In vitro evaluation of antibacterial effect of AH plus incorporated with quaternary ammonium epoxy silicate against enterococcus faecalis

Introduction The purpose of this study was to evaluate the in vitro antibacterial effect of AH Plus (Dentsply, DeTrey, Konstanz, Germany) incorporated with quaternary ammonium epoxy silicate (QAES) against Enterococcus faecalis.

Methods QAES particles were synthesized by the cocondensation of tetraethoxysilane with 2 trialkoxysilanes (3-[trimethoxysilyl]propyldimethyloctadecyl ammonium chloride and 3-glycidyloxypropyltrimethoxysilane) through a 1-pot sol-gel route. Dried QAES particles were then characterized by attenuated total reflection Fourier transform infrared spectroscopy and scanning electron microscopy. AH Plus sealers incorporated with 0-8 wt% QAES were tested after 4 weeks of water aging to assess the in vitro antibacterial activity against E. faecalis by the direct contact test (DCT) and 3-dimensional image analysis of live/dead-stained E. faecalis biofilms using confocal laser scanning microscopy.

Results The Fourier transform infrared spectroscopy spectrum of QAES particles revealed the coexistence of the characteristic absorbance band of the siloxane backbone (Si-O-Si) from 1,000-1,100 cm^-1, epoxide band peaking at ∼916 cm^-1, and C-N stretching vibration peaking at 1,373 cm^-1. The scanning electron microscopic image showed the spherical morphology of QAES particles with ∼120 nm in diameter and a rough surface. DCT results revealed that AH Plus alone (0 wt% QAES) after 4 weeks of water aging had no inhibitory effect on E. faecalis growth (P =.569). AH Plus incorporated with QAES (2-8 wt%) showed antibacterial activity against E. faecalis as shown in DCT and biofilm viability results (P <.001).

Conclusions The incorporation of QAES into epoxy resin-based AH Plus may be a promising approach for controlling endodontic infection at the time of canal filling and preventing subsequent reinfection.