Bond Strength of Pressed and Conventional Porcelain to Zirconia

Objectives: The purpose of this study is to determine the bond strength of pressed and conventionally veneered porcelain to yttria partially stabilized zirconia. The effect of the pressing procedure on the flexural strength of the zirconia is examined. Methods: Shear bond test: rectangles Vita YZ zirconias (14 x 15 x 2 mm) were sintered in a Vita Zyrcomat furnace. A total of 80 specimens were randomly divided into 4 groups. Conventional with/without a dentin wash and Pressed with/without dentin wash. The zirconia was veneered using a conventional powder slurry (Vita VM9, Noritake CZR) using hand vibration and condensation into a mold to create a “button” of 4mm diameter and 2mm height. A resin pattern with the same dimensions was waxed to the zirconia, invested, burned out and a pressable porcelain (Vita PM9, Noritake CZR Press) was pressed onto the zirconia in a propress 100 oven. All specimens were subjected to a shear bond test using a 4 mm notched blade (Instron). Biaxial strength test: YZ blocks were ground into cylinders and sectioned into discs approximately 11 mm diameter and 1.5 mm thick. Specimens were randomly assigned to two groups: As sintered zirconia and sintered zirconia treated with a pressing cycle. Biaxial strength is determined using Instron .

Results:

Group Shear Bond Strength (Mpa)

VM9, No wash 32.389 ± 4.56

VM9, Dentin wash 50.4068 ± 8.15

Noritake Cerabien, No wash 37.29 ± 6.9

Noritake Cerabien, Dentin wash 55.59 ± 13.36

PM9, No wash 22.73 ± 9.24

PM9, Dentin wash 29.38 ± 11.18

Noritake CZR, No wash 15.35 ± 5.75

Noritake CZR, Dentin wash 20.11 ± 7.50

There was no significant difference in YZ flexural strength after pressing.

Conclusion: Conventionally applied porcelain has significantly higher bond strength than pressed porcelain.The pressing procedure did not affect the flexural strength of partially stabilized zirconia.