非手術性根管治療成功的要件在於對於牙根形態及根管系統的充分了解。下顎小臼齒因為有著複雜的根管系統，在進行根管治療時，可能是口內所有牙齒中最具挑戰性的。其中最重要的一種變異就是C形根管。C形根管的牙齒，因為其特殊的根管形態，使器械清創和根管封填格外的困難。因此本文將利用文獻回顧，探討下顎第一小臼齒C形根管的發生原因、盛行率、形態學、診斷及治療方式。

Successful nonsurgical root canal treatment depends on a thorough knowledge of root morphology and canal systems. Among all teeth, the mandibular premolars may be the most difficult to treat because of the complex canal system and numerous variations in these teeth. One of the most important anatomic variations is the “C” configuration of the canal system. Once recognized, the complex canal system of C-shape roots provides a challenge with respect to debridement and obturation. This article will review the literature with respect to the etiology, prevalence, roots and root canal morphology, clinical diagnosis and endodontic treatment of the C-shaped mandibular first premolar.