Impact of curing protocol on the selected properties of a model bis-GMA/TEGDMA dental resin composite

This study investigated the impact of different photo-activation protocols on selected properties of a model composite formulated using bis-GMA/TEGDMA (1:1 mass ratio), camphorquinone/amine (1:2 mass ratio) and 75% of fillers. The protocols tested were: high-intensity continuous (HIC-500 mW cm-2 for 20 s), medium-intensity continuous (MIC-250 mW cm-2 for 40 s), low-intensity continuous (LIC-100 mW cm-2 for 100 s) and pulse-delay-1 min or 3 min (PD-1 min/3 min-100 mW cm-2 for 5 s + 1 or 3 min interval + 500 mW cm-2 for 19 s). Degree of conversion (DC) was evaluated using infrared spectroscopy. Flexural strength (FS) and modulus (FM) were measured in three-point bending mode. Cross-link density was estimated by calculating the swelling coefficient (α) after immersion in chloroform. All methods showed similar values for DC except for PD-1 min, which showed lower DC. HIC and MIC showed similar FS, but were both different than all of the other methods. All curing methods showed similar FM, except for HIC, which presented a different modulus. PD-3 min showed a different swelling than all of the remaining groups, while HIC showed the lowest swelling. A significant relationship was observed between swelling and both FS and FM. In conclusion, the HIC activation protocol generated polymers with properties at least similar, and sometimes improved, in comparison with the alternative protocols.