Chemical Bond Strength of Coupling Agents to Different Zirconia

Objectives: To evaluate the bond strength between polymer cements and zirconia by chemical means of different coupling agents without any micromechanical retention.
Methods: 40 samples, 5x10 mm of each zirconia, NexxxZr, Katana Multil;ayer and Katana Ultratransluscent were sinterized following manufacturer’s instructions before being embeded in acrylic and then polished with 600 grit SiC paper under water. Porcelain was kept un-etched and was not sandblasted. Each group was divided into 4 sub-groups of 10 specimens each to receive silanes: Monobond-S (Ivoclar/Vivadent), Bis Silane (BISCO), Clearfil Ceramic Primer (Kuraray) and zirconia coupling agent Z-prime (BISCO) all following manufacturer’s instructions.
2 mm diameter prefabricated composite cilinders (Brilliant, Coltene) were roughened and cemented on each sample with Variolink II (Ivoclar Vivadent) after a previous coat of Tetric N-Bond (Ivoclar Vivadent), applying a 500gr force and eliminating excess before light curing. Specimens were stored at 37° C for 7 days in 100% relative humidity before being tested in shear at 0.1 cm/min speed until failure. Data were stored in MPa and analyzed with a two-way ANOVA and means were compared with Tukey-Kramer test, both calculated at a 0.05 significance level.
Results: Results shown in table. Clearfil CP showed a statistically significant higher bond strength than others. Monobond-S had statistically higher BS than Bis-silane for Katana Multilayered. All groups showed high variation
Conclusions: There was no significant difference on bond strength among zirconia types, but Clearfil Ceramic Primer showed significantly higher chemical bond strength than the other coupling agents.