Aim: The purpose of this study is to evaluate and compare the effect of immediate dentin sealing on the shear bond strength of both Super translucent and Top translucent monolithic zirconia to monolithic lithium disilicate glass-ceramics.

Materials and Methods: Forty-two sound molars were prepared and embedded in resin blocks. The specimens were divided into three main groups (N=14); 1) Lithium disilicate LD, 2) Super-translucent zirconia ST, 3) Top-translucent zirconia TT. Each group was subdivided into two subgroups (n=7)with and without IDS. LD blocks were cut into 14 discs. ST and TT zirconia blanks were milled with larger sizes to compensate for shrinkage after sintering. LD Discs were surface treated with hydrofluoric acid and a silane coupling agent. The surfaces of zirconia samples were treated by airborne-particle abrasion and ceramic primer. All samples were cemented to teeth specimens. Thermal cycling was performed. The samples were subjected to a shear bond strength test. Data were recorded and statistically analyzed.

Results: IDS, E-Max CAD recorded the highest shear bond strength mean value followed by ST Zirconia, then TT Zirconia (4.28 MPa). Tukey's posthoc showed a non-significant difference between E-Max CAD and ST Zirconia, and a significant difference between both E-max CAD and ST Zirconia to TT Zirconia. Bonding after IDS recorded a statistically significant (P<0.05) higher shear bond strength value than bonding without IDS.

Conclusions: Surface treatment of translucent zirconia showed a reliable bond but lower than lithium disilicate ceramic. The protocol of IDS is recommended before ceramic bonding.