Analysis of the effect of artificial aging on the phase composition of zirconia dominated by the cubic and tetragonal phases with polished and glazed surfaces: An in vitro study

Context: Zirconia ceramics are widely utilized in restorative dentistry due to their strength and aesthetics. They are characterized by having predominantly tetragonal or cubic phases based on yttria content. Aims: The aim of the study was to assess the influence of artificial hydrothermal aging on the phase content of zirconia materials with major cubic or tetragonal phases, and to determine how surface treatments (glazing vs. polishing) affect this response. Subjects and Methods: Commercial 3 mol.% yttria-stabilized tetragonal zirconia polycrystal, 4Y/5Y-PSZ, and hybrid multilayer variants were used to prepare standardized zirconia discs (1 mm thickness, 10 mm diameter). The discs were treated with either glazing or polishing. Artificial aging was conducted at 134°C and 2 atm in an autoclave for 12 h. Phase composition was evaluated before and after aging through X-ray diffraction (XRD). Intensity changes in the peak and full width at half maximum (FWHM) were analyzed. Results: XRD analysis showed that all zirconia materials maintained their major phase composition upon aging. No notable phase transformations to the monoclinic phase were seen in tetragonal or cubic-rich materials. Polished and glazed specimens both maintained initial phase composition. Minor peak broadening in polished specimens suggested surface-level microstructural changes such as decreased crystallite size and internal stress. Statistical processing established the phase composition stability (P > 0.05) and weak, nonsignificant correlation between peak intensity and FWHM (r = -0.253, P = 0.481). Conclusions: Cubic and tetragonal phase-dominant zirconia ceramics show excellent phase stability under simulated aging, which endorses their clinical reliability. Polishing is more effective than glazing in improving resistance to microstructural degradation. © 2025 Elsevier B.V., All rights reserved.