Effect of pretreatments on the metal-ceramic bonding strength of a Pd-Ag alloy.

Objectives: The purpose of this study was to evaluate the efficacy of surface treatments on the bonding properties between a metal and ceramic.

Methods: Sixty metal specimens were divided equally into four groups of 15 samples each. These groups received different treatments (Gr1: 250μm Al2O3+preoxidation; Gr2: 250μm Al2O3+degassing; Gr3: 120μm Al2O3+preoxidation; Gr4: 120μm Al2O3+degassing). Bond strengths were evaluated using a three-point bending test. The results were analyzed using 2-way ANOVA and Tukey's test. Scanning electron microscopy and energy dispersive spectroscopy were used to observe the microscopic features, elemental compositions and distributions, and diffusion in the specimens. Mechanical profiler was used to measure the roughness of metal surface.

Results: The bond strengths of the four groups ranged from 45.00±3.63MPa to 51.61±5.91MPa, with significant differences (P<.05). The specimen that received the pretreatment of 250μm Al2O3 air-particle abrasion+degassing had the highest bond strength. Heating under different oxygen partial pressures caused the final Pd-Ag alloys to have varying degrees of internal oxidation and different quantities of metallic nodules. None of the elements in either the ceramic or the Pd-Ag alloy layer diffused into the other layer.

Conclusions: The metal-ceramic specimen subjected to air-particle abrasion with 250μm Al2O3 and degassed before porcelain firing had significantly higher bond strength than specimens treated differently.