What are the histological features of dentin at the dentinoenamel junction (DEJ)?

• A. The DEJ is a scalloped interface where dentin and enamel meet; dentinal tubules extend to the DEJ and enamel prismatic structure meets the dentin.
• B. The DEJ is a flat, layer-like line with no tubules reaching it.
• C. The DEJ contains enamel tubules extending into dentin.
• D. The DEJ is a gap between enamel and dentin leading to unmineralized tissue.

Answer: (A)

The dentinoenamel junction is a scalloped, interdigitated border where dentin and enamel meet. This wavy interface results from the inward extensions of dentin (and its tubules) and the outward fold of enamel prisms, creating more surface area for a strong seal between the two tissues and better distribution of masticatory stresses. Dentinal tubules run from the pulp toward the DEJ and approach it closely, while enamel consists of prisms that terminate at this junction and meet dentin along the scalloped edge. There is no gap or unmineralized tissue at the junction, and enamel tubules do not extend into dentin. This combination of a scalloped border with dentin tubules near the junction and enamel prisms meeting dentin describes the histology at the DEJ.