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Objective To study fluid flow within alveolar bone under orthodontic and occlusal loading, so as to provide references for understanding the regulatory mechanism of bone remodeling during orthodontics. Methods An animal model for orthodontic tooth movement on rats was first constructed. The finite element model of tooth-periodontal ligament-alveolar bone was established based on micro-CT images and the strain field in alveolar bone under orthodontic or constant occlusal loading was analyzed. Then finite element model of alveolar bone was constructed from the bone near the cervical margin or apical root of mesial root. The fluid flow in this model under orthodontic and cyclic occlusal loading was further predicted by using fluid-solid coupling numerical simulation. Results The fluid velocity within alveolar bone cavity mainly distributed at 0-10 μm/s, and the fluid shear stress (FSS) was mainly distributed at 0-10 Pa. FSS on the surface of alveolar bone near the apical root was higher than that close to the cervical margin. Conclusions FSS at different levels could be produced at different location within alveolar bone cavity under orthodontic and cyclic occlusal loading, which might further activate biological response of bone cells on the surface of trabeculae and finally regulate the remodeling of alveolar bone and orthodontic movement of tooth. The results provide theoretical guidance for the clinical treatment of orthodontics.
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Fluid shear stress (FSS) caused by interstitial fluid flow within trabecular bone cavities under mechanical loading is the key factor of stimulating biological response of bone cells. Therefore, to investigate the FSS distribution within cancellous bone is important for understanding the transduction process of mechanical forces within alveolar bone and the regulatory mechanism at cell level during tooth development and orthodontics. In the present study, the orthodontic tooth movement experiment on rats was first performed. Finite element model of tooth-periodontal ligament-alveolar bone based on micro computed tomography (micro-CT) images was established and the strain field in alveolar bone was analyzed. An ideal model was constructed mimicking the porous structure of actual rat alveolar bone. Fluid flow in bone was predicted by using fluid-solid coupling numerical simulation. Dynamic occlusal loading with orthodontic tension loading or compression loading was applied on the ideal model. The results showed that FSS on the surface of the trabeculae along occlusal direction was higher than that along perpendicular to occlusal direction, and orthodontic force has little effect on FSS within alveolar bone. This study suggests that the orientation of occlusal loading can be changed clinically by adjusting the shape of occlusal surface, then FSS with different level could be produced on trabecular surface, which further activates the biological response of bone cells and finally regulates the remodeling of alveolar bone.
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Objective To study the effect of sand therapy on the hemodynamics of flexural femoral artery, and further reveal the therapeutic mechanism of sand therapy from the perspective of hemodynamics. Methods The three-dimensional finite element model of the curved femoral artery was established based on CT images of human aorta, and the data of heart rate, peak blood flow velocity and inner diameter of femoral artery measured by the experiment were used as initial conditions and boundary conditions to carry out finite element numerical simulation. The blood flow velocity, pressure and wall shear stress before and after sand therapy were analyzed and compared under fluid-solid coupling condition. Results Compared with treatment before sand therapy, the longitudinal velocity of the flexural segment of blood vessel increased significantly, with an increase of 22.76%. The secondary reflux velocity decreased significantly, with a relative decrease of 18.26%. The wall shear stress decreased by 2.01% after sand therapy. Conclusions Sand therapy had a significant effect on blood fluidity, by improving blood flow of femoral arteries, and preventing deposition of arterial platelets. The transverse flow phenomenon was obviously weakened after sand therapy, which could avoid the deposition of substances in blood and had a positive effect on the prevention of atherosclerosis, thrombosis and other vascular diseases.
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Objective To study the effect of sand therapy on the hemodynamics of flexural femoral artery, and further reveal the therapeutic mechanism of sand therapy from the perspective of hemodynamics. Methods The three-dimensional finite element model of the curved femoral artery was established based on CT images of human aorta, and the data of heart rate, peak blood flow velocity and inner diameter of femoral artery measured by the experiment were used as initial conditions and boundary conditions to carry out finite element numerical simulation. The blood flow velocity, pressure and wall shear stress before and after sand therapy were analyzed and compared under fluid-solid coupling condition. Results Compared with treatment before sand therapy, the longitudinal velocity of the flexural segment of blood vessel increased significantly, with an increase of 22.76%. The secondary reflux velocity decreased significantly, with a relative decrease of 18.26%. The wall shear stress decreased by 2.01% after sand therapy. Conclusions Sand therapy had a significant effect on blood fluidity, by improving blood flow of femoral arteries, and preventing deposition of arterial platelets. The transverse flow phenomenon was obviously weakened after sand therapy, which could avoid the deposition of substances in blood and had a positive effect on the prevention of atherosclerosis, thrombosis and other vascular diseases.
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Objective To study the two-phase flow dynamics distribution and red blood cell distribution under the fluid-solid coupling interaction in left coronary artery at the typical time point within one cardiac cycle,and to investigate the formation and development mechanisms of left coronary artery atherosclerotic plaque Methods The blood was regarded as a two-phase fluid.Based on fluid-solid interaction between blood and vascular wall,the computational fluid dynamics method was used to make the transient numerical simulation of two-phase flow in the left coronary artery under fluid-solid interaction;the distribution of blood flow in the left coronary artery at the typical time point within one cardiac cycle was studied,the relationship between hemodynamic parameters and the formation of atherosclerotic plaque was analyzed.Results A lowspeed eddy zone existed in an area between the distal segment of circumferential branch and the proximal outside of blunt-edge branch of the left coronary artery,where both internal wall shear stress and red blood cell volume fraction were very small and the blood flow pattern was very complicated.Conclusion At the lowspeed eddy zone that carries small wall shear stress,the lipid concentration polarization and macromolecular material deposition are easy to be produced.The area that has less red blood cells is liable to develop hypoxia,resulting in increased vascular wall permeability and intimal injury,which will activate the immune system,causing lipid accumulation in vascular wall and intimal hyperplasia and,thus,to induce the formation of atherosclerotic plaque.(J Intervent Radiol,2017,26:253-257)
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Objective To investigate the effects of Uyghur indoor sand therapy on the hemodynamics of femoral artery bidirectional fluid-solid coupling,and to discuss the influence of Uyghur indoor sand therapy on the formation of atherosclerosis as well as on the rupture of blood vessels.Methods This study of indoor Uyghur sand therapy was conducted in young healthy volunteers.The heart rate,peak value of femoral artery blood flow velocity and inner diameter were determined,and the results were statistically analyzed.Three dimensional fluid-solid coupling model of human femoral artery was reconstructed.Taking the sine function as the initial condition,the non-steady field bidirectional fluid-solid coupling simulation was conducted by using Fluent software,and the effect of indoor Uyghur sand therapy on femoral artery wall shear stress as well as on yon Mises equivalent stress was evaluated.Results The average heart rates before and after indoor Uyghur sand therapy were (76.32±11.40) beats per minute and (92.69±16.09) beats per minute respectively,the difference was statistically significant (P＜0.05).The Renolds number of femoral artery before and after indoor Uyghur sand therapy was 1855.35 and 2518.4 respectively.The Uyghur sand therapy had more obvious influence on the increase of femoral artery wall shear stress and von Mises equivalent stress.Conclusion Uyghur sand therapy can increase Renolds number of femoral artery and improve the blood flow state of human femoral artery,but after the treatment the femoral artery blood flow pattern changed from laminar flow to turbulence flow,which may lead to the formation of hemangioma,therefore,for patients whose inner wall of blood vessel are thinner the sand-buried time,burying-sand thickness and temperature should be strictly controlled.Uyghur sand therapy can also increase wall shear stress,which plays a certain positive role in preventing atherosclerosis and thrombosis caused by thickening of the arterial wall.After Uyghur sand therapy,the von Mises equivalent stress is remarkably increased,which can increase the possibility of angiorrhexis at femoral artery bifurcation,thus,full attention should be paid to patients during the performance of Uyghur sand therapy.
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Objective To study the effects of the different connecting mode of artificial ossicle on hearing restoration. Method Geometrical model of human ear was established by an original C++ program based on clinical CT data, and imported this geometrical model into finite element software PATRAN to build up the numerical finite element model of human ear structure. Based on the finite element model, the fluid solid coupling was computed by harmonic response analysis method, and the effect of sound conduction on ear structure was analyzed according to different implantable methods and positions of artificial ossicle. Results The validity of this numerical model is confirmed by comparing the amplitude of umbo and stapes footplate on numerical model which is gained by dynamic response analysis on normal ear structure with published experimental measurements on human temporal bones. ConclusionsConnecting artificial ossicle to tympanic membrane at its central position is optimal for the dynamic response of ear structure as the amplitude of stapes footplate under this situation is slightly higher than other connecting methods since it conforms to physiological function of human ear, and the effect of hearing recovery could be better.