Management of a Non-Vital Central Incisor Tooth with Three Root Canals

maxillary central incisor teeth can vary in their root canal morphology. Although multiple canals
are extremely rare, accessory canals may occur in over 60% of cases and may be impossible to instrument and clean.
Multiple canals usually occur as a result of abnormal dental development, including double roots, fusion,
gemination and dens invaginatus.
There have been a few reports of maxillary central incisors with two root canals within a single root in the
absence of dens invaginatus, fusion or gemination. This case report describes the challenges of endodontic treatment in a maxillary central incisor with three root canals within a single root, in the absence of any of the aforementioned conditions.

CASE REPORT

A healthy 10-year-old girl was referred to the University Dental Hospital of Manchester, Unit of Paediatric Dentistry, for the management of a non-vital upper right permanent central incisor tooth.
There was a history of trauma to the tooth 18 months prior to the development of symptoms.



The tooth had been mobile but did not require splinting. On presentation to the clinic, the main complaint was of spontaneous and intermittent toothache of a one-month duration. 
Clinical examination revealed a macrodont upper right permanent central incisor tooth (Figure 1). The tooth was slightly tender to percussion and sensitive to ethyl chloride. There was no pathological mobility but palpation over the apex was tender. Radiographic examination on a standard viewer revealed that the tooth had a large root and there was a periapical radiolucency associated with the apex (Figure 2).
Despite the positive response to ethyl chloride, a diagnosis of an apical abscess was made and endodontic treatment commenced.
After buccal infiltration with lignocaine (2%) with 1:80,000 epinephrine, a rubber dam was placed and the upper right permanent central incisor tooth was accessed. Initially, a standard-sized access cavity was produced in the palatal surface of the macrodont crown. This was extended mesially and distally to access the two root canals. 
The pulp in the distal of the root canals was non-vital. The pulp in the mesial root canal was hyperaemic and very sensitive, and could not be extirpated. The root canals were therefore dressed with a steroid/antibiotic paste (Ledermix paste, Blackwell Supplies Ltd, Gillingham, Kent) and the access cavity sealed with reinforced zinc oxide eugenol cement.


The Ledermix was sealed into the pulp chamber with the aim of reducing the inflammation of the hyperaemic pulp in order that local anesthetic would be effective at the next visit. Two weeks later, the pulp in the mesial root canal was successfully extirpated under local anesthesia. 

Diagnostic radiographs indicated that both canals were of equal length, this being 19 mm (Figure 3). The canals were filed using Hedstrom files and irrigated with physiological saline.
This was repeated until the canals were clean. Although the root canals were narrow, the apices were still open. 
Both root canals were dressed with calcium hydroxide paste (Hypocal, Ellman International Inc., New York, USA).


Over the next year, the child attended for five visits. Fresh calcium hydroxide paste dressings were placed in the root canals at each visit. By the fifth visit, both root canals had developed complete barriers across their apical foramina.
Root canal obturation was accomplished in both canals using zinc oxide eugenol sealer and lateral condensation of gutta-percha (Figure 4).
The access cavity was sealed using the acid-etch composite.


At a subsequent 2-month review appointment, the patient reported no symptoms. At a further review, 6 months later, the patient had developed a sinus labial to the macrodont tooth.
Radiographic examination showed a periapical radiolucency slightly more mesial to the one that had occurred previously (Figure 5).
 Close examination suggested the presence of a third root canal mesial to the other two canals. With
hindsight, the examination of previous radiographs (Figures 3b and 4) showed the presence of the third root canal.

Digital subtraction radiographs were taken as a baseline record. The tooth was accessed and the third canal located.
Following a diagnostic radiograph, the tooth was dressed with calcium hydroxide paste (Hypocal) and zinc oxide eugenol temporary dressing. On review 3 months later, there were no further symptoms and the labial sinus had disappeared. 
Further digital radiographs were taken and digital subtraction showed that the radiolucency was healing and bone was being laid down.
 This is demonstrated by an increase in bone density which is represented on Digital Subtraction Radiography by a light grey area (Figure 6)




The third canal was filled with zinc oxide eugenol sealer and gutta-percha using a lateral condensation technique. At review one year later the tooth had remained symptom-free with no clinical or radiographic signs of pathology (Figure 7).



DISCUSSION

When performing the endodontic treatment, the clinician must always be prepared for
unexpected root canal morphology.
A careful radiographic examination may lead to the identification of additional canals. In this case, the symptoms recurred after the initial root filling as a result of the infection from the necrotic tissue in the third root canal reaching the periapical tissues. 
Treatment of the infection in the third canal resulted in resolution of the symptoms.
It is not a usual practice in pediatric dentistry to use magnification or microscopy to detect root canals because these are usually so wide that identification is obvious. However, in
this case, it may have been prudent to utilize these aids.



CONCLUSION

This case report describes the endodontic treatment challenge posed by the management of a central incisor with three root canals. Knowledge of dental anomalies and careful pretreatment evaluation is essential for diagnosing unusual canal morphology.