• Journal of the Korea Concrete Institute
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• v.19 no.1
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• pp.19-26
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• 2007

Until recently Korea is considered to be immune from the earthquake hazard because it is located for away from the active fault. However, we have noticed that recent strong earthquakes inflicted enormous losses on human lives and nation's economy all over the world. Hence, there has been raised the importance of the earthquake resistant design for various infrastructures. In this research, new methodologies for the seismic design and performance assessment of reinforced concrete(RC) bridge pier were proposed from experimental results of 82 circular RC bridge piers and 54 rectangular RC bridge piers tested in domestic and aboard. New seismic design method was based on the concept of the limited ductile design, which could be practically used for low or moderate seismic regions like Korea. Further study for the seismic safety of RC bridge piers was carried out to enhance the seismic performance of aged RC bridge piers, which were designed and constructed before implementing the 1992 seismic design provision in Korea. New formula for the seismic performance assessment of RC bridge piers was proposed and practically used for the decision on the need of repair and retrofit of many aged RC bridge piers.

• Journal of Periodontal and Implant Science
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• v.32 no.2
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• pp.403-414
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• 2002

I. Purpose of Study Zea Mays L. has been known to be effective for improving periodontal health and Magnoliae cortex to have effective antibacterial and antimicrobial activity against periodontal pathogens. The purpose of this study was to examine the biologic effects of Zea Mays L. and Magnoliae cortex extract mixtures on healing of rat calvarial bone defects. II. Materials & Methods 8mm circular defects were prepared on rat calvaria during surgical procedures of 180 Sprague-Dawley rats. The ethanolic extracts of Magnoliae cortex and Zea Mays L. and these two natural extract 1:1 and 2:1 (Magnoliae: Zea Mays L.) ratio mixtures were oral administrated by oral zondes once a day at two different dose of 94.5mg/kg, 189mg/kg body weight. There are nine groups of rats in this study: control group (no sample loading), Magnoliae cortex extract loading groups (I,II)(94.5mg/kg,189mg/kg respectively), Zea Mays L. extract loading groups (I,II), M:Z(1:1) loading groups (I,II), M:Z(2:1) loading groups(I,II). Rats were sacrificed at 4 weeks and 6 weeks after surgery. New bone formations around calvarial defects were radiographically and histologically measured by computerassisted histomorphometry. Each data was statistically analyzed by One-way ANOVA test. III. Results There were statistical significances between negative control group and the other test groups on radiographical and histological quantitative assessments. Among test groups, mixture groups showed statistical significances, especially, M:Z (2:1) groups (I and II) were highly significant.(p<0.05) These results implicated that the mixture of Magnoliae and Zea Mays L. (2:1 mixing ratio) with 94.5mg/kg concentration might be highly effective on the wound healing of bony defected site and have potential possibilities as a useful drug to promote bone tissue regeneration.

• Journal of Periodontal and Implant Science
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• v.32 no.2
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• pp.389-402
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• 2002

BMP can induce ectopic bone formation when implanted into sites such as rat muscle and can greatly enhance healing of bony defects when applied exogenously. In addition, BMP stimulated osteoblastic differentiation in vitro in various types of cells. The aim of this study was to investigate the effect of recombinant human bone morphogenetic protein(rhBMP-2) on the proliferation and osteoblastic differentiation of human periodontal ligament cells and gingival fibroblasts. The cell number and alkaline phosphatase activity were measured in 3 experimental groups of human periodontal ligament cells and gingival fibroblasts (control group, rhBMP-2 50ng/ml group, and rhBMP-2 100ng/ml group) at 1 and 2 weeks after culture. At the same time, total RNA of cultured cells were extracted and reverse trascription polymerase chain reaction(RT-PCR) was performed to determine the expression of mRNA of bone matrix protein. RhBMP-2 had no effect on the cell proliferation of human periodontal ligament cells and gingival fibroblasts. Alkaline phosphatase activity was elevated significantly by rhBMP-2 in both cells. And periodontal ligament cells showed significantly higher alkaline phosphatase activity than gingival fibroblasts. ${\beta}$-actin, type I collagen, alkaline phosphatase, BMP-2 mRNA were expressed in all of the samples. Osteopontin, osteocalcin mRNA were expressed in all periodontal ligament cell groups, and rhBMP-2 50ng/ml group, rhBMP-2 100ng/ml group of 2 week culture period of gingival fibroblasts. Bone sialoprotein mRNA was only expressed in rhBMP-2 50ng/ml group and rhBMP-2 100ng/ml group of 2-week culture period. These results suggest that rhBMP-2 stimulates osteoblastic differentiation in human periodontal ligament cells and gingival fibroblasts in vitro.

• Journal of Periodontal and Implant Science
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• v.30 no.3
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• pp.619-632
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• 2000

This clinical study was designed to determine the clinical and microbiological outcomes and safety of using minocycline loaded polycaprolactone strip for pericoronitis patients. 64 patients showing symptoms and signs of pericoronitis were enrolled according to the inclusion criteria in this double blind study. They were randomly assigned to two groups. 32 patients comprised control group and they received only polycaprolactone films in pericoronal spaces, and another 32 patients comprised experimental group and they received polycaprolactone films loaded with 30% minocycline. Informed consent was obtained from all the participants before beginning the study. At the initial visit, gingival index(GI), papillary bleeding index(PBI), amount of gingival crevicular fluid(GCF) were recorded, and microbiological sampling was done. Then, loaded or unloaded polycaprolactone film was inserted into the pericoronal spaces. No drug was prescribed excepting this film. After one week, clinical and microbiological exam was repeated. Presence of any side effects or inconveniences were checked. Chi-square test and t-test was performed to compare outcomes. At baseline, there were no significant differences in all the criteria between experimental group and control group. Experimental group showed significant improvement compared with control group both in GI(p<0.01) and PBI(p<0.01). The amount of GCF of the experimental group was significantly decreased compared with the control group(p<0.01) and baseline(p<0.01). In microbiological study, percentage of motile rod was prominently decreased in the experimental group. Also, aerobic(p<0.001), anaerobic(p<0.001) and black pigmented(p<0.01) bacteria were significantly decreased from the baseline. Furthermore, no side effects or inconveniences was reported in the experimental group. From this study, it was concluded that insertion of polycaprolactone film with 30% minocycline into the pericoronal spaces would be effective and safe treatment for pericoronitis.

• Journal of Periodontal and Implant Science
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• v.29 no.2
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• pp.433-447
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• 1999

The objective of this study was to evaluate the effect a chewable tablet containing sodium flouride and lauroyl sodium sulfate on removing plaque and inhibiting gingival inflammation. A randomized parallel study was designed. 100 voluteers participated in the study. There were two test groups each with 30 subject. Test group A was instructed to brush once in the morning, and to use the tablet once in the afternoon and once in the evening. Test group B was instructed to use the tablet three times a day without brushing. There were two control groups each with 20 subjects. Control group A was instructed to brush once in the morning only. Control group B was instructed not to brush all. Two weeks before the test period, the subjects received through tooth cleaning and polishing. At baseline, GI, PI, BOP, and GCF of the Ramfjord teeth were measured in all groups. Bacteria culture was done with the plaque sampled from tooth with the deepest pocket. After 5 days, clinical indices were measured and the bacterial culture was repeated. Control group B was dropped from the study after this period. All the other groups remained and the indices and the culture was repeated after 2 weeks, and 3weeks. Also whether the oral mucosa showed signs of irritation was monitored throughout the test period. Test group A showed less PI, GI, BOP, probing depth, GCF than test group B or control group A. Especially, PI and the BOP was significantly less than that of the group that was instructed to brush once a day. This implies that the added use of this tablet aids in plaque removal in people who brush just once a day. Test group A showed increase of cocci, decrease of motile rods, and decrease of spirochetes after 14-21 days. And this was significantly different from the control group A. At no time of the test period did any of the subjects show signs of irritation of the oral mucosa or adverse reactions. Following conclusions could be obtained from this study. This chewable tablet for enhanced oral hygiene could be used as an adjunct to oral hygiene in people who do not brush adequately. The use of this tablet decreased the number of subgingival bacteria, and this could be effective in plaque removal and for prevention of gingival inflammation.

• Journal of Periodontal and Implant Science
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• v.30 no.3
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• pp.583-599
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• 2000

조직유도재생술 과정에 사용된 차폐막의 술 후 오염 혹은 시술부위의 감염으로 조직재생유도가 제대로 이루어지지 않는 경우가 많이 있다. 테트라싸이클린은 넓은 범위의 치주 원인균에 효과적이고, 중성구 교원분해효소를 억제 함으로써 결합조직파괴를 억제하기 때문에 전신적 혹은 국소적으로 치주질환 치료에 널리 이용되어져왔다. 이번 연구의 목적은 비글견에 실험적으로 치주염을 유발시킨 후 테트라싸이클린 함유 차폐막을 이용하여 조직유도재생술을 하고서 테트라싸이클린의 유리반응을 관찰하는 것과 테트라싸이클린에 의한 항염, 항균효과를 알아보는 것이다. 실험 2-3개월 전에 비글견의 구강에서 치조골 결손부를 형성하여 치주염을 유발시켰다. 결손부 형성 2-3개월 후 실험군으로 테트라싸이클린 함유 차폐막으로 조직유도재생술을 하였고, 대조군으로 테트라 싸이클린이 함유되지 않은 차폐막으로 조직유도재생술을 하였고, 음성대조군으로 치은판막술만을 하였다. 시술 전과 시술 후 1, 2, 4주 간격으로 치은지수, 치태지수, 치은열구액의 양 및 혐기성 세균과 호기성 세균의 군락수를 측정하였다. 술 후, 1, 3, 5, 7, 및 14일 간격으로 유리된 테트라싸이클린의 농도를 측정하였다. 테트라싸이클린 함유 차폐막은 임상적 치은지수는 술 후 2, 4주째, 치태지수는 1, 2, 4주째 유의하게 감소하였다.(p<0.05) 1주에서 혐기성 및 호기성 세균집락수는 테트라싸이클린 함유 차폐막을 사용한 군이 약물이 함유되지 않은 차폐막보다 유의성있게 적었다.(p<0.001) 테트라싸이클린 함유 차폐막은 처음 1일은 높은 농도로 유리되었고 그 후 1주일 동안 일정하게 MIC 이상으로 유리되었다. 하지만 14일째는 유리가 관찰되지 않았다. 본 연구 결과, 테트라싸이클린 함유 생분해성 차폐막은 1주이상 약제가 MIC 이상 유리되었고, 유리된 테트라싸이클린에 의한 항염, 항균작용이 있어 치주조직 재생유도술시에 초기 치유가 잘 진행되도록 하는 효과가 있을 것이다.

• Journal of Periodontal and Implant Science
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• v.29 no.2
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• pp.289-297
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• 1999

최근 생약 추출물의 항균, 항염효과에 관한 관심이 증대되고 있으며 이를 이용한 치주질환의 예방 및 억제효과에 관한 연구들이진행되고 있다. 이 연구의 목적은 시험관 실험을 통하여 이미 밝혀진 후박 및 대조추출물의 치주질환 원인 균에 대한 항균, 항염효과를 성견에서 인위적으로 치주질환을 일으킨 후 실험 약제의 경구투여를 통하여 질환의 진행에 미치는 영향을 알아보는 것이다. 실험동물은 생후 18개월된 비글견 6마리를 이용하였다. 상악은 제2,3 소구치 및 제4소구치에 하악은 제2, 3, 4 소구치 및 제1 대구치를 실험대상 치아로 하였으며 교정용 철사와 봉합사를 이용하여 치경부주위에 결찰하여 인위적 치주질환을 일으켰다. 염증 유발 8주 후에 결찰을 풀고 실험동물을 아무 것도 투여하지 않은 군(음성대조군, 3마리), 후박 및 대조 추출혼합물 투여군(실험군, 3마리)으로 나누었다. 실험 시작 (-8주), 약제 투여 시작(0주), 투여 후 2, 4, 6, 8주째에 치태지수, 치은지수, Florida Probe를 이용한 치주낭깊이 및 치은열구액 등의 임상지수를 측정하였다. 염증유발 8주동안에 치태지수, 치은지수, 치주낭깊이, 치은열구액은 급속히 증가하였다. 결찰은 제거하고, 약제를 투여한 이후 실험군에서 치은지수, 치주낭깊이, 치은열구액은 가장 높은 값을 나타내고 있었다. 실험군에서는 8주가 될때까지 임상지수 수치가 낮아지고 있었으며, 8주째에는 대부분의 지수에서 음성대조군과 유의성 있는 차이를 보이고 있었다. 양성대조군에서 비해서 실험군은 대부분의 경우에 임상지수가 나이지고 있었지만 6주 또는 8주째의 치은지수, 치주낭깊이 중 일부만을 제외하고는 유의성 있는 차이를 보이지는 않았다. 이 연구결과 후박 및 대조 추출혼합물이 in vitro뿐만 아니라 in vivo 상태에서도 치주염의 치료 및 골재생의 효과가 있음을 알 수 있었으며, 이와 같은 동물실험의 결과를 바탕으로 임상시험을 거쳐 향후 사람에게 유용한 치주염치료제로 개발, 사용될 수 있을 것으로 여겨진다.

• Journal of Periodontal and Implant Science
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• v.28 no.4
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• pp.601-611
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• 1998

Ion irradiation is a very promising tool to modify the chemical structure and physical properities of polymers. This study was aimed to evaluate the cellular adhesion to ion beam-irradiated surface of biodegradable poly-l-lactide(PLLA) membrane. The PLLA membrane samples were irradiated by using 35 KeV $Ar^+$ to fluence of $5{\times}10^{13}$, $5{\times}10^{14}$ and $5{\times}10^{15}\;ion/cm^2$. Water contact angles to control and each dose of ion beam-irradiated PLLA membranes were measured. Cultured fetal rat calvarial osteoblasts were seeded onto control and each dose of ion beam-irradiated PLLA membranes and cultured. After 24 hours, each PLLA membranes onto which osteoblasts attached were examined by scanning electron microscopy(SEM). Osteoblasts were removed from each PLLA membrane and then, the vitality and the number of cells were calibrated. Alkaline phosphatase of detached cells from each PLLA membranes were measured. Ion beam-irradiated PLLA membranes showed no significantly morphological change from control PLLA membranes. In the measurement of water contact angle to each membrane, the dose range of ion beam employed in this study reduced significantly contact angles. Among them, $5{\times}10^{14}\;ion/cm^2$ showed the least contact angle. The vitalities of osteoblastes detached from each membranes were confirmed by flow cytometer and well attached cells with their own morphology onto each membranes were observed by SEM. A very strong improvement of the cell adhesion and proliferation was observed for ion beam-irradiated surfaces of PLLA membranes. $5{\times}10^{15}\;ion/cm^2$ exhibited the most strong effect also in cellular adherence. ALPase activities also tended to increase in ion beam-irradiated membranes but statistical differences were not found. These results suggested that ion beam irradiation is an effective tool to improve the adhesion and spreading behaviour of the cells onto the biodegradable PLLA membranes for the promotion of membrane-tissue integration.

• Journal of Periodontal and Implant Science
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• v.28 no.4
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• pp.577-604
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• 1998

chitosan은 골치유증진 및 골세포의 분화를 촉진하는 것으로 알려진 천연의 생분해성 고분자이다. 이연구에서는 chitosan 및 chitosan/tricalcium phosphate(TCP) 다공성 기질을 제조하여 골이식재 및 조직공학적 골형성을 위한 3차원적 세포배양 지지체로서의 가능성을 평가하고자 하였다. chitosan 용액 및 TCP가 포함된 chitosan 용액을 동결건조함으로써 소공의 크기가 $100-200{\mu}m$인 스폰지형태의 chitosan 및 chitosan/TCP 다공성 기질을 제작하였다. 골이식재로서의 효과를 평가하기 위하여 백서의 두개골 결손부에 제작된 chiosan 및 chitosan/TCP 다공성 기질을 각각 이식하고 2주 및 4주 후에 동물을 희생하여 조직학적으로 치유양상을 관찰하였다. 조직공학적 골형성을 위한 세포배양 지지체로서의 가능성을 평가하기 위하여 백서 태자의 두개골에서 분리된 골아세포를 chitosan 및 chitosan/TCP 다공성 기질에 각각 접종하고 56일간 배양하면서 각 기간 별로 세포수, 염기성 인산효소 활성, 축적된 calcium의 양을 측정하였고 배양된 세포-기질 혼합체를 광학현미경 및 주사전자현 미경하에서 조직학적 관찰을 시행하였다. 백서 두개골결손부에 이식된 chitosan 및 chiosan/TCP 다공성 기질은 별다른 이물반응 없이 자연 분해되면서 신생골조직 내에 매립되었으며 이식하지 않은 대조군에 비해 유의하게 높은 신생골형성 효과를 나타내어 우수한 골전도성이 있음이 확인되었다. 신생골형성 양상이나 형성된 양에 있어서 두 가지 기질간의 유의한 차이는 없었다. 골아세포-기질 혼합체의 배양결과, 접종후 배양 28일 경과 시까지 골아세포수는 지속적으로 증가하다가 이후에는 5 8일까지 성장정도가 둔화되었다. 염기성 인산효소의 활성 및 calcium 축적량은 접종후 배양시간경과에 따라 56일까지 지속적으로 증가하였다. 세포수 및 염기성 인산효소의 활성에서 두 기질간의 유의한 차이는 없었고, calcium 축적량에 있어서는 chitosan/TCP 기질에서 유의하게 높았고 증가속도도 컸다. 배양된 골아세포가 접종된 다공성 기질의 조직학적 관찰결과, 골아세포는 다공성 기질에 잘 부착하여 중층의 형태로 성장하면서 광화된 골기질을 형성함이 관찰되었다. 배양 14일부터 작은 골편형태의 골형성이 기질 표면에 부착되어 관찰되었고, 배양기간이 길어짐에 따라 성장하여 배양 56일째에는 상당한 양의 광화된 골질이 형성됨이 관찰되었다. 배양 56일 경과후의 광화된 골질의 양은 chitosan/TCP 기질에서 더 많았다. 이 연구의 결과, chitosan 및 chitosan/TCP 다공성 기질이 골이식재로서 뿐만 아니라, 조직공학적 골형성에 적용되는 골아세포의 배양을 위한 3차원구조의 세포지지체로 이용되어 골재생술식에 유용한 생체재료로 활용될 수 있음이 확인되었다.

• Journal of Periodontal and Implant Science
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• v.28 no.4
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• pp.545-559
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• 1998

Magnoliae cortex has been used as a drug for treatment of fractures in Chinese medicine and safflower(Carthamus tinctorius $Linn{\acute{e}}$) has been traditionally used for treatment of blood stasis. The purpose of present study was to examine the biologic effects of magnoliae cortex extract and safflower extract mixture(MSM) on human periodontal ligament cells and fetal rat calvarial osteoblasts and on healing of rat calvarial defects. The ethanolic extracts of magnoliae cortex(MCE), safflower seed(SSE), Zea May L(ZML) were prepared as positive control group. MSM mixed to the ratios of 1 : 1, 1 : 2, 1 : 5 and 1 : 10 were used as test group. The effects of each agents on the growth and survival, ALPase activity, cell proliferation and tissue regenerative effect of each extracts was evaluated by histomorphometric measuring of newly formed bone on the 8 mm defect in rat calvaria after oral administration of 2 ratio groups(1 : 5 and 1 : 10) at 3 different doses (0.1, 0.25 and 0.5g/kg per day). MSM stimulated the growth and survival rate of osteoblasts and PDL cells more than any other agents. The growth and survival rate were increased as the proportion of safflower seed extract was increased. MCE, SSE, ZML stimulated the ALPase activity of osteoblast and PDL cell in comparison to the negative control group. But all groups of MSM regardless of ratio of safflower seed extract stimulated the ALPase activity than any other agent. The ALPase activity was also increased as the proportion of safflower seed extract was increased. Although MCE, SSE, ZML stimulated the proliferation of osteoblasts. 1 : 5 and 1 : 10 ratio MSM showed significant increase in stimulation of proliferation of osteoblasts. No agent significantly increased proliferation of PDL cells. Significant new bone formation were seen where 1 : 5 ratio, 0.5g/kg group and 1 : 10 ratio, 0.25, 0.5g/kg groups were used. These results show that magnoliae cortex extract and safflower seed extract mixture can potentially increase bone regeneration ability.