Comparison of the ceramic adherence to alloys fabricated by different manufacturing techniques using two bond...

The objective of this study was to compare the shear bond strength (SBS) and Schwickerath (ST) tests for the adherence of ceramic to cobalt-chromium (Co-Cr) fabricated by different techniques, zirconia, and nickel chromium alloys.

Five different core/veneer combinations were prepared: Group SLM: selective laser melted Co-Cr; Group SM: soft milled Co-Cr; Group C: cast Co-Cr; Group Zi: soft milled zirconia; and Group Ni: cast nickel chromium, layered with ceramic. Disk-shaped specimens (diameter 15 mm, thickness 2 mm) with a ceramic thickness of 2 mm were prepared for SBS, and bars of 25 × 3 × 0.5 mm with applied ceramic of 8 × 3 mm for ST (N = 100 and n = 20/group). Only half of the specimens from each group were thermocycled (5-55°C/5000 times). SBS test was applied to all the disks, and ST to the bars. Two-parameter Weibull distribution values, including shape (m) and scale (σ0), were calculated.

Thermal cycling had only a significant effect on SBS results for the SLM group (p = 0.017). A significant difference was found between testing techniques and materials (p < 0.001). The lowest value was reported for SLM in the SBS method (p < 0.001). Failure types were mostly mixed in SBS and adhesive in ST. The highest Weibull parameters were obtained for group C.

Both the testing methodology and the specimens manufacturing technique influenced the bond strength of ceramic to different alloys. The aging process influenced the results in the laser-sintered group in large specimens.