Finite Element Analysis on Stress Distributions of Proximal Femur in the Elderly During Sit-to-Stand Transition / 医用生物力学

Objective By establishing finite element model of the proximal femur, the injury risk of proximal femur under the conditions of self-selected speed rise and rapid rise at initial stage of standing during sit-to-stand (STS) transition was analyzed.Methods CT images of proximal femur in the elderly were processed with three-dimensional (3D) reconstruction and reverse modeling, so as to complete the solid model. The finite element model was established through material assignment and meshing. Based on the finite element analysis software ANSYS, the boundary conditions were constrained, and 1.733 kN and 1.837 kN loads were applied to obtain stress distributions and strain of proximal femur at different rising speeds. Results The stress concentrated at medial edge of the greater trochanter and the femoral neck. The peak stress and micro-strain appeared on inner edge of the larger rotor. The peak stress was 30.16 MPa and peak micro-strain was 2 553.5 at rapid rising speed. The peak stress and peak micro-strain at self-selected rising speed were 28.69 MPa and 2 430.4, respectively, which were relatively lower. For stress concentration area of femoral neck, the stress ranges at rapid rising speed and self-selected rising speed were 13.42-23.46 MPa and 12.76-25.51 MPa, respectively.Conclusions Frequent STS transition may increase the risk of fatigue fractures for proximal femur in the elderly. Rapid STS transition has a higher injury risk for proximal femur than STS transition at self-selected speed.

Stress distribution of cementless stems with unique flanges in a rectangular cross-section: thermoelastic stress imaging study / Journal of Rural Medicine

Objective: In this study, thermoelastic stress analysis was conducted to clarify the surface stress distribution of a femur in which a BiCONTACT E stem was inserted. The contact sites between the stem and femur were examined to investigate the association with the range of stress distribution.Materials and Methods: BiCONTACT E was set up using two synthetic femurs that mimic the morphology and mechanical properties of living bone. Preoperative planning was performed using three-dimensional imaging software. The synthetic bone was placed in a sample holder. After the stem was implanted into the synthetic bone, computed tomography imaging was performed. The contact sites between the stem and the cortical part of the synthetic bone were examined using the imaging software. Subsequently, thermoelastic stress measurements were performed on the sample.Results: The results of thermoelastic stress analysis indicated a minimum change in the sum of principal stresses [Δ (σ1+σ2)] on the medial side and a maximum change in the sum of principal stresses on the lateral side. Thus, no minimum change was observed in the sum of the principal stresses at the maximum proximal part. It is reasonable to assume that the use of a cementless stem can inevitably lead to bone atrophy in the proximal part of the femur. The contact sites between the stem and femur were also investigated, and the results of the study clearly and quantitatively demonstrated the correlation of the contact sites with a range of stress distributions.Conclusion: The surface stress distribution of a femur, in which a BiCONTACT E stem was inserted, was clarified. The contact sites between the stem and femur were also investigated. Furthermore, the correlation between these results and clinical bone response was investigated in this study.

Effects of the different materials and thicknesses on endocrown stress distribution / 口腔疾病防治

Objective@#To analyze the effects of different restorations and the thickness of the occlusal space on the stress distribution of endodontically treated molars with endocrowns.@*Methods @# The finite element model of the restoration of the first mandibular molar was created, and four different endocrown materials were used including two resin based ceramics (Lava Ultimate, Vita Enamic), one lithium disilicate ceramic (IPS e.max CAD) and one zirconia ceramics (Cercon), and four kinds of surface space thickness were designed: 1 mm, 2 mm, 3 mm and 4 mm. A total of 600 N was loaded to simulate the maximum bite force in the vertical and inclined directions, and the finite element software ANSYS 10.0 was used to analyze the stress distribution@*Results@#The vertical loading analysis showed that the crown stress of the 1 mm-Cercon group was the highest at 211.30 MPa, and that of the 4 mm-Lava Ultimate group was the lowest at 11.56 MPa; the highest dentin stress was 38.84 MPa in the 3 mm-Lava Ultimate group, and the lowest was 11.68 MPa in 1 mm-Cercon group. The stress in the periodontal ligament and alveolar bone had little change. The inclined loading analysis showed that the crown stress of the 1 mm-Cercon group was the highest at 78.73 MPa and that of the 1 mm-Lava Ultimate group was the lowest at 35.51 MPa; the highest dentin stress was 41.63 MPa in the 1 mm-Cercon cervical group, and the lowest was 10.81 MPa in the 4 mm-Cercon coronal group. The stress concentration of cement and cervical dentin under inclined loading was higher than that under vertical loading.@* Conclusion @# The results of finite element analysis show that the elastic modulus of the endocrown increases, the stress of the crown restoration shows an upward trend, and the stress in the tooth shows a downward trend. With increasing crown thickness, the stress of the crown prosthesis decreased.

Finite element analysis of the graft stresses after anterior cruciate ligament reconstruction / 北京大学学报(医学版)

OBJECTIVE@#To explore the stress distribution characteristics of the graft after anterior cruciate ligament (ACL) reconstruction, so as to provide theoretical reference for the surgical plan of ACL reconstruction.@*METHODS@#Based on 3D MRI and CT images, finite element models of the uninjured knee joint and knee joint after ACL reconstruction were established in this study. The uninjured knee model included femur, tibia, fibula, medial collateral ligament, lateral collateral ligament, ACL and posterior cruciate ligament. The ACL reconstruction knee model included femur, tibia, fibula, medial collateral ligament, lateral collateral ligament, ACL graft and posterior cruciate ligament. Linear elastic material properties were used for both the uninjured and ACL reconstruction models. The elastic modulus of bone tissue was set as 17 GPa and Poisson' s ratio was 0.36. The material properties of ligament tissue and graft were set as elastic modulus 390 MPa and Poisson's ratio 0.4. The femur was fixed as the boundary condition, and the tibia anterior tension of 134 N was applied as the loading condition. The stress states of the ACL of the intact joint and the ACL graft after reconstruction were solved and analyzed, including tension, pressure, shear force and von Mises stress.@*RESULTS@#The maximum compressive stress (6.34 MPa), von Mises stress (5.9 MPa) and shear stress (1.83 MPa) of the reconstructed ACL graft were all at the anterior femoral end. It was consistent with the position of maximum compressive stress (8.77 MPa), von Mises stress (8.88 MPa) and shear stress (3.44 MPa) in the ACL of the intact knee joint. The maximum tensile stress of the graft also appeared at the femoral end, but at the posterior side, which was consistent with the position of the maximum tensile stress of ACL of the uninjured knee joint. More-over, the maximum tensile stress of the graft was only 0.88 MPa, which was less than 2.56 MPa of ACL of the uninjured knee joint.@*CONCLUSION@#The maximum compressive stress, von Mises stress and shear stress of the ACL graft are located in the anterior femoral end, and the maximum tensile stress is located in the posterior femoral end, which is consistent with the position of the maximum tensile stress of the ACL of the uninjured knee joint. The anterior part of ACL and the graft bore higher stresses than the posterior part, which is consistent with the biomechanical characteristics of ACL.

Stress distribution of composite resin filling in Class I cavity of molars with different cavosurface angle / 口腔疾病防治

Objective @#To analyze the effect of different cavosurface angles on the stress distribution of ClassⅠ cavity composite resin filling of molars through the three-dimensional finite element method and to provide references for the preparation of ClassⅠ cavities.@*Methods@#Three-dimensional finite element models of ClassⅠ composite resin filling of mandibular first molars with three different cavosurface angles (group A: 90°, group B: 120°, group C: 135°) were established. Polymerization shrinkage of composites was simulated with a thermal expansion approach. The mechanical behavior of the restored models in terms of stress and displacement distributions under the combined effects of polymerization shrinkage and occlusal load (600 N) was analyzed.@*Results@# For ClassⅠ cavities with the same cavity size, the total stress of the restoration model and the maximum stress of the enamel in group A were less than those in groups B and C after cavity composite resin restoration with three cavity cavosurface angles (in which the width of the enamel bevel was 1 mm in groups B and C). The maximum stress of the dentin and adhesive was similar in the three groups, the maximum stress of the composite in group C was the largest, and the maximum stress of the composite in group B was the smallest. In terms of stress distribution, the maximum stress in each restoration model was mainly concentrated in the enamel at the cavosurface, near the enamel-dentin interface and at the edge of the restoration material.@*Conclusion@#From the point of reducing the stress of residual tooth tissue, the preparation of 90° angle without enamel bevel is an ideal method for cavity preparation when composite resin is used to fill ClassⅠ cavities of molars.

Finite element analysis of the stress distribution of dental implant crowns with different all-ceramic materials and thicknesses / 口腔疾病防治

Objective@# To compare the stress distribution of different all-ceramic restoration materials and thicknesses in dental crown restorations using the finite element method and provide a reference for the selection and design of clinical crown restoration materials.@*Methods@#A finite element model of mandibular first molar implant crown restoration was created, and 6 crown thickness designs and 4 different crown restoration materials were evaluated, namely, resin-based ceramics (Lava Ultimate and Vita Enamic), lithium disilicate glass-ceramics (IPS e.max CAD), and zirconia ceramic (Cercon) designs. The mandibular first molars were loaded at 600 N, and the stress distribution was analyzed by using the finite element software ANSYS 10.0.@*Results@#The crown stress analysis showed that 156.05 MPa was the highest in 4 mm Cercon group and 18.85 MPa was the lowest in 1 mm Lava Ultimate group. The stress analysis of resin cement showed that 62.52 MPa was the highest in the 4 mm Lava Ultimate group and 16.74 MPa was the lowest in 1 mm IPS e.max CAD group. During the use of the finished platform, the stress concentration of the Lava Ultimate group in the crown prosthesis and resin cement was higher than that of the personalized platform with the same crown thickness.@*Conclusion@# With increasing crown thickness, the maximum principal stress concentration in crown restoration and resin cement increases. Personalized abutments are more conducive to reducing stress concentrations for resin-based ceramics.

Comparison of finite element models of osteonecrosis of the femoral head based on CT gray-assigned method / 中国组织工程研究

BACKGROUND: Previous studies have reported that femoral head finite element models are mostly modeled with single or few samples for specific biomechanical research, but there is little research on model stability. OBJECTIVE: To compare the models of normal femoral head and osteonecrosis of the femoral head with multiple samples, and to analyze the accuracy and stability of the models through the comparison of stress distribution and mechanical parameters, so as to provide mechanical basis for prevention and treatment of collapse of osteonecrosis of the femoral head. METHODS: Totally 20 sides uncollapsed of osteonecrosis of the femoral head one year of non-surgical treatment were selected as the experimental group, and the healthy side of 20 patients with unilateral osteonecrosis of the femoral head were set as the normal group. The CT data of the femoral head were collected to establish the finite element model. The stress distribution of normal femoral head and osteonecrosis of the femoral head, the maximum equivalent stress and the maximum total deformation at the weight-bearing area of the femoral head were observed and compared. This study was approved by the Medical Ethics Committee of Wangjing Hospital of China Academy of Chinese Medical Sciences. Patients signed the informed consent. RESULTS AND CONCLUSION: (1) The finite element models of normal proximal femur, non-necrotic proximal femur and necrotic bone were established. The number of elements and nodes were 502 568±114 196, 692 608±154 678; 449 954±125 824, 623 311±171 401; 19 133±13 167, 27 577±19 131, respectively. (2) When the load was set by simulating one-foot standing position, the cloud image showed that when 2.5 times body weight applied to the weight-bearing area of the femoral head; the surface stress of the weight-bearing area of the normal femoral head was uniform. The stress was uniformly distributed in the femoral head along the stress trabeculae, and the calcar femorale bears the most. The stress concentration area appeared on the surface of the weight-bearing area and the necrotic area of osteonecrosis of the femoral head. The stress was scattered and distributed on the inner and outer sides of the femoral neck and the femoral head of osteonecrosis of the femoral head produced more deformation than the normal femoral head. (3) The maximum total deformation of the weight-bearing area of the osteonecrosis of the femoral head and the normal femoral head was (4.14±1.31) mm and (1.36±0.22) mm and the maximum equivalent stress was (1.94±0.77) MPa and (0.75±0.19) MPa, respectively, and with statistically significance (P < 0.05). Moreover, two groups of data tend to be concentrated and the models are stable. Through the comparison of multi-sample normal femoral head and osteonecrosis of the femoral head, the CT gray-assigned method reflects the actual mechanical properties of osteonecrosis of the femoral head, and has good accuracy and stability.

Three-dimensional model analysis of trabecular acetabular cup and solid acetabular CUP / 中国组织工程研究

BACKGROUND: Hip arthroplasty is most effective method to treat hip diseases such as femoral head necrosis, osteoarthritis, hip dysplasia and femoral neck fracture in the elderly. Therefore, it is necessary to study the biomechanical behaviors of hip arthroplasty. OBJECTIVE: To simulate the contact stress and Von Mise stress values and distributions of trabecular acetabular cup and solid acetabular cup by finite element analysis method, and to predict its effects on prosthesis and hip joint. METHODS: Two hip joint component models with different structures, trabecular acetabular cup and solid acetabular cup were designed in 3-Matic Research 11.0 software. The well-designed models were imported to Hypermesh 14.0 software to divide meshes and assign material properties. Finite element analysis software Abaqus 6.13 was used to simulate the stress values and distributions of both models. RESULTS AND CONCLUSION: The results of this study showed that the stress of the trabecular acetabular cup was scattered and distributed widely. The solid acetabular cup is prone to stress concentration, and the stress distribution is concentrated near the point of stress. Compared with the solid acetabular cup and the trabecular acetabular cup, the latter has larger contact area of stress distribution and more uniform stress distribution, which can reduce the wear between hip prostheses and the risk of aseptic loosening of hip prostheses.

Effect of meniscus injury on the biomechanical properties of knee joint under gait cycle / 中国组织工程研究

BACKGROUND: The biomechanical characteristics of knee meniscus have been studied extensively at home and abroad, but most of them focus on the knee flexion motion. The finite element analysis of biomechanics of knee joint meniscus under the complete gait cycle is not yet perfect. OBJECTIVE: To understand the mechanism of biomechanical changes after meniscus injury in the complete gait cycle by comparing the lateral meniscus tear model with the healthy meniscus model. METHODS: Based on the CT scan data of healthy adult knee joints, a finite element model of healthy knee joint including tibia, meniscus and articular cartilage was established. The lateral meniscus tear of knee joint was constructed based on the healthy model. The biomechanical mechanism of lateral meniscus tear in the knee during complete gait cycle was explored and compared with the healthy knee model. RESULTS AND CONCLUSION: (1) The instantaneous stress variation of the tibia cartilage during the complete gait cycle was consistent in both models. The tibial cartilage stress at each instant in the meniscus tear model was higher than that of the healthy meniscus model. The maximum stress values of tibia cartilage in the meniscus tear model and the healthy meniscus model was 30 and 20.5 MPa. (2) The instantaneous stress variation of the meniscus during the complete gait cycle was consistent in both models. The meniscus stress at each instant in the meniscus tear model was higher than that of the healthy meniscus model. The maximum stress values of meniscus in the meniscus tear model and the healthy meniscus model was 69.8 and 41.3 MPa. (3) In the first 60% of the gait cycle, the maximum stress distribution of the tibia cartilage in the meniscus tear model was much larger than that in the healthy model, and as the gait cycle grew, the contact range gradually spread to the outer edge of the cartilage. After 60% of the gait cycle, the stress on the tibia cartilage was small, and the distribution range of the maximum stress was also small. (4) The stress distribution of the healthy medial meniscus was basically the same in the two models, while the maximum stress distribution of the torn outer meniscus was wider than that of the healthy medial meniscus. A more severe stress concentration phenomenon occurred around the crack, and with the gait cycle, the stress concentration area gradually shifted toward the crack near the anterior corner of the meniscus. (5) These results suggest that the meniscus is an important load-bearing component in human knee joint. From the perspective of biomechanics, the hazard of the meniscus injury on the human knee joint can be observed more intuitively.

Stress analysis of the molar with the all-ceramic crown prosthesis based on centric occlusal optimization / 生物医学工程学杂志

Stress distribution of denture is an important criterion to evaluate the reasonableness of technological parameters, and the bite force derived from the antagonist is the critical load condition for the calculation of stress distribution. In order to improve the accuracy of stress distribution as much as possible, all-ceramic crown of the mandibular first molar with centric occlusion was taken as the research object, and a bite force loading method reflecting the actual occlusal situation was adopted. Firstly, raster scanning and three dimensional reconstruction of the occlusal surface of molars in the standard dental model were carried out. Meanwhile, the surface modeling of the bonding surface was carried out according to the preparation process. Secondly, the parametric occlusal analysis program was developed with the help of OFA function library, and the genetic algorithm was used to optimize the mandibular centric position. Finally, both the optimized case of the mesh model based on the results of occlusal optimization and the referenced case according to the cusp-fossa contact characteristics were designed. The stress distribution was analyzed and compared by using Abaqus software. The results showed that the genetic algorithm was suitable for solving the occlusal optimization problem. Compared with the reference case, the optimized case had smaller maximum stress and more uniform stress distribution characteristics. The proposed method further improves the stress accuracy of the prosthesis in the finite element model. Also, it provides a new idea for stress analysis of other joints in human body.

Effect of Geometry Variation on the Mechanical Behavior of the Proximal Femur

The mechanical behavior of a proximal femur under a normal body weight loading was examined. The geometry of the proximal femur was created in a finite element model using 29 reference points measured on the CT scan images of a patient. Four additional sets of measurements were calculated using ±(1) and ±(2) the standard deviation of the original set and the result of models was compared. The stress distribution and the locations of critical normal and shearstress, as well as the effect of the femur geometry which may be most susceptible to failure were examined. The findings of this study demonstrate an inferior distribution of stress in the plus-standard deviation models and indicate less ability to bear weight. The minus-standard deviation models appear to be better suited to bearing weight and indicate a more even distribution of the stresses generated within the proximal femur.

Finite element analysis of two different hip prostheses in hip arthroplasty: Comparison of stress concentration and displacement / 吉林大学学报(医学版)

Objective: To apply the finite element method to simulate the stress concentration and displacement of different hip prostheses in total hip arthroplasty, to analyze the clinical outcomes of prosthesis subsidence and loosening after surgery with these two indicators, and to provide reference for clinical surgeons. Methods: The three-dimensional hip from the hip CT data of a normal male volunteer was reconstructed. Two types of prosthesis models were built (Corail and Synergy porous). The femoral heterogeneous properties were assigned by Mimics, ABAQUS and other softwares. The stress concentration and displacement changes of two hip prostheses in the posture of standing were analyzed. Results: The maximum stress of Corail and Synergy porous hip prostheses was mostly concentrated in the one third of distal end and the proximal corner, and the maximum stresses were 31. 82 and 55. 05 MPa, respectively, which were less than the femoral yield strength (138 MPa). The maximum relative displacements of Corail and Synergy porous prosthesis models were 0. 604 and 0. 747 mm, respectively, which were less than the ultimate displacement (1.500 mm). The results above met the hip replacement standards. Conclusion: Corail stem prosthesis has a better behavior in stress concentration and displacement than Synergy porous prosthesis by finite element analysis. The finite element analysis of different hip prosthesis may provide the important references for the prognosis of total hip arthroplasty.

The Influence of Length-diameter Ratio Difference on Stress Distribution at Dental Bone-Implant Interface / 医用生物力学

Objective To investigate the differences in stress distribution at the bone-implant interface of dental implants with different length-diameter ratios, so as to provide references for the design of novel dental implants. Methods The three-dimensional finite element model of mandible was established using Geomagic studio, SolidWorks and ANSYS Workbench software. The mandibular molars were applied with different vertical or oblique forces, to compare and analyze stress distributions on dental implants and the surrounding bone tissues. Results Under the same length-diameter ratio, the maximum peak equivalent stress of implant under oblique loading was significantly higher than that under vertical loading. The Von Mises stresses of implants in Group A and Group B occurred in the neck under oblique and vertical loading. Under oblique loading, the implant stress variation in Group A and Group B was 144.74-374.67 MPa and 161.52-475.38 MPa, respectively. Under vertical loading, the implant stress variation in Group A and Group B was 101.28-187.40 MPa and 110.08-210.32 MPa, respectively. The maximum Von Mises stress of Group A was significantly smaller than that of Group B. Conclusions Dentists should focus on a length-diameter ratio of 2.67 to select the standard implants, and the jawbone quality of patients should be taken into full account.

Morse taper performance: A finite element analysis study

OBJECTIVES: To evaluate and compare the magnitude and distribution of stresses generated on implants, abutments and first molar metal-ceramic crowns using finite element analysis. METHODS: Preliminary three-dimensional models were created using the computer-aided design software SolidWorks. Stress and strain values were observed for two distinct virtual models: model 1 - Morse taper and solid abutment; model 2 - Morse taper and abutment with screw. A load (250 N) was applied to a single point of the occlusal surface at 15° to the implant long axis. Von Mises stresses were recorded for both groups at four main points: 1) abutment-retaining screws; 2) abutment neck; 3) cervical bone area; 4) implant neck. RESULTS AND CONCLUSION: Model 1 showed a higher stress value (1477.5 MPa) at the abutment-retaining screw area than the stresses found in model 2 (1091.1 MPa for the same area). The cervical bone strain values did not exceed 105 µm for either model.

Effect of the restorative technique on load-bearing capacity, cusp deflection, and stress distribution of endodontically-treated premolars with MOD restoration

OBJECTIVES: To evaluate the influence of the restorative technique on the mechanical response of endodontically-treated upper premolars with mesio-occluso-distal (MOD) cavity. MATERIALS AND METHODS: Forty-eight premolars received MOD preparation (4 groups, n = 12) with different restorative techniques: glass ionomer cement + composite resin (the GIC group), a metallic post + composite resin (the MP group), a fiberglass post + composite resin (the FGP group), or no endodontic treatment + restoration with composite resin (the CR group). Cusp strain and load-bearing capacity were evaluated. One-way analysis of variance and the Tukey test were used with α = 5%. Finite element analysis (FEA) was used to calculate displacement and tensile stress for the teeth and restorations. RESULTS: MP showed the highest cusp (p = 0.027) deflection (24.28 ± 5.09 µm/µm), followed by FGP (20.61 ± 5.05 µm/µm), CR (17.72 ± 6.32 µm/µm), and GIC (17.62 ± 7.00 µm/µm). For load-bearing, CR (38.89 ± 3.24 N) showed the highest, followed by GIC (37.51 ± 6.69 N), FGP (29.80 ± 10.03 N), and MP (18.41 ± 4.15 N) (p = 0.001) value. FEA showed similar behavior in the restorations in all groups, while MP showed the highest stress concentration in the tooth and post. CONCLUSIONS: There is no mechanical advantage in using intraradicular posts for endodontically-treated premolars requiring MOD restoration. Filling the pulp chamber with GIC and restoring the tooth with only CR showed the most promising results for cusp deflection, failure load, and stress distribution.

Research progress of three-dimensional finite element analysis in unilateral maxillary defect restorations / 口腔疾病防治

@#Unilateral maxillary defects are common clinical maxillofacial deformities. Because of their large area and the complexity of the maxillary structure, the distribution of pressure from dental prostheses and on the sustentacular tissue is usually uneven, which often results in pain or ulceration of the soft tissue and agomphiasis during the therapeutic process. Recently, the finite element method has been used to guide prosthesis design and implantation. This method is conducive to the restoration and stability of the dental prosthesis and the protection of the remaining tissue, which improves restoration quality and patient satisfaction. This paper summarizes the establishment of a three-dimensional finite element model of unilateral maxillary defects and its application in repairing unilateral maxillary defects with traditional prostheses, implant-supported prostheses and surgical flap transplantation combined with prostheses.

Analysis on mechanical properties and internal flow field distributions of bone scaffold by digital modeling / 医用生物力学

Objective To study mechanical properties of the bone scaffold with different structure and its internal flow field distributions,so as to provide a direct comparison and judgment on model structure and offer an effective guidance for bone scaffold structure design.Methods Bone scaffold with natural,woven and spherical pore structure were reconstructed respectively by using Pro/Engineer and Mimics.The effective elastic modulus for three kinds of scaffolds,as well as their stress distributions and internal flow field distributions under three-dimensional perfusion culture system were analyzed with the finite element method.Results The bone scaffold with natural structure showed smaller effective elastic modulus,smaller peak stress and more uniform stress distributions under the same pressure.With the same initial velocity and fluid viscosity,the bone scaffold with natural structure showed smaller internal velocity,wall shear stress and wall pressure.Conclusions The bone scaffold with natural structure has better biomechanical properties,which corresponds to the design criteria of bone scaffold in bone tissue engineering.

Analysis on mechanical properties and internal flow field distributions of bone scaffold by digital modeling / 医用生物力学

Objective To study mechanical properties of the bone scaffold with different structure and its internal flow field distributions,so as to provide a direct comparison and judgment on model structure and offer an effective guidance for bone scaffold structure design.Methods Bone scaffold with natural,woven and spherical pore structure were reconstructed respectively by using Pro/Engineer and Mimics.The effective elastic modulus for three kinds of scaffolds,as well as their stress distributions and internal flow field distributions under three-dimensional perfusion culture system were analyzed with the finite element method.Results The bone scaffold with natural structure showed smaller effective elastic modulus,smaller peak stress and more uniform stress distributions under the same pressure.With the same initial velocity and fluid viscosity,the bone scaffold with natural structure showed smaller internal velocity,wall shear stress and wall pressure.Conclusions The bone scaffold with natural structure has better biomechanical properties,which corresponds to the design criteria of bone scaffold in bone tissue engineering.

Modeling and analysis for teeth of a patient with periodontal diseases based on four kinds of software / 医用生物力学

Objective To provide references for the clinical treatment of patients with periodontal diseases by modeling and analysis based on four software and obtaining stress distributions of the patient’s teeth, according to CT data and plaster model of the patient’s teeth. Methods The CT data were preliminary processed by using Mimics software to establish three-dimensional (3D) cloud model. The 3D surface model of the teeth was then constructed by using Geomagic software to make parameter modeling and reverse engineering. The 3D surface model was imported into SolidWorks to obtain the 3D entity model by entity conversions. Finally, the 3D entity model was imported to ANSYS for analysis. Results The stress distributions on the upper teeth were obtained, and the location of stress concentration points was determined. The stress concentration points of the teeth were analyzed separately, and the maximum stress was 1 774.8 MPa. The occlusal relationship was adjusted based on stress distributions, and the maximum stress after adjustment was reduced to 1 529 MPa. Conclusions This dental modeling and analysis method can simulate various occlusal relationships and calculate tooth stress distribution after amendment, which provides the theoretical basis for clinical treatment of periodontal diseases.

Analysis on mechanical properties and internal flow field distributions of bone scaffold by digital modeling / 医用生物力学

Objective To study mechanical properties of the bone scaffold with different structure and its internal flow field distributions, so as to provide a direct comparison and judgment on model structure and offer an effective guidance for bone scaffold structure design. Methods Bone scaffold with natural, woven and spherical pore structure were reconstructed respectively by using Pro/Engineer and Mimics. The effective elastic modulus for three kinds of scaffolds, as well as their stress distributions and internal flow field distributions under three dimensional perfusion culture system were analyzed with the finite element method. Results The bone scaffold with natural structure showed smaller effective elastic modulus, smaller peak stress and more uniform stress distributions under the same pressure. With the same initial velocity and fluid viscosity, the bone scaffold with natural structure showed smaller internal velocity, wall shear stress and wall pressure. Conclusions The bone scaffold with natural structure has better biomechanical properties, which corresponds to the design criteria of bone scaffold in bone tissue engineering.