The aim of this in vitro study was to evaluate the mechanical properties of a commercial Bis-GMA resin loaded with filler particles including Ba-Al-F-silicate glass (size 0.02-2.00 μm) and dispersed colloidal silica (size 0.02 to 0.07 μm). The study was conducted through the preparation of samples with thickness of 1.5 mm, length of 25 mm and width of 4.7 mm. Each samples of the resin composite was irradiated with the standard 20s polymerization mode using a LED lamp. The experimental results of the flexural test and micro-hardness test evidenced that the layering technique influences the mechanical performances of the resin-based composite. Particularly, the samples evidence a sandwich structure with a core and two external skins characterized by different hardness and stiffness
