Which of the following show chemical bond with enamel (calcified tissues)?
(A) Composites (B) Direct filling resins (C) Polycarboxylate cements (D) BIS-GMA resins in pit and fissure sealants
(C) When the powder and liquid are mixed, the surface of powder particles are attacked by the acid, releasing zinc, magnesium and tin ions. These ions bind to the polymer chain via the carboxyl groups. They also react with carboxyl groups of adjacent polyacid chains to form cross-linked salts. Structure of set cement the hardened cement consists of an amorphous gel matrix of zinc polyacrylate in which unreacted powder particles are dispersed.
Key concept:-
Zinc polycarboxylate cement was the first dental cement to exhibit chemical bonding to teeth, marking an improvement over the mechanical bonding of zinc phosphate cement. Zinc polycarboxylate cement is not used for restorative purposes because the cement is opaque.
Ref: Phillips Ed 12th P: 318