The most important anatomical variant which presents the first molar is third distolingual additional root called radix entomolaris paramolaris call or oral. In root canal treatment is important to have complete information on variations of the root canals to the extent that this ensures the result substantially. For endodontic treatment to succeed, it is necessary to locate all the canals, clean them thoroughly and completely sealed with an inert material. The endodontist must know the internal morphology of permanent teeth and possible variations that they can have as is the case of an additional root located on the tongue (the radix entomolaris) or buccally (the radix paramolaris). The root canal anatomy is very complex and unpredictable and understanding of the presence of an additional root is important because it determines the success of endodontic treatment.