Type I canal configuration in a single rooted maxillary first molar diagnosed with an aid of cone beam computed tomographic technique: A rare case report.

Anatomic variations in maxillary molars are frequent. These deviations are also one of the major cause for endodontic treatment failure owing to inadequate cleaning, shaping and sealing of root canal system. Diagnosis of such aberrations using newer imaging techniques like cone beam computed tomography is firmly advocated. The present paper highlights the root canal treatment of a rare case of type I canal morphology diagnosed with an aid of cone beam computed tomographic technique.

INTRODUCTION

Adequate cleaning, shaping and obturation of the root canal system are keys to long-term endodontic success. It is absolutely essential to visualize the pulp chamber in three dimensions to facilitate successful access cavity preparations, thereby providing unimpeded access to the apical foramen. This is especially critical in teeth with aberrant morphology.

Morphologic variations in permanent maxillary molars that have been frequently reported pertain to the presence of additional roots, canals or fused roots[12] and “C”- shaped canal.[3] The occurrence of a single root in the maxillary molar is rare, and even rarer in case of permanent maxillary first molar.[456] A case of single root in the deciduous maxillary first molar is also reported.[7]

In the light of the above context, the present paper highlights the diagnosis and treatment of a relatively rare case of single rooted permanent maxillary first molar with type I root canal configuration.

CASE REPORT

A 25-year-old male patient reported to the Department of Conservative Dentistry and Endodontics with the chief complaint of severe pain in the left upper back region of the mouth since 3 days. Pain was continuous and aggravated with the intake of hot and cold beverages. Clinical examination revealed deep mesial caries approximating pulp with respect to tooth # 26. The tooth was not tender to percussion and palpation. Pulp vitality testing using an electric pulp tester (Parkell, Farmingdale, NY, USA) showed exaggerated response lasting for several minutes. Further, the maxillary lateral incisors were missing and the deciduous right maxillary first molar was overretained. Intraoral periapical radiograph of tooth # 26 revealed deep caries involving the pulp space [Figure 1a]. Also, a single root with single canal was seen in relation to 26 and 27. Based on the clinical and radiographic findings, the diagnosis of acute irreversible pulpitis was made and patient was advised root canal treatment in relation to tooth # 26. After obtaining patient's consent, an emergency pulpotomy was performed at the same visit under local anesthesia. In order to confirm the apparent finding of the IOPA radiograph, the patient was referred for CBCT imaging of tooth 26 with 3D reconstruction. The results of the CBCT showed the presence of a single root with the Vertucci's type I canal configuration,[8] and the same was observed for tooth 27 [Figure 2]. Thereafter, the root canal treatment was initiated. The tooth was isolated using rubber dam and access preparation was modified to completely de-roof the pulp chamber, which showed the presence of a single wide root canal orifice. Working length was calculated using an electronic apex locator (Root ZX II™, Morrita, Tokyo, Japan) as well as the radiographic method. Working length radiograph also suggested positioning of endodontic files in a single canal [Figure 1b]. The coronal shaping was carried out using Gates Glidden burs (Dentsply, New Delhi, India) in crown down manner followed by step back technique with an apical enlargement up to size 55 K file (Dentsply) along with copious irrigation with 5% sodium hypochlorite solution. The canal was finally rinsed with 17% EDTA solution and dried with absorbent paper points (Dentsply, New Delhi, India). The root canal was obturated using a resin-based endodontic sealer (AH PLUS™; Dentsply) and laterally condensed gutta percha followed by restoration of access preparation with silver amalgam. Posttreatment radiograph showed the adequate sealing of the root canal system and the patient was asymptomatic [Figure 1c]. The patient was advised complete coverage restoration and referred to the Department of Prosthodontics for the same.

Figure 1

(a) Preoperative radiograph, (b) working length radiograph and (c) posttreatment radiograph

Figure 2

CBCT image showing various tomographic views at the middle third root level of #26. (a) Axial view shows single root as well as canal in # 26, (b) cross-sectional view showing the presence of single root and canal, (c) panoramic view again showing the single root and canal in # 26 (also note the missing maxillary lateral incisors and presence of retained deciduous maxillary molar on the right side) and (d) three-dimensional reconstruction image showing the single root throughout the root length

DISCUSSION

Routine preoperative intraoral periapical radiographs are essential before initiating endodontic treatment due to its usefulness in identifying variations from the normal, thereby influencing the treatment plan. In specific instances, it may be helpful to supplement with periapical radiographs taken at varying horizontal angulations. However, because the radiographs have several inherent shortcomings due to it being a two-dimensional image of a three-dimensional object, erroneous interpretations are very much possible due to the superimposition of multiple anatomic structures questioning its reliability. Recent imaging tools like spiral CT and CBCT have emerged as valuable tools in the field of endodontics due to its accuracy, reliability and three-dimensional imaging capabilities. In CBCT, a cone-shaped beam rotates 360° around the patient to obtain a volume and captures the image in the form of three-dimensional isotropic voxels. These multiple voxels are further combined with the help of viewing software and a 3D image is reconstructed.[9] Its uses in endodontics include identifying dental anatomic variations such as additional roots and/or canals, fused roots, identification of horizontal/vertical fracture line in the tooth root and management of internal and external resorptive defects.[10] Moreover, it helps to avoid overzealous removal of tooth tissue during access preparation and exploration of root canal orifices.

Presence of extra canal is more frequent rather than the presence of fused/less number of canals, especially in the cases of permanent maxillary first molars. Immense disparity in the root/root canal morphology of permanent maxillary molars of Indian origin exists as compared with Caucasian and Mongoloid traits, as reported in a computed tomographic research. The variations reported in the population were the presence of single root and canal, two separate roots, two fused roots, three fused roots and four separate roots.[11] Also, the incidence of single root in the maxillary first molar in the Korean population has been found to be 0.25% in a recent computed tomographic research.[12]

In the present case, several possibilities needed to be ruled out. The first possibility was that the bilateral maxillary first molars were congenitally absent and the tooth in question was maxillary second molar. However, the likelihood of this being the case was ruled out considering the positioning of tooth in the arch vis-a-vis the radiographic anatomic landmarks such as the location of the maxillary sinus and the zygomatic arch. Also, axial inclination of the tooth and lack of tilt precluded the possibility of migration of the maxillary second molar into the position of the maxillary first molar.

Detailed analysis of the 3D reconstruction image at the cervical, middle and apical regions of the root excludes the possibility of multiple fused roots due to the lack of external root eminences on the buccal aspect. Moreover, there is absolutely no indication of any pulp canal space other than the one that is well centered within the confines of the root. Thus, it is safe to assume that the tooth in question is definitely maxillary first molar with single root and canal.

To conclude, the present case highlights the need to develop excellent observation skills on the part of the operator to identify any aberrations from the normal within the tooth, possibly with the use of advance imaging techniques, especially in the presence of anomalies in dentition.