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.

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.

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%.

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

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.

The Local Alternative Ti-6Al-4V Alloy Coating of Surgery Steel Instruments for Laser Deposition Forming / 中国医疗器械杂志

Aiming at the medical practice problems of the surgical steel medical instruments, such as the crevice corrosion, the poor mechanical compatibility and the Ni, Cr plasma exudation, the laser deposition of Ti-6Al-4V alloy cladding layer at the local functional area as alternative coating was proposed and realized as a new process method. The accurate element content and good formability Ti-6Al-4V cladding powder was chosen, the low power and high duty cycle optimized laser process was adopt, the alternative coating of good fusion and low dilution was prepared. Through the elemental line scanning, the interface microstructure analysis and the experiments of basic mechanical properties, the basic properties of the cladding were characterized and verified. The experiments results showed that, the Ti, Al and V contents of the top coating were respectively about 88%, 4.9% and 3.9%, no sensitizing ions such as Cr and Ni were detected. Initial equiaxed α phase, flake β phase dist were distributed in the coating and interface, the α' martensite was precipitated at the boundary of the flake β phase, some refined granular β phase dispersion pinned to the grain boundary of basket structure. The microhardness of cladding layer was 352.08~312.76 HV0.1. The friction coefficient of the cladding layer was about 0.22~0.65. A new technology and method reference for improving and upgrading the performance of surgical medical devices is provided by this research.

Sports supplement induces dental structure corrosion: an in vitro pilot study / El suplemento deportivo induce corrosión en la estructura dental: un estudio piloto in vitro

Dietary supplements are being consumed with an increasingly high frequency among sports practitioners, whether at professional and/or amateur level. The supplements contain some nutritional properties in their composition, so they can dissolute the hydroxyapatite crystals of the enamel and favor the process of dental corrosion. The objective was to measure the corrosive power of protein-based supplementation (Whey Protein), under conditions that resemble the use of the supplement by the athletes, increasing the ecological validity of the study. The teeth of the test group (TG) were placed in contact with the Whey protein solution and then exposed to artificial saliva. And the teeth of the control group (CG) were exposed only to artificial saliva. The analysis occurred in natural healthy molar teeth, so that each tooth of the TG was immersed in 50 mL of supplement for 1.5 minutes and then placed in contact with the artificial saliva for 30 seconds. The same procedure was performed 5 times a day for 30, 60, 90, 120, 150 and 180 days. Each group, in its time (TG0 to TG180), underwent analysis of superficial roughness with the aid of optical profilometer (Talysurf CCI®, 3D model). The control group (CG) did not change its superficial roughness. Half of the teeth of the test group (TG) suffered loss of enamel surface. The values, in micrometers, of surface loss of the TG samples were 1.21; 2.1; 2.0; 1.04; 0.97; 0.8; 0.53; 1.14; 1.9; 2.0; 1.66; 1.80. The dietary supplement (Whey protein®) may be a potential cause of the dental corrosion process, considering the demineralization of hydroxyapatite that occurs along with the surface enamel loss.

Los suplementos dietéticos se consumen con una frecuencia cada vez más alta entre los practicantes de deportes, sea a nivel profesional y / o aficionado. Los suplementos contienen algunas propiedades nutricionales en su composición, por lo que pueden disolver los cristales de hidroxiapatita del esmalte y favorecer el proceso de corrosión dental. El objetivo fue medir el poder corrosivo de la suplementación a base de proteínas (proteína de suero), en condiciones que se asemejan al uso del suplemento por parte de los atletas, aumentando la validez ecológica del estudio. Los dientes del grupo de prueba (TG) se pusieron en contacto con la solución de proteína de suero y luego se expusieron a saliva artificial. Y los dientes del grupo de control (CG) estuvieron expuestos solo a saliva artificial. El análisis se realizó en dientes molares sanos naturales, cada diente del TG se sumergió en 50 ml de suplemento durante 1,5 minutos y luego se puso en contacto con la saliva artificial durante 30 segundos. El mismo procedimiento se realizó 5 veces al día durante 30, 60, 90, 120, 150 y 180 días. Cada grupo, en su momento (TG0 a TG180), se sometió a un análisis de rugosidad superficial con la ayuda de un perfilómetro óptico (Talysurf CCI®, modelo 3D). El grupo de control (CG) no cambió su rugosidad superficial. La mitad de los dientes del grupo de prueba (TG) sufrieron pérdida de la superficie del esmalte. Los valores, en micrómetros, de pérdida de superficie de las muestras de TG fueron 1.21; 2.1; 2,0; 1.04; 0,97; 0.8; 0,53; 1.14; 1.9; 2,0; 1,66; 1.80. El suplemento dietético (Whey protein®) puede ser una causa potencial del proceso de corrosión dental, considerando la desmineralización de la hidroxiapatita que ocurre junto con la pérdida de esmalte superficial.

Effects of some commercial calamansi-containing beverages on the enamel surface / 대한구강보건학회지

OBJECTIVES: The aim of this study was to investigate the effects of some commercial calamansicontaining beverages on the sound surface of bovine teeth as well as the dental erosion inhibitory effects of calcium.METHODS: The pH and titratable acidity of six kinds of commercially available calamansi beverages were determined. Further, 3% calcium was added to the calamansi beverage Oranssi in the experimental group to confirm its dental erosion inhibitory effect. Jeju Samdasoo was used in the negative control group and Coca-Cola in the positive control group. After immersing the sound teeth specimens for 10 min, surface microhardness was measured using the Vickers hardness number (VHN), and surface changes in specimens were observed under a scanning electron microscope.RESULTS: The average pH of the commercial calamansi beverages was 2.54±0.22. After 10 min of treatment with each experimental beverage, the surface hardness difference (ΔVHN) was highest in the Coca-Cola group (−49.05±12.59), followed by the Oranssi calamansi group (−43.77±13.70), 3% calcium-added Oranssi calamansi group (−2.71±12.58), and Samdasoo group (14.03±20.79). There was no significant difference between the bottled water and calcium-added Oranssi calamansi groups or between the Coca-Cola and Oranssi calamansi groups (P>0.05). However, there was a significant difference in the surface hardness between the bottled water and CocaCola groups (P<0.05). On scanning electron microscopy, the Samdasoo group showed a smooth surface without any loss, but Coca-Cola and Oranssi calamansi groups showed a rough surface due to erosion. However, although fine cracks and porosities were seen in the calcium-added Oranssi calamansi group, surfaces in the group were much smoother than those in the Oranssi calamansi group.CONCLUSIONS: Calamansi beverages of low pH may cause corrosion of the tooth surface, and the addition of calcium to the calamansi beverages inhibits demineralization of the tooth surface. Therefore, it is necessary to consider the risk of dental erosion when drinking calamansi beverages of low pH.

Análise de limas endodônticas submetidas a biocorrosão por bactérias redutoras de sulfato in vitro / Analysis of endodontic files submitted to biocorrosion by sulfate reducing bacteria in vitro

Objetivo: Avaliar as alterações químicas presentes na superfície metálica de limas endodônticas fraturadas em canais radiculares, in vitro, após a inoculação intrarradicular de culturas de BRS de três cepas microbianas, Desulfovibrio desulfuricans (uma cepa oral e outra ambiental) e Desulfovibrio fairfieldensis. Métodos: foram analisadas 5 limas kerr #90, sendo uma Lima Kerr nova, sem tratamento, e as outras 4 limas fraturadas dentro de canais radiculares in vitro, com posterior inoculação de Desulfovibrio desulfuricans, cepa oral e ambiental, e Desulfovibrio fairfieldensis e um grupo controle sem inoculação bacteriana, por 477 dias. Os grupos foram analisados no modo EDS (Espectrometria de Energia Dispersiva de Raios-x) do microscópio eletrônico de varredura (FEI-Inspect-S50). Resultados:A presença do S, Cl e O foram relacionados ao processo biocorrosivo, assim como a redução dos elementos de liga nesta área. Conclusão:As análises no modo EDS demonstraram biocorrosão ao longo da superfície metálica das limas quando empregado o biofármaco BACCOR, nas três diferentes cepas empregadas, indicada pela redução dos elementos formadores da liga metálica, Fe, Ni e Cr, com a associação da presença de elementos indicadores de biocorrosão como O, Cl e S. (AU)

Aim:To evaluate the chemical alterations present on the metallic surface of root canal fractured endodontic files in vitro after the intraradicular inoculation of BRS cultures of three microbial strains, Desulfovibrio desulfuricans (one oral and one environmental strain), and Desulfovibrio fairfieldensis. Methods: Five kerr #90 files were analyzed, one new untreated Kerr file and the other 4 files fractured within root canals in vitro, with a subsequent inoculation of Desulfovibrio desulfuricans (oral and environmental strains), and Desulfovibrio fairfieldensis, as well as a control group without bacterial inoculation for 477 days. The groups were analyzed using the scanning electron microscope (FEI-Inspect-S50) EDS (X-ray Dispersive Energy Spectrometry) mode. Results:The presence of S, Cl, and O were related to the biocorrosive process, as well as the reduction of alloying elements in this area. Conclusion: The EDS mode analysis showed biocorrosion along the metallic surface of the files when the BACCOR biopharmaceutical was used in the three different strains employed in this study, indicated by the reduction of the alloying elements ­ Fe, Ni, and Cr ­ with the association of the presence of indicator elements of biocorrosion, such as O, Cl, and S. (AU)

The importance of corrosion resistance test of cannulas in the quality control of hypodermic needles

According to Anvisa risk rating, hypodermic needles offer medium risk to the user's health. This study discussed the importance of the corrosion resistance test in tubes of hypodermic needles, in the product quality control. A review of cannulas of hypodermic needles was carried out according to ISO 9626:2003 and 9259:1997 ABNT NBR. For the results evaluation, a scale which classifies the extent of corrosion was adjusted. 174 samples of PNI needles from 17 States and 9 different record holders were analyzed. According to the methodology of ISO 9626:2003, 100% of the samples were considered satisfactory. However, in accordance with the methodology of ISO 9259:1997, 97.1% of the samples were rejected. Irregularities can lead to impairment of product quality, resulting in risks to the consumer's health. Since 2011 the product has undergone certification, so it is necessary to reflect on the importance of corrosion resistance testing and mandatory certification for health monitoring.

Effects of commercial plum beverage on the dentin surface of bovine teeth / 대한구강보건학회지

OBJECTIVES: We investigated the effects of commercial plum beverage on the dentin surface that could be exposed to caries, gliopathy, and abrasion to investigate the inhibitory effects of dentin corrosion.METHODS: The experimental beverages were Jeju Samdasoo (Group 1, negative control), Coca-Cola (Group 2, positive control), Chorok Maesil (Group 3), and Chorok Maesil with 3% calcium lactate added (Group 4). The specimens were prepared and divided into 4 groups of 12 each. The pH of the experimental beverages was measured using a pH meter, and specimen surface hardness was assessed according to the Vickers hardness number (VHN). The specimens were immersed in the experimental beverage for 1, 3, 5, 10, and 15 minutes. Then, we obtained the average VHN by measuring surface microhardness. Measures of surface microhardness were compared using the paired t-test before and after 15 minutes of immersion in each of the four beverages. Between-group differences in surface microhardness were compared using one-way analysis of variance and the Tukey test after the analysis.RESULTS: After 15 minutes of immersion in the experimental beverages, there was no significant difference in surface microhardness in group 1 (P>0.05). There were significant differences in groups 2, 3, and 4 (P < 0.05). The difference in surface microhardness before and after immersion for 15 minutes was highest in group 3 (−18.1±2.55), followed by group 2 (−13.0±3.53) and group 4 (−7.79±4.47). In group 1, the difference was −1.52±4.30. Moreover, there was a significant difference in each group (P < 0.05). After 10 minutes of immersion, surface microhardness tended to rapidly decrease.CONCLUSIONS: Patients who regularly ingest a commercially available plum drink with low pH should be provided dietary guidance on the risk of dental erosion. Calcium additives should be considered when producing plum beverage products.

An innovative method in venous coronary cast technique / 대한해부학회지

Polyurethane foam (PU foam) is a new material which is being used in producing both macro-anatomical and micro-anatomical specimens. PU foam is simple to use, without need for special equipment. The present study was carried out to evaluate morphology of coronary sinus and its tributaries. During the study, we encountered few problems in carrying out injections. Coronary sinus and its tributaries were difficult to cannulate since the coronary sinus lacks a vascular stem, around which ligature can be tied before injection so that the cannula can be held in place. In contrast, in majority of the organs it is easy to inject since they possess tubular vascular stem to hold the cannula in place. A new device was developed which could be used to cannulate coronary sinus orifice to inject the casting media. The second problem we faced was saponification of adipose tissue. This made corrosion of the soft tissue difficult. Hence in this study, we describe the device we have developed to place in the coronary sinus orifice, and how saponified adipose tissue was taken care during the actual maceration step.

Full mouth rehabilitation of a patient with severe tooth erosion with a digital crown lengthening guide / 대한치과보철학회지

In the oral cavity, the teeth undergo wear and corrosion throughout their lives. Progressive and constant tooth wear is a natural phenomenon of aging, but wear and corrosion due to specific factors are pathological factors. It can cause pathological damage of the occlusal surface, aesthetic problems, dimensional loss and jaw joint disorders. This case is a 26-year-old female patient with general tooth abrasion and erosion on the entire dentition. Diagnostic wax-up was fabricated based on the information including digital facial analysis, physiological stabilization, and evaluation of anterior crown length. Through the digital analysis, the necessary guides for crown lengthening were prepared and the mastication function and esthetics were evaluated by using temporary crowns. Definitive prosthesis was fabricated with the zirconia restorations. The results were satisfactory when they were observed 3 months of follow-up.

Late Onset Disassembly of a Modular Neck-stem Component after Cementless Hip Replacement without Dislocation: A Case Report and Review of Literatures / 대한고관절학회지

Modular femoral prostheses are characterized by a second neck-stem junction. This modularity provides many clinical benefits including hip offset restoration, intraoperative leg length and anteversion adjustment. Although, this extra junction in modular femoral prostheses can contribute to catastrophic consequences like fracture, cold welding, corrosion and fretting of the modularity. However, only few complications related to the modularity itself have been reported in the literature. We report a unique case of neck-stem component dissociation without dislocation of the R-120PC™ Modular Stem (DJO Surgical). Our 71-year-old obese female patient underwent cementless hip replacement 5 years ago. Following radiographic confirmation of neck-stem dissociation open reduction was performed and wiring fixation was applied to secure the neck to the stem. After reduction and fixation, hip joint was stable, and our patient returned to her daily routine 2.5 months postoperatively. The last follow up was at 12 months after surgery with excellent radiographic and clinical evaluation.

Design and 3D-printing of titanium bone implants: brief review of approach and clinical cases

Additive manufacturing (AM) is an alternative metal fabrication technology. The outstanding advantage of AM (3D-printing, direct manufacturing), is the ability to form shapes that cannot be formed with any other traditional technology. 3D-printing began as a new method of prototyping in plastics. Nowadays, AM in metals allows to realize not only net-shape geometry, but also high fatigue strength and corrosion resistant parts. This success of AM in metals enables new applications of the technology in important fields, such as production of medical implants. The 3D-printing of medical implants is an extremely rapidly developing application. The success of this development lies in the fact that patient-specific implants can promote patient recovery, as often it is the only alternative to amputation. The production of AM implants provides a relatively fast and effective solution for complex surgical cases. However, there are still numerous challenging open issues in medical 3D-printing. The goal of the current research review is to explain the whole technological and design chain of bio-medical bone implant production from the computed tomography that is performed by the surgeon, to conversion to a computer aided drawing file, to production of implants, including the necessary post-processing procedures and certification. The current work presents examples that were produced by joint work of Polygon Medical Engineering, Russia and by TechMed, the AM Center of Israel Institute of Metals. Polygon provided 3D-planning and 3D-modelling specifically for the implants production. TechMed were in charge of the optimization of models and they manufactured the implants by Electron-Beam Melting (EBM®), using an Arcam EBM® A2X machine.

Research progress of chromium and its speciation analysis / 中国中药杂志

Chromium has been discovered for more than two hundred years, and it has advantages of wear-resisting, high temperature, corrosion resistance and so on. Chromium has been widely used in industrial production and received extensive attention in China and abroad. Detailed limit standards have been set for chromium in food and fishery product, and chromium can also be enriched in many traditional Chinese medicines. Besides, the toxicities of different chromium speciation are quite different, and thus morphological analysis is necessary. However, the transformation or migration is easily happened among different speciation which brings difficulties to research and analysis. This article summarizes the research status of chromium and its aims to provide reference for scientific research and pollution prevention of chromium.

Corrosion Behaviors of Dental Implant Alloy after Micro-sized Surface Modification in Electrolytes Containing Mn Ion

PURPOSE: The purpose of this study was to investigate the corrosion behaviors of dental implant alloy after micro-sized surface modification in electrolytes containing Mn ion. MATERIALS AND METHODS: Mn-TiO₂ coatings were prepared on the Ti-6Al-4V alloy for dental implants using a plasma electrolytic oxidation (PEO) method carried out in electrolytes containing different concentrations of Mn, namely, 0%, 5%, and 20%. Potentiodynamic method was employed to examine the corrosion behaviors, and the alternating-current (AC) impedance behaviors were examined in 0.9% NaCl solution at 36.5℃±1.0℃ using a potentiostat and an electrochemical impedance spectroscope. The potentiodynamic test was performed with a scanning rate of 1.667 mV s⁻¹ from −1,500 to 2,000 mV. A frequency range of 10⁻¹ to 10⁵ Hz was used for the electrochemical impedance spectroscopy (EIS) measurements. The amplitude of the AC signal was 10 mV, and 5 points per decade were used. The morphology and structure of the samples were examined using field-emission scanning electron microscopy and thin-film X-ray diffraction. The elemental analysis was performed using energy-dispersive X-ray spectroscopy. RESULT: The PEO-treated surface exhibited an irregular pore shape, and the pore size and number of the pores increased with an increase in the Mn concentration. For the PEO-treated surface, a higher corrosion current density (I(corr)) and a lower corrosion potential (E(corr)) was obtained as compared to that of the bulk surface. However, the current density in the passive regions (I(pass)) was found to be more stable for the PEO-treated surface than that of the bulk surface. As the Mn concentration increased, the capacitance values of the outer porous layer and the barrier layer decreased, and the polarization resistance of the barrier layers increased. In the case of the Mn/Ca-P coatings, the corroded surface was found to be covered with corrosion products. CONCLUSION: It is confirmed that corrosion resistance and polarization resistance of PEO-treated alloy increased as Mn content increased, and PEO-treated surface showed lower current density in the passive region.

Effects of conditions for anodization and cyclic precalcification treatments on surface characteristics and bioactivity / 대한치과재료학회지

The purpose of this study was to investigate the effects of the anodization and cyclic calcification treatment on the surface characteristic and bioactivity of the titanium thin sheet in order to obtain basic data for the production of bioactive titanium membrane. A 30×20×0.08 mm titanium sheets were prepared, and then they were pickled for 10 seconds in the solution which was mixed with HNO₃: HF: H₂O in a ratio of 12: 7: 81. The TiO₂ nanotube layer was formed to increase the specific surface area of the titanium, and then the cyclic calcification treatment was performed to induce precipitation of hydroxiapatite by improvement of the bioactivity. The corrosion resistance test, wettability test and immersion test in simulated body solution were conducted to investigate the effect of these surface treatments. The nanotubes formed by the anodization treatment have a dense structure in which small diameter tubes are formed between relatively large diameter tubes, and their inside was hollow and the outer walls were coupled to each other. The hydroxyapatite precipitates were well combined on the nanotubes by the penetration into the nanotube layer by successive cyclic calcification treatment, and the precipitation of hydroxyapatite tended to increase proportionally after immersion in simulated body solution as the number of cycles increased. In conclusion, it was confirmed that induction of precipitation of hydroxyapatite by cyclic calcification treatment after forming the nanotube TiO₂ nanotube layer on the surface of the titanium membrane can contribute to improvement of bioactivity.

Influence of beverage type and ingestion time on tooth corrosion / 대한치과재료학회지

This study was conducted to analyze the effects of beverages on tooth corrosion by selecting drinks that are enjoyed by modern people. Drinks were selected for carbonated beverages (Coca Cola), energy drinks (Red Bull), orange juice, beer (Hite) and water (Evian). Bovine tooth was immersed for 1 hour, 24 hours and 48 hours. The root mean square (RMS) values were obtained by scanning the bovine tooth at pre-immersion and immersion time after impression making. Two-way ANOVA, one-way ANOVA, and Tukey-test were used to compare differences between groups (α=0.05). The RMS value tended to increase with longer immersion times in all beverages, and there was a significant difference (p < 0.05) between before immersion-1hr and before immersion-48 hr. The mean of RMS according to the type of beverage was significantly different and there was a significant difference according to the change of immersion time (p < 0.05). In order to prevent tooth corrosion, it is necessary to change the method of ingestion or to reduce the time of ingestion.