I trends _ re-treatment Practical clinical considerations in endodontic re-treatment Authors_Dr Richard E. Mounce, USA & Dr Gary D. Glassman, Canada _Non-surgical endodontic re-treatment (NSER) of failed root canals is almost exclusively a specialist procedure, owing to the complexity of diagnosis, treatment planning and advance techniques required for re-treatment procedures. As implants have become more predictable, the level of clinical success required with NSER in an attempt to retain the natural dentition has taken on new significance. This article reviews and discusses several key conceptual strategies for the re-treatment of failed root canals that optimise the outcome of the procedure. It is assumed here that the clinician appreciates the value of the surgical operating microscope (SOM; Global Surgical) and ultrasonics in re-treatment procedures. While it is beyond the scope of this article to elaborate at length on the use of the SOM, its use is associated with improved outcomes of NSER and endodontic surgery. Conceptually, NSER can be broken down into several key steps: 1) Determination of restorability The determination of restorability is a key component of NSER success. Treatment on teeth that are non-restorable is obviously contra-indicated. If these teeth were extracted from the pool of candidates for either endodontic therapy or NSER, success rates for both treatments can only go up. Figures 1 to 3 show three different cases that were poorly treated using inappropriate concepts and for which removal was indicated. Had the initial endodontic therapy been correctly conducted, the probabilities of clinical success would obviously have been far greater and the option of implant therapy irrelevant. In the context of NSER, rather than compounding the existing failure, the clinician should carefully examine the case at hand and evaluate whether the tooth can be re-treated, and if so what the likely success will be. The initial treatment of the teeth pictured in Figures 4 to 6 was conducted to a high standard and for Figs. 1–3_Endodontic treatment with significant resulting iatrogenic events and other clinical defects. Figs. 4–6_Endodontic treatment conducted within the standard of care. Fig. 1 Fig. 2 24 I roots 4_ 2009