Introduction
C-shaped canal anatomy was first documented by Cooke and Cox in mandibular second molar in 1979, though Weine et al reported that several clinicians had suggested its presence in lectures earlier.1 This type of Canal configuration has a high prevalence in mandibular second molars (2.7% - 45.5%)2, 3, 4, 5 and has also been reported in maxillary first molars (0.12%), maxillary third molars (4.7%), mandibular third molars (3.5% - 4%)and mandibular second premolars (1%).6, 7, 8, 9 It has been found that there is no correlation of C-shaped canal configuration with gender and also with age and tooth position but ethnic variation is found with highest frequency being reported in the East Asian population groups like Chinese population (29.7%) and Koreans (31.3%-45.5%). 1 The definition of the C-shaped root canal system is that the morphology of its horizontal cross sectionis in the form of a C, with canals which may or may not be separate. 10
This anatomical variation results from the failure of Hertwig’s epithelial sheath to develop or fuse in the furcation area in the developing stage of the teeth. 2
Fan et al modified Melton’s method into the following categories (Figure 1 )
Category I (C1): interrupted “C” with no separation or division.
Category II (C2): resembled a semicolon resulting from a discontinuation of the “C” outline, but either angle α or β should be no less than 60°.
Category III (C3): 2 or 3 separate canals and both angles, α and β less than 60°.
Category IV (C4): Only one round or oval canal in the cross‑ section.
Category V (C5): No canal lumen could be observed (which is usually seen near the apex only)
C‑shapedcanal poses diagnostic difficulty radiographically becauseof the two‑dimensional view of the radiograph. Thepresence of thin fin, slit and web create difficulty in the canal shaping, thorough debridement and obturation. Irregular areas in a C‑shaped canal that may house soft‑tissue remnants or infected debris may escape thorough cleaning or filling and may be a source of bleeding and severe pain.11 Therefore, it is imperative to select the correct obturation technique to obturate C-shape canal. This report presents the management of C-shaped mandibular molar teeth with different obturation systems.
Case 1
A 35 year old female patient reported to the department of Conservative Dentistry and Endodontics with a chief complaint of pain in lower right back tooth.Medical history was non-contributory.Intra oral examination revealed fractured restoration with respect to #47 and tenderness to percussion. Radiographically, the tooth was conical in shape with fused mesial and distal root with a thin radiolucent line between them, with a suspected C-shaped canal and improper obturation with periapical radiolucency suggestive of periapical abscess/periapical granuloma (Figure 2 a). Re endodontic treatment was planned and explained to the patient. After proper isolation and anesthesia, fractured restoration was removed and guttapercha removal was performed using rotary and hand H-files, following which Fan et al’s C3 type canal anatomy was found.After working length determination, canal was prepared with ProTaper rotary files (Dentsply Maillefer, Switzerland) up to F2 followed by circumferential filing with hand K files (Figure 2b) (Dentsply Maillefer, Switzerland). Copious amount of 5% sodium hypochlorite(Acrylates, India) was used for irrigation which was activated using Endo activator (Dentsply Maillefer, Switzerland) and calcium hydroxide dressing was given as an intracanal medicament. The patient was recalled after 2 weeks and was sign and symptom free; obturation was then completed with thermoplasticized gutta-percha (Calamus, Dentsply Maillefer, Switzerland) and post-endodontic restoration done using composite resin (Figure 2c,d).
Case 2
A 24 year old female patient reported to the department with a chief complaint of pain on eating food in lower right back tooth. The medical history was non-significant. Intraoral examination revealed carious # 47 with tenderness on percussion. Radiographically, a large occluso-proximal radiolucency was seen in tooth 47 closely approximating the pulp space along with an associated widening of periodontal ligament space (Figure 3 a). Tooth was conical in shape with fused mesial and distal roots.Cold test using cold spray and Electric pulp testing gave negative response. The tooth was diagnosed with necrotic pulp with acute apical periodontitis. Root canal treatment was planned and explained to the patient. After proper isolation and anesthesia, an access cavity was prepared and Fan et al C1 type canal anatomy was found. After working length determination, canal was prepared with ProTaper rotary files (Dentsply Maillefer, Switzerland) up to F3 followed by circumferential filing with hand K files.5% sodium hypochlorite (Acrylates, India) was used as an endodontic irrigant which was activated with Endo activator (Dentsply Maillefer, Switzerland) (Figure 3b). Calcium hydroxide (RC Cal Prime Dental Products, Thane, India) was placed as an intracanal medicament. After 1 week, patient was recalled and obturation was done using thermoplasticized gutta-percha (Calamus, Dentsply Maillefer, Switzerland). Post endodontic restoration with composite was done (Figure 3c,d).
Case 3
A 27 year old female patient reported to the department with the chief complaint of boil with respect to lower left back tooth. Medical history was non-contributory. Intraoral examination revealed amalgam restored #37 and associated draining sinus. The tooth was tender on percussion.Radiographically the tooth was conical in shape with fused mesial and distal root with a thin radiolucentline between them, with suspected C-shaped canal and improper obturation with periapical radiolucency suggestive of periapical abscess (Figure 4 a). Re-root canal treatment was planned and explained to the patient. After proper isolation and anesthesia, amalgam restoration was removed and Gutta percha removal was performed with the help of rotary files and hand H-files.Working length was determined after locating two separate canals (Fan et al C2 type anatomy) in the pulp chamber floor (Figure 4b). Canals were prepared with ProTaper rotary file system (Dentsply, Maillefer) upto F2 and 5% sodium hypochlorite (Acrylates, India) was used as an endodontic irrigant. Calcium hydroxide (RC Cal Prime Dental Products, Thane, India) was placed as an intracanal medicament. Patient was recalled after 15 days and the calcium hydroxide dressing was replaced. After the next 15 days patient was sign and symptom free so obturation was carried out using thermoplasticized gutta-percha (Calamus, Dentsply Maillefer, Switzerland) and post endodontic restoration was done with composite resin (Figure 4c,d).
Case 4
A29 year old female patient reported to the department with a chief complaint of pain on eating food in lower right back tooth. No relevant medical history. Intraoral examination revealed carious # 47 with tenderness on percussion. Radiographically, a proximal radiolucency was seen in tooth 47 closely approximating the pulp space along with an associated widening of periodontal ligament space (Figure 5 a). Tooth was conical in shape with fused mesial and distal roots and a thin radiolucent line between them, with a suspected C‑shaped canal. After proper isolation and anesthesia, an access cavity was prepared and Fan et al C3 type canal anatomy was found. After working length determination (Figure 5b), cleaning and shaping was done with ProTaper rotary files (Dentsply Maillefer, Switzerland) up to F3 followed by circumferential filing with hand K files (Dentsply Maillefer, Switzerland). 5% sodium hypochlorite (Acrylates, India) was used as an endodontic irrigant which was activated with Endo activator (Dentsply Maillefer, Switzerland). Calcium hydroxide (RC Cal Prime Dental Products, Thane, India) was placed as an intracanal medicament. After a week patient was recalled, radiograph was taken to confirm fit of the master cone and obturation was completed using thermoplasticized gutta percha (Calamus, Dentsply Maillefer, Switzerland) and post endodontic restoration was done with composite resin (Figure 5c,d).
Discussion
The etiology for C-shaped morphology is failure of the Hertwig’s epithelial root sheath to fuse on the lingual or buccal root surface. The C-shaped root may also be formed by coalescence because of deposition of the cementum with time.2
Melton et al’s classification describes the following three types of C shaped canals continuous C shaped (C1), semicolon (C2) and separate canals (C3). This classification was further modified by Fan et al and the most prevalent type of C shape canal was single orifice with an uninterrupted “C ” shape configuration according to this classification.3
Following features are a must for the canal morphology to be called as “C” shape:
Fused roots,
A longitudinal groove onthe lingual or buccal surfaces of the root,
At leastone cross‑section of the canal belongs to the C1, C2,or C3 configuration.12
Management of this type of canal configuration is a highly challenging task for a clinician. However, with the advent of newer technical advancements in the form of Cone beam CT scan, Operating microscopes, sonic, ultrasonic irrigation devices and thermoplasticized obturation techniquessuccessful management of this anatomical aberration has been achieved.
Points to be considered in management of C shaped canal morphology:
Preoperative radiograph will show fused roots so additional 20° mesial or the distal angulation will be useful to deduct this configuration.
Isthmus preparation should be restricted till no 25 file and anti-curvature filing is recommended to avoid strip perforations. Avoid use of Gates-Glidden drills for the same.
Irrigation supplemented with ultrasonic agitation is the key to success as it would clean the inaccessible areas of the complex “C” shape anatomy.
To ensure proper placement of the master cones in C-shaped canals, Walid's technique involves placing the master points simultaneously in the C-shaped canal. A large plugger is placed on one of the seared master points while the other master point is down packed with a smaller plugger.13
Thermoplasticized obturation technique is preferred as it ensures a better 3 dimensional fill than cold lateral compaction technique.
Conclusion
The C-shaped root canal configuration has an ethnicpredilection and a high prevalence rate in mandibular secondmolars. For successful endodontic management proper diagnosis, sound knowledgeabout aberrant root canal anatomy, a thorough chemo-mechanical preparation with a 3-dimensional obturation of C-shaped canals is essential to ensure a good long term prognosis.
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