• 대한치과교정학회지
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• 제53권6호
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• pp.420-430
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• 2023

Objective: The purpose of this finite element method (FEM) study was to analyze the biomechanical differences and tooth displacement patterns according to the traction direction, methods, and sites for total distalization of the mandibular dentition using clear aligner treatment (CAT). Methods: A finite element analysis was performed on four FEM models using different traction methods (via a precision cut hook or button) and traction sites (mandibular canine or first premolar). A distalization force of 1.5 N was applied to the traction site by changing the direction from -30 to +30° to the occlusal plane. The initial tooth displacement and von Mises stress on the clear aligners were analyzed. Results: All CAT-based total distalization groups showed an overall trend of clockwise or counterclockwise rotation of the occlusal plane as the force direction varied. Mesiodistal tipping of individual teeth was more prominent than that of bodily movements. The initial displacement pattern of the mandibular teeth was more predominant based on the traction site than on the traction method. The elastic deformation of clear aligners is attributed to unintentional lingual tipping or extrusion of the mandibular anterior teeth. Conclusions: The initial tooth displacement can vary according to different distalization strategies for CAT-based total distalization. Discreet application and biomechanical understanding of traction sites and directions are necessary for appropriate mandibular total distalization.

• Advances in concrete construction
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• 제17권5호
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• pp.273-284
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• 2024

The steel-concrete composite system has been playing a vital role in the construction sector for the past two decades. By using steel and concrete together, we achieve strong load resistance with minimal deflection and bending stress. The study focuses on the numerical and analytical behaviour of concrete encased steel castellated beams and compared them with previous experiments. The study used five composite beams, including one control reinforced concrete beam (CC), one fully concrete encased steel beam (FCES), and three fully concrete encased castellated beams. The major variable is the opening configuration of the castellated beam, such as openings along the longitudinal axis, above the longitudinal axis, and below the longitudinal axis. The 150 mm × 250 mm cross section and 2000 mm in length of beams were used. Using the finite element software ANSYS, we conduct nonlinear finite element analysis for the entire beam and compare it with test data. The numerical load carrying capacity of concrete encased steel castellated beam with a hexagonal opening above the longitudinal axis (FCESCB H2) is 160 kN is closer to the experimental observation. Von Mises strain of FCESB is 0.004232, which is lower than CB and composite castellated beam. The ductility factor and energy absorption capacity of FCESB are 5.090 and 1688.47 kNm. It was observed that the configuration of the opening will influence the strength of the composite beam. Plastic moment methods were employed to estimate the ultimate load carrying capacity of the beam. In the analytical study the beams were assumed as perfectly plastic. The ultimate analytical load carrying capacity of FCESCB H2 is 21.87% higher than FCESB. It found that performing FCESCB H2 is superior to the entire specimen.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제32권3호
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• pp.207-217
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• 2010

The purpose of this study was to evaluate the effects of the stress distribution and displacement in mandible according to treatment modalities of mandibular angle fractures, using a three dimensional finite element analysis. A mechanical model of an edentulous mandible was generated from 3D scan. A 100-N axial load and four masticatory muscular supporting system were applied to this model. According to the number, location and materials of titanium and biodegradable polymer plates, the experimental groups were divided into five types. Type I had a single titanium plate in the superior border of mandibular angle, type II had two titanium plates in the superior tension border and in the inferior compression border of mandibular angle, type III had a single titanium plate in the ventral area of mandibular angle, type IV had a single biodegradable polymer plate in the superior border of mandibular angle, type V had a single biodegradable polymer plate in the ventral area of mandibular angle. The results obtained from this study were follows: 1. Stress was concentrated on the condylar neck of the fractured side except Type III. 2. The values of von-Mises stress of the screws were the highest in the just-posterior screw of the fracture line, and in the just-anterior screw of Type III. 3. The displacement of mandible in Type III was 0.04 mm, and in Type I, II, IV, and V were 0.10 mm. 4. The plates were the most stable in the ventral area of mandibular angle (Type III, V). In conclusion, the ventral area of mandibular angle is the most stable location in the fixation of mandibular angle fractures, and the just- posterior and/or the just-anterior screws of the fracture line must be longer than the other, and surgeons have to fix accurately these screws, and the biodegradable polymer plate also was suitable for the treatment of mandible angle fracture.

• 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.