Efficacy of three endodontic sealers against Enterococcus faecalis biofilm and its genetic determinants.

Abstract

When a carious tooth is left untreated, the oral microorganisms can pave their path through the tooth dentin into the root pulp. To treat such an infected tooth, a root canal treatment is necessary. Root canal treatments remove the compromised pulp, clean, and disinfect the root canal space, which is then filled with gutta-percha and root canal sealers. Unfortunately, root canal treatments are unsuccessful in 5-7% of patients. The majority of treatment failures are attributed to the presence of bacteria in the root canal. Unsuccessfully treated root canals often contain Peptostreptococcus provetti, Streptococcus sanguis, Streptococcus salivarius, Enterococcus faecalis, and Porphyromonas endodontalis. E. faecalis is most commonly found in post-endodontic therapy pain and infection cases, with prevalence values reaching up to 90%. Persistent E. faecalis adhere to root canals and aggregate in biofilm communities which help E. faecalis survive the adverse nutrient-deficient conditions in the root canal. We hypothesize that specific genes are required for the survival of E. faecalis which prevents the formation of E. faecalis biofilm in the presence of sealers. To identify any differentially expressed genes, RNA sequencing was performed. To a large extent, the ability of the sealers to inhibit biofilm growth depended on the growth conditions. The approach we used here, studying the growth of E. faecalis on TSB (tryptic soy broth) agar plates in aerobic and anaerobic conditions in the presence of 4 different sealers, is distinctive. The focus on E. faecalis growth under anaerobic conditions is vital because once the root canal is sealed with gutta purcha and root-canal sealers, the oxygen reservoir inside the canal is depleted. We tested four endodontic sealers commonly used by dentists and endodontists (AH-plus, Endoseal, Endosequence, and Bioroot RCS) for their ability to prevent E. faecalis biofilm formation. E. faecalis growth on sealers was tested aerobically and anaerobically on sealers that were set and unset. Controls were no sealer (positive control - TSB with E. faecalis) and sterile TSB (negative control). Overnight incubation was carried out, and colony-forming units (CFU) were counted. All the three sealers prevented biofilm formation aerobically. AH-Plus did not show biofilm formation in all the three conditions. RNA sequencing analysis demonstrated differentially expressed genes in all three conditions.