Introduction: This invitro study evaluated the effect of ultrasonic cleanser after casting surface treatment on bond strength of alloy to enamel. Therefore, the aim of this study was to evaluate the effect of ultrasonic on bond strength of etched base metal.
Materials and Methods : 80 sound canines were selected. After cleaning and mounting in cold cured acryle, rectangular Ni-Cr-Br plates with 9 mm² surface area and 0.5 mm thickness were made that adapted with lingual surfaces. One process was created in mid part of each plate. Fitting surface of all samples were sandblasted. They were divided into two groups of 40,based on the type of treatment: A)surface treatment with acidic M3 gel. B) surface treatment with 150-200µ alumina sandblast. Finally each group was divided into two subgroups of 20, based on using the ultrasonic or without using it. Then samples were adhered to lingual surfaces with Scotch Bond Mulit Purpose (3M – Co). and Duo Cement (Coltene). After 1000 thermal cycling, shear test was established by cross head speed of 2mm/min. Data analysis was done by two variables ANOVA with 95% significance level.
Results:  1. Mean bond strength was significantly greater in subgroup without ultrasonic use (60-74 kg) than the other subgroups (45-62kg).
2. The group using just M3 acidic gel without ultrasonic had the greatest bond strength (74.52 kg).
3. Comparing two factors (Sandblast- Acid), bond strength was greater after using acid.
4. Increase in bond strength was observed in all groups without ultrasonic use.
Conclusion : Use of M3 acidic gel without ultrasonic use increases the bond strength of Ni-Cr-Br alloy to enamel significantly.