Modification of the composite resin with the hyperbranched polyester and evaluation of the mechanical properties of the modified composite resin

Abstract

To study the effect of hyperbranched polyester(HBP)on mechanical properties of the conventional resin matrix. Two hyperbranched monomers(HBP2-X and HBP2-Y)were synthesized and incorporated at 40%(by mass)into a 2∶1(by mass)bisphenol-A diglycidyl methacrylate(Bis-GMA): triethylene glycol dimethacrylate(TEGDMA)resin. Bis-GMA/TEGDMA without the incorporation of hyperbranched polyester was used as control(n=8 per group). The mechanical properties of the modified neat resin, including polymerization volumetric shrinkage, Vickers hardness, water absorption and dissolution rate, as well as the flexural strength, compressive strength and diametral tensile strength of the composite resin with different content of filler(0%, 30%, 50%, 70%)were measured. Mechanical properties of the composite resin were measured by universal testing machine. The results were analyzed by the ANOVA and LSD-t-test. The resin with HBP greatly decreased the polymerization shrinkage of the composite resin, and the value of group X was(6.32±0.49)%, and that of group Y was(6.31±0.68)%, whereas that of the control group was(8.14 ± 0.53)%. The value of volumetric shrinkage of the modified groups were significantly lower than that of the control group(P<0.05). By adding HBP, the hardness value of group X([198 ± 5]MPa)and group Y([177 ± 4]MPa)were significantly lower than that of the control group([214±6]MPa)(P<0.05). The HBP significantly influenced the water sorption and solubility of the neat resin(P<0.05). For the composite materials, with 70% inorganic filler, there were no significant difference in the value of flexural strength among the groups(P>0.05). There was no significant difference in the value of compressive strength, between group X([244 ± 13]MPa)and the standard group([234 ± 17]MPa)(P>0.05). However, they were significantly higher than that in group Y([204 ± 24]MPa)(P<0.05). For the value of diametral tensile strength, there was no significant difference between group Y([36.4 ± 2.1]MPa)and the control group([34.4 ± 2.9]MPa)(P>0.05), but both were significantly lower than that in group X([41.1 ± 3.0]MPa)(P<0.05). Although there were certain effect on the mechanical properties of the resin that was modified with the HBP, we should make further analysis and study based on the property of low volumetric shrinkage, to strive for the development of low volumetric shrinkage of HBP, without affecting its mechanical properties.