In 1993 the first endodontic files, made from a nickel-titanium (NiTi) alloy, were introduced to the dental market and definitely contributed to a radical change in the operative approach to endodontic treatment . Compared to previous stainless steel files, they were much more flexible, effective and better performing in shaping root canals. Furthermore, in recent years, advances in knowledge and technology have brought about several interesting changes in these alloys, which were made increasingly resistant to torsional load and, therefore, safer to use.This has led to the manufacturing of a “single file” , which enables dental practitioners to shape the full length of the root canal using a single instrument, such as Wave One ® (Maillefer- Dentsply , Ballaugues, Switzerland) or Reciproc ® (VDW, Munich, Germany) .Despite these structural improvements, the file design has remained unchanged : a solid body with more or less sharpened blades, which cut the canal from different angles and collect treatment debris in their flutes. This suggests that, despite the different endodontic variations recurrent in nature, we do nothing but imprint the instrument shape inside the canal, regardless canal anatomy ; this apparently allows us to use similar procedures with either round-shaped and oval- shaped canals , as well as with more or less tightly curved canals.From the studies carried out by Paqué [3,] analyzing MicroCT sections, it is clear that instrumentation with conventional Ni-Ti tools does not allow us to accomplish a proper cleaning of the whole root canal system (fig.1). In fact, these instruments, due to their shape, cannot contact the entire surface of root walls, thus leaving within a certain amount of unremoved tissue, which also reduces the quality of subsequent obturation , as highlighted by De Deus (Fig2) [4.5].