Tensile strength of the solder joints of some recasted dental alloys

ABSTRACT

The investigation was carried out to study the effect of recasting on the tensile strength of the solder joint of three different types of alloys widely used on the Egyptian dental laboratories, the silver palladium, the nickel chromium and the chromium cobalt alloys. One hundred sixty five specially prepared rods were fabricated in a standardize manner for each alloy and were recasted two, three and four times with and without addition of 50% per weight fresh alloy during each recasting. Every two rods of the same alloy were soldered together with the corresponding alloy of soldering following the manufacture instructions. The specimens were held with a specially constructed metal adaptor and were subjected to tensile force using a universal Instron testing machine. The results were tabulated and statistically analyzed. It was concluded that the first cast specimens of the chromium cobalt solder joints showed the highest tensile strength values, followed by the nickel chromium specimens then the silver palladium specimens. There was no statistical significant decrease in the tensile strength values between the first cast samples and the recasted samples with 50% per weight addition of fresh alloy in the three tested alloys. In the three tested alloys, there was a statistical significant decrease in the tensile strength values between the first cast samples and the recasted samples without addition of fresh alloy. The recasted samples for one, two and three times without the addition of fresh alloy showed significant gradual decrease in the tensile strength values in all the tested alloys