• Design & Manufacturing
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• 제11권2호
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• pp.51-56
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• 2017

Nitinol, a shape memory alloy (SMA), is manufactured from titanium and nickel and it used in various fields such as electrical applications, micro sensors. It is also recommended as a material in medical for implant because it has excellent organic compatibility. Nitinol is intended to be inserted into the human body, products require a high-quality surface and low residual stress. To overcome this problems, explore electrolyte polishing (EP) is being explored that may be appropriate for use with nitinol. EP is a particularly useful machining method because, as a non contact machining method, it produces neither machining heat nor internal stress in the machined materials. Sandpaper polishing is also useful machining method because, as a contact machining method, it can easily good surface roughness in the machined materials. The electrolyte polishing (EP) process has an effect of improving the surface roughness as well as the film polishing process, but has a characteristic that the residual stress is hardly generated because the work hardened layer is not formed on the processed surface. The sandpaper polishing process has the effect of improving the surface roughness but the residual stress remains in the surface. We experimented with three conditions of polishing process. First condition is the conventional polishing. Second condition is the electrochemical polishing(EP). And Last condition is a mixing process with the conventional polishing and the EP. Surface roughness and residual stress of the nitinol before a polishing process were $0.474{\mu}mRa$, -45.38MPa. Surface roughness and residual stress of the nitinol after mixing process of the conventional polishing and the EP were $1.071{\mu}mRa$, -143.157MPa. Surface roughness and residual stress of the nitinol after conventional polishing were $0.385{\mu}mRa$ and -205.15MPa. Surface roughness and residual stress of sandpaper and EP nitinol were $1.071{\mu}mRa$, -143.157MPa. The result shows that the EP process is a residual stress free process that eliminates the residual stress on the surface while eliminating the deformed layer remaining on the surface through composite surface machining rather than single surface machining. The EP process can be used for biomaterials such as nitinol and be applied to polishing of wafers and various fields.

• 한국전기전자재료학회논문지
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• 제20권4호
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• pp.303-307
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• 2007

This paper investigated the effect of the pad buffing process on the material removal characteristics and pad stabilization during silicon chemical mechanical polishing. The pads surface were controlled by the buffing process using a buffer made by the sandpaper. The buffing process is based on abrasive machining by using a high speed sandpaper. The controlled pad by the buffing process show less deformation deviation and stable material removal rate during the CMP process. In addition, the controlled pad ensure better uniformity of removal rate than comparative pads. As a result of monitoring, the controlled pad by the buffing process demonstrated constant and stable friction force signals from initial polishing stage. Therefore, the tufting process could control the pad surface to be uniform and improve the performance of the polishing pad.

• Korean Chemical Engineering Research
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• 제60권1호
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• pp.132-138
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• 2022

본 연구에서는 광경화 3D 프린팅 방식인 SLA (Stereo Lithography Apparatus) 방식 출력물의 후처리 방법에 따른 표면 특성의 변화를 체계적으로 비교하고, 용도에 맞는 후처리 방법에 대한 정보를 제공하기 위한 기초 연구를 수행하였다. SLA 방식 출력물은 연마를 통해 표면의 불규칙한 미세구조를 규칙적으로 변화시켜 투명도를 일부 개선할 수는 있었으나, 유리와 같은 충분한 투명도를 확보하기는 어려웠다. 연마에 따른 접촉각 특성 변화는 연마 시간이 증가할 수록 그리고 사용된 사포의 입도가 작을 수록 다소 증가하는 경향을 보였으나 샘플 간 편차가 크고 평균 77~90°의 접촉각을 나타내어 대부분 통계적으로 유의미한 차이를 보이지는 않았다. 연마 이외 다양한 방법을 통한 표면처리 방법이 시도되었으며, 시판되는 차량용 흠집제거제나 실리콘 오일 등을 도포하여 쉽고 간단하게 투명도를 개선하는 것이 가능함을 확인하였다. 또한, 입도 사이즈를 줄이며 순차적으로 연마한 후 흠집제거제를 사용함으로써 유리와 같은 높은 투명도를 확보할 수 있는 방법을 제안하였다. 마지막으로 연마와 다양한 방법을 통해 표면처리를 하더라도 접촉각은 90° 이상을 확보하기 어려웠으며 소수성의 특성을 필요로 하는 경우, 본 연구에서 사용된 다양한 방법 외 소수성 코팅과 같은 추가적인 처리가 필요함을 확인하였다.

• Restorative Dentistry and Endodontics
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• 제24권2호
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• pp.299-309
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• 1999

The composite resin, due to its esthetic qualities, is considered the material of choice for restoration of anterior teeth. With respect to shade control, the direct-placement resin composites offer some distinct advantages over indirect restorative procedures. Visible-light-cured (VLC) composites allow dentists to match existing tooth shades or to create new shades and to evaluate them immediately at the time of restoration placement. Optimal intraoral color control can be achieved if optical changes occurring during application are minimized. An ideal VLC composite, then, would be one which is optically stable throughout the polymerization process. The shade guides of the resin composites are generally made of plastic, rather than the actual composite material, and do not accurately depict the true shade, translucency, or opacity of the resin composite after polymerization. So the numerous problems associated with these shade guides lead to varied and sometimes unpredictable results. The aim of this study was to assess the color changes of current resin composite restorative materials which occur as a result of the polymerization process and to compare the color differences between the shade guides provided with the products and the actual resin composites before- and after-polymerization. The results obtained from this investigation should provide the clinician with information which may aid in improved color match of esthetic restoration. Five light activated, resin-based materials (${\AE}$litefil, Amelogen Universal, Spectrum TPH VeridonFil-Photo, and Z100) and shade guides were used in this study. Three specimens of each material and shade combination were made. Each material was condensed inside a 1.5mm thick metal mold with 10mm diameter and pressed between glass plates. Each material was measured immediately before polymerization, and polymerized with Curing Light XL 3000 (3M Dental products, USA) visible light-activation unit for 60 seconds at each side. The specimens were then polished sequentially on wet sandpaper. Shade guides were ground with polishing stones and rubber points (Shofu) to a thickness of approximately 1.5mm. Color characteristics were performed with a spectrophotometer (CM-3500d, Minolta Co., LTD). A computer-controlled spectrophotometer was used to determine CIELAB coordinates ($L^*$, $a^*$ and $b^*$) of each specimen and shade guide. The CIELAB measurements made it possible to evaluate the amount of the color difference values (${\Delta}E{^*}ab$) of resin composites before the polymerization process and shade guides using the post-polishing color of the composite as a control, CIE standard D65 was used as the light source. The results were as follows. 1. Each of the resin composites evaluated showed significant color changes during light-curing process. All the resin composites evaluated except all the tested shades of 2100 showed unacceptable level of color changes (${\Delta}E{^*}ab$ greater than 3.3) between pre-polymerization and post-polishing state. 2. Color differences between most of the resin composites tested and their corresponding shade guides were acceptable but those between C2 shade of ${\AE}$litefil and IE shade of Amelogen Universal and their respective shade guides exceeded what is acceptable. 3. Comparison of the mean ${\Delta}E{^*}ab$ values of materials revealed that Z100 showed the least overall color change between pre-polymerization and post-polishing state followed by ${\AE}$litefil, VeridonFil-Photo, Spectrum TPH, and Amelogen Universal in the order of increasing change and Amelogen Universal. Spectrum TPH, 2100, VeridonFil-Photo and ${\AE}$litefil for the color differences between actual resin and shade guide. 4. In the clinical environment, the shade guide is the better choice than the shade of the actual resin before polymerization when matching colors. But, it is recommended that custom shade guides be made from resin material itself for better color matching.

• Restorative Dentistry and Endodontics
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• 제23권1호
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• pp.424-432
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• 1998

To get a satisfactory result in the composite resin restorations, it is necessary to choose correct shade. At present, most of the commercial composite resins are based on the Vita Lumin shade guide or Bioform shade guide, but color differences might be expected even using the same shade in various materials. In this study, five kinds of light-cured composite resins with A2 and B3 shade were used to measure and compare the color each other while one porcelain served as a control. All composite resins (Spectrum TPH (SP), VeridonFil- Photo (VE), Z100 (Z100), Charisma (CH), Prodigy (PRO)) were filled in to the metal mold (12 mm diameter, 2 mm depth), followed by compression, polymerization and polishing with wet sandpaper. The specimens of porcelain were fabricated by using the refractory mold for porcelain. After 24 hours, the specimens were placed on the spectrocolorimeter and spectral reflectance were measured under CIE illuminant D65. After measuring the values of $L^*$, $a^*$, $b^*$ and ${\Delta}E^*$, following results were obtained; 1. The $L^*$, $a^*$ and $b^*$ values of both shade of porcelain specimens showed significantly higher than those of resin specimens(p<0.05). 2. In comparing the resin specimens of the A2 shade, differences were significant except $L^*$ values of SP-CH and PRO-VE, $a^*$ values of the VE-SP and $b^*$ values of the VE-Z100 and SP-PRO(p<0.05), 3. In comparing the resin specimens of the B3 shade, differences were significant except $L^*$ values of PRO-SP, $a^*$ values of the SP-PRO and Z100-VE and b* values of the PRO-SP(p<0.05). 4. In comparing the resin specimens of the A2 shade, color differences between materials (${\Delta}E^*$) showed the lowest value of 1.66, and the highest was 5.16. ${\Delta}E^*$ values of the materials of VE-PRO, CH-PRO, SP-PRO, SP-Z100 and SP-CH were lower than 3.3. 5. In comparing the resin specimens of the B3 shade, the lowest value of the ${\Delta}E^*$ was 0.57 and the highest was 5.92. ${\Delta}E^*$ values of Z100-CH and SP-PRO were lower than 3.3. The present study revealed there was perceptible color difference between materials even if they have the same designated shade based on Vita shade guide. The results of the present study suggested that it would be necessary to establish the reproducible and constant color specification system for an esthetic restoration.

• 구강회복응용과학지
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• 제25권1호
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• pp.13-22
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• 2009

심미적인 특성을 가진 복합레진은 전치부 수복용 재료로 많이 이용되고 있다. 복합레진 수복 시 만족스러운 결과를 얻기 위해서는 색조의 선택이 중요한 역할을 한다. 현재 대부분의 수복용 복합레진은 Vita Lumin 색조견본(shade guide)이나 각각의 회사에서 제공하는 색조견본을 사용하고 있으나, 색조 견본 사이의 색차와 수복물과 견본 사이에 색차가 예상되어 그 차이를 규명하여 임상적인 선택 시에 도움이 되고자 하였다. 4종의 광중합 복합레진(Gradia Direct (GD), Z250 (Z250), Clearfil AP-X (AP-X), $Esthet{\cdot}X$ ($E{\cdot}X$))과 A2와 A3의 색조 견본을 사용하였다. 각 재료마다 3개의 시편과 1개의 색조 견본을 제작하였다. Teflon 주형(깊이 1.35 mm, 직경 8 mm)에 각각의 복합레진을 채우고 응축한 후에 중합하여 젖은 사포로 연마하였다. 색조 견본을 연마용 stone과 고무를 이용하여 1.35 mm 두께로 연마하였다. 컴퓨터에 의해 조절되는 spectrophotometer(color i5, GretagMacbeth, USA)를 이용하여 시편과 색조견본의 색의 특성을 CIELAB coordinates ($L^*$, $a^*$, $b^*$)로 평가하였다. CIELAB 계측을 통하여 복합레진과 색조 견본의 색차(${\Delta}E^*ab$)를 비교 평가 하였다. 광원으로는 CIE standard D65를 사용하였다. 다음과 같은 결과를 얻었다. 1. 동일한 shade로 설계된 여러 제조회사의 복합레진 시편의 $L^*$, $a^*$, $b^*$ 값 간에 유의할 만한 수준의 차이를 나타냈다(p<0.05). 2. 동일한 shade로 설계된 여러 제조회사의 복합레진 시편 간에 대부분 육안으로 인지할 만한 색차(${\Delta}E^*ab>3.3$)값을 나타냈다. 3. 동일한 shade로 설계된 여러 제조회사의 복합레진과 제조회사에서 제공되는 shade guide 및 Vita Lumin shade guide 간에 대부분 육안으로 인지할 만한 색차(${\Delta}E^*ab>3.3$)값을 나타냈다. 4. 임상에서 보다 나은 색 조화를 얻어 심미성을 향상시키기 위해서는 실제 수복물로 제작한 custom shade guide의 제작이 필요할 것으로 생각된다. 제조사에 의해 제공되는 색조 견본이나 Vita Lumin 색조 견본은 임상의에게 복합레진의 색조 선택 시에 정확한 기준을 제공하지는 않았고, 대부분의 제품에서 인지할 수 있는 색차가 있었다. 그러므로 보다 나은 색조 선택을 위해 수복용 레진으로 제작한 맞춤형 색조 견본을 사용하는 것을 추천한다.