New zirconia-based materials for dental applications. Structural, morphological and histological evaluation

Abstract The aim of this study is to investigate the effect of co-doping with aluminum or iron on structure, thermal behavior, morphology and biocompatibility of Y-TZP (yttria-tetragonal zirconia polycrystals). Powders with stoichiometries Zr 0.88 Y 0.12 O 2-δ and Zr 0.85 Y 0.12 M 0.03 O 2-δ (M = Fe, Al) have been synthesized using a Pechini method. Powders were characterized by X-ray diffraction (XRD) and dilatometry. They were further shaped into pellets and sintered at 1300 °C for 10 h. The sinters were investigated by XRD, Raman spectroscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDXS). Sintered discs were inserted in oral mucosa of laboratory rats for six weeks. The local tissular reaction was evaluated by optical microscopy and histological study. Tested discs were investigated by SEM-EDXS and Raman spectroscopy. Small additions of aluminum and iron led to an improvement in powder sintering behavior of tetragonal yttria-stabilized zirconia polycrystals, while the morphology of the sinters is strongly affected. Biocompatibility tests shown that the tested samples tend to be surrounded by fibrous connective tissue. No major adverse reaction was evidenced for the discs inserted into the oral mucosa of lab rats. While single-doped zirconia with 6 mol % yttria is stable, additions of aluminum or iron led to formation of monoclinic secondary phase in the testing conditions. The lack of major adverse reactions in the surrounding tissues make these materials promising candidates for their use in dental prosthetics.