Ethyl 4 dimethylamino benzoate edab

In this study, the resin matrix consisted of 70 wt.% Bisphenol A glycerolate di-methacrylate (Bis-GMA) and 30 wt.% Triethylene glycol dimethacrylate (TEGDMA) (both from BOC Sciences Inc., Shirley County, NY, USA). The photoinitiator camphorquinone (CQ) (0.2 wt.%) and the amine reducing agent ethyl 4-dimethylamino-benzoate (EDAB) (0.8 wt.%) (both from Sigma Aldrich, Milwaukee, WI, USA) were mixed with the matrix by a centrifugal mixer (DAC 150FVZ, FlackTek Inc., Landrum, SC, USA) for 20 min at 2500 RPM to obtain the uniform resin composites [32 (link)]. Then, the nano-SiO₂ particles were respectively incorporated into the matrix with 0, 2, 4, 6, 8, and 10 wt.%, and the average diameter of the nanoparticles was 20 nm. The nano SiO₂ particles with a mass ratio of 1% were added to the resin at a time; then, the mixtures were stirred evenly by the centrifugal mixer at 2500 RPM. Nanoparticles were then gradually added for centrifugal mixing again. The total amount of samples was about 8 g each time. All the mixtures were stirred for about 30 min by using the high-speed centrifuge to ensure the nanoparticles were dispersed homogenously in the resin matrix.

The exothane 8 (Esstech Inc.; Essington, PA, USA); ethoxylated bisphenol A diglycidyl ether dimethacrylate with 30 ethylene oxide units (Esstech Inc.; Essington, PA, USA); triethylene glycol dimethacrylate (TEGDMA, Esstech Inc.; Essington, PA, USA), were used as received. The photosensitizer camphorquinone (CQ - Esstech Inc.; Essington, PA, USA) and the co-initiator ethyl 4-(dimethylamino) benzoate (EDAB - Sigma Aldrich; Saint Louis, Missouri, USA), diphenyliodonium hexafluorophosphate (DPIHFP) were used to render the materials light polymerizable; and as filler, silica particles and zinc methacrylate (Aldrich Chemical Co.; Milwaukee, WI, USA).
The concentrations of zinc methacrylate tested were: 0.5% (Z0.5); 1% (Z1), 2% (Z2), and 5% (Z5) by weight. A formulation without zinc methacrylate was used as experimental control (C). The Fermit-N (Ivoclar Vivadent; Schaan, Liechtenstein) (F) was used as a commercial reference. Light activation procedures were carried out using a light-emitting diode unit (Radii-cal; SDI, Bayswater, Victoria, Australia) with 1200-mW/cm² irradiance and 440-480 nm of light wavelength. The radiance used for light activation of the tested materials was checked by MARC Resin Calibrator system (BlueLight Analytics; Halifax, NS, Canada).