Figure 2. Histology and immunohistochemistry of a 25-week implant. (A) High-magnification photomicrograph (400X) of ameloblasts present in a bioengineered tooth crown on an H&E-stained section. (B) H&E stain of decalcified enamel from a positive control porcine third molar (200X). (C) Amelogenin expression (arrow) in decalcified enamel of a bioengineered tooth crown (200X). (D) Negative pre-immune control for amelogenin (200X). (E) Goldner’s stain of bioengineered tissues revealing enamel matrix (bright red) and bone and dentin (blue-green) (200X). (F) Collagen type I expression in odontoblasts and dentin in bioengineered tissues. Positive brown stain for collagen type I is indicated by the arrow (400X). (G) Negative pre-immune control for collagen type I (400X). (H,J) Bone sialoprotein (BSP) expression in odontoblasts (H) and dentin (J) in 25-week bioengineered tissues (400X). Positive brown stain for BSP is indicated by the arrows. (I,K) Negative pre-immune controls for BSP (400X). Abbreviations as in Fig. 1 and: e, decalcified enamel; am, ameloblast; od, odontoblast; p, pulp.