Four cuspal maxillary second premolar with single root and three root canals: Case report.

Traditional configuration of maxillary second premolars has been described to have two cusps, one root and one or two root canals. The endodontic literature reports considerable anatomic aberrations in the root canal morphology of maxillary second premolar but the literature available on the variation in cuspal anatomy and its relationship to the root canal anatomy is sparse. The purpose of this clinical report was to describe the root and root canal configuration of a maxillary second premolar with four cusps.

INTRODUCTION

The visualization of the internal anatomy of teeth and a thorough knowledge of the root canal anatomy and its variations form the fundamental basis for a successful endodontic therapy.[1] In endodontic literature, the standard anatomy of maxillary second premolar has been described to have two cusps[2] (Buccal-B and Palatal-P), one root and one or two canals (B and P).[3] Unlike most studies on anatomical variations of maxillary second premolars that deal with aberrations only in its root canal configuration, the purpose of this case report is to focus on the “macroscopic” anatomic aberration in addition to the root canal configuration. This case report describes the diagnosis of a rare anatomical variation in maxillary second premolar with four cusps. Cone-beam computed tomography (CBCT) analysis was performed to confirm the root canal configuration.

CASE REPORT

A 23-year-old male patient reported to the Department of Conservative Dentistry and Endodontics, Subharti Dental College and Hospital, Meerut with a chief complaint of decay and food lodgment in relation to his upper left back teeth region for a few months. He also complained of periodic episodes of pain. The pain was mild in intensity, nonradiating, spontaneous in nature, subsided after a short period, and did not require analgesics. Clinical examination of that quadrant revealed deep dentinal caries in relation to the maxillary left first molar. Radiographic examination in relation to the same tooth revealed a coronal radiolucency involving enamel, dentin and pulp, suggestive of caries involving pulp, but there were no signs of any periapical pathology. Based on clinical and radiographic features, a diagnosis of asymptomatic irreversible pulpitis was established, and endodontic treatment was planned.

An atypical anatomy of maxillary left second premolar was also noted on clinical examination. The premolar was rotated distopalataly and presented with four cusps; Buccal (B), Palatal (P) and two accessory cusps termed mesiobuccal accessory cusp and distobuccal accessory cusp (DBAC) [Figure 1]. The term “accessory” has been used to denote that the cusps are lobe-like structures present solely on the buccal surface and not on the occlusal surface per se.

Figure 1

Atypical anatomy of maxillary left second premolar showing four cusps

The intraoral periapical (IOPA) radiograph of the same tooth showed an atypical anatomy of this premolar owing to overlapping of mesiobuccal accessory canal (MBA) cusp, DBA cusp and the B cusp [Figure 2a]. CBCT analysis was done to determine the root canal morphology of this four cuspal premolar. The patient was poorly motivated and did not want any dental treatment to be done.

Figure 2

Representative images of 25 (a) intraoral periapical radiograph, (b) cone beam computed tomography-axial section; 5 mm coronal to cemento-enamel junction (c to f) cone beam computed tomography-axial sections; from cemento-enamel junction to middle third of the root, (g) cone beam computed tomography-coronal section, (h) cone beam computed tomography-sagittal section

Cone beam computed tomography analysis

Axial sections

CBCT scan at 5 mm coronal to cemento-enamel junction (CEJ) revealed three canals in a “split Y” configuration [Figure 2b]; an oval shaped main canal, a DBA and a MBA. The canals have been termed MBA and DBA rather than only MB and DB to maintain and preserve the uniqueness of the case. MBA and DBA canals unite to form a single buccal canal [Figure 2c and d]. At the level of CEJ, this buccal canal disappears into the main canal and from here on, it continues as a single canal and terminates in a single apical foramen [Figure 2e and f].

Coronal section

A typical “inverted tulip” appearance was seen in the coronal scan. The main canal was seen in the center and the MBA and DBA canals were seen originating under the MBA and DBA cusps respectively [Figure 2g].

Sagittal section

Buccal and palatal views of sagittal scan [Figure 2h] reveal the precise relationship between the three canals. MBA and DBA canals originate below the MBC and DBC, respectively, and join the main canal at the level of CEJ.

DISCUSSION

The earliest account of supernumerary cusps dates back to 1925 when Leigh reported an enamel tubercle on the third maxillary molar of an Eskimo skull.[4] Since then, various dental anthropological reports have described occlusal/central cusps in premolars, molars, canines and even incisors.[567] Unlike the previously reported cases, the supernumerary cusps in our case are present solely on the buccal surface and hence cannot be referred to as occlusal or central cusps. To the best of our literature search and knowledge, till date, this is the first case that reports four cusps in a maxillary second premolar.

The etiology of extra cusp formation is not understood clearly. An extra tubercle is thought to develop from an irregular proliferation and folding of the inner enamel epithelium and underlying ectomesenchymal cells of the dental papilla into the stellate reticulum of the enamel during the bell stage of tooth formation.[6] Role of PAX and MSX genes has also been investigated in the formation of abnormal shape of teeth.[8]

The presence of extra cusps possesses problems like increased susceptibility to caries, occlusal interference leading to the worn or fractured cusp, early involvement of pulp by caries or attrition and in some cases, esthetic concern to the patient. Evidently, as seen in the preoperative IOPA radiograph, the malocclusion caused by the rotated maxillary second premolar lead to caries activity between the mesial surface of the first molar and the DBAC of the second premolar. The caries was not evident clinically because of the gingival in-growth into the carious lesion, and the IOPA radiograph was not conclusive due to overlapping of MBA, DBA, and the Buccal cusps. However, it was apparent in the sagittal CBCT scans.

The factors that make endodontic treatment unsuccessful are causes such as failure to recognize extra canal/canals, inadequate debridement of root canals, improper cleaning and poor obturation of the canals. Maxillary second premolars have been reported to have one,[3] two[9] or three roots[10] and root canals. In the present case, three canals were present the main canal and MBA and DBA canals. Although, no case of a four cuspal maxillary second premolar with three canals has been reported in the literature, but an endodontist should have an open mind to the occurrence of such a configuration. In our case, the presence of four cusps prompted us to take CBCT scans of the tooth. According to Sert and Bayirli's classification, our case would be classified as Type XVIII (3-1).

Endodontic literature reports a low incidence of three canals in maxillary second premolars. Pécora et al. in their in vitro study reported 0.3% incidence of three canals in maxillary second premolars (n = 300).[10] Green in his study of pulp morphology in human permanent teeth (n = 50) did not find even a single maxillary second premolar with three canals.[11] Similar to Green, De Deus[12] (n = 108) and Kerekes and Tronstad[13] did not find any maxillary second premolars with three canals in their respective studies. Till date, there are only two case reports of maxillary second premolars with three roots and three canals.[1415] A tabular description of various studies done on the root canal morphology of maxillary second premolars is presented in Table 1.[10]

Table 1

Studies done on root canal number in maxillary second premolars

CONCLUSION

Anatomic aberrations exist in all the teeth and maxillary second premolars are no exception. Although the incidence of accessory cusps associated with accessory canals is very rare, the possibility of the existence of such a configuration cannot be ignored. Thus, clinicians ought to be aware of anatomical variations occurring in teeth and apply this knowledge during endodontic treatment. Newer diagnostic aids like CBCT have overcome the disadvantages of conventional radiography by producing three-dimensional images. Correct diagnosis of such cases is of utmost importance for successful endodontic treatment.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.