[Clinical challenges caused by defective Hertwig's epithelial root sheath proliferation Ⅱ: pathogenesis and treatment of C-shaped root canal].

Defective proliferation of Hertwig's epithelial root sheath can lead to developmental root anomalies, classically represented as taurodontism and C-shaped canals found in fused roots. While taurodontism is primarily caused by a temporal delay in the proliferation of Hertwig's epithelial root sheath epithelial flaps , the formation of C-shaped canals originates from a spatial insufficiency in their proliferation. Clinicians' understanding of C-shaped canals is often limited to the "C"-shaped orifice pattern on the pulp chamber floor, lacking a systematic appreciation of their complex three-dimensional anatomy and the associated clinical challenges. This deficiency can easily lead to iatrogenic complications and even treatment failure. This paper focuses on the etiology of C-shaped canals and their clinical implications. From the developmental perspective, it elucidates the formation mechanism of C-shaped canals, comprehensively reviews the evolution of their classification systems and current research status, and provides an in-depth analysis of the difficulties encountered in key treatment stages, including diagnosis and classification, canal preparation, obturation, and coronal restoration. Corresponding strategies are proposed to help clinicians establish a three-dimensional understanding of C-shaped canals and enhance their diagnostic and therapeutic capabilities.