Disinfection of the root canal system during root canal re‐treatment

In this narrative review, the differences between primary root canal treatments and re‐treatments are explored in view of optimal disinfection of the root canal system. A critical appraisal of the literature raises doubt as to whether the microbiota found in re‐treatment cases per se is more resistant to antiseptics than the counterpart found in primary infections. In reality, primary, refractory, and persisting endodontic infections are all biofilm‐related; their microbial composition is dictated by local ecological factors rather than treatment history. Furthermore, their resistance to antimicrobials is most likely similar. The true difficulty in disinfecting root canal systems during re‐treatment cases is to achieve access to the infected areas. Iatrogenic alterations in canal anatomy and the presence of root filling material hamper the diffusion of disinfectants to these target areas. Consequently, cleaning the canal systems of foreign material and creating a canal shape that can properly be disinfected should be the initial aims. Ways of achieving these goals are discussed. Subsequently, the disinfection regimen can be similar to that in primary root canal infections. However, time is a crucial factor in re‐treatments, and thus a multiple‐visit approach is preferable in more complex cases in order to ensure more complete disinfection has been achieved.