Konstantin Spyropoulos

Purpose. The purpose of this in vitro study was to determine the metal-ceramic bond strength between dental porcelain and cobalt-chromium (Co-Cr) metal substrates fabricated by different techniques. Materials and Methods. Forty Co-Cr metal substrates were fabricated according to ISO 9693-1, by casting, milling, soft milling, and DMLS. Forty additional substrates were fabricated for each technique to record the modulus of elasticity. A commercially available feldspathic porcelain was placed on the substrates, and then the specimens were also tested for metal-ceramic bond strength with the 3-point bend test, according to ISO 9693-1. The fractured specimens were observed with optical and scanning electron microscopy using electron dispersive spectroscopy to define the mode of failure. X-ray diffraction spectroscopy was conducted to determine changes in crystalline phases after fabrication and the 3-point bend test. Statistical analysis was with 1-way analysis of variance and the Tukey post hoc test (α=.05). Results. No statistically significant differences were found for modulus of elasticity among any of the groups. The metal-ceramic bond strength for casting had no statistically significant differences and the mode of failure in all groups was cohesive. The metallographic analysis of the as-received, the after porcelain firing, and the after 3-point bend test specimens revealed changes in microstructure. The crystallographic microstructure revealed that the patterns had minor changes among the groups. Conclusion. The study revealed that all of the techniques showed similar results. The modulus of elasticity and metal-ceramic bond strengths presented no statistically significant differences, and the mode of failure was cohesive.