In-vitro comparison of the antimicrobial activity of intracanal medicaments on mature multispecies biofilm

Abstract

Purpose: To test the antimicrobial activity of the intracanal medicaments calcium hydroxide, double antibiotic paste, and triple antibiotic paste in a direct contact test utilizing Next Generation Sequencing. Materials and Methods: A mature 12-day multispecies biofilm was developed on hydroxyapatite discs using a CDC reactor. Discs were treated with a direct contact test with no treatment (control), propylene glycol, calcium hydroxide, triple antibiotic paste (TAP), and double antibiotic paste (DAP). (n=6 for each treatment group). DNA extraction was completed immediately after removal from the reactor for the control groups. Treatment samples were incubated anaerobically for an additional 7 days. Samples were processed for further analysis with qPCR and NGS. Samples without sufficient reads were excluded from NGS. Statistical analysis was completed using a significance level of 0.05, with exception for when a Bonferroni correction was applicable. Results: A mature multispecies biofilm was confirmed via SEM and DNA sequencing. The calcium hydroxide groups had the lowest number of mean reads and OTUs. Due to significant DNA reduction, NGS analysis was unable to be completed for the calcium hydroxide group. Triple antibiotic paste demonstrated a significant difference in alpha (via Shannon Index) and beta-diversity in comparison to the control. The genera with the highest relative abundance across the groups being Parvimonas, Prevotella, Selenonadaceae spp., Oribacterium, and Campylobacter. Conclusion: Within the limitations of this study, calcium hydroxide was found to be the most effective in disinfecting a mature multispecies biofilm developed on hydroxyapatite discs in a direct contact test. The results of this study also suggest that TAP is more effective than DAP on a mature multispecies biofilm, but neither provide degradation of the bacterial DNA present.