[Premolar anatomy and endodontic treatment].

Endodontic failures on premolars are statistically important. This is mainly due to insufficient knowledge of the typical anatomical diversity shown by premolars. Filling a second root canal is often omitted. Completely treating a complicated root canal system is technically quite difficult which results in a relatively high level of endodontic failure. There are not only the classical technical problems to deal with: calcification of the root canals and delicate probing, given the frequently bent and twisted premolar roots; special attention should also be given to upper premolars with three root canals and those showing a high bifurcation of a principal root canal (configuration IV), and to lower premolars with multiple root canals often showing configuration IV. An additional problem associated with the second lower premolars is a hazardous anatomical zone: the mandibular vasculonervous plexus of the chin.