Fabrication and characterization of polymer-infiltrated ceramic network materials based on nano-tetragonal zirconia

Abstract

Fabrication and characterization of polymer infiltrated ceramic networks (PICNs) were undertaken for use in dentistry. Calcia-stabilized tetragonal zirconia (7-tCSZ) nanoparticles were synthesized via a modified co-precipitation. The composition and particle size of the prepared nanoparticles were studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Densification parameters of porous ceramic samples, with varying amounts of 7-tCSZ, 0, 5, 10, and 15 wt.%, and PICN materials were examined using the Archimedes principle. The flexural strength and elastic modulus of PICNs were measured using a three-point bending strength test. The microhardness and fracture toughness were determined using Vickers microhardness and V-notched bars tests, respectively. The microstructure was investigated for selected materials before and after polymer infiltration using scanning electron microscopy (SEM). The results revealed that the samples with 10 and 15 wt.% of nano-tetragonal zirconia showed the highest elastic modulus (8.24 GPa) and fracture toughness (1.82 MPa m1/2), respectively, which is attributed to transformation toughening of zirconia. The flexural strength and microhardness of PICNs were in the range 66.14–71.72 MPa, 0.18–0.19 GPa, respectively, whilst the brittleness index was maximally 0.21 μm−½, which is significantly below the ultimate brittleness index (4.3 μm−1/2) allowing machinability. Conclusively, the inclusion of nanometric zirconia posed a dramatic enhancement of the mechanical properties without affecting the machinability of these biomimetic materials, making them similar to natural dentin in terms of the elastic modulus and fracture toughness along with ease of machinability, which renders them promising as indirect dental restorative materials.