Aim: This in vitro study was aimed to evaluate the efficacy of a recently introduced universal adhesive in ‎replacing traditional adhesive promoters for bonding resin to ultra translucent zirconia. ‎
Materials and Methods: 8 rectangular disc-shaped ultra translucent zirconia specimens (Katana UTML ‎Kuraray Noritake Dental Inc. Tokyo, Japan) with dimensions of (18 x 10 x 2 mm) were used as bases to ‎attach 56 miniature cylinders of flowable conventional composite material (Polofil NHT Flow, VOCO ‎GmbH, Germany) with a 1 mm diameter. Every zirconia disc served as a substrate for 7composite ‎microtubes. Zirconia plates were divided into 4 groups (2 plates each) according to surface pretreatment ‎as follows: GPI: air abrasion+ Zr primer, GPII: air abrasion+ universal adhesive, GPIII: silica ‎coating+silane and GPIV:silica coating+ universal adhesive. (n=14 each). Using a wire and loop ‎technique, the micro-shear bond strength was evaluated using a universal testing equipment. Failure load ‎‎(N) was determined, and the failure type was determined when the samples were studied under a ‎stereomicroscope.‎ Data were statistically analyzed by the two-way ANOVA test.‎
Results: GPI was significantly highest mean values for micro-shear bond strength (27.83MPa±2.29) ‎followed by GPIII with less mean values (27.45MPa±3.16) but no significant difference, GPII and GPIV: ‎were significantly lowest mean values of microshear bond strength being (14.77MPa±3) and (5.16MPa±1) ‎respectively.‎
Conclusion: The bond strength decreased significantly when traditional zirconia primers with air abrasion ‎or silica coating were replaced with the tested universal adhesive alone.‎