What base requires cavity varnish underneath it for pulp protection?

The base that requires cavity varnish underneath it for pulp protection is Zinc Phosphate. This material is known for its excellent mechanical properties but can be irritating to the pulp due to its acidity when initially mixed. To provide protection for the pulp and prevent potential irritation from the Zinc Phosphate base, a cavity varnish is applied. This varnish acts as a barrier, sealing the tooth structure and providing an additional layer of protection that can help to mitigate any harmful effects associated with the acidic nature of the Zinc Phosphate material.

In contrast, other materials like Calcium Hydroxide, Glass Ionomer, and Resin-modified Glass Ionomer have properties that either do not require additional protection or may even have inherent benefits for pulp health. Calcium Hydroxide is used for its pulp-capping properties due to its ability to promote regeneration and healing of the pulp. Glass Ionomer and Resin-modified Glass Ionomer also bond chemically to tooth structure and are less irritating to pulpal tissue, providing good support without necessitating a varnish underneath.