Comparison of mechanical properties of different types of gypsum applied in dentistry

Abstract

Regardless of the rapid development of various digital scanning techniques of oral tissues, gypsum remains the most widespread material used in the laboratory execution of almost all prosthetic restorations. The mechanical properties of different types of gypsum are affected by the amount and temperature of the water used to preparing the mass, as well as the method and speed of its mixing. The aim of the study was to compare the mechanical properties of type 2, 3 and 4 gypsum during crushing and breaking tests, depending on the way of preparing the mass. Material and methods. For each test, 60 plaster samples in the shape of a cylinder were prepared in two dimensions: 4x10 mm and 4x20 mm. The material used to make the samples were Stodent II (type 2) and Stodent III (type 3) from Zhermapol and Fuji Rock from GC (type 4). Gypsum was mixed by hand or by vacuum machine. Six groups of samples of 10 were obtained. After 1 week, when the samples were stored at room temperature, they were subjected to crushing and breaking tests on the INSTRON 3345 strength machine. Results. The results of compression tests and three-point fracture were analyzed statistically using the Statistica 13.1 software (StatSoft). The greatest strength both crushing and breaking showed samples of type 4 gypsum, the smallest - type 2 plaster cast. Significantly lower standard deviation was observed in the case of mixed gypsum with the use of a vacuum mixer. Conclusion. Gypsum models should be cast from vacuum mixed gypsum.