Scaffold-based and Scaffold-free Strategies in Dental Pulp Regeneration.

Regenerative dentistry has come a long way from pulp capping to pulp regeneration research, which aims to regenerate the pulp-dentin complex and restore its functions compromised by pulp injury and/or inflammation. Because of unique anatomic limitations of the tooth structure, engineering a suitable microenvironment that facilitates angio/vasculogenesis and innervation is a challenging task. Cell-based tissue engineering approaches have shown great potential in achieving this goal. Biomedical approaches in creating a regenerative microenvironment are mainly represented by either scaffold-based or scaffold-free strategies. The scaffold-based strategy mainly relies on the use of biomaterials to create a structural base that supports cells throughout the process of tissue formation. The scaffold could be a classic 3-dimensional construct with interconnected pores, a hydrogel with cells embedded in it, or a combination of these 2. The scaffold-free approach has been considered a bottom-up strategy that uses cell sheets, spheroids, or tissue strands as building blocks. The outcome of this strategy relies on the capacity of these building blocks to secrete a favorable extracellular matrix and to fuse into larger tissue constructs. Both the scaffold-free and scaffold-based systems are required as complementary, rather than competing, approaches for pulp regeneration. A combined synergetic strategy, through which multicellular building blocks could be integrated with robust 3-dimensional scaffolds, might represent an optimal solution to circumvent some of the major drawbacks of the current methods in pulp regeneration while concurrently fostering their advantages.