Faculty of Dentistry, Mansoura University, Egypt.
This study was designed to investigate the influence of different cooling regimens on ion-release, ultimate tensile strength and hardness of two cobalt-chromium (Wironit and Biosil F) and two nickel-chromium (NIADUR and President-PD) casting alloys.
Specimens were prepared according to the manufacturer's instructions of each alloy. Specimens from each alloy were classified according to the cooling methods; bench cooling, quenching in water and 10 minutes bench cooling followed by quenching. For ion release, specimens were immersed in artificial saliva at 37°C for 21 days, then solution was analyzed for cobalt, nickel, chromium and molybdenum ions using a flame atomic absorption spectroscopy. The ultimate tensile strength was tested using a universal testing machine. The hardness was determined using a micro hardness tester. The data were subjected to one-way analysis of variance (ANOVA) and Tukey test at p = 0.05, using a statistical software package (SPSS 10.0 for Windows).
The bench cooled alloys exhibited the highest amount of ions release, while quenching produced the lowest values with almost tested ions. Quenching of most tested alloys showed a significant increase in ultimate tensile strength and Vickers hardness.
It was concluded that, cooling methods had a pronounced effect on some ions released and had no effect on other ions. Cooling methods had a significant effect on ultimate tensile strength and hardness of most tested alloys particularly the cobalt-based alloys.
cooling methods, base metal alloys, casting alloys, ion release, mechanical properties
