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