• 구강회복응용과학지
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• 제19권2호
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• pp.75-86
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• 2003

The purpose of this study was to evaluate their mechanical properties after laser-welding or soldering of precious and non-precious dental alloys. For this study, 30 Co-Cr alloy specimens, 15 gold alloy specimens, 15 palladium alloy specimens were casted and seperated on the middle area. 15 sperated Co-Cr specimens and 15 seperated gold alloy specimens were laser welded (GW Group). 15 sperated Co-Cr specimens and 15 sperated gold alloy specimens were soldered by coventional soldering method (GS Group). 15 sperated Co-Cr specimens and 15 seperated palladium alloy specimens were laser welded (PW Group). 15 sperated Co-Cr specimens and 15 sperated palladium alloy specimens were soldered by coventional soldering method (PS Group). Tensile strength, 0.2% yield strength, % elongation were recorded in nine specimens of each group. Bending strength were record in six specimens of each group. These data for four groups were subjected to a two-way analysis of variance(ANOVA). The fracture locations, fractured surfaces were examined by SEM(scanning electron microscope). The results were as following: 1) In the same alloy combination, the tensile strength and 0.2% yield strength and of the laser welded group with same metal combination were significantly less than soldered groups(p<0.05). 2) In the combination of Co-Cr/Palladium, the bending strength of laser welded group were significantly less than that of soldered groups(p<0.05). In the combination of Co-Cr/Gold, the bending strength of laser welded group were significantly higher than that of soldered groups(p<0.05). 3) In the same method of joint, the tensile strength and 0.2% yield strength and bending strength of the Co-Cr/gold were significantly higher than Co-Cr/palladium(p<0.05). 4) There was no significantly statistical difference between each group in the % elongation(p>0.05). 5) The fracture of the laser welded specimens occured in the welding area and a large void was observed at the center of the fracture surface. 6) The fracture of the soldered specimens occured also inthe soldered area and many porpsities were showed at the fracture sites.

• 대한치과기공학회지
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• 제32권3호
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• pp.195-207
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• 2010

Purpose: The purpose of this study was to observe the microstructural changes of surface in the specimens, performing the shear bond strength testing. The currently most used non-precious alloys are nickel-chromium based alloys with or without beryllium. However, their biocompatibility has been questioned concerning possible damages to the health of the patient and professionals involved in the fabrication of prosthesis caused by long exposure to Ni and Be. An option to nickel-chromium alloys is the cobalt-chromium alloy, an alternative that does not sacrifice the physical properties of the metal porcelain systems. Studies in the animals substantially show that the cobalt-chromium alloys are relatively well tolerated, being therefore more biocompatible than the nickel-chromium alloys. Methods: Non-addition Be to nickel-chromium based alloy(Bellabond plus) and cobalt-chromium alloy which has been widely used(Wirobond C) fused with ZEO light porcelain classified control group and cobalt-chromium alloy which is developing alloy of Alphadent company in Korea(Alphadent alloy) fused with ZEO light porcelain classified experimental group. The specimens of $4mm{\times}4mm{\times}0.5mm$ were prepared as-cast and as-opaque to cast body to analyze the mechanical characteristic change, the microstructure of alloy surface. The phase change was used to observe through XRD analysis and OM/SEM was used to observe the surface of specimens as-cast and as-opaque to cast body. Chemical formation of their elements was measured with EDS. Then hardness was measured with Micro Vicker's hardness tester. Shear bond strength test thirty specimens of $10mm{\times}10mm{\times}2mm$ was prepared, veneered, 3mm high and 3mm in diameter, over the alloy specimens. The shear bond strength test was performed in a universal testing machine(UTM) with a cross head speed of 0.5mm/min. Ultimate shear bond strength data were analyzed with one-way ANOVA and the Scheffe's test (P<0.05). Within the limits of this study, the following conclusions were drawn: The X-ray diffraction analysis results for the as-cast and as-opaque specimens showed that the major relative intensity of Bellabond plus alloy were changed smaller than Wirobond C and Alphadent Co-Cr based alloys. Results: Microstructural analysis results for the opaque specimens showed all the alloys increased carbides and precipitation(PPT). Alphadent Co-Cr based alloy showed the carbides of lamellar type. The Vickers hardness results for the opaque specimens showed Wirobond C and Alphadent Co-Cr based alloys were increaser than before ascast, but Bellabond plus alloy relatively decreased. The mean shear bond strengths (MPa) were: 33.11 for Wirobond C/ZEO light; 25.00 for Alphadent Co-Cr alloy/ZEO light; 18.02 for Bellabond plus/ZEO light. Conclusion: The mean shear bond strengths for Co-Cr and Ni-Cr based alloy were significantly different. But the all groups showed metal-metal oxide modes in shear bond strengths test at the interface.

• 대한치과기공학회지
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• 제34권3호
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• pp.237-245
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• 2012

Purpose: This study was conducted to evaluate the corrosion resistance of metal ions of alloys and use the results as the dental health data. These were performed by examining the corrosion levels of Co-Cr alloys for the full and removable partial denture metal frameworks and porcelain-fused-to-metal crown, among the dental casting nonprecious alloys. Methods: The alloy specimens (N = 10) were manufactured in $15mm{\times}10mm{\times}1.2mm$ and stored in two types of corrosive solutions at $37^{\circ}C$ for seven days. The metal ions were quantitatively analyzed using the Inductively Coupled Plasma-Atomic Emission Spectrometer. Results: Of the three Co-Cr alloys, the Co ion concentration of the porcelain-fused-to-metal alloy was 1.512 ${\mu}g/cm^2$, which indicated the highest metal ion dissolution. The metal corrosion was higher in the more acidic pH 2.2 solution compared with the pH 4.4 solution. In all three Co-Cr alloys, Co ion dissolution was predominant in the two corrosive solutions. Conclusion: The corrosion resistance of the three Co-Cr alloys was high, indicating a good biocompatibility.

• 대한치과기공학회지
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• 제45권3호
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• pp.67-73
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• 2023

Purpose: This in vitro study aimed to evaluate the clinical acceptability of precision of fit of the support thickness of Co-Cr alloy copings fabricated using selective laser melting (SLM). Methods: Thirty dental stone models of maxillary left molar abutments were manufactured, images were taken using a scanner, and a computer-aided design program was used to design the form of a conventional metal ceramic crown coping. Overall, 30 single copings were made from Co-Cr alloy using SLM and divided into three support radius groups (0.1, 0.25, and 0.35 mm) of 10 for each. Digitized data were superimposed with three-dimensional inspection software to quantitatively obtain the machinability of a ceramic crown coping, and visual differences were confirmed using a color map. The root mean square values of the ceramic crown coping group were statistically analyzed using one-way analysis of variance (α=0.05). Results: The precision of fit was superior with 0.25 mm compared with 0.1 mm and 0.35 mm, and the results exhibited significant differences (p<0.05). All specimens showed that various support thicknesses did not exceed the clinically permitted value of 120 ㎛, which mean that more than 0.1 mm and 0.35 mm of support radius for SLM was adequate. Conclusion: The support thickness of Co-Cr alloy restoration fabricated using SLM is shown to affect the adaptation.

• 대한치과기공학회지
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• 제38권3호
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• pp.175-183
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• 2016

Purpose: Observation of Oxide Film Formation and Bonding Strength according to surface treatment of Co-Cr Alloy for porcelain fused to Metal. Methods: metal specimens $0.5mm{\times}25mm{\times}4mm$ in size were made using Co-Cr alloys for porcelain fused to metal crown (Heraenium P, Tae jung Medis). Dental porcelain $0.5mm{\times}25mm{\times}4mm$ in size was sintered on the metal specimens after changing the etching time, sandblasting condition, and heat treatment temperature. Subsequently, the bonding strength was compared by the three-point flexural strength test using a universal testing machine (UTM) to observe the fracture surface and oxidized layers. Results: With regard to the experimental group treated with acid-etching, Specimen 1 treated for 25 minutes (B-3) showed the highest bonding strength, and Specimen 2 treated only with sandblasting showed the most excellent bonding force at 3.5 bar (C-3). With regard to the experimental group treated with sandblasting at 3.5 bar after acid-etching for 25 minutes, Specimen 3 with heat treatment at $980^{\circ}C$ (D-3) showed the highest bonding strength. Conclusion: The specimen which went through both sandblasting and etching, showed an excellent ceramicmetal bond strength.

• 대한치과기공학회지
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• 제31권4호
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• pp.15-23
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• 2009

The aim of this study was to evaluate the bond strength of using a Au bonding agent applied on cp-Ti and nonprecious metal-gold-ceramic system. Metallic frameworks(diameter: 5mm, height: 20mm)(N=56, n=7per group) cast in Ni-Cr alloy, Co-Cr alloy and cp-Ti were obtained using acrylic templates and airborne particle abraded with $110{\mu}m$ aluminum oxide. Au bonding agent was applied on wash opaque firing as intermediate layer. SEM and SEM/EDS line profile were performed on the cutting the cross-section of the metal substrate-porcelain with intermediate Au coating. Groups were tested using shear bond strength(SBS) testing at 0.5mm/min. The mean SBS values for the ceramic-Au layer-metal combination were significantly higher than those ceramic-metal combination. While ceramic-Au layer-cp-Ti combinations failed to increase bond strength instead of using a titanium bonding porcelain. The appication of using Au intermediate layer significantly improve the bond strength combination with metal-ceramic system.

• 대한치과기공학회지
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• 제14권1호
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• pp.119-132
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• 1992

This paper aims to investigate the effect of B and Si upon the mechanical properties, microstructure and corrosion resistance of Co-Cr base alloy. Ten groups of alloy ingot ingot with various contents of B and Si were remelted by high frequency electrical induction furnace and cast into tensile specimen of ADA Specification No. 14 Tensile and hardness test were carried out by Amsler and Rockwell hardness tester(R-30N), respectively. The microstructures of specimen were observed by SEM. The results obtained are summarized as follows : 1. As B content is increased, tensile strength, yield strength and Rockwell hardness number(R-30N) are also increased significantly, while the elongation is decreased significantly. 2. As Si contect os increased, no significant chang in tensile strength is noticed, yield strength is slightly decreased, but Rockwell hardness number(R-30N) is moderately in creased, Elongation marks maxium value with 1% Si content while with more than 1% Si it is decreased. 3. As B content is increased corrosion resistance is decreased and is at best with 1.5% B content. Corrosion resistance is increased with the increase of Si content and the alloys with Si over 3.0% showed corrosion resistance. 4. As B content increased, precipitates are increased in number at grain boundaries. The grain size tends to become coarse with the increase of Si content. 5. Co rich-Cr alloy is present through matrix whereas at the grain boundaries Cr base precipitates are primarily formed.

• 대한치과기공학회지
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• 제45권2호
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• pp.48-53
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• 2023

Purpose: This study aimed to provide the basic data for dental barrel finishing by observing the abrasiveness of the metal body according to the time of the barrel finishing. Methods: This study included three types of Co-Cr alloys. The specimens were manufactured by casting method using 10-mm diameter wax spheres (n=10). The cast alloys were polished for 60 minutes at intervals of 5 minutes in barrel finishing. The weight and volume of the specimens were measured, and the rate of change was calculated. The data obtained from the three groups (α=0.05) were compared and analyzed using one-way ANOVA. Results: As a result, the overall volume and weight of the group decreased after grinding compared with the control group. Conclusion: When grinding dental barrel finishing, no difference was observed in the processing rate depending on the type of alloy and the processing rate of the alloy body is within 30 minutes; hence, dental barrel finishing can be effectively used for grinding.

• 한국산학기술학회논문지
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• 제21권12호
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• pp.434-439
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• 2020

최근, 치과 산업에서 레이저를 열원으로 합금을 제조하는 선택적 레이저 용융법(Selective laser melting, SLM)이 소개되고 있다. 하지만 SLM으로 제작된 금속-세라믹 수복물에 대한 연구가 부족한 실정이다. 따라서 본 연구의 목적은 SLM 그리고 CAST(casting)에 의해 제조된 Co-Cr 합금의 금속-세라믹(metal-ceramic) 결합 강도(bond strength)를 평가하는 것이다. SLM 그리고 CAST 방법을 사용하여 Co-Cr 시편을 제조하고 세라믹을 소결하여 시료를 제작하였다. 연구의 실험은 표본 준비 및 분석을 통해 2020년 1월부터 6월까지 수행되었다. 금속-세라믹 결합 강도는 만능 시험기에 의해 측정되었다. 부착 세라믹의 면적분(The area fraction of adherence ceramic, AFAC)은 SEM/EDS로 시편의 Si 함량을 측정하였다. 금속-세라믹 결합 강도 및 AFAC 결과는 t-test를 사용하여 분석하였다(α = .05). SLM 그리고 CAST Co-Cr 합금 사이의 결합 강도에 대해서는 유의한 차이가 발견되지 않았다(P>.05). SLM은 CAST 그룹보다 많은 세라믹 부착성(ceramic adherence)을 나타냈다(P<.001). 세라믹과 합금의 결합 강도는 제조 방법엥 영향을 받지 않았다. 그러나 SLM은 더 우수한 세라믹 부착성을 보였다. 이는 향후 임플란트 상부 보철물 제작에도 SLM으로 제작한 합금이 사용 가능한 것을 시사한다. CAST 방식의 단점을 극복하고 시간과 비용을 절약할 수 있을 것으로 기대된다.

• 대한치과기공학회지
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• 제36권3호
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• pp.149-158
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• 2014

Purpose: Dental casting Co-Cr-Mo based alloys of five kinds of ingot type and two kinds of shot type were analyzed the melting processes with heating time of high frequency induction centrifugal casting machine using infrared thermal image analyzer. Methods: When Co-Cr-Mo based alloys were put about 30g/charge in the ceramic crucible of high frequency induction centrifugal casting machine and heat, Infrared thermal image analyzer and IR thermometer indicated these alloys in the crucible were set and operated. Results: The melting temperatures of alloys measuring infrared thermal image analyzer were deviated ${\pm}10^{\circ}C$ compared to those of manufacturing company. On the other hand, the melting time of alloys were differently appeared with the shape of alloys(ingot and shot type). Conclusion: The melting temperatures of dental Co-Cr-Mo based alloys were measured the degree of $1,360{\sim}1410^{\circ}C$ and the heating time with the alloys of ingot and shot type were deviated ${\pm}10sec$.