Does Simulated Porcelain Firing Influence Corrosion Properties of Casted and Sintered CoCr Alloys?

Abstract

The aim of the study was to evaluate how heat processing used for dental porcelain firing influences the surface properties of sintered and casted CoCr alloy. Two CoCr alloys, Soft Metal LHK (milling in soft material and sintering) and MoguCera C (casting), were used for the study. The samples were examined using SEM–EDS before and after heat treatment. Next, corrosion examinations (Ecorr, jcorr, polarization curve, Ebr) were performed. Finally, the samples were evaluated under SEM. Based on the results, the following conclusions might be drawn: 1. Thermal treatment (porcelain firing) did not cause chemical impurities formation on the surface of CoCr alloy; 2. The sintered metal exhibited significantly higher corrosion resistance than the casted one due to its homogeneity of structure and chemical composition; 3. Heat treatment (porcelain firing) decreased the resistance of casted and sintered CoCr alloy to electrochemical corrosion. The reduction in corrosion resistance was significantly higher for the casted alloy than for the sintered alloy; 4. The corrosion resistance decrease might be due to an increased thickness and heterogeneity of oxide layers on the surface (especially for the casted alloy). The development of corrosion process started in the low-density areas of the oxide layers; 5. The sintered metal seems to be a favourable framework material for porcelain fused to metal crowns.

Ni–Cr dental alloys - porcelain firing impact on corrosion properties and surface characteristics

“…The results of the work by Tuncdemir et al [56], evaluating the corrosive behavior of Ni-Cr alloys, as well as Co-Cr after porcelain firing, showed that multiple firings also reduce the corrosion resistance of Cr-Co alloys. Similarly, in the works of Rylska et al [57,58] the porcelain firing simulation of Co-Cr alloys obtained by CST, MSM and SLM methods, caused, in each case, a decrease in corrosion resistance. It is essential that the most significant decrease in corrosion resistance was recorded for as-cast samples that presented the most tremendous variation in the composition of oxides on the surface after HT.…”

“…Some researchers find a higher level of ions released before the HT [54], while others' results indicate no differences in corrosion resistance [55]. However, several works reported the reduced corrosion resistance after HT [56][57][58].…”