Dentin Conditioning Codetermines Cell Fate in Regenerative Endodontics

Introduction: Recent successes in dental pulp engineering indicate that regenerative treatment strategies in endodontics are feasible. Clinically, revascularization procedures render completion of root formation in immature teeth. The generation of a pulp-like tissue after seeding of dental pulp stem cells into dentin discs or cylinders and transplantation in vivo is possible. In this experimental setup, which mimics the situation in the root canal, the pretreatment of dentin might influence cellular behavior at the cell-dentin interface. Thus, the objective of this study was to investigate whether dentin conditioning can determine cell fate. Methods: Dental pulp stem cells (DPSCs) were seeded into a growth factor laden peptide hydrogel, transferred into dentin cylinders, and transplanted subcutaneously into immunocompromised mice. Before cell seeding, dentin cylinders were either pretreated with sodium hypochloride (NaOCl) or conditioned with EDTA. The constructs were explanted after 6 weeks and subjected to histological and immunohistochemical analysis. Results: In dentin treated with NaOCl, resorption lacunae were found at the cell-dentin interface created by multinucleated cells with clastic activity. After conditioning with EDTA, DPSCs adjacent to the dentin formed an intimate association with the surface, differentiated into odontoblasts-like cells that expressed dentin sialoprotein, and extended cellular processes into the dentinal tubules. A vascularized soft connective tissue similar to dental pulp was observed inside the dentin cylinder. Conclusions: Dentin conditioning considerably influences DPSC fate when seeded in close proximity to dentin. This information might be critical for optimized strategic planning for future regenerative endodontic treatment. (J Endod 2011;37:1536-1541)