An update on clinical regenerative endodontics

Improvement of apical papilla cell attachment after erbium, chromium-doped yttrium, scandium, gallium, and garnet laser application: a study in an ex vivo immature tooth model

The purposes of this study were (1) to investigate the direct effect of an Er,Cr:YSGG laser on human apical papilla cell (APC) proliferation and mineralization and (2) to examine the effect of Er,Cr:YSGG laser, when applied to an ex vivo immature tooth model, on APC attachment. An Er,Cr:YSGG laser at various power outputs (0.1, 0.5, and 1 W) was used at different positions (2, 5, or 8 mm from the cells) to irradiate cultured APCs. APC proliferation and mineralization were assessed at various intervals. For the cell attachment evaluation, ex vivo tooth models containing dentin samples were irrigated with either EDTA or normal saline solution (NSS) and supplemented with laser activation. Fibronectin-positive-staining cells were counted and analyzed. The number of APCs was significantly greater when power outputs of 0.1 W and 0.5 W were used than when 1 W was used (P < 0.05). The close contact of laser application, at 2 and 5 mm, exerted a negative effect on cell proliferation at 24 and 48 h. The application at 8 mm did not show the deterioration effect. APC mineralization was reduced after laser irradiation, regardless of the power and the tip positioning, at 21 days. APC attachment in all laser-activated groups was significantly greater than in the groups without laser. The use of Er,Cr:YSGG laser significantly promoted APC attachment on the root canal dentin.

Evaluation of the efficacy of a novel antibiotic-steroid paste versus conventionally used intracanal antibiotic pastes and irrigating solutions against a 3-week-old biofilm of Enterococcus faecalis

Introduction

Intracanal medicaments have been used during endodontic regenerative procedures to eradicate endodontic pathogens.

Aims

The aim of our study was (1) to evaluate the antimicrobial efficacy of a novel antibiotic-steroid paste over the regularly used calcium hydroxide (Ca (OH)₂), double antibiotic paste (DAP), and modified triple antibiotic paste (M-TAP) and (2) to check the antimicrobial efficacy of irrigating solutions, Chlorhexidine (CHX), and sodium hypochlorite (NaOCl) against a 3-week-old Enterococcus faecalis (E. faecalis) biofilm.

Materials and Methods

A total of 112 human extracted teeth were contaminated with E. faecalis for a period of 21 days. A novel antibiotic-steroid paste, Ca (OH) ₂, DAP, M-TAP, and a placebo were placed inside the canal, sealed, and incubated in an aerobic environment at 37°C. For irrigating solutions, each prepared sample was immersed in 1 ml of sterile saline for 1 min, followed by irrigating and immersion with 1.5% NaOCl and 2% CHX for 5 min. An antimicrobial assessment was performed at the end of 2 days and 7 days, with seven teeth from each group, for each time interval. Dentin debris collected was transferred to the respective medium for culture. After 24 h, colonies were counted using classical bacterial counting technique as colony-forming units.

Results

Statistical analysis revealed that the novel antibiotic-steroid paste showed a statistically insignificant difference when compared to DAP, which had the highest antimicrobial properties.

Conclusion

This novel functional paste has antimicrobial efficacy comparable with that of DAP.

Clinical and Radiographic Outcomes of Immature Teeth Treated with Different Treatment Protocols of Regenerative Endodontic Procedures: A Retrospective Cohort Study

Regenerative endodontic procedure (REP) is a progressive treatment modality for immature permanent teeth with necrotic pulp. The ambiguousness about the predictability of REP outcome in relation to complete disinfection of the root canal system and the occurrence of discoloration still exists. The aim of this retrospective study was to analyze two treatment protocols on clinical success rate, radiographic root development and the occurrence of discoloration. Eighteen patients were treated by a single operator by either treatment protocol according to the American Association of Endodontists (AAEP, n = 9) or a modified protocol (MP, n = 9) with the use of 5% sodium hypochlorite and sandblasting. Patients were followed up after 3, 6, 9, 12, 18 and 24 months and clinical success, radiographic root development and the occurrence of discoloration were assessed. The clinical success of MP was significantly higher in two years follow-up (p = 0.015), but the change in radiographic root area was higher for AAEP (p = 0.017) and the occurrence of discoloration was higher in AAEP (p = 0.029). The use of 5% sodium hypochlorite for a longer period of time leads to a higher success rate. The sandblasting of the access cavity reduces the occurrence of discoloration.

Regenerative Endodontic Procedures for the Treatment of Necrotic Mature Teeth with Apical Periodontitis: A Systematic Review and Meta-analysis of Randomized Controlled Trials

INTRODUCTION

Regenerative endodontic procedures (REPs) are intended to repair and regenerate part of the pulp-dentin complex. The aim of this study was to systematically appraise the existing evidence on the effectiveness of REPs on mature teeth with pulp necrosis and apical periodontitis.

METHODS

Electronic database and hand searches were performed on 8 databases of published and unpublished literature from inception to January 3, 2021, for the identification of randomized controlled trials (RCTs) or prospective clinical trials. The related key words included "regenerative," "pulp revascularization," "revitalization procedure," and "necrotic mature teeth." A random effects meta-analysis was conducted assessing success as the main outcome treatment. Risk of bias was assessed through the Cochrane Risk of Bias 2.0 tool, and the quality of the evidence was assessed with the Grading of Recommendations Assessment, Development and Evaluation approach.

RESULTS

Of the 337 initial hits, 4 RCTs were eligible for inclusion, whereas 3 were included in the quantitative synthesis. Overall, there was no difference in the relative risk for a successful/unsuccessful treatment outcome between REPs or conventional treatment (3 studies, relative risk = 1.03; 95% confidence interval, 0.92-1.15; P = .61; heterogeneity I² = 0.0%, P = .53; prediction interval = 0.51-2.09). Risk of bias ranged from low to raising some concerns, whereas the quality of the evidence was graded as moderate.

CONCLUSIONS

Based on moderate-quality evidence, REPs appear as a viable treatment alternative for mature necrotic teeth with periapical lesions at present. Furthermore, well-designed RCTs might also provide confirmatory evidence in this respect while also framing a backbone for standardization of the therapeutic protocol of REPs.

Antibacterial agent-releasing scaffolds in dental tissue engineering

It seems quite challenging in tissue engineering to synthesize a base material with a range of essential activities, including biocompatibility, nontoxicity, and antimicrobial activities. Various types of materials are synthesized to solve the problem. This study aimed to provide the latest relevant information for practitioners about antibacterial scaffolds in dental tissue engineering. The PubMed search engine was used to review the relevant studies with a combination of the following terms as search queries: tissue engineering, scaffolds, antimicrobial, dentistry, dental stem cells, and oral diseases. It is noteworthy to state that only the terms related to tissue engineering in dentistry were considered. The antimicrobial scaffolds support the local tissue regeneration and prevent adverse inflammatory reactions; however, not all scaffolds have such positive characteristics. To resolve this potential defect, different antimicrobial agents are used during the synthesis process. Innovative methods in guided tissue engineering are actively working towards new ways to control oral and periodontal diseases.

A comparison of two pulp revascularization techniques using platelet-rich plasma and whole blood clot

Aim:

The aim of this preliminary study was to compare outcomes of two regenerative endodontic protocols in necrotic teeth with open apices.

Methodology:

Forty teeth with open apices in patients with an age range of 15-54 were randomly distributed in two groups: group 1, with whole blood clot in the canal (n=20) and group 2, whole blood with Platelet rich plasma (PRP) in the canal (n=20). Clinical and radiological follow up assessments were undertaken over a period ranging from 6 months to one year. Radiographic Root Area (RRA) was measured using the freeware ImageJ. Statistical analysis was performed using the independent samples t test and the Chi-squared test, the significance level was set at p=0.05.

Results:

There was no difference in the percentage change in RRA between the PRP group and whole blood-clot + PRP group.

Conclusion:

Whole blood clot and PRP are comparable on the grounds of percentage change in RRA and there is no statistically significant difference between the two in a follow-up period of up to one year.

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.

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.

Effects of cold atmospheric pressure plasma jet on human apical papilla cell proliferation, mineralization, and attachment

OBJECTIVES

To investigate the direct effects of cold atmospheric pressure plasma jet on cell proliferation and mineralization on human apical papilla cells and its indirect effect on cell attachment on plasma-treated dentin.

MATERIALS AND METHODS

Plasma was directly applied to cell culture for various durations. Cell proliferation was evaluated using AlamarBlue® assay. Mineralization was assessed using Alizarin Red S staining after 14 and 21 days. The cell attachment to plasma-treated dentin surface was evaluated using an ex vivo immature tooth model, and the protocols varied based on root canal irrigants (NSS or 17% EDTA), the durations of plasma application (0, 30, or 60 s), and the different positions of the plasma needle (coronal or middle). The attached cells were visualized using the immunofluorescence staining and the positive-staining cells were counted.

RESULTS

There was no difference in the cell proliferation between the untreated and plasma-treated cells. However, the plasma-treated cells tended to have lower levels of calcium deposition, especially after the 60-s plasma application (p < 0.05). Finally, significantly greater numbers of attached cells were shown when NSS was combined with plasma treatment when compared to the untreated cells (p < 0.05), whereas no difference was observed when EDTA was used as the irrigant.

CONCLUSIONS

Plasma might disturb the mineralization of the cells. Interestingly, the dentin conditioning process using a plasma jet with NSS irrigation may enhance cell attachment.

CLINICAL RELEVANCE

Cold atmospheric pressure plasma jet may be an alternative treatment in regenerative endodontic procedures in order to improve cell attachment in the root canal system.

Coronal Tooth Discoloration After the Use of White Mineral Trioxide Aggregate

Mineral trioxide aggregate (MTA) has been used in regenerative procedures but observations have indicated that with its use there is dark staining of the tooth structure. This case report describes the treatment of tooth discoloration caused by white mineral trioxide aggregate (WMTA). Revascularization was performed with the use of WMTA in the upper left central incisor. Grayish discoloration appeared 9 months later, the tooth necessitating internal bleaching of the tooth. A significant improvement was observed in the crown after internal bleaching. The choice of material should not rely solely on biological and functional aspects, but aesthetic considerations should also be taken into account. The patient needs to be advised of risks, benefits, and alternatives to internal bleaching, eg, a veneer or a crown. Coronal discoloration is a significant distraction and embarrassment for many people in achieving an aesthetic smile; thus, it must be corrected at the earliest possible stage of discoloration.

Effect of mineral trioxide aggregate plug location on root development in regenerative endodontic procedure

This retrospective study investigated the effect of mineral trioxide aggregate (MTA) plug location on treatment outcome and root maturation after regenerative endodontic procedures (REP) in immature permanent teeth. Thirty-three roots (n = 33) in cohort that underwent REP consistently according to AAE guideline were included to trace radiographic changes for the root and canal dimensions. Based on intraoral radiographs, roots were divided into two groups depending on the location of MTA plug within whole root length: coronal group (n = 14), within the upper half; apical group (n = 19), within the lower half. Periapical radiographs were standardized to assess treatment outcomes and root maturation including root development stages and digital measurements on the change ratios of root length, apex width, radiographic root area (RRA), modified RRA (mRRA), and periapical rarefaction area. The data were statistically analysed using the Mann-Whitney test. The patients' average age was 11 years and 10 months, with no significant between-group difference in sex. Premolars were the most prevalent tooth type (62.1%), followed by incisiors and molars. Pre-existing symptoms and signs subsided within 6 months in all cases. The teeth showed similar radiographic root development in both groups (P > 0.05). However, mRRA increase ratio was significantly higher in apical group than that in coronal group at early (< 6 months) and late (< 24 months) periods of follow-up (P < 0.05). Significant changes of root development stage were observed at early period for apical group and at late period for coronal group (P < 0.05). All the observed cases showed continuing root development after REP. Significant changes in root developments occurred at different follow-up periods according to the location of MTA plugs.

Trigeminal Sensory Neurons and Pulp Regeneration

The pulp-dentin complex is innervated by a high density of trigeminal neurons free nerve endings. These neuronal fibers are highly specialized to sense noxious stimuli such as thermal, mechanical, chemical, and biological cues. This robust alert system provides immediate feedback of potential or actual injury triggering reflex responses that protect the teeth from further injury. In the case of patients, pain is the most important experience that leads them to seek oral health care. The adequate removal of the etiology, such as caries, provides ample opportunity for the robust reparative and regenerative potential of the pulp-dentin complex to restore homeostasis. In addition to this elaborated surveillance system, evidence has accumulated that sensory neuronal fibers can potentially modulate various steps of the reparative and regenerative process through cellular communication processes. These include modulation of immunologic, angiogenic, and mineralization responses. Despite these orchestrated cellular events, the defense of the pulp-dentin complex may be overwhelmed, resulting in pulp necrosis and apical periodontitis. Regenerative endodontic procedures have evolved to restore the once lost function of the pulp-dentin complex. After these procedures, a large subset of successful cases demonstrates a positive response to sensitivity testing, suggesting reinnervation of the canal space. This process is likely mediated through cellular and noncellular release of neurotrophic factors such as brain-derived nerve growth factor. In addition, these newly recruited nerve fibers appear equipped to sense thermal stimuli through nonhydrodynamic mechanisms. Collectively, the significance of innervation in the normal physiology of the pulp-dentin complex and its role in regeneration need to be better appreciated to promote further research in this area that could potentially bring new therapeutic opportunities.

Three-dimensional qualitative and quantitative analyses of the effect of periradicular lesions on the outcome of regenerative endodontic procedures: A prospective clinical study

OBJECTIVES

Qualitative and quantitative evaluation of the outcomes of regenerative endodontic procedure (REP) on human immature necrotic teeth with apical periodontitis using cone-beam computed tomography (CBCT) MATERIALS AND METHODS: Immature permanent teeth (n = 50) with necrotic pulp and periradicular pathosis were treated with a cell-homing concept-based REP. Following the procedure, a limited field-of-view CBCT scan was obtained. At each recall session (6, 12, 18 months), clinical tests were performed, and a digital periapical radiograph was taken. When significant radiographic changes were evident in the follow-up, a final CBCT scan was taken for qualitative and quantitative assessment. These initial and follow-up CBCT scans were assessed for quantification of changes in root length, pulp space diameter and periradicular lesion size. The data were statistically analysed using t test, one-way ANOVA, post hoc test and paired t test (P = 0.05).

RESULTS

Of the teeth, 94.6% were clinically successful based on the lack or regression of signs and symptoms after 48 months follow-up. REP resulted in a statistically significant increase in root length, decrease in pulp space diameter and periradicular radiolucency (P < 0.05). CBCT images illustrated various patterns of root maturation including an increased thickening of the canal walls and continued root maturation (37.1%), continued root development with the apical foramen remaining open (57.1%), severe calcification (obliteration) of the canal space (2.9%) and hard tissue barrier formation in the canal space between the coronal plug and the root apex (2.9%).

CONCLUSION

This study highlighted that the expected outcome of radiographic root development was less predictable when immature permanent teeth with periradicular pathosis were treated with REP.

CLINICAL RELEVANCE

The size and extent (expansion/destruction of the cortical plate) of periradicular lesions and abscesses influence the outcome of REP. These factors must be taken into consideration during treatment planning.

Case Report: Single visit photo-activated disinfection in regenerative endodontics

Background: Root canal disinfection is considered critical for achieving successful regenerative endodontic procedures. Photo-activated disinfection is a novel disinfection method that can help to achieve the goal of regenerative endodontics. This article reports the clinical and radiographic results after single visit regenerative endodontics using photo-activated disinfection. Methods: An 8.5-year-old girl complained of fractured upper right central incisor. Pulp necrosis was diagnosed on the basis of clinical findings. The root canal was irrigated with sodium hypochlorite solution (1.5%) followed by saline. Then, the canal was dried with paper points. A combination of a photosensitizer solution and low power laser light were applied. EDTA solution was used as a final irrigant. Bleeding was induced, followed by placement of collagen resorbable matrix and white mineral trioxide aggregate. Two days later, the tooth was sealed and restored with permanent filling. Results: Clinical findings revealed no pain on percussion or palpation tests. Radiographic examination revealed an increase in root length, an increase of apical root thickness and apical closure at the 12-month follow-up period. Conclusion: Regenerative endodontics using photo-activated disinfection achieved successful outcomes in the necrotic immature permanent tooth.

Oral and Craniofacial Stem Cells: An Untapped Source for Neural Tissue Regeneration

Nerve tissue regeneration continues to represent an intractable obstacle to realizing the promise of tissue engineering. Although neurobiology works to shed light on the mechanisms governing neuronal growth and repair, considerable technical gaps remain that hinder progress. Chief among these is the absence of an appropriate culture environment to faithfully reproduce the neuronal niche ex vivo. We propose that the various multipotent cells found in the oral cavity may represent an important yet underutilized resource for preparing such neurogenic microenvironments. Similar to those of nerve tissue, these cell populations are of ectodermal origin and have clinically demonstrated neurogenic potential. Although there is a lack of consensus on whether putative types of oral and craniofacial stem cells constitute distinct populations, their contribution to neural tissue engineering may be twofold: as a cellular feedstock for neoneurogenesis and for the production of specialized in vitro environments for neurogenic differentiation, phenotype maintenance, and use in therapeutic applications. Impact statement We propose that addressing gaps in understanding the neurogenic role of dental stem cells and their microenvironment may yield efficient and reliable strategies for long-term neuronal cell culture and open new avenues for neural regeneration in both dental, nerve, and other tissues.

Endodontic approach in a replanted tooth with an immature root apex and chronic apical periodontitis: a case report

This study describes the clinical steps taken in the treatment of a patient who had an avulsed right upper central incisor that presented with incomplete root development and chronic apical periodontitis. A 7-year-old boy was referred from a private dentist to a dental office specializing in endodontics. The tooth had remained in a dry environment for 20 minutes, and tooth replantation was performed at an emergency appointment. After clinical and radiographic examinations, root canal decontamination was performed, followed by several changes in intracanal calcium hydroxide medication. Blood clot formation was attempted, but bleeding within the root canal was insufficient; therefore, we opted for an intracanal medication change to stimulate mineralized tissue formation in the apical region. Root obturation was performed 45 days after the last change of intracanal medication, and clinical, radiographic, and tomographic follow-up examinations were performed at 3, 6, 18, and 40 months after the endodontic intervention. The increase in thickness and length of the root structure and the absence of root resorption were verified through follow-up examinations. Therefore, it was concluded that the procedures used were successful for tooth replantation.

Combined Regenerative and Vital Pulp Therapies in an Immature Mandibular Molar: A Case Report

INTRODUCTION

This report describes the treatment of an immature mandibular molar by combining vital pulp therapy (VPT) and regenerative endodontic procedures (REPs). It details the use of REP to regain functionality and continued root development of an immature root with pulp necrosis and VPT for an immature root containing vital pulpal tissues.

METHODS

An 8-year old male presented for evaluation of a mandibular first right molar with mild buccal swelling and a nontraceable sinus tract. He recently had received a restoration. After intraoral and radiographic examination, a diagnosis of pulp necrosis and chronic apical abscess was made. After access, pulp necrosis was confirmed in the distal root; however, vital pulp tissues were present in the mesial canals. It was decided on pulpotomy (VPT) in the mesial and REP in the distal root. At the initial visit, pulpotomy was completed in the mesial root, and REP was initiated in the distal root. Three weeks later, the patient was asymptomatic and the sinus tract absent. REP was completed in the distal root, and the tooth was restored.

RESULTS

At the 6-, 12-, and 18-month follow-up, the patient presented without symptoms, and the tooth responded positively to pulp sensibility tests. Radiographic examinations showed resolution of the apical radiolucency and completed root development.

CONCLUSIONS

Combined treatment using both VPT and REP for immature molars with different pulpal status in individual roots may be a preferable treatment option because preservation of vital pulp tissues and regeneration of new vital tissues allow for continued root development and functionality.

Biomimetic Aspects of Restorative Dentistry Biomaterials

Biomimetic has emerged as a multi-disciplinary science in several biomedical subjects in recent decades, including biomaterials and dentistry. In restorative dentistry, biomimetic approaches have been applied for a range of applications, such as restoring tooth defects using bioinspired peptides to achieve remineralization, bioactive and biomimetic biomaterials, and tissue engineering for regeneration. Advancements in the modern adhesive restorative materials, understanding of biomaterial–tissue interaction at the nano and microscale further enhanced the restorative materials’ properties (such as color, morphology, and strength) to mimic natural teeth. In addition, the tissue-engineering approaches resulted in regeneration of lost or damaged dental tissues mimicking their natural counterpart. The aim of the present article is to review various biomimetic approaches used to replace lost or damaged dental tissues using restorative biomaterials and tissue-engineering techniques. In addition, tooth structure, and various biomimetic properties of dental restorative materials and tissue-engineering scaffold materials, are discussed.

Bioactive molecule carrier systems in endodontics

INTRODUCTION

Bioactive molecule carrier systems (BACS) are biomaterial-based substrates that facilitate the delivery of active signaling molecules for different biologically based therapeutic applications, which include regenerative endodontic procedures. Tissue regeneration or organized repair in regenerative endodontic procedures is governed by the dynamic orchestration of interactions between stem/progenitor cells, bioactive molecules, and extracellular matrix. BACS aid in mimicking some of the complex physiological processes, overcoming some of the challenges faced in the clinical translation of regenerative endodontic procedures.

AREAS COVERED

This narrative review addresses the role of BACS in stem/progenitor cell proliferation, migration, and differentiation with the application for dentin-pulp tissue engineering both in vitro and in vivo. BACS shield the bioactivity of the immobilized molecules against environmental factors, while its design allows the pre-programmed release of bioactive molecules in a spatial and temporal-controlled manner. The polymeric and non-polymeric materials used to synthesize micro and nanoscale-based BACS are reviewed.

EXPERT OPINION

Comprehensive characterization of well-designed and customized BACS is necessary to be able to deliver multiple bioactive molecules in spatiotemporally controlled manner and to address the release kinetics required for potential in vivo application. This warrants further laboratory-based experiments and rigorous clinical investigations to enable their clinical translation for regenerative endodontic procedures.

Allogeneic Cellular Therapy in a Mature Tooth with Apical Periodontitis and Accidental Root Perforation: A Case Report

INTRODUCTION

Cell therapy in regenerative endodontics introduces an alternative option to classic treatment strategies for complex endodontic cases. The aim of this case report was to describe cell-based therapy using allogeneic umbilical cord mesenchymal stem cells (UC-MSCs) encapsulated in a bioscaffold for a complex case of a mature permanent tooth with apical periodontitis and accidental root perforation.

METHODS

A healthy 19-year-old man undergoing orthodontic treatment was referred for endodontic treatment in tooth #7; he was diagnosed with apical periodontitis during a previously initiated treatment associated with accidental perforation of the radicular cervical third. The root perforation was sealed with glass ionomer and composite resin, and the root canal was instrumented, disinfected, and dressed with calcium hydroxide. After 3 weeks, allogeneic UC-MSCs were encapsulated in platelet-poor plasma and then implanted into the root canal, and Biodentine (Septodont, Saint-Maur-des-Fosses, France) was placed below the cementoenamel junction. Finally, the tooth was restored with composite resin.

RESULTS

Follow-up examinations were performed 6 months and 1 year later. The examinations included periapical radiography, cone-beam computed tomographic imaging, and sensitivity and vitality tests. Radiographic and cone-beam computed tomographic images indicated remission of the apical lesion. Clinical evaluations revealed normal responses to percussion and palpation tests; the tooth was responsive to the electric pulp test, and the vitality test indicated low blood perfusion units.

CONCLUSIONS

This case report reveals the potential use of allogeneic cellular therapy using encapsulated UC-MSCS in a platelet-poor plasma scaffold for a complex case of a permanent tooth with apical periodontitis and root perforation.

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.

Evaluation of the Bactericidal Activity of a Hyaluronic Acid-Vehicled Clarithromycin Antibiotic Mixture by Confocal Laser Scanning Microscopy

Confocal laser scanning microscopy (CLSM) was used to evaluate the antibacterial effect and depth of action of a novel clarithromycin-containing triple antibiotic mixture, which was proposed for root canal disinfection in dental pulp regeneration. A previous study reported that this mixture had no tooth discoloration effects in vitro. After infection with Enterococcus faecalis for 3 weeks, the dentinal tubules in the cylindrical root specimens were exposed to different antibiotic mixtures: ciprofloxacin, metronidazole and minocycline (3-MIX); ciprofloxacin, metronidazole and clarithromycin (3-MIXC) and ciprofloxacin and metronidazole (2-MIX). Each antibiotic formulation was mixed with macrogol (MG) or hyaluronic acid (HA) vehicles. CLSM and viability staining were used to quantitatively analyze the mean depth of the antibacterial effect and the proportions of dead and live bacteria inside the dentinal tubules. The 3-MIX and 3-MIXC demonstrated a similar depth of action. The mean proportion of dead bacteria was similar in the 3-MIX and 3-MIXC groups, and both were statistically higher than that of 2-MIX (p = 0.014). Each antibiotic mixture showed a higher bactericidal efficacy if conveyed with HA, compared to MG (3-MIX, p = 0.019; 3-MIXC, p = 0.013 and 2-MIX, p = 0.0125). The depth of action and the antibacterial efficacy of 3-MIXC seemed comparable with 3-MIX.

Effects of transforming growth factor-β1 on plasminogen activation in stem cells from the apical papilla: role of activating receptor-like kinase 5/Smad2 and mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signalling

AIM

To study the effects of TGF-β1 on the plasminogen activation (PA) system of stem cells from the apical papilla (SCAP) and its signalling.

METHODOLOGY

SCAP cells were isolated from the apical papilla of immature permanent teeth extracted for orthodontic reasons. They were exposed to various concentration of TGF-β1 with/without pretreatment and coincubation by SB431542 (ALK/Smad2/3 inhibitor), or U0126 (MEK/ERK inhibitor). MTT assay, Western blotting and enzyme-linked immunosorbent assay (ELISA) were used to detect their effects on cell viability, and the protein expression of plasminogen activator inhibitor-1 (PAI-1), urokinase-type plasminogen activator (uPA), uPA receptor (uPAR) and their secretion. The paired Student's t-test was used for statistical analysis.

RESULTS

TGF-β1 significantly stimulated PAI-1 and soluble uPAR (suPAR) secretion of SCAP cells (P < 0.05), whereas uPA secretion was inhibited. Accordingly, TGF-β1 induced both PAI-1 and uPAR protein expression of SCAP cells. SB431542 (an ALK5/Smad2/3 inhibitor) pretreatment and coincubation prevented the TGF-β1-induced PAI-1 and uPAR of SCAP. U0126 attenuated the TGF-β1-induced expression/secretion of uPAR, but not PAI-1 in SCAP. SB431542 reversed the TGF-β1-induced decline of uPA.

CONCLUSIONS

TGF-β1 may affect the repair/regeneration activities of SCAP via differential increase or decrease of PAI-1, uPA and uPAR. These effects induced by TGF-β1 are associated with ALK5/Smad2/3 and MEK/ERK activation. Elucidation the signalling pathways and effects of TGF-β1 is useful for treatment of immature teeth with open apex by revascularization/revitalization procedures and tissue repair/regeneration.

Does the Etiology of Pulp Necrosis Affect Regenerative Endodontic Treatment Outcomes? A Systematic Review and Meta-analyses

OBJECTIVE

To evaluate if there is a connection between the causes of pulp necrosis (eg, caries, trauma, dental anomaly) and the success of regenerative endodontic treatment.

METHODS

Electronic databases (PubMed, Scopus, Web of Science, Cochrane Central Register of Controlled Trials, Embase) were searched for studies on regenerative endodontic treatment, which used both clinical and radiographic evaluation of root maturation after at least 6 months of follow-up. The search terms "necrotic pulp", "regenerative endodontic treatment", "revascularization", and "revitalization" were combined using Boolean operators. The main journals on endodontics and dental traumatology were additionally hand-searched. Studies were included if they specified the causes of pulp necrosis. The primary question under review was, "Does the cause of pulp necrosis affect the outcome of regenerative endodontic treatment?" Other factors such as tooth type, intracanal medicament, irrigation protocol, use of a collagen matrix, and the type of scaffold were evaluated for possible relation with the outcome. The risk-of-bias assessment for randomized and nonrandomized studies was performed separately, using a modified Cochrane Collaboration's tool and risk of bias in non-randomized studies of interventions-I tool, respectively. Meta-analysis was performed, when possible, between studies comparing treatment outcomes of teeth whose pulp necrosis had different etiology. The search strategy yielded 1197 items. After screening, 18 studies reporting 445 regenerative endodontic treatment cases were included.

RESULTS

The overall success rate for 274 teeth with trauma etiology was 94.8%, for 95 teeth with dens evaginatus etiology was 93.1%, and for 24 teeth with caries etiology was 96%. No significant difference was found between the results of regenerative endodontic treatment among teeth with trauma, dens evaginatus, and caries etiology (P = .055). Meta-analysis of studies comparing teeth with caries vs dens evaginatus and those with trauma vs caries confirmed that there was no evidence for difference in outcomes.

CONCLUSION

Further randomized studies specifically testing such hypothesis are needed to confirm the preliminary results of this review.

Metformin attenuates cartilage degeneration in an experimental osteoarthritis model by regulating AMPK/mTOR

Background: It is generally thought that the occurrence and progression of osteoarthritis (OA) results from multiple causes, including degradation and destruction of the cartilage matrix and aging of chondrocytes. Metformin is a first-line drug for the treatment of diabetes, and has great potential for the treatment of other disorders. However, the role of metformin in OA is unknown.

Results: Metformin displayed a protective effect against OA. There were lower OARSI scores and fewer MMP-13-positive cells in DMM mice and cartilage explants after treatment with metformin. In addition, metformin treatment decreased p16^INK4a levels in OA chondrocytes, and enhanced polarization of AMPK and inhibition of mTORC1 in OA mice and chondrocytes in a dose-dependent manner.

Conclusions: Metformin effectively alleviated cartilage degradation and aging through regulation of the AMPK/mTOR signaling pathways, suggesting that it could be an effective treatment for OA.

Methods: The effects of metformin on cartilage degradation and chondrocyte aging was determined in a destabilization of the medial meniscus (DMM)-induced OA mouse model and in IL-1β-treated mouse chondrocytes and cartilage explants. Articular cartilage degeneration was graded using the Osteoarthritis Research Society International (OARSI) criteria. Immunostaining, RT-PCR, and western blot analyses were conducted to detect the relative expressions of protein and RNA.

Modified Apexification Procedure for Immature Permanent Teeth with a Necrotic Pulp/Apical Periodontitis: A Case Series

The current American Association of Endodontists clinical considerations for a regenerative endodontic procedure state that a regenerative procedure is suitable for immature permanent teeth with necrotic pulp when the pulp space is not needed for a post/core in the final restoration. Therefore, many immature permanent teeth with necrotic pulp that have sustained a substantial loss of coronal tooth structure either from caries or trauma are treated by apexification or mineral trioxide aggregate/Biodentine (Septodent, Lancaster, PA) apical barrier techniques in which no further root maturation would occur. This case series presents 10 immature permanent teeth with necrotic pulp in which a post/core was likely required in the future for adequate coronal restoration because of loss of substantial coronal tooth structure and a modified apexification procedure was used. All 10 cases after the modified apexification procedure showed no clinical symptoms/signs and showed radiographic evidence of healed/healing of periapical lesion after a 2-year review. Eight cases showed increased thickness of the apical root canal walls, increased apical root length, and apical closure. The overall percentage change in root length was 7.52%, in root width at the apical one third it was 18.89%, and in radiographic root area it was 15.04% at the 24- to 72-month follow-up period. This modified apexification procedure allows for the tooth to be restored with a post/core if required for the final restoration in the future as well as continued root development.

Secreted frizzled-related protein 2 promotes the osteo/odontogenic differentiation and paracrine potentials of stem cells from apical papilla under inflammation and hypoxia conditions

Objectives

Mesenchymal stem cell (MSC)‐based dental tissue regeneration is a potential treatment method in future, while inflammation and hypoxia niche will affect MSC‐mediated tissue regeneration. In this research, we intended to investigate the influence and mechanism of secreted frizzled‐related protein 2(SFRP2) on MSC function under inflammation and hypoxia conditions.

Material and methods

Stem cells from apical papilla (SCAPs) were used in this study. The alkaline phosphatase (ALP) activity, Alizarin Red S staining, scratch‐simulated wound migration and transwell chemotaxis assay were used to evaluate the functions of SFRP2. The Western blot, real‐time RT‐PCR and ChIP assays were used to evaluate the mechanism of SFRP2.

Results

Under inflammation and hypoxia conditions, the over‐expression of SFRP2 could enhance the osteo/odontogenic differentiation ability. Mechanismly, SFRP2 inhibited canonical Wnt/β‐catenin signalling pathway and then inhibited the target genes of nuclear factor kappa B (NFkB) signalling pathway. Inflammation or hypoxia conditions could promote the expression of lysine demethylase 2A (KDM2A) and repress SFRP2 transcription through decreasing histone methylation in the SFRP2 promoter. Besides, proteomic analysis showed that SFRP2 promoted SCAPs to secret more functional cytokines, which improve the migration, chemotaxis and osteo/odontogenic ability of MSCs.

Conclusions

Our discoveries revealed that SFRP2 enhanced the osteo/odontogenic differentiation and paracrine potentials of SCAPs under hypoxia and inflammation conditions and provided a potential cytokine for promoting tissue regeneration in hypoxia and inflammatory niche.

Case Report: Single visit photo-activated disinfection in regenerative endodontics

Background: Root canal disinfection is considered critical for achieving successful regenerative endodontic procedures. Photo-activated disinfection is a novel disinfection method that can help to achieve the goal of regenerative endodontics. This article reports the clinical and radiographic results after single visit regenerative endodontics using photo-activated disinfection. Methods: An 8.5-year-old girl complained of fractured upper right central incisor. Pulp necrosis was diagnosed on the basis of clinical findings. The root canal was irrigated with sodium hypochlorite solution (1.5%) followed by saline. Then, the canal was dried with paper points. A combination of a photosensitizer solution and low power laser light were applied. EDTA solution was used as a final irrigant. Bleeding was induced, followed by placement of collagen resorbable matrix and white mineral trioxide aggregate. Two days later, the tooth was sealed and restored with permanent filling. Results: Clinical findings revealed no pain on percussion or palpation tests. Radiographic examination revealed an increase in root length, an increase of apical root thickness and apical closure at the 12-month follow-up period. Conclusion: Regenerative endodontics using photo-activated disinfection achieved successful outcomes in the necrotic immature permanent tooth.

Bioactivity potential of Portland cement in regenerative endodontic procedures: From clinic to lab

OBJECTIVE

The aim of this study was to evaluate the bioactivity potential of an hydraulic calcium-silicate cement, Pure Portland Cement Med-PZ (Medcem, Weinfelden, Switzerland: 'MPC'), applied in a tooth extracted because of failed regenerative endodontic procedures (REP) and by means of ex vivo (EV) specimens.

METHODS

Ten EV cylindrical dentin cavities were prepared and filled with MPC and stored for 1 month in distilled water (DW), Hank's balanced salt solution (HBSS), Dulbecco's phosphate-buffered saline (DPBS), simulated body fluid (SBF), versus no media (NM) serving as control. Six additional EV specimens were filled with MPC and exposed for 2 weeks to leucocyte-and-platelet-rich fibrin (LPRF)-clot (C), LPRF-membrane (M) and LPRF-exudate (E). MPC in the EV specimens and in the coronal part of the REP tooth was analyzed by means of micro-Raman spectroscopy (MR), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS).

RESULTS

SEM showed rough crystallite surfaces for the EV samples and a porous surface for the REP tooth. EDS of the EV samples revealed prominent peaks for Ca, Si and O. Storage in HBSS, DPBS, SBF, exposure to LPRF and the REP tooth showed considerable amounts of P as well. MR exhibited vibrations of phosphate (DPBS, SBF), carbonated hydroxyapatite (DPBS, SBF), calcium carbonate (DW, HBSS, NM, REP-tooth, LPRF-E), oxidized (ferric) proteins (LPRF-E/C/M) and the amide III band (all samples). Hence, only storage of MPC in DPBS and SBF for 1 month revealed bioactivity.

SIGNIFICANCE

The environmental conditions, namely the laboratory and clinical settings, affect the bioactivity potential of MPC.

Comparative Evaluation of the Cytotoxic and Angiogenic Effects of Minocycline and Clindamycin: An In Vitro Study

INTRODUCTION

This study aimed to compare the cytocompatibility and angiogenic potential of 2 antibiotics (clindamycin [CLIN] and minocycline [MINO]) at distinct concentrations on dental pulp stem cells (DPSCs) and human umbilical vein endothelial cells (HUVECs).

METHODS

DPSCs and HUVECs were exposed to cell culture media modified with CLIN or MINO at concentrations ranging from 30 μg/mL-1000 μg/mL. Cell toxicity and proliferation were investigated using the lactate dehydrogenase and tetrazolium reduction assays, respectively. A capillarylike tube formation in vitro assay was conducted to determine the angiogenic potential associated with each antibiotic. Additionally, selected morphometric angiogenesis parameters were determined using dedicated software (WimTube; Onimagin Technologies SCA, Córdoba, Spain). All statistical analyses were performed using 1-way analysis of variance and the Tukey post hoc test (α= .05).

RESULTS

The collected data showed that compared with the control (cell culture media, alpha-minimum essential medium Eagle) increasing the antibiotic concentration significantly decreased cell viability and proliferation of both DPSCs and HUVECs. In terms of angiogenic potential, when tested at 30 μg/mL and 50 μg/mL, CLIN significantly amplified tube formation when compared with MINO with angiogenesis parameters (ie, tube length and tube number) similar to the effect promoted by exogenous vascular endothelial growth factor (50 ng/mL).

CONCLUSIONS

CLIN was less cytotoxic when compared with MINO at higher concentrations. Of note, CLIN did not hinder the proangiogenic activity induced by vascular endothelial growth factor to the same extent as MINO, suggesting that the replacement of MINO by CLIN might translate into positive implications in the overall regenerative outcome.

Personalized Cell Therapy for Pulpitis Using Autologous Dental Pulp Stem Cells and Leukocyte Platelet-rich Fibrin: A Case Report

INTRODUCTION

Regenerative endodontic procedures have emerged as a new treatment. The aim of this case report was to describe a regenerative autologous cellular therapy using mesenchymal stem cells from inflamed dental pulp and leukocyte platelet-rich fibrin (L-PRF) in a mature tooth.

METHODS

A healthy 50-year-old man consulting for spontaneous dental pain was referred for endodontic treatment in tooth #28, which was diagnosed with symptomatic irreversible pulpitis. Inflamed dental pulp was extracted and transported to a good manufacturing practice laboratory for the isolation and culture of dental pulp stem cells (DPSCs). L-PRF was obtained from the patient's blood and was introduced into the instrumented and disinfected root canal, and expanded DPSCs were inoculated into the clot. The cervical part of the root canal was sealed with Biodentine (Septodont, Saint-Maur-des-Fosses, France) and a composite resin.

RESULTS

Follow-up examinations were performed 6 months and 3 years later. The examinations included periapical radiographs (to measure the periapical index [PAI]), cone-beam computed tomographic (CBCT) imaging, sensitivity, and vitality tests. Clinical evaluations revealed normal responses to percussion and palpation tests. The tooth had a delayed response to cold, and the electric pulp test was responsive. The PAI and CBCT imaging revealed that the periapical area remained normal with a PAI score of 1 and a CBCT PAI score of 0. The vitality test performed indicated low blood perfusion units.

CONCLUSIONS

This case study reveals the potential use of a patient's own DPSCs and L-PRF as an alternative procedure for the treatment of pulpitis in mature permanent teeth. It also paves the way for the design of personalized cell-based clinical trials in regenerative endodontics.

A Regenerative Approach for Root Canal Treatment of Mature Permanent Teeth: Comparative Evaluation with 18 Months Follow-up

AIM

SealBio is a novel technique which stimulates the periradicular cells to deposit a biological barrier at the root apex by inducing healing and regeneration. This clinical trial was undertaken to compare the outcome of teeth treated with the SealBio and the obturation technique.

MATERIALS AND METHODS

Thirty patients met the inclusion criteria and consented to participate in the study. Patients were randomly assigned to the SealBio and the obturation group. The time taken for both the techniques and periapical healing was evaluated. The patients of both the groups were evaluated at 6, 12, and 18 months follow up. The periapical index (PAI) was the primary outcome measure to check the apical bone density and healing. The secondary outcome measure was the presence/absence of signs and symptoms. The final outcome measure was the sum of the primary and secondary outcome measures.

RESULTS AND CONCLUSION

The time taken to perform endodontic treatment with the SealBio technique was significantly lesser than that of obturation. Both groups showed equally favorable outcomes at the end of 18 months without any statistically significant differences.

CLINICAL SIGNIFICANCE

The results of the present study have demonstrated that SealBio technique gives similar results as that of conventional gutta-percha obturation. The shortcomings of obturation such as difficulty in obtaining a fluid-tight seal and difficulty in obturating tortuous canals can be overcome by the SealBio method. The SealBio method is cost effective, less technique sensitive, and takes lesser chair time.

HOW TO CITE THIS ARTICLE

Jha P, Virdi MS, et al. A Regenerative Approach for Root Canal Treatment of Mature Permanent Teeth: Comparative Evaluation with 18 Months Follow-up. Int J Clin Pediatr Dent 2019;12(3):182-188.

Neurotrophic Proteins in Dentin and Their Effect on Trigeminal Sensory Neurons

INTRODUCTION

A plethora of bioactive molecules present during tooth formation become sequestered in the mineralized dentin matrix and can be released into the pulp tissue after demineralization from carious lesions. However, neurotrophic factors are differentially expressed and secreted during various stages of odontogenesis. Thus, the aims of this study were (1) to investigate their presence and relative abundance in crown and root dentin and (2) to evaluate the bioactivity of dentin-derived proteins on neuronal cells.

METHODS

Dentin matrix proteins (DMPs) were isolated from matched roots and crowns of extracted healthy human third molars. The total protein amount as well as the concentration of growth factors and neurotrophic proteins were quantified. The impact on neuritogenesis was determined with mouse trigeminal neurons in vitro and by a hydrogel implant model in vivo. Transient receptor potential cation channel subfamily V member 1 (TRPV1) sensitization of DMP-conditioned neurons was evaluated by single-cell calcium imaging.

RESULTS

The relative concentration of neurotrophic molecules revealed that nerve growth factor is the most abundant neurotrophin with 3-fold increased expression in radicular dentin. Similarly, brain-derived neurotrophic factor and neurotrophin 3 are more abundant in radicular than coronal dentin. Conversely, glial cell line-derived neurotrophic factor is more abundant in coronal dentin, whereas neurotrophin 4 is equally distributed. Dentin matrix proteins promoted neurite outgrowth in vitro and axonal targeting in vivo, with a greater effect observed by radicular dentin extracts. Furthermore, DMPs sensitized TRPV1 responses in mouse trigeminal neurons with greater activity seen with extracts from root dentin.

CONCLUSIONS

Neurotrophic factors are differentially distributed between coronal and radicular dentin with different effects of dentin-derived proteins on axonal growth and targeting as well as the sensitization of TRPV1. Thus, extracellular proteins from the dentin matrix are likely involved in neurogenic responses to caries and could be exploited in clinical regenerative endodontics to promote reinnervation and enhance tissue regeneration.

Comprehensive Characterization of 2 Immature Teeth Treated with Regenerative Endodontic Procedures

INTRODUCTION

Regeneration of the pulp-dentin complex is the penultimate goal of regenerative endodontic procedures (REPs). Histological outcomes have demonstrated reparative tissue formation in human teeth extracted post-REPs. However, lack of accurate characterization has precluded identification of the true nature of tissues formed post-REP.

METHODS

Here, we present 2 case reports of tooth #29 and #9 treated with REPs and demonstrate their clinical, radiographic, and histological outcomes.

RESULTS

Clinical outcomes revealed healing of apical periodontitis in both teeth and re-establishment of vitality responses in tooth #29. Moreover, radiographic assessments using 2D and 3D-volumetric analyses demonstrate considerable increase in root development for both teeth. Further, histological outcomes evaluated using Hematoxylin and Eosin and immunohistochemical staining demonstrates presence of vascular and lymphatic structures as well as immune cell markers indicative of regeneration of an immunocompetent pulp. Lastly, examination of hard tissue deposition shows dentin-like tissue in parts of tooth #29 demonstrating for the first time, regeneration of a pulp-dentin complex post-REP.

CONCLUSIONS

Collectively, this is the first study demonstrating recapitulation of several tissues commonly found as part of a pulp-dentin complex in teeth treated with REPs.

Regenerative Endodontic Procedures Using Contemporary Endodontic Materials

Calcium hydroxide apexification and Mineral Trioxide Aggregate (MTA) apexification are classical treatments for necrotic immature permanent teeth. The first tend to fail for lack of compliance given the high number of sessions needed; the second has technical difficulties such as material manipulation and overfilling. With both techniques, the root development is interrupted leaving the tooth with a fragile root structure, a poor crown-to-root ratio, periodontal breakdown, and high risk of fracture, compromising long-term prognosis of the tooth. New scientific literature has described a procedure that allows complete root development of these specific teeth. This regenerative endodontic procedure (REP) proposes the use of a combination of antimicrobials and irrigants, no canal walls instrumentation, induced apical bleeding to form a blood clot and a tight seal into the root canal to promote healing. MTA is the most used material to perform this seal, but updated guidelines advise the use of other bioactive endodontic cements that incorporate calcium and silicate in their compositions. They share most of their characteristics with MTA but claim to have fewer drawbacks with regards to manipulation and aesthetics. The purpose of the present article is to review pertinent literature and to describe the clinical procedures protocol with its variations, and their clinical application.

Expression of Neurotrophic Factors in Human Dentin and Their Regulation of Trigeminal Neurite Outgrowth

INTRODUCTION

Neurotrophic factors play a significant role in the innervation of the pulp-dentin complex during and after organogenesis. There have been numerous bioactive molecules identified in the dentin extracellular matrix; however, the expression of neurotrophic factors in the dentin matrix and their biological activity are largely unknown. The purpose of this study was to characterize the relative expression of neurotrophic factors in human dentin matrix proteins (DMPs) and their effect on neurite outgrowth of trigeminal (TG) neurons.

METHODS

Dentin was powdered in liquid nitrogen from noncarious human third molar teeth. DMPs were solubilized through an EDTA extraction method, dialyzed, and lyophilized until use. The relative expression of nerve growth factor, brain-derived neurotrophic factor, glial cell-line derived neurotrophic factor, neurotrophin 3, and neurotrophin 4/5 was determined by the enzyme-linked immunosorbent assay. Rat TG neurons were cultured and exposed to different concentrations of DMPs (1-10⁵ ng/mL) or vehicle, and a quantitative neurite outgrowth assay was performed.

RESULTS

Human DMPs contained all of the tested neurotrophic factors, with glial cell-line derived neurotrophic factor and neurotrophin 4/5 found at the highest levels. DMPs were able to promote the neurite outgrowth of rat TG neurons at an optimum concentration of 10-10² ng/mL, whereas the effect was partially inhibited at higher concentrations (>10³ ng/mL).

CONCLUSIONS

The human dentin extracellular matrix is a rich reservoir for neurotrophic factors that are key components for neuronal homeostasis, differentiation, and regeneration. These data suggest that neurotrophins in DMPs could play an important role as signaling molecules for the innervation of the pulp-dentin complex during the processes of tooth formation, repair, and regeneration.

MagT1 regulated the odontogenic differentiation of BMMSCs induced byTGC-CM via ERK signaling pathway

Background

Bone marrow mesenchymal stem cells (BMMSCs) are suitable cell sources for dental pulp regeneration, but the mechanism of BMMSCs differentiation into odontogenic lineage remains unknown. The aim of the present study was to reveal the role of magnesium transporter protein 1 (MagT1) and MAPK pathways in the odontogenic differentiation of BMMSCs.

Methods

The RNA sequencing (RNA-seq) was performed to explore the altered transcriptome of BMMSCs undergoing odontogenic differentiation induced by tooth germ cell-condition medium (TGC-CM). Pathway analysis was conducted to explore enriched pathways of the differential expression signature. Automated western blot, real-time PCR, shRNA lentivirus, and flow cytometry were used to detect the function of MagTl and MAPK pathway in odontogenic differentiation of BMMSCs.

Results

RNA-seq identified 622 differentially expressed genes associated with odontogenic differentiation of BMMSCs induced by TGC-CM, some of which were responsible for MAPK pathway. Consistently, we verified that TGC-CM induced odontogenic differentiation of BMMSCs through activating ERK/MAPK pathway, and the inactivation of ERK/MAPK pathway inhibited the odontogenic differentiation induced by TGC-CM. We also found MagT1 protein was significantly increased during odontogenic differentiation of BMMSCs induced by TGC-CMM, in accordance, MagT1 knockdown significantly decreased the extent of mineralized nodules and the protein levels of alkaline phosphatase (ALP), dentin matrix protein 1 (DMP-1), and dentin sialophosphoprotein (DSP). Flow cytometry showed that intracellular Mg²⁺ was significantly reduced in MagT1-knockdown BMMSCs, indicating the suppression of MagT1 inhibited odontogenic differentiation of BMMSCs by decreasing intracellular Mg²⁺. Finally, we performed RNA-seq to explore the altered transcriptome of MagT1-knockdown BMMSCs undergoing odontogenic differentiation and identified 281 differentially expressed genes, some of which were involved in MAPK pathway. Consistently, automated western blot analysis found the ERK/MAPK pathway was inhibited in MagT1-knockdown BMMSCs during odontogenic differentiation, indicating that suppression of MagT1 inhibited odontogenic differentiation of BMMSCs via ERK/MAPK pathway.

Conclusions

This study identified the significant alteration of transcriptome in BMMSCs undergoing odontogenic differentiation induced by TGC-CM. We clarified the pivotal role of MagT1 and ERK/MAPK pathway in odontogenic differentiation of BMMSCs, and suppression of MagT1 inhibited the odontogenic differentiation of BMMSCs by decreasing the intracellular Mg²⁺ and inactivating ERK/MAPK pathway.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1148-6) contains supplementary material, which is available to authorized users.

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

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

Effect of intracanal time of triple antibiotic paste on its removal from simulated immature roots using passive ultrasonic irrigation and XP-endo Finisher

Background. The aim of this study was to evaluate the effectiveness of different irrigation techniques in the removal of triple antibiotic paste (TAP), which was applied for 7, 21 or 90 days, from simulated root canals of immature teeth.

Methods. The root canal spaces of 190 maxillary canine teeth were filled with TAP and randomly divided into a control and 3 experimental groups according to the intracanal medicament period (7, 21 or 90 days). Syringe irrigation (SI), passive ultrasonic irrigation (PUI) and XP-endo Finisher (XP) were used for the removal of TAP (n=20). The amount of remaining medicament was calculated under a stereomicroscope using a 4-grade scoring system. Kruskal-Wallis H and Wilcoxon signedrank tests were used for statistical analyses (P<0.05).

Results. The mean percentage of residual TAP was significantly greater in the SI group compared to PUI and XP at all the time intervals (P<0.05). Paste removal efficacy of PUI was not affected by the intracanal time of TAP (P>0.05), whereas the efficacy of SI and XP was significantly affected (P<0.05). No significant differences were detected between PUI and XP at 7- and 21-day intervals (P>0.05); however, at 90-day interval, PUI removed significantly greater amount of TAP than XP did (P<0.05).

Conclusion. The time of the TAP in the root canal negatively affected the removal efficacy of the SI and XP-Endo Finisher; however, it did not affect the efficacy of the PUI.

Influence of Citric Acid on the Vitality of Stem Cells from Apical Papilla

The endodontic treatment of immature permanent teeth with necrotic pulp is a serious clinical challenge. The chemical agents, used in regenerative procedures, should be selected not only based on their bactericidal/bacteriostatic properties, but also on their ability to ensure the survival of the patient’s stem cells. The aim of this study was to evaluate the effect of citric acid on the vitality of SCAP in a model of an immature tooth root. Models of immature roots were created from 12 freshly extracted teeth. The models were gas sterilized with ethylene oxide and they were separated into three groups, based on the used combinations of irrigants: 1) 1.5% sodium hypochlorite / 17% EDTA; 2) 1.5% sodium hypochlorite / 10% citric acid; 3) saline. SCAPs in a hyaluronic acid–based scaffold were seeded into the canals and cultured for 7 days. Viable cells were quantified using a colorimetric assay. There was no statistically significant difference between the groups, irrigated with NaOCl/EDTA and NaOCl/citric acid. The results from our experiment show that 10% citric acid can be used in combination with 1.5% NaOCl in a regenerative endodontic procedure.