• The Journal of Korean Academy of Prosthodontics
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• v.47 no.2
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• pp.148-155
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• 2009

Statement of problem: The interest in all-ceramic restorations has increased as more techniques have become available. With the introduction of machinable dental ceramics and CAD/CAM systems there is a need to evaluate the quality levels of these new fabrication techniques. Purpose: This study is to evaluate the crown fidelity(absolute marginal discrepancy and internal gap) of various zirconia-based all-ceramic crowns fabricated with different CAD/CAM(computer-assisted design/computer-assisted manufacturing) systems and conventional cast metal-ceramic crowns. Material and methods: A resin tooth of lower right second premolar was prepared. After an impression was taken, one metal master die was made. Then 40 impressions of metal master dies were taken for working dies. 10 crowns per each system were fabricated using 40 working dies. Metal-ceramic crowns were cast by using the conventional method, and Procera, Lava, and Cerec inLab crowns were fabricated with their own CAD/CAM manufactruing procedures. The vertical marginal discrepancies and internal gaps of each crown groups were measured on a metal master die without a luting agent. The results were statistically analyzed using the one-way ANOVA and Tukey's HSD test. Results: 1. Vertical marginal discrepancies were $50.6{\pm}13.9{\mu}m$ for metal-ceramic crowns, $62.3{\pm}15.7{\mu}m$ for Procera crowns, $45.3{\pm}7.9{\mu}m$ for Lava crowns, and $71.2{\pm}2.0{\mu}m$ for Cerec inLab crowns. 2. The Internal gaps were $52.6{\pm}10.1{\mu}m$ for metal-ceramic crowns, $161.7{\pm}18.5{\mu}m$ for Procera crowns, $63.0{\pm}10.2{\mu}m$ for Lava crowns, and $73.7{\pm}10.7{\mu}m$ for Cerec inLab crowns. Conclusion: 1. The vertical marginal discrepancies of, 4 crown groups were all within the clinically acceptable range($120{\mu}m$). 2. The internal gaps of LAVA, Cerec inlab, and metal-ceramic crowns were within clinically acceptable range except Procera crown($140{\mu}m$).

• Korean Journal of Heritage: History & Science
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• v.49 no.3
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• pp.32-51
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• 2016

This study examines, based on the database of the Institute for the Translation of Korean Classics(ITKC), the garden plants and their symbolism, and the landscape culture recorded in 'Jipkyungjaeyoungsi(the Series of Poems on Gardens Poetry)' in relevance to traditional houses. First, Jipkyungjaeyoungsi had been continuously written since mid-Goryeo dynasty, when it was first brought in, until the late Joseon dynasty. It was mainly enjoyed by the upper class who chose the path of civil servants. 33 pieces of Jaeyoungsi(題詠詩) in 25 books out of a total of 165 books are related to residential gardens. The first person who wrote a poem in relation to this is believed to be Lee GyuBo(1168~1241) in the late Goryeo dynasty. He is believed to be the first person to contribute to the expansion of natural materials and the variation of entertainment in landscape culture with such books as 'Toesikjaepalyoung(退食齋八詠)', 'Gabeunjeungyukyoung(家盆中六詠)'and 'Gapoyukyoung(家圃六詠)'. Second, most of the poems used the names of the guesthouses. Out of the 33 sections, 19(57.5%) used 8 yeong(詠), then it was in the sequence of 4 yeong(詠), 6 yeong, 10 yeong, 14 yeong, 15 yeong, 16 yeong, 36 yeong(詠) and so on. In the poem writing, it appears to break the patterns of Sosangpalkyung(瀟湘八景) type of writings and is differentiated by (1) focusing on the independent title of the scenery, (2) combining the names of the place and landscape, (3) focusing on the name of the landscape. Third, the subtitles were derived from (1) mostly natural landscape focused on nature and garden plants(22 sections, 66.7%), (2) cultural landscape focused on landscape facilities such as guesthouses, ponds and pavilions(3 sections), (3) complex cultural scenery focused on the activities of people in nature(8 sections). Residents enjoy not only their aesthetic preferences and actual view, but the ideation of the scenery. Especially, they display attachment to and preference for vegetables and herbs, which had been neglected. Fourth, the percentage of deciduous tree population(17 species) rated higher(80.9%) compared to the evergreens(4 species). These aspects are similar results with the listed rate in 'Imwonkyungjaeji(林園經濟志)' by Seo YuGu [evergreen 18 species(21.2%) and deciduous trees 67 species(78.8%)] and precedent researches [Byun WooHyuk(1976), Jung DongOh(1977), Lee Sun(2006)]. Fifth, the frequency of the occurrence of garden plants were plum blossoms(14 times), bamboos(14 times), pine trees(11 times), lotus(11 times), chrysanthemum(10 times), willows(5 times), pomegranates(4 times), maple trees(14 times), royal foxglove trees, common crapemyrtle, chestnut trees, peony, plantains, reeds and a cockscombs(2 times). Thus, the frequency were higher with symbolic plants in relations to (1) Confucian norms(pine trees, oriental arbor vitae, plum blossoms, chrysanthemums, bamboos and lotus), (2) living philosophy of sustain-ability(chrysanthemum, willow), (3) the ideology of seclusion and seeking peace of mind(royal foxglove ree, bamboo). Sixth, it was possible to trace plants in the courtyard and outer garden, vegetable and herb garden. Many symbolic plants were introduced in the courtyard, and it became cultural landscape beyond aesthetic taste. In the vegetable and herb garden, vegetables, fruits and medicinal plants are apparently introduced for epigenetic use. The plants that were displayed to be observed and enjoyed were the sweet flag, pomegranate, daphne odora, chrysanthemum, bamboo, lotus and plum blossom. Seventh, it was possible to understand garden culture related to landscaping materials through poetic words such as pavilions, ponds, stream, flower pot, oddly shaped stones, backyard, orchard, herb garden, flower bed, chrysanthemum fence, boating, fishing, passing the glass around, feet bathing, flower blossom, forest of apricot trees, peach blossoms, stroking the pine tree, plum flower blossoming through the snow and frosted chrysanthemum.

• Journal of Dental Rehabilitation and Applied Science
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• v.27 no.1
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• pp.51-61
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• 2011

Recently, restoring implants in the esthetically demanding region, zirconia-based materials are widely used due to their superior mechanical properties, accuracies, and esthetics. The purpose of this study was to investigate the load transfer and mechanical stability of zirconia and titanium implant abutments by using the three-dimensional finite element analysis model. The internal conical joint type and external butt joint type implant system was selected as an experimental model. Finite element models of bone/implant/prosthesis complex were constructed. An load of 250N was applied vertically beside 3mm of implant axis. Stress distribution of zirconia and titanium implant abutment is similar. The maximum equivalent stress of titanium implant abutment is lower than zirconia implant abutment about 15%. Howevere considering a high mechanical strength that exceed those of titanium implant abutment, zirconia implant abutment had similar mechanical stability of titanium implant abutment clinically.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.4
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• pp.389-403
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• 2008

In Angle's Class III malocclusion, which has higher incidence in Korean than Western, depressed midfacial profile with protruded lower lips and mandible may give rise to many functional, esthetic, psychological, social problems. Due to the different malocclusion incidence according to racial differences, many previous studies focused on the relationship between Class II malocclusion and nasal airway obstruction. Previous studies used lateral cephalography which has limitations of 2 dimensional image with projection error and identification error. Therefore, the purpose of this study was to analyze morphologic differences in the nasal airway between normal occlusion and Angle's Class III malocclusion patients using 3-dimensional facial computed tomography. Thirteen normal occlusion(7 men and 6 women) and sixteen skeletal Class III(7 men and 9 women) patients were selected and 3-dimensional facial computed tomography taking was performed. Comparison between two group in volume and sectional area of nasal airway were carried out. The results were followed. 1. In the comparison of absolute nasal airway volume, oropharyngeal space of experimental group were larger than control group but there are no significant difference in other. 2. In the comparison of relative nasal airway volume, oropharyngeal space of experimental group were larger than control group but there are no significant difference in other. 3. In the oropharyngeal space width on frontal and lateral view, the similar tendency was revealed between two groups. 4. In the lateral curvature of nasal airway, the similar tendency was revealed between two groups.

• The korean journal of orthodontics
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• v.28 no.6 s.71
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• pp.893-904
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• 1998

There are varieties of severe malocclusions, which can be treated orthodontically, but with a great deal of effort. Anterior openbite, in particular, is one malocclusion thought to be more difficult to treat, and therefore, most of them have to be corrected by means of surgical intervention. To solve these problems, numerous studies pertinent to treatment modalities have been introduced with controversies on the effectiveness of treatment. Suggested treatment modalities for anterior openbite are based directly or indirectly on the neuromuscular and morphological features and on the etiologic and/or the environmental factors. Even though the vertical relationship of the face is increased due to the growth variation, the normal occlusal relationship can be achieved by the adequate dentoalveolar compensatory mechanism, but in the case of inadequate or negative dentoalveolar compensation, openbite is likely to be present. If the skeletal dysplasia is too severe to be solved by orthodontic treatment alone, combined treatment with surgery should be done to restore the function and the esthetics of the orofacial complex. In many cases, however, orthodontic alteration of the dentition pertinent to the given skeletal pattern with the proper diagnosis and treatment planning can bring satisfactory results. The treatment changes with the Multiloop Edgewise Archwire(MEAW) therapy occurred mainly in the dentoalveolar region and showed a considerable similarity to the natural dentoalveolar compensatory mechanism. In other words, the MEAW technique allows orthodontists to produce the natural dentoalveolar compensation orthodontically. Even if an openbite is corrected by the orthodontic dentoalveolar compensation suitable for the skeletal pattern, relapse may still occur by the persisting etiologic factors which originally prohibited the natural dentoalveolar compensation. The etiologic factors should be determined at the time of initial diagnosis and should be controlled during treatment and retention.

• The Journal of the Korea Contents Association
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• v.15 no.5
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• pp.639-650
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• 2015

The purpose of this study was firstly, to explore the acceptability and acceptance intention of parents for smart animal toys and secondly, investigate whether there is a difference by sex and age. For this purpose, the questionnaire survey was conducted with 344 parents of younger children in Seoul and Gyeonggi Province. As a result, there were significant positive correlations among the relative advantage, aesthetics, social image of smart animal toys, the attitude of the new technology and the parents' acceptability. Whereas there were significant negative correlations among the acceptance risk and the parents' acceptability. The parents' acceptability showed differences in the relative advantages and social image according to the age of the parents and no significant difference according to purchasing experience of smart animal toys. These results indicated that the parents' acceptability and acceptance intention of smart animal toys were similar with the adoption process of innovative products or smart devices. And it was also informed that the most impact factors on parents' acceptance for smart toy were the relative advantage, social image, and the attitude of the new technology. This research will be useful in understanding parents purchasing intention of smart toys and provide valuable implication for smart toy companies, manufacturers, and developers.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.1
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• pp.53-60
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• 2009

Statement of problem: At present, as the esthetic demands are on the increase, there are many ongoing studies for tooth-colored post and cores. Most of them are about fiber post and prefabricated zirconia post, but few about one-piece milled zirconia post and core using CAD/CAM (computer-aided design/computer-aided manufacturing) technique. Purpose: The objective of this study was to compare microleakage of endodontically treated teeth restored with three different tooth-colored post and cores. Material and methods: Extracted 27 human maxillary incisors were cut at the cementoenamel junction, and the teeth were endodontically treated. Teeth were divided into 3 groups (n=9); restored with fiber post and resin core, prefabricated zirconia post and heat-pressed ceramic core, and CAD/CAM milled zirconia post and core. After the preparation of post space, each post was cemented with dual-polymerized resin cement (Variolink II). Teeth were thermocycled for 1000 cycles between $5-55^{\circ}C$ and dyed in 2% methylene blue at $37^{\circ}C$ for 24 hours. Teeth were sectioned (bucco-lingual), kept the record of microleakage and then image-analyzed using a microscope and computer program. The data were analyzed by one-way ANOVA and Scheffe's multiple range test (${\alpha}=0.05$). Results: All groups showed microleakage and there were no significant differences among the groups (P>.05). Prefabricated zirconia post and heat-pressed ceramic core showed more leakage in dye penetration at the post-tooth margin, but there was little microleakage at the end of the post. Fiber post and resin core group and CAD/CAM milled zirconia post and core group indicated similar microleakage score in each stage. Conclusion: Prefabricated zirconia post and heat-pressed ceramic core group demonstrated better resistance to leakage, and fiber post and resin core group and CAD/CAM milled zirconia post and core group showed the similar patterns. The ANOVA test didn't indicate significant differences in microleakage among test groups. (P>.05)

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1073-1077
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• 2006

급속한 산업화로 인한 오염물질의 증가와 생물서식처의 감소는 수자원과 생태계를 위협하고 있다. 국내의 경우 수자원의 질을 개선하기 위해 '90년대 초부터 하수처리시설 등의 저감시설을 대폭 확충하였으나 현재까지 팔당호 등 주요상수원이 목표수질에 못 미치고 있으며 그 원인은 유입오염물질의 $22{\sim}37%$를 차지하는 비점오염원으로 지목되고 있다. 또한 생태.경관적 가치가 높은 수변지역은 각종 개발로 생물서식처가 급속도로 감소하여 종 다양성 보전 측면에서 대책마련이 시급한 실정이다. 이와 유사한 상황에 직면한 선진외국에서는 '하천회랑(river corridor)' 또는 '토양 및 생태시스템을 포함하는 수역과 육역의 점이(漸移)지대'를 의미하는 이른바 '수변완충지대(Riparian Buffer Zones)'의 오염정화 및 생태조성 효과 등의 연구를 통해 효율적 조성방안을 제시하고 있으며 다양한 형태로 현장에 적용하고 있다. RBZs의 일반적인 기능으로는, 유사나 오염물질의 여과 및 차단(필터링 효과), 영양염류의 저감, 하천변 식생을 통한 수자원의 정화 및 강턱의 안정화, 홍수로 인한 하천침식의 방지, 수변 생물 서식처 제공, 수변 그늘 제공에 의한 수온상승 방지, 심미 교육 위락 공간 제공 등이다. 본 연구에서는 외국의 RBZs(Riparian Buffer Zones)가이드라인을 참고하여 국내실정에 맞는 파일럿 규모의 시험완충지를 설계 및 조성하였다. 시험완충지는 남한강 연안에 초본류, 갈대류, 관목류, 자연식생, 혼합식생 등 5가지 'dry biotope'형태로 설치하여 1년간 계절별로 운영하였다. 또한 실험의 정량화와 다양한 조건변화를 위해 차수막, 위어, 유량.농도 조절장치, 라이시미터 등 보조시설을 설치하였고, 정기적인 모니터링을 실시하였다. 조사결과 외국사례를 살펴보면 RBZs의 적정 폭은 수질정화기능의 경우 $15{\sim}30m$, 생태서식처 기능은 최소 90m이상으로 제시되며, 시험완충지의 수질정화효과는 SS, T-N, T-P, TOC의 평균저감율이 각각 50%이상으로 나타났다. 식생모니터링 결과, 환삼덩굴 등 우점종의 잠식속도는 약 15일이며 갈대와 갯버들의 경우 우기시 인공목책호안과 동일한 침식방지 효과를 보이는 것으로 관찰되어 식생의 주기적인 모니터링과 지역 특성에 적합한 우점종 선정이 매우 중요한 것으로 판단된다.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.3
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• pp.225-235
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• 2009

A common procedure of restoration of endodonticlly treated tooth with fiber-reinforced post is followed by core build-up after post cementation. However, this technique is complex and time-consuming. The aim of this study was to compare fracture strength of premolar, restored with various methods of core fabrications on fiber-reinforced posts and casting metal restoration. Forty five freshly extracted human mandibular premolars were obtained and devided into 5 groups acconding to the type of post and methods of core build-up. In Group A, D.T. $Light-post^{(R)}$ were cemented with $DUO-LINK^{TM}$ and then $LIGHT-CORE^{TM}$ was used for core restoration. In Group B, D.T. $Light-post^{(R)}$ and $DUO-LINK^{TM}$ were used for cementing in the postspace, and $DUO-LINK^{TM}$ was used again for core restoration. In Group C, $Light-post^{(R)}$ bonding and the core build-up were performed simultaneously by using $DUO-LINK^{TM}$. In Group D, $LuxaPost^{(R)}$ was bonded by using $LuxaCore^{(R)}-Dual$. Again, $LuxaCore^{(R)}-Dual$ was used for core restoration. In Group E, $LuxaPost^{(R)}$ bonding and the core build-up were performed simultaneously by using $LuxaCore^{(R)}-Dual$. Axial reduction was formed parallelly as possible and 45 degree bevel was made at buccal occlusal surface. Crowns were fabricated and cemented. Each tooth was embedded in self-curing acrylic resin to the level of 2mm below the CEJ. Specimens were fixed on universal testing machin such that the axis of the tooth was at 45 degree inclination to the horizontal plane, and compressive force was applied at a crosshead speed of 1mm/min until failure occurred. The mean fracture strength was the highest in group A followed by descending order in group B, D, E and C. However, there were no statistically significant differences between groups with regard to the fracture strength. The type of the post or build-up methods of the core does not seem to influence the fracture strength.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.1
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• pp.61-69
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• 2009

Statement of problem: Porcelain veneers have become a popular treatment modality for aesthetic anterior prosthesis. Fitting porcelain veneers in the mouth usually involve a try-in appointment, which frequently results in salivary contamination of fitting surfaces. Purpose: An in vitro study was carried out to investigate the effect of silane treatment timing and saliva contamination on the resin bond strength to porcelain veneer surface. Material and methods: Cylindrical test specimens (n=360) and rectangular test specimens (n=5) were prepared for shear bond test and contact angle analysis. Whole cylindrical specimens divided into 20 groups, each of which received a different surface treatment and/or storage condition. The composite resin cement stubs were light-polymerized onto porcelain adherends. The shear bond strengths of cemented stubs were measured after dry storage and thermocycling (3,000 cycles) between 5 and $55^{\circ}C$. The silane and their reactions were chemically monitored by using Fourier Transform Infrared Spectroscopy analysis (FTIR) and contact angle analysis. One-way analysis of variance (ANOVA) and Dunnett's multiple comparison were used to analyze the data. Results: FT-IR analysis showed that salivary contamination and silane treatment timing did not affect the surface interactions of silane. Observed water contact angles were lower on the saliva contaminated porcelain surface and the addition of 37% phosphoric acid for 20 seconds on saliva contaminated porcelain increased the degree of contact angle. Silane applied to the porcelain, a few days before cementation, resulted in increasing the bond strength after thermocycling. Conclusion: Within the limitation of this study, it can be concluded that it would be better to protect porcelain prosthesis before saliva contamination with silane treatment and to clean the contaminated surface by use of phosphoric acid.