4 research outputs found
Silver nanoparticles in resin luting cements: antibacterial and physiochemical properties
Background: Silver has a long history of use in medicine as an antimicrobial and anti-inflammatory agent. Silver
nanoparticles (NAg) offer the possibility to control the formation oral biofilms through the use of nanoparticles
with biocidal, anti-adhesive, and delivery abilities. This study aims to evaluate the antibacterial effect of resin luting
cements with and without NAg, and their influence on color, sorption and solubility.
Material and methods: NAg were incorporated to two dual-cured resin cements (RelyX ARC (RA) color A1 and
RelyX U200 (RU) color A2) in two concentrations (0.05% and 0.07%, in weight), obtaining six experimental
groups. Disc specimens (1x6mm) were obtained to verify the antibacterial effect against Streptococcus mutans in
BHI broth after immersion for 1min, 5min, 1h, 6h, and 24h (n=3), through optical density readings. Specimens
were evaluated for color changes after addition of NAg with a spectrophotometer (n=10). Sorption and solubility
tests were also performed, considering storage in water or 75% ethanol for 28 days (n=5), according to ISO
4049:2010. Data were subjected to statistical analysis with ANOVA and Tukey (p=0.05).
Results: The optical density of the culture broths indicated bacterial growth, with and without NAg. NAg produced
significant color change on the resin cements, especially in RA. Solubility values were very low for all groups, while
sorption values raised with NAg. The cements with NAg did not show antibacterial activity against S. mutans.
They also showed perceptible color change and higher sorption than the materials without NAg.
Conclusions: The resin luting cements with NAg addition did not show antibacterial activity against S. mutans.
They also showed perceptible color change and higher sorption than the materials without NAg
Field dependent transition to the non-linear regime in magnetic hyperthermia experiments : comparison between maghemite, copper, zinc, nickel and cobalt ferrite nanoparticles of similar sizes
Further advances inmagnetic hyperthermiamight be limited by biological constraints, such as using sufficiently low frequencies and low field amplitudes to inhibit harmfuleddy currents inside the patient’s body. These incite the need to optimize the heatingefficiency of the nano particles, referred to as the specific absorption rate (SAR).Among the several properties currently under research, one of particular importance is the transition from the linear to the non-linear regime that takes place as the field amplitude is increased, an aspect where the magnetic anisotropy is expected to play a fundamental role. In this paper we investigate the heating properties of cobalt ferrite and maghemite nano particles under the influence of a 500 kHz sinusoidal magneticfield with varying amplitude, up to 134 Oe. The particles were characterized byTEM, XRD, FMR and VSM, from which most relevant morphological, structural and magnetic properties were inferred. Both materials have similar size distributions and saturation magnetization, but strikingly different magnetic anisotropies. Frommagnetic hyperthermia experiments we found that, while at low fields maghemiteis the best nanomaterial for hyperthermia applications, above a critical field, close to the transition from the linear to the non-linear regime, cobalt ferrite becomesmore efficient. The results were also analyzed with respect to the energy conversionefficiency and compared with dynamic hysteresis simulations. Additional analysiswith nickel, zinc and copper-ferrite nanoparticles of similar sizes confirmed the importance of the magnetic anisotropy and the damping factor. Further, the analysis of the characterization parameters suggested core-shell nanostructures, probably due to a surface passivation process during the nanoparticle synthesis. Finally, we discussed the effect of particle-particle interactions and its consequences, in particular regarding discrepancies between estimated parameters and expected theoretical predictions
Cytotoxicity of glass ionomer cements containing silver nanoparticles
Background: Some studies have investigated the possibility of incorporating silver nanoparticles (NAg) into dental
materials to improve their antibacterial properties. However, the potential toxic effect of this material on pulp cells
should be investigated in order to avoid additional damage to the pulp tissue. This study evaluated the cytotoxicity
of conventional and resin-modified glass ionomer cements (GIC) with and without addition of NAg.
Material and Methods: NAg were added to the materials at two different concentrations by weight: 0.1% and 0.2%.
Specimens with standardized dimensions were prepared, immersed in 400 μL of culture medium and incubated at
37°C and 5% CO2 for 48 h to prepare GIC liquid extracts, which were then incubated in contact with cells for 48 h.
Culture medium and 0.78% NAg solution were used as negative and positive controls, respectively. Cell viability
was determined by MTT and Trypan Blue assays. ANOVA and the Tukey test (α=0.05) were used for statistical
analyses.
Results: Both tests revealed a significant decrease in cell viability in all groups of resin modified cements (
p
˂0.001).
There were no statistically significant differences between groups with and without NAg (
p
˃0.05). The differences in cell
viability between any group of conventional GIC and the negativ
e control were not statistically significant (
p
>0.05).
Conclusions: NAg did not affect the cytotoxicity of the GIC under evaluatio