Cone beam computed tomography evaluation and endodontic management of permanent mandibular second molar with four roots: A rare case report and literature review.

The morphological variation in the number of roots and root canals, especially in multi-rooted teeth is a constant challenge for diagnosis and successful endodontic therapy. Knowledge of the most common anatomic characteristics and their possible variations is fundamental. Although, endodontic management of four-rooted mandibular first molars have been observed on a few occasions in the literature, to the best of our knowledge four-rooted mandibular second molars having two mesial and two distal roots have not been reported. This paper highlights endodontic management of mandibular second molar with four roots (two mesial and two distal) with one canal in each root and its cone beam computed tomography (CBCT) evaluation which was primarily done for post treatment assessment for diagnosing post-endodontic complications, at the same time confirmed our radiographic diagnosis of this variation. This also helped us portraying the anatomy of this rare variation.

INTRODUCTION

The intent of endodontic therapy is the chemo-mechanical cleansing of the root canal system, so as to remove all soft tissue debris from the interior of the tooth and its hermetical obturation with an inert material. The main reasons for endodontic failure are apical percolation, incomplete canal obturation and the presence of untreated canals. Thus, a thorough knowledge of root and root-canal morphology and a good anticipation of their possible morphological variations will help to reduce the endodontic failure caused by incomplete debridement and obturation.[1] With the availability of CBCT, new vistas have been opened in the non-invasive evaluation of root-canal morphology and also for post treatment assessment and prognosis. Herein, we present endodontic management and CBCT evaluation of a patient having four-rooted mandibular second molar (two mesial and two distal roots) with a brief review of literature. To the best of our knowledge, such variations in the morphology have not been reported in the literature so far.

CASE REPORT

A 67-year old male patient referred to our department presented with a chief complaint of having pain in lower left back tooth region since one month. On clinical and radiographic examination, a diagnosis of symptomatic irreversible pulpitis; symptomatic apical periodontitis in relation to tooth 37 (lower left mandibular second molar) was made and endodontic therapy was planned.

On preoperative radiographic evaluation of the involved tooth vague outline of the roots, radiopacities adjacent to the root of the multi-rooted tooth, presence of twin periodontal ligament outline of the roots revealed presence of supernumerary roots [Figure 1a]. Following local anesthesia administration, the tooth was isolated under rubber dam and access cavity preparation was done with endo access bur. Exploration of pulp chamber floor using DG 16 explorer revealed four distinct orifices: Mesiobuccal (MBR), mesiolingual (MLR), distobuccal (DBR), distolingual (DLR) [Figure 1b]. The naming for the canals in this case report is based on new anatomically based nomenclature system proposed by Denzil Valerian Albuquerque et al.,[2] this nomenclature has been used since it helps us to understand the variation of roots in relation with the root canals unlike other nomenclature system which considers only the variation in the root canal morphology without giving any consideration to the number of roots and its relation with root canals. Working length was determined [Figure 1c] three radiographs with different angulations was taken. Interpretation of these off angle radiographs revealed presence of four roots. Biomechanical preparation was performed with crown-down technique using NiTi rotary endodontic instruments (Protaper™, Dentsply). Apical canal size was prepared until size F2 for all the canals. Master cone selection was performed. All the root canals were obturated using zinc oxide eugenol sealer and Gutta-percha points (Protaper Gutta Percha™, Dentsply) and access was restored with dental amalgam. Post operative radiograph was taken. [Figure 2a and b].

Figure 1

(a) Preoperative radiographs, (b) access cavity preparation with orifice naming irt to the root based on new nomenclature, (c) working length determination

Figure 2

(a) Post-op radiograph, (b) 3D reconstruction of tooth #37

Following the endodontic therapy, pain did not subside and patient complained of pain. Therefore, for determination of appropriate treatment, to rule out post endodontic complications, for detection of missed canals, perforations and prognosis CBCT (PLANMECA Promax 3D) was planned. Informed consent was obtained from the patient. After determining the region of interest (ROI), field of view was decreased which also reduces patient radiation dose and small volume CBCT in relation to tooth 37 was performed. But CBCT images (PLANMECA Romexis Viewer) did not reveal any of these complications and also confirmed our clinical and radiographic diagnosis of four rooted mandibular second molar.

Axial views of the tooth were obtained at three different levels of the root

At cervical third level: Three axial slices were obtained of 1 mm thickness. On evaluation all the four roots seemed to be fused at this level. (9 mm from the apex-Figure 3a)

Figure 3

CBCT images axial slices (a) cervical third level, (b) middle third, (c) apical third

At middle third level: Three axial slices were obtained of 1 mm thickness. Axial slice at this level revealed fusion of two distal roots and two distinct mesial roots. (6 mm from the apex-Figure 3b)

At apical third level: Three axial slices were obtained of 1 mm thickness. Axial slice at a distance of 3 mm from the apex revealed four distinct roots. (3 mm from the apex-Figure 3c)

Thus CBCT data and their three dimensional reconstruction image [Figure 2b] confirmed our radiographic understanding of presence of four roots each with one canal- MBR, MLR, DBR, DLR. On further evaluation of the CBCT, obturation material was confined within all the root canals seen as — radiopaque filling material in all the four canals, also there was no sign of perforation at any level and sagittal slices did not reveal any missed canals, it also revealed among the four roots Mesio-lingual was the longest root which was longer by 1 mm.

Since source of pain in the present case cannot be attributed to dental origin. The patient was referred to his family physician for identification of origin of pain. Following complete medical work-up, the patient was diagnosed with chronic otitis media and was managed for the same followed by resolution of patient complaint.

DISCUSSION

Morphologically mandibular second molar resembles mandibular first molar except that the roots of the former are shorter, more curved and also show great number of atypias. According to study by Prasanna Neelakantan et al., most of the mandibular second molars had two separate roots (87.8%) with three canals.[3] Manning reported that out of 149 extracted mandibular second molar 22% had single roots, 76% had two roots and 2% had three roots.[4] Costa Rocha et al., in analysis of morphology of mandibular second molar showed that, out of 628 extracted mandibular first and second molars 84.1% had two separate roots, 15.9% had fused roots and 1.5% had three roots.[5]

Ferraz and Pecora et al reported racial variations of the mandibular second molar and showed that the incidence of three rooted mandibular second molars was 2.8% in Mongoloid origin, 1.8% of Negro origin and 1.7% of Caucasian origin patients.[6] Maggiore et al., also reported that the roots of mandibular second molar can vary from one to three roots.[7] Gulabivala et al., reported out of 60 mandibular second molar 10% had single C-shaped roots whilst the rest had two roots.[8]

In a recent review article, study was performed related to variations in roots and root canal morphology of permanent mandibular first molar and they found that the incidence of three rooted mandibular first molar was 3%-33%.[9] Kottor et al., described anatomical variation of four roots in a mandibular permanent first molar which was diagnosed using multiple angulated preoperative radiographs which was the third case to report with four rooted mandibular first molar however first case to report two mesial and two distal roots in mandibular first molar.[10] Recently, Aamir Rashid Purra et al., presented a case of four roots (three mesial roots and one distal root) in mandibular second molar though it was four rooted three out of four were mesial roots and one distal[11] unlike present case which is the second case to report four rooted mandibular second molar however first to report two mesial and two distal roots in a four rooted mandibular second molar.

Occurrence of extra roots in primary teeth have also been reported. Recently published case reported presence of four separate roots and four canals in retained primary maxillary second molar.[12] Occurrence of extra roots is lower in primary teeth as compared with permanent dentition.[13]

Dental radiographic evaluation is a fundamental tool for endodontic diagnosis. Conventional intraoral periapical radiographs are routinely employed to evaluate the root canal anatomy. The examination of X-rays made from various angles and the clinical assessment of the internal anatomy of teeth is very important. In all the cases when the initial X-ray image shows an unusual anatomical structure it is recommended to take additional radiographs of mesial or distal angulation.[14] Present case also was diagnosed and treated according to the clinical and conventional intraoral periapical interpretations. But following endodontic therapy pain did not subside, patient complained of pain. Therefore, for the determination of appropriate treatment and prognosis CBCT was planned to rule out post endodontic complication. But on evaluation of the scanned images there was no sign of any of post endodontic complication. Same time CBCT data and their three dimensional reconstruction image [Figure 2b] confirmed our clinical and radiographic understanding of presence of four roots each with one canal. This case report is the first to report endodontic management in a four rooted mandibular second molar (two mesial and two distal) and its evaluation using CBCT Scan.

CONCLUSION

Successful endodontic treatment begins with proper clinical and radiographic examinations. A practitioner must be vigilant, as variations of root and canal anatomy might be encountered at any time during treatment. This paper may intensify the complexity of mandibular second molar variation and is intended to reinforce clinicians’ awareness of the variable morphology of root canals. At the present time, CBCT is considered a complementary modality for specific applications rather than a replacement for 2-D imaging modalities. This present case diagnosis and endodontic management of mandibular second molar with four roots was made on thorough clinical and radiographic interpretation, CBCT was planned only for the evaluation of source of pain which persisted following endodontic therapy.