• 대한치과보철학회지
• /
• 제50권1호
• /
• pp.1-9
• /
• 2012

연구 목적: 이 연구의 목적은 하악골 충격 시 안면 두개골의 응력분산양상에 미치는 구강보호장치의 효과에 대해 조사하는 것이다. 연구 재료 및 방법: 구강보호장치를 제작하고 사람의 머리부위와 치열의 3차원적 유한요소 모델을 컴퓨터 토모그래피를 사용하여 제작하였다. 머리부위의 finite element model은 356,092요소와, 87,099절점으로 이루어져 있다. 그리고 skull과 maxillae, mandible, articular disc, teeth, 그리고 구강보호장치로 구성되었다. 경부의 움직임을 묘사하기 위하여 스프링이 사용되었다. 하악골의 충격점은 gnathion, center of inferior border 와 anterior edge of gonial angle이었다. 충격방향은 수직, 경사방향($45^{\circ}$), 그리고 수평이다. 충격량은 0.1초당 800 N이었다. 결과: 수직충격을 가한 경우에는 구강보호장치의 장착여부와 무관하게 비슷한 응력과 분산양상이 나타났다(P>.05). 경사충격($45^{\circ}$)을 가한 경우 구강보호장치를 장착한 모델에서는 응력이 치아와 안면골 및 두개골로 넓게 분산되었으나 이에 비하여 장착하지 않은 모델에서는 치아에 응력이 집중되었다(P<.05). 수평충격을 가한 경우 구강보호장치를 장착한 모델에서는 응력이 치아와 안면골 및 두개골로 넓게 분산되었으나 이에 비하여 장착하지 않은 모델에서는 치아에 응력이 집중되었다(P<.05). 구강보호장치를 장착하지 않은 모델에서는 상악 치아에 응력이 집중되는 반면, 장착한 모델에서는 모든 충격실험에서 계측된 응력이 매우 낮았으며, 전달된 응력이 상악 치아와 안면골 및 두개골로 넓게 분산되었다. 결론: 구강보호장치는 외부충격 시에 하악에 수직으로 가해지는 충격에는 완충효과가 적었고, $45^{\circ}$경사 충격과 수평 충격에는 발생하는 응력을 안면골과 두개골의 넓은 범위로 분산시키고 응력을 감소시켜 응력의 완충 효과가 있었다.

• Journal of Mechanical Science and Technology
• /
• 제18권8호
• /
• pp.1435-1450
• /
• 2004

Experimental data are presented which describe the effects of a combustor-level high free-stream turbulence on the near-wall flow structure and heat/mass transfer on the endwall of a linear high-turning turbine rotor cascade. The end wall flow structure is visualized by employing the partial- and total-coverage oil-film technique, and heat/mass transfer rate is measured by the naphthalene sublimation method. A turbulence generator is designed to provide a highly-turbulent flow which has free-stream turbulence intensity and integral length scale of 14.7% and 80mm, respectively, at the cascade entrance. The surface flow visualizations show that the high free-stream turbulence has little effect on the attachment line, but alters the separation line noticeably. Under high free-stream turbulence, the incoming near-wall flow upstream of the adjacent separation lines collides more obliquely with the suction surface. A weaker lift-up force arising from this more oblique collision results in the narrower suction-side corner vortex area in the high turbulence case. The high free-stream turbulence enhances the heat/mass transfer in the central area of the turbine passage, but only a slight augmentation is found in the end wall regions adjacent to the leading and trailing edges. Therefore, the high free-stream turbulence makes the end wall heat load more uniform. It is also observed that the heat/mass transfers along the locus of the pressure-side leg of the leading-edge horseshoe vortex and along the suction-side corner are influenced most strongly by the high free-stream turbulence. In this study, the end wall surface is classified into seven different regions based on the local heat/mass transfer distribution, and the effects of the high free-stream turbulence on the local heat/mass transfer in each region are discussed in detail.

• Journal of Periodontal and Implant Science
• /
• 제46권3호
• /
• pp.152-165
• /
• 2016

Purpose: This study investigated the effects of bone density and crestal cortical bone thickness at the implant-placement site on micromotion (relative displacement between the implant and bone) and the peri-implant bone strain distribution under immediate-loading conditions. Methods: A three-dimensional finite element model of the posterior mandible with an implant was constructed. Various bone parameters were simulated, including low or high cancellous bone density, low or high crestal cortical bone density, and crestal cortical bone thicknesses ranging from 0.5 to 2.5 mm. Delayed- and immediate-loading conditions were simulated. A buccolingual oblique load of 200 N was applied to the top of the abutment. Results: The maximum extent of micromotion was approximately $100{\mu}m$ in the low-density cancellous bone models, whereas it was under $30{\mu}m$ in the high-density cancellous bone models. Crestal cortical bone thickness significantly affected the maximum micromotion in the low-density cancellous bone models. The minimum principal strain in the peri-implant cortical bone was affected by the density of the crestal cortical bone and cancellous bone to the same degree for both delayed and immediate loading. In the low-density cancellous bone models under immediate loading, the minimum principal strain in the peri-implant cortical bone decreased with an increase in crestal cortical bone thickness. Conclusions: Cancellous bone density may be a critical factor for avoiding excessive micromotion in immediately loaded implants. Crestal cortical bone thickness significantly affected the maximum extent of micromotion and peri-implant bone strain in simulations of low-density cancellous bone under immediate loading.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• 제41권3호
• /
• pp.133-138
• /
• 2015

Objectives: To evaluate the influence of the type of osteotomy in the inferior aspect of the mandible on the mechanical performance. Materials and Methods: The study was performed on 20 polyurethane hemimandibles. A sagittal split ramus osteotomy (SSRO) was designed in 10 hemimandibles (group 1) with a vertical osteotomy in the buccal side (second molar level) and final osteotomy was performed horizontally on the lingual aspect, while the mandible body osteotomy was finalized as a straight osteotomy in the basilar area, perpendicular to the body. For group 2, the same osteotomy technique was used, but an oblique osteotomy was done in the basilar aspect of the mandibular body, forming continuity with the sagittal cut in the basilar area. Using a surgical guide, osteosynthesis was performed with bicortical screws using an inverted L scheme. In both groups vertical compression tests were performed with a linear load of 1 mm/min on the central fossa of the first molar and tests were done with models made from photoelastic resin. Data were analyzed using Student's t-test, establishing a statistical significance when P<0.05. Results: A statistical difference was not observed in the maximum displacements obtained in the two osteotomies (P<0.05). In the extensiometric analysis, statistically significant differences were identified only in the middle screw of the fixation. The photoelastic resin models showed force dissipation towards the inferior aspect of the mandible in both SSRO models. Conclusion: We found that osteotomy of the inferior aspect did not influence the mechanical performance for osteosynthesis with an inverted L system.

• 대한치과보철학회지
• /
• 제44권5호
• /
• pp.584-593
• /
• 2006

Statement of problem : Dental implant which has been developed gradually through many experiments and clinical applications is presently used to various dental prosthetic treatments. To conduct a successful function of implant prosthesis in oral cavity for a long time, it is important that not only structure materials must have the biocompatibility, but also the prosthesis must be designed for the stress, which is occurred in occlusion, to scatter adequately of load support. Therefore, it is essential to give the consideration about the stress analysis of supporting tissues for higher successful rates. Purpose : Recently, many implant manufacturing company produce various taper design of root form implant, the fixture is often selected. However, the stress analysis of taper form fixture still requires more studies. Material and method : This study we make the element models that five implant fixture; Branemark system(Nobel Biocare, Gothenberg, Sweden), Camlog system(Altatec, Germany), Astra system(Astra Tech, Sweden), 3i system(Implant Innovations Inc, USA), Avana system(Osstem, Korea) were placed in the area of mandibular first premolar and prosthesis fabricated, which we compared with stress distribution using the three-dimension finite element analysis under two loading condition. Results : This study compares the aspect of stress distribution of each system with the standard of Von mises stress, among many resulted from finite element analysis so that this research gets the following results. 1. In all implant system, oblique loading of maximum Von mises stress of implant, alveolar bone and crown is higher than vertical loading of those. 2. Regardless of loading conditions and type of system, cortical bone which contacts with implant fixture top area has high stress, and cancellous bone has a little stress. under the vertical loading, maximum Von mises stress is more higher in order of Branemark, Camlog, Astra, 3i, Avana. under the horizontal loading, maximum Von mises is more higher in order of Camlog, Branemark, Astra, 3i, Avana.

• The Journal of Advanced Prosthodontics
• /
• 제8권6호
• /
• pp.489-493
• /
• 2016

PURPOSE. This in-vitro study aimed to evaluate the fracture resistances and failure modes of endodontically treated mandibular premolars restored with endocrowns and conventional post-core retained crowns. MATERIALS AND METHODS. Thirty mandibular premolars were assigned into three groups (n=10): GI, intact teeth; GE, teeth with endocrowns; GC, teeth with conventional post-core supported crowns. Except for the teeth in group GI, all specimens were cut to 1.5 mm above the cementoenamel junction and endodontically treated. Both endocrowns and conventional crowns were fabricated from lithium-disilicate blocks using a CEREC 3D CAD/CAM unit. All specimens were subjected to thermocycling and then to $45^{\circ}$ oblique compressive load until fracture occurred. The fracture resistance and failure mode of each specimen were recorded. Data were analyzed with one-way ANOVA and LSD Post Hoc Test (${\alpha}=.05$). RESULTS. The fracture resistances of GE and GC were significantly lower than that of GI (P<.01), while no significant difference was found between GE and GC (P=.702). As of the failure mode, most of the specimens in GE and GC were unfavorable while a higher occurrence of favorable failure mode was presented in GI. CONCLUSION. For the restoration of mandibular premolar, endocrown shows no advantage in fracture resistance when compared with the conventional method. Both of the two methods cannot rehabilitate endodontically treated teeth with the same fracture resistances that intact mandibular premolars have.

• Restorative Dentistry and Endodontics
• /
• 제34권1호
• /
• pp.69-79
• /
• 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.

• 구강회복응용과학지
• /
• 제18권4호
• /
• pp.277-288
• /
• 2002

Seven finite element models were constructed in mandible having single screw-type implant fixture connected to the premolar superstructure, in order to evaluate how the length, diameter and platform shape of a screw-type fixture influence the stress in the supporting tissue around fixtures. Each finite element model was varied in terms of length, diameter, and platform shape of the fixture. In each model, 250N of vertical load was placed on the central pit of an occlusal plane and 250N of oblique load placed on the buccal cusp. The stress distribution in the supporting tissue and the other components was analysed using 2-dimensional finite element analysis and the maximum von Mises stress in each reference area was compared. Under lateral loading, the stress was larger at the abutment/fixture interface, and in the crestal bone, compared to the stress pattern under vertical loading. The amount of stress at the superstructure was similar regardless of the length, diameter and platform shape of a fixture. Around the longer fixture, the stress was decreased at the bone crest and subjacent cancellous bone and increased in the cancellous bone area apical to the fixture. Around the wider fixture, the stress was decreased at the abutment/fixture interface, and the bone crest and increased in the cancellous bone area apical to the fixture. Around the fixture having wider platform, less stress was produced at the abutment/fixture interface and the upper part of the cortical bone, compared to the fixture having standard platform. In conclusion, the stress distribution of the supporting tissue was affected by length, diameter, and platform shape of a fixture, and the fixture which was larger in diameter and length could reduce the stress in the supporting tissues at the bone-fixture interface and bone crest area.

• 구강회복응용과학지
• /
• 제36권3호
• /
• pp.176-182
• /
• 2020

목적: 수복물에 교합력을 가할때 식립된 임플란트의 개수, 배열 및 위치에 따른 임플란트, 보철물 및 지지 골에 발생하는 응력의 차이를 분석하고자 한다. 연구 재료 및 방법: 하악에 임플란트가 식립되어 고정성 보철물을 지지하는 4 종류의 3D 유한요소 모형을 제작하였다. 모델 M1은 2개의 임플란트 가운데에 가공치를 배열하였고, 모델 M2는 2개의 임플란트 외측에 캔티레버 가공치를 배열하였다. 모델 M3과 M4는 3개의 임플란트를 각각 일렬로 배열되거나, 엇갈리게 배열하였다. 총 120 N 크기의 수직력과 45도 측방력을 가하였고, 유한요소 응력 분석을 시행하였다 결과: 측방력 하중에 의해 발생한 최대 응력은 수직력 하중에 의한 것 보다 임플란트 부위에서 3.4 - 5.1배 더 컸고, 지지골 내에서는 3.5 - 8.3배 더 컸다. 모델 M2 의 고정성 보철물의 캔티레버 연결부에서 가장 큰 응력이 집중되었다. 임플란트 개수가 3개인 모델들이 2개인 경우보다 더 낮은 응력이 발생하였으나 M3과 M4에서 일렬 배열과 엇갈린 배열간의 응력 발생 차이는 작았다. 결론: 임플란트 배열의 엇갈림 정도는 응력 크기에 별 차이를 발생하지 않았으나, 캔티래버의 존재나 임플란트의 개수의 차이는 큰 영향을 주었다.

• Composites Research
• /
• 제20권3호
• /
• pp.8-16
• /
• 2007

자동차 충돌이나 전복사고에 있어서 부재들의 변형은 축방향 압축붕괴와 함께 굽힘붕괴가 혼합된 변형양상을 보여주고 있으며, 자동차에 사용되는 대부분의 박벽관 부재는 굽힘붕괴가 주된 붕괴형태로 나타나고 있다. 하지만 혼성 사각관의 굽힘붕괴에 대한 연구는 축방향 붕괴의 연구에 비해 많이 부족한 현실이다. 본 논문에서는 알루미늄-복합재료 혼성 사각관의 굽힘 붕괴 거동 및 에너지 흡수 특성을 실험적 방법으로 연구하여 경량화 구조부재로서의 적용가능성을 조사하였다. 접착필름 살입형 경화법으로 제작된 알루미늄-복합재료 혼성 사각관 보에 대해 복합 재료 층의 적층두께와 적층 각에 따른 굽힘 성능을 평가하였다. 본 혼성 사각관 보는 복합재료만으로 구성된 사각관 보에서 발생할 수 있는 불안정한 붕괴모드를 안정적인 붕괴로 전환시키면서, 단순 알루미늄 사각관에 비해 에너지 흡수 능력이 향상되었고, 특히 $[0^{\circ}/90^{\circ}]s$를 적층한 혼성 사각관의 경우 벽두께 1mm인 알루미늄 사각관 시험편과 비교하여 흡수에너지가 1.78배 증가하였고 단위무게당 흡수에너지는 1.29배로 증가함을 보였다.