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) po wder:liquid ratio and (b) relative amounts of cement on the extent of buffe ring of a lactic acid storage solution using zinc polycarboxylate and glass -ionomer cements (both water-activated). The effect of varying the powder:l iquid ratio was found to be slight and not statistically significant. On th e other hand, increasing the numbers of specimens in a given volume of stor age 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 no t affect the final pH led to the conclusion that attack occurs mainly at th e matrix of these cements, confirming previous findings about the acid eros ion process. The finding that increasing the relative amount of cement to a cid storage solution strongly influenced pH suggested that, under clinical conditions, buffering would be important. When five specimens were used, th e final pH corresponded to that of arrested caries, from which it was concl uded that these cements have the ability to be cariostatic in vivo.