Do Zirconia Translucency Affect Bond Strength of Resin-based Cements?

Objectives: To evaluate if yttria-stabilized tetragonal zirconia polycristals of different translucency affect the bond strength of resin-based cements irradiated with different curing protocols. The null hypothesis was that the bond strength to Y-TZP was not influenced by cement, thickness, and energy density.

Methods: 3 kind of Y-TZP of different translucency were selected (Noritake Katana UTML, Noritake Katana STML, Noritake Katana ML), were cut in order to obtain 1 mm and 2 mm disks (n=36 per thickness) and sintered. The disks were air-abraded with 46 µ Al₂O₃ and divided in two groups according to the luting cement (Rely X Ultimate or Panavia V5) employed to lute 2mm diameter composite cylinders to Y-TZP surface according to the manufacturer instructions. Resin-based cements were light-cured with a multiLED lamp (Valo, Ultradent) and with different energy densities (0 Joule (no light), 14 Joule and 42 Joule) by placing the light-curing tip in contact to the opposite surface of each disk. Bond strength was tested with shear-bond strength test after 24h of water storage. The fracture pattern was evaluated with an optical microscope. Results were statistically analyzed with a ANOVA test and Turkey post-hoc test (p<0.05).
Results: ANOVA test showed that the bond strength was influenced by the translucency of the Y-TZP (p<0.00001) and by the curing procedure (p<0.00001), but was not significantly affected by its thickness (p=0.59). The fracture pattern was mainly adhesive in all samples.
Results: ANOVA test showed that the bond strength was influenced by the translucency of the Y-TZP (p<0.00001) and by the curing procedure (p<0.00001), but was not significantly affected by its thickness (p=0.59). The fracture pattern was mainly adhesive in all samples.

Conclusions: The null hypothesis was partially accepted since the bond strength to zirconia mainly depended to its translucency and the energy density of curing light, but it seems to be not related to thickness. Different cements seem to not influence the bond strength even if Panavia V5 showed slightly higher bond strength.