Diffusion of resin components to the dental pulp occurs through which structures?

• A. Dentin surfaces
• B. Enamel rods
• C. Tubules
• D. Odontoblast processes

Answer: (C)

Diffusion of resin components to the dental pulp travels through the dentinal tubules—the microscopic channels that run from the pulp to the dentin surface and are filled with dentinal fluid. This tubule network provides the conduit for molecules to move toward the pulp, and near the pulp these tubules contain odontoblast processes that extend into them. Enamel rods and the enamel itself do not form a diffusion pathway to the pulp because enamel is highly mineralized and largely avascular, with no tubules connecting to the pulp. Odontoblast processes are located inside the tubules and aren’t separate routes; the primary route is the tubules themselves.