The effect of different surface treatments on the bond strength to zirconia

To evaluate the effect of various surface treatment methods on zirconia as it affects the bond strength to its substrate.

Sintered zirconium dioxide ceramic disks (KATANA Zirconia STML; n = 20; size 12 × 12 × 3 mm) were divided into five groups: no surface treatment (Group C), air-particle abraded with 50 µm aluminum oxide (Group AA), air-particle abraded with glass beads (Group GB), Zircos E etching solution for 2 h (Group ZE), and 48% hydrofluoric acid solution heated at 25°C for 30 min (Group HE). Cylindrical composite resin specimens (2.1 mm in diameter, 3 mm in height) were bonded to the zirconia samples with resin cement (Panavia V5) under a load of 1000 g and light cured for 80 s. Each group was divided into two subgroups, and shear bond strength (SBS) was tested at a crosshead speed of 1 mm/min after storage in distilled water for 24 h at 37°C or after 10,000 thermocycles. The fractured surfaces of specimens were inspected with a stereo microscope, and failure modes were classified as adhesive, cohesive, or mixed failures. One-way ANOVA test and paired t-test were applied for statistical analysis.

Highest mean SBS values [MPa] were observed for Group AA (14.98 ± 3.19) followed by Group HF (14.8 ± 0.83), Group C (8.32  ± 1.95), Group GB (9.29 ± 0.99), and Group ZE (4.83 ± 0.47). Mean SBS values (MPa) of all the groups decreased significantly after thermal cycling and were for 5.45 ± 0.8 (Group C), 13.47 ± 2.33 (Group AA), 8.56 ± 1.35 (Group GB), 4.16 ± 0.63 (Group ZE), and 13.15 ± 1.27 (Group HF).

Air-particle abrasion with alumina and heated 48% hydrofluoric acid provide higher bond strengths than the other surface treatments tested.