EFFECT ON HARDNESS OF REUSED CAST COBALT CHROME ALLOY USING FLAME CENTRIFUGE CASTING METHOD

Abstract

In dentistry lost wax casting method requires more alloy than needed to produce indirect restoration. The surplus casting alloy is re-used in routine. The aim of the present study was to assess the micro-hardness of the commercially available Cobalt-Chromium alloy, when 50 wt. % re-used alloy is added to it; up till six times. The study sample was divided into four groups (n=5). Group 1 was the control group with 100% fresh alloy cast once. In group 2, 3 and 4, a 50 wt.% cut off of previous castings were mixed to the fresh alloy. All the samples were cast using oxy-acetyl flame with broken arm centrifuge casting method. The hardness measurements were carried out under 500 gram force load for 10 second (ASTM-E 384) using micro hardness tester: Model: HVS-1000. Three indents were made on each specimen. The means of micro-hardness in study groups were compared using one-way ANOVA. The group1 had the maximum mean hardness (340+10); followed by group 2 with 305+11; group 3 had 334+10 and group 4 had the least hardness 303+15. F-test was non-significant at 5% level of significance (p-value=0.094) suggesting there was no difference among the hardness of the four groups.