Effective apical irrigation is one of the most important root canal procedures that has stood as a long‐standing challenge for the clinician. Despite the myriad of technological advances seen in the last few decades such as nickel–titanium rotary files of various designs and new irrigation delivery systems, very few seem to reliably impact upon a clinician's ability to deliver and replenish irrigant in the most apical part of a root canal. Replenishing irrigant in the apical third is complicated by the multitude of factors that affect the efficacy of this procedure. The current research provides detailed insight on how the principles of fluid mechanics work to explain the physical impediments to thorough irrigation, and how the biological impediments, in the form of biofilm, prevent disinfection despite adequate irrigation. The recent introduction of new irrigation and agitation modalities, coupled with a new understanding of the old problem through novel research techniques, provides a vision to the future and will establish a new standard of irrigation in this field.