Adhesion to 4YSZ ceramic: Effect of Er:YAG laser irradiation and airborne abrasion

This study evaluated the effect of Er:YAG laser irradiation on the bond strength (BS) to 4 mol% yttria-stabilized zirconia, considering different surface conditions and aging conditions. Zirconia specimens (n = 21) were prepared with two surface conditions (polished or simulated CAD/CAM) and subjected to three surface treatments: Airborne Abrasion (AA - 45 μm), Er:YAG Laser irradiation (LS - wavelength of 2.94 μm, with an output energy of 300 mJ per pulse, a frequency of 10 Hz, and an output power of 3 W, for 30 s), and their combination (AL). A 10-MDP-containing primer was applied to the treated surface and cylinders of a resin cement were built up. BS was evaluated after 24 h (baseline) or after aging (120 days of storage followed by 25,000 thermocycles). Microshear bond strength (μSBS), surface roughness, topography and failures were analyzed. For polished, AA-BS showed the highest μSBS value (27.26 ± 3.74 MPa), while LS-AG showed the lowest value (0.42 ± 0.21 MPa). For simulated CAD/CAM, AA-BS and AA-AG showed the highest values (24.33 ± 5.17 and 24.99 ± 3.77 MPa, respectively), whereas LS-AG showed the lowest value (0.49 ± 0.70 MPa). In both surface conditions, LS showed lower μSBS than AA and AL, and AL did not improve bond strength compared with AA alone. Aging reduced μSBS depending on the surface treatment and was associated with a high incidence of pre-test failures in LS-AG groups (n = 16). SEM showed localized surface modifications after LS. AA provided the most reliable bonding to 4YSZ, whereas LS did not improve adhesion.