|CLINICAL SCIENCE AND TECHNIQUES/CASE REPORT WITH DISCUSSION
|Year : 2014 | Volume
| Issue : 2 | Page : 126-129
Management of a mandibular molar with C-shape root canal using spiral computed tomography as a diagnostic aid
Niharika Jain1, Kabbur Thippanna Chandrashekar2, Abhishek Gupta3, Permanand G Makhija4
1 Departments of Conservative Dentistry and Endodontics, Hitkarni Dental College and Hospital, Jabalpur, Madhya Pradesh, India
2 Departments of Periodontics and Implantology, Hitkarni Dental College and Hospital, Jabalpur, Madhya Pradesh, India
3 Departments of Orthodontics and Dentofacial Orthopaedics, Hitkarni Dental College and Hospital, Jabalpur, Madhya Pradesh, India
4 Department of Orthodontics and Dentofacial Orthopaedics, Modern Dental College and Hospital, Indore, Madhya Pradesh, India
|Date of Web Publication||28-Oct-2014|
Kabbur Thippanna Chandrashekar
Department of Periodontics and Implantology, Hitkarini Dental College and Hospital, Dumna Hills, Jabalpur, Madhya Pradesh
Source of Support: None, Conflict of Interest: None
| Abstract|| |
The aim of this article is to present the use of spiral computed tomography (CT) in endodontic management of a mandibular molar with an unusual morphology of C-shape canal. An accurate assessment of this unusual morphology was made with the help of spiral CT. This report extends the range of known possible anatomical variations to include teeth with an abnormal number of roots and canals. This report also highlights the role of spiral CT, over conventional intra-oral periapical radiographs, as an objective method to confirm the three-dimensional anatomy of teeth.
Keywords: Computed tomography, C-shape canal, molar, root canal treatment
|How to cite this article:|
Jain N, Chandrashekar KT, Gupta A, Makhija PG. Management of a mandibular molar with C-shape root canal using spiral computed tomography as a diagnostic aid
. J Int Clin Dent Res Organ 2014;6:126-9
|How to cite this URL:|
Jain N, Chandrashekar KT, Gupta A, Makhija PG. Management of a mandibular molar with C-shape root canal using spiral computed tomography as a diagnostic aid
. J Int Clin Dent Res Organ [serial online] 2014 [cited 2019 May 20];6:126-9. Available from: http://www.jicdro.org/text.asp?2014/6/2/126/143504
| Introduction|| |
The success of endodontics revolves around knowledge, respect, and appreciation for root canal anatomy and careful, thoughtful, meticulously performed cleaning and shaping procedures. Knowledge of the pulpal anatomy, both the usual and unusual configurations and possible variations is critical for success in endodontics, and lack of such knowledge may lead to treatment failure.  Mandibular second molars are commonly more variable in shape than other molar teeth. One of the most important anatomic variations is the "C" configuration of the canal system. Cooke and Cox (1979) first described the clinical significance of C-shaped canals, which presents the clinician with an immense challenge.  C-shaped canals are most often found in mandibular second molars, though they can be found in mandibular first molars, maxillary molars, mandibular premolars, and maxillary laterals.
Review of literature
The preoperative awareness of a C-shaped canal configuration before treatment can facilitate effective management. The methods most commonly used in analyzing the root canal morphology, include placing files in the canals and shooting multiple radiographs, cutting the teeth at different levels, making polyester resin cast replicas of the pulp space,  canal staining and tooth clearing, ,, conventional radiographs, , digital and contrast medium - enhanced radiographic techniques, , radiographic assessment enhanced with contrast media, , and more recently computed tomographic techniques. ,
Vertucci, Alavi et al., Pineda and Kuttler considered the technique of canal staining and tooth clearing as the gold standard for assessment of root canal anatomy. ,, Weng et al. proposed a modification of this technique, which is more accurate, allows the appreciation of intricate details, and is nondestructive.  However, the biggest drawback with this technique is its invasive nature, preventing its used in vivo. Radiographic examination using conventional intra-oral periapical views is important for the evaluation of the canal configuration. Although, it has its inherent limitation to assess the root canal system completely. The radiographic image is a shadow and has the elusive qualities of all shadows.  Cooke and Cox stated that it was impossible to diagnose C-shaped canals on the preoperative radiograph.  Shearer, Wasti, Wilson (1996) used a water soluble radiopaque contrast medium in conventional periapical dental radiography for the diagnosis and evaluation of root canal systems, and reported this system as a valuable aid in the diagnosis and evaluation of root canal systems.  Gullickson and Montgomery studied root canal morphology using conventional radiographs and xeroradiography. The conventional radiographs were analyzed using a computerized digital image processing program.
Conventional multi-detector computed tomography (CT) imaging has been widely used in medicine since the 1970s and was introduced in the endodontic field in 1990 (10). Nance et al. used the tuned-aperture tomography system of imaging to identify root canal systems in extracted human molars.  The technique of dental CT, also called Dentascan, was developed by Schwarz et al. in 1987, primarily for evaluating the teeth, the jaws and surrounding hard tissue morphology, preevaluation of implant sites, buccolingual extend of cysts, tumors, periapical lesions, which creates images in three-dimensions.  Role of Dental CT in endodontics is still under emerging stages. Recently, cone beam CT imaging has been shown to provide comparable images at reduced dose and costs to be considered as an alternative to multi-detector CT imaging in endodontics.
This article highlights the diagnostic role of spiral CT in the assessment of variations of root canal morphology of a second mandibular molar and thus helpful in predicting the prognosis of a complex case.
| Case report|| |
A 28-year-old female patient reported to our department with a complaint of pain in the left lower back tooth region for the past week. She gave a history of intermittent pain for the past 2 months, and the tooth was tender on percussion. Radiographic examination of the tooth revealed a large carious lesion that was seen encroaching onto the pulp space in left mandibular second molar. Thickening of the periodontal space was also seen. Hence, a diagnosis of acute irreversible pulpitis was made in 37 and the tooth was prepared for endodontic therapy.
After adequate anesthesia (2% Lignox, Warren), the floor of the pulp chamber was observed detecting a C-shaped morphology [Figure 1]a. To ascertain the three-dimensional morphology of this tooth, dental imaging with the help of spiral CT was, therefore, planned. Informed consent from the patient was obtained. CT scan was done with a multi-detector CT scanner (16 slices/second), as per recommendations given by Christoph et al.  to reduce the radiation dosage (collimation, 1 mm; pitch, 2; tube voltage, 80 kV; tube current, 40 mA). Also, all the protective measures were taken to protect the patient from radiation. The scan reconstruction interval was 0.8 mm, resulting in 60-100 overlapping images. Axial images were transmitted to a commercially available dental program (Denta scan, Advantage Windows; General Electric, Buc, France) to reformat panoramic and cross-sectional images in all 3 planes. Slices of the molar were obtained at different levels to determine the canal morphology. CT scan slices revealed a C-shaped canal in the concerned tooth with 3 separate exits (Category III, subdivision III morphology; Melton's classification) [Figure 1]b, [Figure 1]c.
|Figure 1: (a) Clinical presentation of the access opening showing C-shape canal orifice (b) spiral computed tomography (CT) section at coronal third showing a complete C-shape canal (c) spiral CT section at middle third showing incomplete C-shape canal (d) clinical presentation of the obturated C-shaped canal (e) Postobturation radiograph (f) spiral CT section at apical third showing three separate canals|
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Working length was determined using an apex locator (Root ZX, J Morita, USA, Inc.). Cleaning and shaping was done with Protaper Ni-Ti rotary instrumentation (Dentsply Maillefer). Irrigation between each instrument was done using 2.5% sodium hypochlorite solution. Final irrigation with 17% EDTA was done and the root canal space was sealed using the thermoplasticized technique of obturation with Gutta-percha (Calamus Duo, Dentsply Maillefer) and AH-plus (Dentsply Maillefer) as a sealer [Figure 1]d, [Figure 1]e, [Figure 1]f. The tooth was then subsequently restored.
| Discussion|| |
C-shaped canal is so named for the cross-sectional morphology of the root and root canal. Instead of having several discrete orifices, the pulp chamber of the C-shaped canal is a single ribbon-shaped orifice with 180 ° 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.  Melton et al. proposed a classification of C-shaped canals: 
- Category I: Continuous C-shaped canal running from the pulp chamber to the apex.
- Category II: The semicolon-shaped (;) orifice with a main C-shaped canal and one mesial distinct canal.
- Category III: Two or more separate canals: Subdivision I, C-shaped orifice in the coronal third dividing into two or more separate canals that join apically; subdivision II, C-shaped orifice in the coronal third dividing into two or more separate canals in the midroot to the apex; and subdivision III, C-shaped orifice dividing into two or more separate canals in the coronal third to the apex.
Studies on mandibular second molars have shown a high incidence of C-shaped roots and canals in Asians, especially from the Far East. ,, In 1972, Pineda and Kuttler reported no C-shapes and no single-rooted mandibular second molar in a mesiodistal and buccolingual roentgenographic investigation.  Later in 1979, Cooke and Cox reported that 8% of the mandibular second molars treated had the C-shaped, although no total sample size was indicated. 
Yang et al. observed C-shaped roots in approximately 31.5% of mandibular second molars in Chinese population, using a clearing technique, but only one fifth of these teeth (7.4%) had C-shaped canal orifices.  Manning found only 10% with true C-shapes by rendering the roots transparent and observing canal system after black ink infiltration.  Sutalo et al. in 1998, injected methylene blue dye to the prepared teeth and showed the incidence of 12.5%, either total or partial C-configuration.  In 1999, Haddad et al. used radiography and clinical examined 94 mandibular second molars with scheduled endodontic treatment over a 1-year period in the Lebanese population, and indicated the incidence of 19.1%.  They also noted that true C-shaped canals with a single swath of the canal in mandibular second molars were the exception rather than the rule. Gulabivala et al.,reported the incidence of 22.4% in Burmese patients using canal staining and tooth clearing technique.  Simultaneously, Lambrianidis et al. evaluated the periapical radiographs of the patients and compared it with the clinical diagnosis stated on the patient's records and noted that 5% of treated teeth were C-shaped.  Later, in 2002 Gulabivala et al., used injection of Indian ink and noted the prevalence of 10% in Thai population.  At the same time, Al-Fouzan (indicated the incidence of 10.6% in the Saudi Arabian population.  They concluded that all patients showing category III configuration were <40 years of age. This is in contrast to the observation of Manning who reported that age-related deposition of dentine formed separate canals. (Manning also reported that category III [subdivision III] systems occurred most frequently, which is in agreement with Al-Fouzan).
By anatomic evaluation, Fan et al.  indicated that the majority of teeth with C-shaped canal system showed an orifice with an uninterrupted "C" configuration. 32% percent of the canals divided into the apical portion, most of which did so within 2 mm from the apex. The cross-sectional shape varied drastically along the length of the canal. The canal shape in middle and apical thirds of C-shaped canal systems could not be predicted on the basis of the shape at the orifice level. In addition, most orifices were found within 3 mm below the cementoenamel junction. In another study, by radiographic evaluation, they indicated that 30% of mandibular second molars showed type I radiographic image, 40% type II, and 30% type III. In the type I category, the C1 and C4 canal configurations were mostly found in the apical area. Categories C2 and C3 were the main configurations in the middle and apical areas in type II and III. The type III had more C2 canals in the middle area than type II. These results suggested that it was possible to predict the presence and the configuration of C-shaped canal system by the radiographic appearance.
Cimilli et al. observed C-shaped canals in 8% single rooted mandibular second molars by using spiral computed tomographic imaging.  Vertucci type I canals were most frequently seen in these C-shaped molars. Jin et al. reported the incidence of 44.5% by using serial axial CT images.  They observed that continuous C-shaped canal was the most frequently found, and the separated canal was the least.
Conventional intra-oral periapical radiographs are an important diagnostic tool in endodontics for assessing the canal configuration. Cooke and Cox stated that it was impossible to diagnose C-shaped canals on the preoperative radiograph.  Newer diagnostic methods such as spiral CT have been valuable in overcoming the disadvantages of conventional radiography and used for the evaluation of root canal morphology. Tachibana and Matsumoto studied the applicability of CT to endodontics.  They concluded that this method allowed the observation of the morphology of the root canals, the roots, and the appearance of the tooth in every direction. Spiral CT is a recent advance in CT technology. In this method, a three-dimensional data set is acquired and then reconstructed into images representing transverse sections of the object. Images can be easily reconstructed into different planes, especially if thin sections were initially obtained.  By this technique, contiguous 1 mm thick transaxial images of the dental structures can be obtained, with no possibility for missing dental structure and a significant increase in canal detection as compared with conventional radiograph.  In this study, we used spiral CT to evaluate C-shaped canal of single rooted mandibular second molar due to these technical advantages.
A major concern with the use of CT scan is its high radiation dosage. In the present study, guidelines by Christoph et al.  were used. With these guidelines, the effective radiation dosage produced by this method was 0.56 ± 0.06 mGy, which is equivalent to a standard panoramic radiograph.
| Conclusion|| |
A clinician should open his/her mind to the various possible canal morphologies and should not stick only to a limited and standard number of canal patterns. These undetected extra roots or root canals are a major reason for the failure. To avoid this, the endodontist must consider the judicious use of high-end diagnostic imaging techniques for successful management of complicated cases.
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