A comparative evaluation of shear bond strength between feldspathic porcelain and lithium di silicate ceramic layered to a zirconia core– An in vitro study

BACKGROUND: The bond strength between the zirconia core and ceramic veneer is the weakest component in the layered structure. Delamination of veneering ceramic is reported as one of the most frequent problems associated with Veneered Zirconia restorations. The aim of this study is to compare the shear bond strength of lithium di silicate porcelain to that of feldspathic porcelain on a zirconia Substrate. MATERIAL AND METHODS: Two groups (group A and B) of zirconia blocks with each group having 20 samples were fabricated according to Schmitz Schulmeyer method. Group A (n =20 ) samples were veneered with feldspathic veneering porcelain and Group B (n=20) samples were veneered with heat pressed lithium disilicate ceramic. The fabricated samples were then evaluated for shear bond strength in Universal Testing Machine. The values were then statistically analyzed using independent sample t-test. RESULTS: Results of the current study showed that mean shear bond strength of feldspathic porcelain 11.40±1.29 MPa is comparatively lower than the mean shear bond strength of the lithium disilicate group 18.81±1.76 MPa. The statistical analysis indicated that (p value<0.01) there is a statistically significant difference in the shear bond strength between the two groups. CONCLUSIONS: The heat pressed lithium disilicate veneering materials has a better shear bond strength compared to feldspathic veneering ceramic material when layered to a zirconia core and it can be used as a viable alternative material to feldspathic porcelain layering material in bilayered zirconia restorations. Key words:Zirconia, bilayered ceramics, lithium disilicate , shear bond strength, ceramic chipping.