• Korean Journal of Dental Materials
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• v.44 no.3
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• pp.197-206
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• 2017

The hardening effect by ice-quenching after oxidation of a Pd-Ag-Sn-Au metal-ceramic alloy during porcelain firing simulation was investigated by means of hardness test, field emission scanning electron microscopic observations, and X-ray diffraction analysis. The hardness decreased by ice-quenching after oxidation, which was induced by the homogenization of the ice-quenched specimen. The decreased hardness by ice-quenching after oxidation was recovered from the wash stage which was the first stage of the remaining firing process for bonding porcelain. After wash stage, the hardness of the ice-quenched specimens decreased during the subsequent porcelain firing process. But the final hardness of the ice-quenched specimens after oxidation was higher than that of the specimens cooled at stage 0 after oxidation. The increase in hardness of the specimens during the first firing process was caused by the lattice strains generated at the interface between the face-centered cubic Pd-Ag-rich matrix and the face-centered tetragonal Pd3(Sn, Ga, In) precipitate. The decrease in hardness of the specimens during the remaining firing process was caused by the microstructural coarsening.

• Journal of Technologic Dentistry
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• v.11 no.1
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• pp.89-93
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• 1989

The purpose of this study was to evaluate the effect of sprue length and casting pressure on the relative castability of the base metal alloys, commonly used to make porcelain metal restoration. Samples of total 30 were constucted and devided into 6 groups according to three variables (low, medium, high). The total number of complety cast squares were counted, verified and recorded. The results of this 1. main effect of casting pressure was statistically significant.(P<0.05). 2. main effect of sprue length was not statistically significant.

• Journal of Technologic Dentistry
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• v.2 no.1
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• pp.35-38
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• 1980

이 기술은 레진(acrylic resin) 또는 의과용 도재(dental porcelain)에 의한 치아 색깔의 전장부위를 갖고 있는 금속구치 block(metal posterior tooth block)의 개조에 대한 기술의 일면이다. 이 기술은 모든 가철식 보철물(removable dental restoration)에 적용할 수 있으며 특히 자연치열(natural dentition) 대합치에 가철식 국부의치(removable partial denture)를 갖고 있는 만성 이갈음 환자(chronic bruxing patient)에 적용할 수 있다.

• The Journal of Korean Academy of Prosthodontics
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• v.27 no.2
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• pp.79-100
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• 1989

The Purpose of this study was to investigate material differences in stress transmission among various artificial teeth and denture base materials. For this study, a two-dimensional finite element model and a two-dimensional photoelastic model of a mandible with complete denture were made. A resin tooth and a porcelain tooth were used as artificial teeth, and a resin base, a metal lined base, and a soft-liner lined base were used as denture bases. An occlusal load was applied and principal stresses generated in the supporting tissues were compared. To test the impact stress transmission, strain gauge attached to the denture base specimens made of the different materials were made in thick and thin groups. Voltage outputs from hitting the specimen with a steel ball were compared. The results were as follows : 1. In FEM, increasing the mucosal thickness reduced the maximum principal stresses in the supporting tissues, but altering the tooth materials and the base materials induced no difference in the stresses. 2. In photoelastic model study, no difference in fringe order among the specimens were observed, but the thick mucosa group and the soft-liner lined group revealed a more uniform distribution of the load. 3. In strain measuring, the impact force transmission was highest in the soft-liner lined group, and was the lowest in the metal lined group(p<0.01). 4. In the thin group using the resin base, the porcelain tooth showed higher impact stress transmission than the resin tooth(p<0.01), but no difference was observed between them in the thick group. In the soft-liner lined group, the porcelain tooth showed higher impact stress transmission than the resin tooth(p<0.01), but no difference was observed between them in the metal lined group. 5. The thick group showed lower impact stress transmission than the thin group(p<0.01).

• Journal of the Korean institute of surface engineering
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• v.49 no.6
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• pp.560-566
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• 2016

In this study, porcelain bonding strength and mechanical properties of sintered Ni-Cr-Ti alloy for dental prosthodontics have been researched experimentally. Mechanical and morphological characteristics of the alloys were examined by Vickers hardness test, tensile and bonding strength test, surface roughness test, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. In the sintered Ni-13Cr-xTi alloys, morphology of sintered alloy showed porous matrix diffused with alloying elements of Cr and Ti, and showed dendritic structure after melting process. From the XRD results, the second phases of NiCr, $Ni_3Cr$, and $Ni_3Ti$ were formed in the case of sintered and melted Ni-13Cr-xTi alloys. The tensile strength and hardness of Ni-13Cr-xTi alloys increased, as Ti content increased. Surface roughness increased, as Ti content increased. The bonding strength between metal and porcelain of Ni-13Cr-5Ti alloy was higher than those of Ni-13Cr and Ni-13Cr-10Ti alloys

• Journal of Technologic Dentistry
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• v.32 no.3
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• pp.195-207
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• 2010

Purpose: The purpose of this study was to observe the microstructural changes of surface in the specimens, performing the shear bond strength testing. The currently most used non-precious alloys are nickel-chromium based alloys with or without beryllium. However, their biocompatibility has been questioned concerning possible damages to the health of the patient and professionals involved in the fabrication of prosthesis caused by long exposure to Ni and Be. An option to nickel-chromium alloys is the cobalt-chromium alloy, an alternative that does not sacrifice the physical properties of the metal porcelain systems. Studies in the animals substantially show that the cobalt-chromium alloys are relatively well tolerated, being therefore more biocompatible than the nickel-chromium alloys. Methods: Non-addition Be to nickel-chromium based alloy(Bellabond plus) and cobalt-chromium alloy which has been widely used(Wirobond C) fused with ZEO light porcelain classified control group and cobalt-chromium alloy which is developing alloy of Alphadent company in Korea(Alphadent alloy) fused with ZEO light porcelain classified experimental group. The specimens of $4mm{\times}4mm{\times}0.5mm$ were prepared as-cast and as-opaque to cast body to analyze the mechanical characteristic change, the microstructure of alloy surface. The phase change was used to observe through XRD analysis and OM/SEM was used to observe the surface of specimens as-cast and as-opaque to cast body. Chemical formation of their elements was measured with EDS. Then hardness was measured with Micro Vicker's hardness tester. Shear bond strength test thirty specimens of $10mm{\times}10mm{\times}2mm$ was prepared, veneered, 3mm high and 3mm in diameter, over the alloy specimens. The shear bond strength test was performed in a universal testing machine(UTM) with a cross head speed of 0.5mm/min. Ultimate shear bond strength data were analyzed with one-way ANOVA and the Scheffe's test (P<0.05). Within the limits of this study, the following conclusions were drawn: The X-ray diffraction analysis results for the as-cast and as-opaque specimens showed that the major relative intensity of Bellabond plus alloy were changed smaller than Wirobond C and Alphadent Co-Cr based alloys. Results: Microstructural analysis results for the opaque specimens showed all the alloys increased carbides and precipitation(PPT). Alphadent Co-Cr based alloy showed the carbides of lamellar type. The Vickers hardness results for the opaque specimens showed Wirobond C and Alphadent Co-Cr based alloys were increaser than before ascast, but Bellabond plus alloy relatively decreased. The mean shear bond strengths (MPa) were: 33.11 for Wirobond C/ZEO light; 25.00 for Alphadent Co-Cr alloy/ZEO light; 18.02 for Bellabond plus/ZEO light. Conclusion: The mean shear bond strengths for Co-Cr and Ni-Cr based alloy were significantly different. But the all groups showed metal-metal oxide modes in shear bond strengths test at the interface.

• Korean Journal of Dental Materials
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• v.43 no.4
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• pp.343-349
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• 2016

This experiment was carried out to examine whether the post-firing heat treatment is effective in increasing the hardness of metal-ceramic alloy of the Pd-Au-Ag-Sn system. Precipitation hardening by holding at $600^{\circ}C$ after simulated complete porcelain firing in a metal-ceramic alloy of the Pd-Au-Ag-Sn system was examined by observing the change in hardness, crystal structure, and microstructure using a hardness test, X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). The hardness of the alloy increased apparently by holding the specimen at $600^{\circ}C$ for 30 min after simulated complete porcelain firing. The formation of fine grain interior precipitates during holding at $600^{\circ}C$ caused the formation of lattice strain in the grain interior, resulting in apparent hardening. The faster cooling rate (stage 0) during simulated complete porcelain firing resulted in more effective precipitation hardening during holding at $600^{\circ}C$. From the above results, an appropriate post-firing heat treatment, such as holding at $600^{\circ}C$ for 30 min after complete porcelain firing may increase the durability of metal-ceramic prostheses composed of Pd-Au-Ag-Sn alloy.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.4
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• pp.658-664
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• 1997

The effect of metal oxides($K_2O, MgO, CaO,Al_2O_3$, and $TiO_2$) on the kinds of pure $SiO_2$ phase, and $SiO_2$ phases in the composition of vitreous porcelain body was investigated. Also, the effect of the ratio $SiO_2$ to $Al_2O_3$ in the composition of porcelain body with stabilized of cristobalite phase was investigated. In the case of the addition of $K_2O, MgO, CaO, Al_2O_3$, and $TiO_2$ to pure $SiO_2$, the major phase was $\alpha$-cristobalite, $\alpha$-cristobalite, $\alpha$-quartz, $\alpha$-quartz and amorphous, respectively. As the ratio of $SiO_2$ to $Al_2O_3$ in the composition of porcelain body was decreased, the stabilization of cristobalite phase was promoted and only the critical value of $SiO_2/Al_2O_3$ ratio that stabilizing the cristobalite phase in it was 68.10/22.75. The addition of $K_2$O, MgO, CaO,Al_2O_3$, and $TiO_2$ to the composition of porcelain body stabilized already did not affect on the formation of $\alpha$-cristobalite phase which degraded the thermal properties of porcelain body, and suppressed the formation of a, $\beta$-cristobalite.

• Journal of Technologic Dentistry
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• v.32 no.4
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• pp.327-335
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• 2010

Purpose: The purpose of this study was to investigate the correlation between zirconia core thickness and color tone blocking of discolored tooth and metal post. Methods: For this study, we made 20-porcelain sample and 4-metal sample( liechtenstein IPS e.max) bonded to zirconia core of different thickness with cement(Relyx ARC-3M USA)for produce discolored. We measured the color-spectral characteristics, using Shadepilot equipment(Degudent USA).We measured it with Shadepilot equipment set by automated average mode in 3 times And applied the average value obtained from 2 times of measurement in the middle of each sample. Results: As a result of analysing color-spectral characteristics on zirconia core sample, Depending on the thickness of zirconia core, the value of brightness(${\Delta}L*$:color-spectral characteristic) was increased within limited range, value of ${\Delta}a*$, ${\Delta}b*$ was decrease. Conclusion: Consequently, we obtained the following results: Changes of sample color were observed depending on the thickness of zirconia, but the range of change did not exceed the scope range of shade guide. The case of metal posts, shade guide color D2 were observed in 0.5mm of zirconia core thickness. As a result, in case of porcelain, increasing the zirconia thickness of 0.3mm or more is unnecessary for color blocking effect, in case of metal post, considering the discolored tooth, thickness of zirconia with at least 0.5mm or more is recommended.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.2
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• pp.169-181
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• 2007

Statement of problem: Titanium is well known as a proper metal for the dental restorations, because it has an excellent biocompatibility, resistance to corrosion, and mechanical property. However, adhesion between titanium and dental porcelains is related to the diffusion of oxygen to the reaction layers formed on cast-titanium surfaces during porcelain firing and those oxidized layers make the adhesion difficult to be formed. Many studies using mechanical, chemical and physical methods to enhance the titanium-ceramic adhesion have been actively performed. Purpose: This study meant to comparatively analyse the adhesion characteristics depending on different titanium surface coatings after coating the casts and wrought titanium surfaces with Au and TiN. Material and method: In this study, the titanium specimens (CP-Ti, Grade 2, Kobe still Co. Japan) were categorized into cast and wrought titanium. The wrought titanium was cast by using the MgO-based investment(Selevest CB, Selec). The cast and wrought titanium were treated with Au coating($ParaOne^{(R)}$., Gold Ion Sputter, Model PS-1200) and TiN coating(ATEC system, Korea) and the ultra low fusing dental porcelain was fused and fired onto the samples. Biaxial flection test was done on the fired samples and the porcelain was separated. The adhesion characteristics of porcelain and titanium after firing and the specimen surfaces before and after the porcelain fracture test were observed with SEM. The atomic percent of Si on all sample surfaces was comparatively analysed by EDS. In addition, the constituents of specimen surface layers after the porcelain fracture and the formed compound were evaluated by X-ray diffraction diagnosis. Result: The results of this study were obtained as follows : 1. The surface characteristics of cast and wrought titanium after surface treatment(Au, TiN, $Al_2O_3$ sandblasting) were similar and each cast and wrought titanium showed similar bonding characteristics. 2. Before and after the biaxial flection test, the highest atomic weight change of Si component was found in $Al_2O_3$ sandblasted wrought titanium(28.6at.% $\rightarrow$ 8.3at.%). On the other hand, the least change was seen in Au-Pd-In alloy(24.5at.% $\rightarrow$ 9.1at.%). 3. Much amount of Si components was uniformly distributed in Au and TiN coated titanium, but less amount of Si's was unevenly dispersed on Al2O3 sandblasting surfaces. 4. In X-ray diffraction diagnosis after porcelain debonding, we could see $Au_2Ti$ compound and TiN coating layers on Au and TiN coated surfaces and $TiO_2$, typical oxide of titanium, on all titanium surfaces. 5. Debonding of porcelain on cast and wrought titanium surface after the biaxial flection is considered as a result of adhesion deterioration between coating layers and titanium surfaces. We found that there are both adhesive failure and cohesive failure at the same time. Conclusion: These results showed that the titanium-ceramic adhesion could be improved by coating cast and wrought titanium surfaces with Au and TiN when making porcelain fused to metal crowns. In order to use porcelain fused to titanium clinically, it is considered that coating technique to enhance the bonding strength between coating kKlayers and titanium surfaces should be developed first.