• Proceedings of the Korean Society for Language and Information Conference
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• 1996.02a
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• pp.415-424
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• 1996

• The Bulletin of The Korean Astronomical Society
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• v.30 no.1
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• pp.40.2-40.2
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• 2005

• The Bulletin of The Korean Astronomical Society
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• v.23
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• pp.14-14
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• 1998

• The Bulletin of The Korean Astronomical Society
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• v.31 no.2
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• pp.31.2-31.2
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• 2006

• The Bulletin of The Korean Astronomical Society
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• v.33 no.2
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• pp.30.2-30.2
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• 2008

• The Bulletin of The Korean Astronomical Society
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• v.34 no.1
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• pp.83.1-83.1
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• 2009

• The Bulletin of The Korean Astronomical Society
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• v.25 no.1
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• pp.39-39
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• 2000

• Restorative Dentistry and Endodontics
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• v.27 no.6
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• pp.612-621
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• 2002

The purpose of this study was to compare the histomorphological change of curved root canal preparation using GT rotary File, Profile .04 taper and stainless steel K-file. 45 mesial canals(over 20 degree) of extracted human mandibular first molars were mounted in resin using a modified Bramante muffle system and divided into three groups. The roots were cross-sectioned at 2.5mm 5mm and 8mm levels from apical foramen. Tracings of the canals were made from preinstrumentation pictures of the cross section. The canals were prepared using a step-back technique with stainless steel K file(group 1), Profile .04 taper rotary file(group 2) and GT rotary file(group 3). Tracings of the prepared canals were made from postinstrumentation picture. Canal centring ratio. amount of transportation, area of dentin removed and shape of canal were measured and statistically were evaluated with Student-Newman-Keuls test using Sigma Stat(Jandel Scientific Software, USA). The results were as followings : 1 Amount of transportation of group 2 was the lowest at apical part, but there was no statistical difference. The direction of transportation was the outside of curvature at apical part. 2. Centering ratio at the apical part of group 1 was the highest, and there was statistical differences between apical and middle part, apical and coronal part(p＜0.05). Centering ratio at the middle part of group 3 was the lowest, and there was statistical difference between apical and middle part(p＜0.05). Centering ratio of group 2 was the lowest at apical part, but there was no statistical difference. 3. Amount of dentin removed of group 1 was the highest at coronal, middle and apical part among three groups, and there was statistical difference(p＜0.05). 4. The majority of the cross-sectioned canal shape after instrumentation were irregular at coronal, middle and apical part. But there are more number of round shaped canals at group 3 than other group.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.36 no.5
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• pp.360-365
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• 2010

Introduction: Mammalian tooth pulp is densely innervated by sensory nerves that are mostly C fibers and A delta fibers. However, there is evidence suggesting that many unmyelinated axons in the pulp are in fact parent meylinated axons. Immunohistochemical staining for neurofilament protein 200 kDa (NFP200) was performed to identify the demyelinated but parent myelinated axons. Materials and Methods: The pulp was removed from healthy premolars and 3rd molars extracted from juveniles and adults undergoing orthodontic treatment, and immunohistochemical staining were applied with NPF200 antibodies, which specifically dye myelinated axons. The specimens underwent an electron microscopy examination with diaminobenzidine (DAB) immunostaining after observation and analysis by fluorescence and confocal laser scanning microscopy. Results: The NPF200 immuno-positive axons in the radicular pulp areas were observed as bundles of many nerve fibers. Many small bundles were formed with fewer axons when firing to the coronal pulp areas and then reachrd a different direction. In the radicular pulp, unmyelinated axons and myelinated axons were present together. However, in the coronal pulp, unmyelinated axons were most common and NFP200 immuno-positive unmyelinated axons with a larger diameter than those in the radicular pulp were observed more frequently. On the other hand, most of the immuno-positive unmyelinated fibers were similar in size to that of typically well-known unmyelinated fibers. Conclusion: Myelinated fibers innervated to the dental pulp maintain their myelins in the radicular portion, but these fibers lost myelins in the coronal portion. After the loss of myelin, the size of the axoplasm also decreased.

• The Journal of Korean Academy of Prosthodontics
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• v.33 no.3
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• pp.397-412
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• 1995

The purpose of this study was to analyze the stress distribution in the dentin and post structures by the various post core materials and the amount of remaining coronal tooth structures. The 2-dimensional finite element models of mandibular 2nd premolars was divided into seven types according to the various amount of remaining coronal tooth structures. All types were modeled using equal length, diameter and shape of the post. 2 types of post and core materials were used : 1) cast gold post and core 2) stainless steel post and compsite resin core 10 Newton force was applied as follows 1) vertical force on occlusal fossa 2) $45^{\circ}$ oblique force on buccal surface of buccal cusp tip The results were as follows : 1. There was no apparent difference in the pattern of stress distribution according to the amount of remaining coronal tooth structure. 2. There was no apparent difference in the pattern of stress distribution within the dentin according to the post and core materials. A cast gold post and core generated lower dentin stress than a stainless steel post and resin core. 3. Max. dentinal stress resulting from vertical force was observed in the lingual side of dentin around the crown margin.This stress resulting from oblique force was observed in the lingual root surface of alveolar bone crest level.