Linear dimensional change, compressive strength and detail reproduction in type IV dental stone dried at room temperature and in a microwave oven

Abstract

The type IV dental stone is widely used for the fabrication of dyes and master casts for fixed and removable partial prostheses. It is typically normal to wait at least 24 hours for the casts to dry prior to beginning the laboratory procedures. The waiting time has been shown to be greatly reduced by using microwave drying.ObjectiveThis study evaluated the influence of drying techniques at room temperature and microwave oven on the linear dimensional change, compressive strength and detail reproduction in type IV dental stones. Material and MethodsThree type IV dental stone brands were selected; Elite Rock, Shera Premium and Durone IV. Two different drying protocols were tested in 4 groups (n=10); G1 - room temperature (25±4ºC) dried for 2 hours; G2 - room temperature dried for 24 hours; G3 - room temperature dried for 7 days and G4 - microwave oven dried at 800 W for 5 minutes and after 2 hours at room temperature. After drying, the samples were assayed for dimensional charges. The sample surface was submitted to the ImageTool 3.0 software for compressive strength in a universal testing machine with a cell load of 50 KN at a crosshead speed of 0.5 mm/minutes and the detail reproduction was analyzed with a stereomicroscope at 25x magnification. The statistical analysis of the linear dimensional change and compressive strength data were conducted by the ANOVA test followed by the Tukey test (p<0.05). Detailed reproduction values were reported in percentages. ResultsFor the compressive strength test, Elite Rock and Durone IV did not present significant differences between G2 and G4, while Shera Premium did not present differences between G3 and G4. The best reproduction levels were observed for G3. ConclusionsDental stone microwave oven drying showed a linear dimensional change similar to after room temperature drying for 24 hours and 7 days. The compressive strength of the stone dried in the microwave oven was similar to those dried at room temperature for 24 hours, with the exception of Shera Premium, which had similar results for microwave and room temperature drying for 7 days. For the microwave drying method the detail reproduction levels for samples dried at room temperature for 24 hours and 7 days were similar, except for the Durone IV.

Influence of different water types on the physical and mechanical properties of gypsum

“…type IV than for type V gypsum, as expected, because this material has high setting expansion 4 . The mean dimensional change to Durone IV was 0.032 mm in a study that analyzed the effect of dry gypsum specimens at room temperature (25±4 ºC) for 2 h 16 . In the present research, approximate values were also found to Durone IV specimens after 10 min of water/gypsum mix at room temperature.…”

Effect of Different Energy Levels of Microwave on Disinfection of Dental Stone Casts

“…Low to medium energy levels are suggested to be safer than higher levels by some researchers, 20,21 while others claim the preservation of certain properties of the stone by drying at energy levels as high as 800 W. 26 Early irradiation of wet stone casts after pouring results in early drying, thus preventing the completion of the crystallization process and weakening the cast, a fact which is masked by the temporary strengthening as a result of immediate drying caused by irradiation. The assessment of the cast properties after 24 or 48 hours would reveal such severe decrease in the strength of the cast.…”

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“…Scalar energy discovery attributed to the jams clerk Maxwell, and it is non-linear, non-hertzian field-like circles, fills environment, stationary from of energy, ((energy that develop and formed by two similar frequencies coming from opposite directions meet, they cancel each other out, and the energy result usually called stationary [8][9][10].…”