FGF2 and necrosis: Exogenous growth factors have also been used to produce synergistic effect with autologous growth factors in REPs.24,43 Collagen scaffolds loaded with human recombinant platelet‐derived growth factor (rPDGF) have successfully promoted root maturation in an immature tooth with pulp necrosis.43 And a clinical trial demonstrated that injectable hydrogel scaffolds impregnated with basic fibroblast growth factor (bFGF) achieved apical healing and continued root development in teeth with pulp necrosis.44