• Design & Manufacturing
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• 제14권4호
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• pp.65-70
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• 2020

Partial reinforcement of sheet metal parts with CFRP patch is a technology that can realize ultra-lightweight body parts while overcoming the high material cost of carbon fiber. Performing these patchworks with highly productive press equipment solves another issue of CFRP: high process costs. The A-pillar is the main body part and has an undercut shape for fastening with other parts such as roof panels and doors. Therefore, it is difficult to bond CFRP patches to the A-pillar with a general press forming tool. In this paper, a flexible system that applies uniform pressure to complex shapes using ceramic particles and silicone rubber is proposed. By benchmarking various A-pillars, a reference model with an undercut shape was designed, and the system was configured to realize a uniform pressure distribution in the model. The ceramic spherical particles failed to realize the uniform distribution of high pressure due to their high hardness and point contact characteristics, which caused damage to the CFRP patch. Compression equipment made of silicone rubber was able to achieve the required pressure level for curing the epoxy. Non-adhesion defects between the metal and the CFRP patch were confirmed in the area where the bending deformation occurred. This defect could be eliminated by optimizing the process conditions suitable for the newly developed flexible system.

• 대한치과보철학회지
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• 제50권2호
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• pp.112-118
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• 2012

연구 목적: 이 연구의 목적은 실란과 인산 모노머를 혼합한 프라이머인 Monobond plus (Ivoclar Vivadent, Schaan, Liechtenstein)를 사용했을 때 레진 시멘트와 수복물 간의 전단 결합 강도가 귀금속, 비귀금속, 글라스 세라믹과 지르코니아 네 가지 재료 모두에서 기존의 프라이머를 사용했을 때의 결합 강도와 비교하여 유의한지 평가하는 것이다. 연구 재료 및 방법: 디스크 모양(${\phi}\;9mm{\times}3mm$)의 귀금속(Argedent Euro) 시편 16개, 비귀금속(T-4) 시편 20개, 지르코니아(Cercon) 시편 20개, 글라스 세라믹(IPS e.max press) 시편 20개를 제작한 후 아크릴릭 레진(${\phi}\;15mm{\times}15mm$)에 포매하였다. 귀금속 시편에 airborne-particle abrasion을 시행하고 대조군으로 사용한 8개 시편에는 귀금속용 프라이머(Metal primer II)를, 나머지 8개 시편에는 Monobond plus를 도포하였다. 비귀금속 시편과 지르코니아 시편은 airborne-particle abrasion 후 각각 두 그룹으로 나누어 대조군 10개 시편에는 비귀금속 및 지르코니아용 프라이머(Alloy primer)를, 나머지 10개에는 Monobond plus를 도포하였다. 글라스 세라믹 시편은 4% 불산으로 부식한 후, 대조군 10개 시편에는 실란(Monobond-S)을, 나머지 10개에는 Monobond plus를 적용했다. 표면 처리된 시편 위에 디스크 형태(${\phi}\;5mm{\times}2mm$)로 레진 시멘트(Multilink N)를 위치시키고 중합하였다. 제작된 모든 시편을 열순환($5^{\circ}C$와 $55^{\circ}C$, 1분씩 2060회)시킨 후 전단 결합 강도를 측정하였다. 전단 결합 강도의 유의차를 살펴보기 위해 Shapiro-Wilk test를 이용하여 모집단의 분포에 대한 검정을 하고 그 결과에 따라 Two sample $t$-test 또는 Mann-Whitney U test를 실시하였다(${\alpha}$=.05). 파절된 시편을 확대경으로 관찰하여 그 양상을 분류하였다. 결과: 귀금속과 글라스 세라믹 군에서는 두 프라이머간의 전단 결합 강도에 유의한 차이가 존재하지 않았으나($P$>.05) 비귀금속 군과 지르코니아 군에서는 기존 프라이머(Alloy primer)를 사용했을 때 레진 시멘트와 수복물간의 전단 결합 강도가 Monobond plus를 사용한 군보다 통계적으로 유의하게 높았다(비귀금속 군$P$=.004, 지르코니아 군$P$=.001). 결론: 실란과 인산 모노머를 혼합한 다용도 프라이머는 귀금속과 글라스 세라믹 군에서는 기존의 프라이머를 대신하여 사용할 수 있을 것이다. 그러나 비귀금속과 지르코니아 세라믹에서는 10-MDP 프라이머에 비해 접착 강도가 낮아 기존 프라이머를 대신하여 적용하기 위해서는 좀 더 연구가 필요할 것이다.

• 대한치과보철학회지
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• 제35권1호
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• pp.144-164
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• 1997

The purpose of this study were to investigate the chemical composition, mean particle size, linear thermal expansion coefficient and metal-bonding strength of the regular opaque powder and core powder. In this study, 4 types of ceramic powders, namely Duceram Jacket Opaque powder, Duceram Opaque powder, Vita Hi-Ceram powder, Vita VMK Paint On-88 powder were used. Chemical composition was evaluated by EDS(Energy Dispersive X-ray Spectrophotometer, Oxford QX-2000, England), particle size was measured by MALVERN Instruments(MALVERN Instruments SB. OC., U.S.A.. ad linear thermal expansion coefficient was measured by dilatometer(Motoyama, Japan). Bond strength was measured by the Universal tsting machine(Istron Co., Ltd., U.S.A.). The Results were as follows : 1. Through recognition of the relative difference in chemical composition between the core powder and the regular opaque powder, the difference in the proportion of $Al_2O_3$ in each type of material is demonstrated ; Duceram Jaket Opaque powder : 30.16%, Duceram Opaque powder : 16.60%, Vita Hi-Ceram : 63.64%, Vita VMK Paint-On 88 : 16.16%. 2. There was no significant difference in the proportion of metal-bonding materials between the core powder and the regular opaque powder. 3. In the regular opaque powder, alkaline materials were incoporated in order to increase the coefficient of thermal expansion. 4. In the particle size analysis, there was no significant difference in mean particle size or in the particle size distribution between the core powder and the regular opaque powder. 5. In the thermal expansion test for temperature range of $25-600^{\circ}C$, the regular opaque powder had higher coefficient of thermal expansion than that of core powder. 6. In the 4 point flexural bending test, there was no statistically significant difference in the mean bond strength between the core powder and the opaque powder among the Duceram products.

• 대한치과교정학회지
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• 제28권6호
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• pp.955-974
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• 1998

적절한 전단접착강도를 가지면서 법랑질손상과 브라켓파절을 적게 일으키는 브라켓-접착제의 그룹을 찾아내기 위하여 전단접착강도, 법랑질손상, 브라켓탈락양상, 브라켓 주위의 밀봉과 법랑질-접착제-브라켓 사이의 긴밀도를 연구하였다. 교정치료 목적으로 발치한 240개의 치아를 각각 10개씩 24개의 군으로 나누어서 브라켓을 접착한 후 48시간 후에 전단접착강도를 측정하고 브라켓 탈락 양상을 조사하였다. 또한 브라켓 주위의 밀봉과 법랑질-접착제-브라켓 사이의 긴밀도를 평가하기 위하여 브라켓이 접착된 치아를 반으로 자른 후 주사전자현미경상에서 관찰하였다. 6종류의 브라켓과 4종류의 접착제가 사용되었으며 브라켓은 Image, Plastic, Crystaline, Fascination, Transcend, metal bracket을 사용하였으며 접착제로는 No-mix, Light-Bond, OrthoLC, Superbond C&B가 사용되었다. 이와같은 연구로부터 다음과 같은 결론을 내렸다. 1. 전단접착강도는 Fascination-Light Bond 군에서 36.58 Kg(410.07 Kg/$cm^2$)으로 가장 높았으며 Image-OrthoLC 군에 서 8.93 B◎ (75.51 Kg/$cm^2$)으로 가장 낮았다. OrthoLC를 접착제로 사용하였을 때 전단접착강도는 다른 접착제를 사용하였을 때 보다 비교적 낮았다. 2. 접착제의 종류에 관계없이 Fascination bracket의 전단접착강도는 비교적 높았으며 Image, Plastic bracket의 전단접착강도는 비교적 낮았다. Crystaline, Transcend bracket의 전단접착강도는 metal bracket의 전단접착강도와 비슷하거나 낮았다. 3. 전단접착강도와 법랑질 파절, 브라켓 파절은 상관관계가 있었으며, 접착강도가 증가할수록 법랑질 파절과 브라켓 파절은 증가하였다. 4. OrthoLC를 접착제로 사용하였을 때 법랑질 파절과 브라켓 파절은 일어나지 않았으나 Superbond C&B를 접착제로 사용하였을 때는 법랑질 파절과 브라켓 파절의 빈도가 높았다. 5. No-mix, Light-Bond를 접착제로 사용하였을 때 브라켓 주위의 밀봉과 법랑질-접착제-브라켓의 긴밀도는 양호하였다. 접착제의 종류에 관계없이 Ceramic bracket에서 접착제-브라켓의 긴밀도는 양호하였다. 6. 적절한 전단접착강도를 가지면서 법랑질 파절과 브라켓 파절을 일으키지 않는 군은 Crystaline-No mix, Crystaline Light Bond, Crystaline-OrthoLC, metal-No mix, metal-Light Bond, metal-OrthoLC군이였다.

• 한국콘텐츠학회논문지
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• 제10권11호
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• pp.228-234
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• 2010

치과도재용 합금으로 사용되는 합금 중 베릴륨이 함유된 비귀금속 Ni-Cr합금과 베릴륨이 함유되지 않은 비귀금속 Ni-Cr합금 그리고 베릴륨이 함유되지 않은 비귀금속 Co-Cr 합금과 세라믹간의 결합강도와 파절양상 그리고 계면특성을 분석하고자 하였다. 결합강도는 만능시험기를 이용하여 전단력시험을 통하여 전단결합력을 측정하였으며, 전단시험에 의한 파단면을 이용하여 파절양상을 관찰하였다. 그리고 합금-도재간의 계면을 관찰하였다. 전단결합강도 측정 결과, 베릴륨이 포함된 T-3가 41.13(${\pm}5.11$)MPa로 가장 높게 나타났으며, 베릴륨이 포함된 VeraBond(40.72(${\pm}5.98$)MPa), Co-Cr 합금인 Wirobond(38.40(${\pm}9.66$)MPa), 베릴륨이 포함되지 않은 Verabond 2V(32.77(${\pm}4.31$)MPa), Bellabond N(28.63(${\pm}6.39$)MPa), Bellabond plus(24.97(${\pm}6.13$)MPa), Argeloy N.P. Star(22.69(${\pm}3.41$)MPa) 순으로 나타났다. 비귀금속 합금들과 세라믹간의 파절양상은 모든 시편에서 금속표면에 세라믹이 일부 부착된 복합파절(mixed failure) 양상을 보였다.

• 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.

• 한국분말재료학회지
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• 제1권1호
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• pp.42-51
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• 1994

6061Al-SiCP metal matrix composite materials(MMCs) were fabricated by injecting SiCP particles directly into the atomized spray. The main attraction of this technique is the rapid fabrication of semi-finished, composite products in a combined atomization, particulate injection(10 $\mu\textrm{m}$, 40 $\mu\textrm{m}$, SiCP) and deposition operation. Conclusions obtained are as follows; The microstructure of the unreinforced spray formed 6061Al alloy consisted of relatively fine(50 $\mu\textrm{m}$) equiaxed grains. By comparision, the microstructure of the I/M materials was segregated and consisted of relatively coarse(150 $\mu\textrm{m}$) grains. The probability of clustering of SiCP particles in co-sprayed metal matrix composites increased it ceramic particle size(SiCP) was reduced and the volume fraction was held constant. Analysis of overspray powders collected from the spray atomization and deposition experiments indicated that morphology of powders were nearly spherical and degree of powders sphercity was deviated due to composite with SiCp particles. Interfacial bonding between matrix and ceramics was improved by heat treatment and addition of alloying elements(Mg). Maximum hardness values [Hv: 165 kg/mm2 for Al-10 $\mu\textrm{m}$ SiCp Hv--159 kg/mm2 for Al-40 $\mu\textrm{m}$SiCp] were obtained through the solution heat treatment at $530^{\circ}C$ for 2 hrs and aging at $178^{\circ}C$, and there by the resistance were improved.

• The Journal of Advanced Prosthodontics
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• 제12권4호
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• pp.181-188
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• 2020

PURPOSE. The effect of core design on the fracture resistance of zirconia-lithium disilicate (LS2) bilayered crowns for anterior teeth is evaluated by comparing with that of metal-ceramic crowns. MATERIALS AND METHODS. Forty customized titanium abutments for maxillary central incisor were prepared. Each group of 10 units was constructed using the same veneer form of designs A and B, which covered labial surface to approximately one third of the incisal and cervical palatal surface, respectively. LS2 pressed-on-zirconia (POZ) and porcelain-fused-to-metal (PFM) crowns were divided into "POZ_A," "POZ_B," "PFM_A," and "PFM_B" groups, and 6000 thermal cycles (5/55 ℃) were performed after 24 h storage in distilled water at 37 ℃. All specimens were prepared using a single type of self-adhesive resin cement. The fracture resistance was measured using a universal testing machine. Failure mode and elemental analyses of the bonding interface were performed. The data were analyzed using Welch's t-test and the Games-Howell exact test. RESULTS. The PFM_B (1376. 8 ± 93.3 N) group demonstrated significantly higher fracture strength than the PFM_A (915.8 ± 206.3 N) and POZ_B (963.8 ± 316.2 N) groups (P<.05). There was no statistically significant difference in fracture resistance between the POZ_A (1184.4 ± 319.6 N) and POZ_B groups (P>.05). Regardless of the design differences of the zirconia cores, fractures involving cores occurred in all specimens of the POZ groups. CONCLUSION. The bilayered anterior POZ crowns showed different fracture resistance and fracture pattern according to the core design compared to PFM.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1994년도 추계 학술발표 강연 및 논문 개요집
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• pp.1-1
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• 1994

;The electronic state calculations for various types of ceramic materials have beell performed by the use of $DV-X\;{\alpha}$ cluster method. The molecular orbital levels and wave functions for model clusters have been computed to study the electronic properties ami chemical bonding of the ceramics. For ${\beta}-sialon(Si_{6-z}Al_zO_zN_{8-z})$ which is a high temperature structural material based on ${\beta}-Si_3N_4$, we have made model cluster calculations to estimate the strength of chemical bonding between atoms by the Mulliken population analysis. It is found that the covalent bonding between Si and N atoms is very strong in pure ${\beta}-Si_3N_4$, but the covalency around solute atom is considerably weakened when Si atom is substituted by AI. This tendency is enhanced by an additional substitution of oxygen atom for N. The result calculated can well explain the experimental data of changes in mechanical properties such as the reductions of Young's modulus and Vickers hardness with increment of z-value in ${\beta}-sialon$. Various model clusters for transition metal oxides which show many interesting physical and chemical properties have also been calculated. High-valent perovskite-type iron oxides EMFe0_3E(M=Ca and Sr) possess very interesting magnetic and chemical properties. In these oxides, iron exists as $Fe^{4+}$ state, but the experimental measurement of Mossba~er effect suggests that disproportionation $2Fe^{4+}=Fe^{3+}+Fe^{5+}$ takes place for $CaFe0_3$ at low temperatures. The model cluster calculations for these compounds indicated the existence of considerably strong covalent bonding of Fe-O. The calculations of hyperfine interaction at iron neucleus show very good agreement with the experimental Mossbauer measurements. The result calculated also implies that the disproportionation reaction is strongly possible by assuming the quenching of breathing phonon mode at low temperatures.tures.

• 대한치과보철학회지
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• 제30권2호
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• pp.135-154
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• 1992

This study was performed to analyze bond strength, the alterations of the interfaces between metal films which are populary used and considered to contribute to the chemical reaction with porcelain, according to constant ion- beam- mixing, and the relation between interfacial chemical reactions and bond strength in metal/porcelain specimens. For this study, three seperate metals : selected-gold, indium and tin were chosen ; each to be bonded to a seperate body porcelain. Bonding occurs when the metal is deposited to the body porcelain using a vacuum evaporator. The vacuum evaporator used $10^{-5}\sim10^{-6}$ Torr vacuum states for the evaporation of various metals (Au, Sn, In). Ion-beam-mixing of the porcelain/metal interfaces caused reactions when the Ar+ was implanted into thin films using a 80 KeV accelerator. These ion-beam-mixed specimens were then compared with an unmixed control group. An analysis of bond strength and ionic changes between the the metal and porcelain was performed by electron spectroscopy of chemical analysis (ESCA) and scratch test. The finding led to the following conclusions : 1. Light microscopic views of the scratch test : The ion-beam-mixed Au/porcelain specimen showed narrower scratched streams than the unmixed specimen. However, the Sn/porcelain, In/porcelain specimens showed no differences in the two conditions. 2. Acoustic emissions in scratch tests : The ion-mixed Au/porcelain, In/porcelain specimens showed signals closer to the metal/porcelain interfaces than unmixed specimens. Conversely, the ion-mixed Sn/porcelain specimen showed more critical signals in superficial portions than unmixed specimens. 3. After ion- beam-mixing, the Au/porcelain specimen showed apparently increased bond strength, and the In/porcelain specimen showed very slightly increased bond strength. However, the Sn/porcelain specimen showed no differences between ion mixed specimen and the unmixed one. 4. ESCA analysis : The ion-beam-mixed Au/porcelain specimen showed a higher peak separated value (4.3eV) than that of the unmixed specimen(3.65eV), the ion-beam-mixed In/porcelain specimen showed a higher peak separated value (9.43eV) than that of the unmixed specimen(7.6eV) and the ion-beam-mixed Sn/porcelain specimen showed a higher peak separated value (8.79eV) than that of the unmixed specimen(8.5eV). 5. Interfacial changes were observed in the ion-mixed Au/porcelain, In/porcelain and Sn/porcelain specimens. Especially, significant interfacial changes were measured in the ion- mixed Sn/porcelain specimen. Tin dioxide(SnO2) and a combination of pure tin and tin dioxide (Sn+SnO2) were produced. 6. In the Au/porcelain specimen, the interfacial chemical reaction showed increased bond strength between gold and porcelain substrate. But, in the In/porcelain, Sn/porcelain specimens, interfacial chemical reactions did not affected the bond strength between metal and porcelain substrate. Especially, bonding strength on the ion mixed Sn/porcelain specimen showed the least amount of difference.