDX), and X-ray diffraction (XRD) analysis along with pH analysis of the storage solution using pH meter.

Results:

On SEM analysis, all the materials showed crystalline deposition on the cement surface with Biodentine exhibiting the most dense and homogenous microstructure. Calcium-silicate-hydrate and calcium hydroxide (CH) were observed as dark-grey and light-grey matrix material, respectively. EDX analysis revealed a high concentration of calcium. The other major elements were oxygen and carbon. The surface calcium concentration in the tested specimens was as follows: Biodentine (42.59 wt.%) > MTA Angelus (38.51wt.%) > Endocem MTA (30.24wt.%) > TheraCal LC (27.51wt.%) > ApaCal ART (22.02wt.%). On XRD analysis, all the materials exhibited peaks for tricalcium silicate and CH, after 14 days of hydration.

Conclusions:

The higher surface calcium level in Biodentine and MTA Angelus may enhance reparative dentin formation. The surface calcium concentration of Endocem MTA and ApaCal ART was found to be lesser than that of MTA Angelus, but with the added advantage of fast-setting property. Hence, they are potential alternative materials for vital pulp therapy.

An uncommon type of segmental root development after revitalization

AIM

To describe four cases of an uncommon type of segmental root development after endodontic revitalization procedures. The formation, development and prognosis of this phenomenon are discussed, along with the causes and preventive measures.

SUMMARY

This report describes one immature maxillary anterior tooth with an extensive periapical lesion after partial extrusion caused by trauma and three immature mandibular premolars with extensive periapical lesions after fracture of the dens evaginatus. All four teeth underwent revitalization procedures. During follow-up, an uncommon type of segmental root development was observed in each case, where the apical segment appeared to detach from the body of the root and developed separately. In all cases, the detached apical root segments continued to develop with a shape and structure similar to that of a normal root tip. However, further development of the root body did not appear to occur. The follow-up times of the present cases were 11, 60, 41 and 67 months, respectively. All four teeth remain intact and functioned normally without symptoms. Cases 2 and 3 displayed positive reactions to electrical pulp tests during follow-up.

KEY LEARNING POINTS

Trauma and extensive periapical inflammation may result in the detachment of Hertwig's epithelial root sheath (HERS) and apical papilla from the root, thus creating a separate apical root segment. Formation of an apical root segment could be regarded as evidence of displacement of the HERS and apical papilla. Once this occurs, there is no chance that the main root of the tooth will develop into a normal-sized root. This type of segmental root development is always possible. If the teeth have suffered from severe trauma or have long-term and large periapical lesions before revitalization, the possibility of segmental root development should be considered. During the process of revitalization, intracanal bleeding is induced by rotating a pre-curved K-file 2 mm past the apical foramen. This procedure should be done gently to protect the apical structures and avoid iatrogenic factors that could lead to abnormal root development.

Potential Application of Human β-Defensin 4 in Dental Pulp Repair

When pulp tissue is damaged by caries or trauma, vital pulp therapy (VPT) can help preserve the pulp tissue for long-term retention of teeth. However, the choice of pulp capping agent used in VPT is important for the successful preservation of the pulp tissue. Here we investigated the expression and biological function of human β-defensin 4 (HBD4) in dental pulp stem cells (DPSC) and explored its potential as a pulp capping agent. We examined the expression of HBD4 in DPSC in vitro using qPCR and immunofluorescence staining. We also looked at the effect of HBD4 on inflammatory factors in lipopolysaccharide (LPS)-stimulated DPSC, and its effects on mineralizing cell phenotype differentiation, via qPCR and western blot. Finally, we examined the ability of HBD4 to promote the restoration of the pulp-dentin complex in vivo, using male Wistar rats with reversible pulpitis. We found HBD4 was highly expressed in DPSC stimulated by TNF-α and IL-1α. HBD4 down-regulated the expression of inflammatory mediators (i.e., IL-1α, IL-1β, IL-6, TNF-α) in LPS-stimulated DPSC, and suppressed MAPK activity and the NF-κB pathway. HBD4 also enhanced the differentiation of DPSC into osteoblasts or odontoblasts, potentially by modulating the Notch pathway. Furthermore, HBD4 controlled the degree of pulp inflammation in a rat model of reversible pulpitis and induced the formation of restorative dentin. Together our findings indicate HBD4 may be a useful pulp capping agent for use in VPT.

Pulp-Dentin Tissue Healing Response: A Discussion of Current Biomedical Approaches

Dental pulp tissue exposed to mechanical trauma or cariogenic process results in root canal and/or periapical infections, and conventionally treated with root canal procedures. The more recent regenerative endodontic procedure intends to achieve effective root canal disinfection and adequate pulp–dentin tissue regeneration; however, numerous limitations are reported. Because tooth is composed of vital soft pulp enclosed by the mineralized hard tissue in a highly organized structure, complete pulp–dentin tissue regeneration has been challenging to achieve. In consideration of the limitations and unique dental anatomy, it is important to understand the healing and repair processes through inflammatory-proliferative-remodeling phase transformations of pulp–dentin tissue. Upon cause by infectious and mechanical stimuli, the innate defense mechanism is initiated by resident pulp cells including immune cells through chemical signaling. After the expansion of infection and damage to resident pulp–dentin cells, consequent chemical signaling induces pluripotent mesenchymal stem cells (MSCs) to migrate to the injury site to perform the tissue regeneration process. Additionally, innovative biomaterials are necessary to facilitate the immune response and pulp–dentin tissue regeneration roles of MSCs. This review highlights current approaches of pulp–dentin tissue healing process and suggests potential biomedical perspective of the pulp–dentin tissue regeneration.

The effect of hyaluronic acid hydrogels on dental pulp stem cells behavior

Dental caries and trauma, particularly in childhood, are among the most prevalent teeth problems, which result in the creation of cavities and probably tooth loss. Thus, novel regenerative approaches with high efficiency and less toxicity are required. Stem cell therapy along with the implementation of scaffolds has provided excellent opportunities in the regeneration of teeth structure. Hyaluronic acid (HA) hydrogels have enticed great attention in the field of regenerative medicine. The unique chemical and structural properties of HA and its derivatives have enabled their application in tissue engineering. Several factors such as the location and type of the lesion, teeth age, the type of capping materials determine the success rate of pulp therapy. HA hydrogels have been considered as biocompatible and safe scaffold supports in human dental cell therapies.

Autologous transplantation of deciduous tooth pulp into necrotic young permanent teeth for pulp regeneration in a dog model

Objectives

To investigate the potential for pulpal regeneration via autologous transplantation of deciduous tooth pulp into immature necrotic permanent teeth using an experimental dog model.

Methods

Experimental apical periodontitis was induced in 60 teeth of six Beagle dogs. Following canal disinfection and pulpotomy, autologous deciduous pulp tissue was transplanted into the root canals (n = 30); as controls, contralateral teeth were treated in accordance with the recommendations of the American Association of Endodontists. Radiographic examinations were performed immediately before transplant, as well as 3 and 6 months after transplant. At the 6-month examination, root samples were collected and histological and immunohistochemical analyses were used to examine tissue regeneration.

Results

Radiographic analysis showed no significant differences in most histopathological parameters examined; however, apical diameter reduction was greater in the experimental group. Histological and immunohistochemical analyses showed that the canal walls of the experimental group had newly formed dentin-like tissue with dentinal tubules, while the control group had cementum-like deposits along the canal wall and apical foramina.

Conclusions

Autologous transplantation may be useful for regeneration of dental pulp in necrotic young permanent teeth.

Dentist-related factors influencing the use of vital pulp therapy: a survey among dental practitioners in China

Objective

To evaluate dentist-related factors associated with the use of vital pulp therapy (VPT) for the treatment of pulp exposures in permanent teeth.

Methods

This survey-based study sent an online questionnaire to collect data on the demographics of the respondents, the use of VPT and the choice of materials for VPT, to all members of the Society of Endodontology of Guangdong, China.

Results

A total 183 of 380 members responded (48.2%). The majority (89.6%; 164 of 183) had performed direct pulp capping (DPC) while 55.2% (101 of 183) had performed partial pulpotomy (PP) at least once. The most-cited reason for not performing VPT was unfamiliarity with the technique. Mineral trioxide aggregate was the most commonly used material for both DPC (67.1%; 110 of 164) and PP (73.3%; 74 of 101). Endodontists, compared with general practitioners, preferred to perform DPC and chose calcium silicate materials (CSMs) for VPT (odds ratios 5.81 and 8.07, respectively). DPC and CSMs for VPT were also favoured more by respondents who had practised for > 5 years. Senior respondents were more likely to use PP.

Conclusions

Speciality, years of practise and age of dentists influenced the decision making and the choice of materials for VPT. Continuing education is essential to promote the clinical use of VPT.

Evaluation of low-level diode laser irradiation and various irrigant solutions on the biological response of stem cells from exfoliated deciduous teeth

This study aimed to evaluate cytotoxic effects and the apoptosis of Gallium-Aluminum-Arsenide (GaAlAs) diode laser irradiation, sodium hypochlorite (NaOCl), ozonated water and ethylene diamine tetraacetic acid (EDTA) on stem cells from human exfoliated deciduous teeth (SHEDs). Cells were exposed to EDTA (5%, 8.5%, 17%), NaOCl (1%, 2.5%, 5%) ozonated water (5, 10, 20 μg/ml) and GaAlAs diode laser irradiation (energy densities of 0.5, 1, 1.5 j/cm²). Culture medium included D-MEM, supplemented with 15% foetal bovine serum, 1% l-glutamine, 1% penicillin-streptomycin, 1% gentamycin, amphotericin-B and served as control group. The prepared irrigants were added to the relevant wells and incubated with the cells at 37 °C for 5, 10 and 15 min. The cells in the laser group were also incubated at 37 °C for 5, 10 and 15 min after the laser application. Cell viability and proliferation were analysed with the 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay. The percentage of cell viability showed a significant reduction in all concentrations of the EDTA and NaOCl groups when compared to the control group, diode laser irradiation and ozonated water groups at 5th, 10th and 15th minutes respectively but high cytotoxic effects of all EDTA and NaOCl groups with decreased over 50% of cell viability were observed at the 15th minute. Also EDTA group with 17% concentration (17%E) presented the lowest survival rate on SHEDs with mean of 21.67% ± 6.101 at this time interval. The lowest toxic effects were observed at the 5th minutes compared to other time periods at experimental groups. For detection of apoptotic cells, the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling (TUNEL) method was performed. According to the MTT results, doses showed the highest toxicity (cell survival decreased over 50%) in each group were selected for TUNEL assay (17% EDTA; 1% NaOCl; 10 μg/ml Ozonated water; 1.5 j/cm² diode laser irradiation). The significantly lowest percentages of TUNEL-positive cells were detected in ozonated water (10.67% ± 2.93) and diode laser irradiation (13.24% ± 7.61) compared to EDTA (39.89% ± 11.54) and NaOCl (31.15% ± 10.64) respectively. Also the difference between percentage of TUNEL-positive cells in EDTA and NaOCl groups was not significant. Synergistic combination of ozonated water and diode laser irradiation may be used in the disinfection step of necrotic root canals.

Present and future of tissue engineering scaffolds for dentin-pulp complex regeneration

More than two thirds of the global population suffers from tooth decay, which results in cavities with various levels of lesion severity. Clinical interventions to treat tooth decay range from simple coronal fillings to invasive root canal treatment. Pulp capping is the only available clinical option to maintain the pulp vitality in deep lesions, but irreversible pulp inflammation and reinfection are frequent outcomes for this treatment. When affected pulp involvement is beyond repair, the dentist has to perform endodontic therapy leaving the tooth non-vital and brittle. On-going research strategies have failed to overcome the limitations of existing pulp capping materials so that healthy and progressive regeneration of the injured tissues is attained. Preserving pulp vitality is crucial for tooth homeostasis and durability, and thus, there is a critical need for clinical interventions that enable regeneration of the dentin-pulp complex to rescue millions of teeth annually. The identification and development of appropriate biomaterials for dentin-pulp scaffolds are necessary to optimize clinical approaches to regenerate these hybrid dental tissues. Likewise, a deep understanding of the interactions between the micro-environment, growth factors, and progenitor cells will provide design basis for the most fitting scaffolds for this purpose. In this review, we first introduce the long-lasting clinical dental problem of rescuing diseased tooth vitality, the limitations of current clinical therapies and interventions to restore the damaged tissues, and the need for new strategies to fully revitalize the tooth. Then, we comprehensively report on the characteristics of the main materials of naturally-derived and synthetically-engineered polymers, ceramics, and composite scaffolds as well as their use in dentin-pulp complex regeneration strategies. Finally, we present a series of innovative smart polymeric biomaterials with potential to overcome dentin-pulp complex regeneration challenges.

Purinergic Signaling Modulates Survival/Proliferation of Human Dental Pulp Stem Cells

Human dental pulp stem cells (hDPSCs) reside in postnatal dental pulp and exhibit the potential to differentiate into odontoblasts as well as neurons. However, the intercellular signaling niches necessary for hDPSC survival and self-renewal remain largely unknown. The objective of this study is to demonstrate the existence of intercellular purinergic signaling in hDPSCs and to assess the impact of purinergic signaling on hDPSC survival and proliferation. hDPSCs were isolated from extracted third molars and cultured in minimum essential medium. To demonstrate responsiveness to ATP application and inhibitions by purinergic receptor antagonists, whole cell patch-clamp recordings of ATP-induced currents were recorded from cultured hDPSCs. Immunofluorescence and enzymatic histochemistry staining were performed to assess purinergic receptor expression and ectonucleotidase activity in hDPSCs, respectively. To determine the effects of purinergic signaling on hDPSC, purinergic receptor antagonists and an ectonucleotidase inhibitor were applied in culture medium, and hDPSC survival and proliferation were assessed with DAPI staining and Ki67 immunofluorescence staining, respectively. We demonstrated that ATP application induced inward currents in hDPSCs. P2X and P2Y receptors are involved in the generation of ATP-induced inward currents. We also detected expression of NTPDase3 and ectonucleotidase activity in hDPSCs. We further demonstrated that purinergic receptors were tonically activated in hDPSCs and that inhibition of ectonucleotidase activity enhanced ATP-induced inward currents. Furthermore, we found that blocking P2Y and P2X receptors reduced-and inhibition of ecto-ATPase activity enhanced-the survival and proliferation of hDPSCs, while blocking P2X receptors alone affected only hDPSC proliferation. Autocrine/paracrine purinergic signaling is essential for hDPSC survival and proliferation. These results reveal potential targets to manipulate hDPSCs to promote tooth/dental pulp repair and regeneration.

The role of stem cell therapy in regeneration of dentine-pulp complex: a systematic review

Infection of the dental pulp will result in inflammation and eventually tissue necrosis which is treated conventionally by pulpectomy and root canal treatment. Advances in regenerative medicine and tissue engineering along with the introduction of new sources of stem cells have led to the possibility of pulp tissue regeneration. This systematic review analyzes animal studies published since 2010 to determine the ability of stem cell therapy to regenerate the dentine-pulp complex (DPC) and the success of clinical protocols. In vitro and human clinical studies are excluded and only the experimental studies on animal models were included. Dental pulp stem cells constitute the most commonly used cell type. The majority of stem cells are incorporated into various types of scaffold and implanted into root canals. Some of the studies combine growth factors with stem cells in an attempt to improve the outcome. Studies of ectopic transplantation using small animal models are simple and non-systematic evaluation techniques. Stem cell concentrations have not been so far reported; therefore, the translational value of such animal studies remains questionable. Though all types of stem cells appear capable of regenerating a dentine-pulp complex, still several factors have been considered in selecting the cell type. Co-administrative factors are essential for inducing the systemic migration of stem cells, and their vascularization and differentiation into odontoblast-like cells. Scaffolds provide a biodegradable structure able to control the release of growth factors. To identify problems and reduce costs, novel strategies should be initially tested in subcutaneous or renal capsule implantation followed by root canal models to confirm results.

Epigenetic Approaches to the Treatment of Dental Pulp Inflammation and Repair: Opportunities and Obstacles

Concerns over the cost and destructive nature of dental treatment have led to the call for novel minimally invasive, biologically based restorative solutions. For patients with toothache, this has resulted in a shift from invasive root-canal-treatment (RCT) toward more conservative vital-pulp-treatment (VPT) procedures, aimed to protect the pulp and harness its natural regenerative capacity. If the dental pulp is exposed, as long as the infection and inflammation can be controlled, conservative therapies can promote the formation of new tertiary dentine in a stem cell-led reparative process. Crucially, the volume and quality of new dentine is dependent on the material applied; however, currently available dental-materials are limited by non-specific action, cytotoxicity and poor clinical handling. Looking to the future, an improved understanding of the cellular regulators of pulpal inflammation and associated repair mechanisms is critical to predict pulpal responses and devise novel treatment strategies. Epigenetic modifications of DNA-associated proteins and the influences of non-coding RNAs have been demonstrated to control the self-renewal of stem cell populations as well as regulate mineralised tissue development and repair. Notably, the stability of microRNAs and their relative ease of sampling from pulpal blood highlight their potential for application as diagnostic inflammatory biomarkers, while increased understanding of their actions will not only enhance our knowledge of pulpal disease and repair, but also identify novel molecular targets. The potential therapeutic application of epigenetic modifying agents, DNA-methyltransferase-inhibitors (DNMTi) and histone-deacetylase-inhibitors (HDACi), have been shown to promote mineralisation and repair processes in dental-pulp-cell (DPC) populations as well as induce the release of bioactive dentine-matrix-components. Consequently, HDACis and DNMTis have the potential to enhance tertiary dentinogenesis by influencing the cellular and tissue processes at low concentrations with minimal side effects, providing an opportunity to develop a topically placed, inexpensive bio-inductive restorative material. The aim of this review is to highlight the potential role of epigenetic approaches in the treatment of the damaged dental pulp, considering the opportunities and obstacles, such as off-target effects, delivery mechanisms, for the therapeutic use of miRNA as an inflammatory biomarker or molecular target, before discussing the application of HDACi and DNMTi to the damaged pulp to stimulate repair.

Full Pulpotomy with Biodentine in Symptomatic Young Permanent Teeth with Carious Exposure

INTRODUCTION

This prospective study evaluated the outcome of Biodentine (Septodont, Saint Maur des Fosses, France) pulpotomy in young permanent teeth with carious exposure.

METHODS

Twenty permanent molar teeth in 14 patients with carious pulp exposure were treated with Biodentine pulpotomy. The age of the patients ranged from 9-17 years (12.3 ± 2.7 years). A preoperative pulpal and periapical diagnosis was established. After informed consent, the tooth was anesthetized, isolated via a dental dam, and disinfected with 5% sodium hypochlorite before caries excavation. Full pulpotomy was performed by amputating the exposed pulp to the level of the canal orifices, hemostasis was achieved via a cotton pellet moistened with 2.5% sodium hypochlorite, a 3-mm layer of Biodentine was placed as the pulpotomy agent, a Vitrebond liner (3M ESPE, St Paul, MN) was applied, and the tooth was subsequently restored. Postoperative periapical radiographs were taken after placement of the permanent restoration. Clinical and radiographic evaluation was completed after 6 months and 1 year postoperatively. Pain levels were scored preoperatively and 2 days after treatment. Statistical analysis was performed using the Fisher exact test.

RESULTS

Clinical signs and symptoms suggestive of irreversible pulpitis were established in all teeth and symptomatic apical periodontitis in 14 of 20 (70%). Two days after treatment, all patients reported complete relief of pain. All teeth were clinically successful at 6 months and 1 year postoperatively. Radiographically, immature roots showed continued root development; dentin bridge formation was detected in 5 of 20 teeth. Seven of 7 teeth with preoperative periapical rarefaction showed signs of healing; 1 tooth had signs of internal root resorption at 1 year with an overall success rate of 95% (19/20).

CONCLUSIONS

Young permanent teeth with carious exposure can be treated successfully with full pulpotomy using Biodentine, and clinical signs and symptoms of irreversible pulpitis are not a contraindication.

Decellularized Swine Dental Pulp as a Bioscaffold for Pulp Regeneration

Endodontic regeneration shows promise in treating dental pulp diseases; however, no suitable scaffolds exist for pulp regeneration. Acellular natural extracellular matrix (ECM) is a favorable scaffold for tissue regeneration since the anatomical structure and ECM of the natural tissues or organs are well-preserved. Xenogeneic ECM is superior to autologous or allogeneic ECM in tissue engineering for its unlimited resources. This study investigated the characteristics of decellularized dental pulp ECM from swine and evaluated whether it could mediate pulp regeneration. Dental pulps were acquired from the mandible anterior teeth of swine 12 months of age and decellularized with 10% sodium dodecyl sulfate (SDS) combined with Triton X-100. Pulp regeneration was conducted by seeding human dental pulp stem cells into decellularized pulp and transplanted subcutaneously into nude mice for 8 weeks. The decellularized pulp demonstrated preserved natural shape and structure without any cellular components. Histological analysis showed excellent ECM preservation and pulp-like tissue, and newly formed mineralized tissues were regenerated after being transplanted in vivo. In conclusion, decellularized swine dental pulp maintains ECM components favoring stem cell proliferation and differentiation, thus representing a suitable scaffold for improving clinical outcomes and functions of teeth with dental pulp diseases.

Dental Pulp Stem Cells: Their Potential in Reinnervation and Angiogenesis by Using Scaffolds

Dental pulp is a highly vascularized and innervated tissue containing a heterogeneous stem cell population with multilineage differentiation potential. Current endodontic treatments focus on the preservation of the pulp tissue and the regeneration of dental pulp after pathological insults. Human dental pulp stem cells (hDPSCs) are currently investigated as stem cell-based therapy for pulp regeneration and for peripheral nerve injury in which neurons and Schwann cells display limited regenerative capacity. We have developed a neuronal differentiation protocol for hDPSCs that requires neurosphere formation before neuronal maturation. Moreover, Schwann cell differentiation of hDPSCs in our group revealed that differentiated hDPSCs have acquired the ability to myelinate and guide neurites from dorsal root ganglia. Besides their dynamic differentiation capacity, hDPSCs were shown to exert a paracrine effect on neural and endothelial cells. Analysis of hDPSC conditioned medium revealed the secretion of a broad spectrum of growth factors including brain-derived neurotrophic factor, nerve growth factor, vascular endothelial growth factor, and glial-derived neurotrophic factor. Application of the conditioned medium to endothelial cells promoted cell migration and tubulogenesis, indicating a paracrine proangiogenic effect. This hypothesis was enforced by the enhanced formation of blood vessels in the chorioallantoic membrane assay in the presence of hDPSCs. In addition, transplantation of 3-dimensional-printed hydroxyapatite scaffolds containing peptide hydrogels and hDPSCs into immunocompromised mice revealed blood vessel ingrowth, pulplike tissue formation, and osteodentin deposition suggesting osteogenic/odontogenic differentiation of hDPSCs. Future studies in our research group will focus on the pulp regeneration capacity of hDPSCs and the role of fibroblasts within the pulp extracellular matrix.

Current challenges in human tooth revitalization

Tooth vitality and health are related to the presence of a living connective tissue, the dental pulp (DP), in the center of the dental organ. The DP contains the tooth immune defence system that is activated against invading oral cariogenic bacteria during the caries process and the tissue repair/regeneration machinery involved following microorganisms' eradication. However, penetration of oral bacteria into the DP often leads to complete tissue destruction and colonization of the endodontic space by microorganisms. Classical endodontic therapies consist of disinfecting then sealing the endodontic space with a gutta percha-based material. However, re-infections of the endodontic space by oral bacteria can occur, owing to the lack of tightness of the material. Recent findings suggest that regenerating a fully functional pulp tissue may be an ideal therapeutic solution to maintain a tooth defence system that will detect and help manage future injuries. The objective of this paper was to explain the different revascularization and regeneration strategies that have been proposed to reconstitute a living DP tissue and to discuss the main challenges that have to be resolved to improve these therapeutic strategies.

Odontogenic differentiation potential of human dental pulp cells cultured on a calcium-aluminate enriched chitosan-collagen scaffold

OBJECTIVE

The study aims to evaluate the odontogenic potential of human dental pulp cells (HDPCs) in contact with an experimental porous chitosan-collagen scaffold (CHC) enriched or not with a mineral phase of calcium-aluminate (CHC-CA).

MATERIAL AND METHODS

To assess the chemotactic effect of the materials, we placed HDPCs seeded on transwell membranes in intimate contact with the CHC or CHC-CA surface, and the cell migration was monitored for 48 h. Additionally, cells were seeded onto the material surface, and the viability and proliferation were evaluated at several time points. To assess the odontoblastic differentiation, we evaluated ALP activity, DSPP/DMP-1 gene expression, and mineralized matrix deposition. HDPCs cultured onto a polystyrene surface (monolayer) were used as negative control group.

RESULTS

The experimental CHC-CA scaffold induced intense migration of HDPCs through transwell membranes, with cells attaching to and spreading on the material surface after 24-h incubation. Also, the HDPCs seeded onto the CHC-CA scaffold were capable of migrating inside it, remaining viable and featuring a proliferative rate more rapid than that of CHC and control groups at 7 and 14 days of cell culture. At long-term culture, cells in the CHC-CA scaffold featured the highest deposition of mineralized matrix and expression of odontoblastic markers (ALP activity and DSPP/DMP-1 gene expression).

CONCLUSIONS

According to the results, the CHC-CA scaffold is a bioactive and cytocompatible material capable of increasing the odontogenic potential of human pulp cells. Based on analysis of the positive data obtained in this study, one can suggest that the CHC-CA scaffold is an interesting future candidate for the treatment of exposed pulps.

CLINICAL RELEVANCE

The experimental scaffold composed by a chitosan-collagen matrix mineralized with calcium aluminate seems to be an interesting candidate for in vivo application as a cell-free approach to dentin tissue engineering, which may open a new perspective for the treatment of exposed pulp tissue.

Promotive Effect of Zinc Ions on the Vitality, Migration, and Osteogenic Differentiation of Human Dental Pulp Cells

Zinc is an essential trace element for proper cellular function and bone formation. However, its exact role in the osteogenic differentiation of human dental pulp cells (hDPCs) has not been fully clarified before. Here, we speculated that zinc may be effective to regulate their growth and osteogenic differentiation properties. To test this hypothesis, different concentrations (1 × 10^-5, 4 × 10^-5, and 8 × 10^-5 M) of zinc ions (Zn²⁺) were added to the basic growth culture medium and osteogenic inductive medium. Cell viability and migration were measured by cell counting kit-8 (CCK-8) and transwell migration assay in the basic growth culture medium, respectively. The reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to detect the gene expression levels of selective osteogenic differentiation markers and zinc transporters. Alkaline phosphatase (ALP) activity analysis and alizarin red S staining were used to investigate the mineralization of hDPCs. Exposure of hDPCs to Zn²⁺ stimulated their viability and migration capacity in a dose- and time-dependent manner. RT-qPCR assay revealed elevated expression levels of osteogenic differentiation-related genes and zinc transporters genes in various degrees. ALP activity was also increased with elevated Zn²⁺ concentrations and extended culture periods, but enhanced matrix nodules formation were observed only in 4 × 10^-5 and 8 × 10^-5 M Zn²⁺ groups. These findings suggest that specific concentrations of Zn²⁺ could potentiate the vitality, migration, and osteogenic differentiation of hDPCs. We may combine optimum zinc element into pulp capping materials to improve their biological performance.

In Vivo Angiogenic Capacity of Stem Cells from Human Exfoliated Deciduous Teeth with Human Umbilical Vein Endothelial Cells

Dental pulp is a highly vascularized tissue requiring adequate blood supply for successful regeneration. In this study, we investigated the functional role of stem cells from human exfoliated deciduous teeth (SHEDs) as a perivascular source for in vivo formation of vessel-like structures. Primarily isolated SHEDs showed mesenchymal stem cell (MSC)-like characteristics including the expression of surface antigens and in vitro osteogenic and adipogenic differentiation potentials. Moreover, SHEDs were positive for NG2, α-smooth muscle actin (SMA), platelet-derived growth factor receptor beta (PDGFRβ), and CD146 as pericyte markers. To prove feasibility of SHEDs as perivascular source, SHEDs were transplanted into immunodeficient mouse using Matrigel with or without human umbilical vein endothelial cells (HUVECs). Transplantation of SHEDs alone or HUVECs alone resulted in no formation of vessel-like structures with enough red blood cells. However, when SHEDs and HUVECs were transplanted together, extensive vessel-like structures were formed. The presence of murine erythrocytes within lumens suggested the formation of anastomoses between newly formed vessel-like structures in Matrigel plug and the host circulatory system. To understand underlying mechanisms of in vivo angiogenesis, the expression of angiogenic cytokine and chemokine, their receptors, and MMPs was compared between SHEDs and HUVECs. SHEDs showed higher expression of VEGF, SDF-1α, and PDGFRβ than HUVECs. On the contrary, HUVECs showed higher expression of VEGF receptors, CXCR4, and PDGF-BB than SHEDs. This differential expression pattern suggested reciprocal interactions between SHEDs and HUVECs and their involvement during in vivo angiogenesis. In conclusion, SHEDs could be a feasible source of perivascular cells for in vivo angiogenesis.

Effects of Stem Cell Factor on Cell Homing During Functional Pulp Regeneration in Human Immature Teeth

Conventional root canal treatment in immature permanent teeth can lead to early tooth loss in children because root formation is discontinued. We investigated whether the stem cell factor (SCF) could facilitate cell homing in the pulpless immature root canal and promote regeneration of a functional pulp. In vitro, human mesenchymal stem cells (hMSCs) were exposed to SCF at various concentrations for assessing cell migration, proliferation, and differentiation toward odonto/osteoblasts by 3D-chemotaxis slides, WST-1 assay, and alkaline phosphatase activity, respectively. Fibrin gels were used to deliver 15 μg/mL SCF for in vivo experiments. The release kinetic of SCF was assessed in vitro. Two corresponding human immature premolars, with or without SCF, were placed at rat calvariae for 6 and 12 weeks. All tooth specimens were either analyzed histologically and the percentage of tissue ingrowth determined or the cells were extracted from the pulp space, and the mRNA level of DMP1, DSPP, Col1, NGF, and VEGF were assessed by quantitative polymerase chain reaction. In the presence of SCF, we saw an increase in hMSCs directional migration, proliferation, and odonto/osteogenic differentiation. SCF also increased the extent of tissue ingrowth at 6 weeks but not at 12 weeks. However, at this time point, the formed tissue appeared more mature in samples with SCF. In terms of gene transcription, DMP1, Col1, and VEGF were the significantly upregulated genes, while DSPP and NGF were not affected. Our results suggest that SCF can accelerate cell homing and the maturation of the pulp-dentin complex in human immature teeth.

Immunohistochemical Expression of TGF-β1 and Osteonectin in engineered and Ca(OH)2-repaired human pulp tissues

The aim of the present study was to evaluate the expression of transforming growth factor-β1 (TGF-β1) and osteonectin (ON) in pulp-like tissues developed by tissue engineering and to compare it with the expression of these proteins in pulps treated with Ca(OH)2 therapy. Tooth slices were obtained from non-carious human third molars under sterile procedures. The residual periodontal and pulp soft tissues were removed. Empty pulp spaces of the tooth slice were filled with sodium chloride particles (250-425 µm). PLLA solubilized in 5% chloroform was applied over the salt particles. The tooth slice/scaffold (TS/S) set was stored overnight and then rinsed thoroughly to wash out the salt. Scaffolds were previously sterilized with ethanol (100-70°) and washed with phosphate-buffered saline (PBS). TS/S was treated with 10% EDTA and seeded with dental pulp stem cells (DPSC). Then, TS/S was implanted into the dorsum of immunodeficient mice for 28 days. Human third molars previously treated with Ca(OH)2 for 90 days were also evaluated. Samples were prepared and submitted to histological and immunohistochemical (with anti-TGF-β1, 1:100 and anti-ON, 1:350) analyses. After 28 days, TS/S showed morphological characteristics similar to those observed in dental pulp treated with Ca(OH)2. Ca(OH)2-treated pulps showed the usual repaired pulp characteristics. In TS/S, newly formed tissues and pre-dentin was colored, which elucidated the expression of TGF-β1 and ON. Immunohistochemistry staining of Ca(OH)2-treated pulps showed the same expression patterns. The extracellular matrix displayed a fibrillar pattern under both conditions. Regenerative events in the pulp seem to follow a similar pattern of TGF-β1 and ON expression as the repair processes.

The Neurovascular Properties of Dental Stem Cells and Their Importance in Dental Tissue Engineering

Within the field of tissue engineering, natural tissues are reconstructed by combining growth factors, stem cells, and different biomaterials to serve as a scaffold for novel tissue growth. As adequate vascularization and innervation are essential components for the viability of regenerated tissues, there is a high need for easily accessible stem cells that are capable of supporting these functions. Within the human tooth and its surrounding tissues, different stem cell populations can be distinguished, such as dental pulp stem cells, stem cells from human deciduous teeth, stem cells from the apical papilla, dental follicle stem cells, and periodontal ligament stem cells. Given their straightforward and relatively easy isolation from extracted third molars, dental stem cells (DSCs) have become an attractive source of mesenchymal-like stem cells. Over the past decade, there have been numerous studies supporting the angiogenic, neuroprotective, and neurotrophic effects of the DSC secretome. Together with their ability to differentiate into endothelial cells and neural cell types, this makes DSCs suitable candidates for dental tissue engineering and nerve injury repair.

Criteria for the Replacement of Restorations: Academy of Operative Dentistry European Section

The replacement of a restoration is one of the most common procedures in dentistry. However, the criteria for such intervention, excluding catastrophic failure and persistent discomfort and pain, continue to be the subject of considerable debate. The decision-making process remains subjective on the part of the treating clinician, while the evidence base for refurbishment and repair rather than replacement for the management of defective and failing restorations continues to grow and strengthen. This article, prepared as an Academy of Operative Dentistry European Section consensus publication, reviews existing criteria for the replacement of restorations and encourages practitioners to shift, if not already doing so, to considering the replacement of a restoration as a last resort rather than as a prudent action to be taken if in any doubt about clinical acceptability. Further research in the area, spanning the risk assessment of defective and failing restorations and new diagnostic tools and processes, together with work to enhance the evidence base of restoration repair vs replacement, would be of immense value.

Management of incompletely developed teeth requiring root canal treatment

Endodontic management of the permanent immature tooth continues to be a challenge for both clinicians and researchers. Clinical concerns are primarily related to achieving adequate levels of disinfection as 'aggressive' instrumentation is contraindicated and hence there exists a much greater reliance on endodontic irrigants and medicaments. The open apex has also presented obturation difficulties, notably in controlling length. Long-term apexification procedures with calcium hydroxide have proven to be successful in retaining many of these immature infected teeth but due to their thin dentinal walls and perceived problems associated with long-term placement of calcium hydroxide, they have been found to be prone to cervical fracture and subsequent tooth loss. In recent years there has developed an increasing interest in the possibility of 'regenerating' pulp tissue in an infected immature tooth. It is apparent that although the philosophy and hope of 'regeneration' is commendable, recent histologic studies appear to suggest that the calcified material deposited on the canal wall is bone/cementum rather than dentine, hence the absence of pulp tissue with or without an odontoblast layer.