Fig. 5

Histobacteriological analyses of root canals with unsuccessful pulp regeneration. A–F Residual bacteria in the periapical legion detected by gram staining. Gram-negative bacteria (arrows) G, H H-E staining. A–C model A. D–F model B. A, B Outer root surface of cementum (Ce). C, D Periapical lesion (Pa). E, F Periodontal ligament (PdL). G External resorption (arrows) in model B. H Healing of external resorption with formation of cementum (arrow) in model B