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1.
Braz. j. oral sci ; 20: e214873, jan.-dez. 2021. ilus
Artigo em Inglês | LILACS, BBO - Odontologia | ID: biblio-1254742

RESUMO

Aim: To compare the marginal fit of lithium disilicate CAD/CAM crowns and heat-pressed crowns fabricated using milled wax patterns, and evaluate its effect on stress distribution in implantsupported rehabilitation. Methods: A CAD model of a mandibular first molar was designed, and 16 lithium disilicate crowns (8/group) were obtained. The crown-prosthetic abutment set was evaluated in a scanning electron microscopy. The mean misfit for each group was recorded and evaluated using Student's t-test. For in silico analysis, a virtual cement thickness was designed for the two misfit values found previously, and the CAD model was assembled on an implant-abutment set. A load of 100 N was applied at 30° on the central fossa, and the equivalent stress was calculated for the crown, titanium components, bone, and resin cement layer. Results: The CAD/CAM group presented a significantly (p=0.0068) higher misfit (64.99±18.73 µm) than the heat-pressed group (37.64±15.66 µm). In silico results showed that the heat-pressed group presented a decrease in stress concentration of 61% in the crown and 21% in the cement. In addition, a decrease of 14.5% and an increase of 7.8% in the stress for the prosthetic abutment and implant, respectively, was recorded. For the cortical and cancellous bone, a slight increase in stress occurred with an increase in the cement layer thickness of 5.9% and 5.7%, respectively. Conclusion: The milling of wax patterns for subsequent inclusion and obtaining heat-pressed crowns is an option to obtain restorations with an excellent marginal fit and better stress distribution throughout the implant-abutment set


Assuntos
Microscopia Eletrônica de Varredura , Desenho Assistido por Computador , Adaptação Marginal Dentária , Prótese Dentária Fixada por Implante , Análise de Elementos Finitos , Materiais Dentários
2.
Dental Press J Orthod ; 26(4): e21203, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34468562

RESUMO

OBJECTIVE: In this study, simulations were performed by the finite element method (FEM) to determine the tension and displacement in mini-implants and in expander appliance during rapid maxillary expansion, by varying the number and location of the mini-implants. METHODS: For the computational simulation, a three-dimensional mesh was used for the maxilla, mini-implants and expander appliance. Comparisons were made on six different Mini-implant Assisted Rapid Palatal Expander (MARPE) configurations, by varying the amount and location of mini-implants. A closed suture was design and received two activations of 0.25 mm, and an open suture had a 0.5-mm aperture that received 20 activations, also of 0.25 mm. RESULTS: For the closed suture, the maximum displacement values in the mini-implants were between 0.253 and 0.280 mm, and stress was between 1,348.9 and 2,948.2 MPa; in the expander appliance, the displacement values were between 0.256 and 0.281 mm, and stress was between 738.52 and 1,207.6 MPa. For the open suture, the maximum displacement values in the mini-implants were between 2.57 and 2.79 mm, and stress was between 5,765.3 and 10,366 MPa; in the appliance, the maximum displacements was between 2.53 and 2.89 mm, and stress was between 4,859.7 and 9,157.4 MPa. CONCLUSIONS: There were higher stress concentrations in the mini-implant than in the expander arm. In the simulations with a configuration of three mini-implants, stress overload was observed in the isolated mini-implant. Displacements of the mini-implants and arms of the appliance were similar in all simulations.


Assuntos
Implantes Dentários , Técnica de Expansão Palatina , Análise do Estresse Dentário , Análise de Elementos Finitos , Maxila/cirurgia , Palato , Estresse Mecânico
3.
BMC Musculoskelet Disord ; 22(1): 764, 2021 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-34488684

RESUMO

BACKGROUND: Finite element analysis (FEA) has been previously applied for the biomechanical analysis of acetabular dysplasia and osteotomy. However, until now, there have been little reports on the use of FEA to evaluate the effects of pelvic tilt on stress distribution in the acetabulum. METHODS: We used the Mechanical Finder Ver. 7.0 (RCCM, Inc., Japan) to construct finite element models based on 3D-CT data of patients, and designed dysplasia, borderline, and normal pelvic models. For analysis, body weight was placed on the sacrum and the load of the flexor muscles of the hip joint was placed on the ilium. The pelvic tilt was based on the anterior pelvic plane, and the pelvic tilt angles were -20°, 0°, and 20°. The load of the flexor muscle of the hip joint was calculated using the moment arm equation. RESULTS: All three models showed the highest values of von Mises stress in the -20° pelvic tilt angle, and the lowest in the 20° angle. Stress distribution concentrated in the load-bearing area. The maximum values of von Mises stress in the borderline at pelvic tilt angles of -20° was 3.5Mpa, and in the dysplasia at pelvic tilt angles of 0° was 3.1Mpa. CONCLUSIONS: The pelvic tilt angle of -20° of the borderline model showed equal maximum values of von Mises stress than the dysplasia model of pelvic tilt angle of 0°, indicating that pelvic retroversion of -20° in borderline is a risk factor for osteoarthritis of the hip joints, similar to dysplasia.


Assuntos
Luxação Congênita de Quadril , Luxação do Quadril , Acetábulo/diagnóstico por imagem , Análise de Elementos Finitos , Humanos , Tomografia Computadorizada por Raios X
4.
BMC Musculoskelet Disord ; 22(1): 758, 2021 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-34488708

RESUMO

BACKGROUND: The optimal treatment of Pauwels type III femoral neck fracture (FNF) in young patients remains a worldwide challenge in orthopedic surgery. METHODS: Finite element models of four internal fixations were developed to treat Pauwels type III FNF: a: the traditional inverted triangular parallel cannulated screw (PCS) model, b: the F-technique cannulated screw model, c: the modified F-technique cannulated screw model using a fully threaded screw instead of a partially threaded distally, d: the dynamic hip screw coupled with derotational screw (DHS + DS) model. Under the same conditions, finite element analyses were carried out to compare the displacement and von Mises stress distribution of four internal fixations and femurs, the maximum crack distances of the fracture surfaces, Z axis displacements of four models as well as the stress distribution in the subtrochanteric region. RESULTS: The modified F-technique configuration resulted in a more stable fixation as compared to the other three configurations, with respect to the maximum displacement and stress peaks of femur and internal fixations, the maximum crack distances of the fracture surfaces, Z axis displacements of four configurations as well as the stress distribution in the subtrochanteric region. CONCLUSIONS: Our results suggested that modified F-technique configuration show a better performance in resisting shearing and rotational forces in treating Pauwels type III FNF compared to those using traditional inverted triangular PCS, the F-technique configuration or DHS + DS, providing a new choice for the treatment of FNFs.


Assuntos
Fraturas do Colo Femoral , Fenômenos Biomecânicos , Parafusos Ósseos , Fraturas do Colo Femoral/cirurgia , Fêmur , Análise de Elementos Finitos , Fixação Interna de Fraturas , Humanos
5.
Shanghai Kou Qiang Yi Xue ; 30(3): 243-246, 2021 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-34476438

RESUMO

PURPOSE: To explore the mechanism of upper lip pressure on maxilla after cleft lip surgery. METHODS: ANSYS 17.0 software was used to add the upper lip soft tissue to the finite element model of maxilla with cleft palate, and the material properties was assigned to form a three-dimensional finite element model of maxilla with upper lip. The upper lip pressure was applied to the model and force analysis was performed in 2 groups. In the experimental group, upper lip pressure with cleft lip surgery was applied; in the control group, upper lip pressure in normal children of the same age was applied. RESULTS: Maxillary deformation in the experimental group was greater than that in the control group. Maxillary deformation occurred in three-dimensional direction, which was mainly in Z axis, followed by X axis and Y axis. The anterior segment of alveolar process was the most obvious,and from the anterior to the posterior, the change trend was gradually decreased. CONCLUSIONS: Maxillary growth is inhibited in three-dimensional direction,which is mainly sagittal growth inhibition,followed by transverse and vertical growth. The inhibition gradually decreases from anterior to posterior.


Assuntos
Fenda Labial , Fissura Palatina , Criança , Fenda Labial/cirurgia , Fissura Palatina/cirurgia , Análise de Elementos Finitos , Humanos , Lábio , Maxila/cirurgia
6.
Croat Med J ; 62(4): 328-337, 2021 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-34472735

RESUMO

AIM: To develop and test a new posterior stabilization system by augmenting the posterior hook-rod system with screws and rods. METHODS: A biomechanical analysis was performed using the finite element method. The anatomical structures were modeled based on computed tomography data. Instrumentation (hooks, rods, and screws) was modeled based on the data obtained by 3D scanning. The discretized model was verified by converging solutions and validated against data from a previously published experiment. A Th12-L1 spinal segment was modeled and modified by removing the body of the L1 vertebra (corpectomy) and the entire L1 vertebra (spondylectomy). The model was additionally modified by incorporating stabilization systems: i) posterior stabilization (transpedicular screws and rods); ii) combined posterior stabilization with sublaminar hooks; and iii) combined anterior (titanium cage) and posterior (sublaminar hooks) stabilization. The rotation angles in each group, and the strains on each part of the three stabilization constructs, were analyzed separately. RESULTS: The combined anterior and posterior stabilization system was the stiffest, except in the case of lateral bending, where combined posterior stabilization was superior. Stress analysis showed that the posterior stabilization system was significantly unloaded when augmented with a hook-rod system. A significant strain concentration was calculated in the cranially placed hooks. CONCLUSION: Stiffness analysis showed comparable stiffness between the tested and proposed stabilization construct. Stress analysis showed luxation tendency of the cranially placed hooks, which would most likely lead to system failure.


Assuntos
Fusão Vertebral , Fenômenos Biomecânicos , Parafusos Ósseos , Análise de Elementos Finitos , Humanos , Vértebras Lombares
7.
Bone Joint J ; 103-B(9): 1497-1504, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34465153

RESUMO

AIMS: Type 2 diabetes mellitus (T2DM) impairs bone strength and is a significant risk factor for hip fracture, yet currently there is no reliable tool to assess this risk. Most risk stratification methods rely on bone mineral density, which is not impaired by diabetes, rendering current tests ineffective. CT-based finite element analysis (CTFEA) calculates the mechanical response of bone to load and uses the yield strain, which is reduced in T2DM patients, to measure bone strength. The purpose of this feasibility study was to examine whether CTFEA could be used to assess the hip fracture risk for T2DM patients. METHODS: A retrospective cohort study was undertaken using autonomous CTFEA performed on existing abdominal or pelvic CT data comparing two groups of T2DM patients: a study group of 27 patients who had sustained a hip fracture within the year following the CT scan and a control group of 24 patients who did not have a hip fracture within one year. The main outcome of the CTFEA is a novel measure of hip bone strength termed the Hip Strength Score (HSS). RESULTS: The HSS was significantly lower in the study group (1.76 (SD 0.46)) than in the control group (2.31 (SD 0.74); p = 0.002). A multivariate model showed the odds of having a hip fracture were 17 times greater in patients who had an HSS ≤ 2.2. The CTFEA has a sensitivity of 89%, a specificity of 76%, and an area under the curve of 0.90. CONCLUSION: This preliminary study demonstrates the feasibility of using a CTFEA-based bone strength parameter to assess hip fracture risk in a population of T2DM patients. Cite this article: Bone Joint J 2021;103-B(9):1497-1504.


Assuntos
Diabetes Mellitus Tipo 2/complicações , Fraturas do Quadril/diagnóstico por imagem , Fraturas do Quadril/etiologia , Tomografia Computadorizada por Raios X/métodos , Idoso , Estudos de Casos e Controles , Estudos de Viabilidade , Feminino , Análise de Elementos Finitos , Humanos , Masculino , Pessoa de Meia-Idade , Valor Preditivo dos Testes , Estudos Retrospectivos , Sensibilidade e Especificidade
8.
Sensors (Basel) ; 21(17)2021 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-34502772

RESUMO

The optimization performed in this study is based on the finite dimensions model of the concentric ring electrode as opposed to the negligible dimensions model used in the past. This makes the optimization problem comprehensive, as all of the electrode parameters including, for the first time, the radius of the central disc and individual widths of concentric rings, are optimized simultaneously. The optimization criterion used is maximizing the accuracy of the surface Laplacian estimation, as the ability to estimate the Laplacian at each electrode constitutes primary biomedical significance of concentric ring electrodes. For tripolar concentric ring electrodes, the optimal configuration was compared to previously proposed linearly increasing inter-ring distances and constant inter-ring distances configurations of the same size and based on the same finite dimensions model. The obtained analytic results suggest that previously proposed configurations correspond to almost two-fold and more than three-fold increases in the Laplacian estimation error compared with the optimal configuration proposed in this study, respectively. These analytic results are confirmed using finite element method modeling, which was adapted to the finite dimensions model of the concentric ring electrode for the first time. Moreover, the finite element method modeling results suggest that optimal electrode configuration may also offer improved sensitivity and spatial resolution.


Assuntos
Análise de Elementos Finitos , Simulação por Computador , Eletrodos
9.
Spine (Phila Pa 1976) ; 46(19): E1015-E1021, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34517397

RESUMO

STUDY DESIGN: Analytical biomechanical study using a finite-element (FE) model. OBJECTIVE: We investigated the effects of paraspinal muscle volume to the physiological loading on the lower lumbar vertebral column using a FE model. SUMMARY OF BACKGROUND DATA: The FE model analysis can measure the physiological load on the lumbar vertebral column. Which changes as the surrounding environment changes. In this study, our FE model consisted of the sacrum, lumbar spine (L3-L5), intervertebral discs, facet joints, and paraspinal muscles. METHODS: Three-dimensional FE models of healthy lumbar spinal units were reconstructed. The physiological loads exerted on the lumbar vertebra column were evaluated by applying different paraspinal muscle volumes (without muscles, 50%, 80%, and 100% of healthy muscle volume). RESULTS: As the paraspinal muscle volume increased, the loads exerted on the vertebral column decreased. The mean load on the intervertebral disc was 1.42 ±â€Š0.75 MPa in the model without muscle, 1.393 ±â€Š0.73 MPa in the 50% muscle volume model, 1.367 ±â€Š0.71 MPa in the 80% muscle volume model, and 1.362 ±â€Š0.71 MPa in the 100% muscle volume model. The mean loads exerted on the posterior column of lumbar spine were 11.79 ±â€Š4.70 MPa in the model without muscles, 11.57 ±â€Š4.57 MPa in the model with 50% muscle volume, and 11.13 ±â€Š4.51 MPa in the model with 80% muscle volume, and 10.92 ±â€Š4.33 MPa in the model with 100% muscle volume. The mean pressure on the vertebral body in the model without paraspinal muscle, and with 50%, 80%, and 100% paraspinal muscle volume were 14.02 ±â€Š2.82, 13.82 ±â€Š2.62, 13.65 ±â€Š2.61, and 13.59 ±â€Š2.51 MPa, respectively. CONCLUSION: Using FEM, we observed that the paraspinal muscle volume decreases pressure exerted on the lumbar vertebral column. Based on these results, we believe that exercising to increase paraspinal muscle volume would be helpful for spinal pain management and preventing lumbar spine degeneration.Level of Evidence: N/A.


Assuntos
Disco Intervertebral , Articulação Zigapofisária , Fenômenos Biomecânicos , Análise de Elementos Finitos , Humanos , Vértebras Lombares/diagnóstico por imagem , Região Lombossacral , Músculos Paraespinais/diagnóstico por imagem
10.
Acta Chir Orthop Traumatol Cech ; 88(4): 313-320, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34534062

RESUMO

PURPOSE OF THE STUDY In this study, our aim is to examine the effect of proximal fibular osteotomy on knee and ankle kinematics with finite element analysis method. MATERIAL AND METHODS One 62-year-old, female volunteer's radiologic images were used for creating lower limb model. Osteotomized model (OM) which was created according to definition of PFO and non-osteotomized model (NOM) were created. To obtain a stress distribution comparison between the two models, 350 N of axial force was applied to the femoral heads of the models. RESULTS After PFO, the average contact pressure decreased 26.1% at the medial tibial cartilage and increased 42.4% at the lateral tibial cartilage. The Von Mises stresses decreased 57.1% at the femoral cartilage and decreased 79.1% at tibial cartilage. The stress on the tibial cartilage increased 44.6%, and stress on the talar cartilage increased 7.1% at the ankle joint. CONCLUSIONS FEA revealed that main loading at the knee joint shifted from medial tibial cartilage to the lateral tibial cartilage after PFO. Additionally, the stresses on each cartilage were redistributed across a wider and more peripheral area. FEA also demonstrated that the Von Mises stresses of the tibial and talar cartilages of the ankle joint increased after PFO. Key words: knee pain, osteoarthritis, osteotomy, finite element analysis, axial loadings.


Assuntos
Articulação do Tornozelo , Articulação do Joelho , Articulação do Tornozelo/diagnóstico por imagem , Articulação do Tornozelo/cirurgia , Fenômenos Biomecânicos , Feminino , Análise de Elementos Finitos , Humanos , Articulação do Joelho/diagnóstico por imagem , Articulação do Joelho/cirurgia , Osteotomia , Estresse Mecânico , Tíbia/diagnóstico por imagem , Tíbia/cirurgia
11.
Int J Artif Organs ; 44(10): 748-755, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34387526

RESUMO

Anterior cervical discectomy with fusion (ACDF) is the common method to treat the cervical disc degeneration. The most serious problems in the fusion cages are adjacent disc degeneration, loss of lordosis, pain, subsidence, and migration of the cage. The objective of our work is to develop the three-dimensional finite element (FE) model from C3-C6 and virtually implant a designed S-type dynamic cage at C4-C5 segment of the model. The dynamic cage design will provide mobility in the early stage after ACDF surgery. Titanium (Ti) and PEEK (polyether ether ketone) were used as the material property for the cages. We applied the physiological motions at different loads from 0.5, 1, 1.5, 2.0 Nm to evaluate the dynamic cage design and the biomechanical performances of the designed S-type dynamic cage. It was observed that in all the loading condition the range of motion in the adjacent level was maintained and the maximum stress at the adjacent disc was reduced. The clinical significance of the S-type dynamic cage is better stress profile at the fusion level and adjacent segments which translates into higher rate of fusion, lower risk of cage subsidence, lower risk of adjacent segment degeneration, and good mechanical stability.


Assuntos
Discotomia , Titânio , Benzofenonas , Fenômenos Biomecânicos , Vértebras Cervicais/cirurgia , Análise de Elementos Finitos , Cetonas , Polímeros , Amplitude de Movimento Articular
12.
Nat Commun ; 12(1): 4731, 2021 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-34354053

RESUMO

Electrodermal devices that capture the physiological response of skin are crucial for monitoring vital signals, but they often require convoluted layered designs with either electronic or ionic active materials relying on complicated synthesis procedures, encapsulation, and packaging techniques. Here, we report that the ionic transport in living systems can provide a simple mode of iontronic sensing and bypass the need of artificial ionic materials. A simple skin-electrode mechanosensing structure (SEMS) is constructed, exhibiting high pressure-resolution and spatial-resolution, being capable of feeling touch and detecting weak physiological signals such as fingertip pulse under different skin humidity. Our mechanical analysis reveals the critical role of instability in high-aspect-ratio microstructures on sensing. We further demonstrate pressure mapping with millimeter-spatial-resolution using a fully textile SEMS-based glove. The simplicity and reliability of SEMS hold great promise of diverse healthcare applications, such as pulse detection and recovering the sensory capability in patients with tactile dysfunction.


Assuntos
Fenômenos Fisiológicos da Pele , Tato/fisiologia , Dispositivos Eletrônicos Vestíveis , Fenômenos Biomecânicos , Simulação por Computador , Eletrodos , Desenho de Equipamento , Dedos/fisiologia , Análise de Elementos Finitos , Humanos , Mecanorreceptores/fisiologia , Pressão , Processamento de Sinais Assistido por Computador , Razão Sinal-Ruído , Têxteis , Dispositivos Eletrônicos Vestíveis/estatística & dados numéricos
13.
Sci Rep ; 11(1): 16248, 2021 08 10.
Artigo em Inglês | MEDLINE | ID: mdl-34376802

RESUMO

The use of close-fitting PPE is essential to prevent exposure to dispersed airborne matter, including the COVID-19 virus. The current pandemic has increased pressure on healthcare systems around the world, leading to medical professionals using high-grade PPE for prolonged durations, resulting in device-induced skin injuries. This study focuses on computationally improving the interaction between skin and PPE to reduce the likelihood of discomfort and tissue damage. A finite element model is developed to simulate the movement of PPE against the face during day-to-day tasks. Due to limited available data on skin characteristics and how these vary interpersonally between sexes, races and ages, the main objective of this study was to establish the effects and trends that mask modifications have on the resulting subsurface strain energy density distribution in the skin. These modifications include the material, geometric and interfacial properties. Overall, the results show that skin injury can be reduced by using softer mask materials, whilst friction against the skin should be minimised, e.g. through use of micro-textures, humidity control and topical creams. Furthermore, the contact area between the mask and skin should be maximised, whilst the use of soft materials with incompressible behaviour (e.g. many elastomers) should be avoided.


Assuntos
Simulação por Computador , Máscaras/efeitos adversos , Dermatopatias/prevenção & controle , Face/anatomia & histologia , Análise de Elementos Finitos , Fricção , Humanos , Máscaras/normas , Dermatopatias/etiologia , Fenômenos Fisiológicos da Pele , Design Centrado no Usuário
14.
Sensors (Basel) ; 21(16)2021 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-34450940

RESUMO

In this paper, the possibility of using nonlinear ultrasonic guided waves for early-life material degradation in metal plates is investigated through both computational modeling and study. The analysis of the second harmonics of Lamb waves in a free boundary aluminum plate, and the internal resonance conditions between the Lamb wave primary modes and the second harmonics are investigated. Subsequently, Murnaghan's hyperelastic model is implemented in a finite element (FE) analysis to study the response of aluminum plates subjected to a 60 kHz Hanning-windowed tone burst. Different stages of material degradation are reflected as the changes in the third order elastic constants (TOECs) of the Murnaghan's model. The reconstructed degradations match the actual ones well across various degrees of degradation. The effects of several relevant factors on the accuracy of reconstructions are also discussed.


Assuntos
Ondas Ultrassônicas , Vibração , Animais , Simulação por Computador , Análise de Elementos Finitos , Ovinos , Tomografia
15.
Int J Oral Maxillofac Implants ; 36(4): 640-649, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34411203

RESUMO

PURPOSE: The aim of this study was to determine the effect of solid (one-piece) and two-piece abutments on the stress profile of narrow implants with marginal bone loss. MATERIALS AND METHODS: Solid and two-piece abutments were connected to a conical internal octagon-connection implant (3.3 mm in diameter, 10 mm in length) and restored with a single crown. Three-dimensional finite element analysis was used to simulate the stress distribution in implant models with different levels of marginal bone resorption (0, 1, 2, and 3 mm). The effect of the design variables under increased bone resorption scenarios, including abutment screw length and diameter, was assessed. Static loading was applied to determine the mechanical response of the implant and cortical and trabecular bone. RESULTS: Marginal bone resorption levels dominated the mechanical response under static loading conditions. A marginal bone loss of 3 mm significantly increased stress values in the implant vicinity and abutment screw. Both abutment designs displayed similar stress distribution in the surrounding bone, but lower stress values were observed in the implant body with two-piece abutments. The abutment screw length was more effective in the resultant stress, as the longer screws reduced the stress in the implants. CONCLUSION: Marginal bone resorption magnitude is the crucial parameter in biomechanics to determine the mechanical behavior. As bone loss increases, resultant stress around implants under mastication forces may lead to implant failure, regardless of abutment type.


Assuntos
Dente Suporte , Implantes Dentários , Fenômenos Biomecânicos , Projeto do Implante Dentário-Pivô , Implantes Dentários/efeitos adversos , Análise do Estresse Dentário , Análise de Elementos Finitos , Humanos , Estresse Mecânico
16.
Int J Oral Maxillofac Implants ; 36(4): e63-e71, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34411208

RESUMO

PURPOSE: This study aimed to investigate whether axial or radial functionally graded root analog implants can optimize the stress and strain distribution near the implant-bone interface in alveolar bone models under static loads using finite element analysis (FEA). MATERIALS AND METHODS: The 3D profile of the root analog implant was captured from a natural tooth in CBCT data. The implant was separated into different layers (3, 5, and 10 layers) to vary the Young modulus axially or radially. The variation in Young modulus was designed to be linear, exponential, or parabolic. Different occlusal loads were applied. The von Mises stress and strain were used to evaluate the system risk of failure. RESULTS: The difference in the numbers of layers had no significant effect on the alveolar bone. In the radial functionally graded implant models, the maximum von Mises stress of the alveolar bone decreased as the outer layer's elastic modulus increased; however, in the vertical functionally graded implants, this stress varied little. The maximum von Mises stress of the cancellous bone changed only slightly, from 2 to 5 MPa in all models. The maximum strain of the alveolar bone varied from 0.001478 mm to 0.003999 mm. Those FEA results were in line with previous findings. CONCLUSION: The functionally graded root analog implants show no significant biomechanical advantages over dense zirconia implants. Radial functionally graded root analog implants should optimize the peri-implant stresses and are biomechanically favorable for design.


Assuntos
Implantes Dentários , Fenômenos Biomecânicos , Simulação por Computador , Implantes Dentários/efeitos adversos , Análise do Estresse Dentário , Análise de Elementos Finitos , Humanos , Estresse Mecânico
17.
Int J Oral Maxillofac Implants ; 36(4): 715-722, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34411210

RESUMO

PURPOSE: To evaluate the influence of age and trabecular microstructure on peri-implant strain in aging and young mice models under compressive load. MATERIALS AND METHODS: Eighteen 4-week-old female C57BL/6 mice (n = 6) were subjected to a 1.2% calcium content diet (young normal calcium group), and 7-month-old mice (n = 12) were randomly subjected to 0.01% and 1.2% calcium content diets (aging low and normal calcium groups, respectively) for 3 weeks. Histomorphometric and microcomputed tomography (micro-CT) analyses were used to investigate local alveolar bone microstructure. One maxilla segment from each group was reconstructed using micro-CT images to highlight the trabecular microstructure. A finite element analysis based on a computational model of the maxilla segment was performed to investigate peri-implant strain. Implants with three different diameters (0.3, 0.4, and 0.5 mm) were analyzed in these models. RESULTS: The aging low calcium group showed worse cancellous microstructure in hematoxylin and eosin (HE) staining, significantly increased osteoclast numbers (P < .05), and reduced bone volume fraction and trabecular thickness compared with the aging normal calcium group (P < .05). However, the young normal calcium group presented no difference in trabecular microstructure and osteoclast numbers compared with the aging normal calcium group. The aging low calcium group demonstrated increased strain intensity compared with the aging normal calcium group, whereas the young normal calcium and aging normal calcium groups showed comparable strain magnitude. The strain intensity of peri-implant bone increased with worse cancellous microstructure. When the diameter increased from 0.3 mm to 0.4 mm, the percentages of pathologic overload decreased regardless of bone microstructure. CONCLUSION: Deteriorated bone microstructure induced by a low calcium diet determined higher strain intensity, whereas, whenever age had no significant effect on trabecular microstructure, consequently, there was no substantial influence on strain. An increase of implant diameters can improve the strain distribution. Clinical decision-making should take into consideration the patient-specific and site-specific trabecular microstructure in preoperative assessment.


Assuntos
Implantes Dentários , Envelhecimento , Animais , Fenômenos Biomecânicos , Implantes Dentários/efeitos adversos , Feminino , Análise de Elementos Finitos , Humanos , Maxila , Camundongos , Camundongos Endogâmicos C57BL , Microtomografia por Raio-X
18.
Med Biol Eng Comput ; 59(10): 2051-2061, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34431026

RESUMO

Modeling the mechanical behavior of soft tissue probe insertion remains a challenging endeavor due to involved interdependent phenomena comprising tissue nonlinear deformation, contact between the probe and the tissue, crack propagation, and viscoelastic effects. To that matter, cohesive elements allow simulating crack formation and propagation, which provides a promising path to modeling the mechanical behavior of probe insertion in soft tissues. As such, the aim of the present study was to investigate the feasibility of devising and integrating an algorithm in a finite element (FE) case study in efforts of reverse engineering the material properties of non-homogeneous soft tissues. A layered nonlinear tissue model with a cohesive zone was created in the commercial software ABAQUS. Material properties were iteratively modified via a hybrid gradient descent optimization algorithm: minimizing the resultant error to first find optimum Ogden's hyperelastic parameters, followed by obtaining the damage parameters. Perceived material properties were then compared to those obtained via experimental human cadaver testing. Under the investigated four-layered muscle model, numerical results overlapped, to a great extent, with six different force-insertion experimental profiles with an average error of [Formula: see text] 15%. The best profile fit was realized when the highest sudden force drop was less than 60% of the peak force. Lastly, the FE analysis revealed an increase in stiffness as the probe advanced inside the tissue. The optimization algorithm demonstrated its capability to reverse engineer the material parameters required for the FE analysis of real, non-homogeneous, soft tissues. The significance of this procedure lies within its ability to extract tissue material parameters, in real time, with little to no intervention or invasive experimental tests. This could potentially further serve as a database for different muscle layers and force-insertion profiles, used for surgeon and physician clinical training purposes.


Assuntos
Fenômenos Biomecânicos , Análise de Elementos Finitos , Dinâmica não Linear , Software , Elasticidade , Estudos de Viabilidade , Humanos , Modelos Biológicos , Estresse Mecânico
19.
Zhongguo Gu Shang ; 34(8): 732-7, 2021 Aug 25.
Artigo em Chinês | MEDLINE | ID: mdl-34423616

RESUMO

OBJECTIVE: To investigate the biomechanical effects of different bone cement diffusion patterns in the treatment of osteoporotic vertebral compression fractures. METHODS: One volunteer with L1 osteoporotic vertebral compression fracture was selected, male, aged 68 years old, heighed 172 cm, weighted 60 kg, and healthy before. CT scans were used from T10-L5, CT data was extracted with Mimics software, and Geomagic wrap and Solidworks were used to model, and the three-dimensional finite element model (T12-L2) of preoperative osteoporotic vertebral compression fractures in the thoracolumbar segment was established. Similarly, the situations of bone cement dispersion in vertebroplasty were simulated (the situations of bone cement dispersion had the three kinds, including the bone cement not contacts with upper and lower endplates, the bone cement only contacts with upper endplates, and the bone cement contacts with upper and lower endplates). According to different diffusion situations, five types of loads were applied to the model:upright, upright plus forward flexion, upright plus backward extension, upright plus left bending, upright plus right rotation. Meanwhile, the model was compared with the cementless lumbar spine model, and the deformation and stress distribution of each model under load were recorded and compared. RESULTS: After the establishing the finite element model of osteoporotic vertebral compression fracture in the thoracolumbar segment, it was found that the deformation of three different bone cement distribution models above was not significantly different. In L1 cancellous bone, the Von Mises stress of the cementless lumbar spine group was significantly higher than that of the cemented group. Among the three groups of different bone cement injection situations, the Von Mises stress in the group of bone cement contacts with upper and lower endplates was the lowest, followed by the group of bone cement only contacts with upper endplates, and the highest Von Mises stress was the group that bone cement contacts neither the upper or lower endplates. In the comparison of bone cement stress, the Von Mises stress in the group of bone cement contacts with upper and lower endplates was significantly higher than the other two groups (upright 12.375 MPa, upright plus forward flexion 16.411 MPa, upright plus backward extension 16.801 MPa, upright plus left bending 13.425 MPa, upright plus right rotation 13.014 MPa), and the Von Mises stress in the group of bone cement does not contact with upper and lower endplates was the lowest. CONCLUSION: The bone cement contact with both upper and lower endplates can effectively absorb and transfer the stress level brought by the load, reduce the stress level of cancellous bone, and reduce the possibility of refracture of the operative vertebral body.


Assuntos
Fraturas por Compressão , Fraturas da Coluna Vertebral , Vertebroplastia , Idoso , Cimentos Ósseos , Análise de Elementos Finitos , Fraturas por Compressão/cirurgia , Humanos , Masculino , Fraturas da Coluna Vertebral/cirurgia
20.
Med Sci Monit ; 27: e931969, 2021 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-34455415

RESUMO

BACKGROUND Midfoot deformity and injury can affect the internal pressure distribution of the foot. This study aimed to use 3D finite element and biomechanical analyses of midfoot von Mises stress levels in flatfoot, clubfoot, and Lisfranc joint injury. MATERIAL AND METHODS Normal feet, flatfeet, clubfeet (30 individuals each), and Lisfranc injuries (50 individuals) were reconstructed by CT, and 3D finite element models were established by ABAQUS. Spring element was used to simulate the plantar fascia and ligaments and set hyperelastic coefficients in encapsulated bone and ligaments. The stance phase was simulated by applying 350 N on the top of the talus. The von Mises stress of the feet and ankle was visualized and analyzed. RESULTS The von Mises stress on healthy feet was higher in the lateral metatarsal and ankle bones than in the medial metatarsal bone. Among the flatfoot group, the stress on the metatarsals, talus, and navicular bones was significantly increased compared with that on healthy feet. Among patients with clubfeet, stress was mainly concentrated on the talus, and stress on the lateral metatarsal and navicular bones was significantly lower. The von Mises stress on the fractured bone was decreased, and the stress on the bone adjacent to the fractured bone was higher in Lisfranc injury. During bone dislocation alone or fracture accompanied by dislocation, the von Mises stress of the dislocated bone tended to be constant or increased. CONCLUSIONS Prediction of von Mises stress distribution may be used clinically to evaluate the effects of deformity and injury on changes in structure and internal pressure distribution on the midfoot.


Assuntos
Pé Torto Equinovaro/fisiopatologia , Análise de Elementos Finitos/estatística & dados numéricos , Pé Chato/fisiopatologia , Traumatismos do Pé/fisiopatologia , Articulações do Pé/fisiopatologia , Artropatias/fisiopatologia , Estresse Mecânico , Adulto , Fenômenos Biomecânicos , Feminino , Seguimentos , Articulações do Pé/lesões , Humanos , Masculino , Prognóstico
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