Analysis of the irradiance of LED curing units using different portable dental radiometers

Abstract

Objetives. To study and compare the shrinkage, stress and immediate microleakage of a conventional composite resin and two Bulk-Fill type resins.
Methods. A conventional composite resin (Filtek Z250XT, 3M ESPE) and two bulk-fill composite resins (Filtek BulkFill - 3M ESPE and Tetric N-Ceram Bulk-Fill - Ivoclar) were analyzed. Volumetric shrinkage was analyzed indirectly by calculating the density of each material before and after polymerization. To measure the shrinkage stress, a universal testing machine was used with thicknesses of 2 mm and 4 mm for the conventional composite resin and in thicknesses of 4 mm for the bulk-fill composite resins. For the microleakage test, 20 healthy third molars restored according to the corresponding group were used: Group 1: Conventional multilayer composite resin, Group 2: Conventional single-increment composite resin, Groups 3 and 4: Bulk-fill resins in single-increment.
Results. Regarding volumetric shrinkage, no differences were observed between commercial brands. The conventional composite resin generated greater stress and degree of immediate microleakage when used in thicknesses of 4 mm, while when used in multilayers and thicknesses of 2 mm it did not generate significant differences compared to the Bulk-Fill resins used in single increments of 4 mm.
Conclusions. Bulk-Fill resins used in 4 mm increments exhibited in vitro behavior similar to that of a conventional composite resin used in 2 mm increments.