Abstract
The success of metal-ceramic restorations depends on an optimal bond between metal and ceramic. This study evaluated the effect of 3 casting atmospheres on the metal-ceramic bond strength (MCBS) of 2 Ni-Cr alloys, with beryllium (Fit Cast V) and without beryllium (Fit Cast SB). Sixty acrylic resin patterns (8 mm long and 5 mm diameter) were obtained using a fluorocarbon resin matrix. Wax was used to refine the surface of acrylic resin patterns that were invested and cast in an induction casting machine under normal, vacuum, and argon atmospheres at a temperature of 1340 degrees C. The castings were divested manually and airborne-particle abraded with 100-microm aluminum-oxide. Ten castings were obtained for each group. The IPS Classic V ceramic was applied (2 mm high and 5 mm diameter). The shear bond strength was tested in a mechanical testing machine with a crosshead speed of 2.0 mm/min. The MCBS data (MPa) were subjected to 2-way analysis of variance (alpha=0.05). There was no statistically significant difference (p>0.05) between the alloys or among the casting atmospheres. Within the limitations of this study, it may be concluded that the presence of beryllium and the casting atmosphere did not interfere in the MCBS of the evaluated metal-ceramic combinations.
Highlights
Metal-ceramic restorations have been used for several years because of their excellent mechanic and biologic properties
The null hypothesis was accepted because there were no significant differences in the metal-ceramic bond strength (MCBS) among all combinations of alloys and casting atmospheres
The low cost and easy manipulation of Ni-Cr alloys have made them widely used in the fabrication of metal-ceramic restorations [14], which combine the resistance of the metal substructure with esthetic properties of the ceramic [7,15,16]
Summary
Metal-ceramic restorations have been used for several years because of their excellent mechanic and biologic properties. Base metal alloys were developed with nickel, chromium and cobalt, and semi-noble alloys, which include Ag-Pd alloys and all alloys with 10% to 75% of gold in their formulation. Among these alternative alloys, Ni-Cr alloys are the most used for fabrication of metal-ceramic crowns. Base metal alloys have good mechanical properties, most of alternative alloys have disadvantages, such as biologic hazards, higher melting temperatures, need for more critical handling and care with the melting technique, and are more difficult to finish when compared to noble alloys [2,3,4]. Be reduces the melting point and increases the castability of the metal alloy [2,5], in addition to promoting the formation of true oxide bars that extend into the inner part of eutectic Ni-Be phase or the dendrites where Be is maintained in solid solution, increasing the metal-ceramic bond strength (MCBS) [3]
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