The effect of disinfecting solutions on the dimensional stability of dental alginate impression materials

Objectives ional changes occur in set dental alginate impression materials when immersed in disinfecting solutions. In this contribution the dimensional changes of two alginates in two disinfecting solutions, and for two specimen thicknesses, have been studied. The results were analyzed theoretically. s mensional changes of two commercial alginates (Blueprint Cremix and Hydrogum), have been measured, in distilled water and two disinfecting solutions (Perform ID/sodium hypochlorite), using a traveling microscope, at 5 min intervals over a period of 1 h. Samples of simple geometry have been studied, namely rectangular strips with thicknesses of 1.5 and 3 mm, respectively. s cases, both alginates continuously shrank with time, in the three immersion liquids, over the hour of measurement, indicating transfer of water from the alginate into the external water or disinfecting solution. The t1/2 shrinkage plots were generally linear, but with an intercept on the t1/2 axis, indicating the possibility of an initial expansion at very short times. In most cases, the ratios of slopes for both thicknesses were 1.33–1.54, in contrast to the theoretical value of 2. Perform ID however gave anomalous results for the 1.5 mm thick samples. At 10 min their shrinkage was 1.34–1.72%, compared with −0.42% to 0.67% in the other two media. icance fects of thickness observed were not in accord with simple Fickian theory because of the various ions diffusing into and out of the alginate. Moreover, the water content of the alginate decreased consequent on the cross-linking process.