Root canal treatment may be performed on teeth with irreversibly inflamed dental pulps to prevent apical periodontitis or on teeth with apical periodontitis to treat it. The presenting condition of the root canal surface may therefore vary from that of an intact pulp– dentine complex, through partially degraded pulp tissue with infection, to a dentine surface coated with a mature bacterial biofilm (1). Subsequent treatment procedures will alter the surface in ways that depend upon the root canal anatomy, the instruments used, the strategy and mode of their use, and the chemicals used to facilitate debridement. The effects range from displacement and/or deformation of soft and/or hard tissue components, to changes in the biological, mechanical, and chemical properties of the root canal dentine surface. These changes may have a profound effect on the survival of the tooth, both in terms of progression of apical periodontitis and the long-term integrity of the tooth. An evidence-based synthesis of the literature on the chain of events associated with the effects of root canal treatment, on the internal dentine surfaces, has required subjective assimilation. The mass of published, largely laboratory data, relevant to the topic is heterogenous and contradictory, leaving room for conjecture, differences of opinion, and further questions. The original questions posed in laboratory studies were not guided by clinical outcome data and therefore lacked relevant focus. The synthesized view presented below is based on the authors’ interpretation of the literature findings, sought systematically by hand and electronic search methods.