Finite Element Method Comparison of Biomechanics Between Labial and Lingual Orthodontics Involved in Canine Retraction

Background: FEM is a mathematical method in which the shape of complex geometric objects and their physical properties are computer-constructed. Physical interactions of the various components of the model can then be calculated in terms of stress and strain, detailed information which is difficult to obtain by any other experimental or analytical means due to the interaction of anatomical structures with the surrounding tissue.. The aim is to Comparison of biomechanical differences by FEM between labial and lingual orthodontic mechanotherapy involved in canine retraction. Material & Methods: ANSYS software was preferred over others for the analysis. As ANSYS can import computer assisted designing (CAD) data and also enables to build geometry , In the current study, we have shown the simulated individual (sequential) canine retraction using the sliding(friction method) mechanics by an elastic component. Sliding mechanics was preferred over the closing loop mechanics (frictionless method). Results: Stress in the PDL and Alveolar bone were calculated and depicted. Conclusion: On retraction, the high stress was produced with the Labial system in the PDL and alveolar bone that gradually reduced on force degradation. On combined force application slight increase in stress was noticed.

Applications of Finite Element Methods in Foot and Ankle Biomechanics / 医用生物力学

Finite element method (FEM) has become an effective tool for biomechanical researches because of its high efficiency, accuracy and repeatability. Due to the complex anatomical structure and motion characteristics of foot and ankle, FEM can solve the problems that are difficult to be solved in real experiments with the help of powerful simulation modeling and data calculation ability, which has unique advantages and has been widely used. In this paper, the literatures on foot and ankle biomechanics using FEM at home and abroad in recent five years were summarized, and the following 4 aspects were reviewed: biomechanical analysis of foot and ankle under different motion states, researches on tissue characteristics, clinical treatment analysis, and researches on orthosis and shoes, so as to provide theoretical references for the study of foot and ankle biomechanics, as well as new ideas for the application and development of FEM in the field of foot and ankle biomechanics in the future.

Electromechanical Effects of Bone Remodeling Based on Edge Smoothed Finite Element Method / 医用生物力学

Objective Aiming at solving the problem of poor accuracy for numerical solution of traditional finite element method (FEM) in numerical analysis on piezoelectric effects of bone remodelling, a model with an edge-based smoothed FEM (ES-FEM) was proposed. Methods The bone model was discretized by triangular elements, and the smoothing domain was constructed based on edges of the existing mesh element. Based on gradient smoothing technique, the smoothed strain gradient and the smoothed electric field gradient were obtained, and the discrete equations of the system were constructed under the framework of smoothed Galerkin weakform. Results The changes of bone mineral density (BMD) and the distributions of electric potential under piezoelectric effects in the process of bone remodelling were reflected by using the above model. Compared with FEM, ES-FEM could improve the accuracy of simulation result for bone remodelling to a certain extent. Conclusions The proposed ES-FEM can simulate the process of bone remodelling more accurately. The accurate prediction for piezoelectric effect of bone reconstruction by this method provides an effective theoretical basis for clinical research of bone diseases.

Evaluation of stability of three different mini-implants, based on thread shape factor and numerical analysis of stress around mini-implants with different insertion angle, with relation to en-masse retraction force

ABSTRACT Objectives: Assess the stability of three different mini-implants, based on thread shape factor (TSF), and evaluate stresses at the mini-implant site and surrounding cortical bone on application of retraction force, at two different insertion angles. Methods: Mini-implants of three different diameters (M1 - Orthoimplant, 1.8mm), (M2 - Tomas, 1.6mm) and (M3 - Vector TAS, 1.4mm) and length of 8mm were used. Using scanning electronic microscopy, the mean thread depth, pitch and relationship between the two (TSF) were calculated. The mini-implants were loaded into a synthetic bone block and the pull-out strength was tested. One way ANOVA and Tukey post-hoc tests were used to compare the pull-out strength of mini-implants. P values < 0.05 were considered statistically significant. Finite element models (FEM) were constructed with insertion angulation at 90° and 60°, with retraction force of 150 g. The results were analyzed using ANSYS software. Results: Statistically significant difference was found among all the three mini-implants for thread depth and pitch (< 0.001). Statistically significant higher pull-out force value was seen for Orthoimplant. The stress distribution level in mini-implant and surrounding bone was observed to be smaller for Orthoimplant. Conclusion: Orthoimplant mini-implants have more favorable geometric characteristics among the three types, and less stress with 90°angulation.

RESUMO Objetivos: Avaliar a estabilidade de três diferentes tipos de mini-implantes, com base no fator formato da rosca (thread shape factor, TSF), e avaliar a tensão no local de inserção e no osso cortical ao redor dos mini-implantes inseridos com dois ângulos diferentes, durante a aplicação de força para retração. Métodos: Foram usados três diferentes diâmetros de mini-implantes, sendo eles 1,8 mm (M1, ORTHO Implant), 1,6 mm (M2, Tomas) e 1,4 mm (M3, Vector TAS), todos com comprimento de 8 mm. Por meio da microscopia eletrônica de varredura, foram calculados a profundidade da rosca, o passo da rosca (distância entre os filetes da rosca) e a relação entre os dois (TSF). Para realização do teste de tração (pull-out), os mini-implantes foram inseridos em um bloco de osso sintético. Os testes ANOVA de uma via e post-hoc de Tukey foram usados para comparar as forças de resistência à tração dos mini-implantes, considerando-se estatisticamente significativos valores de p< 0,05. Modelos de elementos finitos (MEF) foram gerados com ângulos de inserção dos mini-implantes a 90° e 60°, com força de retração em 150g. Os resultados foram analisados usando-se o software ANSYS. Resultados: Diferenças estatisticamente significativas foram encontradas entre os três mini-implantes quanto à profundidade da rosca e o passo da rosca (p< 0,001). O ORTHO Implant apresentou a maior força de resistência à tração, com significância estatística. O nível de distribuição das tensões no mini-implante e no osso circundante também foi menor para o ORTHO Implant. Resultados: Entre os diferentes tipos de mini-implantes analisados, o ORTHO Implant apresentou as características geométricas mais favoráveis e a menor tensão com o ângulo de inserção de 90°.

Review on the Progress in Development of Finite Element Models for Functional Spinal Units: Focus on Lumbar and Lumbosacral Levels

@#Functional spinal unit (FSU) has been of major interest in research related to the human spine as it is the simplest entity of spine that is believed to provide vital information useful in analyzing the biomechanics of the spine. In-vitro experiments and in-vivo tests are implemented for this purpose, but due to many restraints in using them, the use of an alternate approach such as Finite Element Analysis (FEA) seems preferential. FEA offers an edge in evaluating significant parameters that may or may not be possible through experiments. The finite element analysis of FSU’s has evolved to handle complexity with the increase in computing capacity and advancement in the software packages. This paper reviews the progress in the development of finite element analysis of FSU’s and also focuses on the application of FEA to analyse the lumbar (L1-L5) and lumbosacral (L5-S1) levels of the spine where spinal disorders are more prevalent.

Study on finite element modeling approach of mandible with full dentition based on CBCT images / 实用口腔医学杂志

Objective: To explore an efficient method for the establishment of 3D finite element model based on CBCT images. Methods: Mandible of a male volunteer was scanned by CBCT, and the resulting DICOM data was used for 3D reconstruction in Mimics17 software. Then with the. stl format file, the result of 3D reconstruction was imported into Geomagic Warp 2015, in which 3D models consisting of triangular patches for dentition, periodontal ligament and alveolar bone were created. With free meshing algorithm, the 3D finite element model of mandible with full dentition consisting of 10-node tetrahedron elements was obtained under the constraint that the maximum inner angle was set to be 25°. Results: The 3D finite element model for human mandible with full dentition was established. The total number of nodes is 299286, the elements number for dentition, periodontal ligament and alveolar bone are105805, 122427 and 577529, respectively. Conclusion: The proposed method can be used for the establishment of 3D finite element model of mandible with full dentition based on CBCT images, and it has the merits of good stability, high precision and wide application compared with the traditional modeling method.

Finite element analysis of cornea deformation and curvature change during the keratoplasty suturing process

Keratoplasty, which is cornea transplant surgery, is one of the treatment methods for patients with turbidity or keratitis. Recently, keratoplasty using a surgical robot was studied to increase precision. In this study, the effect of surgical factors on the deformation and curvature of the cornea were analyzed in order to improve the accuracy of keratoplasty and derive the optimal surgical factors using finite element method (FEM). Suturing tension and depth were selected as surgical factors. An FEM model, a constitutive equation, and boundary conditions were determined using experiments and reference data. Suturing tension significantly impacted deformation and curvature change, and suturing depth affected the position of the thread-cornea contact point. Both factors have a significant impact on a focal point in the retina and the patient's visual acuity after keratoplasty.

Platelet-rich plasma combined with surgical hip joint dislocation:An effective option for femoral head necrosis in the peri-collapse stage / 医学研究生学报

Objective Reports are rarely seen about the application of platelet-rich plasma (PRP) combined with surgical dislocation of head and neck fenestration (HNF) in the treatment of osteonecrosis of the femoral head (ONFH) in the peri-collapse stage. The purpose of this study was to investigate the clinical effects of PRP combined with surgical dislocation of HNF in the treatment of ONFH. Methods Using PRP combined with surgical dislocation of HNF,we treated 18 ONFH patients with 22 hips involved,in-cluding 7 cases of ARCO stage Ⅱc,10 cases of stage Ⅲa,and 5 cases of stage Ⅲb, and followed them up for 12.40±3.12 months. We evaluated the clinical results and compared the Harris scores and radiographic manifestations obtained before and after surgery. Results The overall Harris scores of the patients at 12 months after surgery were significantly higher than the baseline(86.84±6.44 vs 73.73±5.42,P=0.04),(87.73±2.43 vs 74.23±7.30,P<0.05) in the stageⅡc group,(85.22±7.63 vs 72.82±5.31,P<0.05) in the stageⅢa group,and(78.86±5.91 vs 69.37±6.13,P<0.05) in the stageⅢb group. The rate of excellence was 90.91% and that of im-provement was 95.45%.There were no such postoperative complications as nonunion,infection,or osteothrombosis. Conclusion PRP com-bined with surgical dislocation of HNF exhibited an excellent short-term effect in the treatment of ONFH in the peri-collapse stage, which has provided a new option for the management of the disease.

Design and experimental study of new type of external fixation device for bone fracture / 医疗卫生装备

Objective To design a new type of external fixator for bone fracture and verify its rationality and feasibility. Methods The frame and screw of stainless steel achieved fracture fixation in vitro with a threaded locking structure.At the same time the increasing thickness of body frame, the inclined nail holes and the raised bottoms were designed to greatly enhance the strength and overall stability of body frame.FEM (finite element method),measuring the relative displacement and stress distribution after axial load,was used to verify the rationality of the design.An animal experiment with sheep was used to verify the feasibility of fracture treatment. Results Simulated result of FEM indicated that the biggest relative displacement between the separated bones was 0.04 mm,which was much less than the minimum value 1 mm required for fracture healing.The maximum stresses applied on the frame of the fixator,fixator screw,and bone were 35,26,and 6 MPa, respectively, which was much less than the allowable stress. In the animal experiment, fracture site was fixed firmly after operation and was well cured 3 months later.Conclusion The design of this new device is feasible and it can be used as a new method of fracture treatment.

Simulation Platform of Photoacoustic Imaging Based on Finite Element and -space Pseudospectral Method / 中国医疗器械杂志

Numerical simulation is a powerful technology for photoacoustic imaging (PAI) in both theory studies and practical applications. In this paper, a simulation platform for PAI was designed and implemented based on Matlab. The simulation platform utilized finite element method (FEM) and -space pseudospectral method to calculate the forward and inverse problem of PAI. And a graphical user interface (GUI) was realized. Structural design, work process and other operating details of the platform was also provided. By compared with theoretical temporal waveform of photoacoustic signal and reconstruction results of COMSOL, the validity and reliability was verified. And a reliable simulation tool was proposed for PAI.

Progress of Finite Element Method Applied in Biomechanical Researches on Lumbar Fusion and Replacement / 医用生物力学

The research progress of finite element method (FEM) applied in biomechanics of lumbar fusion and artificial lumbar disc replacement was reviewed and its prospect was forecasted. The main research directions of FEM are optimal selection of operation plans before the surgery, performance evaluation of implanted devices and prediction of postoperative outcomes. Based on the recent research progress, the application prospects of FEM in simulation of personalized surgery, evaluation of elastic implants and postoperative prediction of novel operation method were discussed. By reviewing and prospecting the application of FEM in biomechanical research of lumbar fusion and artificial lumbar disc replacement, the purpose of this paper is to provide theoretical references and practical guidance for the treatment of lumbar diseases in clinic.

Research progress and application of head finite element model / 医用生物力学

The finite element method (FEM) is a technology for numerical analysis which based on the development of the electronic computer,and also a more advanced biomechanical research method.Early FEM was applied in the fields of engineering science and technology.In recent years,FEM has been widely used for brain research in biomedical engineering.With the rapid development of traffic and transportation,the high incident of craniocerebral injury has become a serious threat to human health year by year.The biomechanical mechanism of craniocerebral injury can be well researched by establishing the finite element model of human head.In this review,establishment,development and application of human head finite element model are summarized,and the future research direction is discussed as well.

Research progress and application of head finite element model / 医用生物力学

The finite element method (FEM) is a technology for numerical analysis which based on the development of the electronic computer, and also a more advanced biomechanical research method. Early FEM was applied in the fields of engineering science and technology. In recent years, FEM has been widely used for brain research in biomedical engineering. With the rapid development of traffic and transportation, the high incident of craniocerebral injury has become a serious threat to human health year by year. The biomechanical mechanism of craniocerebral injury can be well researched by establishing the finite element model of human head. In this review, establishment, development and application of human head finite element model are summarized, and the future research direction is discussed as well.

Three-dimensional finite element analysis of angled abutments in anterior maxilla implant restoration / 西安交通大学学报(医学版)

Objective To explore the effects of angled abutments on the anterior maxilla implant restoration. Methods We analyzed the biomechanical properties of implants of different sizes (Φ3.5 mm,4.0 mm and 4.5 mm in diameter;L11.5 mm and L13 mm in length)after connecting different angled abutments (0°,10°,20°,and 30°) using finite element method.Results The stresses and strains of loading parts of restorations increased and their distribution became more concentrated as the angle of abutment increased.Cortical bone of Φ3 .5 implants with smaller angle (10°or less)andΦ4.0 implants with abutments had the risk of overpassing the bone elastic threshold when the angle approached 30°.However,the cortical bone elastic deformation was within a safe range at all angles inΦ4.5 group.Conclusion We should consider the diameter of the implant when selecting angled abutments.The angled abutments are not suitable for small diameter implants.The bite force should be under control when needed. The larger angled abutments can be applied in the standard and major diameter implants and it is necessary to avoid occlusal overloading.

Modal and Vibration Analysis of Functionally Graded Dental Implant.

Dental implant is considered to be the best treatment when dealing with the loss of teeth. It gives beautiful results and can last longer than most of other treatments. Since the Osseo-integration period is a critical period for implant stability, so the used material for dental implant is one of the most factors affecting the stability and Functionally Graded Material (FGM) is one of the opportunities to improve it. The aim of this research is to carry out modal analysis and vibration analysis analytically for functionally graded Dental Implant. In this study several models for dental implant was analyzed by ANSYS15.0 APDL. The functionally graded material was considered in three models. The same materials, Ti-HA, where used in all of them but with different ratio in each. The natural frequency and mode shapes were extracted for all models. The frequency responses of functionally graded Dental Implant after performing a static analysis for each modal have been studied. It was noticed using modal analysis that all of the extracted results for FGM are vary between the two basic materials and it is affected by the concentration of each. It is firmly believed that FGM is the future of dental implant due to the ability of designing a specific material property to be more stable. A comparison of the materials that utilized in FGM when the ration of each 100% was performed as well as an evaluation for the classical dental implant. It is firmly believed that FGM is the future of dental implant due to the ability of designing a specific material property to be more stable.

Diseño mecánico de un exoesqueleto para rehabilitación de miembro superior / Mechanical design of an exoskeleton for upper limb rehabilitation

El ritmo de vida actual, tanto sociocultural como tecnológico, ha desembocado en un aumento de enfermedades y padecimientos que afectan las capacidades físico-motrices de los individuos. Esto ha originado el desarrollo de prototipos para auxiliar al paciente a recuperar la movilidad y la fortaleza de las extremidades superiores afectadas. El presente trabajo aborda el diseño de una estructura mecánica de un exoesqueleto con 4 grados de libertad para miembro superior. La cual tiene como principales atributos la capacidad de ajustarse a la antropometría del paciente mexicano (longitud del brazo, extensión del antebrazo, condiciones geométricas de la espalda y altura del paciente). Se aplicó el método BLITZ QFD para obtener el diseño conceptual óptimo y establecer adecuadamente las condiciones de carga de servicio. Por lo que, se definieron 5 casos de estudio cuasi-estáticos e implantaron condiciones para rehabilitación de los pacientes. Asimismo, mediante el Método de Elemento Finito (MEF) se analizaron los esfuerzos y deformaciones a los que la estructura está sometida durante la aplicación de los agentes externos de servicio. Los resultados presentados en éste trabajo exhiben una nueva propuesta para la rehabilitación de pacientes con problemas de movilidad en miembro superior. Donde el equipo propuesto permite la rehabilitación del miembro superior apoyado en 4 grados de libertad (tres grados de libertad en el hombro y uno en el codo), el cual es adecuado para realizar terapias activas y pasivas. Asimismo, es un dispositivo que está al alcance de un mayor porcentaje de la población por su bajo costo y fácil desarrollo en la fabricación.

The pace of modern life, both socio-cultural and technologically, has led to an increase of diseases and conditions that affect the physical-motor capabilities of persons. This increase has originated the development of prototypes to help patients to regain mobility and strength of the affected upper limb. This work, deals with the mechanical structure design of an exoskeleton with 4 degrees freedom for upper limb. Which has the capacity to adjust to the Mexican patient anthropometry (arm length, forearm extension, geometry conditions of the back and the patient's height) BLITZ QFD method was applied to establish the conceptual design and loading service conditions on the structure. So, 5 quasi-static cases of study were defined and conditions for patient rehabilitation were subjected. Also by applying the finite element method the structure was analyzed due to service loading. The results presented in this work, show a new method for patient rehabilitation with mobility deficiencies in the upper limb. The proposed new design allows the rehabilitation of the upper limb under 4 degrees of freedom (tree degrees of freedom at shoulder and one at the elbow), which is perfect to perform active and passive therapy. Additionally, it is an equipment of low cost, which can be affordable to almost all the country population.

Species Identification Based on Morphological Variability of Femur / 法医学杂志

Objective To study the morphological characteristics of femurs of adult human and 11 kinds of adult animals fromcattle, horses, pigs, goats, sheep, dogs, cats, rabbits, geese, ducks, chickens, and to establish an effective species identification method among various species. Methods The 4 cmmid-dia-physeal segment of the femur fromadult human (older than 20 years old) at autopsy w as obtained. Addi-tionally, the 4 cmones from11 kinds of adult animals w ere obtained. After decalcification, all femurs w ere made into slices, and then w ere observed by optical microscope. The 25 indexes w ere selected and analyzed by step discriminant analysis according to differences betw een human and mammal, human and poultry, and human and 11 kinds of animals. Results The histological structure of bone mineral density of middle part of femur had obvious characteristics among the species. And the morphology and number of osteon show ed the trend of obvious biological evolution. There w ere 11 indexes w ith significant differ-ences betw een human and 11 kinds of animals to establish some mathematical models to discriminate all species. The correct discrimination rate w as 96.3% betw een human and mammal. The correct discrimina-tion rate w as up to 100% betw een human and poultry, and w as 89.4% among human, mammal and poultry. Conclusion The mathematical models have good correct discrimination rate among human and the other animals, w hich could be applied in the practical species identification cases.

Apical stress distribution on maxillary central incisor during various orthodontic tooth movements by varying cemental and two different periodontal ligament thicknesses: A FEM study.

Context: During fixed orthodontic therapy, when the stress levels in the periodontal ligament (PDL) exceedsan optimum level, it could lead to root resorption. Aims: To determine an apical stress incident on the maxillary central incisor during tooth movement with varying cemental and periodontal ligament thickness by Finite Element Method (FEM) modeling. Settings and Design: A three dimensional finite element model of a maxillary central incisor along with enamel, dentin, cementum, PDL and alveolar bone was recreated using EZIDCOM and AUTOCAD software. ALTAIR Hyper mesh 7.0 version was used to create the Finite Element meshwork of the tooth. This virtual model was transferred to Finite Element Analysis software, ANSYS where different tooth movements were performed. Materials and Methods: Cemental thickness at the root apex was varied from 200 μm to 1000 μm in increments of 200 μm. PDL thickness was varied as 0.24 mm and 0.15 mm. Intrusive, Extrusive, Rotation and Tipping forces were delivered to determine an apical stress for each set of parameters. Results: Results indicated that an apical stress induced in the cementum and PDL, increased with an increase in cementum and PDL thickness respectively. Apical stress induced in the cementum remained the same or decreased with an increase in the PDL thickness. Apical stress induced in the PDL decreased with an increase in the cementum thickness. Conclusion: The study concluded that the clinical delivery of an orthodontic forces will cause stress in the cementum and PDL. Hence, it is necessary to limit the orthodontic force to prevent root resorption.

A 3-D Analysis To Study The Center of Resistance Modification With Alveolar Bone Resorption - A Finite Element Method.

The aims of this investigation were to define the modified location of CRES and CROT in a maxillary central incisor with different alveolar bone heights. A three dimensional finite element model of the upper central incisor with its supporting structures was created using ANSYS software on a PIII computer. Five three dimensional models of an upper central incisor with 1 to 6.5 mm of alveolar bone loss were formulated and used by the author. Center of resistance and center of rotation were located for the various stages of alveolar bone loss. The results revealed that the moment/force ratio (at the bracket level) required to produce bodily movement increases in association with alveolar bone loss. Bone loss causes center of resistance movement towards the apex, but its relative distance to the alveolar crest decreases at the same time. Greater amounts of displacements of incisal edge and apex were observed with increased alveolar bone loss for a constant applied force. Center of rotation of the tipping movement also shifted towards the cervical line. Among the many differences between orthodontic treatment of an adolescent and an adult patient is the presence of alveolar bone loss in the adult cases. Alveolar bone loss causes change in center of resistance as a result of alteration in bone support. This necessitates modifications in the applied force system to produce the same movement as in a tooth with a healthy supporting structure.

Embryonal rhabdomyosarcoma of the adult soft palate.

Embryonal rhabdomyosarcoma is the most common soft tissue sarcoma in children. We report a rare case of embryonal rhabdomyosarcoma of the soft palate in a 32-year-old Caucasian female. Detailed histology of the tumor is described. Positive staining with desmin, myogenin and myoD1 confirmed the tumor to be embryonal rhabdomyosarcoma. A genetic association between rhabdomyosarcoma, polycystic ovary syndrome and the FEM1A gene on the human chromosome is speculated upon.