Comparative evaluation of few physical properties of epoxy resin, resin-modified gypsum and conventional type IV gypsum die materials: an in vitro study.

AIM: To compare and evaluate few physical properties of epoxy resin, resin-modified gypsum and conventional type-IV gypsum die material. MATERIALS AND METHODS: In the present study, dimensional accuracy, surface detail reproduction and transverse strength of three die materials like epoxy resin (Diemet-E), resin-modified gypsum (Synarock) and conventional type-IV gypsum (Ultrarock) are analyzed. For dimensional accuracy, master die (Bailey's die) is used and calibrations were made with digital microscope. For surface detail reproduction and transverse strength, rectangular stainless steel master die (Duke's die) was used and calibrations were made with Toolmaker's microscope and Instron universal testing machine respectively. One-way analysis of variance (ANOVA) was performed on the means and standard deviation for groups of each test. RESULTS: The results of the study showed statistically significant difference among these materials in dimensional accuracy, surface detail reproduction and transverse strength. CONCLUSION: Epoxy resin exhibited superiority in dimensional accuracy, surface detail reproduction and transverse strength and is nearest to the standards of accurate die material.

Development of noncarcinogenic ring liner for dental casting and its basic properties.

Although ceramic fiber is widely used in ring liners for dental casting, its carcinogenicity is a matter of concern. We investigated the use of noncarcinogenic biosoluble fiber for ring liners. Plate-shaped biosoluble fiber was modified to obtain the same setting expansion as that of a commercial ring liner as a prototype, and we subjected it to scanning electron microscopic observation, energy-dispersive X-ray spectrometry, X-ray diffraction, and a tensile test. The main components of the prototype were Mg, Si, and O and those of the commercial sample were Al, Si, and O. The prototype and commercial samples were mostly amorphous when not heated, and crystalline components were observed after heating. The tensile strength was significantly different between the prototype and commercial samples, but the difference was small and not problematic with regard to the ring liner strength.

[Characterization of homemade fast investment material for the IPS-Empress2 castable ceramic].

The aim of this study is to evaluate the physical and mechanical properties of our homemade investment material for the IPS-Empress2 castable ceramic. The IPS specific investment material was taken as control. Results show that the setting time, density before heating, density after heating, rate of open hole, compressive strength at 2 hours after setting and the compressive strength after heating to 920 degrees C of the homemade investment material are 9 minutes, 1.813 g/cm3, 1.402 g/cm3, 38.1%, 5.42 MPa and 8.37 MPa respectively, which are comparable or even better than the specific material. Under the SEM, the crystals of the phosphate hydrate in our homemade material are smaller than those in the special material. Since the physical and mechanical properties of our homemade investment material are comparable or superior to those of the specific material, a conclusion is drawn that it has a promising prospect of future clinical application.