Microstructure and mechanical properties of zirconia stabilized with increasing Y ₂ O ₃ , for use in dental restorations

Abstract The present in vitro study aims at characterizing dental zirconia ceramics, which are stabilized with a high amount of Y ₂ O ₃ . Two groups of specimens were fabricated by computer‐aided design/computer‐aided manufacturing technique. The specimens of each group were divided into two subgroups (SGs): SGs 1a and 2a contained a relatively low amount of Y ₂ O ₃ (6–8 wt.%), whereas SGs 1b and 2b contained a higher amount of Y ₂ O ₃ (8–10 wt.%). The influence of yttria content on their microstructure and mechanical properties was experimentally determined. The statistical significance of the differences in the mechanical properties between the SGs was evaluated by the t ‐test ( p < 5% was considered statistically significant). Homogeneous and dense ceramics with fine nanostructure, comprising grains of yttria‐stabilized tetragonal and cubic zirconia, sized between ∼160 and ∼800 nm, were produced. The increase of yttria content, which causes an increase in grain size, favors the formation of cubic zirconia, resulting in mechanical properties’ slight reduction; yet, the differences were not statistically significant. Consequently, the mechanical properties (HV 11.74–12.91 GPa, and K _IC 2.66–4.25 MPa m ^0.5 ) and the good esthetics of the investigated zirconia ceramics stabilized with high yttria content qualify these zirconia materials for fabricating dental restorations, because they can approach the properties and the esthetics of dental hard tissues as well as the tooth structure.