• The Journal of Korean Academy of Prosthodontics
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• v.54 no.3
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• pp.253-258
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• 2016

The development of translucent zirconia enabled clinicians to choose a monolithic zirconia crown as one treatment modality in the posterior dentition. Careful occlusal adjustments are recommended for monolithic zirconia crowns because grinding zirconia inevitably causes phase transformation, which may deteriorate mechanical properties. intraoral scanners enable the clinician to scan and superimpose a complete tooth structure before preparation onto the prepared abutment. This technique helps to reproduce the original tooth form and occlusion of the patient. In this case report, prostheses were fabricated for patients with cracked or fractured tooth by applying intraoral scanner, Computer aided design-computer aided manufacturing (CAD-CAM) and monolithic zirconia crown to reproduce the occlusion of original tooth and to minimize occlusal adjustment. The clinical results were satisfactory in both esthetic and functional aspects.

• Journal of Dental Rehabilitation and Applied Science
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• v.36 no.1
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• pp.41-47
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• 2020

Purpose: The purpose of this study was to evaluate the flexural strength and reliability of highly translucent colored zirconia for all ceramic restoration. Materials and Methods: Bar-shaped specimens (25 × 4 × 2.5 mm) were prepared from highly translucent monolithic zirconia. Three experimental groups were set up according to color (shade A0, A1, and A3). For each group, 20 specimens were prepared. Flexural strength was determined using a 3-point flexural test and results were analyzed with one-way ANOVA test. Weibull statistical analysis provided 2 parameter estimates: Weibull modulus and characteristic strength. X-ray diffraction (XRD) analysis was performed. Results: There was statistically significant difference between uncolored (Shade A0) and colored (shade A1 and A3) (P < 0.05), but there was no difference between colored groups (P > 0.05). The uncolored group had higher reliability compared with colored study groups. On x-ray diffraction analysis of each group, typical peaks of tetragonal phase appeared in all groups. Conclusion: Within the limitations of this in vitro study, coloring highly translucent zirconia had significant effect on flexural strength and reliability. Therefore, clinicians should be careful when using highly translucent colored zirconia to prevent breakage of veneering ceramic and enhance aesthetics.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.8
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• pp.1783-1788
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• 2009

We newly propose that we may reuse scrap powders ($Z_rO_2$+8 mol%-$Y_2O_3$) as $Y_2O_3$-stabilized zirconia (YSZ) sintered products through sintering process at 1550$^{circ}C$ for 2hrs. We also prepared the reference specimen from fresh $Z_rO_2$+30 mol%-$Y_2O_3$ powder mixture (celluar type with 1㎛-length). The reference sample showed a dense microstructure with grains of $\sim$10㎛ in diameter, while the sintered sample from scrap powder showed irregular grains of 1$\sim$30 ㎛ in diameter. Through XRD analysis, we confirmed that the reference sample has mixed phases of $Y_2O_3$(cubic), $Z_{r0.8}O_{1.9}$(cubic), and $Z_rO_2$(monoclinic), while the sintered YSZ sample from scrap powder has only tetragonal phase. Moreover, the sintered YSZ from scrap powder showed vickers hardness and apparent density more than 70 and 4.11 g/cc, which implies that it can be suitable for structural material application.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06b
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• pp.55-85
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• 1996

지르코니아 분말은 ZrO2 결정상이 온도변화에 따라 부피변화를 수반하는 상전이변태를 나타낸다. 단사정 ZrO2가 110$0^{\circ}C$에서는 정방정으로, 2$700^{\circ}C$ 내외에서는 입방정으로 결정구조가 가역적으로 변한다. 이 ZrO2에 금속산화물을 고용시키면 형석 (CaF2:Florite)형의 입방정 결정구조가 실온에서도 안정하게 존재하게 된다. 안정화제 산화물은 caO, MgO등 2가 산화물외에 3가 또는 4가의 금속산화물로서 Sc2O3, Y2O3, Sm2O3, Nd2O3, Gd2O3, Y2O3, CeO2 등이며 이들은 금속이온의 원자가가 변하기 쉬운 희토류 산화물이다. 안정화 지르코니아는 형석형 결정구조이며 결정화학적으로 보면 금속양이온이 산소이온에 대해서 정육면체형의 8배위를 하고 있다. 이때 이온반경비(양이온/음이온)에 따라 Zr+4자리와 O-2자리의 격자위치와 모양이 형성되므로 비틀어진 정육면체구조이건 이상적인 정육면체 형석구조를 이룬다. 이는 지르코니아의 결정상의 2상-3상인 부분안정화 지르코니아다결정체(PSZ : partially stabilized zirconia)이거나 단일상-2상인 정방정 지르코니아다결정체(TZP : tetragonal zirconia polycrystal)의 결정구조를 가지는데 기인한다. PSZ는 주로 MgO, CaO를 안정화제로 고용시켜 입방정 영역에서 소결하고 이를 다시 입방정과 정방정의 상 영역에서 열처리하여 입방정 입자내부에 정방정을 석출 형성시킨 것이며 TZP는 Y2O3 및 CeO2를 고용시켜 PSZ와 다르게 일반적인 상압소결한 정방정 결정상의 미립자이다. 산화지르코늄 분말은 지르콘사에서 열분해시킨 지르코늄소결.융해괴(caustic fusion clinker)를 산처리하여얻어진 지르코늄산용액(zirconyl acid solution : cloride, sulfide, nitride 등)으로부터 제조된다. 고순도 산화지르코늄은 용액 결정석출법에 의해 ZrOCl2.8H2O, 5ZrO2.3SO3.15H2O, ZrO(NO3)2.xH2O 등의 지르코늄 수화물만을 재결정화시킨 것으로부터 얻을 수 있으며 이 지르코늄염 수용액으로부터 입자미세구조를 효과적으로 제어하여 산화지르코늄 및 안정화 지르코니아 분말제조가 가능하다. 안정화 지르코니아 분말은 ZrO2와 안정화산화물의 고용을위하여 가열처리를 필요로 하며 일정온도에서 최적상태로 숙성하므로서 2가지 상(phase) 이상의 고용체를 가지게 된다. 안정화 지르코니아 분말은 고용처리온도를 낮추고 효과적으로 생성시키기 위해서는 지르코늄 및 안정화제염을 혼합하고 습식 직접합성하여 저온에서 고용체의 합해진상 영역을 생성시키는 것이다. 이는 지르코니아 원료분말의 미세구조를 제어하므로서 가능하며 이때 화학성분조성과 크기형태가 균일하게 분포된 입자분말을 얻을 수 있다.

• Membrane Journal
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• v.20 no.3
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• pp.210-216
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• 2010

The hydrogen permselective membrane were prepared by chemical vapor deposition (CVD) aiming at the applications to hydrogen iodide decomposition in the thermochemical IS process, and it was evaluated for the possibility as a separation membrane. An electron probe X-ray microanalyzer (EPMA) and SEM picture were used to analyze the morphology and structure of the prepared membranes. It was confirmed that Zr-Si-O layer exist in the surface of the prepared membrane using zirconia coated support. Single-component permeance to $H_2$ and $N_2$ were measured at $300{\sim}600^{\circ}C$. Hydrogen permeance through the Z-1 membrane at a permeation temperature of $600^{\circ}C$ was about $1{\times}10^{-7}\;mol{\cdot}Pa^{-1}{\cdot}m^{-2}{\cdot}s^{-1}$. The selectivities of $H_2/N_2$ at $600^{\circ}C$ were 5.0 and 5.75 for Z-1 and Z-2 membrane, respectively.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.2
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• pp.135-142
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• 2023

Resin-bonded fixed partial denture (RBFPD)as known as Maryland bridge is is a well-known conservative method for its minimized invasion of the teeth for an anterior single tooth edentulous area. Despite of its various advantages, RBFPD was not widespread because of its high debonding rates, non-esthetic look or weak structure for material property. Currently, with the introduction of zirconia to dental material for RBFPD, Maryland bridge entered upon a new phase. Zirconia surmounts poor esthetics of metal framework, having proper strength, and overcomes ceramic's structural weakness, being sufficiently esthetic. In this case, edentulous area of maxillary left lateral incisor was restored using zirconia resin-bonded fixed partial denture. Restoration of missing tooth in anterior area was achieved using non-invasive and esthetic prosthesis, then we report this case as satisfactory results were obtained for both the operator and the patient.

• Transactions of the Korean hydrogen and new energy society
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• v.14 no.3
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• pp.258-267
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• 2003

A new kind of oxygen carrier material is tested for chemical-looping combustion. NiO, CoO, $Fe_2O_3$ is chosen as metal oxide and YSZ as a binder. Hydrogen fuel is reacted with metal oxide (reduction of metal oxide) and then the reduced metal is successively oxidized by air. Dissolution method is examined to prepare the oxygen carriers. The effects of reaction temperature are measured by a TGA, mechanical strength and regenerability after 10 cycle are examined. $Fe_2O_3/YSZ$ oxygen carrier is bested in mechanical strength and we consider that NiO/YSZ after 3rd cycle are good oxygen carrier in according to reactor design.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.3
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• pp.227-233
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• 2023

Tardive dyskinesia is an involuntary neurological movement disorder caused by long-term use of dopamine receptor-blocking drugs leading to dental implications like uncontrolled gnashing and grinding of teeth which in turn imperil the oral rehabilitation procedures as the excessive load increases the risk of prosthesis fracture. A 40-year male with a medical history of tardive dyskinesia visited the hospital to receive oral rehabilitation for missing maxillary anterior teeth. After the oral examination, tooth preparation was done on teeth 13, 15, and 23. After that silicon impression was made and the gypsum cast was digitalized using a desktop scanner and an interim prosthesis was fabricated by milling a resin block. During the try-in, the occlusal one-third of the interim prosthesis was trimmed, and an auto-polymerizing acrylic resin was applied on the occlusal surfaces and inserted in the patient's mouth. Then, the functionally generated path (FGP) of occluding surfaces of opposing arches was traced on the resin surface. When the resin was hardened, the modified interim prosthesis was removed and digitized using an intraoral scanner. The scan image was used in designing the occlusal morphology of definitive prosthesis by modifying the design of the interim prosthesis using the dual scan method. Lastly, a monolithic zirconia prosthesis was fabricated by milling a zirconia block. The definitive prosthesis was delivered reflecting the patient's occlusal scheme. This case report shows that the FGP technique with the dual scan method can help in fabricating fixed prosthesis with harmonious occlusion in a tardive dyskinesia patient.