Abstract
The metal restorations are used in Dentistry a long time ago. Nowadays we have resources that can get casting more accurate, with new material and equipments and techniques more precise. The purpose of this study was to evaluate the metallurgical and mechanical aspects of the AgPd dental alloy when it was submitted to different casting temperatures. It was used 30 specimens, divided in three groups (n=10): a) control group (no cast); b) casting temperature in accordance with the manufactures’ instructions (T1); b) casting temperature above manufactures´ instructions (like a torch) (T2). It was evaluated chemical and metallographic aspects, mechanical properties and Vickers hardness. The results showed a microstructure similar to T1 and T2 conditions, but with greater amount of light phase and particles in this last one. It was observed that the rupture tensile strength for the T1 condition was greater than the T2. The alloy in the no cast condition presented greater hardness but there was no statistically significant difference between T1 and T2. Supporting by the metallographic and mechanical results, it may predict that when elevated temperatures was used, above manufacture´s recommendations, it can occur failures in the prosthesis, like porosities, fissures or cracks.
Highlights
Alloys are composed of two or more elements, and sometimes non-metal elements are included
Twenty specimens were obtained by means of lost wax casting technique and divided in two groups of ten, so that each one was submitted to a different temperature: T1 – recommended by the manufacturer (1100oC), and T2 – above the recommended temperature (1300 ±20oC) (Table 1)
There was no significant difference in chemical analysis among NC, T1 and T2 groups
Summary
Alloys are composed of two or more elements, and sometimes non-metal elements are included. The firstly employed alloys were gold-based alloys, whose main characteristic was their resistance to oxidation, which was more noticeable than the other properties, almost unknown at that time[3]. With the improvement on research methods, it was verified that besides resisting oxidation, the different gold-based alloys presented mechanical and biological properties perfectly compatible for oral use. The choice of an alloy is based on several factors. Other factors that shall be considered are biocompatibility and corrosion resistance[18]. These factors in particular limited the use of alloys for dental prostheses, and the choice of an specific application is primarily determined by their mechanical properties, such as hardness, mechanical strength and ductility[14]
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