RESUMO
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 (ZnOQDs) and to develop and evaluate an adhesive resin with the addition of ZnOQDs. ZnOQDs were formulated by self-organization in chemical reaction with isopropanol and added to 2-hydroxyethyl methacrylate (HEMA). HEMA containing ZnOQDs was used for the experimental group and neat HEMA for the control group. Mean ZnOQD 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-1). 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.
Assuntos
Adesivos Dentinários/química , Metacrilatos/química , Pontos Quânticos/química , Óxido de Zinco/química , 2-Propanol/química , Dureza , Teste de Materiais , Microscopia Confocal , Microscopia Eletrônica de Varredura , Polímeros/química , Espectrofotometria Ultravioleta , Propriedades de Superfície , Resistência à TraçãoRESUMO
AIM: To evaluate the influence of several niobium pentoxide (Nb(2) O(5) ) concentrations on the radio-opacity, flow, film thickness, microhardness and degree of conversion of an experimental root canal sealer. METHODOLOGY: An experimental dual-cured root canal sealer was produced with a methacrylate-based comonomer blend. Nb(2) O(5) was added at four different concentrations: 0, 80, 100 and 120 wt%. Radio-opacity was evaluated according to ISO 6876 using a digital system (n = 5). Flow and film thickness were determined in accordance with ISO 6876 (n = 3). Microhardness was evaluated with 50 g for 15 s (n = 5). Degree of conversion was evaluated with FTIR immediately after photocuring and after 1, 7 and 14 days. The data were analysed using anova and Tukey's test. The degree of conversion over time was evaluated using RM-anova (α = 0.05). RESULTS: The groups with 80 wt% and 100 wt% of filler showed no significant difference in radio-opacity from that of equivalent 2 mmAl (P > 0.05). The addition of 120 wt% resulted in radio-opacity values higher than 2 mmAl (P < 0.05). The flow was not significantly different amongst the different groups (P > 0.05). All groups had a film thickness of <50 µm (ISO 6876). All groups with Nb(2) O(5) were associated with higher values of microhardness than the control group. The group with 0 wt% was associated with a higher degree of conversion at all times. All groups except those with 80 wt% had higher values for degree of conversion after 14 days than immediately after photocuring. CONCLUSION: The addition of Nb(2) O(5) increases radio-opacity and microhardness; this material may be a promising filler for the production of a new endodontic sealer.