Effect of Recycling Cobalt-Chromium Alloy Powder on Metal-Ceramic Bond Strength and Microstructure.

This article investigates the effects of recycling cobalt-chromium (CoCr) alloy powder containing tungsten (W) on the metal-ceramic (MC) bond strength and microstructure of dental frameworks produced by selective laser melting (SLM). The study compared frameworks made from virgin powder, powder reused 25 times, and conventional casting ingots, finding no significant differences in MC bond strength among these groups. However, reused powder exhibited a larger grain size and a threefold increase in nitrogen content, which corresponded with a porous microstructure in the recycled powder frameworks. Despite these microstructural changes, recycling CoCr alloy powder up to 25 times is considered advisable as it does not compromise MC bond strength, though the presence of porosity suggests further research is needed to determine the maximum safe number of reuses for clinical applications.