Dimensional changes in alginate impression during immersion in a disinfectant solution

To determine the effect of a commercially available disinfectant solution (Perform ID) on the dimensional stability of two different commercially available alginate impression materials.

Linear changes in standardized impression samples (1.5 mm & 3.0 mm thickness) made in two commercial alginates were recorded at 5 minute intervals, over a period of an hour after immersion in a disinfectant. The alginate impression samples were prepared placing the alginate mixes into a wax mould. After the material had set, each of the samples was removed from the mould. It was then placed in a Polytetraflouroethylene (PTFE) trough before measuring the dimensional changes using a Chesterman travelling microscope.

3mm BluePrint Cremix showed greater shrinkage than 3mm Hydrogum. While, 1.5mm Hydrogum appeared to have uniformly greater shrinkage as compared to 1.5mm BluePrint Cremix. There was significant difference between 1.5 and 3mm thicknesses of both Hydrogum and BluePrint Cremix (PAIRED SAMPLE t test p < 0.05). The 1.5mm samples showed much higher shrinkage than 3mm samples.

Immersion of the alginates in the same disinfectant showed variable linear shrinkage indicating that slight changes in composition could lead to variable results. In addition, there were significant differences in the linear shrinkage between the two thicknesses of the same alginate material; this indicates the possibility of distortion in actual impressions where the geometry is complex.