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

From left to right: Enamel with fine striation (composition of enamel rods or prisms); darker zones almost perpendicular to the striation are the incremental lines (Retzius) due to successive apposition of layers of enamel as the crown is formed. Dentinoenamel junction is shown as a narrow fissure from top to bottom. Superficial dentin in the crown with S-shaped course of the dentinal tubules that passes uninterrupted through the irregular black structures (due to filling with air) representing hypocalcified areas interglobular areas of interglobular dentine). Mineralization of dentin starts in small globular areas normally fusing in uniformly calcified dentin. If fusion does not take place hypomineralized regions remain between these globular areas localized in line (Owen's line).