Minivis d’ancrage : étude de l’état de surface sous microscopie optique

Introduction

The aim of this study was to assess the surface changes in orthodontic miniscrew implants retrieved after usage and compare them with brand-new, as-received control miniscrews.

Material and methods

The study sample consisted of 28 miniscrews from the same manufacturer: Dual Top Anchor system^® (Korea) of different diameters and lengths. One brand-new miniscrew served as a control. Surface characterization was carried out using optical microscopy (Leica DM2500 M^®) and image magnification (×5, ×10 and ×20).

Results

Observations under optical microscopy showed signs of pitting and crevice corrosion mainly at manufacturing defects. Retrieved miniscrew implants displayed larger surface cracks from corrosive attacks (pitting and crevice). Qualitative sample analysis suggested a loss of gloss and texture, giving the surface a dull appearance. Localized pitting was the most frequent form of corrosion observed in our sample.

Discussion and conclusion

Despite a smooth appearance to the naked eye, the miniscrews all had crack-like surface manufacturing defects. Examination of the surface of these miniscrews, after usage, evidenced pitting or crevice corrosion principally in the area of enhance corrosion resistance.     

SLM钴铬合金在含氟人工唾液中的电化学耐腐蚀性能研究

目的通过电化学阻抗谱方法研究选择性激光熔覆（Selective laser melting,SLM）技术制作的钴铬合金在含氟人工唾液中的耐腐蚀性能。方法运用SLM技术和传统铸造（CAST）技术,使用相同成分的钴铬合金,分别制作40个直径10mm×3mm厚度的圆柱形试件。在p H值为2.5和5.0,含氟浓度为0.00%、0.05%、0.1%和0.2%的人工唾液中,利用电化学阻抗谱检测2种加工方法制作的钴铬合金的耐腐蚀性能。结果当p H=5.0时,Na F 0.1%环境下SLM组和CAST组Rp值分别为3.49±0.44和1.59±0.88;Na F 0.2%环境下SLM组和CAST组Rp值分别为5.30±3.29和1.71±1.10。当p H=2.5时,Na F0.00%环境下SLM组和CAST组Rp值分别为6.40±0.26和2.05±0.35;Na F0.05%环境下SLM组和CAST组Rp值分别为5.67±0.25和1.15±0.83;Na F0.1%环境下SLM组和CAST组Rp值分别为4.74±0.50和0.24±0.10;Na F0.2%环境下SLM组和CAST组Rp值分别为4.76±0.97和0.30±0.09。在以上各实验条件下,SLM组和CAST组之间的表面氧化层电阻Rp值差异均具有统计学意义（P〈0.05）。结论 SLM技术制作的钴铬合金耐腐蚀性能优于铸造组。     

Oxygen reduction on copper in neutral NaCl solution

The reduction of oxygen on copper in neutral unbuffered 1 mol dm^?3 NaCl has been studied using rotating ring-disc electrodes at six oxygen concentrations equivalent to atmospheres of 2% O₂ + N₂ to 100% O₂. Steady-state potentiostatic measurements show that the reaction is first order with respect to [O₂] and that, following adsorption of O₂, the first electron transfer is rate determining. In 50% O₂ + N₂ and 100% O₂, a cathodic oxygen reduction peak is observed in both potentiodynamic and potentiostatic experiments at a disc potential of ?0.3 to ?0.4 V/SCE. The reaction is dominated by the overall four-electron reduction to OH^?, with only small amounts of peroxide detected by the ring electrode at disc potentials corresponding to the formation of the cathodic oxygen reduction peak. Tafel slopes increase with [O₂] and vary from ?0.13₅ V in 2% O₂ + N₂ to a limiting value of ?0.16 V to ?0.18 V in air, 50% O₂ + N₂ and 100% O₂.The results are explained by a mechanism involving oxygen reduction on two types of surface site with different reactivities. The most catalytic surface is believed to comprise Cu(0) and Cu(I) sites, where the Cu(I) species is stabilized as Cu(OH)_ads and/or submonolayer Cu₂O. The less catalytic site consists of Cu(0) only. Oxygen reduction is believed to proceed by a series pathway involving an adsorbed peroxide intermediate on both sites. Peroxide is reduced to OH^? prior to desorption at Cu(0) sites, but some is released before being reduced at Cu(0)/Cu(I) sites. Surface coverage by catalytic Cu(0)/Cu(I) species is favoured by a higher interfacial pH and more positive disc potentials.     

纤维蛋白原对模拟人工体液中不锈钢腐蚀行为的影响

在模拟人工体液PBS溶液中采用电化学测试技术考察了纤维蛋白原对冠状动脉支架用SUS316L和SUS317L不锈钢腐蚀行为的影响。结果表明：纤维蛋白原的存在增大了介质对材料的浸蚀性。在含纤维蛋白原的溶液中,试样的自腐蚀电位负移,维钝电流密度增大,点蚀击穿电位（Eb)降低。并利用扫描电镜观察了吸附现象,发现吸附的纤维蛋白原呈白色条状,不连续地分布在材料表面。     

医院高温蒸汽灭菌器排水管道锈蚀的原因分析与设计探讨

文章结合中国医学科学院肿瘤医院外科楼地下二层漏水问题,对排水管道锈蚀原因进行了分析,并针对高温蒸汽灭菌器排水管道的设计与施工提出了一些建议。     

A Method to Visualize and Quantify the Intraosseous Arteries of the Femoral Head by Vascular Corrosion Casting

ObjectiveTo describe a method to display the three‐dimensional distribution of intraosseous arteries in the femoral head by vascular corrosion casting.MethodsAn experimental study was done to expose the intraosseous arteries of the femoral head by a microperfusion corrosion method between January 2021 and May 2021. Specimens were 23 swine femoral heads (12 female specimens and 11 male specimens, where age of swine ranged from 8 to 12 months, and the weight was approximately 150 kg). The femoral heads were microperfused with the vascular casting resin through retinacular arteries, and the bone of the femoral head was dissolved with 50% sodium hydroxide and 10% hydrochloric acid and rinsed under the microscope until the vessel casts were completely exposed. The distribution and anastomosis of the arteries in the femoral head were observed under direct vision and microscopy. The diameter of the artery in the femoral head was measured at 0.5 cm after its entry into the bone of the femoral head with a microscale under the microscope. The number of internal arteries with diameter ≥0.05 mm was counted. The number and diameter of the main trunk of the epiphyseal arteries in the femoral head between male and female swine were compared.ResultsThe vascular casting specimen of the swine femoral head was successfully produced by using epoxy resin as a casting agent, and the three‐dimensional intraosseous vascular structures were clearly visible. The number of epiphyseal arteries in male and female swine was 8.55 ± 2.15 and 8.83 ± 2.15 (t = −0.31, p = 0.38), respectively. The diameters of the superior epiphyseal arteries in male and female swine were 0.35 ± 0.09 and 0.31 ± 0.08 mm (t = 1.03, p = 0.16), the diameters of the inferior epiphyseal arteries were 0.47 ± 0.05 and 0.49 ± 0.09 mm (t = −0.57, p = 0.29), and the diameters of the anterior epiphyseal arteries were 0.34 ± 0.08 and 0.33 ± 0.13 mm (t = 0.32, p = 0.37). There was no significant difference in the number and diameter of the main trunk of intraosseous arteries between male and female swine (p > 0.05). The main trunk of intraosseous arteries formed an anastomosis in the center of the femoral head. Among 23 swine femoral head samples, three types of intraosseous anastomosis were observed, including 13 (57%) posterior superior‐posterior inferior, seven (30%) posterior inferior‐anterior, and three (13%) uniform intraosseous anastomosis.ConclusionThe microperfusion corrosion method can produce the vascular casting specimen of swine femoral head revealing the three‐dimensional structure of the intraosseous artery, which clearly shows the origin, course and branches, and diameter, as well as the anastomosis, of nutrient arteries in the femoral head. This method provides a simple and rapid technique for quantifying and visualizing intraosseous arteries.     

Corrosion of orthodontic brackets: qualitative and quantitative surface analysis

ObjectivesTo determine and compare surface characteristics and presence of corrosion in new and used brackets with optical light microscopy (OLM) and scanning electron microscopy (SEM), and with elemental chemical analysis with energy-dispersive X-ray spectroscopy (EDS).Materials and MethodsOLM and SEM were used to analyze 24 new and 24 used conventional premolar brackets. EDS analysis was performed in six used brackets and four new brackets with corrosion-suspected spots.ResultsOLM and SEM images showed wear/abfraction signs, striations, pits/crevices, and adherent material. Used brackets showed more deterioration than new brackets. SEM images disclosed more morphological features than OLM images. EDS analysis revealed a significantly higher phosphorus (P = .001) and sodium (P < .005) weight fraction and significantly lower amounts of chromium (P < .001) in used brackets. The iron, chromium, and nickel weight fractions did not differ significantly between the clean and corrosion-suspected spots. Of the corrosion-suspected spots analyzed by combined SEM and EDS, 44.14% and 6.90% remained corrosion-suspected on used and new brackets, respectively.ConclusionsUsed brackets showed more signs of corrosion than new ones. Combined assessment of SEM and EDS indicates that the bracket surface is affected during orthodontic treatment as a result of corrosion.     

Differences in the fretting corrosion of metal-metal and ceramic-metal modular junctions of total hip replacements.

The use of modular interlocking components is a central design feature of total joint replacements. In this investigation we hypothesized that clinically available ceramic-metal modular connections used in total hip arthroplasty release more metal through fretting corrosion than traditional metal-metal modular connections. This was investigated using an in vitro comparison of ceramic (zirconia, ZrO2) and metal (Co-alloy) femoral-head fretting upon Co-alloy stem components. In vitro fretting corrosion testing consisted of potentiodynamic monitoring and analysis of metal release from zirconia and Co-alloy 28 mm femoral heads with similar surface roughnesses (Ra=0.46 microm) on identical Co-alloy stems at 2.2 kN for 1x10(6) cycles at 2 Hz. In contrast to our original hypothesis, we found greater metal release (approximately 11-fold increase in Co and 3-fold increase in Cr) and potentiodynamic fretting of metal-metal modular junctions when compared to ceramic-metal. Potentiodynamic testing demonstrated that lower initial voltages (-266<153 mV), greater maximum voltage changes (116>56 mV, p<0.05, t-test) and voltage variability (3>0.5 mV, p<0.05, t-test) were associated with the open circuit potentials of Co-alloy on Co-alloy junctions when compared to zirconia on Co-alloy junctions. In this study of a single total hip replacement stem and head design, zirconia heads mated with Co-alloy stems produced less fretting than Co-alloy heads mated with Co-alloy stems. Although further studies are necessary with a variety of implant designs and under different experimental conditions, the evidence presented here should, in part, alleviate concerns of increases in fretting corrosion at modular junctions of ceramic-metal coupled components.     

Corrosion of a stainless steel with low nickel content under static conditions

The pattern of selective release of chromium, iron and molybdenum from a non-prepassivated ferritic stainless steel, with the designation SS 2326 and a nickel content of 0.3%, has been measured in artificial saliva under static conditions using nuclear tracer and ESCA techniques. The ICP-method was used to detect nickel which was found only in one case. The release rate of chromium, iron and molybdenum showed a strong time-dependent decrease as a consequence of chromium enrichment in the surface. This was shown by ESCA-measurements. This kinetics is characteristic for a passivating alloy i.e. self passivation. In view of the low nickel content of the SS 2326 steel compared to conventional stainless steel, the material may possess potential for use as a dental or orthopaedic biomaterial.     

Preparation of four-color arterial corrosion casts of the laryngeal arteries

Summary The supply areas of the superior and inferior laryngeal arteries were studied in order to plan tissue-sparing laryngeal surgery. Arterial corrosion casts with and without preservation of the laryngeal skeleton were prepared and the supply areas of the superior and inferior laryngeal arteries were distinguished from each other by injecting differently colored methacrylates. The ramifications of the laryngeal arteries could be classified clearly in the macerated specimens which preserved the laryngeal skeleton.

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Etude des artères laryngées par injection corrosion en quatre couleurs

Résumé Les territoires vasculaires des artères laryngées supérieure et inférieure ont été étudiés afin de préciser l'abord chirurgical de ces artères. Des injections corrosions artérielles ont été réalisées avec ou sans conservation du squelette laryngé et les territoires vasculaires des différentes artères ont été différenciés grâce à l'utilisation de quatre couleurs. Les rameaux des artères laryngées ont pu être facilement analysés sur les pièces où le squelette laryngé avait été conservé.