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)

Effects of copper content on the antibacterial performance and corrosion resistance of CoCrMoCu alloy / 华西口腔医学杂志

<p><b>OBJECTIVE</b>This study aimed to determine the effects of copper content on the corrosion resistance of CoCrMoCu alloy and its in vitro antibacterial performance.</p><p><b>METHODS</b>CoCrMoCu specimens with different Cu contents (2%, 3%, 5%, and 7%) were prepared by vacuum melting method. CoCrMo without Cu served as control. The corrosion resistance of the specimens was measured by electrochemistry. The antibacterial effects of the specimens on Staphylococcus aureus and Escherichia coli were analyzed by coating-film method.</p><p><b>RESULTS</b>Compared with CoCrMo without Cu, the addition of 2%-5% Cu to CoCrMo improved the pitting and uniform corrosion of CoCrMo alloy and decreased the corrosion current density. The antibacterial performance of CoCrMoCu alloy increased with increased Cu content. The antibacterial rate of alloy was 99% when Cu content exceeded 5%.</p><p><b>CONCLUSIONS</b>Cu addition had a statistically significant influence on the corrosion resistance and antibacterial performance of CoCrMoCu. CoCrMoCu has better corrosion resistance and antibacterial performance when Cu content is 5%.</p>

The effect of fluoride-containing oral rinses on the corrosion resistance of titanium alloy (Ti-6Al-4V) / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to examine the effect of commercially available fluoride-containing oral rinses on the corrosion behavior of titanium alloys, which are the main components of orthodontic miniscrews. METHODS: Four commercially available oral rinses (solution A, pH 4.46/260 ppm fluoride; solution B, pH 4.41/178 ppm fluoride; solution C, pH 6.30/117 ppm fluoride; and solution D, pH 4.17/3.92 ppm fluoride) were tested on titanium alloy (Ti-6Al-4V) circular plates, and saline was used as the control. The open-circuit potential and potentiodynamic polarization of these materials were measured. Thereafter, all samples were evaluated under a field-emission scanning electron microscope. RESULTS: Among the tested oral rinses, except solution D, the more the fluoride content was, the greater was the corrosion potential downtrend; the corrosion resistance of the titanium alloy sample was also lowered significantly (p < 0.05). Field-emission scanning electron microscopic analysis of the surface morphology of the titanium alloy samples revealed that all samples had some defects, crevices, or pitting after exposure to the oral rinses than before treatment. In particular, the samples in solution A showed the most changes. CONCLUSIONS: Commercially available oral rinses having a high fluoride concentration and a low pH may reduce the corrosion resistance of titanium alloys used in dental appliances such as orthodontic titanium miniscrews and brackets.

A research on the corrosion resistance of Ni-Cr alloy with different coatings / 实用口腔医学杂志

Objective: To evaluate the corrosion resistance of Ni-Cr alloy with different coatings in neutral and acid saliva by electrochemistry method. Methods: Measured the self-corrosion potential (Ecorr) and polarization resistance(Rp) curves of Ni-Cr alloy models with different coatings in neutral and acid artificial salivas. Results: The Ecorr of the Ni-Cr alloys all showed positive values, the electrochemistry corrosion and galvanic corrosion were not detected. Conclusion: Ni-Cr alloy with titanium nitride coating, gold electroplating coating, gold-paste layer and gold-porcelain blended layer have both anti-corrosion and esthetical function without changing its own property.

Effects of TiN coating on corrosion resistance of dental Co-Cr alloy / 上海第二医科大学学报

Objective To investigate the effects of titanium nitride(TiN) coating on corrosion resistance of dental Co-Cr alloy in the simulated oral environment. Methods The Co-Cr alloy commonly used was casted with specimen sized of 10 mm× 10 mm×3 mm. Then the specimen was coated with a thickness of 2.5 μm TiN coating on the surface by multi-arc physical vapor deposition. The Tafel polarization curves of the specimen before and after coating titanium nitride in artificial saliva were measured by electrochemical station. Results From the Tafel polarization curves, the specimen after coating TiN showed that both anodic polarization curve and cathodal polarization curve were fiat, natural corrosion potential moved to the positive way, and passivation interval got longer. From the annular anodic polarization curves, the specimen after coating TiN had almost no "delay area". Conclusion TiN coating can improve corrosion resistance of Co-Cr alloy.

Comportamento do titânio comercialmente puro obtido por diferentes processamentos submetidos a soluções fluoretadas / Behavior of commercially pure titanium obtained by different processing under the action of different fluoride solutions

O objetivo deste estudo in vitro foi analisar o comportamento superficial do titânio comercialmente puro (grau 2 ASTM) usinado e obtido pelo processamento de metalurgia do pó sob a ação de diferentes soluções fluoretadas, através da análise do grau de corrosão em microscopia óptica (MO) e da rugosidade superficial. Além disso, o estudo se propôs a comparar essas análises com os resultados obtidos com o titânio fundido da dissertação de mestrado de Barros (2004). Todas as amostras receberam procedimento metalográfico padrão e foram divididas em grupos: Gr.1- saliva artificial com pH 7.0 (controle), Gr.2- gel de flúor fosfato acidulado a 1,23% com pH 3.5, Gr.3- gel de NaF a 2% com pH 6.5, Gr.4- solução de NaF a 0,05% com pH 4.0 e Gr.5- solução de NaF a 0,05% com pH 7.5. As amostras foram expostas a estas soluções por 1, 4, 8 e 16 min, intercaladas com imersão em saliva artificial por 24 h, e depois foram observadas em MO e MEV, a cada intervalo de tempo. As imagens em MO, 100x, foram classificadas através de escores de 0 a 4, conforme o grau de corrosão. A rugosidade foi analisada utilizando o parâmetro Ra. Os resultados da análise de MO foram tratados estatisticamente pelo teste qui-quadrado e da rugosidade pelo teste “F” de Snedecor e de Bonferroni (p<0,05). Nos três tipos de amostras, o Gr2 apresentou a corrosão mais severa, e os Gr.4 e 5 apresentaram os menores graus de corrosão. Entretanto, nas amostras usinadas o Gr5 apresentou uma corrosão menos acentuada em relação ao Gr4. No Gr3 houve um aumento da corrosão em função do tempo, sendo que as amostras fundidas mostraram este aumento mais rapidamente. Houve um aumento significativo na rugosidade superficial no Gr.2 nos três tipos de amostras...

The purpose of this in vitro study was to analyze the superficial behavior of commercially pure titanium (grade 2, ASTM), obtained by milling or powder metallurgical process, under the action of different fluoride solutions through the analysis of corrosion grade under an optical microscope (OM) and superficial roughness. Furthermore the results obtained from such analyses were compared with the ones of cast titanium from Barros’s master’s degree dissertation (2004). All specimens received the standard metallography procedure for titanium, and were divided into the following groups, according to the attack solution received: Gr.1- synthetic saliva with pH 7.0 (control), Gr.2- 1.23% acidulated phosphate fluoride gel with pH 3.5, Gr.3- 2% NaF gel with pH 6.5, Gr.4- 0.05% NaF solution with pH 4.0, and Gr.5- 0.05% NaF solution with pH 7.5. The specimens were exposed to these solutions for 1, 4, 8, and 16 minutes, and between each of these times they were immersed in synthetic saliva for 24 h. The surfaces of samples were observed under OM and SEM at each interval time. The images of 100x in OM were classified by means of scores which ranged from 0 to 4, according to corrosion grade. The rugosity was analyzed using Ra parameter. The results of OM analysis were statistically treated by means of Chi-square test and of rugosity through Snededor “F” test and Bonferroni test (p<0,05). In the three different types of samples, the Gr2 presented the most severe corrosion, and the Gr.4 and 5 showed the smallest corrosion grade. However in the milled samples Gr5 showed a less Sharp corrosion than Gr4. The corrosion grade of Gr3 increased according to time, but the cast specimens showed this increase more quickly...

Comportamento do titânio comercialmente puro obtido por diferentes processamentos submetidos a soluções fluoretadas / Behavior of commercially pure titanium obtained by different processing under the action of different fluoride solutions

O objetivo deste estudo in vitro foi analisar o comportamento superficial do titânio comercialmente puro (grau 2 ASTM) usinado e obtido pelo processamento de metalurgia do pó sob a ação de diferentes soluções fluoretadas, através da análise do grau de corrosão em microscopia óptica (MO) e da rugosidade superficial. Além disso, o estudo se propôs a comparar essas análises com os resultados obtidos com o titânio fundido da dissertação de mestrado de Barros (2004). Todas as amostras receberam procedimento metalográfico padrão e foram divididas em grupos: Gr.1- saliva artificial com pH 7.0 (controle), Gr.2- gel de flúor fosfato acidulado a 1,23% com pH 3.5, Gr.3- gel de NaF a 2% com pH 6.5, Gr.4- solução de NaF a 0,05% com pH 4.0 e Gr.5- solução de NaF a 0,05% com pH 7.5. As amostras foram expostas a estas soluções por 1, 4, 8 e 16 min, intercaladas com imersão em saliva artificial por 24 h, e depois foram observadas em MO e MEV, a cada intervalo de tempo. As imagens em MO, 100x, foram classificadas através de escores de 0 a 4, conforme o grau de corrosão. A rugosidade foi analisada utilizando o parâmetro Ra. Os resultados da análise de MO foram tratados estatisticamente pelo teste qui-quadrado e da rugosidade pelo teste “F” de Snedecor e de Bonferroni (p<0,05). Nos três tipos de amostras, o Gr2 apresentou a corrosão mais severa, e os Gr.4 e 5 apresentaram os menores graus de corrosão. Entretanto, nas amostras usinadas o Gr5 apresentou uma corrosão menos acentuada em relação ao Gr4. No Gr3 houve um aumento da corrosão em função do tempo, sendo que as amostras fundidas mostraram este aumento mais rapidamente. Houve um aumento significativo na rugosidade superficial no Gr.2 nos três tipos de amostras...

The purpose of this in vitro study was to analyze the superficial behavior of commercially pure titanium (grade 2, ASTM), obtained by milling or powder metallurgical process, under the action of different fluoride solutions through the analysis of corrosion grade under an optical microscope (OM) and superficial roughness. Furthermore the results obtained from such analyses were compared with the ones of cast titanium from Barros’s master’s degree dissertation (2004). All specimens received the standard metallography procedure for titanium, and were divided into the following groups, according to the attack solution received: Gr.1- synthetic saliva with pH 7.0 (control), Gr.2- 1.23% acidulated phosphate fluoride gel with pH 3.5, Gr.3- 2% NaF gel with pH 6.5, Gr.4- 0.05% NaF solution with pH 4.0, and Gr.5- 0.05% NaF solution with pH 7.5. The specimens were exposed to these solutions for 1, 4, 8, and 16 minutes, and between each of these times they were immersed in synthetic saliva for 24 h. The surfaces of samples were observed under OM and SEM at each interval time. The images of 100x in OM were classified by means of scores which ranged from 0 to 4, according to corrosion grade. The rugosity was analyzed using Ra parameter. The results of OM analysis were statistically treated by means of Chi-square test and of rugosity through Snededor “F” test and Bonferroni test (p<0,05). In the three different types of samples, the Gr2 presented the most severe corrosion, and the Gr.4 and 5 showed the smallest corrosion grade. However in the milled samples Gr5 showed a less Sharp corrosion than Gr4. The corrosion grade of Gr3 increased according to time, but the cast specimens showed this increase more quickly...

Effect of Mutans Streptococcus on Corrosion Resistance of Ni-Cr Alloy / 上海第二医科大学学报

Objective To study the effect of Mutans Streptococcus(S.Mutans) on the corrosion resistance of Ni-Cr alloy. Methods S.Mutans were isolated in TSB,and then 10~(5)10~6 CFU/mL of bacterial population was reached.The self-corrosion electrical current density and the corrosion electrical current potential of Ni-Cr alloy were found from polarization curves under the condition with or without media plus S.Mutans.The surface of Ni-Cr alloy after bacterial corrosion was examined with X-ray photoelectron spectroscopy(XPS) to find out different element contents.(Results)From polarization curves,it could be found that the self-corrosion electrical current density and the corrosion electrical current potential of Ni-Cr alloy without S.Mutans were 53.5 ?A/cm~(2)and-62 mV,and those with S.Mutans were 75.7 ?A/cm~(2)and-220 mV.Examination of XPS showed that besides Ni and Cr,the element of chlorine(Cl),sulphur(S),calcium(Ca) could be found on the surface of Ni-Cr alloy after bacterial corrosion.(Conclusion Because of) the metabolism of S.Mutans,an oxide film could be destroyed and a biofilm be formed on the surface of Ni-Cr alloy.Bacterial corrosion could lower the corrosion resistance performance of Ni-Cr alloy.

Improvement effects of electrochemical stability of magnetic materials for prosthetic dentistry / 대한치과보철학회지

STATEMENT OF PROBLEM: Dental magnetic materials have been applied to removable prosthetic appliances, maxillofacial prostheses, obturator and dental implant but they still have some problems such as low corrosion resistance in oral environments. PURPOSE: To increase the corrosion resistance of dental magnetic materials, surfaces of Sm-Co and Nd-Fe-B based magnetic materials were plated with TiN and sealed with stainless steels. MATERIALS AND METHODS: Surfaces of Sm-Co and Nd-Fe-B based magnetic materials were plated with TiN and sealed with stainless steels, and then three kinds of electrochemical corrosion test were performed in 0.9% NaCl solution; potentiodynamic, potentiostatic, and electrochemical impedance test. From this study, corrosion behavior, amount of elements released, mean average surface roughness values, the changing of retention force, and magnetic force values were measured comparing with control group of non-coated magnetic materials. RESULTS: The values of surface roughness of TiN coated Sm-Co and TiN coated Nd-Fe-B based magnetic materials were lower than those of non coated Sm-Co and Nd-Fe-B alloy. From results of potentiodynamic test, the passive current density of TiN coated Sm-Co alloy were smaller than those of TiN coated Nd-Fe-B alloy and non coated alloys in 0.9% NaCl solution. From results of potentiostatic and electrochemical impedance test, the surface stability of the TiN coated Sm-Co alloy was more drastically increased than that of the TiN coated Nd-Fe-B alloy and non-coated alloy. The retention and magnetic force after and before corrosion test did not change in the case of TiN coated magnetic alloy sealed with stainless steel. CONCLUSION: It is considered that the corrosion problem and improvement for surface stability of dental magnetic materials could be solved by ion plating with TiN on the surface of dental magnetic materials and by sealing with stainless steels.

Corrosion resistance of orthodontic magnet coated with titanium nitride in artificial saliva / 实用口腔医学杂志

Objective: To study the corrosion resistance of orthodontic magnet with titanium nitride coating in artificial saliva. Methods: 6 samples of magnet in the size 3 mm?5 mm?7 mm were prepared.3 of them were coated with titanium nitride by plasma enhanced chemical vapor deposition,another 3 without coating were used as controls.The samples were immersed into artificial saliva at 37 ℃ for one month. Then the surface characters of two kinds of magnets were observed with the naked eye and by electron-probe microanalysis (EPMA). Results: The surface of the magnets with titanium nitride coating was fine and close in texture and there were no cleft and disintegrated area. However, that of the magnets without titanium nitride coating was uneven and coarse in texture,and there were evident clefts and disintegrated areas. Conclusion: The corrosion resistance of orthodontic magnets with titanium nitride coating is stronger than that without coating.

Effects of cryogenic treatment on the corrosion resistance of the nickel-chromium alloys / 实用口腔医学杂志

Objective:To investigate the feasibility of improving the corrosion resistance of nickel-chromium alloys by the means of cryogenic treatment. Methods:16 disk samples were divided into 4 groups, including control group(C), cryotreat group(E1),tempering after cryotreat group(E2) and simulative porcelain sintering after cryotreat group(E3). All samples were subjected to electrochemical potentiodynamic polarization after immersed in the artificial saliva ISO/TR 10271:1993(E) pH 6.8 for 24 h at ambient temperature. The metallography of all groups were observed by SEM. Results:①Cryogenic treatment elevated the pitting corrosion potential and dropped the corrosion current of Ni-Cr alloys. Following simulative porcelain sintering,as well as tempering after cryotreat, decreased the corrosion current. But the corrosion potential of Ni-Cr alloys fell after cryotreat and following simulative porcelain sintering. Tempering after cryotreat did not affect the pitting corrosion potential. ②Much small secondary substance separated out and evenly distributed along the crystals of Ni-Cr alloys after cryotreat. Conclusion:Cryogenic treatment effectively improves the electrochemical corrosion resistance of Ni-Cr alloys, and tempering following cryotreat is unnecessary. It is not recommended to sintering porcelain after cryogenic treatment.

The effects of Streptococcus sobrinus on corrosion behavior of metal-ceramic alloys / 实用口腔医学杂志

Objective:To study the corrosion resistance of four metal-ceramic alloys in the presence of Streptococcus sobrinus, and to compare the effects of bacteria action in liquid and solid environment.Methods:Four metal-ceramic alloys were exposured to BHIA or BHI media with or without Streptococcus sobrinus and served as different groups. After inoculating 10 weeks, their I_ corr ,E_ corr ,E_ tp through cyclic polarization curves were obtained through Corrview 2 corrosion analyses software;and their surface changes after electrochemical corrosion were observed by field emission scanning electron microscopy (FESEM).Results:The E_ corr of four alloys were decreased in presence of oral microorganism, and the declines were more remarkable in BHI with bacteria. SEM observation showed the pittings in their surface.The corrosion resistance in BHI without bacteria were significant increased than that in the blank control. Conclusion:Streptococcus sobrinus can promote the corrosion behavior of metal-ceramic alloys and the corrosion resistance is more worse in BHI than BHIA with bacteria.