Comparative analysis on occupational hazards of three welding operations / 中华劳动卫生职业病杂志

Objective: To explore the occupational hazards caused by three kinds of welding operations, and to provide data support for individual protection. Methods: In October 2020, the welding fumes, metal elements and welding arc generated by three welding operations of argon gas shielded welding (JS80 welding wire) , manual welding (ZS60A welding rod) and carbon dioxide shielded welding (907A flux cored wire) were collected and measured in the welding laboratory. The samples were analyze and compare in the laboratory, and the differences of the occupational hazard factors of the three welding operations were judged. Results: The concentration of welding fume produced by carbon dioxide shielded welding, manual welding (ZS60A electrode) , and argon gas shielded welding (JS80 welding wires) were 6.80 mg/m(3), 6.17 mg/m(3), and 3.13 mg/m(3), respectively. The effective irradiance of the welding arc outside the welding mask from high to low is manual welding (ZS60A electrode) , carbon dioxide shielded welding (907A flux-cored welding wire) , and argon shielded welding (JS80 welding wire) , respectively 1 010.7, 740.9, 589.5 μW/cm(2). The long-wave ultraviolet UVA intensity generated by argon shielded welding (JS80 welding wire) is the largest, which is 1 500 μW/cm(2). The content of Mn in the three welding operations is the highest, and JS80 welding wire has the highest Mn content of 128493.2 mg/kg. 907A flux cored wire has the highest Ti content, which is 24355.5mg/kg. The electrode ZS60A has the highest Cu content, which is 24422.12 mg/kg. Conclusion: The intensity of occupational hazards is different in the three kinds of welding operations, so the methods of personal protective equipment, field exposure assessment and health monitoring should be more targeted.

Influência do tratamento do substrato com plasma não térmico na resistência de união em cimentação adesiva / Influence of the substrate treatment with non-thermal plasma on bond strength of adhesive cementation

Objetivo: avaliar a influência do tratamento de superfície com plasma não térmico de argônio (PLA) na resistência de união de cimentos resinosos ao esmalte, à dentina e à cerâmica de dissilicato de lítio. Observar, no esmalte e na dentina, através de espectroscopia de infravermelho por transformada de Fourier (FTIR) os compostos inorgânicos e da cromatografia gasosa a alteração dos compostos orgânicos voláteis nas condições experimentais propostas. Material e Método: Foram avaliados 3 cimentos resinosos: Variolink Esthetic LC e N (Ivoclar Vivadent), e Panavia V5 (Kuraray). Foram utilizados 240 dentes bovinos, dos quais 150 tiveram a superfície do esmalte exposta e 90 a de dentina. Foram obtidas 150 lâminas de cerâmica de dissilicato de lítio (12 x 14 x 0,5 mm). Os grupos foram divididos de acordo com o tratamento de superfície e o substrato. Os tratamentos para as superfícies de esmalte e dentina foram: EA (esmalte/ácido fosfórico); DA (dentina/ácido fosfórico); EPS (esmalte/PLA 30 s); EPM (esmalte/PLA 1 min); DPS (dentina/PLA 30 s); EAPS (esmalte/ácido fosfórico/PLA 30 s) e EAPM (esmalte/ácido fosfórico/PLA 1 min); e, DAPS (dentina/ácido fosfórico/PLA 30 s). Os tratamentos para as superfícies da cerâmica foram: CA (cerâmica/ácido fluorídrico), CPS (cerâmica/PLA 30 s); CPM (cerâmica/PLA 1 min); CAPS (cerâmica/ácido fluorídrico/PLA 30 s) e CAPM (cerâmica/ácido fluorídrico/PLA 1 min). Posterior aos tratamentos, cilindros dos cimentos resinosos (0,8 mm/1,5 mm) foram confeccionados sobre as superfícies dos substratos. Após 48 h, os espécimes foram submetidos ao ensaio mecânico de microcisalhamento (10 Kgf/1 mm/min) até a fratura. A área fraturada foi analisada em estereomicroscópio. As superfícies tratadas e a interface adesiva foram analisadas por Microscopia Eletrônica de Varredura (MEV). Através do FTIR foram observados os espectros de amostras tratadas de esmalte e dentina. Os dados da resistência de união foram submetidos à análise estatística ANOVA e teste de Tukey (5%). Resultados: Para o esmalte os tratamentos de superfície não apresentaram diferença estatisticamente significante entre si; para a dentina o grupo DPS apresentou os maiores valores de resistência de união; e, para a cerâmica o tratamento CA apresentou os maiores valores de resistência de união. Para esmalte e dentina, o FTIR, mostrou alterações do conteúdo da água, carbonato e fosfato e a cromatografia gasosa das substâncias orgânicas voláteis. Conclusão: O tratamento de superfície com PLA não influencia a resistência de união de cimentos resinosos ao esmalte, aumenta à dentina e diminui ao dissilicato de lítio. As análises observacionais no FTIR sugerem que o plasma não altera compostos do esmalte e da dentina(AU)

Objective: to evaluate the influence of surface treatment with non - thermal argon plasma (PLA) on bond strength of resin cements to enamel, dentin and lithium disilicate glass ceramic; and, to observe, through Fourier Transform Modified Infrared Spectroscopy (FTIR), the inorganic compounds and through gas chromatography, the alteration of the volatile organic compounds, on the enamel and dentin, under the experimental conditions. Material and Method: Three resin cements: Variolink Esthetic LC and N (Ivoclar Vivadent) and Panavia V5 (Kuraray) were evaluated. Twenty hundred and forty bovine teeth were used, among which 150 specimens with enamel surface exposure and 90 with dentine exposure. One hundred and fifty lithium disilicate glass ceramic slices (12 x 14 x 0.5 mm) were obtained. The groups were divided according to the substrate and surface treatment. The treatments for enamel and dentin surfaces were: EA (enamel / phosphoric acid); DA (dentin / phosphoric acid); EPS (enamel / PLA 30 s); EPM (enamel / PLA 1 min); DPS (dentin / PLA 30 s); EAPS (enamel / phosphoric acid / PLA 30 s) and EAPM (enamel / phosphoric acid / PLA 1 min); and, DAPS (dentin / phosphoric acid / PLA 30 s). The treatments for the ceramic surfaces were: CA (ceramic / hydrofluoric acid), CPS (ceramic / PLA 30 s); CPM (ceramic / PLA 1 min); CAPS (ceramic / hydrofluoric acid / PLA 30s) and CAPM (ceramic / hydrofluoric acid / PLA 1 min). After the treatments, resin cement cylinders (0.8 mm / 1.5 mm) were built on the substrate's surfaces. After 48 h storage bond strength tests (µSBS) were performed in a universal testing machine (10 Kgf / 1 mm / min) until failure to fracture, and failure mode was analyzed under a stereomicroscope. The treated surfaces and the adhesive interface were analyzed by Scanning Electron Microscopy (SEM). The FTIR was used to observe the spectra of enamel and dentin treated samples. Bond strength data were submitted to ANOVA and Tukey test (5%). Results: for the enamel there was not a statistically significant difference among surface treatments; for the dentin, the DPS group presented the highest bond strength; and for the ceramic the AC treatment presented the highest values of bond strength. For the enamel and the dentin samples, the FTIR observations showed changes in water, carbonate and phosphate contents and the gas chromatography in the volatile organic substances. Conclusion: Surface treatment with PLA does not influence the bond strength of resin cements to the enamel, increases the bonding to dentin and decreases to the lithium disilicate. Observational analysis on FTIR suggest that non-thermal plasma does not alter enamel and dentin compounds(AU)