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Statement of problem The crystallization process of lithium disilicate crowns has been reported to cause dimensional change, but whether the fit of chairside computer-aided design and computer-aided manufactured (CAD-CAM) zirconia-reinforced lithium silicate crowns is affected is unclear. Purpose The purpose of this in vitro study was to evaluate with a 3-dimensional superimposition analysis technique the marginal and internal adaptation of fully crystallized versus partially crystallized zirconia-reinforced lithium silicate ceramic CAD-CAM fabricated crowns. Additionally, the silicone replica technique and direct viewing of marginal gap values were compared with the 3-dimensional superimposition analysis technique. Material and methods The marginal and internal adaptation of a fully crystallized zirconia-reinforced lithium silicate (CELTRA DUO) were compared with those of a partially crystallized zirconia-reinforced lithium silicate (VITA SUPRINITY) after crystallization. Sixteen crowns (n=8) were fabricated with a chairside CAD-CAM system. The crowns and die and crown assembly were scanned with an optical scanner for the 3-dimensional superimposition analysis. Four hundred sixty-eight measurements were made for each crown, 78 in each 2-dimensional section. Marginal discrepancy was measured by using the direct viewing technique. The internal adaptation of the shoulder area, axial space, and occlusal space was measured by using the silicone replica technique. Both gap values were compared with the 3-dimensional superimposition analysis results by using the independent t test. The 2-way ANOVA was used to detect the effect of each variable (group and site) (α=.05). Results The VITA SUPRINITY crowns showed statistically higher marginal discrepancy values than the CELTRA DUO crowns in both 3-dimensional superimposition analysis and the direct viewing method, and the lingual aspect recorded the highest marginal discrepancy mean value when compared with other aspects. The 3-dimensional superimposition analysis and the direct viewing method were statistically similar (P=.076). The VITA SUPRINTY crowns showed higher internal gap mean values than the CELTRA DUO crowns in both 3-dimensional superimposition analysis and silicone replica techniques. The occlusal space recorded the highest mean value in both groups. Assessment by 3-dimensional superimposition analysis and silicone replica techniques showed statistical difference in internal gap values (P=.04). Conclusions CELTRA DUO showed better precision fit values than VITA SUPRINITY. Three-dimensional superimposition analysis is a reliable method of evaluating marginal and internal adaptation.

Translucent zirconias have been developed with better esthetics than high-strength zirconias by reducing opacity. However, studies on their translucency and strength are sparse.The purpose of this in vitro study was to compare the relationship between translucency and biaxial flexural strength of recently developed high-translucency zirconia, high-strength zirconia, and lithium disilicate ceramics.Disks (n=12) were fabricated for 5 ceramic materials: high-strength zirconia (BruxZir 16 shaded), translucent zirconia (BruxZir Anterior shaded, Katana UTML, Katana STML), and lithium disilicate (IPS e.max, Press HT, and LT). A standard tessellation language (STL) file was designed, and the specimen milled, finished, and glazed according to manufacturer's instructions for each material. The translucency parameter was calculated against black and white backgrounds and white and stump shade with ND4 background by using a spectrophotometer. Biaxial flexural strength was calculated by using the 3-ball test. The load was applied at a crosshead speed of 0.5 mm/min with a 49-N load cell until failure occurred. Translucency parameter and biaxial flexural strength data were analyzed with 1-way analysis of variance (ANOVA). A Tukey honest significant difference multiple comparison test was used to determine significant differences (α=.05).The IPS e.max HT was more translucent against both backgrounds (32.85 for black/white and 15.34 for white/stump), while BruxZir 16 was the least translucent (19.78 for B/W and 8.83 for W/S). All groups tested differed in translucency (P.001) except for BruxZir Anterior and Katana STML, which were not significantly different (P=.052). For biaxial flexural strength, BruxZir 16 had the highest strength (995.44 MPa) and e.max HT, the lowest (186.75 MPa). No significant differences were found between BruxZir anterior and Katana STML, Katana UTML and IPS e.max LT, or IPS e.max LT and IPS e.max HT (P.05). Translucency parameter values using both backgrounds were strongly correlated (r=0.99). However, biaxial flexural strength values were inversely related to translucency parameter values when using black/white and white/stump shade but with high correlation (r=-0.777 and -0.756 respectively).Lithium disilicate was the most translucent and yet the weakest material, whereas high-strength zirconia was the most opaque ceramic and the strongest. Katana UTML had the highest translucency but was weakest among translucent and high-strength zirconia materials. Overall, translucency was negatively correlated with biaxial flexural strength.

Anatomic-contour zirconia prostheses are usually cemented with resin cement. However, information regarding the effects of the zirconia shade and thicknesses on the translucency of the prosthesis, the intensity of the transmitted light beneath the prosthesis, and the subsequent degree of conversion in the resin cement is sparse.The purpose of this in vitro study was to investigate the translucency parameter in 3 anatomic-contour zirconia specimens of 2 shades at 5 different thicknesses and to investigate the transmitted light intensity and degree of conversion of the resin cement beneath the ceramic specimens by using a traditional zirconia and a lithium disilicate glass ceramic as controls.Ceramic specimens from 1 anatomic-contour zirconia in a generic shade (CAP FZ) and 2 anatomic-contour zirconias in A2 shade (Zirlux and Luxisse) were used. Lithium disilicate in HT A2 shade (IPS e.max CAD) and traditional zirconia in a generic shade (CAP QZ) were used as controls. A total of 125 ceramic specimens (n=25) were fabricated to a final specimen dimension of 12×12 mm and in thicknesses of 1.0, 1.25, 1.5, 1.75, and 2.0 mm according to the manufacturers' recommendations. The CIELab color space for all specimens placed against a white and black ground was measured with a spectrophotometer (CM-2600D), and the translucency parameters were calculated for the materials at various thicknesses. A light-polymerizing unit (DEMI LED) was used to polymerize the resin cement (Variolink II) placed beneath the ceramic specimens. Transmitted light intensity from the polymerization unit beneath the ceramic specimens was measured by using a spectrophotometer (MARC Resin Calibrator), and the transmittance of each specimen was calculated. The coefficient of absorption of each material was calculated from the regression analysis between the natural log of transmittance and specimen thickness. The degree of conversion of resin cement was measured by using a Fourier transformation infrared (FTIR) spectrophotometer. The results were analyzed by using 2-way ANOVA (α=.05). The relationship between the transmittance and the translucency parameter was evaluated by plotting the transmittance against the translucency parameter value of each specimen.The translucency parameter decreased with increasing thickness in all 5 material groups. All anatomic-contour zirconia had lower translucency parameters than e-max CAD (P.001). The same results were found for the intensity of the transmitted light (P.001). Both A2 shade anatomic-contour zirconia (Zirlux and Luxisse) showed significantly lower light transmittance than a generic shade anatomic-contour zirconia (CAP FZ) (P.001). The coefficients of absorption were found to range from 0.63 to 1.72 mmThe translucency parameter and the transmitted light intensity of ceramic material were influenced by the type of ceramic and the shade and thickness of the ceramic. The combined effects of layer thickness and the intensity of the transmitted light in the A2 shade anatomic-contour zirconia (Zirlux and Luxisse) resulted in a lower degree of conversion in resin cement than in a generic shade anatomic-contour zirconia (CAP FZ) at layer thicknesses of 1.75 and 2 mm.

Using a newly developed two-step hydrothermal process, flowerlike Ce0.5Zr0.5O2 with an oxygen storage capacity (OSC) of 536 μmol O2 g−1, almost twice as high as that of pure flowerlike CeO2 (284 μmol O2 g−1), can be synthesized. The synthesized ceria-based oxide supports loaded with Ni are dispersed in a ceramic fiber network to form paper-structured catalysts (PSCs). Among the prepared PSCs, the PSC with the flowerlike Ce0.5Zr0.5O2 exhibits the highest catalytic performance for dry reforming of methane (DRM) at 750 °C with the initial methane conversion of 88.4%, degradation rate of 0.1% h−1 and amount of deposited carbon of 0.04 g per gram catalyst, whereas for the Ce0.5Zr0.5O2 synthesized by the one-step hydrothermal process, the values are 83.7%, 0.62% h−1 and 0.07 g per gram catalyst, respectively. This is attributed to the Ni anti-sintering on the petals of the flowerlike structure and the coking tolerance resulting from the high OSC.

Purpose To determine and compare the mechanical properties of 3D-printed yttriastabilized zirconia to milled isostatic pressed yttria-stabilized zirconia, with the following hypotheses: (1) The flexural strength of 3D-printed yttria-stabilized zirconia is comparable to milled yttria-stabilized isostatic pressed zirconia; and (2) thermocycling and chewing simulation do not affect the flexural strength of 3D-printed yttria-stabilized zirconia. Materials and methods A total of 30 bars of an experimental 3D-printed 3 mol% yttriastabilized zirconia (LithaCon 3Y 230, Lithoz) and 10 bars of milled isostatic pressed zirconia (Prettau Zirconia, Zirkonzahn) were utilized. The printed zirconia bars were divided into three groups (n = 10 bars per group): (1) untreated (control); (2) thermocycled; and (3) tested after chewing simulation. A flexural strength test was performed on all samples using a three-point bend test in an Instron Universal testing machine. One-way analysis of variance on ranks was used to compare milled to printed zirconia. The effects of thermocycling and load cycling on 3D-printed zirconia were also determined. Results The flexural strength values for milled and printed zirconia were 936.3 ± 255.0 MPa and 855.4 ± 112.6 MPa, respectively. There was no statistically significant difference in flexural strength between the milled and printed zirconia (P = .178). No statistically significant differences were observed between the control 3D-printed zirconia group and the thermocycled (888.4 ± 59.3 MPa) or load-cycled printed zirconia (789.6 ± 133.8 MPa; P = .119). Conclusion Printed 3 mol% yttria-stabilized zirconia has comparable flexural strength to milled yttria-stabilized isostatic pressed zirconia. The thermocycling and chewing simulation used in this study did not significantly alter the flexural strength of the printed 3 mol% yttria-stabilized zirconia. These results indicate a promising role for 3D printing in the fabrication of zirconia restorations. Additional studies are needed to explore the full potential of this technology.

Ceria-zirconia mixed oxides (CZMO) is widely used in many important catalysis fields. However, pure CZMO is known to have poor thermal stability. In this paper, a strategy was proposed to design high thermal stability Ce0.475Zr0.475M0.05O2 (M=La, Y, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Er, Lu, and, Yb) oxide surface by using first-principles molecular dynamics (FPMD) simulation and experiment method. Through the structure stability analysis at different temperatures, the surface energy γ as a function of Rion/Dave is identified as a quantitative structure descriptor for analyzing the doping effect of rare earth (RE) elements on the thermal stability of Ce0.475Zr0.475M0.05O2. By doping the suitable RE, the γ can be adjusted to the optimal range to enhance the thermal stability of Ce0.475Zr0.475M0.05O2. With this strategy, it can be predicted that the sequence of thermal stability improvement is Y > La > Gd > Nd > Pr > Pm > Sm > Eu > Tb > Er > Yb > Lu, which was further verified by our experiment results. After thermal treatment at 1100 °C for 10 h, the specific surface area (SSA) of aged Y-CZ and La-CZ samples can reach 21.34 m2/g and 19.51 m2/g, which is 63.02% and 49.04% higher than the CZMO sample without doping because the surface doping of Y and La is in favor of inhibiting the surface atoms thermal displacement. In a word, the strategy proposed in this work can be expected to provide a viable way for designing the highly efficient CZMO materials in extensive applications and promoting the usages of the high-abundance rare-earth elements Y and La.

Hydrogenation of aldehydes (RHO) is one of the frequently used reactions in organic synthesis and pharmaceuticals industries. In this contribution, we have synthesized control shaped and nano-sized tetragonal zirconia (t-ZrO2), palladium supported on zirconia (Pd/t-ZrO2) and nickel promoted palladium supported on zirconia (Ni-Pd/t-ZrO2) though modified microwave irradiation method. All the prepared samples were characterized by Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), X-ray Diffractometry (XRD), Thermal Gravimetric Analysis (TGA), Brunauer-Emmett-Teller (BET) surface area and pore size analysis, and Fourier Transform Infrared Spectroscopy (FT-IR). Theoretical calculation (DFT) revealed high interaction of Pd with t-ZrO2(101) surface. Furthermore, adsorption energy, support relaxation and charge transfer studies confirmed the stability of Pd on t-ZrO2(101) surface. The catalytic activity of catalysts was tested for cinnamaldehyde (CAL) hydrogenation in a modified microwave reactor. The comparative study of microwave irradiated (MW) and conventional heating (C-Heating) systems show supremacy of MW over C-Heating by a factor of 46% under optimal reaction parameters for Pd/t-ZrO2 catalyst. The stability, life span, conversion and selectivity of Pd/t-ZrO2 under MW system suggest the applicability of the catalysts for a variety of organic hydrogenation reactions.

PURPOSE To assess the influence of substructure and dimension on the fracture strength of ceramic discs made from both lithium disilicate ceramic and zirconia. MATERIALS AND METHODS A total of 128 intact maxillary third molars were collected, and standardized enamel and dentin discs were fabricated. Lithium disilicate ceramic (IPS e.max CAD, Ivoclar Vivadent; n = 64) and zirconia (Katana, Kuraray; n = 64) discs with 0.5-mm (n = 32 IPS and n = 32 Katana) and 1-mm (n = 32 IPS and n = 32 Katana) thickness were produced, and each group was divided into two subgroups (n = 16 each) that were luted to the enamel or dentin discs using Panavia V5 (Kuraray). Half of the specimens in each subgroup were aged (chewing simulation and thermocycling), and all specimens were loaded until fracture in a universal testing machine (Z010, Zwick/Roell). Differences between Katana and IPS with respect to enamel and dentin as substructure and the thickness of the ceramic were analyzed by use of a nonparametric test (Mann-Whitney U test). RESULTS In un-aged specimens, fracture loads were not significantly (P > .05) different between zirconia and IPS specimens for 1- or 0.5-mm thickness. However, fracture loads were significantly higher (P < .001) in specimens supported by enamel, independent of the ceramic material. In aged specimens, the fracture loads of all specimens were significantly (P < .01) higher when supported by enamel; however, in the 0.5-mm groups, zirconia achieved significantly higher breaking loads than IPS when luted to dentin. CONCLUSION When 0.5-mm ceramic discs were luted to dentin, zirconia outperformed IPS with respect to breaking loads.

PURPOSE To evaluate the effects of airborne-particle abrasion with alumina particles or silicamodified alumina particles on the bond strength between zirconia and conventional MDP-based (Ph; Panavia F 2.0, Kuraray) or self-adhesive (SA; RelyX U200, 3M ESPE) resin cements. MATERIALS AND METHODS Five surface treatments were evaluated: C = no surface treatment; AB = airborne-particle abrasion with alumina particles (BIO-ART Dental Supplies and Equipment); ABP = AB combined with MDP-based primer (Alloy Primer, Kuraray); SS = airborne-particle abrasion with silica-modified alumina particles (CoJet, 3M ESPE) combined with silane (RelyX Ceramic Primer, 3M ESPE); and SSP = SS combined with MDP-based primer. The surface roughness (Ra) of the airborne particle-abraded samples (n = 5) was measured by a contact profilometer (Mitutoyo Surftest SJ-401, Mitutoyo). Cylinders of the resin cements tested were bonded to the surface-treated zirconia. The microshear test was performed by the application of a load with a wire loop parallel to the adhesive interface until debonding of the resin cement cylinders. The microshear bond strength (μSBS) of the samples was measured before and after being subjected to thermocycling (TC; 5°C to 55°C, 60 seconds dwell time for 3,000 cycles; MSCT, Marcelo Nucci). One-way (Ra) and two-way (μSBS) analysis of variance followed by Tukey post hoc test (α = .05) were used. RESULTS The SS (Ph: 12.6 MPa; Ph-TC: 6.37 MPa; SA: 11.8 MPa; SA-TC: 9.37) and SSP (Ph: 10.4 MPa; Ph-TC: 5.82 MPa; SA: 10.4 MPa; SA-TC: 10.0) surface treatments produced the highest surface roughness values (P < .001). The SS samples achieved the highest immediate bond strength for both resin cements. However, after TC, SA resin cement associated with any surface treatment produced the highest bond strength values. CONCLUSION The self-adhesive resin cement promoted higher and more stable bond strength values when associated with a surface roughening method.

To test the bond strength of one-piece zirconia implants with either standard or reduced height using different luting agents and pretreatments of the ceramic crowns' inner surfaces.Twenty monolithic CAD/CAM-fabricated zirconia single crowns were cemented onto 10 one-piece zirconia implants with either 5-mm or 4-mm abutment height (Z-Look3 Evo SLM, Z-Systems) using 13 different luting agents. After water storage, the crowns were removed using a specially developed test fixture in a universal testing machine (Z010, Zwick/Roell). The maximum force was recorded (N), and the force per area was calculated (MPa). The statistical evaluation was performed using univariate analysis of variance (SPSS version 25.0, IBM).A mean of 4.19 MPa (SD 2.90) at 5 mm and 3.89 MPa (SD 2.85) at 4 mm was obtained for all luting agents. The highest values were achieved for a resinmodified glass-ionomer cement, with 12.37 MPa (4 mm)/12.00 MPa (5mm). The lowest values were shown for a long-term temporary material, with 0.73 MPa (4 mm)/1.07 MPa (5 mm). Only a polycarboxylate cement (P.001) and a glass-ionomer cement (P = .006) showed statistically significant differences, in favor of the reduced abutment height. The latter did not significantly reduce bond strength for any of the materials examined.Implants with a reduced abutment height are clinically suitable. Pretreatment of the crowns' inner surfaces with ceramic primer showed to be advantageous.

Studies investigating the mechanical stability of lithium disilicate-strengthened aluminosilicate glass-ceramic that do not require sintering after milling compared with other computer-aided design and computer-aided manufacturing (CAD-CAM) materials are lacking.The purpose of this in vitro study was to investigate the flexural strength of CAD-CAM zirconia, lithium disilicate, and lithium disilicate-strengthened aluminosilicate glass-ceramics with and without fatigue conditions.Specimens (N=90, n=15) (12×4×3 mm) from the following CAD-CAM materials were prepared and polished: lithium disilicate glass-ceramic (IPS e.max CAD); lithium disilicate-strengthened aluminosilicate glass-ceramic (N!ce); and zirconium dioxide ceramic (IPS e.max ZirCAD). All specimens were divided into 2 subgroups: immediate testing without aging and simulation of aging by using a mastication simulator for 1 200 000 cycles (5 °C-55 °C). Thereafter, flexural strength testing was performed by using a universal testing machine (1 mm/min) on nonaged and aged specimens. The data were evaluated by using nonparametric 2-way ANOVA and Wilcoxon rank post hoc tests (α=.05).Both the material type and aging significantly affected the results (P.001). The interaction was not significant (P.05). Under nonaged conditions, zirconium dioxide ceramic (1136 ±162 MPa) showed significantly higher mean ±standard deviation flexural strength (P.001) than lithium disilicate (304 ±34 MPa) and lithium disilicate-strengthened aluminosilicate glass-ceramic (202 ±17 MPa). The glass-ceramic groups were also significantly different from each other (P.001). After aging, zirconium dioxide (1087.9 ±185.3 MPa) also presented significantly higher mean ±standard deviation flexural strength (P.001) than lithium disilicate (259 ±62 MPa) and lithium disilicate-strengthened aluminosilicate glass-ceramic (172 ±11 MPa) (P.001). Aging significantly decreased the flexural strength of lithium disilicate (14.6%) (P=.03) and lithium disilicate-strengthened aluminosilicate glass-ceramic (14.5%) (P=.01) but had minimal effect on the zirconium dioxide ceramic (4.3%) (P=.29).Among the tested CAD-CAM materials, the mechanical performance of lithium disilicate-strengthened aluminosilicate glass-ceramic was comparable with that of lithium disilicate and considerably lower than that of zirconia. Aging decreased the flexural strength of both lithium disilicate and lithium disilicate-strengthened aluminosilicate glass-ceramic.

Purpose To measure the retrieval force required to remove 1.5-mm-thick CAD/CAM zirconia copings cemented on zirconia (Zr) and titanium (Ti) stock implant abutments after a single application of erbium-doped yttrium scandium gallium garnet (Er:YSGG) laser. Materials and methods A total of 60 monolithic Zr copings were cemented on Zr and Ti implant abutments with either a resin-modified glass-ionomer (RelyX Luting Plus Cement, 3M ESPE; Rx) or a zinc oxide eugenol cement (Temp-Bond, Kerr; Tb). These abutment-coping specimens were randomly divided into 12 groups based on laser application (vs control [C]), abutment type (Zr vs Ti), cement (Rx vs Tb), and storage condition (dry [D] vs saline water [W]). Er:YSGG laser was applied at 6 W, 30% water-60% air, and 20 Hz (300 mJ/pulse energy) postcementation following a defined pattern. The force required to remove all the cemented copings from their abutments was measured on a universal testing machine (Instron model 4204). Descriptive statistics, multi-factor analysis of variance, and post hoc Tukey honest significant difference tests (α = .05) were performed. Results The mean peak force values at removal of the Zr abutment groups were 470.3 ± 151.33 N (ZrRxC), 161.7 ± 19.29 N (ZrRxD), 316.03 ± 95.24 N (ZrRxW), 103.27 ± 24.53 N (ZrTbC), 39.33 ± 6.21 N (ZrTbD), and 20.33 ± 6.45 N (ZrTbW); and for the Ti abutment groups were 349.80 ± 106.82 N (TiRxC), 84.63 ± 14.02 N (TiRxD), 177 ± 62.57 N (TiRxW), 54.77 ± 9.10 N (TiTbC), 22.67 ± 4.32 N (TiTbD), and 11.57 ± 2.30 N (TiTbW). Conclusion Within the limitations of this study, it can be concluded that Er:YSGG laser allows for easier removal of cemented Zr copings with lower removal forces, with Ti abutment groups requiring lower forces than Zr abutment specimens. No significant difference was seen between laser and control groups for Tb compared to Rx. Er:YSGG laser shows great clinical promise for predictable retrievability of cemented, monolithic Zr implant crowns, especially with stronger resin-based cement such as Rx. With further clinical evidence, this could be very useful for clinicians managing cement-retained implant crown complications.

Purpose To evaluate the occlusal reproductive trueness of zirconia crowns fabricated using additive manufacturing (AM) and to compare the surface roughness of crowns fabricated using AM and conventional milling (CM). Materials and methods Crowns were manufactured using AM and CM on abutments with total occlusal convergence angles of 16 and 20 degrees. Results The surface roughness of the AM crowns was less than that of the CM crowns. The differences in reproduction of the occlusal morphology of the abutment crown were greater at 16 degrees than at 20 degrees. Conclusion AM could be an effective method for manufacturing zirconia crowns.

Martensitic crystal structures are usually obtained by rapid thermal quenching of certain alloys, which induces stress and subsequent shear deformation. Here, we demonstrate that it is also possible to intentionally excite a suitable transverse acoustic phonon mode to induce a local shear deformation. We irradiate the surface of a partially stabilized zirconia plate with intense terahertz pulses and verify martensitic transformation from the tetragonal to the monoclinic phases by Raman spectroscopy and the observed destructive spallation of the zirconia microcrystals. We calculate the phonon modes in tetragonal zirconia and determine the effective channel that triggers the transformation. These modes can be excited via the Klemens process. Since terahertz pulses can induce a specific local shear deformation beyond thermal equilibrium, they can be used to elucidate phase transformation mechanisms with dynamical approaches. Terahertz-induced martensitic transformation is considered to be useful for material strengthening and shape memory ceramics.

Background: Yttria stabilized zirconia (YSZ) is an attractive material which exhibits a characteristic combination of physical and chemical properties of YSZ in terms of inertness, resistant to corrosion, high mechanical strength, thermal stability, chemical stability and photostability. Because of these properties and applications, it is very important to synthesize yttrium stabilized zirconia (YSZ) powder. Till date, various preparative techniques have been reported for the synthesis of high porous YSZ nano powders. However, special equipment, long time with multistep processing, high calcination temperature, small surface area and low product yield are the usual drawbacks of most of the methods. Therefore. Solution combustion method (SCS) method has been established for the synthesis of YSZ nanopowder with high surface area. Objective: The main objective of our present research work is to effectively synthesized the Yttrium stabilized zirconia (YSZ) Zr0.72 Y0.28 O1.862 nanopowder by solution combustion method using yttrium nitrate (Y(NO3)3.6H2O), zirconyl nitrate (ZrO(NO3)2.XH3O) as oxidizers and ethylenediamine tetra acetic acid (EDTA) as a fuel and the synthesized powder was used in the application of photodegradation of dyes. Methods: YSZ nanopowder was synthesized by using Solution combustion synthesis. Solution combustion synthesis (SCS) is a simple exothermic self-sustaining one step chemical reaction, which will produce a large number of pores in the oxide material and inhibit their agglomeration leading to a large specific surface area and small crystallite size of the resulting material. Results and Discussion: Powder X-ray diffraction (PXRD) revealed the formation of pure cubic phase of YSZ (Zr0.72 Y0.28 O1.862) nanopowder and the crystallite size of 15.4 nm was calculated by using Scherrer’s formula. The porous morphology of the product was observed by SEM images. BET surface area reveals that the relatively larger surface area of 87.17 m2g-1. TEM analysis revealed uniform particle size distribution with average particle sizes varying in the range of 20-100 nm. The UV-Vis DRS spectrum was used to calculate the absorption wavelength (339 nm) and the corresponding band gap (3.72 eV) using Tauc plot. The photoluminescence spectrum of YSZ nanopowder showed an emission peak at 339 nm. The photodegradation (decolourisation) of methylene blue (MB) dye was increased from 75-90% with increase in the concentration of YSZ photocatalyst from 100 mg to 400 mg due to availability of OH radicals in the presence of UV radiation. The electrochemical studies using cyclic voltammetry reveal a substantial increase in current density of YSZ electrode from 0.0001A to 0.0005A when compared with bare carbon electrode and the instantaneous rise in redox current for the YSZ electrodes from 0.0001A to 0.0005A with increasing scan rate from 10 mVs-1 to 90 mVs-1. Conclusion: In our reported work, we start a simple and rapid solution combustion synthetic approach to produce highly effective YSZ nanopowder using EDTA as organic fuel. Because of large surface area and small particle size of the YSZ nanopowder shows 85% of degradation of MB takes place in presence of UV light. In order to understand the electrochemical property of YSZ, the redox current measurement was carried out using cyclic voltametry and resulted that increase in redox current for the YSZ electrodes with increasing scan rate from 10 mVs-1 to 90 mVs-1.

As the oxygen redox ability shows great effects on the catalytic performances of ceria-zirconia based materials, many strategies have been utilized to improve the oxygen storage capacity. Here in this study, we report a simple and facile approach to prepare a SO42–-modified La, Y-doped ceria-zirconia material (SO/CZLY-f) with high oxygen storage capacity. Due to the additional redox process between SO42− and S2−, oxygen storage capacity of SO/CZLY-f (745.3 μmol O2/g) is about 1.6 times higher than that of La, Y-doped ceria-zirconia material without SO42– modification. Moreover, the catalytic activities and stability of the corresponding Pd-only three-way catalyst were measured. Compared to that of Pd@CZLY-f, the operation window of CO, full conversion temperature of HC and NO over Pd@SO/CZLY-f are obviously widened and lowered, respectively. After aging treatment at 1100 °C for 4 h, the superiority of aged Pd-loading composite is still maintained.

More translucent dental zirconias have been developed by incorporating the cubic phase and reducing the tetragonal phase content that undergoes transformation toughening, leading to reduced mechanical properties. Whether the clinically relevant mechanical property of the edge chipping toughness of the material is also reduced is unclear.The purpose of this in vitro study was to evaluate the edge chipping toughness and translucency of translucent zirconia, 3mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP), and lithium disilicate.Two translucent zirconia products, Katana and Lava Esthetic; one 3Y-TZP, Lava Plus; and one lithium disilicate, IPS e.max Press were prepared and tested for phase composition via X-ray diffraction (XRD) (n=3), translucency via a spectrophotometer (n=20), and edge chipping via a universal testing machine with a custom-machined specimen holder and diamond indenter (n=20). The 3Y-TZP and lithium disilicate served as the optimal control materials for edge chipping and translucency, respectively. Translucency was compared with 1-way ANOVA and edge toughness with ANCOVA (α=.05).The XRD showed the 3Y-TZP to be almost completely tetragonal phase compared with the 2 translucent zirconia products that were predominantly cubic. Katana UTML and IPS e.max Press had a statistically similar (P.05) translucency that was significantly (P.05) greater than that of Lava Esthetic and Lava Plus. The edge toughness of Katana UTML was 304 N/mm, IPS e.max Press was 354 N/mm, Lava Esthetic was 394 N/mm, and Lava Plus was 717 N/mm, with significance rankings of Katana UTMIPS e.max Press=Lava EstheticLava Plus.Some translucent zirconias had translucency similar to that of lithium disilicate; however, as translucency increased with increased cubic content, edge toughness decreased.

This work explores the incorporation of graphene-based two-dimensional nanostructures as moisture barriers to delay hydrothermal ageing of yttria-stabilized zirconia and strengthen its use in biomedical applications. Two sets of highly dense zirconia composites incorporating multilayered graphene with very different lateral dimensions, few layer graphene and exfoliated graphene nanoplatelets, were prepared. The effect of the addition of graphene nanostructures on zirconia ageing was investigated by conducting accelerated hydrothermal degradation experiments in an autoclave. An improved resistance to low-temperature degradation and a high tolerance to damage were achieved in the composites compared to those of monolithic zirconia. The incorporation of 1 vol% multilayered graphene was very effective in restricting the hydrothermal degradation. In particular, the composite incorporating exfoliated graphene nanosheets exhibited outstanding resistance to ageing because of their fine dispersion throughout the matrix, which effectively seemed to restrict grain growth and slow the propagation of the transformation front to the ceramic bulk.

This study investigated changes in the retentive force of telescopic crowns fabricated by combining a zirconia primary crown and a fiber-reinforced composite (FRC) secondary crown.Primary zirconia crowns were produced with a nominal convergence angle of 0°. Forty-eight secondary crowns were milled from FRC and divided into three study groups (n=16/group) based on milling parameters and post-milling adjustment. The offset parameter used for the final milling step of the inner crown surface was adjusted for a tight initial fit in Group 1 (milling offset: +10 µm, i.e., 2 × 10 µm = 20 µm lower inner diameter compared with the CAD file of the crown) and for improved initial fit (milling offset: -10 µm, i.e., an enlargement of the inner crown diameter by 2 × 20 µm = 40 µm in relation to Group 1) in Groups 2 and 3. The inner surfaces of the secondary crowns were polished with diamond paste in Groups 1 and 2, and silicon points were used for Group 3. The retentive force was measured using a universal testing device. The secondary crown was placed on the primary crown, with the final fitting force set to a load of 100 N. This test was conducted before and after aging (10,000 insertion/removal cycles) under dry and wet conditions. A generalized linear model was used to estimate the differences in the retentive force to elucidate the effects of the milling parameters and polishing methods.We realized an initial retentive force of approximately 10 N. In Groups 2 and 3, the difference was statistically significant between the dry and wet conditions before aging (P0.05). There was no significant difference between the dry and wet conditions after aging in any of the groups (P0.05).An adequate initial retentive force can be achieved with telescopic crowns combining zirconia and FRC.

The chemical and structural stability of two commercial multicomponent silicate glasses (SCN and G6) in contact with yttria-stabilized zirconia (YSZ) was investigated after exposure times of up to 40,000 hours in air at 800 °C. With exposure time, interfacial layers develop at the SCN-YSZ and G6-YSZ interfaces, which were characterized in detail using both quantitative chemical analysis and atomic-resolution imaging. At the SCN-YSZ interface, a Ca-Ba-Si-O reaction phase was found to grow by diffusion control. In G6-YSZ, Raman spectroscopy and electron microscopy revealed a disorganized interfacial reaction later between G6 and YSZ, and the occurrence of cubic to tetragonal to monoclinic phase transformations in YSZ. This microstructural evolution is discussed in terms of devitrification resistance of glass and diffusion processes at interfaces.

PURPOSE To report on pilot tests for a planned study on single implant-supported crowns made from different restorative materials using finite element analysis (FEA) and in vitro load-to-failure testing. MATERIALS AND METHODS Within this pilot study, FEA was conducted using Ansys 2019 R2 to simulate stress and deformation for implant-supported crowns made of lithium disilicate ceramic (LiS2) and zirconia (3Y-TZP). Additionally, an in vitro load to failure test was conducted using two specimens per group to evaluate the failure mode and to confirm the findings from the FEA. RESULTS/CONCLUSION FEA revealed stress areas at the palatal cervical areas of the crowns. In the load to failure test, both hybrid abutment crowns made of LiS2 fractured (410 N and 510 N) before plastic deformation of the metal implant components occurred. The monolithic hybrid abutment crowns made of 3Y-TZP did not fracture until tests were interrupted at 646-N and 690-N occlusal force, when plastic deformation of the metal implant components was visually observed.

Zirconia ceramics have excellent physical and chemical properties and have several applications. However, owing to their hardness and brittleness, it is difficult to realise the non-destructive high-efficiency machining of zirconia ceramics. Herein, we propose an efficient non-Newtonian fluid polishing method for zirconia ceramics based on the weak magnetorheological strengthening thickening effect. The nanoscale material removal and evolution mechanisms of the zirconia ceramic surface were investigated. Based on the results obtained through scanning electron microscopy and a derivation of the fluid shear stress model in the polishing zone, we clarify the microscopic material removal mechanism during the machining process, and establish the prediction model of material removal rate. The detection results of the surface quality were in good agreement with the established material removal mechanism. The model of material removal rate could predict the processing effectively, and the average relative error was 4.45%. The experimental results demonstrate that the proposed weak magnetorheological shear thickening polishing (WMRSTP) method can realise lossless, self-adaptive, ultra-precision machining of a hemispherical zirconia ceramic workpiece. Compared to the traditional non-Newtonian fluid polishing method, the polishing quality and polishing efficiency of this method are significantly improved. The surface roughness Sa, the surface accuracy PV, and the material removal rate MRR of the zirconia hemispherical workpiece after 1 h of WMRSTP were 13.2 nm, 0.104 μm, and 5.96 μm/h, respectively.

The effect of copper oxide doping (0.05–1 wt%) on the densification, microstructure evolution and mechanical characteristics of alumina toughened zirconia (ATZ: 80 wt% Y-TZP + 20 wt% Al2O3) ceramic composites was investigated. Green samples were pressureless sintered using a short hold time of 12 min at temperatures varying from 1250 °C to 1500 °C. The incorporation of up to 0.2 wt% copper oxide was beneficial in promoting densification at low sintering temperature and improving the mechanical properties of ATZ without affecting the tetragonal phase stability. It was found that 0.2 wt% copper oxide addition was most efficacious, and the samples could attain a relative density of approximately 92% at 1250 °C, approximately 97% dense at 1350 °C and above 99% dense at 1450–1500 °C. This approach was also accompanied by an improvement in the Vickers hardness (12.7 GPa) and fracture toughness (6.94 MPam1/2) when consolidated at 1450 °C/12 min. In comparison, the undoped composite exhibited relative densities of approximately 80% at 1250 °C, 87% at 1350 °C and approximately 97%–98% at 1450 °C-1500 °C. However, the study also found that higher dopant levels (0.5 wt% and 1 wt%) was not beneficial because the tetragonal zirconia phase was disrupted upon cooling from sintering, resulting in the monoclinic phase formation. In addition, low densification and poor mechanical properties were obtained.

The additive composition of an AlN ceramic substrate material was optimized to achieve high strength and thermal conductivity. MgO-CaO-Al2O3-SiO2 (MCAS) glass and Y2O3 were used as basic additives for improved sintering properties and thermal conductivity, thereby allowing for AlN to be sintered at a relatively low temperature of 1600 °C without pressurization. Yttria-stabilized zirconia (YSZ) was added (0–3 wt%) to further improve the strength of the AlN ceramic. YSZ and Y2O3 reacted with AlN to produce ZrN, Y4Al2O9, and Y3Al5O12 secondary phases. The formation of these yttrium aluminate phases improved the thermal conductivity by removing oxygen impurities, while ZrN formed at the AlN grain boundaries provided resistance to grain boundary fractures for improved strength. Overall, the AlN ceramic with 1 wt% MCAS, 3 wt% Y2O3, and 1 wt% YSZ exhibited excellent thermal and mechanical properties, including a thermal conductivity of 109 W/mK and flexural strength of 608 MPa.

Zirconia ceramic is a significant structural material, but its use under some extreme circumstances is limited by its mechanical properties. In this work, SiC particles (SiCp) were added into alumina toughened zirconia ceramics to prepare ZrO2–Al2O3-SiCp ceramics with high performance by using oscillatory pressure sintering (OPS). Results showed that the best OPS temperature of 1600 °C was obtained, and the optimal SiCp particle size and content were 200 nm and 10 vol% respectively. Under these conditions, the specimen exhibited higher mechanical properties including Vickers hardness of 15.43 GPa, bending strength of 1162 MPa and fracture toughness of 6.36 MPa m1/2. Moreover, it was found that the atomic matching between ZrO2/SiCp, Al2O3/SiCp, and ZrO2/Al2O3 was much higher, showing the coherent interface relationship. Therefore, it was favorable for enhanced mechanical properties of as-prepared ZrO2–Al2O3-SiCp ceramics.

In this study, a La0.8Ba0.2TiO3−δ (LBT) upper layer was deposited on an yttria-stabilized zirconia (YSZ) thermal barrier coating (TBC) through atmospheric plasma spraying. The thermal cycling behaviors of the YSZ single-ceramic-layer and LBT–YSZ double-ceramic-layer coatings at 1000 °C were investigated through a water quenching method. Moreover, phases, microstructural evolution, and elemental distributions were studied through by X-ray diffraction and scanning electron microscopy–energy-dispersive X-ray spectroscopy. The results showed that the thermal cycling lifetime of the LBT–YSZ coating was 27% higher than that of conventional YSZ coating. The conventional YSZ coating failed after 251 cycles because of the joining of the continuous horizontal and vertical cracks caused by the formation of thermal growth oxides and the bending effect of the single-ceramic-layer structure. The thermal cycling behavior of the LBT–YSZ coating was different from that of the YSZ coating at the edge and center. Although the former was similar to the failure behavior of the YSZ coating, the cracks in the vertical direction were deflected as a result of the bending effect of the double-ceramic-layer structure during quenching. This deflection led to the formation of slope cracks with longer propagation paths and slope spallation zones. The latter showed small-debris spallation on top of the LBT upper layer due to the lower fracture toughness of the LBT, which protected the central coating from the structural damage of the ceramic coating. These two behaviors would either release the thermal stress or increase the crack-propagation energy requirement in the ceramic coating, consequently improving the thermal cycling lifetime of the LBT–YSZ coating. In summary, depositing an LBT upper layer could potentially improve the thermal cycling lifetimes of TBCs.

Made available in DSpace on 2022-04-28T19:48:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-03-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The objective of this study was to assess the wear behavior and its effects on the flexural strength of silica-infiltrated zirconia compared to glaze and polishing finishing treatments. To do so, disc-shaped samples of a second-generation zirconia were prepared and divided into three groups: silica infiltration, glazing, or polishing. Half of the samples of each finishing were subjected to sliding wear testing using a steatite antagonist. The discs and antagonists had their volume loss measured. The wear-tested and the other half of samples were subjected to biaxial flexural strength testing and the following characterization analyses were also performed: roughness, hardness, X-ray diffraction, profilometry, and scanning electron microscopy (SEM). Data were evaluated with ANOVA and Weibull analyses. Glazing caused greater antagonist volume loss, followed by silica infiltration, and polishing. Silica-infiltrated zirconia surface was similarly worn to polished, which was lower than that for glazed zirconia. Polished zirconia presented the highest flexural strength. However,the strength decreased and became similar in all worn groups. Silica infiltration showed slightly lower characteristic strength after sliding wear. The highest roughness and hardness values were observed on glazed zirconia. These values decreased after wear testing and became similar to the other groups. SEM evidenced an irregular surface for glazing. No phase transformation occurred after sliding wear. Despite producing some volume loss on zirconia and antagonist surfaces, silica infiltration is a promising alternative for finishing monolithic restorations. Moreover, the damage caused by sliding wear leads to decreasing the strength of zirconia regardless of the surface finishing. Department of Dental Materials and Prosthodontics São Paulo State University (Unesp) Institute of Science and Technology, Av. Eng. Francisco José Longo, 777, Jardim São Dimas, SP Department of Physics Aeronautics Technological Institute (ITA), Praça Marechal Eduardo Gomes, 50, SP Department of Dental Materials and Prosthodontics São Paulo State University (Unesp) Institute of Science and Technology, Av. Eng. Francisco José Longo, 777, Jardim São Dimas, SP FAPESP: 2015/11405-7 FAPESP: 2016/07920-6 FAPESP: 2017/20633-9 FAPESP: 2018/22627-9 CNPq: 408932/2016-3