Corrosion behavior of dental CoCr alloys made by different digital workflow processes compared to cast CoCr alloysPart of:
Objectives: Traditionally metallic dental restorations are cast. Since a few years dental metallic restorations can be made additionally by CAD-CAM procedure using different technologies such as milling, selective laser melting or metal powder sintering. The aim of this study was to evaluate the corrosion behavior of dental porcelain fused CoCr alloys manufactured by the CAD-CAM techniques milling (Organic), selective laser melting (Remanium Star CL) and powder sintering (Ceramill Sintron) compared to the cast CoCr alloys Remanium Star, Girobond NB, Ankatit U.
Material and Methods: From each alloy and for each corrosion measurement 6 samples were prepared according to ISO 10271. With each alloy electrochemical corrosion measurements which consist of open-circuit-potential over 2 h, followed by anodic polarization were performed in an electrochemical cell which was filled with 0.9% saline and heated at 37°C which was connected to a potentiostat (PAR 273A, Software: M352, EG & G). From each measurement the parameters Ecorr after 2 h, Ez, Ep with corresponding ip, icorr and i(300 mV +Ez) were calculated. With all alloys static immersion tests over 7 days were done and ion release was determined using ICP-OES (Optima 4300 DV, Perkin Elmer). The total ion release and the mass loss rate were calculated. For statistical evaluation Student’s t-Test was applied.
Results: Organic showed the lowest icorr value with 59 ± 14, followed by Girobond NB (65 ± 8) and Ankatit U (87 ± 3), Ceramill Sintron (96 ± 10), Remanium (106 ± 87) and Remanium CL with 183 ± 78 nA/cm². After 7 days immersion the accumulated total ion release was 0.34 ± 0.02 for Organic, 1.69 ± 0.36 for Ceramill Sintron, 2.93 ± 1.01 for Remanium Star CL, 3.41 ± 0.29 for Ankatit U, 20 ± 7.19 for Remanium Star and 26.86 ± 8.79 µg/cm² for Girobond NB. All values were clearly below the limit value of 200 µg/cm² given in ISO 22674.
Conclusion: Based on this study the CoCr alloys made with the different CAD-CAM technologies showed a similar electrochemical corrosion behavior as the cast ones. The ion release of the CAD-CAM made CoCr alloys and cast Ankatit U was statistically lower compared to the cast alloys Remanium Star and Girobond NB.