It is generally believed that the dental papilla contributes to tooth formation and eventually converts to pulp tissue within the pulp chamber. In this study, we found that the root apical papilla contained mesenchymal stem cells that appear to have a greater capacity for dentin regeneration than DPSCs. These findings suggest that developing tissue may contain a good stem cell resource for tissue regeneration. SCAP represent a novel population of multipotent stem cells as demonstrated by their capacity to develop into odontoblast-like cells and adipocytes in vitro. This cell population was found to express high levels of survivin and telomerase, which are both important molecules in mediating cell proliferation. In addition, CD24, marker for undifferentiated SCAP, which is downregulated following odontogenic differentiation. These data support the notion that SCAP are a unique population of postnatal stem cells.
Although dental pulp contains DPSCs with dentin/pulp regenerative capacity, developing tissue-derived SCAP showed a superior tissue regeneration potential than that of DPSCs. SCAP collected from just one tooth are capable of providing a large number of stem cells probably sufficient for human transplantation because they have high proliferative potential, reflected in high telomerase activity 
. Human SCAP-mediated tissue regeneration may offer a promising cell-based therapy for root regeneration.
Since most human tissue at the developing stage is not clinically available for stem cell isolation, this apical papilla stem cell population, accessible in dental clinical practice, is unusual. SCAP can be isolated from extracted wisdom teeth. Therefore, it may be possible to bank these high quality dental stem cells for future autologous use. Their survival in freeze-thawing requires exploration. Allogeneic cells may be another resource of stem cells for treating those aged individuals who have already have had their wisdom teeth extracted, however the immunogenicity of these cells requires further study.
Although newly formed bio-roots show a lower compressive strength than that of natural swine root dentin, they seemed capable of supporting porcelain crown and resulted in normal functions. It may be possible to improve the compressive strength and hardness of the bio-roots by selecting optimal bioengineered materials and by optimizing the implanted stem cell numbers and quality. Stem cell-mediated root regeneration hybridized with clinical crown technology may be a promising approach for functional tooth restoration owing to the availability of high-quality dental stem cells for autologous transplantation as well as long-term experience with clinical dental implant procedures. In addition, the orofacial region is an open system for directly delivering stem cells for tissue engineering. Our studies demonstrate that minipigs offer an excellent translational model for the concept of functional tooth regeneration and the feasibility of using autologous stem cells for transplantation.