IADR Abstract Archives
Functional Nanogels for Filler Surface Treatment in Dental Composites
Objectives: Nanogel additives in the resin phase of dental composites can reduce polymerization stress. Here the feasibility of reactive nanogels localized at the resin/filler interface is examined.
Methods: An isocyanate-functionalized nanogel was synthesized from isocyanatoethyl methacrylate, isobornyl methacrylate and BisEMA (20:50:30 mol%). This nanogel was added to a slurry of thiol silane-modified, 0.4µm barium glass filler. Residual isocyanate groups within the thiourethane-tethered nanogel layer were reacted with HEMA to provide polymerizable methacrylate groups. The nanogel particles were characterized by GPC. Filler surface functionalization was assessed by diffuse reflectance FT-IR and thermogravimetric analysis (TGA). Composite samples were prepared from BisGMA/TEGDMA resin and either the reactive nanogel-modified glass filler or the analogous conventional silane-methacrylate treated filler. Paste consistency, polymer degree of conversion, polymerization stress and modulus of the composites were measured.
Results: Nanogel molecular weight was 340kDa with a hydrodynamic radius of 7.4nm. This nanoparticle-based dimension is much greater than conventional silane surface treatments. Successful attachment of the nanogel particles to the filler surface was demonstrated by TGA analysis, which displayed greater surface coverage with higher nanogel loading levels. FT-IR verified the presence of interfacial methacrylate groups. Paste consistency testing showed greater particle/particle interaction for the experimental composite with approximately half the spread diameter versus the control material. The composite with nanogel-modified filler produced a degree of conversion of 73.3% and flexural modulus of 9.0±1.1GPa compared to 63.6±0.6% and 6.2±0.7GPa for the control. Despite enhanced composite stiffness and conversion, polymerization stress was 1.88±0.06MPa compared to 2.30±0.07MPa for the control.
Conclusions: This approach enables the potential for unique interactions between the matrix resin and the reinforcing filler via an extended nanogel interphase that readily accommodates swelling by and copolymerization with the resin phase. Increased composite paste viscosity, reduced polymerization stress, as well as increased conversion and mechanical strength were achieved compared with conventional composite materials.
Methods: An isocyanate-functionalized nanogel was synthesized from isocyanatoethyl methacrylate, isobornyl methacrylate and BisEMA (20:50:30 mol%). This nanogel was added to a slurry of thiol silane-modified, 0.4µm barium glass filler. Residual isocyanate groups within the thiourethane-tethered nanogel layer were reacted with HEMA to provide polymerizable methacrylate groups. The nanogel particles were characterized by GPC. Filler surface functionalization was assessed by diffuse reflectance FT-IR and thermogravimetric analysis (TGA). Composite samples were prepared from BisGMA/TEGDMA resin and either the reactive nanogel-modified glass filler or the analogous conventional silane-methacrylate treated filler. Paste consistency, polymer degree of conversion, polymerization stress and modulus of the composites were measured.
Results: Nanogel molecular weight was 340kDa with a hydrodynamic radius of 7.4nm. This nanoparticle-based dimension is much greater than conventional silane surface treatments. Successful attachment of the nanogel particles to the filler surface was demonstrated by TGA analysis, which displayed greater surface coverage with higher nanogel loading levels. FT-IR verified the presence of interfacial methacrylate groups. Paste consistency testing showed greater particle/particle interaction for the experimental composite with approximately half the spread diameter versus the control material. The composite with nanogel-modified filler produced a degree of conversion of 73.3% and flexural modulus of 9.0±1.1GPa compared to 63.6±0.6% and 6.2±0.7GPa for the control. Despite enhanced composite stiffness and conversion, polymerization stress was 1.88±0.06MPa compared to 2.30±0.07MPa for the control.
Conclusions: This approach enables the potential for unique interactions between the matrix resin and the reinforcing filler via an extended nanogel interphase that readily accommodates swelling by and copolymerization with the resin phase. Increased composite paste viscosity, reduced polymerization stress, as well as increased conversion and mechanical strength were achieved compared with conventional composite materials.