In Vitro Degradation of Mg-Doped ZrO₂ Bioceramics at the Interface with Xerostom^® Saliva Substitute Gel

Zirconia-based bioceramics, one of the most important materials used for dental applications, have been intensively studied in recent years due to their excellent mechanical resistance and chemical inertness in the mouth. In this work, the structural, morphological and dissolution properties of the Zr_1-xMg_xO₂ (x = 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3) system, prepared by the conventional ceramic method, were evaluated before and after immersion in saliva substitute gel (Xerostom^®, Biocosmetics Laboratories, Madrid, Spain), one of the most common topical dry mouth products used in dentistry. The X-ray powder diffraction (XRPD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) techniques were employed to investigate the phase transformations and morphology of the ceramics during the degradation process in Xerostom^®. In vitro analyses showed overall good stability in the Xerostom^® environment, except for the x = 0.05 composition, where significant t- to m-ZrO₂ transformation occurred. In addition, the strong interconnection of the grains was maintained after immersion, which could allow a high mechanical strength of the ceramics to be obtained.