• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1082-1083
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• 2006

Carbon nanotube (CNT) reinforced hydroxyapatite (HAp) composites were fabricated by using the spark plasma sintering process with surfactant modified CNT and HAp nano powder. Without the dependency on sintering temperature, the main crystal phase existed with the HAp phase although a few contents of ${\beta}-TCP$ (Tri calcium phosphate) phase were detected. The maximum fracture toughness, $(1.27\;MPa.m^{1/2})$ was obtained in the sample sintered at $1100^{\circ}C$ and on the fracture surface a typical intergranular fracture mode, as well as the pull-out pmhenomenon of CNT, was observed.

• 한국세라믹학회지
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• 제26권2호
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• pp.147-156
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• 1989

The effects of starting composition, sintering temperature and porosity on the mechanical properties of hydroxyapatite ceramics were investigated. The hydroxyapatite powder were prepared by precipitation method using Ca(NO3)2.4H2O and (NH4)2.HPO4. The obtained powders were Ca-deficient hydroxyapatites and as the Ca/P mole ration in the initial solution was increased, the particle size of the precipitates was decreased, and the decomposition of hydroxyapatite to $\beta$-TCP was controlled. The porosity, as well as Ca/P mole ratio in starting composition and sintering temperature, plays major role in the mechanical properties of dense hydroxyapatite ceramics.

• 대한치과의사협회지
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• 제48권4호
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• pp.263-274
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• 2010

I classified the bone graft material according to the component. Most bone graft material is composed of inorganic and organic constituent. Organic component such DBM is associated with osteoinduction. Inorganic components such as hydroxyapatite, $\beta$-TCP, calcium sulfate, bioactive glass, polymer are associated with osteoconduction. Autogenous bone graft is ideal material. We can select any biocompatible material for the restoration of small filling defect with intact bony wall. However, we should select first osteogenetic and osteoinductive material to regenerate the viable bone tissue.

• 생물정신의학
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• 제7권2호
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• pp.174-179
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• 2000

연구목적 : 환청이 자기감시체계의 이상이라고 주장하는 일부 학자들은 청각적 언어상상과 관련된 뇌 활성화 소견을 이용하여 환청의 병리기전을 밝히고자 하였다. 그런데 대부분의 환청의 내용은 부정적 감정을 동반하는 내용이다. 이런 점에서 저자들은 부정적 감정이 청각적 언어상상에 의해 유발된 대뇌 피질 활성에 어떤 식으로 영향을 미치는지 알아보고, 이를 통해 부정적 감정이 환청발생에 미칠 수 있는 영향을 이해해 보고자 하였다. 방법 : 정상인과 정신분열병 환자를 대상으로 부정적 내용의 청각적 언어상상 과제와 부정적 내용의 청각적 언어상상 과제를 수행토록 하였다. 이 두 가지 과제를 수행하면서 정량화뇌파검사를 시행하였고, 이때의 대뇌피질 활성의 차이를 paired t-test를 이용하여 분석하였다. 그리고 이러한 차이가 정신분열병 환자와 정상인에서 각기 어떤 식으로 달리 나타나는가 비교하였다. 결과 : 정상인의 경우 중립적 감정일 때에 비해 부정적 감정의 청각적 언어상상시, 좌측 측두엽 부위(TCP1)에서 beta주파수대의 뇌파 진폭이 증가하였고, 대뇌 우반구의 몇몇 부위(FP2, F4, C4, CP2, P4)에서 theta주파수대의 뇌파 진폭이 감소하였다. 그러나 정신분열병 환자의 경우, 두 가지 과제를 수행하는 동안 모든 주파수대에서 뇌파 진폭의 차이가 관찰되지 않았다. 결론 : 본 연구 결과는 좌측 측두엽의 더 많은 활성이 요구되는 부정적 내용의 청각적 언어상상을 하게 될 때, 정신분열병 환자에서는 적절한 활성화가 이루어지지 못하는 것을 지지하는 소견으로 생각된다. 그리고 이에 따른 자기감시체계의 활성의 저하가 환청과 밀접하게 관련될 수 있는 것으로 시사된다.

• 대한임상검사과학회지
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• 제47권3호
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• pp.117-124
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• 2015

중간엽줄기세포는 손상된 관절연골 치유능력을 가지고 있어 줄기세포 치료 분야에서 대표적인 성체줄기세포로 알려져 있다. 자외선이 조사된 생체 친화성 필름 조성물인 DTOPV (S-triazine bridged p-phenylenevinylene)는 친수성 특성의 표면을 가진 형광 화합물이다. 이전의연구에서 물질표면의 습윤성과 친수성이 세포부착 및 증식에 중요한 역할을 하는 것이 확인 되었으며, 이번 연구에서는 DTOPV를 이용하여 중간엽줄기세포의 연골분화능을 향상시키고자 하였다. 일반 배양용기로 사용하고 있는 TCPS (tissue culture polystyrene)와 자외선이 조사된 패턴된 DTOPV 필름을 이 실험에 사용하였고 TGF (transforming growth factor)-${\beta}3$가 포함된연골분화배지로 중간엽줄기세포를 2주동안 분화유도를 하였다. TCPS에서 배양된 중간엽줄기세포는 단층으로 자라면서 분화가 유도된 반면, 자외선이 조사된 DTOPV 필름 위에서 배양된 세포는덩어리진 구형으로 형태가 변하였으며, 연골세포에 특이적으로 염색되는 Safranine O 염색으로 DTOPV 조건에서 더 붉게 염색됨을 관찰하였다. 또한 연골세포 특이적인 유전자인 Type II collage이 DTOPV 조건에서 더 강하게 발현되는 것을 확인함으로써 TCPS보다 DTOPV에서 연골세포로 분화가 향상된 것을 알 수 있었다. 따라서 자외선이 조사된 생체 친화성 필름 조성물인 DTOPV을 이용한 경우에 일반 배양용기보다 빠르게 연골분화가 이루어짐을 알 수 있었다. 결론적으로 향후 조직공학 분야에서 DTOPV가 중간엽줄기세포의 효과적인 연골분화 물질로서 활용될 수 있는 가능성을 확인 하였으며, 더 나아가 약물 스크리닝과 같은 진단분야에 활용될 수 있음을 알 수 있었다.

• 한국결정성장학회지
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• 제22권2호
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• pp.92-98
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• 2012

이온이 첨가된 BCP(biphasic calcium phosphate) 분말을 제조하기 위하여 $Ca(NO_3)_2{\cdot}4H_2O$, $(NH_4)_2HPO_4$를 출발 물질로 공침법(co-precipitation process)을 이용하여 합성하였다. Si-BCP 합성을 위하여 TEOS를 Mg-BCP 합성을 위해서는 $Mg(NO_3)_2{\cdot}6H_2O$를 사용하였다. 합성된 분말의 열처리 후 결정상을 분석한 결과 HAp와 ${\beta}$-TCP가 혼재된 상을 관찰할 수 있었다. 분광학적 분석에서도 인산칼슘의 $PO^{3-}_4$와 $OH^-$ 그룹에 해당하는 밴드도 관찰되었다. 이온이 첨가된 BCP 분말의 생체활성 거동을 평가하기 위하여 Hanks' Balanced Salt Solution(HBSS)에 침적시켜 시간에 따라 형상의 변화 및 결정상을 분석한 결과, 두 샘플 모두에서 빠른 표면 활성을 나타내었다. 세포 성장률 평가에서도 대조군에 비하여 세포성장률이 우수함을 관찰하였다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제34권1호
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• pp.36-48
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• 2008

To repair bone defects in the oral and maxillofacial field, bone grafts including autografts, allografts, and artificial bone are used in clinical dentistry despite several disadvantages. The purpose of this study was to evaluate new bone formation and healing in rat calvarial bone defects using hydroxyapatite (HA, $Ca_{10}[PO_4]_6[OH]_2,\;Bongros^{(R)}$, Bio@ Co., KOREA) and tricalcium phosphate (${\beta}-TCP,\;Ca_3[PO_4]_2$, Sigma-Aldrich Co., USA) mixed at various ratios. Additionally, this study evaluated the effects of type I collagen (Rat tail, BD Biosciences Co., Sweden) as a basement membrane organic matrix. A total of twenty, 8-week-old, male Sprague-Dawley rats, weighing 250-300g, were divided equally into a control group (n=2) and nine experimental groups (n=2, each). Bilateral, standardized transosseous circular calvarial defects, 5.0 mm in diameter, were created. In each experimental group, the defect was filled with HA and TCP at a ratio of 100:0, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80, and 0:100 with or without type I collagen. Rats were sacrificed 4 and 8 weeks post-operation for radiographic (standardized plain film, Kodak Co., USA), histomorphologic (H&E [Hematoxylin and Eosin], MT [Masson Trichrome]), immunohistochemical staining (for BMP-2, -4, VEGF, and vWF), and elementary analysis (Atomic absorption spectrophotometer, Perkin Elmer AAnalyst $100^{(R)}$). As the HA proportion increased, denser radiopacity was seen in most groups at 4 and 8 weeks. In general radiopacity in type I collagen groups was greater than the non-collagen groups, especially in the 100% HA group at 8 weeks. No new bone formation was seen in calvarial defects in any group at 4 weeks. Bridging bone formation from the defect margin was marked at 8 weeks in most type I collagen groups. Although immunohistochemical findings with BMP-2, -4, and VEGF were not significantly different, marked vWF immunoreactivity was present. vWF staining was especially strong in endothelial cells in newly formed bone margins in the 100:0, 80:20, and 70:30 ratio type I collagen groups at 8 weeks. The calcium compositions from the elementary analysis were not statistically significant. Many types of artificial bone have been used as bone graft materials, but most of them can only be applied as an inorganic material. This study confirmed improved bony regeneration by adding organic type I collagen to inorganic HA and TCP mixtures. Therefore, these new artificial bone graft materials, which are under strict storage and distribution systems, will be suggested to be available to clinical dentistry demands.

• Restorative Dentistry and Endodontics
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• 제25권3호
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• pp.435-445
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• 2000

The purpose of this study was to compare the leakage of four different obturation techniques in conjunction with immediate apical barrier of ${\beta}$-tricalcium phosphate(TCP) in teeth with open apex. Eighty single-rooted human premolar teeth were prepared and sectioned horizontally, so maximum diameter in apex was 4mm. Apical defects that were similar to open apex, were created with #1/2 round bur and SF104R bur. The apical foramen were opened to a size 80 file extended 3mm beyond the apex. The teeth were placed into the oasis block soaked saline to simulate periapical tissue often associated with pulpless teeth and received apical barriers consisting of TCP followed by obturation using lateral condensation technique, vertical condensation technique, continuous wave technique and thermoplasticized gutta-percha injection technique. Two unobturated teeth served as positive and negative controls. Teeth were immersed in resorcinol-formaldehyde resin for S days at $4^{\circ}C$, and the resin was allowed to polymerize completely for 4 days at room temperature. Teeth were then sectioned horizontally at 1.5mm(level 1), 2.5mm(level 2) and 3.5mm(level 3) from the apex, and examined under a stereomicroscope at ${\times}40$ magnification. The photographs were taken at ${\times}40$ magnification of the filling in each level and scanned. The leakage length in tooth/resin interface was measured at each of the three levels. Each ratio of leakage was obtained by calculating the ratio of the leakage length of canal wall infiltrated with resin to the total length of the canal and was analyzed statistically(One-way ANOVA and Scheffe test). The result were as follows : 1. At the level 1, there was the least leakage in the thermoplasticized gutta-percha injection technique group(group 4), but there was statistically significant(p<0.05). 2. At the level 2, there was the least leakage in the thermoplasticized gutta-percha injection technique group(group 4), and the most leakage in the continuous wave technique group(group 3). There was statistically significant difference between the thermoplasticized gutta-percha injection technique group and the continuous wave technique group(p<0.05). 3. At the level 3, there was the least leakage in the thermoplasticized gutta-percha injection technique group(group 4), but there were no statistically significant differences between other groups(p>0.05). These results suggest that thermoplasticized gutta-percha injection technique which had 1mm apical gutta-percha matrix after the formation of TCP apical barrier, can demonstrate favorable apical sealing.

• 한국결정성장학회지
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• 제22권2호
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• pp.99-104
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• 2012

BCP(biphasic calcium phosphate) 분말을 제조하기 위하여 $Ca(NO_3)_2{\cdot}4H_2O$, $(NH_4)_2HPO_4$를 출발 물질로 공침법(co-precipitation process)을 이용하여 합성하였다. 합성된 분말의 열처리 전 후의 HAp(Hydroxyapatite)/${\beta}$-TCP(${\beta}$-Tricalcium phosphate) 결정상 비율 및 분광학적 특성을 XRD 및 FT-IR를 이용하여 분석하였다. BCP 분말의 생체활성 거동을 평가하기 위하여 Hanks' Balanced Salt Solution(HBSS)에 침적시켜 시간에 따라 형상, 이온농도의 변화 및 결정상을 분석한 결과 낮은 결정화도의 HAp가 생성됨을 확인하였다. BCP분말의 세포독성 평가에서도 대조군에 비하여 세포성장률이 우수함을 관찰하였다.

• International Journal of Oral Biology
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• 제30권3호
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• pp.99-103
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• 2005

Bone morphogenetic proteins (BMPs), members of a large group of TGF-beta family, are important molecular regulators of morphogenesis of numerous tissues and organs, including bones and teeth. Most BMPs are capable of inducing bone formation in vivo and therefore are of considerable clinical interest for regenerating mineralized tissues. Recently, we have developed a method to culture cells from human cementum (human cementum-derived cells, HCDCs). HCDCs, when attached to synthetic hydroxyapatite/tricalcium phosphate (HA/TCP) ceramic and transplanted into immunodeficient mice, formed histologically identifiable cementum-like tissue. Since it is unclear to what extent BMPs are involved in cementogenesis, the aim of this study was to establish which BMPs are expressed by cementogenic HCDCs and whether the expression of BMPs is related to the degree of cellular differentiation in vitro. HCDCs were maintained in growth medium (DMEM/F12 supplemented with 10% FBS) until confluent (proliferation stage). Upon reaching confluence, cells were incubated in the differentiation medium (DMEM/F12 medium containing 10% FBS and 50 mg/ml ascorbic acid) for 14 days (differentiation stage). Next, HCDCs were incubated in mineralization medium (DMEM/F12, 50 mg/ml ascorbic acid, 2.5 mg/ml of ITS (insulin-transferrinselenium), 5 mM beta-glycerophosphate and $10^{-8}M$ dexamethasone) for another 14 days (mineralization stage). At the end of each differentiation stage, total RNA was isolated and evaluated for BMPs (2 through 8) expression by employing real time RT-PCR. HCDCs expressed most of BMPs examined except BMP-7 and BMP-8. Furthermore, on average, the highest levels of BMPs were expressed at the earlier differentiation stage, prior to the initiation of mineralization in vitro. These results indicate that several BMPs are expressed during cementoblastic differentiation and suggest that BMPs may be involved in the homeostasis of human cementum.