Effects of low-pressure plasma and ytterbium fiber laser on zirconia surface properties and bond strength to gingiva-colored composite.

PURPOSE: To evaluate and compare the effects of surface activation by low-pressure plasma (LPP) and surface texturing by ytterbium fiber laser (YFL) treatments on zirconia surface properties and shear bond strength (SBS) to a gingiva-colored indirect composite under aged and non-aged conditions. MATERIALS AND METHODS: Sixty zirconia specimens were prepared, polished, sintered, and air-abraded under standardized conditions. The specimens were randomly assigned to three groups according to the applied surface treatment: control, LPP, and YFL. Surface roughness and contact angle were measured before and after surface treatments. A gingiva-colored indirect composite was bonded to the zirconia surfaces using an 10-Methacryloyloxydecyl dihydrogen phosphate (MDP) containing primer and standardized mold. Each group was further divided into aged and non-aged subgroups (n = 10). Thermal aging was performed using thermocycling (5000 cycles, 5°C-55°C). SBS was measured, and failure modes were analyzed. Surface morphology, phase composition, and representative failure modes were evaluated using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. RESULTS: Surface treatments influenced zirconia wettability, with LPP showing a greater reduction in contact angle compared to YFL. YFL groups exhibited higher SBS values than both LPP and control groups under both aged and non-aged conditions. Thermal aging showed a significant overall effect on SBS, although no significant differences were observed between aged and non-aged specimens within each surface treatment group. Failure modes were predominantly adhesive in low-strength groups, whereas mixed failures were more frequent in high-strength groups. CONCLUSION: YFL enhanced bond strength at the zirconia and gingiva-colored composite interface compared to LPP, whereas aging showed a small but significant overall effect on bond strength, with no significant interaction between aging and surface treatment.