• 대한치과보철학회지
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• 제44권3호
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• pp.295-313
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• 2006

Statement of problem. Higher fracture rates were reported for Branemark implants placed in the maxilla and for 3.75 mm diameter implants installed in the posterior region. Purpose. The purpose of this study was to investigate the fracture of a fixture by finite element analysis and to compare different diameter of fixtures according to the level of alveolar bone resorption. Material and Methods. The single implant and prosthesis was modeled in accordance with the geometric designs for the 3i implant systems. Models were processed by the software programs HyperMesh and ANSA. Three-dimensional finite element models were developed for; (1) a regular titanium implant 3.75 mm in diameter and 13 mm in length (2) a regular titanium implant 4.0 mm in diameter and 13 mm in length (3) a wide titanium implant 5.0 mm in diameter and 13 mm in length each with a cementation type abutment and titanium alloy screw. The abutment screws were subjected to a tightening torque of 30 Ncm. The amount of preload was hypothesized as 650 N, and round and flat type prostheses were 12 mm in diameter, 9 mm in height were loaded to 600 N. Four loading offset points (0, 2, 4, and 6 mm from the center of the implants) were evaluated. To evaluate fixture fracture by alveolar bone resorption, we investigated the stress distribution of the fixtures according to different alveola. bone loss levels (0, 1.5, 3.5, and 5.0 mm of alveolar bone loss). Using these 12 models (four degrees of bone loss and three implant diameters), the effects of load-ing offset, the effect of alveolar bone resorption and the size of fixtures were evaluated. The PAM-CRASH 2G simulation software was used for analysis of stress. The PAM-VIEW and HyperView programs were used for post processing. Results. The results from our experiment are as follows: 1. Preload maintains implant-abutment joint stability within a limited offset point against occlusal force. 2. Von Mises stress of the implant, abutment screw, abutment, and bone was decreased with in-creasing of the implant diameter. 3. With severe advancing of alveolar bone resorption, fracture of the 3.75 and the 4.0 mm diameter implant was possible. 4. With increasing of bending stress by loading offset, fracture of the abutment screw was possible.

• 대한의용생체공학회:의공학회지
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• 제21권3호
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• pp.295-301
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• 2000

뼈의 성장에 미치는 많은 요소들 중에서 implant의 상대적인 미세운동(relative micromotion)은 뼈의 implant와의 접합을 방해하는 것으로 알려져 왔다. 그런데 이러한 상대적인 운동 및 spinal stability에 직접적으로 영향을 주는 하중조건, spinal material의 물성치, spinal geometry 및 뼈와 implant의 접촉면에서의 마찰계수를 고려하기 위하여, 하나의 titanium interbody cage 가 삽입된 human lumbar segments (L4-L5)의 유한요소 모델이 개발되었다. 이러한 유한요소 모델의 해석을 통하여 상대적인 미세운동, Posterior의 수직적인 변위, von Mises 응력 및 마찰력이 예측되었다. Cancellous bone. annulus fibers 및 ligaments의 기계적인 물성치의 감소 또는 접촉면에서의 마찰계수의 감소는 상대적인 미세운동 (relative micromotion or slip distance)을 증가 시켰다. 접촉면에서의 normal force는 뼈의 밀도 (cancellous bone density) 가 감소하거나 접촉마찰계수가 증가하면 감소했다. 특히 하중조건에 있어서, compressive preload에 대한 torsion의 추가는 접촉면의 anterior부위에서 상대적인 미세운동을 증가 시켰다. 하지만 디스크면적이 증가할수록 상대적인 미세운동은 감소했다. 결론적으로, 접촉면의 기계공학적 거동 (Relative micromotion, stress response, posterior axial displacement and contact normal force)은 접촉면의 마찰계수 뼈의 밀도, 하중조건 및 노화에 따른 형상/물성의 변화에 매우 민감함을 보이고있다.

• 대한치과교정학회지
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• 제41권5호
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• pp.324-336
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• 2011

전치의 후방 견인 시 적절한 치아 이동 상태 조절은 필수적이다. 설측 장치를 이용한 레버 암 길이의 조절을 통하여 치아 이동에 관한 연구는 있었으나 3차원적인 변위 양상에 대한 연구는 많이 이루어지지 않은 실정이다. 이에 본 연구는 상악 전치부의 레버 암(lever arm)의 길이를 5 mm 단위로 20 mm까지 증가시켰으며 대구치와 TPA (trans palatal arch) 상에 있는 견인 훅(hook)의 위치를 달리 하여 200 gm의 후방 견인력을 가했을 때 나타나는 치아 변위 양상과 응력분포를 3차원적 유한요소분석을 통하여 알아보고자 하였다. 이를 위하여 아시아 성인의 표본조사를 통해 제작된 치아모형(Nissan Dental Product, Kyoto, Japan)을 3차원적으로 스캐닝한 후 상악치아, 치주인대, 치조골에 대한 유한요소 모델을 제작하였다. 각 치아의 절단연과 치근첨의 이동량을 x, y, z 좌표에서 각각 계산하여 치열의 변위 양상을 분석하고 von Mises 응력 분포를 계측하였다. 연구 결과, 정상 교합 모형의 레버 암 길이가 15 mm, 20 mm인 경우 전치 절단연과 치근첨의 설측 변위가 유도되었다. 본 실험의 조건 중 20 mm에서 치근첨의 설측 변위는 최대로 나타났다. 구치부 견인 훅이 치근첨에 있을 때 대구치 치관은 원심 방향으로 변위되었다. 또한 레버 암의 길이가 20 mm인 경우 전치부의 정출은 미약하였고 견치 치관은 협측 방향으로 전위되었다. 이 때 구치부 견인 훅의 위치가 TPA의 구개 중앙 측에 있을 때보다 가장자리 측에 있을 때 견치 치관은 더 많이 전위되었다. 이상의 결과를 토대로 설측 장치를 이용한 상악 6전치의 후방 견인 시 레버 암의 길이가 길고 구치부 견인 훅의 위치가 구개 중앙부에 있을 때 전치부 절단연(incisal edge)의 정출 없이 견치의 측방 전위 및 전치부 절단연과 치근첨의 설측 변위가 공히 나타남을 알 수 있었다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 춘계학술대회
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• pp.374-378
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• 1997

Operative procedures such as core drilling with and without fibular bone grafting have been recognized as the treatment methods for osteonecrosis of femoral head(ONFH) by delaying or preventing the collapse of the femoral head. In addition, core drilling with cementation using polymethylmethacrylate (PMMA) has been proposed recently as another surgical method. However, no definite treatment modality has been found yet while operative procedures remain controversial to many clinicians In this study, a finite element method(FEM) was employed to analyze and compare various surgical procedures of ONFH to provide a biomechanical insight. This study was based upon biomechanical findings which suggest stress concentration within the femoral head may facilitate the progression of the necrosis and eventual collapse. For this purpose, five anatomically relevant hip models were constructed in three dimensions : they were (1) intact(Type I), (2) necrotic(Type II), (3) core drilled only(Type III), (4) core drilled with fibular bone graft(Type IV), and (5) core drilled with cementation(Type V). Physiologically relevant loading were simulated. Resulting stresses were calculated. Our results showed that the volumetric percentage subjected to high stress in the necrotic cancellous region was greatest in the core drilled only model(Type III), followed by the necrotic(Type II), the bone graft (Type IV), and the cemented(Type V) models. Von Mises stresses at the tip of the graft(Type IV) was found to be twice more than those of cemented core(Type V) indicating the likelihood of the implant failure. In addition, stresses within the cemented core(Type V) were more evenly distributed and relatively lower than within the fibular bone graft(Type IV). In conclusion, our biomechanical analyses have demonstrated that the bone graft method(Type IV) and the cementation method(Type V) are both superior to the core decompression method(Type III) by reducing the high stress regions within the necrotic cancellous bone. Also it was found that the core region filled with PMMA(Type V) provides far smoother transfer of physiological load without causing the concentration of malignant stresses which may lead to the failure than with the fibular bone graft(Type IV). Therefore, considering the above results along with the degree of difficulties and risk of infection involved with preparation of the fibular bone graft, the cementation method appears to be a promising surgical treatment for the early stage of osteonecrosis of the femoral head.

• 구강회복응용과학지
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• 제21권1호
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• pp.1-14
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• 2005

The purpose of this study was to assess the loading distributing characteristics of implant prosthesis of internal connection system(ITI system) according to position and direction of load, under vertical and inclined loading using finite element analysis (FEA). The finite element model of a synOcta implant and a solid abutment with $8^{\circ}$ internal conical joint used by the ITI implant was constructed. The gold crown for mandibular first molar was made on solid abutment. Each three-dimensional finite element model was created with the physical properties of the implant and surrounding bone. This study simulated loads of 200N at the central fossa in a vertical direction (loading condition A), 200N at the outside point of the central fossa with resin filling into screw hole in a vertical direction (loading condition B), 200N at the centric cusp in a $15^{\circ}$ inward oblique direction (loading condition C), 200N at the in a $30^{\circ}$ inward oblique direction (loading condition D) or 200N at the centric cusp in a $30^{\circ}$ outward oblique direction (loading condition E) individually. Von Mises stresses were recorded and compared in the supporting bone, fixture, and abutment. The following results have been made based on this study: 1. Stresses were concentrated mainly at the ridge crest around implant under both vertical and oblique loading but stresses in the cancellous bone were low under both vertical and oblique loading. 2. Bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. The magnitude of the stress was greater with the oblique loading than with the vertical loading. 3. An offset of the vertical occlusal force in the buccolingual direction relative to the implant axis gave rise to increased bending of the implant. So, the relative positions of the resultant line of force from occlusal contact and the center of rotation seems to be more important. 4. In this internal conical joint, vertical and oblique loads were resisted mainly by the implant-abutment joint at the screw level and by the implant collar. Conclusively, It seems to be more important that how long the distance is from center of rotation of the implant itself to the resultant line of force from occlusal contact (leverage). In a morse taper implant, vertical and oblique loads are resisted mainly by the implant-abutment joint at the screw level and by the implant collar. This type of implant-abutment connection can also distribute forces deeper within the implant and shield the retention screw from excessive loading. Lateral forces are transmitted directly to the walls of the implant and the implant abutment mating bevels, providing greater resistance to interface opening.

• 생물환경조절학회지
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• 제14권3호
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• pp.166-173
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• 2005

길이 40m,폭 5.5m의 단일피복 구조의 8연동 무가온하우스 상단부에 설계적설심 19.1 cm의 눈이 쌓인다는 조건과 시설 측면으로 설계풍속 $36.6\;m{\cdot}s^{-1}$의 바람이 분다는 조건 그리고 참고자료로 활용하기 위해 적용한 최대적설심 37.8cm의 눈이 쌓인다는 조건과 순간최대풍속 $60.0\;m{\cdot}s^{-1}$의 강풍이 분다는 조건에서 유동 및 구조강도 해석을 수행하였다. 적설하중 조건에서는 설계적설심 19.1 cm와 최대적설심 37.8cm에서 파이프에 걸리는 최대응력이 각각 $53.8\;N{\cdot}mm^{-2}$과 $107\;N{\cdot}mm^{-2}$으로 재료의 허용응력 보다 작은 것으로 나타나 안전한 것으로 분석되었으나, 설계풍속 $36.6\;m{\cdot}s^{-1}$와 순간최대풍속 $60.0\;m{\cdot}s^{-1}$의 풍하중 조건에서는 파이프에 걸리는 최대응력이 각각 $250\;N{\cdot}mm^{-2}$과 $672\;N{\cdot}mm^{-2}$으로 재료의 허용응력을 모두 초과하여 플라스틱하우스가 불안전한 것으로 분석되었다.

• 대한치과보철학회지
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• 제43권1호
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• pp.105-119
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• 2005

Statement of problem. As the effects of the various diameters of fixture and abutment screw on stress distribution was not yet examined, this study focused on the different design of single implant restoration using three dimensional finite element analysis. Purpose. This study was to compare five different fixture-abutment combinations for single implant supported restorations with different fixture and abutment screw diameters. Material of methods. The five kinds of finite element models were designed by 3 diameter fixtures ($\oslash$3.3, 3.75, 5.0 mm) with 3 different abutment screws $\oslash$1.5, 1.7, 2.0 mm). The crown for mandibular first molar was made using UCLA abutment according to Wheeler's anatomy. 244 N was applied at the central fossa with two different loading directions, vertically and obliquely (30$^{\circ}$) and at the buccal cusp vertically. Maximum von Mises stresses were recorded and compared in the supporting bone, crowns, fixtures, and abutment screws. Results. 1. The stresses in supporting bone and implant-abutment structure under oblique loading were greater than those under vertical or offset loading. The stresses under vertical loading were the least among 3 loading conditions regardless of the implant and abutment screw diameters. 2. The stresses in the narrow implants were greater than the wider implants. The narrow implant with narrow abutment screw showed highest stresses in the lingual crest, but the narrow implant with standard abutment screw showed highest stress in abutment screw. 3. The stresses of abutment screws were influenced by the diameter of fixtures and loading conditions. The wide implants showed least difference between two different abutment screw diameters. Conclusions. The wide implants showed lesser stresses than the narrow implants and affected least by the different abutment screw diameters. The narrow implants with standard abutment screw showed highest stresses in the lingual bony crest under oblique loading.

• 구강회복응용과학지
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• 제17권4호
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• pp.283-305
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• 2001

The purpose of this study was to analyze the stress distribution of condylar regions and edentulous mandible with implant-supported cantilever prostheses on the certain conditions, such as amount of load, location of load, direction of load, fixation or non-fixation on the condylar regions. Three dimensional finite element analysis was used for this study. FEM model was created by using commercial software, ANSYS(Swanson, Inc., U.S.A.). Fixed model which was fixed on the condylar regions was modeled with 74323 elements and 15387 nodes and spring model which was sprung on the condylar regions was modeled with 75020 elements and 15887 nodes. Six Br${\aa}$nemark implants with 3.75 mm diameter and 13 mm length were incorporated in the models. The placement was 4.4 mm from the midline for the first implant; the other two in each quardrant were 6.5 mm apart. The stress distribution on each model through the designed mandible was evaluated under 500N vertical load, 250N horizontal load linguobuccally, buccal 20 degree 250N oblique load and buccal 45 degree 250N oblique load. The load points were at 0 mm, 10 mm, 20 mm along the cantilever prostheses from the center of the distal fixture. The results were as follows; 1. The stress distribution of condylar regions between two models showed conspicuous differences. Fixed model showed conspicuous stress concentration on the condylar regions than spring model under vertical load only. On the other hand, spring model showed conspicuous stress concentration on the condylar regions than fixed model under 250N horizontal load linguobuccally, buccal 20 degree 250N oblique load and buccal 45 degree 250N oblique load. 2. Fixed model showed stress concentration on the posterior and mesial side of working and balancing condylar necks but spring model showed stress concentration on the posterior and mesial side of working condylar neck and the posterior and lateral side of balancing condylar neck under vertical load. 3. Fixed model showed stress concentration on the posterior and lateral side of working condylar neck and the anterior and mesial side of balancing condylar neck but spring model showed stress concentration on the anterior sides of working and balancing condylar necks under horizontal load linguobuccally. 4. Fixed model showed stress concentration on the posterior side of working condylar neck and the posterior and lateral side of balancing condylar neck but spring model showed stress concentration on the anterior side of working condylar neck and the anterior and lateral side of balancing condylar neck under buccal 20 degree oblique load. 5. Fixed model showed stress concentration on the anterior and lateral side of working condylar neck and the posterior and mesial side of balancing condylar neck but spring model showed stress concentration on the anterior side of working condylar neck and the anterior and lateral side of balancing condylar neck under buccal 45 degree oblique load.. 6. The stress distribution of bone around implants between two models revealed difference slightly. In general, magnitude of Von Mises stress was the greatest at the bone around the most distal implant and the progressive decrease more and more mesially. Under vertical load, the stress values were similar between implant neck and superstructure vertically, besides the greatest on the distal side horizontally. 7. Under horizontal load linguobuccally, buccal 20 degree oblique load and buccal 45 degree oblique load, the stress values were the greatest on the implant neck vertically, and great on the labial and lingual sides horizontally. After all, it was considered that spring model was an indispensable condition for the comprehension of the stress distributions of condylar regions.

• 대한치과보철학회지
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• 제50권1호
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• pp.36-43
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• 2012

연구 목적: 본 연구는 hexagon 높이에 따른 임플란트 각 부위와 주위 지지조직의 응력분포를 3차원 유한요소 해석을 통해 평가하여 hexagon 높이가 기계적 안정성에 미치는 영향을 평가하고자 시행되었다. 연구 재료 및 방법: 외측 연결 형태의 ${\phi}4.0mm{\times}11.5mm$ USII (Osstem Co., Pusan, Korea) 임플란트 시스템을 이용하여 하악 제 1대구치 부위에 임플란트를 식립하여 보철 수복한 경우를 연구 모델로 가정하고 임플란트 고정체의 외측 연결부인 hexagon의 높이를 각각 0.0 mm, 0.7 mm, 1.2 mm, 1.5 mm로 적용한 CAD data를 유한요소 모형화하였다. ABAQUS 6.4 (ABAQUS Inc., Providence, RI, USA)를 이용하여 산출된 응력 값 중에서 등가응력을 기준으로 각 요소(상부 치관, 지대주 나사, 고정체, 치밀골, 해면골)에서 나타나는 최대 응력 값을 비교 하였다. 결과: 외측 연결을 갖는 임플란트의 hexagon의 높이는 고정체, 지대주 나사, 상부 보철물 그리고 주위 지지골에 대해 응력 분산에 영향을 주었다. Hexagon의 높이가 증가할수록 임플란트의 응력 분산은 더 잘 이루어졌으며, 최대 응력 값의 감소를 보였다. Hexagon의 높이가 1.2 mm 이상이 되면 응력 분포에 더 이상 크게 기여하지 않았다. 결론: 외측연결을 갖는 임플란트에서 hexagon은 응력 분산에 필수적인 요소이며 그 높이가 증가할수록 더욱 효과적인 응력의 분산이 나타났다.

• 구강회복응용과학지
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• 제26권2호
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• pp.179-195
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• 2010

임플란트 보철물에 저작력 등 외부 하중이 작용하면 내부 반응으로 응력이 발생되는데 지지골에 나타난 응력은 골재생 및 흡수 파괴, 임플란트에 나타난 응력은 임플란트 자체의 파절이나 나사의 풀림현상 및 파절, 상부 구조물에 나타난 응력은 보철물의 파절 등을 예견하는 지침이 될 수 있을 것이다. 지대주의 형상과 재질에 따라 연결방법과 보철방법이 달라지고 임플란트 내부의 하중전달 기전이 변하게 되고 이에 따라 악골에 발생하는 응력분포 역시 달라질 수 있다. 본 연구에서는 하악 제 1대구치 부위에 이중나사 구조를 갖고 원추형 내측연결 임플란트 시스템인 GSII$^{(R)}$ (Osstem, Korea)임플란트를 이용해 지대주의 종류를 티타늄 소재의 2-piece Transfer$^{TM}$ abutment (GST), 금합금 소재의 2-piece GoldCast$^{TM}$ abutment(GSG), 외부 연결형태를 가진 3-piece Convertible$^{TM}$ abutment (GSC) 로 분류하여 이에 따른 응력분포 양상을 비교 분석하여 보았다. 결과 하중조건에 관계없이 응력은 주로 지대주와 고정체가 접촉하는 경부에 집중되었다. 또한 하중조건에 관계없이 임플란트의 고정체 상부와 접촉하는 치밀골에 높은 응력이 나타나고 해면골에는 아주 작은 응력이 나타났다. 축하중보다는 중심축을 벗어난 하중조건에서 더 높은 응력이 발생되었고 수직하중보다 경사하중에서 더 높은 응력이 발생되었다. 전체에 걸친 최대응력은 GSG에서는 지대주, 치관 및 고정체에 고르게 분포되었고 GST는 주로 고정체와 지대주 나사에, GSC는 고정체와 지대주에 집중되었다. 세 지대주 간 골내의 최대응력에는 유의한 차이가 없었고 GSG가 전체 구성부의 응력분포에 있어 유리한 것으로 나타났다.