Study of the physical properties of type IV gypsum, resin-containing, and epoxy die materials

Statement of problem. Little published information is available comparing t he properties of recently developed resin-modified gypsum and epoxy! resin die materials, which are claimed to bt: superior to conventional type IV gy psum die materials. Purpose. This study compared the properties of 3 new die materials and 2 co nventional type IV gypsum products. Methods and material. The linear dimensional change, detail reproduction, s urface hardness, al,abrasion resistance, and transverse strength of 2 recen tly introduced, resin-modified gypsum die materials (Resinrock and Mileston e), a new epoxy resin die material (Epoxy-Die), and 2 conventional type: IV gypsum die materials (Silky-Rock and Die-Stone) were studied. Results. All gypsum products expanded, whereas the epoxy resin material con tracted during setting. The epoxy resin exhibited. much better detail repro duction, abrasion resistance, and transverse strength than the gypsum mater ials, which were similar in these properties. A conventional type IV gypsum exhibited the highest surface hardness, whereas the epoxy resin had thr lo west value. Conclusion. The resin-modified gypsum products were not significantly super ior to the conventional type IV gypsum die materials. In general, the epoxy resin exhibited the best properties of the materials studied; however, its setting shrinkage may necessitate alterations in technique to achieve well -adapted castings.