Análise mecânica e microestrutural das ligas de níquel-cromo e cobalto-cromo de uso odontológico após refundição

Abstract

Nickel-Chromium (Ni-Cr) and Cobalt-Chromium (Co-Cr) alloys are used for the fabrication of metal infrastructures for fixed and removable prostheses. Due to economic factors, some laboratories reuse these dental alloys. This fact can lead to the qualitative and quantitative loss of the elements of the alloys and to cause differences in their properties, being a great indicator of failures. The mechanical behavior of Ni-Cr alloys and Co-Cr alloys after melting and melting were evaluated by means of mechanical test of flexural strength, scanning electron microscopy (SEM) and dispersive energy spectrometer (EDS). 40 bars (40 x 4 mm) were divided into 4 groups (n = 10): G1 (Ni-CrP) and G2 (CoCrP) composed of pure alloys; G3 (Ni-CrR), composed of 50% pure Ni-Cr alloy and 50% recast alloy and G4 (CoCrR) by 50% pure Co-Cr and 50% recast alloy. After casting, the samples were subjected to radiographic inspection and three-point flexural strength test. After the fracture, samples were taken in SEM to characterize the fracture pattern and in EDS for semi-quantitative chemical analysis. There was no statistically significant difference between the types of alloys (P = .324) and between types of alloys and types of treatments (P =.841). However, there was a statistically significant difference between the types of treatment (P =.01). The ESD analysis showed no significant changes in chemical composition. It was concluded that the process of melting of Co-Cr and Ni-Cr alloys influence the strength values of the material; therefore a single use of alloys for prosthetic work is recommended.