Finite element analysis on correction effect of varus foot orthosis based on the three-point force principle / 中国组织工程研究

BACKGROUND:Three-point mechanics is an effective method for ankle foot orthosis correction and prevention of various foot diseases.At present,the clinical application research on 3D printing ankle foot orthosis has been widespread;however,there are relatively few reports on numerical simulation and finite element analysis involving three-point mechanical correction.There is a lack of relevant biomechanical experimental verification. OBJECTIVE:Three-point force was loaded to analyze the composite model of ankle foot orthosis and foot by finite element method,observing the effect of foot correction with ankle foot orthosis under three-point force intervention,verifying the effectiveness of three-point force and the reliability of ankle foot orthosis. METHODS:A three-dimensional foot and ankle model of a healthy volunteer was constructed based on the medical image processing software Mimics.Rodin 4D and Geomagic reverse engineering software were used to optimize the models and design personalized ankle foot orthosis models.Solidworks software was utilized to turn the ankle model inside for 10° to simulate the foot varus disease.Static loading was carried out on the foot force application area by ANSYS software combined with the three-point mechanics principle.The deformation and stress changes of the foot and ankle tissues were analyzed when the human foot pain threshold was met.The display dynamics was used to further verify the effectiveness of the three-point force applied by the ankle foot orthosis. RESULTS AND CONCLUSION:(1)The personalized ankle foot orthosis designed in this paper had the effect of preventing and fixing foot and ankle varus.The ankle varus was 1.81 mm after being loaded with 1 N·m of varus when not wearing ankle foot orthosis,while it was only 0.44 mm after wearing ankle foot orthosis,the deformation rate was reduced by 75.7%,and the effect of preventing varus was significantly enhanced.(2)When only coronal correction was performed,the low calcaneal force would aggravate the varus angle of the front foot.After adjusting the correction force on the inside of the heel and above the medial malleolus,the varus angle of the front foot and the calcaneus position were improved;however,the medial phalangeal region of the foot still had different degrees of adduction and displacement,which would aggravate the adduction deformity of the patient's front foot.(3)The correction effect of the coronal plane and horizontal plane was better than that of the single coronal plane.There was no adduction and displacement of the medial phalanges of the front foot and the varus angle of the front foot decreased under the force(25,10,10,20 N)of the medial heel,the medial shaft of the first metatarsal,below the lateral malleolus and above the medial malleolus,and the valgus along the X-axis was corrected by 1.395 mm,the calcaneus valgus was corrected by 1.227 mm.The calcaneus varus angle was corrected from 10.21° to 7.25°,and the varus angle was improved by 28.9%.(4)The lateral plantar metatarsal load decreased,the medial plantar metatarsal load increased under the action of a two-plane three-point force,and the plantar bone stress was significantly improved after correction.Thus,the reliability of the three-point force principle was further verified.This study provides an important theoretical support for the implementation of ankle foot orthosis in the treatment of varus in clinical practice.

Prediction of critical energy release rate for cortical bone structure under different failure modes / 中国组织工程研究

BACKGROUND:Critical energy release rate is a global fracture parameter that could be measured during the failing process,and its value may change under different failure modes even in the same structure. OBJECTIVE:To propose an approach to predict the critical energy release rate in the femoral cortical bone structure under different failure modes. METHODS:Three-point bending and axial compression experiments and the corresponding fracture simulations were performed on the rat femoral cortical bone structures.Different critical energy release rates were repeatedly assigned to the models to perform fracture simulation,and the predicted load-displacement curves in each simulation were compared with the experimental data to back-calculate the critical energy release rate.The successful fit was that the differences in the fracture parameters between the predicted and experimental results were less than 5%. RESULTS AND CONCLUSION:(1)The results showed that the cortical bone structure occurred tensile open failure under three-point bending load,and the predicted critical energy release rate was 0.16 N/mm.(2)The same cortical bone structure occurred shear open failure under axial compression load,and the predicted critical energy release rate was 0.12 N/mm,which indicates that the critical energy release rate of the same cortical bone structure under different failure modes was different.(3)A comprehensive analysis from the perspectives of material mechanical properties and damage mechanism was conducted to reveal the reasons for the differences in the critical energy release rate in the cortical bone structure under different failure modes,which provided a theoretical basis for the measurement of the energy release rate and the accurate fracture simulation.

Effects of Different Running Speeds on Tissue-Level Failure Strain in Rat Femoral Cortical Bone / 医用生物力学

Objective To predict the tissue-level failure strain of the cortical bone and discuss the effects of different running speeds on the mechanical properties of rat femoral cortical bone.Methods The threshold for cortical bone tissue-level failure strain was assigned,and fracture simulation under three-point bending was performed on a rat femoral finite element model.The predicted load-displacement curves in each simulation were compared and fitted with the experimental data to back-calculate the tissue-level failure strain.Results The cortical bone tissue-level failure strains at different running speeds were statistically different,which indicated that different running speeds had certain impacts on the micromechanical properties of the cortical bone structures.At a running speed of 12 m/min,the cortical bone structure expressed the greatest tissue-level failure strain,and at a running speed of 20 m/min,the cortical bone structure expressed the lowest tissue-level failure strain.Conclusions Based on the changing trends of tissue-level failure strain and in combination with the changes in macro-level failure load and tissue-level elastic modulus of cortical bone structures,the effects of different running speeds on the mechanical properties of cortical bone structures were discussed in this study.The appropriate running speed for improving the mechanical properties of the cortical bone was explored,thereby providing a theoretical basis for improving bone strength through running exercises.

The value of three-point localization method for four-chamber view acquisition in cardiac magnetic resonance imaging / 西安交通大学学报(医学版)

【Objective】 To evaluate the application value of the three-point localization method in improving the quality and efficiency of four-chamber view acquisition in cardiac magnetic resonance (CMR) imaging. 【Methods】 A total of 215 patients who underwent four-chamber view in CMR imaging from January 2022 to October 2023 were retrospectively enrolled and divided into two groups. The control group (n=109) received traditional localization method while the study group (n=106) received three-point localization method. The image quality of mitral valve, tricuspid valve and cruciform structure in four-chamber view images were assessed by two radiologists using a Likert 4-piont scale. The time-consumption from scout imaging to the finish of four-chamber view imaging was recorded. Constituent data and numeral data were compared by Chi-square test and two-sample t test, respectively. Kappa test was used to analyze the inter-observer consistency. 【Results】 There were no significant inter-group differences in gender, age, disease profile, or the radiographers’ experience. The mean quality scores of the mitral valve, tricuspid valve and cruciform structure in the control group and the study group were 3.44±0.64 and 3.63±0.49 (P=0.023), 3.43±0.67 and 3.53±0.60(P=0.202), 3.71±0.49 and 3.83±0.35 (P=0.047), respectively. The image quality score was higher in the study group than in the control group, with the differences in mitral valve and cruciform structure reaching statistical significance. The time-consumption for obtaining four-chamber view for the control group and the study group was 11.67±3.49 minutes and 7.212±1.83 minutes, respectively, with statistically significant differences (P<0.001). 【Conclusion】 Compared with the traditional localization method, the three-point localization method provides better image quality in four-chamber view imaging with shortened imaging time.

Biomechanical Effects of Angiotensin 1-7 in Diabetes Rats Femur / Efectos Biomecánicos de la Angiotensina 1-7 en el Fémur de Ratas Diabéticas

SUMMARY: It is known that diabetes mellitus has late complications, including microvascular and macrovascular diseases. Diabetes can affect bones through biochemical markers of bone structure, density, and turnover. This study aimed to biomechanically investigate the bone-protective effects of angiotensin 1-7 (Ang 1-7), one of the active peptides in the renin-angiotensin system, in rats with diabetes. Thirty male Wistar albino rats, three months old and weighing 250-300 g, were divided into four groups: diabetes, Ang 1- 7, diabetes plus Ang 1-7, and control. One month later, diabetes developed in rats; the rats were sacrificed, and their right femur was removed. Three-point bending biomechanical tests were performed on the femurs. The diabetic group had significantly higher bone fragility than the other groups (Pr >.05). Bone fragility was lower, and bone flexibility was higher in the Ang 1-7 groups (Pr>F value 0.05). As a result of our study, the effect of Ang 1-7 on the bones of rats with diabetes was investigated biomechanically. Ang 1-7 has a protective impact on the bones of rats with diabetes.

Se sabe que la diabetes mellitus tiene complicaciones tardías, incluyendo enfermedades microvasculares y macrovasculares. La diabetes puede afectar los huesos a través de los marcadores bioquímicos de la estructura, la densidad y el recambio óseo. Este estudio tuvo como objetivo investigar biomecánicamente los efectos protectores en los huesos de la angiotensina 1-7 (Ang 1-7), uno de los péptidos activos en el sistema renina-angiotensina, en ratas con diabetes. Treinta ratas albinas Wistar macho, de tres meses de edad y con un peso de 250-300 g, se dividieron en cuatro grupos: diabetes, Ang 1-7, diabetes más Ang 1-7 y control. Un mes después, se desarrolló diabetes en ratas; se sacrificaron los animales y se extrajo su fémur derecho. Se realizaron pruebas biomecánicas de flexión de tres puntos en los fémures. El grupo diabéticos tenía una fragilidad ósea significativamente mayor que los otros grupos (Pr > 0,05). La fragilidad ósea fue menor y la flexibilidad ósea fue mayor en los grupos Ang 1-7 (valor Pr>F 0,05). Como resultado de nuestro estudio, se determinó biomecánicamente el efecto de Ang 1-7 en los huesos de ratas con diabetes. Se concluye que Ang 1-7 tiene un impacto protector en los huesos de ratas diabéticas.

Establishment and evaluation of rabbit model of closed tibial fracture / 中国骨伤

OBJECTIVE@#To explore the effect of a modified three-point bending fracture device for establishing a rabbit model of closed tibial fracture.@*METHODS@#The model of closed tibial fracture was established in 40 6-month-old male New Zealand white rabbits with a body weight of 2.5 to 3.0 kg, and the model was verified at 6 weeks after operation. Five rabbits underwent pre modeling without temporary external fixation before modeling, and then were fractured with a modified three-point bending fracture device;35 rabbits underwent formal modeling. Before modeling, needles were inserted, and splints were fixed externally, and then the fracture was performed with a modified three-point bending fracture device. The fracture model and healing process were evaluated by imaging and histopathology at 2 hours, 4 weeks, and 6 weeks after operation.@*RESULTS@#Two hours after modeling, the prefabricated module showed oblique fracture in varying degrees and the broken end shifted significantly;Except for 1 comminuted fracture, 2 curved butterfly fractures and 2 without obvious fracture line, the rest were simple transverse and oblique fractures without obvious displacement in formal modeling group. According to the judgment criteria, the success rate of the model was 85.71%. Four weeks after modeling, the fixed needle and splint of the experimental rabbits were in good position, the fracture alignment was good, the fracture line was blurred, many continuous callus growths could be seen around the fracture end, and the callus density was high. Six weeks after modeling, many thick new bone trabeculae at the fracture, marginal osteoblasts attached, and a small number of macrophages were seen under the microscope. The intramembrane osteogenesis area was in the preparation bone stage, the medullary cavity at the fracture had been partially reopened, the callus was in the absorption plastic stage, and many osteoclasts were visible. The X-ray showed that the fracture line almost disappeared, part of the medullary cavity had been opened, the external callus was reduced around, the callus was in the plastic stage, and the bone cortex was continuous. It suggests that the fracture model showed secondary healing.@*CONCLUSION@#The improved three-point bending fracture device can establish a stable rabbit model of closed tibial fracture, and the operation is simple, which meets the requirements of closed fracture model in basic research related to fracture healing.

Simulation accuracy of cortical bone fracture based on different types of strain criterion / 中国组织工程研究

BACKGROUND: Cortical bone crack caused by accident or other external factors is one of the main causes of fracture, so the mechanism of crack formation and propagation for cortical bone under different loads should be understood primarily to avoid fracture. Bone specimens may be destructed in experiments, which can lead to a difficulty to observe the interior mechanical state of bone structure before and after fracture. Therefore, it is important to find a finite element method that can accurately simulate the processes of cortical bone crack formation, propagation, and fracture. Current simulations mainly use the principal strain or the equivalent strain to determine the mechanical state of the element in the finite element model and to perform fracture simulation, but there are few studies on the simulation accuracy when using these two types of strains. OBJECTIVE: To testify the simulation accuracy of cortical bone fracture with the principal strain and the equivalent strain. METHODS: The principal strain and the equivalent strain were applied to perform the three-point bending simulation, and the simulation results were compared with the experimental results to determine which strain was more accurate. RESULTS AND CONCLUSION: (1) The failure time of the cortical bone simulated by the principal strain was significantly later than that obtained by the equivalent strain. (2) Compared with the experimental results, it was found that the simulation results obtained by equivalent strain were closer to the experimental results. (3) Therefore, simulating cortical bone crack and fracture using the equivalent strain is accurate.

Mechanical properties of rat tibia under high-G environment / 中国组织工程研究

BACKGROUND: With the development of Chinese space industry, pilots are exposed to high-G mechanical environment, which will seriously affect their bones. However, as one of the bones that are most prone to fracture, the biomechanical behavior of the tibia under extreme mechanical environment is rarely reported. OBJECTIVE: To explore the effects of different high-G mechanical environments on the rat growth and development and the mechanical properties of the tibia. METHODS: Male Wistar rats were provided by Laboratory Animal Center of Academy of Military Sciences. The cantilever was set to run at different speeds and accelerations with a high-G centrifugal loading device, and the high-G rat model was made. The rats were weighed weekly. The left tibia of rats was used for undergoing a three-point bending experiment, and the deflection and elastic modulus of the tibia were calculated. The right tibia was subjected to a creep test, and constant stress was applied on the surface of tibial cortical bone and kept 3 600 seconds, so as to observe the changes of creep strain. The study was approved by the Laboratory Animal Ethical Committee of Tianjin University of Technology. RESULTS AND CONCLUSION: The high-G environment affected the normal growth and development of rats, inhibited weight gain and reduced the mechanical properties of the tibia, and reduced the limit deflection of the tibia by 8.1%, 12.2%, 37.8%, and 51.4%, respectively. Limit loads were decreased by 16%, 9%, 25.2%, and 29% respectively. To conclude, extremely high-G environment exerts serious negative effects on rats.

Three point fixation is superior to two point fixation technique for zygomatic complex fracture

Background:Isolated zygomatic or malar bone fractures are second most common fracture among facial skeletal injuries. It has been reported that three point fixation is appropriate for isolated zygomaticbone fracture. The objective of current study was to compare the mean difference in terms of malar height outcome by using different fixation techniques (two point and three point)in patients with zygomatic complex fracture.Methods:This randomized controlled trial was conducted at Department of Oral and Maxillofacial Surgery, MMDC, Multan, during a period of six months from 1st June 2017 to 30th November 2017. A total 182 patients of both genders were included in this study. Two point fixation techniques were used in Group-A patients. While 3 point fixation was used in Group-B patients. After 6 weeks follow-up, patients were assessed for malar height. Outcome was measured by comparing the mean difference of pre and postoperative malar height of both techniques. Data were analyzed using computer program SPSS-21. P≤0.05 was taken as significant in all analysis.Results:Among patients in two pointfixation group, the mean malar height was 67.55±2.98 mm and in three pointfixation group, meansmalar height was 71.55±2.36 mm. The difference of malar height among two treatments was highly significant with p<0.01. Conclusions: Using three point fixation results better as compared to two point fixations in terms of malar height outcome

Penoplasty with T-shaped incision and three-point fixation for concealed penis / 中华男科学杂志

<p><b>Objective</b>To search for a safe and effective method of penoplasty with low incidence of complications for concealed penis by evaluating penoplasty with T-shaped incision and three-point fixation in comparison with modified Devine's technique.</p><p><b>METHODS</b>We retrospectively analyzed 169 cases of concealed penis treated in our center by penoplasty with T-shaped incision and three-point fixation (group A, n = 110) or modified Devine's surgery (group B, n = 59). We compared the operation time, postoperative complications, and recurrence rate between the two groups of patients.</p><p><b>RESULTS</b>Operations were successfully completed in all the cases, the urinary catheters removed at 3 days and the elastic bandages applied for 2 to 4 weeks. The patients were followed up for 4 to 12 months. The penis was satisfactorily exposed. The operative time was significantly shorter in group A than in B (［52.8 ± 6.9］ vs ［61.5 ± 10.6］ min, P < 0.001), the postoperative complication rate was obviously lower in the former than in the latter (prepuce edema: 17.27% ［19/110］ vs 33.89% ［20/59］, P = 0.021; bleeding: 0.90% ［1/110］ vs 3.38% ［2/59］, P = 0.552; skin necrosis: 0.90% ［1/110］ vs 5.08% ［3/59］, P = 0.123; skin infection: 0.90% ［1/110］ vs 5.08% ［3/59］, P = 0.123), and so was the recurrence rate (0.90% ［1/110］ vs 6.77% ［4/59］, P = 0.032).</p><p><b>CONCLUSIONS</b>Penoplasty with T-shaped incision and three-point fixation deserves to be popularized clinically for its advantages of minor invasion, clear exposure, reliable penile fixation, low incidence of postoperative complications and recurrence, and satisfactory outcomes.</p>

Metal-ceramic bond strength between a feldspathic porcelain and a Co-Cr alloy fabricated with Direct Metal Laser Sintering technique

PURPOSE: The aim of the present study was to record the metal-ceramic bond strength of a feldspathic dental porcelain and a Co-Cr alloy, using the Direct Metal Laser Sintering technique (DMLS) for the fabrication of metal substrates. MATERIALS AND METHODS: Ten metal substrates were fabricated with powder of a dental Co-Cr alloy using DMLS technique (test group) in dimensions according to ISO 9693. Another ten substrates were fabricated with a casing dental Co-Cr alloy using classic casting technique (control group) for comparison. Another three substrates were fabricated using each technique to record the Modulus of Elasticity (E) of the used alloys. All substrates were examined to record external and internal porosity. Feldspathic porcelain was applied on the substrates. Specimens were tested using the three-point bending test. The failure mode was determined using optical and scanning electron microscopy. The statistical analysis was performed using t-test. RESULTS: Substrates prepared using DMLS technique did not show internal porosity as compared to those produced using the casting technique. The E of control and test group was 222 ± 5.13 GPa and 227 ± 3 GPa, respectively. The bond strength was 51.87 ± 7.50 MPa for test group and 54.60 ± 6.20 MPa for control group. No statistically significant differences between the two groups were recorded. The mode of failure was mainly cohesive for all specimens. CONCLUSION: Specimens produced by the DMLS technique cover the lowest acceptable metal-ceramic bond strength of 25 MPa specified in ISO 9693 and present satisfactory bond strength for clinical use.

Application of three-point double eyelid blepharoplasty combined with correcting epicanthal folds by using asymmetric Z-plasty with a two curve design / 中华医学美学美容杂志

Objective To explore the clinical effect of three-point double eyelid blepharoplasty combined with correcting epicanthal folds by using asymmetric Z-plasty with a two curve design.Methods We retrospectively reviewed the application and effect of three-point double eyelid blepharoplasty combined with correcting epicanthal folds by using asymmetric Z-plasty with a two curve design between January 2015 and June 2016.There were 36 cases of severe epicanthus in this group,including 20 cases of thin eyelid,13 cases of mild swollen eye and 3 cases of moderate swollen eye.Results Follow-up by telephone or WeChat,satisfactory for the 26 cases,the basic satisfaction of 9 cases,1 case of dissatisfaction,moderate swollen eye and severe epicanthus.Conclusions In the case of severe epicanthus with a single eyelid and a mild swollen eyelid without thinning of the eyelid,the use of three-point double eyelid blepharoplasty combined with correcting epicanthal folds by using asymmet ric Z-plasty with a two curve design is one of good choices of methods for the correction of epicanthus.

Influence of airborne-particle abrasion on flexural strength of fiber-reinforced composite post

PURPOSE: Many studies have shown that airborne-particle abrasion of fiber post can improve the bonding strength to resin cement. But, airborne-particle abrasion may influence the property of fiber post. The purpose of this study is to evaluate the influence of airborne-particle abrasion on flexural strength of fiber post. MATERIALS AND METHODS: Two fiber-reinforced posts; DT Light Post Size 2 (1.8 mm diameter, Bisco Inc) and RelyX Fiber Post Size 3 (1.9 mm diameter, 3M ESPE); were used in this study. Each group was divided into 3 subgroups according to different surface treatments; without pretreatment: 50 µm aluminum oxide (Cobra®, Renfert): and 30 µm aluminum oxide modified with silica (Rocatec Soft®, 3M ESPE). After airborne-particle abrasion procedure, three-point bending test was done to determine the flexural strength and flexural modulus. The diameter of each posts was measured to an accuracy of 0.01 mm using a digital micrometer. There was no diameter change before and after airborneparticle abrasion. The mean flexural moduli and flexural strengths calculated using the appropriate equations. The results were statistically analyzed using One-way ANOVA and Scheffe's post-hoc test at 95% confidencial level. RESULTS: There was no significant difference on flexural strength between groups. CONCLUSION: In the limitation of this study, flexural strength and flexural modulus of fiber post are not affected by airborne-particle abrasion.

Comparative study on bond strength of porcelain fused to CAD/CAM and to cast pure titanium / 实用口腔医学杂志

Objective:To compare the titanium-porcelain bonding strength between CAD/CAM and cast pure titanium.Methods:Pure titanium samples were prepaired by CAD/CAMand casting respectively and fused with porcelain.The bond strength between tita-nium and porcelain of the samples was measured with three-point test.The titanium-porcelain interface was investigated under scanning electronic microscope(SEM).Results:The bond strength of CAD/CAMpure titanium to porcelain was (35.95 ±3.74)MPa and cast pure titanium to porcelain was (28.37 ±1 .98)MPa(P <0.05).SEMobservation showed that there was thin transition layer between titanium substrate and ceramic in CAD/CAM bond interface,titanium and porcelain combined closely,no obvious pores.However, there was thicker transition layer and small pore in cast pure titanium to porcelain bonding interface.Conclusion:The bonding strength of porcelain to CAD/CAMpure titanium is greater than that of porcelain to casting pure titanium.

Biomechanical study on helical long PHILOS plate fixation for proximal metaphyseal-diaphyseal humeral shaft fractures / 医用生物力学

Objective To compare biomechanical properties of the helical and straight long PHILOS (proximal humerus internal locking system) plates (Synthes Inc., Switzerland), so as to provide some biomechanical evidence for treating proximal metaphyseal-diaphyseal humeral shaft fractures in clinic. Methods Twelve Synbone artificial bones of right humerus (SYNBONE Inc., Switzerland) were divided into two groups. In control group (n=6), the humerus was fixed with the 10 hole long straight PHILOS plate, while in experimental group (n=6), the humerus was fixed with the same long PHILOS plate which was precontoured for moulding (i.e. helical PHILOS plate). After the proximal metaphyseal-diaphyseal humeral shaft fractures were made in all artificial bones, the biomechanical properties of the specimens in two groups under 6 loading modes (i.e., axial tension and compression, torsion in the same and reverse direction, medial-lateral and anterior-posterior three-point bending) were tested en bloc and compared. ResultsCompare with control group, under 100-500 N tensile and compressive loads, the axial displacement at the fractured end in experimental group increased by about 95% and 58%, respectively. Under 0.6-3 N•m torsional moment in reversed direction, the tensional angle in experimental group was obviously smaller than that in control group, with a decrease of 55%-64%. Under medial-lateral bending moment of 1.5 and 3 N•m, no significant difference was found in deflection of the experiment and control group, while under medial-lateral bending moment of 4.5, 6 and 7.5 N•m, the deflection in experimental group decreased by 20%-30% as compared to control group. Under 0.6-3 N•m torsional moment in the same direction and 1.5-7.5 N•m anterior-posterior bending moment, both the torsional angle and the deflection in experimental group were larger than those in control group, with a significant difference (P＜0.05). Compared with control group, the tensile stiffness and compressive stiffness decreased by 49% and 36%, the torsional stiffness in the same direction decreased by 19% and that in reversed direction increased by 150%, three-point bending stiffness in medial lateral direction increased by 18% and that in anterior posterior direction decreased by 70% in experimental group, all with a significant difference (P＜0.05). ConclusionsCompared with the long straight PHILO plate, the long helical PHILOS plate has better biomechanical properties, which can meet the clinical need of proximal metaphyseal-diaphyseal humeral shaft fracture fixation and postoperative rehabilitation. This surgical technique is expected to be widely applied in clinic, especially with the advantage of minimal invasive surgery.

Construction and identification of humerus three-dimensional finite element model in children / 中国组织工程研究

BACKGROUND:Mechanical experiment of finite element numerical simulation is the effective method to research the biomechanical structure of human body. OBJECTIVE:To establish the three-dimensional finite element model of a normal 6-year-old child’s humerus. METHODS:CT images of a 6-year-old child volunteer were imported to the Mimics 10.01 software. The threshold segmentation method was used to rebuild the humerus three-dimensional model. The surface optimization treatment and surface patches dicision were performed on the surface of the model with Geomagic Studio 12.0 software. Then the mesh generation was completed in the software TrueGrid. Final y, the material properties were set and the finite element model was completed. The boundary conditions and constrains were exerted to simulate the three-point-bending test of humeurs. After the simulation, the results were outputted. RESULTS AND CONCLUSION:The humerus finite element model included 3 024 nodes and 18 758 nodes-hexahedron elements. The 0.01 m/s and 3 m/s dynamic loads were loaded respectively, then the central humerus fracture occurred and the load-displacement curve was close to the cadaver test results. The simulation results show that the simulation results of children humerus finite element model are close to the cadaver’s test, and the finite element simulation method can simulate the physical properties of the human skeleton very wel .

Propriedades em flexão de fios de liga de Ni-Ti / Bending properties of Ni-Ti alloys wires

As ligas de niquel-titânio (Ni-Ti) são usadas na fabricação de fios ortodônticos devido principalmente a sua maior resiliência e menor módulo de elasticidade quando comparadas com outras ligas metálicas, especialmente o aço inoxidável. O objetivo do presente trabalho foi comparar as propriedades mecânicas em flexão de fios de liga com memória de forma de diferentes fabricantes e lotes. Dois lotes de três fabricantes foram ensaiados em flexão três pontos de acordo com a norma ISO 15841:2006(E). Os resultados mostraram que os fios designados como termoativados geram tensões menores que os fios designados como superelásticos, observou-se variações de até 28% entre fios designados como superelásticos e 31% entre fios designados como termoativados. Na comparação dos lotes do mesmo fabricante observou-se também a não homogeneidade entre os fios.

The nickel-titanium (Ni-Ti) alloys are used in the manufacture of orthodontic wires mainly due to its greater resilience and low modulus of elasticity when compared to other alloys, particularly stainless steel. The aim of this study was to compare the mechanical properties of shape memory alloys wires in three-point bending in different manufacturers. Two lots of three manufacturers were tested in three-point bending according to ISO 15841:2006 (E). The results showed that wires designated as termoactivated generated lower tensions than the designated as superelastic, variations of up to 28% between wires designated as superelastic and 31% between wires d esignated as termoactivated were found. In the manufacturer lots comparison was also not observed homogeneity between wires.

Transformation Behaviour, Bending Properties and Surface Quality of 22 Commercial Nickel- Titanium Wires: A Batch-to-Batch Evaluation.

Aims: The aims of this study were to investigate batch-to-batch differences in mechanical and thermal properties of 22 commercial nickel-titanium wires and evaluate the surface quality. Secondly the percentages of superelasticity at mouth temperature were measured. Study Design: In vitro laboratory study. Place and Duration of Study: Sample: Department of Oral Health Sciences – Orthodontics and Metallurgy and Materials Engineering KU Leuven, between January 2010 and May 2011. Methodology: The sample comprised 22 NiTi wires of the upper jaw from 7 different manufacturers. For each brand two different batches were investigated (LOT A, LOT B). Three different investigations were carried out. First transformation behaviour and transition temperatures were determined by differential scanning calorimetry, second a three point bending test was done to evaluate the mechanical properties and third scanning electron microscopy was performed on all samples to evaluate surface quality. Results: Absolute batch-to-batch differences in the investigated properties were all deviating from zero, although most differences were clinically acceptable. Significant interbatch differences in thermal properties were found in 4 wires. Mechanical interbatch differences were found remarkable for 5 wires. Percentage of elasticity showed a non- superelastic curve below a deflection of 1500 μm, which represents clinical small deflections. Surface topography showed also interbatch differences for 4 wires. Conclusion: This study shows that batch-to-batch differences are obvious in each sample. One has to be careful in the selection of archwires. Therefore more standardized consument information should be provided.

Influence of fluoride-containing acidic artificial saliva on the mechanical properties of Nickel-Titanium orthodontics wires.

Objective: This study aimed to investigate the influence of fluoride and an acidic environment on the mechanical properties of NiTi orthodontic wires (NiTiW) in artificial saliva. Design: A prospective laboratory investigation. Setting: Department of Stomatology, First Affiliated Hospital, Zhejiang University, Hangzhou, China. Materials and Methods: Commercial, round 0.016-inch NiTiW were immersed in 0% or 0.05% Natrium-Fluoride-containing artificial saliva at a pH of 4 or 6 for one or three days, respectively. NiTiW were examined with a three-point bending test, Vickers' microhardness tests and surface morphology observation (SEM). Results: A pH of 4 increased microhardness and decreased the three-point bending strength significantly (P≤0.05), whereas immersion time and fluoride concentration had no significant influence on the microhardness or on the three-point bending strength (P>0.05). When examining the test group NiTiWs after three days of immersion at a pH of 4 the SEM revealed a rough surface morphology, a damaged oxide layer and signs of corrosion. Conclusions: The most influential factor for decreasing the unloading force and increasing the hardness seems to be the pH value, whereas immersion time and NaF addition do not have a major influence.

The clinical value of using a four-point method to measure joint angles / 中华物理医学与康复杂志

Objective To study the clinical value of using a four-point method (FP) in measuring joint angles.Method Methods Twenty-five subjects without knee dysfunction were studied.Every knee joint was tested in extension,below 90° of flexion and above 90° of flexion with the traditional three-point method (TP) and the new four-point method.X-rays were taken as a gold standard measurement.The reliability and validity were analyzed using Bland-Altman plots,which can yield 95% limits of agreement (LOA).Results (1) The joint axis centers moved with changes in joint angle.(2) The 95% LOA of inter-tester reliability was (-5.0,2.7) with the FP and (-6.5,4.4) with the TP.The 95% LOAs of intra-tester reliability were (-3.6,4.0) for tester A and (-4.1,4.8) for tester B with the FP,while (-5.0,6.4) for tester A and (-6.1,5.8) for tester B with the TP.(3) The 95% LOAs in the three positions were (3.5,2.6) in extension,(-3.3,3.6) in mild flexion and (-1.9,5.7) in greater flexion with the FP,and ( 6.8,1.1),(-4.0,7.1) and (0,8.5) with the TP.Conclusions The FP gives better reliability and validity than the TP in joint angle measurement.