Superficial Treatments and Bond Strength of Composite-Resin to Zirconia

Objectives: To evaluate the shear bond strength of composite-resin to zirconia applying z-Prime™Plus after three different surface treatments.
Methods: Twenty zirconia slabs (Katana, Noritake )(18mm x 10mm x 1.8mm) were equally divided in four groups and received randomly one of the following mechanical treatments: Group 1= no mechanical superficial treatment, Group 2= Sandblasting with 50µm Al₂O₃, Group 3= Sandblasting with 100µm Al₂O₃, Group 4= 30µm fine diamond rotary cutting instrument with water irrigation. After the mechanical treatments z-Prime™Plus (Bisco Inc., Schaumburg, IL) was applied on all zirconia slabs according to the manufacturers' instructions. After surface conditioning, two cylinders of composite resin (P60, 3M ESPE, Seefeld, Germany) were fabricated directly on the zirconia surface using a mold (2mm diameter, 3mm in length). All specimens in each experimental group (n=10) were stored in distilled water for 24 hours at 37°C and afterwards subjected to a shear bond strength test (SBS) at a crosshead speed of 1 mm/min until fracture on a universal testing machine (Tinius Olsen H10K-S). Bond strength was calculated in MPa, and analyzed with one-way ANOVA and Tukey-Kramer test (p=0.05).
Results: Means and standard deviations are depicted in the table below. The fourth experimental group presented the highest SBS values, which were significantly different from the other treatment groups. The group that didn't receive any mechanical superficial treatment showed the lowest SBS values.
Conclusions: Mechanical superficial treatments increase SBS of composite resins to a zirconia surface when using z-Prime™Plus. The highest bond strength values were observed in specimens grinded with diamond burs.