In this work, three different commercial lithium silicate (LS) glass‐ceramics for computer aided design/computer aided machining systems, CeltraDuo‐Dentsply (LS‐C), E‐MaxCAD‐Ivoclar (LS‐E), and Suprinity‐Vita (LS‐S), were comparatively characterized. Following the protocols recommended by the manufacturers, the glass‐ceramics were heat‐treated under low vacuum and characterized by X‐ray diffraction, scanning electron microscopy, hardness, fracture toughness, Young's modulus, and flexural strength. Rietveld refinement indicated that the materials “as‐received” present mostly amorphous phase and Li2SiO3 as secondary crystalline phase in LS‐E and LS‐S specimens, while LS‐C specimens also present Li2Si2O5 and Li3PO4 as crystalline phases. All “as‐received” glass‐ceramics present hardness, fracture toughness, and Young's modulus of around 647‐678 HV, 1.15‐1.40 MPa.m1/2, and 82‐92 GPa, respectively. After heat treatment, the LS‐C and LS‐S specimens presented decreasing of amorphous phase associated to Li2SiO3 and Li2Si2O5 grains with low aspect ratio, while LS‐E indicates a reduction of amorphous phase and Li2Si2O5 elongated grains. Fracture toughness and Young's modulus increase about 10% due to the crystallization of residual amorphous phase for all materials. Moreover, crystallographic and microstructural characteristics are responsible for the higher flexural strength of LS‐E (327 MPa), regarding LS‐C and LS‐S. However, the glass‐ceramics LS‐E present lower Weibull modulus (m = 5.4) comparatively to LS‐C (m = 9) and LS‐S (m = 6).

The objectives of this study were to characterize and evaluate the physical and mechanical properties of an experimental zirconia for dental application and compare the biaxial flexural strength results with the finite element simulation (FEM). Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic samples were sintered at 1475 °C/2 h and characterized by X-ray diffraction, scanning electron microscopy, relative density, flexural strength using piston-on-three balls (P-3B) test and Young’s modulus. From the flexural strength results, numerical simulations were performed using Abaqus software. The complete model used 70216 elements, considering the components of the test. The results indicated full densification of sintered samples, ZrO2-tetragonal and ZrO2-cubic as crystalline phases, and average grain size of 0.6±0.2 μm. Mechanical characterization of sintered samples indicated Young’s modulus of 195±4 GPa, flexural strength of 1191±9 MPa and Weibull modulus m=16.3. FEM simulation indicated a flexural strength close to 1100 MPa, with a difference lower than 7% in relation to the experimental results. The results were compared associating the physical and mechanical properties of Y-TZP with its intrinsic phenomena such as tgm transformation and ferroelastic domain.

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This work evaluates the effects of grain growth and tetragonality of the t-ZrO2 phase on the mechanical properties of 3Y-TZP ceramics. Samples were sintered at 1475 °C for 2 h, and at 1600 °C for 2, 12, or 24 h. After sintering, the tetragonal ZrO2 polytypes t and t′ were observed under all sintering conditions, while a residual content of monoclinic ZrO2 was detected in samples sintered at 1600 °C for 24 h. The average grain size was found to vary from 0.65 ± 0.10 to 2.20 ± 0.35 μm. Moreover, zirconia ceramics sintered at 1475 °C for 2 h exhibit higher flexural strength (1210 ± 85 MPa), while samples sintered at 1600 °C for 24 h exhibit the lowest flexural strength (910 ± 90 MPa). These results were related to the progressive formation of Y3+-rich grains (t′-ZrO2) due to the grain boundary segregation-induced phase (GBSIPT) mechanism. Due to the high stabilizer concentration in the solid solution, these grains present lower tetragonality, being highly stable at room temperature. Consequently, the observed strength reduction of samples sintered at 1600 °C for 24 h is related to the presence of the t′-ZrO2 phase, which is less prompt to the phase transformation toughening process, limiting shielding zones’ effectiveness at the crack tip.

In this work, dental ceramics based on ZrO2-Y2O3, made by cold isostatic pressing, were characterized and the properties were compared to conventional uniaxially pressed blocks. Pre-sintered ZrO2-3%mol Y2O3 blocks were sintered at 1530oC-120min. The crystalline phases were identified by X-ray diffraction (XRD) and microstructural analysis was performed using Scanning Electron Microscopy (SEM). The materials were mechanically evaluated for their hardness, fracture toughness and its bending strength. The results of mechanical tests indicate that the ceramics studied showed hardness greater than 1220HV, fracture toughness of about 8.2 MPam1/2 and bending strength higher than 1000 MPa. The results indicate excellent mechanical behaviour and negligible differences between uniaxial and isostatic products, but it is possible to see an increase of homogeneity in the final shrinkage after sintering.