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.
Highlights
Despite an increasing popularity of all-ceramic reconstructions, porcelain fused-tometal (PFM) crowns remain the gold standard in fixed prosthodontics
The first two elements accumulated mostly in the austenitic matrix, while Mo gathered in the areas of interdendritic precipitates (Figure 2b)
Within the limitations of the study, the following conclusions might be drawn: 1. Thermal treatment did not cause chemical impurities formation on the surface of CoCr alloy
Summary
Despite an increasing popularity of all-ceramic reconstructions, porcelain fused-tometal (PFM) crowns remain the gold standard in fixed prosthodontics. This is due to the combination of aesthetics (provided by porcelain) and strength (ensured by metal alloy). Metallic materials in the oral cavity are subjected to galvanic pitting, crevice, fritting, fatigue corrosion and, eventually, stress corrosion cracking (SCC) [1]. The corrosion of metals and alloys may be caused by chloride ions, high oxidation level and a relatively high temperature (370 ◦C) of the electrolyte solution present in the oral cavity. Cobalt–chromium (CoCr) and nickel-chromium (NiCr) alloys are not exempt from corrosion processes [2,3,4,5]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
