Effect of Antimicrobials Used in Regenerative Endodontic Procedures on 3-week-old Enterococcus faecalis Biofilm

We evaluated the effect of various antimicrobials used in endodontic regeneration on a 3-week-old Enterococcus faecalis biofilm.

E. faecalis biofilm was grown on standardized dentin samples for 3 weeks. Infected dentin samples were randomized into 8 experimental groups (n = 8) and treated with calcium hydroxide (Ca[OH]2), 500 mg/mL of double antibiotic paste (DAP, equal portions of metronidazole and ciprofloxacin), low dilutions of DAP (1 or 0.1 mg/mL loaded into a methylcellulose vehicle system), sterile saline, or placebo paste (only methylcellulose) for 7 days. The other experimental groups were treated with 1.5% sodium hypochlorite (NaOCl) or 2% chlorhexidine gluconate (CHX) solutions for 5 minutes. After the assigned treatments, the bacterial biofilms were detached from dentin, spiral plated, and quantified using an automated counting machine. Permutation tests followed by Sidak post hoc multiple comparisons were used for statistical analyses (α = 0.05).

The infected dentin treated with 1.5% NaOCl or 500 mg/mL of DAP provided complete eradication of bacterial biofilm. Furthermore, the infected dentin treated with 2% CHX, Ca(OH)2, or 1 mg/mL of DAP had a comparable antibiofilm effect, but they were not able to completely eradicate bacterial biofilm. No significant difference in the antibiofilm effect was observed between 500 mg/mL of DAP, Ca(OH)2, 1.5% NaOCl, and 2% CHX.

At least 1 mg/mL of DAP in a methylcellulose vehicle system is required to eliminate a substantial amount of E. faecalis biofilm. Furthermore, the antibiofilm effects of 1.5% NaOCl and 2% CHX irrigation solutions were comparable with that of 500 mg/mL of DAP and Ca(OH)2.