Influence of high irradiance light curing on the micromechanical properties of bulk fill resin-based composites.

Objective: Proficient polymerization of resin composites is essential to obtain long term clinical success and has a great significance attaining improved mechanical properties. The purpose of this study was to investigate the effects of two curing light intensities on the mechanical properties (Vickers microhardness) of bulk-fill resin-based composites. Materials and methods: An in vitro investigation was carried out, where a total of 40 cylinders were fabricated utilizing Tetric N-Ceram bulk fill (TNC) and SDR Plus bulk fill flowable (SDR) (n=20). Each material group, specimens were divided into two subgroups according to the light intensities; full mode and turbo mode (n=10). Resin composite specimens were prepared in clinically realistic layer thicknesses (4 mm). The specimens were irradiated from only one side for the suggested time for both curing modes. Vickers hardness number (VHN) was measured on the top and bottom surfaces of resin composite specimens 24h after light-curing. Bottom/top ratio [Vickers hardness ratio (VHR)] was calculated as a measure of depth-dependent during effectiveness. Results: The results revealed that the irradiation of TNC with either full mode or turbo mode showed no statistical significant difference in VHN values either on top or bottom surfaces and VHR. Meanwhile, SDR irradiated with full mode showed higher VHN values compared to samples irradiated with turbo mode on both top and bottom surfaces and VHR. Conclusion: Rapid and high curing light intensity could be used for polymerizing TNC restorations. TNC reported higher hardness values when compared with SDR employing both curing modes.