Analysis of Cause of Endodontic Failure of C-Shaped Root Canals

Abstract

The purpose of this study was to analyze various characteristics and classification of C-shaped root canals and evaluate the causes of endodontic failure of C-shaped root canals by examining the resected root surface with an endodontic microscope and a scanning electron microscope (SEM). Forty-two teeth with C-shaped root canals were included in this study and had undergone intentional replantation surgery. Before surgery, periapical radiography and cone-beam computed tomography were taken. The root canal configuration was analyzed and classified according to Melton's classification at coronal and apical level. After injection of 1 : 100,000 epinephrine with 2% lidocaine, the tooth was carefully extracted. After the root-end resection, the resected root surface was examined using an operating microscope and SEM. Mandibular second molars were most frequently involved teeth (90.4%). The most frequently observed root canal configurations were C1 at the coronal level (45.2%) and C3 at the apical 3 mm level (45.2%). The most common cause of failure for a C-shaped root canal treatment was a leaky canal (45.2%), followed by an isthmus (23.8%), missing canal, overfilling, and iatrogenic problems. In conclusion, C-shaped root canals were most frequently found in mandibular second molars. The most common cause of failure was a leaky canal and isthmus.

Figure 1

Modified Melton's classification of C-shaped canal configuration [1].

Figure 2

Classification of C-shaped canal configuration using cone-beam computed tomography. (a) C1 configuration at coronal level. (b) C2 configuration at coronal level. (c) C3 configuration at coronal level. (d) C4 configuration at coronal level. (e) C1 configuration at apical 3 mm level. (f) C2 configuration at apical 3 mm level. (g) C3 configuration at apical 3 mm level. (h) C4 configuration at apical 3 mm level.

Figure 3

Percentage of the possible causes of failure in the previous endodontic treatment of C-shaped root canals (p < 0.05).

Figure 4

Representative photos of various causes of endodontic failure of C-shaped root canals. (a1) Calcified canal: preoperative periapical radiography. (a2) Root-resected surface of calcified C-shaped root canals. (b1) File separation: preoperative periapical radiography. (b2) Postoperative periapical radiography. (c1) Leaky canal. (c2) Retrograde filling with MTA. (d1) Isthmus connecting mesial and distal canals. (d2) Retrograde filling with MTA. (e1, e2) Overfilling: overextended gutta-percha. (f) Missing canal: only the mesiolingual canal is filled with gutta-percha in the mandibular left second molar. (g) Missing canal: only the palatal canal is filled with gutta-percha in the maxillary right first molar.

Figure 5

SEM images of resected root tip of C-shaped root canals. (a1) Leakage around the gutta-percha filling area on the distal canal (×100). (a2) Pulp tissue and debris were observed (×500). (a3) Remaining microorganisms were found in the gap between the gutta-percha and the canal wall (×5000). (b1) Isthmus connecting mesiolingual and distal canals (×100). (b2, b3) Pulp tissue and debris were observed. (c1) Leakage around the gutta-percha filling area on the mesiolingual canal (×100). (c2) Pulp tissue and debris were observed (×500). (c3) Remaining microorganisms were found in the gap between the gutta-percha and the canal wall (×5000).