Dentinoenamel junction in the tooth - human, adult. Thin ground section of crown.

From left to right: Superficial dentin (bluish) in the crown with S-shaped course of dentinal tubules; They pass uninterrupted through the irregular black structures (due to filling with air) representing hypocalcified areas (interglobular dentin); Mineralization of dentin starts in small globular areas normally fusing in uniformly calcified dentin. If fusion does not take place hypomineralized regions remain visible as the mentioned black structures; Dentinoenamel junction is shown as a narrow scalloped dark fissure from top to bottom. Enamel (brownish)with fine striation (composition of enamel rods or prisms); darker stained zones with oblique course are the incremental lines (striae of Retzius) due to successive apposition of layers of enamel as the crown is formed.