New Perspectives on Zirconia Composites as Biomaterials

Abstract

Zirconia–alumina composites couple the high toughness of zirconia with the peculiar properties of alumina, i.e., hardness, wear, and chemical resistance, so they are considered promising materials for orthopedic and dental implants. The design of high performance zirconia composites needs to consider different aspects, such as the type and amount of stabilizer and the sintering process, that affect the mechanics of toughening and, hence, the mechanical properties. In this study, several stabilizers (Y2O3, CuO, Ta2O5, and CeO2) were tested together with different sintering processes to analyze the in situ toughening mechanism induced by the tetragonal–monoclinic (t–m) transformation of zirconia. One of the most important outcomes is the comprehension of the opposite effect played by the grain size and the tetragonality of the zirconia lattice on mechanical properties, such as fracture toughness and bending strength. These results allow for the design of materials with customized properties and open new perspectives for the development of high-performance zirconia composites for orthopedic implants with high hydrothermal resistance. Moreover, a near-net shape forming process based on the additive manufacturing technology of digital light processing (DLP) was also studied to produce ceramic dental implants with a new type of resin–ceramic powder mixture. This represents a new frontier in the development of zirconia composites thanks to the possibility to obtain a customized component with limited consumption of material and reduced machining costs.

Porous Biocoatings Based on Diatomite with Incorporated ZrO2 Particles for Biodegradable Magnesium Implants

“…The analysis of the phase composition of the coatings showed the presence of an amorphous phase and crystalline phases in the coatings-zirconium oxide in monoclinic and tetragonal modifications, as well as magnesium oxide. Ceramics based on zirconium dioxide are known to have high mechanical strength, chemical resistance, and wear resistance [63,64]. In the presented study, the incorporation of ZrO 2 particles into the diatomite coating managed to increase the mechanical strength and corrosion resistance of the coatings.…”

Three-Dimensional-Printed Molds from Water-Soluble Sulfate Ceramics for Biocomposite Formation through Low-Pressure Injection Molding

“…phase stabilizing; otherwise, with a higher amount of Y2O3 (7 wt.%), the mechanical characteristics tended to worsen [62,63]. In the current research, we proposed adding 5 wt.% Y-TZP to the raw mixture of sulfates.…”

“…Tetragonal phase is thermodynamically stable until 1367 K [59]; so, under sintering conditions, T→M transformation is not likely to occur [60,61]. Another significant feature is that 3 wt.% of yttrium oxide is optimal for tetragonal phase stabilizing; otherwise, with a higher amount of Y 2 O 3 (7 wt.%), the mechanical characteristics tended to worsen [62,63]. In the current research, we proposed adding 5 wt.% Y-TZP to the raw mixture of sulfates.…”

Manufacturing and Characterization of Dental Crowns Made of 5-mol% Yttria Stabilized Zirconia by Digital Light Processing

“…However, these values were lower than those obtained using dental CAD/CAM due to lower densification. Thus, enhancing densification behavior of zirconia, for example, by increasing solid loading in zirconia suspensions and/or using new sintering processes (e.g., microwave sintering [ 62 ] and two-step sintering [ 63 ]), still remains as one of the most challenging tasks in DLP of zirconia for dental applications [ 6 ].…”