Release of Metal Ions from Orthodontic Appliances: An In Vitro Study

In this paper, we report the results of an in vitro experiment on the release of metal ions from orthodontic appliances composed of alloys containing iron, chromium, nickel, silicon, and molybdenum into artificial saliva. The concentrations of magnesium, aluminum, silicon, phosphorus, sulfur, potassium, calcium, titanium, vanadium, manganese, iron, cobalt, copper, zinc, nickel, and chromium were significantly higher in artificial saliva in which metal brackets, bands, and wires used in orthodontics were incubated. In relation to the maximum acceptable concentrations of metal ions in drinking water and to recommended daily doses, two elements of concern were nickel (573 vs. 15 μg/l in the controls) and chromium (101 vs. 8 μg/l in the controls). Three ion release coefficients were defined: α, a dimensionless multiplication factor; β, the difference in concentrations (in micrograms per liter); and γ, the ion release coefficient (in percent). The elevated levels of metals in saliva are thought to occur by corrosion of the chemical elements in the alloys or welding materials. The concentrations of some groups of dissolved elements appear to be interrelated

Silica@zirconia@poly(malic acid) nanoparticles: promising nanocarriers for theranostic applications

Silica@zirconia@poly(malic acid) nanocarriers of 130 nm mean diameter were designed, synthesized and characterized for the targeted delivery of diagnostic and therapeutic 99mTc isotope to folate-overexpressing tumors. An important achievement was that a multifunctional L-(−)-malic-acid-based copolymer was formed in situ at the surface of the inorganic cores in a single synthetic step incorporating L-(-)-malic acid, β-cyclodextrin rings, folic acid moieties, and polyethylene glycol chains. Morphological and in-depth structural analysis of the particles proved their core@shell structure. Stability experiments in aqueous media evidenced that stable suspensions can be obtained from the lyophilized powder in 10 mM phosphate buffer at pH 7.4. During 14-day degradation experiments, the nanoparticles were found to be slowly dissolving (including inorganic core) in saline and also in total cell medium. In vitro toxicity assay on hepatocytes showed a concentration-dependent decrease of cell viability down to 63±1% at the highest applied concentration (0.5 mg/ml). Proof of concept experiments of technetium-99m radiolabelling and in vivo labelling stability are presented