Ceramic Core Materials Research Articles

Enhancing creep resistance performance in silica-based ceramic core materials through shell-core structure

The creep behavior of silica-based ceramic cores significantly impacts dimensional precision in investment casting. This study focuses on synthesizing an alumina coating on fused silica surfaces to create a shell-core structure. The creep behavior of silica-based ceramic cores was explored. Specifically, the influence of the shell-core structure on their creep mechanism was investigated. The results revealed the excellent creep resistance of silica-based ceramic cores with shell-core structures. The softening deformation of particles and the viscous flow of the glass phase were observed to account for the differences in creep behavior. The alumina shell structure reinforced the powders, effectively inhibiting the softening deformation of the core structure. Notably, the shell-core structure not only suppressed the viscous flow of the glass phase, thereby weaking the pore filling process, but also promoted the mullitization reaction. This reaction accelerated the consumption of the glass phase, enhancing the creep resistance of the silica-based ceramic cores.

The effect of the viscoelastic support and GRPL-reinforced foam material on the thermomechanical vibration response of piezomagnetic sandwich nanosensor plates

This paper investigates the vibration characteristics of a sandwich nanosensor plate composed of piezoelectric materials, specifically barium and cobalt, in the upper and lower layers, and a core material consisting of either ceramic (silicon nitride) or metal (stainless steel) foams reinforced with graphene (GPRL). The study utilized the novel sinosoidal higher-order deformation theory and nonlocal strain gradient elasticity theory. The equations of motion for nanosensor sandwich graphene were derived using Hamilton's principle, considering the thermal, electroelastic, and magnetostrictive characteristics of the piezomagnetic surface plates. These equations were then solved using the Navier method. The core element of the sandwich nanosensor plate can be represented using three distinct foam variants: a uniform foam model, as well as two symmetric foam models. The investigation focused on analyzing the dimensionless fundamental natural frequencies of the sandwich nanosensor plate. This analysis considered the influence of three distinct foam types, the volumetric graphene ratio, temperature variation, nonlocal parameters, porosity ratio, electric and magnetic potential, as well as spring and shear viscoelastic support. Furthermore, an analysis was conducted on the impact of the metal and ceramic composition of the central section of the sandwich nanosensor plate on its dimensionless fundamental natural frequencies. In this context, the use of ceramic as the central material results in a mean enhancement of 33% in the fundamental natural frequencies. In contrast, the incorporation of graphene into the core material results in an average enhancement of 27%. The thermomechanical vibration behavior of the nanosensor plate reveals that the presence of graphene-supported foam and a viscoelastic support structure in the core layer leads to an increase in thermal resistance. This increase is dependent on factors such as the ratio of graphene, porosity ratio of the foam, and parameters of the viscoelastic support. Metal foam or ceramic foam has been found to enhance thermal resistance when compared to solid metal or ceramic core materials. The analysis results showed that it is important to take into account the temperature-dependent thermal properties of barium and cobalt, which are piezo-electromagnetic materials, and the core layer materials ceramics and metal, as well as the graphene used to strengthen the core. The research is anticipated to generate valuable findings regarding the advancement and utilization of nanosensors, transducers, and nano-electromechanical systems engineered for operation in high-temperature environments.

Technical research on recycling waste blades of single crystal superalloy through ultrasonic alkali cleaning combined with electron beam smelting

The waste blades of single crystal superalloys have not been formally applied on a large scale, resulting in serious waste. This study proposes to treat the waste blades through ultrasonic alkali cleaning combined with electron beam smelting (EBS). The theoretical model is proposed to study the elements volatilization, which provides a reference for controlling the alloy composition. After EBS, the secondary dendrite spacing and the size of γ′ phases of DD5 alloy is significantly reduced. The EBS technology can effectively reduce the element segregation in superalloys, especially W and Mo elements. The purity of DD5 revert alloy after EBS is consistent with or even exceeds that of DD5 virgin alloy. Especially for the removal of ceramic shell and core materials in the waste blades, EBS has a new technological advantage. Under the combined action of Marangoni effect and buoyancy, the inclusions floating to the melt surface can not only be directly decomposed by the bombardment of the electron beam, but also can be dissolved under the condition of local melt superheating.

Mechanical and Functional Improvement of β-TCP Scaffolds for Use in Bone Tissue Engineering.

Autologous bone transplantation is still considered as the gold standard therapeutic option for bone defect repair. The alternative tissue engineering approaches have to combine good hardiness of biomaterials whilst allowing good stem cell functionality. To become more useful for load-bearing applications, mechanical properties of calcium phosphate materials have to be improved. In the present study, we aimed to reduce the brittleness of β-tricalcium phosphate (β-TCP). For this purpose, we used three polymers (PDL-02, -02a, -04) for coatings and compared resulting mechanical and degradation properties as well as their impact on seeded periosteal stem cells. Mechanical properties of coated and uncoated β-TCP scaffolds were analyzed. In addition, degradation kinetics analyses of the polymers employed and of the polymer-coated scaffolds were performed. For bioactivity assessment, the scaffolds were seeded with jaw periosteal cells (JPCs) and cultured under untreated and osteogenic conditions. JPC adhesion/proliferation, gene and protein expression by immunofluorescent staining of embedded scaffolds were analyzed. Raman spectroscopy measurements gave an insight into material properties and cell mineralization. PDL-coated β-TCP scaffolds showed a significantly higher flexural strength in comparison to that of uncoated scaffolds. Degradation kinetics showed considerable differences in pH and electrical conductivity of the three different polymer types, while the core material β-TCP was able to stabilize pH and conductivity. Material differences seemed to have an impact on JPC proliferation and differentiation potential, as reflected by the expression of osteogenic marker genes. A homogenous cell colonialization of coated and uncoated scaffolds was detected. Most interesting from a bone engineer's point of view, the PDL-04 coating enabled detection of cell matrix mineralization by Raman spectroscopy. This was not feasible with uncoated scaffolds, due to intercalating effects of the β-TCP material and the JPC-formed calcium phosphate. In conclusion, the use of PDL-04 coating improved the mechanical properties of the β-TCP scaffold and promoted cell adhesion and osteogenic differentiation, whilst allowing detection of cell mineralization within the ceramic core material.

Codes and standards for ceramic composite core materials for High Temperature Reactor applications

Fiber-reinforced ceramic matrix composites are attractive for high-temperature nuclear applications due to excellent thermal and mechanical properties as well as reasonable-to-outstanding radiation resistance. Over the past 20 years, the use of ceramic matrix composite applications expanded to many commercial non-nuclear industries as fabrication and application of the technologies mature.The ASME Boiler Pressure Vessel Code, under Section III Division 5, provides the design and construction rules for High Temperature Reactor components. It published the first rules for ceramic matrix composites to be used for reactor core components. The rules lay out the quality requirements together with the design and materials criteria for the use and application of silicon carbide- and carbon-based matrix material technologies. As with the established graphite rules, the ceramic composite material rules are structured in Subsection HH (from Section III), that addresses the criteria for class SN nonmetallic core components. The code rules rely heavily on the development and publication of standards for composite specification, classification, and testing of mechanical, thermal, and other properties. These test methods are developed in ASTM Committee C28 on Advanced Ceramics, with a current focus on ceramic composite tubes. This article describes the detail of the composites code, the design methodology and similarities to the graphite code, the guidance for the development of specifications for ceramic composites (for nuclear applications) including recent standard developments, and it mentions the next steps to support licensing aspects by validating the code with benchmarking data.

Investigation of the effect of different experimental acid solutions applied on the zirconia surface on the bond strength between zirconia and resin cement: A pilot study

Aim: The purpose of this study is to examine the effects of two different experimental acid solutions and sandblasting on the bond strength between zirconia ceramic core material and resin cement. Methodology: Forty zirconia core materials were prepared and separated into four groups based on the surface treatment to be applied (n = 10) as follows: 1) Control Group: no surface treatment was performed; 2) Sandblasting Group: the specimen surfaces were sandblasted with 50 µm aluminum oxide particles from a distance of 10 mm at 3 bar pressure for 15 seconds; 3) Sol-1 Group: H2O:HF:H2O2 solution was applied for 60 seconds, washed, and then dried; and 4) Sol-2 Group: H2O:HF:HNO3 solution was applied to the surfaces of the specimens for 60 seconds, washed, and then dried. All specimens were coated with a dual-cure resin cement with a 2.8-mm diameter. After 24 hours, the specimens were tested for shear bond strength (SBS) at 1 mm/min using a universal testing device. Statistical analysis was conducted using one-way analysis of variance (ANOVA) and Tukey HSD tests with a confidence interval of 95%. Results: The difference among the groups was statistically significant (p = 0.002) based on the one-way ANOVA results. The Control Group had the lowest SBS (8.06 ± 4.52), whereas the Sol-1 Group had the highest SBS (17.10 ± 5.67). The Sol-1 and Sol-2 Groups demonstrated comparable bonding strength values (p = 0.17). The Sandblasting and Sol-1 Groups exhibited considerably stronger bond strength than the Control Group (p = 0.05). Conclusion: The experimental acid solutions enhanced the bond strength between the resin cement and the zirconia ceramic at the sandblasting treatment level. How to cite this article: Yılmaz Savaş T, Savaş A, Akın C, Tunçdemir AR. Investigation of the effect of different experimental acid solutions applied on the zirconia surface on the bond strength between zirconia and resin cement: A pilot study. Int Dent Res 2022;12(Suppl.1):69-73. https://doi.org/10.5577/intdentres.458 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Sensitivity of SC-HTGR Conduction Cooldown to Reactor Cavity Cooling System Failure

The inherent passive heat removal characteristics of modular High Temperature Gas-Cooled Reactors (HTGRs) are well known. Modular HTGRs use a combination of coated-particle fuel, ceramic core materials, core geometry, and power level to maintain acceptable fuel temperatures for all credible operating and accident conditions. Heat from the reactor vessel is radiated to a passive reactor cavity cooling system (RCCS), which removes excess heat from the reactor cavity. The RCCS for Framatome’s Steam Cycle–High Temperature Gas-Cooled Reactor (SC-HTGR) is a highly reliable, redundant system. Similar to most other modular HTGR concepts, RCCS failure is not considered credible for any accident scenario. Nonetheless, reactor module performance with a compromised RCCS is still of interest. Evaluation of such beyond-design-basis scenarios supports safety assessment of extremely low probability beyond-design-basis events (BDBEs) as well as the development of RCCS design requirements and plant emergency procedures. This study evaluates the performance of the SC-HTGR during a long-term depressurized loss of forced circulation event without RCCS operation. Boundary conditions are varied to determine their effect on reactor temperatures. Safety and investment risk considerations are addressed. The results of this study indicate that the safety impact is modest since fuel temperatures remain within their limits. However, the investment risk is more significant since vessel temperatures could significantly exceed design limits for these hypothetical BDBEs.

ASME Code Rules and ASTM Standards Integration for Ceramic Composite Core Materials and Components1

Fiber-reinforced ceramic matrix composites have many desirable properties for high-temperature nuclear applications, including excellent thermal and mechanical properties and reasonable to outstanding radiation resistance. Over the last 20 years, the use of ceramic composite materials has already expanded in many commercial nonnuclear industries as fabrication and application technologies mature. The new ASME design and construction rules under Section III, Subsection HH, Subpart B lay out the requirements and criteria for materials, design, machining and installation, inspection, examination, testing, and the marking procedure for ceramic composite core components, which is similar to the established graphite code under Section III, Subsection HH, Subpart A. Moreover, the general requirements listed in Section III, Subsection HA, Subpart B are also expanded to include ceramic composite materials. The code rules rely heavily on the development and publication of standards for composite specification, classification, and testing of mechanical, thermal, and other properties. These test methods are developed in the American Society for Testing and Materials Committee C28 on Advanced Ceramics with a current focus on ceramic composite tubes. Details of the composites code, design methodology, and similarities to the graphite code, as well as guidance for the development of specifications for ceramic composites for nuclear application and recent standard developments, are discussed. The next step is to “close the gap” to support licensing aspects by validating the code with benchmarking data.

Effect of CaO and SiO2 on the properties of Y2O3-based ceramic core materials

ABSTRACT Nb-Si alloy is an important candidate material to produce hollow turbine blades in the aerospace industry. However, the ultra-high melting temperature of Nb-Si alloy (≥1750°C) makes the traditional ceramic core made of Al2O3 (poor leachibility) or SiO2 (melting temperature) invalid in the production of Nb-Si hollow turbine blades. In this study, Y2O3 were used as the ceramic core matrix due to its high melting points, high strength, and low interfacial reactivity. CaO and SiO2 were added in Y2O3 matrix to improve the leachability and high temperature flexural strength (1500°C) of ceramic cores. The other properties such as porosity, shrinkage and bulk density were investigated as well. The results showed that the introduction of CaO in Y2O3-based ceramic cores improved the leachability. The addition of SiO2 in the Y2O3-CaO matrix could greatly improve the high temperature flexural strength, and keep a good leachability at the same time. The best comprehensive properties of Y2O3-based ceramic cores were obtained when it contained 12 wt% CaO and 4 wt% SiO2. The new developed Y2O3-based ceramic cores with the addition of CaO and SiO2 has the potential to meet the extreme requirements in the casting of Nb-Si alloy hollow turbine blades.

Preparation, mechanical, and leaching properties of CaZrO3 ceramic cores

AbstractThe CaZrO3 ceramic core materials with excellent mechanical and chemical properties were successfully prepared using single‐phase CaZrO3 powders. Effects of particle size ratio and sintering temperature on the mechanical and chemical properties of CaZrO3 ceramic core materials were researched. The chemical property was analyzed by leaching research of core materials in 10 wt% and 20 wt% HNO3 solution at the boiling point. Results showed that the suitable particle size ratio was important for the preparation of CaZrO3 ceramic core materials with excellent comprehensive properties. The addition of fine particles in ceramic core materials promoted the densification process owing to the framework formed by coarser particles and sintering neck formed by fine particles between coarse particles, which was beneficial for further improving their bending strength. When the content of particles with 200 mesh size was 80wt%, the highest bending strength was obtained, 54.38 ± 5.28 MPa. The porosity was 17.45% and the volume density was 3.86 g/cm3. The increasing sintering temperature increased the densification of CaZrO3 ceramic core materials by offering the sintering driving force, further leading to the improvement of bending strength. When the temperature was 1650℃, at the 20% content of particles with 200 mesh size, the highest bending strength of CaZrO3 cores reached 51.01 ± 5.18 MPa. Meanwhile, the porosity was 18.65% and the volume density was 3.83 g/cm3. Additionally, the CaZrO3 samples could be effectively leached in 10 wt% HNO3 solution. Therefore, CaZrO3 materials with good mechanical and leaching properties were believed to be a suitable candidate for ceramic core materials in the investment casting of alloys with high melting point.

A n-order refined theory for free vibration of sandwich beams with functionally graded porous layers

In this paper, a simple n-order refined theory is developed for free vibration of a simply supported sandwich beam with functionally graded porous layers. The present theory is variationally consistent, uses the n-order polynomial term to represent the displacement field, and does not require a shear correction factor. The variation of shear stress is parabolic across the thickness and the condition at the top and bottom surface are shear stress-free. Equations of motion are derived from Hamilton's principle. In the solution of the governing equations, the Navier procedure is implemented. For porosity effect, four different porosity distributions namely O, X, V, and homogeneous distribution types are modelled; power-law variation of functionally graded face sheets is considered. Results show the effects of varying gradients, thickness to length ratios, effects of the porosity parameters and porosity types on free vibration of functionally graded sandwich beams for simply supported boundary conditions. The results of the present method were validated with existing literature for both hard (ceramic) core material and soft (metal) core material, and good agreement with the benchmarks is seen. The effect of hard-core and soft-core material on natural frequency is found to be contrasting in nature.

Effect of Two Connector Designs on the Fracture Resistance of All-Ceramic Core Materials for Fixed Dental Prostheses: An In-Vitro Study

Background: The aim of this study was to test the difference in fracture resistance of 3 ceramic core materials used for simulated 3-unit all-ceramic FPDs with 2 fabrication techniques (lost-wax/heat-pressing and CAD/CAM methods) and 2 connector designs (round and sharp). Material and method: The present in vitro study was conducted in the Department of Prosthodontics and Crown & Bridge, Subharti Dental College & Hospital, Meerut, Uttar Pradesh. For the purpose of this study, 3 all ceramic core materials were selected viz. Yittrium-tetragonal zirconia polycrystals, Milled Lithium disilicate glass ceramic and Lost-wax/heat-pressed lithium disilicate glass ceramic. A total of 10 rectangular bars of dimensions 30 mm (L) x 5 mm (W) x 5 mm (H) from each material were manufactured. Of these 10 bars, 5 bars were fabricated with sharp notch connector and 5 bars were fabricated with round notch connector. The dimensions of all specimens were measured and verified individually by an electronic caliper with an accuracy of 0.05 mm. The radius of each connector was measured with a measuring tool. Results: The failure load was more in Press-R in comparison to Press-S and the difference was found to be statistically significant. The FS was more in CAD-R in comparison to CAD-S and the difference was found to be statistically significant. Conclusion: The round connector design in yittrium stabilized zirconia and heat pressed lithium disilicate both may be considered to be the all-ceramic core material of choice for FDP’s as they have highest failure load and flexural strength.

Performance characteristics of collapsible CaO-SiO2 based ceramic core material via layered extrusion forming

An additive manufacturing method, named layered extrusion forming (LEF), was adopted to fabricate collapsible ceramic cores. Green samples were first fabricated using CaCO3 and SiO2 powders as precursor materials and aqueous polyethylene glycol solution-silica sol as a composite binder and then calcined at 1100 °C − 1300 °C for 2 h. The effect of CaO-SiO2 molar (C/S) ratio on the performance characteristics of green and sintered samples was investigated. The results showed that the slurries exhibited a pseudoplastic behavior for different C/S ratios, and the linear shrinkage of the green samples showed a slight increase with decreasing C/S ratio. After sintering, the reduction of C/S ratio obviously decreased linear shrinkage and bending strength, whereas strengthened the hydration resistance. The microstructure analysis demonstrated that the porosity was increased with decreasing C/S ratio, thereby weakening the bending strength. The ceramic cores samples were constituted by Ca2SiO4 and CaO phases. The existence of the Ca2SiO4 improved the hydration resistance, leading to relative lower collapsibility. The sintered samples with a C/S ratio of 2.45 obtained a superior collapsibility in water, especially in the higher water temperature, which is significant for industry applications.

Corrosion behavior of alumina‐based ceramic core materials in caustic alkali solutions

AbstractCorrosion behaviors of the porous alumina‐based ceramic core materials in KOH and NaOH solution were investigated. Corrosion tests were carried out at 100°C, 150°C, and 200°C, and the concentration of KOH and NaOH was 50, 67, and 75 wt%, respectively. The results indicated that the optimal concentration was 67 wt% for KOH solution and 50 wt% for NaOH solution, respectively. Increasing corrosion temperature and prolonging corrosion time were helpful to enhance the corrosion effect, and temperature played an extra important role during the whole corrosion process. NaOH solution was better than KOH solution for corrosion at the same temperature and concentration.

Effect of specimen thickness on the creep deformation of a silica-based ceramic core material

In this study, the effect of the thickness of a silica-based ceramic core on its creep deformation, either in air or under vacuum, was studied. Specimens with different thicknesses after sintering were heated to 1550 °C and by maintaining the same temperature for 40, 70 or 100 min. Scanning electronic microscopy (SEM) was employed to observe the surface microstructures and fracture morphologies of the samples. X-ray diffraction (XRD) was used to characterize the phases that formed after creep deformation. The 3D distribution of micropores and the porosities of the specimens at different states were tested by X-ray computerized tomography (XCT). The experimental results show that the effect of the thickness of the specimen on the creep deformation was notably different under different atmospheres. The creep deformation of samples with the same thicknesses under vacuum atmosphere was clearly higher than the deformation in air.In air, the creep resistance was slightly affected by the thickness of the specimen. However, the creep deformation was significantly affected by the thickness of the specimen under vacuum. The creep resistance of the 4-mm-thick specimen is noticeably higher than that of the 0.5-mm-thick specimens. The creep rate of the 0.5-mm-thick specimen is linear with the porosity of the surface layer and higher compared to the 4-mm-thick specimen, which exhibited non-linear behaviour. Reactive micropores were formed on the surface layer of these specimens under vacuum. The volume fraction of the micropores increased with increasing creep time, which resulted in the different characterization of creep for specimens with different thicknesses under vacuum.

Effect of adhesive resin cements on bond strength of ceramic core materials to dentin.

The aim of the present study was to evaluate the effects of self-etch and self-adhesive resin cements on the shear bond strength of ceramic core materials bonded to dentin. Extracted, caries-free, human central maxillary incisor teeth were selected, and the vestibule surfaces were cut flat to obtain dentin surfaces. Ceramic core materials (IPS e.max Press and Prettau Zirconia) were luted to the dentin surfaces using three self-etch adhesive systems (Duo-Link, Panavia F 2.0, and RelyX Ultimate Clicker) and two self-adhesive resin systems (RelyX U200 Automix and Maxcem Elite). A shear bond strength test was performed using a universal testing machine. Failure modes were observed under a stereomicroscope, and bonding interfaces between the adhesive resin cements and the teeth were evaluated with a scanning electron microscope. Data were analyzed with Student's t-test and one-way analysis of variance followed by Tukey's test (α = 0.05). The type of adhesive resin cement significantly affected the shear bond strengths of ceramic core materials bonded to dentin (P < 0.05). Significant differences were noted between the ceramic core materials when the specimens were luted with self-adhesive resin cements (P < 0.05). The specimens luted with RelyX Ultimate Clicker had the highest shear bond strengths. The self-etch adhesive resin cements exhibited better shear bond strength than the self-adhesive resin cements, except for Panavia cement in the IPS e.max Press group. However, shear bond strengths of the self-adhesive resin cements were dependent on the nature of the ceramic core materials.

Effect of silica fiber on the mechanical and chemical behavior of alumina-based ceramic core material

In order to improve the chemical leachability, the alumina-based ceramic core material with the silica fiber was injected and sintered at 1100 °C/4 h, 1200 °C/4 h, 1300 °C/4 h and 1400 °C/4 h, respectively. The micrographs of ceramic core materials at sintered and leached state were characterized by scanning electron microscopy (SEM). The phase composition of ceramic core material after sintering and the leaching product after leaching were detected by X-ray diffraction (XRD). The porosity, room temperature bend strength, creep property at elevated temperature and the leaching rate in aqueous caustic solution were studied. The experimental results show that the ceramic core material with silica fiber obtain a fair balance between mechanical and chemical properties at sintering of 1300 °C/4 h. Specifically, the leach rate of ceramic core material with silica fiber is increased apparently. High leaching surface and weak adhesive strength between agglomerated alumina particles are the reasons that responsible for the ceramic core material with silica fiber be leaching fast than that of the ceramic core material without fiber.

Effect of number of firings on the color and translucency of ceramic core materials with veneer ceramic of different thicknesses

Statement of problemWhether masking or translucency should be the goal for achieving an esthetic restoration with ceramic materials is unknown. PurposeThe purpose of this in vitro study was to examine the effect of the number of firings on the color and translucency of ceramic core material with different thicknesses of veneer ceramic. Material and methodsThree different ceramic systems were used: IPS Empress (IE), IPS e.max Press (IEP), and Turkom Cera (TC). Ninety disk-shaped cores, 10 mm in diameter and 0.8 mm in thickness were prepared using each system (n=30). The specimens were divided into 3 subgroups (n=10) according to the thickness of the veneering ceramic: 0.5, 1.0, and 1.5 mm. The specimens were fired 1, 3, and 5 times, and the color parameters of the specimens were measured. The color measurements were repeated, and the data were statistically evaluated using 2-way and multifactorial analysis of variance, the Duncan test, and the Bonferroni post hoc test. ResultsThe number of firings affected the translucency parameter and CIELab values. Increased porcelain thickness led to decreased translucency parameter and L* values and increased a* and b* values (P<.05). The IE system was the most translucent (P<.001). The changes with increased firing periods were not statistically significant (P>.05). The number of firings affected the color change of the IE and IEP systems but not of the translucency parameter system. ConclusionsRepeated firings and porcelain thickness affected the final color and translucency of the ceramic systems tested. These 2 factors adversely affected the esthetic result and should be considered in both the preparation and the laboratory phase.

Fe(NO3)3수용액의 농도와 침지시간에 따른 지르코니아의 색상 및 특성 변화

Purpose: The increased aesthetic requirements and demands of patients have resulted in the developments of coloring liquid for zirconia. Methods: In this study, zirconia block was dipped into <TEX>$Fe(NO_3)_3$</TEX>solution, which showed a color and then concentration of <TEX>$Fe(NO_3)_3$</TEX>and zirconia's color and physical properties depending on the dipping time were observed and compared with exclusive coloring solutions. As the result, the following conclusions were obtained. Results: When compared with the specimens that were colored using exclusive solutions, <TEX>$L^*$</TEX> value rose overall depending on the concentration of <TEX>$Fe(NO_3)_3$</TEX>and <TEX>$a^*$</TEX> value was red in the form of (+) in all the specimens. Also, <TEX>$b^*$</TEX> value was in the form of (+) at 0.5 to <TEX>$1{\ss}fl$</TEX>, but was in the form of (-) at 1.5 to <TEX>$2{\ss}fl$</TEX>. The dipping time did not highly influence <TEX>$L^*$</TEX> value, but <TEX>$a^*$</TEX> value and <TEX>$b^*$</TEX> value were directly opposite to the specimens, which were not colored, except the sample that was dipped for only 2 seconds. When compared with exclusive coloring solutions, <TEX>$Fe(NO_3)_3$</TEX>had the most similar color at 0.5 to <TEX>$1{\ss}fl$</TEX> and the longer the coloring time, the higher the rate of color change became. In relation to the density change depending on the addition of <TEX>$Fe(NO_3)_3$</TEX>, there was the lowest density at <TEX>$2{\ss}fl$</TEX> and the density was increased in the specimens that were not colored. Conclusion: These results show that <TEX>$Fe(NO_3)_3$</TEX>solution can be used to make colored zirconia. It is expected that newly made colored zirconia can be used in clinical practice because the colored zirconia not only possesses the mechanical properties that all ceramic core material should have but also was biocompatible to a living cells.

The effect of sodalite zeolite infiltrated material on the fracture toughness, elastic modulus and optical properties of all-ceramic dental prostheses

All-ceramic dental prostheses have been advocated for their superior esthetics. Although different materials and systems have been fabricated to improve the fracture resistance, their influence on the opacity of all-ceramic systems remains unclear. The purpose of this study was to investigate the effect of infiltrated materials on the fracture and optical properties of alumina and zirconia-toughened alumina (ZTA) frameworks. Ceramic core materials were prepared as disc-shaped samples measuring 16mm in diameter and 1.2±0.2mm in thickness for fracture toughness and elastic modulus tests, and 11mm in diameter and 0.7±0.2mm in thickness for translucency test. The case-study groups were synthesized sodalite zeolite-infiltrated alumina (IA-SOD) and synthesized sodalite zeolite-infiltrated ZTA (IZ-SOD), while the control groups were glass-infiltrated alumina (IA-glass) and glass-infiltrated ZTA (IZ-glass). The values of fracture toughness (Vickers microhardness), elastic modulus (fracture stress curve), as well as the relative translucency and brightness (contrast ratio from luminous reflectance) were compared among the groups (n=10). Scanning electron microscopy and energy dispersive X-ray spectroscopy were used to investigate the structural characteristics and crack patterns of the samples at the surface impression of a Vickers indenter. The collected data were analyzed with a one-way ANOVA and Tukey HSD test (α=0.05). IZ-SOD and IA-glass exhibited the highest fracture toughness and elastic modulus among the groups, respectively. Whereas IA-SOD showed the highest translucency and brightness. The results of this study thus confirmed the improvement in the optical properties of newly-developed IA-SOD as well as the fracture toughness of IZ-SOD frameworks and reveal the lower values of elastic modulus in SOD-infiltrated frameworks than glass-infiltrated samples (IA-glass and IZ-glass). These desirable features of SOD-infiltrated frameworks could thus make them suitable for anterior teeth restorations.