0.5-1 mm dentin cavity should be ______ to reduce thermal conductivity and microleakage.

• A. Lined
• B. Sealed
• C. Coated
• D. Covered

Answer: (A)

Lining the cavity introduces a thin protective layer between the dentin and the restoration, which serves two important roles in a 0.5–1 mm dentin thickness. First, it reduces heat transfer to the pulp by adding an insulating barrier, helping to prevent thermal injury from hot or cold stimuli. Second, it helps seal the dentin and tubules, lowering the chance of fluid and bacterial leakage into the restoration—i.e., microleakage. In this depth of dentin, placing a liner (often with pulp-protective materials like calcium hydroxide or a glass ionomer liner) is the standard way to provide both thermal protection and a barrier to leakage. Sealing, coating, or covering alone do not establish the same dedicated pulp-protective liner layer needed in this scenario.