Biofilms in Root Canal Infections

This chapter describes the general characteristics of biofilms and analyzes biofilms associated with root canal (RC) infections. Microbial cells occupy only a small portion of the biofilm. The majority of the biofilm structure is a highly heterogeneous matrix composed of extracellular polymeric substances (EPS) produced by cells within the biofilm. The distance between microorganisms and their spatial distribution within biofilms are critical factors for intermicrobial communication processes in biofilms. In the ever-changing biofilm environment, microbial cells encounter a multitude of stresses and challenges. These include exposure to nutrient limitation, reactive oxygen and nitrogen species, membrane damage, and elevated temperature. Infected RCs harbor a multispecies population of facultative and strict anaerobic gram-positive and gram-negative bacteria, spirochetes, yeasts, archaea, and other unidentified species. Several in-vitro models have been used to study biofilms of relevance to RC treatment. These studies typically focus on the efficacy of antimicrobial agents against single- or multispecies biofilms.