A Preliminary Study on pH Changes of Storage Solution and Weight Changes of Ionomer Cements: Influence of Phosphate Content

Abstract

This in vitro study was carried out to investigate the impact of varying phosphate fractions on pH changes of storage solution of artificial saliva and weight changes for four experimental ionomer cements at specific time intervals. Three disc-form specimens for each composition were prepared, weighed-out (initial weight = W0) and then immersed individually in 10 ml of artificial saliva (initial pH = 6.5) for the experimental periods at 37oC. At 7, 14 and 28 days, the final pH values of artificial saliva solutions were measured using a pH electrode meter. The discs were immediately collected, dried and re-weighted (final weight = W1) to calculate the weight changes by percentage. All tested cements were bringing the pH slightly down towards the acidity level after 7 days, and then the values became relatively stable when the time progressed further up to 28 days. As well, the data showed that the less phosphate was added to the basic ionomer glasses, the less in fluence on pH rate was evaluated. A linear relationship between the pH values as a function of phosphate content was obtained at all time points. In terms of weight changes, there was a moderate increase in the mass during the entire experimental period. The extent of the changes in pH values of artificial saliva and in specimen's weights led to the conclusion that the ionomer glass components have a crucial role in controlling the material behaviour. Further studies have to be done