Long-Term Corrosion Behavior of Y-TZP Dental Ceramics

Zirconia-based ceramics are widely used in dental applications due to their excellent mechanical and chemical properties. The aim of this study was to evaluate the chemi-cal stability of yttria partially stabilized zirconia (Y-TZP) dental ceramics using a modified testing protocol based on ISO 6872. Two sample groups of Y-TZP material were used: Group 1 - pure polished zirconia, and Group 2 - pure polished zirconia with an additional glaze layer. Chemical stability, defined as corrosion resistance, was as-sessed by measuring ion release using inductively coupled plasma mass spectrometry (ICP-MS) and by analysing the phase composition using X-ray diffraction (XRD). While ISO 6872 prescribes chemical stability testing in a 4 wt.% aqueous acetic acid (CH₃COOH) solution at 80 °C for 16 hours, the exposure duration in this study was extended to 768 hours (32 days) to enable more accurate determination of long-term corrosion behaviour. Kinetic analysis revealed that degradation followed a near-parabolic rate law, with power-law exponents of n = 2.261 for Group 1 and n = 1.935 for Group 2. The corresponding corrosion rate constants were 3.85 × 10−5 µgn⋅cm−2n⋅h−1 for Sample 1 and 132.3 µgn⋅cm−2n⋅h−1 for Sample 2. XRD results indicated that the corrosion process led to a partial phase transformation of zirconia from the tetragonal to the monoclinic phase.