• The Journal of Korean Academy of Prosthodontics
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• v.40 no.6
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• pp.545-559
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• 2002

There has been increasing use of IPS Empress $2^{(R)}$ owing to easy fabrication method, high esthetics similar to natural teeth, good marginal accuracy, and sufficient fracture strength. However, in clinical application, although a luting agent and the tooth cementation bonding procedure influence the marginal accuracy and fracture strength restoration, there has been a controversy in the selection of proper luting agent. This study was to measure the marginal fidelites and fracture strength of IPS Empress crowns according to three cement types, Protec $cem^{(R)}$, Variolink $II^{(R)}$ and Panavia $21^{(R)}$. After construction of 12 experimental dies for each group, IPS Empress $2^{(R)}$ crowns were fabricated and luted the metal master die prepartion of the maxillary right premolar. Marginal gaps before cementation and after cementation were measured. Buccal incline on the functional cusp of specimens were loaded until the catastrophic failure and fracture strength was measured. The results of this study were as follows: 1. The range of gap was $34.04{\pm}4.84{\mu}m$ before cementation and $37.88{\pm}5.00{\mu}m$ after cementation, which showed significant difference by paired t-test (p<0.05). The difference in the results from marginal accuracy according to measuring point proved to be not statistically significant by two-way ANOVA test (p>0.05). 2. The difference in the results from marginal accuracy according to three cement types Proved that The Variolink $II^{(R)}$ cement group had the least gap, $35.43{\pm}5.03{\mu}m$, and showed superior marginal accuracy while there existed statistic significance in Protec $cem^{(R)}$ cement group, $39.06{\pm}4.41{\mu}m$ or Panavia $21^{(R)}$ cement group, $39.16{\pm}4.39{\mu}m$ by two-way ANOVA test & multiple range test (p<0.05). 3. The difference in the results from fractures strength testing according to three cement type groups proved to be statistically significant (p<0.05). The Variolink $II^{(R)}$ cement group shows highest fracture strength of $1257.33{\pm}226.77N$, Panavia $21^{(R)}$ cement group has $1098.08{\pm}138.45N$, and Protec $cem^{(R)}$ cement group represents the lowest fracture strength of $926.75{\pm}115.75N$. 4. Three different cement groups of different components showed acceptable marginal fidelity and fracture strength. It is concluded that IPS Empress $2^{(R)}$ crowns luted using Variolink $II^{(R)}$ cement group had stronger fracture strength and smaller marginal gap than the other cement groups. Although Variolink $II^{(R)}$ resin cement seemed acceptable to clinical applications in IPS Empress $2^{(R)}$ system, the IPS Empress $2^{(R)}$ system still requires long-term research due to the lack of data in clinical applications.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.2
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• pp.264-279
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• 2005

Statement of problem. Intraoral corrosion not only affects the esthetic and function of metallic dental restoration, but also has biologic consequences as well. Therefore, corrosion is considered a primary factor when choosing the dental alloy and laboratory technique. Purpose. The objective of this study was to compare the effects of solder and laser weld on corrosion Material and methods. Test specimens were made of 2 types of gold alloys, Co-Cr and Ni-Cr alloy and fabricated 3 methods, respectively: as cast, solder, and laser weld. For the analysis of corroding properties, potentiodynamic polarization test and immersion test conducted. The potentiodynamic polarization scan curve were recorded in 0.9% NaCl solution(pH 7) using Potentiostat/Galyanostat Model 273A. All specimens were exposed to 0.9% NaCl solution(pH 2.3) during 14 days. Elemental release into corrosive solution was measured by atomic emission spectrometry Differences in corrosion potential and mass release were determined using ANOVA. Results and conclusion. Through analyses of the data, following results were obtained. 1. In Pontor MPF and Wiron 99, corrosion potential of the solder group was statistically lower than as cast and laser weld group (p<0.05) , but there was no difference between corrosion potential of solder group and laser weld group in Pontor MPF and no differences between as cast and laser weld group (p>0.05). In Jel-Bios 10 and Wirobond, there was no difference of corrosion potential according to joining methods(p>0.05). 2. In all tested alloys, the amount of released metallic ion was greatest in the solder group(p<0.05). There was no difference between as cast group and laser weld group in Jel-Bios 10 and Wirobond(p>0.05). 3. In scanning electron microscopic examination. except soldered Wiron 99 specimens, it is impossible to discriminate the corrosive property of solder and laser weld. 4. Under the this experimental circumstances, laser weld appears superior to the solder when corrosion is considered.

• KOMUNHWA
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• no.70
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• pp.5-15
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• 2007

Octagonal green glass bottle with long neck(녹유리장경각병) was found in the tomb of the princess Hwayu who was King Youngjo's daughter by a concubine while the tomb was exhumed and buried in another place around Bucheon City, Gyeonggi-do. This octagonal glass bottle is dark green. It was made in AD 1736-A1795 because it was cngraved an inscription of "건륭년제" the bottom. This glass bottle was taken an X-ray radiography and tested adhesives and restoration materials for the conservation. Loctite 401 was suitable as considering the translucency of the glass bottle, good adhesive property and reversibility of the adhesive so it was chosen. A minute piece of the glass was analyzed the composition and lead isotope ratio. Major chemical composition of the glass bottle consisted of SiO2, K2O, and PbO system and the ratio was 68: 18.5:5.7. Green color of glass bottle was due to Fe2O3 and CuO. When the glass bottle was made, quartz as raw material of silica and K2O as natural saltpeter(KNO3) were utilized. As a result of lead isotope ratio analysis, it was suggested that the galena as raw material of lead for glass making came from the southern part of China. These results are expected to become useful data in background of glass culture and circulation study of old glass.

• Korean Journal of Environment and Ecology
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• v.20 no.4
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• pp.448-463
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• 2006

This study analyzed the changes in vegetation structure of Quercus mongolica communities, Pinus densiflora communities, Robinia pseudo-acacia communities and Pinus rigida communities for the last 11 years$(1994{\sim}2005)$ to provide basic data for ecological restoration. We studied the vegetation structure of four communities within a plot$(unit:\;1,200m^2)$) and concluded that Canopy Layer continuously preserved and expanded existing superior species, Understory Layer grew Styrax japonica which is highly adaptive to urban environment, and Shrub Layer grew more Stephanandra incise. An analysis on species diversity indicated that Quercus mongolica communities$(1.0921{\rightarrow}1.0381{\rightarrow}1.0633)$, Pin us densiflora communities$(0.7071{\rightarrow}0.8553{\rightarrow}1.0164)$, and Robinia pseudo-acacia communities$(0.9255{\rightarrow}0.8392{\rightarrow}0.8721)$ sharply decreased in 1998 and are gradually increasing these days. Also, Pinus rigida communities decreased from 0.9008 in 1998 to 0.8850 in 2005. Fluctuation in numbers of species and trees were similar. Acidity of soil was $4.34{\sim}5.31$ and improved compared to 20 years ago.

• Korean Journal of Environment and Ecology
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• v.26 no.1
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• pp.1-10
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• 2012

The habitats characteristics of Polypodium vulgare L. in Ulleung-do were investigated to compile basic data for conservation and restoration. Natural habitats were located at altitudes of 410~748m with inclinations of $12{\sim}80^{\circ}$. Sixty six vascular plants were identified from 10 quadrats in 4 habitats. Dominant species among the woody plants, based on importance value, were Acer pictum subsp. mono(49.52%) in the tree (T1) layer, Sorbus amurensis(28.99%) in the subtree (T2) and Schizophragma hydrangeoides(51.99%), Ligustrum foliosum(8.82%), Fagus engleriana(7.25%) in the shrub (S) layer. Importance value for members of the herb (H) layer were as follows: Polypodium vulgare 23.23%; Maianthemum dilatatum 9.65%; Phryma leptostachya var. asiatica 9.23%; Dryopteris crassirhizoma 8.40%; Carex shimidzensis 6.75% and Dystaenia takesimana 5.42%. The importance value of the last five species were high, so they were at affinity with Polypodium vulgare in their habitats. Species diversity was 1.18, and dominance and evenness were found to be 0.11 and 0.84, respectively. The soil types were sandy loam. Average field capacity was 30.42%, and the organic matter and pH were 17.95%, and 4.70. Correlation coefficients based on environmental factors, vegetation and soil analysis were showed that positive correlations between species diversity and species richness, whereas between species diversity and dominance, coverage of Polypodium vulgare and species richness were showed negative correlations.

• Korean Journal of Plant Resources
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• v.18 no.2
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• pp.315-324
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• 2005

The study was carried out to offer the raw data on counterplan of restoration and conservation by systematical and objective analyzing the flora and herbaceous communities around Abeliophyllum distichum habitats. In the results of flora survey, as the site that the most taxa were showed was Yulji-ri, Geosan-gun III, there was surveyed as 114 ones; 48 families, 91 genera, 99 species and 15 varieties, and as Younjeong-ri, Jincheon-gun V was showed the fewest ones, there was appeared 54 ones; 28 families, 49 genera, 47 species and 7 varieties. The dominant species of herbaceous communities were verified Humulus japonicus${\cdot}$Artemisia princeps var. orientalis(Chujeom-ri, Goesan-gun I), Oplismenus undulatifolius(Songdeok-ri, Goesan-gun II and Maechon-ri, Yeongdong-eup IV), Carex siderosticta${\cdot}$Pueraria thunbergiana${\cdot}$Artemisia princeps var. orientalis(Yulji-ri, Geosan-gun III), Streptolirion cordifolium(Younjeong-ri, Jincheon-Eun V) and Sasa borealis(Junggye-ri, Buan-gun IV). In correlation analysis, Artemisia princeps var. orientalis${\cdot}$Carex siderosticta, Sasa borealis${\cdot}$Festuca ovina, Sasa borealis${\cdot}$Smilax china and Festuca ovina${\cdot}$Smilax china were showed the highest relativity. In similarity index analysis, as the site that was showed highest value was Yulji-ri, Geosan-gun III and Maechon-ri, Yeongdong-eup IV, there was turned up about some $27.27\%$. In the results of regression analysis between environmental factors and number of species, R-square of altitude and number of species was some $70.0\%$.

• Korean Journal of Plant Resources
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• v.28 no.1
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• pp.64-78
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• 2015

The environmental characteristics of Astilboides tabularis were investigated to compile basic data for conservation and restoration. Natural habitats, according to investigations, were mostly located on the slopes of mountains facing north at an altitude of 432 m to 1,413 m above sea level with angles of inclination ranging from 16 degree to 49.5 degree. A total of 246 vascular plant taxa were identified from 12 quadrats in 11 habitats. The importance value of Astilboides tabularis is 20.40%, and 6 highly ranked species such as Dryopteris crassirhizoma (4.56%), Rodgersia podophylla (3.72%), Astilbe rubra (2.81%), Carex siderosticta (2.67%), Ainsliaea acerifolia (2.65%), and Meehania urticifolia (2.46%) are considered to be an affinity with Astilboides tabularis in their habitats. Average species diversity was 1.23, dominance and evenness were found to be 0.11 and 0.86, respectively. The litter depth above the soil surface was 2 to 10 cm, and soil depth was 20.8 to 67.5 cm. The soil texture of habitats were divided three types such as loam, silt loam, and sandy loam. The soil pH was 5.63 to 7.74, and the organic matter and nitrogen contents were ranged from 8.88 to 42.55%, and 1.40 to 6.58 mg/g, respectively.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.34 no.4
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• pp.428-434
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• 2008

Introduction: Piezosurgery device is one of the most commonly used instrument on the intraoral surgery such as maxillary sinus lift and autogeneous bone graft. Piezosurgery instrument also contains the tips that are manufactured especially for the convenient bone graft, which now many surgeons apply them for collecting bone graft materials in the curettage method for the restoration of skull defects. However, objective data has not been shown concerning the effects about bone graft with using Piezosurgery. Therefore we investigated the effects of Piezosurgery on the rabbit-skull defect healing. Materials & Methods: To investigate the regeneration of the bony defect with various bone graft, 10 adult New Zealand white rabbits (average weight : $2.8{\pm}0.3kg$, about 12weeks) were used. The four circular bony defects measuring 6mm in diameter were made with Piezosurgery device on each rabbit cranial bone. The harvested bone tissues during defect formation were also used for autogeneous bone graft. They were grafted into the defects in a various type; block type (Group 1), particulated type by the bone mill (Group 2), chopped type by curette shaped Piezosurgery tip (Group 3), the defect without any graft was served as control (control group). The animals were sacrificed after 6 weeks and bone regeneration capacity was evaluated histomorphometrically. Result & Conclusion: Autogeneous bone graft harvested using a Piezosurgery instrument showed satisfactory bone regeneration. There was no conspicuous difference bone prepared among by bone mill or Piezosurgery and block bone graft. Therefore, the bone harvested from the intraoral site near the operation field using the piezosurgery device can be a feasible and reliable graft for intraoral bony defects.

• Korean Journal of Environment and Ecology
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• v.30 no.5
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• pp.896-907
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• 2016

The habitat characteristics of Aconitum austrokoreense Koidz. were investigated to provide basic data for conservation and restoration. The altitude ranged from 260m to 728m with inclinations of $4-39^{\circ}$. As a result of vegetation survey within natural populations, a total of 147 taxa were identified inside 20 quadrates in 7 natural habitats. The importance value of Aconitum austrokoreense was 23.0% based on the coverage and frequency of the herbaceous layer and sat is more dominant. Species diversity was 1.23, and dominace and evenness were found to be 0.22 and 0.77, respectively. The soil type were silty loam (four sites), sandy loam (two sites) and loam (one site). The average field organic matter was 7.83% and the total nitrogen and pH were 0.35, and 5.69. Correlation analysis between environmental factors and population characteristic showed the correlations between chlorophyll content and slope, flowering rate and soil humidity. Conservation on habitats conditions is important for stable maintenance the flora and the surrounding area including habitats has to be designated a protection area for habitats conservation.

• The Journal of Korean Academy of Prosthodontics
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• v.54 no.1
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• pp.14-20
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• 2016

Purpose: The aim of this study was to know whether there is significant difference of peri-implant bone density according to the state of antagonist region. Materials and methods: 51 patients who had implant operation in Daejeon Dental Hospital of Wonkwang University participated in this study and total of 51 implants were analyzed. Implants were classified depending on opposing antagonist region, gender, age and location of jaw. The opposing antagonist region was divided into four groups; natural tooth, implant, pontic and edentulous region. Fractal analysis was performed using two periapical radiographs; one after implant placement and the other after 10 weeks following prosthetic restoration. The analysis was done by Image J. The data was statistically analyzed using one-way ANOVA and Tukey multiple comparison test. Results: The mean value of fractal difference was $0.009{\pm}0.048$ with opposing natural tooth, $0.026{\pm}0.080$ with opposing implant, $0.025{\pm}0.068$ with opposing pontic and $0.093{\pm}0.171$ with opposing edentulous area. There was a statistically significant difference in fractal value between opposing implant and opposing edentulous state. And there was no statistically significant difference according to age, gender and location of jaw. Conclusion: There was no statistically significant difference between 3 groups except opposing edentulous region and there was a statistically significant difference between opposing implant and edentulous region. And there was no statistically significant difference according to age, gender and location of jaw.