Research status and development of biodegradable zinc alloy as orthopedics implant / 生物医学工程学杂志

Znic (Zn) alloys with good cytocompatibility and suitable degradation rate have been a kind of biodegradable metal with great potential for clinical applications. This paper summarizes the biological role of degradable Zn alloy as bone implant materials, discusses the mechanical properties of different Zn alloys and their advantages and disadvantages as bone implant materials, and analyzes the influence of different processing strategies (such as alloying and additive manufacturing) on the mechanical properties of Zn alloys. This paper provides systematic design approaches for biodegradable Zn alloys as bone implant materials in terms of the material selection, product processing, structural topology optimization, and assesses their application prospects with a view to better serve the clinic.

Dosimetric Impact of Titanium Alloy Implant in Spinal IMRT Plan / 中国医疗器械杂志

The purpose of this study is to establish and apply a correction method for titanium alloy implant in spinal IMRT plan, a corrected CT-density table was revised from normal CT-density table to include the density of titanium alloy implant. Dose distribution after and before correction were calculated and compared to evaluate the dose deviation. Plans were also copied to a spinal cancer simulation phantom. A titanium alloy fixation system for spine was implanted in this phantom. Plans were recalculated and compared with the measurement result. The result of this study shows that the max dose of spinal cord showed significant difference after correction, and the deviation between calculation results and measurement results was reduced after correction. The method for expanding the range CT-density table, which means that the density of titanium alloy was included, can reduce the error in calculation.

Theoretical Verification of Dynamic Lumbar Interspinous Process Stabilization Device with Memory Alloys / 中国医疗器械杂志

To find an effective method of minimally invasive treatment combining prevention and assistance in the middle zone of conservative treatment and fusion surgery for lumbar degenerative diseases, through the clinical effect observation and the advantage and disadvantage comparison of several commonly used lumbar interspinous dynamic stabilization systems, by analyzing the physiological structure, biomechanics and relevant data of lumbar interspinous processes, based on fully understanding of memory alloy materials, a new dynamic lumbar interspinous fixation device with a memory alloy material has been independently designed and researched, which can not only reconstruct the normal biomechanical characteristics of the lumbar spine and satisfy the normal activities of the human spine, but also avoid damage to the original structure and reduce the incidence of postoperative complications. In addition, the device can be used to optimize the current therapeutic methods. According to our research, the dynamic lumbar interspinous process stabilization device with a memory alloy has theoretically achieved satisfactory results, which can be used to overcome the shortcomings of the existing technology and is superior to the current several dynamic lumbar interspinous process stabilization systems.

Comparison of Four-hook Needle and Memory Alloy Coil in Localization of Pulmonary Nodules / 中国肺癌杂志

BACKGROUND@#With the extensive development of minimally invasive surgery for pulmonary nodules, preoperative localization becomes more and more critical. There are some defects in traditional localization methods, so it is necessary to improve. The aim of this study was to compare and analyze the safety and effectiveness of two new methods, namely four-hook needle and memory alloy coil, in the localization of pulmonary nodules.@*METHODS@#A retrospective analysis of 152 patients was performed. 76 cases were in four-hook needle group, and 76 cases were in memory alloy coil group. Pulmonary nodules were located before operation, and then video-assisted wedge resection was performed. The average procedure time, localization complications and nodule resection time were counted.@*RESULTS@#The target pulmonary nodules were successfully removed in both groups. In four-hook needle group, 76 patients found localization devices, all the pulmonary nodules were successfully removed, and one case was transferred to open the chest for wedge resection of pulmonary nodules due to severe thoracic adhesion. All 76 patients in memory alloy coil group were successfully resected with pulmonary nodules, and one patient underwent compromising enlarged resection because no lesion was found after the specimen was removed during the operation. There was no significant difference in the incidence of pneumothorax and pulmonary hemorrhage, the success rate of localization and nodule wedge resection time between the two groups. The average time of localization in four-hook needle group was (13.66±3.11) min, lower than that of memory alloy coil group (15.51±3.65) min, and the difference was statistically significant (P=0.001). In memory alloy coil group, when the distance from the nodule to the pleura was ≥1.5 cm and <1.5 cm, the average localization time was (17.20±4.46) min and (14.91±3.15) min, respectively, and there was a statistical difference between the two distance (P=0.044).@*CONCLUSIONS@#Four-hook needle and memory alloy coil have good safety and effectiveness, and the localization time of four-hook needle is shorter. When using memory alloy coil, the effect of the method is better for pulmonary nodules with a distance less than 1.5 cm to pleura.

Comparative study on the mechanical properties of lower limb arterial stents under various deformation modes / 生物医学工程学杂志

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

Design and Clinical Application of Split Memory Alloy Sternum Plate / 中国医疗器械杂志

OBJECTIVE@#The design and development of split memory alloy sternum bone plate are discussed, and the effect of split memory alloy sternum bone plate internal fixation in the treatment of sternal fractures are analysed.@*METHODS@#The structure of the product is designed according to the anatomy and physiological characteristics of human bones, and the cross section shape of the product is designed according to the cross section shape of human bones. Internal fixation is effective in the treatment of sternal fracture.@*RESULTS@#The split memory alloy sternal plate was successfully designed and developed, and all the patients with sternal fractures treated by internal fixation were clinically healed, the hospitalization and fracture healing time were significantly shortened, and no obvious complications occurred.@*CONCLUSIONS@#The application of split memory alloy sternal plate internal fixation in the treatment of sternal fracture has the advantages of small trauma, simple operation, safety, reliable fixation, good histocompatibility and less complications, and is conducive to promoting fracture healing and respiratory function improvement.

Effects of Heat Treatment Conditions on Shape Memory Recovery of NiTi Self-expanding Vascular Stents / 中国医疗器械杂志

Effects of heat treatment conditions (including temperature and time) on the shape memory recovery and corrosion resistance of NiTi self-expanding vascular stents were studied based on working mechanism and clinical use. The

Pulpal blood flow changes and pain scores related to using Superelastic 0. 018-inch Nickel Titanium as the first orthodontic alignment archwire: a prospective clinical trial

Abstract Background Optimal orthodontic force results in maximum rate of tooth movement without tissue damage. Even though starting orthodontic treatment with a thicker archwire may shorten treatment duration, the evidence on the effect of using 0.018-inch NiTi as the first alignment archwire on pulpal blood flow (PBF) status is still scarce. Objectives to record PBF changes and pain scores associated with using 0.018-inch NiTi as the first alignment archwire during fixed orthodontic treatment. Methodology Patients were selected from subjects attending postgraduate orthodontic teaching clinics at Jordan University of Science and Technology. In total, forty healthy patients who exhibited mild lower arch crowding were included. A split-mouth trial design was used. Each patient received two archwire sizes at one time joined in the midline by crimpable hook and applied in the lower arch. Patients were assigned into one of two groups based on archwire sizes used. Group 1: 0.014-inch and 0.018-inch NiTi (Six males, 14 females aged 19.4±1.33 years) and Group 2: 0.016-inch and 0.018-inch NiTi (Seven males, 13 females aged 19.6±1.45 years). The archwire size group was randomly allocated with a 1:1 allocation ratio. A Laser Doppler Flowmeter was used to measure PBF at different time intervals (T0-T5). Pain scores were recorded using a visual analogue scale (VAS). A repeated measures ANOVA and a post-hoc Bonferroni comparison tests were conducted to examine differences at the different time points before and during orthodontic alignment. Results For all studied archwire sizes, PBF decreased 20 minutes after their placement. Most PBF changes occurred within 24hours and continued to decrease until 72 hours after archwire placement where the maximum reduction was reached. Eventually, normal values were reverted within 1 month. PBF changes were similar between all alignment - groups. Conclusions Initial orthodontic alignment with 0.018-inch NiTi does not cause irreversible changes to pulpal vasculature or produces higher pain scores.

Evaluación de la resistencia a la flexión de limas rotatorias Protaper Gold, 2Shape, V-Taper Fanta Gold / Evaluation of flexion resistance of Protaper Gold rotary limes, 2Shape, V-Tapert Fanta Gold

Antecedentes: Las limas rotatorias de níquel-titanio con tratamiento termomecánico se desarrollaron para permitir una mayor flexibilidad al instrumentar los conductos radiculares. Los instrumentos permitieron a los operadores tratar las curvaturas de los conductos con mayor facilidad. Los fabricantes están tratando de producir limas que funcionen de manera más eficiente y segura. Conocer las propiedades de las limas comercializadas es especialmente importante porque ayuda a elegir un sistema de lima apropiado. El objetivo de este estudio fue evaluar la flexibilidad de tres limas diferentes de níquel-titanio (NiTi) con tratamiento termomecánico en dos puntos diferentes. Materiales y métodos: Se midió la flexibilidad de tres limas NiTi con tratamiento termomecánico (ProTaper Gold, 2Shape y V-Taper Fanta Gold). Cada lima fue sujetada a 3 mm y 7 mm (n = 10/longitud/lima) y se utilizó una máquina de ensayo universal para doblarla a una fuerza máxima. Todos los datos fueron analizados estadísticamente por análisis de varianza de una vía y prueba de Tukey post hoc (p = 0,05) para determinar cualquier diferencia significativa. Resultados: Se halló diferencias estadísticamente significativas (p < 0,05). En general, V-Taper Fanta Gold fue la más rígida, ProTaper Gold mostró los mayores valores de fuerza y su deformación fue significativamente más flexible. Conclusión: Las limas ProTaper Gold mostraron una mayor flexibilidad en comparación con las otras limas estudiadas. (AU)

Background: Nickel-titanium rotary files with thermomechanical treatment were developed to allow greater flexibility when instrumenting the root canals. The instruments allowed operators to deal with duct curvatures more easily. Manufacturers are trying to produce files that work better efficiently and safely. Knowing the properties of marketed files is especially important in helping you choose an appropriate file system. The objective of this study was to evaluate the flexibility of three different nickel-titanium (NiTi) files with thermomechanical treatment at two different points along the file. Materials and methods: The flexibility of three NiTi files with thermomechanical treatment (Protaper Gold, 2Shape and V-Taper Fanta Gold) was measured. Each file was clamped at 3 mm and 7 mm (n = 10 / length / file) and a universal testing machine was used to bend the files to a maximum strength. All data were statistically analyzed by one-way analysis of variance and post-hoc Tukey test (P = 0.05) to determine any significant differences. Results: There were statistically significant differences (P <0.05). In general, V-Taper Fanta Gold was the most rigid, Protaper Gold showed the highest values of force and deformation was significantly more flexible. Conclusión: Protaper Gold files showed greater flexibility compared to the other files studied. (AU)

CoCrMo alloy as biomaterial for bone reconstruction in oral and maxillofacial surgery: a scoping review / Aleación de CoCrMo como biomaterial para la reconstrucción ósea en cirugía oral y maxilofacial: una revisión del alcance

Background: Osseointegration allowed for a breakthrough in biomaterials and techniques and it has contributed to increased application of dental implants. However, insufficient bone level is a frequent problem and it creates an anatomically less favourable base for implant placement. The first surgical procedure should comprise the reconstruction of the alveolar bone height. CoCrMo alloys are nowadays considered as highly corrosion resistant and biocompatible materials in dentistry, and therefore has been suggested as a suitable biomaterial for guided bone regeneration and tissue engineering. Aim: To determine the use of CoCrMo alloy for implantable devices in oral and maxillofacial surgery and to discuss the potential of this alloy for bone regeneration and repair through a scoping review. Material and methods: The search was done by using various databases including PubMed, Thomson Reuters and Scopus. We selected English literature related to studies reporting the CoCrMo properties and manufacturing processes and findings related to bone-forming techniques. Data was compared qualitatively. Results: 90 studies were selected according to the inclusion criteria. We reported different manufacturing techniques and their advantages related to mechanical, chemical and biocompatible properties. Conclusion: Improved tissue reactions of CoCrMo implant devices can be acquired by the application of novel techniques and surface modifications. Moreover, several processes have demonstrated to improve the in vitro and in vivo biocompatibility of the CoCrMo alloy to promote the attachment, proliferation and guided differentiation of seeding cells.

Antecedentes: La osteointegración ha permitido un gran avance en biomateriales y técnicas, y ha contribuido un mayor uso de implantes dentales. Sin embargo, la existencia de un nivel óseo insuficiente es un problema frecuente y crea una base anatómicamente menos favorable para la colocación de implantes. El primer procedimiento quirúrgico debe comprender la reconstrucción de la altura del hueso alveolar. Las aleaciones de CoCrMo se consideran hoy en día como materiales altamente resistentes a la corrosión y biocompatibles en odontología y, por lo tanto, se ha sugerido como un biomaterial adecuado para la regeneración ósea guiada y la ingeniería de tejidos. Objetivo: Determinar el uso de la aleación CoCrMo para dispositivos implantables en cirugía oral y maxilofacial y discutir sobre el potencial de esta aleación para la regeneración y reparación ósea a través de una revisión de alcance. Material y Métodos: La búsqueda se realizó utilizando varias bases de datos, incluidas PubMed, Thomson Reuters y Scopus. Se seleccionó literatura inglesa relacionada con estudios que informan sobre las propiedades de CoCrMo y los procesos de fabricación y los hallazgos relacionados con las técnicas de formación de huesos. Los datos se compararon cualitativamente. Resultados: Se seleccionaron 90 estudios según los criterios de inclusión. y se reportaron diferentes técnicas de fabricación y sus ventajas relacionadas con propiedades mecánicas, químicas y biocompatibles. Conclusión: Las reacciones tisulares mejoradas de los dispositivos de implante CoCrMo pueden adquirirse mediante la aplicación de nuevas técnicas y modificaciones de la superficie. Además, varios procesos han demostrado mejorar la biocompatibilidad in vitro e in vivo de la aleación CoCrMo para promover la unión, proliferación y diferenciación guiada de las células de siembra.

Enhanced osseointegration of porous titanium scaffold implanted with preload: an experiment study in rabbits / Osteointegración mejorada de malla de titanio poroso implantada con precarga: un estudio experimental en conejos

Porous titanium alloy scaffold was widely used in treating bone defect caused by traumatic injury and osteomyelitis, which was incapable of self-healing. The implantation of scaffold produced stress shielding thereby forming osteolysis. The objective of this study was to analysis trabecular morphological features of osseointegrated bone. 14 New Zealand rabbits were divided into two groups, surgery group and healthy control group. 7 rabbits in surgery group were selected to perform 3D printed porous titanium alloy scaffold implantation surgery with preload at the defect of femoral condyle for osseointegration. The other 7 rabbits in control group were feed free. After 90 days healing, femoral condyles were extracted to perform micro-CT scanning with hydroxyapatite calibration phantom. Mean bone mineral density (BMD), bone volume fraction (BV/TV), BS/TV (bone surface area ratio), Tb.Th (thickness of trabeculae), Tb.N (number of trabeculae), Tb.Sp (trabecular separation) and DA (degree of anisotropy) were calculated from micro-CT images. The results revealed that osseointegration inside and at the surface of scaffolds worked well from grey values of micro-CT images. After 12 weeks healing, mean bone mineral densities (BMD) in surgery group and healthy control group were calculated as 800±20mg/cm3 and 980±90mg/cm3, respectively. This revealed that the strength of trabeculae in surgery group might lower than that in the healthy group. Trabecular morphological parameters test showed that trabecular morphological parameters at the surface of scaffolds in the surgery group deteriorated significantly. It was found from micro-CT images that ingrowth bone was filled with pores of scaffold. Overall, the effect of osseointegration was promoted through the change of mechanical micro-environment in the scaffold region. Overall, preload could improve osseointegration effect in the long-term after surgery. However, the trabecular morphology in the surgery group was deteriorated, which might bring secondary fracture risk again.

La malla de aleación de titanio poroso se usó ampliamente en el tratamiento de defectos óseos causados por lesiones traumáticas y osteomielitis. El implante de la malla generó una protección contra el estrés, formando así osteolisis. El objetivo de este estudio fue analizar las características morfológicas trabeculares del hueso osteointegrado. Se dividieron 14 conejos (Neozelandeses) en dos grupos, grupo cirugía y grupo control saludable. Se seleccionaron 7 conejos en el grupo de cirugía para realizar una implantación de mallas de aleación de titanio poroso, impresas en 3D con precarga en el defecto del cóndilo femoral para la osteointegración. Los 7 conejos restantes del grupo control se mantuvieron sin alimentación. Después de 90 días de curación, se extrajeron los cóndilos femorales para realizar una exploración por micro-CT con un espectro de calibración de hidroxiapatita. Se calcularon a partir de imágenes de micro-CTDensidad mineral ósea media (DMO), fracción de volumen óseo (BV / TV), BS / TV (relación de área de superficie ósea), Tb.Th (espesor de trabéculas), Tb.N (número de trabéculas), Tb.Sp (trabecular separación) y DA (grado de anisotropía). Los resultados revelaron que la osteointegración dentro y en la superficie de los andamios funcionó bien a partir de los valores grises de las imágenes de micro-CT. Después de 12 semanas de curación, las densidades medias de minerales óseos (DMO) en el grupo cirugía y en el grupo control sano se calcularon como 800 ± 20 mg/cm3 y 980 ± 90 mg/cm3, respectivamente. Esto reveló que la fuerza de las trabéculas en el grupo de cirugía podría ser menor que la del grupo sano. La prueba de parámetros morfológicos trabeculares mostró que en el grupo de cirugía, la superficie de las mallas, se deterioraron significativamente. Se descubrió a partir de imágenes de microCT que el hueso en crecimiento estaba lleno de poros de andamio. En general, el efecto de la osteointegración se promovió mediante el cambio del microambiente mecánico en la región de la malla. En general, la precarga podría mejorar el efecto de osteointegración a largo plazo después de la cirugía. Sin embargo, la morfología trabecular en el grupo de cirugía se deterioró, lo que podría traer un nuevo riesgo de fractura secundaria.

Secuencia de arcos para el alineado y nivelado / Archwire sequence for alignment and leveling

La secuencia de arcos en ortodoncia, sobre todo, durante el alineado y nivelado es un tema de gran interés. Para esta etapa se han sugerido fuerzas de 50 gf que no superan la presión hidrostática capilar y no producen reabsorción radicular. El Nitinol es la aleación indicada en sus distintas variantes. Las revisiones sistemáticas no han hallado ventaja de ninguna secuencia de arcos, incluso, equiparando arcos de acero con figuras con el Nitinol termoelástico. La selección de la secuencia de arcos para un paciente depende de las características de la maloclusión(AU)

The sequence of arches in orthodontics especially during alignment and leveling is a subject of great interest. For this stage 50 g forces that do not exceed the capillary hydrostatic pressure and do not produce root resorption have been suggested. Nitinol is the indicated alloy in its different variants. Systematic Reviews have found no advantage of any arch sequence even by matching steel arches with figures with thermoelastic Nitinol. The selection of arch sequence for a patient depends on the characteristics of malocclusion(AU)

The Local Alternative Ti-6Al-4V Alloy Coating of Surgery Steel Instruments for Laser Deposition Forming / 中国医疗器械杂志

Aiming at the medical practice problems of the surgical steel medical instruments, such as the crevice corrosion, the poor mechanical compatibility and the Ni, Cr plasma exudation, the laser deposition of Ti-6Al-4V alloy cladding layer at the local functional area as alternative coating was proposed and realized as a new process method. The accurate element content and good formability Ti-6Al-4V cladding powder was chosen, the low power and high duty cycle optimized laser process was adopt, the alternative coating of good fusion and low dilution was prepared. Through the elemental line scanning, the interface microstructure analysis and the experiments of basic mechanical properties, the basic properties of the cladding were characterized and verified. The experiments results showed that, the Ti, Al and V contents of the top coating were respectively about 88%, 4.9% and 3.9%, no sensitizing ions such as Cr and Ni were detected. Initial equiaxed α phase, flake β phase dist were distributed in the coating and interface, the α' martensite was precipitated at the boundary of the flake β phase, some refined granular β phase dispersion pinned to the grain boundary of basket structure. The microhardness of cladding layer was 352.08~312.76 HV0.1. The friction coefficient of the cladding layer was about 0.22~0.65. A new technology and method reference for improving and upgrading the performance of surgical medical devices is provided by this research.

Safety performance of self-expandable NiTi alloy stent / 生物医学工程学杂志

In order to evaluate the safety performance of self-expandable NiTi alloy stents systematically, the dynamic safety factor drawn up by International Organization for Standardization, was used to quantitatively reflect the safety performance of stents. Based on the constitutive model of super-elastic memory alloy material in Abaqus and uniaxial tensile test data of NiTi alloy tube, finite element method and experiments on accelerated fatigue life were carried out to simulate the self-expansion process and the shape change process under the action of high and low blood pressure for three -type stents of 8×30 mm, 10×30 mm, 12×30 mm. By analyzing the changes of stress and strain of self-expanding NiTi alloy stent, the maximum stress and strain, stress concentration position, fatigue strength and possible failure modes were studied, thus the dynamic safety factor of stent was calculated. The results showed that the maximum stress and plastic strain of the stent increased with the increase of grip pressure, but the maximum stress and strain distribution area of the stent had no significant change, which were all concentrated in the inner arc between the support and the connector. The dynamic safety factors of the three stents were 1.31, 1.23 and 1.14, respectively, which indicates that the three stents have better safety and reliability, and can meet the fatigue life requirements of more than 10 years, and safety performance of the three stents decreases with the increase of stent's original diameter.

The biofilm removal effect of MnO₂-diatom microbubbler from the dental prosthetic surfaces: In vitro study / 대한치과보철학회지

PURPOSE: The aim of this study is to evaluate the effectiveness of MnO₂-diatom microbubbler (DM) on the surface of prosthetic materials as a mouthwash by comparing the biofilm removal effect with those previously used as a mouthwash in dental clinic.MATERIALS AND METHODS: DM was fabricated by doping manganese dioxide nanosheets to the diatom cylinder surface. Scanning electron microscopy (SEM) was used to observe the morphology of DM and to analyze the composition of doped MnO₂. Stereomicroscope was used to observe the reaction of DM in 3% hydrogen peroxide. Non-precious metal alloys, zirconia and resin specimens were prepared to evaluate the effect of biofilm removal on the surface of prosthetic materials. And then Streptococcus mutans and Porphyromonas gingivalis biofilms were formed on the specimens. When 3% hydrogen peroxide solution and DM were treated on the biofilms, the decontamination effect was compared with chlorhexidine gluconate and 3% hydrogen peroxide solution by crystal violet staining.RESULTS: Manganese dioxide was found on the surface of the diatom cylinder, and it was found to produce bubble of oxygen gas when added to 3% hydrogen peroxide. For all materials used in the experiments, biofilms of the DM-treated groups got effectively removed compared to the groups used with chlorhexidine gluconate or 3% hydrogen peroxide alone.CONCLUSION: MnO₂-diatom microbubbler can remove bacterial membranes on the surface of prosthetic materials more effectively than conventional mouthwashes.

Research advance in surface modification of titanium alloys with chitosan / 中国骨伤

Titanium alloy has good biological properties and is commonly used in orthopedics, but its bone integrity and antibacterial properties are poor, so surface modification is needed to make up for its shortcomings. Chitosan has good biocompatibility and film forming ability, and can be used as a carrier to introduce the target drug to the surface of titanium alloy, which can effectively improve the biological properties of titanium alloy materials and increase its application range. In this paper, the related research of chitosan surface modified titanium alloy materials in recent years is summarized. The modification methods of chitosan coating, the improvement of osteogenesisand antibacterial properties of titanium alloy materials are discussed in order to provide guidance for the clinical application of coating modification of titanium alloy materials.

Numerical study on the mechanical coupling of external vascular stent and vein graft in coronary artery bypass surgery / 生物医学工程学杂志

External support stent is a potential means for restricting the deformation and reducing wall stress of the vein graft, thereby improving the long-term patency of the graft in coronary artery bypass surgery. However, there still lacks a theoretical reference for choosing the size of stent based on the diameter of graft. Taking the VEST (venous external support) stent currently used in the clinical practice as the object of study, we constructed three models of VEST stents with different diameters and coupled them respectively to a model of the great saphenous vein graft, and numerically simulated the expansion-contraction process of the vein graft under the constraint of the stents to quantitatively evaluate the influence of stent size on the radial deformation and wall stress of the vein graft. The results showed that while the stent with a small diameter had a high restrictive effect in comparison with larger stents, it led to more severe concentration of wall stress and sharper changes in radial deformation along the axis of the graft, which may have adverse influence on the graft. In order to solve the aforementioned problems, we ameliorated the design of the stent by means of changing the cross-sectional shape of the thick and thin alloy wires from circle into rectangle and square, respectively, while keeping the cross-sectional areas of alloy wires and stent topology unchanged. Further numerical simulations demonstrated that the ameliorated stent evidently reduced the degrees of wall stress concentration and abrupt changes in radial deformation, which may help improve the biomechanical environment of the graft while maintaining the restrictive role of the stent.

Effect of dlc films with and without silver nanoparticles deposited on titanium alloy

Abstract Diamond-like carbon (DLC) film is a biocompatible hard coating material that can prevent the leaching of metal ions. This study evaluates the structural characteristics of DLC, with and without silver nanoparticles, deposited by plasma (PECVD) on titanium alloy (Ti-6Al-4V) and bone formation in contact with DLC films. Sixty Ti-6Al-4V samples were used divided in: uncoated, coated with DLC and coated with DLC-Ag. After structural characterization, samples were fixed bilaterally at the rabbit's mandible. After 15 and 90 days, samples were characterized again and bone formation in the area was analyzed by histomorphometry. Statistical analysis was performed by two-way ANOVA. Both the DLC and DLC-Ag films were firmly adhered and showed a high electrical resistance without significant changes in the Raman spectrum after in vivo integration. After 15 days, there were immature bone trabeculae in the interface and partially covering the surface. After 90 days, mature bone filled the interface and coved the surface. There was no statistically significant difference among the three groups in both periods. In conclusion, osseointegration with DLC, DLC-Ag and uncoated Ti-6Al-4V is similar. However, DLC and DLC-Ag coverings have the advantage of electrical insulation and can presumably control bacterial activity and ion leaching.

Resumo O filme de carbono semelhante a diamante (DLC) é um material de revestimento duro e biocompatível que pode impedir a corrosão com liberação de íons metálicos. Este estudo avaliou as características estruturais do filme de DLC, com e sem nanopartículas de prata (Ag), depositadas por plasma (PECVD) em liga de titânio (Ti-6Al-4V) e formação óssea em contato com filmes de DLC. Foram utilizadas 60 amostras de Ti-6Al-4V divididas em: não recobertas, recobertas com DLC e recobertas com DLC-Ag. Após caracterização estrutural, amostras foram fixadas bilateralmente na mandíbula de coelhos. Após 15 e 90 dias, as amostras foram novamente caracterizadas e a formação óssea na área foi analisada por histomorfometria. A análise estatística foi realizada por ANOVA dois fatores. Ambos os filmes DLC e DLC-Ag foram firmemente aderidos e mostraram uma alta resistência elétrica sem alterações significativas no espectro Raman após a osseointegração in vivo. Após 15 dias, havia trabéculas ósseas imaturas na interface e cobrindo parcialmente a superfície. Após 90 dias, o osso maduro preencheu a interface e a superfície. Não houve diferença estatisticamente significante entre os três grupos nos dois períodos. Em conclusão, a osseointegração com DLC, DLC-Ag e Ti-6Al-4V não revestido é similar. No entanto, os revestimentos DLC e DLC-Ag têm a vantagem do isolamento elétrico e podem presumivelmente controlar a atividade bacteriana e a corrosão com liberação de íons.

Bionic mechanical design and 3D printing of novel porous Ti6Al4V implants for biomedical applications / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

In maxillofacial surgery, there is a significant need for the design and fabrication of porous scaffolds with customizable bionic structures and mechanical properties suitable for bone tissue engineering. In this paper, we characterize the porous Ti6Al4V implant, which is one of the most promising and attractive biomedical applications due to the similarity of its modulus to human bones. We describe the mechanical properties of this implant, which we suggest is capable of providing important biological functions for bone tissue regeneration. We characterize a novel bionic design and fabrication process for porous implants. A design concept of "reducing dimensions and designing layer by layer" was used to construct layered slice and rod-connected mesh structure (LSRCMS) implants. Porous LSRCMS implants with different parameters and porosities were fabricated by selective laser melting (SLM). Printed samples were evaluated by microstructure characterization, specific mechanical properties were analyzed by mechanical tests, and finite element analysis was used to digitally calculate the stress characteristics of the LSRCMS under loading forces. Our results show that the samples fabricated by SLM had good structure printing quality with reasonable pore sizes. The porosity, pore size, and strut thickness of manufactured samples ranged from (60.95± 0.27)% to (81.23±0.32)%, (480±28) to (685±31) μm, and (263±28) to (265±28) μm, respectively. The compression results show that the Young's modulus and the yield strength ranged from (2.23±0.03) to (6.36±0.06) GPa and (21.36±0.42) to (122.85±3.85) MPa, respectively. We also show that the Young's modulus and yield strength of the LSRCMS samples can be predicted by the Gibson-Ashby model. Further, we prove the structural stability of our novel design by finite element analysis. Our results illustrate that our novel SLM-fabricated porous Ti6Al4V scaffolds based on an LSRCMS are a promising material for bone implants, and are potentially applicable to the field of bone defect repair.

Effects of CAD/CAM titanium alloy surface treatment and resin luting on shear bond strength and durability of composite resin / 北京大学学报(医学版)

OBJECTIVE@#To assess the effects of two surface treatments (sandblasting, SB; microarc-oxidation, MAO) and resin luting on shear bond strength and durability of titanium alloy and composite-resin.@*METHODS@#Eighty cylindrical titanium alloy specimens with a diameter of 10 mm and a height of 8 mm were fabricated by CAD/CAM technique. It was divided into two groups according to the surface treatment methods: sandblasting with Al2O3 particles on the surface of SB specimens; porous ceramic film structure could be formed on the surface of MAO specimens after surface treatment. Each group was classified into SB-resin luting-N group (not used), SB-resin luting-Y group (used), MAO-resin luting-N group (not used), MAO-resin luting-Y group (used) depending on whether or not resin luting was applied. Each specimen was bonded and cured with the Cemerage resin, and the shear bond strength after 0 and 5 000 thermocycling was tested. The results were statistically analyzed. The surface morphology of titanium alloy specimens before and after the shear bond strength test was observed by scanning electron microscopy (SEM).@*RESULTS@#The shear bond strength between titanium alloy and composite-resin was the highest in the SB combined with resin luting group after 0 thermocycling (16.2±1.8) MPa; was the lowest in MAO group after 5 000 thermocycling (8.9±1.5) MPa. The shear bond strength of SB and MAO surface treatment methods combined without resin luting group after 5 000 thermocycling were (10.7±2.2) MPa and (8.9±1.5) MPa, which were statistically lower than those in the thermocycling 0 (P=0.000 and P=0.001). The shear bond strength of SB and MAO surface treatment methods combined with resin luting group after 5 000 thermocycling were (15.5±2.1) MPa and (11.7±1.3) MPa, respectively, which were lower than those in the thermocycling 0 group, but there was no statistical significance (P=0.087 and P=0.234).@*CONCLUSION@#Both the surface treatment methods of SB and MAO combined with resin luting can improve the shear bond strength and durability of titanium alloy and composite-resin. The SB combined with resin luting is more significant. At present, the effect of SB is better than that of MAO due to the limitation of technical parameters of micro-arc oxidation.