Background: The present study was conducted to assess the effect of lithium disilicate glass–ceramic liner, silicon dioxide based liner, and glass–ceramic interlayer on the shear bond strength (SBS) of a commercially available veneered zirconia block. Materials & Methods: The present study was conducted on 40 samples fabricated from VITA zirconia discs. Samples were divided into 4 groups. Each group had 10 samples. Group I is control group, group II is lithium disilicate glass–ceramic liner group, group III is silicon dioxide based liner, and group IV is glass–ceramic interlayer group. SBS of samples was recorded using universal testing machine. Results: The mean shear bond strength in group I was 22.3 MPa, in group II was 61.3 MPA, in group III was 62.5 MPa and in group IV was 34.2 MPa. The difference was significant (P< 0.05). The mode of failure was cohesive seen 8 in group I and 7 in group IV, adhesive seen 10 in group II and 8 in group III and combined seen 2 in group I, 2 in group III and 3 in group IV. Conclusion: Authors found that disilicate liner showed maximum shear bond strength. Maximum adhesive failures were found with lithium disilicate liner, and silicon dioxide-based liner group showed cohesive failures.
Key words: Cohesive failures, disilicate liner, shear bond strength