Influence of photoactivation time on flexural strength of restorative composites

Abstract

The objective of this study is to evaluate the influence of two times of light-curing on flexural strength of four commercial composites. The specimens in bar shape (25 mm x 2 mm x 2 mm) were made in stainless steel matrix according to ISO 4049 and then photoactivated through a LED unit with five activations of 20 or 60 seconds in different points along the surfaces of the top and botton of the sample. The test was achieved in a mechanical test machine at a cross head speed of 0.5 mm/min. The average (MPa) were submitted to analyis of variance of two factors and to the Tukey test (p < 0.05). In both times of light-curing the composites Filtek SupremeTM and Esthet-XTM showed higher mean values concerning flexural strength considering both lightcuring times tested. The composite OpallisTM showed intermediate mean values with 20 seconds activation, therefore statistically higher than those observed for four SeasonsTM. The composites OpallisTM and four SeasonsTM obtained significantly lower mean values than the others with 60seconds activation, but they were not different among themselves. All composites showed significant increase of flexural strength values with the increase of activation time. Therefore, it is concluded that, the 60-second light-curing increased the flexural strength mean values of the composites tested.