The effect of indium on porcelain bonding between porcelain and Au?Pd?In alloy

Abstract

The effect of small In additions on oxide structure and porcelain adherence to Au-Pd alloys was studied. In was oxidized internally as In203. No uniform external oxide layer could be seen. Small In addition (1 at%) did not have any detectable effect on porcelain adherence (~12 MPa), whereas higher In concentration (5 at%) caused significant increase in bond strength (~,26 MPa). This increase was probably a result of higher In203 concentration at the surface. IntroductionPd-containing alloys have become recognized as alternatives to high-Au and non-precious alloys for metal-ceramic restorations. The main reasons for the popularity of palladium alloys are good corrosion and tarnish resistance along with acceptable biocompatibility and the price of Pd, which is approximately one-half of that for Au. Pd-rich alloys suitable for metal-ceramic restorations can be roughly divided into following groups: Au-Pd-, Pd-Co-, Pd-Cuand Pd-Ag-based alloys [1]. Considering the physical properties, processing characterics and the amount of precious metal components, the Au-Pd-system is very attractive because of the excellent compromise between these three factors [2].The importance of the oxide layer on the bonding of metal to porcelain is generally accepted for all kinds of metal-ceramic materials. The theory of glass/metalbonding was largely developed by Pask [3][4][5]. He postulated that chemical bonding across the interface is achieved by having therodynamically stable equilibrium in the interfacial zone and having both phases saturated with an oxide of the substrate metal. The oxide layer formed on metal by preoxidation is supposed to be dissolved by molten glass. The chemical bonding is maximized when a monomolecular oxide layer remains at the interface. The importance of oxide adherence to its alloy substrate has been emphasized by Mackert [6,7], who found a correlation between oxide adherence and porcelain adherence to metal. The dental noble alloys are normally alloyed by base metals like In, Sn and Ga, which form an oxide layer on the alloy. Accumulation of oxidizing elements within a few micrometres of the metal/porcelain interface has been reported in several studies [8-t3], in which concentration profiles of alloy components over a metal/porcelain interface were measured by electron microprobe. Such data are generally found to support the theory that chemical bonding mechanisms are controlled by oxidizing metal components. More de-

Discrepancy in alloy composition of imported and non-imported porcelain-fused-to-metal (PFM) crowns produced by Norwegian dental laboratories

“…15 and 20 nonimported, 3 and 44 imported) had <1 wt.% In, where two had no trace of this element. Several crowns had lower content amounts of either In and/ or Ga making this a likely contributor to future porcelain fractures due to reduced bonding between metal and ceramic [34,35]. Iridium (Ir), rhodium (Rh) and ruthenium (Ru) are all grain refiners, and it is only with these elements that one can harden an alloy without decreasing ductility [35].…”

Experimental Investigations on the Influence of Adhesive Oxides on the Metal-Ceramic Bond

“…The values measured for the reference alloy, Degutan, are similar to other metal-ceramic combinations with low fusing point dental ceramics. In addition to Sn and Fe, In was selected as an alloy component, because it ensures chemical bonding of the ceramic as a result of adhesive oxide formation in the firing process [25].…”

Interfacial analysis of porcelain fused to high-palladium alloy with different observation methods

“…Commercially relevant Pd−Ag alloys typically have compositions of approximately 50–60% Pd and 30–40% Ag, and contain small amounts of low-melting-point metals, such as Zn, In, and Sn, to improve castability by increasing the fluidity of the molten alloy 3 . Adherence of porcelain to noble alloys is usually improved by adding easily oxidized alloy components, such as In, Sn, and Ga 4, 5, 6. Accumulation of these elements at the metal–ceramic interface has been reported in several studies 7, 8, 9, 10.…”