Incorporation of antimicrobial agents can be used to enhance the antibacterial effect of endodontic sealers

**Aim** The antibacterial activity of five endodontic sealers against three different microorganism strains alone and following incorporation of 2% benzalkonium chloride (BC) and 2% cetylpyridinium chloride (CPC) was evaluated. **Methodology** The agar diffusion method was used to determine the inhibitory effect of the following endodontic sealers: RoekoSeal, Endomethasone N, N2, Apexit Plus and AH plus, on Streptococcus mutans – ATCC 25175, Lactobacillus casei – ATCC 4646 and Actinomyces viscosus – ATCC 19246. Bacterial strains were inoculated into BHIB, and incubated in an anaerobic atmosphere (37 °C). From the bacteria grown in the liquid medium, the density of the inoculum was set to be equivalent to McFarland 2 standard. In Shaedler agar, 350 μL of the bacterial suspension were equally spread. Specimens (4 mm × 6 mm) were prepared from each material without and with addition of 2% BC or 2% CPC. The inhibition zones were determined after 2 days, after 7 days and after 21 days of incubation. **Results** The largest inhibition zones were shown at zero time in all cases, with progressively less inhibition at 7 and 21 days. Endomethasone N and N2 showed the most intense antimicrobial activity, while RoekoSeal showed the least antimicrobial effect. The most susceptible microorganism was A. viscosus. Greater antimicrobial effects were found following incorporation of BC or CPC, and generally, BC gave greater inhibition zones than CPC. **Conclusions** Adding either BC or CPC has the potential to improve clinical outcomes with endodontic sealers, as these substances enhance the short-term antimicrobial effects of the sealers.