A comparison of bond strength of layered veneering porcelains to zirconia and metal

Statement of problem High chipping rates of veneering porcelain for zirconia ceramic restorations have been reported in clinical studies. The information on the bonding behavior of veneering porcelain to zirconia frameworks is limited. Purpose This study assessed the relationship between coefficient of thermal expansion (CTE) and shear bond strength of veneering porcelain to zirconia frameworks. Material and methods Zirconia ceramics (Katana; ZrO2 ), casting gold alloy (DeguDent U; DEG), and feldspathic porcelain (Cerabien ZR; CZR) were used as the bonding substrates. Five types of porcelain (CZR, Cercon ceramkiss (CER), IPS e.max Ceram (EMX), Vintage ZR (VZR), and VITA VM 9 (VM9)) were fired to ZrO2 discs (n=8). Feldspathic porcelain (Super Porcelain AAA; AAA) designed for metal ceramic systems was fired to DEG discs. To evaluate the strength of veneering porcelain, CZR was veneered on CZR discs. The porcelain with a strong thermal mismatch for each substrate was applied; AAA and CZR were applied to ZrO2 and DEG substrates, respectively. Shear bond strength was tested after 24 hours of water storage. Debonded surfaces were examined with an optical microscope and SEM. Data were analyzed with 1- and 2-way ANOVA followed by Dunnett and Tukey multiple comparison tests (α=.05). Results No significant differences in the mean shear bond strength (MPa) were found between groups ZrO2 -VZR (24.8), ZrO2 -CZR (27.0), and ZrO2 -VM9 (30.9). ZrO2 -CER (22.0) ( P =.017) and -EMX (22.1) ( P =.020) groups had significantly lower bond strengths than the ZrO2 -CZR group. ZrO2 -CZR, -VM9, -CER, -VZR, and -EMX groups demonstrated cohesive failures in veneering porcelain. There was no significant difference among the groups ZrO2 -CZR, DEG-AAA, and CZR-CZR. Two-way ANOVA showed that interaction between the 2 factors was significant ( P