Effects of self-ligating brackets on the surfaces of stainless steel wires following clinical use: AFM investigation

In orthodontic treatment, the frictional force between the archwire and bracket reduces the effectiveness of orthodontic treatment. The frictional force is affected not only by the geometry of the self‐ligating brackets but also by physical changes between the bracket slots and archwire surfaces during sliding movement. This study examined quantitatively the effect of self‐ligating treatments on the surfaces of stainless steel (SS) archwires during tooth movement in vivo by atomic force microscopy. Orthodontic 0.019″ × 0.025″ SS archwires after clinical use with the first bicuspid‐extraction treatment were employed using the Damon 3MX^® SS self‐ligating brackets, Clippy‐C^® ceramic self‐ligating brackets, and Kosaka^® SS brackets. Intact SS archwires were used as the control group. All SS archwires after clinical use showed severe scratches and significantly higher roughness caused by frictional interactions between the brackets and archwires (p < 0.0001 vs. control). The descending order of surface roughness was the SS archwires treated, with ceramic self‐ligating brackets, with conventional SS brackets, and with SS self‐ligating brackets (p < 0.001). These findings suggest that an orthodontic treatment with SS self‐ligating brackets may require smaller orthodontic forces than that with ceramic self‐ligating brackets or conventional SS brackets.     

Changes in ultrastructure and properties of bracket slots after orthodontic treatment with bicuspid extraction

This study examined the effects of an orthodontic treatment using a bicuspid extraction on the surface roughness and mechanical properties of stainless steel (SS) brackets adjacent to the extraction space. Four experimental groups were employed; groups 1 and 2 used the Archist^® SS brackets before and after the extraction treatment, respectively, and groups 3 and 4 used the Victory^® SS brackets before and after the extraction treatment, respectively. The slot surfaces of the bracket were scanned in air at a resolution of 512 × 512 pixels with a scan speed of 0.8 line/s. The visco‐elasticity of the bracket slot was determined from the force–distance curves of atomic force microscopy. The orthodontic treatment with bicuspid extraction led to a significant increase (p<0.0001) in surface roughness in both groups. In particular, the Archist^® SS brackets showed more changes than the Victory^® SS brackets (p<0.0005). However, there was no significant difference in properties of the Victory^® and Archist^® brackets between before and after treatment. This suggests that the orthodontic treatment with bicuspid extraction is more responsible for the changes in surface roughness than the properties of the brackets. SCANNING 33: 25–32, 2011. © 2011 Wiley Periodicals, Inc.     

Morphological investigation of various orthodontic lingual bracket slots using scanning electron microscopy and atomic force microscopy

Various labial and lingual orthodontic appliances with aesthetic materials have been developed due to an increased demand in aesthetic orthodontic treatment. However, there are few reports regarding the morphology of lingual orthodontic appliances. Therefore, this study evaluates the roughness of slot surfaces of various orthodontic lingual brackets using field emission scanning electron microscopy (FE‐SEM) and atomic force microscopy (AFM). Three types of stainless steel lingual brackets (Stealth^®, 7th Generation^®, and Clippy L^®) and one gold lingual bracket (Incognito?) with a slot size of 0.018 inches × 0.025 inches (0.457 × 0.635 mm²) were selected as representative lingual materials. Both FE‐SEM and AFM examinations showed that the Stealth^® and Clippy L^® brackets had the lowest surface roughness, while the 7th Generation^® bracket had the highest surface roughness. There was a significant difference in surface morphology between the types of lingual brackets, even when composed of the same material. The surface roughness of the bracket slot was dependent on the manufacturing process or surface polishing process rather than the fundamental properties of the bracket materials. There was no significant difference in the mean surface roughness of the slot floor between gold and stainless steel lingual brackets. These findings suggest that, although the gold lingual bracket is very expensive, it has great potential for use in patients with nickel allergy.     

Fretting wear behavior of superelastic nickel titanium shape memory alloy

The fretting behavior of superelastic nickel titanium (NiTi) shape memory alloy was studied at various displacement amplitudes on a serve-hydraulic dynamic test machine. The results showed that the superelastic properties of the material played a key role in the observed excellent fretting behavior of NiTi alloy. Due to the low phase transition stress (only 1/4 the value of its plastic yield stress) and the large recoverable phase transition strain (5%) of NiTi, the friction force of NiTi/GCr15 stainless steel pair is smaller than the value of GCr15/GCr15 pair and at the same time the Rabinowicz wear coefficient of NiTi plate is about 1/9 the value of GCr15 plate under the same fretting conditions. For NiTi/GCr15 pair, even NiTi has a much lower hardness than GCr15, the superelastic NiTi alloy exhibits superior fretting wear property than GCr15 steel. It was found that the weak ploughing was the main wear mechanism of NiTi alloy in the partial slip regime. While in the mixed regime and gross slip regime, the wear of NiTi was mainly caused by the abrasive wear of the GCr15 debris in the three-body wear mode.     

不锈钢微丝的制备及组织和性能研究

研究了不同直径的316L不锈钢微丝的组织和性能，并探讨了微丝制备过程中断丝的原因。结果表明，冷拉丝材退火后，随直径减小微丝的晶粒不断细化；随直径减小抗拉强度变化不大，而伸长率却逐渐下降；扫描电镜观察表明，微丝表面局部存在缺陷，而断口观察发现有非金属夹杂物存在；缺陷的存在将影响拉伸试样的伸长率，也是微丝制备过程中引起断丝的主要原因之一。     

陶瓷衬垫和药芯焊丝在焊接厚壁复合钢板中的应用

介绍了采用陶瓷衬垫,埋弧机械化焊,药芯焊丝CO2自动焊来焊接16MnR／316L不锈钢复合板的焊接工艺,解决了厚壁不锈钢复合板的焊接和热处理问题;通过检查焊缝的化学成分和力学性能等,证明了该焊接工艺的可行性,并成功应用于生产中。     

In vitro frictional behavior and wear patterns between contemporary and aesthetic composite orthodontic brackets and archwires

This study evaluates the effects of surface roughness, saliva and bracket materials on in vitro frictional resistance of contemporary and aesthetic orthodontic brackets during the sliding of archwires against elastomeric ligature. Eight various brackets were investigated together with stainless steel (SS) archwires of several shapes. The sliding force involved in a ligated bracket-archwire combination was measured in an Instron by a self-designed jig. The interfaces were also examined using scanning electron microscope (SEM) to simulate sliding mechanics and abrasive/adhesive wear of the bottom surfaces of the bracket slots, which were observed under dry condition. Round SS archwires (SRO-OR) demonstrated the lower frictional force compared to coated round SS archwire (SRO-AW) and the flat SS archwire (rectangular and square) surfaces for most of the brackets. Braided composite bracket without a metal slot had the least resistance when sliding with SRO-OR archwire whilst the composite bracket (Spirit MB) with a metal slot demonstrated the lower resistance. Ceramic bracket (Inspire) without a metal slot, which also reflected severe wear patterns produced a significantly larger frictional force for SRO-AW. The presence of saliva had a consistent effect in increasing the friction, which counters the inconsistency reported in the literature. The soft-coated surface of SRO-AW archwire confirms sliding difficulty in sliding on the hard surface of bracket slot. A smoother surface correlates with a lower frictional force according to the surface roughness values.     

表面粗糙度对Al2O3增强Y-TZP陶瓷材料生物摩擦学特性的影响

采用销-盘式摩擦磨损试验机研究了氧化铝增强氧化锆陶瓷(ADZ)的表面粗糙度对ADZ/316L不锈钢摩擦副的摩擦磨损性能的影响。结果表明:在小牛血清润滑下,随着陶瓷表面粗糙度的降低,ADZ陶瓷和316L不锈钢的摩擦因数和磨损率均呈降低趋势。但是对于表面粗糙度最高的陶瓷,由于Fe转移膜的物理吸附,出现了“负磨损”现象。     

Mechanical behaviour of shape memory alloys for seismic applications 2. Austenite NiTi wires subjected to tension

The results of cyclic tensile tests on superelastic NiTi shape memory alloy (SMA) wires are presented and discussed. The tests were carried out within a large experimental test programme for the MANSIDE Project, with the scope of verifying the suitability of SMA superelastic wires as kernel components for seismic protection devices.The mechanical behaviour is described by means of four fundamental quantities, namely: secant stiffness, energy loss per cycle, equivalent damping and residual strain. The sensitivity to temperature and strain rate, as well as the influence of strain amplitude and the effects due to repeated cyclic deformation, are analysed in detail.The experimental results show that the characteristics of the superelastic wires are well suited for seismic applications, as both the recentring and the energy dissipating features of the devices can be easily obtained. Moreover, the influence of the investigated parameters, within their usual range of variation in seismic protection devices, is compatible with the use of superelastic wires for practical applications.     

不锈钢热丝TIG堆焊缓冷工艺研究

先将不锈钢热丝TIG堆焊后缓冷,然后对不锈钢堆焊层进行无损探伤和力学性能试验,分析焊后缓冷对不锈钢堆焊层物理性能的影响,再从理论上分析焊后缓冷对不锈钢热丝TIG堆焊层中氢含量,证明焊后缓冷不会对堆焊层产生不利影响,且堆焊层中氢含量极少。     

Role of phase transition in the unusual microwear behavior of superelastic NiTi shape memory alloy

The excellent microwear performance of nano-grained superelastic nickel titanium (NiTi) polycrystalline shape memory alloy (SMA) is reported in this paper. The microwear test was conducted at temperatures ranging from 22 to 120 °C by a Hysitron triboindenter. The results showed that the NiTi SMA has superior microwear resistance compared to traditional tribo-materials such as stainless steel AISI 304 and that the material exhibits unusual hardness dependence of wear within certain temperature regimes. With the increase in temperature from 22 to 120 °C, wear resistance was found to decrease anomalously with an increase in hardness. Further investigation and analysis confirmed that the stress-induced phase transition during contact and wear play an essential role in the material's high wear resistance. It is demonstrated through contact mechanics analysis that the increase of hardness with temperature was mainly due to the increase in the phase transition stress. The observed applied threshold load that corresponds to the onset of the plastic deformation in the contact area was strongly influenced by the phase transition process at the tip region. For the investigated superelastic NiTi, the temperature-dependent interplay between reversible phase transition and irreversible plastic yielding plays a key role in the temperature dependence of the wear performance and is responsible for the observed apparent unusual hardness–wear relationships.     

The effects of acid passivation,tricresyl phosphate presoak,and UV/ozone treatment on the tribology of perfluoropolyether‐lubricated 440C stainless steel couples

Research on the boundary lubrication performance of two perfluoropolyether (PFPE) thin films in the presence of passirated 440C stainless steel is presented. The study used a standard ball‐on‐disc (BoD) tribometer operating in dry nitrogen and a vacuum spiral orbit tribometer (SOT). Stainless steel surfaces were passivated using one of four techniques: a high‐temperature and low‐temperature chromic acid bath, a tricresyl phosphate (TCP) soak, or UV/ozone treatment for 15 min. After passivation, each BoD disc had a 400 Å film of Krytox® 16256 (PFPE) applied to it. The lives of these films were quantified by measuring the number of sliding cycles before an increase in friction occurred. The lubricated life of the 440C couple was not altered as a result of the various passivation techniques. The resulting surface chemistry of each passivation technique was examined using X‐ray photoelectron spectroscopy. The SOT was used to examine the effects of the TCP treatment on the lubricated life of another PFPE, Brayco® 815Z, under rolling conditions. None of the passivation techniques were found to increase dramatically the oxide film thickness or lubricated life.     

陶瓷与不锈钢的焊接

用电弧焊方法焊接陶瓷与不锈钢,研究了焊接电流、电弧长度等工艺参数对焊接质量的影响。结果表明,在陶瓷金属复合材料的陶瓷层上焊接不锈钢,焊接加热不仅可以改善复合钢管中陶瓷与金属的结合方式,在焊接区实现的陶瓷与金属的微冶金结合,而且焊接后的陶瓷内衬复合钢管的压－剪强度明显增加,焊缝为柱状枝晶组织,焊接熔合区的陶瓷受焊接热作用由原来的树枝晶改变为细小的等轴晶,陶瓷与母材呈现微冶金结合方式,焊接影响区陶瓷仍保留树枝晶特征。     

Antimicrobial effect,frictional resistance,and surface roughness of stainless steel orthodontic brackets coated with nanofilms of silver and titanium oxide: a preliminary study

Nano‐silver and nano‐titanium oxide films can be coated over brackets in order to reduce bacterial aggregation and friction. However, their antimicrobial efficacy, surface roughness, and frictional resistance are not assessed before. Fifty‐five stainless‐steel brackets were divided into 5 groups of 11 brackets each: uncoated brackets, brackets coated with 60 µm silver, 100 µm silver, 60 µm titanium, and 100 µm titanium. Coating was performed using physical vapor deposition method. For friction test, three brackets from each group were randomly selected and tested. For scanning electron microscopy and atomic‐force microscopy assessments, one and one brackets were selected from each group. For antibacterial assessment, six brackets were selected from each group. Of them, three were immediately subjected to direct contact with S. mutans. Colonies were counted 3, 6, 24, and 48 h of contact. The other three were stored in water for 3 months. Then were subjected to a similar direct contact test. Results pertaining to both subgroups were combined. Groups were compared statistically. Mean (SD) friction values of the groups 'control, silver‐60, silver‐100, titanium‐60, and titanium‐100' were 0.55 ± 0.14, 0.77 ± 0.08, 0.82 ± 0.11, 1.52 ± 0.24, and 1.57 ± 0.41 N, respectively (p = .0004, Kruskal–Wallis). Titanium frictions were significantly greater than control (p < .05), but silver groups were not (p > .05, Dunn). In the uncoated group, colony count increased exponentially within 48 h. The coated groups showed significant reductions in colony count (p < .05, two‐way‐repeated‐measures ANOVA). In conclusions, all four explained coatings reduce surface roughness and bacterial growth. Nano‐titanium films are not suitable for friction reduction. Nano‐silver results were not conclusive and need future larger studies.     

不锈钢表面阻氚渗透涂层研究现状及进展

阻氚渗透是聚变堆设计中一项关键技术,综述了不锈钢表面氧化物涂层、铝化物涂层、钛基陶瓷涂层、硅化物涂层等阻挡氚渗透陶瓷涂层的研究现状,比较了铝化物涂层几种制备方法的特点,概述了陶瓷涂层的阻氚机理,并对阻氚涂层未来的研究重点进行了展望.     

Changes in the surface roughness and friction coefficient of orthodontic bracket slots before and after treatment

In this study, we tested the surface roughness of bracket slots and the friction coefficient between the bracket and the stainless steel archwire before and after orthodontic treatment. There were four experimental groups: groups 1 and 2 were 3M new and retrieved brackets, respectively, and groups 3 and 4 were BioQuick new and retrieved brackets, respectively. All retrieved brackets were taken from patients with the first premolar extraction and using sliding mechanics to close the extraction space. The surface roughness of specimens was evaluated using an optical interferometry profilometer, which is faster and nondestructive compared with a stylus profilometer, and provided a larger field, needing no sample preparation, compared with atomic force microscopy. Orthodontic treatment resulted in significant increases in surface roughness and coefficient of friction for both brands of brackets. However, there was no significant difference by brand for new or retrieved brackets. These retrieval analysis results highlight the necessity of reevaluating the properties and clinical behavior of brackets during treatment to make appropriate treatment decisions. SCANNING 35: 265‐272, 2013. © 2012 Wiley Periodicals, Inc.     

OPTIMIZATION STUDIES ON HOLE-MAKING TOOLS FOR HIGH-PERFORMANCE CUTTING AUSTENITIC STAINLESS STEEL

Austenitic stainless steel is a kind of difficult-to-cut material utilized widely in various industry fields. Hole-making tools are the uppermost obstacle of high performance cutting, so the optimizations of tools are imperative. This paper presents respectively the optimal geometrical characteristics and corresponding coating for high performance cutting austenitic stainless steel. The appreciated cutting performance of optimized tools with optimized cutting parameters has also been evaluated completely through experiments. Optimized special drills with point angle 138° and helix angle 38° was decided and TiCN coating was selected as the best coating. However optimized taps had different geometry structures for tapping through holes and blind holes. The former adopted the spiral pointed tap with inclination angle 15 °. The latter was spiral fluted tap with helix angle 34°. In high-performance cutting austenitic stainless steel, the optimized cutting parameters of special drills are 16 m/min and 0.13 mm/rev. The research results will be of great benefit for the development and application of high efficient and precise drills and taps of high performance cutting austenitic stainless steel.     

浅议水轮机转轮室中环不锈钢药芯焊丝的焊接

通过对材料为0Cr13Ni5Mo(低碳马氏体不锈钢)、且属厚板大型组焊结构件的水轮机转轮室中环的焊接性分析,找出了影响焊接质量和提高生产效率的技术难题,并选用新型的不锈钢药芯焊丝的焊接材料,改进相应的工艺措施,提高操作技能水平,从而达到了保证产品质量和提高生产效率的目标。     

不锈钢厨具旋压成形工艺的探讨

本文概述了旋压工艺特点和不锈钢的性能、特点 ,并对不锈钢旋压成形工艺进行了初步探讨 ,最后介绍了数控技术在旋压设备上的应用     

奥氏体不锈钢管的现场焊接

采用药芯焊丝对奥氏体不锈钢管道进行打底焊接,MAG焊填充及盖面焊,立向上的水平固定全位置焊接.具有工艺性能良好、操作方便和焊接品质稳定等特点,在复杂的工艺管道施工及高空作业时其优点更为突出.