Avaliação in vitro da solda elétrica em fios de níquel-titânio
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Data
2016-11-25
Autores
Mesquita, Tatyane Ribeiro [UNESP]
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Universidade Estadual Paulista (Unesp)
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OBJETIVO: Determinar a potência mais adequada para a solda elétrica em fios de NiTi; mensurar a resistência à tração desta solda; avaliar a superfície da solda microscopicamente e com um rugosímetro digital. MATERIAIS E MÉTODOS: Cento e oitenta pares de fios de NiTi foram divididos em grupos de acordo com seus fabricantes: GI (Orthometric, Marília, Brazil), GII (3M OralCare, St. Paul, CA) e GIII (GAC,York, PA); e soldados por uma máquina de solda elétrica. Cada grupo foi subdividido em subgrupos com soldas de diferentes potências. O estudo foi dividido em duas partes: a primeira parte testou noventa pares de fios soldados desde a potência mínima de união até a potência 0.5 menor àquela que provocou a fratura dos fios durante a solda, de modo que o GI e GII compreendem 6 subgrupos (potências 2.5, 3, 3.5, 4, 4.5 e 5) e o GIII 4 subgrupos (potências 2.5, 3, 3.5 e 4), sendo que cada unidade de potência da máquina utilizada representa 500W. Os pares de fios soldados foram testados em uma máquina de ensaios mecânicos até a ruptura e os valores de resistência máxima foram registrados. Análise de variância (ANOVA) e teste de Tukey foram realizados para determinar qual potência dentro de cada grupo apresentava a melhor resistência à tração. A segunda parte do estudo utilizou a potência mais adequada para cada fabricante, obtida no estudo anterior, e variou a potência 0.25 para mais e para menos em cada grupo, assim o GI e GII testou as potências 3.75, 4 e 4.25 e o GIII as potências 3.25, 3.5 e 3.75. De maneira análoga à primeira parte do estudo, mais noventa pares de fios foram soldados de acordo com seu grupo e testados até a ruptura. Adicionalmente, foi realizado microscopia eletrônica de varredura com feixe de emissão de campo e testes de rugosidade superficial para refinar os resultados sobre a potência mais adequada. ANOVA e teste de Tukey foram realizados para definir qual subgrupo dentro de cada grupo obteve a maior resistência, e testes de Friedman e Wilcoxon foram utilizados para os resultados da rugosidade. RESULTADOS: No primeiro estudo, a potência 2.5 exibiu a menor resistência à tração (43.75N GI, 28.41N GII e 47.57N GIII), enquanto que a potência 4 apresentou melhor performance nos GI e GII (97.90N e 99.61N, respectivamente), e a potência 3.5 no GIII (79.28N). No segundo estudo, houve diferença entre as resistências à ruptura apenas nos GI e GII. A potência 4 apresentou uma resistência de 95.37N (GI) e 101.90N (GII), entretanto semelhantes às potências 3.75 e 4.25 para seu respectivo grupo. O diâmetro da área de solda e o extravasamento do material aumentaram conforme as potências foram aumentadas nos três grupos. A rugosidade mostrou-se diferente no GII, já no GI e GIII as potências mais altas apresentaram rugosidades semelhantes (1.15Ra e 1.47Ra no GI, e 0.54Ra e 0.71Ra no GIII). CONCLUSÕES: A potência mais adequada para solda elétrica a ponto em fios de NiTi das marcas Orthometric e 3M foi 4 e para a marca GAC 3.5.
OBJECTIVE: To determine the most appropriate power for the electric welding of NiTi wires; measure the weld tensile strength; asses the weld surface microscopically and by a digital profilometer. MATERIALS AND METHODS: One hundred and eighty pairs of NiTi wires were divided into groups according to their manufacturers: GI (Orthometric, Marília, Brazil), GII (OralCare 3M, St. Paul, CA) and GIII (GAC, York, PA); and welded by a welding machine. Each group was divided into subgroups with different powers welding. The study was divided into two parts: the first one tested ninety pairs of welded wires from the minimum power up to a 0.5 below that of the weld fracture, such the GI and GII incluses 6 subgroups (powers 2.5, 3, 3.5, 4, 4.5 and 5) and GIII 4 subgroups (powers 2.5, 3, 3.5 and 4), where in each power unit of the machine is 500W. The welding were tested in a mechanical testing machine until failure and maximum resistance values were recorded. Analysis of variance (ANOVA) and Tukey tests were performed to determine which subgroup showed the best tensile strength. The second part of the study used the most appropriate power for each manufacturer, obtained in the previous study, and varied 0.25 power to up or down in each group, so the GI and GII tested the powers 3.75, 4 and 4.25 and GIII the powers 3.25, 3.5 and 3.75. In a similar way, ninety pairs of wires were welded according to their group and tested to fracture. Scanning electron microscopy with field emission beam and surface roughness testing were made to refine the results on the most appropriate power. ANOVA and Tukey tests were conducted to determine which subgroup within each group had the highest strength and Friedman and Wilcoxon tests were used for the roughness results. RESULTS: In the first study, the 2.5 power exhibited the lower tensile strength (43.75N GI, GII and 28.41N 47.57N GIII), while the 4 power showed better performance in GI and GII (97.90N and 99.61N, respectively)and 3.5 power in GIII (79.28N). In the second study, there was a difference between the tensile strengths only in GI and GII. The 4 power showed a resistance of 95.37N (GI) and 101.90N (GII), but similar to the 3.75 power and 4.25 for these groups. The weld area diameter and material leakage increased as the power was increased in all three groups. At GI and GIII the higher powers had similar roughness (1.15Ra and 1.47Ra in GI and 0.54Ra and 0.71Ra in GIII), while was different in the GII. CONCLUSIONS: The most suitable power to electric spot welding of NiTi wires of Orthometric and 3M brands was 4 and 3.5 to GAC brand.
OBJECTIVE: To determine the most appropriate power for the electric welding of NiTi wires; measure the weld tensile strength; asses the weld surface microscopically and by a digital profilometer. MATERIALS AND METHODS: One hundred and eighty pairs of NiTi wires were divided into groups according to their manufacturers: GI (Orthometric, Marília, Brazil), GII (OralCare 3M, St. Paul, CA) and GIII (GAC, York, PA); and welded by a welding machine. Each group was divided into subgroups with different powers welding. The study was divided into two parts: the first one tested ninety pairs of welded wires from the minimum power up to a 0.5 below that of the weld fracture, such the GI and GII incluses 6 subgroups (powers 2.5, 3, 3.5, 4, 4.5 and 5) and GIII 4 subgroups (powers 2.5, 3, 3.5 and 4), where in each power unit of the machine is 500W. The welding were tested in a mechanical testing machine until failure and maximum resistance values were recorded. Analysis of variance (ANOVA) and Tukey tests were performed to determine which subgroup showed the best tensile strength. The second part of the study used the most appropriate power for each manufacturer, obtained in the previous study, and varied 0.25 power to up or down in each group, so the GI and GII tested the powers 3.75, 4 and 4.25 and GIII the powers 3.25, 3.5 and 3.75. In a similar way, ninety pairs of wires were welded according to their group and tested to fracture. Scanning electron microscopy with field emission beam and surface roughness testing were made to refine the results on the most appropriate power. ANOVA and Tukey tests were conducted to determine which subgroup within each group had the highest strength and Friedman and Wilcoxon tests were used for the roughness results. RESULTS: In the first study, the 2.5 power exhibited the lower tensile strength (43.75N GI, GII and 28.41N 47.57N GIII), while the 4 power showed better performance in GI and GII (97.90N and 99.61N, respectively)and 3.5 power in GIII (79.28N). In the second study, there was a difference between the tensile strengths only in GI and GII. The 4 power showed a resistance of 95.37N (GI) and 101.90N (GII), but similar to the 3.75 power and 4.25 for these groups. The weld area diameter and material leakage increased as the power was increased in all three groups. At GI and GIII the higher powers had similar roughness (1.15Ra and 1.47Ra in GI and 0.54Ra and 0.71Ra in GIII), while was different in the GII. CONCLUSIONS: The most suitable power to electric spot welding of NiTi wires of Orthometric and 3M brands was 4 and 3.5 to GAC brand.
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Palavras-chave
Soldagem, Titânio, Ortodontia, Topografia, Titanium, Orthodontics, Topography