Evaluation of the mechanical properties and porcelain bond strength of cobalt-chromium dental alloy fabricated by selective laser melting.

STATEMENT OF PROBLEM: Limited information is available regarding the microstructure and mechanical properties of dental alloy fabricated by selective laser melting (SLM). PURPOSE: The purpose of this study was to evaluate the mechanical properties of a cobalt-chromium (Co-Cr) dental alloy fabricated by SLM and to determine the correlation between its microstructure and mechanical properties and its porcelain bond strength. MATERIAL AND METHODS: Five metal specimens and 10 metal ceramic specimens were fabricated to evaluate the mechanical properties of SLM Co-Cr dental alloy (SLM alloy) with a tensile test and its porcelain bond strength with a 3-point bending test. The relevant properties of the SLM alloy were compared with those of the currently used Co-Cr dental alloy fabricated with conventional cast technology (cast alloy). The Student t test was used to compare the results of the SLM alloy and the cast alloy (alpha=.05). The microstructure of the SLM alloy was analyzed with a metallographic microscope; the metal ceramic interface of the SLM porcelain bonded alloy was studied with scanning electron microscopy, energy dispersive x-ray spectroscopy, and an electron probe microanalyzer. RESULTS: Both the mean (standard deviation) yield strength (884.37 +/- 8.96 MPa) and tensile strength (1307.50 +/-10.65 MPa) of the SLM alloy were notably higher than yield strength (568.10 +/- 30.94 MPa) and tensile strength (758.73 +/- 25.85 MPa) of the currently used cast alloy, and the differences were significant (P<.05). The porcelain bond strength of the SLM alloy was 55.78 +/- 3.02 MPa, which was similar to that of the cast alloy, 54.17 +/- 4.96 MPa (P>.05). Microstructure analysis suggested that the SLM alloy had a dense and obviously orientated microstructure, which led to excellent mechanical properties. Analysis from scanning electron microscopy, energy dispersive x-ray spectroscopy, and the electron probe microanalyzer indicated that the SLM alloy had an intermediate layer with elemental interpenetration between the alloy and the porcelain, which resulted in an improved bonding interface. CONCLUSIONS: Compared with the currently used cast alloy, SLM alloy possessed improved mechanical properties and similar porcelain bond strength.