Effect of Sintering Conditions and Acidic Environments on the Wear of 5Y-ZP Zirconia

Background/Objectives: This study evaluated the influence of sintering conditions and acidic environments on the wear of 5 mol% yttria-stabilized zirconia (5Y-ZP). Methods: Sixty zirconia specimens were divided into two sintering groups (conventional and speed) and three immersion media (n = 10): distilled water, Coca-Cola, and vinegar. Wear testing was performed using a chewing simulator under a 49 N load for 120,000 cycles, simulating 6 months of clinical function. Volume loss, mean wear depth, and surface roughness were measured using a 3D profilometer. Surface and compositional analyses were performed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). Results: Significant differences in wear were observed (p < 0.05). The greatest wear occurred in distilled water (58.927 ± 13.199 µm; 0.3518 ± 0.1062 mm3 for speed-sintered and 53.408 ± 6.784 µm; 0.3211 ± 0.0546 mm3 for conventional). Vinegar produced moderate wear (15.478 ± 2.584 µm; 0.0482 ± 0.0142 mm3 and 11.575 ± 3.334 µm; 0.0360 ± 0.0116 mm3), whereas Coca-Cola produced the least (2.899 ± 1.377 µm; 0.0049 ± 0.0027 mm3 and 1.870 ± 0.688 µm; 0.0027 ± 0.0012 mm3). Sintering condition affected only wear depth. SEM showed localized surface alterations in acidic media, EDS revealed reduced yttria content, and XRD revealed no detectable monoclinic phase, with no interaction between variables. Conclusions: Acidic environments had a greater influence on the wear of 5Y-ZP zirconia than sintering conditions. Speed sintering influenced wear far less than the immersion medium, supporting its use in patients exposed to acidic conditions.