Representative photomicrographs demonstrating pulpal appearance of the mesial root of the maxillary first molars. Photomicrographs (×100 H & E) of the pulp chamber from the mesial root of the upper left first molar (control) and upper right first molar of the experimental groups (sham, collagen, EGF and NGF). Note the normal appearance of the control with a well-vascularised pulp (red arrows) and well-defined odontoblastic layer (white arrows). Vascularisation in the experimental groups is reduced compared to the control, especially for the collagen and NGF groups, with the EGF group showing improved vascularisation compared to other groups involving a collagen membrane. An odontoblastic layer is present in the sham, EGF and NGF groups, although these are not at as well defined as the control group. The pulp of the collagen group had lost this odontoblastic layer and was found to contain extensive inflammatory regions (black arrow) and even some hard tissue formation (blue arrows). EGF and NGF groups also had increased inflammatory cell infiltrate (black arrows), while the EGF group had signs of hard tissue formation (blue arrow). However, the pulpal architecture and cell organisation in the NGF group more closely resembled that of the control group compared to the other experimental groups involving a collagen membrane (collagen and EGF groups).