Abstract
The purpose of this study was to detect the effects of additives in gypsum products and hydrocolloid impression materials, which tend to retard the setting of gypsums, on the compatibility of gypsum with hydrocolloid impressions.A type IV gypsum powder was mixed with the solutions of 0.03% sodium citrate, 0.3% borax and 0.5% sodium phosphate, and poured into agar, agar/alginate combined and alginate impressions.Surface roughnesses(Ra)of the stone models were measured.The stone surfaces were also observed with a scanning electron microscope.Mixing with sodium citrate increased the Ra in large for the stone models obtained from the agar impression, though it only slightly affected stone models obtained from other impressions.Borax was the main cause of the incompatibility of gypsum with agar and agar/alginate combined impressions.Sodium phosphate increased the Ra of models obtained from the alginate impression.
