Mechanical Characteristics and Bond Strengths of Gold-Titanium Alloys to Porcelains

Abstract

Purpose: It is desirable to apply a multi-purpose alloy with good biocompatibility. A recently introduced gold-titanium alloy is reported to show good corrosion resistance and good biocompatibility. The purpose of this study was to evaluate the mechanical properties and the metal-fused-to-porcelain bond strengths of this alloy.
Methods: A commercial gold-titanium alloy was selected. Cast specimens were prepared according to the manufacturer's instructions. The tensile test, the Vickers hardness test and the thermal expansion test were performed. The bond strengths of the gold-titanium alloy to a conventional porcelain and an ultra low-fusing porcelain for metal veneering were evaluated according to DIN 13 927. The bond strength of a conventional gold alloy to the conventional porcelain was also measured as a control. The sectioned specimen of the conventional porcelain fused to the goldtitanium alloy was analyzed with X-ray micro probe analysis.
Results: Mechanical properties, such as Vickers hardness, tensile strength, yield strength and elastic modulus, were modified with heat treatment; the value of the mechanical properties after softening were significantly smaller than those after hardening and those of “as cast”; the properties after hardening nearly reached the classification of the ISO type 4 gold alloy. The coefficient of thermal expansion of this alloy was larger than that of the conventional gold alloy for porcelain. There were statistically no significant differences among bond strengths of three metal-porcelain combinations, all of which were above 40MPa. Elements of the porcelain and titanium were observed on the detached metal surface and the detached porcelain surface respectively. Particles of titanium oxide were observed at the interfacial layer on the sectioned specimens.
Conclusions: This gold-titanium alloy could be applied to various restorations because of its sufficient mechanical properties and bond strengths with porcelain.