Dimensional stability of newer alginate impression materials over seven days

The aim of this study was to determine the dimensional stability of the so called '5 day stable' alginates. Ten specimens each of three alginate materials were prepared using a standardised impression technique and a typodont model. Travelling microscope measurements were recorded for six distances at 24 hour intervals. SEM and EDX analysis was undertaken. Changes in dimension over time and differences between materials were tested using analysis of variance. 95% confidence intervals were calculated for the percentage change for comparison with a target of 1.5% based on the ISO Standard. Statistically significant dimensional changes were observed in some measured distances for all materials, but only six out of fifty four distances measured at 1, 5 and 7 days in three materials showed 95% confidence intervals that included the 1.5% ISO standard. There were no statistically significant differences in the proportional change between the three materials. The three materials showed similar appearance under SEM and similar composition by EDX analysis. It is concluded that all materials demonstrated good dimensional stability over the recommended maximum of 5 days.