Endodontic retreatment - unusual anatomy of a maxillary second and mandibular first premolar: Report of two cases.

An accurate diagnosis of the morphology of the root canal system is a prerequisite for successful root canal treatment. A major cause of endodontic treatment failure in missed (or) untreated root canals is that they still harbor infection. Careful radiographic interpretation and examination of pulp chamber floors are helpful in locating root canal entrances. These case reports present anatomical variations in upper and lower premolars.