Endodontic treatment is a predictable procedure with high success rates and cleaning is a key part of successful root canal treatment. The aim of endodontic therapy is the debridement of all vital or necrotic tissue, microorganisms, and their products from the root canal system and even to prevent the reinfection to get a positive outcome of the therapy. The efficiency of the irrigation has a key role as in the endodontic failures, microbes are always present in the root canal system: irregular and oval canal cross-sections, accessory canals, isthmuses, anastomoses, curves and apical delta can make difficult an effective cleaning of this areas. The apical area is a special challenge to irrigation: the action of irrigating solution is really important in the apical third to get a positive outcome, but the challenge is to be effective avoiding the extrusion of the solution. In the last years many techniques have been proposed to increase the quality of the cleaning after the shaping and before the obturation; among these techniques, the activation of irrigating solutions using ultrasonic dedicated devices seems to be very efficient, improving the cleaning even in irregular and oval canal cross-sections, accessory canals, isthmuses, anastomoses, curves and apical delta thanks to cavitation and acoustic streaming effect. However, in the scientific literature there is not an agreement on the fact that this technique is more effective of other techniques, positive pressure included. Aim of the lecture is, starting from literature analysis, sharing with the attendees the experience of the clinician with the use of ultrasonic activation, highlighting benefits and limitation of this technique and how, when and why to use it in the clinical practice.