LARISSA OLIVEIRA BERBEL

LARISSA OLIVEIRA BERBEL

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Corrosion mechanism of Ti-6Al-4V morse taper dental implants connected to 316 L stainless steel prosthetic abutment
2022 - BERBEL, LARISSA O.; VIVEIROS, BARBARA V.G. de; MICELLI, ANA L.P.; NIGRO, FREDERICO; ROSSI, JESUALDO L.; COSTA, ISOLDA
The aim of this work was to investigate the effect of galvanic coupling between stainless steel AISI 316 L abutment type Morse taper and implant made of ASTM F1108–14 Ti-6Al-4V alloy. The assembly of the two alloys was carried out using mechanical imbrication by means of successive strikes at 0.05 J force onto the abutment inserted in the implant along the centerline. Corrosion attack at the interface of the alloys was evaluated according to the number of strikes used for joining the parts. Corrosion resistance was evaluated for the samples by open circuit potential measurements as function of time and scanning vibrating electrode technique (SVET) and scanning ion selective electrode technique (SIET) in phosphate buffer solution with pH adjusted to 3.0, and into which hydrogen peroxide was added to simulate tissue inflammatory conditions. Samples were evaluated at the cross and longitudinal sections. Results indicated that the number of strikes used in assembling affected corrosion susceptibility. The lowest amount of corrosion products was associated to the highest number of strikes used. The corrosion resistance was related to the characteristics of the crevice between the implant and the abutment.
Corrosion of dental implants made of Ti-6Al-4V connected to 316L SS in agressive environment
2021 - BERBEL, LARISSA O.; VIVEIROS, BARBARA V.G. de; MICELLI, ANA L.; NIGRO, FREDERICO; ROSSI, JESUALDO L.; COSTA, ISOLDA
Implants made of dissimilar alloys, such as Ti-6Al-4V, connected to abutment of stainless steel (SS), are being considered for application as dental implants leading to galvanic corrosion. Body fluids are corrosive electrolytes that contain aggressive ions, such as chlorides, leading to localized attack at weak points of the passive film on materials used for implants fabrication. Another reason of apprehension concerning corrosion is the method of joining the different materials. This might lead to small gaps between the two materials and promote crevice conditions that stimulate localized corrosion. In this study, the corrosion resistance of a Morse taper dental implants made of Ti-6Al-4V alloy in contact to a prosthetic abutment of 316L, with the two parts joined by mechanical forces consisting of strikes, using different numbers of strikes (3, 5 and 7), was studied. The study was carried out by SVET technique in phosphate buffer solution (PBS) with an addition of H2O2 and pH adjust to 3 to simulate inflammatory conditions. The results showed high electrochemical activity at the interface between the two alloys. SVET maps showed that the Ti alloy acted as anode whereas the 316L SS as cathode. At the interface of the dissimilar alloys, large amounts of corrosion products accumulated showing the effect of the galvanic corrosion. This was mainly observed for the samples with 3 strikes for joining both alloys. The electrochemical activity was the lowest for the dental implant mounted with 5 strikes. SVET maps and SEM images showed a strong effect of crevice corrosion for the implants joined by lowest number of strikes among the testes.
A study on corrosion resistance of ISO 5832-1 austenitic stainless steel used as orthopedic implant
2020 - BRAGUIN, L.N.M.; SILVA, C.A.J. da; BERBEL, L.O.; VIVEIROS, B.V.G. de; ROSSI, J.L.; COSTA, I.; SAIKI, M.
The ISO 5832-1 austenitic stainless steel used as biomaterial is largely applied in the area of orthopedics, especially in the manufacture of implants, such as temporary or permanent replacement of bone structures. The objective of this study was to evaluate the localized corrosion resistance of the ISO 5832-1 stainless steel used in orthopedic implants by electrochemical tests in two different solutions. The results of this study are of great interest to evaluate the corrosion of metallic implants that can result in the release of corrosion products into bodily fluids causing possible adverse biological reactions. The determination of the chemical elements in the composition of the ISO 5832-1 stainless steel was performed by neutron activation analysis (NAA). The samples for electrochemical tests were grinded with silicon carbide paper up to #4000 finishing, followed by mechanical polishing with diamond paste. The open circuit potential measurements and anodic polarization curves were obtained in solution of 0.90 wt. % of NaCl and of simulated body fluid (SBF). The results indicated that the ISO 5832-1 stainless steel presented a high resistance to crevice corrosion in simulated body fluid solution but high susceptibility to this form of corrosion in the chloride solution.
Study of ph effect on AZ31 magnesium alloy corrosion for using in temporary implants
2020 - SILVA, CAIO A.J. da; BRAGUIN, LILIAN N.M.; BERBEL, LARISSA O.; VIVEIROS, BARBARA V.G.; ROSSI, J.L.; SAIKI, M.; COSTA, I.
Currently, magnesium alloys are gaining great interest for medical applications due to their degrading properties in the human body ensuring a great biocompatibility. These alloys also provide profitable mechanical properties due similarities with human bone. However, a difficulty in applying these materials in the biomaterials industries is the corrosion prior to cell healing. The effect of the chemical composition of Mg alloys on their corrosion behavior is well known. In this study, samples of AZ31 magnesium alloy were cut into chips for elemental chemical analysis by neutron activation analysis (NAA). Concentrations of the elements As, La, Mg, Mn, Na, Sb and Zn were determined in the AZ31 alloy. Visualization tests of agar corrosion development in various media, of 0.90% sodium chloride solution (mass), phosphate buffer saline (PBS) and simulated body fluid (SBF) were performed. Visualizations of the effect of agar gel corrosion revealed pH variation during the corrosion process due to the released into the cathode. The highest released of hydroxyl ions occurred in NaCl solution compared to PBS and SBF solutions indicating that NaCl solution was much more aggressive to the alloy compared to the others.
Modifications of titanium and zirconium alloy surfaces for use as dental implants
2020 - LEITE, DANIELA M.C.; ALENCAR, MAICON C. de; MUCSI, CRISTIANO S.; ARAUJO, JOAO V.S.; TAVARES, LUIZ A.; BERBEL, LARISSA O.; ARANHA, LUIS C.; ROSSI, JESUALDO L.
The use of dental implants of titanium and its alloys has proved to be effective, through well established and documented parameters, both in the dimensions and in the manufacturing processes and also in the surgical techniques. There are clinical situations where there is a need to reduce the diameter of the implants, below 3.75 mm in diameter. In the current state of art of the implant technology it is desirable that these also have surfaces capable of decreasing the period of osseointegration. In the present work, to improve the mechanical strength of the material, an alloy of 80% of Ti and 20% of Zr % in mass was proposed and elaborated, aiming its use as biomaterial. Physical, chemical, microstructural and mechanical characterization was carried out. The surfaces of the treated samples were observed using: scanning electron microscopy (SEM); semi quantitatively chemically analyzed using dispersive energy spectroscopy (EDS: wettability of the samples was determined and, finally, the roughness was measured using optical profilometry. For the conditions used in the present work, it was concluded, that the best surface treatment for the TiZr 80/20 alloy was acid etching with 1% vol. hydrofluoric acid for 5 minutes, as this treatment presented the most prominent results of wettability and roughness simultaneously.
Effect of galvanic coupling between titanium alloy and stainless steel on behavior of corrosion of dental implants
2020 - BERBEL, LARISSA O.; VIVEIROS, BARBARA V.G. de; MICELLI, ANA L.; ROSSI, JESUALDO; NIGRO, FREDERICO; ARANHA, LUIS C.; COSTA, ISOLDA
Titanium and its alloys are widely used in dental implant manufacturing due its favorable properties, such as, biocompatibility, high mechanical strength and high corrosion resistance. This last one, is a result of the ability of titanium to form an oxide film (TiO2) in contact with oxygen. However, a several factors can accelerate the corrosion process of implants in contact with the oral environment, such as, acidification of the medium, differential aeration, inflammatory conditions, presence of protein and the junction of diferent metals. The goals of this research is to investigate the corrosion effect of galvanic coupling between titanium alloy (grade V) and stainless steel 316L. The investigative technique adopted was the scanning vibrating electrode technique (SVET) in phosphate buffer solution simulating inflammatory conditions. The results showed detrimental effects of acidity of the environment, induced by inflammatory conditions, accelerate the oxidation of Ti-6Al-4V. SVET maps and SEM images for the junction of the different metals showed that the region with the highest electrochemical activity it is at the interface between the metals, mostly concentrated on the Ti-6Al-4V alloy, depending on the conditions of the medium.
Estudo do comportamento frente à corrosão da liga de magnésio AZ31 de uso em implantes temporários utilizando soluções simuladoras de fluidos corpóreos
2019 - SILVA, C.A.J.; BRAGUIN, L.N.M.; VIVEIROS, B.G.; BERBEL, L.O.; ROSSI, J.L.; COSTA, I.; SAIKI, M.
Atualmente, ligas de magnésio estão ganhando grande interesse para aplicações médicas devido a sua propriedade de degradação no corpo humano, principalmente para aplicações de interesse como stents cardiovasculares e próteses ortopédicas. Estes implantes temporários fornecem uma estabilidade mecânica necessária para o reparo e corroem completamente após o tempo de vida útil e fim do tratamento. Contudo, uma dificuldade na aplicação destes materiais na indústria de biomateriais é a corrosão antecipada e precoce à cura celular. Amostras da liga de magnésio AZ31 foram cortadas em lascas e a técnica escolhida para análise química elementar foi a Análise por Ativação com Nêutrons (NAA). Irradiações de curta e longa duração foram realizadas nas amostras juntamente com padrões sintéticos no reator IEA-R1 em um fluxo de nêutrons térmicos abaixo de 4,0x1012 n cm-2s-1. Concentrações dos elementos As, La, Mg, Mn, Na, Sb e Zn foram determinadas na liga AZ31, calculadas pelo método comparativo. Para os ensaios de corrosão, as amostras foram limpas com álcool etílico, acetona e água purificada MilliQ por agitação ultrassônica, e, em seguida foram lixadas com lixas de SiC com granulometria de #500, #800, #1200, #2000 e #4000. Testes de visualização em ágar-ágar e imersão foram realizados em solução de cloreto de sódio 0,90 % (massa), solução tampão de fosfato (PBS) e solução simuladora de fluidos corpóreos (SBF) utilizando fenolftaleína como indicador ácido-base. A observação das superfícies das amostras, antes e após exposição às soluções, foi realizada por microscopia óptica (MO) e microscopia eletrônica de varredura (MEV). A superfície também foi observada após remoção dos produtos de corrosão por desmutting e irradiação para análise quantitativa pela técnica NAA. Visualizações em gel ágarágar revelaram aumento do pH local proveniente da liberação de íons hidroxila da reação catódica e menor liberação de íons ocorreu em SBF em comparação às soluções de NaCl e PBS. As micrografias da superfície evidenciaram a formação instantânea de uma camada de produtos de corrosão após uma hora de ensaio e o desmutting revelou microcavidades caracterizadas por pites.