Comparison of the bond strength of selective laser melting and cast Cobalt-Chromium alloys to porcelain

Abstract

Objective To compare the bond strength of selective laser melting (SLM) and cast Cobalt-Chromium (Co-Cr) alloys to porcelain. Methods Co-Cr alloy specimens (25 mm × 3 mm × 0.5 mm) were prepared using either a cast or CAD/CAM SLM methods. A 8 mm × 3 mm × 1.1 mm ceramic layer was fused to the central portion (8 mm × 3 mm) of the surface of the metal specimens. The bond strengths of the metal-ceramic were tested using a three-point bending test according to the ISO 9693 standard. Scanning electron microscopy and energy dispersive spectroscopy were used to determine the morphology, elemental composition, failure types, and area fraction of adherence porcelain. Metallographic microscope was used to observe the metallurgical structure of alloy specimens. The data of metal ceramic bond strength and area fraction of adherence porcelain were analyzed using independent sample t-test (α= 0.05) . Results The metal-ceramic bond strength of SLM and cast Co-Cr alloy were (32.41 ± 3.21) and (32.93 ± 4.33) MPa, respectively. No statistical difference was found between two groups (t= 0.095, P= 0.163) . After three-point bending test a mixture of adhesive and cohesive failure types was observed in all specimens. The area fraction of adherence porcelain of SLM and cast Co-Cr alloy was (79.67 ± 3.92) and (62.73 ± 7.34) , respectively. Significant differences were found between two groups (t=-6.46, P< 0.001) , suggesting that the SLM alloy surface had larger area of residual ceramic. Conclusions No difference was found in the metal-ceramic bond strength between SLM and cast Co-Cr alloy. In terms of the porcelain-bonding area, SLM alloys even had a greater advantage than cast alloys. Key words: Selective laser melting; Cobalt-Chromium alloy; Metal-ceramic bond strength