Jarvis R G, Earnshaw R
Aust Dent J. 1980 Dec;25(6):349-56. doi: 10.1111/j.1834-7819.1980.tb03894.x.
The surface of cast gypsum which has set against alginate impression material has been shown to vary according to the specific impression material used. The variation is both physical and chemical. Poor cast surfaces have been shown to consist completely of unreacted calcium sulphate hemihydrate to a depth of at least 80 micrometer. The best cast surfaces consist of considerable amounts of syngenite (potassium calcium sulphate), along with a small amount of gypsum and unreacted hemihydrate. Cast surfaces with a lower syngenite content were intermediate between these two extremes. No cast surfaces which had set against any alginate impression exhibited complete conversion of hemihydrate to gypsum, which characterized the surface formed when the same gypsum products set against Teflon. Although dental stones may contain a small amount of a potassium salt as an accelerator, it was shown that this amount does not significantly alter gypsum surfaces cast against alginates. The potassium ions involved in the setting reaction to form syngenite clearly enter the cast at its interface with the impression, presumably by way of an exudate from the gelled impression.
已证实，与藻酸盐印模材料贴合凝固的铸型石膏表面会因所用特定印模材料的不同而有所变化。这种变化既有物理方面的，也有化学方面的。已表明，质量差的铸型表面在至少80微米的深度内完全由未反应的半水硫酸钙组成。最佳的铸型表面含有大量的钾石膏（硫酸钾钙），以及少量的石膏和未反应的半水合物。钾石膏含量较低的铸型表面处于这两个极端情况之间。与任何藻酸盐印模贴合凝固的铸型表面均未出现半水合物完全转化为石膏的情况，而这是相同石膏产品与特氟龙贴合凝固时形成的表面的特征。尽管牙科石膏可能含有少量钾盐作为促凝剂，但已表明，这一含量不会显著改变与藻酸盐贴合凝固的石膏表面。参与形成钾石膏的凝固反应的钾离子显然是在铸型与印模的界面处进入铸型的，大概是通过凝胶化印模渗出的液体进入的。
