Pulp regeneration after non-infected and infected necrosis, what type of tissue do we want? A review

Analysis of the achievement of primary and secondary goals and influencing factors in single-rooted immature permanent teeth after regenerative endodontic procedures: a retrospective study

OBJECTIVE

This study explored the achievement of primary and secondary goals and factors influencing their achievement in regenerative endodontic procedures (REPs) for immature permanent teeth.

METHODS

Dental records of all patients who received REPs for immature permanent teeth at the Department of Pediatric Dentistry, Peking University School and Hospital of Stomatology between January 2012 and January 2023 were retrieved. The evaluation of the primary goal was based on medical and radiographic records. The achievement of the primary goal was defined as the absence of clinical signs and symptoms, such as pain, swelling, or sinus tract and the absence of periapical radiolucency, as assessed on postoperative periapical radiographs. The achievement of secondary goal represented increased root wall thickness and/or increased root length, that is, continued root development. Periapical radiographs before and after treatment were used to evaluate the achievement of the secondary goal. The secondary goal was required to be achieved alongside the achievement of primary goal.

RESULTS

A total of 436 teeth (136 anterior and 300 posterior teeth) were included in this study, 96.1% of which demonstrated achievement of the primary goal. Signs of failure (17 teeth) included crown fracture and uncontrolled and recurrent periapical lesions. In addition, 77.8% of teeth demonstrated achievement of the secondary goal, and more than half of the teeth exhibited a complete root development. Evaluation factors included patients' age, sex, tooth type, etiology, preoperative periapical lesion, duration of clinical signs and symptoms, follow-up period, and stage of root development. The achievement of the primary and secondary goals were significantly related to age and tooth type (p < 0.05).

CONCLUSIONS

Children with a younger initial visit age are more likely to achieve primary and secondary goals. Additionally, posterior teeth had an advantage over anterior teeth in achieving primary and secondary goals.

Long-term Outcome of Endodontically Treated Traumatized Immature Upper Incisors

INTRODUCTION

In a growing child, preservation of traumatized immature permanent upper incisors is challenging. This study aimed to evaluate the long-term outcome of endodontically treated traumatized immature upper incisors and associated variables.

METHODS

A total of 183 traumatized immature upper incisors treated with pulpotomy, apexification, or regenerative endodontic procedure (REP), with follow-up between 4 and 15 years, were assessed for presence of pulpal responses or periodontal/bone responses using standardized clinical and radiologic criteria. Logistic regression, including stage of root development, type and complexity of traumatic event, type of endodontic intervention, and history of orthodontic management, were used to estimate impact on tooth survival and occurrence of tissue responses. Study approved by Ethics Committee Research UZ/KU Leuven (S60597).

RESULTS

After a median follow-up of 7.3 years (interquartile range, 6.1-9.2), 159 teeth (86.9%) were still functional. From these teeth, 58 (36.5%) developed tissue responses. This was significantly associated with stage of root development at moment of trauma (root length <¾) and type of endodontic intervention (REP presenting worst outcome). Tooth loss (24 teeth, 13.1%) occurred after a mean time span of 3.2 years (±1.5) and was significantly associated with type and complexity of the traumatic event and type of endodontic intervention, with apexification showing better results than REP (odds ratio, 0.30; 95% confidence interval, 0.11-0.79).

CONCLUSIONS

A large number of endodontically treated traumatized immature teeth could be kept functional. Very immature teeth, teeth with periodontal tissue damage, and teeth treated with REP were at highest risk for an unfavorable outcome.

Impact of Dental Trauma on Orthodontic Parameters-A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVES

Investigation into the impact of dental trauma on the results of orthodontic treatment is crucial because it can have a major influence on patient care. However, there has not yet been a thorough review or meta-analysis of the available data, which is inconsistent and scant. Therefore, the goal of this systematic review and meta-analysis is to investigate the impact of dental trauma on orthodontic parameters. Search methods and criterion of selection: Major online databases were searched (beginning from the year 2011) for relevant articles using a properly defined search strategy. Analysis protocol: Risk of bias (RoB) and the Cochrane risk of bias tool were utilized for the purposes of bias evaluation within the individual studies and within the review, respectively.

RESULTS

Out of the six clinical trials selected, a significant impact of trauma was observed in individuals in all but one paper. Gender predilection varied across studies and could not be conclusively determined. The follow-up period ranged from two months to two years in the trials. The odds ratio (OR) 0.38 [0.19, 0.77] and the risk ratio (RR) 0.52 [0.32, 0.85] indicated that both the odds as well as the relative risk of experiencing dental trauma were lower in the group with negligible impact compared to the group with noticeable impact. Conclusion and further implications: The findings show that dental trauma significantly affects orthodontic parameters, with lower risk and likelihood of suffering dental trauma in the group with negligible impact than in the group with noticeable impact. However, given the substantial heterogeneity among the studies, it is advised to exercise caution when extrapolating the findings to all populations. Registration and protocol: Registration in the PROSPERO database was carried out before initiating the investigation [CRD42023407218].

Endodontic management strategies for permanent teeth with immature apices

This article will provide a summary of causes of incomplete root end closure and the implications of this on endodontic treatment. The limitations and benefits of traditional and more contemporary materials including the use of bioceramic cements are considered. The apical barrier technique is described in detail for teeth with immature apices utilising a variety of bioceramic cements and regenerative endodontic procedures with an overview of appropriate instruments to successfully complete the procedure.

Anti-Inflammatory and Mineralization Effects of Bromelain on Lipopolysaccharide-Induced Inflammation of Human Dental Pulp Cells

Background and Objectives: Bromelain is a mixture of protease obtained from pineapple fruits or stems. Even though the biological mechanism of action of bromelain has not been completely understood, it is well known that bromelain possesses anticancer, anti-inflammatory and immunomodulatory effects. This study investigated the anti-inflammatory effects of bromelain on lipopolysaccharide (LPS)-induced human dental pulp cells (hDPCs). Materials and Methods: Cell viability after bromelain treatment was measured using WST-1 assay. We exposed hDPCs to 5 µg/mL of LPS with 2.5 or 5 µg/mL of bromelain. We performed reverse-transcription polymerase chain reaction and enzyme-linked immunosorbent assay to detect interleukin-1β, interleukin-6, and interleukin-8 levels. Western blots were used to detect intercellular adhesion molecules-1 (ICAM-1) and vascular cell adhesion molecules-1 (VCAM-1) levels. Immunofluorescence staining and Western blots were used to determine bromelain’s anti-inflammatory mechanism. We also performed alkaline phosphatase and Alizarin red staining to verify mineralization nodule formation. Results: Bromelain at 2.5, 5, 10, or 20 µg/mL did not affect the viability of hDPCs significantly. LPS increased interleukin-1β, interleukin-6, interleukin-8, ICAM-1 and VCAM-1 expression in hDPCs. Bromelain significantly decreased interleukin-1β, interleukin-6, interleukin-8, ICAM-1, and VCAM-1 levels in hDPCs, which were stimulated by LPS. Bromelain treatment significantly reduced p65 phosphorylation in the cytoplasm and the nucleus. It also significantly decreased phosphorylation levels of extracellular signal-related kinases (ERK) and p38 mitogen-activated protein kinases (p38). Bromelain also promoted ALP activity and mineralized nodule formation. Conclusions: Bromelain inhibits the expression of inflammatory cytokines in LPS-stimulated hDPCs. The inhibitory effect of bromelain on inflammatory mediators is related to decreased NF-κB and the MAPK pathway. Therefore, bromelain might have the potential to be used for regenerative endodontics, including vital pulp therapy.

Ingrowth of Mineralized Tissue into the Root Canal of Immature Permanent Teeth after a Traumatic Injury: A Report of 3 Cases

The aim of this case series was to describe the endodontic management of 3 immature permanent teeth that sustained traumatic injuries and subsequently presented with complete ingrowth of mineralized tissue into the canal space. Ingrowth of bone/mineralized tissue into the canal has been considered a poor long-term outcome with an inherent risk of ankylosis. In cases 1 and 2, no endodontic treatment was undertaken, except for emergency management requiring splinting. The cases were followed for 36 and 23 months, respectively. No ankylosis was evident over the review period, and normal teeth eruption was apparent. In case 1, the tooth was treated orthodontically and was responsive to pulp sensibility testing. In both cases, there was an appearance of an internal periodontal ligament-like space on the inner root wall of the canal. In case 3, 2 years postinjury, pulp necrosis and apical periodontitis occurred, and the tooth was managed with regenerative endodontic treatment consistent with the European Society of Endodontology and the American Association of Endodontists guidelines/recommendations for a regenerative procedure. The case was followed for 8 years after regenerative endodontic treatment. No ankylosis was noted with normal eruption of the teeth. The tooth was responsive to pulp sensibility testing despite the ingrowth of mineralized tissue, which was confirmed clinically.

Roles of Dental Mesenchymal Stem Cells in the Management of Immature Necrotic Permanent Teeth

Dental caries and trauma always lead to pulp necrosis and subsequent root development arrest of young permanent teeth. The traditional treatment, apexification, with the absence of further root formation, results in abnormal root morphology and compromises long-term prognosis. Regeneration endodontics procedures (REPs) have been developed and considered as an alternative strategy for management of immature permanent teeth with pulpal necrosis, including cell-free and cell-based REPs. Cell-free REPs, including revascularization and cell homing with molecules recruiting endogenous mesenchymal stem cells (MSCs), have been widely applied in clinical treatment, showing optimistic periapical lesion healing and continued root development. However, the regenerated pulp-dentin complex is still absent in these cases. Dental MSCs, as one of the essentials of tissue engineering, are vital seed cells in regenerative medicine. Dental MSC-based REPs have presented promising potential with pulp-dentin regeneration in large animal studies and clinical trials via cell transplantation. In the present review, we summarize current understanding of the biological basis of clinical treatments for immature necrotic permanent teeth and the roles of dental MSCs during this process and update the progress of MSC-based REPs in the administration of immature necrotic permanent teeth.

Endodontic management of traumatized permanent teeth: a comprehensive review

The pulp plays a key role in the treatment of traumatic dental injuries (TDIs) and is strongly associated with the outcome, particularly in severe cases. A correct pulp diagnosis is essential as it forms the basis for developing the appropriate management strategy. However, many TDIs are complex, and their treatment requires a profound knowledge of the physiological and pathological responses of the affected tissues. This comprehensive review will look at the dentine-pulp complex and its interaction with the surrounding tissues following TDIs. The literature up to 2020 was reviewed based on several searches on PubMed and the Cochrane Library using relevant terms. In addition to the recently revised guidelines of the International Association of Dental Traumatology, this article aims to provide background information with a focus on endodontic aspects and to gather evidence on which a clinician can make decisions on the choice of the appropriate endodontic approach for traumatized permanent teeth.

Regenerative endodontic therapy: a follow-up of 47 anterior traumatised teeth

PURPOSE

To collect long-term survival data in anterior traumatised teeth on the outcome of Regenerative Endodontic Treatments (RET) with a network of dentists working in different clinics to overcome the problem of anecdotical evidence.

METHODS

The seven dentists from Paediatric REsearch Project (PREP) performed RET treatments following the same protocol in five different secondary dental care clinics in the Netherlands. Treatment resulting in pain, apical problems, sinus tracts, resorption or fracture were considered as failure of treatment.

RESULTS

47 teeth in 38 children were treated between January 2009 and September 2017 and had at least 6 month follow-up (mean 35 months). Apical closure was seen in 27 teeth (25 cases) and root length growth in 6 teeth (6 cases). Thickening of the root walls was seen in 20 teeth (20 cases) and obliteration of the root canal in 30 teeth (25 cases). Of 38 teeth with apical inflammation at the start of treatment, no radiographic sign of apical inflammation was visible at 3 months in 13 of 28 teeth; taking up to 42 months for radiographic signs of apical inflammation to be not visible. Nineteen of 35 teeth showed discoloration at the beginning of treatment. After 18 months two teeth showed signs of ankylosis, but were still functional. After 36 months one more tooth showed signs of new apical inflammation and 2 months later it was extracted.

CONCLUSIONS

With three failures in 47 treated teeth, RET seems to be a promising treatment for difficult to treat anterior traumatised teeth with an open apex.

Regenerating the Pulp-Dentine Complex Using Autologous Platelet Concentrates: A Critical Appraisal of the Current Histological Evidence

Background:

Autologous platelet concentrates such as platelet-rich plasma (PRP) and platelet-rich fibrin (PRF) have gained overwhelming popularity in regenerative endodontics. Clinical evidence reveals the lack of a particular advantage of using PRP or PRF over an evoked blood clot in promoting canal wall thickening and/or continued root development in immature necrotic teeth. Moreover, despite stimulating tissue repair and repopulating the root canals of immature and mature permanent teeth, the new vital tissue may not possess the functional activity of the native pulp tissue.

Methods:

To better understand the origin, nature, and long-term fate of the tissue types found within the pulp space, we critically examine all available histo-/morphological evidence for pulp–dentine complex regeneration using PRP and/or PRF, alone or together with an evoked blood clot, specialised or unspecialised primary cells, and other biomaterials.

Results:

Histological data from clinical studies is scant. Reportedly, the inner dentinal surface supports cementum-like tissue formation, but this interface likely deviates in structure and function from the native cementodentinal junction. Presence of bone-like tissue within the pulp space is intriguing since de novo osteogenesis requires closely coordinated recruitment and differentiation of osteoprogenitor cells. Compared to untreated necrotic teeth, an evoked blood clot (with/without PRF) improves fracture resistance. Tooth regeneration using PRF and dental bud cells is unreliable and the constituent neoformed tissues are poorly organised.

Conclusion:

PRP/PRF fail to demonstrate a significant advantage over an induced blood clot, alone. The true nature of neoformed tissues remains poorly characterised while their response to subsequent insult/injury is unexplored.

Antimicrobial Therapeutics in Regenerative Endodontics: A Scoping Review

INTRODUCTION

This review aimed to provide a critical appraisal of alternative antimicrobial strategies in lieu of traditional triple antibiotic paste (TAP).

METHODS

This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The literature search was performed in 8 databases (PubMed/Medline, Embase, LILACS, Web of Science, Scopus, BVS, SciELO, and the Cochrane Library), selecting clinical, in vitro, in vivo, and in situ studies that evaluated antimicrobial alternatives to TAP in regenerative endodontics. Studies lacking an experimental TAP group were excluded.

RESULTS

A total of 1705 potentially relevant records were initially identified. From the 38 studies retrieved for full-text reading, 16 fulfilled all selection criteria and were included in the qualitative analysis. According to the study design, 11 studies were solely in vitro, 1 study was both in vitro and in vivo (animal model), 2 studies were solely animal experiments, and 2 studies were clinical trials. The alternative antimicrobial agents to TAP consisted of modified TAP formulations (eg, a combination of TAP with chitosan); TAP-eluting nanofibers; propolis; chlorhexidine (CHX) gels/solutions; double antibiotic pastes composed of distinct combinations of antibiotics; Ca(OH)₂-based formulations; and sodium hypochlorite. Overall, most of the alternative agents performed similarly to TAP, although some strategies (eg, Ca(OH)₂- and CHX-based formulations) seemed to present dubious importance in the control of infection.

CONCLUSIONS

TAP still remains an excellent option in terms of the complete elimination of microorganisms. This review points to the use of electrospun fibers as a drug delivery system to offer a controlled release of the antimicrobial agent, as well as the use of natural compounds, deserving future investigation.

Regenerative Endodontics: A Paradigm Shift in Clinical Endodontics

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

Orthodontic treatment recommendation and expected adverse reactions in patients with a history of dental trauma: A survey among general dentists, paediatric dentists, and orthodontic specialists

BACKGROUND

Trauma-induced adverse reactions may trigger complications when moving teeth orthodontically.

AIM

The purpose of this study was to evaluate the knowledge of dental practitioners about this topic.

DESIGN

A questionnaire survey was organized among general dentists, paediatric dentists, and orthodontists in Flanders (Belgium). Three clinical cases describing trauma-induced tooth damage (tooth ankylosis, apical root resorption, and pulp/root canal obliteration) were presented, followed by a set of questions.

RESULTS

The questionnaire was completed by 121 general dentists (GD), 47 paediatric dentists (PD), and 99 orthodontic specialists (OS). In the case with ankylosis, impossibility to move the tooth orthodontically was reported as most frequent adverse reaction (82.8% of GD, 95.7% of PD, and 100.0% of OS) (P < .001). In the situation of apical root resorption, the most frequently reported adverse event was progressive apical root resorption (78.9%, 85.7%, and 88.8% respectively; P = .265). Most frequently mentioned adverse reaction in the case with pulp and root canal obliteration was tooth discoloration (64.1%, 57.1%, and 78.3%; P = .055), followed by apical root resorption (57.4%, 56.8%, and 68.7%; P = .283). Orthodontic treatment recommendation differed among specific clinical situations but also among groups of dental practitioners.

CONCLUSIONS

Important knowledge gaps exist regarding the orthodontic managment of traumatized teeth. This topic requires more attention in undergraduate training, specialist training, and continuing education.

Dens evaginatus: Current treatment options

BACKGROUND

Teeth with dens evaginatus (DE) are more commonly observed in Western countries than previously. This is due to the increase in populations of patients of Asian origin, in whom DE is more common than in people of European origin. The interest in DE has also increased with the introduction of a procedure called regenerative endodontics.

CASE DESCRIPTION

A narrative review of treatment options for teeth with DE is presented, based on pulpal conditions and maturity of the teeth.

PRACTICAL IMPLICATIONS

Early recognition of teeth with DE allows for treatment choices that generally lead to good outcomes and can aid in preserving developing teeth in young patients.

Calcific metamorphosis of pulp after extrusive luxation

BACKGROUND/AIM

The literature on the pathogenesis of extrusive dental luxation has been focused on periodontal tissue responses, with little attention given to the pulp. The aim of this study was to evaluate the response of dental pulp of teeth following extrusive luxation in a rat model.

MATERIAL AND METHODS

The maxillary right central incisors of 30 rats were extrusively luxated and repositioned after 5 minutes. The animals were euthanized after 7, 15, and 30 days to provide three groups: I, II, and III, respectively (n = 10). Histological sections were stained with H and E for histomorphometric analysis of the odontoblast layer, reparative dentin deposition, Hertwig's epithelial root sheath, pulp necrosis, and periapical inflammatory infiltrate.

RESULTS

In most cases, new vascular formation occured in association with reparative dentin deposition on the root walls and within the pulp. In some cases, dentin deposition occupied the entire pulp space over time, with no other types of non-odontogenic hard tissues being observed. Pulp necrosis with the presence of periapical inflammatory infiltrate was also observed in a few cases. No statistical differences were observed among the studied groups.

CONCLUSIONS

Following extrusive luxation, calcific metamorphosis of the pulp is very likely to occur.

Top-cited Articles in Regenerative Endodontics: A Bibliometric Analysis

INTRODUCTION

Bibliometric analysis is a method for quantifying the research productivity, author performance, and manuscript impact. The citation count received by a scientific article is one of the indicators of its impact within a field. The purpose of this study was to identify the 100 top-cited articles published in regenerative endodontics and to analyze their main characteristics.

METHODS

Thomson Reuters Web of Science was searched to retrieve the 100 most-cited articles in "regenerative endodontics" published from January 1991 to February 2018 in the category of "Dentistry, Oral Surgery and Medicine." Among the included top-cited articles, the following parameters were recorded and analyzed: journal name, authors, institution, country, publication title and year, number of citations and average citations, type of study, collaborations, and key words. The data were analyzed using SPSS version 19.0 (IBM Corp, Armonk, NY) and VOS viewer software (version 1.6.7; Leiden University Center for Science and Technology Studies, Leiden, Netherlands).

RESULTS

Among the 100 top cited articles, the highest number of citations that an article received was 309. The top cited articles appeared in 14 different journals, and the Journal of Endodontics published the greatest number of these articles (66%). The majority of articles were published in the year 2014 (n = 17). The majority of articles originated from the United States (n = 51) with the most contribution from The University of Texas Health Science Center, San Antonio, TX. The most frequent first authors were Torabinejad (n = 4), Nosrat (n = 3), and Thibodeau (n = 3). In vitro studies were the most common study design (n = 29) followed by reviews (n = 21). "Regenerative endodontics" was the most frequently used key word.

CONCLUSIONS

This bibliometric analysis reveals the progress and trend of research in the field of regenerative endodontics. The in vitro articles published in the field of regenerative endodontics had the highest number of citations and average citation rates.

Regenerative endodontics: a comprehensive review

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

Iloprost Induces Dental Pulp Angiogenesis in a Growth Factor-free 3-Dimensional Organ Culture System

INTRODUCTION

Angiogenesis is a key determinant in dental pulp regeneration. Iloprost is a synthetic prostacyclin that promotes angiogenesis. A three-dimensional culture that mimics the in vivo condition has been used in tissue engineering. This study investigated the effect of iloprost on promoting dental pulp angiogenesis by using the tooth slice organ culture system.

METHODS

Tooth slices with intact pulp tissue were cut from molars extracted from 12 patients. Dental pulp tissue viability was determined by live/dead staining. The tooth slices were cultured with iloprost for 1 or 3 days. The microvessel density and expression of vascular endothelial growth factor were determined by immunohistochemical staining. Collagen density was determined by using Masson trichrome and immunofluorescent staining.

RESULTS

The pulp tissue in the tooth slices remained viable when cultured in serum-free medium. Iloprost increased the microvessel density as shown by a higher number of von Willebrand factor-positive cells. A significant increase in vascular endothelial growth factor expression was observed in the tooth slices cultured with iloprost. Iloprost stimulated collagen deposition, and this effect was abolished after inhibition of protein kinase A activity.

CONCLUSIONS

Human tooth slices provide a valuable and easy-to-obtain model to investigate the effect of bioactive molecules used in dental pulp regeneration. This study showed for the first time that tooth slices could be kept viable under serum-free conditions for up to 3 days. Iloprost promoted angiogenesis, increased new vessel formation, and induced collagen deposition. This study proposes the clinical value of iloprost as a drug for inducing angiogenesis that can increase the success of pulp regeneration.

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

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

Paradigm Shift from Stem Cells to Cell-Free Regenerative Endodontic Procedures: A Critical Review

Regenerative endodontic procedures of immature teeth with necrotic pulp have become a part of therapeutic endodontic spectrum and are considered as an alternative to calcium hydroxide or mineral trioxide aggregate apexification. In last decade, numerous case reports and series with usage of cell-free approaches known as revascularization, revitalization, or maturogenesis have been published. This cell-free approach prevails in clinical regenerative endodontics because of its relative ease of performance, lower financial demands, and absence of complications such as tumorigenesis of used stem cells. In this article, the integral steps of cell-free treatment approaches such as source of stem cells, possible endogenous scaffolds, sources of growth factors, and width of apical foramen in the context of sufficient disinfection of root canal system and outcome of treatment are discussed. Despite not being a fully established treatment protocol, the achieved outcomes are promising regardless of it having a reparative character than a regenerative one.

After-Hours Versus Office-Hours Dental Injuries in Children: Does Timing Influence Outcome?

AIM

The aim of this study was to analyze the outcomes and factors associated with after-hours dental trauma.

METHODS

Study sample consisted of 1762 permanent teeth injuries in children, gender and age matched with office-hours injuries. Epidemiological and clinical data were collected from 4 university dental trauma centers.

RESULTS

During median follow-up time of 4.3 years, complications have occurred in 14.5% of injured teeth. Age, type, and degree of tissue injury and after-hours time of injury were significantly associated with complications. Unfavorable outcomes were 34% more likely in the after-hours group compared with office-hours. Urgent treatment was significantly delayed in after-hours group with a delay of more than 3 hours in 90.5% versus 38.9% in the office-hours group. Multivariate regression model showed that after-hours time of injury was significant predictor of complications.

CONCLUSION

Delayed urgent treatment was one of the main factors associated with unfavorable outcome of after-hours injuries.

Dental Stem Cells in Pulp Regeneration: Near Future or Long Road Ahead?

Although regenerative endodontic procedures have yielded an impressive body of favorable outcomes, the treatment of necrotic immature permanent teeth in particular remains to be a challenge. Recent advances in dental stem cell (DSC) research have gained increasing insight in their regenerative potential and prospective use in the formation of viable dental tissues. Numerous studies have already reported successful dental pulp regeneration following application of dental pulp stem cells, stem cells from the apical papilla, or dental follicle precursor cells in different in vivo models. Next to responsive cells, dental tissue engineering also requires the support of an appropriate scaffold material, ranging from naturally occurring polymers to treated dentin matrix components. However, the routine use and banking of DSCs still holds some major challenges, such as culture-associated differences, patient-related variability, and the effects of culture medium additives. Only in-depth evaluation of these problems and the implementation of standardized models and protocols will effectively lead to better alternatives for patients who no longer benefit from current treatment protocols.

Considerations for regeneration procedures

When pulp tissue becomes necrotic in immature teeth, the prognosis of the teeth is compromised. Disinfection of the root(s) presents several challenges including difficulties in cleaning and shaping large canals with open apices, obturation of canals with open apices, and potential root fractures caused by thin and/or weakened root walls. Regenerative endodontic procedures may increase the prognosis of the compromised immature tooth by re-establishment of a functional pulp tissue that fosters continued root development and immune competency. This article reviews the literature related to and discuss considerations for regenerative endodontic procedures and how these procedures may increase the prognosis for immature teeth with necrotic pulp tissue.

Regeneration of the dentine-pulp complex with revitalization/revascularization therapy: challenges and hopes

The concept of regenerative endodontics has gained much attention in clinical endodontics in the past decade. One aspect of this discipline is the application of revitalization/revascularization therapies for infected and/or necrotic immature pulps in permanent teeth. Following the publication of a case report (Iwaya et al. ), investigators have been rigorously examining the types of tissues formed in the canals as well as exploring strategies to regenerate the pulp-dentine complex in revitalized teeth. This review will provide an update on the types of tissues generated in the canals after revitalization/revascularization therapy in both animal and human studies. The understanding of the role of stem cells and microenvironment in the process of wound healing resulting in either regeneration or repair will be thoroughly discussed. Stem cells and microenvironmental cues introduced into the canal during revitalization/revascularization procedures will be examined. In addition, requirement of a sterile microenvironment in the canal and vital tissue generation in revitalization/revascularization therapy will be emphasized. The challenges that we face and the hopes that we have in revitalization/revascularization therapy for regenerative endodontics will be presented.

Challenges of stem cell-based pulp and dentin regeneration: a clinical perspective

There are two types of approaches to regenerate tissues: cell-based and cell-free. The former approach is to introduce exogenous cells into the host to regenerate tissues, and the latter is to use materials other than cells in an attempt to regenerate tissues. There has been a significant advancement in stem cell-based pulp and dentin regeneration research in the past few years. Studies in small and large animals have demonstrated that pulp/dentin-like tissues can be regenerated partially or completely in the root canal space with apical openings of 0.7-3.0 mm using dental pulp stem cells, including stem cells from apical papilla (SCAP) and subpopulations of pulp stem cells. Bone marrow mesenchymal stem cells (BMMSCs) and adipose tissue-derived MSCs (ADMSCs) have also been shown to regenerate pulp-like tissue. In contrast, the cell-free approach has not produced convincing evidence on pulp regeneration. However, one crucial concept has not been considered nor defined in the field of pulp/dentin regeneration and that is the critical size defect of dentin and pulp. Without such consideration and definition, it is difficult to predict or anticipate the extent of cell-free pulp regeneration that would occur. By reasoning, cell-free therapy is unlikely to regenerate an organ/tissue after total loss. Similarly, after a total loss of pulp, it is unlikely to regenerate without using exogenously introduced cells. A cell homing approach may provide a limited amount of tissue regeneration. Although stem cell-based pulp/dentin regeneration has shown great promise, clinical trials are difficult to launch at present. This article will address several issues that challenge and hinder the clinical applications of pulp/dentin regeneration which need to be overcome before stem cell-based pulp/dentin regeneration can occur in the clinic.

Treatment options: biological basis of regenerative endodontic procedures

Dental trauma occurs frequently in children and often can lead to pulpal necrosis. The occurrence of pulpal necrosis in the permanent but immature tooth represents a challenging clinical situation because the thin and often short roots increase the risk of subsequent fracture. Current approaches for treating the traumatized immature tooth with pulpal necrosis do not reliably achieve the desired clinical outcomes, consisting of healing of apical periodontitis, promotion of continued root development, and restoration of the functional competence of pulpal tissue. An optimal approach for treating the immature permanent tooth with a necrotic pulp would be to regenerate functional pulpal tissue. This review summarizes the current literature supporting a biological rationale for considering regenerative endodontic treatment procedures in treating the immature permanent tooth with pulp necrosis.

Outcomes of regenerative endodontic procedures

The use of regenerative endodontic techniques holds great promise for the treatment of immature teeth with necrotic pulp tissue. Several published case reports and case series have demonstrated radiographic evidence of apical bone healing, increases in root length, and root wall thickness. Although histologic changes have been demonstrated in animal models, histology in human teeth is lacking. A summary of these outcomes is discussed in this article.

Transplantation of dental pulp stem cells and platelet-rich plasma for pulp regeneration

INTRODUCTION

The loss of dental pulp may weaken teeth, rendering them susceptible to reinfection, fracture, and subsequent tooth loss. Therefore, regeneration of pulp is considered an ideal treatment to preserve teeth. The aim of this study was to explore the capacity of dental pulp stem cells (DPSCs) and platelet-rich plasma (PRP) to regenerate dental pulp in canine mature permanent teeth.

METHODS

Pulpectomy with apical foramen enlarged to a #80 file was performed in 16 upper premolars of 4 beagle dogs. Four experimental groups were randomly established: (1) the blood clot group, (2) the autologous DPSCs group, (3) the PRP group, and (4) the DP + PRP group (a mixture of DPSCs and PRP). Four lower premolars without any further treatment after pulpectomy were used as the control group. All teeth were sealed with mineral trioxide aggregate and composite. Twelve weeks after transplantation, the teeth were subjected to radiographic and histologic examination.

RESULTS

Twenty-four of 32 experimental root canals gained newly formed tissues. All canals with an introduction of a blood clot showed histologic evidence of vital tissue formation. Cementum-like and periodontal ligament-like tissues along the internal root canal walls were typical structures in most cases. There is no significant difference between groups with or without autologous DPSC transplantation (exact chi-square test, P < .05).

CONCLUSIONS

New vital tissues can be regenerated in permanent canine teeth after pulpectomy and enlargement of the apical foramen. Histologically, transplantation of DPSCs and/or PRP into root canals showed no enhancement in new tissue formation compared with inducement of a blood clot into the root canals alone.