• The Journal of Advanced Prosthodontics
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• v.2 no.3
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• pp.81-87
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• 2010

PURPOSE. The purpose of this study was to compare the linear sintering behavior of presintered zirconia blocks of various densities. The mechanical properties of the resulting sintered zirconia blocks were then analyzed. MATERIALS AND METHODS. Three experimental groups of dental zirconia blocks, with a different presintering density each, were designed in the present study. Kavo $Everest^{(R)}$ ZS blanks (Kavo, Biberach, Germany) were used as a control group. The experimental group blocks were fabricated from commercial yttria-stabilized tetragonal zirconia powder (KZ-3YF (SD) Type A, KCM. Corporation, Nagoya, Japan). The biaxial flexural strengths, microhardnesses, and microstructures of the sintered blocks were then investigated. The linear sintering shrinkages of blocks were calculated and compared. RESULTS. Despite their different presintered densities, the sintered blocks of the control and experimental groups showed similar mechanical properties. However, the sintered block had different linear sintering shrinkage rate depending on the density of the presintered block. As the density of the presintered block increased, the linear sintering shrinkage decreased. In the experimental blocks, the three sectioned pieces of each block showed the different linear shrinkage depending on the area. The tops of the experimental blocks showed the lowest linear sintering shrinkage, whereas the bottoms of the experimental blocks showed the highest linear sintering shrinkage. CONCLUSION. Within the limitations of this study, the density difference of the presintered zirconia block did not affect the mechanical properties of the sintered zirconia block, but affected the linear sintering shrinkage of the zirconia block.

• Korean Journal of Materials Research
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• v.33 no.8
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• pp.337-343
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• 2023

3Y-TZP (3 mol% yttria-stabilized tetragonal zirconia polycrystals) ceramics have excellent mechanical properties including high fracture toughness, good abrasion resistance as well as chemical and biological stability. As a result, they are widely used in mechanical and medical components such as bearings, grinding balls, and hip implants. In addition, they provide excellent light transmittance, biocompatibility, and can match tooth color when used as a dental implant. Recently, given the materials' resemblance to human teeth, these ceramics have emerged as an alternative to titanium implants. Since the introduction of CAD/CAM in the manufacture of ceramic implants, they've been increasingly used for prosthetic restoration where aesthetics and strength are required. In this study, to improve the surface roughness of zirconia implants, we modified the 3Y-TZP surface with a biocomposite of hydroxyapatite and forsterite using room temperature spray coating methods, and investigated the mixed effect of the two powders on the evolution of surface microstructure, i.e., coating thickness and roughness, and biological interaction during the in vitro test in SBF solution. We compared improvement in bioactivity by observing dissolution and re-precipitation on the specimen surface. From the results of in vitro testing in SBF solution, we confirmed improvement in the bioactivity of the 3Y-TZP substrate after surface modification with a biocomposite of hydroxyapatite and forsterite. Surface dissolution of the coating layer and the precipitation of new hydroxyapatite particles was observed on the modified surface, indicating the improvement in bioactivity of the zirconia substrate.

• Journal of the Korean Applied Science and Technology
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• v.33 no.2
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• pp.247-254
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• 2016

Since microzirconia has excellent thermal and mechanical properties with high chemical and electrical resistance, it can be used in various fields. When the surface of zirconia becomes hydrophilic, its dispersibility in water will be improved as well as the resistance to most hydrophobic contaminants will be increased. In this study, we investigated the introduction of a hydrophilic groups on the microzircornia surface through hydrolysis and condensation reactions with two different silanes containing hydrophilic functional groups, such as ${\gamma}$-aminopropyltrimethoxysilane (APS) and ${\gamma}$-ureidopropyltrimethoxysilane (UPS) at different pH and concentration conditions. A covalent bond formation between the surface hydroxyl groups of zirconia and that of hydrolyzed silanes was confirmed by ninhydrin test and FT-IR spectroscopy. However, the presence of Si on the surfaces of both silane modified microzirconias was unable to detect by SEM/EDS technique. In addition, particle size analysis results provide that the size of microzirconia was changed to smaller or bigger than that of original zirconia due to crushing and aggregation during the modification process. The water dispersibility was improved for only APS modifed zirconia (AS-2 and AS-3) under neutral pH condition, but the water dispersibility and stability for all cases of 0.5~2% UPS modifed zirconia (US series) were much improved.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.2
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• pp.199-205
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• 2009

Purpose: The purpose of this research was to evaluate the shear bond strength between zirconia core and veneer ceramic after surface treatment. Material and methods: Zirconia cores(N=40, n=10, $10mm{\times}10mm{\times}3mm$) were fabricated according to the manufacturers' instructions and ultrasonically cleaned. The veneering ceramics(thickness 3 mm) were built and fired onto the zirconia core materials. Four groups of specimens with different surface treatment were prepared. Group I: without any pre-treatment, Group II: treated with sandblasting, Group III: treated with liner, Group IV: treated with sandblasting and liner. The shear bond strength was tested in a universal testing machine. Data were compared with an ANOVA and $Scheff{\acute{e}}$ post hoc test(P=.05). Results: The shear bond strength of group VI was significantly higher than the other groups. Conclusion: Both mechanically and chemically treated simultaneously on zirconia core surface influenced the shear bond strength between the core and veneering ceramic in all-ceramic systems.

• Journal of dental hygiene science
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• v.13 no.4
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• pp.487-492
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• 2013

This study aimed to illuminate the correlatives between the surface processing of Zirconia core and the shear bond strength. The specimens were made by precipitating for two minutes in color liquid and drying to produce a colored Zirconia core following the manufacturer's instructions. The specimens were divided into 4 subgroups according to the surface treatment-sandblasted+liner treatment, SLT group; sandblasted treatment, ST group; liner treatment, LT group; non treatment (control), NT group. The specimens were put on the device with regard to ISO/TS 11405, then tested the shear bond strength with 1 mm shearing speed per minute using the Instron multi-purpose tester. The collected data was analysed by one way ANOVA and t-test. After applying the liner and sandblast to the Zirconia core, shear bond strength value were SLT (23.19 MPa), ST (21.17 MPa), LT (20.53 MPa) and NT (16.46 MPa) in the order. There was a significant difference in the surface roughness between NT and ST group (p<0.001), and in the compressive shear bond strength between NT and SLT group (p<0.05). Therefore, sandblasted plus liner treatment on pre-sintered substructure increased the bond strength of veneering ceramic, compared with other surface treatments.

• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1809-1813
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• 2013

Sulfated ${\beta}$-cyclodextrin (SCD)-coated zirconia monolith was used as the chiral stationary phase in capillary electrochromatography for enantiomeric separation of basic chiral compounds. SCD adsorbed on the zirconia surface provided a stable chiral stationary phase in reversed-phase eluents. Retention, chiral selectivity and resolution of a set of six basic chiral compounds were measured in eluents of varying pH, composition of methanol and buffer. Optimum mobile phase condition for the separation of the compounds was found to be methanol content of 30%, buffer concentration of 30 mM and pH of 4.0.

• Journal of Sensor Science and Technology
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• v.18 no.6
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• pp.441-448
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• 2009

Magnesia partially stabilized zirconia(Mg-PSZ) solid electrolytes for an improvement of thermal shock resistance, which is suitable for the measurement of oxygen activity in a molten steel, were prepared by post-thermal aging treatment. The steelmaking oxygen sensor elements were formed by an injection molding method, sintered at $1650^{\circ}C$, and then thermal aged ranged from 1250 to $1400^{\circ}C$. Sintered density and porosity were decreased as increasing the magnesia content in a zirconia-magnesia solid solution. Fractions of cubic phase to the synthesized Mg-PSZ solid electrolytes were ranged from 13.13 to 79.54.% after post-thermal aging treatment. Very dense microstructure without voids in the grains was obtained by the post-thermal aging process. Fine tetragonal phase crystallites precipitated on the cubic surface during post-thermal aging up to $1300^{\circ}C$ improve a thermal shock resistance and reappearance of electro motive force(EMF) curve.

• The Journal of the Korean dental association
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• v.51 no.1
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• pp.6-11
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• 2013

Dental ceramics is well known to have excellent esthetics, biocompatibility as well as high compressive strength. However, the fragility of ceramics against tensile and shear loads leading to the delayed fracture of micro crack on ceramic surface and the backwardness of ceramic fabrication technique limit the usage of ceramic materials in dentistry. Among all ceramic materials, zirconia has been introduced to overcome the drawback of conventional dental ceramics in the field of dentistry due to the nature of zirconia featuring proper opalescence and high fracture toughness. Also, novel manufacturing techniques enable ceramic materials to prepare high esthetic anterior and posterior all ceramic system. In this paper, it is introduced and discussed that novel techniques characterizing the bond strength between zirconia core and veneering ceramics and analyzing the fluorescence of dental ceramics in order to overcome the gap between the results of basic research and the feasibility of the results in the field of dental clinics.

• Bulletin of the Korean Chemical Society
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• v.17 no.3
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• pp.274-278
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• 1996

Vanadium oxide-zirconia catalysts were prepared by dry impregnation of powdered Zr(OH)4 with aqueous solution of NH4VO3. The characterization of prepared catalysts was performed using 51V solid state NMR, XRD, and DSC. The addition of vanadium oxide up to 9 mol% to zirconia shifted the phase transitions of ZrO2 from amorphous to tetragonal toward higher temperatures due to the interaction between vanadium oxide and zirconia. On the basis of results of XRD and DSC, it is concluded that the content of V2O5 monolayer covering most of the available zirconia was 9 mol%. The crystalline V2O5 was observed only with the samples containing V2O5 content exceeding the formation of complete monolayer (9 mol%) on the surface of ZrO2.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.3
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• pp.179-188
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• 2023

Purpose. The purpose of this study was to evaluate the effect of surface treatments on the shear bond strength of two types of zirconia (3-TZP and 5Y-PSZ) with resin cement. Materials and methods. Two different types of zirconia specimens with a fully sintered size of 14.0×14.0×2.0 mm³ were prepared, polished with 400, 600, and 800 grit silicon carbide paper, and buried in epoxy resin. They were classified into four groups each control, sandblasting, primer, and sandblasting & primer. Cylindrical resin adhered to the surface-treated zirconia with resin cement. It was stored in distilled water (37℃) for 24 hours, and a shear bond strength test was performed. The normality of the experimental group was confirmed with the Kolmogorov-Smirnov & Shapiro-Wilk test. The interaction and statistical difference were analyzed using a two-way ANOVA. A post-hoc analysis was performed using Dunnett T3. Results. As a result of two-way ANOVA, there was no significant difference in shear bonding strength between zirconia types (P > .05), but there was a significant correlation in the sandblasting, primer, and alumina sandblasting & primer group (P < .05). Dunnett T3 post-test showed that, regardless of the type of zirconia, shear bonding strength was sandblasting & primer > Primer > sandblasting > control group (P < .05). Conclusion. There was no difference in shear bond strength between the types of zirconia. The highest shear bond strength was shown when the mechanical and chemical treatments of the zirconia surface was performed simultaneously.