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The main aim of any endodontic treatment is to thoroughly debride and disinfect the root canal system followed by the contouring of root canal walls and apical tip, for the purpose of sealing the root canal completely with a condensed, inert filling material. Failure to acknowledge the presence of an additional root canal during an endodontic treatment is amongst the major causes of an endodontic treatment failure. Other causes include inappropriate canal instrumentation, incomplete obturation and untreated major canals.
An important key to success of any root canal treatment is proper understanding of the anatomy of root canal system this can be achieved by knowledge of the morphology of the root and root canal systems of teeth and diagnostic imaging techniques are required for successful root canal treatment, especially in mandibular premolar teeth (England et al. 1991). In-depth knowledge about the occurrence of atypical external and internal root canal morphologies contributes to the success of root canal treatment.
It has been indicated by slowey that due to the variations in the root canal anatomy of mandibular premolars, they have a high flare up and failure rate and are hence the most difficult teeth to treat. Both the mandibular first and second premolars most often have a single root and a single canal, however, anomalies of the root and root canal systems as well as multiple canals have been reported in the literature (Baisden et al. 1992, Robinson et al. 2002).4
Zillich and Dowson have, in a definitive anatomical study, unveiled the occurrence of three canals in mandibular second premolars to be 0.4%.5
The mandibular first premolars show a large variation in the occurrence of number of root canals and apical foramina. Data from anatomical studies report that three rooted mandibular first premolars are rare, about 0.2%.6
This case report presents a case of a successful nonsurgical endodontic management of a mandibular first premolar with three separate roots using Cone Beam Computed Tomography (CBCT).
A twenty four year old female patient of Indian origin, with the chief complaint of intermittent pain along with food lodgement in the lower left back region of jaw since 3 months, was referred to the Post Graduate Department of Conservative Dentistry and Endodontics. Patient also complained of bleeding from gums while brushing since eight months. Medical and dental history was non-contributory.
On clinical examination, patient’s oral hygiene was found to be moderate. Deep occlusal carious lesion was seen with respect to tooth # 34 and 35 and both the teeth were found to be tender on percussion, with no associated periodontal pockets. Neither the affected nor the contralateral side of the crown of the mandibular first premolar showed any unusual anatomy in terms of number of cusps and dimensions. A lingering response was seen on heat testing and electric pulp testing. No evidence of swelling or sinus tract was seen.
Intra oral periapical radiographic evaluation of the involved tooth revealed normal mandibular first premolar root anatomy. There was widening of the periodontal ligament space with periapical radiolucency around the root of tooth #34.
A diagnosis of irreversible pulpitis was made based on clinical and radiographic evidences.
After the administration of local anesthesia (2% Lidocaine with1:80,000 adrenaline), access was gained to the pulp chamber under isolation and conventional access opening was done to locate the canal. Tactile examination of the walls of the major canals was done with a small precurved pathfinder file, while locating the canal, which was proceeded slowly down each wall of the major canal, probing for a catch. A slight catch may indicate the orifice of an additional canal, especially in case of the buccal and lingual walls, because these are not generally visible on the radiograph. . On thorough inspection of the pulp chamber floor, three separate root canal orifices were detected (one mesiobuccal, one mesiolingual, and one distal). With the help of a pathfinder file, access cavity was temporarily sealed with Cavit, and to confirm the root morphology, the patient was referred to an oral and maxillofacial radiologist for a cone-beam computed tomography. CBCT of the mandible was performed using the CS 3D imaging, after obtaining an informed consent of the patient. A three-dimensional image of the mandible was obtained. The involved tooth was focused, and the morphology was obtained in transverse, axial, and sagittal sections with a thickness of 0.48 mm, along with three-dimensional reconstructed images.
The axial image obtained from CBCT confirmed the presence of three roots in mandibular first pre molar # 34. The roots were found to be mesiobuccal, mesiolingual and distal .
After re-isolating the tooth, coronal flaring of all the three canals was carried out using Gates Glidden drills and working length was determined using an apex locator, which was later confirmed by a radiograph. The canals were cleaned and shaped up to ISO #35 masterapical file under copious irrigation with 2.5% sodium hypochlorite and 17% EDTA. The root canals were dried with sterile paper points, followed by temporary sealing of the access cavity with Cavit (3M ESPE AG, Seefeld, Germany). The patient was re-scheduled a week after for follow up. The tooth was found to be completely asymptomatic after a week, and the roots canals were obturated by cold lateral compaction of gutta-percha using AH26 sealer (Kemdent; Associated Dental Products Ltd, Wiltshire, UK). A postoperative radiograph was taken (Figure 3B), and the access cavity was permanently restored using universal amalgam restorative material.
Diagnosis and management of extra roots and root canals in mandibular premolars is one of the major challenges in endodontics. 8-18 Therefore, the clinician must have an appropriate knowledge about the normal root canal anatomy and the most common variations associated. Inability to find, debride and obturate a root canal has been reported to be a major reason for failures in endodontic treatment. 19Based on race, only one study by Trope et al. has showed an increased prevalence of two or more canals in mandibular first premolar in African American patients as compared to Caucasian American patients .20 The failure rate in mandibular first premolar was shown to be 11.45% according to the Washington study. 21This might be due to the extreme variations in the root canal morphology of the mandibular premolar teeth and therefore poses an endodontic challenge to the clinician. Considering the high prevalence of aberrations in these teeth, an endodontist must suspect the presence of one or more missed canals, when a patient returns with persistent post-operative pain or sensitivity to hot and cold. Judicious use of high-end diagnostic aids should also be considered in such cases. Radiographs obtain two-dimensional images of three dimensional objects, resulting in superimposition of the images. Therefore, they are of limited use in complex root canal anatomy cases.
Interpretation based on a two-dimensional radiograph may circumspect the clinician of the presence of aberrant root canal anatomy but cannot completely show the morphological structure of the root canals and their interrelations .22 Based on the results of previous studies carried out by Kottoor et al., and La et al. wherein spiral CT was used for the confirmatory diagnosis of morphological aberrations in the root canal anatomy, CBCT of the involved tooth was planned in the present case .23-25
The 3D CBCT images in this study revealed three roots (mesiobuccal, mesiolingual and distal ), with three distinct canals, each canal having a separate apical orifice as compared to the two dimensional radiograph which showed only one root, just like the anatomy of a typical single-rooted mandibular first premolar, that led to a false diagnosis and treatment plan. This is probably why the mandibular first premolar is known as an “enigma” to the endodontist. However, the high cost and inaccessibility to the patient as well as the extra radiations as compared to the standard radiographic methods makes its routine use limited.
We can therefore conclude that a thorough knowledge of the root canal anatomy and its variations, careful interpretation of the radiographs, close clinical examination of the floor of the chamber and proper techniques of access opening along with adequate magnification are essential for successful treatment outcome.
The mandibular premolar teeth can present with extremely complex root and root canal system morphology, and if not considered during treatment can lead to difficulties when performing root canal treatment. The use of 3D CBCT is a valuable tool in studying the variations that may occur in root canal anatomy.
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