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

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

Materials and methods: 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.

Results: 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).

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