Histological assessment of regenerative endodontic treatment in animal studies with different scaffolds: A systematic review

BACKGROUND/AIM

The concept of regenerative endodontic procedures remains controversial. The aim of this study was to evaluate the histology of the tissues formed in immature animal teeth with necrotic and infected pulps after attempted endodontic regeneration procedures using different scaffolds.

DESIGN

A systematic electronic literature search was performed in PubMed, Web of Science, Scopus, EMBASE, DOSS, and Cochrane Library databases. The terms used were a combination of the following: "immature permanent necrotic tooth or teeth" or "open apex or apices" and "regeneration or revitalization or revascularization" and "histology." The inclusion criteria comprised animal studies with histological examination following regenerative endodontics in immature necrotic-infected permanent teeth.

RESULTS

From 123 screened studies, 13 met the inclusion criteria. Formation of dentin-like tissue on the dentinal walls was reported in only 4% of teeth treated with blood clot scaffold and 2% treated with blood clot with additional materials. Cementum-like hard tissue was found in 64% of teeth with blood clot, 80% treated with blood clot with additional materials, 50% treated with alternative scaffolds, and 5% that were left empty. Bone-like tissue was reported in 10% of teeth treated with blood clot, 2% treated with blood clot with additional materials, and 4% treated with alternative scaffolds. The tissues in the canal space were found to be connective tissue with infiltration of fibroblast-like cells and blood vessels. Forty-six percent of the studies reported formation of periodontal ligament-like tissues.

CONCLUSIONS

None of the regeneration protocols resulted in the predictable formation of a true pulp-dentin complex.

Direct and Indirect Effect of Chlorhexidine on Survival of Stem Cells from the Apical Papilla and Its Neutralization

INTRODUCTION

Several irrigants have been used for disinfection in regenerative endodontic procedures including chlorhexidine (CHX). In this context, the antibacterial properties of disinfectants are mainly in focus of research even though they may have an undesirable impact on the fate of stem cells. In this study, we hypothesized that CHX has both a direct effect when applied to stem cells of the apical papilla (SCAPs) and an indirect effect when SCAPs are exposed to dentin previously conditioned with CHX.

METHODS

Cell toxicity was evaluated in vitro using the CellTox green fluorescence assay (Promega, Madison, WI) and CellTiter-Glo (Promega) after SCAPs were exposed directly to a dynamic concentration range of CHX; apical papilla explant cultures were stained with ApopTag (Merck Millipore, Billerica, MA) after culture with CHX. Furthermore, standardized slabs from human dentin were treated with CHX and consecutively rinsed in EDTA, L-α-lecithin (Sigma-Aldrich, St Louis, MO), or L-α-lecithin followed by EDTA. After that, SCAPs were cultured on the slabs for 5 days, and cellular viability was determined (indirect effect). Data were treated nonparametrically and analyzed using the Krukal-Wallis test (P ≤ .05).

RESULTS

Direct exposure of SCAPs to CHX highly affected cell viability at concentrations above 10^-3%, whereas lower concentrations had no adverse effect. During the initial 60 minutes, concentrations of 10^-2% CHX or higher resulted in early pronounced toxicity with a maximum effect within 15 minutes after exposure. Likewise, CHX-conditioned dentin slabs were detrimental to SCAP survival; however, the deleterious effects were completely reversed by neutralization with L-α-lecithin.

CONCLUSIONS

Chlorhexidine is toxic to SCAPs when applied directly or indirectly via conditioned dentin. If applied for a short time and neutralized by L-α-lecithin, it can be a gentle and cell-preserving disinfectant before endodontic regeneration.

The effects of radicular dentine treated with double antibiotic paste and ethylenediaminetetraacetic acid on the attachment and proliferation of dental pulp stem cells

AIM

This study explored the effects of dentine treated with two concentrations of double antibiotic paste (DAP) and ethylenediaminetetraacetic acid (EDTA) on the attachment and proliferation of dental pulp stem cells (DPSCs).

MATERIALS AND METHODS

Radicular dentine samples were prepared with identical dimensions and randomized into six groups (n = 4). Four groups were treated with double antibiotic paste (DAP) at concentrations of 500 mg ml(-1) or 1 mg ml(-1) with or without EDTA. The other two groups were treated with EDTA only or received no treatment. DPSCs were seeded on each dentine sample (10 000 cells per sample). Lactate dehydrogenase activity assays were used to calculate the attached DPSCs after 1 day of incubation. Water soluble tetrazolium assays were performed to investigate DPSCs proliferation on the treated dentine samples after three additional days of incubation. Two-way anova followed by Tukey-Kramer tests was used for statistical analyses (α = 0.05).

RESULTS

Dentine treated with 1 or 500 mg ml(-1) of DAP followed by EDTA caused significant increases in DPSCs attachment compared to the dentine treated with the DAP alone. The 500 mg ml(-1) of DAP with or without EDTA caused significant reductions in DPSCs proliferation. However, the treatment of dentine with 1 mg ml(-1) of DAP did not have significant negative effects on DPSCs proliferation regardless of the use of EDTA.

CONCLUSION

The use of 1 mg ml(-1) of DAP followed by 10 min of irrigation with EDTA in endodontic regeneration procedure may have no negative effects on the attachment and proliferation of DPSCs.

Active Nanomaterials to Meet the Challenge of Dental Pulp Regeneration

The vitality of the pulp is fundamental to the functional life of the tooth. For this aim, active and living biomaterials are required to avoid the current drastic treatment, which is the removal of all the cellular and molecular content regardless of its regenerative potential. The regeneration of the pulp tissue is the dream of many generations of dental surgeons and will revolutionize clinical practices. Recently, the potential of the regenerative medicine field suggests that it would be possible to achieve such complex regeneration. Indeed, three crucial steps are needed: the control of infection and inflammation and the regeneration of lost pulp tissues. For regenerative medicine, in particular for dental pulp regeneration, the use of nano-structured biomaterials becomes decisive. Nano-designed materials allow the concentration of many different functions in a small volume, the increase in the quality of targeting, as well as the control of cost and delivery of active molecules. Nanomaterials based on extracellular mimetic nanostructure and functionalized with multi-active therapeutics appear essential to reverse infection and inflammation and concomitantly to orchestrate pulp cell colonization and differentiation. This novel generation of nanomaterials seems very promising to meet the challenge of the complex dental pulp regeneration.

The use of traditional and novel techniques to determine the hardness and indentation properties of immature radicular dentin treated with antibiotic medicaments followed by ethylenediaminetetraacetic acid

Objective:

The objective was to investigate the effect of intracanal antibiotic medicaments followed by ethylenediaminetetraacetic acid (EDTA) on the indentation properties and hardness of radicular dentin using a BioDent reference point indenter and a traditional microhardness technique, respectively.

Materials and Methods:

Specimens with intact root canal dentin surfaces and polished radicular dentin specimens were obtained from immature human premolars. Each type of specimen was randomly assigned (n = 10 per group) and treated with either double antibiotic paste (DAP) for 4-week followed by EDTA for 5 min, triple antibiotic paste (TAP) for 4-week followed by EDTA for 5 min, EDTA for 5 min or Hank's balanced salt solution (control). The BioDent reference point indentor and Vickers microhardness tester were used to measure the indentation properties of root canal surfaces and the hardness of polished dentin specimens, respectively. One-way ANOVA followed by Fisher's protected least significant differences were used for statistical analyses.

Results:

Both types of radicular dentin treated with antibiotic pastes and/or EDTA had a significant increase in the majority of indentation properties and a significant reduction in hardness compared to the untreated dentin. Furthermore, treatment of dentin with antibiotic pastes and EDTA caused significant increases in indentation properties and a significant reduction in hardness compared to EDTA-treated dentin. However, the RPI technique was not able to significantly differentiate between DAP + EDTA and TAP + EDTA-treated dentin.

Conclusion:

Dentin treated with antibiotic medicaments followed by EDTA had a significant increase the indentation properties and significantly reduction in hardness of radicular dentin.

Silver Nanoparticles Alone or in Combination with Calcium Hydroxide Modulate the Viability, Attachment, Migration, and Osteogenic Differentiation of Human Mesenchymal Stem Cells

This study aimed to evaluate the effect of silver nanoparticles (AgNPs) alone or in combination with calcium hydroxide (Ca(OH)2) on the proliferation, viability, attachment, migration, and osteogenic differentiation of human mesenchymal stem cells (hMSCs). Different concentrations of AgNPs alone or mixed with Ca(OH)2 were prepared. Cell proliferation was measured using AlamarBlue, and hMSCs attachment to dentin disks was evaluated using scanning electron microscopy. Live-dead imaging was performed to assess apoptosis. Wound healing ability was determined using the scratch-migration assay. To evaluate osteogenic differentiation, the expression of Runt-related transcription factor (RUNX2), Transforming growth factor beta-1 (TGF-β1), Alkaline Phosphatase (ALP), and Osteocalcin (OCN) were measured using real-time reverse transcriptase polymerase chain reaction. ALP staining and activity were also performed as indicators of osteogenic differentiation. AgNPs alone seemed to favor cell attachment. Lower concentrations of AgNPs enhanced cell proliferation. AgNP groups showed markedly less apoptosis. None of the medicaments had adverse effects on wound closure. The expression of TGF-β1 was significantly upregulated in all groups, and OCN was highly expressed in the AgNP groups. AgNPs 0.06% showed the most enhanced ALP gene expression levels, activity, and marked cytochemical staining. In conclusion, AgNPs positively affect hMSCs, making them a potential biomaterial for various clinical applications.

Copper-Calcium Hydroxide and Permanent Electrophoretic Current for Treatment of Apical Periodontitis

Endodontic failure has been and continues to be a problem for endodontics-specialists. Complicated anatomy, numerous foramens, and accessory canals are an environment for microorganisms to infect the teeth. The purpose of the present work was to evaluate the regeneration of copper–calcium hydroxide (Cupral)-endodontically treated teeth diagnosed with apical periodontitis using an electrophoresis technique. In total, 132 patients, aging from 19 to 65 years old, underwent endodontic treatment mono- and multi-radicular teeth, with complicated canals from January 2019 to June 2020. The patients were divided into two groups: (i) the control group—which included 54 patients (n = 62 teeth) receiving endodontic paste (Calcipast + 1) and, as final filling, the AH-Plus^TM cement—and (ii) the Cupral group, which included 78 patients (n = 80 teeth) receiving Cupral paste plus the electrophoretic current and, as final filling, the Atacamit-alkaline cement. The clinical cases were periodically observed along an 18-month follow-up period via radiography. Data were expressed as focal size of the lesions (mean ± standard error (SEM) of all the radiographic outcomes) observed in each group at each interval point. Statistical analysis was performed using the Student’s t-test that allowed us to compare the control and Cupral groups; the statistical significance was set at p < 0.05 and p < 0.01, where the latter was highly significant. Before treatments, the focal sizes were 4.8 mm and 4.95 mm for control and Cupral-treated groups, respectively. After 6 months, the mean focal sizes were 3.9 mm and 2.14 mm for the control and Cupral groups, respectively. After 12 months, in the control group, the mean focal size was measured at 2.8 mm, while, in Cupral group, the lesion size decreased down to 0.31 mm and a highly dynamic regeneration of the destructive focal-bone occurred. After 18 months, the lesions were further significantly reduced in the control group (mean values of 2.62 mm), while they were barely detectable in the Cupral group (0.2 mm). In conclusion, we provide initial evidence that the Cupral-electrophoresis methodology is effective in treating destructive periodontitis of teeth with problematic canals up to 18 months, thus allowing teeth preservation.

Overexpression of ephrinB2 in stem cells from apical papilla accelerates angiogenesis

OBJECTIVES

We aimed to accelerate angiogenesis in pulp regeneration by modulating ephrinB2 expression in stem cells from apical papilla (SCAPs).

MATERIALS AND METHODS

Stem cells from apical papilla were transducted with ephrinB2-lentiviral expression vector (ephrinB2-SCAPs) in experimental group and green fluorescent protein (GFP-SCAPs) in control group. The transduction efficiency was confirmed by real-time PCR and Western blot assays. MTT assay was performed to detect the proliferative capacity of SCAPs after transduction. In vitro Matrigel assay and in vivo Matrigel plug assay were carried out to evaluate the angiogenic capacity.

RESULTS

Results showed that ephrinB2-SCAPs had significantly higher ephrinB2 expression than GFP-SCAPs. EphrinB2-SCAPs upregulated vascular endothelial growth factor (VEGF) secretion under hypoxia. In vitro Matrigel assay demonstrated that human umbilical vein endothelial cells (HUVECs) cocultured with ephrinB2-SCAPs under hypoxia formed vascular-like structures earlier than GFP-SCAPs. Animal experiments confirmed that SCAPs co-transplanted with HUVECs enabled to generate greater amount of blood vessels than SCAPs alone. EphrinB2-SCAPs produced increased number of blood vessels with references to GFP-SCAPs, and those co-transplanted with HUVECs generated vessels with larger and functional tubule volumes.

CONCLUSIONS

Regulating ephrinB2 expression in SCAPs may act as a new avenue for enhancing angiogenesis in dental pulp regeneration.

The Effects of Double Antibiotic Paste and Amoxicillin-clavulanate Paste Used in Endodontic Regeneration on Microhardness of Radicular Dentine: An In vitro Study

OBJECTIVE

Double antibiotic paste is a root canal medicament used in regenerative endodontics and its long-term exposure to dental hard tissues was shown to reduce its mechanical properties. The amoxicillin-clavulanate paste is a medicament effective against endodontic pathogens and is effective in endodontic regeneration. Its effect on radicular dentine is yet to be investigated. The purpose of this study is to investigate and compare the effects of double antibiotic paste and amoxicillin-clavulanate paste on the microhardness of radicular dentine.

MATERIALS AND METHODS

The root canal of 45 premolars was mechanically prepared and divided into three groups for the placement of intracanal medicament: Group 1 (n = 15) double antibiotic paste, Group 2 (n = 15) amoxicillin-clavulanate paste, and Group 3 control group (n = 15). All the specimens were subject to microhardness testing at 500 and 1000 microns depth for 1 week, 1 month, and 3 months and analyzed.

RESULTS

There is no significant reduction in microhardness of radicular dentin at 1 week on all the three groups. At 1 month and 3 month period, the amoxicillin-clavulanate paste is found to have no significant effect on dentin microhardness when compared to double antibiotic paste.

CONCLUSION

The use of amoxicillin-clavulanate paste as an intracanal medicament does not cause significant weakening of dentin even after its long-term use.

Effect of amniotic membrane and platelet-rich fibrin membrane on bone healing post endodontic surgery: An ultrasonographic, randomized controlled study

The use of membrane barriers and bone grafting materials in endodontic surgery promotes healing by regeneration rather than repair by scar tissue. Due to its valuable regenerative and therapeutic properties, the human amniotic membrane can support ideal periapical rehabilitation and promote better healing after surgery. The current trial aimed to evaluate the amniotic membrane's healing potential and compare it with platelet-rich fibrin using color doppler sonography. The current study is a randomized, double-blinded, parallel-group, single-center study. Thirty-four systematically healthy individuals requiring endodontic surgery who fulfilled all inclusion and exclusion criteria were selected and randomly placed in two groups. Surgical curettage of the bony lesion was performed and filled with hydroxyapatite graft. Amniotic membrane (Group 1) and platelet-rich fibrin (Group 2) were placed over the bony crypt, and the flap was sutured back. The lesion's surface area and vascularity were the parameters assessed with ultrasound and color doppler. and observations: The groups found a significant difference in mean vascularity at 1 month and mean vascularity change from baseline to 1 month (p < 0.05). Mean surface area had no statistically significant difference between the groups. However, in terms of the percentage change in surface area, a significant difference was found from baseline to 6 months (p < 0.05). Amniotic membrane was a significantly better promoter of angiogenesis than platelet-rich fibrin in the current trial. The osteogenic potential of both materials was similar. However, the clinical application, availability, and cost-effectiveness of amniotic membrane support it as a promising therapeutic alternative in clinical translation. Further large-scale trials and histologic studies are warranted.

Regenerative endodontic treatment: A systematic review of successful clinical cases

This systematic review was designed to evaluate and compare successful cases of regenerative endodontic treatment (RET) in terms of etiology, diagnosis, treatment protocols, and signs of success. An electronic search was performed in the PubMed and Google Scholar databases. The search was completed by 2 independent reviewers following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. All in vivo studies in humans that reported at least 1 successful case of RET were included in this review. Successful RET cases were defined as any case that involved the absence of clinical signs/symptoms of periapical inflammation and the presence of continued root maturation, especially apical closure, after the completion of the initial RET. A total of 250 successful cases of RET from 18 studies were selected in this review. A total of 98 (39%) successful cases were detected at least 2.5 years after the initiation of RET. A total of 239 (96%) successful RET cases were presented with the healing/absence of periapical lesions, and no further treatment was required. Furthermore, 45% of the successful RET cases showed root development maturation (stage V). Finally, the clinical outcomes of these RET cases are presented in this systematic review. Prudent case selection and excellent operative protocols are considered to be essential to achieve successful RET outcomes. Future studies are needed to identify a variety of relevant data, including preoperative, intraoperative and postoperative factors, in order to provide a better understanding of successful cases after RET.

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.

The Therapeutic Use of Dental Mesenchymal Stem Cells in Human Clinical Trials

Mesenchymal stem cells (MSCs), characterized by their undifferentiated and multipotent nature, can be derived from various sources, including bone marrow, adipose, and dental tissues. Among these, dental MSCs (DSCs) exhibit universal MSC characteristics and are attracting considerable attention for regenerating oral and craniofacial tissues. This review provides a contemporary overview of recently published clinical studies using DSCs for various orodental and maxillofacial regenerative applications, including bone, periodontal, and endodontic regeneration. It also explores the utilization of DSCs in treating systemic conditions, exemplified by their application in managing conditions such as COVID-19 and osteoarthritis. The available evidence underscores the potential of DSCs and their secretome as efficacious tools in regenerative medicine for both dental and nondental clinical applications, supporting the continued promise of stem cell-based therapies. It is nevertheless evident that there are a number of important challenges that restrict the widespread utilization of DSCs, namely, difficulty in standardizing autologous preparations, insufficient cell surface marker characterization, high production costs, and regulatory compliance requirements. Further, the unique requirements of dental applications, especially complex structures such as the periodontium, where temporospatial control over the healing process is required, necessitate the combination of stem cells with appropriate scaffolds according to the principles of tissue engineering. There is currently insufficient evidence to support the clinical translation of DSCs into clinical practice, and phase 3 clinical trials with standardized protocols for cell sourcing, propagation, dosing, and delivery are required to move the field forward. In summary, this review provides a contemporary overview of the evolving landscape of stem cell therapy, offering insights into the latest developments and trends as well as the challenges that need to be addressed for the widespread application of DSC-based cell therapies.

Unlocking the Potential of Cellular Guidance in Endodontics: Advancing the Process of Pulp Regeneration and Beyond

Regenerative endodontics represents a paradigm shift in dental therapy, with the potential to not only restore damaged dental tissues but also to preserve the vitality of teeth. At the heart of this innovative approach is cell homing, a technique that harnesses the body's own healing mechanisms by recruiting endogenous stem cells to the site of dental injury for effective tissue regeneration. This review delves into the intricate processes of cell homing in the context of regenerative endodontics, particularly focusing on its application in immature teeth with open apices. It examines the role of bioactive molecules, scaffolds, and growth factors in orchestrating cell migration and differentiation within the root canal space. In addition, the review addresses the current limitations in clinical practice, such as the challenges in completely regenerating the pulp-dentin complex and the unpredictability in long-term outcomes. It also explores future possibilities, including the potential for more refined and effective regenerative strategies. By providing a comprehensive overview of the current state of cell homing in regenerative endodontics, this article aims to contribute to the ongoing development of advanced therapeutic techniques that could revolutionize endodontic treatment and improve patient care.

Microspheres and their Potential in Endodontic Regeneration Application

Microspheres have been widely utilised as versatile carriers in biomedical applications. In recent years, as a new type of injectable scaffold, microspheres have attracted increasing attention in the field of regenerative medicine owing to their various advantages including their small size, large specific surface area and mimicry of the 3D native environment. These characteristics enable them to adopt the narrow and irregular anatomy of the tooth and become an ideal scaffold for endodontic regeneration. Microspheres play an important role in carrying biologics (cells, biomolecules and drugs), which effectively regulate the fate of stem cells and control the release of growth factors and drugs. Cell-laden microspheres, which can be divided into microcarriers and microcapsules, have great application prospects in dental pulp regeneration. This paper summarises the properties and characteristics of microsphere scaffolds used in tissue engineering, placing emphasis on their advantages and applications in endodontic regeneration.

Comparative Evaluation of the Effects of Calcium Hydroxide Intracanal Medicament and Antibiotic Paste on Dentin Microhardness: A Systematic Review

An infectious environment is reported to hinder the process of pulp tissue regeneration by damaging the cells responsible for tissue formation, including stem cells in the periapical tissues. Therefore, a sterile environment is critical for pulp tissue regeneration, which can be achieved by copious irrigation and intracanal medicament (ICM) placement. This systematic review compares the effect of calcium hydroxide (Ca(OH)2) and various antibiotic pastes, such as triple antibiotic paste (TAP), modified triple antibiotic paste (MTAP), and double antibiotic paste (DAP), on dentin microhardness when used as ICMs. MeSH terms and specific keywords were used to search Scopus, EBSCOhost, Cochrane Library, and PubMed. In vitro studies that compared the impact of Ca(OH)2 and antibiotic pastes, such as TAP, MTAP, and DAP, on dentin microhardness were included. Data from the included articles were extracted, and their quality was assessed using the revised Quality Assessment Tool for In Vitro Studies (QUIN) tool. Seven articles were included for the qualitative synthesis, and data were extracted from each. Within the scope of this systematic review, Ca(OH)2, an alternative ICM recommended by the American Association of Endodontics Glossary of Endodontic Terms for REPs, showed a lesser reduction in microhardness than TAP. DAP and MTAP caused a reduction in dentin microhardness compared to that of Ca(OH)2.