Quantum Dots as Nonagglomerated Nanofillers for Adhesive Resins

Abstract

Nanoparticles used in adhesive resins are prone to agglomeration, turning the material susceptible to physical failure. Quantum dots are nonagglomerated inorganic nanoparticles (1 to 10 nm) when in equilibrium. The aim of the present study was to synthesize and characterize zinc oxide quantum dots (ZnO) and to develop and evaluate an adhesive resin with the addition of ZnO. ZnO were formulated by self-organization in chemical reaction with isopropanol and added to 2-hydroxyethyl methacrylate (HEMA). HEMA containing ZnO was used for the experimental group and neat HEMA for the control group. Mean ZnO diameter was evaluated in isopropanol and in HEMA by ultraviolet-visible spectroscopy. The adhesives were evaluated for degree of conversion ( n = 5), softening in solvent ( n = 5), ultimate tensile strength ( n = 5), microtensile bond strength ( n = 20) at 24 h and after 6 mo, SEM-EDS (scanning electron microscopy-energy-dispersive x-ray spectroscopy; n = 3), and superresolution confocal microscopy ( n = 3). Data of microtensile bond strength after 6 mo and Knoop hardness after solvent immersion were evaluated by paired t test with a 0.05 level of significance. The other data were evaluated by independent t test with a 0.05 level of significance. Ultraviolet-visible spectroscopy indicated that the mean ZnOQD diameter remained stable in isopropanol and in HEMA (1.19 to 1.24 nm). Fourier transform infrared spectroscopy analysis showed the peak corresponding to zinc and oxygen bond (440 cm). The experimental group achieved a higher degree of conversion as compared with the control group and presented dentin/adhesive interface stability after 6 mo without altering other properties tested. SEM-EDS indicated 1.54 ± 0.46 wt% of zinc, and the superresolution confocal microscopy indicated nonagglomerated nanoparticles with fluorescence blinking in the polymerized adhesive. The findings of this study showed a possible and reliable method to formulate composites with nonagglomerated nanoscale fillers, shedding light on the nanoparticle agglomeration concern.

Triazine Compound as Copolymerized Antibacterial Agent in Adhesive Resins

“…Besides that, from 2.5% wt on, the resistance to solvent degradation was improved. This is an advantage among antibacterial adhesives, as it was observed that other adhesives with antibacterial fillers could not present this result (18). In this study, although the materials presented no statistical difference in degree of conversion, the polymer chains may have been organized differently.…”

“…Specimens were then subjected to softening in absolute ethanol for 2 h at 37 °C and the microhardness values were measured again (KHN2). The percent difference was calculated according to a previous study (18).…”

“…Opus software (Bruker Optics) was used, with a Blackman-Harris 3-Term apodization in a range of 4000 to 400 cm -1 and 64 scans at 4 cm -1 resolution. The samples (n=3) were directly dispensed onto the diamond crystal and a spectrum was obtained prior to photoactivation and immediately after photoactivation for 20 s. The degree of conversion was calculated as in a previous study (18).…”

Tantalum oxide as filler for dental adhesive resin

“…It decreases the composite's organic phase and the adhesives may be more hydrolytic stable, as the water sorption occurs mainly in the organic matrix 29) . The adhesive resin must promote the distinction of the demineralized tissue (dentin or 4…”

“…Tests were performed in a test machine Shimadzu (EZ-SX; Shimadzu) at a crosshead speed of 1-mm/min. UTSs were calculated according to previous study 29) .…”