• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.190-190
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• 2008

자연적으로 발생되는 파도, 비, 우박 등과 철도, 차량 및 엘리베이터 등과 같은 인위적인 설치, 이동에 의해 발생되는 진동에너지는 우리 일상생활에서 가장 흔하게 발생할 수 있는 에너지원인데, 이러한 진동에너지는 압전 소재를 이용하여 재생 가능하여 최근에는 이에 대한 연구가 활발히 진행되어 왔다. 예를 들면, 미국의 MIT에서는 인간이 걸을 때 신발에 가해지는 압력을 이용하여 전력을 발생시키는 연구를 진행하여 2.9 mW의 전력을 얻었다. 특히 이러한 기술은 인간의 걷기 운동 등과 같은 일상적인 동작으로 필요한 전력을 얻을 수 있고, 세라믹 소자를 이용하기 때문에 전자노이즈가 발생되지 않을 뿐 아니라 반영구적으로 사용할 수가 있어서, 소형 전자기기 등에 서 기존 이차전지를 대체 또는 보완 할 수 있는 기술로 검토되고 있다. PZT계 세라믹스는 높은 유전상수와 우수한 압전특성으로 이러한 압전발전 분야에서 가장 널리 사용되어지고 있다. 하지만 에너지 효율을 높이기 위하여 적층 구조의 제작 시 구조적 특성상 내부전극이 도포된 상태에서 동시 소결이 필요한데, $1000^{\circ}C$ 이상의 높은 소결온도 때문에 소재 원가가 낮은 Ag전극 대신 값비싼 Pd나 pt가 다량 함유된 Ag/Pd, Ag/Pt 전극이 사용되고 있어 경제성이 떨어지는 단점을 갖게 된다. 순수 Ag 전극을 사용하거나 Ag의 비율이 높은 내부전극을 사용하기 위해서는 $900^{\circ}C$ 이하에서 소결되고 우수한 전기적 특성을 보이는 압전 세라믹스 소재를 개발 하는 것이 필요하다. 따라서 본 연구에서는 압전특성이 우수한 $(Pb_{1-x}Cd_x)(Ni_{1/3}Nb_{2/3})_{0.25}(Zr_{0.35}/Ti_{0.4})O_3$ 계의 조성을 설계하고, 소결온도를 낮추기 위해서 2 단계 하소법을 이용하였다. 또한 $MnCO_3$, $SiO_2$, $Pb_3O_4$ 등을 소랑 첨가하여 액상 소걸 특성을 부여하여 소결 온도를 감소시키려는 시도도 하였다. 소결체의 전체적인 제조 공정은 일반적인 벌크 세라믹의 소걸 공정을 따랐다. 최종 소결된 시편을 XRD분석을 통하여 상을 확인하였고 SEM을 이용하여 미세조직을 관찰 하였다. 전기적 특성을 평가하기 위하여 두께를 1mm로 연마한 시편에 Ag 전극을 도포하여 $650^{\circ}C$ 에서 열처리한 후, 분극처리 하였다. Impedance analyzer를 이용하여 압전 특성 (전기기계결합계수 및 기계적품질계수)을 측정 하였고, 압전전하상수는 $d_{33}$-meter로 측정하였다. 본 연구에서는 압전체에 가해지는 하중의 크기, 시편의 크기, 하중을 가하는 방법, 에너지 저장회로의 최적화 등을 다양하게 시도하면서 에너지 변환 및 저장 효율을 평가하였다.

• Journal of Oral Medicine and Pain
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• v.33 no.1
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• pp.35-40
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• 2008

This experiment was designed to clarify the effect of high concentrations of extracellular glucose on the periodontal ligament cells. The cells were incubated for 24 and 48 hours with ${\alpha}-MEM$ including 1,000 mg/L(control group) and 4,500 mg/L(experimental group) of glucose. Then, the expressions of ${\alpha}5$ integrin, cathepsin-B and -L were examined using RT-PCR method. The results were as follows: 1. ${\alpha}5$ integrin expression was increased after incubation in high glucose media. 2. Cathepsin-B expression was increased after the 24-H incubation with high glucose media, but was decreased after the 48-H incubation. 3. The expression of cathepsin-L was decreased by the high glucose media. Theses results suggest that extracellular glucose at high concentration may be attributed to delayed wound healing in diabetes patients through increase in ${\alpha}5$ integrin and decrease in cathepsins, which lead to accumulation of extracellular matrices and adhesion molecules.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.33 no.4
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• pp.340-349
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• 2007

Free flap transplantation with microvascular anastomosis has been successfully performed by development of surgical technique, materials and postoperative monitoring equipments of flap. But success rate of microvascular anastomosis is influenced by various factors, and failure rate is about 5-10%. The most influential factor for success rate is surgical technique and other factors that influence failure of microvascular anastomosis are ischemic time of free flap, thrombus formation of anastomosis region and vascular spasm. In this study, vascular patency and thrombus formation in experimental micro-venous anastomosis, and endothelial repair were observed with histologic analysis, scanning electron microscopy, transmission electron microscopic examination. The results were obtained as follows: 1. In vascular patency test in 30 minute and 7 days after micro-venous anastomosis with heparin irrigation, all of 12 anastomosis site were good vascular patency. 2. In thrombus formation in 2 weeks group(Experimental I), 2 site of 6 cases were observed thrombus, and in 4 weeks group(Experimental II), 1 site of 6 cases were observed thrombus. 3. In histologic examination, normal vein(Control Group) showed continued internal elastic lamina, well formed thick smooth muscle layer and connective tissue. The group of 2 weeks after microvenous anastomosis(Experimental I) showd locally recovered internal lamina, discontinued internal lamina, disorganized smooth muscle cells and granulation tissue around suture silk. In the group of 4 weeks after micro-venous anastomosis(Experimental II), anastomosis site showed almostly continued internal lamina, disorganized smooth muscle cells and cicartrized tissue around suture silk. 4. In scanning electron microscope examination in 2 weeks(Experimental I) after micro-venous anastomosis, mesh fibrin formation showed near to endothelial cells, and in 4 weeks after micro-venous anastomosis(EXperimental II), numerous blood cells and fibrin mesh formation was seen associated with irregular endothelial cell arrangement. 5. In transmission electron microscope examination in 2 weeks after micro-venous anastomosis(Experimental I), irregular arrangement of smooth muscle cells was seen adjacent to collagenized tissue around suture silk. In 4 weeks after micro-venous anastomosis(Experimental II), denuded venous wall composed of relatively well arranged smooth muscle cells was covered by endothelial cells, but fibroblast cells and foreign body giant cells near to suture silk was remained. From the results obtained in this study, results of good vascular patiency and anti-thrombotic effect of heparin were obtained as a local irrigation solution, and repair of venous endothelial cell was observed in 2 weeks after micro-venous anastomosis.

• Journal of Periodontal and Implant Science
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• v.26 no.4
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• pp.967-987
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• 1996

The present study was to evaluate the healing patterns of guided tissue regeneration( GTR) using resorbable $Vicryl^{(R)}$(polyglactin 910) mesh and nonresorbable expanded polytetrafluoroethylene(ePTFE) membrane with or without bone grafting using autogeneous bone and demineralized freeze-dried bone allograft(DFDBA) in the grade II furcation defects. Mucoperiosteal flaps were reflected buccally in the mandibular 2nd, 3rd and 4th premolar areas and furcation defects were created surgically by removing $5{\times}6mm$ alveolar bone in 4 dogs. Root surfaces were thoroughly debrided of periodontal ligament and cementum, and notches were placed on root surface at the most apical bone level. In the right and left mandibular quadrant, each tooth was received $Vicryl^{(R)}$ mesh(ACE Surgical Supply Co., USA) only, $Vicryl^{(R)}$ mesh with DFDBA, $Vicryl^{(R)}$ mesh with autogeneous bone grafts, ePTFE membrane($Core-tex^{(R)}$ membrane, W.L. Gore & Associates Inc., USA) only, ePTFE membrane with DFDBA or ePTFE membrane with autogeneous bone grafts. For the fluorescent microscopic examination, fluorescent agents were injected at 2, 4 and 8 weeks after surgery. Four weeks after surgery, 2 dogs were sacrificed and ePTFE membranes were removed from remaining 2 dogs, which were sacrificed at 12 weeks after surgery. Undecalcified tissues were embedded in methylmethacrylate and $10{\mu}m$ thick sections were cut in a buccolingual direction. These sections were stained with hematoxylin-eosin stain and Masson's trichrome stain, and evaluated by descriptive histology and linear measurements. The results were as follows : 1) $Vicryl^{(R)}$ mesh group showed less connective tissue attachment than ePTFE membrane group. 2) The combination of GTR using $Vicryl^{(R)}$ mesh and osseous grafts resulted in new attachment and new bone formation more than GTR using $Vicryl^{(R)}$ mesh only. 3) GTR using ePTFE membrane, with or without osseous grafts, enhanced periodontal regeneration. 4) Root resorption and dentoalveolar ankylosis were observed in the areas treated with the combination of GTR and DFDBA. It was suggested that the effect of adjunctive bone grafting in GTR procedure depends on the materials and the physical properties of barrier membranes. $Vicryl^{(R)}$ mesh performed a barrier function and the use of adjunctive bone grafting may enhance the periodontal regeneration.

• 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.25 no.3
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• pp.603-613
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• 1995

The purpose of this investigation was to evaluate on the biodegradability, biocompatibility and tissue regenerative capacity of synthetic bioabsorbable membranes in beagle dogs. For animal study, 9 adult beagle dogs were used to examination, on the surgical implantation of membranes and histological analysis. In each animal, the 3rd and 4th premolars of the both sides of the mandible were selected as test teeth. Two types of bioresorbable membranes including "Guidor membrane", "S-membranes" were used to examining for biological activity, and also Gore-tex membranes was used for positive control. Surgically created defects were made in 2 premolars of both sides of the mandible at $3{\times}4mm^2$ in size and tested membranes were implanted in the defected area. A plaque control regimen was instituted with daily tooth brushing with a 0.1% chlorhexidine digluconate during experimental periods. All the experimental animals were sacrificed after 2, 4, and 8 weeks from surgery and undecalcified slides were prepared using the "sawing and grinding" technique described by Donath and Breuner". In biodegradability, all the membranes were started their biodegradation from two weeks after implantation and gradually demolished of their frame morphology from eight weeks. However, demolition of membranes in 8 weeks after implantation was highest in Guidor membranes and followed by S-membranes. Biocompatibilityof two kinds of biodegradable membranes including Guidor and S-mambrane were shown to be well tolerated to the surrounding tissue, and were minimal accumulation of inflammatory cell infiltration around the implanted membranes to compare with Gore-tex membrane. Regeneration of defected alveolar bone was initiated from two weeks of membrane implantation and new bone formation was gradually increased from that time. However, pattern of new bone formation on the defected areas of two kinds of biodegrable membranes was almost similar and quite competitive comparing with Gore-tex membrane. These results implicate that bioresorbable membranes should be highly useful tool for guided tissue regeneration of periodontal defects.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.4
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• pp.686-692
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• 2006

The impacted teeth were surgically exposed by the closed-eruption technique and orthodontically retracted. The subject of this study are 24 patients(Mx. insiors; 10 Mx. canines; 14) who finished their treatment. The periodontal condition of the impacted teeth and the normally erupted proximal and opposed teeth were compared and analysed. The results are the followings ; 1. When the gingival index, plaque index, pocket depth and attached gingiva in periodontal evaluation were compared, there was no significant difference between the study group and the control group (P>0.05). 2. When the alveolar bone support of the mesial and the distal surface of the maxillary central incisors and proximal teeth was compared, there was no significant difference between the study group and the control group (P<0.05). 3. When the alveolar bone support of the maxillary canines was compared, there was no significant difference between the retracted teeth and the normally erupted teeth(P>0.05). The results above showed that the surgical exposure by closed-eruption technique followed by the orthodontic retraction of the impacted teeth has a positive influence on the regeneration of gingival tissue in clinical practice and is esthetically more stable. And it is considered that the clinicians should give attention to the direction of retraction power and the maintenance of normal shape of the alveolar bone in treatment of maxillary central incisors.

• Archives of Plastic Surgery
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• v.33 no.2
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• pp.205-212
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• 2006

Using adipose derived stem cells(ASCs), neurogenic differentiation was induced in a mono layered culture medium containing neuronal induction agents. Cells differentiated to the neuronal cells were observed with a inverted microscope and immunofluorecent study. We made a 15 mm long defect in the sciatic nerve of 14 rats and connected a silicone tube to the defect. Then, we mixed neuronal progenitor cells differentiated from ASCs with collagen gel and grafted them to a group of rats(experimental group) and grafted only collagen gel into another group(control group). In 4 and 8 weeks after the graft, histological observation was made. According to the result, the number and diameter of myelinated axons were significantly increased in the experimental group. In addition, the nerve conduction velocity was improved more in the experimental group and neovascularity also increased. Moreover, reaction with S100 and p75 was observed in regenerated nerves in the experimental group, suggesting that the grafted cells were differentiated into supportive cells such as Schwann's cells. In conclusion, this research proved that ASCs can multiply and differentiate into neuronal cells. If they are grafted into nerve defects, the grafted cells are differ entiated into supportive cells such as Schwann's cells and thus contribute to nerve regeneration. Accordingly, the use of adipose tissue obtained easily without the limitation of donor site can be greatly helpful in treating peripheral nerve defects.

• Journal of the Korean Society of Food Science and Nutrition
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• v.31 no.6
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• pp.1107-1111
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• 2002

This study has been carried out to investigate the effects of the Phenolic compound on the hyperglycemic mice induced with strentozotocin (STZ). The effects of the phenolic compound were assayed by the changes of the blood glucose creatinine and blood urea nitrogen (BUN ) levels, and insulin-immunohistochemical staining and electron microscopical observation for $\beta$ -cells of the Langerhan's islet, under the same experimental conditions. For this purpose male mice were fed with phenolic compound (PA group, IS mg/kg/day; PB group, 90 mg/kg/day)in their diet while the control group received the same commercial diet, for 6 weeks. The blood glucose contents was examined by tail vein blood once a week for 6 weeks. Samples of the pancreas removed after that period were processed for the immunohistochemical identification of $\beta$ -cells as well as for measuring ultrastructural changes of $\beta$-cells. The levels of serum glucose were decreased significantly (p<0.05) on the PB group compared with the control and PA group. The blood BUN and creatinine levels are slightly decreased in the phenolic compound feeding groups compared with control group. The $\beta$-cells on Langerhnan's islet were destructed by administration of STZ, so that a few of insulin-positive cells were observed in the control group. A lot of insulin-positive cells were observed in the PB group compared with the control group. According to the electron microscopical observation $\beta$-cells are recovered from the damage in the PA group. The $\beta$-cell contained a lot of electron dense and pale granules compared with control group. These results suggest that administration of the pear phenolic compound to the mice helped recovery from the damage induced by STZ.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.34 no.2
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• pp.220-229
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• 2008

Purpose: The present study was aimed to examine the effect of acellular dermal matrix ($AlloDerm^{(R)}$) grafted to the experimental tissue defect on tissue regeneration. Materials and Methods: Male albino rabbits were used. Soft tissue defects were prepared in the external abdominal oblique muscle. The animals were then divided into 3 groups by the graft material used: no graft, autogenous dermis graft, and $AlloDerm^{(R)}$ graft. The healing sites were histologically examined at weeks 4 and 8 after the graft. In another series, critical sized defects with 8-mm diameter were prepared in the right and left iliac bones. The animals were then divided into 5 groups: no graft, grafted with autogenous iliac bone, $AlloDerm^{(R)}$ graft, $AlloDerm^{(R)}$ graft impregnated with rhBMP-2, and $AlloDerm^{(R)}$ graft with rhTGF-${\beta}1$. The healing sites of bone defect were investigated with radiologic densitometry and histological evaluation at weeks 4 and 8 after the graft. Results: In the soft tissue defect, normal healing was seen in the group of no graft. Inflammatory cells and foreign body reactions were observed in the group of autogenous dermis graft, and the migration of fibroblasts and the formation of vessels into the collagen fibers were observed in the group of $AlloDerm^{(R)}$ graft. In the bone defect, the site of bone defect was healed by fibrous tissues in the group of no graft. The marked radiopacity and good regeneration were seen in the group of autogenous bone graft. There remained the traces of $AlloDerm^{(R)}$ with no satisfactory results in the group of $AlloDerm^{(R)}$ graft. In the groups of the $AlloDerm^{(R)}$ graft with rhBMP-2 or rhTGF-${\beta}1$, there were numerous osteoblasts in the boundary of the adjacent bone which was closely approximated to the $AlloDerm^{(R)}$ with regeneration features. However, the fibrous capsule also remained as in the group of $AlloDerm^{(R)}$ graft, which separated the $AlloDerm^{(R)}$ and the adjacent bone. Conclusions: These results suggest that $AlloDerm^{(R)}$ can be useful to substitute the autogenous dermis in the soft tissue defect. However, it may not be useful as a bone graft material or a carrier, since the bone defect was not completely healed by the bony tissue, regardless of the presence of osteogenic factors like rhBMP-2 or rhTGF-${\beta}1$.