Representative photomicrographs demonstrating root resorption of the mesial root of the maxillary first molars. Photomicrographs (×40 H & E) of the mesial root of the upper right first molar from the experimental groups (sham, collagen, EGF and NGF) and a representative photomicrograph of the upper left first molar mesial root (control). No root resorption was noted in the control while all experimental groups showed resorption defects of varying extent (blue arrows). Resorption was particularly severe in the experimental teeth involving a collagen membrane (collagen, EGF and NGF). Ankylosis was not detected in the histology sections assessed from any group.