Yttria-stabilized Zirconia Surface Research Articles

A novel etching technique for surface treatment of zirconia ceramics to improve adhesion of resin-based luting cements

Objectives: Bonding of zirconia crowns and bridges to abutments is important, not only bonding of the thin resin layer to the abutment, but also bonding to the zirconia ceramic is crucial. Both mechanical and chemical adhesion are desired. Mechanical retention of dental porcelain achieved by etching with moderately concentrated hydrofluoric acid is not possible with zirconia ceramics.The purpose of this study was to show that etching is possible with relative low melting fluoride compounds such as ammonium hydrogen difluoride and potassium hydrogen difluoride.Materials and methods: Before melting, the fluorides can be introduced as powders or as aqueous slurries to the contact surfaces of the zirconia. After melting, the yttria-stabilized zirconia surface revealed a surface similar to an HF-etched dental feldspathic porcelain surface. Shear bond testing (n = 10) was performed with zirconia attached to zirconia with the Duo-Link composite luting cement (Bisco) after treatment of the etched zirconia surfaces with Bis-Silane (Bisco) and the Porcelain Bonding Resin (Bisco).Results: Values for adhesive strength (mean ± standard deviation) after melt etching of the surfaces with initially dry powders were for K[FHF], (31.2 ± 7.5) MPa and for NH4[FHF] (31.0 ± 11.8) MPa. When initially aqueous slurries were applied, the values were for K[FHF] (42.7 ± 12.7) MPa and for NH4[FHF] (40.3 ± 10.0) MPa.Conclusion: Good adhesion to zirconia can be achieved by a procedure including etching with selected melted fluoride compounds.

Stabilizing Ir(001) Epitaxy on Yttria-Stabilized Zirconia Using a Thin Ir Seed Layer Grown by Pulsed Laser Deposition

We demonstrate the reproducible epitaxial growth of 100 nm thick Ir(001) films on a heteroepitaxial stack consisting of 5 nm Ir and 100 nm yttria-stabilized zirconia (YSZ) grown on Si(001) substrat...

Thermal effusivity measurement based on analysis of 3D heat flow by modulated spot heating using a phase lag matrix with a combination of thermal effusivity and volumetric heat capacity

The study goal was to establish a standard industrial procedure for the measurement of thermal effusivity by a thermal microscope (TM), using a periodic heating method with a thermoreflectance (TR) technique. To accomplish this goal, a working group was organized that included four research institutes. Each institute followed the same procedure: a molybdenum (Mo) film was sputtered on the surface of Pyrex, yttria-stabilized zirconia (YSZ), alumina (Al2O3), Germanium (Ge), and silicon (Si) samples, and then the phase lag of the laser intensity modulation was measured by the resultant surface temperature. A procedure was proposed to calibrate the effect of 3D heat flow, based on the analytical solution of the heat conduction equation, and thermal effusivity was measured. The derived values show good agreement with literature values. As a result, the TM calibration procedure can be recommended for practical use in measuring the thermal effusivity in a small region of the materials.

Enhancement of Thermal Stability of Sputtered Nanoporous Pt Thin Film Using Oxygen Plasma Treatment in Low Temperature Solid Oxide Fuel Cells

Sputtered nanoporous platinum (Pt) thin films are common choices as catalytic cathodes for low temperature (300~500°C) solid oxide fuel cells (LT-SOFCs) for its high catalytic activity towards oxygen reduction reaction. However, the nanoporous pure Pt is vulnerable to thermal coagulation during high temperature operation, which often causes irreversible deterioration to the cell performance. In our earlier work, physical confinement of the nanoporous Pt with a few nanometers of zirconia (ZrO2) conformal coating by atomic layer deposition (ALD) improved the thermal stability of Pt significantly, with more than 50% of the cell power density retained after 80 hours of operation. Still, around 29.5% of cell power density degradation was observed in cells using ALD-ZrO2 capped nanoporous Pt cathode. It is likely that the poor adhesion between the Pt cathode and the yttria-stabilized zirconia (YSZ) electrolyte that caused the triple phase boundaries to be unstable under high temperature operation and therefore a significant thermal degradation is still observed. In this work, we studied the effect of adhesion between Pt and YSZ on the morphological stability of nanoporous Pt at the Pt/YSZ interface. The surface of YSZ electrolyte was treated with oxygen plasma to modify the wettability between ALD-ZrO2 capped Pt and YSZ. The contact angle of a water droplet on the untreated YSZ surface was 80˚, while it dropped to 16˚ on the oxygen-plasma treated YSZ surface, meaning a more hydrophilic YSZ surface was obtained. The oxygen-based functional groups may have formed after the oxygen plasma treatment and increased the YSZ-water interfacial energy. The additional chemical bonding may exist if the nanoporous Pt films are deposited on surface-treated YSZ to stabilize the morphology of nanoporous Pt at the Pt/YSZ interface. The surface confined nanoporous Pt thin film cathodes were annealed at 600°C to induce the agglomeration, followed by delamination of the Pt cathode film from the YSZ substrate using double cantilever beam (DCB), in order to investigate the morphological stability of the nanoporous Pt at the Pt/YSZ interface after oxygen plasma treatment. The interfacial morphology observation showed that the Pt agglomeration at the Pt/YSZ interface remained significantly severe for Pt cathode with only ALD-ZrO2 surface capping. For Pt cathode deposited on YSZ substrate treated with 5 minutes of oxygen plasma at 18 watts showed improved interfacial thermal stability. A fuel cell with ALD-ZrO2 capped nanoporous Pt cathode thin film deposited on the oxygen-plasma treated YSZ electrolyte was tested. It was observed that the performance degradation was effectively hindered by the oxygen plasma treatment after 75 hours of operation at 450°C. Figure 1

Developing Cost-Effective Dense Continuous SDC Barrier Layers for SOFCs

Solid oxide fuel cells (SOFCs) with lanthanum strontium cobalt ferrite (LSCF) cathodes often employ a samaria-doped or gadolinia-doped ceria (SDC or GDC, respectively) barrier layer between the cathode and the yttria-stabilized zirconia (YSZ) electrolyte to inhibit Sr from migrating to the YSZ surface where it reacts to form electrically-resistive strontium zirconate during cathode sintering. Because the SDC must be sintered at limited temperatures (generally ≤1200°C) to avoid forming a CeO2-ZrO2 solid solution that has significantly lower ionic conductivity, screen printed barrier layers are often porous after firing. Electrochemical tests of cells with dense, continuous pulsed laser deposited (PLD) SDC found that these cells exhibited significantly higher performance than those with the conventional screen-printed porous SDC layers. Thus, PNNL began investigating the fabrication of dense, continuous SDC barrier layers using cost-effective deposition by screen printing which is amenable to industrial production of SOFCs. Many approaches to improve the SDC density have been explored including the use of powder with reduced particle sizes, inks with increased solids loading, and doping with sintering aids. While some of these tests were successful in enhancing the density of the SDC, the stresses induced by constrained sintering on the surface of previously-fired YSZ caused cracks and discontinuities in the SDC barrier layer. These results together with steps that have been taken to address the constrained sintering issue will be presented.

Hydration Structures and Water Chemistry at Zirconia-Water Interface

The life cycle of zirconium cladding is a key safety factor and design parameter for higher fuel burnups in pressurized water reactors. The degradation of the metal alloy is primarily attributed to interactions of native oxide with water. Here we probe the detailed interfacial hydration structures at the 8 mol% yttria-stabilized cubic zirconia (YSZ) surfaces as a model system using synchrotron-based high-resolution X-ray reflectivity technique. Interfacial hydration structures in the major crystallographic orientations, (100), (110), and (111), were determined with sub-angstrom resolution and compared with each other to identify common features as well as different surface chemistry effects on the interfacial processes. All three surfaces terminate with significant number of point defects originating from the metal depletion and the intrinsic oxygen vacancies. Water molecules fill those vacancies, forming an ordered, layered structure on the top surface. Above the termination layer on each surface, two additional adsorbed layers form characteristic interfacial hydration structures. The first adsorbed layers likely include metal species based on the observed local densities, whereas the second layers consist of pure water. The current results provide valuable references for future studies of water chemistry effect on the interfacial hydration structure and the high temperature stability test of the zirconia in pressurized water conditions simulating realistic environment in pressurized water reactors of nuclear power plants. We also studied the effect of zinc adsorption on the interfacial hydration structure in zinc acetate solutions. Zinc injection into the reactor coolant system has been known to be effective in reducing the radioactive wastes as well as stabilizing crud oxide layers of the cladding materials. Our X-ray reflectivity data qualitatively reveal that there are obvious hydration structure changes at (100) and (111) surfaces while (110) surface show little changes. The interfacial electron density profiles were derived from the structure factor analysis of the measured reflectivity data. The structure factor analysis indicated an inner-sphere adsorption of Zn2+ layer at YSZ (111)-water interface, while there appeared to be an outer-sphere adsorption of Zn2+ layer at YSZ (100)-water interface. We further confirmed the detailed element specific adsorption profile of Zn2+ ions on YSZ (110) and (111)-water interfaces with resonant anomalous X-ray reflectivity measurements.

Density functional theory study of the interaction of H2O, CO2 and CO with the ZrO2 (111), Ni/ZrO2 (111), YSZ (111) and Ni/YSZ (111) surfaces

The triple phase boundary (TPB), where the gas phase, Ni particles and the yttria-stabilised zirconia (YSZ) surface meet, plays a significant role in the performance of solid oxide fuel cells (SOFC). Indeed, the key reactions take place at the TPB, where molecules such as H2O, CO2 and CO interact and react. We have systematically studied the interaction of H2O, CO2 and CO with the dominant surfaces of four materials that are relevant to SOFC, i.e. ZrO2(111), Ni/ZrO2(111), YSZ(111) and Ni/YSZ(111) of cubic ZrO2 stabilized with 9% of yttria (Y2O3). The study employed spin polarized density functional theory (DFT), taking into account the long-range dispersion forces. We have investigated up to five initial adsorption sites for the three molecules and have identified the geometries and electronic structures of the most stable adsorption configurations. We have also analysed the vibrational modes of the three molecules in the gas phase and compared them with the adsorbed molecules. A decrease of the wavenumbers of the vibrational modes for the three adsorbed molecules was observed, confirming the influence of the surface on the molecules' intra-molecular bonds. These results are in line with the important role of Ni in this system, in particular for the CO adsorption and activation.

The Hydration Structure at Yttria-Stabilized Cubic Zirconia (110)-Water Interface with Sub-Ångström Resolution.

The interfacial hydration structure of yttria-stabilized cubic zirconia (110) surface in contact with water was determined with ~0.5 Å resolution by high-resolution X-ray reflectivity measurement. The terminal layer shows a reduced electron density compared to the following substrate lattice layers, which indicates there are additional defects generated by metal depletion as well as intrinsic oxygen vacancies, both of which are apparently filled by water species. Above this top surface layer, two additional adsorbed layers are observed forming a characteristic interfacial hydration structure. The first adsorbed layer shows abnormally high density as pure water and likely includes metal species, whereas the second layer consists of pure water. The observed interfacial hydration structure seems responsible for local equilibration of the defective surface in water and eventually regulating the long-term degradation processes. The multitude of water interactions with the zirconia surface results in the complex but highly ordered interfacial structure constituting the reaction front.

Operando X-ray Investigation of Electrode/Electrolyte Interfaces in Model Solid Oxide Fuel Cells.

We employed operando anomalous surface X-ray diffraction to investigate the buried interface between the cathode and the electrolyte of a model solid oxide fuel cell with atomic resolution. The cell was studied under different oxygen pressures at elevated temperatures and polarizations by external potential control. Making use of anomalous X-ray diffraction effects at the Y and Zr K-edges allowed us to resolve the interfacial structure and chemical composition of a (100)-oriented, 9.5 mol % yttria-stabilized zirconia (YSZ) single crystal electrolyte below a La0.6Sr0.4CoO3−δ (LSC) electrode. We observe yttrium segregation toward the YSZ/LSC electrolyte/electrode interface under reducing conditions. Under oxidizing conditions, the interface becomes Y depleted. The yttrium segregation is corroborated by an enhanced outward relaxation of the YSZ interfacial metal ion layer. At the same time, an increase in point defect concentration in the electrolyte at the interface was observed, as evidenced by reduced YSZ crystallographic site occupancies for the cations as well as the oxygen ions. Such changes in composition are expected to strongly influence the oxygen ion transport through this interface which plays an important role for the performance of solid oxide fuel cells. The structure of the interface is compared to the bare YSZ(100) surface structure near the microelectrode under identical conditions and to the structure of the YSZ(100) surface prepared under ultrahigh vacuum conditions.

Adsorption of Water on Yttria-Stabilized Zirconia

Water adsorption on the cubic (111) surface of yttria-stabilized zirconia (YSZ) was investigated using density functional theory calculations. Relaxation of atomic positions away from ideal cubic lattice sites, in particular of the oxygen anion sublattice, is observed on including both phase-stabilizing dopants and water adsorption. A large slab model has been used to explore the effects of extended relaxation throughout the anionic sublattice and the role of vacancy–vacancy interactions on water adsorption. Dissociative adsorption of water to fill a surface vacancy site, accompanied by concerted oxygen movement in the vacancy cluster region of the slab, leads to a very strong adsorption of −2.20 eV, blocking surface sites for oxygen activation. We show that the use of larger slab models leads to a more detailed representation of the YSZ surface system.

In situcharacterization of the formation of a mixed conducting phase on the surface of yttria-stabilized zirconia near Pt electrodes

The electrochemical reactions of solid oxide fuel cells occur in the region where gas-phase species, electrode, and electrolyte coincide. When the electrode is an ionic insulator and the electrolyte is an electronic insulator, this `triple phase boundary' is assumed to have atomic dimensions. Here we use photoemission electron microscopy to show that the reduced surface of the electrolyte yttria-stabilized zirconia (YSZ) undergoes a metal-insulator transition near Pt negative electrodes. YSZ's electron conducting region functions as an extended triple phase boundary that can be many microns in size, depending on oxygen pressure, temperature, applied voltage, and time.

First-Principles Study of Surface Peroxo in Oxygen-Rich Yttria Stabilized Zirconia (110)

Introduction Yttria-stabilized zirconia (YSZ) is used as the most common solid electrolyte in solid oxide fuel cells (SOFC) because of its high ionic conductivity, and the Ni-YSZ cermet is a standard electrode material for SOFC anodes because it satisfies the basic requirements for anodes such as catalytic activity and stability in addition to high ionic and electronic conductivity. To design SOFC system for much higher energy conversion rate, atomistic simulations have been conducted to capture the intrinsic properties in the SOFC materials. For example, the previous theoretical works [1-3] on the anode have been performed for the chemical reaction from O2- and H­2 to water at the triple phase boundary of Ni-YSZ, where oxygen ions in YSZ are naturally O2- ions. However, we can expect other charged state of oxygen such as peroxo O2 2-, which is one of the important intermediate for catalytic reactions on oxides [4-6]. Therefore a careful consideration on the adsorbed state of oxygen at the YSZ surface is quite important because the catalytic activity is affected by the adsorbed state of the oxygen molecule. In this study, we investigated the electronic structure of an excess oxygen atom adsorbed on YSZ and its dependence on the surface indices from first-principles calculations [7]. Computational Details We used the low index surfaces (111), (110), and (100) of YSZ to analyze the oxygen adsorbed state. All first-principles calculations were performed by using the Vienna ab initio simulation package with Perdew-Burke-Ernzerh type generalized gradient approximation for the exchange-correlation functional. The core electrons were replaced by projector-augmented wave pseudopotentials, and wave functions were expanded in a basis set of plane waves up to a cutoff energy of 400 eV. We chose a Monkhorst-Pack 3×3×1 k-point grid for the first Brillouin zone sampling. Results and Discussion From the analysis of the partial density of states (PDOS) for the relaxed oxygen rich YSZ(110), we revealed that an excess oxygen atom on YSZ(110) spontaneously moves from an ideal lattice site to an interstitial site for bonding with an adjacent lattice O, yielding a surface peroxo OO (Fig. 1(a)). Figure 1(b) shows PDOS of OO, the surface oxygen atoms Osurf except for OO, the bulk oxygen atoms Obulk, and the surface Zr atoms Zrsurf. PDOS of OO are clearly different from those of Osurf and Obluk because the sharp peaks indicated with arrows in PDOS of OO are observed, on the other hands, such peaks are absent in the PDOS of Osurf and Obulk. We found that the sharp peaks originate primarily from the interaction between two oxygen pair OO because the partial charge densities of the sharp peaks show a particular property of the molecular orbitals in oxygen gas (Fig. 1(c)). According to the orbital occupation, the charged state of OO is 2- per two oxygen, that is peroxo O2 2-; the 1πg *-like orbitals in OO are fully occupied by electrons. Our finding will expand the reaction path designing on the SOFC anode.

Nanoporous silver cathodes surface-treated by atomic layer deposition of Y:ZrO2 for high-performance low-temperature solid oxide fuel cells

We report high-performance solid-oxide fuel cells (SOFCs) with silver cathodes surface-treated using yttria-stabilized zirconia (YSZ) nano-particulates fabricated by atomic layer deposition (ALD). Fuel cell tests are conducted on gadolinia-doped ceria electrolyte pellets with a platinum anode at 250–450 °C. In our tests, the fuel cell performance of the SOFCs with an optimized ALD YSZ surface treatment is close to that of SOFCs with porous Pt, which is known as the best performing catalyst in the low-temperature regime. Electrochemical impedance spectroscopy confirms that the performance enhancement is due to improved electrode kinetics by the increase in charge transfer reaction sites between the surface of supporting silver and the ALD–YSZ particulates. Fuel cell durability tests shows that the ALD YSZ surface treatment improves the long-term stability. X-ray photoelectron spectroscopy also confirms that the ALD YSZ capping prevents reduction of the surface silver oxide and destruction of the mesh morphology.

Effects of surface chemistry and microstructure of electrolyte on oxygen reduction kinetics of solid oxide fuel cells

We report systematic investigation of the surface properties of yttria-stabilized zirconia (YSZ) electrolytes with the control of the grain boundary (GB) density at the surface, and its effects on electrochemical activities. The GB density of thin surface layers deposited on single crystal YSZ substrates is controlled by changing the annealing temperature (750–1450 °C). Higher oxygen reduction reactions (ORR) kinetics is observed in samples annealed at lower temperatures. The higher ORR activity is ascribed to the higher GB density at the YSZ surface where ‘mobile’ oxide ion vacancies are more populated. Meanwhile, oxide ion vacancies concurrently created with yttrium segregation at the surface at the higher annealing temperature are considered inactive to oxygen incorporation reactions. Our results provide additional insight into the interplay between the surface chemistry, microstructures, and electrochemical activity. They potentially provide important guidelines for engineering the electrolyte–electrode interfaces of solid oxide fuel cells for higher electrochemical performance.

The influence of temperature gradient across YSZ on thermal cyclic lifetime of plasma-sprayed thermal barrier coatings

The influence of the temperature gradient within plasma-sprayed yttria-stabilized zirconia (YSZ) on the thermal cyclic lifetime of thermal barrier coatings (TBCs) was investigated via gradient thermal cycling test and theoretical model. YSZ surface was heated to the peak temperature in 70s, then kept for a dwell time of 50s at the peak temperature and cooled down to 100°C in 120s. YSZ surface temperatures were set to be 1150°C, 1200°C and 1250°C, corresponding to temperature differences of 150°C, 200°C and 250°C across 250µm thick YSZ coating, respectively. A theoretical model is introduced to describe the correlation between thermal cyclic lifetime and temperature gradient. Experimental results show that the temperature gradient has a remarkable impact on the thermal cyclic lifetime of TBCs, which decreases with increasing temperature gradient. The theoretical model reveals that thermal cyclic lifetime of TBCs decreases with the increase of the temperature gradient following a power function, which reasonably agrees with the experimental results. Moreover, it was found that the temperature gradient has little effect on the cracking mode of the TBCs because the stress distribution characteristics in TBCs subjected to thermal cycling with different temperature gradients remain unchanged based on the numerical simulation results.

Quinone-rich polydopamine functionalization of yttria stabilized zirconia for apatite biomineralization: The effects of coating temperature

The use of yttria stabilized zirconia (YSZ) as biomedical implants is often offset by its bioinert nature that prevents its osseointegration to occur. Therefore, the functionalization of YSZ surface by polydopamine to facilitate the biomineralization of apatite layer on top of the coated film has incessantly been studied. In this study YSZ discs were first immersed in 2mg/mL of stirred dopamine solution at coating temperatures between 25 and 80°C. The specimens were then incubated for 7d in 1.5 SBF. The effect of coating temperature on the properties (chemical compositions and wettability) and the apatite mineralization on top of the generated films was investigated. It was found that at 50°C, the specimen displayed the highest intensity of Ca 2p peak (1.55±0.42 cps) with Ca/P ratio of 1.67 due to the presence of abundant quinone groups (CO). However, the hydrophilicity (40.9±01.7°) was greatly improved at 60°C accompanied by the highest film thickness of 306nm. Therefore, it was concluded that the presence of high intensity of quinone groups (CO) in polydopamine film at elevated temperature affects the chelation of Ca2+ ions and thus enhance the growth of apatite layer on top of the functionalized YSZ surface.

Novel microstructural strategies to enhance the electrochemical performance of La0.8Sr0.2MnO3-δ cathodes.

Novel strategies based on spray-pyrolysis deposition are proposed to increase the triple-phase boundary (TPB) of La0.8Sr0.2MnO3-δ (LSM) cathodes in contact with yttria-stabilized zirconia (YSZ) electrolyte: (i) nanocrystalline LSM films deposited on as-prepared YSZ surface; (ii) the addition of poly(methyl methacrylate) microspheres as pore formers to further increase the porosity of the film cathodes; and (iii) the deposition of LSM by spray pyrolysis on backbones of Zr0.84Y0.16O1.92 (YSZ), Ce0.9Gd0.1O1.95 (CGO), and Bi1.5Y0.5O3-δ (BYO) previously fixed onto the YSZ. This last method is an alternative to the classical infiltration process with several advantages for large-scale manufacturing of planar solid oxide fuel cells (SOFCs), including easier industrial implementation, shorter preparation time, and low cost. The morphology and electrochemical performance of the electrodes are investigated by scanning electron microscopy and impedance spectroscopy. Very low values of area specific resistance are obtained, ranging from 1.4 Ω·cm(2) for LSM films deposited on as-prepared YSZ surface to 0.06 Ω-cm(2) for LSM deposited onto BYO backbone at a measured temperature of 650 °C. These electrodes exhibit high performance even after annealing at 950 °C, making them potentially suitable for applications in SOFCs at intermediate temperatures.

Ni Deposition on Yttria-Stabilized ZrO2(111) Surfaces: A Density Functional Theory Study

Nickel particles supported on yttria-stabilized zirconia (YSZ) play a significant role in the performance of solid oxide fuel cells (SOFC). We have investigated both pristine and doped ZrO2 surfaces using spin polarized density functional theory (DFT) and also considering long-range dispersion forces. We have systematically studied Ni deposition on the bare ZrO2(111) surface and on surfaces with two concentrations of Y, all at both high and low oxygen chemical potential. Among the several independent sites explored, the Ni adsorption preference is as follows: YSZ(111) without oxygen vacancy > YSZ(111) with oxygen vacancy > stoichiometric ZrO2(111). For each surface, the adsorption site is similar: over the top oxygen. The evaluation of the geometric and electronic structure shows a mixing of Ni orbitals with surface atom orbitals. We have also investigated the influence of the yttrium atom on the Ni adsorption by considering up to 52 different configurations, which showed that Ni tends to adsorb away from the yttrium atom for any YSZ(111) surface, leading to a mixed electronic structure with enhanced charge transfer.

New insights on the role of YSZ in a NiAl2O4/Al2O3–YSZ catalyst

Abstract Yttria stabilized zirconia (YSZ) role as co-support in alumina (Al2O3) supported Al–Ni spinel (NiAl2O4) was investigated from three perspectives: (a) influence on catalyst morphology, (b) influence on catalyst crystalline phases, and (c) role during diesel steam reforming tests. For the first objective, YSZ surface properties were related to NiAl2O4/Al2O3 morphology. The interaction between these two species was examined using scanning electron microscopy (SEM); surface properties were determined using the multipoint Brunauer, Emmet, and Teller (BET) method for the specific surface area, and mass titration for the zero point charge (PZC) of the surface. The second objective demonstrated, mainly through X-ray diffraction (XRD) analysis, that YSZ enhanced the stabilization of a single Al2O3 phase and inhibited the formation of a metastable aluminates phase. Finally, for the third objective, Y2O3% used to stabilize ZrO2 was varied. Diesel steam reforming tests, using the various YSZ formulations were performed in a fixed-bed reactor setup, with a proprietary diesel–water emulsion mixture at 760 °C. It has been shown that there is a direct dependence of the catalytic activity on the support oxygen vacancies and a maximal Y2O3% was determined.

Microstructured zirconia surfaces modulate osteogenic marker genes in human primary osteoblasts.

In dentistry, zirconia has been used since the early 1990s for endodontic posts, more recently for implant abutments and frameworks for fixed dental prostheses. Zirconia is biocompatible and mechanically strong enough to serve as implant material for oral implants. Although several zirconia implant systems are available, currently the scientific and clinical data for zirconia implants are not sufficient to recommend them for routine clinical use. Here the influence of microstructured yttria-stabilized zirconia (YZ) on human primary osteoblast (HOB) behavior was determined. YZ surfaces were treated by sandblasting (YZ-S), acid etching (YZ-SE) and additionally heat treatment (YZ-SEH). Morphological changes of HOB were determined by scanning electron microscopy. Actin cytoskeleton was investigated by laser scanning microscopy and analyzed by novel actin quantification software. Differentiation of HOB was determined by real time RT-PCR. Improved mechanical interlocking of primary HOB into the porous microstructure of the acid etched and additionally heat treated YZ-surfaces correlates with drastically increased osteocalcin (OCN) gene expression. In particular, OCN was considerably elevated in primary HOB after 3 days on YZ-SE (13-fold) as well as YZ-SEH (12-fold) surfaces. Shorter actin filaments without any favored orientation on YZ-SE and YZ-SEH surfaces are associated with higher roughness (Ra) values. Topographically modified yttria-stabilized zirconia is a likely material for dental implants with cell stimulating properties achieving or actually exceeding those of titanium.