Zirconia Ceramics Research Articles

The Effect of Layer Thickness and Nozzle Diameter in Fused Deposition Modelling Printing on the Flexural Strength of Zirconia Ceramic Samples Produced by a Multistage Manufacturing Process

The process of creating ceramic items using fused deposition modelling (FDM) enables the creation of intricate shapes for a variety of purposes, including tooling and prototyping. However, due to the numerous variables involved in the process, it is challenging to discern the impact of each parameter on the final characteristics of FDM components, which impedes the advancement of this technology. This paper deals with the application of statistical analysis in the study of the dependence of the flexural strength of sintered zirconia disks on the printing parameters (nozzle diameter, layer thickness, and infill pattern) of the fused deposition method printing of a ceramic–polymer filament containing 80 wt.% zirconia and 20 wt.% polylactide. X-ray-computed tomography and diffraction systems, scanning electron microscopy combined with energy-dispersive spectroscopy, were used for a microstructural analysis of the sintered samples. It was found that the nozzle diameter and infill pattern have no significant influence on the flexural strength values. It was assumed that this is due to the heterogeneous distribution of the ceramic phase in the manufactured filament during extrusion. On the other hand, correlation analysis and analysis of correlation diagrams have shown that the thickness of the filling layer has the greatest effect on flexural strength. The maximum (684 МPa) strength value was found in a sample printed with a layer thickness of 0.2 mm. The minimum layer thickness ensures a more uniform distribution of ceramic particles and minimizes defects in samples that occur during FDM printing. The results obtained make it possible to optimize the considered process of manufacturing ceramic products from ZrO2 printed using FDM technology from extruded composite filaments.

Fracture Resistance and Wear Behavior of Ultra‐Thin Occlusal Veneers Made From Translucent Zirconia Ceramics Bonded to Different Tooth Substrates

ABSTRACTObjectiveInvestigation of the mechanical properties of occlusal veneers made from zirconia with varying translucency, bonded to different tooth substrates.Materials and MethodsSixty‐four extracted molars were divided into two groups: preparation within enamel (E) or extending into dentin (D). Veneers were milled from four zirconia ceramics (n = 8): 5Y‐TZP (HT), a multilayer of 5 and 3Y‐TZP (GT), 3Y‐TZP (LT), and 4Y‐TZP (MT). After bonding, specimens underwent thermocycling (7500 cycles; 5°C–55°C) and chewing simulation (1,200,000 cycles; 10 kg), followed by investigation of the wear behavior using optical and laser scanning microscopy. Specimens were then loaded to examine fracture resistance.ResultsAll specimens except one in the HT group survived artificial aging. Zirconia wear was below the resolution of the 3D scanner, with no significant difference in antagonist vertical loss across materials (p > 0.05). Fracture resistance was significantly higher in E‐LT compared with E‐HT (p = 0.003). No significant differences (p > 0.05) were observed in fracture resistance between materials bonded to dentin, or between the materials within different substrates.ConclusionsVeneers made of 3 and 4Y‐TZP zirconia showed promising in vitro performance and fracture resistance, regardless of the tooth substrate. All zirconia ceramics exhibited favorable wear behavior.Clinical SignificanceAs tooth wear rates increase, the use of minimally invasive occlusal veneers is becoming more important. The goal is to create restorations that are both esthetically pleasing and mechanically durable, while keeping them thin to minimize occlusal preparation and still ensure sufficient fracture resistance. Ultra‐thin (0.3 mm in the fissures/0.6 mm at the cusps) occlusal veneers made of 4Y‐TZP, multilayer and 3Y‐TZP zirconia ceramics survived chewing simulation corresponding 5‐years. All zirconia restorations showed wear‐resistant behavior.

Bond strength and chemical interaction between experimental primers containing 10-MDP and zirconia ceramics

Bond strength and chemical interaction between experimental primers containing 10-MDP and zirconia ceramics

Bonding efficacy of highly translucent zirconia and lithium disilicate glass ceramics after femtosecond laser irradiation

This study investigated the effects of femtosecond laser (FL) irradiation on the surface roughness and shear bond strength of high-translucency zirconia (6 mol% yttria-partially stabilized zirconia [6Y-PSZ]) and lithium disilicate (Li2SiO3) glass ceramics. Fully sintered square-shaped specimens of 6Y-PSZ (7 groups; 20 specimens/group) and Li2SiO3 (8 groups; 20 specimens/group) were surface-treated via sandblasting (50-μm alumina sand or glass beads) or FL irradiation (20- or 40-μm dot or cross-line patterns) or using Monobond Etch & Prime (Ivoclar Vivadent AG; only for Li2SiO3 specimens). The surface roughness (arithmetic average [Sa] and developed interfacial area ratio [Sdr]) and shear bond strength after 24 h and 10,000 thermal cycles were measured and statistically analyzed. The surface roughness of both ceramics significantly increased after 40-μm cross-line FL irradiation. The Sdr also significantly increased after FL irradiation. The 20- and 40-μm cross-line laser-irradiated 6Y-PSZ samples showed the highest shear bond strength after 24 h and 10,000 thermal cycles, respectively. Li2SiO3 glass-ceramic specimens showed the highest shear bond strength after Monobond Etch & Prime treatment for both groups. The 40-μm cross-line laser-irradiated Li2SiO3 glass-ceramic specimens exhibited high shear bond strength after thermal cycling. FL significantly increases the bonding efficacy of 6Y-PSZ and Li2SiO3 glass ceramics. Furthermore, Monobond Etch & Prime is effective for the surface treatment of Li2SiO3 glass ceramics. Therefore, FL can be used to effectively treat the surfaces of dental restorations in clinical settings, facilitating enhanced adhesion between the restoration and the tooth.

Design and reinforcement mechanisms of the blue dual-phase zirconia ceramics with excellent mechanical properties

Design and reinforcement mechanisms of the blue dual-phase zirconia ceramics with excellent mechanical properties

Bonding of Resin Cement to Monolithic Zirconia Ceramic After Different Artificial Aging.

Bonding of Resin Cement to Monolithic Zirconia Ceramic After Different Artificial Aging.

Effect of filling strategy on surface topography and strength of 3D–printed dense zirconia ceramics

Effect of filling strategy on surface topography and strength of 3D–printed dense zirconia ceramics

Effect of graphene oxide on the biaxial flexural strength and translucency of ultrathin monolithic zirconia

The purpose of this study was to investigate the influence of graphene oxide (GO) and hydrothermal aging on the biaxial flexural strength (BFS) and translucency (TP) of ultrathin monolithic zirconia with different yttria concentrations. Disc shaped specimens (n = 120) were milled using zirconia blocks (YZ-HT [HT], YZ-ST [ST], and YZ-XT [XT]) with a diameter of 15.0 mm and a thickness of 0.5 mm. Half of the specimens were immersed in 0.2 wt% GO-water dispersion (HTG, STG, and XTG) and subjected to hydrothermal aging for 10 h. The TP was measured using a reflection spectrophotometer and BFS was tested in a universal testing machine. Data were statistically analyzed with 2-way analysis of variance followed by post-hoc comparisons (α = 0.05). The lowest mean TP was found in the group of STG aged for 10 h. Hydrothermal aging significantly decreased the TP values in the groups of HTG, STG, and XTG (P < 0.05). Significantly higher TP values were obtained in the groups of XT. Immersion in 0.2 wt% GO-water dispersion significantly improved the BFS values of STG, and XTG for the control and aged groups. GO leads to decreased translucency while improving BFS for highly translucent zirconia ceramics.

Effect of Sintering Temperature on Microstructure and Properties of Zirconia Ceramics for the Needs of Nuclear Energy

The paper provides experimental results of obtaining high-density ZrO2+3%Y2O3 ceramics, which is promising for use as a matrix for immobilization of HLW. The effect of sintering temperature in the range of 1100...1650 °C on the microstructure of the sintered tablets was studied. Phase composition and microstructure of experimental samples were characterized by XRD and SEM. Grain size distribution analysis was carried out using the "Thixomet" image analyzer. Microhardness was determined using a metallographic complex LECO (USA), an inverted microscope IM-3MET and a hardness tester UIT HVB-30. It was established that increase in the sintering temperature leads to a significant increase in the average grain size (from 85 nm to 1000 nm) and increase in the density of the sintered tablets. Sintering temperature should be at least 1550...1650 ºС to produce high-dense ceramics (97...98 % of theoretical value). Obtained ceramics is characterized by high values of microhardness HV &gt; 12 GPa and crack resistance of 5.5...6.3 MPa·m1/2.

The influence of core-build up materials on biaxial flexural strength of strength-gradient zirconia and lithium disilicate ceramics: an in-vitro study

The aim of this study was to investigate the effect of using different core build-up materials on biaxial flexural strength (BFS) of multilayered strength-gradient zirconia ceramic in comparison to lithium disilicate ceramic. Thirty zirconia discs were fabricated from IPS e.max ZirCAD Prime (Zir), 30 discs from IPS e.max CAD (LS2), 30 composite discs were prepared from Tetric N-Ceram (TNC) and 30 from MultiCore Flow (MCF). The ceramic discs were adhesively cemented to composite discs forming 4 groups (n = 15) (Zir-MCF, Zir-TNC, LS2-MCF and LS2-TNC). BFS was determined using a piston-on-3-ball test. The data were statistically analyzed with independent t-tests for significant differences (p = 0.05). In zirconia groups, significantly higher stress values were recorded in the composite and the ceramic for Zir-TNC, compared to Zir-MCF (p < 0.001), while for LS2 groups, no significant differences were found between the 2 composites (p = 0.157) but stresses in LS2 were significantly higher for LS2-TNC than LS2-MCF (p < 0.001). Comparing the values between the ceramic groups, stresses were significantly higher for zirconia than LS2 (p < 0.001). It was concluded that the tested composite materials significantly differ in their strength, which also influenced the strength of the overlying ceramics, and that strength-gradient zirconia had higher strength than LS2. Monolithic strength-gradient zirconia restorations supported by composite core build-up materials with superior mechanical properties can be durable restorative options for high stress-bearing areas.

Two-stage firing of wear-resistant products of complex configuration made of aluminum-zirconium ceramics

The modes of two-stage firing of wear-resistant products of complex configuration made of aluminum-zirconium ceramics are described. The firing mode of ceramics in the first stage is carried out in air at a maximum temperature of 1500 oC with isothermal exposures of 2 and 8 hours at 1300 and 1500 oC, respectively. At the second stage, the method of hot isostatic pressing (НIР) was used at a maximum temperature of 1490 °C with a short-term exposure of 1 hour. The established modes of two-stage firing ensure the production of aluminum zirconium ceramics with a fine-grained structure (0.5‒2.5 microns), a relative density of 99.3 %, with a high level of physical and mechanical properties and resistance to aging.

Are Dental Prophylaxis Protocols Safe for CAD-CAM Restorative Materials? Surface Characteristics and Fatigue Strength

The surface of dental materials is exposed to various prophylaxis protocols during routine dental care. However, the impact of these protocols on the functional properties of the material’s surface remains unclear. This study investigates the influence of different dental prophylaxis protocols on the surface properties and their effect on the mechanical performance of CAD-CAM restorative materials. Discs (Ø = 15 mm, thickness = 1.2 mm) were fabricated from resin composite (RC, Tetric CAD), leucite-reinforced (LEU, IPS Empress CAD), lithium disilicate (LD, IPS e.max CAD), and zirconia ceramics (ZIR, IPS e.max ZirCAD MT). The materials were subjected to six prophylactic treatments: untreated (CTRL), prophylactic paste fine (PPF), prophylactic paste coarse (PPC), pumice stone (PS), air abrasion with sodium bicarbonate jet (BJ), and ultrasonic scaling (US). Biaxial flexural fatigue tests, along with fractographic, roughness, and topographic analyses, were conducted. No significant changes in fatigue strength were observed for RC, LD, and ZIR under any prophylaxis protocols. However, LEU subjected to BJ treatment exhibited significantly reduced fatigue strength (p = 0.004), with a 22% strength reduction compared to the monotonic test and substantial surface alterations. Surface roughness analyses revealed increased roughness for RC treated with PPF, PPC, and PS compared to CTRL (p &lt; 0.05), while LD exhibited decreased roughness following PPF, PS, and US treatments (p &lt; 0.05). In ZIR, only the BJ protocol increased roughness (p = 0.001). In conclusion, dental prophylaxis protocols do not significantly affect the mechanical strength of RC, LD, and ZIR materials, thus allowing any protocol to be used for these materials. However, for LEU ceramics, the BJ protocol should be avoided due to its effect of reducing fatigue strength and damaging the surface.

COMPARATIVE PERFORMANCE EVALUATION BETWEEN AJM AND HOT-AJM DURING MACHINING OF ZIRCONIA CERAMIC USING SILICON CARBIDE ABRASIVES

Abrasive jet machining (AJM) process is commonly used for cutting and drilling of brittle materials in which the phenomenon of material removal can be considered as mechanical erosion by the impingement of high-velocity abrasives. The focus of this research is to compare the performance and economic benefits of recently developed hot abrasive jet machining (hot-AJM) with traditional AJM techniques when machining zirconia ceramic using silicon carbide (SiC) grain particles. The modified AJM employed abrasive air jet (combination of hot abrasive and compressed air) to strike on the work surface for material erosion. Briefly, the cutting performance is investigated by comparing the technological characteristics like material removal rate, machining cost, and taper angle of the developed hole. Abrasive grain size, nozzle pressure, and stand-off distance are considered as the variable factors for machining trials in accordance with the design of experiments. The usage of hot abrasives in AJM improved the material erosion owing to the occurrence of plastic deformation followed by deep chipping on the machined surfaces. From the results, it was observed that the hot-AJM outperformed the normal AJM with regard to improved material removal, reduced dimensional deviation of hole and minimal machining cost. According to the findings of the cost assessment, the machining of zirconia ceramic using hot-AJM was more cost-effective than using normal AJM since it resulted 25% reduction in the total cost of production. The overall machining cost expenditure per unit in hot-AJM was lower (INR 123.12) than expenditure in traditional AJM (INR 153.47). Machining with hot-modified AJM, compared to normal AJM, offers a more techno-economically viable solution for enhancing machinability.

Advanced oxide-stabilized zirconia ceramics for flue gas filtration in air purification systems

Air pollution, largely driven by industrial activities and fossil fuel combustion, poses a critical threat to both the environment and public health. Addressing emissions, particularly from factories operating at extremely high temperatures, demands advanced filtration technologies capable of withstanding such severe conditions. Ceramic filters have emerged as a promising solution due to their superior thermal stability, chemical resistance, and mechanical durability. Among these, oxide-stabilized zirconia (OSZ) ceramics have garnered significant attention for their potential in high-temperature flue gas filtration. OSZ ceramics enhance the intrinsic properties of zirconia, such as its high melting point and mechanical strength, while stabilizing its phases to prevent performance-degrading phase transformations. This review comprehensively examines the role of phase transformations in ZrO2 materials, alongside the fabrication methods, structural characteristics, and advantages of ZrO2 ceramics in air filtration applications. The review examines various stabilizing agents used to maintain phase stability and optimize material performance under extreme conditions, highlighting the benefits of OSZ in flue gas filtration. Additionally, it covers recent advancements in OSZ synthesis and application, addressing critical limitations such as production challenges and the environmental impacts of large-scale use. The discussion emphasizes the move toward sustainable development in air filtration technologies. Finally, the review provides a forward-looking perspective on future research needs, aiming to further optimize OSZ ceramics for more effective and widespread industrial air pollution control, with a focus on improving performance, scalability, and environmental sustainability.

Effects of Er:YAG laser debonding on changes in the properties of dental zirconia.

To investigate changes in the optical and mechanical properties of novel zirconia ceramics applied in dentistry after Er:YAG laser debonding and to evaluate the feasibility and value of reusing zirconia restorations debonded by an Er:YAG laser. Four types of zirconia ceramics were investigated: self-glazed zirconia (SGZ), 3Y-TZP, 4Y-PSZ and 5Y-PSZ. Forty rectangular (25 mm*8 mm*1.5 mm) specimens were fabricated for each zirconia type, and a total of 160 specimens were manufactured. The zirconia specimens were divided into four subgroups according to the applied Er:YAG laser debonding process: the control group, 4 W laser group, 5 W laser group, and 6 W laser group. For each subgroup, 10 specimens were subjected to color tests (color difference (△E) and transparency parameter (TP) tests) and subsequent mechanical tests (flexural strength (FS), elastic modulus (EM), Vickers hardness (VH) and surface roughness (Ra) tests). The △E, TP, FS, EM, VH and Ra values were measured and calculated. One random sample from each subgroup was observed by SEM. Statistical analyses were performed by one-way ANOVA followed by post hoc comparisons (α = 0.05). The △E and TP values after Er:YAG laser debonding were not significantly different among the subgroups (P > 0.05). However, the 6 W laser group had the highest △E and lowest TP. The ranges of changes in △E and TP were below the clinically detectable threshold (△E = 1.2, △TP = 1.33). In terms of the mechanical properties, there were no significant differences in the FS, EM, VH or Ra among the subgroups. No obvious microcracks were detected on the surfaces of the zirconia specimens during SEM. Er:YAG laser debonding does not obviously affect the optical or mechanical properties of novel zirconia ceramics in dentistry. Moreover, it is potentially feasible and valuable to reuse zirconia restorations after Er:YAG laser debonding.

The generation mechanism of cutting heat and the theoretical prediction model for temperature on the rake face of the cutting tool in Zirconia ceramics

Cutting temperature and its distribution are crucial factors influencing tool strength and wear rate, due to the hardness and brittleness of Zirconia (ZrO2) ceramics, significant challenges arise in both direct temperature measurement in the cutting zone and theoretical analysis of cutting heat. Thus, focusing on the turning characteristics of ZrO2 ceramics, this study analyzes the mechanism of cutting heat generation and proposes utilizing thermodynamic state equations to determine the cutting heat source on rake face of tool. Based on the heat source method, a theoretically prediction model for temperature distribution on rake face is established. This model considers primary cutting parameters, workpiece material properties, crack fracture characteristics of the machined surface, and thermal characterizations of the tool material. The relationship between tool wear and cutting temperature is experimentally analyzed to determine the characteristic temperature that indicates the initial stage of tool wear. The validity of the theoretical model is verified, as the predicted results show high consistency with experimental results within the range of experimental parameters, with a relative error within 15.2 %.The results reveal the highest temperature during brittle cutting occurs within the cutting layer area, with the highest temperature occurring approximately 50 μm from the tool tip, followed by a gradual decrease beyond 150-200 μm. This study also demonstrates that cutting heat in ceramic turning does not solely originate from friction heat between tool flank-workpiece but also includes impact heat from tool rake face-workpiece, which under certain cutting parameters exerts a more significant influence on cutting temperature. This model can facilitate the selection and optimization of cutting process parameters for brittle materials and provide a theoretical basis for analyzing the relationship between tool thermal damage, thermophysical properties, and tool wear.

Survival and Complication Rates of Feldspathic, Leucite-Reinforced, Lithium Disilicate and Zirconia Ceramic Laminate Veneers: A Systematic Review and Meta-Analysis.

To analyze survival and complication rates for anterior and premolar laminate-veneers out of different ceramic materials (feldspathic, leucite-reinforced glass-ceramic [LRGC], lithium-disilicate [LDS] and zirconia). A systematic literature search was conducted across multiple databases for clinical studies on ceramic laminate-veneers with a minimum-follow-up of ≥ 1 year. The date of last search was on February 19, 2024. Survival, technical, esthetic and biological events were assessed for different laminate-veneer materials at three observation periods (short- [1-3 years], mid- [4-6 years] and long-term [≥ 7 years]). Twenty-nine studies were included. Meta-analysis revealed a pooled survival-rate of 96.13% for feldspathic, 93.70% for LRGC and 96.81% for LDS at 10.4 years. No difference was found between materials. Complication rates (technical/esthetic/biological) were as follows: Feldspathic: 41.48%/19.64%/6.51%; LRGC: 29.87%/17.89%/4.4%; LDS: 6.1%/1.9%/0.45% at 10.4 years. Zirconia showed a 100% survival-rate with no complications at 2.6 years. No long-term data was available for zirconia. Feldspathic, LRGC and LDS laminate-veneers showed high survival-rates at long-term observation. LDS slightly outperforms feldspathic and LRGC laminate-veneers with lower long-term complication rates. More studies providing long-term data on zirconia laminate-veneers are needed. Ceramic laminate-veneers are a reliable treatment option. LDS may be preferred as a restorative material for long-term success.

Ultra–fast plastic forming of zirconia ceramics under a low temperature and high electric field

The low–temperature plastic forming ability of ceramics with complex structures is unsatisfied due to the strong covalent and ionic bonds, restricting their widespread applications. Herein, a technique is proposed for the ultra–fast plastic forming of zirconia ceramics using a low temperature and high electric field. The high electric field–assisted plastic forming temperature and rate are 1000 °C and 10 mm/min, respectively, which are much lower and faster than those of conventional plastic forming methods for ceramics. The deformed “Ω”–shape zirconia part exhibits a uniform microstructure without microcracks/cavities and a high hardness, demonstrating that the high electric field–assisted plastic forming technique enables the rapid fabrication of complex ceramic components with beneficial properties at low temperatures.

Low sintering shrinkage and high strength of porous mullite–zirconia ceramics: Effect of AlF3 and ZrSi2 contents

AbstractLow‐shrinkage porous mullite–zirconia ceramics were prepared using Al and ZrSi2 as raw materials and AlF3 as the whisker catalyst through foam‐gelcasting and freeze‐drying methods. The oxidation of Al and ZrSi2 combined with the Kirkendall effect and volume expansion was employed to reduce the sintering shrinkage, while the mullitization was promoted by the reaction between AlF3 and extra ZrSi2, and ZrO2 were generated to enhance the compressive strength as the reinforcing phase. The effect of AlF3 and ZrSi2 content on the microstructure and properties of porous mullite‐zirconia were explored. These ceramics exhibited high porosity (73.75%–85.02%) and compressive strength (2.98–17.71 MPa), low shrinkage (0.47%–10.89%) and thermal conductivity (0.228–0.462 W/(m·K)). In particular, the porous mullite–zirconia ceramics with great compressive strength (4.01 MPa) companied with near‐zero shrinkage (0.47%) at the AlF3 content of 15 wt% and extra ZrSi2 content of 20 wt% by introducing the reinforcing phase (ZrO2). Additionally, the temperature difference around 950°C of the porous ceramics during the heating test proved the exceptional application on thermal insulation.

Effect of Doping ZrO2 on Structural and Thermal Properties

The aim of this paper was to investigate the structure and thermal properties of zirconia ceramics co-doped with rare earth (RE) elements in equimolar concentrations. We prepared (1 − x)ZrO2 − x(yLa2O3 + yNd2O3 + ySm2O3 + yGd2O3 + yYb2O3) (x = 0.2; y = 0.2) powders by a hydrothermal method in mild conditions (200 °C, 2 h, 60–100 atm.) The powder was analyzed by XRD, SEM-EDAX, BET, and FT-IR after synthesis and heat treatments at 1200 °C and 1500 °C. The samples exhibit good thermal stability, with a single cubic phase presented after heat treatment at 1500 °C. The compound exhibits a low thermal conductivity (0.61 W·m−1·K−1), a low heat capacity (0.42 J·g−1K−1), and a low thermal diffusivity (0.34 mm2·s−1). The values are lower than reported for conventional RE-doped zirconia.