FLOW, STRESS RELAXATION AND COMPRESSIVE STRENGTH OF DENTAL AMALGAM

Abstract

Since the flow test is carried out by a static compressive load, there seems to be little occurrence of variations and errors among the persons doing the test and the machines used for the test. Recently as the JIS and ADA specifications for the flow test were changed, the effect and analysis of the setting mechanism based on these were investigated. Besides, a study of the stress relaxation, compressive strength and early flow were conducted. The relations among these properties were studied and pursued. Though the early flow includes many complicated factors influencing it, the understanding of these factors is urgently necessary in solving the setting mechanism. The effect of temperature and load on this property was also determined. Temperature has much effect on the flow, a 20℃ rise in temperature resulting in a flow 2 times larger in a spherical amalgam, 2.5 times larger in a fine-cut amalgam, and 3 times larger in a regular cut amalgam. In comparing the flow of the regular-cut, fine-cut and spherical amalgam, the total flow showed a ratio of 4:3:1. It is understood that the grain size or the surface area is a subordinate factor in the flow as compared to the setting reaction. But the spherical amalgam showed a higher flow in a 5-minute old specimen under a load of 50 kg/㎠. This seems to be due to its consistency. However, testing of consistency was affected much by its load, and the effect of a small load diminished it and the reaction factor overwhelmed it.