Surface Characterization and Short-term Adhesion to Zirconia after Ultra-short Pulsed Laser Irradiation

Purpose: To evaluate the suitability of an ultra-short pulsed laser (USPL) to treat zirconia ceramic surfaces and increase their adhesion to dual-curing resin cement. Materials and Methods: Twenty 10 × 10 × 5 mm³ blocks were prepared from a zirconia ceramic (Y-TZP). The specimens were polished and randomly assigned to four groups (n = 5) which received the following surface treatments: sandblasting (SB) with Al₂O₃ particles and silica coating (SC) with SiO₂ particles as positive controls; two groups received USPL irradiation, one with 10 scan repetitions (L10) and the other with 20 (L20). Laser irradiation was performed at 1030 nm, 2.3 J/cm², 6 ps pulse duration. The ceramic blocks were duplicated in composite resin and cemented with a dual-curing resin cement. Half of the blocks were then stored in water (37°C) for 24 h and the other half for 1 month. At each time, 40 to 60 sticks per group were subjected to microtensile bond strength testing. Data were analyzed statistically using the Kruskal-Wallis test (α = 0.05). Results: Laser-treated zirconia presented statistically significantly higher roughness than did SB and SC. After 24 h, the highest bond strength means (MPa) were achieved by L10 (42.3 ± 10.8) and L20 (37.9 ± 14.4), and both of them were statistically significantly higher than SB (22.0 ± 5.3) and SC (20.8 ± 7.1) (p 0.05). After 1 month of storage, L10- and L20-treated zirconia still showed significantly higher bond strengths than did SB- and SC-treated zirconia (p 0.05). Conclusion: USPL irradiation significantly increases bond strength of zirconia ceramic to dual-curing resin cement and might be an alternative for improving adhesion to this material. Keywords: yttria-stabilized tetragonal zirconia polycrystal, luting, laser, sandblasting, silica coating, roughness