Faculty Bibliography

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. (2001) and Banchs & Trope (2004). 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; 1) Resolution of clinical signs and symptoms; 2) further root maturation; and 3) 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 signaling molecules that true pulp regeneration is an achievable goal. This review discusses current knowledge as well as future directions for regenerative endodontics. Patient-centered outcomes such as tooth discoloration and possibly more appointments with the potential for adverse effects needs to be discussed with patients and parents. Based on the classification of Cvek (1992), it is proposed that regenerative endodontics should be considered for teeth with incomplete root formation though 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.

Revascularization-associated intracanal calcification (RAIC) is a common finding in immature teeth managed with regenerative endodontic treatment (RET). The aim of this report was to illustrate a case in which 2 mandibular premolar teeth developed complete canal obliteration and have been reviewed for 8 years. The 3 primary outcome goals as defined by the American Association of Endodontists after RET are resolution of signs and symptoms of pulp necrosis, further root maturation, and achievement of responses to pulp vitality testing. The teeth had been included in an earlier quantitative study in which an increase in root canal width of 72.1% and 39.6% and an increase in root length of 1.7% and 0% were reported for teeth #20 and #29, respectively. Qualitative assessments over the 8-year review period showed no pathosis and a response to electric pulp testing at the final review. A quantitative assessment at the 8-year review showed an increase of 100% for canal width because complete calcification had occurred and no substantive change in root length (-0.17% and 0.68% for teeth #20 and #29, respectively). In this report, complete RAIC occurred in both teeth over time. RAIC has the potential to complicate future endodontic or prosthodontic treatment if necessary. Therefore, it is recommended that the American Association of Endodontists clinical considerations for a regenerative endodontic procedure be updated to include the incidence of RAIC after RET.

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

INTRODUCTION: Two fundamental assumptions for teeth treated with regenerative endodontic procedures (REPs) are (1) that the clinical outcome is comparable with the traditional techniques of calcium hydroxide apexification and mineral trioxide aggregate apical barrier techniques and (2) that REPs will result in further root maturation. METHODS: A systematic review of the electronic databases (Scopus, PubMed, and Web of Science) involved a search for studies that used quantitative assessments of root maturation. The search terms were "dental pulp," "regenerative endodontic therapy," "revascularization," and "revitalization." The identified studies were further screened for cohort studies that compared clinical outcomes between teeth treated with REPs and apexification/apical barrier approaches. The primary question under review was framed according to the population, exposure, and outcome format. RESULTS: Of the 368 studies identified by the search, 6 cohort studies used quantitative assessments of any further root maturation after REPs, and a subset of 4 of these cohort studies assessed and compared clinical outcomes between the different treatment approaches. CONCLUSIONS: Immature teeth with pulp necrosis treated with REPs generally show further root maturation although the results are variable. Clinical outcomes were similar for both groups. Patient-based criteria such as tooth discoloration, indications for changing the treatment option, and number of treatment appointments are all important for discussion before electing the appropriate treatment plan for the management of immature teeth with pulp necrosis.

Descriptions of the pathologic changes in the pulp and associated apical structures of human immature teeth in response to deep caries are lacking in the literature. OBJECTIVES: This article describes the histologic events associated with the radicular pulp and the apical tissues of human immature teeth following pulp inflammation and necrosis. METHODS: Twelve immature teeth with destructive caries lesions were obtained from 8 patients. Two intact immature teeth served as controls. Teeth were extracted for reasons not related to this study and immediately processed for histopathologic and histobacteriologic analyses. Serial sections were examined for the pulp conditions and classified as reversible or irreversible pulp inflammation, or pulp necrosis. Other histologic parameters were also evaluated. RESULTS: In the 3 cases with reversible pulp inflammation, tissue in the pulp chamber showed mild to moderate inflammation and tertiary dentin formation related to tubules involved in the caries process. Overall, the radicular pulp tissue, apical papilla and Hertwig's epithelial root sheath (HERS) exhibited characteristics of normality. In the 3 cases with irreversible pulp inflammation, the pulps were exposed and severe inflammation occurred in the pulp chamber, with minor areas of necrosis and infection. Large areas of the canal walls were free from odontoblasts and lined by an atubular mineralized tissue. The apical papilla showed extremely reduced cellularity or lack of cells and HERS was discontinuous or absent. In the 6 cases with pulp necrosis, the coronal and radicular pulp tissue was necrotic and colonized by bacterial biofilms. The apical papilla could not be discerned, except for one case. HERS was absent in the necrotic cases. CONCLUSION: While immature teeth with reversible pulpitis showed histologic features almost similar to normal teeth in the canal and in the apical region, those with irreversible pulpitis and necrosis exhibited significant alterations not only in the radicular pulp but also in the apical tissues, including the apical papilla and HERS. CLINICAL SIGNIFICANCE: Alterations in the radicular pulp and apical tissues help explain the outcome of current regenerative/reparative therapies and should be taken into account when devising more predictable therapeutic protocols for teeth with incomplete root formation.

The primary goal of conventional endodontic treatment is prevention and/or elimination of apical periodontitis for both mature permanent teeth and immature teeth with an open apex. Besides these goals, the objectives of endodontic treatment of immature teeth include preservation of pulp vitality and often further root maturation. Robust criteria for outcome assessment are an essential determinant for any measure of treatment success for both mature and immature teeth.

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

INTRODUCTION: Traumatic injury to the teeth can cause horizontal root fractures and inflammatory root resorptions (external and internal). Traditionally, traumatized teeth with horizontal root fractures resulting in pulp necrosis and inflammatory root resorptions are treated with conventional root canal therapy. METHODS: A 15-year-old boy had a history of traumatic injury to mature tooth #8 resulting in horizontal root fracture and pulp necrosis of the coronal fragment. A 7-year-old girl suffered an avulsion injury to immature tooth #9, which developed inflammatory replacement resorption and subsequently root fractured 15 months later. Another 16-year-old boy also suffered a history of traumatic injury to mature tooth #8, resulting in perforating root resorption. All teeth were treated with regenerative endodontic procedures using chemomechanical debridement, calcium hydroxide/triple antibiotic paste dressing, EDTA rinse, induction of periapical bleeding into the canal space, and a coronal mineral trioxide aggregate plug. In the tooth presenting with horizontal root fracture, only the coronal fragment was treated to preserve pulp vitality in the apical fragment for possible pulp tissue regeneration. RESULTS: After regenerative endodontic procedures, clinical signs/symptoms subsided, and inflammatory osteolytic lesions resolved in all traumatized teeth. Two teeth were followed for 19 months and 1 tooth for 5 years. At the last review of the teeth with horizontal root fractures, the first case showed healing by calcified tissue and the second case showed healing by fibrous connective and hard tissue. Tooth with perforating root resorption demonstrated a decrease in size of the resorptive defect. CONCLUSIONS: Based on these case reports, regenerative endodontic procedures have the potential to be used to treat traumatized teeth with horizontal root fracture and inflammatory root resorption.

Caries is the most common cause of pulp-periapical disease. When the pulp tissue involved in caries becomes irreversibly inflamed and progresses to necrosis, the treatment option is root canal therapy because the infected or non-infected necrotic pulp tissue in the root canal system is not accessible to the host's innate and adaptive immune defense mechanisms and antimicrobial agents. Therefore, the infected or non-infected necrotic pulp tissue must be removed from the canal space by pulpectomy. As our knowledge in pulp biology advances, the concept of treatment of pulpal and periapical disease also changes. Endodontists have been looking for biologically based treatment procedures, which could promote regeneration or repair of the dentin-pulp complex destroyed by infection or trauma for several decades. After a long, extensive search inin vitrolaboratory andin vivopreclinical animal experiments, the dental stem cells capable of regenerating the dentin-pulp complex were discovered. Consequently, the biological concept of 'regenerative endodontics' emerged and has highlighted the paradigm shift in the treatment of immature permanent teeth with necrotic pulps in clinical endodontics. Regenerative endodontics is defined as biologically based procedures designed to physiologically replace damaged tooth structures, including dentin and root structures, as well as the pulp-dentin complex. According to the American Association of Endodontists' Clinical Considerations for a Regenerative Procedure, the primary goal of the regenerative procedure is the elimination of clinical symptoms and the resolution of apical periodontitis. Thickening of canal walls and continued root maturation is the secondary goal. Therefore, the primary goal of regenerative endodontics and traditional non-surgical root canal therapy is the same. The difference between non-surgical root canal therapy and regenerative endodontic therapy is that the disinfected root canals in the former therapy are filled with biocompatible foreign materials and the root canals in the latter therapy are filled with the host's own vital tissue. The purpose of this article is to review the potential of using regenerative endodontic therapy for human immature and mature permanent teeth with necrotic pulps and/or apical periodontitis, teeth with persistent apical periodontitis after root canal therapy, traumatized teeth with external inflammatory root resorption, and avulsed teeth in terms of elimination of clinical symptoms and resolution of apical periodontitis.