Gold and titanium nitride coatings on cast and machined commercially pure titanium to improve titanium–porcelain adhesion

The objective of this study was to determine the effects of coating titanium with Au or TiN on its adhesion to dental porcelain. Cast and machined ASTM grade II CP titanium samples that were either uncoated, coated with Au, or coated with TiN were examined. The specimen surfaces were characterized by SEM/EDS and XRD. An ultra-low-fusing dental porcelain (Vita Titankeramik) was fused onto the titanium surfaces. Biaxial flexure tests and X-ray spectroscopy, the latter of which was used to determine the area fraction of adherent porcelain (AFAP), were performed to characterize the titanium–ceramic adhesion. The TiN-coated surfaces (prepared by arc ion plating) exhibited well-networked surface structures with small dimples on their Ti surfaces. The surface morphologies of the Au-coated samples were similar to those of the uncoated titanium surfaces. The AFAP value for the machined titanium was independent of the surface treatment. All of the cast and machined titanium samples had similar AFAP values, except for the uncoated cast titanium, which had a significantly lower AFAP value. On the surfaces of the gold-coated cast and machined titanium samples, a new Au2Ti phase with a tetragonal structure was identified. The improved adherence between the porcelain and commercially pure titanium upon coating the latter with Au or TiN is of great clinical importance.