Resistencia a la corrosión y citotoxicidad de los aceros inoxidables expuestos a soluciones de cloruro / Corrosion resistance and cytotoxicity of stainless steels exposed to chloride solutions / Resistência à corrosão e citotoxicidade de aços inoxidáveis expostos a soluções de cloretos

Objetivo: Analizar la resistencia a la corrosión por picaduras de aceros inoxidables AISI 304 y AISI 420 en un medio que contiene cloruros (solu-ción de NaCl al 0,9 y 3,5%, en masa), así como su citotoxicidad, in vitro, en muestras con y sin corrosión por picaduras. Método: Estudio experimental. Se utilizaron técnicas de polarización potenciodinámica cíclica (PPC) para caracterizar el alcance y la forma del ataque corrosivo a las muestras. Se utilizó el método de difusión en agar y evaluación de la viabilidad de la línea celular NCTC clon 929 (CCIAL 020) para evaluar la citotoxicidad de las muestras de acero con y sin picaduras. Resultados: El acero AISI 304 presentó una resistencia a la corrosión superior al acero AISI 420. Los valores de potencial de picadura disminuyeron para ambos aceros cuando aumentó la concentración de cloruros en la solución agresiva. Hubo toxicidad celular moderada (grado 3 ­ ISO 10993-5) en todas las muestras. Conclusión: Los resultados corroboraron las recomendaciones para evitar la inmersión innecesaria de instrumentos en soluciones salinas. La citotoxicidad moderada de estos aceros desaconseja su uso en dispositivos implantables, reservándolos solo para instrumentos quirúrgicos. (AU)

Objective: To analyze the pitting corrosion resistance of AISI 304 and AISI 420 stainless steels in chloride-containing medium (0.9 and 3.5% NaCl solution, by weight), as well as their cytotoxicity,in vitro, in samples with and without pitting corrosion. Method: This is an experimental study. Cyclic potentiodynamic polarization (CPP) techniques were used to characterize the extent and shape of the corrosive attack on the samples. The agar diffusion and viability evaluation method of the NCTC clone 929 cell line (CCIAL 020) was used to evaluate the cytotoxicity of samples of steels with and without pitting. Results: The AISI 304 steel showed superior corrosion resistance to the AISI 420 steel. The values of the pitting potentials decreased for both steels when the chloride concentration in the aggressive solution was increased. There was moderate cell toxicity (grade 3 ­ ISO 10993-5) in all samples. Conclusions: The results corroborated the recommendations to avoid unnecessary immersion of the instruments in saline solutions. Moderate cytotoxicity to these steels contraindicates their use in implantable devices, only in surgical instruments. (AU)

Objetivo: Analisar a resistência à corrosão por pites dos aços inoxidáveis AISI 304 e AISI 420 em meio contendo cloretos (solução de NaCl a 0,9 e 3,5%, em massa), assim como sua citotoxicidade,in vitro, em amostras com e sem corrosão por pites. Método: Estudo experimental. Utilizaram-se téc-nicas de polarização potenciodinâmica cíclica (PPC) para caracterizar extensão e forma do ataque corrosivo nas amostras. O método de difusão em ágar e avaliação da viabilidade da linhagem celular NCTC clone 929 (CCIAL 020) foi empregado para avaliar a citotoxicidade de amostras dos aços com e sem pites. Resultados: O aço AISI 304 apresentou resistência à corrosão superior ao aço AISI 420. Os valores dos potenciais de pite caíram para ambos os aços quando se aumentou a concentração de cloretos na solução agressiva. Houve moderada toxicidade celular (grau 3 ­ ISO 10993-5) em todas as amostras. Conclusão: Os resultados corroboraram as recomendações para evitar a imersão desnecessária dos instrumentais em soluções salinas. A citotoxicidade moderada para esses aços contraindica seu uso em dispositivos implantáveis, apenas em instrumentos cirúrgicos. (AU)

Effect of micro-arc oxidation treatment on biological activity of medical metals / 中国组织工程研究

BACKGROUND:Among the surface modification technologies of metal implants,micro-arc oxidation has been widely concerned for its convenience,low cost and ability to effectively adjust the microstructure and elements of surface coatings. OBJECTIVE:To summarize research advances in physical and chemical properties and biological activities of oxidation coatings prepared by micro-arc oxidation on different materials. METHODS:The articles about the effects of micro-arc oxidation on the biological activity of medical metals were searched in PubMed and Web of Science based on the English search terms"MAO,micro-arc oxidation,osseointegration,mechanical property,biological activity,angiogenesis,fibrogenesis".The search time was from January 2016 to December 2022.According to the inclusion and exclusion criteria,82 articles were finally retained for review. RESULTS AND CONCLUSION:Micro-arc oxidation is a potential surface modification technology,which can greatly improve the success rate of implantation,and can be widely used in other fields.The specific reasons are as follows:(1)Micro-arc oxidation technology forms special porous morphology on the surface of materials,which can optimize the mechanical properties such as wear resistance and corrosion resistance,contributing to the reduction of the degradation rate of magnesium alloys.(2)Micro-arc oxidation technology can significantly enhance the bioactivity and improve the bioinertness of titanium and titanium alloys through the addition of strontium,hydroxyapatite and other metallic or nonmetallic substances to its porous morphology for helping elevate its osteogenic differentiation,angiogenesis,fibrogenesis and other biological activities.

Research status on element selection of medical magnesium alloy / 中国组织工程研究

BACKGROUND:Due to natural degradation,excellent biocompatibility and good mechanical properties,magnesium alloy has become a very valuable implant material in the biomedical field.However,the rapid degradation rate of magnesium alloy limits its further development and application. OBJECTIVE:To review the principle of the degradation of magnesium and its alloys in a physiological environment.The current research status of alloying elements selection is mainly introduced from the aspects of the safety of elements and their influence on the properties of magnesium and its alloys. METHODS:The articles were searched by using the databases of CNKI,PubMed,Web of Science and Elsevier.The key words were"magnesium(alloy),metal name(such as:bismuth(Bi),aluminum(Al)),corrosion,biocompatibility,metal toxicity,scaffold(stent)/screw"in Chinese and English.The search period was from 2013 to 2023.As a result,70 articles were applied for analysis after reading the contents of the articles. RESULTS AND CONCLUSION:Magnesium alloy has been widely studied in the medical field.Although some products have been applied in clinical practice,the high degradation rate of magnesium alloy in the human environment is still the main limitation of large-scale clinical application.The focus of future development is to control its corrosion rate.Alloying is a kind of method to improve the corrosion resistance of magnesium alloys,and various properties can also be improved by adding different alloy components.However,simple alloying cannot satisfy the pursuit of diversified properties of magnesium alloys.To develop multifunctional magnesium alloy products with excellent performance,it is necessary to combine various optimization methods,such as alloying and surface modification,to make up for the shortcomings of their respective methods in the future.In addition,the alloy structure updating with preparation process improvement is combined to enhance the properties of magnesium alloy.

Application of machine learning in key properties of medical metal materials / 中国组织工程研究

BACKGROUND:The combination of machine learning and medical metal materials can make up for the inefficiency and high cost of traditional experiments and computational simulations,and quickly and accurately predict the characteristics of metal materials by analyzing large amounts of data,optimize material design and performance,and improve the safety and efficiency of medical applications. OBJECTIVE:To summarize the research progress and shortcomings of machine learning in the characteristics of medical materials. METHODS:The first author searched CNKI,PubMed,X-MOL,and Web of Science databases by computer to search all relevant articles from January 2013 to April 2023.The Chinese search terms were"machine learning of medical metal materials,medical titanium alloy,medical magnesium alloy,medical metal material properties".The English search terms were"machine learning medical metal materials,medical stainless steel alloy,medical cobalt-chromium alloy,medical titanium alloy,medical magnesium alloy".Finally,70 relevant articles were included for a summary. RESULTS AND CONCLUSION:(1)The introduction of machine learning as a material design methodology has opened up new paradigms for material science research as the accessibility of large amounts of data generated by traditional experimental and computational simulation methods increases.(2)The machine learning workflow is divided into four main parts:data collection and preprocessing,feature engineering,model selection and training,and model evaluation,each of which is indispensable.(3)Medical metal materials are categorized into:stainless steel co-base alloys,cobalt-chromium alloys,titanium alloys,and magnesium alloys.For stainless steel co-base alloy,machine learning predicts its mechanical properties,to improve the generalization ability of machine learning.For cobalt-chromium alloy,machine learning predicts its mechanical properties,and it can conclude that cobalt-chromium alloy is the optimal material for hip implants.For titanium alloy,machine learning predicts its mechanical properties,and it can select the implant with the best mechanical properties.For magnesium alloy,machine learning predicts its corrosion resistance and mechanical properties;the ensemble model can accurately predict the mechanical properties of magnesium alloys,and the random forest model can predict the optimal elemental contents of magnesium alloys as vascular stents.(4)Machine learning has deficiencies in the field of medical materials.For example,the model is relatively lagging;the data failed to be standardized,and the generalization is low.To solve such problems,we should make full use of deep learning and segmentation algorithm technology,use unified standard data,and improve the model to increase the generalization ability.

Fatigue Performance and Numerical Simulation of Medical Titanium Alloy Subjected to Simulated Body Fluid / 医用生物力学

Objective To study the corrosion-fatigue properties of a novel low modulus Ti-3Zr-2Sn-3Mo-25Nb(TLM)titanium alloy subjected to simulated body fluid(SBF).Methods Ti-6Al-4V(TC4)alloy was used as the control group.The electrochemical corrosion polarization curves of the two titanium alloys were measured in SBF.The pre-corroded TC4 and TLM titanium alloy samples were subjected to rotational bending fatigue tests.The loading stress amplitude and fatigue fracture cycle relationship was established using the experimental data,and the stress life curves were drawn.Subsequently,the fracture mechanism was analyzed by analyzing the corrosion fatigue micro-fracture morphology of the sample,and fatigue analysis on the titanium alloy sample was then conducted combined with the finite element software.Results The self-corrosion potential of the TC4 titanium alloy under stress annealing was lower than that of the TLM titanium alloy after heat treatment.The TLM titanium alloy was most sensitive to changes in cyclic stress.A comparison between the simulation and experimental results showed that the TC4 titanium alloy under stress annealing had a higher fatigue strength and stronger resistance to crack propagation than the TLM titanium alloy did after heat treatment,whereas its corrosion resistance was the opposite.Compared to the specimens without pre-corrosion treatment,the brittleness of the TLM titanium alloy increased,and its fatigue performance decreased after pre-immersion in SBF.Conclusions Through comparative analysis,the reliability of the test results proved to be high,and the COMSOL finite element software could effectively predict the fatigue life of titanium alloy materials.

Preliminary studies on microbial induced corrosion of ferrous materials (EN-8 and 411143 steels) in the presence of Acidithiobacillus ferrooxidans

An electrochemical investigation was conducted to evaluate the corrosion behaviour of Iron alloys such as EN-8 and 411143 in absence and in presence of microbes Acidithiobacillus ferrooxidans. Linear polarization technique was employed to measure the Polarization Resistance and corrosion rates of two different ferrous metal samples. Polarization resistance (Rp) values of EN-8 were initially higher in the presence of Acidithiobacillus ferrooxidans than the values of 411143. Growth rate of the Acidithiobacillus ferrooxidans was more and sustained longer period with EN-8 in the presence of media than in the case of alloy ‘411143’. It was observed that there was a 1.5 fold increase in corrosion rate in both the cases of EN-8 and 411143 in the presence of bacteria.High corrosion rates were recorded with the steel 41143 rather than the En-8 with respect to the optical density of the microbes. It was concluded that EN-8 was exhibited high resistance to the microbial attack.

Thermal expansion and corrosion resistance of cobalt-chromium alloys fabricated by contemporary manufacturing processes: an in vitro study / Expansión térmica y resistencia a la corrosión de aleaciones de cobalto-cromo fabricadas mediante procesos de abricación contemporáneos: un estudio in vitro

In Purpose: The fabrication technique can influence the mechanical properties of Cobalt-Chromium (Co-Cr) dental alloys. Hence, the present study aims to determine the corrosion resistance and thermal expansion of alloys manufactured using three contemporary techniques. Material and Methods: A total of nine specimens of Co-Cr alloy were prepared according to ISO 22674 by each one of the three manufacturing processes (three in each process); conventional casting, direct metal laser sintering (DMLS) and milling (MIL). All these specimens were tested for coefficient of thermal expansion and corrosion resistance. The data was tabulated and analyzed statistically. Results: The difference in the thermal expansion of alloys fabricated using three techniques was non-significant at almost all the temperatures from 50 ºC to 950 ºC (p>0.05), except 450 ºC and 600 °C. The polarization resistance of specimens manufactured using the conventional method was more compared to DMLS and MIL at pH 5 (Conventional>MIL>DMLS) (p<0.001). Conclusion: The thermal expansion behavior of alloys manufactured using the three selected techniques were similar, whereas, at acidic pH, the corrosion resistance of conventional and MIL were better than the DMLS.

Antecedentes: La técnica de fabricación puede influir en las propiedades mecánicas de las aleaciones dentales de cobalto-cromo (Co-Cr). Por lo tanto, el presente estudio tiene como objetivo determinar la resistencia a la corrosión y la expansión térmica de aleaciones fabricadas con tres técnicas contemporáneas. Material y Métodos: Se prepararon un total de nueve probetas de aleación de Co-Cr según ISO 22674 por cada uno de los tres procesos de fabricación (tres en cada proceso); fundición convencional, sinterización directa de metal por láser (DMLS) y fresado (MIL). Todos estos especímenes fueron probados para determinar el coeficiente de expansión térmica y la resistencia a la corrosión. Los datos fueron tabulados y analizados estadísticamente. Resultados: La diferencia en la dilatación térmica de las aleaciones fabricadas con las tres técnicas no fue significativa en casi todas las temperaturas desde 50ºC hasta 950ºC (p>0,05), excepto 450ºC y 600ºC. La resistencia a la polarización de las muestras fabricadas con el método convencional fue mayor en comparación con DMLS y MIL a pH 5 (Convencional>MIL>DMLS) (p<0, 0 01). Conclusión: El comportamiento de expansión térmica de las aleaciones fabricadas con las tres técnicas seleccionadas fue similar, mientras que, a pH ácido, la resistencia a la corrosión de la convencional y la MIL fue mejor que la de la DMLS.

Corrosión en los mini-implantes de ortodoncia: una revisión de la literatura / Corrosion in orthodontic mini-implants: a literature review

RESUMEN Los mini-implantes son dispositivos metálicos que son temporalmente fijados al hueso y son utilizados para lograr una gran variedad de movimientos ortodónticos. Actualmente, se convirtieron en un importante dispositivo que ayuda al ortodoncista en todas las etapas del tratamiento. Los mini-implantes son hechos con uniones de diferentes metales, por lo que están expuestos al proceso de corrosión en la cavidad bucal. La liberación de iones puede causar efectos fisiológicos adversos, incluyendo citotoxicidad, genotoxicidad, carcinogenicidad y efectos alergénicos. El presente artículo busca hacer una revisión acerca de la corrosión de los mini-implantes de ortodoncia. La literatura reporta que la corrosión de mini-implantes contribuye a la inflamación, que es a su vez un factor que influye en la pérdida de estos dispositivos y la liberación de los iones metálicos es una de sus principales causas. Adicionalmente la corrosión puede producir perforaciones y pérdida de espesor del metal, lo que disminuye la resistencia mecánica y aumenta el riesgo de fractura.

ABSTRACT Mini-implants are metallic devices that are temporarily fixed to the bone and are used to achieve a wide variety of orthodontic movements. Today, they have become an important device that helps the orthodontist in all stages of treatment. The mini-implants are made with joints of different metals, so they are exposed to the corrosion process in the oral cavity. The release of ions can cause adverse physiological effects, including cytotoxicity, genotoxicity, carcinogenicity, and allergenic effects. This article seeks to review the corrosion of orthodontic mini-implants. The literature reports that the corrosion of mini-implants contributes to inflammation, which is a factor that influences the loss of these devices and the release of metal ions is one of its main causes. Additionally, corrosion can produce perforations and loss of thickness of the metal, which reduces the mechanical resistance and increases the risk of fracture.

A agressividade da água e a possibilidade de alteração da qualidade para o consumo humano / Water aggressiveness and the possibility of changing quality for human consumption

RESUMO A característica físico-química da água subterrânea resulta das interações com a mineralogia do solo/rocha durante sua infiltração e do seu tempo de permanência nos aquíferos, além das influências antrópicas decorrentes do uso e ocupação do solo. Assim, é comum encontrar águas com elevados índices de agressividade corrosiva ou incrustante. O índice de saturação de Langelier é um dos indicadores para avaliar o grau de agressividade da água. Neste trabalho, foram expostas amostras de tubos de cobre à água bruta e à água potável, em que nesta foi empregado hipoclorito de sódio como desinfetante. As amostras de água foram classificadas como "moderadamente corrosivas" (Índice de Saturação de Langelier = -3,2). Amostras de tubos de cobre ficaram imersas em água durante um mês, uma semana e um dia, mantendo-se a taxa de exposição da tubulação em água em 0,5205 cm3.cm−2. Ao fim do tempo de exposição, foram identificadas concentrações de 1,006 ± 0,025 mgCu.L−1 a 1,614 ± 0,051 mgCu.L−1 nas amostras com água bruta e 1,073 ± 0,034 mgCu.L−1 a 1,979 ± 0,222 mgCu.L−1 nas amostras com água potável. As concentrações de cobre nas amostras de água bruta e potável apresentaram diferenças estatísticas (p > 0,005). A velocidade de corrosão da tubulação de cobre variou de 0,0225 cm.ano−1 a 0,0012 cm.ano−1 em função do tempo de exposição das amostras de água. Não foram identificadas diferenças estatísticas na velocidade de corrosão quando submetidas as amostras à água bruta e à água potável (p < 0,005). Os resultados comprovaram que águas agressivamente corrosivas podem proporcionar a corrosão da tubulação de cobre, alterando sua qualidade.

ABSTRACT The physicochemical characteristic of groundwater is a function of the interactions with the soil/rock mineralogy during its infiltration and its length of permanence in the aquifers, in addition to anthropogenic influences resulting from the use and occupation of the soil. Thus, it is common to find waters with high levels of corrosive or fouling aggressiveness. The Langelier Saturation Index is one of the indicators to assess the degree of water aggressiveness. In this work, samples of copper tubes were exposed to raw and drinking water, in which sodium hypochlorite was used as a disinfectant. The water samples were classified as "moderately corrosive" (Langelier Saturation Index = -3.2). Copper tube samples were immersed in water for 1 month, 1 week and 1 day, keeping the exposure rate of the tube in water at 0.5205 cm3.cm−2. After the exposure time, concentrations of 1.006 ± 0.025 mgCu.L−1 to 1.614 ± 0.051 mgCu.L−1 were identified in the samples with raw water and 1.073 ± 0.034 mgCu.L−1 to 1.979 ± 0.222 mgCu.L−1 in the samples with drinking water. The copper concentrations in the raw and drinking water samples showed statistical differences (p > 0.005). The corrosion rate of copper tubing ranged from 0.0225 cm.year−1 to 0.0012 cm.year−1 depending on the exposure time of the water samples. No statistical differences were identified in the corrosion rate when the samples were subjected to raw water and drinking water (p < 0.005). The results proved that aggressively corrosive waters can cause copper pipe corrosion, changing its quality.

Influência do hipoclorito de sódio na resistência à fadiga cíclica em instrumentos rotatórios endodônticos de memória controlada de NiTi: uma avaliação experimental / Influence of sodium hypochlorite on cyclic fatigue resistance in niti controlled memory endodontics rotary instruments: an experimental evaluation

Introdução: É importante saber se o hipoclorito de sódio (NaOCl) influencia a resistência à fadiga cíclica das limas de níquel-titânio (NiTi). Objetivo: Avaliar a influência de NaOCl 2,5% na resistência à fadiga cíclica de dois sistemas de NiTi. Material e método: 40 instrumentos rotatórios - 20 TruNatomy® (TRU, Dentsply Sirona, Maillefer, Ballaigues, Suíça) e 20 Prodesing Logic2® (PDL2, Bassi, Belo Horizonte, Minas Gerais, Brasil) - foram aleatoriamente distribuídos em 4 grupos experimentais (n = 10) imersos em água destilada (H2O) e NaOCl 2,5% em temperatura a 37°C. Foram submetidos a testes de fadiga cíclica mensurando o número de ciclos para fratura (NCF) e análise dessas superfícies pós-teste em microscópio eletrônico por varredura. Para a análise estatística entre os grupos, foi aplicada a análise de variância (ANOVA), complementada com o pós-teste de Tukey. Resultado: Houve diferença estatística em todos os grupos (P<0.05). Os instrumentos PDL2 obtiveram maior resistência à fratura nas condições em H2O e em NaOCl 2,5% comparados aos instrumentos TRU. Na análise de grupos de instrumentos nas soluções de NaOCl e H2O, foi observado que o NaOCl 2,5% diminuiu o NCF. Conclusão: A resistência à fadiga cíclica dos instrumentos TRU e PDL2 diminuiu com NaOCl 2,5%. Os instrumentos PDL2 foram mais resistentes à fratura em relação aos instrumentos TRU.

Introduction: It is important to know whether sodium hypochlorite (NaOCl) influences the cyclic fatigue resistance of nickel-titanium (NiTi) files. Objective: To evaluate the influence of NaOCl 2.5% on the cyclic fatigue resistance of two NiTi systems. Material and method: Forty rotary instruments - 20 TruNatomy® (TRU, Dentsply Sirona, Maillefer, Ballaigues, Switzerland) and 20 Prodesign Logic2® (PDL2, Bassi, Belo Horizonte, Minas Gerais, Brazil) - were distributed randomly across four experimental groups (n=10) and submerged in distilled water (H2O) or 2.5% NaOCl at 37°C according to allocation. Cyclic fatigue testing was then performed, measuring the number of cycles to fracture (NCF), and post-test surfaces were analysed by scanning electron microscopy (SEM). Statistical Analysis: Analysis of variance (ANOVA) was applied for between-group analysis, followed by Tukey's post-hoc test. Result: A significant difference was observed in all groups (P<0.05). PDL2 instruments showed higher fracture resistance under H2O and 2.5% NaOCl conditions compared to TRU. Analysis of all instrument groups showed that exposure to 2.5% NaOCl decreased the NCF compared to H2O. Conclusion: Cyclic fatigue resistance of the TRU and PDL2 instruments was decreased by exposure to 2.5% NaOCl. PDL2 instruments were more resistant to fracture than TRU instruments.

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

Influence of Khat Extract (Catha edulis) on corrosion resistance of Co-Cr dental alloys / Influência do extrato de Khat (Catha edulis) na resistência à corrosão de ligas dentais Co-Cr

Objective: The aim of this experimental study was to assess the effect of khat extract with different concentrations on the corrosion resistance of cobalt-chromium (Co-Cr) dental alloys used for removable denture. Material and Methods:The corrosion resistance of three Co-Cr alloys (Neobond II®, Kera 501® and PD Casta H®) was evaluated in artificial saliva in presence of three different concentrations of khat extracts. Fusayama-Meyer artificial saliva was used as a reference solution. The corrosion properties of the alloys were analyzed using potentiodynamic polarization, electrochemical impedance spectroscopy and surface analysis. The data was presented in means, standard deviations, and related figures. Comparison between the different concentrations was done using 1-way ANOVA test. The surface analysis was performed using scanning electron microscopy (SEM). Results: the results showed that the corrosion resistance of the three alloys tested (Neobond II®, Kera 501® and PD Casta H®) decreased in artificial saliva containing khat extract compared with that of the reference solution. Additionally, the corrosion resistance of the three Co-Cr dental alloys decreased by increasing the concentration of khat extract. Furthermore, the results indicate that Neobond II® alloy showed the least corrosion resistance compared with that of Kera 501® and PD Casta H® alloys. Conclusion: Khat extract with different concentrations had negative impact on the corrosion resistance of Cr-Co alloys. More in-vivo studies are highly recommended to confirm the results of the present study (AU)

Objetivo: O objetivo deste estudo experimental foi avaliar o efeito do extrato de khat em diferentes concentrações na resistência à corrosão de ligas dentárias de cobalto-cromo (Co-Cr) utilizadas em próteses removíveis. Material e Métodos:A resistência à corrosão de três ligas de Co-Cr (Neobond II®, Kera 501® e PD Casta H®) foi avaliada em saliva artificial na presença de três concentrações diferentes de extratos khat. A saliva artificial de Fusayama-Meyer foi usada como solução de referência. As propriedades de corrosão das ligas foram analisadas usando polarização potenciodinâmica, espectroscopia de impedância eletroquímica e análise de superfície. Os dados foram apresentados em médias, desvios-padrão e figuras relacionadas. A comparação entre as diferentes concentrações foi feita usando o teste One-way ANOVA. A análise de superfície foi realizada em microscopia eletrônica de varredura (MEV). Resultados: os resultados mostraram que a resistência à corrosão das três ligas testadas (Neobond II®, Kera 501® e PD Casta H®) diminuiu na saliva artificial contendo extrato khat em comparação com a solução de referência. Além disso, a resistência à corrosão das três ligas dentais Co-Cr diminuiu com o aumento da concentração de extrato de khat. Além disso, os resultados indicam que a liga Neobond II® apresentou a menor resistência à corrosão em comparação com as ligas Kera 501® e PD Casta H®. Conclusão: O extrato de Khat com diferentes concentrações teve impacto negativo na resistência à corrosão de ligas de Cr-Co. Mais estudos in vivo são altamente recomendados para confirmar os resultados do presente estudo. (AU)

Análise da resistência à fadiga e resistência à corrosão em instrumentos, HyFlex EDM, HyFlex CM e RaCe / Analysis of fatigue resistance and corrosion resistance in instruments, HyFlex EDM, HyFlex CM and RaCe

O objetivo deste trabalho foi avaliar a resistência à fadiga e a resistência à corrosão em instrumentos endodônticos de NiTi dos sistemas HyFlex EDM, Hyflex CM, e RaCe, além de relacionar estes resultados às características físicas, químicas e estruturais destes instrumentos. Para tal, instrumentos 25/.~ do sistema HyFlex EDM (EDM), instrumentos 30/.06 do sistema HyFlex CM (CM) e RaCe (RC) foram utilizados. A composição química foi determinada por espectroscopia dispersiva de raios-X, as fases presentes nos materiais foram determinadas por difratometria de raios-X (DRX) e as temperaturas de transformação de fases por calorimetria exploratória diferencial (DSC). A análise da rugosidade superficial dos instrumentos foi realizada por microscopia de força atômica (AFM) e a caracterização dimensional dos instrumentos foi realizada através da mensuração do diâmetro a 3mm da ponta. Ensaios de fadiga até a ruptura foram realizados nos três grupos (n=10) e o tempo médio até a fratura determinado. Instrumentos novos foram subdivididos em grupos controle e experimental para cada sistema. Os grupos experimentais foram submetidos à ensaios de fadiga, até 3/4 do tempo médio para a ruptura e posteriormente a testes de corrosão (potencial de circuito aberto e polarização). Os grupos controle foram diretamente submetidos aos mesmos testes de corrosão. A análise de Weibull foi aplicada para avaliação da probabilidade de falha em relação ao tempo nos instrumentos testados em fadiga até a ruptura. Análise de variância com índice de significância de 0,05% foi adotada para os resultados de composição química, temperatura de transformação de fases, diâmetro, rugosidade e testes de corrosão. A composição química foi praticamente equiatomica em instrumentos RaCe, com presença de Níquel e Titânio. Já instrumentos EDM e CM apresentaram, além destes elementos, Oxigênio na composição. A caracterização estrutural evidenciou maiores temperaturas de transformação de fase Af (austenite finish) para os grupos tratados termicamente (CM e EDM), este dado foi comprovado pelos resultados da difratometria de raios-X com a presença de fase-R e austenita (fase ß) à temperatura ambiente para ambos. O grupo RC, apresentou menores temperaturas Af (p<.05), além de apenas austenita na análise por DRX. As medidas de diâmetro apresentaram-se sem diferenças estatisticamente significativas entre os grupos CM e RC, ambos significativamente maiores que EDM. Os testes de fadiga flexural apresentaram tempo até a fratura sem diferença entre EDM e CM (p>0,05) e ambos foram superiores em relação à RC (p<0.05). Por outro lado, a análise de Weibull apresentou melhores parâmetros de confiabilidade para RC e CM. Os ensaios de corrosão apresentaram diferenças significativas entre os sistemas analisados, mas não entre instrumentos novos e ciclados. Os grupos CM apresentaram maior resistência à corrosão, seguido de EDM e RC. A rugosidade superficial foi maior em instrumentos CM, seguidos de EDM e RC. De acordo com os resultados a microestrutura dos instrumentos tratados termicamente melhora a resistência à fadiga e resistência à corrosão, independentemente do tipo de usinagem.

The aim of this study was to assess the fatigue and corrosion resistance of NiTi endodontic instruments. HyFlex EDM 25 /. ~, HyFlex CM 30/.06 and RaCe 30/.06 were used. Chemical composition was determined by energy-dispersive X-ray spectroscopy, phase constitution by X-ray diffraction and transformation temperatures by differential scanning calorimetry. Surface roughness was analyzed by atomic microscopic force (AFM) and the geometric characterization of the instruments was performed by measuring the diameter at 3mm from the tip. Initially, 10 instruments from each group were tested until rupture in the flexural fatigue bench to obtain the mean time until fracture. Then, new instruments were subdivided into control and experimental groups for each system. Experimental groups were subjected to fatigue tests, up to 3/4 of the mean time to rupture and subsequently to corrosion tests. Control groups were directly subjected to the same corrosion tests. Weibull analysis was applied to assess the reliability in the tested instruments to failure. Analysis of variance with a significance of 0.05% was adopted for the results of chemical composition, phase transformation temperature, diameter, roughness, and corrosion tests. The chemical composition was near equiatomic in RaCe instruments, with the presence of Nickel and Titanium. On the other hand, EDM and CM instruments presented, in addition to these elements, Oxygen in the composition. The structural characterization showed higher Af phase transformation temperatures (austenite finish) for the heat-treated groups (CM and EDM), this data was confirmed by the results of X-ray diffractometry with the presence of R-phase and austenite (phase ß) at room temperature for both. The RC group had lower temperatures Af (p<.05), in addition to only austenite in the XRD analysis. Diameter measurements showed no statistically significant differences between the CM and RC groups, both significantly larger than EDM. Flexural fatigue tests showed time to fracture with no difference between EDM and CM (p>0.05) and both were superior to RC (p<0.05). However, the Weibull analysis showed better reliability parameters for RC and CM. The corrosion tests showed significant differences between the analyzed systems, but not between new and cycled instruments. The CM groups showed greater resistance to corrosion, followed by EDM and RC. Surface roughness was higher in CM instruments, followed by EDM and RC. According to the results, the microstructure of the thermally treated instruments improves fatigue resistance and corrosion resistance, regardless of the type of machining.

In vitro comparison of peracetic acid and autoclave sterilization in the corrosion of orthodontic pliers: a pilot study

ABSTRACT Introduction: The most currently recommended method for sterilization of orthodontic pliers is the autoclave, while peracetic acid has also been shown to be effective in the chemical sterilization process. Objective: This study sought to compare the corrosive effects of peracetic acid and autoclave sterilization process of orthodontic pliers. Methods: Four active tungsten carbide (WC) stainless steel tie-cutting pliers from the manufacturers Quinelato (Rio Claro, SP, Brazil) and ICE (Cajamar, SP, Brazil) were selected. The active ends of the pliers were sectioned, and six active tips were obtained and distributed into the following groups: 1) control group (no sterilization); 2) AC group (two active pliers tips submitted to 100 autoclave sterilization cycles); and 3) AP group (two active pliers tips submitted to 100 cycles of sterilization by immersion in 2% peracetic acid solution for 30 minutes). Results: Chemical analysis using X-ray dispersive energy spectroscopy showed that after autoclave sterilization, only the ICE pliers presented oxidation corrosion (Δ[O] = +24.5%; Δ[Fe] = +5.8%; Δ[WC] = -1.9%). In comparison, following peracetic acid sterilization, both manufacturers ICE (Δ[O] = +1.8%; Δ[Fe] = +18.0%; Δ[WC] = -1.1%) and Quinelato (Δ[O] = +5.3%; Δ[Fe] = -10.4%; Δ[WC] = -15.2%) showed corrosion. The morphological analysis revealed that peracetic acid caused a pitting and localized corrosion in both brands, while the autoclave caused uniform surface corrosion on the ICE pliers. Conclusion: Autoclave application was the sterilization method that generated less corrosive damage to the orthodontic cutting pliers, when compared to the immersion in 2% peracetic acid.

RESUMO Introdução: O método mais recomendado para a esterilização dos alicates ortodônticos é a autoclave; porém, o ácido peracético mostrou-se eficaz no processo de esterilização química. Objetivo: O objetivo do presente estudo foi avaliar o efeito corrosivo do ácido peracético e da autoclave no processo de esterilização de alicates ortodônticos. Métodos: Foram selecionados quatro alicates de corte de amarrilho de aço inoxidável, com ponta ativa de carboneto de tungstênio (WC), das marcas Quinelato (Rio Claro/SP, Brasil) e ICE (Cajamar/SP, Brasil), que foram distribuídos em três grupos: 1) Controle (C), o qual não foi submetido à esterilização; 2) Grupo AC, constituído por duas pontas ativas de alicates submetidas a 100 ciclos de esterilização em autoclave; e 3) Grupo AP, formado por duas pontas ativas de alicates submetidas a 100 ciclos de esterilização por imersão em solução de ácido peracético a 2% durante 30 minutos. Resultados: Por meio da análise química (EDS, energia dispersiva de raios X), constatou-se que, após esterilização em autoclave, somente o alicate ICE apresentou corrosão por oxidação (Δ[O] = +24,5%; Δ[Fe] = +5,8% e Δ[WC] = -1,9%), enquanto na esterilização em ácido peracético, ambas as marcas, ICE (Δ[O] = +1,8%; Δ[Fe] = +18,0% e Δ[WC] = -1,1%) e Quinelato (Δ[O] = +5,3%; Δ[Fe] = -10,4% e Δ[WC] = -15,2%), apresentaram corrosão. A análise morfológica demonstrou que o ácido peracético causou uma corrosão localizada em pite em ambas as marcas, enquanto a autoclave ocasionou uma corrosão superficial uniforme no alicate ICE. Conclusão: A autoclave foi o método de esterilização que gerou menor dano corrosivo aos alicates ortodônticos, em comparação à imersão em ácido peracético a 2%.

Avaliação do grau de corrosão de fios ortodônticos submetidos a desafio de pH / Evaluation of the corrosion degree of orthodontic wires subjected to pH challenge

Introdução: a movimentação dentária requer a aplicação de um sistema de forças que é orientado com o uso de acessórios, incluindo fios ortodônticos. Existem diversos materiais e fabricantes disponíveis no mercado, por isso é importante que o profissional conheça a composição deste material, uma vez que estará em contato com a mucosa oral, podendo sofrer corrosão e liberação de íons metálicos. Objetivo: avaliar, in vitro, o grau de corrosão de duas ligas metálicas que compõem fios ortodônticos de três fabricantes diferentes, submetidos à ciclagem de pH. Metodologia: 60 corpos de prova foram confeccionados com dois tipos de ligas metálicas (NiTi e CrNiaço 302) produzidas por três fabricantes diferentes, divididos em 6 Grupos de Testes com 10 unidades cada. Os corpos-de-prova foram submetidos à ciclagem ácida de pH 4,3, diariamente, e mantidos em estufa a 37 ° C por 14 dias. A massa foi pesada antes e após a ciclagem, por meio de balança analítica de precisão. A avaliação das características visuais dos fios foi realizada por um único observador em lupa estereomicroscópica. Resultados: a ciclagem de pH dos fios ortodônticos não promoveu perda significativa de massa ou corrosão, apesar da análise das características visuais terem mudado após a ciclagem. Conclusão: com base nos resultados do protocolo experimental estabelecido no presente estudo, a análise do comportamento das ligas de aço NiTi e CrNi ­ 302 que compõem os fios ortodônticos, frente ao desafio ácido de pH 4,3, por duas semanas, concluiu-se que esses materiais não apresentaram perdas de massa, opacidade, brilho e lisura consideradas significativas. Outros estudos são recomendados para fornecer maiores esclarecimentos sobre o tema.

Introduction: the tooth movement requires the application of a force system that is guided with the use of accessories, including orthodontic wires. There are several materials and manufacturers available on the market, so it is important that the professional knows the composition of this material, since it will be in contact with the oral mucosa, and may suffer corrosion and release metal ions. Objective: to evaluate, in vitro, the degree of corrosion of two metal alloys that make up orthodontic wires from three different manufacturers, submitted to pH cycling. Methodology: 60 specimens were made from two types of metal alloys (NiTi and CrNi ­ steel 302) produced by three different manufacturers, divided into 6 Test Groups with 10 units each. The specimens were subjected to acid pH 4.3 cycling, daily, and kept in an oven at 37 ° C for 14 days. The mass was obtained before and after cycling, using a precision analytical balance. The evaluation of the visual characteristics of the wires was performed by a single observer using a stereomicroscopic loupe. Results: the pH cycling of orthodontic wires did not promote significant loss of mass or corrosion, despite the analysis of visual characteristics having changed after cycling. Conclusion: based on the results of the experimental protocol established in the present study, the analysis of the behavior of the NiTi and CrNi ­ 302 steel alloys that make up the orthodontic wires, facing the acid challenge of pH 4.3, for two weeks, it was concluded that these materials did not present loss of mass, opacity, brightness and smoothness considered significant. Other studies are recommended to provide further clarification on the topic.

Studies on features, physical, mechanical, tribological properties and applications of Ti-6Al-4V in aerospace industry

This research article gives an overview of the extensive research of Ti-6Al-4V from past few decades helped in studying about the features, properties, characteristics and application of aerospace industries. The final objective of study is to obtain the inherent advantages of Ti-6Al-4V like low elasticity modulus, high strength, low density and more resistant to fatigue and corrosion that leads to rely on the required knowledge for the employment of application which improves all physical and mechanical properties.

Comportamiento de la rugosidad superficial del acero luego de exposición natural en exterior e interior / Behavior of superficial roughness of the steel after natural outdoor and indoor exposure

RESUMEN El conocimiento de los fenómenos que tienen lugar en el medio que nos rodea permite garantizar la preservación y el uso adecuado de los recursos, elevando la calidad de vida en el planeta, para el bienestar presente y futuro de los hombres que lo habitan. Uno de los procesos naturales a los que nos enfrentamos todos y cada uno de los seres que coexistimos en este planeta, sean vivos o no, es el deterioro, debido a la interacción con el medio ambiente. La forma más natural de deterioro en que los metales regresan a minerales, como se encuentran en la naturaleza, es conocida como corrosión, proceso que es afectado por múltiples factores ambientales. El estado superficial de una muestra metálica resulta en un aspecto que influye en la magnitud y tipo de corrosión. En el presente trabajo, se evalúo el comportamiento de la rugosidad superficial en condiciones de exposición natural en exteriores e interiores, durante un corto tiempo, de 360h. A partir del diseño multifactorial, se demuestra la incidencia de las condiciones de exposición y el tiempo de ensayo en la rugosidad superficial, con un nivel de confianza del 95%. Las ecuaciones del modelo lineal describen la relación entre la rugosidad superficial y el tiempo de exposición, posibilitando posibles predicciones en el futuro, para condiciones del clima, similares a las descritas en el estudio.

ABSTRACT Knowledge of the phenomena that take place in the environment that surrounds us, ensures the preservation and proper use of resources, raising the quality of life on the planet for the present and future well-being of the men who inhabit it. One of the natural processes that we face each and every one of the beings that coexist on this planet, whether alive or not, is the deterioration due to interaction with the environment. The most natural form of deterioration in which metals return to minerals, as they are found in nature, is known as corrosion, a process that is affected by multiple environmental factors. The surface condition of a metal sample is an aspect that influences the magnitude and type of corrosion. In the present work we evaluated the behavior of the surface roughness in conditions of natural exposure in exteriors and interiors during a short time of 360 h. Based on the multifactorial design, the incidence of exposure conditions and the test time on surface roughness with a 95% confidence level are demonstrated. The equations of the linear model describe the relationship between surface roughness and exposure time, making possible predictions in the future for climate conditions similar to those described in the study.

Nickel and Chromium Ion Levels in Hair and Gingival Crevicular Fluid with the Corrosion of Brackets in Orthodontic Patients: A Longitudinal Study

Objective: To assess the levels of nickel and chromium ions in hair and Gingival Crevicular Fluid (GCF) of orthodontic patients and to evaluate the corrosion of orthodontic bracket surfaces. Material and Methods: Nickel and chromium ion concentrations were measured in hair and GCF of 15 patients (9 females and 6 males, aged 16-28 years old) who had fixed orthodontic treatment using atomic absorption spectroscopy. The samples were taken before treatment (baseline), 4, 8, and 16 months later during treatment. Along with ionic sampling, microscopic sampling was done. One of each patient brackets was removed to get 15 brackets per group. Five brackets were taken randomly from each group to be examined under scanning electron microscope (SEM). Data obtained were analyzed using paired t-tests. Results: After 16 months, compared with the baseline, average hair nickel level changed from 0.125 µg/g to 0.956 µg/g with statistically significant difference (p=0.00); average chromium level changed from 0.090 µg/g to 0.295 µg/g but no significant difference (p>0.05); average GCF nickel level changed from 3.335 µg/g to 10.410 µg/g; average chromium level changed from 1.859 µg/g to 9.818 µg/g. Both of these increases were significant (p=0.000). SEM examinations showed that the corrosion on brackets was seen in the fourth month, and more severely visible after 8 and 16 months of uses. Conclusion: After 16 months of treatment, compared with the baseline, the hair nickel level was increased by 7.7 times; while for chromium was by 3.3 times. Gingival crevicular fluid nickel level was increased by 3.1 times and chromium level was by 5.3 times. The longer time of treatment, the more ions released and the more corrosion of brackets will be.

Corrosion Resistance of Stainless Steel Brackets After Thermal Recycling by Direct Flaming

Objective: To determine and compare the corrosion resistance (based on the release of nickel and chromium in artificial saliva) of various brands of stainless steel brackets after thermal recycling by direct flaming. Material and Methods: This research study employed 40 stainlesssteel maxillary premolar brackets from different brands (Ormco, GAC, Versadent, S-Ortho, and Protect), which were divided into 5 groups consisting of 8 brackets. The nickel and chromium content of the metal brackets were analyzed by inductively coupled plasma mass spectrometry (ICP-MS), conducted before immersion. For the first treatment, each group was immersed in artificial saliva without direct flaming (recycling); for the second treatment, each group was immersed in artificial saliva with direct flaming (recycling) for 30 days in a pH-neutral (pH=7) solution. ICP-MS was employed to analyze the nickel and chromium released in saliva. The mean differences were measured with Wilcoxon, Kruskal Wallis test, and Post-Hoc Mann Whitney test. Differences were considered statistically significant when p-value<0.05. Results: The mean corrosion resistance based on the nickel content released by the new brackets was 99.95%, 99.87%, 87.09%, 90.58%, and 90.26% for groups A, B, C, D, and E, respectively. The mean corrosion resistance based on the nickel content released by the recycled brackets was 99.90%, 99.80%, 98.19%, 89.76%, and 72.82%, respectively. There was a significant difference in corrosion resistance among the 5 groups after recycling by direct flaming and between new and recycled brackets in each group. Conclusion: The corrosion resistance of the brackets in groups A (Ormco), B (GAC), D (S-Ortho), and E (Protect) decreased after thermal recycling by direct flaming. The Ormco brackets had the highest corrosion resistance after thermal recycling by direct faming.

Corrosion Cast- Comparison of Different Techniques and Materials Used in Corrosion Casting

In medical terms, cast refers to the replica obtained after filling a luminal structure with resin to reproduce its morphology. It can be accomplished by removing the soft tissue around it, termed corrosion or maceration. Corrosion casts form very important material in learning morphology of various structures like- vascular tree, tracheobronchial tree, luminal casts of various organs. Vascular casts have been studied using scanning electron microscopy, which has contributed to understanding the biological processes. If the specimen is fixed after resin injection, it can be used for surgical training, medical teaching etc. In the present review, the authors have tried to analyse the technical aspects of corrosion casting. We have also added note on polyurethane foam cast of coronary vessels, which was carried out in our laboratory.