Color stability of esthetic coatings applied to nickel-titanium archwires
Estabilidade de cor de revestimentos estéticos aplicados em fios de níquel-titânio
Marcus Vinicius Neiva Nunes do REGO, Geórgia Wain Thi LAU, Yago Carneiro ARAÚJO, Rayssa Melo e SILVA
Abstract
Introduction: Color stability is an important feature to be considered when using esthetic coated archwires. Objective: To evaluate color changes on the surface of esthetic nickel-titanium archwires coated with Teflon (Ortho Organizers, USA) or epoxy resin (Tecnident, Brazil) after immersion in staining solution. Material and method: Twelve 20-mm-long wire segments were used for each type of coating, which were mounted as two test specimens with a width of 7 mm each. The buccal surface of the archwires was evaluated for fluorescence and color measurements both at baseline and after immersion in a staining solution for 21 days using the VITA Easyshade Compact spectrophotometer (Model DEASYC220). Differences in total color change according to coating type were compared using an independent samples t-test (p<0.05). The surface characteristics of as-received coated archwires were assessed using scanning electron microscopy. Result: Color changes were observed on the esthetic coatings, with a significant difference between the two brands analyzed. Surface analysis revealed flaws such as wear, pitting, elevations, lack of material, granulation, grooves, cracks, and lack of standardization in the coating process in all as-received archwires, but flaws were less evident in epoxy-resin coatings. Conclusion: The two esthetic coatings did not show color stability, but Teflon coatings showed a more intense color change than epoxy-resin coatings.
Keywords
Resumo
Introdução: A estabilidade de cor é uma característica importante quando da utilização de fios com revestimentos estéticos. Objetivo: Avaliar, por meio de um estudo in vitro, as alterações de cor na superfície de fios ortodônticos estéticos de níquel-titânio, revestidos por teflon (Ortho Organizers, EUA) ou resina epóxi (Tecnident, Brasil), quando em contato com solução de corante. Material e método: Foram utilizados 12 segmentos de 20 mm de comprimento para cada tipo de revestimento, os quais foram montados em dois corpos de prova com a largura de 7 mm. Os fios foram submetidos à avaliação da superfície vestibular quanto à fluorescência e à leitura colorimétrica inicial e após a imersão em solução de corante por 21 dias, utilizando o espectrofotômetro digital portátil VITA Easyshade Compact. Alterações na diferença de cor total de acordo com o tipo de revestimento foram verificadas utilizando-se teste o T para amostras independentes (p<0.05). As características da superfície dos revestimentos, nos fios originais, foram avaliadas por meio do microscópio eletrônico de varredura. Resultado: Verificou-se que o revestimento estético sofreu alteração de cor e a diferença foi estatisticamente significante entre os grupos. A análise da superfície demonstrou falhas como: desgaste, depressões, elevações, falta de material, granulações, ranhuras e trincas e falta de padronização na aplicação do revestimento nos fios da mesma marca comercial, sendo essas menos evidentes nos revestimentos de resina epóxi. Conclusão: Os revestimentos estéticos não apresentaram estabilidade de cor e, dentre os tipos, os de teflon evidenciaram alteração mais intensa que os de resina epóxi.
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References
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