Synthesis and characterization of silver nanoparticle-loaded amorphous calcium phosphate microspheres for dental applications

The goals of this work were (1) to synthesize composite nanostructures comprised of amorphous calcium phosphate (ACP) loaded with silver nanoparticles using a spray pyrolysis method and (2) to demonstrate their potential for use in dental adhesives. Release of silver ions from these nanostructures could provide antibacterial activity, while release of calcium and phosphate ions could promote tooth remineralization. Precursor solutions were prepared with varying silver concentrations corresponding to 5, 10, and 15 mol% of the calcium content, then sprayed into a furnace (550 degrees C) as droplets with a mean diameter near 2 mu m. In this process, each droplet is converted into a single solid microsphere via rapid heating. The synthesized particles were collected using a polymeric filter installed at the end of the reaction zone. Different quantities (2, 5, and 10 wt%) of the nanocomposite material were mixed with a commercially available dental adhesive (Single Bond, 3M ESPE) which was then polymerized into discs for incubation in a solution simulating cariogenic conditions. Release of silver, calcium and phosphorus ions into the solution was measured for 1 month. The nanostructures of similar to 10 nm silver nanoparticles embedded into 100 nm to 2 mu m ACP particles demonstrated good dispersion in the adhesive resin blend, which in application would shield surrounding tissues from direct contact with silver. The composite nanoparticles provided a quick initial release of ions after which the concentration of calcium, phosphorous, and silver in the incubation solution remained constant or increased slightly. The dispersibility and ion release of the new nanostructures may offer potential for use in dental materials to achieve anti-bacterial and remineralization effects.