European Journal of Molecular & Clinical Medicine

Introduction: All ceramic restorations which are comprised of porcelain veneer on a
zirconia substructure are gaining more interest since it almost replaced all the metal
ceramic restorations. The evaluation of bond strength of layered porcelain over zirconia
substructure could be just subjected to shear bond strength test, three & four points
flexure, tensile and micro-tensile bond test.
Materials and Methods: The study was designed as an in-vitro study which was
conducted in Surendera Dental College & Research Institute, Sri Ganganagar,
Rajasthan, India. The number of study samples were set at 80 which are fabricated
from VITA zirconia discs. Samples were divided into 4 groups. Each group having 20
samples. All the 80 samples were loaded under a standard shear load at a crosshead
speed of 0.5 mm/min and load was noted using universal testing machine (Asian
Universal Testing Machine, LRX 2K5, Hants, UK). Sample was taken for further
evaluation of the fracture mode. SEM study was done at 49 X, 350 X and 1000 X.
Statistical analysis was performed.
Results: 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. Mean shear bond strength in group I was 22.5 MPa, in group II was 62.2 MPA,
in group III was 63.4 MPa and in group IV was 34.9 MPa. The difference was
significant (P< 0.01).
Conclusion: SBS was reported maximum after the application of lithium disilicate
glass–ceramic liner at 930°C followed by glass–ceramic interlayer at the same sintering
temperature which is 930°C and silicon dioxide-based liner at 930°C. The fractographic
behaviour analyses that zirconia samples lined with lithium disilicate glass–ceramic
liner presented with adhesive failures (failure between glass–ceramic liner) whereas the
use of silicon dioxide-based liner showed cohesive failures (failure within veneering
porcelain) while the control group revealed with both cohesive and combined failures.