Material components may use tubules as ______ to pulp?

• A. Barriers
• B. Reservoirs
• C. Conduits
• D. Sinks

Answer: (C)

Tubinal dentin tubules run from the outer dentin surface toward the pulp, forming open channels that substances can travel through. When material components are in contact with exposed dentin or can diffuse through the dentin, these tubules provide a pathway to the pulp. In other words, they act as conduits, allowing diffusion of fluids, solvents, monomers, or even bacteria toward the pulpal tissue. This is why sealing dentin and controlling permeability is a key part of biocompatibility: it limits the movement of potentially irritating substances to the pulp. The other options describe roles that don’t match this channel-like function—barriers would block movement, reservoirs would store material, and sinks would remove material—whereas tubules specifically serve as passages.