Compared with the tubule density near the DEJ, tubule density near the pulp is

• A. lower
• B. higher
• C. the same
• D. variable

Answer: (B)

Tubules in dentin run from the pulp outward toward the dentin–enamel junction, and their number and size are greatest near the pulp. Odontoblast processes are most abundant at the pulp, and as dentin forms toward the DEJ, tubules become fewer and more constricted due to the deposition of peritubular dentin. This creates a higher tubule density near the pulp than near the DEJ. The increased number of diffusion pathways near the pulp also means substances and stimuli can more readily reach the pulp tissue in that region. In aging or sclerotic dentin, some tubules may occlude, reducing apparent density, but the typical pattern is a higher density near the pulp.