• Corrosion Science and Technology
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• 제8권4호
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• pp.162-169
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• 2009

Pure titanium and its alloys are drastically used in implant materials due to their excellent mechanical properties, high corrosion resistance and good biocompatibility. However, the widely used Ti-6Al-4V is found to release toxic ions (Al and V) into the body, leading to undesirable long-term effects. Ti-6Al-4V has much higher elastic modulus than cortical bone. Therefore, titanium alloys with low elastic modulus have been developed as biomaterials to minimize stress shielding. For this reason, Ti-30Ta-xZr alloy systems have been studied in this study. The Ti-30Ta containing Zr(5, 10 and 15 wt%) were 10 times melted to improve chemical homogeneity by using a vacuum furnace and then homogenized for 24 hrs at $1000^{\circ}C$. The specimens were cut and polished for corrosion test and Ti coating and then coated with TiN, respectively, by using DC magnetron sputtering method. The analyses of coated surface were carried out by field emission scanning electron microscope(FE-SEM). The electrochemical characteristics were examined using potentiodynamic (- 1500 mV~+ 2000 mV) and AC impedance spectroscopy(100 kHz~10 mHz) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The equiaxed structure was changed to needle-like structure with increasing Zr content. The surface defects and structures were covered with TiN/Ti coated layer. From the polarization behavior in 0.9% NaCl solution, The corrosion current density of Ti-30Ta-xZr alloys decreased as Zr content increased, whereas, the corrosion potential of Ti-30Ta-xZr alloys increased as Zr content increased. The corrosion resistance of TiN/Ti-coated Ti-30Ta-xZr alloys were higher than that of the TiN-coated Ti-30Ta-xZr alloys. From the AC impedance in 0.9% NaCl solution, polarization resistance($R_p$) value of TiN/Ti coated Ti-30Ta-xZr alloys showed higher than that of TiN-coated Ti-30Ta-xZr alloys.

• 구강회복응용과학지
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• 제25권4호
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• pp.375-390
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• 2009

하악 완전 무치악 환자에서 이공 사이에 2개의 임플란트를 식립한 후 4종류의 어태치먼트를 사용한 하악 오버덴쳐를 제작하여 유한요소 모델을 만들고 여기에 3가지 하중 조건을 가하여 유한요소 해석 프로그램인 ANSYS 10.0을 이용하여 어태치먼트 종류에 따른 임플란트 주위골과 보철물 및 임플란트와 골 사이 계면에 발생하는 최대 응력의 크기와 응력 분포양상을 분석하였다. 하악골체의 전체적인 골격구조에서 치아 부분은 오버덴쳐로 모델을 형성하였고 오버덴쳐와 하악골 사이에 2mm 두께의 점막을 삽입하였다. 임플란트 오버덴쳐의 유한요소 모델은 ball and socket, Locator, magnet, bar의 각각 4가지 형태를 제작하였다. 고정체의 식립 위치는 양측 이공 전방이고, 경계 조건 중 고정점은 하악각 부위와 모형의 최후방 절점들을 고정점으로 설정하였다. 하중조건은 오버덴쳐의 좌측 제 2소구치에서 제 2대구치 편측 부위에 170N의 하중을, 좌 우측 제 2소구치에서 제 2대구치 양측 부위에 170N의 하중을, $90^{\circ}$수직 방향, $45^{\circ}$경사, 그리고 $0^{\circ}$ 수평 방향으로 가하였다. 결과 분석시 모든 하중방향에서 응력의 크기는 bar에서 임플란트나 오버덴쳐에서 가장 크게 나타났으며, 계면에서의 응력은 모든 어태치먼트에서 비슷한 응력분포가 나타났다. Ball and socket, Locator, magnet에서는 유의성을 보이지 않았다. 응력의 분포도에서는 4종류의 어태치먼트 모두 임플란트 치경부에서 응력이 집중된 양상을 보였으며 bar타입에서는 bar의 중앙에 응력이 크게나타났다. 이상의 결과로 볼 때 어태치먼트의 종류에 따라 응력분포의 차이가 있었음을 확인할 수 있었다. 어태치먼트의 선정 시 응력집중을 완화시킬 수 있는 바람직한 설계와 선택이 필요하리라 사료된다.

• Structural Engineering and Mechanics
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• 제74권4호
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• pp.567-576
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• 2020

Considerable controversy surrounds the choice of the best abutment type for implant prosthetics. The two most common structures are hex and non-hex abutments. The non-hex abutment typically furnishes a larger contact area between itself and the implant than that provided by a hex structure. However, when a hex abutment is loaded, the position of its contact area may be deeper than that of a non-hex abutment. Hence, the purpose of this study is to determine the different biomechanical behaviors of an internal bone-level implant based on the abutment type-hex or non-hex-and clinical crown length under static and cyclic loadings using finite element analysis (FEA). The hex structure was found to increase the implant and abutment stability more than the nonhex structure among several criteria. The use of the hex structure resulted in a smaller volume of bone tissues being at risk of hypertrophy and fatigue failure. It also reduced micromovement (separation) between the implant components, which is significantly related to the pumping effect and possible inflammation. Both static and fatigue analyses, used to examine short- and long-term stability, demonstrated the advantages of the hex abutment over the non-hex type for the stability of the implant components. Moreover, although its impact was not as significant as that of the abutment type, a large crown-implant ratio (CIR) increased bone strain and stress in the implant components, particularly under oblique loading.

• 대한치과교정학회지
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• 제41권1호
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• pp.51-58
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• 2011

Objective: To evaluate the shear bond strength (SBS), fracture mode, wire pull out (WPO) resistance and microleakage between low-shrinking and conventional composites used as a lingual retainer adhesive. Methods: A total of 120 human mandibular incisor teeth, extracted for periodontal reasons, were collected. Sixty of them were separated into two groups. To determine the SBS, either Transbond-LR (3M-Unitek) or Silorane (3M-Espe) was applied to the lingual surface of the teeth by packing the material into standard cylindrical plastic matrices (Ultradent) to simulate the lingual retainer bonding area. To test WPO resistance, 20 samples were prepared for each composite where the wire was embedded in the composite materialand cured. Then tensile stress was applied until failure of the composite occurred. The remaining 60 teeth were divided into two groups and multi-stranded 0.0215-inch diameter wire was bonded with the same composites. Microleakage was evaluated by the dye penetration method. Statistical analyses were performed by Wilcoxon, Pearson chi-square, and Mann-Whitney-U tests at p < 0.05 level. Results: The SBS and WPO results were not statistically significant between the two groups. Significant differences were found between the groups in terms of fracture mode (p < 0.001). Greater percentages of the fractures showed mix type failure (85%) for Silorane and adhesive (60%) for Transbond-LR. Microleakage values were lower in low-shrinking composite than the control and this difference was found to be statistically significant (p < 0.001). Conclusions: Low-shrinking composite produced sufficient SBS, WPO and microleakage values on the etched enamel surfaces, when used as a lingual retainer composite.