A thorough understanding of root canal anatomy and morphology is required for achieving high levels of success in endodontic treatment. The possible anatomic configurations of premolars are well documented in the literature, except for the small incidence of bilateral multi-rooted maxillary and mandibular premolars with three canals.
Karale R, Hegde J, Srirekha A, Sravanthi Y (2012) Multirooted- Bilateral Maxillary and Mandibular First and Second Premolars- A Rare Anatomical Variation. Dentistry 2:140.
https://www.omicsonline.org/multirooted-bilateral-maxillary-and-mandibular-first-and-second-premolars-a-rare-anatomical-variation-2161-1122.1000140.php?aid=8227