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1.
Hua Xi Kou Qiang Yi Xue Za Zhi ; 38(5): 537-540, 2020 Oct 01.
Artigo em Chinês | MEDLINE | ID: mdl-33085238

RESUMO

OBJECTIVE: To study the stress distribution under dynamic loading in the presence or absence of an abutment buffer layer by using three-dimensional finite element analysis. METHODS: A three-dimensional solid geometric model of an implant in a human mandible was established on the basis of CT scan data. A buffer-free abutment prosthesis and a buffer-abutment abutment prosthesis were installed above the implant. The buffer layer was made of high-density polyethylene. A vertical load of 200 N and a horizontal load of 100 N (45°) were concentrated on the centers of the implant restorations of the two groups. Stresses on the implant neck and body, abutment neck and body, central bolt neck and body, and bone interface were compared via three-dimensional finite element analysis. RESULTS: Stresses on the implant neck and body, abutment neck and body, central bolt neck and body, and bone interface on the abutment with a buffer layer were significantly lower than those on the abutment without a buffer layer. CONCLUSIONS: The increase in the buffer layer of the abutment neck significantly reduced stress on the implant neck, abutment, central bolt neck, and bone interface.


Assuntos
Dente Suporte , Implantes Dentários , Análise do Estresse Dentário , Análise de Elementos Finitos , Humanos , Estresse Mecânico
2.
Shanghai Kou Qiang Yi Xue ; 29(4): 355-358, 2020 Aug.
Artigo em Chinês | MEDLINE | ID: mdl-33089281

RESUMO

PURPOSE: To compare the stress distribution of dental implants with different body shapes after maxillary sinus augmentation. MRTHODS: Three different implant models varying in implant shape were investigated in D3-type maxilla. All materials were assumed to be linear elastic, homogenous and isotropic. An oblique force of 150 N was applied to the implant. Maximal equivalent von-Mises of supporting bone around implants were measured. All of the models were measured by Ansys Workbench 14.5. Statistical analysis was performed using SPSS 17.0 software package. RESULTS: Highest stress of supporting bone emerged on the crestal cortical site around the implant neck. There was no significant difference in the maximum EQV of supporting cortical bone between different groups; the maximum EQV of supporting trabecular bone in the tapered implant group was much higher than other groups; application of grafts reduced the maximum EQV of both cortical and trabecular bone in all groups. CONCLUSIONS: Tampered implant can induce elevated stress distribution of the upper trabecular bone, which may promote marginal bone loss. Application of grafts after maxillary sinus augmentation could favors in reducing the stress loading of dental implants.


Assuntos
Implantes Dentários , Maxila , Planejamento de Prótese Dentária , Análise de Elementos Finitos , Maxila/cirurgia , Seio Maxilar/diagnóstico por imagem , Seio Maxilar/cirurgia , Estresse Mecânico
3.
Shanghai Kou Qiang Yi Xue ; 29(3): 237-241, 2020 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-33043338

RESUMO

PURPOSE: The aim of this study was to compare the stress distribution of microtitanium plate and bioresorbable plates in fixation of mandibulotomy. METHODS: Three dimensional models of different internal fixation systems in mandibular resection were established, and three dimensional finite element analysis was carried out to compare the displacement changes of fracture segments and stress distribution of titanium plates under the same stress conditions. RESULTS: The maximum stress value of titanium plate was 49.8 MPa, and that of absorbable plate was 4.42 MPa. The maximum stress value of titanium plate was far greater than that of absorbable plate. However, all the stresses were less than their yield limits. It can be seen from the relative displacement comparison that when the mini-titanium plate was fixed on the mandible, the maximum displacement value was 0.1 mm; when absorbable plate was used for fixation, the maximum displacement value was 0.2 mm, and the relative displacement of both plates was small. CONCLUSIONS: These results suggest that the stiffness and internal strength of bioabsorbable fixation system are sufficient to support bone healing at the mandible site.


Assuntos
Implantes Absorvíveis , Osteotomia Mandibular , Placas Ósseas , Análise de Elementos Finitos , Fixação Interna de Fraturas
4.
Shanghai Kou Qiang Yi Xue ; 29(3): 262-266, 2020 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-33043342

RESUMO

PURPOSE: To observe and compare the stress distribution of implant, crown, abutment and surrounding bone tissues in the aesthetic zone after restoration of resin-ceramic composite single crown, and provide theoretical basis for clinical restoration. METHODS: Three-dimensional finite element models of alveolar bone, implant, crown, and the thickness of different adhesives between crown and abutment (0.05 mm and 0.1 mm) were established by using Mimics 17.0 software.Force was applied at the angle of 130° with the long axis of the implant, the loading position was 2 mm from the incisal cingulum, and other force on the incisal margin was loaded in parallel to the long axis of the implant. The size was 100 N. Linear static stress analysis was carried out to compare the Von Mises stress after single crown restoration with different materials. RESULTS: When the thickness of adhesive was 0.05 mm, and resin cement was selected, after restoration of Enamic, Ultimate resin ceramic composite crown, the peak stress of alveolar bone, implant, crown and abutment was more uniform and decreased slightly, but the difference was not significant compared with that of IPS Empress, blocs Mark Ⅱ ceramic crown. When the thickness of adhesive was 0.05 mm, the peak stress was significantly lower than that of 0.1 mm. There was no significant difference in the stress between glass ionomer cement and resin cement.Under the same conditions, restoration with Ultimate crown had smaller stress value of peak Von Mises. CONCLUSIONS: The stress of resin composite ceramics single crown when applied to implantation in aesthetic area is slightly less and more uniform. The proportion of resin in composites and the thickness of adhesive can affect the stress distribution and peak value.


Assuntos
Implantes Dentários , Cerâmica , Coroas , Análise do Estresse Dentário , Estética Dentária , Análise de Elementos Finitos
5.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 4844-4847, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33019075

RESUMO

With commercial space travel on the horizon, it is important to understand how the microgravity environment of space effects bone strength. The reduction in skeletal loading is known to cause a rapid loss in bone density. How this corresponds to losses of bone strength is not well known, especially when combined with the osteoporotic effects of aging. In this study, a mouse model of hind limb suspension (HLS) was used to simulate the effects of gravitational unloading. This was combined with soluble receptor activator of nuclear factor kappa beta ligand (sRANK-L), which simulates age related osteoporosis. The proximal region of the tibia in mouse legs was scanned in-vivo pre-treatment as well as at the conclusion of the study with high resolution micro computed tomography (µCT). Subject specific finite element (FE) models were constructed from these 3D images to assess bone strength by simulating mechanical loading on these bone microstructures. Parameters indicative of bone strength obtained from the FE models were bone volume, stiffness, structural efficiency, and the 10th and 90th percentile nodal Von-Mises Stresses. Additionally, a model sensitivity analysis was performed to assess how these parameters varied with changes in anatomic model height. In regards to FE stiffness, HLS resulted in a 31% decline, sRANK-L resulted in a 16.8% decline, and HLS combined with sRANK-L (HLS+sRANK-L) resulted in a 38.6% decline. One interesting finding is that HLS caused a reduction in both bone stiffness and bone structural efficiency, while sRANK-L did not cause changes in bone structural efficiency, suggesting the importance of skeletal loading for maintaining bone health. In addition, sRANK-L combined with HLS caused an additional decline in bone stiffness, but did not further alter bone structural efficiency. In conclusion, this study shows that depending on the cause of osteoporosis, bone strength changes are not necessarily proportional to bone density changes. Thus, it is important to develop new clinical bone assessments beyond the current bone density measurement.Clinical Relevance- These parameters are associated with the microstructural mechanics of bone, and understanding how strength is decreased on a structural level may lead to the development of in-vivo bone strength testing clinically.


Assuntos
Osso e Ossos , Elevação dos Membros Posteriores , Animais , Análise de Elementos Finitos , Camundongos , Modelos Anatômicos , Microtomografia por Raio-X
6.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2536-2539, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018523

RESUMO

Atherosclerosis is one of the most common vascular pathologies in the world. Among the most commonly performed endovascular treatments, percutaneous transluminal angioplasty (PTA) has been showing significantly positive clinical outcomes. Due to the complex geometries, material properties and interactions that characterize PTA procedures, finite element analyses of acute angioplasty balloon deployment are limited. In this work, finite element method (FEM) was used to simulate the inflation and deflation of a semi-compliant balloon within the 3D model of a stenosed artery with two different plaque types (lipid and calcified). Self-defined constitutive models for the balloon and the plaque were developed based on experimental and literature data respectively. Balloon deployment was simulated at three different inflation pressures (10, 12 and 14 atm) within the two plaque types. Balloon sizing influence on the arterial elastic recoil obtained immediately after PTA was then investigated. The simulated results show that calcified plaques may lead to higher elastic recoil ratios compared to lipid stenosis, when the same balloon inflation pressures are applied. Also, elastic recoil increases for higher balloon inflation pressure independent of the plaque type. These findings open the way for a data-driven assessment of angioplasty balloon sizing selection and clinical procedures optimization.Clinical Relevance- The FE model developed in this work aims at providing quantitative evaluation of recoil after balloon angioplasty. It may be useful for both manufacturers and clinicians to improve efficiency of angioplasty balloon device design and sizing selection with respect to plaque geometry and constitution, consequently enhancing clinical outcomes.


Assuntos
Angioplastia com Balão , Técnica para Retentor Intrarradicular , Angioplastia , Animais , Constrição Patológica , Análise de Elementos Finitos
7.
J Orofac Orthop ; 81(6): 385-395, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33034698

RESUMO

OBJECTIVE: The present study compared the skeletal effects of surgically assisted rapid maxillary expansion (SARME) with different surgeries in three representative finite element (FE) models. STUDY DESIGN: According to the ossification level of midpalatal suture, three FE models, with different elasticity moduli of sutures (E = 1 MPa, 500 MPa, and 13,700 MPa) were constructed, to represent three age groups of patients. Within each model, four groups were set up according to different surgeries: group I (control group without surgery), II (paramedian osteotomy), III (pterygomaxillary separation), and IV (paramedian osteotomy and pterygomaxillary separation). An expansion force of 100 N and 1 mm displacement were applied via a bone-borne distraction to simulate the expansion process. RESULTS: By analyzing these models, the maximum displacement of maxilla was observed in group IV, with E = 1 MPa model exhibiting the most displacement (28.5â€¯× 10-6 mm), followed by group II (21.4â€¯× 10-6 mm). Group IV showed a unique backward-downward rotation with minimum stress distributions in three models (9 MPa, 131 MPa, and 140 MPa, respectively), and group II exhibited comparable low stress distributions (12 MPa, 151 MPa, and 230 MPa, respectively). Lowest stress was found in E = 1 MPa model, compared with the other two models. CONCLUSION: There is no need to perform surgeries when the midpalatal suture is open, and surgery guidelines are the same for partial and complete fusion sutures. Furthermore, exclusive use of partial paramedian osteotomy is sufficient enough to reduce stress and expand the posterior part of maxilla, and it is less invasive.


Assuntos
Maxila , Técnica de Expansão Palatina , Análise de Elementos Finitos , Humanos , Maxila/cirurgia , Osteotomia
8.
Am J Dent ; 33(5): 251-257, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-33017528

RESUMO

PURPOSE: To compare the stresses generated after the use of low elastic modulus polyetheretherketone (PEEK) as dental post and crown material with glass fiber post and metal supported ceramic crowns using finite element analysis. METHODS: First an image of a maxillary central incisor taken on micro-computed tomography (micro-CT) was uploaded to a computer program. Modeling was made of all the materials in the computer environment and 3-dimensional (3D) virtual models were obtained. Using two different post materials (glass fiber and PEEK post) and two different crown materials (metal supported ceramic and PEEK crown), the modeling of the maxillary central tooth was completed and a total of four groups were obtained. Finally, 135° and 100 N forces were applied from the midpoint of the palatal surface. RESULTS: The FEA analysis showed the use of PEEK as post material decreased the stress values in the post, post cement and composite core models and did not have any significant change in the dentin and crown cement models. The use of composite veneer with PEEK substructure as crown material reduced stress values in dentin, the post and composite core and increased stress values in both the post cement and the crown cement. CLINICAL SIGNIFICANCE: Since the elastic modulus of the PEEK material is very close to dentin tissue, finite element stress analysis, less stress formation in the tooth and post core restoration compared to other post systems was observed. In this context, PEEK post may reduce irreversible complications.


Assuntos
Técnica para Retentor Intrarradicular , Coroas , Análise de Elementos Finitos , Cetonas , Polietilenoglicóis , Microtomografia por Raio-X
9.
Nan Fang Yi Ke Da Xue Xue Bao ; 40(6): 911-915, 2020 Jun 30.
Artigo em Chinês | MEDLINE | ID: mdl-32895206

RESUMO

OBJECTIVE: To analyze the biomechanics of cystic lesions in the mandibular body in a three-dimensional (3D) finite element model. METHODS: A 3D finite element model of cystic lesion of the mandibular body was constructed based on the CT images of the mandible of a healthy adult female volunteer with normal occlusion. The size of the cyst and the residual bone wall were analyzed when the lesion area approached the stress peak under certain constraints and loading conditions. RESULTS: When the size of the cyst reached 37.63 mm×11.32 mm×21.45 mm, the maximal von Mises stress in the lesion area reached 77.295 MPa, close to the yield strength of the mandible with a risk of pathological fracture. At this point, the remaining bone thickness of the buccal and lingual sides and the lower margin of the mandible in the lesion area was 1.52 mm, 0.76 mm and 1.04 mm, respectively. CONCLUSIONS: Residual bone mass is an important factor to affect the risk of pathological fracture after curettage of cystic lesions. A thickness as low as 1 mm of the residual bone cortex in the cystic lesion area of the mandibular body can be used as the threshold for a clinical decision on one-stage windowing decompression combined with two- stage curettage.


Assuntos
Imageamento Tridimensional , Mandíbula , Adulto , Fenômenos Biomecânicos , Feminino , Análise de Elementos Finitos , Humanos , Estresse Mecânico
10.
Dental Press J Orthod ; 25(4): 44-50, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32965386

RESUMO

OBJECTIVE: To perform a numerical simulation using FEM to study the von Mises stresses on Mushroom archwires. METHODS: Mushroom archwires made of titanium-molybdenum alloy with 0.017 x 0.025-in cross-section were used in this study. A YS of 1240 MPa and a Young's modulus of 69 GPa were adopted. The archwire was modeled in Autodesk Inventor software and its behavior was simulated using the finite element code Ansys Workbench (Swanson Analysis Systems, Houston, Pennsylvania, USA). A large displacement simulation was used for non-linear analysis. The archwires were deformed in their extremities with 0° and 45°, and activated by their vertical extremities separated at 4.0 or 5.0 mm. RESULTS: Tensions revealed a maximum of 1158 MPa at the whole part of the loop at 5.0mm of activation, except in a very small area situated at the top of the loop, in which a maximum of 1324 Mpa was found. CONCLUSIONS: Mushroom loops are capable to produce tension levels in an elastic range and could be safely activated up to 5.0mm.


Assuntos
Agaricales , Incisivo , Fenômenos Biomecânicos , Módulo de Elasticidade , Análise de Elementos Finitos , Estresse Mecânico
11.
Zhongguo Gu Shang ; 33(9): 867-72, 2020 Sep 25.
Artigo em Chinês | MEDLINE | ID: mdl-32959577

RESUMO

OBJECTIVE: To explore the biomechanical characteristics of "three-dimensional balanced manipulation" for the treatment of cervical spondylotic radiculopathy(CSR). METHODS: A CSR patient was treated with "three-dimensional balanced manipulation", and the mechanical changes during the manipulation were monitored by mechanical testing system. Using spiral CT to scan the neck of the patient to obtain DICOM data. The three-dimensional finite element model of cervical spondylotic radiculopathy was established by using Mimics software, Geographic Studio software. The "three-dimensional balance manipulation" was simulated and loaded, and the mechanical parameters of each part were replaced into the finite element model, and the finite element analysis was carried out by using ANSYS software to study the internal stress changes and displacement deformation of vertebral body and intervertebral disc under the action of "three-dimensional balance manipulation". RESULTS: The established C3-C7 finite element model of the CSR patient consisted of 5 vertebrae, 4 intervertebral discs and 3 ligaments, involving 153 471 nodes and 64 978 units. The stress of C3-C7 vertebral body was mainly located in anterior and root of C5 spinous processes, arch, vertebral arch and the combination of the two after full loading of manipulation, and the maximum stress was 17.781 MPa. The deformation sites were mainly concentrated in articular processes and anterior transverse processes of C3, superior articular processes and transverse processes of C4, articular processes of C5. The stress of C3-C7 intervertebral disc mainly distributed in the anterior part of C3, 4 intervertebral disc and the nucleus pulposus of C4, 5 and C5, 6. The displace mentextended to the middle and posterior part of C3, 4 nucleus pulposus, around the nucleus of C4, 5 and C5, 6 and anterior part of cervical intervertebral disc. CONCLUSION: The establishment of three-dimensional finite element model of C3-C7 cervical spondylotic radiculopathy can simulate the geometry and material properties of cervical spine, and also accurately reflects the biomechanical characteristics of cervical spine, verifys the internal mechanism of "three-dimensional balanced manipulation" on CSR, proves the safety and effectiveness of treatment, guides more standardized manipulation, and avoids medical accidents.


Assuntos
Disco Intervertebral , Radiculopatia , Espondilose , Fenômenos Biomecânicos , Vértebras Cervicais , Análise de Elementos Finitos , Humanos , Amplitude de Movimento Articular
12.
Zhonghua Yi Xue Za Zhi ; 100(33): 2628-2632, 2020 Sep 08.
Artigo em Chinês | MEDLINE | ID: mdl-32892611

RESUMO

Objective: To evaluate the stress status of femoral head and neck, screws and acetabulum caused by femoral neck shortening after internal fixation of femoral neck fracture with finite element method, and to analyze the stress of proximal femoral neck and acetabulum from the mechanical point of view. Methods: CT scan data of hip of a healthy adult female were collected. Three-dimensional reconstruction MICs and related module function simulation was used to establish the postoperative shortening model of femoral neck fracture with Pauwells angle>50°, which was treated with cannulated screws. The models were divided into four groups: normal femoral neck without shortening, shortening for 2.5 mm, shortening for 7.5 mm and shortening for 12.5 mm. The finite element analysis software MSC. Nastran2012 was used to do the mechanical analysis. The acetabulum surface, femoral head surface, proximal femur and the maximum stress, stress nephogram and other relevant data were collected. Results: The maximum tensile stress and the maximum stress at the fracture site of the femoral neck increased gradually with the increasing of shortening of femoral neck, however, the maximum compressive stress under the femoral neck and the medial cortex decreased gradually; the maximum stress on the surface of the femoral head was 14.9, 15.0, 16.3 and 16.3 MPa, respectively; the maximum stress on the surface of the acetabulum was 10.1, 10.1 and 10.5,11.7 MPa, respectively. Conclusion: The mechanical environment of the hip joint changes with femoral neck shortening. With the increasing of femoral neck shortening, the peak stress of the acetabulum increases continuously. When the femoral neck is shortened seriously, the load distribution is uneven and the complex mobility of hip joint is decreased. In addition, the change of shortening might play a role in the necrosis of femoral head.


Assuntos
Fraturas do Colo Femoral , Adulto , Parafusos Ósseos , Feminino , Colo do Fêmur , Análise de Elementos Finitos , Fixação Interna de Fraturas , Articulação do Quadril , Humanos
13.
Zhongguo Gu Shang ; 33(8): 766-70, 2020 Aug 25.
Artigo em Chinês | MEDLINE | ID: mdl-32875770

RESUMO

OBJECTIVE: To establish a 3D finite element model of normal knee joint involved its meniscus, which can be used to simulate the anatomical morphology and characteristics of human knee joint, to verify the validity of the model by preliminary FEA mechanical analysis, and explain partially biomechanical mechanisms of meniscus. METHODS: CT and MRI data were harvested by scanning the knee joint of a healthy male volunteer, and then these data were imported into Mimics 10.01 software and Geomagic Studio software to constructed the 3D models of tissue structures of knee joint. These models were combined to constructed the 3D model of intact knee joint and meshed in ANSA software. Therefore the finite element model of intact knee joint was established. Finally, after the definitionof its material behavior, boundary conditions and loading. The finite element model of knee joint was analyzed and verified using ANSYS software. Meanwhile The biomechanical properties of meniscus were analyzed. RESULTS: The complete knee finite element model composed of bone, meniscus, articular cartilage, and major ligaments was established. It could effectively simulate the anatomical morphology and characteristics of knee joint and its meniscus. The contact area of medial meniscus was 771.05 mm2, while the contact area of lateral meniscus was 634.31 mm2, and the ratio was 1.216. The stress distribution was uniform, but the stress of the medial meniscus was higher than that of the lateral meniscus, and the peak stress located in the posterior horn of the medial meniscus and the anterior horn of the lateral meniscus, respectively, and the peak stress value was 4.11 MPa. The maximum displacement of the meniscus was located in body, and the displacement of the medial meniscus was more remarkable than that of the lateral meniscus, and the maximum displacement value is 0.33 mm. The obtained finite element analysis results corresponded to that reported in the literature, which mean the model's reliability. CONCLUSION: The established finite element model of knee joint are proved to be have validity, and is a useful model for finite element analysis of meniscus tear and menisectomy. The results of finite element analysis can explain partially biomechanical mechanisms of meniscus which can provide theoretical guidance for clinical treatment of meniscus injury.


Assuntos
Menisco , Fenômenos Biomecânicos , Análise de Elementos Finitos , Humanos , Articulação do Joelho , Masculino , Meniscos Tibiais , Reprodutibilidade dos Testes , Estresse Mecânico
14.
J Oral Sci ; 62(4): 377-381, 2020 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-32741850

RESUMO

In this study, analytic models were used to simulate marginal resection in the area of the second premolar to the second molar region, and the mechanical effects on the mandible of residual bone mass, a maxillofacial prosthesis, and a reconstruction plate were evaluated by three-dimensional finite element analysis. As residual bone mass decreased, maximum principal stress increased near the anterior ramus of the mandible, and maximum shear stress increased at the anterior buccal region of the resected area. In the mandible with a maxillofacial prosthesis, the maximum principal stress distribution at the anterior ramus was lower, and the distribution of maximum shear stress at the anterior buccal region of the resected area was higher. When a reconstruction plate was used, maximum principal stress and maximum shear stress were lower. Thus, lower residual bone mass was associated with increased mandible deflection and torsion. In addition, presence of a maxillofacial prosthesis decreased deflection but increased torsion, and presence of a reconstruction plate decreased deflection and greatly decreased torsion. These findings suggest that decreased residual bone mass and maxillofacial prostheses increase fracture risk; however, presence of a reconstruction plate was effective in decreasing torsional stress, thereby reducing fracture risk in the mandible.


Assuntos
Placas Ósseas , Prótese Maxilofacial , Fenômenos Biomecânicos , Análise de Elementos Finitos , Mandíbula/cirurgia , Estresse Mecânico
15.
PLoS One ; 15(8): e0236409, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32853253

RESUMO

This paper proposes an alternative approach to extract transformer's winding parameters of resistance (R), inductance (L), capacitance (C) and conductance (G) based on Finite Element Method (FEM). The capacitance and conductance were computed based on Fast Multiple Method (FMM) and Method of Moment (MoM) through quasi-electrostatics approach. The AC resistances and inductances were computed based on MoM through quasi-magnetostatics approach. Maxwell's equations were used to compute the DC resistances and inductances. Based on the FEM computed parameters, the frequency response of the winding was obtained through the Bode plot function. The simulated frequency response by FEM model was compared with the simulated frequency response based on the Multi-conductor Transmission Line (MTL) model and the measured frequency response of a 33/11 kV, 30 MVA transformer. The statistical indices such as Root Mean Square Error (RMSE) and Absolute Sum of Logarithmic Error (ASLE) were used to analyze the performance of the proposed FEM model. It is found that the simulated frequency response by FEM model is quite close to measured frequency response at low and mid frequency regions as compared to simulated frequency response by MTL model based on RMSE and ASLE analysis.


Assuntos
Capacitância Elétrica , Fontes de Energia Elétrica , Análise de Elementos Finitos , Simulação por Computador , Condutividade Elétrica , Eletricidade Estática
16.
Ultrasonics ; 108: 106223, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32771811

RESUMO

Quantitative ultrasound can be used to characterize the evolution of the bone-implant interface (BII), which is a complex system due to the implant surface roughness and to partial contact between bone and the implant. The determination of the constitutive law of the BII would be of interest in the context of implant acoustical modeling in order to take into account the imperfect characteristics of the BII. The aim of the present study is to propose an analytical effective model describing the interaction between an ultrasonic wave and a rough BII. To do so, a spring model was considered to determine the equivalent stiffness K of the BII. The stiffness contributions related (i) to the partial contact between the bone and the implant and (ii) to the presence of soft tissues at the BII during the process of osseointegration were assessed independently. K was found to be comprised between 1013 and 1017 N/m3 depending on the roughness and osseointegration of the BII. Analytical values of the reflection and transmission coefficients at the BII were derived from values of K. A good agreement with numerical results obtained through finite element simulation was obtained. This model may be used for future finite element bone-implant models to replace the BII conditions.


Assuntos
Interface Osso-Implante , Osseointegração , Ondas Ultrassônicas , Módulo de Elasticidade , Análise de Elementos Finitos , Modelos Teóricos , Propriedades de Superfície , Resistência à Tração , Titânio
17.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi ; 37(4): 608-613, 2020 Aug 25.
Artigo em Chinês | MEDLINE | ID: mdl-32840077

RESUMO

The decrease of corneal stiffness is the key factor leading to keratoconus, and the corneal collagen fiber stiffness and fiber dispersion are closely related to the corneal biomechanical properties. In this paper, a finite element model of human cornea based on corneal microstructure, namely collagen fiber, was established before and after laser assisted in situ keratomileusis (LASIK). By simulating the Corvis ST process and comparing with the actual clinical results, the hyperelastic constitutive parameters and corneal collagen fiber stiffness modulus of the corneal material were determined before and after refractive surgery. After LASIK, the corneal collagen fiber stiffness modulus increased significantly, and was highly correlated with central corneal thickness (CCT). The predictive relationship between the corneal collagen fiber stiffness modulus and the corresponding CCT before and after surgery was: k 1 before = exp(9.14 - 0.009CCT before), k 1 after = exp(8.82 - 0.008CCT after). According to the results of this study, the central corneal thickness of the patient can be used to estimate the preoperative and postoperative collagen fiber stiffness modulus, and then a personalized corneal model that is more consistent with the actual situation of the patient can be established, providing a theoretical reference for more accurately predicting the safe surgical cutting amount of the cornea.


Assuntos
Córnea , Fenômenos Biomecânicos , Topografia da Córnea , Análise de Elementos Finitos , Humanos , Ceratomileuse Assistida por Excimer Laser In Situ , Miopia
18.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi ; 37(4): 622-629, 2020 Aug 25.
Artigo em Chinês | MEDLINE | ID: mdl-32840079

RESUMO

The dynamic analysis of the implantation process of a new vena cava filter was carried out by finite element analysis method to reveal the influence of the angle, length, width and thickness of the filter rod on its mechanical properties and the inner wall of the blood vessel. The results showed that the high-stress and high-strain areas of the filter were mainly concentrated in the connection between the filter rod and the filter wire. With the increase of the angle of the filter rod, the maximum equivalent stress and the maximum elastic strain on the filter wall decreased, while the maximum equivalent stress on the vascular wall increased. With the increase of the length of the filter rod, the maximum equivalent stress and strain peak of the filter wall increased, but the maximum equivalent stress of the vessel wall decreased. With the increase of the width and thickness of the filter rod, the maximum equivalent stress of the filter wall, the maximum elastic strain and the maximum equivalent stress of the vessel wall all showed an upward trend. The static safety factor of all filter models was greater than 1, and the structure after implantation was safe and reliable. The results of this study are expected to provide a theoretical basis for the structural optimization and deformation mechanism of the new type vena cava filter.


Assuntos
Filtros de Veia Cava , Análise de Elementos Finitos , Veia Cava Inferior
19.
PLoS One ; 15(8): e0237379, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32780753

RESUMO

This paper provides a solution for fast haptic information gain during soft tissue palpation using a Variable Lever Mechanism (VLM) probe. More specifically, we investigate the impact of stiffness variation of the probe to condition likelihood functions of the kinesthetic force and tactile sensors measurements during a palpation task for two sweeping directions. Using knowledge obtained from past probing trials or Finite Element (FE) simulations, we implemented this likelihood conditioning in an autonomous palpation control strategy. Based on a recursive Bayesian inferencing framework, this new control strategy adapts the sweeping direction and the stiffness of the probe to detect abnormal stiff inclusions in soft tissues. This original control strategy for compliant palpation probes shows a sub-millimeter accuracy for the 3D localization of the nodules in a soft tissue phantom as well as a 100% reliability detecting the existence of nodules in a soft phantom.


Assuntos
Fenômenos Mecânicos , Palpação , Percepção do Tato , Algoritmos , Fenômenos Biomecânicos , Análise de Elementos Finitos , Imagens de Fantasmas
20.
PLoS One ; 15(8): e0237042, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32813735

RESUMO

The largest dinosaurs were enormous animals whose body mass placed massive gravitational loads on their skeleton. Previous studies investigated dinosaurian bone strength and biomechanics, but the relationships between dinosaurian trabecular bone architecture and mechanical behavior has not been studied. In this study, trabecular bone samples from the distal femur and proximal tibia of dinosaurs ranging in body mass from 23-8,000 kg were investigated. The trabecular architecture was quantified from micro-computed tomography scans and allometric scaling relationships were used to determine how the trabecular bone architectural indices changed with body mass. Trabecular bone mechanical behavior was investigated by finite element modeling. It was found that dinosaurian trabecular bone volume fraction is positively correlated with body mass similar to what is observed for extant mammalian species, while trabecular spacing, number, and connectivity density in dinosaurs is negatively correlated with body mass, exhibiting opposite behavior from extant mammals. Furthermore, it was found that trabecular bone apparent modulus is positively correlated with body mass in dinosaurian species, while no correlation was observed for mammalian species. Additionally, trabecular bone tensile and compressive principal strains were not correlated with body mass in mammalian or dinosaurian species. Trabecular bone apparent modulus was positively correlated with trabecular spacing in mammals and positively correlated with connectivity density in dinosaurs, but these differential architectural effects on trabecular bone apparent modulus limit average trabecular bone tissue strains to below 3,000 microstrain for estimated high levels of physiological loading in both mammals and dinosaurs.


Assuntos
Osso Esponjoso/anatomia & histologia , Osso Esponjoso/fisiologia , Dinossauros/anatomia & histologia , Animais , Anisotropia , Fenômenos Biomecânicos , Densidade Óssea/fisiologia , Osso e Ossos/anatomia & histologia , Força Compressiva/fisiologia , Simulação por Computador , Fêmur/anatomia & histologia , Análise de Elementos Finitos , Fósseis , Processamento de Imagem Assistida por Computador/métodos , Mamíferos/anatomia & histologia , Estresse Mecânico , Tíbia/anatomia & histologia , Microtomografia por Raio-X/métodos
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