Evaluation of ceramic adherence to cobalt-chromium alloys fabricated by different manufacturing techniques

Selective laser melting has been increasingly used in the fabrication of metal-ceramic prostheses. The longevity of the prostheses depends on the strength of the metal-ceramic bond, which may differ with the framework manufacturing technique.

The purpose of this in vitro study was to compare the bond strength of ceramic to cobalt-chromium (Co-Cr) alloys fabricated by different manufacturing methods.

Sixty Ø15×2-mm disk-shaped specimens were prepared and assigned to 3 groups (n=20) with different manufacturing methods: milled Co-Cr (M), selective laser melted Co-Cr (SLM), and cast Co-Cr (C). The disks were ceramic layered with a 2-mm thickness. Half of the specimens from each group were thermocycled. The shear bond strength (SBS) test was applied to all specimens. The microstructure changes after ceramic layering were evaluated by X-ray diffraction (XRD). The specimens' surface morphology was analyzed by using scanning electron microscopy (SEM).

Thermocycling had a significant effect on SBS values in the SLM group (P=.017). Considering the registered F_max (force inducing bonding failure), a significant difference was found between SLM and both M and C groups (P<.001). No significant difference was found between milled and cast Co-Cr (P=.885). The failure types were mostly mixed failures. Ceramic layering induced a crystallization increase in groups C and SLM.

The adhesion strength of ceramic to Co-Cr differed with alloy composition and manufacturing technique. The aging process influenced the results in the SLM group.