Characterisation of the antibacterial effect of polyethyleneimine nanoparticles in relation to particle distribution in resin composite

Abstract Objectives To characterise the antibacterial effect of resin composite incorporating cross-linked quaternised polyethyleneimine (QPEI) nanoparticles in relation to their distribution in the bulk material. Methods The antibacterial effect of resin composite incorporating QPEI nanoparticle was tested against various oral pathogens, including Enterococcus faecalis, Streptococcus mutans, Actinomyces viscousus, Lactobacilus casei and whole saliva. Nanoparticle distribution in the modified resin composite was assessed using X-ray photoelectron spectroscopy (XPS). Additionally, the degree of conversion was recorded. Results Total bacterial inhibition was detected against all the tested pathogens following direct contact with the outer surface of the modified resin composite. Similarly, the inner surface of the modified resin composite caused total inhibition. Electron microscope images showed bacterial death. XPS revealed surface I− ions on both the outer and the inner surfaces of the modified composite. No I− ions were detected in the unmodified composite. Nanoparticle distribution was higher on the inner surface of the modified composite. The composite's degree of conversion was unaffected by nanoparticle addition. Conclusions QPEI nanoparticles represent a new generation of antibacterial nanoparticles which are highly promising in preventing bacterial recontamination when restoring teeth.