Which premolar is MOST likely to have 2 roots and 2 canals?

The maxillary first premolar is the most likely premolar to have two roots and two canals. Approximately 60 to 70% of maxillary first premolars have two roots (buccal and palatal) and two separate canals. The maxillary second premolar most commonly has one root with one canal (about 75%). Mandibular premolars typically have one root and one canal (mandibular first premolar in approximately 75%, mandibular second premolar in approximately 90% of cases). Knowledge of root canal morphology is essential for successful endodontic treatment.