Pulp Regeneration Concepts for Nonvital Teeth: From Tissue Engineering to Clinical Approaches.

Following the basis of tissue engineering (Cells-Scaffold-Bioactive molecules), regenerative endodontic has emerged as a new concept of dental treatment. Clinical procedures have been proposed by endodontic practitioners willing to promote regenerative therapy. Preserving pulp vitality was a first approach. Later procedures aimed to regenerate a vascularized pulp in necrotic root canals. However, there is still no protocol allowing an effective regeneration of necrotic pulp tissue either in immature or mature teeth. This review explores in vitro and preclinical concepts developed during the last decade, especially the potential use of stem cells, bioactive molecules, and scaffolds, and makes a comparison with the goals achieved so far in clinical practice. Regeneration of pulp-like tissue has been shown in various experimental conditions. However, the appropriate techniques are currently in a developmental stage. The ideal combination of scaffolds and growth factors to obtain a complete regeneration of the pulp-dentin complex is still unknown. The use of stem cells, especially from pulp origin, sounds promising for pulp regeneration therapy, but it has not been applied so far for clinical endodontics, in case of necrotic teeth. The gap observed between the hope raised from in vitro experiments and the reality of endodontic treatments suggests that clinical success may be achieved without external stem cell application. Therefore, procedures using the concept of cell homing, through evoked bleeding that permit to recreate a living tissue that mimics the original pulp has been proposed. Perspectives for pulp tissue engineering in the near future include a better control of clinical parameters and pragmatic approach of the experimental results (autologous stem cells from cell homing, controlled release of growth factors). In the coming years, this therapeutic strategy will probably become a clinical reality, even for mature necrotic teeth.