Antibacterial, physicochemical and mechanical properties of endodontic sealers containing quaternary ammonium polyethylenimine nanoparticles

Aim To evaluate the antibacterial, physicochemical and mechanical properties of two endodontic sealers incorporating quaternary ammonium polyethylenimine (QPEI) nanoparticles at concentrations of 1% and 2% (w/w). Methodology The sealers tested were AH Plus and Pulp Canal Sealer EWT in the commercial unmodified form or containing 1% or 2% QPEI. Antibacterial activity was evaluated using a direct contact test (DCT) against Enterococcus faecalis ATCC 29212 and two endodontic isolates (RW35 and RN44). Sealers freshly mixed or set for 7 days were exposed to bacterial suspensions for 10, 30 and 60 min. Setting time, flow test, solubility, apparent porosity, dimensional change following setting, wettability, zeta potential and compressive strength were assessed according to the International Standard Organization 6876: 2001 (ISO 6876). Results DCT results revealed that both freshly prepared sealers had antibacterial effects unaffected by QPEI incorporation. Both unmodified sealers had lost much of their antibacterial effects after 7 days. However, for Pulp Canal Sealer EWT incorporated with 1% and 2% QPEI nanoparticles, the antibacterial effects against all test E. faecalis strains within 30 and 60 min of contact were significantly greater than the unmodified formula. Addition of QPEI resulted in no significant increase in the antibacterial effects of AH Plus after ageing. As for physicochemical and mechanical tests, setting time, wettability and zeta potential were influenced by the presence of QPEI nanoparticles. Conclusion Incorporation of QPEI nanoparticles can improve the long-term antibacterial activity of Pulp Canal Sealer EWT without relevant changes in physicochemical and mechanical properties.