Oxide layer characteristics and interfacial analysis of porcelain fused to high-gold alloy using multitechnique analysis methods

BACKGROUND/PURPOSE: In a previous fractural study, high-gold crowns possessed the second highest fracture force. The objective of this study is to analyze the interface of porcelain fused to high-gold alloy using different observation devices. MATERIALS AND METHODS: High-gold crowns specimens with the morphology of a maxillary second premolar were compressed vertically in the center of the occlusal surface until fracture using a universal testing machine. The fractured surfaces were examined using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM/EDX) to determine the failure mode. The ceramic–metal interface of the crown was examined with electron probe microanalysis (EPMA). In addition, sheet specimens with dimensions of 10 × 9 × 4 mm(3) were prepared to examine the surface morphology and composition of high-gold alloy after oxidation using X-ray photoelectron spectrometer (XPS). RESULTS: The average fracture force was 1368 ± 312 N. Photograph of fractured crown and SEM/EDX analyses reveal that the crown initially suffered from cohesive failure in the upper and middle regions, with the fracture occurring mostly within the ceramic. XPS results and both EPMA color photomicrographs of crown and sheet specimens show that indium was observed along the porcelain–metal interface with a 1- to 2-μm disrupted zone of oxide layer. CONCLUSION: In(2)O(3) and Au were found along the interface from the multitechnique analysis methods; the presence of this oxide at the boundary promotes ceramic–metal adhesion. In(2)O(3) is suggested to be beneficial for the second highest fracture resistance in a previous fractural study of implant-supported crowns.