• Korean Journal of Materials Research
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• v.25 no.3
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• pp.155-164
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• 2015

Porous metals are called as a new material of 21th century because they show not only extremely low density, but also novel physical, thermal, mechanical, electrical, and acoustic properties. Since the late in the 1990's, considerable progress has been made in the production technologies of many kinds of porous metals such as aluminum, titanium, nickel, copper, stainless steel, etc. The commercial applications of porous metals have been increased in the field of light weight structures, sound absorption, mechanical damping, bio-materials, thermal management for heat exchanger and heat sink. Especially, the porous metals are promising in automotive applications for light-weighting body sheets and various structural components due to the good relation between weight and stiffness. This paper reviews the recent progress of production techniques using molten metal bubbling, metal foaming, gas expansion, hollow sphere structure, unidirectional solidification, etc, which have been commercialized or under developing, and finally introduces several case studies on the potential applications of porous metals in the area of heat sink, automotive pannel, cathod for Ni-MH battery, golf putter and medical implant.

• Korean Journal of Metals and Materials
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• v.50 no.1
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• pp.86-91
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• 2012

Ti-6Al-4V extra low interstitial (ELI) alloy has been widely used as an orthopedic implant material because of its excellent biocompatibility, corrosion resistance and mechanical properties. However, V-free titanium alloys such as Ti-6%Al-7%Nb and Ti-5%Al-2.5%Fe have recently been developed because of the toxicity of V. Hydroxyapatite (HA) is used as a coating material on Ti or Ti biomaterials due to its good biocompatibility. However, HA coated on Ti alloy causes a problem for tissue by peeling off during usage. Therefore, such peeling off during long time usage can be suppressed by adding HA in Ti or Ti alloy composites. The aim of this study was to manufacture an ultra fine grained (UFG) Ti-Nb-HA bulk alloy, which is usually difficult to fabricate using melting and casting technology, by rapid sintering process using high energy mechanical milled (HEMM) powder.

• Journal of the Korean institute of surface engineering
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• v.51 no.5
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• pp.309-315
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• 2018

The purpose of this study is to assess the mechanical properties of the ceramic abutment with washer. In this study, ceramic abutment were used, tested with $30^{\circ}$ compression load, shear fatigue, adaptation accuracy test(rotation angle, contact interval), removal torque force test, torsional breaking force test. The $30^{\circ}$ compression load was 729 N, the shear fatigue load was 275 N, adaptation accuracy test of rotation angle was within $3^{\circ}$, contact interval within $10{\mu}m$, and removal torque force test value is $18.88N{\cdot}cm$, torsional breaking force test value is $35.52N{\cdot}cm$. Ceramic abutment with a washer fitted have sufficient mechanical strength and may be substituted for titanium abutment.

• The Journal of Advanced Prosthodontics
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• v.11 no.5
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• pp.253-261
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• 2019

PURPOSE. To evaluate the influence of cyclic loading on phase transformation of zirconia abutments and to compare the effectiveness of three different quantitative ageing assessment techniques. MATERIALS AND METHODS. Thirty two Y-TZP prostheses fabricated from two brands, InCoris ZI and Ceramill ZI, were cemented to titanium bases and equally divided into two subgroups (n=8): control group without any treatment and aged group with cyclic loading between 20 N and 98 N for 100,000 cycles at 4 Hz in distilled water at $37^{\circ}C$. The tetragonal-to-monoclinic phase transformation was assessed by (i) conventional x-ray diffraction (XRD), (ii) micro x-ray diffraction (${\mu}XRD$), and (iii) micro-Raman spectroscopy. The monoclinic-phase fractions (M%) were compared by two-way ANOVA. RESULTS. InCoris Zi presented significantly higher M% than Ceramill Zi in both control and aged groups (P<.001). Both materials exhibited significant phase transformation with monoclinicphase of 1 to 3% more in aged groups than controls for all three assessment techniques. The comparable M% was quantified by both ${\mu}XRD$ and XRD. The highest M% was assessed with micro-Raman. CONCLUSION. Cyclic loading produced significant phase transformation in tested Y-TZP prostheses. The micro-Raman spectroscopy could be used as an alternative to XRD and ${\mu}XRD$.

• Journal of Periodontal and Implant Science
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• v.25 no.2
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• pp.301-320
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• 1995

The purpose of this study was to evaluate a new biodegradable membrane - atelocollagen as a guided tissue regeneration barrier on the dehiscence defects adjacent to the dental implants. 3 beagle dogs were selected for this study and all the mandibular premolars($P_1,P_2,P_3&P_4$) were extracted. Twelve weeks after the extraction, the edentulous ridges were formed to be placed the titanium plasma-sprayed IMZ implants. Four implant osteotomies were performed on each side of the mandible. The osteotomies were placed facially in the edentulous ridges to approximate an actual dehiscence defect as closely as possible, The standardized dehiscence defects were created 3 mm in width and 4 mm in height by osteotomy. A total 24 implants were placed. e-PTFE, ateloco11agen and $Collatape^{(R)}$ were placed to cover the defects and the one defect served as a control, not covered any membrane. By random selection, three dogs were sacrificed at 2 weeks, 4weeks and 8 weeks after fixation with 3% glutaraldehyde. A week before sacrificing, 8-week dog was infused intravenously with oxy-tetracycline 30mg/kg. The left mandibular blocks were used for full decalcified histologic preparation and the right mandibular blocks were selected for undeca1cified preparation, At 2 weeks, the regenerated bone of e-PTFE and atelocollagen groups appeared to be more dense than other groups and the percentage of bone defect fill was highest for e-PTFE and follwed by ateloco1lagen group. However, the $Collatape^{(R)}$ and control groups showed a little new bone formation. $Collatape^{(R)}$ was almost degraded within 2 weeks. At 4 weeks, the regenerated new bone were much greater and denser than at 2 weeks for e-PTFE and ateloco11agen group. Although a part of atelocollagen bagan to be degraded at the margin and surrounded by foreign body giant cells related to foreign body reaction, it was generally intact and the regenerated new bone was shown much more than at 2 weeks. The amount of new bone in $Collatape^{(R)}$ and control groups at 4 weeks were similar to that of 2 weeks group. At 8 weeks, the regenerated bone was matured and observed along the implant fixture. Direct new bone formation and calcium deposits beneath the e-PTFE were observed. No further bone growth was seen in the $Collatape^{(R)}$ and control groups. In reflected fluoromicrcocopic observation, the osteogenic activity was pronounced between e-PTFE membrane and the old bone. High osteogenic activity was also observed in atelocol1agen group. This study suggested that the ateloco11agen as well as e-PTFE could be used for guided tissue regeneration on dehiscence defects adjacent to the dental implants. But the $Collatape^{(R)}$ was completely resorbed within 2 weeks and was not a suitable membrane for guided bone regeneration.

• Journal of Periodontal and Implant Science
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• v.50 no.2
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• pp.106-120
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• 2020

Purpose: A new form of porous polyethylene, characterized by higher porosity and pore interconnectivity, was developed for use as a tissue-integrated implant. This study evaluated the effectiveness of porous polyethylene blocks used as an onlay bone graft in rabbit mandible in terms of tissue reaction, bone ingrowth, fibrovascularization, and graft-bone interfacial integrity. Methods: Twelve New Zealand white rabbits were randomized into 3 treatment groups according to the study period (4, 12, or 24 weeks). Cylindrical specimens measuring 5 mm in diameter and 4.5 mm in thickness were placed directly on the body of the mandible without bone bed decortication, fixed in place with a titanium screw, and covered with a collagen membrane. Histologic and histomorphometric analyses were done using hematoxylin and eosin-stained bone slices. Interfacial shear strength was tested to quantify graft-bone interfacial integrity. Results: The porous polyethylene graft was observed to integrate with the mandibular bone and exhibited tissue-bridge connections. At all postoperative time points, it was noted that the host tissues had grown deep into the pores of the porous polyethylene in the direction from the interface to the center of the graft. Both fibrovascular tissue and bone were found within the pores, but most bone ingrowth was observed at the graft-mandibular bone interface. Bone ingrowth depth and interfacial shear strength were in the range of 2.76-3.89 mm and 1.11-1.43 MPa, respectively. No significant differences among post-implantation time points were found for tissue ingrowth percentage and interfacial shear strength (P>0.05). Conclusions: Within the limits of the study, the present study revealed that the new porous polyethylene did not provoke any adverse systemic reactions. The material promoted fibrovascularization and displayed osteoconductive and osteogenic properties within and outside the contact interface. Stable interfacial integration between the graft and bone also took place.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.1
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• pp.41-52
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• 2009

The surface treatment of titanium implant could bring out the biochemical bonding between bone and implant. The purpose of this study was to evaluate the biomechanical bone response of Mg-ion implanted implants with plasma source ion implantation method. Twelve New Zealand white rabbits were included in this study. Each rabbit received one control fixture (blasted with resorbable blasting media, RBM) and three types of Mg ion implanted fixtures in tibiae. The implants were left in place for 6 weeks before the rabbits were sacrificed. Removal torque value and resonance frequency analysis (ISQ) were compared. The repeated measured analysis of variance was used with $P{\leq}0.05$ as level of statistical significance. ISQ was not different among all groups. However, the ISQ was increased after 6 weeks healing. The group had lowest ISQ value showed the greatest increment. Mg-1 implants with 9.4% retained ion dose showed significantly higher removal torque value than that of the other implants. From this results, it is concluded that the Mg-1 implants has stronger bone response than control RBM surface implant.

• Journal of Periodontal and Implant Science
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• v.35 no.3
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• pp.525-536
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• 2005

여러 연구들을 통해 많은 학자들이 임프란트 안정성(stability)은 표면의 특징에 달려있다고 생각하게 되었다. 표면의 구조, 에너지, 산화물(oxide) 두께와 표면성상(topography)등 임프란트의 표면의 특징은 임프란트와 골조직의 반응에서 중요한 역할을 하는 것이 알려짐에 따라 티타뮨 임프란트의 표면의 처리 방법에 큰 관심을 가지게 되었다. 그 중에서 티타늄 임프란트 표면의 산화피막화(anodization)가 한 방법으로 대두되었다. 이 방법은 전기화학적 방식으로 임프란트 표면에 거칠고(rough)두꺼우며(thick), 기공(pore)을 가지는 산화물 막을 형성하는 것으로 산화물의 두께는 coronal 부분(l-2 ${\mu}m$)으로부터 apical부분(7-10 ${\mu}m$)까지 증가하게 된다. 산화피막의 표면에는 다양한 크기의 수많은 기공이 주로 1-2 ${\mu}m$ 두께로 임프란트의 apical 부분에서 존재하며, 임프란트 표면의 거칠기는 conical 위부분에서 apical 부분까지 계속 증가한다(평균 Ra value=1.2 ${\mu}m$). 또 다른 표면 처리 방법으로는 blasting 후에 etching을 한 SLA 표면이 있다. 이 연구의 목적은 일반적으로 많이 이용되고 있는 anodized 표면과 SLA 표면의 조직학적 반응을 비교 분석하는 것이다. 24개 임프란트를(anodized surfaced implant-12개 , SLA-12개, 8mm ${\times}\;{\Phi}$ 4.3) 6마리 토끼의 오른쪽과 왼쪽 femur에 식립하였다. 12주후에 동물들을 희생하여 EXACT cutting-grinding system을 이용하여 샘플을 절단하고 800, 1200 및 4000 번 연마제(abrasive) paper로 20-50 ${\mu}m$ 까지 grinding하였다. 샘플은 Multiple staining 용액으로 염색하여 SLA 임프란트 군과 비교하였다. 골과 임프란트 사이에 연결을 TDI 프로그램을 이용하여 %로 측정하였다. SLA 임프란트 군 경우에는 골과 임프란트 사이의 연결이 $74{\pm}19%$ 이고, 양극 산화한 임프란트 군 경우에는 $77{\pm}9%$이었다. 양극 산화한 티타늄 임프란트의 골 접촉률이 SLA 표면 임프란트 경우과 통계학적으로 유의한 차이는 보이지 않았다.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.2
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• pp.209-216
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• 2008

Statement of problem: It is difficult about assessing the loosening tendency of conical connection type implant after cyclic loading with diamond like carbon coating one-piece abutments, and also about the retightening effect. Purpose: This study was performed to investigate the influence of one-piece abutment screw retightening after $5.0{\times}10^{4}$ cyclic loading and Diamond like coating Material and methods: Thirty two ITI implant were divided to 4 groups. Group 1,3-titanium abutment, group 2,4 - diamond like carbon coated abutment. Group 1,2 - $20.0{\times}10^{4}$ cyclic loading after $5.0{\times}10^{4}$ cyclic loading, Group 3,4- after $20.0{\times}10^{4}$ Cyclic loading. After cyclic loading, periotest values were taken and removal torque values of abutments were measured with a digital torque gauge. Results: 1. The removal torque of group 2 after $5.0{\times}10^{4}$ cyclic loading is slightly greater than the other groups but not significantly higher than others (P>0.05). 2. The final removal torque values after $20.0{\times}10^{4}$ cyclic loading of group 1 is bigger than group 3, and group 2 is bigger than group 4, but not significantly higher (P>0.05). 3. The final removal torque values after $20.0{\times}10^{4}$ cyclic loading of all groups are not significantly different (P>0.05).

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.1
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• pp.85-97
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• 2007

Statement of problem: Recently, anodic oxidation of cp-titanium is a popular method for treatment of titanium implant surfaces. It is a relatively easy process, and the thickness, structure, composition, and the microstructure of the oxide layer can be variably modified. Moreover the biological properties of the oxide layer can be controlled. Purpose: In this study, the roughness, microstructure, crystal structure of the variously treated groups (current, voltage, frequency, electrolyte, thermal treatment) were evaluated. And the specimens were soaked in simulated body fluid (SBF) to evaluate the effects of the surface characteristics and the oxide layers on the bioactivity of the specimens which were directly related to bone formation and integration. Materials and methods: Surface treatments consisted of either anodization or anodization followed thermal treatment. Specimens were divided into seven groups, depending on their anodizing treatment conditions: constant current mode (350V for group 2), constant voltage mode (155V for group 3), 60 Hz pulse series (230V for group 4, 300V for group 5), and 1000 Hz pulse series (400V for group 6, 460V for group 7). Non-treated native surfaces were used as controls (group 1). In addition, for the purpose of evaluating the effects of thermal treatment, each group was heat treated by elevating the temperature by $5^{\circ}C$ per minute until $600^{\circ}C$ for 1 hour, and then bench cured. Using scanning electron microscope (SEM), porous oxide layers were observed on treated surfaces. The crystal structures and phases of titania were identified by thin-film x-ray diffractmeter (TF-XRD). Atomic force microscope (AFM) was used for roughness measurement (Sa, Sq). To evaluate bioactivity of modified titanium surfaces, each group was soaked in SBF for 168 hours (1 week), and then changed surface characteristics were analyzed by SEM and TF-XRD. Results: On basis of our findings, we concluded the following results. 1. Most groups showed morphologically porous structures. Except group 2, all groups showed fine to coarse convex structures, and the groups with superior quantity of oxide products showed superior morphology. 2. As a result of combined anodization and thermal treatment, there were no effects on composition of crystalline structure. But, heat treatment influenced the quantity of formation of the oxide products (rutile / anatase). 3. Roughness decreased in the order of groups 7,5,2,3,6,4,1 and there was statistical difference between group 7 and the others (p<0.05), but group 7 did not show any bioactivity within a week. 4. In groups that implanted ions (Ca/P) on the oxide layer through current and voltage control, showed superior morphology, and oxide products, but did not express any bioactivity within a week. 5. In group 3, the oxide layer was uniformly organized with rutile, with almost no titanium peak. And there were abnormally more [101] orientations of rutile crystalline structure, and bonelike apatite formation could be seen around these crystalline structures. Conclusion: As a result of control of various factors in anodization (current, voltage, frequency, electrolytes, thermal treatment), the surface morphology, micro-porosity, the 2nd phase formation, crystalline structure, thickness of the oxide layer could be modified. And even more, the bioactivity of the specimens in vitro could be induced. Thus anodic oxidation can be considered as an excellent surface treatment method that will able to not only control the physical properties but enhance the biological characteristics of the oxide layer. Furthermore, it is recommended in near future animal research to prove these results.