• 구강회복응용과학지
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• 제22권1호
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• pp.75-87
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• 2006

The purpose of this study was to investigate the effects of prostheses misfit, cantilever on the stress distribution in the implant components and surrounding bone using three dimensional finite element analysis. Two standard 3-dimensional finite element models were constructed: (1) 3 ITI implant supported, 3-unit fixed partial denture and (2) 3 ITI implant supported, 3-unit fixed partial denture with a distal cantilever. variations of the standard finite element models were made by placing a $100{\mu}m$ or $200{\mu}m$ gap between the fixture, the abutment and the crown on the second premolar and first molar. Total 14 models were constructed. In each model, 244 N of vertical load and 244 N of $30^{\circ}$ oblique load were placed on the distal marginal ridge of the distal molar. von Mises stresses were recorded and compared in the crowns, abutments, crestal compact bones, and trabecular bones. The results were obtained as follows: 1. In the ITI implant system, cement-retained prostheses showed comparatively low stress distributions on all the implant components and fixtures regardless of the misfit sizes under vertical loading. The stresses were increased twice under oblique loading especially in the prostheses with cantilever, but neither showed the effects of misfit size. 2. Under the oblique loading and posterior cantilever, the stresses were highly increased in the crestal bones around ITI implants, but effects of misfit were not shown. Although higher stresses were shown on the apical portion of trabecular bones, the effects by misfit were little and the stresses were increased by the posterior cantilever. 3. When the cement loss happened in the ITI implant supported FPD with misfit, the stresses were increased in the implant componets and supporting structures.

• 대한치과보철학회지
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• 제29권1호
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• pp.167-213
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• 1991

The successful replacement of missing teeth has been one driving aim behind the emergence of implant dentistry as both a technology and clinical vocation for over four decades. To date, a multitude of dental implant devices had been designed and utilized in the patient population. Most of these devices have been designed without support of the engineering criteria. The long-term success of any dental implant is dependent upon the optimization of stresses which occurs during oral function and parafunction. Although many studies have examined the biologic interactions between dental implants and living tissue, few studies have been reported on the biomechanical aspects of dental implants. The purpose of this study was to analyze the stress distribution of osseointegrated prosthesis on certain conditions, such as amount of load, location of load, length of fixtures, number of fixtures used, arch shape, bone quality, etc. Three dimentional finite element analysis was used for this study. FEM models were created using commercial software(Super SAP. for IBM 16 bit AT computer. All elements were 8-node brick, isoparametric. Mandible and prosthesis was modeled with 780 elements and 1074 nodes. The results were as follows : 1. In case of cantilever extension, there was a compressive stress at the base of the first implant and a tensile stress at the base of the second implant. 2. The stresses were linearly proportional to the amount of load. 3. The stresses were linearly proportional to the length of cantilever. 4. There was a stress concentration at the neck of the implant and bone under horizontal loads.

• 대한치과보철학회지
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• 제43권2호
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• pp.218-231
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• 2005

Statement of problem. In the partially edentulous patients, removable partial dentures have been working as a important treatment modality. Clasps, a kind of direct retainers, received some amount of stresses during the insertion and removal of partial denture on the abutment tooth. Purpose. The study is to investigate stresses of the different clasps. Material and methods. In order to investigate the degree of stresses, maxillary partial edentulism (Kennedy Class II modification I) was assumed and removable partial dentures were designed on it with three kinds of metallic materials; cobalt-chromium alloy, type IV gold alloy and commercially pure (c.p.) titanium. Aker's clasp was applied on the left second molar. RPA (mesial rest-proximal plate-Aker's) clasp was on the left first premolar and wrought wire clasp was on the right first premolar. Three dimensional, non-linear, dynamic finite element analysis method was run to solve this process. Results. 1. Cobalt-chromium alloy had the highest von Mises stress value and c.p. titanium had the lowest one irrespective of the types of clasps. 2. In the Aker's clasps, stress on the retentive tips was shown shortly after the appearance of stresses of the middle and minor connector areas. These time lag was much shorter in the RPA clasps than in the Aker's clasp. 3. In general. retentive tips of wrought wire clasps had much less amount of stress than other clasps. Conclusion. The amount of stress was the highest in the RPA clasp and the lowest in the wrought wire clasp, in general.

• 구강회복응용과학지
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• 제18권4호
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• pp.251-276
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• 2002

The purpose of this study was to compare and analyze the stress distribution and displacement of the fully bone anchored bridge and implant-supported overdenture in edentulous mandible on certain conditions such as number of implants, different design of superstructure. Three dimensional analysis was used and nine kinds of models designed for this study. FEM models were created using commercial software[$Rhinoceros^{(R)}$ (Ver. 1.0 Robert McNeel & Associates, USA)], and analyze using commercial software [Cosmos/$Works^{TM}$(Ver. 4.0 Structural Research & Analysis Corp., US A)]. A vertical load and $45^{\circ}$ oblique load of 17kgf were applied at the left 1st. molar. The results were as follows : (1) In the group of OVD, the displacement was reduced as increasing the number of fixture under vertical loading but there was no specific difference in Von Mises stress. Under oblique loading, the displacement was same at the vertical loading but Von Mises stress was reduced in order of OVD-3, OVD-4, OVD-2. But, bending moment reduced according to increasing the number of fixture. (2) In the group of FBAB, under vertical and oblique loading, the magnitude of Von Mises stress and displacement reduced according to increasing the number of fixtures. FBAB-4 and FBAB-5 showed similar score and distribution, but FBAB-6 showed lower value relatively. (3) In cantilever design, the maximum displacement reduced under vertical loading but increased under oblique loading. However, von mises stresses on fixtures increased under vertical and oblique loading. (4) In comparing OVD-group with FBAB-group, FBAB showed low magnitude of displacement in respect of oblique loading. However OVD-group was more stable in respect of stress distribution.

• 대한치과보철학회지
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• 제34권3호
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• pp.501-532
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• 1996

This study investigated the effects of cantilever length, location and load condition on stress distribution developed in the implants, prostheses and supporting tissues. The osseointegrated prostheses with two 10mm Branemark implants at 2nd premolar and 1st molar sites with cantilever extensions at 1st premolar, 2nd and 3rd molar sites were constructed. Under 100N, 200N of vertical and $45^{\circ}$ oblique loads at the cantilever pontics, stress distribution patterns and displacement were analyzed with three dimensional finite element method. The results were as follows : 1. The stress was concentrated at the joint of the cantilever pontic and implant superstructure, the neck of implant and the ridge crest near the cantilever But there was little load transfer to the lower supporting tissues of implants. 2. The implant near the cantilever was displaced inferiorly while the implant far from the cantilever was displaced superiorly. In horizontal direction the implants were displaced to the direction where the loads were applied, except the apexes of the implants. 3. In case of anterior cantilever, the stress and displacement were higher than the prosthesis connected with natural tooth. 4. The stress developed in the posterior cantilevered type was higher than in the anterior cantilevered type. The greastest stress was concentrated at the ridge crest near the posterior cantilever. 5. The longer the cantilever, the more the stress was developed and was concentrated at the joint of the cantilever pontic and implant superstructure. 6. Under oblique load, the stress was concentrated at the necks of implants and the ridge crests, but decreased at the joint of the cantilever pontic and implant superstructure than under vertical load.

• 대한치과보철학회지
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• 제31권3호
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• pp.351-384
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• 1993

Complete denture occlusion must be developed to function efficiently and with the least amount of trauma to the supporting tissues. For the preservation of supporting tissues, it is imperative to reduce to a minimum the functional stress induced by dentures. The magnitude of the horizontal component of functional stress contributed by various occlusal teeth forms has not been studied. This study was aimed to investigate the influence of different occlusal teeth forms on the mode of distribution of the stresses in the mandibular tissue, and the displacement of lower dentures during the variant functional movement of mandible for this study three dimensional finite element analysis was used. FEM models were created using commercial software Super Sap for IBM 32 bit computer. The model was composed of 3380 brick elements and 4346 nodes. The results were as follows. 1. The magnitude of stress was similar between two models in centric occlusion, in the case of anatomic model, the stress was concentrated on the buccal side of alveolar ridge beneath the bicuspids. 2. During the protrusive movement, the increasing of stress from the posterior to anterior part of mandible was seen in the case of anatomic model. 3. During the lateral movement, the stress of anatomic model was greater than that of nonanatomic model. 4. The stress of anatomic model was concentrated on the anterior region of residual ridge during the lateral movement. 5. In the case of anatomic model the anterior part of denture was displaced severely at the centric and lateral position, but the denture of nonanatomic model was displaced minutely at the protrusive and lateral position.

• 한국항공우주학회지
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• 제48권12호
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• pp.961-968
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• 2020

본 연구에서는 미시역학 전산 모형을 통해 열 보호 시스템에 사용되는 내열 코팅 재료의 유효 열전도도와 탄성 계수를 산출하고 분석하였다. 상용 프로그램 Simpleware를 이용하여 HfC로 코팅된 탄소/탄소 복합재료의 삼차원 전산 모형을 생성한 후 유한요소 해석을 수행하였다. 유효 물성의 경향을 확인하기 위해 코팅층의 기공도와 두께 변화를 고려하였다. 또한, 실제 시편을 제작하여 실험에서 온도에 따라 측정된 열전도도와 해석에서 산출된 열전도도를 서로 비교하였으며 해석 결과가 측정값에 근접하였다. 이를 통해 내열 코팅 재료의 유효 물성을 산출하는데 있어서 미시역학 전산 해석이 적절함을 확인하였다.

• 대한치과교정학회지
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• 제31권3호
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• pp.335-346
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• 2001

본 연구의 목적은 교정치료의 마무리 단계에서 비람직하지 못한 순설측 경사를 가진 한 개 치아의 이동을 원할 때 브라켓 슬롯의 크기와 각형선재의 종류, 크기에 따라 부여하여야 할 적절한 임상적 torque (SWA의 각형선재에서 나머지 편평한 부분과 이동을 위해 변형시킨 부분의 단면이 이루는 각도만큼의 torque)의 양을 구하고자 하는 것이다. 임상적 torque는 play와 active torque(브라켓에 모멘트를 전달할 수 있는 torque)의 합으로 구성되는데, play는 수학적 공식을 이용하여 계산하였고 active torque는 컴퓨터를 이용한 삼차원 유한요소법으로 구하였다. 유한요소모델은 일렬로 배열된 세 개의 브라켓과 여기에 삽입된 stainless steel, TMA , NiTi 이렇게 3가지 종류의 교정용 각형선재로 구성된 다. 양쪽의 브라켓을 일정한 각도로 비틀어서 가운데 브라켓에 발생하는 모멘트를 계산하였다. 선재의 크기는 많이 사용되는 각형선재인 .016"X.022", .017"X.022", .017"X.025", .018"X.025", .019"X.025", .020"X.025". .021"X.025"의 7개로 디자인하였다. .018" 브라켓에는 .016"X.022", .017"X.022", .017"X.025" 선재를 삽입하여 실험하였고, .022" 브라켓에는 .016"X.022" 선재를 제외한 나미지 선재를 삽입하여 실험하였다. 실험으로 다음과 같은 결과를 얻었다. 1. 삽입된 브라켓 슬롯의 크기에 상관없이 같은 크기와 재질의 교정용 각형선재에 같은 active torque를 가하면 동일한 모멘트가 발생하였다. 2. 선재의 크기가 증가될 수록 동일한 active torque에 의해 발생되는 모멘트의 양은 증가하였다. 실험에 사용한 가장 굵은 선재인 .021"X.033" 선재는 동일한 재질의 가장 가는 .015"X.022" 선재에 비해 약 1.75배 더 큰 torsional stiffness를 가졌다. 3. 선재의 재질에 따라서는 stainless steel, TMA, NiTi순으로 torsional stiffness가 감소하였는데 stainless steel에 비해 TMA는 0.35배, NiTi는 0.16배였다. 4. 브라켓간 거리의 증가와 발생되는 torsional .stiffness는 반비례하였다. 브라켓간 거리의 증가에 의해 감소되는 torsional stiffness의 비율은 선재의 재질과 상관이 있었고 크기에 따라서는 큰 차이가 없었다. 5. 교정치료의 마무리 단계에서 이상적인 순설측 경사이동을 일으키는 임상적 torque의 공식과 값을 구하였다.

• 대한치과보철학회지
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• 제46권4호
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• pp.359-371
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• 2008

연구목적: 본 연구에서는 하악의 동일한 부위에 4개의 임플랜트를 식립하여 임플랜트 피개의치를 설계하는 경우, 바 구조와 이중관 구조 간의 응력분포에 대해 비교 분석하고자 하였다. 연구재료 및 방법: 하악골, 하악골에 식립한 4개의 임플랜트, 일차고정의 바 연결 상부구조, 이차고정의 이중관 상부구조를 삼차원 유한요소 모델링하였고, 상부 구조물에 최대 교두 감합위를 재현하는 수직하중과 측방운동시 작업측의 군기능을 재현하는 경사하중을 가하고, 최대 응력과 응력분포를 하악골, 임플랜트 지대주, 임플랜트 상부 구조물에서 분석하였다. 결과: 1. 악골에서의 최대 응력값은 경사하중을 제외하고 수직하중과 작업측 경사하중에서 이중관 구조가 바 구조에 비해 다소 적은 응력값을 보였다. 이중관 구조가 바 구조에 비해 비교적 악골 전체에 고르게 응력이 분포되었다. 2. 지대주에서는 모든 하중 조건에서 이중관 구조가 바 구조에 비해 낮은 응력값을 보였다. 응력 분포 양상은 두 구조에서 모두 비슷한 양상을 나타내었으며, 최후방 지대주의 원심면에 응력이 집중되었다. 3. 상부구조물에서는 모든 하중 조건에서 이중관 구조가 바 구조에 비해 높은 응력값을 나타냈다. 그러나, 바 구조에서는 바의 각 중심부와 지대주와의 연결부위, 지대주의 치경부에 응력이 집중된 반면, 이중관 구조에서는 상부 구조물 전체에 비교적 고른 응력 분포를 보였다. 결론: 본 연구 결과 이중관 구조가 바 구조보다 악골과 지대주에서는 더 낮은 응력을, 상부 구조물에서는 더 큰 응력을 나타냈다. 상부 구조물에 비교적 크게 전달되는 응력을 견딜 수 있는 상부구조물의 설계와 재료 선택만 이루진다면, 응력분포 면에서 이차고정을 하는 이중관 구조가 일차 고정하는 바 구조에 비해 유리하리라 생각된다.

• 대한치과보철학회지
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• 제41권4호
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• pp.393-404
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• 2003

Statement of problem. Higher incidence of prosthetic complications such as screw loosening, screw fracture has been reported for posterior single tooth implant. So, there is ongoing research regarding stability of implant-abutment interface. One of those research is increasing the implant diameter and prosthetic table width to improve joint stability. In another part of this research, internal conical type implant-abutment interface was developed and reported joint strength is higher than traditional external hex interface. Purpose. The purpose of this study is to compare stress distribution in single molar implant between external hex butt joint implant and internal conical joint implant when increasing the implant diameter and prosthetic table width : 4mm diameter, 5mm diameter, 5mm diameter/6mm prosthetic table width. Material and method. Non-linear finite element models were created and the 3-dimensional finite element analysis was performed to see the distribution of stress when 300N static loading was applied to model at $0^{\circ},\;15^{\circ},\;30^{\circ}$ off-axis angle. Results. The following results were obtained : 1. Internal conical joint showed lower tensile stress value than that of external hex butt joint. 2. When off-axis loading was applied, internal conical joint showed more effective stress distribution than external hex butt joint. 3. External hex butt joint showed lower tensile stress value when the implant diameter was increased. 4. Internal conical joint showed lower tensile stress value than external hex butt joint when the implant diameter was increased. 5. Both of these joint mechanism showed lower tensile stress value when the prosthetic table width was increased. Conclusion. Internal conical joint showed more effective stress distribution than external hex joint. Increasing implant diameter showed more effective stress distribution than increasing prosthetic table width.