Management of a maxillary first molar having atypical anatomy of two roots diagnosed using cone beam computed tomography.

Most often, a clinician working on maxillary first molar when anticipates an aberration thinks of an extra canal but rarely does he preempt fewer canals. Maxillary first molar is a tooth, which has been extensively reviewed with respect to its external and internal morphology. Abundant literature related to its anatomy is available, but reports on incidence of two roots and two root canals in maxillary first molar are very limited. Here, a case of maxillary first molar is presented that had two roots: one palatal root with Type I canal configuration and one bulbous fused buccal root with Type V canal configuration; a unique root and canal configuration not seen in any of the earlier reported cases. Diagnosis of root canal aberrancy and subsequently, accurate management of the tooth was greatly facilitated by cone beam computed tomography (CBCT) scan. The relevance of CBCT in improving treatment prognosis is greatly emphasized in this report.

INTRODUCTION

Complete familiarity with external and internal anatomy of a tooth is highly important before initiating any root canal treatment. Further, thorough debridement, disinfection, and hermetic obturation of existing canal system are necessary prerequisites to accomplish success in endodontic therapy. A clinician's inability to recognize exact root canal anatomy, consequentially resulting in undiagnosed and subsequently nontreated canals has often been ascribed as one of the most common causes of endodontic failures. Amongst all teeth undergoing endodontic treatment; maxillary first molars owing to their complex root and canal morphology are often known to present with a high incidence of failures, mostly relating to nonidentification of the second mesiobuccal canal.

Several studies have utilized range of assessment methods such as magnification, radiography, dye infusion, clinical evaluation, sectioning, and microscopic observation to ascertain tooth morphology. Results have mainly revealed variations with respect to the number of roots and root canals in maxillary first molars.[1] More recently, cone beam computed tomography (CBCT) studies have also been conducted to establish the root canal anatomy more precisely.[23] Roots in maxillary first molar have shown to vary from a minimum one to a maximum four while canals have shown to vary from 1 to 7.[45] The predominant morphological variation reported in these teeth has been three roots and four canals: one palatal, one distal, and two mesiobuccal canals. Incidence of second mesiobuccal canal is seen to be quite high ranging from 18% to 96%.[1] Apart from this common variation, other less frequent variations have also been reported.

Studies and reports showing roots and canals fewer than three in number are not very frequent. Particularly, presence of two roots and two canals in maxillary first molar is very unusual. This variation is more likely to be seen in maxillary second molars. When a thorough search of literature was conducted, very few reports showing the presence of such anatomical variation were found. Canals in all these cases typically had a Vertucci Type I canal pattern. Here, we present a case of maxillary first molar having two roots with atypical canal configuration, which was successfully diagnosed and treated using CBCT as a diagnostic aid. The root canal configuration was quite uncharacteristic with Type V canal configuration in the fused buccal root and Type I canal configuration in the palatal root. We failed to find any previously reported description of permanent maxillary molar having such an anatomical description.

CASE REPORT

A 48-year-old male patient presented with chief complaint of pain in left maxillary posterior region for past several days. The patient started experiencing pain 3 months back but reported to the dentist only when it had increased in intensity and was not relieved by medication. The pain was continuous and moderate in intensity, which aggravated on consuming hot and cold food stuffs. Medical history was noncontributory. On clinical examination, left maxillary first and second molars were found to be carious. Tooth #26 seemed to be deeply carious while tooth #27 appeared to have moderate caries. None of the carious teeth showed any presence of pain on palpation or tenderness on percussion. Periodontal probing was within physiologic limits around both teeth. In tooth #26, tooth sensibility testing with electric pulp tester elicited an early response while on thermal pulp testing with heated Gutta-percha, a lingering intense response was seen. In tooth #27, pulp vitality responses were within normal limits. Preoperative radiograph of tooth #26 showed a disto-occlusal radiolucency in the crown approaching the pulp space with no widening of the periodontal ligament space and a normal periapical tissue. There seemed to be present only two roots, but the canal architecture was difficult to comprehend [Figure 1a]. Preoperative radiograph of tooth #27 [Figure 1a] showed moderate depth mesio-occlusal radiolucency extending into dentin. Based on all clinical and radiographic findings, a diagnosis of symptomatic irreversible pulpitis was established in tooth #26. Endodontic treatment was hence planned in tooth #26 while a simple restoration was indicated in tooth #27.

Figure 1

(a) Radiograph showing presence of two roots in maxillary right first molar, (b) clinical photograph showing two canal orifices at the ends of dentinal map, and (c) cone beam computed tomography axial image of 16 and 26 showing presence of two roots and two canals-Type V canal configuration in buccal root and Type I canal configuration in palatal root

Treatment was initiated after administering 2% lignocaine with 1:200,000 epinephrine to achieve local anesthesia. Under complete rubber dam isolation, tooth #27 was restored with composite resin while in tooth #26; access cavity was prepared using Endo Access Kit (Dentsply, Switzerland). Clinical examination of pulp chamber floor revealed the existence of only two canal orifices [Figure 1b]. One orifice was located toward the buccal and was larger when compared to the typically found buccal orifice in a maxillary first molar. The second orifice was located towards the palatal side. Thorough examination with a DG 16 endodontic explorer under ×2.5 magnification using dental loupes (Daray, Derbyshire) failed to reveal any additional orifices. Moreover, the dentinal map also suggested presence of two canals. Angulated radiographs with 20° horizontal angulation were additionally shot but did not add to any diagnostic detail. Since the buccal root was quite bulbous, and the canal outline was not very discrete in the apical portion of the root, need was felt to use CBCT scan to ascertain the presence of any aberration in the canal architecture.

A multislice CBCT scan (Next Generation i-CAT, Imaging Sciences International, Hatfield, PA, USA) of the maxillofacial region was undertaken with exposure parameters of 120 kV and 5.0 mA. An ultra-low radiation dose scan was done using a focused field of view. The images were reconstructed in increments of 0.2 mm thickness. CBCT scanning provided valuable information with respect to canal configuration. In the CBCT images, Type V (1–2) canal configuration was observed in the fused buccal root while Type I canal configuration was observed in the palatal root of tooth #26 [Figure 1c]. On the contralateral side, tooth #16 similarly possessed two roots, which was confirmed radiographically and with CBCT [Figure 2a]. The canal pattern was also found to be identical.

Figure 2

Radiographs of (a) left maxillary first molar showing identical two rooted anatomy, (b) working length determination, (c) obturation in maxillary first molar, and (d) sound periradicular architecture at 1-year

On subsequent visit, taking into account the available information, the coronal third of root canal was enlarged using Gates Glidden burs (Nos 1-3, Dentsply, Maillefer, Switzerland) to facilitate access to the two apical divisions of buccal root canal. When careful exploration of the buccal canal was performed using pathfinder files, it was possible to negotiate the two divisions of the canal. Working length of each canal was determined using electronic apex locator (Root ZX, J Morita Mfg. Corp., Japan) and confirmed radiographically [Figure 2b]. The canals were cleaned and shaped using manual ProTaper nickel-titanium instruments (Dentsply Maillefer) using crown down technique (Dentsply, Maillefer, Switzerland) under copious irrigation with 2.5% NaOCl and 17% EDTA. After the canals were properly dried using paper points, calcium hydroxide (Metapex, Meta Biomed Co. Ltd., Korea) intracanal dressing was placed and access cavity provisionally sealed with IRM (Caulk, Dentsply, USA). On recall appointment at 1-week, the patient was completely asymptomatic. Root canals were obturated with Gutta-percha (Dentsply, Maillefer, Switzerland) using cold lateral compaction technique and AH Plus resin as a sealer (Dentsply, De Trey, Germany) [Figure 2c]. The access cavity was permanently restored with resin composite and the patient recalled at 1-year for follow-up. At recall appointment, the patient continued to be asymptomatic, and radiograph showed a sound periapex [Figure 2d].

DISCUSSION

Needless to say, success in any endodontic treatment relies on a clinician's sound scientific knowledge, accurate diagnosis and precise clinical skills. Understanding and determining the complex root and canal morphology, as well as debriding and filling the canal in entirety are instrumental in improving outcomes of any root canal procedure. Maxillary first molar belongs to a group of teeth which is known to have three separate roots – two buccal and one palatal. Most studies have reported the existence of this classic three root morphology in maxillary first molars to range from 97.6% to 100% and two root configurations to range from 0% to 2.4%.[367] Neelakantan et al. in their CBCT investigation conducted on maxillary first molars in an Indian population also concluded with similar findings.[2] They established that the most predominant root morphology in maxillary first molars was the three root morphology (96.8%) while root configurations other than this were found to be very low (3.1%). Reported incidence of one, two, and four separate roots was found to be 0.9%, 1.3%, and 0.9%, respectively. When root canal configuration is considered, three rooted maxillary first molars are known to present chiefly with three or four canals; the fourth canal in most cases being the second mesiobuccal canal.

Existence of two roots and two canals is quite uncharacteristic of a maxillary first molar. Fusion of roots may take place between mesiobuccal and distobuccal roots, mesiobuccal and palatal roots or distobuccal and palatal roots. Buccal root fusion, as was seen in our case, is known to have a reported incidence of only 1.6%.[3] When a thorough search of literature using PubMed was conducted, only a few case reports showing the unusual anatomy of two roots: one buccal and one palatal, in a maxillary first molar, were found. These cases along with the details of their canal system are summarized in Table 1.[8910111213] In all these teeth, primary canal pattern evident in each of the two roots was Vertucci's Type 1 canal configuration. Type IV canal configuration was also elicited though less frequently in the fused buccal roots of a maxillary first molar. None of the reported literature has shown the presence of Type V (1-2) canal configuration, which was existent in our case and diagnosed using CBCT scan.

Table 1

Case reports showing unusual anatomy of maxillary first molar having one buccal root and one palatal root along with details of their canal system

Failure to locate and cleanse the entire canal system during root canal treatment can result in persistent viable microbes, which in communication with the periapical tissues can result in the perpetuation of complaint or pathology. It is therefore highly critical to recognize any variations in root canal morphology prior to performing a root canal procedure as it alerts the clinician while locating and negotiating the canals, thereby minimizing procedural errors. Recently, CBCT, an advanced three-dimensional imaging modality is showing diverse applications in dentistry especially endodontics relating to diagnosis, planning, and several treatment procedures. CBCT is known to overcome significantly the limitations and errors of interpretation often associated with two-dimensional radiographs. Matherne et al. in their study compared CBCT scanning in identifying root canal systems with images obtained using digital radiography.[14] They concluded that CBCT images resulted in identifying a greater number of root canal systems. The potential applications of CBCT in improving final outcomes of an endodontic treatment are beyond doubt very promising.

In our case, maxillary first molar had a buccal root, which was broad and nontapering. Its radiographic impression did suggest some abnormal canal architecture but was non confirmatory. Additional use of CBCT scanning greatly aided in determining the tooth morphology more perfectly and precisely. Prior knowledge of the exact root canal anatomy helped in accurately detecting and preparing the existent canal system, thereby improving the effectiveness and predictability of root canal treatment in 26. Particularly in Type V canals, where one root canal leaves the pulp chamber and divides short of the apex into two separate and distinct canals with independent apical foramina, it becomes highly essential to negotiate both divisions so as to remove all infectious debris and close all communications with the periapex, thus ensuring successful management.

Furthermore, rarer the anatomic aberration, more probable is its bilateral occurrence.[15] The impression of bilateral presentation was confirmed in this case when CBCT axial images of contralateral 16 similarly showed the existence of one fused buccal root, one palatal root, and two canals. The root and canal configuration in both teeth were similar except that the level of bifurcation in buccal canal seemed to be more coronal in tooth #16 compared to tooth #26 [Figure 1c].

Follow-up radiograph of tooth #26 at 1-year showed resolution of periapical radiolucency and a healthy periradicular architecture. The key role played by CBCT in identifying unusual canal morphology and successfully managing the aberrancy cannot be underestimated here.

CONCLUSION

Even if infrequent, a clinician should always be prepared to encounter any aberrant morphology when undertaking endodontic treatment. One should not hesitate to use advanced diagnostic modalities like CBCT for identifying root and canal aberrations in order to ascertain favorable root canal treatment outcomes while respecting the challenges of pulp space anatomy.