Biofilms Formed in Root Canals
Microorganisms in root canals have been found to colonize by adhering to dentin walls in all the extension of the root canals, such as the inner walls of complex apex anatomies and accessory canals [26,27]. In 2004, Svensater and Bergenholtz proposed a hypothesis for biofilm formation in root canals. Root canal biofilm formation is initiated directly after the first invasion of the pulp chamber by oral organisms following pulp tissue inflammatory breakdown. The inflammatory lesion frontage will then move successively toward the apex providing the fluid vehicle for the invading organisms so these can multiply and continue attaching to the root canal walls. This hypothesis has been confirmed by light microscopy observations, where
Fig. 2.2 Development of a multispecies biofilm over time. (1) Formation of conditioning film on the surface, (2) initial adherence of bacterial cells, (3) irreversible attachment and multiplication and formation of microcolonies, and (4) maturation of the biofilm, matrix formation
bacteria have been observed to detach from inner root canal surfaces and occasionally mass in the inflammatory lesion per se. This observation could explain how the inflammatory lesion would serve as a fluid source for bacterial biofilm detachment and colonization of apical areas of root canals and beyond.