Corrosion, ion release, and surface hardness of Ti-6Al-4V and cobalt-chromium alloys produced by CAD-CAM milling and laser

Abstract

Statement of problem. How the corrosion properties of cobalt-chromium (Co-Cr) and Ti (Ti-6Al-4V) alloys, frequently used in dental prostheses, are affected by different production methods is unclear.

Purpose. The purpose of this in vitro study was to compare Co-Cr and Ti-6Al-4V alloys produced by computer-aided design and computer-aided manufacturing (CAD-CAM) milling or laser sintering in terms of corrosion, ion release, and surface hardness.

Material and methods. Co-Cr and Ti-6Al-4V specimens were produced by CAD-CAM milling and direct metal laser sintering/selective laser sintering techniques. Testing included Vickers hardness and then open circuit potential (OCP), Tafel extrapolation, and static immersion to determine the corrosion behavior. The study used an inductively coupled plasma mass spectrometer to measure ion release. The data were analyzed by using the Kruskal-Wallis and Mann-Whitney U tests, with Bonferroni correction (alpha=.05).

Results. The Ti-6Al-4V laser-sintered group showed the highest Vickers hardness value (P<.008), the lowest OCP value (P<.008), and the lowest corrosion potential (V-corr) value (P<.008). The corrosion current density (I-corr) level of the Co-Cr CAD-CAM milling group was statistically significantly lower than that of the Ti-6Al-4V CAD-CAM milling and the Ti-6Al-4V laser-sintered groups (P<.008). The highest weight change was observed in the Ti-6Al-4V laser-sintered group. The Co, Cr, and Ti ion emissions were higher in specimens produced by laser sintering (P<.05), and no statistically significant difference in terms of Al and V oscillations was found among the groups (P>.05).

Conclusions. Ti-6Al-4V alloys may be a good alternative for patients with Co-Cr allergies, but as per the results of this study, Co-Cr still seems more suitable for clinical use.