• 제목/요약/키워드: crown restoration

검색결과 303건 처리시간 0.021초

반복 하중이 Full veneer crown의 유지력에 미치는 영향에 관한 연구 (THE EFFECT OF CYCLIC LOADING ON THE RETENTIVE STRENGTH OF FULL VENEER CROWNS)

  • 김기연;이선형;정헌영;양재호;허성주
    • 대한치과보철학회지
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    • 제38권5호
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    • pp.583-594
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    • 2000
  • Dislodgement of a crown or extension bridge and the loosening of a retainer of a bridge is a serious clinical problem in fixed restoration. Generally these problems are considered to be associated with deformation of the restoration. During biting, the restoration is subjected to complex forces and deforms considerably within the limit of its elasticity. Deformation of the restoration under the occlusal force induces excessive stress in the cement film, which then leads to the cement fracture. Such a fracture may eventually cause loss of the restoration. Because most of the past retention tests for full veneer crown were done without fatigue loading, they were not exactly simulating intraoral environment. And the purpose of this study was to evaluate the effect of cyclic cantilever loading on the retentive strength of full veneer crowns depending on different type of cements and taper of prepared abutment. Steel dies with $8^{\circ}\;or\;16^{\circ}$ convergence angle were fabricated through milling and crowns with the same method. These dies and crowns were divided into 8 groups. Group 1 : $16^{\circ}$ taper die, cementation with zinc phosphate cement, without loading Group 2 : $16^{\circ}$ taper die, cementation with zinc phosphate cement, with loading Group 3 : $8^{\circ}$ taper die, cementation with zinc phosphate cement, without loading Group 4 : $8^{\circ}$ taper die, cementation with zinc phosphate cement, with loading Group 5 : $16^{\circ}$ taper die, cementation with Panavia 21, without loading Group 6 : $16^{\circ}$ taper die, cementation with Panavia 21, with loading Group 7 : $8^{\circ}$ taper die, cementation with Panavia 21 without loading Group 8 : $8^{\circ}$ taper die, cementation with Panavia 21, with loading After checking the fit of die and crown, the luting surface of dies and inner surface of crowns were air-abraded for 10 seconds. The crowns were cemented to the dies, with cements mixed according to the manufacturer's recommendations. A static load of 5kg was then applied for 10 minutes with static loading device. Twenty-four hours later, group 1, 3, 5, 7 were only thermocycled, group 2, 4, 6, 8 were subjected to cyclic loading after thermocycling. Retentive tests were performed on the Instron machine. From the finding of this study, the following conclusions were obtained 1. Panavia 21 showed significantly higher retentive strength than zinc phosphate cement for all groups (p<0.05). 2. There was a significant difference in the retentive strength between $8^{\circ}\;and\;16^{\circ}$ taper for zinc phosphate cement(p<0.05), but no significant difference for Panavia 21 (p>0.05). 3. Cyclic loading significantly decreased the retentive strength for all groups(p<0.05). 4. For zinc phosphate cement, there was 35% reduction of the retentive strength after loading in the $16^{\circ}$ taper die, 25% in the $8^{\circ}$ taper die, and for Panavia 21, 21% in the $16^{\circ}$ taper die, 18% in the $8^{\circ}$ taper die.

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외과적 정출술을 이용한 치관-치근 파절된 미성숙 영구치의 치험례 (SURGICAL EXTRUSION OF THE CROWN-ROOT FRACTURED INCISORS: CASE REPORTS)

  • 이은미;김태완;김현정;김영진;남순현
    • 대한소아치과학회지
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    • 제35권2호
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    • pp.305-312
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    • 2008
  • 치아의 치관-치근 파절은 치아파절이 치관과 치근에 걸쳐 발생되어 법랑질, 상아질 및 백악질까지 이환된 경우로 정의되며, 치수이환여부에 따라 복잡파절과 비복잡파절로 분류될 수 있다. 치관-치근 파절의 빈도는 유치열에서 2%, 영구치열에서 5%로 나타나며, 보통 상악 전치부에 호발한다. 이러한 치관-치근 파절된 치아의 수복을 위해서는 생물학적 폭경이 유지되어야 한다. 이를 위하여 사용되는 방법은 골삭제 후 치은절제술, 교정적 견인, 외과적 정출 후 수복하는 방법과, 인위적으로 발치하여 근관치료와 수복 후 재식하는 방법 등이 있다. 이중 외과적 정출술은 치아를 발거하여 파절부를 치은 연상으로 이동시켜 재식하는 방법으로서, 이는 치관부 파절편이 임상치근의 1/2 미만인 경우에 적응증이 될 수 있으며, 발견하지 못한 다른 파절편을 직접 시진할 수 있고 때로는 파절선을 순측에 위치시켜 치료시 시야확보 및 접근이 용이하다는 등의 장점이 있다. 본 증례에서는 외상으로 치관-치근 파절된 미완성 치근단의 상악 중절치를 가진 환아에서 외과적 정출술 후 근관치료와 광중합복합레진을 이용한 치관수복을 시행하였으며, 정기적 검진시 양호한 결과가 관찰됨을 확인할 수 있었다.

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금속코핑 설계에 따른 Collarless Metal Ceramic Crown의 파절강도에 관한 연구 (A STUDY ON FRACTURE STRENGTH OF COLLARLESS METAL CERAMIC CROWN WITH DIFFERENT METAL COPING DESIGN)

  • 윤종욱;양재호;장익태;이선형;정헌영
    • 대한치과보철학회지
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    • 제37권4호
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    • pp.454-464
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    • 1999
  • The metal ceramic crown is currently the most popular complete veneer restoration in dentistry, but in many cases, the metal cervical collar at the facial margin is unesthetic and unacceptable. Facial porcelain margin has been used in place of it. But this dose not solve the problems, such as dark gingival discoloration and cervical opaque reflection of porcelain veneer. Recently, metal copings which were designed to terminate its labio-cervical end on the axial walls coronal to the shoulder have been clinically used to solve the esthetic problem of metal ceramic crown. But in this design, porcelain veneer of labio-cervical area which is not supported by metal may not be able to resist the stress during cementation and mastication. The purpose of this study was to evaluate fracture strength and fractured appearance of crowns according to different coping designs. A resin maxillary left central incisor analogue was prepared for a metal ceramic crown, and metal dies were made with duplication mold. Metal copings were made and assigned to one of four groups based on facial framework designs: group 1, coping with 0.5mm metal collar; group 2, metal extended to the shoulder; group 3, metal extended to 1mm coronal tn the shoulder: group 4, metal extended to 2mm coronal to the shoulder. Copings and crowns were adjusted to be same size and thickness, and cemented to metal dies with zinc phosphate cement by finger pressure. Fracture strength was measured with Instron Universal Testing Machine. Metal dies were anchored in Three-way-vice at 3mm below finish line and at $130^{\circ}$ inclined to the long axis of the crown. Load was directed lingually at 2mm below midincisal edge. Load value at initial crack and at catastrophic fracture was recorded. The results obtained were as follows : 1. Fracture strength values at initial crack were higher in groups 1, 2 than in groups 3, 4 but this difference was not statistically significant(P<0.05). 2. Conventional metal collared crown had greater catastrophic fracture strength than any other collarless crowns. 3. The greater the labial metal coping reduction, the lower the catastrophic fracture strength of crowns but when more than 1mm of labial metal reduction was done, the difference in strengths was not statistically significant(p<0.05). 4. The strongest collarless coping design was group 2.

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TETRACYCLINE에 의한 변색치의 심미적 치료

  • 황병각;이철원;김석균
    • 대한심미치과학회지
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    • 제1권1호
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    • pp.50-57
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    • 1992
  • Intrinsic discoloration of permanent anterior teeth is a continuing esthetic problem. Tetracycline ingested during amelogenesis has long been recognized as predisposing factor in intrinsic staining. Methods for restoring original tooth color have included (1) complete PFM crown coverage (2) porcelain laminate veneers (3) direct bonding of composite resin, and (4) bleaching. In the case of tetracycline-stained upper anterior teeth, We authors, obtained the satisfactory results by means of gingivectomy, preliminary bleaching and porcelain laminate veneer restoration.

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상이한 방법으로 수복한 근관치료된 상악 제2소구치의 응력분포: 3차원 유한요소법적 분석 (STRESS DISTRIBUTION OF ENDODONTICALLY TREATED MAXILLARY SECOND PREMOLARS RESTORED WITH DIFFERENT METHODS: THREE-DIMENSIONAL FINITE ELEMENT ANALYSIS)

  • 임동열;김현철;허복;김광훈;손권;박정길
    • Restorative Dentistry and Endodontics
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    • 제34권1호
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    • pp.69-79
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    • 2009
  • 본 연구의 목적은 근관치료 된 치아를 구조와 물성이 다른 post와 core 그리고 전장관으로 수복한 후 과도한 교합하중을 가했을 때 치아에 나타나는 응력분포를 조사하기 위함이다. 발치 된 상악 제2소구치를 micro-CT로 단층촬영하고 3D Doctor로 윤곽선을 추출한 다음 HyperMesh Ver. 6으로 삼차원 치아모형을 만들고 다음과 같은 세 가지 방법으로 수복한 유한요소모형을 제작하였다. 1) 스테인레스 스틸 포스트와 복합레진 코어 그리고 도재소부전장금관으로 수복한 모형. 2) fiber 포스트와 복합레진 코어 그리고 전부도재관으로 수복한 모형 3) 포스트, 코어와 전장관이 일체형인 간접복합레진 EndoCrown으로 수복한 모형 형성된 모형의 협측 또는 설측교두에 500N의 하중을 가하였으며 하중의 방향은 치아 장축에 대해 45도 이었다. 치관부와 치근부의 von Mises 응력을 ANSYS 9.0프로그램으로 분석한 결과 포스트와 코어의 형태보다는 전장관 재료의 탄성 계수가 근관치료된 상악 소구치의 응력분포를 좌우하였다. 치관부에서는 재료의 탄성계수가 높은 전 장관으로 수복한 모형이 낮은 응력분포를 보였다. 치근부에서는 재료의 탄성계수가 낮은 전 장관으로 수복한 모형 이 낮은 응력분포를 보였다.

열쾌적성에 대한 가로수 수직적 구조의 영향 분석 (The Effects of Street Tree's Vertical Structures on Thermal Comfort)

  • 이수빈;최혜영;조현길;윤영조;길승호
    • 한국환경복원기술학회지
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    • 제24권4호
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    • pp.15-29
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    • 2021
  • Urban green spaces offer a variety of benefits to living things and humans. However, existing green spaces have been reduced and fragmented due to urbanization, and there is a limit to creating new large green spaces in densely developed cities. Street trees have fewer restrictions on land use, which can be a measure to secure green areas in cities. In Korea, excessive pruning is being done on some street trees for reasons such as blocking of building signboards, contact with electric wires, and restrictions on sidewalk widths. Therefore, it is necessary to quantitatively understand the relationship between the benefits provided by street trees and their structures to come up with an efficient and systematic planning and management plan for urban street trees. In this study, we quantitatively analyzed the relationship between the thermal comfort improvement by the shades of street trees and the vertical structure, planting environment, and types of street trees. To calculate the thermal comfort felt by human body, we calculated UTCI (Universal Thermal Climate Index) of each street tree. For the vertical structure of street trees, we used Terrestrial LiDAR and the point clouds of street tree's crown was sliced vertically at 1m intervals. We conducted a multiple regression analysis on the thermal comfort improvement using the variables we obtained from fields. As a result, in the case of a street tree's vertical structure, the lager the volume of tree's crown located 3-4m (β=0.298, p<.05) and 6-7m (β=0.568, p<.001) above clear length, the better the cooling effect. In addition, the thermal comfort improvement was assessed to decrease as the DBH increased (β=-0.435, p<.001). In general, the crown diameter and DBH are positively correlated, with a cooling effect occurring as crown diameter increases. In this study, the opposite result was obtained due to the small number of trees measured, so additional research is needed by increasing the number of tree samples. In the case of the planting environment, the effect of improving thermal comfort was higher in the shaded area of trees planted to the south (β=-0.541, p<.001). Since unsystematic management of street trees can deteriorate the function of them, quantitative evaluations of the vertical structure of street trees are required, which can provide specific measures for planning and management of urban street trees with thermal comfort effect.

지르코니아 완전도재 수복 방법을 사용한 회전되고 변색된 상악중절치의 수복 (Restoration of Rotated and Discolored Maxillary Incisors with a Zirconia All-Ceramic System: A Case Report)

  • 백연화;임영준;김명주;권호범
    • 구강회복응용과학지
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    • 제29권1호
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    • pp.95-101
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    • 2013
  • 최근 단시간에 비침윤적 방법으로 심미적인 개선을 바라는 치과 치료에 대한 요구가 증가하고 있다. 환자는 심미성의 한계에도 불구하고 교정, 치주, 신경치료 없이 보철적 치료방법만으로 상악 전치부의 심미적 개선을 원하였다. 이 증례에서는 최근에 소개된 여러 종류의 완전도재수복방법 중에서 변색된 치아를 차단하기 위해 지르코니아를 이용한 수복방법을 선택하였으며, 만족된 결과를 얻었다.

In-Ceram Alumina Bridge Restoration의 단기예후에 관한 임상적연구 (THE CLINICAL STUDY ON SHORT TERM PROGNOSIS OF IN-CERAM ALUMINA BRIDGE RESTORATION)

  • 조병완;박재범;안재진
    • 대한치과보철학회지
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    • 제35권3호
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    • pp.544-556
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    • 1997
  • All ceramic restorations except In-Ceram Alumina system gave a good esthetics and an exellent marginal fidelity. The flexural strength of them had about 150MPa, so the indication is only single crown. By using In-ceram Alumina System(450Mpa), it is thought to be possible to construct bridge for its high flexural strength. But the prognosis is unclear, The purposes of this study are to clear short term prognosis of In-Ceram bridge restorations, to elucidate its clinical significance. Among 22 In-Ceram Bridge restored in our department, 11 In-Ceram bridges with follow up were used. The period of placement is from 1 to 18 months. The results were as follows : 1. Among follow up 11 bridges, 2 bridges were fractured. One is 4 unit in maxillary lateral incisors, the other is 3 unit bridge in maxillary canine and premolar. Including 11 bridge without follow up, failure rate is very low(2/22). 2. The fracture sites are connector areas between abutment and pontic. To maintain In-Ceram bridge for long term period, it is needed to remove the nonphysiologic occlusal force and to have sufficient thickness of alumina core. For estabilishing clinical use of In-Ceram bridges, it is thought to need clinical research during long term period.

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치과용 지르코니아로 제작된 심미보철물의 임상적 예후에 관한 문헌고찰 (Review of clinical studies applying yttrium tetragonal zirconia polycrystal-based esthetic dental restoration)

  • 김재홍
    • 대한치과기공학회지
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    • 제42권4호
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    • pp.307-312
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    • 2020
  • Application of ceramic materials for fabrication of dental restoration materials has been a focus of interest in the field of esthetic dentistry. The ceramic materials of choice are glass ceramics, spinel, alumina, and zirconia. The development of yttrium tetragonal zirconia polycrystal (YTZP)-based systems is a recent addition to all-ceramic systems that have high strength and are used for crowns and fixed partial dentures. Computer-aided design/computer-aided manufacturing (CAD/CAM)-produced, YTZP-based systems are popular with respect to their esthetic appeal for use in stress-bearing regions. The highly esthetic nature of zirconia and its superior physical properties and biocompatibility have enabled the development of restorative systems that meet the demands of today's patients. Many in vitro trials have been performed on the use of zirconia; however, relatively fewer long-term clinical studies have been published on this subject. The use of zirconia frameworks for long-span fixed partial dentures is currently being evaluated; in the future, more in vivo research and long-term clinical studies are required to provide scientific evidence for drawing solid guidelines. Further clinical and in vitro studies are required to obtain data regarding the long-term clinical use of zirconia-based restorations.