• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.2
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• pp.71-79
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• 2017

Purpose: Ni-Cr alloy does not contain Beryllium, causing the metal compound to form oxides in the furnace but by using Titanium as a chemical catalyst the forming of the oxides can be controlled, and by controlling the impurities formed on the metal surface, the possibility of the Ni-Cr alloy bond strength being increased can be analysed. Materials and Methods: Titanium was used as a chemical catalyst in the porcelain for the oxidation of beryllium-free metal (Ni-Cr) alloy. The T1 group, which does not use Titanium power as a chemical catalyst is a reference model for comparison. The T2 group and T3 group used 10 g and 20 g of Titanium power, respectively. They are fabricated to observe the shear bond strength and surface properties. There was no significance when One-way ANOVA analysis/Tukey Honestly Significant Difference Test was conducted for statistical analysis among groups (P > 0.05). Results: Results of measuring the three-point flexural bond strength of the Ni-Cr alloy and thickness of the oxide film. Experiment T3 using 20 g Titanium chemical catalyst: $39.22{\pm}3.41MPa$ and $6.66{\mu}m$, having the highest bond strength and thinness of oxide film. Experiment T2 using 10 g Titanium chemical catalyst: $34.65{\pm}1.39MPa$ and $13.22{\mu}m$. Experiment T1 using no Titanium chemical catalyst: $32.37{\pm}1.91MPa$ and $22.22{\mu}m$. Conclusion: The T2 and T3 experiments using Titanium chemical catalyst showed higher bond strength for the Ni-Cr alloy and lower thickness of oxide film than experiment T1, and the titanium catalyst being able to increase bond strength was observed.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.2
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• pp.151-157
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• 2010

Purpose: The purposes of this study was to evaluates shear bond strength between zirconia core and veneer-ceramic in order to examine the clinical practice of colored zirconia block fabricated by infiltration method into the metal chloride solution. Material and methods: CNU block and $Everest{(R)}$ ZS blank were used. VITA In-$Ceram{(R)}$2000 YZ Coloring liquid (LL1) and 3 aqueous metal chloride solutions containing chromium and molybdenum ingredients were used. 40 zirconia specimens were prepared into cuboid shape ($5{\times}5{\times}10 mm$). All specimens were divided into 5 groups by infiltrating into the coloring liquids. After that, porcelain was build up into the shape of $5{\times}5{\times}4mm^3$, followed by sintering. The maximum loading and shear bond strength was measured. Failure patterns and failure sites were examined. Results: 1. There were no statistical differences in shear bond strength between zirconia blocks (P > .05). 2. There were no statistically significant differences in shear bond strength between non-colored and colored zirconia blocks, while shear bond strength of non-colored zirconia blocks is higher than that of colored specimen (P > .05). 3. In the comparison with shear bond strength among colored zirconia blocks, there were no statistical differences according to kinds of coloring liquid (P > .05). 4. Mixed failure patterns were mainly observed in the failure between zirconia and veneering ceramic. The veneering ceramic failure of all specimens was observed in either interface of zirconia or veneering ceramic. Conclusion: Shear bond strength between colored zirconia and veneering ceramic shows lower tendency than non-colored zirconia, but there was clinically allowable value.

• Korean Journal of Heritage: History & Science
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• v.53 no.1
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• pp.150-167
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• 2020

The purpose of this paper is to share the status and introduce a scientific analysis of the GeumguJagi (gilt-silver overlay porcelain, 金釦瓷器) excavated from Seongneung (石陵). This analysis aimed to highlight the GeumguJagi excavated from the Royal Tombs of Goryeo with a clear lower year (1237) and to aid research into the GeumguJagi. In 2001, the National Institute of Cultural Heritage excavated and investigated Seongneung in Heejong (熙宗). Various artifacts such as celadon, gold, bronze, and iron products were collected from the chambers inside of the tomb. There were a total of 160 celadon items including bowls, dishes, glasses, and saucers. Of those, there were 58 celadon items (including fragments) with metal frames on the openings. These consisted of bowls, plates, lids, and saucers. Until recently, in various exhibitions and papers, only one GeumguJagi was known to have been excavated from Seongneung, which was a . However, the survey identified a number of further GeumguJagis. It had been understood from inherited and excavated products that the materials used for ornaments were restricted to high-quality celadon. However, this study confirmed that the excavation of Seongneung demonstrated the use of various other materials for different models and qualities of GeumguJagis. It can be said that it is characteristic that various models and quality are confirmed together through the excavation of Seongneung. A scientific analysis was carried out that selected 12 of 58 products excavated from Seongneung. Results showed that the main component used for Geumgu ornaments was tin (Sn), and trace amounts of copper (Cu) and lead (Pb) were also commonly identified. When analyzing the material used to affix the metal fittings, this was found to be glue (膠) made from animal skins, muscle, and bones. This pattern matches that of the GeumguJagi excavated from Paju Hyeeumwonji, and the reason for this could be assumed on the basis of the contents of the 『Cheongonggaemul (天工開物)』 written by Song Ongsung (宋應星) during the Ming Dynasty. At that time, metals such as tin and copper would have been difficult to obtain. 『Xuānhwafengshi Gaolitujing (宣和奉使高麗圖經)』 shows that the use of metal was limited to certain classes; thus, the use of the GeumguJagi seems to have been centered around the royal family.

• Journal of Technologic Dentistry
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• v.28 no.1
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• pp.177-198
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• 2006

This study purposed to offer basic data for safety education of the dental laboratory technology after the investigation of how much the students in the dept. of dental laboratory technology are aware of the danger of each instrument, equipment or laboratory procedure that they use during laboratory and how much they demand safety education for this. The objects for this study were 423 students who were in the dept. of dental laboratory technology. In this regard, four colleges which have the dept. of dental laboratory technology were randomly selected to do a questionnaire survey. SPSS 12.0 was used to analyze the collected data. The results were as follows: As for satisfaction with their major, the respondents answered Satisfied (59.1%), Average (35.5%) and Dissatisfied (5.4%). In terms of the production process of a partial denture, they considered casting, polishing the casting body, polishing denture and burn out were most dangerous in order. As for the production process of a full denture, what they regarded as the most dangerous in order was polishing denture, deflasking and wax wash. Regarding the laboratory procedures of porcelain material, casting, trimming casting body, polishing porcelain material and burn out were the most dangerous procedures that they perceived. With regard to materials for use, alcohol, polishing, metal and wire were the most dangerous ones they thought. As for the handling characteristics of each material, small towns showed a higher demand for safety of the handling characteristics of alcohol. In terms of school year and sex, juniors and girls had higher scores in the demand for safety of the handling characteristics of acid. Regarding the handling characteristics of each equipment and instrument, all of small towns, juniors and girls showed the highest demand for safety of the handling characteristics of alcohol lamps. With regard to scores in the demand for safety of other characteristics, all of small towns, juniors and girls had the highest demand for safety of emergency treatment. Concerning the demand for safety education by the completion of safety education, in terms of each material, highest was the demand for safety of acid from the group which completed safety education. In regard to equipments and instruments, when it came to the demand for safety of the handling characteristics of casting machine, the educated group's demand for safety of acid was higher. Regarding other characteristics, the group which was not educated gained higher scores in the demand for safety of emergency treatment. 11. In all areas(materials, machines and others), small towns, girls and juniors showed higher scores in the demand for safety. Based on the above results, it was found that when students conduct the laboratory of dental technology, they would think that many materials, instruments or equipments for use are very dangerous. However, safety education was not fully given to them. Regarding the scores in the damned for safety education, the highest was 4.16 and the lowest was 3.43, which suggests that the scores were generally very high. In this regard, it is necessary to continue delivering a systematic safety education of materials, equipments or instruments used during the laboratory of dental technology. Therefore, through the analysis of each material, instruments or facility used in every laboratory and each process, safety accident types and accident risk factors should be investigated to develop educational materials for this. Moreover, it is required to open safety education as a single course of study or insert safety contents of all materials and machines into the class of dental laboratory instrument or dental materials for the purpose of a systematic and thorough safety education to prevent a safety accident during laboratory.

• Journal of Technologic Dentistry
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• v.25 no.1
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• pp.41-62
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• 2003

In this research, we manufactured the paste opaque porcelains using Propylene Glycol (PG) and Buthylene Glycol (BG) as a solvent, and compared the composition of solvents, the coefficient of thermal expansion, the particle size distribution, the viscosity and bonding strength to metal, and the tone with those of the commercial products(Duceram Plus, Duceram GmbH; VMK 95, Vita Co.; Noritake EX-3, Noritake Co.)used in the clinical field. The results of the research were as follows: 1. The result of solvent analysis indicated that the solvents included in the paste opaque porcelains of the control group were mainly composed of Glycols. 2. From the Coefficient of thermal expansion measurement, we drew out the following results; testing group: $14.0\times10^{-6}/^{\circ}C$, Duceram Plus: $13.9\times10^{-6}/^{\circ}C$, VMK 95: $14.3\times10^{-6}/^{\circ}C$, and Noritake EX-3: $13.3\times10^{-6}/^{\circ}C$. 3. Seen from the result of particle size distribution measurement, the experimental group was similar to the control group in 1$\mu m$ below, but the experimental group marked the highest distribution of 61% in the case of between 1$\mu m$ and 5$\mu m$. Between 5$\mu m$ and 10$\mu m$, they showed relatively similar distribution, and Noritake EX-3 was turned out the highest distribution of 29% in 10$\mu m$ above. 4. From the result of viscosity measurement, Duceram plus showed the highest viscosity throughout all the measurements followed by Noritake Ex-3, experimental group and VMK 95 in decreasing order. 5. The result of bonding strength measurement was EX 35.53 $\beta\acute{A}$, DU 40.88 $\beta\acute{A}$, VM 39.43 $\beta\acute{A}$, and NO 35.39 $\beta\acute{A}$, and no significant difference was found between the experimental group and the control groups(P>0.05). 6. The measurement of the tone indicated that the $L^*$ value of the experimental group was 86.89 0.63 in average, which is higher than the control group in its brightness. In the case of the $a^*$ value, Duceram Plus, VMK 95 and EX-3 showed positive value, whereas the testing group was turned out negative value. In $b^*$ value, Duceram Plus proved the highest. From the results of this research, the paste opaque porcelains using Propylene Glycol (PG) and Buthylene Glycol (BG) as a solvent did not make differences from the commercial products that are actually used in the clinical fields. Therefore, it is possible to utilize Propylene Glycol (PG) and Buthylene Glycol (BG) for the paste opaque porcelains of P.F.M crown. It is also recommended that further researches concerning the compositions and forms of powder, the types of organic solvent components and the ratio of mixture proceeded in order to improve the level of productivity in the future.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.1
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• pp.47-51
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• 2013

With the introduction of dental implants, restoration of missing teeth with conventional fixed or removable partial dentures is being replaced with implants. Especially, with young patients, not only longevity but also esthetic factors need to be considered. Implant restorations provide long-term success functionally but, esthetic complications such as, marginal exposure due to gingival recession, loss of the papilla and dark color of metal abutments may occur. Recently, zirconia restorations with CAD/CAM technology provide functional, biocompatible and esthetic restorations possible. All-ceramic restorations using the pressed ceramic technique show better fracture toughness values than those of the conventional porcelain veneering technique. Pressed ceramic technique creates the veneer design in wax and the lost wax technique is used to create the restoration. The final contour of the restoration may be controlled during wax-up. A 22-year old female patient was restored with dental implants and zirconia restorations using the pressed ceramic technique presenting short-term but optimistic prognosis.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.4
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• pp.477-482
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• 2010

In a case of multiple posterior teeth loss, antagonistic teeth extrude to the edentulous space and compensatory occlusion on the remained anterior teeth leads to occlusal trauma. Extrusion of antagonistic teeth breaks down occlusion plane and loss of posterior support bring about severe wear of remained teeth. In this situation, it is needed to restore remained teeth and edentulous space by increasing vertical dimension to obtain prosthodontic rehabilitation space and to correct occlusion plane. In this case report, the patient had a masticatory problem with loss of posterior teeth support and an esthetic problem of shortened anterior teeth. Before the tooth preparation for the prosthodontic restoration, the patient used removable device for 2 months to increase vertical dimension reversibly. After that, he got provisional fixed restoration with irreversible tooth reduction and used it for 3 months. It had spent 5 month to evaluate the adaptation state on final restoration with incresed vertical dimension. The increasing amount was 3 mm, which was relatively in less degree and masticatory system adapted to the increased vertical dimension without any pathologic changes. Final restoration was made to have equal-intensity contacts on all teeth in a verifiable centric relations and immediate disclusion of all posterior contacts the moment the mandible moves in any direction from centric relation. In addition, metal occlusion surface on posterior teeth was applied to prevent excessive muscle activation, occlusal trauma and the porcelain fracture.

• Journal of Korean Society on Water Environment
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• v.26 no.1
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• pp.1-9
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• 2010

Technology-Based Effluent Limitations (TBELs) is a permit limits for a pollutant that is based on the capability of a treatment technology to reduce the pollutant to a certain concentration. Widely practiced for regulations of industrial wastewater in US, TBELs has been accepted as an effective means that can achieve balanced goals between complete elimination of pollutants discharge and economic feasibility for industries. The review of TBELs application in US and the applicability of TBELs to the domestic industry categories was given in three papers. In the first paper, the development and practices of TBELs in US were reviewed including case studies. The developments of TBELs in US in the four major categories, the metal products & machinery, the petroleum refining, the porcelain enameling and the meat & poultry products were reviewed. The applicability of TBELs to the domestic industrial categories was also assessed. In the second paper, the pollution loads analysis for domestic industrial wastewater was conducted based on risk assessment indicator using Toxic Weighting Factors (TWFs). This is an essential part to determine the priority of TBELs application for the domestic industrial categories. In the last paper, the application of TBELs to the domestic industries was demonstrated through a case-study for the pulp/paper/paperboard category. Direct application of TBELs of US into the Korean regulation system may not be desirable because the specific goals and the environment for the regulations for the two countries may not be identical. For example, unlike US, Korea does not adopt the individual permit system for pollution sources. However, among the unproductive and exhaustive controversies over the uniform regulations regardless of the industrial categories in Korea, the introduction of the principles of TBELs are inevitable and more extensive study for applications of TBELs optimized for Korean regulation system will be necessary.

• The Journal of Korean Academy of Prosthodontics
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• v.53 no.4
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• pp.301-309
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• 2015

Purpose: The aim of this study was to evaluate the clinical performance of screw- and cement-retained implant prosthesis (SCP) design in terms of retained preload of abutment screws and cement washout. Materials and methods: Patients with the partial posterior edentulous areas comprised the study group. Implants were placed, and SCPs were delivered after 3 to 6 months healing. Follow-up examinations were performed. The implant survival rate and the prosthetic success rate were evaluated. The retained preload ratio of abutment screws and the prosthetic decementation ratio were measured. Results: Twenty one SCPs (forty three implants)in twenty patients were followed up to 64 months. All of the implants survived during the follow-up period (mean follow-up: 34 months). The prosthetic success rate was 100 % considering no abutment, screw, porcelain or metal frame fractures, as well as no screw loosening. The retained preload ratio of SCPs at the end of follow-up period was 97.61% (${\pm}16.29$) and the decementation ratio was 9.5 %. Conclusion: Within the limitations of this clinical study, SCP design showed favorable short-term clinical performances in respect of screw loosening and cement washout.

• Journal of Technologic Dentistry
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• v.28 no.2
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• pp.355-366
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• 2006

The purpose of this study was to determine if repeated casting has a detrimental effect on the corrosion behavior of nickel-chrome casting alloys. The X-ray diffraction analysis, vickers hardness test, SEM, EDX and corrosion test were performed to determine the effects of recasting on chemical composition, microstructure, physical property, castability and corrosion behavior of nickel-chrome casting alloys. The X-ray diffraction analysis results for the cast and recast specimens of the VeraBond and the Rexillium V showed that major crystal phase contained nickel-chrome compounds, Nickel carbide and Chrome carbide. Microstructure analysis results for the cast and recast specimens of the VeraBond and the Rexillium V showed recasting has no effect on microstructure. EDX analysis results indicated the percentage of the main component nickel(Ni) in the specimens of the VeraBond showed a tendency to increase with recasting, but those of other components Carbon(C) showed a tendency to decrease with recasting, Chrome(Cr), Silicon(Si), Aluminium(Al) and molybdenum(Mo) showed no changes in the percentage. The percentage of the main component nickel(Ni) in the specimens of the Rexillium V showed a tendency to increase with recasting, but those of other components silicon(Si), carbon(C) and molybdenum(Mo) showed a tendency to decrease with recasting, chrome(Cr) and aluminium(Al) showed no changes in the percentage. The vickers hardness results for the cast and recast specimens of the VeraBond and the Rexillium V showed a tendency to decrease with recasting, but the differences for the first to fifth cast were not statistically significant. The castability results for the cast and recast specimens of the VeraBond and the Rexillium V showed a tendency to decrease with recasting, but the differences for the first to fifth cast were not statistically significant. The cast and recast specimens of the VeraBond and the Rexillium V showed no differences in the corrosion resistance. The results indicate that the VeraBond and the Rexillium V can be safely recast.