• Restorative Dentistry and Endodontics
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• v.23 no.1
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• pp.54-67
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• 1998

The purposes of this study were to evaluate the efficiency of dentin cutting and root-end cavity preparation, and to determine the incidence of tooth crack when root-end retrograde cavity preparation was done with. ultrasonic diamond instruments. To evaluate the efficiency of dentin cutting, ultrasonic diamond and stainless steel instruments were applied to 20 exposed bovine dentin surfaces perpendicularly or parallely at the low, and medium power settings for 1 minute ($Miniendo^{TM}$, EIE, CA, U.S.A.). The resultant cavity depth was measured. To evaluate the efficiency of cavity preparation and to investigate the incidence of tooth crack, 165 mesiobuccal, distobuccal and palatal root-ends of extracted human maxillary first molars were resected by 3 mm perpendicularly to the long axis of tooth using a slow speed diamond saw after root canal preparation and filling. Retrocavities were prepared using a ultrasonic diamond instrument or a stainless steel one of the low- or medium power settings of 2 or 6. Time consumed and the number of strokes used for the cavity preparation were measured and the incidence of tooth cracks was evaluated under a stereomicroscope. The results were as follows: Both at the low and medium power settings, and both with perpendicularly- and parallely applied tips to dentin, diamond instruments showed higher dentin cutting efficiency than stainless steel ones did (p<0.01). When tips were applied to dentin perpendicularly, both diamond instrument and stainless steel one showed higher cutting efficiency with medium power setting than with low power one (p<0.01). Both at the low- and medium power settings, both diamond instrument and stainless steel one showed higher cutting efficiency when tips were applied perpendicularly to dentin surface than applied parallely (p<0.01). At the medium power setting, the number of stroke and time consumed were less with diamond instrument than with stainless steel one (p<0.05) for the retrograde cavity preparation. At the low power setting, diamond instrument induced less tooth cracks than stainless steel one did (p<0.01).

• Restorative Dentistry and Endodontics
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• v.34 no.4
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• pp.324-332
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• 2009

The purpose of this study was to investigate the effect of rigidity of post core systems on stress distribution by the theoretical technique, finite element stress-analysis method. Three-dimensional finite element models simulating an endodontically treated maxillary central incisor restored with a zirconia ceramic crown were prepared and 1.5 mm ferrule height was provided. Each model contained cortical bone, trabecular bone, periodontal ligament, 4 mm apical root canal filling, and post-and-core. Six combinations of three parallel type post (zirconia ceramic, glass fiber, and stainless steel) and two core (Paracore and Tetric ceram) materials were evaluated, respectively. A 50 N static occlusal load was applied to the palatal surface of the crown with a $60^{\circ}$angle to the long axis of the tooth. The differences in stress transfer characteristics of the models were analyzed. von Mises stresses were chosen for presentation of results and maximum displacement and hydrostatic pressure were also calculated. An increase of the elastic modulus of the post material increased the stress, but shifted the maximum stress location from the dentin surface to the post material. Buccal side of cervical region (junction of core and crown) of the glass fiber post restored tooth was subjected to the highest stress concentration. Maximum von Mises stress in the remaining radicular tooth structure for low elastic modulus resin core (29.21 MPa) was slightly higher than that for high elastic modulus resin core (29.14 MPa) in case of glass fiber post. Maximum displacement of glass fiber post restored tooth was higher than that of zirconia ceramic or stainless steel post restored tooth.

• Restorative Dentistry and Endodontics
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• v.32 no.1
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• pp.37-46
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• 2007

The C-shaped canal system is an anatomical variation mostly seen in mandibular second molars, although it can also occur in maxillary and other mandibular molars. The main anatomical feature of C-shaped canals is the presence of fins or web connecting the individual root canals. The complexity of C-shaped canals prevents these canals from being cleaned, shaped, and obturated effectively during root canal therapy, and sometimes it leads to an iatrogenic perforation from the extravagant preparation. The purpose of this study was to provide further knowledge of the anatomical configuration and the minimal thickness of dentinal wall according to the level of the root. Thirty extracted mandibular second molars with fused roots and longitudinal grooves on lingual or buccal surface of the root were collected from a native Korean population. The photo images and radiographs from buccal, lingual, apical direction were taken. After access cavity was prepared, teeth were placed in 5.25% sodium hypochlorite solution for 2 hours to dissolve the organic tissue of the root surface and from the root canal system. After bench dried and all the teeth were embedded in a self-curing resin. Each block was sectioned using a microtome (Accutom-50, Struers, Denmark) at interval of 1 mm. The sectioned surface photograph was taken using a digital camera (Coolpix 995, Nikon, Japan) connected to the microscope. 197 images were evaluated for canal configurations and the minimal thickness of dentinal wall between canal and external wall using 'Root Thickness Gauge Program' designed with Visual Basic. The results were as follows : 1. At the orifice level of all teeth, the most frequent observed configuration was Melton's Type C I (73%), however the patterns were changed to type C II and C III when the sections were observed at the apical third. On the other hand, the type C III was observed at the orifice level of only 2 teeth but this type could be seen at apical region of the rest of the teeth. 2. The C-shaped canal showed continuous and semi-colon shape at the orifice level, but at the apical portion of the canal there was high possibility of having 2 or 3 canals 3. Lingual wall was thinner than buccal wall at coronal, middle, apical thirds of root but there was no statistical differences.

• Restorative Dentistry and Endodontics
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• v.32 no.1
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• pp.28-36
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• 2007

The purpose of this study was to compare the effect of exponential curing method with conventional curing and soft start curing method on polymerization shrinkage of composite resins. Three brands of composite resins (Synergy Duo Shade, Z250, Filtek Supreme) and three brands of light curing units (Spectrum 800, Elipar Highlight, Elipar Trilight) were used. 40 seconds curing time was given. The shrinkage was measured using linometer for 90 seconds. The effect of time on polymerization shrinkage was analysed by one-way ANOVA and the effect of curing modes and materials on polymerization shrinkage at the time of 90s were analysed by two-way ANOVA. The shrinkage ratios at the time of 20s to 90s were taken and analysed the same way. The results were as follows : 1. All the groups except Supreme shrank almost within 20s Supreme cured by soft start and exponential curing had no further shrinkage after 30s (p < 0.05). 2. Statistical analysis revealed that polymerization shrinkage varied among materials (p = 0.000) and curing modes (p = 0.003). There was no significant interaction between material and curing mode. 3. The groups cured by exponential curing showed the statistically lower polymerization shrinkage at 90s than the groups cured by conventional curing and soft start curing (p < 0.05). 4. The initial shrinkage ratios of soft start and exponential curing were statistically lower than conventional curing (p < 0.05). From this study, the use of low initial light intensities may reduce the polymerization rate and, as a result, reduce the stress of polymerization shrinkage.

• Restorative Dentistry and Endodontics
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• v.32 no.1
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• pp.47-60
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• 2007

The purpose of this study is to compare and to evaluate the effect of pH and lactic acid concentration on the progression of artificial root caries lesion using polarizing microscope, and to evaluate the morphological changes of hydroxyapatite crystals of the demineralized area and to investigate the process of demineralization using scanning electron microscope. Artificial root caries lesion was created by dividing specimens into 3 pH groups (pH 4.3, 5.0, 5.5), and each pH group was divided into 3 lactic acid concentration groups (25 mM, 50 mM, 100 mM). Each group was immersed in acid buffer solution for 5 days and examined. The results were as follows : 1. Under polarized microscope, the depth of lesion was more effected by the lactic acid concentration rather than the pH. 2. Under scanning electron microscope, dissolution of hydroxyapatite crystals were increased as the lactic acid concentration increased and the pH decreased. 3. Demineralized hydroxyapatite crystals showed peripheral dissolution and decreased size and number within cluster of hydroxyapatite crystals and widening of intercluster and intercrystal spaces as the pH decreased and the lactic acid concentration increased. 4. Under scanning electron microscope evaluation of the surface zone, clusters of hydroxyapatite crystals were dissolved, and dissolution and reattachment of crystals on the surface of collagen fibrils were observed as the lactic acid concentration increased. 5. Under scanning electron microscope, demineralizatlon of dentin occurred not only independently but also with remineralization simultaneously. In conclusion, the study showed that pH and lactic acid concentration influenced the rate of progression of the lesion in artificial root caries. Demineralization process was progressed from the surface of the cluster of hydroxyapatite crystals and the morphology of hydroxyapatite crystals changed from round or elliptical shape into irregular shape as time elapsed.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.31 no.4
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• pp.95-112
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• 2013

Jangchungdan Park is now perceived as a mere park at the foot of Namsan mountain, but originally it was created to commemorate soldiers of Korean Empire on a site which name was Namsoyeong(南小營) during Joseon Dynasty. During the period of Japanese colonial rule, it was transformed into a park due to the rapidly changing circumstances, so the components expressing the validity of the colonial rule were introduced into the park. This paper examines the time sequential changes of Jangchungdan Park during the period of Japanese colonial rule, and the conclusions can be summarized as given below. Firstly, the park originally was a space to commemorate the soldiers who fought for the Korean Empire. It was built on formerly restricted area at the foot of Namsan Mountain in 1900, and it was arranged putting the ceremonial shrine Dansa (壇祠) as a central building and the annexes in the surroundings of it. The memorial ceremonies were held regularly in spring and autumn until 1909. Secondly, it became a city park for citizens of Gyeongseong-bu(the name of Seoul under the Japanese colonial rule). The authorities of Gyeongseong-bu reorganized Jangchungdan as a park in 1919, prohibited the performance of memorial ceremonies, and the existing buildings except the ceremonial shrine Dansa began to be used as park management facilities. Resting areas and amenities were supplemented for the usage of people from various backgrounds, and the large scale planting of cherry trees made the park a famous place to enjoy cherry-blossoms and other flowers in spring. Thirdly, it was reconstructed as a space to honor the influential personalities of Japanese colonial system. In 1932, Bankmun temple (博文寺) to commemorate Ito Hirobumi was constructed at a location that made it possible for a number of people to overlook Jangchungdan area. During that time, the buildings of traditional Joseon architecture were removed and reconstructed to serve as annexes to Bankmun temple. Due to the strategy to make Jangchungdan park a tourist attraction, Bankmun temple was included into the Gyeongseong sightseeing course, since the wide panorama of Jangchungdan Park and the whole city of Gyeongseong was opening from the temple. Various different components were introduced into Jangchungdan Park due to the rapidly changing circumstances; therefore the nature of the park was either altered or reproduced. Hopefully, the park rearrangement works will be executed paying respects to the memories of the past hereafter.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.34 no.4
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• pp.37-50
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• 2016

Recognizing the problem of fallacy in geographical name of Changokbyeong(蒼玉屛), assumption has been made on the location of Changokbyeong through literature research on antique maps, ancient paintings, and old prose, through field survey on rock inscriptions and landscape characteristics, and through interviews with local people. Furthermore, Baegyeonwa, the Cuckoo Hut, and Iyangjung(二養亭), an annex to the cottage, both of which were managed by Saahm Park Soon(思菴 朴淳), the Subject of Jouissance, were studied in depth with emphasis on the spatial structure as well as special features of the area as a garden. The major findings are as follows: Changokbyeong is a spatial threshold that imparts a sense of unity with Okbyeng seowon(玉屛書院) and indeed Changokbyeong is presumed to have been the frontal river terrace of Okbyeng seowon according to the analysis of antique maps and rock inscriptions. This ancient location and the Ogari Stone Wall, the present day Changokbyeong, are only 460m away so that both areas are considered as falling under the influence of Changokbyeong landscape. The expression "Changokbyeong Geupsangeum(蒼玉屛及散襟)" written in an old prose tells us that the high rock wall with Sangeumdae inscribed on the rock might be the rock wall of Changokbyeong. In addition, while not a single rock inscription has been found on the Ogari Stone Wall, 11 rock inscriptions designed and ordered by Saahm Park Soon, the Subject of Jouissance, are found on every corner of the high rock wall standing in front of Okbyeng seowon, 8 of those 11 being place names and recitative poems(known as Jeyeongsi: 題詠詩) in close formation resembling the handwritings in a little notebook. This provides a strong evidence for assuming the location of Changokbyeong to be the frontal river terrace of Okbyeng seowon. The "Songgyun Jeoljo Suwol Jeongshin(松筠節調 水月精神)" rock inscription on Changokbyeong should be considered as the stamping ground and as the symbolic language of Changokbyeong that bears the high character and nobility of the Subject of Jouissance, Saahm Park Soon. The inscription should also be recognized as the handwritings of Wooahm Song Si-Yeol(尤庵 宋時烈) correcting the misconceptions that persisted until today. Meanwhile, the garden remains of Saahm's Changokbyeong are composed of four sites: Sangeumdae-Sugyeongdae-Cheonghakdae-Baekhakdae from the left. At the back of Sangeumdae, there is the original house, the Baegyeonwa(拜鵑窩), and on the fantastically shaped stone wall at the left of Baekhakdae, there is the annex, the Iyangjung, together creating a landscape composition that overlooks the splendor of the Ogari Stone Wall. The Iyangjung is located on the highest spot to the left of the four sites, and it is believed to have been a little outhouse and library for Saahm which remains to the present day as a place where Saahm's character can be felt. The drinking plates[窪樽] made of rock that are affectionately arranged on the broad flat rock in front of Iyangjung is part of the garden remains that reflects the artistic taste of Saahm regarding the drinking culture at the time.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.35 no.4
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• pp.1-13
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• 2017

This thesis aims to research the original landscape of an area in Chirwon by comparing and interpreting the current and the former landscape of the time around 1860, in which was created. Inside the painting, MuGi-YeonDang(舞沂蓮塘), its nearby garden facilities and landscape are described. The conclusions of the research are as follows. Around the inner garden(內園) called Gukdam(菊潭), core spaces of Mugi-YeonDang were Hahwanjeong(何換亭) and Pungyongnu(風浴樓). After 1971, Chunghyosa(忠孝祠), Yeongjeonggak(影幀閣) which was built as inheritance of Giyangseowon (沂陽書院), and other buildings were added. On the opposite of Hahwanjeong, there is a designed pond inside Gukdam, in which three pieces of bizarre stones and colorful flower plants and trees reside. In the middle of the pond, there is an center island(中島), constructed with Bonghwangseok(鳳凰石) and Napduseok(衲頭石). Two different kinds of trees are settled on top of the stones, and one of them is identified as a maple. In the external scenery(外境), Jakdaesan Mountain and Cheonjusan Mountain are located at the upper part of Mugi-Yeondang, and Bibo Forest(裨補林), which does not exist anymore, was located at the lower part of it. A notable achievement in own research was to discover the Ju family's graveyard(朱氏墓群) consisted of more than 10 murals at the lower part of Mt. Jakdaesan in the outer space and the remains of 'Byeoreop(別業) Yuhoejeong(有懷亭)' at the nearby Sanjeong-ri(山亭里) area, which was the Ju family's gravesite(Seonsan, 先山). The discovered remains showed the presence of a square pond(方塘) and an island in the center of it(中島) in the form of Seokgasan(an artificial mountain made with stones), a stone monument called Mangchudae(望楸臺), etc. The Seokgasan was consisted of processed natural stones, and layers of the stones were piled up for it. On the side of the layered stones, 'Gyeongam(敬嵒)' and 'Sesim(洗心)' are engraved. Especially, Gyeongja(letter Gyeong, 敬字) is a copy of the Gyeongja Rock(敬字岩) of Sosu-Seowon(紹修書院), which is a symbolic garden language mutually used in the signboards of Pungyongnu and Musansa(武山祠), a place built to enshrine Ju, Sebung(周世鵬). Through the written names of the building found in , it can be assumed that the name of the square pond with Seokgasan was Taehwaji or Jeongwudang, and the name of the Seokgasan was Sogeumgang(小金剛) or Sobangjang(小方丈). The names correspond to the names of the Seokgasan of Gukdam, which was Yangsimdae(養心臺) and Bongnaesan(蓬萊山). By means of the corresponding names, it can be inferred that the relations between the spaces were intended. was originally created as 'a manor painting(莊園圖)', led by the 15th generation of the Ju family who moved into Chirwon-ri, Haman. The painting describes not only the back garden but also the external scenery, thus it provides important evidences for understanding Mugi-YeonDang and its nearby landscape, and is helpful to its maintenance and restoration.

• Journal of Nutrition and Health
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• v.44 no.1
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• pp.49-60
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• 2011

This study was performed to develop a children's dietary life safety index required by the Special Act on Safety Management of Children's Dietary Life enacted in 2009. An analytical hierarchy process was used to obtain initial weights of dietary life safety evaluation indicators. The Delphi method was applied to develop the weights along with 98 food and nutrition professionals. Three representative policy indicators, nine strategy indicators, 11 main evaluation indicators, and 20 detailed evaluation indicators were selected for the children's dietary life safety assessment. Three policy indicators and nine strategy indicators were the following: children's food safety indicator (support level of children' safety, safety management level of children's favorite foods, and safety management level of institutional food service), children's nutrition safety indicator (management level of missing meals and obesity, nutrition management level of children's favorite foods, and nutrition management level of institutional food service), and children's perception and practice level indicator ("Dietary Life Law" perception level, perception, and practice level for dietary life safety management, perception, and practice level for nutrition management). Weights of 40%, 40%, and 20% were given for the three representative policy indicators. The relative importance of nine strategic indicators, which were determined by the Delphi method is as follows: For children’s food safety, support level of children's safety, safety management level of children's favorite foods, and safety management level of institutional food service were given weights of 12%, 9%, and 19%, respectively. For children's nutrition safety, the missing meals and obesity management level, nutrition management level of children's favorite foods, and the nutrition management level of institutional food service were given weights of 13%, 11%, and 16%, respectively. The "Dietary Life Law" perception level, perception and practice level of dietary life safety management, and perception and practice level of nutrition management were given weights of 4%, 7%, and 9%, respectively.

• Journal of Nutrition and Health
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• v.47 no.2
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• pp.145-156
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• 2014

Purpose: The purpose of this study was to establish accreditation systems of reliable educational materials for nutrition and dietary life which could be used in schools, workplace, and health promotion. Methods: The study was conducted from April 2011 to October 2011. Literature reviews, institutional visits, and telephone interviews were conducted. Expert meetings and advisory councils were held in order to receive feedback on development of the accreditation systems. A survey was conducted for the accreditation procedures on 143 professionals, including professors, researchers, health and medical experts, teachers, nutrition teachers, dietitians, and clinical nutritionists. Results: The final procedure of the developed accreditation system was finalized as follows: 1) receiving application twice per year 2) complete desk review (written evaluation) by three reviewers within two months, 3) board review (all board members) and decision, and 4) notification of results. The accreditation system is set for printed materials, web-site, and materials for activities. The certificate and accreditation mark is issued to the final certified educational materials. Expiration date is established only for the web-site form. The accreditation length lasts for two years, and can be extended by renewal application. Conclusion: The dietary and nutrition related materials, which are certificated by this accreditation system, could impart reliable information and knowledge to both learners and educators, and help them in effective selection of educational materials. Therefore, this accreditation system might be expected to increase satisfaction for teaching and learning about nutrition and healthy dietary life.