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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.

Endodontics has made significant progress in regenerative approaches in recent years, thanks to advances in biologically based procedures or regenerative endodontic therapy (RET). In recent years, our profession has witnessed a clear conceptual shift in this therapy. RET was initially based on a blood clot induced by apical bleeding without harvesting the patient’s cells or cell-free RET. Later, the RET encompassed the three principles of tissue engineering, stromal/stem cells, scaffolds, and growth factors, aiming for the regeneration of a functional dentin pulp complex. The regenerated dental pulp will recover the protective mechanisms including innate immunity, tertiary dentin formation, and pain sensitivity. This comprehensive review covers the basic knowledge and practical information for translational applications of stem cell-based RET and tissue engineering procedures for the regeneration of dental pulp. It will also provide overall information on the emerging technologies in biological and synthetic matrices, biomaterials, and signaling molecules, recent advances in stem cell therapy, and updated experimental results. This review brings useful and timely clinical evidence for practitioners to understand the challenges faced for a successful cell-based RET and the importance of preserving or reestablishing tooth vitality. The clinical translation of these current bioengineering approaches will undoubtedly be beneficial to the future practice of endodontics.

This study investigated a colloidal microgel for angiogenic and odontogenic differentiation of cells in the presence of cell-derived extracellular matrix (ECM) proteins using a 3-dimensional culture model.Viscoelastic properties of human dental pulp were determined to understand the native ECM environment. ECM proteins were extracted from dental pulp stem cell (DPSC) cultures, and MaxGel (Millipore Sigma, Burlington, MA) was used as a commercially available ECM protein. DPSCs were incubated in colloidal microgels in the presence of ECM proteins or gelatin methacryloyl (GelMA) as a bulk hydrogel (n = 9/group). The viability and odontogenic differentiation of DPSCs within hydrogels was determined using viability assays, mineralization staining, calcium and alkaline phosphatase assays, and quantitative polymerase chain reaction for odontogenic gene expression. Angiogenic properties of endothelial cells were determined using tubule formation assays and quantitative polymerase chain reaction to detect angiogenic gene expression.Dental pulp had a higher elastic modulus than the viscous modulus, showing a solidlike response similar to hydrogels. DPSC-derived ECM showed higher collagen and GAG than MaxGel (P .05). The viability of DPSCs was similar in colloidal microgels, whereas higher cell viability, calcium deposition, and alkaline phosphatase activity were observed in GelMA (P .05). Colloidal microgels allowed tubule-like structures by endothelial cells, whereas no tubular formation was observed in GelMA. DPSC-derived ECM in colloidal microgel up-regulated odontogenic gene expression, whereas MaxGel up-regulated angiogenic gene expression (P .05).Colloidal microgels allowed cellular organization that can improve penetration and nutritional supply in a full-length root canal system. The bioactivity of cell-derived ECM proteins can be modified depending on the external stimulus.

Objective : This study explored if human primary mesenchymal stem cells (MSCs), derived from two donors and cultivated in a medium made with intentionally treated water, would exhibit more growth and pluripotency than MSCs from the same source but grown in untreated (control) water. Design : To create the treated water, three Buddhist monks directed their attention toward commercially bottled water while holding the intention that the water would enhance the growth of MSCs. Under double-blind conditions, cell culture growth mediums were prepared with the treated and untreated water, which was in turn used to grow the primary MSCs. Primary cells obtained from two donors were designated as Cells #1 and Cells #2. The prediction was that treated water would result in increased cell proliferation, that more cells would enter the cell cycle growth phase, and that there would be increased expression of genes (NANOG, OCT4 and SOX2) associated with improved cell growth and decreased expression of genes (p16, p21, and p53) associated with a decline in cell growth. The improved growth hypothesis was directional, thus one-tailed p-values were used to evaluate the results. Results : Proliferation averaged across Cells #1 and #2 showed overall increased growth in treated as compared to control water (p = 0.0008). Cells #1 and #2 considered separately had differences in the same direction but only Cells #2 showed a significant difference on day 6 (p = 0.01). For cell cycle, there was a significantly greater percentage of Cells #2 in the S interphase with treated vs. control water (p = 0.04). For the gene expression analysis, when considering the average across the two donor cells, only the NANOG gene expression was in the predicted direction (p = 0.01); by contrast, the p16 gene expression was significantly opposite to the predicted direction (p = 0.005, one-tailed, post-hoc). For Cells #1 considered separately, no differences were significant except for p16, which resulted in an effect opposite to the predicted outcome (p = 0.05). For Cells #2, three genes were significantly in the predicted directions: NANOG (p = 0.0008), OCT4 (p = 0.005), and P53 (p = 0.05); p16 was significantly opposite to the prediction (p = 0.001). Conclusion : Intentionally treated water appeared to have some biological effects on the growth, pluripotency and senescence of human MSCs. This was especially the case in one of the two donor cells tested, but the effects were not consistently in the predicted direction. As an exploratory study, caution is warranted in interpreting these outcomes, and adjustment for multiple testing would likely reduce some of the weaker effects to nonsignificant. But given the double-blind protocol, as well as several more significant outcomes in the predicted directions, further research is warranted.

2-Aminoethyl methacrylate (AEMA)–modified hyaluronic acid (HA) hydrogels with tunable swelling, degradation, and rheological properties were developed to maintain the native spherical and stemness of human dental pulp stem cells (DPSCs). Two molecular weights (MW) of HA, 18 and 270 kDa, and 25% degree of AEMA substitution were used to synthesize the HA macromers and hydrogels. The HA macromers were characterized by 1H NMR, and the AEMA-HA hydrogels were synthesized by UV polymerization. The swelling, hydrolytic degradation, and rheological properties of the hydrogels strongly depended on the MW of HA. The degradation rate decreased and the storage modulus increased with the increase in the MW of HA. The storage modulus of the hydrogels decreased with degradation of the hydrogels. The hydrogels were not cytotoxic to DPSCs evidenced by MTT assay, Hoechst 33342 live cell staining, and propidium iodide dead cell staining. The hydrogels maintained the native spherical morphology and stemness of DPSCs when the hydrogels’ storage moduli were in the ranges of 486–681 Pa. In contrast, DPSCs grown on 2D cell culture substrates showed a flat and elongated shape and could not maintain their native spherical shape. The hydrogels increased the expression of the stemness including NANOG and SOX2 of DPSCs (3 and 24 folds, respectively) when their storage modulus was 681.41 ± 92.81 Pa in comparison with DPSCs grown on 2D cell culture plates. The designed AEMA-HA hydrogels mimic the in vivo 3D environment to grow DPSCs. Thus, they appear to have great potential for clinical applications in regenerative medicine and other therapeutic remedies after further optimization in the future. Regenerative medicine is a translational approach that offers the possibility to replace or heal the diseased or damaged tissues caused by trauma, age, infection, cancer, or inherited defects. Such reinstatement of the functionality or healing of the damaged cells or tissues often includes the combination of numerous strategies including the use of biomaterials/scaffolds, stem cells, growth factors, and small molecules. In this study, we used hyaluronic acid (HA), a naturally occurring polysaccharide biopolymer commonly found in the extracellular matrix of connective tissues, to synthesize 3D hydrogel scaffolds for growing human dental pulp stem cells (DPSCs). We evaluated the effects of the molecular weight of HA, and the swelling, degradation, and rheological properties of the hydrogels on maintaining the native spherical and stemness of DPSCs for future therapeutic applications including regenerative medicine.

Rapid progress has been made in the last decade related to stem cell-mediated pulp–dentin regeneration, from characterization of dental pulp stem cells (DPSCs) to the first-ever reported clinical case in humans. However, many challenges still need to be addressed before such technology can become a common clinical practice; therefore, further rigorous research is needed. Animal study models are very important to test new ideas, concepts, and technologies. This review summarizes and discusses several key animal models that have been utilized to investigate pulp–dentin regeneration. From a tissue regeneration perspective, we categorize the animal model by the location where the regenerated pulp tissue is formed: ectopic, semiorthotopic, and orthotopic. Several animal species are discussed, including mouse, ferret, dog, and miniswine. Mouse is used for ectopic pulp–dentin regeneration in the dorsum subcutaneous space. A commonly tested approach is hydroxyapatite/tricalcium phosphate (HA-TCP) granules model used to observe ectopic pulp–dentin complex formation. The semiorthotopic model includes tooth slices or fragments with which de novo pulp regeneration in a root canal space can be tested in the mouse subcutaneous space. For orthotopic pulp regeneration, the canine teeth of ferrets are large enough for such purposes. As nonprimate large animal models, dog and miniswine teeth have many aspects quite similar to those of humans, allowing researchers to perform experiments that mimic clinical conditions in humans. The protocols established and the data obtained from large animal studies may directly relate to and apply to future human studies. Complete orthotopic pulp regeneration has been demonstrated in dogs and miniswine. The use of allogeneic and subpopulations of DPSCs for pulp regeneration, and testing of the periapical disease model and aging model have been performed in miniswine or dogs. In sum, all these animal models will help address challenges that still face pulp regeneration in humans. We need to thoroughly utilize these models to test new ideas, technologies, and strategies before reliable and predictable clinical protocols can be established for human clinical trials or treatment. IMPACT STATEMENT: Animal models are essential for tissue regeneration studies. This review summarizes and discusses the small and large animal models, including mouse, ferret, dog, and miniswine that have been utilized to experiment and to demonstrate stem cell-mediated dental pulp tissue regeneration. We describe the models based on the location where the tissue regeneration is tested—either ectopic, semiorthotopic, or orthotopic. Developing and utilizing optimal animal models for both mechanistic and translational studies of pulp regeneration are of critical importance to advance this field.

Craniofacial and dental tissues are unique and contain specialized cell types. The embryonic origins and characteristics of craniofacial bone are different from long bone. Craniofacial tissues are derived from neural crest cells (NCCs). The evidence has shown that MSCs derived from craniofacial tissue behave differently from those of other tissue origin. Thus, using craniofacial MSCs appears to be a better cell source for craniofacial tissue regeneration. While adult stem cells offer various clinical benefits for tissue regeneration, their key drawback is the limited lifespan and differentiation potential for certain applications. Induced pluripotent stem cells (iPSCs) can overcome these deficiencies. Oral and dental stem cells are also a good source of cells to generate iPSCs. Generated iPSCs either from dental and nondental cell sources have been investigated for their capacity in neurogenesis as well as for craniofacial tissue regeneration, including craniofacial bone regeneration, pulp regeneration, periodontal tissue regeneration, and whole tooth regeneration. Before iPSCs can provide significant clinical benefits for patients, issues revolving iPSC biology, their translation, and clinical advancement that pose various challenges need to be resolved.