A 65-year-old male wants a denture made for him. Intraoral examination reveals edentulous arches with firm ridges and good alveolar height. The impression is made with ZOE and the patient reports a burning sensation. The cause of the sensation may be:
One of the chief disadvantages of the ZOE pastes is the possible stinging or burning sensation caused by the eugenol as it leaches out and contacts soft tissues. Zinc oxide can react with various carboxylic acids and form ZOE-like  materials. Orthoethoxybenzoic  acid (EBA) is a valuable substitute for eugenol in this regard. Bactericidal agents and other medicaments can be incorporated without interfering with the reaction.
Key Concept: One of the chief disadvantages of the ZOE pastes is the possible stinging or burning sensation caused by the eugenol.
Reference: Phillips’ science of dental materials / Kenneth J. Anusavice, Chiayi Shen, H. Ralph Rawls.—12th ed.Page no 179
Eugenol
Orthoethoxybenzoic acid
Calcium chloride
Lead dioxide