Cavity preparation may section tubules in which orientation?

• A. Longitudinal
• B. Cross-section
• C. Diagonal
• D. Circular

Answer: (A)

Dentin tubules run from the pulp toward the outer dentin surface, forming channels that extend along the tooth’s internal axis. When a cavity is prepared, the cutting action tends to follow that axis, so the bur encounters tubules along their length rather than across their diameter. This results in a longitudinal section of the tubules.

If the cut were perpendicular to the tubule direction, you’d see cross-sections, and a perpendicular cut would reveal circular openings. A diagonal orientation would be less representative of the typical tubule exposure created by standard cavity prep.

So, because dentin tubules align with the tooth’s internal axis and cavity preparation generally runs parallel to that axis, the tubules are most often sectioned longitudinally.