IADR Abstract Archives
Isocyanate-Methacrylate Nanogels as Filler Surface Treatment to Reduce Shrinkage Stress of Composites
Objectives:
The objectives of this study were to modify fillers surface treatment using alternative silanes and isocyanate-methacrylate reactive nanogel additives, in order to create an interphase between filler and resin matrix that is able to modulate shrinkage stress development during polymerization of dental composites.
Methods: Glass fillers were treated with γ-methacryloxypropyltrimethoxysilane, n-methylaminopropyltrimethoxy and n-allylaminopropyltrimethoxy silanes. Nanogels were synthesized from isobornyl methacrylate, BisEMA and isocyanatoethyl methacrylate (50:30:20mol%) presenting isocyanate functional groups, which were partially reacted with HEMA to create available methacrylate groups. Nanogels were characterized by gel permeation chromatography (GPC) and dynamic mechanical analysis (DMA), and reacted with the silanated fillers. Surface treatment was assessed by thermogravimetric analysis (TGA) and diffuse reflectance spectroscopy (DFTIR). Composites (60wt% fillers) were manipulated with silanated fillers, used as control, and nanogel modified fillers. Shrinkage stress, volumetric shrinkage, polymerization kinetics, rheological and mechanical properties of composites were evaluated.
Results: Nanogels were within a range of 400-484 Kg/mol, 1.4-2.0 polydispersity index, 8-9 nm hydrodynamic radius, and 57-63 oC glass transition temperature. Amount of nanogel deposited on the fillers estimated as 2.5±0.5% by TGA and verified by DFTIR assessing presence of methacrylate carbonyl peak (1706 cm-1) and multiple aliphatic peaks (2856-2962 cm-1). Nanogels modified fillers demonstrated a significantly shrinkage stress reduction up to 20% in magnitude, while volumetric shrinkage, degree of conversion, elastic modulus, and rheological properties were similar to control group. Polymerization rate was significantly higher when nanogels were present. A decrease on flexural strength was observed for amino silane control groups, but it was not statistically different from MPS control group when nanogels were combined to the amino silanes.
Conclusions:
The approach of using reactive nanogels to modify the fillers surface treatment enables the potential for reducing shrinkage stress, without compromising physical properties of composites.
The objectives of this study were to modify fillers surface treatment using alternative silanes and isocyanate-methacrylate reactive nanogel additives, in order to create an interphase between filler and resin matrix that is able to modulate shrinkage stress development during polymerization of dental composites.
Methods: Glass fillers were treated with γ-methacryloxypropyltrimethoxysilane, n-methylaminopropyltrimethoxy and n-allylaminopropyltrimethoxy silanes. Nanogels were synthesized from isobornyl methacrylate, BisEMA and isocyanatoethyl methacrylate (50:30:20mol%) presenting isocyanate functional groups, which were partially reacted with HEMA to create available methacrylate groups. Nanogels were characterized by gel permeation chromatography (GPC) and dynamic mechanical analysis (DMA), and reacted with the silanated fillers. Surface treatment was assessed by thermogravimetric analysis (TGA) and diffuse reflectance spectroscopy (DFTIR). Composites (60wt% fillers) were manipulated with silanated fillers, used as control, and nanogel modified fillers. Shrinkage stress, volumetric shrinkage, polymerization kinetics, rheological and mechanical properties of composites were evaluated.
Results: Nanogels were within a range of 400-484 Kg/mol, 1.4-2.0 polydispersity index, 8-9 nm hydrodynamic radius, and 57-63 oC glass transition temperature. Amount of nanogel deposited on the fillers estimated as 2.5±0.5% by TGA and verified by DFTIR assessing presence of methacrylate carbonyl peak (1706 cm-1) and multiple aliphatic peaks (2856-2962 cm-1). Nanogels modified fillers demonstrated a significantly shrinkage stress reduction up to 20% in magnitude, while volumetric shrinkage, degree of conversion, elastic modulus, and rheological properties were similar to control group. Polymerization rate was significantly higher when nanogels were present. A decrease on flexural strength was observed for amino silane control groups, but it was not statistically different from MPS control group when nanogels were combined to the amino silanes.
Conclusions:
The approach of using reactive nanogels to modify the fillers surface treatment enables the potential for reducing shrinkage stress, without compromising physical properties of composites.