Which materials require copal varnish before placement in a tooth?

Copal varnish is used as a sealing agent applied to the dentin surfaces of a prepared tooth before the placement of certain dental materials. It serves the purpose of reducing postoperative sensitivity and preventing the penetration of microleakage beneath restorative materials.

In the context of the choices provided, amalgam and zinc phosphate cement are the materials that typically require copal varnish due to their interactions with dental tissues. Amalgam, when placed directly onto dentin, can create a sensitivity issue due to its reaction with the oral environment. The copal varnish acts as a barrier, protecting the exposed dentin and reducing potential irritation.

Zinc phosphate cement, while it is a reliable cement for many applications, can also be acidic and may be detrimental to the pulp if placed directly on dentin. Therefore, using copal varnish before applying it helps mitigate this risk.

This combination of materials supports the need for a protective layer, making varnish an appropriate choice in this case. Understanding the characteristics of these materials and the need for copal varnish is crucial for ensuring patient comfort and the longevity of the restoration.