Fig 1.

Diagrams of the cell transplantation and cell-free approaches. (a) In the cell transplantation approach, stem/progenitor cells are placed into root canals in the form of cell-seeded scaffolds. The transplanted cells are thought to participate in the regeneration process not only by supplying cells per se but also by providing growth factors released from the transplanted cells as trophic factors. (b) In the cell-free approach, scaffolds impregnated with growth factors are injected into root canals to induce the migration, proliferation, and differentiation of endogenous stem/progenitor cells residing around the apex of a root.