• 한국세라믹학회지
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• 제21권4호
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• pp.366-372
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• 1984

Unstabilized Zirconia was added to basic composition under 44$mu extrm{m}$ of 57.80wt% Clay-22.20wt% Chamotte-20.00wt% Agalmatolite system. Here the amount and the particle size of Zirconia were 5-25wt% and -20${\mu}{\textrm}{m}$ respectively and the body of these composition was first at 135$0^{\circ}C$. The results obtained from examining the properties of sintered body were as follows. 1. Firing linear shrinkage apparent density and bulk density apparent porosity and water absorption of the samples had the tend to increase according as the particle size of zirconia became larger and the amount of zirconia increased. 2. Modulus of rupture was inversely proportional to the particle size and the additive amount of zirconia, . Especially in case that the particle size of zirconia over 5${\mu}{\textrm}{m}$ and the additive amount of zirconia was 25wt% the modulus of rupture had shrunk drastically. 3. The maximum value of KIC was obtained at 20wt% additive amount of zirconia according to the each particle size of zirconia. Especially the highest value of KIC is 2, 173 M. Pa. M1/2 when the particle size of zirconia is 5~10${\mu}{\textrm}{m}$ and the additive amount is 20wt%.

• 한국표면공학회지
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• 제42권1호
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• pp.41-46
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• 2009

The fit between dental implant fixture and zirconia abutment is affected by many variables during the fabrication process by CAD/CAM program and milling working. The purpose of this study was to evaluate the surface compatibility and electrochemical behaviors of zirconia abutment for prosthodontics. Zirconia abutments were prepared and fabricated using zirconia block and milling machine. For stabilization of zirconia abutments, sintering was carried out at $1500^{\circ}F$ for 7 hrs. The specimens were cut and polished for gap observation. The gap between dental implant fixture and zirconia abutment was observed using field-emission scanning electron microscopy (FE-SEM). The hardness and corrosion resistance of zirconia abutments were observed with vickers hardness tester and potentiostat. The gap between dental implant fixture and zirconia abutment was $5{\sim}12{\mu}m$ for small gap, and $40{\sim}60{\mu}m$ for large gap. The hardness of zirconia surface was 1275.5 Hv and showed micro-machined scratch on the surface. The corrosion potentials of zirconia abutment/fixture was .290 mV and metal abutment/fixture was .280 mV, whereas $|E_{pit}-E_{corr}|$ of zirconia abutment/fixture (172 mV) was higher than that of metal abutment/fixture (150 mV). The corrosion morphology of metal abutment/fixture showed the many pit on the surface in compared with zirconia abutment/fixture.

• 대한치과기공학회지
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• 제33권2호
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• pp.137-145
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• 2011

Purpose: To evaluate the accuracy of zirconia copings in terms of clinical verified for the clinical application of CAD/CAM. Methods: Zirconia copings (n=5) were prepared using CAD/CAM system and were sintered using the relevant electrical induction furnace, which uses a 2h sintering program with a maximum temperature of $1500^{\circ}C$. The copings placed at the models and the interval values were measured. Results: The meas interval values between the die and the zirconia copings were $44.14{\mu}m$(A), $44.57{\mu}m$(B), $44.72{\mu}m$(C). 51.05 ${\mu}m$(D). Conclusion: The maximum interval values between the die and the zirconia copings were $51.3{\mu}m$ which is acceptable for clinical use. ${\mu}m$ Proper understanding of the test conditions will help enhancing the accuracy of zirconia coping.

• 한국콘텐츠학회논문지
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• 제16권1호
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• pp.151-157
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• 2016

구강인기방법과 지르코니아 블록 종류에 따른 지르코니아 코핑의 변연적합도 변화를 관찰하기 위해 2종의 고무인상재와 1종의 구강스캐너를 사용한 구강인기방법과 3종의 지르코니아 블록을 사용하여 지르코니아 코핑을 10개씩 제작하여 표면 거칠기와 변연적합도를 측정하였다. 표면 거칠기는 LUXEN Smile($2.3{\pm}0.9{\mu}m$) 블록이 가장 우수하였다. 그리고 협측 변연간격은 HL시편($26.5{\pm}2.1{\mu}m$), 설측 변연간격은 HL시편($27.2{\pm}2.1{\mu}m$), 근심 변연간격은 HJ시편($29.6{\pm}4.0{\mu}m$), 원심 변연간격은 HJ시편($29.0{\pm}3.0{\mu}m$)이 가장 낮게 나타났으며, 통계학적으로 유의차가 있었다(p<0.05). 이 결과, 구강인기방법과 지르코니아 블록 종류가 변연적합도에 영향을 준 것으로 나타났으며, 변연간격은 모든 군에서 임상적 허용 범위 내에 속했다.

• 구강회복응용과학지
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• 제34권4호
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• pp.306-316
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• 2018

단일 구조 지르코니아는 높은 강도와 파괴 인성을 갖고 있어 고정성 보철 치료에 많이 활용되고 있으나 지르코니아 자체의 불투과성으로 인한 심미적인 한계 때문에 전치부 사용에서 어려움이 있었다. 최근에는 기존 단일 구조 지르코니아보다 투과성이 우수하며, 다양한 착색법을 이용하여 심미성을 개선한 지르코니아 블록들이 개발되고 있다. 3M $Lava^{TM}$ Esthetic 지르코니아는 제조사에 따르면 육방정계 결정상의 비율을 증가시키고 형광성 성분을 추가하여 기존 지르코니아보다 심미성이 우수하다고 소개되고 있다. 본 증례들에서는 심미성을 개선한 단일 구조 지르코니아를 이용하여 전치부를 수복하였으며 기능적, 심미적으로 만족한 결과를 얻었기에 이를 보고하는 바이다.

• 대한치과보철학회지
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• 제43권5호
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• pp.611-621
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• 2005

State of problem: Zirconia all-ceramic restoration fabricated with CAM system is on an increasing trend in dentistry. However, evaluation of the marginal and internal fits of zirconia bridge seldomly have been reported. Purpose: This study was to evaluate the at of margin and internal surface in posterior 3-unit zirconia bridge framework fabricated with CAM system(DeguDent, Germany). Material and Method: Preparations of secondary premolar and secondary molar on artificial resin model were performed for fabrication of 3-unit posterior bridge framework. Fits of 5 zirconia bridge framework were compared with 5 precious ceramo-metal alloy framework(V-GnathosPlus, Metalor, Switzerland), and prepared margins were designed to chamfer and shoulder finishing line. Each framework was cemented to epoxy resin model with reinforced glass ionomer(FujiCEM, GC Co., Japan), embedded in acrylic resin and sectioned in two planes, mesio-distal and buccolingual. Samples were divided into six pieces by sectioning and had two pieces of each surface(i.e mesial, distal, buccal and lingual surface) per abutment, so there were eight measuring points in each abutment. External gap was measured at the margin and internal gaps were measured at the margin, axial and occlusal surface. Gaps were observed under the measuring microscope(Compact measuring microscope STM5; Olympus, Japan) at a magnification of $\times100$. T-test were used to determine the statistic significance of the different gaps between zirconia and metal framework. Results and Conclusion: 1. External and internal marginal gaps of zirconia and metal framework were in clinically acceptable range. External marginal gaps were not different significantly between zirconia$(81.9{\mu}m)$ and metal $(81.3{\mu}m)$ framework and internal marginal gaps of zirconia $(44.6{\mu}m)$ were smaller than those of metal framework $(58.6{\mu}m)$. 2. Internal axial gaps of zirconia framework$(96.7{\mu}m)$ were larger than those of metal frame-work$(78.1{\mu}m)$ significantly and adversely, internal occlusal gaps of zirconia frame-work$(89.4{\mu}m)$ were smaller than those of metal framework $(104.9{\mu}m)$ significantly. 3. There were no significant differences in external and internal marginal gaps between chamfer and shoulder finish line when zirconia frameworks were fabricated.

• 한국재료학회지
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• 제24권12호
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• pp.652-657
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• 2014

The purpose of this study was to investigate the microstructures and mechanical properties of zirconia toughened alumina (ZTA) ceramics prepared from two kinds of 3Y-TZP powders. ZTA composites were prepared by adding two kinds of 3Y-TZP powders, 3YEH (BET = $7m^2/g$) and 3YEM (BET = $16m^2/g$), to ${\alpha}$-alumina in the range of 5-25 wt%. It was found that the microstructure photographs of the ZTA composites showed that the average grain size of alumina decreased as the content of zirconia increased. In our present study, specimens containing 3YEM zirconia exhibited smaller grain sizes compared to those of 3YEH zirconia. The Vickers hardness of the ZTA composites that were sintered at $1600^{\circ}C$ for 2 hrs was found to smoothly decrease with increasing zirconia content because of the low Young modulus in zirconia. The Vickers hardness of the ZTA containing 3YEH zirconia was greater than that of the 3YEM zirconia. In substance, the fracture toughness ($K_{1c}$) of the ZTA composites increased as the content of zirconia increased. The fracture toughness ($K_{1c}$) of ZTA containing 3YEM zirconia was greater than that of 3YEH zirconia.

• The Journal of Advanced Prosthodontics
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• 제10권2호
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• pp.132-137
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• 2018

PURPOSE. The purpose of this study was to evaluate and compare three polishing systems on the surface roughness and phase transformation of monolithic zirconia. MATERIALS AND METHODS. 100 disk shaped specimens (10 mm diameter, 3 mm thickness) were fabricated from monolithic zirconia blocks. 20 specimens were left as a control group and remaining specimens were grinded by diamond bur to simulate the occlusal adjustments. Grinded specimens were randomly divided into 4 groups: group G (no polishing), group M (Meisinger, zirconia polishing kit), group E (EVE Diacera, zirconia polishing kit), and group P (EVE Diapol, porcelain polishing kit). Surface roughness was measured with profilometer and surface topography was observed with SEM. XRD analysis was performed to investigate the phase transformation. Statistical analysis was performed with one-way ANOVA and Tukey's post hoc tests at a significance level of P=.05. RESULTS. All polishing groups showed a smoother surface than group G. Among 3 polishing systems, group M and group E exhibited a smoother surface than the group P. However, no significant differences were observed between group M and group E (P>.05). Grinding and polishing did not cause phase transformations in zirconia specimens. CONCLUSION. Zirconia polishing systems created a smoother surface on zirconia than the porcelain polishing system. Phase transformation did not occur during the polishing procedure.

• 한국세라믹학회지
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• 제29권10호
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• pp.757-764
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• 1992

The platelet reinforced mullite-zirconia composites were prepared by pressurelss sintering with addition of Al2O3 or SiC platelets. The sintered density of 10 vol% Al2O3 platelet reinforced mullite-zirconia composite was 98.3% at 1700$^{\circ}C$. The fracture strength (290 MPa) and fracture toughness (4.9 MPa$.${{{{ SQRT { m} }}) in the Al2O3 platelet reinforced mullite-zirconia composite were enhanced compared with those of mullite-zirconia due to the crack deflection and load transfer effect of platelets. Whereas, the SiC platelet reinforced mullite-zirconia composite sintered at 1650$^{\circ}C$ showed relatively lower density (95.7%), fracture strength (170 MPa), and fracture toughness (3.9 MPa$.${{{{ SQRT { m} }} than the Al2O3 platelet reinforced mullite-zirconia composite.

• 한국세라믹학회지
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• 제45권9호
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• pp.537-543
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• 2008

Effect of template size ratio on porosity and mechanical properties of porous zirconia ceramics were investigated using two different size (${\sim}8{\mu}m$ and ${\sim}50{\mu}m$ in diameter) of polymethyl methacrylate-coethylene glycol dimethacrylate (PMMA) microbeads as sacrificial templates. Porosity of the porous zirconia ceramics increased with decreasing the template size ratio ($8{\mu}m: 50{\mu}m$) whereas the compressive and flexural strengths of the porous zirconia ceramics increased with increasing the template size ratio. By controlling the template size ratio, sintering temperature and sintering time, it was possible to produce porous zirconia ceramics with porosities ranging from 57% to 69%. Typical flexural and compressive strength values of porous zirconia ceramics with ${\sim}60%$ porosity were ${\sim}37\;MPa$ and ${\sim}85\;MPa$, respectively.