Five root canals in peg lateral incisor with dens invaginatus: A case report with new nomenclature for the five canals.

This case report describes endodontic treatment completed in a peg-shaped maxillary lateral incisor, with single root and five root canals of which, one is due to dens invaginatus. Cone beam computed tomogram scanning confirmed the unique morphology of the tooth. New nomenclature for the five canals is proposed.

INTRODUCTION

Success in endodontic treatment is best defined by the contemporary endodontic triad of diagnosis, anatomy, and debridement.[1] In the learning curve of endodontics, the incisor tooth forms the basics due to its simple morphology of one root-one canal.[2] The common developmental anomalies in a maxillary lateral incisor (MLI) includes peg-shaped crown, radicular groove, talon cusp, and dens invaginatus (DI).[2] From an endodontic perspective additional canals than the normally expected is considered as an anomaly.[3]

Considering the occurrence of additional canals, the literature shows that, MLI with a maximum of four canals[4] and with dens formation, three root canals[5] have been reported. Zillich et al. have reported MLI with two roots and dens formation.[6]

Teeth with DI are often recognized clinically due to their unusual crown form or extremely marked foramen caecum[7] and many a time may show no clinical signs of the malformation.[8] Thus, a thorough clinical and radiological examination is imperative. However, due to the limitation of conventional radiographs in assessing root canal configuration, complex root canal morphology due to dental anomalies such as multiple root canals, two roots and dens formation poses a considerable diagnostic challenge to achieve the required success.[56] Nevertheless, advanced radiographic techniques such as the cone beam computed tomogram (CBCT) helps in a three-dimensional evaluation of a particular tooth to overcome the limitations of conventional radiography.[910]

The purpose of the present case report is to discuss the endodontic procedure adopted to negotiate the complex tooth morphology of a peg-shaped MLI with DI and five root canals (FRC).

CASE REPORT

The present case is about a 17-year-old male patient who was referred to the Department of Endodontics with a primary complaint of heaviness and pain in relation to the upper front tooth. There was no preceding history of trauma or similar episodes of heaviness and pain.

Clinical evaluation revealed no significant extraoral findings. On intraoral examination, both the MLIs appeared peg-shaped. However, the right lateral incisor was associated with a soft tissue swelling in the labial vestibule [Figure 1a], tender on percussion and gave a negative response to electric pulp testing. Intra oral periapical radiograph of the maxillary right lateral incisor revealed ill-defined periapical radiolucency associated with an unusual canal morphology and DI [Figure 1b]. Based on the clinical and radiological findings, a diagnosis of acute periapical abscess was made.

Figure 1

(a) Peg-shaped lateral incisor with intra-oral swelling in the labial vestibule. (b) Radiograph revealing periapical radiolucency associated with right lateral incisor and presence of dens invaginatus. (c) Canal orifice location and nomenclature. (d) Radiograph with instruments in five canals

The need for an endodontic therapy was explained to the patient and was advised to take a course of analgesics and antibiotics (amoxicillin 500 mg, metronidazole 400 mg, ibuprofen 400 mg thrice daily for 5 days). The patient was administered local anesthesia of 2% lidocaine with 1:100,000 epinephrine. Under rubber dam isolation, an access opening was made and an orifice (C1) was visualized after copious amount of purulent discharge was allowed to drain through the C1. The endodontic explorer was placed in the C1 and verified with an apex locator (Sybron Endo Mini, Sybron Endo, Glendora, USA) and radiograph. It was found in the canal space corresponding to the DI. However, as the drainage of purulent discharge persisted, a calcium hydroxide intra-canal medicament (Calcicur, VOCO, Cuxhaven, Germany) was placed and access cavity was temporarily sealed. (Cavit, 3M ESPE AG, Seefold, Germany).

After 3 days, the calcium hydroxide was removed from C1 and subtle changes were noted at some points over the sub-pulpal floor, which suggested the possibility of additional canals away from the C1 that was located on the labial half. In order to locate the possibility of a palatal canal, the access cavity was redefined in the distopalatal (DP) region and the second canal (C2) was identified and negotiated successfully. On further probing in the distolabial (DL) region, two additional orifices (C3 and C4) were noted labial to (C2). However, the orifices of C3 and C4 were interconnected. With four instruments placed in the respective canals, the radiograph showed the presence of another unidentified canal. The fifth canal orifice (C5) was located at the mesiopalatal (MP) aspect, summing-up to five canals all with separate apical exit [Figure 1c and d]. Each time an orifice was identified, it was checked with an apex locator to rule out perforation.

Coronal flaring alone was performed with ProTaper rotary Ni Ti instruments (Dentsply, Maillefer) and subsequent cleaning and shaping was completed by hand instrumentation (Dentsply, Maillefer) due to the constricted coronal pulp space. The apical enlargement of all canals was maintained at size 25 ISO. Intra-canal calcium hydroxide medication was placed and access cavity was temporarily sealed.

A CBCT scanning was done to study the tooth morphology, which confirmed the presence of a single root with five canals with separate apical exit and a type III DI [Figure 2a and b].

Figure 2

(a) cone beam computed tomogram (CBCT)– sagittal view. (b) CBCT– axial view. (c) Radiograph taken after root canal filling and placement of temporary restoration in the access cavity. (d) Follow-up radiograph after 12 months showing signs of healing

One week later the tooth was obturated in the third visit, with Gutta-percha and sealer (Apexit, Ivoclar Vivadent) by cold lateral compaction technique [Figure 2c]. The patient was periodically monitored, with satisfactory healing and the follow-up period of 12 months was uneventful [Figure 2d].

DISCUSSION

Dens invaginatus is a developmental malformation resulting from invagination of the crown or root before calcification has occurred.[11] With a reported incidence from 0.04% to 10%, DI can be found affecting either the primary[12] or the permanent dentition,[13] and commonly involving the MLIs.[14] Cases of bilateral occurrence[151617] and rare cases are reported in molars,[18] premolars,[19] and maxillary central incisors.[20] An Indian study reported a prevalence of 0.5% of surveyed teeth;[21] however, according to a Chinese study, DI was found in 517 permanent teeth from 67 Chinese individuals, which account for 5% of DI. These authors believe that the prevalence of DI may be related to ethnic origin.[22]

The literature shows that MLI with a maximum of four canals has been reported,[4] but as far as the author's knowledge, this is the first case with FRC, especially in a peg-shaped lateral incisor complicated by the presence of DI. According to the literature, DI in a MLI is considered as unusual. DI is classified into three types. Type 1 is an invagination confined to the crown. Type 2 involves the root, but does not reach the apex, and in Type 3, the invagination extends past the periapical region with and without manifesting an additional apical foramen.[11]

The pathways of infection in a DI is found to be due to hypomineralized internal enamel and the thin canals or fissures in the dentin connecting the invagination to the pulp cavity through which microorganisms and irritating agents from the oral cavity gain access to the pulpal space leading to pulp alterations.[23]

The challenge posed in this case is the restricted access coupled with complex and unpredictable morphology of the root canal system. Krapež and Fidler emphasized the need and suggested incisal edge as the predominant location of straight-line access in anterior teeth.[24] Various treatment techniques have been reported in the literature, including preventive sealing or filling of the invagination, root canal treatment with or without endodontic apical surgery, intentional replantation and extraction.[252627] Removal of DI using hand files and Gates Glidden drills[28] and with the aid of an operating microscope and subsequent root canal treatment has also been described.[19]

The presence of multiple root canals in a peg-shaped MLI complicated by DI poses substantial difficulty in diagnosis and treatment as well as achieving endodontic success for better prognosis. The present case has been evaluated and negotiated with the aid of conventional radiographs and by applying law of symmetry, cemento enamel junction and orifice location.[29] The complicated tooth morphology with multiple root canals warrant use of CBCT to define and confirm the canal morphology. In line with a molar tooth, the multiple canals in this case is named according to the surface in which it is located namely C1 – mesiolabial, C2 – DP, C3 and C4 – DL1 and DL2, and C5 – MP, respectively [Figure 1c].

CONCLUSION

Case selection is the key in successful outcome of a treatment. Treating a tooth with a unique morphology definitely tests the clinical knowledge, skill of the operator and one should be ready for any kind of pulp space variant that could exist. Although, CBCT would have been beneficial to precisely define and confirm the canal location in a complicated morphology, the present case illustrates the successful negotiation with conventional radiographs.