The effect of adding a new monomer "Phene" on the polymerization shrinkage reduction of a dental resin composite

Objective. A new photocurable monomer, "Phene" (N-methyl-bis(ethyl-carbamate-isoproply-alpha-methylstyryl)amine) was synthesized and incorporated into Bis-GMA/TEGDMA with the aim of reducing polymerization shrinkage swithout detriment to the physical properties and wearing of the resin composites. Methods. Phene was synthesized through a 2-step reaction route, and its structure was confirmed by FT-IR and H-1-NMR spectra. Phene was incorporated into Bis-GMA/TEGDMA (50/50, wt/wt) with a series of mass fraction (from 0 wt% to 40 wt%). Experimental resin composites were prepared by mixing 29 wt% of resin matrix to 71 wt% of particulate-fillers. Degree of conversion (DC) was determined by FT-IR analysis. The volumetric shrinkage (VS) was calculated as a buoyancy change in distilled water by means of the Archimedes principle. Polymerization shrinkage-stress (SS) was measured using the tensilometer technique. The flexural strength (FS), modulus (FM), and fracture toughness (FT) were measured using a three-point bending setup. A wear test was conducted with 15000 cycles using a dual-axis chewing simulator. Wear depth was measured by a three-dimensional (3D) non-contact optical-profilometer. Results. ANOVA analysis showed that when mass fraction of Phene in resin matrix was more than 10 wt%, the obtained resin composite formulation had lower DC, VS and SS than control resin composite (p < 0.05). In general, the experimental resin composites had comparable FS and FM (p > 0.05) when the mass fraction of Phene in resin matrix was not more than 20 wt %. Resin composite with 20 wt% Phene had the lowest wear depth and fracture toughness values. Significance. The overall tested properties prove that including Phene up to 20 wt% into Bis-GMA/TEGDMA resin could be potentially useful in the formulation of low-shrinkage resin composites. (C) 2019 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.