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This study aimed to identify the potential use of the ceramic composite ZrO 2 (CeO 2 )-Al 2 O 3 as a dental implant due to its intrinsic geometry and different masticatory loads based on finite element simulations. Ceramic samples were sintered at 1500 °C-2h, and characterized: The mechanical properties of the ceramic composite (hardness, fracture toughness, flexural strength, Young's Modulus, and Poisson ratio) were determined, in addition to the relative density and its structural characteristics. Commercial dental implant designs (incisal and third-molar) on CAD models were used in this study as an initial implant geometry applied in a typical simulated mandible anatomy. Finite element models were generated for implant geometries using CAD and CAE techniques. Loading cases were considered based on different intensities (100-500 N) and orientation angles to the implant axis (0° and 45°) to reproduce human masticatory conditions. For comparison purposes, the numerical predictions were compared with finite element simulations of gold-standard titanium implants. Ce-TZP/Al 2 O 3 sintered ceramics showed flexural strength of 952.6 ± 88 MPa, hardness and fracture toughness of 1427 ± 46 HV and 11.3 ± 0.4 MPa m 1/2 , respectively, beside Young's modulus of 228.3 ± 65 GPa and Poisson ratio of 0.28. For both Ce-TZP/Al 2 O 3 dental implant geometries, the implant prototypes showed adequate mechanical behavior regardless of the masticatory load value or the orientation angle applied in the simulations: All finite element predictions are lower than the values established by Mohr Coulomb's failure criterion, allowing the feasibility, preliminarily, of the proposed ceramics for dental implant applications without fracture risk., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Vickers indentation (IF) and single-edge-V-notched beam (SEVNB), to measure the fracture toughness (K IC ) of zirconia-based dental ceramics and mathematical models were proposed to establish a correlation between both. Zirconia (ZrO 2 ) stabilized with 3 mol. % of Y 2 O 3 (3Y-TZP) and 5 mol% of Y 2 O 3 (5Y-PSZ) were compacted (n = 42) and sintered for 2 h at different temperatures (1475°C, 1500°C, 1550°C, or 1600°C). After sintering, they were characterized by relative density using the ASTM C373-88 standard, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The average grain size was measured according to the ASTM E1382-97 standard. The fracture toughness (K IC ) was determined using two methods: Vickers indentation fracture toughness (K IC-IF ): method based on mathematical modeling that considers the parameters used for the Vickers hardness test and Fracture toughness by the single-edge-V-notch-beam (K IC-SEVNB ): method proposed by ISO 23146:08. The main phases of the 3Y-TZP and 5Y-PSZ ceramics were ZrO 2 -tetragonal and ZrO 2 -cubic, respectively. The 3Y-TZP specimens showed equiaxed grains with average grain sizes ranging from 0.55 to 0.79 μm. The grain sizes of 5Y-PSZ of specimens sintered at 1475°C and 1600°C were 0.62 and 2.32 μm, respectively. For all ceramics the crack size ratio was c/a < 2.5, suggesting a Palmqvist-type crack system. The fracture toughness measured by the Vickers indentation method (K IC-IF ) and by the SEVNB method (K IC-SEVNB ) was the same when the experimental data were fit to a mathematical model., (© 2022 Wiley Periodicals LLC.)

Objective: This study aimed to investigate the role of the incorporation of an antibacterial nanoceramic (AgVO 3 ) on the properties of a restorative dental glass-ceramic., Method: A commercially available restorative glass-ceramic, commonly designated as porcelain (IPS d.SIGN) was functionalized with an antibacterial agent (nanostructured β-AgVO 3 ), synthesized by a hydrothermal route. Both functionalized and pristine samples were processed according to the manufacturer's instructions. All samples were characterized by X-ray diffraction, Rietveld refinement, particle size distribution, Scanning Electron Microscopy, chemical solubility, and Inductively Coupled Plasma Spectroscopy. Their antibacterial potential (Mueller-Hinton test) was analyzed against gram-positive (Staphylococcus aureus) and gram-negative bacteria (Escherichia coli)., Results: The commercial glass-ceramic showed leucite (KAlSi 2 O 6 ) as the only detectable crystalline phase, and, for both strains, no antibacterial activity could be detected in the Mueller-Hinton agar plates test. A monophasic, needle-shaped, and nanometric β-AgVO 3 powder was successfully synthesized by a simple hydrothermal route. After thermal treatment, glass-ceramic samples containing different percentages of β-AgVO 3 showed a second crystalline phase of microline [K 0.95 (AlSi 3 O 8 )]. For modified samples, inhibition halos were easily visible on the Mueller-Hinton test, which ranged from 11.1 ± 0.5 mm to 16.6 ± 0.5 mm and 12.7 ± 0.3 mm to 15.5 ± 0.3 mm in the S. aureus and E.coli cultures, respectively, showing that the halos formed were dose-dependent. Also, increasing the percentage of β-AgVO 3 promoted a significant increase in chemical solubility, from 72 µg/cm 2 (samples with 1 wt% of β-AgVO 3 ) to 136 µg/cm 2 (samples with 2 wt% of β-AgVO 3 ), which was associated with the silver and vanadium ions released from the glass matrix., Significance: Our in vitro results indicate that IPS d.SIGN, as most of the dental glass-ceramics, do not exhibit antibacterial activity per se. Nonetheless, in this concept test, we demonstrated that it is possible to modify dental veneering materials giving them antibacterial properties by adding at least 2 wt% of β-AgVO 3 , a nanomaterial easily synthesized by a simple route., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Objectives: This study investigates the simulation of the mechanical behavior of a bioceramic composite based on (Ce,Y)-TZP reinforced with equiaxed Al 2 O 3 and platelet-shaped hexaaluminate (H6A) grains using Finit Element Method (FEM)., Methods: A commercial (Ce, Y)-TZP/Al 2 O 3 ceramic powder was compacted into disc-shaped specimens that were sintered at 1500 °C for 2 h. The sintered samples were further subjected to hydrothermal degradation in an autoclave at 134 °C, 0.2 MPa, for 10 h and characterized according to their phase composition, microstructure, and relative density. Their flexural strength values were determined by the piston-on-three-ball test, and Weibull statistics was used to evaluate the results. Their hardness, fracture toughness and elastic parameters were also measured. Numerical simulations of the biaxial strength test were performed using the ABAQUS finite element code., Results: The sintered ceramic composite material presented relative density >99%, high resistance to hydrothermal degradation, average hardness of 1435 ± 35 HV, fracture toughness K IC of 9.7 ± 0.5 MPa m 1/2 , and average biaxial flexural strength of 952.6 ± 88 MPa. The numerical predictions of the biaxial flexural strength showed a consistently lower average biaxial flexural strength value of 880.9 MPa, ∼10% lower than the average experimental results., Conclusions: The differences observed are attributed to the complex coupled toughness mechanisms of this material, not included in the finite element simulations., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Objectives: This study aimed to optimize the crystallization process and the microstructure of a new bioactive glass-ceramic (GC) previously developed by our research group to obtain machinable glass-ceramics., Methods: Differential scanning calorimetry (DSC) analyses were conducted to explore the characteristic temperatures and construct a semi-quantitative nucleation curve. The GC specimens were characterized by X-ray diffraction (XRD) and Rietveld refinement. Their brittleness index (B) and machinability were characterized and compared with IPS e.max-CAD®. Their Young's modulus, fracture toughness, and hardness were assessed., Results: We found that the maximum crystal nucleation rate temperature of this GC is ~470 °C. Treatments were designed based on the 1st DSC peak onset (570 °C), 1st peak offset (650 °C), and 2nd peak offset (705 °C) crystallization temperatures of lithium metasilicate (LS, LiSi 2 O 3 ) and lithium disilicate (LS2, Li 2 Si 2 O 5 ). Rietveld refinement indicated an increase in LS2 and a reduction in LS and amorphous phase for increased temperatures and longer treatment times. Their B values indicate good machinability compared with that of the control group based on statistical analyses. As expected, lower levels of LS2 increase the machinability regardless of the rotation speed adopted, leading to a greater depth of cut and reduced Edge Chipping Damage Depth (ECDD)., Conclusion: This bioactive GC with optimized microstructure presents high machinability. For treatment temperatures above 570 °C, the number of elongated LS2 crystals increases and decreases the amorphous phase content, which reduce the machinability of the GC, and should therefore be avoided. The best results were obtained using heat treatment at 570 °C, which produces LS crystals embedded in a glassy matrix (67%) with small contents of secondary phases., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Objectives: The objective of this work was the development and characterization of a ceramic composite based on (Ce,Y)-TZP/Al 2 O 3 aiming an application on dental implants, comparing it with conventional monolithic 3Y-TZP ceramics, currently used for the same type of application., Methods: Ceramic samples, 3Y-TZP (n = 40) and (Ce,Y)-TZP/Al 2 O 3 (n = 40), were sintered at 1500 °C - 2h and characterized by relative density, X-Ray diffraction (XRD) and microstructure. Then, the samples of both materials were divided into two groups: 1) samples with original (as sintered) surfaces; 2) samples with conditioned, polished, surfaces. All samples were submitted to hydrothermal degradation tests, on an autoclave (134 °C - 2 bar), for 10 h in artificial saliva. The degraded samples were characterized by XRD and the polished group were also characterized by their elastic moduli, Vickers hardness and fracture toughness (Vickers indentation method). Both groups were also submitted to a flexural strength test, 3B-P testing, for which the data were interpreted using Weibull statistics., Results: All sintered specimens presented nearly full densification. After the hydrothermal degradation tests, 3Y-TZP samples presented 16.4% of monoclinic (m)-ZrO 2 phase while the composite samples withheld 100% of tetragonal (t)-ZrO 2 phase. Both materials presented equiaxial ZrO 2 grains with an average size of 0.48 ± 0.17 μm and 0.75 ± 0.22 μm, respectively, for the monolithic and composite ceramics. In the composites, is observed the presence of well distributed Al 2 O 3 grains on the ZrO 2 matrix, in two distinct morphologies: equiaxial grains and platelets. The composites (Ce,Y)-TZP/Al 2 O 3 presented average values of elastic moduli, Vickers hardness and fracture toughness of 228.3 ± 6.5 GPa, 1427 ± 46 HV e 11.3 ± 0.4 MPa m 1/2 , respectively. An inversely proportional relationship is observed between the roughness and the bending strength, since the 3Y-TZP samples presented a average strength of 860.7 ± 81 MPa (as-sintered) and 965.4 ± 93 MPa (polished) while the (Ce,Y)-TZP/Al 2 O 3 composites presented average strength of 810.6 ± 147 MPa (as-sintered) and 952.6 ± 88 MPa (polished)., Conclusions: The composites (Ce,Y)-TZP/Al 2 O 3 showed high resistance to degradation in saliva and adequate properties for use as dental implants. Values of flexural strength (>950 MPa) and Weibull modulus (m > 10) were similar to the conventional 3Y-TZP ceramics. Moreover, its hardness, elastic modulus and fracture toughness were higher than those obtained for 3Y-TZP. The expressive values of K IC obtained for (Ce,Y)-TZP/Al 2 O 3 composites are results of association of different toughening mechanisms acting simultaneously in the material., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Objectives: The properties of lithium-silicate dental glass-ceramics are very sensitive to heat treatments which are conducted after CAD/CAM (Computer Aided Design/Computer Aided Machining) processing. In particular, temperature variations inside the furnace chamber which may occur between different models of furnaces may result in altered mechanical properties of these materials. In this work, the effect of thermal treatment parameters on the transformation of lithium metasilicate (Li 2 SiO 3 ) into lithium disilicate (Li 2 Si 2 O 5 ) and on the resulting mechanical properties has been investigated., Methods: Lithium metasilicate samples. containing 59 vol% of amorphous phase, were thermal treated under vacuum at 820 °C for up to 9 min or at 840 °C for 7min (as control group). The samples were characterized by X-ray diffraction analysis using the Rietveld refinement and scanning electron microscopy. Hardness and fracture toughness (n = 30 indentations/group) were evaluated by the Vickers indentation technique. The elastic properties were measured by the Impulse Excitation Technique and the flexural strength (n = 15/group) was measured using the piston-on-three-ball (P-3B) testing assembly. Complementary Weibull statistic were conducted as statistical analysis., Results: The results indicate a progressive reduction of the Li 2 SiO 3 phase with increasing isothermal holding time at 820 °C until the conversion into Li 2 Si 2 O 5 , is completed for treatments longer than 7 min. A complete transformation of Li 2 SiO 3 into Li 2 Si 2 O 5 has also been observed for the control group of samples treated at 840 °C for 7min. Samples of the control group exhibited hardness, fracture toughness, Young's modulus and Poisson ratio 5.76 ± 0.17 GPa, 1.60 ± 0.03 MPa m 1/2 , 100.3 GPa e 0.21, respectively. The reduction of the thermal treatment temperature to 820 °C reduced the fracture toughness and the Young's modulus between 5-10%. Furthermore, the fracture strength was significantly reduced by approximately 71%, because of the lower amount of elongated Li 2 Si 2 O 5 grains and higher amount of residual amorphous phase., Conclusion: In general, the glass-ceramic material containing residual amorphous phase associated with various crystalline phases, presented a reduction of its mechanical properties in relation to the lithium disilicate glass-ceramic. The reasons for these differences in the mechanical behavior are discussed by analyzing the influences of different phenomena such as thermal expansion anisotropy, residual stresses, amorphous phase content and microstructure on the properties., (Copyright © 2019 Elsevier Ltd. All rights reserved.)