• 한국기계가공학회지
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• 제9권5호
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• pp.40-49
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• 2010

Conical involute gears are being used for marine gearboxes, automotive transmissions, and robots, and so on, but not much. As involute profile gear, conical involute gear not only can be engaged with spur and helical gear but also can be used for power transmission of parallel, crossed and skewed axis with small angle. Hence, conical involute gears are likely to develop in future. Through a study on the basic theory of conical involute gear, tooth surface compressive stress analysis was performed by using commercial modeling program, comparing before and after profile modification. As a result, it noticed that tooth profile modification is able to relieve more tooth surface compressive stress than before modification.

• 대한치과보철학회지
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• 제33권3호
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• pp.413-439
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• 1995

The purpose of this study was to evaluate the stress distribution developed in the supporting structures by mandibular distal extension removable partial dentures with 2 different direct retainer designs and with or without indirect retainer and abutment splinting. The examined direct retainers on the second bicuspid abutment tooth were Akers clasp and RPA clasp, the indirect retainer was located on the mesial fossa of the first bicuspid, and the first and second bicuspid were splinted in case of tooth splinting. Total 8 cases were compared and analyzed with 3-dimensional finite element method. 150N were applied vertically on the artificial teeth of the removable partial denture, and then stress distribution patterns were analyzed and compared. The results were as follows : 1. The forces transmitted to the abutment tooth were primarily from the occlusal rests. 2. The abutment tooth was displaced distally when the force was applied. The compressive stress was observed at the distal root surface of the abutment tooth and the tensile stress, at the mesial root surface. 3. The denture base was displaced posteriorly and inferiorly when the force was applied. At the more distal portion of the denture base, the greater displacement was observed.And the anterior portion of the major connector was displaced superiorly. 4. The occlusal rest placed on the distal part of the abutment tooth tended to tip the tooth more posteriorly than did one on the mesial part of that tooth. 5. Severe superior displacement was observed at the anterior portion of the major connector in case of removable partial dentures without indirect retainer. 6. In case of tooth-splinting, the stress was distributed through all the root surface of both abuments. In case of no tooth-splinting, the stress was concentrated on the distal root surface of the primary abutment.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 춘계학술대회 논문집(한국공작기계학회)
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• pp.352-357
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• 2001

In this study, residual stress was investigated to evaluate damaged layer in high speed machining through simulation. In machining steel(STDll), residual stress remaining in machined surface was mainly appeared as compressive stress. The scale of this damaged layer more depends on feed per tooth and radial depth than spindle speed. Damaged layer was measured by optical microscope and hardness method. The micro-structure of damaged layer was a martensite because of cutting force and cutting temperature. Thickness of damaged layer is increased with incresing of feed per tooth and radial depth.

• 대한치과보철학회지
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• 제29권2호
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• pp.129-145
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• 1991

The purpose of this study was to analyze the stresses and displacements of various esthetic restorations and abutment teeth. The finite element models of central incisor were divided into four groups according to the types of restoration. Three load cases were applied; 1) 45 degrees on the incisal edge, 2) horizontal force on the labial surface, and 3) 26 degrees diagonally on the lingual surface. Material property, geometry, and load conditions of each model were inputed to the two dimensional finite element program and stresses and displacements were analyzed. Results were as follows; 1. In the cases of porcelain fused gold ann and porcelain laminate venner, stresses were equally distributed in supporting abutment tooth. 2. The metal coping of porcelain fused gold u and collarless porcelain fused gold crown functioned as a good stress distributor. 3. When the horizontal load applied, the highest tensile and compressive stresses were seen in the cervical margin of restoration and the dentin of the abutment tooth. 4. The highest displacement of restoration was seen when load was applied at an mee of 26 degrees diagonally in lingual surface of tooth in centric occlusion. 5. The influence of loading direction on the stresses and displacements in the restoration was greater than that of various design. 6. The possibility of fracture was highest in porcelain jacket crown.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.326-331
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• 2000

In this study, residual stress was investigated experimentally to evaluate damaged layer in high-sped machining. In machining difficult-to-cut material, residual stress remaining in machined surface was mainly speared as compressive stress. The scale of this damaged layer depends upon cutting speed, feed per tooth and radial cutting depth. Damaged layer was measured by optical microscope. The micro-structure of damaged layer was a mixed maternsite and austenite. depth of damaged layer is increased with increasing of cutting temperature, cutting force and radial depth. On the other hand, that is slightly decreased with decreasing of cutting force. The increase of tool wear causes a shift of the maximum residual stress in machined surface layer.

• 대한치과교정학회지
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• 제54권5호
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• pp.316-324
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• 2024

Objective: To evaluate tooth displacement and periodontal stress generated by the dual action vertical intra-arch technique (DAVIT) for open-bite correction using three-dimensional finite element analysis. Methods: A three-dimensional model of the maxilla was created by modeling the cortical bone, cancellous bone, periodontal ligament, and teeth from the second molar to the central incisor of a hemiarch. All orthodontic devices were designed using specific software to reproduce their morpho-dimensional characteristics, and their physical properties were determined using Young's modulus and Poisson's coefficient of each material. A linear static simulation was performed to analyze the tooth displacements (mm) and maximum stresses (Mpa) induced in the periodontal ligament by the posterior intrusion and anterior extrusion forces generated by the DAVIT. Results: The first and second molars showed the greatest intrusion, whereas the canines and lateral incisors showed the greatest extrusion displacement. A neutral zone of displacement corresponding to the fulcrum of occlusal plane rotation was observed in the premolar region. Buccal tipping of the molars and lingual tipping of the anterior teeth occurred with intrusion and extrusion, respectively. Posterior intrusion generated compressive stress at the apex of the buccal roots and furcation of the molars, while anterior extrusion generated tensile stress at the apex and apical third of the palatal root surface of the incisors and canines. Conclusions: DAVIT mechanics produced a set of beneficial effects for open-bite correction, including molar intrusion, extrusion and palatal tipping of the anterior teeth, and occlusal plane rotation with posterior teeth uprighting.

• 대한치과보철학회지
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• 제25권1호
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• pp.55-69
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• 1987

The purpose of this study was to evaluate the stress distributions of the fixed partial denture with five unit intermediate abutment. This fixed partial denture was attached to a three dimensional photoelastic epoxy resin model. Three dimensional photoelastic models were used, with the stress areas recorded photographically. A vertical load was applied to the second molar, which is the most posterior abutment of the fixed partial denture. Similarly, a vertical load was applied to the first molar because this tooth receives the heaviest masticatory load. These loads were added to two types of fixed partial denture. the rigid connector, and the nonrigid connector which was connected on the distal side of the intermediate abutment by a key and keyway device. After the stress patterns in surrounding tissues were observed, the following conclusions were as follows: 1. When the vertical load was applied to the first and second molars on the occlusal surfaces, the surrounding tissues of the roots of the canine, the second premolar, and the second molar were all compressive stresses. 2. When the vertical load was applied on the occlusal surface of the second molar, the tissue surrounding the roots of the canine, the second premolar, and the second molar all showed more stresses with the nonrigid connector than with the rigid connector. 3. When the vertical load was applied to the occlusal surface of the first molar, the stress concentration on the canine and the second molar was similar, whether the rigid or nonrigic connectors were used. However, on the second premolar, the stress concentration shown by the nonrigid connector was noticeably more than that shown by the rigid connector. 4. Whether the rigid or nonrigid connectors were used, when the load was placed on the first molar, the stress concentration on the canine and the second premolar was greater than that observed for the second molar. When the load was placed on the second molar, the load affected the second molar more than the canine and the second premolar.

• 대한치과보철학회지
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• 제35권4호
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• pp.742-766
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• 1997

The purpose of this study was to determine the effect of finish line design, amount of incisal reduction, and loading condition on the stress distribution in anterior all-ceramic crowns. Three-dimensional finite element models of an incisor all-ceramic crown with 3 different finish line designs : 1) shoulder with sharp line angle 2) shoulder with rounded line angle 3) chamfer : and 2 different incisal reductions : 2mm and 4mm were developed. 300 N force with the direction of 45 degree to the long axis of the tooth was applied at 3 different positions : A) incisal 1/3, B) incisal edge, C) cervical 1/5. Stresses developed in ceramic and cement were analyzed using three-dimensional finite element method. The results were as follows : 1. Stresses were concentrated in the margin region, which were primarily compressive in the labial and tensile in the lingual. 2. Stresses were larger in the area near line angle than on the crown surface of the margin region. In case of shoulder with sharp line angle, stresses were highly concentrated in the porcelain near line angle. 3. At the interface between porcelain and cement and at the porcelain above the margin on crown surface, stresses were the highest in chamfer, and decreased in shoulder with sharp line angle and shoulder with rounded line angle, respectively. 4. At the interface between cement and abutment on crown surface, stresses were the highest in shoulder with sharp line angle, and decreased in shoulder with rounded line angle and chamfer, respectively. 5. The amount of incisal reduction had little influence on the stress distribution in all-ceramic crowns. 6. When load was applied at the incisal edge, higher stresses were developed in the margin region and the incisal edge than under the other loading conditions. 7. When load was applied at the cervical 1/5, stresses were very low as a whole.