Erosion process of polycarboxylate cements in organic acids.

The amounts of Zn and Mg eluted from the zinc polycarboxylate cement into acetic, lactic and citric acids increased with an increase in the formation constant of the acid-Zn or -Mg complexes. The erosion process consisted of two processes, namely, dissolution of the unreacted cement powder and decomposition of the matrix. The matrix was remarkably eroded by 0.01M citric acid which formed stable complexes with Zn and Mg. Erosion of the matrix took place with the exchange reaction between H+ ion in the acid and Zn2+ or Mg2+ in the matrix.