New insights in the disinfection of the root canal system using different research models

An endodontic infection is a biofilm-caused disease that affects teeth’s inner part, a connective tissue called pulp. The pulp space is divided into the pulp chamber, located within the anatomic dental crown, and the root canal, found inside the radicular portion of the tooth. This last part is often complex, comprising canals that divide and rejoin, isthmuses, fins, anastomosis, accessory and lateral canals, and apical deltas. Biofilm removal from this complex root canal system is a challenge during the endodontic treatment. Thus, the aim of this study was to investigate the efficacy of disinfection procedures performed during endodontic treatment, such as the intracanal medication between sessions and irrigation, in order to optimize these procedures to increase the success rate. The most common intracanal medication, calcium hydroxide, was further investigated trying to improve its antimicrobial effectiveness and physicochemical properties. Removal of a real biofilm from a root canal model with lateral morphological features filled with biofilm was for the first time analyzed by Optical Coherence Tomography. The gold standard irrigant sodium hypochlorite was used at different concentrations, flow rates and exposure times and compared with other new experimental irrigants. The irrigation protocols were evaluated regarding their efficacy on intratubular decontamination, ability in killing bacteria in a biofilm configuration, and removing biofilm from simulated anatomic complexities. The mechanical and chemical effect of irrigation were separately evaluated. The irrigant flow rate (mechanical) had more influence on biofilm removal than the irrigant concentration (chemical). Sodium hypochlorite and the higher flow rate can improve biofilm removal.