Antibacterial Effects of Antimicrobials Used in Regenerative Endodontics against Biofilm Bacteria Obtained from Mature and Immature Teeth with Necrotic Pulps

Abstract Introduction We investigated the direct and residual antibacterial effects of intracanal antimicrobials against bacterial biofilms obtained from infected mature and immature teeth with necrotic pulps. Methods Sterile dentin slabs ( n = 100) were inoculated with bacterial biofilms obtained from root canals of an immature or a mature tooth with pulpal necrosis and incubated anaerobically for 3 weeks ( n = 50 per biofilm). Dentin infected with each type of biofilm received 1 week of treatment with 1 or 5 mg/mL double antibiotic paste (DAP) in methylcellulose hydrogels, calcium hydroxide, or placebo paste or received no treatment ( n = 10). The pastes were removed, and biofilm disruption assays were performed. Additional dentin slabs ( n = 100) were pretreated with the same treatments ( n = 20). The pastes were rinsed off, and the samples were immersed in phosphate-buffered saline for 1 week. Thereafter, samples from the treatment groups were infected with bacterial biofilm from both clinical sources mentioned earlier ( n = 10 per biofilm) and incubated anaerobically for 3 weeks before conducting biofilm disruption assays. Uninfected dentin slabs were used for both antibacterial experiments as negative control groups ( n = 20). Results All antimicrobials showed significant direct antibacterial effects regardless of the biofilm source. Dentin pretreated with 5 mg/mL DAP provided significantly higher residual antibacterial effects in comparison with all other groups regardless of the source of biofilm. Dentin pretreated with calcium hydroxide did not show any residual antibacterial effects. Conclusions Tested antimicrobials showed significant direct antibacterial effects. Only 5 mg/mL DAP exhibited significant residual antibacterial effects against bacterial biofilms from an infected root canal of an immature tooth.