The inhibitory effect of quaternary ammonium salt on bacteria in root canal

Abstract

Persisting apical periodontitis is a primary reason for multiple intervention in root canal. Persisting bacteria in root canal is related with the persisting infection. Despite the advancement in treatment strategies the persisting infection is a major challenge for endodontist. Here we tested two newly developed quaternary ammonium methacrylates (QAMs) against endodontic bacteria and their biofilms. Their antibacterial and antibiofilm efficiency were compared with chlorhexidine (CHX) and sodium hypochlorite (NaOCl). We measured the MIC, MBC and MBIC of DMADDM and DMAHDM respectively. We also detected the ratio of live/dead bacteria and bacterial composition in the biofilms treated by DMADDM and DMAHDM. We found that DMADDM and DMAHDM could inhibit the growth of bacteria and biofilms formation. The result showed that novel QAMs were remarkably efficient than CHX against biofilms. In addition, we found that Streptococcus gordonii (S. gordonii) and Enterococcus faecalis (E. faecalis) were frequent isolates after treatment with antimicrobial compounds.

Figure 1

(A) Planktonic bacteria eradication analysis by DMADDM, DMAHDM, CHX and NaOCl at different concentrations for 3 min, 5 min and 10 min. Each value is mean ± standard deviation (n = 9) *P < 0.05. (B) log CFUs of bacteria after treatment with different concentrations of DMADDM, DMAHDM, CHX and NaOCl for 3 min, 5 min and 10 min. Each value is mean ± standard deviation.

Figure 2

CLSM image of control biofilm. (A) Image of base of Biofilm, it shows base of biofilm dominated by rod shaped bacteria. (B) Surface of biofilm shows the dominance of coccid shaped bacteria. (C) 3D image of control biofilm.

Figure 3

CLSM image of 48 h biofilms after treatment with different concentrations of DMADDM for 3 min, 5 min and 10 min.

Figure 4

CLSM image of 48 h biofilms after treatment with different concentrations of DMAHDM for 3 min, 5 min and 10 min.

Figure 5

CLSM image of 48 h biofilms after treatment with different concentrations of CHX for 3 min, 5 min and 10 min.

Figure 6

CLSM image of 48 h biofilms after treatment with different concentrations of NaOCl for 3 min, 5 min and 10 min.

Figure 7

(A) Proportion of live bacteria in biofilm after treatment with DMADDM, DMAHDM, CHX and NaOCl for 3 min, 5 min and 10 min. (B) Thickness of biofilm after treatment with antimicrobial compounds. Each group name and contact duration is indicated in Image. Higher concentrations of DMADDM and DMAHDM, and increased duration of contact with biofilm provided stronger antimicrobial effect. Data is presented in mean ± standard deviation. *P < 0.05.

Figure 8

The compositions shift of A. naeslundii, L. acidophilus, S. gordonii and E. faecalis in biofilms after treatment with DMADDM, DMAHDM, CHX and NaOCl for 3 min, 5 min and 10 min. The composition shift was determined by TaqMan real-time polymerase chain reaction. No significant differences in proportions shifts were observed among groups.