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Zirconia (ZrO2) ceramic has excellent mechanical properties and superior chemical stability, making it widely used in aerospace, microelectronics, biomedicine, and mechanical manufacturing. However, due to its difficult-to-machine characteristics, traditional machining methods struggle with fabricating large-aspect-ratio (LAR) microchannels in zirconia ceramics. This study compares direct laser machining (DLM) and waterjet-assisted laser micromachining (WJALM) in preparing LAR zirconia microchannels, focusing on surface morphology, heat-affected zones, microhardness, chemical and phase composition. Subsequently, parameter experiments of WJALM were carried out to achieve superior machined quality LAR zirconia microchannels by assessing the geometric profile and ablation-area-ratio. Experimental results indicated that WJALM significantly surpasses DLM, achieving a 46 % decrease in areal surface roughness (Sa), WJALM reduced the heat-affected zone depth by approximately 37 % compared to DLM. The WJALM process also enhanced the ablation-area-ratio by 61 %, achieving superior machining quality under optimized conditions of 27 W laser power, 100 mm/s scanning speed, and 8 m/s waterjet velocity.

Three mole percent yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) ceramics are exemplary materials for dental restoration due to their high mechanical strength, fracture toughness, chemical endurance, and biocompatibility. Nevertheless, 3Y-TZP ceramics are opaque and their CAD/CAM manufacturing process may cause micro-cracks in conventional clinical practice. In this study, 3Y-TZP ceramic samples were prepared using vat photopolymerization, pre-sintering, external staining, and final high-temperature sintering. The microstructures, mechanical properties, optical properties, and cytotoxicity of the 3Y-TZP ceramic samples were investigated. The results indicate that with increasing Fe3+ concentration of staining solution from 0.1 mol/L to 0.3 mol/L and increasing staining time from 5 s to 30 min, the 3Y-TZP ceramic samples showed a tetragonal crystal structure of zirconia with densely packed grains and a slight increase in grain size. The flexural strength, Vickers hardness, and fracture toughness of 3Y-TZP ceramic samples stained in 0.1–0.3 mol/L Fe3+ solution for 5 s to 3 min were all greater than 665 MPa, 11.9 GPa, and 5 MPa m1/2, respectively, meeting the mechanical requirements for clinical application. Colorimetric analysis revealed a decrease in L* (black-white index) from 90.4 to 81.3, an increase in a* (green-red index) from −1.5 to 3.2, and an increase in b* (blue-yellow index) from 11.6 to 20.3, approximating the commercial VITA 3D-Master Shade Guide chromaticity. Furthermore, the 3Y-TZP ceramic samples exhibited a cell viability of 90% or higher toward L929 cells.

Zirconia ceramic (ZrO2) has been widely utilized in industrial areas for its excellent physical and mechanical properties. It is essential to study the grinding effect and the parameters optimization, to achieve high efficiency and precision grinding. The response surface experiments of ZrO2 grinding are designed, where the grinding wheel speed, workpiece speed, and grinding depth are selected as the three grinding parameters. The experiment is carried out on a surface grinding machine with a diamond grinding wheel. The four response surface quadratic regression models are built for the grinding force, the surface roughness, the surface breakage rate, and the subsurface damage depth. Combined with the four regression models and the maximum undeformed chip thickness model, the effect of grinding parameters on the grinding results is comprehensively assessed. For the integrated minimum of the machining time and the four grinding results, the multi-objective optimization is carried out on the grinding parameters. The correctness of the optimization model is verified by experiment. [ABSTRACT FROM AUTHOR]

Zirconia dental ceramics incorporated with inert dental glass (IDG) were fabricated by digital light processing (DLP). The effects of the amount of added IDG on the physical properties and microstructure of sintered samples were investigated. Highly dense zirconia dental ceramic samples with a relative density of 98.9% were obtained by adding different amounts of IDG sintered at 1500°C. With the addition of 1 wt% IDG, the Vickers hardness, fracture toughness, and wear resistance increased to 13.03 GPa, 6.33 MPa m1/2, and 0.03 mg/(mm2 min), respectively. However, with the incremental addition of IDG at 3 and 5 wt%, a slight reduction in Vickers hardness, fracture toughness, and wear resistance was observed. The values recorded were 12.68 GPa, 5.90 MPa m1/2, and 0.05 mg/(mm2 min) for the former, and 11.86 GPa, 5.48 MPa m1/2, and 0.06 mg/(mm2 min) for the latter. Scanning electron microscopy observation suggested that 1 wt% IDG incorporated into zirconia dental ceramic samples resulted in an optimal microstructure, with IDG existing at triple junctions of zirconia grains to form a discrete secondary phase. The broken surface revealed transgranular fracture features. This investigation indicates that adding a proper amount of IDG is an effective method to enhance the properties of DLP‐fabricated zirconia dental ceramics. [ABSTRACT FROM AUTHOR]

Yttria-Stabilized Zirconia (YSZ)-enhanced Cr3C2-25NiCr coatings were applied to T22 boiler tube steel using the High Velocity Oxy Fuel (HVOF) method. Conventional Ni-20Cr, 5 wt.% YSZ- Cr3C2-25NiCr, and 10 wt.% YSZ- Cr3C2-25NiCr composite coatings were prepared. High-temperature corrosion tests were conducted on both uncoated and coated samples in a Na2SO4-60%V2O5 environment at 850°C under fluctuating thermal conditions. These experiments were carried out in a silicon tube furnace at high temperatures, with each sample subjected to 50 cycles of exposure. Each cycle consisted of 1 hour in the corrosive environment followed by 20 minutes of cooling at room temperature. Corrosion products were analyzed using energy-dispersive x-ray analysis (EDS) and scanning electron microscopy (SEM). The addition of YSZ to the Cr3C2-25NiCr coatings significantly improved corrosion resistance, with the Ni-20Cr, 5 wt.% YSZ-Ni-20Cr, and 10 wt.% Cr3C2-25NiCr coatings reducing overall weight gain by 73.08%, 84.70%, and 89.96%, respectively, compared to uncoated T22 steel.

With the increasing application of ceramic structural parts, how to realize the ductile cutting of ceramics and high-quality machining of ceramic structural parts have become an important research direction. In this paper, the micromilling of fully sintered zirconia ceramics is studied using customized PCD end mills with three different rake angles. The critical thickness for microcutting of ceramics during the micromilling process is theoretically analyzed and experimentally identified. Then, the ductile cutting of ceramic materials is to be realized by controlling the key cutting parameter (feed per tooth f z) considering the critical cutting thickness. Under the condition of ductile cutting, the high-aspect-ratio vortex curved thin walls of fully sintered zirconia ceramics are successfully fabricated. Furthermore, the tool wear of the customized PCD end mill is analyzed. The tool geometric parameters that are beneficial to ensure both ductile cutting and high tool life are identified. [ABSTRACT FROM AUTHOR]

PURPOSE. This study aimed to evaluate the effect of pretreatment of three different universal adhesives (Single Bond Universal [SBU], All-Bond Universal [ABU], and Prime&Bond universal [PBU]) on the bonding durability of an adhesive (Panavia F 2.0, PF) and a conventional (Duo-Link, DL) resin cements to air-abraded zirconia. MATERIALS AND METHODS. Rectangular-shaped zirconia specimens were prepared. The chemical composition and surface energy parameters of the materials were studied by Fourier transform infrared spectroscopy and contact angle measurement, respectively. To evaluate resin bonding to the zirconia, all the bonding specimens were immersed in water for 24 h and the specimens to be aged were additionally thermocycled 10000 times before the shear bond strength (SBS) test. RESULTS. The materials showed different surface energy parameters, including the degree of hydrophilicity/hydrophobicity. While the DL/CON (no pretreatment) showed the lowest SBS and a significant decrease in the value after thermocycling (P < .001), the PF/CON obtained a higher SBS value than the DL/CON (P < .001) and no decrease even after thermocycling (P = .839). When the universal adhesives were used with DL, their SBS values were higher than the CON (P < .05), but the trend was adhesive-specific. In conjunction with PF, the PF/SBU produced the highest SBS followed by the PF/ABU (P = .002), showing no significant decrease after thermocycling (P > .05). The initial SBS of the PF/PBU was similar to the PF/CON (P = .999), but the value decreased after thermocycling (P < .001). CONCLUSION. The universal adhesive pretreatment did not necessarily show a synergistic effect on the bonding performance of an adhesive resin cement, whereas the pretreatment was beneficial to bond strength and durability of a conventional resin cement. [ABSTRACT FROM AUTHOR]

In this paper, a kind of half-loop Yagi-Uda antenna made of high-permittivity dielectric is proposed to realize end-fire radiation. As two typical materials with high permittivity, low-loss zirconia ceramic and liquid pure water are here employed for the proposed antenna to attain high radiation efficiency and support the characteristic of pattern reconfigurability, respectively. The thin dielectric waveguide with high permittivity is here used as the metal wire of conventional wire antennas, due to its traveling-wave radiation under TM01 mode. The different radiation characteristics of the electrically small loop and full-wave loop antennas are discussed. And the dielectric large half-loop antenna with ground plane and bi-directional radiation is utilized to form a Yagi-Uda array for desired end-fire radiation. Moreover, circular loop elements are subsequently transformed into rectangular shape to reduce the profile of antenna and a comparison between the conventional metal Yagi-Uda antenna and the proposed dielectric one is provided. It is found that the dielectric parasitic element could play a more flexible role. Both ceramic and pure-water antenna prototypes are fabricated and tested. Measured results match the simulated ones well, which validates the predicted antenna performance.

In order to deposit diamond films on zirconia ceramic substrates, a three-dimensional finite element simulation of the substrate temperature field is proposed to optimize the deposition process parameters. First, the validity of the simulation results is verified by experiments in the actual deposition system. Second, the influence of parameters such as the height of the hot filament (h ), the distance of the hot filament (d ), the number of hot filaments (N ), and the presence or absence of cemented carbide ingots on the uniformity of the temperature field of the substrate is analyzed through temperature field simulation. Third, according to the optimal parameters obtained from the simulation results, the diamond film was deposited on the zirconia ceramic substrate by experiment. Finally, the properties of diamond films deposited on zirconia ceramic substrates with optimized parameters are characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. The simulation results have indicated that the optimal parameters obtained are h = 4 mm , d = 7 mm , and N = 7 , and the protective cemented carbide ingot is acceptable due to its negligible temperature impact. The diamond film prepared according to the optimized parameters is a typical micro-diamond film, with relatively dense growth, grain size of about 0.6 ~ 1 μ m , deposition rate of about 0.625 μ m / h , residual stress of about − 6.61 GPa , and FWHM of 18 cm −1. However, impurities are present on the surface of the diamond film prepared without optimization parameters, and the graphitization is more serious. The residual stress is about − 9.07 GPa , and the FWHM is 23 cm −1. The quality of diamond films is significantly improved through parameter optimization. [ABSTRACT FROM AUTHOR]

Femtosecond lasers have been applied in the machining of zirconia ( ZrO 2 ) ceramics because of their ultrashort pulse duration and high peak power. However, the high-precision micromachining of zirconia remains challenging owing to an unclear understanding of the ultrafast laser–material interaction mechanisms. In this study, the transient processing phenomenon induced by a femtosecond laser pulse, namely electron excitation (filament), occurring on a picosecond to nanosecond timescale, was directly observed and quantitatively investigated inside ZrO 2 . A pump-probe imaging method comprising a focusing probe beam integrated with a high-speed camera was used. The evolution process, type variation, and related interaction mechanisms of the filament were revealed under different parameters, including laser pulse energy, sample position, and pulse duration. Finally, the generation mechanism of multiple filaments was clarified and successfully elucidated. This study reveals the ultrafast laser–material interaction mechanisms and the high-precision processing in the laser drilling of zirconia ceramics. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shanghai University / Shanghai Daxue Xuebao is the property of Journal of Shanghai University (Natural Sciences) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This laboratory study was conducted to evaluate and compare the resin bond strength of different adhesive resin systems in different combinations and the durability of their bonds with zirconia ceramic. Materials and methods: One hundred and twenty-eight specimens were milled from 3Y-TZP zirconia ceramic. The bonding surfaces of all disks were wet polished, steam cleaned, airborne-particle abraded and ultrasonically cleaned in 99% isopropanol. The specimens were randomly divided into four main groups according to the applied resin system; two conventional and two self-adhesive systems were used. Each group was further subdivided into two subgroups; the first was conditioned with the specified primer for conventional luting resins or not conditioned for the self-adhesive systems, whereas the second subgroup of each was conditioned with the same phosphate monomer-containing primer (Alloy Primer). The zirconia specimens were adhesively bonded, using the allocated luting resin, to plexiglass tubes filled with self-curing composite resin (Clearfil FII). Half of the specimens of each subgroup were stored in distilled water at 37 °C for 3 days, whereas the other half were subjected to artificial aging, 150 days of storage and additional thermal cycling. Thereafter, all specimens were subjected to TBS testing using a universal testing machine. Statistical analysis was conducted using two-way ANOVA followed by separate one-way ANOVAs. The Games–Howell post-hoc test was applied for pairwise comparisons. Results: All specimens survived storage with thermal cycling. The mean TBS values ranged from a minimum of 43.4 ± 5.0 MPa to a maximum of 66.4 ± 3.5 after 3 days and from a minimum of 13.6 ± 2.5 MPa to a maximum of 50.1 ± 9.4 MPa after 150 days. Conclusions: Artificial aging had a significantly negative effect on all test groups. The chosen adhesive-resin system had a significant effect on the resulting TBS values. The highest TBS values were achieved for the self-adhesive luting resin G-Cem One but were statistically comparable to the results obtained for the dual-cure luting resin G-Cem LinkForce. [ABSTRACT FROM AUTHOR]

Background: The bond capacity of universal adhesives should be comparable to a specific primer for zirconia. Thus, this study evaluated the bond strength to zirconia of four universal adhesives and a zirconia primer over long-term storage. Materials and Methods: The surfaces of 75 samples of zirconia were sandblasted with 50 μm aluminum oxide particles and then divided into groups (n = 15): G1 – Single Bond Universal (SBU); G2 – All Bond Universal; G3 – Peak Universal Bond; G4 – Ambar Universal (AU), and G5 – Z-Prime Plus (ZP). A cone of resin composite was constructed on the applied materials. The samples were submitted to a tensile bond strength test after 24 h using a universal testing machine. Then, the remaining materials were removed from the sample surfaces, and the surfaces were polished and sandblasted again as previously described to obtain the same groups. These new samples were stored in distilled water at 37°C for 12 months and then submitted to a tensile bond strength test. The data were analyzed by two-way analysis of variance and Tukey's test (α =0.05). Results: The material factor (P = 0.001) and the storage factor (P = 0.001) were significant, and the interaction was not significant (P = 0.117). According to Tukey's test, bond strength mean values (in MPa) followed by distinct letters were significantly different. After 24 h, G5 = 21.12 A, G1 = 20.55 A, G4 = 19.19 AB, G2 = 14.22 B, and G3 = 8.44 C. After 12 months, G1 = 7.37 A, G5 = 5.61 AB, G4 = 4.97 B, G2 = 3.32 C, and G3 = 1.93 D. After 12 months of storage, all groups' bond strength significantly decreased. Conclusions: SBU and AU had bond strengths comparable to ZP after 24 h. No material resisted water degradation. [ABSTRACT FROM AUTHOR]

This laboratory study aimed to evaluate the effect of different surface patterns using femtosecond laser treatment on the enclosed mold shear bond strength (EM-SBS) of resin composite to zirconia (ZrO2) surfaces and to contrast it with the widely used tribochemical silica coating (TBC) surface conditioning method. A set of fifteen rectangular ZrO2 blocks were randomly divided into five groups according to surface pretreatment: Control G0—no treatment; G1—TBC with silane application; G2—femtosecond laser irradiation with horizontal lines 30 µm apart; G3—femtosecond laser irradiation with horizontal lines 15 µm apart; and G4—femtosecond laser irradiation with cross lines 30 µm apart. The pretreated surfaces were characterized by a surface profilometer, tensiometer and scanning electron microscope. The EM-SBS of resin composite stubs to ZrO2 was measured followed by fractographic analysis. The surface roughness and water contact angle were observed to be statistically higher among the femtosecond laser groups compared to the TBC and control groups. The G4 group exhibited the highest EM-SBS among all the groups, irrespective of the ageing conditions used. At the end of 5000 thermocycles, G4 exhibited EM-SBS of 14.05 ± 4.21 MPa compared to 13.80 ± 3.01 MPa in G1 and 5.47 ± 0.97 MPa in G0. The two-way ANOVA revealed a significant effect of both study groups and ageing conditions on the EM-SBS (p < 0.001). Utilization of femtosecond laser technology holds promise as a potential and alternative mechanical retention approach for enhancing the bonding strength of the resin composite to ZrO2. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the mechanical properties and cost efficiency of direct ink writing (DIW) printing of two different zirconia inks compared to casting and subtractive manufacturing. Zirconia disks were manufactured by DIW printing and the casting process and divided into six subgroups (n = 20) according to sintering temperatures (1350 °C, 1450 °C and 1550 °C) and two different ink compositions (Ink 1, Ink 2). A CAD/CAM-milled high strength zirconia (3Y-TZP) was added as reference group. The biaxial flexural strength (BFS) was measured using the piston-on-three-balls test. X-ray-diffraction (XRD) was used for microstructural analysis. The cost efficiency was compared for DIW printing and subtractive manufacturing by calculation of the manufacturing costs of one dental crown. Using XRD, monoclinic and tetragonal phases were detected for Ink 1, for all other groups no monoclinic phase was detected. The CAD/CAM-milled ceramic showed a significantly higher BFS than all other groups. The BFS of Ink 2 was significantly higher than the BFS of Ink 1. At a sintering temperature of 1550 °C the mean BFS of the printed Ink 2 was 822 ± 174 MPa. The BFS of the cast materials did not show a significantly higher BFS than the corresponding printed group for any tested parameter-set. The manufacturing costs of DIW printed crowns are lower than the manufacturing costs of CAD/CAM-milled crowns. DIW has a high potential to replace subtractive processes for dental applications, as it shows promising mechanical properties for appropriate ink compositions and facilitates a highly cost effective production. [ABSTRACT FROM AUTHOR]

Copyright of Implantologie is the property of Quintessenz Verlags GmbH and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The "Window to the Brain" is a transparent cranial implant under development, based on nanocrystalline yttria-stabilized zirconia (nc-YSZ) transparent ceramic material. Previous work has demonstrated the feasibility of this material to facilitate brain imaging over time, but the long-term stability of the material over decades in the body is unknown. In this study, the low-temperature degradation (LTD) of nc-YSZ of 3, 6, and 8 mol % yttria is compared before and after accelerated ageing treatments following ISO standards for assessing the ageing resistance of zirconia ceramics. After 100 hr of accelerated ageing (equivalent to many decades of ageing in the body), the samples do not show any signs of phase transformation to monoclinic by X-ray diffraction and micro-Raman spectroscopy. Moreover, the mechanical hardness of the samples did not decrease, and changes in optical transmittance from 500 to 1000 nm due to ageing treatments was minimal (below 3% for all samples), and unlikely to be due to phase transformation of surface crystals to monoclinic. These results indicate the nc-YSZ has excellent ageing resistance and can withstand long-term implantation conditions without exhibiting LTD.

Background: The bond capacity of universal adhesives should be comparable to a specific primer for zirconia. Thus, this study evaluated the bond strength to zirconia of four universal adhesives and a zirconia primer over long-term storage. Materials and Methods: The surfaces of 75 samples of zirconia were sandblasted with 50 μm aluminum oxide particles and then divided into groups (n = 15): G1 – Single Bond Universal (SBU); G2 – All Bond Universal; G3 – Peak Universal Bond; G4 – Ambar Universal (AU), and G5 – Z-Prime Plus (ZP). A cone of resin composite was constructed on the applied materials. The samples were submitted to a tensile bond strength test after 24 h using a universal testing machine. Then, the remaining materials were removed from the sample surfaces, and the surfaces were polished and sandblasted again as previously described to obtain the same groups. These new samples were stored in distilled water at 37°C for 12 months and then submitted to a tensile bond strength test. The data were analyzed by two-way analysis of variance and Tukey's test (α =0.05). Results: The material factor (P = 0.001) and the storage factor (P = 0.001) were significant, and the interaction was not significant (P = 0.117). According to Tukey's test, bond strength mean values (in MPa) followed by distinct letters were significantly different. After 24 h, G5 = 21.12 A, G1 = 20.55 A, G4 = 19.19 AB, G2 = 14.22 B, and G3 = 8.44 C. After 12 months, G1 = 7.37 A, G5 = 5.61 AB, G4 = 4.97 B, G2 = 3.32 C, and G3 = 1.93 D. After 12 months of storage, all groups' bond strength significantly decreased. Conclusions: SBU and AU had bond strengths comparable to ZP after 24 h. No material resisted water degradation.

Abstract Objectives Mechanical properties are cardinal for the long‐term clinical success of laminate veneer restorations but the selection of new restorative materials should ideally be based on clinical evidence, therefore, in vitro testing of dental materials is a good alternative to evaluate their properties and understand their behavior so this study aimed to compare and evaluate the effect of two different thicknesses and yttria percentage on the fracture resistance of laminate veneer zirconia restorations. Materials and Methods Forty laminate veneer restoration prepared from partial sintering zirconia of 3Y (yttria), 5Y (yttria), combined 3Y&5Y (yttria), and lithium disilicate. Specimens were assigned into four main groups according to their percentage of yttria content (n = 10) and subgrouped into two thicknesses (0.5 mm thickness and 0.3 mm thickness) (n = 5) as follows: Group I, II, III, and IV (Group I for lithium disilicate (control), Group II for 3Y zirconia, Group III for 5Y zirconia, and Group IV for combined 3Y&5Y zirconia), each of them subdivided according to their thickness into two subgroups (n = 5 for each one) and resistance to fracture for each restoration was evaluated using a universal testing machine. Data were analyzed using a one‐way analysis of variance and Duncan's tests at a 5% level of significance. Results The thickness of laminate veneer restoration significantly affects the fracture resistance value of all type of laminate veneers restorations (fracture resistance mean value was highest for 0.5 mm thickness and lower for 0.3 mm thickness restorations) and yttria percentage significantly affect fracture resistance value of zirconia laminate veneer restorations (fracture resistance mean value was highest for 0.5 mm thickness of 3Y zirconia [865 N] and combined 3Y&5Y zirconia [846 N]). Conclusions Reducing the thickness of laminate zirconia veneer restorations to 0.3 mm reduces its fracture resistance and increasing yttria percentage had an adverse effect on fracture resistance of zirconia laminate veneer restorations.

Laser-assisted machining (LAM) is regarded as a useful technique which can process ceramic materials without damage and efficiently. This work reported a study on the mechanism by which LAM technology can improve the machinability of zirconia ceramic. The absorptivity of zirconia ceramic to fiber laser energy was obtained through the combination of experiment and simulation. The temperature-dependent mechanical property of zirconia ceramic was studied by nanoindentation experiments. Meanwhile, scratch tests were used to investigate the plastic-brittle transition and damage mechanism under various high-temperature conditions. The results showed that the absorptivity of zirconia ceramic to fiber laser energy is 0.52. The hardness and elasticity modulus are decreasing as the temperature increases. The functions that relate them to temperature are fitted. Moreover, the increase in temperature can enhance the plastic-brittle transition depth of ceramic and suppress median cracks and chipping. Furthermore, the shape of the chips is changed from discontinuous lumpy chips to continuous coiled chips. These evidence and research can clearly explain the mechanism by which LAM technology can improve the machinability of zirconia ceramics. They can also provide guidance and theory for the industrialization of LAM technology. [ABSTRACT FROM AUTHOR]

Alumina-toughened calcia-stabilized tetragonal zirconia ceramics are produced using baddeleyite as raw material. A 3 wt.% CaO-ZrO2/Al2O3 ceramic containing 15 wt.% Al2O3 is characterized by sufficiently high mechanical properties: a hardness of 12.6 GPa, Young's modulus of 248 GPa and fracture toughness of 10.3 MPa⋅m0.5. The hardness and Young's modulus of this ceramic exceed those of alumina-free 3 wt.% CaO-ZrO2 ceramic by about 8.6% and 9.3%, respectively. However, fracture toughness of the prepared composite ceramic is lower than that of 3 wt.% CaO-ZrO2 ceramic by about 13.7%. It is revealed that in the fabricated 3 wt.% CaO-ZrO2/Al2O3 ceramic in the range of used Al2O3 concentrations transformation toughening prevails over residual stress toughening and crack deflection toughening. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shanghai University / Shanghai Daxue Xuebao is the property of Journal of Shanghai University (Natural Sciences) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Implant-supported prostheses could serve as a reliable restorative option for partial edentulism. Various restorative materials have been utilized in fabricating these prostheses, impacting both esthetics and peri-implant health. The present systematic review aimed to assess the survival rate and mechanical complications of zirconia ceramic compared to metal-ceramic implant-supported multiunit fixed dental prostheses (FDPs). We conducted searches in online databases such as MEDLINE (PubMed), Scopus, and Cochrane up until December 2022. A risk-of-bias assessment was done for all the included studies. Data extraction was performed based on the following parameters: author, year, study design, number of implants, abutment material, age range, observation period, incidence of mechanical complications, and survival rate. This systematic review included six studies (four randomized controlled trials and two retrospective studies). The meta-analysis significantly favored metal-ceramic restorations regarding mechanical complications with a risk ratio (RR) value of 1.64 and P = 0.001. Meta-analysis showed no difference in metal-ceramic FDPs in prostheses survival rate (P = 0.63; RR: 1.27, 95% confidence interval: 0.52–3.37; heterogeneity: P = 0.65; I2: 0%). While metal-ceramic multiunit implant-supported prostheses exhibited fewer mechanical complications compared to zirconia-ceramic prostheses, there was no significant difference in terms of prosthesis survival rate between the two. Hence, both treatments appear to be viable options for long-term implant-supported prostheses.

Purpose: Fast wound healing after abutment connection may reduce infectious complications. Cold atmospheric pressure plasma can increase the hydrophilicity of abutment surfaces, and therefore, the cell attachment, cell density, and sealing could help hamper microbial penetration into the wound cavity. In this in vitro study, the effect of three different plasma devices and common antiseptics on cell growth after treatment on zirconia ceramic and titanium disks was analyzed. Materials and Methods: Specimens were treated for 5 minutes with the plasma devices kINPen 08, kINPen 09, or kINPen Chamber and for 15 minutes with the antiseptics chlorhexidine digluconate (0.2%), octenidine (0.1%), and ethanol (70%). After treatment, primary human fibroblast cells (HGF-1) were seeded and incubated for 1 and 24 hours. The cell area after 1 hour and cell density after 24 hours were analyzed by scanning electron microscopy images. Results: Water contact angles of both surfaces (95/96 degrees) were significantly reduced to 26 to 36 degrees (titanium) or 9 to 28 degrees (zirconia ceramic) after plasma treatment. On titanium only, the average cell area was significantly increased after 1 hour of cell incubation following kINPen 08 and kINPen 09 treatment. No significant differences between all three plasma devices and the untreated control were determined on both materials after 24 hours, whereas octenidine and chlorhexidine reduced cell surface covering. The cell density was significantly lower for all treatment regimens except octenidine on zirconia ceramic compared with titanium. Conclusion: Plasma reduced the water contact angle and supported cell covering on titanium in the early stage. Plasma devices had no discernible influence on cell covering after 24 hours of cell incubation, whereas chlorhexidine and octenidine hampered cell covering on both abutment surfaces. [ABSTRACT FROM AUTHOR]

This study evaluates how pre-treatment with an MDP-containing cleaning agent (Katana Cleaner, Kuraray) influences the micro-shear bond strength (µSBS) of saliva-contaminated zirconia when used with universal adhesive (UA) systems. Rectangular specimens (2 mm × 12 mm × 15 mm) were obtained (IPS, e.max ZirCAD, MO, B65L17, Ivoclar Vivadent) and divided into three groups; a non-contaminated group (control group)(CON), a contaminated and cleaned with isopropyl alcohol group(ISP), and lastly, a group contaminated and cleaned with an MDP-containing cleaning agent(KAC). Each group was then subdivided into three subgroups according to the UAs used (n = 12). Composite cylinders were prepared and bonded to each surface with Panavia V5 (Kuraray, Noritake Dental). A µSBS test was performed and the data were evaluated with the two-way analysis of variance (two-way ANOVA) and multiple comparisons test (α = 0.05). The highest µSBS values were obtained in the non-contaminated group (p < 0.001), regardless of UAs. All subgroups showed lower µSBS values after saliva contamination, but KAC resulted in significantly higher µSBS values than 99% isopropanol (p < 0.001). Overall, the lowest µSBS value was obtained with 99% isopropanol. The KAC-Clearfil UA subgroup resulted in statistically significantly higher µSBS values than the other UAs (p = 0.035 and 0.007), although all three UAs resulted in sufficient µSBS values. This study revealed that applying KAC followed by a UA containing phosphate monomers produces promising results for improving µSBS values of zirconia, greater than results using 99% isopropanol. Clinical relevance: An MDP-containing cleaning agent followed by a phosphate monomer containing a universal adhesive is a promising method to obtain acceptable bonds with saliva-contaminated zirconia ceramics. [ABSTRACT FROM AUTHOR]

The monitoring of tool wear plays an important role in improving the processing efficiency and reducing the production cost of enterprises. This paper is focused on the detection of electroplated diamond mill-grinding tools by using the acoustic emission sensor. The wear stages of mill-grinding tools are divided into three parts, namely initial wear stage, normal wear stage, and severe wear stage. The characteristic parameter method and the waveform analysis method are applied to analyze the acoustic emission signals. The wear characteristics of the tool and workpiece in different wear stages are observed and analyzed. The results indicate that the acoustic emission waveform is relatively stable in the initial wear stage, and the continuous acoustic emission signal is dominated. Moreover, the diamond abrasive grains are mainly worn and slightly broken in the normal wear stage, and there are some pits on the machined workpiece surface after the initial wear stage. In the severe wear stage, most of the abrasive grains are broken or broken in a large area, and there are burst acoustic emission signals in the waveform. [ABSTRACT FROM AUTHOR]

Zirconia ceramic is a modern material used for different types of prosthetic constructions, characterized by high mechanical resistance and aesthetics. The main difficulties in treatment are related to ensuring a stable and durable bond between the ceramic and dentin. This study examined the bonding strength of ZirCAD Multi (3rd generation) and ZirCAD Prime (5th generation) ceramics when using different types of cements before and after sandblasting the surface of zirconia with Al2O3. For this purpose, an experimental setup was created by 3D printing, in which sintered ceramic cylinders were cemented to dentin slices of natural teeth with different types of cements. From the formed ceramic-dentin constructions, test specimens were cut with a microtome and tested for tensile strength. The results showed an increase in the strength of the bond after sandblasting from 1.1 MPa to 2.4 MPa for ZirCAD Multi and from 1.6 MPa to 3.3 MPa for ZirCAD Prime. Zirconia ceramic ZirCAD Prime (5th generation) showed higher adhesion resistance, with the strongest bond being with the Speed Cem Plus and Panavia V5 cements. With ZirCAD Multi, the maximum tensile strength was achieved with the Rely X Luting Plus and Speed Cem Plus cements. Optimal strength and bond resistance were registered between the new fifth-generation zirconia ceramic and composite cements with MDP (10-methacryloyloxydecyl dihydrogen phosphate) primers. [ABSTRACT FROM AUTHOR]

All-ceramic restorations are widely used in oral restoration because of their beauty and high strength. Glass ceramics and zirconia all-ceramic materials are the two most widely used all-ceramic materials in the clinic. However, when all-ceramic restorations need to be removed due to marginal microleakage and secondary caries, its high strength and high bonding strength greatly increase the difficulty of removal. In recent years, clinicians have tried to use Er: YAG lasers to remove all-ceramic restorations. The Er: YAG laser can be safely and efficiently applied to the removal of glass restorations, and it can also play a role in thinner zirconia restorations. Various factors, such as the material and thickness of the all-ceramic restoration, the type of cement, and the laser power, can affect the speed of removal of the Er: YAG laser. However, the current research is limited to case reports and in vitro studies, lacking systematic clinical research. The specific mechanism of Er: YAG laser removal of all-ceramic restorations and the influence of laser frequency, adhesive type, and abutment on the removal speed need to be further demonstrated by follow-up research.

This laboratory study aimed to evaluate the effect of different surface patterns using femtosecond laser treatment on the enclosed mold shear bond strength (EM-SBS) of resin composite to zirconia (ZrO2) surfaces and to contrast it with the widely used tribochemical silica coating (TBC) surface conditioning method. A set of fifteen rectangular ZrO2 blocks were randomly divided into five groups according to surface pretreatment: Control G0—no treatment; G1—TBC with silane application; G2—femtosecond laser irradiation with horizontal lines 30 µm apart; G3—femtosecond laser irradiation with horizontal lines 15 µm apart; and G4—femtosecond laser irradiation with cross lines 30 µm apart. The pretreated surfaces were characterized by a surface profilometer, tensiometer and scanning electron microscope. The EM-SBS of resin composite stubs to ZrO2 was measured followed by fractographic analysis. The surface roughness and water contact angle were observed to be statistically higher among the femtosecond laser groups compared to the TBC and control groups. The G4 group exhibited the highest EM-SBS among all the groups, irrespective of the ageing conditions used. At the end of 5000 thermocycles, G4 exhibited EM-SBS of 14.05 ± 4.21 MPa compared to 13.80 ± 3.01 MPa in G1 and 5.47 ± 0.97 MPa in G0. The two-way ANOVA revealed a significant effect of both study groups and ageing conditions on the EM-SBS (p < 0.001). Utilization of femtosecond laser technology holds promise as a potential and alternative mechanical retention approach for enhancing the bonding strength of the resin composite to ZrO2.

Introduction and aim: Zirconia is currently the most commonly used representative of polycrystalline dental ceramics. It is highly valued for its mechanical properties: hardness, strength and toughness. On the contrary, its aesthetics is percieved as a disadvantage. Its insufficient transparency makes it impossible to mimic the optical properties of enamel, and therefore its indication in monolithic form is often limited to distal sections only. This article discusses the properties of zirconia ceramics and its evolution. Particular emphasis is placed on the chemical-physical nature of the phenomena involved in determining the properties of dental zirconia. Conclusion: The economic potential of zirconia ceramics is proving to be a strong stimulant of its development. The aesthetic disadvantages of the material were the biggest limiting factor for its wider use. The simplest and earliest solution to this problem was the veneering of zirconia using high glass content ceramics. This combination of materials, however, was found to have relatively frequent complications associated with chipping of the surface layers of the veneer. The use of zirconia ceramics in monolithic form proved to be the most advantageous from a mechanical point of view. Therefore, the development of zirconia ceramics in the last ten years has gone in the direction of increasing the transparency of the zirconia ceramic itself. The result of these efforts has been the latest generation of zirconia ceramics, which have significantly improved aesthetics and can be used even in relatively aesthetically exposed areas. These new materials retain only a fraction of the mechanical durability of their predecessors, and therefore their indications are limited to three-unit bridges. However, they still significantly expand the portfolio of applications for monolithic zirconia ceramics and are becoming a suitable alternative to older materials used for crown and bridge fabrication.

Zirconia ceramic is a modern material used for different types of prosthetic constructions, characterized by high mechanical resistance and aesthetics. The main difficulties in treatment are related to ensuring a stable and durable bond between the ceramic and dentin. This study examined the bonding strength of ZirCAD Multi (3rd generation) and ZirCAD Prime (5th generation) ceramics when using different types of cements before and after sandblasting the surface of zirconia with Al2O3. For this purpose, an experimental setup was created by 3D printing, in which sintered ceramic cylinders were cemented to dentin slices of natural teeth with different types of cements. From the formed ceramic-dentin constructions, test specimens were cut with a microtome and tested for tensile strength. The results showed an increase in the strength of the bond after sandblasting from 1.1 MPa to 2.4 MPa for ZirCAD Multi and from 1.6 MPa to 3.3 MPa for ZirCAD Prime. Zirconia ceramic ZirCAD Prime (5th generation) showed higher adhesion resistance, with the strongest bond being with the Speed Cem Plus and Panavia V5 cements. With ZirCAD Multi, the maximum tensile strength was achieved with the Rely X Luting Plus and Speed Cem Plus cements. Optimal strength and bond resistance were registered between the new fifth-generation zirconia ceramic and composite cements with MDP (10-methacryloyloxydecyl dihydrogen phosphate) primers.

Objectives: Mechanical properties are cardinal for the long‐term clinical success of laminate veneer restorations but the selection of new restorative materials should ideally be based on clinical evidence, therefore, in vitro testing of dental materials is a good alternative to evaluate their properties and understand their behavior so this study aimed to compare and evaluate the effect of two different thicknesses and yttria percentage on the fracture resistance of laminate veneer zirconia restorations. Materials and Methods: Forty laminate veneer restoration prepared from partial sintering zirconia of 3Y (yttria), 5Y (yttria), combined 3Y&5Y (yttria), and lithium disilicate. Specimens were assigned into four main groups according to their percentage of yttria content (n = 10) and subgrouped into two thicknesses (0.5 mm thickness and 0.3 mm thickness) (n = 5) as follows: Group I, II, III, and IV (Group I for lithium disilicate (control), Group II for 3Y zirconia, Group III for 5Y zirconia, and Group IV for combined 3Y&5Y zirconia), each of them subdivided according to their thickness into two subgroups (n = 5 for each one) and resistance to fracture for each restoration was evaluated using a universal testing machine. Data were analyzed using a one‐way analysis of variance and Duncan's tests at a 5% level of significance. Results: The thickness of laminate veneer restoration significantly affects the fracture resistance value of all type of laminate veneers restorations (fracture resistance mean value was highest for 0.5 mm thickness and lower for 0.3 mm thickness restorations) and yttria percentage significantly affect fracture resistance value of zirconia laminate veneer restorations (fracture resistance mean value was highest for 0.5 mm thickness of 3Y zirconia [865 N] and combined 3Y&5Y zirconia [846 N]). Conclusions: Reducing the thickness of laminate zirconia veneer restorations to 0.3 mm reduces its fracture resistance and increasing yttria percentage had an adverse effect on fracture resistance of zirconia laminate veneer restorations. [ABSTRACT FROM AUTHOR]

To improve the dimensional accuracy, surface quality, and mechanical properties of binder jet additive manufactured ceramic parts, in this work, nanozirconia dispersion and binder were used to prepare a jet solution to investigate the effect of nanozirconia content of the jet solution on the properties of zirconia ceramic green and sintered bodies. When the nanozirconia content of the jet solution increased from 0 to 20 wt%, the forming precision of the zirconia ceramic green bodies improved, the surface roughness decreased, and the density increased. After sintering at 1400 °C for 2 h, linear shrinkage along the height, width, and length of the zirconia ceramics decreased by 6.27%, 10.20%, and 5.45%, respectively, while the surface roughness decreased by 42.87%, and the bending strength increased by 145.60%. With increasing nanozirconia content of the jet solution, the spreading and infiltration distance of the jetted solution in the powder layer decreased, the thickness of the deposition layer of nanozirconia on the surface of the zirconia particles in the powder layer increased, and the pore size of the powder layer decreased significantly. This increased the density of the green bodies; thus, improving the sintering properties of the zirconia ceramics. [ABSTRACT FROM AUTHOR]

Additive manufacturing has received tremendous attention in the manufacturing and materials industry in the past three decades. Zirconia-based advanced ceramics have been the subject of substantial interest related to structural and functional ceramics. NanoParticle Jetting (NPJ), a novel material jetting process for selectively depositing nanoparticles, is capable of fabricating dense zirconia components with a highlydetailed surface, precisely controllable shrinkage, and remarkable mechanical properties. The use of NPJ greatly improves the 3D printing process and increases the printing accuracy. An investigation into the performance of NPJ-printed ceramic components evaluated the physical and mechanical properties and microstructure. The experimental results suggested that the NPJ-fabricated ZrO 2 cuboids exhibited a high relative density of 99.5%, a glossy surface with minimum roughness of 0.33 μm, a general linear shrinkage factor of 17.47%, acceptable hardness of 12.43 ± 0.09 GPa, outstanding fracture toughness of 7.52 ± 0.34 MPa m1/2, comparable flexural strength of 699 ± 104 MPa, dense grain distribution of the microstructure, and representative features of the fracture. Subsequently, the exclusive printing scheme that achieved these favorable properties was analyzed. The innovative NanoParticle Jetting™ system was shown to have significant potential for additive manufacturing. [Display omitted] [ABSTRACT FROM AUTHOR]

In order to verify the feasibility of surface glazing of zirconia ceramics, the experimental study of continuous laser surface glazing of zirconia ceramics at room temperature was carried out, the laser processing parameters were studied. The results show that the morphology of the glaze structure on the surface of zirconia ceramics can be optimized by changing the laser processing parameters. It is concluded that changing the laser output power and scanning speed can reduce the occurrence of thermal cracks and overheated structures. The change of defocus can broaden the glazed area and improve the morphology of glazed structure. [ABSTRACT FROM AUTHOR]

The present study comprehensively compared the microstructure, flexural strength, and fracture toughness of zirconia ceramics prepared via two different methods, subtractive milling (SM) and stereolithography (SLA). Disc- or rectangular-shaped zirconia specimens (Prettau (SM) and 3DMix Zirconia (SLA)) were prepared following each manufacturer's instructions and polished. The microstructures of the two different zirconia specimens were studied by scanning electron microscopy, X-ray diffractometry, energy-dispersive X-ray spectroscopy, and electron backscattered diffractometry. The flexural strength and fracture toughness based on the indentation fracture method were measured for the two different zirconia ceramics. A greater number of small pores and smaller grains were found in the SLA specimen than in the SM specimen. The crystal structure and microstructure analysis revealed that both ceramics had a similar phase composition to each other. No significant differences in flexural strength (p = 0.242) or fracture toughness (p = 0.101) were detected between the two ceramics. The mean flexural strength of the SLA-fabricated zirconia as well as the SM zirconia satisfied the class 5 criteria (>800 MPa) in the ISO 6872 standard. [ABSTRACT FROM AUTHOR]

Microcracks and surface/subsurface damage are easily generated in engineering ceramics grinding. Fracture toughness is an important mechanical property that affects the grinding performance of engineering ceramics, and dynamic fracture toughness accurately reflects the mechanism of crack generation and propagation mechanism in different grinding conditions. Considering the dynamic fracture toughness and grinding process parameters for zirconia ceramics with different grain sizes (50 nm/500 nm/5000 nm) in this paper, the critical grinding force and maximum subsurface damage depth models for the crack generation were established and verified by grinding experiments. The effects of dynamic fracture toughness on the material removal mechanism during the ductile–brittle transition with different process parameters were analyzed, and the influence of different grain sizes on grinding force, workpiece surface roughness, surface cracking rate, and subsurface damage depth were discussed. Experiment results showed that the dynamic fracture toughness values range from 13.0 to 15.0 Mpam1/2 with grain size 50 nm, 9.8 to 11.3 Mpam1/2 with grain size 500 nm, and 6.1 to 6.8 Mpam1/2 with grain size 5000 nm in the experimental process parameters. The relative error of the dynamic maximum subsurface damage depth is respectively 15.77%, 11.65%, and 18.36%. And the subsurface damage depth of zirconia ceramics is respectively 27 μm, 31 μm, and 40 μm with the grain size of 50 nm, 500 nm, and 5000 nm in the 5th group process parameters, which showed that the small grain size exhibited excellent grinding quality. But the influence of grain size on dynamic fracture toughness was weaker than that of grinding process parameters. [ABSTRACT FROM AUTHOR]

Zirconia ceramics are the promising materials for cell phone backplanes in the 5G era, and smoother surfaces and higher removal efficiency are sought after for their precision machining. Although nanodiamond abrasives have high polishing rates, it is easy to bring mechanical scratches and pits on the ceramic surface because of their high hardness, resulting in degradation of the surface quality of the finished workpiece. Therefore, polyacrylamide grafted nanodiamond particles were prepared by solution polymerization method for polishing ceramic wafers. As confirmed by Fourier transform infrared spectroscopy (FTIR), the polyacrylamide has been grafted on the nanodiamond surface. According to the scanning electron microscopy (SEM) and particle size distribution, the composite abrasives have better dispersion than pure nanodiamond abrasives. The results of chemical mechanical polishing (CMP) experiments showed that the composite abrasives could reduce the average surface roughness (Sa, arithmetic mean height) of zirconia ceramic from 28.31 nm to 2.68 nm (scanning area is 500 μm × 500 μm), and the polishing rate remained high compared to pure nanodiamond abrasives, showing superior CMP performance. X-ray photoelectron spectroscopy (XPS) demonstrated that solid-phase chemical reactions occurred during the polishing process to form ZrSiO 4. Meanwhile, contact-wear model combined with contact angle testing indicates that the introduction of polyacrylamide increases the contact area of the nanodiamond on the zirconia wafer surface, thereby significantly enhanced the mechanical effect. [ABSTRACT FROM AUTHOR]

The direct welding of alumina and zirconia ceramics by ultrashort pulse laser is presented for the first time. Compared to traditional dissimilar ceramic joining techniques such as brazing and diffusion welding, this method shows various advantages, including operation at room-temperature, higher welding efficiency, and negligible impact on base materials. The joint microstructure consists of a combination of Al 2 O 3 and ZrO 2 phases, without new phases detected. By adjusting the laser focal point position, the phase content within joint is effectively regulated, successfully preventing crack formation in alumina substrate. The influence of laser power and welding speed on joint morphology and mechanical property is fully investigated. The highest four-point bending strength of 365.5 MPa and shear strength of 33.4 MPa are achieved. After experiencing thermal cycling test at 1000°C, the joint strength and microstructure does not exhibit significant changes, demonstrating the excellent high-temperature durability of the sample. [ABSTRACT FROM AUTHOR]

Femtosecond laser ablation can offer a promising solution for precise and efficient processing of zirconia-based ceramics taking advantage of ultrafast photon-material interaction. However, due to the nonlinear nature of the process, the selection of the laser parameters in 3D processing is complicated, often leading to reduced efficiency or low material integrity. Here, we address this problem through static (D2) and dynamic (grooving) testing, establishing a comprehensive understanding of the femtosecond ablation behaviour of zirconia on micro- and macro- scales. The ablation threshold of zirconia shows a significant dependence not only on the irradiation history but also on the material temperature. While the processing efficiency can be increased, a critical interpulse duration or a high heat input can facilitate a melting regime, negating the advantages of pulsed laser ablation. Morphological evolution of the surface impacts the ablation behaviour further affecting the process efficiency. Additionally, zirconia semitransparency leads to the formation of nanopores compromising residual material integrity. Based on the analysis of these elementary ablation events, we built an ultrafast computational model, simulating the surface evolution during femtosecond laser ablation with various beam-surface kinematics. Validating the model on a 3D dental crown surface underscores its potential for computer aided design-manufacturing frameworks given its efficiency. [Display omitted] • The ablation testing revealed micro- and macro heat accumulation effects in zirconia. • Upon the critical interpulse period the ablation mechanism shifts to severe melting. • Nanoporosity due to intergranular ablation in zirconia is linked to laser parameters. • The ultrafast computational femtosecond ablation model is introduced and validated. [ABSTRACT FROM AUTHOR]

Zirconia has occupied an increasingly important role in oral clinical applications in recent years. However, how to achieve the ideal bonding effect of zirconia is a significant problem that needs to be solved urgently in oral clinics. Hot etching treatment of zirconia is a hot spot of current research, but it is still unclear about the optimal acid solution and the effect of hot etching on the surface topography and bond strength of zirconia. This study evaluated the effect of hot etching with HF and HCl on the surface topography, roughness, crystalline phase, zirconia/resin cement interfacial evaluation and shear bond strength of zirconia. The results showed that the hot etching groups produced completely different topographical changes on the surface of zirconia than the sandblasting group. Obvious interfacial cracks were observed in the sandblasting group. The HF hot etching group achieved the highest roughness values (78.17 ± 4.94 nm) and the highest shear bond strength (25.09 ± 4.09 MPa). Compared with HCl, hot etching with HF could achieve more uniform and dense porous morphology, greater roughness and shear bond strength. Moreover, there were no prominent zirconia/resin cement interfacial cracks and crystal phase transformations on the surface of zirconia.

We describe our study of the treatment of ceramics based on zirconium dioxide (ZrO 2), partially stabilized with yttrium oxide (Y 2 O 3) (5.15 % wt.), by continuous and pulsed electron beams in the forevacuum pressure range. We find that continuous electron beam treatment at certain heating rates can lead to changes in the surface structure, with increase in roughness and change in crystalline phase composition. High heating rate leads to increase in the cubic phase of ZrO 2. The results of irradiation by a pulsed electron beam depends on the pulse energy density and pulse power of the beam, with noticeable changes in the surface characteristics when the energy density reaches about 10 J/cm2; increased roughness of the ceramic surface is observed at this energy density. Further increase in pulse energy density (>10 J/cm2) and/or power can lead to increase in roughness by an order of magnitude. A change in color of the ceramic surface and formation of a layer with a columnar structure is observed when the energy density reaches 21 J/cm2 at a pulse power of 320 kW. These results show the suitability of electron beam treatment for controlled modification of zirconium dioxide ceramic materials. • Treatment by continuous and pulsed electron beams modify surface of ZrO 2 ceramics. • The heating rate of a sample influences on surface structure of zirconia ceramics. • Surface roughness can be changed by varying the parameters of the electron beam. • The layer with a columnar structure on the treated ceramic surface is observed. [ABSTRACT FROM AUTHOR]

Based on the radiation from high-permittivity dielectric waveguide and ceramic three-dimensional (3-D) printing technology, a dielectric Archimedean spiral antenna made of zirconia is proposed in this letter. Its operational mechanism and performance are here discussed in comparison with its metal counterpart. It is found that although the radiation principles of metal and dielectric spiral antennas are different, similar impedance and radiation characteristics can be achieved. Moreover, compared with the conventional metal spiral antenna, the proposed dielectric one possesses lower profile, lower radar cross section at high-frequency spectrum (9–13 GHz), and better prospect on radiation efficiency. The profile of fabricated antenna prototype is 9.5 mm and the radiation efficiency is more than 92%. The measured impedance and axial ratio bandwidths cover from 4.65 to 6.23 GHz and 4.75 to 6.1 GHz, respectively, with the maximal radiation gain of 9 dBic. The proposed antenna is suitable for C-band electronic countermeasures and navigation systems. This study provides a novel dielectric Archimedean spiral antenna, as well as its unique characteristics compared withthe metal counterpart. [ABSTRACT FROM AUTHOR]

Objectives: To assess the efficacy of experimental cleaners containing 10-methacryloyloxydecyl dihydrogen phosphate (MDP) on the saliva decontamination of ceramic and their influence in restoring zirconia's adherence to resin cement. Materials and methods: Four hundred sixty alumina-blasted zirconia specimens were categorized into saliva-contaminated and uncontaminated groups which were treated with ceramic primer (P), experimental cleaner 1 (C1), C1 followed by P (C1P), experimental cleaner 2 (C2), and C2 followed by P (C2P). Stainless-steel rods were then attached to the specimens using PanaviaV5 cement (Kuraray Noritake Dental; Tokyo, Japan). Tensile bond strength (TBS) test was performed after 24 h and 5000 thermocycling processes. X-ray photoelectron spectroscopy (XPS) analysis and contact angle measurement of the specimen were performed. The TBS data were analyzed by Weibull analysis and three-way ANOVA. Contact angle data were analyzed by two-way ANOVA (α = 0.05). Results: C2P groups showed the highest TBS in all conditions among tested groups. Saliva contamination led to a significant reduction of TBS in primer- and cleaner-treated groups, with no significant impact on C2P. Adhesive failure was predominant in contaminated groups except with the C1P and C2P groups. XPS revealed that a nitrogen peak was observed on contaminated groups but not in primed groups. The contact angle was significantly affected by saliva contamination, the cleaners, and/or ceramic primer usage (p < 0.001). Conclusions: The MDP cleaner followed by the MDP primer protocol may overcome the effect of saliva contamination and improve the resin-ceramic bond strength. Clinical relevance: It is recommended to use a combination of MDP-containing cleaner 2 and ceramic primer as a chair-side chemical pretreatment for zirconia substrate with or without saliva contamination. [ABSTRACT FROM AUTHOR]

Parts made of zirconia ceramics have been used in various high-end fields, and some of these parts exhibit complex styles with various curved surfaces. As a prominent machining technique for manufacturing zirconia ceramic parts, tangential ultrasonic-assisted grinding has mainly been employed in improving the processing efficiency and simultaneously ensuring the surface quality. With the aim of further improving the processing performance of tangential ultrasonic-assisted curved surface grinding, the effects of the grinding paths with α = 0°, α = 45°, and α = 90° on the surface quality and profile of a workpiece were studied for a specific curved surface, and the wear of the grinding wheel with different paths was analyzed. In addition, the material removal mechanisms were discussed for single diamond grit grinding tests. The obtained results demonstrated that (1) the surface roughness Sa was different at different grinding paths, i.e., at different values of α, and the surface finish mainly depended on the ultrasonic amplitude. (2) The profile error of the curved work-surface was different at different values of α. (3) The wear of the grinding wheel at α = 45° was the most serious, and at α = 0° and α = 90°, the abrasive grain wear was slight. These tendencies agreed with the case of the work-surface quality. (4) The material removal mechanism was different with and without ultrasonics, which resulted in the differences in the work-surface finish. [ABSTRACT FROM AUTHOR]

The proposed research work accomplishes the experimental study and computational fluid dynamics (CFD) technique for erosive footprint prediction extent in hot abrasive jet machining (HAJMing) constraints on target surface erosion rate, surface roughness of intricately shaped tapered holes generation. The CFD-obtained footprints were in superior agreement with experimentally measured data. HAJMing process uses a relatively high speed air-hot abrasive stream to produce both high accuracy micro-channels and tapered holes. HAJM also defines itself phenomenal competence over all advanced manufacturing techniques due to its growing demands for better surface reliability with defects (mostly stress, heat) free surfaces. Zirconia is widely accepted and associated in the non-conventional machining processes and industries with the years of track on record of proven performance in a vast number of brittle materials. Most perceptible act in this research is the selection of abrasive particle to achieve the appropriate intricate shaped holes on zirconia ceramic with hot silicon carbide (SiC) abrasives. Machining of these features are done with varying the abrasive temperature. Optical microscopic view was considered for the generation of machined holes during HAJMing. All the experimental data were presented to study the effect of machining constraints on target surface erosion rate and surface roughness using HAJMing. Single impact experiments were executed to measure the target surface erosion due to impact of individual hot silicon carbide abrasive particles. An experimental setup has been designed to conduct the machining trials using Box-Behnken design of experiments. It is also shown that the generated workpiece surface contour and erosion rate are the function of machining constraints which have a negligible influence on air-abrasive flow characteristics. This research work also deals with the sustainability assessment under environmental-friendly hot abrasive-assisted machining conditions. [ABSTRACT FROM AUTHOR]

This study aims to achieve higher-efficiency zirconia ceramic polishing demands, using a novel rod-shaped SiO 2 @C abrasive that was synthesized by a simple three-step method. The scanning electron microscopy and transmission electron microscopy results showed that composite abrasives were rod-shaped. As confirmed by Fourier transform infrared spectrometer and Raman spectra, the composite particle had a core-shell structure with a core of silica and a shell of carbon. According to the N 2 adsorption-desorption results, this composite abrasive had a mesoporous structure. The material removal rate of 242.5 nm/h and the zirconia ceramic surface roughness of 1.86 nm are 70.4% higher and 27.9% lower, respectively, than those achieved with conventional silica abrasives. The improved polishing performance may be attributed to its line contact mode, the reduction of Young's modulus and the improvement of tribochemical reaction. This study highlights the interaction between the surface microstructure of abrasives and the surface planarization of ceramics. [Display omitted] • Preparation of rod-shaped carbon coated silica abrasives by a three-step method. • The material removal rate of composite abrasives is increased by 70.4% compared with conventional silica abrasives. • The surface roughness of zirconia ceramics is reduced to the lowest known 1.8 nm. • The polishing performance is related to the morphology and structure of abrasives. • Line contact mode, enhanced adhesion and tribochemical reaction resulted in superior CMP behavior. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the shear bond strength (SBS) of different zirconia ceramic surface treatments to resin composite after thermocycles. Methods: Two hundred and seven zirconia specimens (LAVA, 3M ESPE) were divided into 9 groups and treated as follows: Group C─no treatment (served as the control); Group PC─Clearfil Ceramic primer (CP); Group PZ─Z-Prime Plus primer (ZP); Group A─sandblasted with 50 µm Al2O3 at 0.25 MPa for 20 s at a distance of 10 mm; Group AC─sandblasted and coated with CP; Group AZ─sandblasted and coated with ZP; Group L─GaAlAs diode laser with 808±5 mm wavelength, 3 watts power, and 10 Hz frequency; Group LC─GaAlAs diode laser coated with CP; and Group LZ─GaAlAs diode laser coated with ZP. All zirconia specimens were then directly bonded with a resin composite cylinder using Adper Scotchbond Multi-Purpose Plus (3M ESPE). Specimens were stored at 37ºC for 30 days with 2,500 thermocycles from 5ºC and 55ºC before the SBS was tested. One-way ANOVA and Tukey’s HSD test (α = .05) were performed. Surface topography changes were evaluated with a scanning electron microscope (SEM). Results: Sandblasting associated with CP or ZP (24.98±0.58 and 24.75±0.31 MPa, respectively) produced the highest SBS and was significantly different from other treatments (P < .05). SEM photographs presented various degrees of changes depending on different surface treatments. Surface treatment by sandblasting combined with a CP or ZP significantly provides the highest SBS between zirconia and resin composite. Clinical Significance: For repairing fractured zirconia ceramics, surface treatment by sandblasting combined with a CP or ZP is suitable with direct resin composite. [ABSTRACT FROM AUTHOR]