Avaliação do grau de conversão e contração de polimerização de diferentes compósitos Bulk-fill

Abstract

Composite resins are aesthetic materials with good physical and mechanical properties. However, due to their chemical composition, these composites contract during polymerization, which can generate stress and, in some cases, lead to failures in the adhesive interface. The insertion of these materials must be done in an incremental way, which demands more time, greater risk of contamination, in addition to failures between the layers. In order to minimize these problems, bulk-fill composites were developed, which can be inserted in layers up to 4mm thick without compromising their degree of conversion and mechanical properties. The objective of the study was to evaluate the bulk-fill resins SonicFill (Kerr), Filtek BulkFill (3M ESPE) and the conventional resin Z350XT (3M ESPE) applied in layers and in a single increment, evaluating the degree of conversion through Micro-Raman spectroscopy, Knoop microhardness, polymerization shrinkage stress using mechanical test with an extensometer and volumetric contraction using computed micro-tomography (μCT). There was no difference in the values of degree of conversion of the materials, except for the conventional light- cured resin at a distance of 4mm, which presented a lower conversion rate (p <0.05). In the microhardness test, Filtek BulkFilll (3M ESPE) and Z350XT (3M ESPE) showed better results than the Z350XT (3M ESPE) inserted in a single 4mm increment, while SonicFill (Kerr) did not show statistical difference between the bulk resin and the conventional resin applied incrementally (p <0.05). There was no statistical difference in the polymerization shrinkage tension and volumetric shrinkage (p <0.05) between the tested composite resins. Thus, it can be seen that the bulk- fill and conventional composite resins showed similar mechanical properties. However, bulk-fill resins stand out for offering a simplified way of insertion, thus reducing the clinical time.