Biofilms are complex three-dimensional communities of microorganisms adhering to a surface and encased in a protective exopolymeric substance. The anatomical complexities in the root canal systems shelter the adhering bacteria in a biofilm from cleaning and shaping procedures. Microbial communities growing in biofilms are remarkably more difficult to eradicate with antimicrobial agents and microorganisms in mature biofilms can be extremely resistant for reasons that have yet to be fully explained. As the influence of root canal dentin and other surfaces on the expression of novel biofilm...