Effect of dentin treatment on proliferation and differentiation of human dental pulp stem cells

Effect of erbium yttrium aluminium garnet laser dentin conditioning on dental pulp stem cells viability

Objective

This study aims to investigate the effect of dentin conditioning by subablative Er:YAG (erbium-doped yttrium aluminium garnet) laser on dental pulp stem cells (DPSCs) viability.

Methods

For this in-vitro experimental study, root fragments were longitudinally hemisected after decoronation of single-rooted extracted teeth and preparation of root canals. Prepared samples were randomly assigned to 2 experimental groups (n = 17) as follows; 1) laser conditioning: irradiation with Er:YAG laser beams (2940 nm, 50 mJ per pulse, 20 Hz) 2) Chemical conditioning: 1.5% NaOCl, followed by phosphate-buffered saline (PBS), 17% EDTA, followed by PBS as a final rinse. The samples were ultraviolet-sterilized, and DPSCs were seeded on the samples. MTT assay was performed after 1, 4 and 7 days of incubation to assess the cell viability (n = 5/group per day). Also, after 7 days, two samples of each group underwent SEM (scanning electron microscope) analysis. Statistical analysis was done using independent t-test, one-way ANOVA and two-way ANOVA at a significance level of 0.05.

Results

Laser irradiated samples exhibited significantly higher cell viability of DPSCs on days 4 (p < 0.0001) and 7 (p < 0.0001), unlike day 1 (p = 0.131). SEM photomicrographs revealed that Er:YAG laser performed much better smear layer removal and created surface irregularities. Several different cell morphologies were observable on the laser-treated samples, which cells with cytoplasmic extensions being the most frequent.

Conclusions

Dentin conditioning by Er:YAG laser enhances DPSCs viability and can be a valuable modality for conditioning dentin to perform regenerative endodontic procedures. Further clinical studies are suggested.

Comparison of the effect of NaOCL, curcumin, and EDTA on differentiation, proliferation, and adhesion of dental pulp stem cells

Introduction

This study examined the effect of 1.5% NaOCl, 17% EDTA, and curcumin on the proliferation, attachment, and differentiation of dental pulp stem cells (DPSCs) placed on the dentin specimens.

Methods

MTT assay was performed to evaluate the proliferation of DPSCs on the dentin specimens treated with different concentrations of NaOCl, 17% EDTA, and curcumin (0.97-250 μM). Cell-adhering ability of DPSCs was tested via the LDH assay to calculate the attached DPSCs. In addition, the western blotting assay was performed to investigate the expression levels of fibronectin as a cell-adhesion marker and analyze the expressions level of differentiation markers, including DMP-1, OCN, ALP, and DSPP, to detect the odontogenic potential of hDPCs.

Results

NaOCl had lower toxicity on DPSCs at lower concentrations (P < 0.001). The cytotoxicity of irrigants increased with increased dosage. The difference between the cell-adhesion ability of NaOCl and curcumin was not significant (∼4.4 MU/mL), whereas EDTA (∼3.8 MU/mL) exhibited the lowest release of LDH and less damage to hDPSCs. Regarding fibronectin expression, the pattern differed between irrigants in inducing cell adhesion. NaOCl increased fibronectin expression more than EDTA and curcumin. All the treated groups upregulated the expression of DSPP, DMP-1, OCN, and ALP compared to the control group, in which NaOCl showed a higher effect on the overexpression of differentiation markers.

Conclusion

The results showed that all the tested irrigants could be used in regenerative endodontic treatment. However, as an herbal-based and biocompatible irrigant, curcumin exhibited fewer adverse effects than NaOCl and EDTA.

Differential Effects of Extracellular Matrix Glycoproteins Fibronectin and Laminin-5 on Dental Pulp Stem Cell Phenotypes and Responsiveness

Dental pulp stem cells (DPSCs) are mesenchymal stem cells (MSCs) with the potential to differentiate in a limited number of other tissue types. Some evidence has suggested the modulation of DPSC growth may be mediated, in part, by exogenous extracellular matrix (ECM) glycoproteins, including fibronectin (FN) and laminin-5 (LN5). Although preliminary research suggests that some ECM glycoproteins may work as functional biomaterials to modulate DPSC growth responses, the primary goal of this project is to determine the specific effects of FN and LN5 on DPSC growth and viability. Using an existing DPSC repository, n = 16 DPSC isolates were cultured and 96-well growth assays were performed, which revealed FN, LN5 and the combination of these were sufficient to induce statistically significant changes in growth among five (n = 5) DPSC isolates. In addition, the administration of FN (either alone or in combination) was sufficient to induce the expression of alkaline phosphatase (ALP) and dentin sialophosphoprotein (DSPP), while LN5 induced the expression of ALP only, suggesting differential responsiveness among DPSCs. Moreover, these responses appeared to correlate with the expression of MSC biomarkers NANOG, Oct4 and Sox2. These results add to the growing body of evidence suggesting that functional biomaterials, such as ECM glycoproteins FN and LN5, are sufficient to induce phenotypic and differentiation-specific effects in a specific subset of DPSC isolates. More research will be needed to determine which biomarkers or additional factors are necessary and sufficient to induce the differentiation and development of DPSCs ex vivo and in vitro for biomedical applications.

Assessment of the Influence of Various Concentrations of Sodium Hypochlorite on Stem Cell Derived From Human Exfoliated Deciduous Teeth (SHED) Proliferation and Differentiation

Objectives  Previous research has established that sodium hypochlorite (NaOCl) has a detrimental effect on dental stem cell viability and maturation. However, a review of the literature revealed no study evaluating the response of NaOCl to the survival of stem cells derived from human exfoliated deciduous teeth (SHEDs). Hence, the aim of the present trial was to assess the influence of various dilutions of NaOCl on SHED proliferation and differentiation. Materials and Methods The 5.25% NaOCl solutions at concentrations of 0.5, 0.1, 0.025, 0.0125, and 0.005 mg/ml were used to assess the response to SHED proliferation and differentiation through methyl tetrazolium (MTT) assay, alkaline phosphatase (ALP) assay, and reverse transcription polymerase chain reaction gene expression analysis at various time point intervals. Results  MTT assay showed that the viability of SHEDs decreased with an increase in the concentration of NaOCl and an increase in incubation time. The ALP activity decreased with an increase in the concentration of NaOCl up to 14 days of incubation. However, the ALP activity of all the test specimens further decreased after 14 days of incubation. The gene expression levels of osteocalcin, dentin sialophosphoprotein, and STRO-1 were statistically significant when compared to the control after one, three, and seven days of incubation. Conclusion  Different doses of NaOCl other than 0.5 mg/ml revealed encouraging outcomes in terms of proliferation, long-term ALP functioning, and odontogenic differentiation potential when cultivated in SHEDs.

Assessment of Cytotoxicity and Odontogenic/Osteogenic Differentiation Potential of Nano-Dentine Cement Against Stem Cells from Apical Papilla

OBJECTIVE

Assessment of the cytotoxicity of novel calcium silicate-based cement is imperative in endodontics. This experimental study aimed to assess the cytotoxicity and odontogenic/osteogenic differentiation potential of a new calcium silicate/pectin cement called Nano-dentine against stem cells from the apical papilla (SCAPs).

MATERIALS AND METHODS

In this experimental study, the cement powder was synthesized by the sol-gel technique. Zirconium oxide was added as opacifier and Pectin, a plant-based polymer, and calcium chloride as the liquid to prepare the nano-based dental cement. Thirty-six root canal dentin blocks of human extracted single-canal premolars with 2 mm height, flared with #1, 2 and 3 Gates-Glidden drills were used to prepare the cement specimens. The cement, namely mineral trioxide aggregate (MTA), Biodentine, and the Nano-dentine were mixed according to the manufacturers' instructions and applied to the roots of canal dentin blocks. The cytotoxicity and odontogenic/osteogenic potential of the cement were evaluated by using SCAPs.

RESULTS

SCAPs were characterized by the expression of routine mesenchymal cell markers and differentiation potential to adipocytes, osteoblasts, and chondrocytes. Cement displayed no significant differences in cytotoxicity or calcified nodules formation. Gene expression analysis showed that all three types of cement induced significant down- regulation of COLA1; however, the new cement induced significant up-regulation of RUNX2 and SPP1 compared to the control group and MTA. The new cement also induced significant up-regulation of TGFB1 and inducible nitric oxide synthase (iNOS) compared with Biodentine and MTA.

CONCLUSION

The new Nano-dentin cement has higher odontogenic/osteogenic potential compared to Biodentine and MTA for differentiation of SCAPs to adipocytes, osteoblasts, and chondrocytes.

Influence of ethylenediaminetetraacetic acid on regenerative endodontics: a systematic review

BACKGROUND

The effects of ethylenediaminetetraacetic acid (EDTA) on regenerative endodontic procedures (REPs) are controversial, because, despite releasing growth factors from dentine, some studies show negative effects on cell behaviour.

OBJECTIVES

To investigate the influence of the use of EDTA in REP on the growth factors' release, cell behaviour, and tissue regeneration.

METHODS

A systematic search was conducted (PubMed/Medline, Scopus, Cochrane Library, Web of Science, Embase, OpenGrey, and reference lists) up to February 2021. Only in vivo and in vitro studies evaluating the effects of EDTA on the biological factors of dentine, pulp/periapical tissues, and cell behaviour were eligible. Studies without a control group or available full text were excluded. The growth factors' release was the primary outcome. Risk of bias in the in vitro and in vivo studies was performed according to Joanna Briggs Institute's Checklist and SYRCLE's RoB tool, respectively.

RESULTS

Of the 1848 articles retrieved, 36 were selected. Among these, 32 were in vitro, three animal studies, and one with both models. The EDTA concentrations ranged from 3%-15%, at different times. Regarding growth factors' release (17 studies), 15 studies found significant transforming growth factor (TGF)-β release after dentine conditioning with EDTA, and most found no influence on vascular endothelial growth factor (VEGF) release. Regarding cell behaviour (26 studies), eight studies showed no influence of EDTA-treated dentine on cell viability; whereas, five, nine, and six studies showed higher cell migration, adhesion, and differentiation, respectively. No influence of EDTA conditioning was observed in animal studies. In vitro studies had a low risk of bias, whereas animal studies had high risk of bias. Meta-analysis was unfeasible.

DISCUSSION

This review found that EDTA increased TGF-β release and improved cell activity. However, well-designed histological analyses using immature teeth models are needed.

CONCLUSIONS

High quality in vitro evidence suggests that EDTA-treated dentine positively influences TGF-β release, cell migration, attachment, and differentiation; further research to evaluate its influence on tissue regeneration is necessary due to low methodological quality of the animal studies.

The Effects of Intracanal Irrigants and Medicaments on Dental-Derived Stem Cells Fate in Regenerative Endodontics: An update

Regenerative endodontics is a biologically based treatment designed for immature permanent teeth with necrotic pulp to replace dentin and root structures, as well as dental pulp cells. This procedure has become a part of novel modality in endodontics therapeutic manner, and it is considered as an alternative to apexification. In the last decade, numerous case reports, which describe this procedure, have been published. This therapeutic approach succeeded due to its lower financial cost and ease of performance. Although the clinical protocol of this procedure is not standardized and the effects of irrigants and medicaments on dental stem cells fate remain somewhat ambiguous, however when successful, it is an improvement of endodontics treatment protocols which leads to continued root development, increased dentinal wall thickness, and apical closure of immature teeth. To ensure a successful regenerative procedure, it is essential to investigate the appropriate disinfection protocols and the use of biocompatible molecules in order to control the release of growth factors and the differentiation of stem cells. This is the first review in the literature to summarize the present knowledge regarding the effect of intracanal irrigants and medicaments on the dental derived stem cells fate in regenerative endodontic procedures.

Matin M. Odontoblast-like Cytodifferentiation of Dental Stem Cells: A Review

Dental problems are common in human populations. Traditional treatments are focused on managing caries, soft tissue impairments, functional defects, poor aesthetics, digestive disorders and alveolar bone resorption. During the last two decades, basic and clinical researches on adult stem cells have established a potential therapeutic concept in tissue regeneration. Among major cells responsible for tooth development, odontoblasts play a key role in the formation of organic and inorganic constituents of dental tissue. A premier stride in the development of novel stem cell-based strategies for the treatment of reversible and irreversible pulpitis is odontoblast regeneration. Among different candidate cell sources for odontoblastic regeneration, use of dental adult stem cells is a preferred option because of their great ability to differentiate into odontoblasts and also their minimally invasive isolation procedure. This review emphasizes on articles that report successful odontoblast-like differentiation of dental mesenchymal stem cells which in turn provide a background for dentin-pulp complex cell therapies, using genetic or chemical manipulation. The series of experiments both in vitro and in vivo asserted that dental mesenchymal stem cells can efficiently differentiate into functional odontoblast-like cells. However, the review shows there are drawbacks in present methods. Future research should focus on optimizing protocols on odontoblast differentiation of dental stem cells by simultaneously introducing different genes with mutual synergy, combined with chemical or recombinant protein introduction.

Dynamic Irrigation Promotes Apical Papilla Cell Attachment in an Ex Vivo Immature Root Canal Model

INTRODUCTION

The use of dentin preconditioning techniques in regenerative endodontic procedures is currently promising. Several growth factors have been detected on dentin after ultrasonic irrigation with EDTA. This study aimed to evaluate the effects of dynamic irrigation with different solution regimens on apical papilla cell (APC) attachment in an ex vivo immature tooth model.

METHODS

Various dynamic irrigation techniques, needle irrigation (NI), NI with EndoActivator, and NI with passive ultrasonic irrigation, were used with different solution regimens, normal saline solution (NSS), EDTA, and chlorhexidine digluconate followed by EDTA, in enlarged root canal models where calcium hydroxide-medicated dentin slices were inserted. The initial number of attached fibronectin-positive APCs was counted. Dentin surface morphology was also inspected by using scanning electron microscopy.

RESULTS

The number of APCs was significantly greater in the dynamic irrigation groups than in the control group (P < .001). Greater APC numbers were observed in the groups in which NSS was used than in those in which EDTA or chlorhexidine digluconate/EDTA was used, when using the same techniques (P < .001). Cell numbers were similar at all levels of the root canals; however, in the ultrasonically supplemented group irrigated with NSS, the number of attached cells was significantly increased at the middle and apical levels (P < .05).

CONCLUSIONS

The use of dynamic irrigation techniques in an immature tooth model definitely promoted APC attachment to calcium hydroxide-medicated dentin. Furthermore, when NSS was used as a final irrigant, the number of attached cells was significantly increased.

Effects of Epigallocatechin Gallate, an Antibacterial Cross-linking Agent, on Proliferation and Differentiation of Human Dental Pulp Cells Cultured in Collagen Scaffolds

INTRODUCTION

This study aimed to evaluate the efficacy of epigallocatechin gallate (EGCG), an antibacterial cross-linking agent, on the proliferation and differentiation of human dental pulp cells (hDPCs) cultured in hydrogel collagen scaffolds.

METHODS

The odontogenic differentiation induced by EGCG was evaluated by alkaline phosphatase (ALP) activity and odontogenic-related gene expression using real-time polymerase chain reaction. The antibacterial effect of EGCG was investigated by a disc diffusion assay in comparison with glutaraldehyde. Proliferation was analyzed by cell number counting under both optical and confocal laser scanning microscopes. To assess the mechanical properties of collagen treated with EGCG, the setting time, surface roughness, and compressive strength were measured.

RESULTS

EGCG itself did not up-regulate the odontogenic-related markers (P > .05) although ALP activity was slightly increased. The proliferation and differentiation of hDPCs cultured in collagen increased significantly in the presence of EGCG (P < .05). The antibacterial activity of EGCG was similar to that of glutaraldehyde. The setting time of collagen was significantly shortened when it was treated with EGCG (P < .05). The surface roughness and compressive strength of the cross-linked collagen were higher than those of collagen without EGCG (P < .05).

CONCLUSIONS

Our results showed that EGCG, the antibacterial cross-linking agent, promoted the proliferation and differentiation of hDPCs cultured in collagen scaffolds. Furthermore, the enhanced mechanical properties of collagen scaffolds induced by EGCG may play important roles in cell behavior. Consequently, the application of EGCG to collagen scaffolds might be beneficial for regenerative endodontic therapy.

Odontoblast-like differentiation and mineral formation of pulpsphere derived cells on human root canal dentin in vitro

BACKGROUND

The revitalization or regeneration of the dental pulp is a preferable goal in current endodontic research. In this study, human dental pulp cell (DPC) spheres were applied to human root canal samples to evaluate their potential adoption for physiological tissue-like regeneration of the dental root canal by odontoblastic differentiation as well as cell-induced mineral formation.

METHODS

DPC were cultivated into three-dimensional cell spheres and seeded on human root canal specimens. The evaluation of sphere formation, tissue-like behavior and differentiation as well as mineral formation of the cells was carried out with the aid of optical light microscopy, immunohistochemical staining and scanning electron microscopy (SEM).

RESULTS

Spheres and cells migrated out of the spheres showed an intense cell-cell- and cell-dentin-contact with the formation of extra cellular matrix. In addition, the ingrowth of cell processes into dentinal tubules and the interaction of cell processes with the tubule walls were detected by SEM-imaging. Immunohistochemical staining of the odontoblast specific matrix proteins, dentin matrix protein-1, and dentin sialoprotein revealed an odontoblast-like cell differentiation in contact with the dentin surface. This differentiation was confirmed by SEM-imaging of cells with an odontoblast specific phenotype and cell induced mineral formation.

CONCLUSIONS

The results of the present study reveal the high potential of pulp cells organized in spheres for dental tissue engineering. The odontoblast-like differentiation and the cell induced mineral formation display the possibility of a complete or partial "dentinal filling" of the root canal and the opportunity to combine this method with other current strategies.