bond strength of porcelain to milled sintered and casting base metal alloys

Statement of the problem: the 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/computer-aided manufacturing (cad/cam) techniques. purpose: this study aimed to compare the bond strength of porcelain to milled sintered (sintron) and casting (co-cr and ni-cr) base metal alloys. materials and method: 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 micro-scope. data were analyzed with one-way anova and tukey's post hoc test (α=0.05). results: 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). the failure mode in all specimens was of cohesive type. conclusion: bond strength of cad/cam milled sintered co-cr alloy was better than that of the conventional casting alloys and could serve as a suitable alternative to those alloys.