Surface Properties Of Zirconia Research Articles

Optimized Gingiva Cell Behavior on Dental Zirconia as a Result of Atmospheric Argon Plasma Activation.

Several physico-chemical modifications have been developed to improve cell contact with prosthetic oral implant surfaces. The activation with non-thermal plasmas was one option. Previous studies found that gingiva fibroblasts on laser-microstructured ceramics were hindered in their migration into cavities. However, after argon (Ar) plasma activation, the cells concentrated in and around the niches. The change in surface properties of zirconia and, subsequently, the effect on cell behavior is unclear. In this study, polished zirconia discs were activated by atmospheric pressure Ar plasma using the kINPen®09 jet for 1 min. Surfaces were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), and water contact angle. In vitro studies with human gingival fibroblasts (HGF-1) focused on spreading, actin cytoskeleton organization, and calcium ion signaling within 24 h. After Ar plasma activation, surfaces were more hydrophilic. XPS revealed decreased carbon and increased oxygen, zirconia, and yttrium content after Ar plasma. The Ar plasma activation boosted the spreading (2 h), and HGF-1 cells formed strong actin filaments with pronounced lamellipodia. Interestingly, the cells' calcium ion signaling was also promoted. Therefore, argon plasma activation of zirconia seems to be a valuable tool to bioactivate the surface for optimal surface occupation by cells and active cell signaling.

Comparison of the wear behavior and surface properties of zirconia and resin-based CAD/CAM restorative materials after different sandblasting procedures

Objective: To evaluate the effects of different sandblasting procedures on the wear and surface properties of zirconia and resin-based CAD/CAM restorative materials and to evaluate the relationships among materials and procedures. Materials and Methods: A total of 160 specimens of 2 mm thickness were prepared from Cerasmart, Vita-Enamic, Tetric-CAD, and Katana-Zirconia CAD/CAM materials. Each material was divided into four groups. Group-1: Control; Group-2: 29 μm Al2O3; Group-3: 30 μm CoJet; and Group-4: 50 μm Al2O3. Sandblasting procedures were applied from a distance of 10 mm for 15 s at 2 bar pressure. The volume loss resulting from sandblasting was calculated. The samples were then scanned with a Nanovea-PS50 non-contact profilometer. The Ra, Rz, and Sa values were recorded. The data were analyzed with the Shapiro-Wilk test and two-way ANOVA. Results: Group-4 showed the highest Ra and Rz values in all materials. The highest Sa and volume differences values were observed for Cerasmart, Vita-Enamic, and Tetric-CAD in Group-4; similar values were obtained for Katana-Zirconia. When the materials were compared, Cerasmart exhibited the highest volume differences, Ra, Rz, and Sa values in Group-4, while Katana-Zirconia demonstrated the lowest. Conclusions: Sandblasting procedure and material type showed a significant impact on the wear and surface properties. The abrasive effect increased with the increasing Al2O3 particle sizes for resin-matrix materials. Sandblasting with 50 μm Al2O3 exhibited the lowest wear and surface roughness values for Katana-Zirconia and the highest for Cerasmart.

55 - Dental Ceramic Surface Properties after Resin-Cement Removal by Burning Technique

There are situations in which resin-cement needs to be removed from the crown's intaglio surface before it can be recemented. Some authors have proposed to burn off this cement; however, questions remain related to the effect of this technique on the surface properties of the ceramics. The goal was to test the effect of burning cements off on the surface properties of zirconia and lithium disilicate dental ceramics. The mechanical properties (hardness and elastic modulus) and removal effectiveness were tested in this study. Two kinds of ceramics: zirconia (Cercon, Dentsply Sirona) and lithium disilicate glass-ceramics (Emax, Ivoclar Vivadent) and two universal resin-cements; Calibra Universal (Dentsply) and Multilink Automix (Ivoclar Vivadent), were used in this research. Samples (n=8) were 1.3 mm thick and were sintered according to manufacturer recommendations. Zirconia samples were sandblasted with 150 aluminum oxide, and lithium-disilicate were etched with 9.6% hydrofluoric acid and then thoroughly rinsed. The application of each resin-cement followed the manufacturer's recommendations, and the samples were light-cured for 20 s. After 15 days of storage (100% humidity and 36 C), the samples were placed into a furnace at a temperature of ~150 C then heated a rate of ~30 C/min until reaching a temperature of 400 C where the temperature was held for 1 minute. The samples were removed from the furnace and allowed to cool before the cement was removed. Fourier Transformed Infra-Red (FTIR) was used, before and after cementation, to check the surface chemical composition and the effectiveness of the resin-cement removal. A nanoindenter (Hysitron TI 750 Ubi Triboindenter) using a Berkovich tip (100 mN) was used to assess the surface properties. Statistical analyses of the results were performed using two-way ANOVA and a post hoc Tukey test (α = 0.05). FTIR showed that the burning technique was effective to remove the residual resin-cement from the ceramic samples. Also, there was no significant statistical difference between the hardness and the elastic modulus of the dental ceramic surfaces from before and after the burning technique. This study showed that the removal of the resin-cements from crowns intaglio by the burning technique could be a viable clinical solution before recementing dental ceramics.

Synthesis and characterization of gold nanoparticles (AuNPs) and ZnO decorated zirconia as a potential adsorbent for enhanced arsenic removal from aqueous solution

In this study, gold nanoparticles (AuNPs) and ZnO-decorated zirconia (AuNPs/ZnO-ZrO2) were synthesized through co-precipitation and hydrolysis coupled with heat treatment, and explored as a novel adsorbent for arsenic removal from aqueous solution. The effects of synthesis parameters were examined, such as support type, Zn/Zr mole ratio, co-precipitation method and calcination temperature. X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and N2 adsorption were used to investigate the enhancement of arsenic adsorption on the hybrid composites. It was found that the adsorption property of AuNPs/ZnO-ZrO2 was strongly dependent on support type, Zn/Zr mole ratio, co-precipitation method and calcination temperature. The optimized AuNPs/ZnO-ZrO2 exhibited the best adsorption capacity for arsenic at lower concentrations (less than 8 mg L−1), compared with ZnO-decorated zirconia (ZnO-ZrO2) and bare zirconia (ZrO2). The enhanced adsorption of arsenic by AuNPs/ZnO-ZrO2 was ascribed to the larger specific surface area, abundant hydroxyl groups and co-existance of ionic gold (Au(OH)2+) and gold clusters (Auδ+) highly dispersed on the surface which could act as smart scavengers for low-concentration arsenic from water. The adsorption equilibrium of arsenic on AuNPs/ZnO-ZrO2 fitted to the Langmuir, Brunauer–Emmett–Teller (BET) and Gunary models well and the Gunary model gave the best fit. Isotherm analysis results showed that the adsorption of arsenic on AuNPs/ZnO-ZrO2 occurred dominantly through monolayer formation but was a non-ideal Langmuir type adsorption. However, ZnO-ZrO2 showed much higher adsorption capacity for arsenic than that of ZrO2, which was mainly attributed to the formation of basic zinc carbonate (BZC) with rich structural hydroxyl groups and to the improvement in surface properties of zirconia. Significant multilayer adsorption was able to proceed on the surface at higher arsenic concentrations (more than 8 mg L−1), obeying the BET isotherm.

Synergistic reinforcement of surface modification on improving the bonding of veneering ceramics to zirconia

Veneering ceramics should be strongly bonded to zirconia core in order to achieve successfully long-term clinical practice. Indeed, to pursue the high zirconia core–veneering ceramic bonding is still a concerned issue. In this regard, this study was to treat zirconia surface using a 3 wt% Si3N4 solution in 4 M NaOH and to investigate the effect of soaking time (5, 10, and 20 days) on the surface properties of zirconia and shear bond strength between zirconia and veneering ceramics. The residual veneering ceramics on zirconia surfaces and failure modes were also examined after fracture. The results showed that the phase composition of zirconia before and after surface modification was not changed. The elemental mapping and depth profiling consistently revealed the soaking-time-dependent Si content on the zirconia surface. The surface roughness of zirconia was significantly (P < 0.05) increased with the increasing soaking time. When zirconia was treated for 10 days, the shear bond strength value of 27.4 MPa was significantly (P < 0.05) higher than the control (18.6 MPa), associated with greater remaining amounts of veneering ceramics on the zirconia surface. The failure mode of the treated zirconia was almost the mixed failure. On the basis of the data, surface modification using Si3N4 in NaOH solution for zirconia core could be a simple and effective method for enhancing the veneering ceramic–zirconia bonding.

Influence of plasma treatment on surface properties of zirconia

Influence of plasma treatment on surface properties of zirconia

Effect of simulated chairside grinding procedures using commercially available abrasive agents on the surface properties of zirconia.

Aim:The aim of the present study was to assess the change in physical properties (surface roughness, surface hardness and phase transformation) after surface grinding of zirconia by using three commercially available abrasives.Materials and Methods:Thirty sintered zirconia specimens were prepared and divided into three groups namely Group M (grinded using Mani Dia diamond bur standard grit), Group T (grinded using Tri Hawk diamond bur coarse grit) and Group P (grinded using Predator carbide bur). A customised assembly was used to follow a standardised protocol for surface grinding. The surface roughness, surface hardness and phase transformation was recorded before and after the grinding procedure.Statistical Analysis Used:ANOVA and Bonferroni post hoc test were used to assess the values obtained after the testing the surface roughness and surface hardness.Results:The results of the present study revealed the average values of change in surface roughness as Group M (0.44 μm) and Group T (1.235 μm) and Group P (-0.88 μm). The average values of change in surface hardness were Group T (19.578 HV), Group M (46.722 HV) and Group P (36.429 HV). The change in surface hardness was not statistically significant. There was no phase transformation seen after the grinding procedure.Clinical Significance:Carbide burs along with copious water irrigation when used to grind zirconia intra-orally produces has a polishing effect, minimal change in hardness & no phase transformation. The present study advocates the use of carbides for chair-side grinding of zirconia.

Enhanced Hydrophilicity and Biocompatibility of Dental Zirconia Ceramics by Oxygen Plasma Treatment.

Surface properties play a critical role in influencing cell responses to a biomaterial. The objectives of this study were (1) to characterize changes in surface properties of zirconia (ZrO2) ceramic after oxygen plasma treatment; and (2) to determine the effect of such changes on biological responses of human osteoblast-like cells (MG63). The results indicated that the surface morphology was not changed by oxygen plasma treatment. In contrast, oxygen plasma treatment to ZrO2 not only resulted in an increase in hydrophilicity, but also it retained surface hydrophilicity after 5-min treatment time. More importantly, surface properties of ZrO2 modified by oxygen plasma treatment were beneficial for cell growth, whereas the surface roughness of the materials did not have a significant efficacy. It is concluded that oxygen plasma treatment was certified to be effective in modifying the surface state of ZrO2 and has the potential in the creation and maintenance of hydrophilic surfaces and the enhancement of cell proliferation and differentiation.

Benzene hydrogenation over oxide-modified MCM-41 supported ruthenium–lanthanum catalyst: The influence of zirconia crystal form and surface hydrophilicity

The effects of the preparation conditions on the crystal form and surface properties of zirconia were studied. Mesoporous MCM-41 modified by tetragonal and monoclinic zirconia were synthesized by hydrothermal and precipitation methods. Then MCM-41 and zirconia-modified MCM-41 supported ruthenium–lanthanum catalysts were prepared via cyclohexane–water double solvent impregnation method. The obtained supports and catalysts were characterized by powder X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy, N2 adsorption–desorption, thermogravimetric and differential scanning calorimetry, temperature programmed desorption of NH3, static water/benzene adsorption techniques. It has been found that MCM-41 modified by tetragonal zirconia with exclusive Lewis-acidic sites exhibits more surface hydroxyl groups and higher hydrophilicity than MCM-41 modified by monoclinic and amorphous zirconia. Tetragonal zirconia-modified MCM-41 supported ruthenium–lanthanum catalyst shows better catalytic performance in benzene hydrogenation to cyclohexene with benzene conversion of 54.4% and cyclohexene selectivity of 84.7%.

Change in surface properties of zirconia and initial attachment of osteoblastlike cells with hydrophilic treatment

The objectives of this study were to characterize change in surface properties of tetragonal zirconia polycrystals (TZP) after hydrophilic treatment, and to determine the effect of such changes on initial attachment of osteoblast-like cells. Roughened surfaces were produced by alumina-blasting and acid-etching. Hydrophilic treatment comprised application of immediately after blasting and acid-etching (Blast/Etch), oxygen plasma (O2-Plasma), ultraviolet light (UV). Specimens stored in air were used as a control. The water contact angle was determined and surface analysis was performed using an X-ray photoelectron spectroscopy. Blast/Etch, O2-Plasma and UV specimens showed superhydrophilicity, and these hydrophilic treatments to TZP elicited a marked decrease in carbon content and an increase in hydroxyl groups. Hydrophilic treatments enhanced initial attachment of osteoblast-like cells and a change in cell morphologies. These results indicate that Blast/Etch, O2-Plasma, or UV treatment has potential in the creation and maintenance of superhydrophilic surfaces and enhancing initial attachment of osteoblast-like cells.

Charge transfer at oxygen/zirconia interface at elevated temperatures: Part 4: Work function v. defect chemistry

The present work considers the physical meaning of the work function of zirconia at elevated temperatures, corresponding to gas/solid equilibrium, as well as changes in work function as a result of surface reactions such as oxidation and reduction. The relationship between changes in work function and the oxygen partial pressure of both undoped zirconia and yttria-stabilised zirconia (YSZ) is considered in terms of the defect disorder of the outermost surface layer. Experimental work function data indicate that the surface properties of zirconia and its solid solutions are entirely different from those of the bulk phase. These differences are considered in terms of the functional properties of YSZ. The importance of work function measurements for the elucidation of surface semiconducting properties of metal oxides is discussed.

Polymorphic Transitions and Surface Properties of Zirconia Modified by Doping with d, p and s Oxides

Polymorphic Transitions and Surface Properties of Zirconia Modified by Doping with d, p and s Oxides

The preparation and surface characterization of zirconia polymorphs

Zirconium hydroxides were obtained by precipitation of zirconium chloride with aqueous ammonia at constant pH followed by hydrothermal treatment The effect of thermal activation of the zirconium hydroxide on physical properties, and the effect of crystalline phase on the surface properties of zirconia were studied. The pressure during the hydrothermal treatment of zirconium hydroxide affected the surface area, particle growth, and phase transformation of the zirconia product. Hydrothermally treated zirconia under atmospheric pressure (LP) shows higher surface area than that under high pressure (HP) and untreated (UT). HP zirconia shows a mixture of tetragonal and monoclinic phase after hydrothermal treatment due to the higher solubility and reprecipitation rate, whereas LP sample shows a tetragonal crystal structure from 600 to 1,050 ℴC. Monoclinic phase zirconia shows greater CO2 and NH3 surface adsorption than amorphous and tetragonal phase zirconia. This suggests that the crystal structure of zirconia strongly affects the amount and strength of the surface adsorption site.

The effects of synthesis and pretreatment conditions on the bulk structure and surface properties of zirconia

An investigation has been conducted to establish the effects of synthesis conditions and subsequent calcination conditions on the bulk and surface properties of zirconia. Samples of zirconia were prepared by precipitation from an aqueous solution of zirconyl chloride at both high and low pH. Precipitation at high pH (10) produced an amorphous material with a surface area of 280 m 2/g. Extended digestion of this material in a boiling NH 4OH solution at 1 atm increased the surface area to 400 m 2/g. When digestion was carried out at ∼3 atm, the amorphous zirconia became crystalline and its surface area reduced to 200 m 2/g. Precipitation of zirconia at low pH (<1.5) with extended reflux produced monoclinic ZrO 2 with a surface area of 110 m 2/g. Calcination at temperatures in the range of 300–1200 K caused a loss in surface area with increasing temperature and induced the amorphous-tetragonal and tetragonal-to-monoclinic phase transformations. The surface concentration of hydroxyl groups on monoclinic ZrO 2 is always higher than that on tetragonal ZrO 2. In the former case the dominant species are tribridged hydroxyl groups and in the latter, a combination of bibridged and terminal hydroxyl groups. CO 2 adsorbs on zirconia at 298 K to form bicarbonate species and a smaller amount of carbonate species. The surface concentration of bicarbonate species grows monotonically with the surface concentration of hydroxyl groups. A similar relationship is observed for the adsorption of CO as formate species. Consistent with these results, monoclinic zirconia adsorbs more CO and CO 2 than tetragonal zirconia.

The Effect of Boron on Selective Benzene Hydrogenation to Cyclohexene over Ruthenium Boride Powders

The effects of the preparation conditions on the crystal form and surface properties of zirconia were studied. Mesoporous MCM-41 modified by tetragonal and monoclinic zirconia were synthesized by hydrothermal and precipitation methods. Then MCM-41 and zirconia-modified MCM-41 supported ruthenium–lanthanum catalysts were prepared via cyclohexane–water double solvent impregnation method. The obtained supports and catalysts were characterized by powder X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy, N2 adsorption–desorption, thermogravimetric and differential scanning calorimetry, temperature programmed desorption of NH3, static water/benzene adsorption techniques. It has been found that MCM-41 modified by tetragonal zirconia with exclusive Lewis-acidic sites exhibits more surface hydroxyl groups and higher hydrophilicity than MCM-41 modified by monoclinic and amorphous zirconia. Tetragonal zirconia-modified MCM-41 supported ruthenium–lanthanum catalyst shows better catalytic performance in benzene hydrogenation to cyclohexene with benzene conversion of 54.4% and cyclohexene selectivity of 84.7%.

Surface chemistry and rheological properties of zirconia suspensions

The pH and nature of anions were found to have a very significant effect on the rheological properties of zirconia suspensions. The variation in rheological properties with pH and anion type correlated well with the change in surface properties of zirconia. Zirconia suspensions with maximum yield stress and viscosity occurred at and near the isoelectric point (IEP). At a pH where the magnitude of the electrophoretic mobility of the zirconia is high, a low viscosity dispersed suspension was obtained. The zirconia suspensions were dispersed with potassium hydroxide at high pH while hydrochloric acid or nitric acid was used for dispersion at low pH. Sulfuric acid however did not disperse the suspensions at low pH because of significant sulfate adsorption on the zirconia particle. Polycarboxylate additives (polyacrylate) shifted the pH of maximum yield stress of zirconia to a lower pH. The degree of pH shift increased with increasing concentration of polycarboxylate; an effect attributed to the adsorption of polycarboxylate on the zirconia particle and to the degree of adsorption which increased with increasing concentration of polycarboxylate.