COMPRESSIVE STRENGTH OF MIXES WITH DIFFERENT PROPORTIONS OF PLASTER TO STONE

Abstract

Dental plaster and stone are widely used in dentistry especially in prosthodontics. A mixture of stone and plaster may be used for filling the upper half of the flask during construction of complete dentures .In this study the compressive strength of seven ratios of stone to plaster (S/P) were measured [ 1:1 , 1:2 , 1:3 , 1:4, 2:1 , 3:1 , and 4:1 ] . The water/powder ratio was 40:100 for all combination. According to the experimental data , samples of stone to plaster in the ratios of 1:1, 1:3 , and 1:4 gave an increased compressive strength of (9.8 , 9.7 , and 9.3 MPa) compared with the strength of plaster alone (7.9 MPa) . The result reveals that the highest amount of compressive strength was recorded by the samples made in the ratio of stone / plaster equal to 1:1. Thus, the mix made with this ratio of stone to plaster may be the material of choice for filling the upper half of the flask that can withstand stresses created during the packing of methyl methacrylate acrylic resin.