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1.
Braz. j. oral sci ; 20: e214873, jan.-dez. 2021. ilus
Article in English | LILACS, BBO | ID: biblio-1254742

ABSTRACT

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


Subject(s)
Microscopy, Electron, Scanning , Computer-Aided Design , Dental Marginal Adaptation , Dental Prosthesis, Implant-Supported , Finite Element Analysis , Dental Materials
2.
São José dos Campos; s.n; 20210000. 66 p. ilus, graf.
Thesis in Portuguese | LILACS, BBO | ID: biblio-1358950

ABSTRACT

O presente trabalho teve como objetivos: (1) relatar uma série de casos e apresentar uma metodologia para medição de desgaste usando software de metrologia comparando dois tipos de materiais em blocos CAD-CAM (dissilicato de lítio e resina composta) usados para restaurações onlay; (2) avaliar, in silico, a distribuição de tensões de dois materiais restauradores, IPS emax CAD e Grandio Blocs, em dois tipos de desenho de preparo dentário para onlay envolvendo cúspides funcionais ou não funcionais. (1) O estudo clínico foi registrado para avaliação do comitê de ética local e foi realizado com voluntários que necessitaram de procedimento restaurador indireto, seguindo os critérios de inclusão/exclusão. Quatro restaurações do tipo onlay (IPS emax CAD e GrandioBlocs) foram confeccionadas pelo método CAD-CAM chairside por um único operador treinado. A alocação dos tratamentos foi feita de forma aleatória. Após a cimentação das restaurações, a avaliação foi feita por examinador calibrado, não sendo o operador, nos períodos de 7 dias, 6 meses e 1 ano. Neste estudo foi analisada a quantidade de desgaste das restaurações por software de medição de dados (Gom Inspect) com acompanhamento de 6 meses e 1 ano com 4 pacientes avaliados sendo 2 restaurações de GrandioBlocs e 2 para IPS emax CAD. O resultado foi representado por um mapeamento de cores onde cada tonalidade representa uma quantidade de desgaste. O resultado obtido pelas imagens foi insignificante mostrando leve diferença nas imagens com restauração de GrandioBlocs. (2) Os molares foram modelados em quatro desenhos de preparação para restauração onlay: preparo tradicional com cobertura da cúspide funcional (TFC), preparo não retentivo com cobertura da cúspide funcional (NFC), preparo tradicional com cobertura da cúspide não funcional (TNFC), preparo não retentivo com cobertura de cúspide não funcional (NNFC). As restaurações foram simuladas com dois materiais restauradores CAD / CAM: LD - dissilicato de lítio (IPS emax CAD) e RC - resina composta (GrandioBlocs). Uma carga axial de 100 N foi aplicada à superfície oclusal simulando o ponto de contato cêntrico. As tensões de Von Mises (VM) e as tensões principais máximas (Pmax) foram avaliadas tanto para restaurações onlay, camada de cimento e substrato dentário. O desenho do preparo não retentivo melhorou a concentração de tensões na estrutura dentária em comparação com o desenho retentivo convencional. Para as onlays LD, a distribuição de tensões na superfície interna da restauração mostrou que o desenho da preparação influenciou a distribuição de tensões, bem como a opção de cúspide preparada. O desenho do preparo não retentivo proporcionou melhor distribuição de carga em ambos os materiais restauradores e mais vantajoso para a estrutura dentária. A restauração de resina composta em cúspides não funcionais é recomendada quando a cúspide funcional está preservada, para ser mais conservadora.


The aim of the present study was (1) to report a series of cases and to present a methodology for measurement of wear using metrology software comparing two types of CAD-CAM materials (lithium disilicate and composite resin) used for onlay restorations; (2) to evaluate, in silico, the stress distribution of two restorative materials, IPS emax CAD and Grandio Blocs, in two types of dental preparation design for onlay involving functional or non-functional cusps. (1) The clinical study was registered for evaluation by the local ethics committee and was carried out with volunteers who needed an indirect restorative procedure, following the inclusion / exclusion criteria. Four onlay restorations (IPS emax CAD and Grandio Blocs) were made using the chairside CAD-CAM method by a single trained operator. The allocation of treatments was done at random. After the cementation of the restorations, the assessment was made by a calibrated examiner, not being the operator, in the periods of 7 days, 6 months and 1 year. In this study, the amount of wear of the restorations was analyzed by data measurement software with 6-month and 1-year follow-up with 4 patients evaluated, 2 of which were GrandioBlocs and 2 for , IPS emax CAD restorations. The result is represented by a color mapping where each shade represents a quantity of wear. The result obtained by the images was insignificant, showing a slight difference in the images with restoration of GrandioBlocs. (2) Molars were modeled in four preparation designs for onlay restoration: traditional design with functional cusp coverage (TFC), non- retentive design with functional cusp coverage (NFC), traditional design with non-functional cusp coverage (TNFC), non-retentive design with non-functional cusp coverage (NNFC). Restorations were simulated with two CAD-CAM restorative materials: LD - lithium-disilicate (IPS emax CAD) and RC - resin composite (GrandioBloc). A 100 N axial load was applied to the occlusal surface simulating the centric contact point. Von Mises (VM) and maximum principal (Pmax) stresses were evaluated for onlay restorations, the cement layer and the dental substrate. The non-retentive preparation design improved the stress concentration in the tooth structure in comparison to the conventional retentive design. For LD onlays, the stress distribution on the restoration intaglio surface showed that the preparation design influenced the stress distribution as well as the prepared cusp option. The design of non-retentive preparation provided better load distribution in both restorative materials and more advantageous for tooth structure. The resin composite restoration on non- functional cusp is recommended when functional cusp is preserved, in order to be more conservative.


Subject(s)
Ceramics , Computer-Aided Design , Composite Resins , Finite Element Analysis , Inlays
3.
São Paulo; s.n; 20210519. 205 p.
Thesis in Portuguese | LILACS, BBO | ID: biblio-1369382

ABSTRACT

No âmbito da Cirurgia Buco-Maxilo-Facial, a reconstrução de desarticulação / ressecção mandibular é considerada um dos procedimentos mais complexos, meticulosos e desafiadores; sendo que uma das principais causas para essas deformidades são as cirurgias ablativas mandibulares que ocorrem em decorrência do tratamento e manejo de tumores malignos (carcinomas/sarcomas), tumores benignos agressivos (ameloblastoma, mixoma, ceratocisto) e lesões traumáticas avulsivas (arma de fogo). A mandíbula define o contorno estético da face e estabelece a estrutura da cavidade oral permitindo a mastigação, fonação, deglutição. A reconstrução da desarticulação mandibular pode ser realizada com próteses tipo standard, enxerto ósseo autógeno livre ou vascularizado fixados com Sistemas bidimensionais de placas de titânio. Nesse trabalho foi desenvolvida uma proposta inovadora de desenho de prótese tridimensional personalizada de 0,6 milímetros de espessura, para reconstrução de desarticulação mandibular. São estabelecidos parâmetros fixos e personalizados, para proposta em manufatura em Ti6AL4V pelo processo Fusão por Feixe de Elétrons (EBM), Sinterização a Laser Direta em Metal (DLMS), ou Fusão Seletiva a Laser (SLM), conforme a regulamentação preconizada pela Agência Nacional de Vigilância Sanitária (ANVISA). A Prótese tridimensional condilar-mandibular personalizada (Prótese TC-MP) é composta de três partes: côndilo-ramo mandibular, scaffolds de reconstrução e fixação em três tamanhos (MD-1/FS-30mm, MD-2/FS-40mm, MD-3/FS-48mm), os modelos foram submetidos a análise de elementos finitos em quatro atividades estáticas de apertamento (API-Apertamento Incisal, APCPM-Apertamento Canino/Pré-Molares, APUMD-Apertamento Unilateral Molar Direito, APGFD-Apertamento Grupo Funcional Direito), para os seguintes parâmetros biomecânicos: micromovimentação máxima relativa entre a Prótese TC-MP e o osso; máxima Tensão de Von-Mises na Prótese TC-MP e os parafusos de fixação no osso; máxima Tensão e Deformação de Von-Mises em toda a mandíbula; máxima Tensão e Deformação de Von- Mises no osso cortical e esponjoso ao redor dos parafusos de fixação (8/MD-1, 10/MD-2, 12/MD-3); máxima tensão e Deformação de Von-Mises no ponto de união do scaffold de fixação com o scaffold de reconstrução. MD-2 apresentou os melhores resultados, comprovando a viabilidade do projeto com aplicação imediata.


Subject(s)
Finite Element Analysis
4.
Braz. dent. j ; 32(1): 34-41, Jan.-Feb. 2021. tab, graf
Article in English | LILACS, BBO | ID: biblio-1180717

ABSTRACT

Abstract The objective of this study was to compare the biomechanical behavior of peri-implant bone tissue and prosthetic components in two modalities of treatment for posterior region of the maxilla, using short implants or standard-length implants associated with bone graft in the maxillary sinus. Four 3D models of a crown supported by an implant fixed in the posterior maxilla were constructed. The type of implant: short implant (S) or standard-length implant with the presence of sinus graft (L) and type of crown retention: cemented (C) or screwed (S) were the study factors. The models were divided into SC- cemented crown on a short implant; SS- screwed crown on the short implant; LC- cemented crown on a standard-length implant after bone graft in the maxillary sinus and LS- crown screwed on a standard-length implant after bone graft in the maxillary sinus. An axial occlusal loading of 300 N was applied, divided into five points (60N each) corresponding to occlusal contact. The following analysis criteria were observed: Shear Stress, Maximum and Minimum Main Stress for bone tissue and von Mises Stress for the implant and prosthetic components. The use of standard-length implants reduced the shear stress in the cortical bone by 35.75% and the medullary bone by 51% when compared to short implants. The length of the implant did not affect the stress concentration in the crown, and the cement layer acted by reducing the stresses in the ceramic veneer and framework by 42%. Standard-implants associated with cemented crowns showed better biomechanical behavior.


Resumo O objetivo do estudo foi avaliar o comportamento biomecânico do tecido ósseo peri-implantar e dos componentes protéticos em duas modalidades de tratamento para região posterior da maxila, utilizando implantes curtos ou implantes de comprimento padrão associados a enxerto ósseo em seio maxilar. Foram construídos quatro modelos 3D de uma coroa suportada por um implante osseointegrado na região posterior da maxila. O tipo de implante: implante curto (S) ou implante de comprimento padrão com presença de enxerto sinusal (L) e tipo de retenção da restauração: cimentada (C) ou parafusada (S) foram os fatores de estudo. Foi aplicada uma força oclusal de 300N, dividida em cinco pontos (60 N cada) correspondentes ao contato oclusal de um primeiro molar superior. Foram observados os seguintes critérios de análise: tensão de cisalhamento, tensão principal máxima e mínima para o tecido ósseo e tensão de Von Mises para o implante e componentes protéticos. O uso de implantes de comprimento padrão reduziu a tensão de cisalhamento no osso cortical em 35,75% e no osso medular em 51% quando comparado aos implantes curtos. O comprimento do implante não afetou a concentração de tensão na restauração. A camada de cimento atuou reduzindo as tensões na cerâmica de cobertura e infraestrutura de cerâmica em 42%. Os implantes de tamanho padrão associados às coroas cimentadas apresentaram o melhor comportamento biomecânico.


Subject(s)
Dental Implants , Maxilla/surgery , Stress, Mechanical , Dental Prosthesis Design , Dental Prosthesis, Implant-Supported , Finite Element Analysis , Crowns , Dental Stress Analysis
5.
Rev. bras. ortop ; 56(1): 36-41, Jan.-Feb. 2021. tab, graf
Article in English | LILACS | ID: biblio-1288660

ABSTRACT

Abstract Objective To virtually prototype a device for external circular fixation of long bone fractures with controlled dynamization made of two different materials and predict their mechanical behavior by using the finite element analysis (FEA) method. Method A software was used for 3D modeling two metal parts closely attached by a sliding dovetail joint and a high-density silicone damper. Distinctive FEAs were simulated by considering two different materials (stainless steel or titanium), modes (locked or dynamized) and loading conditions (static/point or dynamic/0.5 sec) with uniform 150 kg axial load on top of the device. Results The finite elements (FEs) model presented 81,872 nodes and 45,922 elements. Considering stainless steel, the maximum stress peak (140.98 MPa) was reached with the device locked under static loading, while the greatest displacement (2.415 × 10−3 mm) was observed with the device locked and under dynamic loading. Regarding titanium, the device presented the maximum stress peak (141.45 MPa) under static loading and with the device locked, while the greatest displacement (3.975 × 10−3 mm) was found with the device locked and under dynamic loading. Conclusion The prototyped device played the role of stress support with acceptable deformation in both locked and dynamized modes and may be fabricated with both stainless steel and titanium.


Resumo Objetivo Construir um protótipo virtual de um dispositivo de fixação circular externa para fraturas em ossos longos com dinamização controlada a partir de dois materiais diferentes e prever seu comportamento mecânico por meio da análise de elementos finitos AEF). Método Modelos tridimensionais compostos de duas peças metálicas unidas por uma junta deslizante em rabo de andorinha e um amortecedor de silicone de alta densidade foram criados em um software. Análises de elementos finitos distintas foram simuladas considerando dois materiais (aço inoxidável ou titânio), modos (bloqueado ou dinamizado) e condições de carregamento (estático/pontual ou dinâmico/0,5 segundo) diferentes com carga axial uniforme de 150 kg na porção superior do dispositivo. Resultados O modelo de elementos finitos (EFs) apresentou 81.872 nós e 45.922 elementos. Com aço inoxidável, o pico de tensão máxima (140,98 MPa) foi alcançado com o dispositivo bloqueado e sob carga estática, enquanto o maior deslocamento (2.415 × 10−3 mm) foi obtido com o dispositivo bloqueado e sob carga dinâmica. Com titânio, o pico de tensão máxima (141,45 MPa) ocorreu com o dispositivo bloqueado e sob carga estática, enquanto o maior deslocamento (3.975 × 10−3 mm) foi observado com o dispositivo bloqueado e sob carga dinâmica. Conclusão O protótipo do dispositivo desempenhou o papel de suporte de tensão com deformação aceitável nos dois modos, bloqueado ou dinamizado, e pode ser fabricado com aço inoxidável ou titânio.


Subject(s)
Humans , Adult , Scoliosis/physiopathology , Scoliosis/therapy , Finite Element Analysis , Intervertebral Disc Degeneration
6.
Article in Chinese | WPRIM | ID: wpr-922049

ABSTRACT

OBJECTIVE@#A rapid fixation device is developed to solve the problems of emergency fixation and transportation of patients with spinal injury.@*METHODS@#Through the analysis of the function,3D modeling design, finite element analysis and optimization design based on ANSYS Workbench, tensile strength verification experiment, we produced the prototype, and tested it, conducted a simulated rescue experiment.@*RESULTS@#The fixation device designed can meet the demand of spinal injury patients for safe rescue after accidents, and the quality of the rapid fixation device was lighten by about 30% without reducing the intensity.@*CONCLUSIONS@#The method based on optimal design can obviously improve the structure design, and has reference significance for other related rescue equipment design.


Subject(s)
Equipment Design , Finite Element Analysis , Humans , Tensile Strength
7.
Journal of Biomedical Engineering ; (6): 1103-1110, 2021.
Article in Chinese | WPRIM | ID: wpr-921851

ABSTRACT

China is the country with high incidence of high myopia in the world. High myopia can cause severe vision impairment. So far, there is no effective treatment for high myopia in clinic. Scleral collagen cross-linking surgery has been proven to be effective in preventing animal eye axial elongation


Subject(s)
Animals , Collagen , Cross-Linking Reagents , Finite Element Analysis , Photosensitizing Agents , Riboflavin , Sclera
8.
Article in Chinese | WPRIM | ID: wpr-921825

ABSTRACT

The human spine injury and various lumbar spine diseases caused by vibration have attracted extensive attention at home and abroad. To explore the biomechanical characteristics of different approaches for lumbar interbody fusion surgery combined with an interspinous internal fixator, device for intervertebral assisted motion (DIAM), finite element models of anterior lumbar interbody fusion (ALIF), transforaminal lumbar interbody fusion (TLIF) and lateral lumbar interbody fusion (LLIF) are created by simulating clinical operation based on a three-dimensional finite element model of normal human whole lumbar spine. The fusion level is at L4-L5, and the DIAM is implanted between spinous process of L4 and L5. Transient dynamic analysis is conducted on the ALIF, TLIF and LLIF models, respectively, to compute and compare their stress responses to an axial cyclic load. The results show that compared with those in ALIF and TILF models, contact forces between endplate and cage are higher in LLIF model, where the von-Mises stress in endplate and DIAM is lower. This implies that the LLIF have a better biomechanical performance under vibration. After bony fusion between vertebrae, the endplate and DIAM stresses for all the three surgical models are decreased. It is expected that this study can provide references for selection of surgical approaches in the fusion surgery and vibration protection for the postsurgical lumbar spine.


Subject(s)
Biomechanical Phenomena , Finite Element Analysis , Humans , Lumbar Vertebrae/surgery , Pedicle Screws , Range of Motion, Articular , Spinal Fusion , Vibration
9.
Article in Chinese | WPRIM | ID: wpr-888348

ABSTRACT

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 T@*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 L@*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.


Subject(s)
Aged , Bone Cements , Finite Element Analysis , Fractures, Compression/surgery , Humans , Male , Spinal Fractures/surgery , Vertebroplasty
10.
Article in Chinese | WPRIM | ID: wpr-888335

ABSTRACT

OBJECTIVE@#To evaluate the biomechanical stability of elastic intramedullary nail in the treatment of pubic ramus fractures by finite element analysis, and to compare the stability of elastic intramedullary nail with cannulated screw intramedullary fixation.@*METHODS@#The CT data of the pelvis of a volunteer were selected, and the three-dimensional model of the pelvis was reconstructed by reverse engineering software and the fracture of the pubic ramus fractures was simulated by osteotomy. The hollow nail model, single elastic nail model and double elastic nailmodel were assembled with different implants respectively. The mesh division, material assignment loading and other steps were carried out in the ANSYS software, and then the calculation was submitted.@*RESULTS@#The overall displacement of the pelvis of the elastic nail model was smaller than that of the cannulated screw model, in which the double elastic nail model had the smallest overall displacement, but the cannulated screw model had the smallest plant displacement and the single elastic nail model had the largest plant displacement. Although the stress of cannulated screw was small, there was obvious stress concentration, the stress of elastic nail was large, but there was no obvious stress concentration, especially the stress distribution of double elastic nail was more uniform and the overall stress of pelvis was the smallest.@*CONCLUSION@#All the three fixation methods can effectively improve the stability of the anterior ring of the pelvis. Among them, there is no significant difference in the overall biomechanical propertiesof hollow nail fixation and double elastic nail fixation, which is better than that of single elastic nail fixation. Elastic nail fixation has the advantages of minimally invasive surgery and good biomechanical stability, so it can be used as a better surgical method for the treatment of pubic ramus fractures.


Subject(s)
Biomechanical Phenomena , Bone Screws , Finite Element Analysis , Fracture Fixation, Internal , Fracture Fixation, Intramedullary , Fractures, Bone/surgery , Humans , Spinal Fractures
11.
Article in Chinese | WPRIM | ID: wpr-888213

ABSTRACT

This study aims to overcome the shortcomings such as low efficiency, high cost and difficult to carry out multi-parameter research, which limited the optimization of infusion bag configuration and manufacture technique by experiment method. We put forward a fluid cavity based finite element method, and it could be used to simulate the stress distribution and deformation process of infusion bag under external load. In this paper, numerical models of infusion bag with different sizes was built, and the fluid-solid coupling deformation process was calculated using the fluid cavity method in software ABAQUS subject to the same boundary conditions with the burst test. The peeling strength which was obtained from the peeling adhesion test was used as failure criterion. The calculated resultant force which makes the computed peeling stress reach the peeling strength was compared with experiment data, and the stress distribution was analyzed compared with the rupture process of burst test. The results showed that considering the errors caused by the difference of weak welding and eccentric load, the flow cavity based finite element method can accurately model the stress distribution and deformation process of infusion bag. It could be useful for the optimization of multi chamber infusion bag configuration and manufacture technique, leading to cost reduction and study efficiency improvement.


Subject(s)
Finite Element Analysis , Software , Stress, Mechanical
12.
Article in English | WPRIM | ID: wpr-887757

ABSTRACT

OBJECTIVES@#The safety of root canal filling with 200 °C hot gutta-percha was investigated to study the effect of continuous wave technique combined with high-temperature injectable gutta-percha condensation technique on the surface temperature of periodontal tissue.@*METHODS@#CT technique and Mimics, Geomagic, and Solidworks software were utilized to build the entity models of alveolar bone, dentin and root canal, periodontal ligament, and blood flow, respectively, which were then assembled in Solidworks into a finite element model of tooth with blood flow. By utilizing ABAQUS collaborative simulation platform, fluid-structure coupling was analyzed on the whole process of root canal filling. Consequently, the surface temperature of the periodontal tissue was obtained.@*RESULTS@#In the absence of blood flow, the temperature of the periodontal ligament surface reached 50.048 ℃ during root canal filling with 200 ℃ gutta-percha. Considering blood flow, the temperature of periodontal ligament surface was 39.570 ℃.@*CONCLUSIONS@#The temperature of the periodontal ligament surface increased when the continuous wave root canal was filled with 200 ℃ gutta-percha, and the periodontal tissue was not damaged.


Subject(s)
Dental Pulp Cavity , Finite Element Analysis , Gutta-Percha , Hot Temperature , Humans , Periodontium , Root Canal Filling Materials , Root Canal Obturation , Temperature
13.
Article in Chinese | WPRIM | ID: wpr-879447

ABSTRACT

OBJECTIVE@#Using the method of finite element analysis, to compare the biomechanical properties between the plate deviating from the long axis of the cervical spine and the standard placement of the plate in the anterior cervical fusion surgery.@*METHODS@#A healthy female volunteer was selected and CT scan (C@*RESULTS@#The lower cervical spine (C@*CONCLUSION@#Little effect on the mechanical stability of the cervical spine was anticipated when the anterior cervical plate was not perfectly aligned with the long axis of the cervical spine. If the tilt of the plate in clinical surgery is less than 20°, there is no need to readjust the position of the plate.


Subject(s)
Biomechanical Phenomena , Cervical Vertebrae/surgery , Female , Finite Element Analysis , Humans , Range of Motion, Articular , Reproducibility of Results , Spinal Fusion
14.
Article in Chinese | WPRIM | ID: wpr-879403

ABSTRACT

OBJECTIVE@#To investigate the biomechanical affect of percutaneous transforaminal endoscopic discectomy(PTED) on adjacent segments with different degrees of degeneration and related risk of adjacent segment diseases (ASD) caused by this operation.@*METHODS@#A healthy male adult volunteer was selected, and the lumbosacral vertebra image data was obtained by CT scan, and the external contour of the bone structure was reconstructed. On this basis, the external contour of the bone structure was fitted by using the smooth curve in 3D-CAD software, and the complete three-dimensional finite element modelof the non degenerate L@*RESULTS@#In the finite element model without adjacent segmental disc degeneration, the annulus fibrosus von Mises stress and intradiscal pressure of the PTED model showed only a slight increase under most stress conditions, and a slight decrease in a few conditions, and there was no significant change trend before and after surgery. In the original degenerated adjacent segment disc model, the biomechanical indicators related to disc degeneration in the pre- and post-PTED model showed significant deterioration, leading to an increased risk of potential adjacent spondylopathy.@*CONCLUSION@#PTED surgery will not lead to the significant deterioration of postoperative biomechanical environment of non-degeneration adjacent intervertebral discs, and the original degeneration of adjacent intervertebral discs is a important risk factor for ASD.


Subject(s)
Adult , Biomechanical Phenomena , Diskectomy, Percutaneous , Finite Element Analysis , Humans , Intervertebral Disc/surgery , Intervertebral Disc Degeneration/surgery , Lumbar Vertebrae/surgery , Male , Range of Motion, Articular
15.
Article in Chinese | WPRIM | ID: wpr-879401

ABSTRACT

OBJECTIVE@#To establish a three-dimensional finite element model of osteoporosis and to study the stiffness recovery of injured vertebrae and stress analysis of adjacent vertebrae after percutaneous vertebroplasty under different perfusion and distribution conditions by simulating fluid flow into the vertebral body.@*METHODS@#A male healthy volunteer was selected. CT scans were performed from T@*RESULTS@#(1) The VonMises stress of T@*CONCLUSION@#Reliable biomechanical model of lumbar vertebral fracture can be established by using CT scanning data through software simulation. Vertebral fracture and vertebroplasty will cause biomechanical changes of adjacent vertebral bodies. With the increase of bone cement injection, the influence of biomechanical changes will increase significantly. Neighbouring vertebral fractures are more likely. For this experiment, percutaneous vertebroplasty has a suitable amount of cement injection of 4 ml.


Subject(s)
Biomechanical Phenomena , Bone Cements , Finite Element Analysis , Fractures, Compression/surgery , Humans , Lumbar Vertebrae/surgery , Male , Osteoporotic Fractures/surgery , Spinal Fractures/surgery , Vertebroplasty
16.
Article in Chinese | WPRIM | ID: wpr-879385

ABSTRACT

OBJECTIVE@#To explore biomechanical characteristics of minimally invasive different screw fixations in treating Sanders typeⅡcalcaneal fractures.@*METHODS@#Dicom data of calcaneus by CT scan were input into Mimics 21.0 software and Ansys15.0 software to construct three-dimensional finite element digital model of calcaneus;this model was input into UG NX 10.0 software, and calcaneus was cut according to Sanders classification to establish Sanders typeⅡ calcaneus model with posterior articular surface collapse;then simulated minimally invasive screw internal fixation after calcaneal fracture:a screw from posterior articular surface was used to outside-in fix sustentaculum tali, other 4 screws were used to fix calcaneus by different methods through calcaneal tuberosity, and 4 different calcaneal models were obtained. Under the same conditions, 4 types of internal fixation models were loaded respectively, and nonlinear finite element analysis was performed to calculate the stress distribution of different internal fixation models.@*RESULTS@#Under the same condition of loading, the model 3 had smaller displacement value, maximum calcaneus displacement value and maximum equivalent stress value of the screw than other three internal fixation models, and the stress was more dispersed.@*CONCLUSION@#In minimally invasive screw internal fixation of calcaneus fracture, after 1 sustentaculum tali screw fixation, 2 screws crossed fix posterior articular surface from calcaneal tuberosity, 2 screws fix parallelly calcaneocuboid joint from calcaneal tuberosity are more suitable for biomechanical requirements, and could provide basic theory for clinical treatment.


Subject(s)
Bone Screws , Calcaneus/surgery , Finite Element Analysis , Fracture Fixation, Internal , Fractures, Bone/surgery , Humans , Treatment Outcome
17.
Article in Chinese | WPRIM | ID: wpr-879383

ABSTRACT

OBJECTIVE@#To study mechanism of improvement of stress concentration on patellofemoral joint by stiletto needle releasing lateral patellar retinaculum guided by the theory of Jinshugu() and based on the finite element model of knee joint. and to elucidate the biomechanical mechanism of stiletto needle releasing changing patellar trajectory and reducing patellofemoral joint pressure.@*METHODS@#CT data of knee joint from a normal male (aged 29, heighted 171 cm, weighted 58 kg) was selected. Starting with construction of three-dimensional model of knee joint by using finite element software, the finite element model of knee joint with complete tendonand bone structures were established through several steps, such as geometric reconstruction, reverse engineering, meshing, material assignment and loading analysis. The loading condition was set as 500 N load on knee joint, and the average tensile stress of quadriceps femoris tendon was about 200 N. To simulate the release of lateral patellar retinaculum by stiletto needle at 30 and 90 position of knee flexion in finite element model separately, and to compare the improvement of stress concentration of patellofemoral joint by stiletto needle intervention under different knee flexion conditions.@*RESULTS@#The peak stress of patellofemoral joint and tibiofemoral joint decreased after stiletto needle releasing of patellofemoral lateral retinaculum compared with before intervention, which was(1) knee flexion at 30 degrees:patellar cartilage decreased by 0.498 MPa (decreased 9.06%), femoral trochlea decreased by 0.886 MPa(decreased 16.27%);(2) knee flexion at 90 degrees:patellar cartilage decreased by 0.558 MPa (decreased 8.6%), femoral trochlea decreasedby 0.607 MPa (decreased 9.94%).@*CONCLUSION@#Releasing lateral patellofemoral retinaculum with stiletto needle could effectively alleviate the stress concentration of patellofemoral joint and reduce local stress peak value, which it is helpful to improve patellar trajectory and make stress distribution more uniform.


Subject(s)
Adult , Biomechanical Phenomena , Finite Element Analysis , Humans , Knee Joint , Male , Patella , Patellofemoral Joint , Quadriceps Muscle , Range of Motion, Articular
18.
Article in Chinese | WPRIM | ID: wpr-879278

ABSTRACT

Lower extremity movement is a complex and large range of limb movement. Arterial stents implanted in lower extremity are prone to complex mechanical deformation, so the stent is required to have high comprehensive mechanical properties. In order to evaluate the mechanical property of different stents, in this paper, finite element method was used to simulate and compare the mechanical properties of six nitinol stents (Absolute Pro, Complete SE, Lifestent, Protégé EverFlex, Pulsar-35 and New) under different deformation modes, such as radial compression, axial compression/tension, bending and torsion, and the radial support performance of the stents was verified by experiments. The results showed that the comprehensive performance of New stent was better than other stents. Among which the radial support performance was higher than Absolute Pro and Pulsar-35 stent, the axial support performance was better than Complete SE, Lifestent and Protégé EverFlex stent, the flexibility was superior to Protégé Everflex stent, and the torsion performance was better than Complete SE, Lifestent and Protégé Everflex stent. The TTR2 type radial support force tester was used to test the radial support performance of 6 types, and the finite element analysis results were verified. The mechanical properties of the stent are closely related to the structural size. The result provides a reference for choosing a suitable stent according to the needs of the diseased location in clinical applications.


Subject(s)
Alloys , Femoral Artery , Finite Element Analysis , Lower Extremity , Mechanical Phenomena , Prosthesis Design , Stents , Stress, Mechanical
19.
Article in Chinese | WPRIM | ID: wpr-879277

ABSTRACT

In the study of oral orthodontics, the dental tissue models play an important role in finite element analysis results. Currently, the commonly used alveolar bone models mainly have two kinds: the uniform and the non-uniform models. The material of the uniform model was defined with the whole alveolar bone, and each mesh element has a uniform mechanical property. While the material of the elements in non-uniform model was differently determined by the Hounsfield unit (HU) value of computed tomography (CT) images where the element was located. To investigate the effects of different alveolar bone models on the biomechanical responses of periodontal ligament (PDL), a clinical patient was chosen as the research object, his mandibular canine, PDL and two kinds of alveolar bone models were constructed, and intrusive force of 1 N and moment of 2 Nmm were exerted on the canine along its root direction, respectively, which were used to analyze the hydrostatic stress and the maximal logarithmic principal strain of PDL under different loads. Research results indicated that the mechanical responses of PDL had been affected by alveolar bone models, no matter the canine translation or rotation. Compared to the uniform model, if the alveolar bone was defined as the non-uniform model, the maximal stress and strain of PDL were decreased by 13.13% and 35.57%, respectively, when the canine translation along its root direction; while the maximal stress and strain of PDL were decreased by 19.55% and 35.64%, respectively, when the canine rotation along its root direction. The uniform alveolar bone model will induce orthodontists to choose a smaller orthodontic force. The non-uniform alveolar bone model can better reflect the differences of bone characteristics in the real alveolar bone, and more conducive to obtain accurate analysis results.


Subject(s)
Biomechanical Phenomena , Computer Simulation , Finite Element Analysis , Humans , Models, Biological , Periodontal Ligament , Stress, Mechanical , Tooth Movement Techniques
20.
São José dos Campos; s.n; 2021. 99 p. ilus, graf, tab.
Thesis in Portuguese | LILACS, BBO | ID: biblio-1362094

ABSTRACT

Este estudo avaliou o efeito de 3 desenhos de preparos dentários para restaurações parciais indiretas de cobertura total na veracidade e precisão de modelos digitais obtidos por 3 escâneres intraorais; e na tensão de contração de polimerização residual por meio de análise de elementos finitos. Foram considerados os seguintes preparos: contendo redução de istmo (IST); sem redução de istmo (wIST) e preparo não retentivo (nRET). Para avaliação da veracidade e precisão, 10 varreduras foram realizadas em modelos referência de resina epóxi de contendo os dentes 45, 47 e com preparo no 46. Os modelos de referência digital foram obtidos usando um escâner industrial. Três escâneres intraorais foram comparados (n=10): Element 2 (ELE); Trios 3 (TRI); Primescan (PRI). A veracidade (µm) e a precisão (µm) foram analisadas em um software de sobreposição tridimensional. Os dados foram analisados utilizando os testes de Kruskal-Wallis e Dunn (α = 0,05). Para avaliar a tensão de contração, os preparos foram modelados em um dente 46 contendo: esmalte, dentina, cimento, restauração de cerâmica, polpa, ligamento periodontal, osso cortical e esponjoso. As interfaces foram consideradas coladas e os volumes considerados homogêneos, lineares e isotrópicos. A contração do cimento foi simulada e critério de Tensão Máxima Principal foi adotado para análise dos resultados. O preparo não retentivo obteve maior veracidade (3,8 µm) e precisão (2,7 µm) em comparação com os demais (veracidade = 6-7 µm, precisão = 4-5 µm). A veracidade foi menor no grupo ELE × IST (16), seguido por ELE × wIST (13 µm) e PRI × IST (7,8 µm). Não foi encontrada diferença entre os escâneres PRI e TRI (6 µm), com desempenho inferior para ELE (13 µm). As discrepâncias positivas foram maiores na proximal em IST e wIST. Os picos de tensão (MPa) de contração seguiram a seguinte sequência: restauração=IST (13,4) > wIST (9,3) > nRET (9); cimento=IST (16,9) > wIST (12,6) > nRET (10-7,5); dente=IST (10,7) > wIST (10,5) > (9). Conclui-se que o preparo nRET foi vantajoso para a redução da tensão de contração e para a obtenção de modelos com maior veracidade e precisão.


This study evaluated the effect of 3 preparations designs for full-coverage onlay on the accuracy of digital models obtained by intraoral scanners; and in the polymerization residual shrinkage stress by means of finite element analysis. The following preparations were evaluated: with isthmus preparation (IST); without isthmus preparation (sIST) and non-retentive preparation (nRET). For the evaluation of accuracy, 10 digital impressions were performed in a reference epoxy resin model from a lower hemiarch (teeth 45, 46 and 47) with a preparation on the teeth 46. The digital reference models were obtained using an industrial scanner. Three intraoral scanners were compared (n=10): Element 2 (ELE); Trios 3 (TRI); Primescan (PRI). Trueness (µm) and precision (µm) were analyzed using a three-dimensional superimposition software. Data were analyzed using Kruskal-Wallis and Dunn tests (α = 0.05). To assess the shrinkage stress, the preparations were modeled on a tooth #46 containing: enamel, dentin, cement, ceramic restoration, pulp, periodontal ligament, cortical and cancellous bone. The interfaces were considered bonded and the volumes as homogeneous, linear and isotropic. The cement shrinkage was simulated, and the Maximum Principal Stress criterion was adopted to analyze the results. The non-retentive preparation had greater trueness (3.8 µm) and precision (2.7 µm) compared to the others (trueness = 6-7 µm, precision = 4-5 µm). The trueness was lower in the ELE × IST (16), followed by ELE × wIST (13 µm) and PRI × IST (7.8 µm). No difference was found between PRI and TRI scanners (6 µm), with lower performance for ELE (13 µm). Positive discrepancies were greater in the proximal in IST and wIST. The stress (MPa) of followed the sequence: restoration=IST (13.4) > wIST (9.3) > nRET (9); cement=IST (16.9) > wIST (12.6) > nRET (10-7.5); tooth=IST (10.7) > wIST (10.5) > (9). It can be concluded that the nRET preparation was advantageous for reducing the contraction stress and for obtaining models with greater accuracy and precision.


Subject(s)
Stress, Mechanical , Finite Element Analysis , Data Accuracy , Inlays
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