Evaluation of monomer elution, microhardness, and roughness of experimental dental composite resins prepared from Bis-EFMA, a novel monomer system

This study aimed to compare the monomer elution, microhardness, and roughness of experimental resin-based composites (RBCs) prepared from a novel monomer system derived from 9,9-Bis[4-(2-hydroxyethoxy)phenyl]fluorene) (Bis-EFMA), bisphenol A-glycidyl methacrylate (Bis-GMA), and urethane dimethacrylate (UDMA) with each other, also with a commercial RBC, 3 M ESPE FiltekTM Z250 (FZ). Experimental Bis-EFMA (ET), Bis-GMA (BT), and UDMA (UT) based composites were prepared (20% Bis-EFMA or 20% Bis-GMA or 20% UDMA, and 20% triethylene glycol dimethacrylate [TEGDMA], and 60% glass filler). 60 specimens were produced (n = 5) and exposed to ethanol solution for 7 days. Then specimens were tested at baseline (T0), first (T1), third (T2), and seventh (T3) days. ET and FZ released significantly lower TEGDMA than other RBCs did (p < 0.05). BT released significantly higher TEGDMA than other RBCs did at T1 (p < 0.05). However, no significant difference was found between FZ and ET at T1 (p > 0.05). FZ exhibited the highest microhardness at all-time points; besides, the microhardness of BT was lowest at T0, while the microhardness of BT and UT was lower than that of FZ and ET at T1, T2, and T3 (p < 0.05). BT exhibited higher roughness at T2 than the UT did at T0 and T1, significantly (p < 0.05). However, no significant difference was found between the other RBCs (p > 0.05). Bis-EFMA, a novel bisphenol A-free monomer system, has the potential to be used in commercial RBCs as a substitute for Bis-GMA in terms of lower monomer elution and higher microhardness.