Methods: Plastic patterns (l:25, w:3, h:0.6, n: 240) were equally shared in four groups and cast with Au-Pt (d.Sign 98, Ivovlar Vivadent), Ni-Cr (4 all, Ivocalr Vivadent), Co-Cr alloys (d.Sign 30, Ivocalr Vivadent) and cpTi grade II (J Morita Co) respectively. The specimens of each alloy were metallographically ground/polished and divided in 12 subgroups, which were sandblasted employing all combinations of Al2O3 grit-sizes (50, 100, 250) and propulsion pressures (0.15, 0.30, 0.45, 0.60 MPa). The surfaces were then imaged using backscattered electron emission and analyzed by SEM/EDX in area scan mode. The results of Al (%at) content were statistically analyzed by two-way ANOVA (grit-size and pressure discriminating variables). Significant differences among subgroups were determined by using Tukey multiple comparison test (a:0.05).
Results: All alloys showed a substantially amount of retained Al within the following range (%at): Au-Pt(10.0~20.0), Ni-Cr(16.5~26.3), Co-Cr(10.7~20.9), cpTi(8.1~12.4) with significant differences among subgroups. The discriminating variables showed significant interactions for Au-Pt, Ni-Cr and Co-Cr alloys, implying a synergistic effect on the extent of embedded Al2O3 fragments. For cpTi, no significant differences were found, denoting that the extent of retained Al2O3 fragments was independent of the selected sandblasting conditions.
Conclusions: Specific sandblasting conditions showed less retained Al2O3 fragments on Au-Pt, Ni-Cr and Co-Cr alloys, decreasing their detrimental effect on metal-ceramic strength.