Effect of annealing procedure on the bonding of ceramic to cobalt-chromium alloys fabricated by rapid prototyping

Statement of problem. An annealing procedure is a heat treatment process to improve the mechanical properties of cobalt-chromium (Co-Cr) alloys. However, information is lacking about the effect of the annealing process on the bonding ability of ceramic to Co-Cr alloys fabricated by rapid prototyping. Purpose. The purpose of this in vitro study was to evaluate the effects of the fabrication techniques and the annealing procedure on the shear bond strength of ceramic to Co-Cr alloys fabricated by different techniques. Material and methods. Ninety-six cylindrical specimens (10-mm diameter, 10-mm height) made of Co-Cr alloy were prepared by casting (C), milling (M), direct process powder-bed (LaserCUSING) with and without annealing (CL+, CL), and direct metal laser sintering (DMLS) with annealing (EL+) and without annealing (EL). After the application of ceramic to the metal specimens, the metal-ceramic bond strength was assessed using a shear force test at a crosshead speed of 0.5 mm/min. Shear bond strength values were statistically analyzed by 1-way ANOVA and Tukey multiple comparison tests (alpha=.05). Results. Although statistically significant differences were found among the 3 groups (M, 29.87 +/- 2.06; EL, 38.92 +/- 2.04; and CL+, 40.93 +/- 2.21; P=.002), no significant differences were found among the others (P>.05). The debonding surfaces of all specimens exhibited mixed failure mode. Conclusions. These results showed that the direct process powder-bed method is promising in terms of metal-ceramic bonding ability. The manufacturing technique of Co-Cr alloys and the annealing process influence metal-ceramic bonding.