• The Journal of Advanced Prosthodontics
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• 제5권2호
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• pp.179-186
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• 2013

PURPOSE. One of the most important factors in evaluating the quality of fixed dental prostheses (FDPs) is their gap. The purpose of this study was to compare the marginal and internal gap of two different metal-ceramic crowns, casting and selective laser sintering (SLS), before and after porcelain firing. Furthermore, this study evaluated whether metal-ceramic crowns made using the SLS have the same clinical acceptability as crowns made by the traditional casting. MATERIALS AND METHODS. The 10 study models were produced using stone. The 20 specimens were produced using the casting and the SLS methods; 10 samples were made in each group. After the core gap measurements, 10 metal-ceramic crowns in each group were finished using the conventional technique of firing porcelain. The gap of the metal-ceramic crowns was measured. The marginal and internal gaps were measured by two-dimensional and three-dimensional replica techniques, respectively. The Wilcoxon signed-rank test, the Wilcoxon rank-sum test and nonparametric ANCOVA were used for statistical analysis (${\alpha}$=.05). RESULTS. In both groups, the gap increased after completion of the metal-ceramic crown compared to the core. In all measured areas, the gap of the metal cores and metal-ceramic crowns produced by the SLS was greater than that of the metal cores and metal-ceramic crowns produced using the casting. Statistically significant differences were found between cast and SLS (metal cores and metal-ceramic crown). CONCLUSION. Although the gap of the FDPs produced by the SLS was greater than that of the FDPs produced by the conventional casting in all measured areas, none exceeded the clinically acceptable range.

• 대한치과보철학회지
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• 제43권3호
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• pp.293-305
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• 2005

Statement of problems. Conventional feldspathic porcelain is used extensively as a restorative material and it is subjected to grinding and polishing during fabrication and delivery procedures. There is still considerable controversy concerning the best methods to achieve the strongest porcelain restorations after such adjustments. Purpose. The objective of this study was to investigate the effects of (1) overglazing, (2) selfglazing, and (3) fine polishing on the flexural strength and fracture toughness of feldspathic dental porcelain. Material and method. Ninety porcelain disks were prepared for flexural strength test and sixty porcelain disks were fabricated for fracture toughness test. Specimens were divided into three groups for each test as follows: 1) overglazed 2) self-glazed 3) polished. The flexural strength of feldspathic porcelains was determined by ring-on-ring biaxial flexural strength test. The fracture toughness values of three experimental groups were obtained by indentation fracture toughness test. Results. The flexural strength of overglazed group was significantly higher than that of selfglazed and polished group (P<0.05), while the difference between self-glazed and polished group was not significant (P>0.05). The fracture toughness values of overglazed and polished group were significantly higher than that of self-glazed group (P<0.05), while the difference between overglazed and polished group was not significant (P>0.05). Conclusions. This results supported the use of polishing as an alternative to glazing metal ceramic restorations, as it was not detrimental in flexural strength and fracture toughness. But, under the conditions of this study, overglazing was the ideal surface finishing method of feldspathic dental porcelain.

• 구강회복응용과학지
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• 제31권2호
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• pp.96-103
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• 2015

목적: 본 연구는 하부구조물과 축성된 도재의 두께 차이에 따른 색상의 차이를 비교연구하여 보고자 함이다. 연구 재료 및 방법: 금속하부구조물과 완전도재 하부구조물위에 0.5 mm 간격으로 도재의 두께를 다르게 축성을 한 후에 spectrophotometer를 이용하여, 색상을 측정하였다. 이후 측색값과 ${\Delta}E*$값을 통계학적으로 비교 분석하였다. 결과: 도재의 두께가 증가함에 따라 명도가 감소하였다(P < 0.05). 세라믹 하부구조물의 경우 축성된 도재의 두께가 증가할수록 $a^*$값이 감소였으나(P < 0.05), 두께는 $b^*$값에 유의한 영향을 주지 않았다. 도재 두께 차이가 0.5 mm 이하일 경우 ${\Delta}E*$값이 1이하였다. 결론: 하부구조물의 종류에 따라 차이가 있으나, 도재의 두께가 색상에 영향을 주는 요소이며, 두께에 따른 색조 변화 양상의 인지를 통하여, 임상에서 도재 두께변화를 이용한 색상조절에 도움이 될 것이라 사료된다.

• 대한치과보철학회지
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• 제29권2호
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• pp.129-145
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• 1991

The purpose of this study was to analyze the stresses and displacements of various esthetic restorations and abutment teeth. The finite element models of central incisor were divided into four groups according to the types of restoration. Three load cases were applied; 1) 45 degrees on the incisal edge, 2) horizontal force on the labial surface, and 3) 26 degrees diagonally on the lingual surface. Material property, geometry, and load conditions of each model were inputed to the two dimensional finite element program and stresses and displacements were analyzed. Results were as follows; 1. In the cases of porcelain fused gold ann and porcelain laminate venner, stresses were equally distributed in supporting abutment tooth. 2. The metal coping of porcelain fused gold u and collarless porcelain fused gold crown functioned as a good stress distributor. 3. When the horizontal load applied, the highest tensile and compressive stresses were seen in the cervical margin of restoration and the dentin of the abutment tooth. 4. The highest displacement of restoration was seen when load was applied at an mee of 26 degrees diagonally in lingual surface of tooth in centric occlusion. 5. The influence of loading direction on the stresses and displacements in the restoration was greater than that of various design. 6. The possibility of fracture was highest in porcelain jacket crown.

• 대한치과보철학회지
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• 제19권1호
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• pp.61-73
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• 1981

The effects of the opaque porcelain firing temperature, the bonding agent and the degassing prior to the opaque firing On the bond strength were investigated by means of the tensile shear stIe$. The diffusional behaviours at the interface of the porcelain and the alloy, and .the microstructures of the ceramic and metal composite were studied for understanding the bonding mechanism. The results obtained in this experiment were summarizd as follow; 1. With no application of bonding agent, the tensile shear strength of the specimen firing at $1840^{\circ}F$ was higher than that of the specimen firing at $1760^{\circ}F$. 2. The highest bond strength was obtained by application of bonding agent without degassing prior to the opaque firing. 3. Application of bonding agent after the degassing showed the lowest bond strength. 4. The greater number of pores were observed at the firing temperature of $1840^{\circ}F$ than that of $1760^{\circ}F$ in the porcelain and the interface respectively.

• 대한치과기공학회지
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• 제28권1호
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• pp.19-26
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• 2006

The effect of Nb on interfacial bonding characteristics of Ni-Cr alloy for porcelain fused to metal crown (PFM) has been studied in order to investigate oxide layer. A specimens of Ni-Cr alloy, which is 0.8mm in thickness, within the porcelain furnace of 1,000$^{\circ}C$ with four tests such as air, vacuum, air for 5 minutes and vacuum for 5 minutes in order to examine an oxide behavior of alloy surface generated by the adding of Nb to be controlled at a rate of 0, 1, 3 and 5. Oxide film was observed form of the fired specimens with scanning electron microscope (SEM), and at the same time it measured Electron Probe Micro Analyzer (EPMA). The result of this study were as follows: 1. Cr oxide film and Nb oxide film were observed from the surface of specimen to be controlled at a rate of Nb 1%. 2. Nb oxide film was observed from the interface of specimens to be controlled at a rate of Nb 1% and 3%. 3. The stability of oxide films that treated in air were more stable than treated under vacuum.

• 대한치과기공학회지
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• 제25권1호
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• pp.63-70
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• 2003

The microstructure and hardness of a porcelain fused Au-Pt-Cu-In alloy was investigated using optical microscopy, secondary electron microscopy, electron probe microanalyzer, transmission electron microscope, and vickers hardness. The hardness of the heat-treated Au-Pt-Cu-In quartenary alloy reached a maximum value in 30 min at 550$^{\circ}C$ in the range of 150 to 950$^{\circ}C$. In the aged Au-Pt-Cu-0.5In alloy at 550$^{\circ}C$, the hardness of the alloy rapidly increased until 30min with increasing aging time and after that it was remained nearly constant value. Based on above results, glazing and final aging of the porcelain fused Au-Pt-Cu-0.5In alloy were performed at 920 and 550$^{\circ}C$, respectively. The hardness of Au-Pt-Cu-0.5In alloy glazed at 920$^{\circ}C$ was 90 Hv and that of the alloy aged for 30 min at 550$^{\circ}C$ increased to 160 Hv. This indicates that a ceramic-metal crown with high strength can be manufactured using the glazing at 920$^{\circ}C$ and followed final aging at 550$^{\circ}C$ for 30 min.

• 대한치과보철학회지
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• 제34권3호
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• pp.533-538
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• 1996

도재 소부용 비귀금속합금의 표면처리가 금속과 도재간의 전단결합강도에 어떠한 영향을 미치는지 알아보기 위하여, 비귀금속 합금의 표면에 어떠한 처리도 하지 않는 대조군과 샌드브라스팅한 실험군, 스퍼트 에칭한 실험군, 그리고 샌드브라스팅후 스퍼트 에칭한 실험군으로 나눈 후에 각각의 시편에 통상적인 방법으로 도재를 소성한 후 인스트론 만능 시험기를 사용하여 전단결합강도를 측정하여 다음과 같은 결론을 얻었다. 1. 샌드브라스팅후 스퍼트 에칭한 실험군과 샌드브라스팅한 군은 대조군에 대해 높은 값을 나타내었다(P<0.05). 2. 스퍼트 에칭한 실험군은 대조군에 대해 차이가 없었다(P>0.05).

• 대한치과보철학회지
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• 제49권3호
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• pp.191-196
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• 2011

연구 목적: 본 연구는 여러 가지 금속-도재 합금의 도재결합강도를 측정하여 임상에 적용하는 것이 적절한지 평가하고자 하였다. 연구 재료 및 방법: 금속도재소부 전장관으로 가장 많이 사용되는 Ni-Cr 합금(Group 1)과 75% 금합금(Group 2) 및 최근 도재금 합금으로 판매되고 있는 52.5% (Group 3), 51.5% (Group 4), 32% (Group 5), 10% 금합금(Group 6)이 시편으로 제작되었다. 시편은 각각 5개씩 제작되었으며, 제작된 시편에 전용 도재를 소성하고 3점 굴곡 시험을 통하여 도재와 각 금속간의 결합강도를 측정하였다. 결과: Group 1의 도재 결합강도가 $40.62{\pm}3.32$ MPa로 다른 실험군의 도재결합 강도에 비해 통계학적으로 유의성 있게 가장 높은 결합강도를 보였고(P<.05), 다음으로 Group 2가 $37.47{\pm}1.57$ MPa, Group 3이 $35.85{\pm}1.48$ MPa, Group 4가 $35.04{\pm}1.34$ MPa, Group 5가 $33.17{\pm}1.62$ MPa, Group 6가 $30.75{\pm}1.21$ MPa 순으로 결합강도가 감소하였다. Group 2, 3, 4 의 도재결합 강도는 Group 6와 통계학적으로 유의성을 보여주고 있으나(Duncan's test, P<.05), Group 3과 4는 Group 5와 서로 유의한 차이를 보이지 않았다(Duncan's test, P>.05). 도재 결합 강도 차이는 금 함량이 높을수록 강도가 높았고, 모든 실험군에서 ISO 9693에서 제시하는 기준치(25 MPa)보다 높은 수치를 나타내었다. 결론: 실험에 포함된 모든 합금들이 임상적으로 사용 가능할 것으로 추정된다.

• 대한치과기공학회지
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• 제38권2호
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• pp.69-77
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• 2016

Purpose: This study was to evaluate the shear bond strength of ceramic fused to Ni-Cr alloy(Alophaloy) by heat treatment. Methods: The specimens were divided into 5 groups according to heat treatment conditions prior to porcelain application. Eighteen specimens from each group were subjected to the shear load a universal testing machine using a 0.1mm/min cross-head speed and two specimens from each group were observed with SEM and EDX line profile. Results: The observation of the oxide film on the metal surface by SEM photograph showed a coarsening with an increasing degassing hold time. The diffusion of metal oxide was observed farther from the opaque layer in the heat treated specimen than no heat treated specimen. The shear bond strength measured highest to A5(55.23MPa) in the 10min holding group and measured lowest from A1(24.38MPa) in the no heat treated group, and there was a significant difference(p<0.05). Conclusion: The shear bond strength of Ni-Cr alloy improved in the heat treatment compared to the no heat treatment specimen.