Influência das variações durante a confecção de amostras em ensaio mecânico de microcisalhamento

Abstract

The advent of adhesive dentistry has brought great improvement of materials and restorative techniques, however, evaluating these new products as to their properties (physical and mechanical) is also a challenge. The objective of this study was to compare the effect of stress distribution and bond strength for the micro-shear test, by varying the distance between the specimens and the wire thickness of the micro-shear device (orthodontic wire). The specimens were made with resin cement on a ceramic base reinforced by lithium disilicate, varying the distance between them of 1.5mm and 3.0mm, and the wire thickness of 0.3mm and 0.7mm. For finite element method, four three-dimensional models were generated according to the study factors and on these applied static load of 29.985N. For the mechanical test, 40 samples (n = 10) were made: GA - distance between 1.5mm and 0.3mm thick test pieces; GB - distance of 1.5mm and wire with 0.7mm; GC – 3.0mm distance and 0.3mm wire; GD - distance of 3.0mm and wire with 0.7mm. The Union Resistance values were tabulated and analyzed by analysis of variance ANOVA two-way and test of comparison of mean, Tukey's test, (α = 0.05). The Finite element method showed a small concentration of stresses, where GA and GB presented the highest values. The values of bond strength showed differences only for wire thickness, where 0.3 mm (GA and GC) resulted in the highest values. There was a predominance of mixed failure in the GA, GB and GC groups and adhesive failure in GD. Different thicknesses of the micro-cutting device wire and the distance between the test specimens interfered in the Union Resistance results and the stress concentrations respectively.