New photocurable "Phene" like monomers Hexaethylene glycol bis(carbamate-isoproply-α-methylstyrene) (HE-Phene) and Triethylene glycol bis(carbamate-isoproply-α-methylstyrene) (TE-Phene) were synthesized and incorporated into Bis-GMA/TEGDMA with the aim of reducing polymerization shrinkage without detriment to the physical and handling properties of the resin composites. Phene like monomers (HE/TE-Phene) were synthesized through a one-step reaction route, and their structures were confirmed by FT-IR and 1H-NMR spectra. HE/TE-Phene were 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. Viscosity was analyzed with a rotating disk rheometer. Water sorption and solubility were also measured. ANOVA analysis showed that DC (after 40 s), VS, and SS were in a trend of decreasing with the increasing of HE/TE-Phene concentration. In general, the experimental resin composites had comparable FT, FS and FM (p > 0.05) when the mass fraction of HE/TE-Phene in resin matrix was not more than 30 wt.%. The overall tested properties prove that including HE/TE-Phene up to 30 wt.% into Bis-GMA/TEGDMA resin could be potentially useful in the formulation of low-shrinkage resin composites.
Keywords: Degree of conversion; Physical properties; Shrinkage stress; Volumetric shrinkage.
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