Spiral computed tomographic evaluation and endodontic management of a maxillary canine with two canals.

Aberrations in the root canal system can pose a considerable challenge to the endodontist during root canal treatment. These anatomical variations are more commonly seen in maxillary molars and mandibular teeth, but only a few cases have been reported with alteration in the internal canal anatomy of maxillary canine. The present report describes the diagnosis of bilateral occurrence of two root canals in maxillary canines with single root and the endodontic management of the right maxillary canine with the aid of spiral computed tomography (CT). The CT images revealed the presence of Vertucci's type-III canal configuration in the right maxillary canine. The same canal pattern was found in the contra-lateral canine, which was absolutely healthy; and also all the mandibular anterior teeth and first premolars showed bifid canal pattern.

INTRODUCTION

The etiology of endodontic failure is multifaceted, but a significant percentage of failures are related to the lack of knowledge of pulp cavity anatomy and failure to negotiate and obturate the canal in its entirety.[123] The rate of failures after endodontic treatment as apical percolation because of incompletely obturated or a totally missed out canal.[3] These missed canals contain tissue, as well as microbiota and irritants, which inevitably contribute to failure of endodontic treatment.

From early work by Hess and Zurcher in 1925, to the more recent studies demonstrating the complex morphological variations of the root canal system, researchers have shown multiple orifices, fins, deltas, loops, accessory canals, and other variations in most teeth. Weine et al. (1969) observed that failures related to the mesiobuccal root of maxillary molars jeopardized the success of the endodontic treatment and found that teeth with a fourth canal occurred more frequently than those with three canals.[4] The incidence of two or three root canals in mandibular anterior teeth has been well documented, where 43% of cases had additional canals and the frequency of mandibular canines with two canals has been reported to be between 19.3% and 31.2%.[5] However, aberrations of maxillary canine are less frequently reported in the literature.

Maxillary canines are considered to be single-rooted, single-canalled teeth and two root canals in a permanent maxillary canine is a rare condition; but cases with two roots have been reported in the literature (Barkhordar and Nyugen, 1985;[5] Weisman, 2000[6]) and a case of endodontic retreatment of maxillary canine with a single root and two root canals was reported by Alapati et al. (2006).[7] A case report of type II canal in mandibular canine and a recent case report of similar canal configuration in a maxillary canine have also been reported.[89] All the previous case reports were based on the radiographic examinations of the teeth, both pre-operatively and post-operatively. The radiographic image is a 2-dimensional representation of a 3-dimensional object and an ideal method of precise determination of the root canal morphology of a tooth is serial sectioning of the tooth, which is impractical in clinical situations.[10] Therefore, other diagnostic methods like spiral computed tomography (CT),[101112131415] cone-beam CT,[11] peripheral quantitative CT,[11] 3D accuitomo XYZ slice view tomography[12] are useful in such conditions, to analyze the root canal morphology.

Although bilateral occurrence of bi-rooted canines has been reported in primary dentition, there is lack of literature regarding its pertinence in permanent dentition.[16171819] This case report describes the diagnosis of bilateral occurrence of two root canals in a single root of maxillary canines and the endodontic management of the right maxillary canine with the aid of spiral CT.

CASE REPORT

A 25-year-old, South-Indian female patient reported with the chief complaint of intermittent pain in the front right upper jaw region for the past 2 months, which had increased in intensity for the past 3 days. She also complained of food impaction in the same region for the past 1 year. The patient's medical history was non-contributory. On clinical examination, the patient's oral hygiene was moderate and there was a deep carious lesion in relation to the right maxillary canine, which was tender on percussion [Figure 1]. Electrical pulp testing and cold pulp testing elicited a delayed response. A pre-operative radiograph [Figure 2] was obtained, which revealed encroachment of pulp space by dental caries and there was widening of periodontal ligament space. On the basis of clinical and radiographic findings, a diagnosis of acute exacerbation of a chronic apical periodontitis was made. Hence, the tooth was prepared for non-surgical endodontic treatment. The patient received local anesthesia of 2% lignocaine with 1:80,000 epinephrine (Indoco remedies Ltd., Promoted by Warren pharmaceuticals, Goa, India). A rubber dam was placed, and a conventional endodontic access cavity was prepared in the right maxillary canine.

Figure 1

Preoperative view of right maxillary canine

Figure 2

Preoperative radiograph.

The pre-operative radiograph showed a thin layer of dentin in the middle-third of the canal, indicating that there were two separate canals in the body of the root. This followed the Vertucci's Type-III canal configuration (single canal leaving the access preparation, which divides into two within the body and re-unites to exit as one canal). Clinical view of the prepared access cavity portrayed the canals like premolars, where one was placed buccally and the other placed palatally [Figure 3]. The access cavity was sealed with a sterile cotton pellet and Coltosol (Coltene Whaledent, Switzerland). To confirm the unusual morphology and to search for any additional roots and root canals a spiral CT scanning was decided to be performed.

Figure 3

Clinical view of the right maxillary canine

CT scan was done with a multi-detector CT scanner taken at 16 slices/second, as per recommendations given by Diederichs et al. to reduce the radiation dosage (collimation, 1 mm; pitch, 2; tube voltage, 80 kV; tube current, 40 mA) and all the protective measures were taken to protect the patient from radiation.[18] 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 three planes. The CT images confirmed the radiographic findings of Vertucci's type-III canal configuration [Figures 4 and 5] and no additional canals or roots other than the two located canals. A striking feature was that the same canal configuration was found in the contra-lateral canine, which was absolutely healthy [Figure 4]; and also the mandibular central and lateral incisors, canine and the first premolars showed bifid canal pattern bilaterally. These findings can help the patient in the future because, at any point if the patient needs to undergo an endodontic procedure, these CT images can serve as an excellent guide to provide a quality endodontic treatment.

Figure 4

Sagittal view showing the bifid canal pattern (a) Right maxillary canine; (b) Left maxila canine; (c) Right mandibular canine

Figure 5

Axial view of maxilla (canal bifurcation is indicated with arrows) (a) Coronal third; (b) Middle third; (c) Apical third

At the next visit, the working lengths of each canal were estimated by means of an electronic apex locator (Root ZX; Morita, Tokyo, Japan) and then confirmed by a radiograph. The canals were initially instrumented with #15 nickel-titanium files (Dentsply Maillefer, Switzerland) under irrigation with 2.5% sodium hypochlorite (Prime Dental Products Pvt. Ltd, Thane, India). Coronal flaring was carried out by using Gates-Glidden drills (numbers 3 and 2; Mani. Inc, Japan). Both the canals were cleaned and prepared by hand nickel-titanium files with the conventional step-back technique. Calcium hydroxide intracanal medicament (Apexcal, Ivoclar, Vivadent, Liechtenstein) was placed in the root canal and the orifice was sealed with a sterile cotton pellet and Coltosol. One week later, calcium hydroxide was removed and the canals were obturated with zinc oxide – Eugenol sealer and laterally condensed gutta-percha points. After completion of root canal treatment, a final radiograph was taken to establish the quality of the obturation [Figure 6]. The tooth was restored with a visible light-cured composite (Ceram-X duo, Dentsply India Pvt ltd, Delhi, India) to build up the missing tooth structure. The adjacent lateral incisor, which was non vital, was also root canal treated and restored with light cured composite restoration.

Figure 6

Postoperative radiograph

DISCUSSION

Variations in root canal anatomy can pose a considerable challenge to endodontic diagnosis and treatment. A previously treated tooth with unusual root morphology may serve as an excellent reference to determine if that condition exists in the corresponding contralateral tooth currently being considered for therapy.[20] The prevalence of maxillary canine with bilateral occurrence of 2 canals is rare and the literature regarding its existence is scarce.[16171819] The present case report confirms the presence of two canals bilaterally, with the help of spiral CT [Figures 2 and 3] and also the current case had a Vertucci's type-III canal configuration, which has not been reported in the literature so far. Vertucci's classification was used for classification of the canal morphology as this is a standardized and a versatile method for categorizing known root canal anatomical variations.[15] Alapati et al.(2006) reported a case of endodontic retreatment with Vertucci's type-II canal configuration and cases have been reported with 2 roots previously but, all these cases were diagnosed and treated with the aid of an intra-oral periapical radiograph.[56789]

Conventional intra-oral periapical radiograph is an important diagnostic tool in endodontics for assessing the canal configuration when taken with different angulations.[15] Nevertheless, it is not a completely reliable diagnostic tool in analyzing complex root canal systems. The current report is one such case wherein we suspected a single canal initially, but ended finding two canals. In such doubtful cases, a radiograph cannot be considered to be foolproof because of its inherent limitations.[15] This paper highlights the role of Spiral CT as a prime analytical tool to ascertain root canal morphology. The applicability of CT to endodontics was studied by Tachibana and Matsumoto who suggested that this method allowed the observation of the morphology of the roots and root canals and the appearance of the tooth in every direction.[21] Moreover, the image could be analyzed, altered, and reconstructed by the computer to produce a rapid protyping model using stereolithiography or 3-D printing of the tooth;[22] which may serve as a physical guide to the endodontist to identify the presence of additional roots.

One of the major concerns regarding usage of CT in dentistry is radiation dosage. In the present study, guidelines by Diederichs et al. were used. With these guidelines, the effective radiation dosage was reduced to 0.56 ± 0.06 mGy, which is equivalent to a standard panoramic radiograph (0.59 ± 0.04 mGy).[23] The newly developed dental CT, the 3D aAccuitomo XYZ slice view tomography (J. Morita Mfg Co, Kyoto, Japan), which is called 3DX multi-image micro CT (3DX) in Japan, is excellent in generating an informative image database at a low irradiation dose.[11] The radiation dose was found to be as low as 0.006-0.012 mSv when using this technique, as compared to the effective dose of two periapical radiographs in the molar regions 0.01-0.02 mSv.[24]

Shape of pulp cavity is variable, making every treatment unique. Properly designed and prepared access cavities help the clinician to diagnose and negotiate the root canal morphology. In certain conditions the root canals might be left untreated during the endodontic therapy if the practitioner is unable to detect their presence. These undetected extra roots or root canals are a major reason for the failure.[7101215] Hence the ability to locate all the canals in the root canal system is an important factor in determining the eventual success of a case.

CONCLUSION

“Expect the Unexpected;” this is the scenario any endodontist can confront, as baffling cases like these do prevail. With the advent of latest technology like surgical operating microscope, magnification loupes, ophthalmic dyes, ultrasonic tips, CT, detection of extra canals has become easier and it is the responsibility of the clinician to utilize these tools and deliver a quality endodontic treatment, for ensuring optimal success.