Impact of light-cure protocols on the porosity and shrinkage of commercial bulk fill dental resin composites with different flowability

Abstract

This research aimed to probe the degree of conversion (DoC), porosity and polymerization shrinkage strain (PSS) from three different commercial bulk fill resin composites (BFRCs) with different flowability submitted to two different irradiation protocols. Samples (n = 3) of Tetric N-Ceram (TNF), Opus Bulk Fill (OBF) and Filltek Bulk Fill Flow (FBFF) were studied by FT-IR (for DoC) and micro-CT (for porosity and PSS analysis) after submitted to the following light-cure protocols: P1 (1000 mW/cm2 for 20 s) and P2 (3200 mW/cm2 for 6 s). All data were statistically treated. The material’s viscosity interfered on its porosity, as well as in the response to the irradiation protocol. Furthermore, data showed that the greater the polymerization shrinkage strain the lower the porosity. On the other hand, the lower the DoC the greater the polymerization shrinkage strain. We conclude that samples of high viscosity composites submitted to extended curing time with lower irradiation showed best physical characteristics for clinical use. The low viscosity FBFF and high power light-cure protocol should be used carefully since it presented the poorest results, which may result in undesirable clinical outcomes.