Abstract:Objective:To investigate the initial bond strength of zirconia etched with two kinds of hot acid mixtures to resin. Methods: Total 32 zirconia ceramic blocks were manufactured and divided into 4 groups received different surface treatments. Group A, sandblasting; group B, sandblasting combined with hot H2SO4 and(NH4)2SO4 mixture etching 30 min, and applying Clearfil Ceramic Primer; group C, sandblasting combined with HF and HNO3 mixture etching 30 min, and applying Clearfil Ceramic Primer; group D, sandblasting and applying Clearfil Ceramic Primer. Thirty-two composite resin columns were prepared and cemented on the pre-treated zirconia blocks with composite resin cement. Shear bond strength(SBS) test were executed after water storage for 24 hours. The zirconia surfaces treated with different treatments were observed with a scanning electron microscope. Results: The SBS values were lowest in group A, and higher in group B and group C, among 4 groups, and had no significant difference between group B and group C. There were differences in surface morphology between the hot acid etched groups and the sandblasted group by SEM observation. Conclusion: Both the two acid mixtures are able to etch to zirconia surface, and the initial SBS of zirconia to resin can be improved thereby.