辉光等离子渗氮 阳极氧化对纯钛腐蚀性的影响

目的:模拟口腔环境,研究辉光等离子渗氮纯钛试样及阳极氧化纯钛试样在pH=6.8的人工唾液中的腐蚀情况。方法:采用塔菲尔(tafel)曲线测试,测定辉光等离子渗氮纯钛试样及阳极氧化纯钛试样在pH=6.8的人工唾液中的自腐蚀电流密度(Icorr)、极化电阻(Rp),并以自然氧化纯钛试样为对照组进行比较分析。结果:辉光等离子渗氮及阳极氧化对纯钛腐蚀性的影响均有显著性,P<0.01。Icorr均明显减小,Rp明显增大,腐蚀速度减慢。辉光等离子渗氮纯钛试样在pH=6.8的人工唾液中Icorr最小,Rp最大,耐腐蚀性能最好。结论:辉光等离子渗氮及阳极氧化两种表面处理方法可以显著提高纯钛试样在pH=6.8的人工唾液中的耐腐蚀性;进行辉光等离子渗氮表面处理后纯钛试样的耐腐蚀性能更优。     

Influence of surface layer on mechanical and corrosion properties of nickel-titanium orthodontic wires

Objective:To analyze the effect of various coating formulations on the mechanical and corrosion properties of nickel-titanium (NiTi) orthodontic wires.Materials and Methods:Uncoated, rhodium-coated, and nitrified NiTi wires were observed with a three-point-bend test, surface roughness (Ra) measurement, scanning electron microscopy, energy dispersive spectroscopy, and electrochemical testing (open circuit potential, electrochemical impedance spectroscopy, and cyclic polarization scan). Differences in the properties of tested wire types were analyzed with analysis of variance and Tukey post hoc test.Results:Uncoated and nitrified NiTi wires showed similar mechanical and anticorrosive properties, while rhodium-coated NiTi wires showed the highest Ra and significantly higher modulus of elasticity, yield strength, and delivery of forces during loading but not in unloading. Rhodium-coated NiTi wires also had the highest corrosion current density and corrosion potential, lowest impedance modulus, and two time constants on Bode plot, one related to the Rh/Au coating and the other to underlying NiTi.Conclusion:Working properties of NiTi wires were unaffected by various coatings in unloading. Nitrification improved corrosion resistance. Rhodium coating reduced corrosion resistance and pronounced susceptibility to pitting corrosion in artificial saliva because of galvanic coupling between the noble coating and the base alloy.     

A layer-by-layer approach to natural polymer-derived bioactive coatings on magnesium alloys

The development of polyelectrolyte multilayered coatings on magnesium alloy substrates that can be used for controlled delivery of growth factors and required biomolecules from the surface of these degradable implants could have a significant impact in the field of bone tissue regeneration. The current work reports on the fabrication of multilayered coatings of alginate and poly-l-lysine on alkaline- and fluoride-pretreated AZ31 substrates using a layer-by-layer (LbL) technique under physiological conditions. Furthermore, these coatings were surface functionalized by chemical cross-linking and fibronectin immobilization, and the resultant changes in surface properties have been shown to influence the cellular activity of these multilayered films. The physicochemical characteristics of these coated substrates have been investigated using attenuated total reflectance Fourier transform infrared spectroscopy, atomic force microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Cytocompatibility studies using MC3T3-E1 osteoblasts show that the fluoride-pretreated, cross-linked and fibronectin-immobilized LbL-coated substrates are more bioactive and less cytotoxic than the hydroxide-pretreated, cross-linked and fibronectin-immobilized LbL-coated samples. The in vitro degradation results show that the multilayered coatings of these natural polysaccharide- and synthetic polyamino acid-based polyelectrolytes do not alter the degradation kinetics of the substrates; however, the pretreatment conditions have a significant impact on the overall coating degradation behavior. These preliminary results collectively show the potential use of LbL coatings on magnesium-based degradable scaffolds to improve their surface bioactivity.     

Corrosion properties of low carbon CoCrMo and additively manufactured CoCr alloys for dental applications

ObjectivesAdditive manufacturing (AM) is being applied to metallic biomaterials and dental alloys, including CoCrMo. CoCrMo mechanical properties and corrosion resistance are vital to the structural integrity of implants and dental appliances. The goal of this work is to assess the resistivity of AM cobalt chromium alloys by comparing them with traditional CoCrMo, regarding electrochemical properties resulting from microstructural and oxide film differences.MethodsIn this work, selective laser melting (SLM), was used to manufacture CoCrMoW. The corrosion characteristics of AM alloy were compared to that of wrought LC CoCrMo (ASTM F-1537) in both phosphate buffered saline (PBS) and PBS with 10 mM H₂O₂ to simulate increased inflammatory conditions. Anodic polarization and electrochemical impedance spectroscopy (EIS) were performed.ResultsBoth alloys were substantially similar in corrosion behavior in both solutions. They exhibited changes with the different solutions. Polarization resistances were statistically lower (R_p^AM = 1.4 MΩcm² (PBS) vs. 0.72 MΩcm² (H₂O₂), R_p^LC = 1.86 MΩcm² (PBS) vs. 0.55 MΩcm² (H₂O₂)), and open circuit potentials (OCP’s) were statistically higher in 10 mM H₂O₂ for both alloys (0.20 V (in H₂O₂) vs. ? 0.09 V in PBS). Chemistry variations were revealed by the corrosion tests indicating that wrought LC CoCrMo retained its casting-based chemical heterogeneity, while AM CoCrMoW had sub-cell structures within the solidified grains.SignificanceAs novel production methods like AM arise, it is necessary to understand any microstructural differences that may diminish the corrosion resistance properties. AM CoCrMoW alloys hold significant promise for use in dentistry where complex geometries are required.     

COMPRESSIVE FATIGUE IN TITANIUM DENTAL IMPLANTS SUBMITTED TO FLUORIDE IONS ACTION

The aim of this study was to assess the influence of a fluoridated medium on the mechanical properties of an internal hexagon implant-abutment set, by means of compression, mechanical cycling and metallographic characterization by scanning electronic microscopy. Five years of regular use of oral hygiene with a sodium fluoride solution content of 1500 ppm were simulated, immersing the samples in this medium for 184 hours, with the solutions being changed every 12 hours. Data were analyzed at a 95% confidence level with Fisher''s exact test. After the action of fluoride ions, a negative influence occurred in the mechanical cycling test performed in a servohydraulic machine (Material Test System-810) set to a frequency of 15 Hz with 100,000 cycles and programmed to 60% of the maximum resistance of static compression test. The sets tended to fracture by compression on the screw, characterized by mixed ruptures with predominance of fragile fracture, as observed by microscopy. An evidence of corrosion by pitting on sample surfaces was found after the fluoride ions action. It may be concluded that prolonged contact with fluoride ions is harmful to the mechanical properties of commercially pure titanium structures.     

A new inhibitor for mild carbon steel: Electrochemical and DFT studies

The anti-corrosive properties of 2-aminomethylbenzimidazole (AMB) and bis(benzimidazol-2-ylethyl)sulfide (BBES) were analyzed by electrochemical techniques such as polarization curves and electrochemical impedance spectroscopy (EIS). The results show that AMB behaves as a cathodic inhibitor, while BBES functions as mixture inhibitor. Furthermore, BBES inhibits the corrosive process more strongly than AMB; because in the former benzimidazoles and thioether sulfur work as active sites for the adsorption process over the metal surfaces. This observation is supported by density functional theoretical (DFT) parameters such as frontier molecular orbitals (HOMO and LUMO), Mulliken charges and the electrostatic potential map.     

钴铬钼微孔表面人工髋关节材料细菌源性生物腐蚀的初步研究

作者针对由于绿脓杆菌感染造成焊接型ＰＣＡ全髋置换失败，再次手术中发现关节材料表面有绿色锈斑、金属珠粒易脱落等问题，采用同种材料和工艺制成的金属试样进行细菌学研究。细菌培养分为需氧培养和厌氧培养两大组，菌株为绿脓、金葡、大肠、产气荚膜等六种常见致病菌，接种成单一菌落和混合菌落，金属试样分别浸泡在含有上述菌落的普通肉汤培养基（用于需氧培养）和庖肉培养基（用于厌氧培养）中。半年后取出，在实体工具镜下观察金属材料表面的情况。结果发现，需氧培养中产绿色绿脓色素的绿脓杆菌和厌氧培养下的大肠杆菌可以在金属材料表面形成点蚀及色斑，与临床所见相符。这一结果说明，在感染的全髋置换病例中，人工关节材料的细菌源性生物腐蚀确实存在，并且是手术失败的原因之一。     

电子束熔融制造医用Ti6Al4V在人工模拟体液中耐腐蚀行为

目的 研究电子束熔融技术（EBM）3D打印制备的医用Ti6Al4V不同打印截面在Hank''s模拟人工体液中的电化学腐蚀行为。方法 采用开路电位和动电位极化曲线方法研究了Ti6Al4V不同打印截面,分别记为EBM-XOY面（垂直于打印方向的钛合金截面）和EBM-YOZ面（平行于打印方向的钛合金截面）,在Hank''s模拟人工体液中的电化学腐蚀行为,利用SEM、XRD和金相显微镜分析了其表面形貌和物相组成及其腐蚀机理,并与传统医用锻造Ti6Al4V进行了对比研究。结果 与传统医用锻造Ti6Al4V合金相比,EBM-YOZ面钛合金在Hank’s模拟人工体液中的开路电位、腐蚀电位和腐蚀电流与之相当,显示出与之接近的耐腐蚀性能;EBM-XOY面钛合金的耐腐蚀性能较EBM-XOZ面和传统锻造钛合金稍差,主要原因是EBM-XOY面的α+β相界面积大,α相含量较高,且被优先溶解,因此,耐腐蚀性能较差。结论 电子束熔融制造的Ti6Al4V不同截面的耐腐蚀性能不同,EBM-YOZ面的耐腐蚀性能与传统医用锻造钛合金相当,EBM-XOY面的耐腐蚀性能稍差。     

Metal ion release from silver soldering and laser welding caused by different types of mouthwash

Objective:To compare metal ion release from samples welded with silver soldering and laser welding when immersed into mouthwashes with different ingredients.Materials and Methods:A total of 72 samples were prepared: 36 laser welded and 36 silver soldered. Four samples were chosen from each subgroup to study the morphologic changes on their surfaces via scanning electron microscopy (SEM). Each group was further divided into four groups where the samples were submerged into mouthwash containing sodium fluoride (NaF), mouthwash containing sodium fluoride + alcohol (NaF + alcohol), mouthwash containing chlorhexidine (CHX), or artificial saliva (AS) for 24 hours and removed thereafter. Subsequently, the metal ion release from the samples was measured with inductively coupled plasma mass spectrometry (ICP-MS). The metal ion release among the solutions and the welding methods were compared. The Kruskal-Wallis and analysis of variance (ANOVA) tests were used for the group comparisons, and post hoc Dunn multiple comparison test was utilized for the two group comparisons.Results:The level of metal ion release from samples of silver soldering was higher than from samples of laser welding. Furthermore, greater amounts of nickel, chrome, and iron were released from silver soldering. With regard to the mouthwash solutions, the lowest amounts of metal ions were released in CHX, and the highest amounts of metal ions were released in NaF + alcohol. SEM images were in accord with these findings.Conclusions:The laser welding should be preferred over silver soldering. CHX can be recommended for patients who have welded appliances for orthodontic reasons.     

Improved biological performance of magnesium by micro-arc oxidation

Magnesium and its alloys have recently been used in the development of lightweight, biodegradable implant materials. However, the corrosion properties of magnesium limit its clinical application. The purpose of this study was to comprehensively evaluate the degradation behavior and biomechanical properties of magnesium materials treated with micro-arc oxidation (MAO), which is a new promising surface treatment for developing corrosion resistance in magnesium, and to provide a theoretical basis for its further optimization and clinical application. The degradation behavior of MAO-treated magnesium was studied systematically by immersion and electrochemical tests, and its biomechanical performance when exposed to simulated body fluids was evaluated by tensile tests. In addition, the cell toxicity of MAO-treated magnesium samples during the corrosion process was evaluated, and its biocompatibility was investigated under in vivo conditions. The results of this study showed that the oxide coating layers could elevate the corrosion potential of magnesium and reduce its degradation rate. In addition, the MAO-coated sample showed no cytotoxicity and more new bone was formed around it during in vivo degradation. MAO treatment could effectively enhance the corrosion resistance of the magnesium specimen and help to keep its original mechanical properties. The MAO-coated magnesium material had good cytocompatibility and biocompatibility. This technique has an advantage for developing novel implant materials and may potentially be used for future clinical applications.