What is the purpose of placing a liner under a restorative material?

• A. To protect the pulp from thermal irritation and chemical irritants, and to reduce microleakage.
• B. To color the tooth for aesthetics.
• C. To shorten chair time.
• D. To increase adhesion strength.

Answer: (B)

Placing a liner under a restorative material mainly serves to protect the pulp and help seal the prep area. It acts as a buffer against thermal irritation from hot and cold substances and against chemical irritants from saliva, acids, or the restorative itself. By adding a barrier over exposed dentin and helping to seal dentinal tubules, the liner can reduce microleakage, which lowers the risk of postoperative sensitivity and secondary decay. Some liners also release therapeutic ions (like calcium or fluoride) that support pulp health and dentin remineralization. Coloring the tooth is not a function of the liner—shade and esthetics come from the restorative material itself. Liners aren’t used to shorten chair time and they don’t primarily increase adhesion strength; bonding systems and preparation techniques govern adhesion.