Factors affecting the ability of dental cements to alter the pH of lactic acid solutions.

Two related studies have been carried out to determine the effect of (a) powder:liquid ratio and (b) relative amounts of cement on the extent of buffering of a lactic acid storage solution using zinc polycarboxylate and glass-ionomer cements (both water-activated). The effect of varying the powder:liquid ratio was found to be slight and not statistically significant. On the other hand, increasing the numbers of specimens in a given volume of storage solution was found to have a significant influence on the final pH (at the 0.0005 level of significance). The fact that powder:liquid ratio did not affect the final pH led to the conclusion that attack occurs mainly at the matrix of these cements, confirming previous findings about the acid erosion process. The finding that increasing the relative amount of cement to acid storage solution strongly influenced pH suggested that, under clinical conditions, buffering would be important. When five specimens were used, the final pH corresponded to that of arrested caries, from which it was concluded that these cements have the ability to be cariostatic in vivo.