論文

The aim of this study was to develop and evaluate a dental implant surgery simulator that allows learners to experience the drilling forces necessary to perform an osteotomy in the posterior mandibular bone. The simulator contains a force-sensing device that receives input and counteracts this force, which is felt as resistance by the user. The device consists of an actuator, a load cell, and a control unit. A mandibular bone model was fabricated in which the predicted forces necessary to drill the cortical and trabecular bone were determined via micro CT image-based 3D finite element analysis. The simulator was evaluated by five dentists from the Department of Implantology at Tokyo Dental College. The ability of the evaluators to distinguish the drilling resistance through different regions of the mandibular bone was investigated. Of the five dentists, four sensed the change in resistance when the drill perforated the upper cortical bone. All five dentists were able to detect when the drill made contact with lingual cortical bone and when the lingual bone was perforated. This project successfully developed a dental implant surgery simulator that allows users to experience the forces necessary to drill through types of bone encountered during osteotomy. Furthermore, the researchers were able to build a device by which excessive drilling simulates a situation in which the lingual cortical bone is perforated-A situation that could lead to negative repercussions in a clinical setting. The simulator was found to be useful to train users to recognize the differences in resistance when drilling through the mandibular bone.

© 2016 by the Japan Society for Computational Engineering and Science. The aim of this study is that with consideration of geometrical fluctuation, robust design is made to assure performance of material more reliable to fabrication process. Firstly a target microstructure is defined as the optimum solution for coated particulate material. Then a slightly fluctuated computational models are generated in which some random variables are defined. Multiscale analysis is done to obtain homogenized Young’s modulus, shear modulus and an index with respect to strength. Probabilistic sensitivity for those quantities of interest against design variables is analyzed by means of response surface method. For response surface, this paper studies a case where the scattering of sampling points is clustered. The characteristics of cluster sampling points determine the response surface strategy as quadratic polynomial and least square regression method. Finally the numerical result of a specific robust design for coated particulate composite material reveals that when the mean radius of particle is bigger and mean coating thickness is smaller, the less sensitive index is. It will provide a reliable guidance and save cost in the development of wide range of composite materials.

© 2016 Elsevier Ltd. Multiscale analysis of a semi-periodically perforated plate based on a homogenization theory is experimentally validated both macroscopically and microscopically, using a full-field strain measurement. To do this, a plate-fin-type perforated plate with a misaligned microstructure is considered as a semi-periodically perforated plate. Then, a homogenization theory that can analyze macroscopic behavior and microscopic stress and strain distributions of the perforated plate is presented. To validate the theory, a tensile test of a plate-fin-type semi-periodically perforated plate made of epoxy resin is conducted. During the test, the microscopic deformation of the specimen is observed with a digital image correlation (DIC) full-field measurement system, from which microscopic strain distribution of the specimen is calculated. It is shown that the obtained strain distribution satisfies the unit-cell periodicity except at edges of the periodic structure, and that the strain distribution is in good agreement with the result of analysis using the homogenization theory. It is also shown that the macroscopic stress-strain relationships obtained by the experiment and analysis agree well, supporting the macroscopic and microscopic validity of the multiscale analysis using the homogenization theory.

© 2016, Springer-Verlag Wien. A probabilistic multiscale framework is proposed to characterize the probabilistic behaviors of macroscopic elastic properties of multiphase composite materials. The first-order perturbation-based stochastic homogenization method is extended to incorporate inherent randomness existed in multiphase constituents materials on basis of our previous work for porous material. Moreover, a generalized stochastic method is introduced to combine above with morphological nonparametric uncertainties. A numerical example for coated particulate composite material demonstrated the feasibility and effectiveness of proposed methods.

© 2016 The Japan Society of Mechanical Engineers. To a nalyze the biomechanical behavior of human bone, micro-CT image-based static FEM analyse s considering trabecular architecture have been carried out. In the field of dental biomechanics, not only the static analysis but also dynamic analysis against impact load is required. In this paper, a desktop micro-CT was used for the right half of a human mandible with 0.103 mm resolution after dissecting. The lost information by a saw was recovered by the homogenization model. The impact load was applied to the implant in the molar part and the load transfer from the implant to the cortical bone and trabecular bone was considered. The stress wave pathways from the implant to the condyle were analyzed by comparison with virtual FEM models with eliminated materials on pathways. It was revealed that the stress wave transferred from the implant neck and end part to peri-implant trabecular bone played a significant mechanical role. It was also found that the apparent wave speed in the trabecular bone region was as fast as that in the cortical bone.

© 2016 World Scientific Publishing Europe Ltd. To avoid procedural accidents during/after oral implant surgery in a jawbone (e.g., perforation of the lingual side due to an inadequate drilling angle or scratching the mandibular canal), it is important for dentists to develop skilled drilling techniques. We have developed a stochastic multi-scale prediction of apparent elastic moduli of the jawbone with modified first-order perturbation-based stochastic homogenization in which individual differences of drilling properties relating to bone quality can be evaluated with a force-sensitive device. To establish drilling properties in various types of jawbone and the perforation case, and for drill diameters, we propose an original computational method that avoids procedural accidents by defining the drilling angle as a parameter and quantifying individual differences and the inner distribution of bone quality in several jawbones as a drilling force. Three samples demonstrated that drilling forces changed depending on the trabecular structure, with the drilling force changing little around the mandibular canal and increasing just before perforation. Drilling force also depended on the drill diameter but did not always match its size. Estimated drilling forces of the expected value and 50% and 90% probability results suggested prominent differences in drilling properties. This information enables dentists to develop a skillful surgical technique.

© 2017 Elsevier Ltd Aiming at the future applications of a lattice structure manufactured by selective laser sintering for bone scaffold in the biomedical field, by putting highlight on the possible imperfections influenced by different manufacturing strategies, a numerical prediction method was studied and compared with compressive test results. To consider the geometrical imperfections as well as the uncertainty in sintered material property, the first-order perturbation based stochastic homogenization (FPSH) method was employed. To be able to compare products made by three different printing service companies, maraging steel was used in this study, which was commonly available. Several geometrical imperfections were categorized into kink, notch and hole, and representative dimensions were parameterized and measured statistically using micro-CT images. They were also correlated to the building direction and support types. The numerical prediction revealed the reduction of stiffness in a stochastic way qualitatively. The constructed database of the geometrical imperfections and the FPSH method will be useful in the next occasion of manufacturing unexperienced product.

© 2018, Springer-Verlag GmbH Austria, part of Springer Nature. In the numerical prediction of the homogenized macroscopic properties of an arbitrary heterogeneous material with periodic microstructure, a general formulation of the first-order perturbation-based stochastic homogenization method is presented in a discretized form based on the finite element method in order to consider the variability or uncertainty of the mechanical properties of the material models. Many random parameters are defined for each material model and for each component of the stress–strain matrix of the constituent’s material model. The first-order terms of the characteristic displacement are thoroughly studied both theoretically and numerically, and are also used in the verification of the developed computer code. The comparison with the Monte Carlo simulation also supports the proposed formulation.

© 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. Purpose: Detection of optic canal fractures is often difficult because of the subtleness of the fracture. If we could clarify impact on which region around the orbit is likely to accompany the fracture of the optic canal, the knowledge should be useful to make early diagnosis of optic canal fractures. The present study was conducted to elucidate this issue. Methods: Ten finite element models were produced simulating the skulls of ten humans (8 males and 2 females; 43.8 ± 10.2 y/o). The peri-orbital area of each of the ten models was divided into eight regions in a clockwise fashion per 45 degrees. These regions were defined as Superior-Medial (0–45 degrees), Medial-Superior (45–90 degrees), Medial-Inferior (90 to 135 degrees), Inferior-Medial (135 to 180 degrees), Inferior-Lateral (180–225 degrees), Lateral-Inferior (225 to 270 degrees), Lateral-Superior (270–315 degrees), and Superior-Lateral regions (315–360 degrees), respectively. Dynamic simulation of applying traumatic energy on each of these regions was conducted. Resultant fracture patterns were evaluated using finite element analyses. Thereafter, frequencies of fracture involvement of the optic canal were evaluated for each of the eight regions. Results: The involvement of the optic canal was most frequent for the Superior-Medial region (7/10), followed by the Medial-Superior region (5/10). Conclusion: Optic canal fracture is likely to occur when the area between the supra-orbital notch and the medial canthus are strongly impacted. When evident fracture or serious damage of soft tissue is observed in this area, occurrence of optic canal fracture should be suspected.

© 2018, Springer-Verlag GmbH Austria, part of Springer Nature. In this paper, a first-order perturbation-based stochastic homogenization method was developed to predict the probabilities of not only macroscopic properties but also microscopic strain damage in multiphase composite materials, considering many random physical parameters. From the stochastic solution of microscopic strains, damage propagation was analyzed to predict where progressive damage would occur in the microstructures of composites subject to a given macroscopic strain. As an example, a short fiber-reinforced plastic, consisting of short fibers, matrix, and interphase, was used to show the influence of random physical parameters for each constituent material on the variability of the homogenized properties and microscopic strain. In another example, a coated particle-embedded composite material was stochastically analyzed to consider even slight influences of uncertainty in the mechanical properties of the coating material and show damage propagation in this coating layer. Characteristic displacements representing material heterogeneity were thoroughly investigated and extensively used with the aim of reducing the computational cost of finding them in a nonlinear analysis of the microscopic damage propagation.