Pr-doped 3Y-TZP nanopowders for colored dental restorations: Mechanochemical processing, chromaticity and cytotoxicity

Motivated by dental applications, Pr-colored 3Y-TZP nanopowders were prepared via the mechanical activation of ZrOCl2·8H2O, YCl3·6H2O and PrCl3·7H2O and NaOH in a planetary ball mill and subsequent heat treatment. The preparation processes were investigated using thermogravimetric and differential thermal analyses (TG-DTA) and X-ray diffraction (XRD). The obtained samples were characterized by transmission electron microscopy (TEM), XRD and X-ray photoelectron spectroscopy (XPS). The effects of the doped Pr content on chromaticity and cytotoxicity of the sintered ceramic discs were evaluated from the esthetic and biocompatible viewpoints. The results indicated that the obtained 3Y-TZP powders were tetragonal-structured and less than 10 nm in average size. The doping of trace Pr into 3Y-TZP endowed the sintered sample with shades similar to the natural teeth but showed high biological safety according to in vitro cytotoxicity tests. Therefore, Pr-colored 3Y-TZP nanopowders synthesized by mechanochemical processing are the promising materials for colored dental restorations combining esthetic with biocompatibility.