• 대한치과보철학회지
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• 제33권2호
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• pp.198-209
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• 1995

In order to evaluate the fitness and the degree of rounding of porcelain margins in collarless metal cermic restorations, collarless metal ceramic restorations were fabricated with shoulder margins of 90 and 120 degress, each consisting of ten specimens, on master dies through the direct lift technique. And ten metal ceramic restorations with a shoulder 90 degrees were fabricated. All specimens were embedded in resin and sectioned longitudinally. The sections were observed under a stereomicroscope and photographed(${\times}$200). The labial marginal gap between the die and the porcelain margin were measured with a scale. The space between the porcelain margin and the die, that is formed from marginal rounding and cementation were calculated with a computer coordinating area curvimeter. The following results were obtained. 1. There was no statistical difference between the fitness of porcelain margin of collarless metal ceramic restorations and marginal fitness of metal ceramic restoration. 2. There was no statistical difference between a shoulder of 90 and 120 degrees in the fitness of porcelain margin of collarless metal ceramic resorations. 3. Collarless metal ceramic restorations with a shoulder of 90 degrees and 120 degrees showed significantly more labial marginal rounding than metal ceramic restorations. 4. There was no statistical difference between a shoulder of 90 and 120 degrees in rounding of porcelain margin of collarless metal ceramic restorations. According to the results, rounding of porcelain margins can be observed in collarless metal ceramic restorations. Thus, there is a need for improvement in dental materials and techniques to minimize this problem, Furthermore, care should be exercised during the clinical procedure.

• 대한치과기공학회지
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• 제31권1호
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• pp.23-36
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• 2009

The goal of esthetic restoration is to achieve morphologic, optical, and biologic acceptance. Creation of a natural looking ceramic restoration, which blends harmoniously with surrounding dentition, is not always achieved. A successful color match is an important aspect of any esthetic dental restoration. Since natural enamel has inherent translucency, it is important that ceramic restorations reproduce the translucency and color of the natural teeth. However, the final color match of porcelain crowns to adjacent natural dentition remains some problem. Difficulties related to color matching arise from the structural differences that exist between metal ceramic crowns and natural teeth, the limited range of available ceramic shades, inadequate shade guides, different types of metal alloys, repeated firing, the condensation technique, and varying compositions of ceramic materials. Many factors contribute to the esthetic success of dental restoration: optical properties such as color and its elements of hue, value, and chroma; translucency and opacity; light transmission and scattering; and metamerism and fluorescence. The purpose of this study was to determine the color changes of metal-ceramic system with different veneering porcelain powder after repeated firing. The objectives of this in vitro study were to measure the lightness($L^*$), chromaticity($a^*$), chromaticity($b^*$), chroma($C^*$), hue(h), reflectance(%), color difference(${\Delta}E$). The following conclusions were obtained: 1. An increase in the number of firings resulted in decrease in lightness($L^*$) but increase in chromacticity($a^*$) with all porcelain. After the second sintering resulted in decrease in chromacticity($b^*$) with opaque-dentin porcelain and dentin porcelain but in increase with enamel porcelain and translucency porcelain. And after the second sintering resulted in decrease in chroma($C^*$) with opaque-dentin porcelain and dentin porcelain, but on the whole side in decrease with enamel porcelain and translucency porcelain. 2. After the second firing, a increase in the number of firings resulted in decrease reflectance(%) in all wavelength. 3. There were noticeable color differences(${\Delta}E$) between first sintering and multiple firings(dentin porcelain: 5.29~8.15, opaque-dentin porcelain: 4.83~8.2, enamel porcelain: 8.93~13.15, translucency porcelain: 9.37~12.91), but the color difference(${\Delta}E$) after second sintering were down to 4.87 in all porcelain. 4. Given the NBS Criteria, a 'trace' was not found this study but a 'slight' was found 2-3, 3-5 in dentin porcelain, 2-3 in opaque-dentin porcelain, 3-5, 5-10 in enamel porcelain and translucency porcelain, a 'noticeable' was 2-5, 3-10, 5-10 in dentin porcelain and opaque-dentin porcelain, 2-3, 2-5, 3-10 in enamel porcelain 2-3, 3-10 in translucency porcelain, an 'appreciable' was 1-2, 1-3, 2-10 in dentin porcelain 1-2, 1-3, 2-10, 3-10 in opaque-dentin porcelain, 2-10 in enamel porcelain, 2-5, 2-10 in translucency porcelain, a 'much' was 1-5, 1-10 in dentin porcelain and opaque-dentin porcelain, 1-2, 1-3, 1-5 in enamel porcelain 1-2, 1-3, 1-5, 1-10 in translucency porcelain, a 'very much' was 1-10 in enamel porcelain.

• 구강회복응용과학지
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• 제28권3호
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• pp.223-232
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• 2012

이번 연구는 금속 내관에 축성된 도재의 두께가 도재의 전단 결합 강도에 어떠한 영향을 주는지 알아보기 위하여 장석계 도재와 열가압 성형 도재를 다양한 두께로 축성하여 비교하였다. 120개의 금속 정육면체($4{\times}4{\times}4mm$)를 주조하여 제작한 후, 60개는 장석계 도재를, 나머지 60개는 열가압 성형 도재를 각각 1mm, 1.5mm, 2mm, 2.5mm, 3mm 그리고 3.5mm 두께로 축성하여 시편을 제작하였다. 전단 결합 강도 측정을 위해 Instron univeral testing machine에서 측정하여 비교하여 다음과 같은 결과를 얻었다. 1) 장석계 도재에서는 도재 두께가 두꺼워지면서 전단 결합 강도가 낮아지는 것으로 나왔으며, 1mm 도재 두께에서 전단 결합강도가 유의하게 높게 나왔다. 2) 열가압 성형 도재에서 도재 두께에 따른 전단 결합 강도에는 유의한 차이가 없었다. 3) 같은 두께의 장석계 도재와 열가압 성형 도재의 전단 결합강도 비교에서 장석계 도재가 높은 전단 결합강도를 나타냈으며, 두께가 1mm와 3mm일 때 유의하게 높게 나타났다. 4) 금속과 도재 사이 파절 양상은 대부분의 시편에서 금속면과 도재면이 함께 관찰되는 cohesive failure와 adhesive failure가 혼재된 양상으로 나타났으며, 도재의 두께가 증가함에 따라 금속 노출면이 감소하였다.

• 대한치과기공학회지
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• 제31권3호
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• pp.15-20
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• 2009

The success of the porcelain fused to gold alloy restoration depends not only on the choice of materials but to a larger degree on the technical skills. The porcelain fused to metal(PFM) alloys containing gold are commonly use for dental purposes in dental laboratory. The gold-colored alloys contain primarily gold, platinum, palladium, and silver, with minimum amounts of such metals as tin, iridium, or titanium. The purpose of this study is on the metal-porcelain fusing layer in porcelain fused to high gold alloy Principal results are as follows. The hardness number(Hv) of PFG is respectively $140.2{\pm}12.6$ in as-casted, $164.3{\pm}14.3$ in heat-treated, $186.6{\pm}20.4$ in fired-treated. The formation of the fusing(intermediate) layer caused by components fusing the interface of porcelain and gold alloy. The main components of the fusing(intermediate) layer are Na, Al, Si, K, Zn, Zr and Ce. The intermediate layer formed by the 2nd firing is more larger than the intermediate layer formed by the 1st firing.

• 대한치과기공학회지
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• 제29권2호
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• pp.173-180
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• 2007

There was a great problem about the deposition between materials of a different kind at the beginnings of the introduction of porcelains, however, thereafter the deposition efficiency was settlded to the sufficient level of all user thanks to effort to have studied by many scholars and clinical authorities. But in a clinical process, as the difference of designs has an effect on fractures of porcelains, this researcher divided them into 4 groups of A: 1 mm, B: 2 mm, C: 3 mm, and D: 4 mm, and made 40 pieces to each 10 as the test samples to consider a length axis of tooth for studies in accordance with a position of a finishing line to meet between porcelain and metal at the contact point at the adjacent side to a metal porcelain. The sample materials are those to be use at the open market and the test samples wer completed by the same manufacturing technique to that of existent metal porcelain tube. s a result of the strength test on fractures, the average value is as in the following, A: 1 mm - 8.5bar, B: 2 mm - 10.5bar, C: 3 mm - 14.3bar, and D: 4 mm - 15.0bar. In case of the metal porcelain tube, the more faraway to process parts of metal and porcelain from the contact point of adjacent side has the stronger strength of fractures, Accordingly, the research shows that it had better to keep off more than 3 to consider a ledngth axis of tooth.

• 대한치과기공학회지
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• 제33권1호
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• pp.37-45
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• 2011

Purpose: Heat pressed ceramics, used for all ceramic restorations, have the additional advantage of being technically less change through using of the lost-wax technique. Conceptually, combining the ceramic with the clinically proven reinforcing ability of a metal framework would be advantageous; however, cause of mismatching of fusion between ceramics and metal frameworks which from differences of casting temperature and coefficient of thermal expansion, pressed ceramics could not be used with a metal framework. The purpose of this study was to compare shear bond strength of press-to metal ceramic to porcelain fused non precious metal and feldspatic porcelain fused non precious metal. Methods: The 30 metal specimens were casted in a porcelain fused non precious metal nickel-chromium alloy. They were divided into 3 groups by surface treatment and applied ceramic: $125{\mu}m$ aluminium oxide sandblasting and veneered feldspatic porcelain (group FP), $125{\mu}m$ aluminium oxide sandblasting and had press-to-metal ceramic applied (group PC), porcelain bonder (gold bonder) fused on surface of metal specimens and had press-to-metal ceramic applied (group PCG). In each group 10 metal specimens were used. The press-to-metal ceramic applied 20 specimens had ash-free wax pattern applied, the metal-wax complexes invested, and were pressed with heat press ceramic. All specimens were subjected to shear bond strength test at a crosshead speed of 1.0 mm/min. Results: The results of measured in Mean SD and data were analyzed by one-way AVOVA (p= .05) and Tukey HSD test (p= .05).: group FP $16.090{\pm}1.841$ MPa, group PC $12.620{\pm}1.8256$ MPa, group PCG $10.920{\pm}0.9283$, significant differences between all groups (p < .05). Significant differences were found in each between group FP and group PC, group FP and group PCG (p < .05). Conclusion: The shear bond strength of press-to-metal ceramic to porcelain fused non precious metal was described higher in unused gold bonder group than used gold bonder groups.

• 대한치과보철학회지
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• 제25권1호
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• pp.161-179
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• 1987

To study the mechanical behaviors of the margins of porcelain-fused-to-metal crown on the posterior teeth, 5 types of margins on the lower first molar were chosen, and then the finite element models were constructed. 50kg forces were applied to the porcelain on the axial wall supported by the metal vertically. The displacements and stresses of the porcelain-fused-to-metal crown were analyzed to investigate the influence of the type of margins. The results were as follows; 1. High tensile stresses were exhibited on the porcelain of the portion of the coronal line angle insufficient metallic support. 2. In case metal coping had a good supporting form to vertical force, uniform compressive stresses were exhibited on their supporting form. 3. Tensile stresses in the inframetallic margin on the series of the shoulder with a bevel margins were decreased in the bevel portion. 4. Principal stresses on the metal of the chamfer marginal portion were decreased comparing with the series of the shoulder margins. 5. The noticeable compressive stress gradients were exhibited between axial cement layer and metal on the series of the shoulder margins. 6. The principal stresses on the marginal cement layer were higher than that of the occlusal surface and axial wall.

• 대한심미치과학회지
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• 제11권2호
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• pp.33-36
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• 2002

As patients have concerned the esthetics of dental restorations, the porcelain fused to metal restorations have gain their popularity due to their strength and esthetic appearance for many years. However, metal collar in subgingival level of porcelain fused to metal restoration often causes black shadows. Inadequately positioned metal collar causes plaque depositions, gingival inflammations, black shadows, and discolorations of margin area. Those problems can be avoided by a clear finishing line, well-fabricated provisional restorations with precise margin and fine polishing, collarless porcelain fused to metal restoration, and all ceramic restoration. In this case report, collarless porcelain fused to metal restoration was used to treat cervical discoloration from old restorations.

• 대한치과기공학회지
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• 제5권1호
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• pp.27-30
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• 1983

적은 경비로써 보다 양호한 치경부의 적합과 Shade를 얻고 치경부의 변색을 막기 위하여 도재소부용 귀금속과 비금속, 그리고 귀금속과 비금속위에 도금을 하는 4가지 유형으로 나누어 실험하였던 바 다음과 같은 결과를 얻게 되었다. 1. 도재소부용 귀금속으로 치관전체를 주조하는 경우는 수축율이 적고 연성이 뛰어나 경비가 많이 소요된다. 2. 비금속으로 치관전체를 주조하는 경우는 경비는 저렴하나 치경부의 적합성이 금속에 따라 차이가 있으며 그 중 Gemini II가 가장 우수하였다. 3. 비금속으로 치관 전체를 주조하고 10K의 Gold로 도금하는 경우는 적합성에서는 비금속과 동일하나 도금이 고리게 되지 않고 Shade에서도 별 효과가 없었다. 4. 치관의 윗부분은 비금속으로 먼저 주조하여 Degassing한 후 나머지 2mmwjd도의 치경부를 귀금속으로 주조하는 경우는 치경부의 적합성은 귀금속과 동일하게 우수하고 경비 또한 매우 저렴하였다.

• 대한치과보철학회지
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• 제18권1호
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• pp.49-57
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• 1980

The adhesive mechanisms on the metal-ceramic restorations have been reported to be mechanical interlocking, chemical bonding, compressive force, and Van der Waal's force, etc. Of these, the mechanical interlocking and chemical bonding forces are thought to affect the adhesive force between Ni-Cr alloy and porcelain. This study investigates the adhesion of Ni-Cr alloy to porcelain according to surface treatment. For this purpose, the following experiments were made; The compositions of Ni-Cr alloy as cast by emission spectrograph, and the oxides produced on Ni-Cr alloy during degassing at $1850^{\circ}F$ for 30 minutes in air and in vacuum were analyzed by X-ray diffractograph. The metal phases of Ni-Cr alloy were observed according to porcelain-baking cyclic heat treatment by photo microscope and the distribution and the shift of elements of Ni-Cr alloy and porcelain and the failure phases between Ni-Cr alloy and porcelain by scanning electron microscope. The adhesive force between Ni-Cr alloy and porcelain was measured according to surface treatment with oxidization and roughening by Instron Universal Testing Machine. Results were as follows; 1. The metal phases of Ni-Cr alloy as cast and degassing state showed the enlarged and fused core, but when subjected to porcelain-baking cyclic heat treatment, showed a dendrite growing. 2. The kinds of metal oxides produced on Ni-Cr alloy during degassing were found to be NiO and $Cr_2O_3$. 3. The distribution of elements at the interface of Ni-Cr alloy and porcelain in degassing state showed demarcation line, but in roughening state, showed mechanical interlocking phase. 4. The shift of elements at the interface occurred in both states, but the shift amount was found to be larger in roughening than in degassing. 5. The adhesive force between Ni-Cr alloy and porcelain was found to be $3.45{\pm}0.93kg/mm^2$, in degassing and $3.82{\pm}0.99kg/mm^2$, in roughening. 6. The failure phase between Ni-Cr alloy and porcelain showed the mixed type failure.