Self-powered therapeutic release from conducting polymer/graphene oxide films on magnesium

Magnesium's complete in vivo degradation is appealing for medical implant applications. Rapid corrosion and hydrogen bubble generation along with inflammatory host tissue response have limited its clinical use. Here we electropolymerized a poly (3,4-ethylenedioxythiophene) (PEDOT) and graphene oxide (GO) film directly on Mg surface. GO acted as nano-drug carrier to carry anti-inflammatory drug dexamethasone (Dex). PEDOT/GO/Dex coatings improved Mg corrosion resistance and decreased the rate of hydrogen production. Dex could be released driven by the electrical current generated from Mg corrosion. The anti-inflammatory activity of the released Dex was confirmed in microglia cultures. This PEDOT/GO/Dex film displayed the ability to both control Mg corrosion and act as an on demand release coating that delivers Dex at the corrosion site to minimize detrimental effects of corrosion byproducts. Such multi-functional smart coating will improve the clinical use of Mg implants. Furthermore, the PEDOT/GO/Drug/Mg system may be developed into self-powered implantable drug delivery devices.     

Microstructural,mechanical, ionic release and tarnish resistance characterization of porcelain fused to metal Co–Cr alloys manufactured via casting and three different CAD/CAM techniques

PurposeTo perform a comparative analysis of the microstructure, porosity, mechanical properties, corrosion, and tarnish resistance of Co–Cr alloys prepared by casting and three different computer aided designed/computer aided manufacturing (CAD/CAM) techniques.MethodsFour groups of metallic specimens were prepared, one each by conventional casting (CST), milling (MIL), selective laser melting (SLM), and milling soft metal (MSM). Ten samples were tested by X-rays, after which their microstructure and elemental composition were tested by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) analysis. Martens hardness (HM) and elastic index (η_IT) were determined by instrumented indentation testing (IIT), while modulus of elasticity (E) was determined by three-point bending. Corrosion measurements were tested according to International Organization for Standardization (ISO) 10271. The electrolytes were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The results were analyzed by one-way ANOVA and Holm–Sidak’s multiple-comparison test (α = 0.05).ResultsThe CST group illustrated internal flaws while all CAD/CAM group samples were found to be free of them. No statistically significant differences were identified among groups in their elemental composition. SLM showed the highest HM, followed by the MIL, CST, and MSM. Elastic index showed significant differences among all groups, with CST showing the lowest and SLM the highest values. SLM showed the highest elastic modulus values, followed by MSM, MIL, and CST. No significant differences were found in ionic release among groups. No surface deterioration after static and cyclic tarnish testing was determined.ConclusionsThe manufacturing procedure significantly affects the microstructure, porosity, and mechanical properties of Co–Cr alloys. In contrast, ionic release and tarnish resistance are independent of the manufacturing technique used.     

3D打印和铸造钴铬合金耐蚀性及力学稳定性比较

目的研究3D打印和铸造钴铬合金的耐蚀性及腐蚀对其力学稳定性的影响。 方法采用3D打印技术中选择性激光熔融技术（SLM）和传统铸造技术共制作钴铬合金试件72个,根据是否腐蚀采用随机数字法随机平均分为12组（每组6个）,各组用于不同的测试及进入腐蚀。采用静态浸泡腐蚀法对试件进行腐蚀实验,激光扫描共聚焦显微镜（CLSM）检测试件表面粗糙度（Ra）及表面形貌,显微硬度计测量显微维氏硬度（VHN）,万能测试机测试拉伸强度（TS）及弯曲强度（BS）。工艺和腐蚀对Ra、VHN、TS、BS等值的影响采用双因素析因方差分析进行分析（α= 0.05）,Bonferroni法进行组间两两比较。 结果工艺和腐蚀对Ra和BS无交互效应（F_Ra= 2.989,P_Ra= 0.099;F_BS= 0.480,P_BS= 0.496）。两因素对Co-Cr合金的Ra值的主效应均有统计学意义（F_工艺=6.262,P_工艺=0.021;F_腐蚀= 6.581,P_腐蚀= 0.018）,3D组的Ra值[（0.084 ± 0.026）μm]低于铸造组[（0.111 ± 0.024）μm],对照组的Ra值[（0.084 ± 0.025）μm]低于腐蚀组[（0.111 ± 0.025）μm]。两因素对Co-Cr合金的BS值的主效应均有统计学意义（F_工艺= 6.753,P_工艺= 0.013;F_腐蚀= 7.384,P_腐蚀= 0.017）,3D组的BS值[（1651 ± 242）MPa]高于铸造组[（1371 ± 252）MPa],对照组的BS值[（1645±183）MPa]高于腐蚀组[（1377±310）MPa]。两因素对VHN和TS有交互效应（F_VHN=5.018,P_VHN=0.037;F_TS= 5.903,P_TS= 0.025）。Bonferroni法组间两两比较结果显示,3D对照组VHN值和TS值[VHN_3D=（469 ± 4）HV,TS_3D=（1010 ± 46）MPa]与铸造对照组[VHN_铸造=（418 ± 4）HV,TS_铸造=（827 ± 25）MPa]比较,差异有统计学意义（P_VHN<0.001,P_TS<0.001）;3D腐蚀组VHN值及TS值[VHN_3D=（418±3）HV,TS_3D=（985 ± 30）MPa]与铸造腐蚀组[VHN_铸造=（375 ± 5）HV,TS_铸造=（728 ± 45）MPa]比较,差异有统计学意义（P_VHN<0.001,P_TS<0.001）;3D对照组VHN值与3D腐蚀组比较差异有统计学意义（P<0.001）,3D对照组TS值与3D腐蚀组比较差异无统计学意义（P= 1.000）;铸造对照组VHN值及TS值与铸造腐蚀组差异有统计学意义（P_VHN<0.001,P_TS= 0.001）。 结论3D打印钴铬合金较铸造钴铬合金耐蚀性更优;前者TS、BS的稳定性均大于后者,两者的VHN稳定性相当。     

Corrosion Resistance of Different Nickel-Titanium Archwires in Acidic Fluoride-containing Artificial Saliva

Objective:To test the hypothesis that different nickel-titanium (NiTi) archwires may have dissimilar corrosion resistance in a fluoride-containing oral environment.Materials and Methods:Linear polarization test, a fast electrochemical technique, was used to evaluate the corrosion resistance, in terms of polarization resistance (R_p), of four different commercial NiTi archwires in artificial saliva (pH 6.5) with various NaF concentrations (0%, 0.01%, 0.1%, 0.25%, and 0.5%). Two-way analysis of variance was used to analyze R_p with the factors of archwire manufacturer and NaF concentration. Surface characterizations of archwires were analyzed using scanning electron microscopy, atomic force microscopy, and x-ray photoelectron spectroscopy.Results:Both archwire manufacturer and NaF concentration had a significant influence on R_p of NiTi archwires. Different surface topography was present on the test NiTi archwires that contained the similar surface chemical structure (TiO₂ and trace NiO). The surface topography did not correspond to the difference in corrosion resistance of the NiTi archwires. Increasing the NaF concentration in artificial saliva resulted in a decrease in R_p, or corrosion resistance, of all test NiTi archwires. The NiTi archwires severely corroded and showed similar corrosion resistance in 0.5% NaF-containing environment.Conclusions:Different NiTi archwires had dissimilar corrosion resistance in acidic fluoride-containing artificial saliva, which did not correspond to the variation in the surface topography of the archwires. The presence of fluoride in artificial saliva was detrimental to the corrosion resistance of the test NiTi archwires, especially at a 0.5% NaF concentration.     

新型钛铜合金的耐蚀性初探

目的 对新型钛铜合金进行耐蚀性评价,探讨其在口腔环境中应用的可能性.方法 分别制备Cu质量分数为5%和10%的钛铜合金(Ti-5Cu和Ti-10Cu),用X射线衍射仪对钛铜合金进行物相分析,以纯钛、不锈钢(316L)作为对照,测量4种金属在0.9%NaCl溶液、添加1.0%乳酸的0.9%NaCl溶液中的开路电位和动电位极化曲线.结果 X射线衍射分析显示,两种钛铜合金主要由α相和Ti2Cu金属间化合物构成.在两种溶液中两种钛铜合金表现出类似的腐蚀行为.经3500 s浸泡,纯钛、Ti-5Cu、Ti-10Cu在0.9%NaCl溶液中的开路电位分别为-188、-181和-173 mV,在添加乳酸的0.9%NaCl溶液中的开路电位分别为-143、-158和-109 mV.动电位极化曲线显示,纯钛和Ti-5Cu在500 mV附近的维钝电流密度约为20 μA/cm2,而不锈钢出现明显的点蚀现象.结论 钛铜合金在0.9%NaCl溶液中表现出良好的耐蚀性,Ti-5Cu合金的耐蚀性与纯钛相当,Ti-10Cu合金的耐蚀性虽比纯钛有所降低,但仍大大优于不锈钢.乳酸的加入对钛铜合金的耐蚀性影响不大.     

电化学阻抗法研究口腔含氟环境中纯钛的腐蚀行为

目的：电化学阻抗法研究钛修复材料在口腔含氟环境中的腐蚀性能。方法：采用高级电化学分析仪获得钛在人工唾液和含氟人工唾液中的电化学阻抗谱,利用EIS-Nyquist图、EIS-Bode图及等效电路的拟合解析,系统研究F-对钛腐蚀性能的影响。结果：当人工唾液中F-浓度为0.1%,钛表面氧化膜的阻抗值及相位角无显著变化,当人工唾液中F-浓度达到0.2%时,钛表面氧化膜的阻抗值显著下降,而低频区的相位角下降到30°。结论：电化学阻抗法可以用来研究钛在口腔含氟环境下的腐蚀性能,较高浓度的氟可以对钛产生严重的腐蚀作用。     

人工唾液中氯化钠浓度对钴铬、镍铬、含钛镍铬合金腐蚀行为的影响

目的：在人工唾液中氯化钠浓度升高的条件下,用电化学阻抗谱研究3种牙科常用合金（钴铬、镍铬、含钛镍铬合金）腐蚀行为的变化。方法：测定在人工唾液中氯化钠浓度分别为0.9%、2%、3%的条件下,3种合金的电化学阻抗谱,将各体系中合金界面电容和电荷转移电阻拟合,分析其腐蚀机制和耐腐蚀性能的变化。结果：随着氯化钠浓度升高,3种合金的界面电荷转移电阻（Rt值）都分别减小,界面电容（Qdl）增大,腐蚀反应过程加剧,抗蚀能力降低。但钴铬合金的Rt值是最大的。结论：在高氯环境中,3种合金腐蚀反应加快,抗腐蚀能力均降低,但钴铬合金抗腐蚀能力相对较强,这将影响它们的使用寿命。     

THE ELECTROCHEMICAL PROPERTIES OF FOUR DENTAL CASTING SUPRASTRUCTURE ALLOYS COUPLED WITH TITANIUM IMPLANTS

Objectives:

As the choice of suprastructure alloy to be combined with titanium for the oral cavity is still a much debated issue, the aim of this study was to investigate the electrochemical interaction of the suprastructure/implant couples under the determined experiment conditions.

Material and Methods:

The potentiodynamic polarization curves and open-circuit potentials (OCP) of four UCLA type suprastructures coupled with straight Swiss Plus implant fixtures were taken in Afnor type artificial saliva solution at 37°C. The concentration of ions leached into artificial saliva solutions was estimated with ICP-MS. SEM images of the margins of suprastructure/implant couples were obtained before and after the electrochemical tests.

Results:

The OCP value of titanium became passive at the most negative potential. The lowest difference between the initial and constant OCP value was exhibited by the Au based suprastructure. Suprastructures made greater contributions to the potentiodynamic polarization curves of the implant/suprastructure couples. According to the ICP-MS results, Pd based and Au based couples dissolved less than Co-Ni based and Co-Cr based couples.

Conclusions:

Within the conditions this study, it may be concluded that the titanium implant forms a stable passive oxide layer in artificial saliva exposed to open air and does not affect the corrosion properties of the suprastructures. Pd based and Au based couples have been found to be more corrosion-resistant than base alloy couples.     

Spatial growth and pattern formation in the small intestine microvascular bed from larval to adult Xenopus laevis: a scanning electron microscope study of microvascular corrosion casts

The microvascular anatomy of the small intestine of metamorphosing tadpoles of the South African Clawed Toad, Xenopus laevis (Daudin) is studied from developmental stages 55 to 65 and in adults by scanning electron microscopy (SEM) of vascular corrosion casts (VCCs) and light microscopy. Up to stage 62, VCCs reveal a dense two-dimensional vascular network ensheating the intestinal tube, whose proximal portion forms a clockwise spiralling outer and its distal portion an anti-clockwise spiralling inner coil. Vessels of the intestinal network impose flat and run circularly to slightly obliquely. Locally, dense capillary plexus with small “holes” indicating ongoing intussusceptive microvascular growth (IMG) and vessel maturation, are present. The typhlosole, an invagination along the proximal portion of the small intestine, reveals a dense capillary bed with locally ongoing IMG. VCCs of stages 62/63 for the first time reveal a three-dimensional vascular bed with longitudinal intestinal folds of varying size and heights greatly enlarging the luminal exchange area of the intestinal tube. From stage 65 onwards, longitudinal intestinal folds undulate and, though smaller in size and less mature as indicated in VCCs by the presence of wider, sinus-like vessels with small “holes” interposed between, closely resemble the intestinal folds present in the small intestine of adult Xenopus. Our data suggest that maturation of the vascular pattern in the small intestine of X. laevis tadpoles takes place successively after stages 62–63, and growth during this period is preferentially by intussusception.     

人工髋关节股骨头－颈锥度侵蚀研究

锥度侵蚀是指股骨头颈锥度界面的磨损和腐蚀,是目前逐渐被认识的全髋关节置换失败原因之一。近来有不少的报道锥度侵蚀与金对金假体一样引起局部组织不良反应,可能生物力学和生物电化学因素有关,锥度设计,假体材料,股骨头直径等是导致锥度侵蚀的可能机制,并可促进其发生局部组织不良反应。诊断,主要依靠金属离子分析以及影像学检查,而治疗则关注翻修手术是否能够保留股骨颈锥度,以及避免锥度侵蚀适宜的股骨头材料。本文对人工髋关节股骨头颈交界锥度侵蚀的病因、发病机制、危险因素、诊断以及治疗作一综述。