Abstract:

BACKGROUND: Bond failure between the core and veneering ceramics is the most common cause of failure in all-ceramic restorations. Several studies have shown that the accession of colored granules can decrease the bond strength of zirconia cores materials with veneering ceramics, thereby influencing the success ratio of zirconia restorations.
OBJECTIVE: To test shear bond strength of four kinds of colored zirconia core materials and veneering ceramics, as well as to investigate the effect of colored granules on the bond strength of zirconia cores materials with veneering ceramics compared with white zirconia cores materials.
METHODS: White and colored Lava Frame, IPS E.max Zircad, Vita In-Ceram Zirconia, Cercon Smart zirconia blanks and their corresponding veneering ceramics were produced into disks with a diameter of 7 mm and a thickness of 3 mm following each manufacturers’ recommendations, such as spray sand and ultrasonic cleaning. At the center of core materials, the veneering ceramics each manufacturer recommended were veneered with handmade porcelain method. After that, the volume of veneering ceramics (with diameter of 5 mm, and thickness of 3 mm) was controlled by homemade stencils and sintered.
RESULTS AND CONCLUSION: The shear bond strength between four kinds of colored zirconia based combinations and white zirconia based combinations had no significant difference (P > 0.05).These showed that the accession of colored granules had no influence on the bond strength between zirconia and veneering ceramics. The proportions of failures at the zironia-ceramic combinations interface and shear bond strength values from high to low were Lava, IPS E.max, Vita In-Ceram Zirconia and Cercon, respectively. Focal laser scanning microscope showed that the failure mode of combinations at fractured surface was cohesive failure within the veneering ceramics and interface adhesion failure. Besides, the major failure was cohesive failure within the veneering ceramics rather than core failure.