Gold-based bonding agents between palladium-alloys and ceramic veneer

The influence of GoldbonderTM and pre-heat treatment on the adhesion of titanium alloy and porcelain

The present study examines the influence of a goldbonder and pre-heat treatment of the titanium on the adhesion of porcelain. Three groups of titanium substrates were given various heat treatments, namely; none, 200 degrees and 600 degrees C, respectively before applying goldbonder. The surfaces of the titanium specimens following heat treatment were examined with an electron spectroscopy for chemical analysis (ESCA). The adhesion strength was measured by the strain energy release rate (G), which was proposed by Suansuwan N and Swain MV (Int J Prosthodont. 1999;12:547). After bonding porcelain onto titanium substrates with the aid of the goldbonder, the porcelain side of specimens was notched to the interface with a thin diamond saw. Then the samples were subject to a four-point bending test. Following fracture testing, specimens were examined with a scanning electron microscope (SEM) and SEM with energy-dispersive spectroscopic analysis (EDS). The mean G-values were 38.87, 28.64 and 16.33 J m(-2), respectively. ESCA analysis showed the composition of aluminium of the surface of 600 degrees C pre-heat treatment became richer than that of the others. SEM images of the fracture surfaces showed that for the 600 degrees C pre-heat treatment fracture occurred within the oxidation layer on the titanium. High temperature pre-heat treatment prior to bonding significantly reduces porcelain bonded to titanium with the goldbonder. The Influence of Goldbonder and Pre-heat Treatment on the Adhesion of Titanium Alloy and Porcelain.

Effects of dental laboratory processing variables and in vitro testing medium on the porcelain adherence of high-palladium casting alloys

PURPOSE

This study assessed the effects of dental laboratory processing variables and testing medium on porcelain adherence of representative high-palladium alloys.

MATERIAL AND METHODS

The processing variables were recasting two and three times, porcelain stripping with hydrofluoric acid and rebuilding, and changing the recommended oxidation procedures. The testing medium was air for these four groups and the nontreatment group. In the last group, the specimens were stored and tested in artificial saliva. The metal ceramic specimens were fractured with biaxial flexure in constant strain. The area fraction of adherent porcelain (%) was calculated with a standardized spectrometric technique. A gold-palladium alloy served as the control.

RESULTS

Recasting without adding new alloy negatively affected some high-palladium alloys. Porcelain stripping did not cause a decrease in adherence of the tested alloys. The alternate oxidation treatment reduced significantly the porcelain adherence of the Au-Pd and one Pd-Cu-Ga alloy. Storage and testing in artificial saliva did not significantly affect the porcelain adherence of the alloys. The Au-Pd alloy exhibited the highest porcelain adherence.

Bond characteristics of porcelain fused to milled titanium

OBJECTIVES

A bonding agent has recently been introduced that prepares the surface of milled titanium copings for bonding to low fusing dental porcelains. This study evaluated the effectiveness of the bonding agent by comparing the shear and three-point bending strength of specimens made with three combinations of materials: 1) milled titanium/porcelain with bonding agent, 2) the same milled titanium/porcelain without bonding agent, and 3) cast high palladium/conventional porcelain.

METHODS

Shear specimens consisting of porcelain cylinders 6 mm in diameter and 8 mm in length were fired to the ends of metal cylinders 6 mm in diameter and 13 mm in length. Three-point bend specimens made of 25 x 3 x 0.5 mm metal bars were veneered with 8 x 3 x 1 mm of porcelain in the bar's center. Specimens were tested in shear and bending in a universal testing machine. The data were analyzed using one-way ANOVA and Newman-Kuels post hoc tests (p = 0.05).

RESULTS

When a titanium bonding agent was used, porcelain to titanium bond strength was slightly but statistically significantly greater than the porcelain to high palladium bond strength. The result was the same when measured by both shear and three-point bending tests. Without the bonding agent, the shear strength of porcelain to titanium was significantly lower than that of the bonding agent and high palladium groups.

SIGNIFICANCE

The use of a bonding agent improves the bond strength of porcelain-fused-to-milled titanium.

Porcelain adherence to high-palladium alloys

The adherence of porcelain to four representative high-palladium alloys of the first generation (Pd-Cu-Ga) and second generation (Pd-Ga) was measured by use of a gold-palladium alloy as a control. The area fraction of adherent porcelain after metal-ceramic specimens were debonded in biaxial flexure at constant strain was calculated from the characteristic Si x-ray intensity with a standardized scanning electron microscope/energy-dispersive spectroscopy technique (SEM/EDS). The gold-palladium alloy exhibited the highest percentage of cohesive fracture through the porcelain, the two first-generation alloys were intermediate, and the two second-generation alloys exhibited the lowest area fractions. This study demonstrated that conventional visual (naked eye) or microscopic examination of the fractured metal-ceramic specimens at moderate magnification and the use of standard quantitative metallographic techniques were inadequate to provide accurate measurements of the area fraction covered with porcelain.