Fig. 5

EAP in rats causes loss of bone structures and disorganized roots. a–c Representative H&E staining of the distal apical region of rats’ mandibular first molar with or without the induction of EAP. a Two weeks after induction, widened PDL (double arrow) and increased bone (black asterisk) are indicated. b Four weeks after induction, bone loss (red arrow) was found around the distal root. c Six weeks after induction, dramatic bone loss occupied the mesial and distal apical area (red arrow), thin root canal wall (white asterisk) and increased bone-like cementum tissue (red dotted line). Bone marrow (black arrow) was decreased, and blood vessels were increased (blue asterisk). d Representative TRAP staining on the root wall 4 weeks after induction. The root wall was thinner (double arrow), with resorption pits (red arrow). e Representative Masson trichrome staining of the apical area 6 weeks after induction. The collagen fibres were increased and thickened (red arrow). The cementum area was enlarged (yellow asterisk). Bone surface, grey dotted line; m, mesial; d, distal; dr, distal root (black dotted line); f, furcation area. Green/blue dotted boxes are shown at higher magnification below. Scale bar: 100 µm