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Effect of Co-Cr coating by EB-PVD on the bonding strength between titanium and porcelain.

OBJECTIVES
To investigate the effect of the deposited Co-Cr coatings on the bonding strength of titanium-porcelain restoration, Co-Cr coatings with different thickness were deposited onto the pure titanium substrate by electron beam physical vapor deposition (EB-PVD).


METHODS
Sixty pure titanium specimens (25.0 mm×3.0 mm×0.5 mm) were randomly divided into 5 groups. Four Co-Cr coatings with different thickness, including 20, 40, 60 and 80 nm, were deposited onto the specimens (group A, B, C and D, respectively). Sandblasting treatment was selected as a control group (group E). After porcelain fusion, bonding strengths of titanium-porcelain restoration were measured by three-point bending test according to ISO 9 693. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were employed to evaluate the morphology and elemental composition of both Co-Cr coatings and interfaces of the titanium-porcelain restoration.


RESULTS
The bonding strengths in the group E and the test groups (groups A, B, C, and D) were (30.23±1.94), (36.11±1.17), (43.33±1.17), (39.95±2.22), (38.85±1.10) MPa, respectively. In contrast to the group E, the Co-Cr coatings significantly improved the bonding strength between titanium and porcelain (P<0.05). Moreover, some cracks and pores were found at the titanium-porcelain interface in the group E, while the titanium-porcelain interface in the group B was tight and compact (P<0.05). Meanwhile, comparing to the group E, more residual porcelains were found on the substrate of group B (P<0.05).


CONCLUSIONS
Co-Cr coating with appreciate thickness using EB-PVD could significantly improve bonding strength between titanium and porcelain.