What materials can be used as bases or liners?

• A. Glass ionomer
• B. Zinc oxide
• C. Calcium hydroxide
• D. All of the above

Answer: (A)

Bases and liners should protect the pulp, seal dentin, and provide some insulating support under a restoration. Glass ionomer is best here because it bonds chemically to tooth structure, releases fluoride which can help resist decay, and can function in both roles—applied as a thin liner directly over dentin or as a thicker base to add insulation and support. Zinc oxide by itself isn’t used as a base or liner (it’s typically part of a cement formulation, not a standalone liner/base). Calcium hydroxide is mainly used as a liner to encourage dentin repair and pulp protection, but it lacks the strength needed for a base. So glass ionomer is the material that can serve as both a base and a liner.