• 대한치과보철학회:학술대회논문집
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• 1996.11a
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• pp.72-73
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• 1996

• Journal of the Korean Academy of Esthetic Dentistry
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• v.9 no.1
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• pp.82-90
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• 2000

In esthetic dentistry, color and strength are basic requirements for the long-term success of the restorative materials. Several all ceramic systems have been introduced to esthetic dentistry recently. However, the inherent natures of ceramic material, the application of all ceramic system is mainly limited to single tooth restorations. With the improvement of material science, the alumina and zirconia/alumina composite power and block can be applied to fabrication of all ceramic bridges. The conventional inceram core fabrication takes time for sintering however, the shaping of block with a copy milling machine can reduce great amount of time. The block is easy to manipulate and prepare in any shape accurately. This clinical report demonstrates the application of all ceramic ante rior 3 unit bridge with a alumina block in CELAY system.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.5 no.1
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• pp.23-33
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• 1996

• Journal of Technologic Dentistry
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• v.34 no.2
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• pp.95-103
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• 2012

Purpose: Fracture strength of all-ceramic 3-unit fixed partial dentures manufactured by CAD/CAM and copy-milling systems were evaluated. Methods: Zirconia cores were made by milling the pre-sintered zirconia block by CAD/CAM or copy milling method followed by subsequent sintering. By building-up the corresponding porcelains on the core, all-ceramic bridges were fabricated, and those were evaluated in comparison with PFM fixed partial denture. Results: During the flexural test of the 3-unit PFM bridge, the porcelain started to chip or break at 507.28(${\pm}62.82$)kgf and the metal framework did not break until the maximum load level of 800kgf which was set in the testing instrument of this study. However, among all-ceramic restoration test groups, Everest(EV) group showed a peeling off or breakage of the porcelain from 365.64(${\pm}64.96$)kgf and the core was broken at 491.77(${\pm}55.62$)kgf. Those values of Zirkonzahn(ZR) were 431.03(${\pm}58.47$)kgf and 602.74(${\pm}48.44$)kgf, respectively. The break strength of the porcelain of PFM(PM) group was significantly higher than that of EV (p<0.05) group and there was no significant difference when comparing to that of ZR (p>0.05). ZR group showed higher break strength than that of EV group however there was no significant difference (p>0.05). The break strength of cores were in the increasing order of EV < ZR < PM (p<0.05). Conclusion: We could find that even though the PM group fractured at much higher value than all-ceramic cores, the breakage values of the porcelain of PM group with crack formation or delamination, which will be regarded as clinical failure, was significantly higher than that of EV group and not significantly higher than that of ZR group at p-values of 0.05. The break strength of ZR group was higher than that of EV group at an insignificant level(p>0.05).

• Journal of Powder Materials
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• v.20 no.1
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• pp.53-59
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• 2013

Fe-TiC composite powder was fabricated via two steps. The first step was a high-energy milling of FeO and carbon powders followed by heat treatment for reduction to obtain a (Fe+C) powder mixture. The optimal condition for high-energy milling was 500 rpm for 1h, which had been determined by a series of preliminary experiment. Reduction heat-treatment was carried out at $900^{\circ}C$ for 1h in flowing argon gas atmosphere. Reduced powder mixture was investigated by X-ray Diffraction (XRD), Field Emission-Scanning Electron Microscopy (FE-SEM) and Laser Particle Size Analyser (LPSA). The second step was a high-energy milling of (Fe+C) powder mixture and additional $TiH_2$ powder, and subsequent in-situ synthesis of TiC particulate in Fe matrix through a reaction of carbon and Ti. High-energy milling was carried out at 500 rpm for 1 h. Heat treatment for reaction synthesis was carried out at $1000{\sim}1200^{\circ}C$ for 1 h in flowing argon gas atmosphere. X-ray diffraction (XRD) results of the fabricated Fe-TiC composite powder showed that only TiC and Fe phases exist. Results from FE-SEM observation and Energy-Dispersive X-ray Spectros-copy (EDS) revealed that TiC phase exists uniformly dispersed in the Fe matrix in a form of particulate with a size of submicron.

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.2
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• pp.417-430
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• 1997

The purpose of this study was to compare the fracture resistance of copy-milled and conventional In-Ceram crown. Four groups of ten uniform sized all-ceramic crowns were fabricated. In-Ceram Spinell and In-Ceram Alumina crowns were fabricated as control group, Celay In-Ceram Spinell and Celay In-Ceram Alumina crowns were fabricated as test group. All specimen were cemented on stainless steel master die with resin cement, and stored in $37^{\circ}C$ water for 1 day prior to loading in Instron testing machine. Using a steel ball at a crosshead surfed of 0.5mm/min, the crowns were loaded at $30^{\circ}C$ angle until catastrophic failure occurred. The results obtained were as follows : 1. With the value of $984.8N{\pm}103.67N$, the strength of Celay In-Ceram Alumina crowns had a significantly higher fracture strength than conventional In-Ceram Alumina crowns ($876.2N{\pm}92.20N$) (P<0.05) 2. The fracture strength of Celay In-Ceram Spinell crowns($706.3{\pm}70.59N$) was greater than that of conventional In-Ceram Spinell crowns($687.4{\pm}90.26N$), but there was no significant difference(P>0.05). 3. The In-Ceram Alumina crowns had a significantly higher fracture strength than In-Ceram Spinell crowns in both methods(P<0.05). 4. Ther order of fracture strength was as followed : Celay In-Ceram Alumina, In-Ceram Alumina, Celay In-Ceram Spinell and In-Ceram Spinell crowns

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.3
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• pp.243-249
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• 2001

Statement of the problem. The interest in all-ceramic restorations has increased as more techniques have become available. With the introduction of machinable dental ceramics and CAD/CAM systems or Copy-milling systems there is a need for evaluating the quality levels of these new fabrication techniques. Purpose. This study was to evaluate the fitting accuracy of machined all-ceramic crowns made out of an industrially prefabricated feldspathic porcelain. Material and Methods. Three master models with different cutting depth (0.8mm/1.0mm/1.2mm)were produced using a palladium-silver alloy. A total of 36 working dies, 12 of each form, was used for the modellation of prototype resin copings and 36 additional crowns, 12 of each cutting depth, were produced by using the $CEREC^{(R)}2$ system for all crowns. The maginal fit of all 72 crowns was then evaluated on their respective master die at 54 circularly staggered points of measurement per crown under a fixation pressure of 30 N by using a computerized video image system. Results. The medians of the copy-milled $CELAY^{(R)}$ crowns ranged from 29 to $36{\mu}m$. The highest value for the marginal gap was found in group B (cutting depth 1.0mm) at $107{\mu}m$. The median for the $CEREC^{(R)}2$ crowns was found between 43.5 and $70{\mu}m$. The maximum values for all three groups ranged from $181{\mu}m$ to $286{\mu}m$. With $286{\mu}m$ the highest value for marginal gap was found in group C. the Kruskal-Wallis test and multiple comparisons analysis procedure revealed a significant influence of the production technique on the marginal fit in all three groups (p<0,02). Conclusion. 1. The $CELAY^{(R)}$ system is capable to produce all-ceramic crowns with a significantly better marginal fit than the $CEREC^{(R)}2$ system. 2. As far as premolar crowns produced with the $CEREC^{(R)}2$ system are concerned, the cutting depth has a significant influence on fitting accuracy. 3. The production of crowns with an acceptable marginal fit is possible with both systems. However, adhesive luting is recommended for milled feldspathic porcelain crowns.

• Journal of Technologic Dentistry
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• v.35 no.1
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• pp.49-56
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• 2013

Purpose: The deformation characteristics induced by non-destructive stresses using piezoelectric transducer(PZT) were analyzed for 3-unit fixed partial dentures manufactured PFM, Everest(CAD/CAM) and Zirkonzahn(copy milling, MAD/MAM) by electron speckle pattern interferometery(ESPI). Methods: The ESPI analysis after loading the restoration with PZT by applying electric voltage of 900mV at the points of 10 mm above the base of the prostheses. Results: PFM and All-Ceramic Everest prostheses showed about 0.1 ${\mu}m$ while that of All- Ceramic Zirkonzahn prostheses showed 0.085 ${\mu}m$, demonstrating that Zirkonzahn displaced less. For PFM and All-Ceramic Zirkonzahn prostheses, the displacements were large at just below the loading point, while generalize displacement was shown over the loading point and weak connector areas for All-Ceramic Everest prostheses. Conclusion: We could find that the deformation characteristics induced by non-destructive stresses using PZT analyzed by ESPI were similar to the fracture strengths evaluated using universal testing machine.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.2
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• pp.131-139
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• 2002

There have been many studies about marginal discrepancy of single restorations made by various systems and materials. But many of statistical inferences are not definite because of sample size, measurement number, measuring instruments. etc. The purpose of this study was to compare the marginal adaptations of the anterior single restorations made by different systems and to consider more desirable statistical methods in analysing the marginal fit. The in vitro marginal discrepancies of three different all-ceramic crown systems (Celay In-Ceram. Conventional In-Ceram. IPS Empress 2 layering technique) and one control group (PFM) were evaluated and compared. The crowns were made from one extracted maxillary central incisor prepared with a 1mm shoulder margin and $6^{\circ}$ taper walls by milling machine. 10 crowns per each system were fabricated. Measurements or a crown were recorded at 50 points that were randomly selected for marginal gap evaluation. Non-parametric statistical analysis was performed for the results. Within the limits of this study, the following conclusions were drawn: 1 Mean gap dimensions and standard deviations at the marginal opening for the maxillary incisor crowns were $98.2{\pm}40.6{\mu}m$ for PFM, $83.5{\pm}18.7{\mu}m$ for Celay In-Ceram, $104.9{\pm}44.1{\mu}m$ for conventional In-Ceram, and $45.5{\pm}11.5{\mu}m$ for IPS Empress 2 layering technique. The IPS Empress 2 system showed the smallest marginal gap (P<0.05). The marginal openings of the other three groups were not significantly different (P<0.05). 2 The marginal discrepancies found in this study were all within clinically acceptable standards ($100\sim150{\mu}m$). 3. When the variable is so controlled that the system may be the only one, mean value is interpreted to be the marginal discrepancy of a restoration which is made by each system and standard deviation is to be technique-sensitivity of each one. 4. From the standard deviations. the copy-milling technique (Celay/In-Ceram) was not considered to be technique-sensitive in comparison with other methods. 5. Parametric analysis is more reliable than non-parametric one in interpretation of the mean and standard deviation. The sample size of each group has to be more than 30 to use parametric statistics. The level of clinically acceptable marginal fit has not been established. Further studies are needed.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.6
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• pp.757-764
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• 2000

Statement of the problem. All-ceramic post-and-core restorations offer a number of advantages compared with systems that use metal build-ups. In certain clinical cases, however, fractures at the joint between the post and core build-up have been reported. Purpose. The objective, therefore, is to improve the joint between the post and the core build-up. Material and methods. Three different methods were used to prepare all-ceramic post-and-core restorations; pressing IPS Empress core build-ups to CosmoPost zirconia posts, cement-ing IPS Empress core build-ups to CosmoPost zirconia posts and Celay-milling of zirconia blanks. A series of ten restorations was prepared for each of the three methods. The post-and-core complexes were tested to failure with the load applied perpendicular to the post axis. The load and deflection at fracture were recorded. Results. The highest breaking load and highest deflection were recorded for the cementing technique with values of 25.3 N and $394{\mu}m$, respectively, The corresponding values for the pressed core build-ups and the milled zirconia core build-ups were 22 N and $301{\mu}m$, and 13 N and $160{\mu}m$, respectively. All the differences are statistically significant (p=0.05). Regarding the load-dependence of the deflection, the cemented core build-ups again demonstrated the highest value with $15.5{\mu}m/N$. The difference in the values of $13.6{\mu}m/N\;and\;13{\mu}m/N$ recorded for the pressed-on and milled core build-ups, respectively, were statistically insignificant. Conclusion. In regard to the high fracture resistance of zirconia post, adhesive cementing the core build-up to the post offers a viable alternative to the conventional pressing technique. The elastic bond between the rigid high-strength zirconia post and the core build-up presents an additional advantage.