Characterization of noble metal implant cylinders: as-received cylinders and cast interfaces with noble metal alloys.

A common procedure in the fabrication of implant prostheses is the use of premade wrought cylinders in cast frameworks. Although manufacturers outline some precautions in the use of these components, detailed information about the metal interface between cylinders and cast alloys is lacking. This article, following a previous report that compared titanium-based implant cylinders used with two different classes of cast alloys, compares conventional noble metal cylinders from three different manufacturers combined with these two classes of cast noble alloys. Analysis of the as-received cylinders revealed that the implant cylinders as a group are predominantly composed of metals commonly found in noble dental alloys, namely, platinum, palladium, gold, and silver. The interfaces created by casting both high-fusing and low-fusing alloys around the cylinders exhibited a general elemental concentration variability compared with the bulk alloy regions, but continuous concentrations for shared elements suggested alloy-cylinder compatibility. Vickers hardness values, which ranged from 212 to 276 for the as-received cylinders, decreased from 12% to 43% for the various cylinders after casting. This study suggests characteristics of an ideal cast interface that include maintenance of the cylinder and casting alloy microstructures up to the interface, absence of interfacial reaction regions, lack of porosity created by volatilization of components from either alloy or the casting process, and sufficient strength to maintain anticipated loads.