[Effect of sandblast treatment on resin-alloys bond strength by silicoating technique]

The purpose of this study was to investigate why sandblast treatment increases the bond strength of resin-alloy by the Silicoating technique. In this study, two types of alloy specimens, namely Ag-Pd alloy and Ni-Cr alloy, were prepared by casting. These specimens were given sandblast treatment by 37 microns or 250 microns Al2O3 particle under the following conditions: 3 kg/cm2 for 30 sec, 5 kg/cm2 for 10 sec, 30 sec and 45 sec, and 7 kg/cm2 for 30 sec. Under each condition of sandblast treatment, changes in roughness and wettability of the alloy surface were measured. After this treatment, the alloy surface was Silicoated, and then a light-cured resin was bonded to it. Specimens were stored in air for one week and thermal cycled from 4 to 60 degrees C for 10(4) cycles. The bond strength was measured by compressive shear stress. It was shown that the sandblast treatment caused the surface area to increase in the range of 1.3-1.9 times. Also, the sandblast treatment made the alloy-water contact angle smaller and wettability greater. Maximum bond strengths for Ag-Pd alloy and Ni-Cr alloy, when sandblast treated and stored in the air for one week, were 213.7 kg/cm2 and 198.7 kg/cm2 respectively. On the other hand, bond strengths for Ag-Pd alloy and Ni-Cr alloy after thermal cycling were 129.5 kg/cm2 and 159.9 kg/cm2 respectively. These values of bond strength were 2-3 times greater than those of for specimens not given the sandblast treatment. However, varying the conditions of sandblast treatment did not produce any significant differences.