|Year : 2013 | Volume
| Issue : 1 | Page : 37-41
Management of C-shaped canals: Two case reports
Nilesh Suryakant Kadam, Ida de Noronha de Ataide
Department of Conservative Dentistry, Goa Dental College and Hospital, Bambolim, Goa, India
|Date of Web Publication||20-Jun-2013|
Nilesh Suryakant Kadam
Department of Conservative Dentistry and Endodontics, Goa Dental College and Hospital,Bambolim, Goa - 403 202
Source of Support: None, Conflict of Interest: None
A C-shaped canal with varying configuration is commonly observed in single-rooted mandibular second molars. Cooke and Cox (1979) first documented the C-shaped canal in endodontic literature. The presence of high incidence of transverse anastomoses, lateral canals, and apical deltas makes it difficult to clean and seal the root canal system in these teeth. The main reason for failure in endodontic treatment of mandibular second molars is the inability to detect the presence of C-shaped canals prior to an endodontic therapy. This case report presents successful management of two rare cases of C-shaped canal configurations.
Keywords: C-shaped canals, mandibular second molar, single canal
|How to cite this article:|
Kadam NS, Ataide IN. Management of C-shaped canals: Two case reports. J Orofac Sci 2013;5:37-41
| Introduction|| |
The main objective of root canal therapy is thorough shaping and cleaning of all pulp spaces and its complete obturation with an inert filling material. The presence of an untreated canal may be a reason for failure. Together with diagnosis and treatment planning, knowledge of the canal morphology and its frequent variations is a basic requirement for endodontic success.  One of the most important anatomic variations is the "C" configuration of the canal system. Cooke and Cox (1979) first documented the C-shaped canal in endodontic literature and named it for the cross-sectional morphology of the root and root canal. 
This C-shaped canal is an anatomical variation of a root fusion and a type of taurodontism. This results from the failure of Hertwig's epithelial sheath to develop or fuse in the furcation area in the developing stage of the teeth.  Failure on the buccal side results in a lingual groove, and the opposite cases is possible. Failure on both sides results in the formation of a conical or prism-shaped root. 
Due to the high incidence of root fusion in the mandibular second molars, C-shaped canals are frequent. This anatomy is much more common in Asians than in whites.  Gulabivala et al.,  using a canal staining and tooth clearing technique, reported the incidence of 22.4% in Burmese patients; in another study,  the same author used the injection of Indian ink and noted the prevalence of 10% in Thai population, while Wang et al.,  found a high incidence of C-shaped canal system (41.27%) in mandibular second molars of a Chinese population.
Melton et al.,  proposed the following classification of C-shaped canals based on their cross-sectional shape:
- Category I: Continuous C-shaped canal running from the pulp chamber to the apex defines a C-shaped outline without any separation (i.e., C1 in [Figure 1]).
- Category II: The semicolon-shaped (;) orifice in which dentine separates a main C-shaped canal from one mesial distinct canal (i.e., C2 in [Figure 1]) and
- Category III: Refers to those with two or more discrete and separate canals: Subdivision Seo et al.,  the most prevalent configuration types were Melton's type I (coronal region) and type III (apical region).
Fan et al.,  modified Melton's method into the following categories:
- Category I (C1): The shape was an interrupted "C" with no separation or division [Figure 1]a.
- Category II (C2): The canal shape resembled a semicolon resulting from a discontinuation of the "C" outline [Figure 1]b, but either angle α or β [Figure 2] should be no less than 60°.
- Category III (C3): 2 or 3 separate canals [Figure 1]c and d and both angles, α and β, less than 60° [Figure 3].
- Category IV (C4): Only one round or oval canal in the cross-section [Figure 1]e.
- Category V (C5): No canal lumen could be observed (which is usually seen near the apex only) [Figure 1]f.
|Figure 2: Measurement of angles for the C2 canal. Angle β is more than 60°. (a and b) Ends of one canal cross-section, (c and d) ends of the other canal cross-section, M, middle point of line AD; angle between line AM and line BM; β, angle between line CM and line DM|
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|Figure 3: Measurement of angles for the C3 canal. Both angle α and angle β are less than 60°. (a and b) Ends of one canal cross-section; (c and d) ends of another canal cross-section; M, middle point of line AD; angle between line AM and line BM; angle between line CM and line DM|
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Fan et al.,  classified C-shaped roots according to their radiographic appearance into three types:
- Type I: Conical or square root with a vague, radiolucent longitudinal line separating the root into distal and mesial parts. There was a mesial and a distal canal that merged into one before exiting at the apical foramen (foramina) [Figure 4]a.
- Type II: Conical or square root with a vague, radiolucent longitudinal line separating the root into distal and mesial parts. There was a mesial and a distal canal, and the two canals appeared to continue on their own pathway to the apex [Figure 4]b.
- Type III: Conical or square root with a vague, radiolucent longitudinal line separating the root into distal and mesial parts. There was a mesial and a distal canal, one canal curved to and superimposed on this radiolucent line when running toward the apex, and the other canal appeared to continue on its own pathway to the apex [Figure 4]c.
Instead of having several discrete orifices, the pulp chamber of the C-shaped canal is a single ribbon shaped orifice with 1800 arc, which, in mandibular molar, starts at the mesiolingual line angle and sweeps around the buccal to the end at the distal aspect of the pulp chamber. Typically, this canal configuration is found in the teeth with fusion of the roots either on its buccal or lingual aspect. 
Recent studies done on mandibular molars with C-shaped roots, NiTi rotary instrumentation was associated with a higher percentage (59.6%) of uninstrumented canal areas than the manual K-file group (41.6%) with more dentine removed from the convex aspect of the C-shaped canal. , The C-shaped canal system thus represents a challenge to its proper debridement and obturation.
This paper describes successful management of two unusual cases of C-shaped canal.
A 33-year-old female patient reported to the Department of Conservative Dentistry with a chief complaint of pain in the lower right back tooth region. Medical history of the patient was noncontributory. There was presence of prolonged sensitivity to hot and cold. Clinically, there was a presence of deep distoproximal carious lesion approaching pulp, the tooth was nonresponsive to vitality tests and it was nontender to percussion. Radiographically, radiolucency was seen involving pulp without any peri-radicular changes. The patient was diagnosed with pulp necrosis. The radiograph also showed a single conical root with outline of single root canal, suggesting presence of C-shaped canal [Figure 5]a.
|Figure 5: (a) Preoperative radiograph, (b) Working length radiograph, (c) Master cone radiograph, (d) Obturation radiograph|
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After gaining profound anesthesia and rubber dam application, an access cavity was prepared. After pulp extirpation, a single round orifice, located in the middle portion of the floor of the pulp chamber was seen [Figure 2]. The pulp chamber was irrigated with 5% sodium hypochlorite. Working length was determined using apex locator (Root ZX, J. Morita CO, Tustin, CA) and radiographs [Figure 5]b. Cleaning and shaping was done with rotary ProTaper rotary files (Dentsply Maillefer, Ballaigues, Switzerland) till the size of F3. The canal showed a bifurcation at the apical third of the root. Calcium hydroxide (RC-Cal, India), an intracanal medicament was used and the patient was recalled after 1 week. In the next appointment, Master cone was fitted to the working length and radiograph was taken [Figure 5]c, and the canal was obturated with selected master gutta-percha cone along with accessory cones with AH-Plus endodontic sealer (Dentsply Maillefer Company, USA) [Figure 5]d. A temporary restoration was placed. The patient was recalled after 1 week for a post endodontic restoration.
A 26-year-old male patient reported to the Department of Conservative Dentistry with a chief complaint of pain in the lower right back tooth region. Medical history of the patient was noncontributory. There was a presence of prolonged sensitivity to hot and cold. Clinically, there was a presence of deep occlusal carious lesion with 46 and 47 approaching pulp, 36 was nonresponsive to vitality tests and was associated with mild tenderness, while 37 showed delayed response. Radiographically, occlusal radiolucency was seen with 46 and 47 involving pulp chamber. There was a presence of periapical radiolucency with mesial root of 46, while periradicular area of 47 was without any periradicular changes. The patient was diagnosed with irreversible pulpitis with 47. The radiograph also showed a single conical root with slight distal curvature with three radiolucent canal outline, which were joining at the apical third of the root, suggesting presence of C-shaped canal pattern [Figure 6]a. After proper isolation and profound anesthesia, an access cavity was prepared. On exploration of pulp chamber, three orifices were recognized, which were then negotiated till apex with the use of multiple small K files with the help of RC-Help (Prime Dent, India) and 3% NaOCl. After proper working length determination, an IOPA was taken [Figure 6]b and it showed that all the canals were joined at the apical third of the root. Then, cleaning, shaping [Figure 6]c, and obturation [Figure 6]d was done as mentioned in Case 1. The patient is currently asymptomatic and under follow-up.
|Figure 6: (a) Preoperative radiograph, (b) Working length radiograph, (c) Master cone radiograph, (d) Obturation radiograph|
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| Discussion|| |
The deﬁnition of a C-shaped canal is not yet clear. Some authors consider C-shaped canals as all those with a general outline of a "C" and present in a C-shaped root, regardless of whether a separate canal or oriﬁce was observed (Al-Fouzan 2002).  Fan et al.,  analyzed the C-shaped canal system using micro-computed tomography (CT) and modiﬁed the classiﬁcation of the C-shaped canal system. They considered that this type of canal system had to exhibit all of the following three features: (i) Fused roots, (ii) a longitudinal groove on the lingual or buccal surface of the root, and (iii) at least one cross-section of the canal belonging to the C1, C2, or C3 conﬁguration. They found that although the C3-type oriﬁce may look like two or three separate oriﬁces, an isthmus linking them is often discernible. 
Clinical recognition of C-shaped canals is based on the definite observable criteria (i.e., the anatomy of the floor of the pulp chamber and the persistence of hemorrhage or pain when separate canal orifices were found).  When a deep groove is present on lingual or buccal surfaces of the root, a C-shaped canal is to be expected. New methods should be developed to diagnose not only the existence but also the configuration of the entire C-shaped canal system. 
The basic feature of C-shaped canals is the presence of a fin or web connecting the individual canals.  The convergence of root canal instruments at the apex or being centered and exiting the furcation were used as the criteria for identifying C-shaped canals.  In the first case, initial evaluation of the radiograph suggested the presence of single root with a wide centrally located canal space, suggesting that there may be a C-shaped configuration of the canal. After access preparation, only one canal with a round orifice was negotiated, which showed presence of a single root canal. While in the second case, we found a single conical root with three canals centered on the tooth. On exploration of the chamber, 3 orifices were seen which were joining at the apical third of the root.
The morphological variant of single root and single canal is easily detected in routine radiographs. However, care should be taken to assess the correct anatomy on the preoperative radiograph to rule out the clinical condition of two roots, one buccal and one palatal that could be superimposed on the diagnostic radiograph. A study by Weine et al.,  reported that 1.3% of mandibular second molars had single canal configuration. First case report was with a single root and single canal having two portal of exit.
The use of ultrasonics along with conventional therapy would be more effective. An increased volume of irrigant and deeper penetration with small instruments using sonics or ultrasonics may allow for more cleansibility in fan-shaped areas of the C-shaped canal. 
It should be emphasized that, in C-shaped mandibular molars, the mesiolingual canal is separate and distinct from the apex, although it may be significantly shorter than the mesiobuccal and distal canals. These canals are easily overinstrumented in C-shaped molars with a single apex.  In our second case, mesiolingual canal was found to be separate and it was clearly distinct from apex. However, first case reported with a single canal configuration.
Thermoplasticized gutta-percha technique is the recommended technique for canal irregularities. , Since most of dental practitioners use only lateral condensation technique, we used the same and found excellent results with gutta-percha and AH Plus sealer into the complex anatomy of the canal.
| Conclusion|| |
Knowledge of different possible alterations in the internal anatomy of teeth is important for successful endodontic therapy. This C-shaped canal system tends to vary considerably in their anatomical configuration and thus leads to difficulties in debridement, filling, and restoration.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]