Bond Strength of Porcelain to Milled Sintered and Casting Base Metal Alloys

Statement of the Problem: 

Success of metal-ceramic restorations depends on the bond strength between porcelain and alloy. These restorations can be fabricated through different casting and computer-aided design/compute-aided manufacturing (CAD-CAM) techniques.

This study aimed to compare the bond strength of porcelain to milled sintered (Sintron) and casting (Co-Cr and Ni-Cr) base metal alloys.

In this in-vitro experimental study, 63 rectangular bars (25×3×0.5 mm) were fabricated of three base metal alloys: casting Ni-Cr, casting Co-Cr, and milled sintered Co-Cr alloy. Feldspathic porcelain (3×8 mm) was applied at the center of each bar with 1.5 mm thickness. The specimens were thermally aged. Bond strength was evaluated through three-point flexural test. Failure mode was evaluated by optical and electron microscope. Data were analyzed with one-way ANOVA and Tukey's post hoc test (α=0.05).

The mean flexural bond strength of porcelain to milled sintered Co-Cr alloy (24.58±5.16 MPa) was significantly higher than that of casting Ni-Cr (21.13±6.34 MPa) (p = 0.03) and casting Co-Cr (20.98±4.84 MPa) alloys (p = 0.04). However, the two casting alloys were not significantly different in this regard (p = 0.93). Failure mode in all specimens was of cohesive type.

Bond strength of CAD-CAM milled sintered Co-Cr alloy was better than that of the conventional casting alloys and can serve as a suitable alternative to those alloys.