EDTA conditioning of dentine promotes adhesion, migration and differentiation of dental pulp stem cells

Clinical cell-based versus cell-free regenerative endodontics: clarification of concept and term

There is no consensus on the true meaning of clinical regenerative endodontics, and there is confusion over the concept and the term. Commonly used terms include revitalization and revascularization. The clinical methods for endodontic revitalization procedures and the tissue engineering concept differ depending on whether there is exogenous delivery of cells - called cell therapy, or not. Here, in this review, the difference is clarified by emphasizing the correct terminology: cell-free versus cell-based regenerative endodontic therapy (CF-RET versus CB-RET). The revitalization procedures practised clinically do not fit into the modern tissue engineering concepts of pulp regeneration but can be categorized as CF-RET. The modern tissue engineering concept in pulp regeneration is a CB-RET, which so far is at the clinical trial stage. However, histological examination of teeth following regenerative endodontic treatments reveals healing with repair derived from stem cells that originate from the periodontal, bone and other tissues. The aim of regenerative endodontics is regeneration of the pulp-dentine complex. This review discusses why CF-RET is unlikely to regenerate a pulp-dentine complex with current protocols. The American Association of Endodontists and the European Society of Endodontology have not yet recommended autologous stem cell transplantation (CB-RERT) which aspires for regeneration. Therefore, an understanding of the concept, term, difficulties and differences in current protocols is important for the clinician. However, rather than being discouraged that ideal regeneration has not been achieved to date, repair can be an acceptable outcome in clinical regenerative endodontics as it has also been accepted in medicine. Repair should also be considered in the context that resolution of the clinical signs/symptoms of pulp necrosis/apical periodontitis is generally reliably obtained in clinical regenerative endodontics.

The trends of dental biomaterials research and future directions: A mapping review

Objective

This literature research aimed to compare, contrast and quantify the innovations in the most commonly used dental biomaterials.

Methodology

Original research articles based on experimental dental biomaterials published between 2007 and 2019 were retrieved and reviewed. A search of electronic databases, PubMed, Scopus, and Web of Science indexed dental/biomaterials journals, has been conducted. The inclusion criteria in this research were: synthesis of experimental dental materials, whereas commercial dental materials, review articles, and clinical trials (case reports) were excluded.

Results

It was found that the amount of publications related to dental subgingival implants, computer-aided modeling ceramics, aesthetic restorative materials, adhesives cements, ceramics, bioceramics, endodontic materials, bioactive scaffolds, stem cells, and guided-tissue membranes had increased significantly from 2007. At the same time, the number of publications related to dental cements, silver amalgam, and dental alloys has decreased. For characterization of dental materials it was noted that mechanical properties were tested mostly for restorative materials. On the other hand, biological properties were most assessed for dental subgingival implants and endodontic materials, however, physical properties predominantly for bioceramics.

Conclusion

It is concluded that to meet clinical demands there was more focus on restorative materials that provided better aesthetics, including resin composites, adhesive resin composites (luting cements), zirconia, and other ceramics. The boost in laboratory and animal research related to bioceramics was attributed to their regenerative potential. This current literature study will help growing researchers to consider and judge the direction to which research might be guided in order to plan prospective research projects.

EDTA Promotes the Mineralization of Dental Pulp In Vitro and In Vivo

INTRODUCTION

Dentin regeneration is one of the main goals of vital pulp treatment in which the biological properties of dental pulp cells (DPCs) need to be considered. In our previous study, we showed that EDTA could enhance the stromal cell-derived factor 1 alpha-induced migration of DPCs. The purpose of this study was to explore the effects of EDTA on the mineralization of dental pulp in vitro and in vivo.

METHODS

DPCs were obtained from human premolars or third molars. Alkaline phosphatase assays and alizarin red S staining were used to examine the degree of differentiation and mineralized nodule formation of DPCs. Real-time polymerase chain reaction and Western blot analysis were performed to detect the messenger RNA and protein expressions of mineralization-related markers in DPCs. Extracellular-regulated protein kinase and Smad inhibitors were used to study the roles of these 2 signaling pathways in this process. In addition, pulp exposures were created on 18 premolars of 2 beagle dogs (>12 months) using a high-speed dental handpiece. The experimental group (n = 9) was treated with 12% EDTA for 5 minutes, and the control group (n = 9) was treated with sterile saline for the same duration. Mineral trioxide aggregate was used for direct pulp capping followed by glass ionomer cement sealing. Samples were collected 3 months later, and the regenerated dentin was assessed by micro-computed tomographic and histologic analyses.

RESULTS

Exposure to 12% EDTA promoted the activity of alkaline phosphatase, the formation of mineralized nodules, and the messenger RNA and protein expressions of mineralization-related markers in DPCs. Furthermore, the process of 12% EDTA enhancing the differentiation of DPCs was mediated by the extracellular-regulated protein kinase 1/2 signaling pathway and inhibited by the Smad2/3 signaling pathway. In vivo, compared with the control group, more regenerated dentin that had fewer tunnel defects was formed in the 12% EDTA-treated group.

CONCLUSIONS

Our results showed that 12% EDTA could promote the mineralization of dental pulp in vitro and in vivo.

Regenerative Endodontic Procedures, Disinfectants and Outcomes: A Systematic Review

AIMS

This systematic review aims to identify and synthesise available evidence to determine the clinical and radiographic outcomes of REP involving any disinfection irrigant together with a non-antibiotic intracanal medicament.

METHODS

Experimental and observational studies evaluating the outcomes of REP in immature non-vital permanent teeth in 6-16 year olds, where the protocol used any type of disinfectant irrigant together with a non-antibiotic intracanal medicament (non-setting calcium hydroxide) were included. Data was narratively synthesised and presented in respect to the primary outcome (elimination of symptoms and infection) and secondary outcomes (increase in root length/width; positive response to vitality testing; patient-reported outcomes; adverse effects).

MAIN FINDINGS

1628 studies were identified, of which five met the eligibility criteria for inclusion in the review. Studies included one randomised control trial and four observational studies. All five studies showed an absence of clinical signs and symptoms for all teeth postoperatively with radiographic resolution or absence of pathology following the disinfection stages of the REP used. Choice of secondary outcomes were inconsistent but included further root development, coronal discolouration and root canal calcifications postoperatively. There was a high risk of bias in all five studies and subsequently the quality of the evidence base was judged to be low.

PRINCIPLE CONCLUSIONS

REP using a non-antibiotic disinfectant approach appears capable of providing satisfactory outcomes for a non-vital immature permanent tooth. Further high-quality research is required before solid recommendations towards clinical practice guidelines for the disinfection portion of REP can be implemented.

Advanced Biomaterials and Techniques for Oral Tissue Engineering and Regeneration-A Review

The reconstruction or repair of oral and maxillofacial functionalities and aesthetics is a priority for patients affected by tooth loss, congenital defects, trauma deformities, or various dental diseases. Therefore, in dental medicine, tissue reconstruction represents a major interest in oral and maxillofacial surgery, periodontics, orthodontics, endodontics, and even daily clinical practice. The current clinical approaches involve a vast array of techniques ranging from the traditional use of tissue grafts to the most innovative regenerative procedures, such as tissue engineering. In recent decades, a wide range of both artificial and natural biomaterials and scaffolds, genes, stem cells isolated from the mouth area (dental follicle, deciduous teeth, periodontal ligament, dental pulp, salivary glands, and adipose tissue), and various growth factors have been tested in tissue engineering approaches in dentistry, with many being proven successful. However, to fully eliminate the problems of traditional bone and tissue reconstruction in dentistry, continuous research is needed. Based on a recent literature review, this paper creates a picture of current innovative strategies applying dental stem cells for tissue regeneration in different dental fields and maxillofacial surgery, and offers detailed information regarding the available scientific data and practical applications.

Cytotoxic, migration, and angiogenic effects of intracanal irrigants on cells involved in revascularization of immature teeth

OBJECTIVE

To evaluate protocols of root canal irrigation and dentin pretreatment in a cell culture model simulating immature teeth. Cytotoxic, migration, and angiogenic effects of Sodium hypochlorite associated with EDTA (NaOCl/EDTA), NaOCl associated with Smear Clear (NaOCl/SC), and QMix were compared.

DESIGN

Three roots of mandibular first premolars had their length and root canal diameter standardized. Root canals were irrigated, and the resulting solutions were diluted in culture medium. Sulforhodamine B (SRB) assay was performed with apical papilla cells and with endothelial cells (HUVECs) to assess cytotoxicity. Polarity index and migration assays of apical papilla cells and sprouting of HUVECs were evaluated. Data were analyzed by ANOVA and Tukey post-hoc tests (p < .05).

RESULTS

In apical papilla cells, NaOCl/SC and QMix promoted higher cytotoxicity, decreased fraction of elongated cells, and had lower migration speed and shorter migration distance of cells compared to NaOCl/EDTA. Also, HUVECs treated with NaOCl/SC and QMix showed decreased tubule formation in comparison with NaOCl/EDTA.

CONCLUSIONS

NaOCl/SC and QMix showed unfavorable biological responses of cells involved in revascularization in comparison to NaOCl/EDTA. Further studies with other intracanal irrigants should be performed to improve the balance of root canal disinfection with biological responses.

12-Year Follow-Up of Regenerative Endodontic Treatment of Immature Permanent Upper Incisors with Acute Abscess

This case report discusses the endodontic treatment of a 7-year-old girl who suffered trauma (intrusion) to the immature upper central incisors secondary to a fall from a bicycle. Thirty days after the accident the patient was brought by her mother for clinical and radiographic assessment with a chief complaint of swelling and tenderness to percussion and palpation. Acute apical abscess associated with immature teeth were diagnosed. A decision was made to perform regenerative endodontic treatment. Access cavities were made and the root canals were disinfected by irrigation with 2.5% sodium hypochlorite. Final irrigation was performed with 17% EDTA. Due to pain and presence of secretions, 2% chlorhexidine gel was applied as an intracanal medicament. Seven days later, at the second visit, the root canals were once again disinfected and the canals of the right and left permanent upper central incisors were filled with double antibiotic paste (metronidazole/ciprofloxacin) and calcium hydroxide paste, respectively. Zinc oxide was mixed in both pastes. At the third visit, after 21 more days, the pastes were removed and the periapical areas were stimulated with a #80 K-file to encourage clot formation within the pulp cavities. A mineral trioxide aggregate (MTA) paste cervical plug was placed and the teeth were restored with glass ionomer cement. Radiographs and CBCT scans demonstrated complete root formations. The patient has been followed for 12 years, with evidence of clinical success throughout.

Effectiveness of Autologous Platelet Concentrates in Management of Young Immature Necrotic Permanent Teeth-A Systematic Review and Meta-Analysis

The use of autologous platelet concentrates (APCs) in regenerative endodontic procedures is inconsistent and unclear. The aim of this meta-analysis was to evaluate the effectiveness of autologous platelet concentrates compared to traditional blood-clot regeneration for the management of young, immature, necrotic, permanent teeth. The digital databases MEDLINE, SCOPUS, CENTRAL, Web of Science, and EMBASE were searched to identify ten randomized clinical trials. The outcomes at postoperative follow-up, such as dentinal wall thickness (DWT), increase in root length (RL), calcific barrier formation (CB), apical closure (AC), vitality response (VR), and success rate (SR), were subjected to both qualitative synthesis and quantitative meta-analysis. The meta-analysis showed that APCs significantly improved apical closure (risk ratio (RR) = 1.17; 95% CI: 1.01, 1.37; p = 0.04) and response to vitality pulp tests (RR = 1.61; 95% CI: 1.03, 2.52; p = 0.04), whereas no significant effect was observed on root lengthening, dentin wall thickness, or success rate of immature, necrotic teeth treated with regenerative endodontics. APCs could be beneficial when treating young, immature, necrotic, permanent teeth regarding better apical closure and improved response to vitality tests.

Pulp Regeneration: Current Approaches, Challenges, and Novel Rejuvenating Strategies for an Aging Population

We showed the safety and efficacy of pulp regenerative therapy by the autologous transplantation of mobilized dental pulp stem cells with granulocyte colony-stimulating factor in a pilot clinical study of young and middle-aged pulpectomized teeth. An experimental study in dogs further demonstrated an age-dependent decline in the amount of regenerated pulp tissue. In our society, in which people will soon live beyond 100 years, this therapy should be efficacious for contributing to the functional survival and endurance of the tooth not only for pulpectomized young teeth but also for aged teeth with periapical disease. However, there are 2 challenges: 1 is enhancing pulp regeneration in aged teeth, and another is complete disinfection before cell transplantation. Thus, this review presents trypsin pretreatment for the former and a novel irrigant, nanobubbles with antibacterial nanopolymers, for the latter, thus demonstrating potential utility for pulp regenerative therapy in aged teeth with periapical disease.

Equivalence of human and bovine dentin matrix molecules for dental pulp regeneration: proteomic analysis and biological function

OBJECTIVE

To compare proteomics and biological function of human dentin matrix molecules (hDMMs) and bovine dentin matrix molecules (bDMMs).

DESIGN

Dentin powder from human or bovine teeth (n = 4) was demineralized in 10% (v/v) ethylenediaminetetraacetic acid for 7 days. The extracts were dialyzed, lyophilized and proteins were characterized using liquid chromatography-tandem mass spectrometry and shotgun proteomic analysis. To study biological function, mouse-derived undifferentiated dental pulp cells (OD21) were treated with 0.01, 0.1 or 1 μg/mL of hDMMs or bDMMs and proliferation was measured after 24 hours and 48 hours using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell migration was assessed after 24 hours using a Boyden chamber. Alizarin Red S staining was used to evaluate mineral formation.

RESULTS

There were 307 proteins identified, of which 93 proteins were common to both species. Gene Ontology functional analysis demonstrated similar pattern of biological process in both species which consisted mainly of tissue development and biomineralization. hDMMs and bDMMs both enhanced cell proliferation. After 24 hours, all concentrations of bDMMs promoted cell proliferation (p ≤ 0.05), while hDMMs did not affect proliferation. After 48 hours, groups with 1μg/mL of bDMMs and 0.01μg/mL of hDMMs had increased cell proliferation compared to control (p ≤ 0.0001). All concentrations of hDMMs and bDMMs enhanced cell migration and mineralization (p ≤ 0.0001).

CONCLUSION

bDMMs has similar biological functions as hDMMs. Moreover, bDMMs stimulated cell proliferation, migration and differentiation similar to hDMMs.

Regenerative Endodontics: A Paradigm Shift in Clinical Endodontics

Preserving the natural dentition in its normal form and function is one of the major goals of endodontic treatment. Re-establishing the lost vitality and development of root maturation in immature permanent teeth with pulp necrosis/apical periodontitis is quiet challenging clinically. The very basis of regenerative endodontics relies on the concept of tissue engineering using stem cells, biomimetic scaffold, and bioactive growth factors to regenerate the pulp tissue damaged by microbial infection, injury, or developmental defects. In clinical endodontics, this approach is referred to as a “paradigm shift.” Even though repair instead of true regeneration is achieved with current protocols, it is hoped that further research in the area of stem-cell-based tissue engineering will allow for true regeneration and improved treatment outcomes. The aim of this review is to discuss about the various aspects of regenerative endodontics, current clinical protocols, and the future of pulp regeneration techniques.

Effect of Intracanal Medicaments and Irrigants on the Release of Transforming Growth Factor Beta 1 and Vascular Endothelial Growth Factor from Cervical Root Dentin

INTRODUCTION

This study aimed to evaluate (1) the effect of irrigating solutions and intracanal medicaments on the release of transforming growth factor beta 1 (TGF-β1) and vascular endothelial growth factor (VEGF) from cervical root dentin and (2) the effect of associating triple antibiotic paste (TAP) and calcium hydroxide paste (CH) with 2% chlorhexidine (CHX) on TGF-β1 release.

METHODS

First, 119 specimens from roots (cervical thirds) were obtained and were distributed into 5 groups: 2% CHX, 2.5% sodium hypochlorite, TAP, CH, and 10% EDTA by each growth factor (TGF-β1 [n = 8] and VEGF [n = 8]). Then, specimens were distributed as follows (n = 13): TAP + 2% CHX, CH + 2% CHX, and 10% EDTA and treated with irrigating solutions and intracanal medicaments. After the treatments, the specimens were immersed in 10% EDTA (20 minutes), and the solution was analyzed using the enzyme-linked immunosorbent assay. The data were submitted to normality, homogeneity of variance, and Mann-Whitney tests (P < .05).

RESULTS

Significant differences were found between the irrigating solutions (P < .05) and intracanal medicaments for TGF-β1 (P < .05). No VEGF release was detected for any group. Our results showed no significant differences among the TAP + 2% CHX and EDTA groups for TGF-β1 but a significant difference between CH + 2% CHX and the other groups (P < .05).

CONCLUSIONS

The use of 2% CHX as the irrigating solution, CH as the intracanal medicament, and 10% EDTA as the final irrigation provides higher TGF-β1 release from the cervical root dentin, whereas VEGF was not detected. Moreover, TAP and 2% CHX with 10% EDTA as the final irrigation resulted in greater TGF-β1 release from cervical root dentin than CH + 2% CHX.

Treatment of Pulpectomized Teeth With Trypsin Prior to Transplantation of Mobilized Dental Pulp Stem Cells Enhances Pulp Regeneration in Aged Dogs

There is an age-dependent decline of pulp regeneration, due to the decline of migration, proliferation, and cell survival of resident stem cells. Trypsin is a proteolytic enzyme clinically used for tissue repair. Here, we investigated the effects of trypsin pretreatment of pulpectomized teeth prior to cell transplantation on pulp regeneration in aged dogs. The amount of regenerated pulp was significantly higher in trypsin-pretreated teeth compared to untreated teeth. Trypsin pretreatment increased the number of cells attached to the dentinal wall that differentiated into odontoblast-like cells. The trypsin receptor, PAR2, was higher in vitro expression in the periodontal ligament cells (PDLCs) from aged dogs compared to those from young. The direct effects of trypsin on aged PDLCs were increased expression of genes related to immunomodulation, cell survival, and extracellular matrix degradation. To examine the indirect effects on microenvironment, highly extracted proteins from aged cementum were identified by proteomic analyses. Western blotting demonstrated that significantly increased fibronectin was released by the trypsin treatment of aged cementum compared to young cementum. The aged cementum extract (CE) and dentin extract (DE) by trypsin treatment increased angiogenesis, neurite extension and migration activities as elicited by fibronectin. Furthermore, the DE significantly increased the mRNA expression of immunomodulatory factors and pulp markers in the aged DPSCs. These results demonstrated the effects of trypsin on the microenvironment in addition to the resident cells including PDLCs in the aged teeth. In conclusion, the potential utility of trypsin pretreatment to stimulate pulp regeneration in aged teeth and the underlying mechanisms were demonstrated.

Effect of benzalkonium chloride addition to EDTA on attachment and proliferation of dental pulp stem cells on dentin and on transforming growth factor-β1 release

To investigate the effect of benzalkonium chloride (BAC) addition to ethylenediaminetetraacetic acid (EDTA) on transforming growth factor-β1 (TGF-β1) release, as well as attachment and proliferation of dental pulp stem cells (DPSCs) on dentin. A total of standard 268 human dentin disks were prepared and immersed in 1.5% sodium hypochlorite (NaOCl) for 5 min. The disks were rinsed with distilled water and randomly divided into seven groups. In control group, the disks received no further treatment. The remaining disks were immersed in following solutions: 17% EDTA or 17% EDTA + 0.008% BAC for 1, 5 or 10 min and rinsed with distilled water. DPSCs were seeded in part of the disks since the TGF-β1 release assay was performed with disks with and without cells. The attachment and proliferation of DPSCs on dentin disks were analyzed using lactate dehydrogenase activity and WST-1 assays, respectively. The cell morphology was observed by scanning electron microscopy. The release of TGF-β1 was quantified using ELISA. Data were analyzed using three- and two-way analysis of variance with Bonferroni corrections. Both EDTA solutions increased the attachment and proliferation of DPSCs (p < .05) while there was no significant difference between them (p > .05). The exposure time of both EDTA solutions had no influence on cell attachment, proliferation and TGF-β1 release (p > .05). There was no significant difference in TGF-β1 release between the control and experimental groups (p > .05). The amount of released TGF-β1 from dentin disks was similar whether or not they were seeded with cells (p > .05). Dentin treatment with either of the EDTA solutions had no effect on the amount of TGF-β1 release while both EDTA solutions improved cell attachment and proliferation on dentin surface regardless of exposure time.

Surface and structural changes in root dentine by various chelating solutions used in regenerative endodontics

AIM

To evaluate the effects of the prolonged use of various irrigant solutions used during regenerative endodontic procedures on the physical and chemical structure of root canal dentine in extracted human teeth.

METHODOLOGY

Sixtyroot dentine samples from extracted, single-rooted, human teeth were assigned to 10 groups. Eight groups were irrigated with 1.5% NaOCl for 5 min, followed by 3%, 10%, 17% EDTA or 10% citric acid (CA) for 5 or 10 min. One group received only NaOCl irrigation, and samples with only distilled water irrigation were used as a control group. The changes in microhardness and flexural strength were determined using Vickers and 3-point flexural tester, respectively. Molecular and elemental compositions were recorded using FTIR and EDS spectroscopy. Data were analysed using one-way anova, Kruskal-Wallis and Mann-Whitney U tests.

RESULTS

The application of 1.5% NaOCl for 5 min did not affect the mineral content or microhardness of dentine (P > 0.05). However, it significantly decreased the dentine collagen peak values (P < 0.05), which was similar to the control group after the use of chelating agents (EDTA and 10% of CA) (P > 0.05). The effect of EDTA on the inorganic content was not concentration and time dependent (P > 0.05). CA resulted in a significantly greater reduction in the inorganic contents compared with the control and EDTA groups (P < 0.05). Regardless of the time, EDTA and CA significantly decreased dentine microhardness compared to the control (P < 0.05) with the greatest reduction in the CA groups (P < 0.05). NaOCl alone was associated with the lowest flexural strength, while none of the other irrigation regimens significantly decreased the flexural strength compared to the control group (P> 0.05).

CONCLUSIONS

Use of 1.5% NaOCl for 5 min decreased the collagen content of samples of human dentine from extracted teeth while EDTA and 10% citric acid mostly affected the inorganic content and microhardness of dentine surfaces. None of the irrigant solutions significantly decreased the mechanical properties of the entire dentine specimen.

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.

Pulp stem cells derived from human permanent and deciduous teeth: Biological characteristics and therapeutic applications

Human pulp stem cells (PSCs) include dental pulp stem cells (DPSCs) isolated from dental pulp tissues of human extracted permanent teeth and stem cells from human exfoliated deciduous teeth (SHED). Depending on their multipotency and sensitivity to local paracrine activity, DPSCs and SHED exert therapeutic applications at multiple levels beyond the scope of the stomatognathic system. This review is specifically concentrated on PSC-updated biological characteristics and their promising therapeutic applications in (pre)clinical practice. Biologically, distinguished from conventional mesenchymal stem cell markers in vitro, NG2, Gli1, and Celsr1 have been evidenced as PSC markers in vivo. Both perivascular cells and glial cells account for PSC origin. Therapeutically, endodontic regeneration is where PSCs hold the most promises, attributable of PSCs' robust angiogenic, neurogenic, and odontogenic capabilities. More recently, the interplay between cell homing and liberated growth factors from dentin matrix has endowed a novel approach for pulp-dentin complex regeneration. In addition, PSC transplantation for extraoral tissue repair and regeneration has achieved immense progress, following their multipotential differentiation and paracrine mechanism. Accordingly, PSC banking is undergoing extensively with the intent of advancing tissue engineering, disease remodeling, and (pre)clinical treatments.

Transforming Growth Factor Beta 1 Distribution and Content in the Root Dentin of Young Mature and Immature Human Premolars

INTRODUCTION

Transforming growth factor beta 1 (TGF-β1) is a key morphogen in regenerative endodontics; yet, its location within the hard tissue phase of dentin and its availability in mature roots have not been fully elucidated.

METHODS

Young mature (n = 8) and immature (n = 11) roots from sound premolars were obtained from 13 orthodontic patients aged 17 ± 1 and 12 ± 1 years, respectively. Roots were cleaned of organic remnants in 5% sodium hypochlorite. The width of the minor foramen was measured using a digital microscope. TGF-β1 distribution was assessed in 3 roots per group by immunostaining combined with confocal laser scanning microscopy. The root dentin of the remaining 13 roots was powdered and decalcified in 17% EDTA to determine the overall levels of hard tissue-embedded TGF-β1 by enzyme-linked immunosorbent assay. Data were compared between groups using the Student t test (α = .05).

RESULTS

The minor foramen was 168 ± 49 μm versus 557 ± 295 μm in mature compared with immature roots (P < .05). TGF-β1 was highly stainable toward the pulp space in both groups. It was clearly associated with peritubular dentin and apparently absent in nontubular outer dentin. TGF-β1 content was 115 ± 31 pg and 74 ± 35 pg/100 mg mature versus immature root dentin, respectively (P > .05).

CONCLUSIONS

TGF-β1 is deposited into the peritubular dentin. It should be possible to release this molecule in regenerative endodontic procedures from young mature roots as well as immature roots.

Hand-held bioprinting for de novo vascular formation applicable to dental pulp regeneration

Aim of the study: Deep carious lesions may cause irreversible pulpitis and the current endodontic treatment typically removes the whole dental pulp tissue, which finally reduces lifespan of the teeth. Nowadays, the most frequent treatment is based on removing the infected tissue and filling the root canal with inert synthetic materials. Tissue engineering approaches are important alternatives to the current treatment, because they can potentially maintain the biological function of the tooth instead of sacrificing it.Materials and Methods: In this study, we propose a tissue engineering approach based on a hand-held in situ bioprinting strategy. Our approach enabled bioprinting of cell-loaded collagen-based bioinks with suitable rheological, structural and biological properties, which allowed for vasculogenesis in the root canal.Results: The rheological properties of the bioprintable bioink were measured by oscillatory amplitude sweep testing and were corroborated by macroscopic evaluation after in vitro culture, in which printed bioinks maintained their original form without contraction. Moreover, we showed evidence for successful vasculogenesis in bioprintable bioinks with comparable quality and quantity to control fibrin and collagen non-bioprintable hydrogels.Conclusions: We conclude that hand-held bioprinting holds potential for in situ treatment of dental diseases with successful evidence for vascular tube formation, as an asset for maintenance of the biological function of the tooth.

Limited Evidence Suggests Benefits of Single Visit Revascularization Endodontic Procedures - A Systematic Review

Abstract Revascularization endodontic procedures commonly require multiple treatment sessions. However, single visit procedures may be advantageous from the clinical and patient management standpoints. The purpose of this review was to evaluate the outcomes of single-visit revascularization endodontic procedures for the management of immature permanent teeth with non-vital pulp. Two electronic databases (Scopus and PubMed) were searched, from their inception to July 2018, for studies that assessed clinical and/or radiographic and/or histologic outcomes of single-visit revascularization endodontic procedures performed in immature permanent teeth with non-vital pulp. Case reports, animal studies and clinical trials were included. The quality of case reports was appraised by Joanna Briggs Institute Critical Appraisal Checklist for Case Reports. The quality of randomized clinical trials was assessed by the revised Cochrane risk of bias tool for randomized trials. The risk of bias for animal studies was assessed using SYRCLE’s risk of bias tool. Tabulation followed by narrative synthesis was used to draw conclusions. Seven studies satisfied the selection criteria. Five were classified as case reports, one as a randomized clinical trial and one as animal study. The latter presented with a high risk of bias, whilst the remaining showed a low risk. The evidence supporting the potential use of single-visit revascularization endodontic procedures is scarce. Successful single-visit revascularization endodontic procedures commonly include the use of high concentrations of sodium hypochlorite and EDTA combined with the use of agitation systems. Further clinical trials with long term follow up are needed to confirm the results of the current review.

Similar inductive effects of enamel and dentin matrix derivatives on osteoblast-like cell response over SLA titanium surface

OBJECTIVES

The aim of this in vitro study was to investigate the behavior of osteoblasts on titanium discs under different concentrations of enamel matrix derivatives (EMD) and dentin matrix derivative (DMD).

MATERIALS AND METHODS

MC3T3-E1 osteoblast-like cells were cultivated on coated titanium SLA discs with EMD or DMD at 100 μg/ml, 1 mg/ml, 10 mg/ml and 30 mg/ml or left uncoated. Cell viability, proliferation, adhesion and migration were assessed respectively with MTT, BrdU, DAPI and scratch wound healing assays. Messenger ribonucleic acid of different genes related to osteoblastic differentiation was quantified by means of real-time quantitative PCR. Data were analyzed using student t-test for adhesion and migration assay and ANOVA for proliferation assay (p < 0.05).

RESULTS

BrdU incorporation was found in proliferative osteoblasts for both test solutions at all concentrations. Osteoblast migrated and covered approximately 70% of the wound area observed at time zero when exposed to EMD and DMD to all concentrations. The increase of gene expression was dependent on the concentration enhancement of EMD and DMD. Higher concentrations showed proliferation augmentation if compared to lower concentrations.

CONCLUSIONS

Roughness surface of Ti SLA can limit cell adhesion independent of the presence EMD or DMD. DMD enhances cell migration of osteoblasts on SLA titanium implants in a concentration-dependent manner.

Number of Dental Stem Cells on Root Canal Dentin after Application of Triple Antibiotic Paste or Calcium Hydroxide: An In Vitro Study

OBJECTIVE

The aim of this study was to evaluate the viability of stem cells from exfoliated and deciduous teeth (SHED) on dentin surface treated with triple antibiotic paste or calcium hydroxide.

MATERIALS AND METHODS

Nine single-rooted extracted premolars were prepared appropriately and divided into three groups. In group A, the root canals were left empty, a triple antibiotic paste was placed in the root canals of group B, and calcium hydroxide was placed in the root canals of group C. After 1 week, the intracanal medicaments were removed, and stem cells were seeded on the treated surface of the specimens for 1 more week. The cells were stained and then observed under confocal microscope over the entire surface of each test material. Counting of the cells was made by Image J (3D) software, as well as manually.

STATISTICAL ANALYSIS

To investigate any statistically significant differences between the experimental groups, statistical tests including Kruskal-Wallis and Mann-Whitney U-test were performed. Significance level was set to P < 0.05, and all analyses were performed with SPSS IBM program, v. 21.

RESULTS

Groups B and C showed statistically significantly higher number of cells compared to Group A, whereas cells developed in a substrate of calcium hydroxide residues appeared in majority with distinct cores and widened unlike other groups.

CONCLUSIONS

The effect of calcium hydroxide manifested better results regarding the number of stems cells on root canal surfaces.

The effect of different chelating agents on the push-out bond strength of proroot mta and endosequence root repair material

Purpose

This study aimed to evaluate the effects of 17% ethylenediaminetetraacetic acid (EDTA), 7% maleic acid (MA), and 10% citric acid (CA) on the push-out bond strength of ProRooT MTA and Endosequence Root Repair Material (ERRM) putty.

Materials and methods

Eighty single-rooted extracted human teeth were instrumented to obtain a standardized immature teeth model. Based on the chelating agents tested, the specimens were randomly divided into three experimental groups: Group 1 (17% EDTA), Group 2 (7% MA), Group 3 (10% CA), and Group 4 (Positive Control) (n=20 for each group). Each group was further classified into two subgroups: Group A (ProRoot MTA) and Group B (Endosequence Root Repair Material (ERRM) putty) (n=10 for each subgroup). After irrigation and placement of cements, teeth were stored at 37°C and in 100% humidity for a week. A total of 240 dentine discs (three discs per teeth) were obtained and subjected to push-out assay. Data was analyzed using two-way analysis of variance and Tukey's post hoc t-test.

Results

Both types of chelating agent and calcium silicate-based cement were significantly associated with the push-out bond strength values. The push-out bond strength was significantly less for CA as compared to EDTA or MA. ERRM had higher bond strength values than ProRoot MTA (p<0.05).

Conclusion

The use of chelating agents increased the push-out bond strength of CSC. Regardless of tested chelating agents, ERRM had higher bond strength values than ProRoot MTA.

Management of deep caries and the exposed pulp

Caries prevalence remains high throughout the world, with the burden of disease increasingly affecting older and socially disadvantaged groups in Western cultures. If left untreated, caries will advance through dentine stimulating pulpitis and eventually pulp infection and necrosis; however, if conservatively managed, pulpal recovery occurs even in deep carious lesions. Traditionally, deep caries management was destructive with nonselective (complete) removal of all carious dentine; however, the promotion of minimally invasive biologically based treatment strategies has been advocated for selective (partial) caries removal and a reduced risk of pulp exposure. Selective caries removal strategies can be one-visit as indirect pulp treatment or two-visit using a stepwise approach. Management strategies for the treatment of the cariously exposed pulp are also shifting with avoidance of pulpectomy and the re-emergence of vital pulp treatment (VPT) techniques such as partial and complete pulpotomy. These changes stem from an improved understanding of the pulp-dentine complex's defensive and reparative response to irritation, with harnessing the release of bioactive dentine matrix components and careful handling of the damaged tissue considered critical. Notably, the development of new pulp capping materials such as mineral trioxide aggregate, which although not an ideal material, has resulted in more predictable treatments from both a histological and a clinical perspective. Unfortunately, the changes in management are only supported by relatively weak evidence with case series, cohort studies and preliminary studies containing low patient numbers forming the bulk of the evidence. As a result, critical questions related to the superiority of one caries removal technique over another, the best pulp capping biomaterial or whether pulp exposure is a negative prognostic factor remain unanswered. There is an urgent need to promote minimally invasive treatment strategies in Operative Dentistry and Endodontology; however, the development of accurate diagnostic tools, evidence-based management strategies and education in management of the exposed pulp are critical in the future.

Apical Papilla Cells Are Capable of Forming a Pulplike Tissue with Odontoblastlike Cells without the Use of Exogenous Growth Factors

INTRODUCTION

Dental pulp is a complex tissue with highly differentiated cells, which makes its reconstruction a challenging task. The apical papilla is an undifferentiated tissue considered as the remnant of the dental papilla that forms the dentin-pulp complex. Aiming to analyze morphologic features of the tissue formed in an in vivo pulp model, we used human apical papilla as a cell source without the use of exogenous growth factors.

METHODS

A construct was built using newborn mice molar crowns treated with TrypLE (Fisher Scientific, Loughborough, UK) and EDTA. The crowns were filled with PuraMatrix (Corning Inc, Corning, NY) and a pool population of human apical papilla cells. As a control, we used crowns filled only with PuraMatrix and empty crowns. The constructs were transplanted under severe combined immunodeficient mice kidney capsules. Immunohistochemistry for lamin A, dentin sialophosphoprotein, and dentin matrix protein 1 was performed.

RESULTS

Morphologic analysis of all transplanted crowns showed the formation of a loose connective tissue of variable cellularity with the presence of well-formed functional vessels. In the study group, lamin A-positive cells represented the majority of cells within the pulp chamber and a few cells in the vessel lining. We also found positivity for dentin sialophosphoprotein and dentin matrix protein 1, an indicator of odontoblast differentiation.

CONCLUSIONS

In our study model, human transplanted apical papilla cells mixed with the host cells and formed a vascularized viable tissue, and these cells were able to differentiate into odontoblastlike cells without the use of exogenous growth factors.

Growth Factors and Cell Homing in Dental Tissue Regeneration

Purpose of Review

To summarize current views on the role and therapeutic potential of growth factors (GFs) within endodontic cell homing.

Recent Findings

Cell homing/revitalization techniques aim to regenerate dentin and pulp using endogenous cells. Clinically, revitalization has successfully created new vital tissue in necrotic permanent teeth with an open apex; however, there is no evidence of new odontoblasts, pulp tissue, or predictable extension in root length. Although the response is reparative rather than regenerative, exciting opportunities to improve these biologically-based strategies remain by (1) efficiently sequestering dentin-matrix-components (DMCs) using irrigants and dental materials (2) designing next-generation GF-releasing scaffold materials and (3) utilizing other sources of GF such as cells and plasma-rich plasma and plasma-rich fibrin.

Summary

GFs can promote reparative-dentinogenesis and pulp-like tissue formation. The future development and clinical approval of GF-functionalized-scaffolds is a priority; however, current focus should be to harness DMCs and target the interaction of stem cells and GFs.

Regenerative endodontics: a comprehensive review

The European Society of Endodontology and the American Association for Endodontists have released position statements and clinical considerations for regenerative endodontics. There is increasing literature on this field since the initial reports of Iwaya et al. (Dental Traumatology, 17, 2001, 185) and Banchs & Trope (Journal of Endodontics, 30, 2004, 196). Endogenous stem cells from an induced periapical bleeding and scaffolds using blood clot, platelet rich plasma or platelet-rich fibrin have been utilized in regenerative endodontics. This approach has been described as a 'paradigm shift' and considered the first treatment option for immature teeth with pulp necrosis. There are three treatment outcomes of regenerative endodontics; (i) resolution of clinical signs and symptoms; (ii) further root maturation; and (iii) return of neurogenesis. It is known that results are variable for these objectives, and true regeneration of the pulp/dentine complex is not achieved. Repair derived primarily from the periodontal and osseous tissues has been shown histologically. It is hoped that with the concept of tissue engineering, namely stem cells, scaffolds and signalling molecules, that true pulp regeneration is an achievable goal. This review discusses current knowledge as well as future directions for regenerative endodontics. Patient-centred outcomes such as tooth discolouration and possibly more appointments with the potential for adverse effects needs to be discussed with patients and parents. Based on the classification of Cvek (Endodontics and Dental Traumatology, 8, 1992, 45), it is proposed that regenerative endodontics should be considered for teeth with incomplete root formation although teeth with near or complete root formation may be more suited for conventional endodontic therapy or MTA barrier techniques. However, much is still not known about clinical and biological aspects of regenerative endodontics.

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.

Interactive effects of LPS and dentine matrix proteins on human dental pulp stem cells

AIM

To investigate the combinatorial effects of lipopolysaccharide (LPS) and extracted dentine matrix proteins (eDMP) on regenerative and inflammatory responses in human dental pulp stem cells (DPSCs).

METHODOLOGY

Culture media were supplemented with several concentrations of LPS, eDMP and combinations of both. Cell viability was assessed over 1 week by MTT assay; cell survival was evaluated after 24 h and 7 days by flow cytometry. The expression of mineralization-associated marker genes was determined by real-time quantitative polymerase chain reaction (RT-qPCR). To analyse the inflammatory response, secretion of interleukin 6 (IL-6) was quantified in the initial and the late phase of cell culture by enzyme-linked immunosorbent assay (ELISA). Data were treated nonparametrically and Mann-Whitney U-tests were performed to compare all experimental groups (α = 0.05).

RESULTS

Whereas LPS had no impact on viability, eDMP led to a concentration-dependent decrease, which was significant after 7 days (P ≤ 0.024). A moderate decline of cell survival induced by LPS was detected after 48 h (P ≤ 0.026), whereas eDMP was able to reverse this effect. eDMP alone caused increased expression of tested marker genes, LPS had no regulatory effect. Combined eDMP and LPS induced an upregulation of collagen type I and osteocalcin, whereas expression levels of dentine matrix acidic phosphoprotein and dentine sialophosphoprotein were similar to the control. IL-6-secretion was increased by LPS over time. eDMP markedly elevated initial production of IL-6 (P ≤ 0.002), but suppressed LPS-induced cytokine production in the later phase.

CONCLUSIONS

Lipopolysaccharide did not affect cell viability but interfered with odontoblast-like cell differentiation of DPSCs. Proteins from the dentine matrix may have a protective effect, attenuate the detrimental impact of LPS and thus play an important role during pulp repair.

Effects of mineral trioxide aggregate, BiodentineTM and calcium hydroxide on viability, proliferation, migration and differentiation of stem cells from human exfoliated deciduous teeth

The aim of the study was to evaluate the effects of the capping materials mineral trioxide aggregate (MTA), calcium hydroxide (CH) and BiodentineTM (BD) on stem cells from human exfoliated deciduous teeth (SHED) in vitro. SHED were cultured for 1 - 7 days in medium conditioned by incubation with MTA, BD or CH (1 mg/mL), and tested for viability (MTT assay) and proliferation (SRB assay). Also, the migration of serum-starved SHED towards conditioned media was assayed in companion plates, with 8 μm-pore-sized membranes, for 24 h. Gene expression of dentin matrix protein-1 (DMP-1) was evaluated by reverse-transcription polymerase chain reaction. Regular culture medium with 10% FBS (without conditioning) and culture medium supplemented with 20% FBS were used as controls. MTA, CH and BD conditioned media maintained cell viability and allowed continuous SHED proliferation, with CH conditioned medium causing the highest positive effect on proliferation at the end of the treatment period (compared with BD and MTA) (p<0.05). In contrast, we observed increased SHED migration towards BD and MTA conditioned media (compared with CH) (p<0.05). A greater amount of DMP-1 gene was expressed in MTA group compared with the other groups from day 7 up to day 21. Our results show that the three capping materials are biocompatible, maintain viability and stimulate proliferation, migration and differentiation in a key dental stem cell population.

EDTA Treatment for Sodium Hypochlorite-treated Dentin Recovers Disturbed Attachment and Induces Differentiation of Mouse Dental Papilla Cells

INTRODUCTION

The disturbance of cellular attachment to dentin by sodium hypochlorite (NaOCl) may hamper pulp tissue regeneration. The aims of this study were to examine the recovering effect of EDTA on the attachment/differentiation of stemlike cells and to address the mechanisms of EDTA-induced recovery under the hypothesis that attachment to the exposed dentin matrix and the subsequent activation of integrin/phosphatidylinositol 3-kinase (PI3K) signaling play a crucial role.

METHODS

Mouse dental papilla (MDP) cells were cultured on bovine dentin disks treated with NaOCl (0%, 1.5%, or 6%) followed by EDTA (0%, 3%, or 17%). Cell attachment was evaluated by cell density, viability, and scanning and transmission electron microscopy. Odonto-/osteoblastic gene expression in attached MDP cells was analyzed with or without a pan-PI3K inhibitor (LY294002) using real-time polymerase chain reaction.

RESULTS

NaOCl treatment (1.5%, 10 minutes) significantly diminished attached MDP cells (P < .00001), but EDTA treatment (3% and 17%, ≥10 minutes) of NaOCl-pretreated dentin induced a significant increase in attached cells (P < .05). Ultrastructurally, MDP cells on EDTA-treated dentin showed attachment to exposed collagen fibers. MDP cells cultured on EDTA-treated disks (with or without 1.5% NaOCl pretreatment) showed significant up-regulation of alkaline phosphatase, dentin matrix protein 1, and dentin sialophosphoprotein messenger RNAs (P < .05). Alkaline phosphatase expression was down-regulated by LY294002 (P < .05).

CONCLUSIONS

Under the present experimental conditions, 10 minutes of EDTA treatment was sufficient to recover attachment/differentiation of MDP cells on 1.5% NaOCl-pretreated dentin. EDTA-induced exposure of collagen fibers and subsequent activation of integrin/PI3K signaling may contribute, at least partly, to the recovery.

Alkaline Materials and Regenerative Endodontics: A Review

Periapical health is the primary goal of endodontic treatment in mature and immature teeth. In addition, the goals of treatment of immature teeth with arrested root development include root growth to length and maturation of the apex, as well as thickening of the canal wall. These goals are valid for immature teeth that have been subjected to trauma and dental caries or that are the result of developmental anomalies that expose the tooth to the risk of pulp necrosis and consequently result in the cessation of root maturation. Regenerative endodontic procedures (REPs) have been described as a “paradigm shift” in the treatment of immature teeth with pulp necrosis and underdeveloped roots, as there is the potential for further root maturation and return of vitality. Treatment with REPs is advocated as the treatment of choice for immature teeth with pulp necrosis. REP protocols involve the use of alkaline biomaterials, primarily sodium hypochlorite, calcium hydroxide, mineral trioxide aggregates and Biodentine, and are the essential components of a successful treatment regimen.

A review of regenerative endodontics: current protocols and future directions

This review outlines the biological basis and clinical protocols currently used in regenerative endodontic procedures (REPs) and discuss future directions in pulp regeneration approaches. The treatment of immature teeth with REPs has been described as a ‘paradigm shift’ as there is the potential for further root maturation. Clinically, REPs involve disinfection of the root canal system without damaging the endogenous stem cell potential present in the apical papilla and other tissues. These stems cells are introduced into the root canal space by inducing a blood clot followed by placement of an intracanal barrier to prevent microleakage. The biological concept of REPs involves the triad of stem cells, scaffold and signalling molecules. Currently, repair rather than true regeneration of the ‘pulp-dentine complex’ is achieved and further root maturation is variable. However, may clinicians consider the treatment of teeth with REPs as the optimal treatment approach for immature teeth with pulp necrosis.

Bleaching of a Discolored Tooth with Retrieval of Remnants after Successful Regenerative Endodontics

INTRODUCTION

This report presents the retrieval of remnants from a discolored mandibular right second premolar (tooth #29) of a 17-year-old female after a successful regenerative endodontic procedure (REP).

METHODS

The REP was performed in October 2011. Coronal discoloration became of great concern to the patient at a review visit in 2016. A cone-beam computed tomographic scan was taken to investigate the formation of hard tissues within the root canal as well as a region of no calcified tissue formation. During internal bleaching of tooth #29, a black material with particulate inclusions was retrieved and examined histopathologically.

RESULTS

Five years after the REP, there was complete periapical healing, hard tissue formation within the root canal, and complete maturation of the root apex. A hard tissue bridge was noted at the cementoenamel junction when the pulp chamber of #29 was reaccessed. The remnants retrieved from the pulp chamber were confirmed to be partly mineral trioxide aggregate (MTA). A normal tooth color was achieved after 3 weeks of internal bleaching.

CONCLUSIONS

MTA remnants within the pulp chamber contributed to the tooth discoloration and appear to have obstructed hard tissue formation. A matrix of oxidized regenerated cellulose seems not to hinder tissue regeneration and is resorbed by these tissues. Other materials with color stability should be selected as coronal barriers for REPs to avoid a potential adverse effect of the MTA on the REP outcome and discoloration.