Abstract
The effects of additives in reversible (agar) impression materials and gypsums on the compatibility of both materials were investigated. Based on a pure 9% agar material, six types of agar impression materials including ones that contained no additive, 0.5% benzalkonium chloride, 0.3% potassium sulfate, 0.5% starch, 0.1% borax and 0.3% potassium sulfate +borax were respectively prepared. Pure gypsum was mixed with distilled water or solutions of 0.3% potassium sulfate and 0.3% potassium sulfate +0.01% sodium citrate. The surface roughness of stone models obtained from the agar and agar/alginate combined impressions was measured. As a result, borax in agar was the main cause of the incompatibility of agar impression with gypsum. The addition of potassium sulfate with borax improved the incompatibility of both impressions with gypsums mixed with any solution.
