Development of Laser Welding and Surface Treatment of Metals.

This Special Issue on Development of Laser Welding and Surface Treatment of Metals contains as many as twenty-two research articles mainly related to the application of lasers, but also on other welding processes that may be competitive to laser technologies under specific conditions. Despite the introduction of lasers for material processing in the 1960s, the continuous development of laser devices also leads to the development and expansion of laser technology applications. This Special Issue is a compendium of knowledge in the field of fusion welding, the manufacturing of surface layers and coatings with increased wear resistance and tribological characteristics, as well as corrosion resistance and the characterization of coatings and surface layers. The topics of the presented research articles include aspects related to laser welding (eight articles), especially technological conditions, the properties of different types of joints, and analytical and numerical aspects of modelling the laser heat sources. The second dominant issue concerns laser cladding and laser surface treatment of different ferrous and nonferrous metallic and composite materials (six articles). In addition, there are interesting results of the study of fusion welding under forced cooling of the deposit or underwater conditions (four articles), results on the characterization of wear resistance coating produced by different technologies that can be competitive for laser cladding (three articles), and an original study on local strengthening of the thin-walled structure by laser treatment (one article). This Special Issue provides very wide and valuable knowledge based on theoretical and empirical study in the field of laser and fusion welding, laser and related coating technologies, characterization of coatings, and wear phenomena.

Avaliação da rugosidade superficial e análise morfológica de cimentos de ionômero de vidro: influência do armazenamento em saliva artificial / Evaluation of surface roughness and morphological analysis of glass ionomer cements: influence of storage in artificial saliva

Introdução: O desenvolvimento dos cimentos de ionômero de vidro (CIVs) proporcionou vantagens aos procedimentos restauradores diretos devido a suas propriedades, como adesão química à estrutura dentária e liberação de flúor. No entanto, o ambiente bucal pode promover condições capazes de alterar a superfície deste material. Objetivo: Avaliar a rugosidade superficial e a morfologia de superfície de quatro cimentos de ionômero de vidro (Ketac Molar Easy Mix, Vitremer, Vitro Molar e Maxxion), quando imersos em diferentes soluções de saliva artificial. Material e método: Dez amostras de cada material foram confeccionadas e a rugosidade superficial foi avaliada antes e após imersão em saliva artificial ácida e neutra, durante 28 dias, por meio de um rugosímetro (Surftest SJ - 40), e a análise morfológica deu-se através de microscopia eletrônica de varredura. Os valores médios de rugosidade foram submetidos aos testes de Kruskal-Wallis e de Wilcoxon, além do teste de Mann Whitney, com nível de significância de 5%. Resultado: Os valores de rugosidade foram maiores estatisticamente após a imersão em saliva ácida e neutra para todos os materiais, exceto o Vitromolar, que não apresentou diferença estatística entre as médias de rugosidade antes e após imersão em saliva neutra. O Maxxion R apresentou estatisticamente maiores valores de rugosidade quando comparado aos outros materiais após imersão em saliva neutra e ácida. Conclusão: A rugosidade superficial dos cimentos de ionômero de vidro aumentou após imersão em saliva neutra e ácida para a maioria dos cimentos estudados. A solução de armazenagem ácida promoveu aumento da rugosidade superficial para o Maxxion R e o Vitro Molar.

Introducion: The development of glass ionomer cements brought advantages to direct restorative procedures due to properties such as chemical adhesion to dental structure and fluoride release. Nevertheless, oral environment may provide conditions which can alter material surface. Objective: To evaluate surface roughness and surface morphology of four glass ionomer cements (Ketac Molar Easy Mix, Vitremer, Vitro Molar e Maxxion) when immersing on different artificial saliva. Material and method: Ten specimens of each material were fabricated and surface roughness was measured before and after immersion on neutral and acid artificial saliva for 28 days using a rugosimeter (Surftest SJ–40) and microscopy analysis by scanning electron microscopy. Roughness data were analyzed statistically by Kruskal-Wallis test, Wilcoxon test and Mann Whitney test, at 5% significance level. Result: Roughness values were statistically higher after immersion on neutral and acid artificial saliva for all materials, except for Vitromolar that did not presented no statistical difference between roughness values before and after immersion on neutral saliva. The Maxxion R presented statistically higher roughness values compared to all materials after immersion on neutral and acid artificial saliva. Conclusion: The superficial roughness of glass ionomer cement increased after immersion on neutral and acid artificial saliva for most of the materials. Acid storage solution promoted a greater increase in surface roughness after immersion of the specimens for Maxxion and Vitro Molar.

Influência da aplicação tópica de géis de flúor na rugosidade superficial de cimentos de ionômero / Influence of topical applications of fluoride of gels of the surface roughness of glass ionomer cements

Avaliar a morfologia de superfície de quatro CIVs (cimentos de ionômero de vidro) quando submetidos à ação tópica do flúor fosfato acidulado a 1,23% e gel de fluoreto de sódio neutro a 2%. Foram confeccionados 10 espécimes de cada CIVs (Ketac Molar Easymix, Maxxion R, Vitro Molar e Vitremer). Um ensaio de rugosidade foi efetuado antes e após aplicação tópica de gel de flúor. Os dados obtidos foram analisados através do teste de Tukey e do teste T. Os valores de rugosidade apresentados pelos materiais, segui a ordem descrescente: Maxxion>Ketac Molar Easy Mix> Vitro Molar. A aplicação tópica de flúor acidulado apresentou alterações de superfície nos materiais avaliados.

To evaluate the surface morphology of four glass ionomer cements when submitted to 1.23% acidulated phosphate fluoride topical application and 2% sodium fluoride. Ten specimens of each material (Ketac Molar Easymix, Maxxion R, Vitro Molar and Vitremer) were made. Surface roughness testing was made before and after topical application of fluoride. Data were analyzed statistically by Tukey’s test and T´s test. Maxxion presented the biggest variation on morphological standard after treatment with acidulated gel, continuing, in decreasing order, by Ketac Molar Easy Mix and Vitromolar. The topical acidulated fluoride presented surface alterations in all evaluated materials.