• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.6
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• pp.533-539
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• 2009

In this study, the femur, the tibia, the articular cartilage and the menisci are three dimensionally reconstructed using MR images of healthy knee joint in full extension of 26-year-old male. Three dimensional finite element model of the knee joint is fabricated on the reconstructed model. Also, the FE models of ligaments and tendons are attached on the biologically suitable position of the FE model. Bones, articular cartilages and menisci are considered as homogeneous, isotropic and linear elastic materials, and ligaments and tendons are modeled as truss element and nonlinear elastic springs. The numerical results show the contact pressure and the von Mises stress distribution in the soft tissues such as articular cartilages and menisci which can be regarded as important parameters to estimate the failure of the tissues and the pain of the patients.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.2
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• pp.207-216
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• 2006

Statement of Problem: 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 within the limitation of alveolar bone around implant and bio-capacity of load support. Now implant which is used in clinical part has a very various shapes, recently the fixture that has tapered form of internal connection is often selected. However the stress analysis of fixtures still requires more studies. Purpose: The purpose of this study is to stress analysis of the implant prosthesis according to the different implant systems using finite element method. Material and methods: This study we make the finite element models that three type implant fixture ; $Br{\aa}nemark$, Camlog, Frialit-2 were placed in the area of mandibular first premolar and prosthesis fabricated, which we compared with stress distribution using the finite element analysis under two loading condition. Conclusion: The conclusions were as follows: 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 the type of system. cortical bone which contacts with implant fixture top area has high stress, and cancellous bone has a little stress. 3. Under the vertical loading, maximum Von mises stress of $Br{\aa}nemark$ system with external connection type and tapered form is lower than Camlog and Frialit-2 system with internal connection type and tapered form, but under oblique loading Camlog and Frialit-2 system is lower than $Br{\aa}nemark$ system.

• The Journal of Advanced Prosthodontics
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• v.13 no.6
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• pp.396-407
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• 2021

PURPOSE. Zirconia has exceptional biocompatibility and good mechanical properties in clinical situations. However, finite element analysis (FEA) studies on the biomechanical stability of two-piece zirconia implant systems are limited. Therefore, the aim of this study was to compare the biomechanical properties of the two-piece zirconia and titanium implants using FEA. MATERIALS AND METHODS. Two groups of finite element (FE) models, the zirconia (Zircon) and titanium (Titan) models, were generated for the exam. Oblique (175 N) and vertical (175 N) loads were applied to the FE model generated for FEA simulation, and the stress levels and distributions were investigated. RESULTS. In oblique loading, von Mises stress values were the highest in the abutment of the Zircon model. The von Mises stress values of the Titan model for the abutment screw and implant fixture were slightly higher than those of the Zircon model. Minimum principal stress in the cortical bone was higher in the Titan model than Zircon model under oblique and vertical loading. Under both vertical and oblique loads, stress concentrations in the implant components and bone occurred in the same area. Because the material itself has high stiffness and elastic modulus, the Zircon model exhibited a higher von Mises stress value in the abutments than the Titan model, but at a level lower than the fracture strength of the material. CONCLUSION. Owing to the good esthetics and stress controllability of the Zircon model, it can be considered for clinical use.

• The Journal of Korean Academy of Prosthodontics
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• v.49 no.3
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• pp.214-221
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• 2011

Purpose: To date most of finite element analysis assumed the presence of 100% contact between bone and implant, which is inconsistent with clinical reality. In human retrieval study bone-implant contact (BIC) ratio ranged from 20 to 80%. The objective of this study was to explore the influence of bone-implant contact pattern on bone of the interface using nonlinear 3-dimensional finite element analysis. Materials and methods: A computer tomography-based finite element models with two types of implant (Mark III Br${\aa}$nemark$^{(R)}$, Inplant$^{(R)}$) which placed in the maxillary 2nd premolar area were constructed. Two different degrees of bone-implant contact ratio (40, 70%) each implant design were simulated. 5 finite element models were constructed each bone-implant contact ratio and implant design, and sum of models was 40. The position of bone-implant contact was determined according to random shuffle method. Elements of bone-implant contact in group W (wholly randomized osseointegration) was randomly selected in terms of total implant length including cortical and cancellous bone, while ones in group S (segmentally randomized osseointegration) was randomly selected each 0.75 mm vertically and horizontally. Results: Maximum von Mises strain between group W and group S was not significantly different regardless of bone-implant contact ratio and implant design (P=.939). Peak von Mises strain of 40% BIC was significantly lower than one of 70% BIC (P=.007). There was no significant difference between Mark III Br${\aa}$nemark$^{(R)}$ and Inplant$^{(R)}$ in 40% BIC, while average of peak von Mises strain for Inplant$^{(R)}$ was significantly lower ($4886{\pm}1034\;{\mu}m/m$) compared with MK III Br${\aa}$nemark$^{(R)}$ ($7134{\pm}1232\;{\mu}m/m$) in BIC 70% (P<.0001). Conclusion: Assuming bone-implant contact in finite element method, whether the contact elements in bone were wholly randomly or segmentally randomly selected using random shuffle method, both methods could be effective to be no significant difference regardless of sample size.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.3
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• pp.290-297
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• 2008

STATEMENT OF PROBLEM: Implant-supported fixed cantilever prostheses are influenced by various biomechanical factors. The information that shows the effect of implant number and position of cantilever on stress in the supporting bone is limited. PURPOSE: The purpose of this study was to investigate the effect of implant number variation and the effect of 2 different cantilever types on stress distribution in the supporting bone, using 3-dimensional finite element analysis. MATERIAL AND METHODS: A 3-D FE model of a mandibular section of bone with a missing second premolar, first molar, and second molar was developed. $4.1{\times}10$ mm screw-type dental implant was selected. 4.0 mm height solid abutments were fixed over all implant fixtures. Type III gold alloy was selected for implant-supported fixed prostheses. For mesial cantilever test, model 1-1 which has three $4.1{\times}10$ mm implants and fixed prosthesis with no pontic, model 1-2 which has two $4.1{\times}10$ mm implants and fixed prosthesis with a central pontic and model 1-3 which has two $4.1{\times}10$ mm implants and fixed prosthesis with mesial cantilever were simulated. And then, 155N oblique force was applied to the buccal cusp of second premolar. For distal cantilever test, model 2-1 which has three $4.1{\times}10$ mm implants and fixed prosthesis with no pontic, model 2-2 which has two $4.1{\times}10$ mm implants and fixed prosthesis with a central pontic and model 2-3 which has two $4.1{\times}10$ mm implants and fixed prosthesis with distal cantilever were simulated. And then, 206N oblique force was applied to the buccal cusp of second premolar. The implant and superstructure were simulated in finite element software(Pro/Engineer wildfire 2.0). The stress values were observed with the maximum von Mises stresses. RESULTS: Among the models without a cantilever, model 1-1 and 2-1 which had three implants, showed lower stress than model 1-2 and 2-2 which had two implants. Although model 2-1 was applied with 206N, it showed lower stress than model 1-2 which was applied with 155N. In models that implant positions of models were same, the amount of applied occlusal load largely influenced the maximum von Mises stress. Model 1-1, 1-2 and 1-3, which were loaded with 155N, showed less stress than corresponding model 2-1, 2-2 and 2- 3 which were loaded with 206N. For the same number of implants, the existence of a cantilever induced the obvious increase of maximum stress. Model 1-3 and 2-3 which had a cantilever, showed much higher stress than the others which had no cantilever. In all models, the von Mises stresses were concentrated at the cortical bone around the cervical region of the implants. Meanwhile, in model 1-1, 1-2 and 1-3, which were loaded on second premolar position, the first premolar participated in stress distribution. First premolars of model 2-1, 2-2 and 2-3 did not participate in stress distribution. CONCLUSION: 1. The more implants supported, the less stress was induced, regardless of applied occlusal loads. 2. The maximum von Mises stress in the bone of the implant-supported three unit fixed dental prosthesis with a mesial cantilever was 1.38 times that with a central pontic. The maximum von Mises stress in the bone of the implant-supported three-unit fixed dental prosthesis with a distal cantilever was 1.59 times that with a central pontic. 3. A distal cantilever induced larger stress in the bone than a mesial cantilever. 4. A adjacent tooth which contacts implant-supported fixed prosthesis participated in the stress distribution.

• Journal of Biomedical Engineering Research
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• v.24 no.5
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• pp.401-410
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• 2003

This study investigates the biomechanical efficacies of various cement augmentation techniques with or without pressurization for varying degrees of osteoporotic femur. For this study, a biomechanical analysis using a finite element method (FEM) was undertaken to evaluate surgical procedures, Simulated models include the non-cemented(i.e., hip screw only, Type I), the cement-augmented(Type II), and the cemented augmented with pressurization(Type III) models. To simulate the fracture plane and other interfacial regions, 3-D contact elements were used with appropriate friction coefficients. Material properties of the cancellous bone were varied to accommodate varying degrees of osteoporosis(Singh indices, II∼V). For each model. the following items were analyzed to investigate the effect surgical procedures in relation to osteoporosis of varying degrees : (a) von Mises stress distribution within the femoral head in terms of volumetric percentages. (b) Peak von Mises stress(PVMS) within the femoral head and the surgical constructs. (c) Maximum von Mises strain(MVMS) within the femoral head, (d) micromotions at the fracture plane and at the interfacial region between surgical construct and surrounding bone. Type III showed the lowest PVMS and MVMS at the cancellous bone near the bone-construct interface regardless of bone densities. an indication of its least likelihood of construct loosening due to failure of the host bone. Particularly, its efficacy was more prominent when the bone density level was low. Micromotions at the interfacial surgical construct was lowest in Type III. followed by Type I and Type II. They were about 15-20% of other types. which suggested that pressurization was most effective in limiting the interfacial motion. Our results demonstrated the cement augmentation with hip screw could be more effective when used with pressurization technique for the treatment of intertrochanteric fractures. For patients with low bone density. its effectiveness can be more pronounced in limiting construct loosening and promoting bone union.

• The Journal of Korean Academy of Prosthodontics
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• v.54 no.2
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• pp.110-119
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• 2016

Purpose: This study is aimed to assess changes of stress distribution dependent on different connection lengths and placement of the fixture top relative to the ridge crest. Materials and methods: The internal-conical connection implant which has a hexagonal anti-rotation index was used for FEM analysis on stress distribution in accordance with connection length of fixture-abutment. Different connection lengths of 2.5 mm, 3.5 mm, and 4.5 mm were designed respectively with the top of the fixture flush with residual ridge crest level, or 2 mm above. Therefore, a total of 6 models were made for the FEM analysis. The load was 170 N and 30-degree tilted. Results: In all cases, the maximum von Mises stress was located adjacent to the top portion of the fixture and ridge crest in the bone. The longer the connection length was, the lower the maximum von Mises stress was in the fixture, abutment, screw and bone. The reduction rate of the maximum von Mises stress depending on increased connection length was greater in the case of the fixture top at 2 mm above the ridge crest versus flush with the ridge crest. Conclusion: It was found that the longer the connection length, the lower the maximum von Mises stress appears. Furthermore, it will help prevent mechanical or biological complications of implants.

• The korean journal of orthodontics
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• v.41 no.6
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• pp.384-398
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• 2011

Objective: The purpose of this study was to analyze the stress distribution and the displacement pattern of mandibular anterior teeth under various intrusive force vectors according to the position of orthodontic miniscrews and hooks, using three-dimensional finite element analysis. Methods: A three-dimensional finite element model was constructed to simulate mandibular teeth, periodontal ligament, and alveolar bone. The displacement of individual tooth on three-dimensional planes and the von Mises stress distribution were compared when various intrusion force vectors were applied. Results: Intrusive forces applied to 4 mandibular anterior teeth largely resulted in remarkable labial tipping of the segment according to the miniscrew position. All 6 mandibular anterior teeth were labially tipped and the stress concentrated on the labiogingival area by intrusive force from miniscrews placed mesial to the canine. The distointrusive force vector led to pure intrusion and the stress was evenly distributed in the whole periodontal ligament when the hook was placed between the central and lateral incisors and the miniscrew was placed distal to the canine. Conclusions: Within the limits of this study, it can be concluded that predictable pure intrusion of the 6 anterior teeth segment may be accomplished using miniscrews placed distal to the canine and hooks located between the central and lateral incisors.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.30 no.4
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• pp.345-352
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• 2008

Purpose: This study was performed to evaluate the stress distribution in the bone and the displacement distribution of the miniscrew under orthopedic force with two different types of miniplate design as skeletal anchorage for orthopedic treatment. Materials and methods: Finite element models were made for 6-hole miniplate (0.8mm in thickness), which were designed in two different shapes-one is curvilinear shaped (C plate, Jeil Medical Co., Korea) and another, Y shaped (Y plate), fixed with 3 pieces of miniscrew 2mm-diameter and 6mm-long respectively. A traction force of 4 N was applied in $0^{\circ}$, $30^{\circ}$ and $60^{\circ}$ to imaginary axis connecting two unfixed distalmost holes of the miniplate. Results: The maximum von Mises stress in the bone was much greater in the cortical portion rather than in the cancellous portion. C plate showed greater maximum von Mises stress in the cortical bone than Y plate. The maximum displacement of the miniscrew was greater in C plate than Y plate. The more increased the angle of the applied orthopedic force, the greater maximum von Mises stress in the bone and maximum displacement of the miniscrew. It was observed that in C plate, the von Mises stress in the bone and displacement of the miniscrew were distributed around the distalmost screw-fixed area. Conclusions: The results suggest that Y plate should have the advantage over C plate and in the placement of the miniplate, its imaginary axis should be placed as parallel as possible to the direction of orthopedic force to obtain its primary stability.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.1
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• pp.29-33
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• 2019

With shrinking form factor and improving performance of electronic packages, high input/output (I/O) density is considered as an important factor. Fan out wafer-level packaging (FO-WLP) has been paid great attention as an alternative. However, FO-WLP is vulnerable to warpage during its manufacturing process. Minimizing warpage is essential for controlling production yield, and in turn, package reliability. While many studies investigated the effect of process and design parameters on warpage using finite element analysis, they did not take uncertainty into consideration. As parameters, including material properties, chip positions, have uncertainty from the point of manufacturing view, the uncertainty should be considered to reduce the gap between the results from the field and the finite element analysis. This paper focuses on the effect of uncertainty of Young's modulus of chip on fan-out wafer level packaging warpage using finite element analysis. It is assumed that Young's modulus of each chip follows the normal distribution. Simulation results show that the uncertainty of Young's modulus affects the maximum von Mises stress. As a result, it is necessary to control the uncertainty of Young's modulus of silicon chip since the maximum von Mises stress is a parameter related to the package reliability.