RESUMO
The aim of this work was to estimate the internal friction of dental gypsum products by measuring their loss factor with the use of the peak-amplitude method of vibration analysis. Cylindrical specimens for the measurement of compressive strength and rectangular specimens for the measurement of loss factor were constructed from plaster, dental stone, and high-strength dental stone. The loss factor was measured by vibrating specimens up to their resonance frequency, where the peak-amplitude method was applied. It was found that the peak-amplitude method is a simple, quick, and reliable method for measuring the loss factor of dental gypsum products. Furthermore, it was also found that the drying process of these materials reduces their internal friction and hence lowers the loss factor, whereas the use of excess water in their formulation has the reverse result. The correlation between strength and loss factor was found to be strongly negative. The results of this study are in agreement with the results from research on the microstructure of dental gypsum.
