What property of zinc-oxide-eugenol makes it unsuitable for use under glass ionomer and composite?

Zinc-oxide-eugenol (ZOE) is known for its soothing properties towards the pulp when used as a temporary restorative material or as a base under permanent restorations. However, one of its significant characteristics that makes it unsuitable for use under glass ionomer and composite materials is its potential to irritate the pulp.

When ZOE is placed beneath these types of restorations, particularly glass ionomer and composite, the eugenol present in the formulation can interfere with the setting reaction of these materials and may lead to pulp irritation. Glass ionomer and composite materials rely on a bonding mechanism that can be compromised by the presence of eugenol, which can cause postoperative sensitivity or reactions in the underlying dental pulp.

The other properties of ZOE, such as its setting time and thermal conductivity, have less relevance when discussing its compatibility with glass ionomer and composite. Its ability to provide no bonding strength can be a concern, but not directly for the basis of pulpal health. Therefore, the potential to irritate the pulp is the key reason that limits the use of ZOE under such materials.