Which cement is irritating to the pulp?
(A) Carboxylate cement (B) Zinc oxide-eugenol cement (C) Zinc phosphate (D) Ethoxybenzoic acid
(C) The phosphoric acid in the liquid makes the mixture quite acidic and therefore cytotoxic, when a prosthesis is luted with this cement on a prepared tooth. As setting occurs, the acidity is partially neutralized, but the cement remains acidic after 24 hours, with the pH rising from about 3 to about 6. For thin layers of dentin, a cavity liner (i.e.,Ca2) is recommended to prevent an adverse pulpal response from the pressure of luting, which forces acid into the pulp tissue. Younger patients are especially susceptible, because they have a more open dentin tubule area, whereas older patients with sclerotic dentin will have a more tortuous path that restricts the penetration of acid toward the pulp.
Key concept​​ :
pH of the cement
The acidity is high at the time of insertion due to phosphoric acid. At the time of cementation, the pH is 2 (approx.). As time passes, the acidity reduces. By the end of 24 hours, the pH is 5.5, which is still in the acidic range (neutral value is 7).
Pulpal response: The pulp response may be classified as moderate.