C-shaped root canal systems in the bilateral mandibular first molars: a case report and literature review

Abstract

Background: Mandibular first molars typically exhibit complex root and canal anatomy. A thorough understanding of their morphological variations is crucial for endodontists to achieve successful root canal treatment. A C-shaped root canal system is a unique anatomical variation characterized by a C-shaped or semi-circular cross-sectional morphology, observed predominantly in mandibular second molars. The prevalence rate of the C-shaped root canal system is approximately 2.7-48.7% in the mandibular second molar, while the condition is rarely seen in mandibular first molars, particularly in bilateral cases.

Case presentation: This report details an uncommon case of a C-shaped root canal system in bilateral mandibular first molars: the right molar exhibited a fused root with two separate mesial and two distal canals, while the left molar displayed a single oval mesial canal and a semicolon-shaped distal canal. To our knowledge, this is the first report of the presence of four separate canals within a fused C-shaped root in the mandibular first molar.

Conclusions: While C-shaped root variations are detected in mandibular first molars, a thorough knowledge of normal root canal anatomy and associated variations presents a significant challenge for clinicians in terms of successful endodontic treatment.

Keywords: C-shaped root canal system; Mandibular first molar; Root canal treatment, CBCT.

Fig. 1

Images of the right mandibular first molar. (a). Preoperative radiograph showed a mesio-occlusal radiolucency approaching the pulp space. (b). Clinical view of the C-shaped orifice on the pulp floor (B: buccal, L:lingual). (c). Clinical view of the access cavity preparation showing four distinct root canal orifices (red arrow; DM: mesiobuccal, ML: mesiolingual, DB: distobuccal, DL: distolingual). (d). Axial CBCT section from the pulp chamber: C-shaped orifice. (e). Axial CBCT section from the coronal third: two canals separately, either canal cross-sectional angles less than 60° (C3c). (f). Axial CBCT section from the middle third: four canals separately (C3?). (g). Axial CBCT section from the apical third: one fused mesial canal and one fused distal canal (C3c). (h). Periapical radiography for working length determination with gutta-percha (size 25, 06 taper) in four separate canals. (i). Postoperative radiograph for root obturation. (j). Intraoral photograph showing four separate canals after root obtruation. (k). Postoperative radiograph with resin composite restoration. (l). Six-month follow-up radiograph indicates the health periapical tissue

Fig. 2

3D reconstruction views. (a, b). 3D reconstruction for the right mandibular moral. (a). A fused root showed in the buccal side. (b). A longitudinal groove (orange arrow) showed in the lingual side. (c, d). 3D reconstruction for the left mandibular moral. (a). A fused root showed in the buccal side. (d). A longitudinal groove (orange arrow) showed in the lingual side

Fig. 3

Images of the left mandibular first molar. (a). Preoperative radiograph showed an fused root with a well-circumscribed radiolucent lesion. (b). Clinical view of the C-shaped orifice on the pulp floor (B: buccal, L:lingual). (c). An elongated narrow orifice (red arrow) form the distal canal. (d). Axial CBCT section from the pulp chamber: C-shaped orifice. (e). Axial CBCT section from the coronal third: an ovalshaped single canal in the mesial and an elongated narrow canal (angle of canal cross-section more than 60°) in the distal (C2). (f). Axial CBCT section from the middle third: an elongated narrow canal in the distal root (C2). (g). Axial CBCT section from the apical third: one canal in the mesial and one in the distal (C3c). (h). Intraoral photograph showing C-shaped canal after root obtruation. (i). Postoperative radiograph for root obturation. (i). Six month follow-up radiograph indicated the healed periapical tissue

Fig. 4

CBCT imaging for the mandibular molars. (a). Axial CBCT section from the coronal one-third. (b). Axial CBCT section from the middle one-third