Root canal treatment follows a series of procedures for cleaning, shaping and filling of the root canal. One of the most important procedures during treatment is the chemomechanical preparation based on the correct use of instruments and irrigating solutions. However, there are some cases in which the treatment has followed the highest technical standards and yet still results in failure. In most of these cases, the endodontic failure results from persistent intraradicular infection. Bacteria located in areas such as isthmuses, ramifications, deltas, irregularities and dentinal tubules may sometimes be unaffected by endodontic disinfection procedures.S tudies showed that part of the root canal space often remains untouched during chemomechanical preparation, regardless of the instruments used for preparation.T hat’s why recent researches and innovations are directed nowadays towards activation of the root canal irrigating solution or modifying its properties and using new techniques and devices to improve its action and eradication of bacteria from inside the canal, to increase the success rate of root canal treatment and avoid failure. So in this presentation we will discuss the different causes of failure of root canal treatment and how to avoid, to increase the success rate of endodontic treatment, the main goal of chemomechanical preparation, and how to improve the antibacterial action of root canal irrigant against root canal bacteria, recent devices and techniques and newly designed instruments used in cleaning of the root canal wall will also be explained. Recent researches are directed towards using new techniques, devices and and newly designed instruments to improve the action of irrigant against bacteria inside the root canal and to increase the success rate of root canal treatment and avoid failure.