• The Journal of Korean Academy of Prosthodontics
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• v.38 no.2
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• pp.214-225
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• 2000

The purpose of this study was to investigate the effects of investing conditions on the marginal discrepancy of conical telescope outer crown with Co-Cr-Ti alloy(Dentitan) and to compare the marginal discrepancy and the retention force of outer crowns using different pattern materials(plastic foil, casting wax, pattern resin). To evaluate the effects of investing conditions on the marginal discrepancy, patterns with plastic foil were invested under three different liquid/powder ratio conditions using phosphate bonded investment(Univest-nonprecious): standard, 10% decreased and 10% increased. At each liquid/powder ratio condition, metal ring was lined with single or double layers of ceramic ring liner. The marginal discrepancy of outer crown at different investing conditions was measured by ${\times}100$ compact measuring microscope(STM5, Olympus, Japan). For measurement of the marginal discrepancy and the retention force of outer crown using different pattern materials, the investing condition of 10% decreased liquid/powder ratio and double layers of ring liner was selected because this investing condition resulted in the best fit of outer crown. Marginal discrepancy was measured in the same way above and retention force on universal testing machine. Under the conditions of this study, the following conclusions were drawn: 1. The thickness of ring liner had more influence on the marginal discrepancy of outer crown than the liquid/powder ratio, and the acceptable marginal fitness could not be expected at the investing condition directed by investment manufacturer 2. There were no differences in the marginal discrepancy of outer crown among three different pattern materials(P>0.05). 3. Casting wax showed the greatest retention force(1640g) of outer crown, followed by pattern resin(1110g), plastic foil(820g). However, there was no significant difference between plastic foil and pattern resin(P>0.05). 4. Plastic foil showed the least variation in marginal discrepancy and retention force.

• Journal of the korean academy of Pediatric Dentistry
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• v.4 no.1
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• pp.35-38
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• 1977

The study was performed to evaluate effects of Conservative treatment between amalgam filling and stainless steel crown. The selected subjects for this study was 350 children who have amalgam filling or stainless steel crown. The obtained results are as followings. 1. In amalgam filling teeth, 120 teeth (60.0%) showed marginal leakage, 57 teeth (28.5%) showed fracture of filling material and 28 teeth (14.0%) teeth showed periapical lesion. 2. In crowned teeth, 6 teeth (3.0%) showed hole on the surface of crown, 29 teeth (14.5%) showed avulsion of crown and 10 teeth (5.0%) showed periapical lesion. 3. After 12 months from examining date, 69 teeth (34.5%) showed sound condition in amalgam filling teeth and 155 teeth (75.2%) showed sound condition in crowned teeth.

• Journal of Ocean Engineering and Technology
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• v.26 no.5
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• pp.1-4
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• 2012

A energy saving device "Crown duct" has been developed and its efficiency gain has been verified experimentally in the towing tank of SSPA. The preswirl stator is well known as one of energy saving devices, which recovering the rotational energy of propeller slipstream. Crown duct has two functions of recovers the rotational energy by three blades on top of duct and of flow concentration by semi-duct. The model tests showed 4.4% efficiency gain with Crown Duct at full load condition and 6.9% at ballast condition compared with the bare hull ones for the middle class tanker.

• Journal of Technologic Dentistry
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• v.29 no.1
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• pp.93-101
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• 2007

The purpose of this study is to evaluate the effect of three different oblique mechanical loading to occlusal surfaces of posterior implant partial dentures on the stress distributions in surrounding bone, using 3-dimensional finite element method. A 3-dimensional finite element model of a posterior implant partial dentures composed of three unit implants, simplified 3 gold alloy crown and supporting bone was developed according to the design of AVANA self tapping implant for this study. Three kinds of surface distributed oblique loads(300 N) are applied to following occlusal surfaces in the three crowns; 1) All occlusal surfaces in the three crown(load of 300 N was shared to three crown), 2) Occlusal surface of centered crown (load of 300 N was applied to a centered crown), 3) Occlusal surface of proximal crown(load of 300 N was applied to a distal proximal crown). In the results, 141 MPa of maximum von Mises stress was calculated at third loading condition and 98 MPa of minimum von Mises stress was calculated at first loading condition. From the results, location and type of occlusive loading conditions are important for the safety of supporting bone.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.15 no.3
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• pp.45-54
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• 2012

This study intended to analyze growth condition of each object by protected tree's ground for 45 places registered to Pyeongtaek protected tree list in locational characteristics, conduct exchange analysis for impediment extent rate in crown area and tree type to the result and suggest the measures to manage artificial impediment which is an effect on protected tree condition. In this study, the tree whose area of impediment for crown area is less than 21% is tree condition of grade 1~2, less than 21~50% is grade 2~3 and more than 50% is grade 3~5. The more impediment is, the more inconvenience causes on growth and development. So, it verified that the area rate must maintain less than 21% for the root system management of protected tree. For the standard of managing artificial impediment which is an effect on the tree condition of protected trees, the below matters intend to be suggested. The first, the impediment in crown area should be less than 21%. But, if there is not artificial impediment out of crown area, the rate of impediment area is considered to increase somewhat. The second, growth space of protected tree should be maintained by crown area at least and impediment should be established out of the crown area. The third, during the national project and land development, surroundings of protected tree must be applied as park, resting place, etc. and the establishment area of impediment (artificial impediment and natural impediment) in crown area must be limited. The forth, publicity for regional people (especially, land owner) is necessary for the protection of natural inheritance and the value of dependence on local government and village which are the subject of management must be announced widely through the internet media, etc, so its importance must be recognized. The fifth, the matters related to protected tree management must be able to limit artificial damage which is for surroundings of protected tree through the mutual connection among the local governments; construction, civil engineering, architecture, water and sewage, agriculture and forest and others. Also, following studies on the effects of kinds, thickness, etc. of impediment around the protected tree on trees should be continued.

• Journal of Technologic Dentistry
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• v.31 no.1
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• pp.7-15
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• 2009

Purpose: This study was to propose the clear understanding for stress distribution of supporting bone by use of staggered buccal offset tripodal placement of fixtures of posterior 3 crown implant partial dentures. We realized posterior 3 crown implant fixed partial dentures through finite element modeling and analysed stress effect of implant arrangement location to supporting bone under external load using finite element method. Method: To understand stress distribution of 3 crown implant fixed partial dentures which have 2 different arrangement by finite element analysis. In each model, for loading condition, we applied $45^{\circ}$ oblique load to occlusal surface of crown and applied 100 N for 3 crown individually(total 300 N) for imitating possible oral loading condition. at this time, we calculated Von Mises stress distribution in supporting bone through finite element method. Result: When apply $45^{\circ}$ oblique load to in-line arrangement model, maximum stress result for 100 N for each 3 crown 47.566MPa. In tripodal placement, result for 1mm buccal offset tripodal placement implant model was maximum distributed load 51.418MPa, so result was higher than in-line arrangement model. Conclusion: In stress distribution result by placement of implant fixture, the most effective structure was in-line arrangement. The tripodal placement does not effective for stress distribution, gap cause more damage to supporting bone.

• Journal of Ocean Engineering and Technology
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• v.28 no.1
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• pp.1-5
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• 2014

Chosun University, in cooperation with SPP shipyard, has developed an energy saving device based on a new concept: "Crown Duct." Crown Duct is composed of a semi-duct with short struts inside and outside the duct. Theoretical calculations for two different designs were carried out using the CFD code "Ship Flow." The design selected from these two different forms by the CFD code analysis was tested in a towing tank at SSPA. The results showed about 4% efficiency gain under a full-load condition and about 7% gain under a ballast condition in the towing tank test.

• The Journal of Korean Academy of Prosthodontics
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• v.52 no.4
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• pp.359-365
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• 2014

Successful results of treatments using double crown prostheses for the partially edentulous patients who have a few remaining teeth have been reported in several journals. A double crown removable partial denture can be an alternative treatment for the patients with a poor periodontal condition of remaining teeth. Since a double crown removable partial denture can be applied without the risk of surgical operation to the medically compromised patients with a poor periodontal condition which is inadequate for dental implants, it has psychological and economical advantages. In this case, there were sufficient remaining teeth to be restored with fixed prostheses in maxilla, while there were a few remaining teeth with a very poor periodontal condition so that it was almost impossible to restore with a clasp removable partial denture using these remaining teeth in mandible. In addition, the patient had the medical history of surgical operation due to osteomyelitis in the mandibular anterior areas a year ago, thus difficult to conduct an implant placement. The main objective of this report is to introduce our case because a double crown partial denture using a few mandibular remaining teeth showed satisfactory results in functional and esthetical aspects during more than two years follow-up period in this unfavorable condition.

• The Journal of Korean Academy of Prosthodontics
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• v.54 no.3
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• pp.246-252
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• 2016

Double crown prostheses can be used in patients who have a few remaining teeth and poor periodontal condition because of secondary splinting of abutments, vertical loading, decrease of the length of lever arm due to fulcrum line located on margin of inner and outer crown. Successful results of treatments using double crown prostheses for the partially edentulous patients who have a few remaining teeth and implant overdenture using a small number of implants have been reported. In this case, there were a few remaining teeth with a very poor periodontal condition in maxilla, and there were a failed implant with severe alveolar bone resorption and shrinkage in the mandible. The main objective of this report is to introduce our case because a double crown partial denture showed satisfactory results in functional and esthetical aspects during more than one-year follow-up period.

• The Journal of Korean Academy of Prosthodontics
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• v.25 no.1
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• pp.341-353
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• 1987

The purpose of this study was to investigate the gingival response to the location of the crown margin and the gingival response to the period of crown placement. Twenty one patients were selected for this study. The patients fitted into the research condition. The crown margins of anterior teeth were located at crest and supragingivally. The crown margins of posterior teeth were located at crest, subgingivally and supragingivally. Plaque index and gingival index were measured before tooth preparation and 1 week,4 weeks, 6 weeks after crown placement. The results were as follows: 1. There was no significance in the gingival response to the location of crown margin in short term period. 2. As the period of crown placement was extended, plaque index and gingival index were gradually increased. 3. Plaque index and gingival index of tooth surfaces were increased in the order of the interproximal surfaces, lingual surfaces and buccal or labial surfaces.