Aesthetic management of a fractured mandibular central incisor with two canals using fibre post

Abstract

Mandibular incisors show variations in their root canal anatomy from regular pattern in some cases. Magnification plays a vital role to identify those unusual canal morphologies. A certain modification in access cavity preparation is required to locate those extra canals. Not only the functional restoration but also aesthetic harmony should be restored while treating anterior teeth. In these cases, post space preparation should be done with extra care to prevent vertical root fracture. This case report illustrates the importance of proper radiograph and magnification in the successful identification and management of complex canal systems in mandibular incisors.

Background

Prerequisite for a successful endodontic treatment is to have thorough knowledge about the common root canal morphology and its variations. The most common cause of endodontic failure in mandibular incisors is the presence of a missed canal, especially a lingual canal. The first step prior to access cavity preparation is to study the radiographs taken at different angulations. Abrupt changes in the radiographical density of the pulp space indicate presence of an additional canal. A sudden narrowing or even a disappearance of the root canal space indicates bifurcation or a trifurcation of the canal.^{1 2} When it comes to clinical situations, finding accessory canals is not an easy task. In the past few decades, the use of magnification for improved treatment outcome has been stressed upon. Success of endodontic treatment is enhanced under magnification. Dental operative microscopes (DOMs) or magnifying loupes can be used to identify extra canals and also improve the quality of treatment outcome.

Most of the time in mandibular incisors, labial canals are easy to find and lingual canals are not located. If only one of the existing two canals is treated, pulp tissue of the untreated canal becomes necrotic and produces toxic agents that reach the periodontal ligament space via an accessory, or the lateral canal leads to pathosis.³ The use of a specially designed instrument such as a DG16 endodontic explorer significantly facilitates the inspection of the pulp chamber floor and the discovery of canal orifices once the pulp chamber is exposed. Disparity in tooth anatomy due to racial differences is again a matter of concern for the understanding and management of root canals.^4–6

Many cases have been reported on the endodontic treatment of mandibular incisors with two canals, but placement of fibre post in those teeth is very rare. So the purposes of this case report were to illustrate the outcome of endodontic treatment of a mandibular incisor with two canals in which fibre post was placed and to discuss the signs suggesting the presence of second canals in mandibular incisors.

Case presentation

A 23-year-old male patient reported to the department of conservative dentistry and endodontics with chief complaints of broken tooth and pain at the lower front tooth region for 1 week. The medical history was non-contributory. The patient had experienced trauma to the mandibular anterior region 1 week back. The clinical examination revealed Ellis class III fracture extending to the cervical region in the mandibular right central incisor (figure 1). There was pain on percussion. Ellis class II fracture was seen in the right lateral and left central incisors, and normal response was elicited for thermal and electrical pulp sensitivity test.

Figure 1.

Preoperative clinical photograph.

Investigations

In the preoperative radiograph (figure 2), widening of periodontal ligament space was seen and there were no signs of these teeth having two root canals.

Figure 2.

Preoperative periapical radiograph of the mandibular right central and lateral incisors.

Treatment

Non-surgical endodontic treatment was planned for the mandibular right central incisor with exploration, cleaning, shaping and filling of the root canal followed by placement of fibre post. Direct composite restoration was done for the adjacent two teeth with Ellis class II fracture.

In the first appointment, the mandibular central incisor was anaesthetised by local infiltration with 1 mL lidocaine (Warren Lignox Lignocaine 2%) followed by access cavity preparation with endo access bur (Dentsply Maillefer, Tulsa, Oklahoma, USA). During exploration of the pulp canal with a DG16 endo explorer (Hu-Friedy, Chicago, Illinois, USA), a catch was detected at the lingual portion of the access cavity. While using a DOM with ×2.5 magnification, a second root canal orifice was found in the lingual portion of the pulp chamber after widening the access cavity labiolingually. The patency was confirmed using a number 10 k file (K-files, Mani, Japan). Working length determination was done with the help of an apex locator (Root ZX Mini; J Morita, Japan) (figure 3). The presence of two separate canals was confirmed by taking a periapical radiograph in distal angulation (15°–20°). The chemomechanical debridement of the canal was done using hand files from 15 to 20 k file, followed by rotary instrumentation up to 4% 20 size in both canals. Copious irrigation was done after each instrumentation with 3% NaOCl followed by 17% EDTA solution. Final irrigation was done by 2% chlorohexidine solution. Master cone radiograph was taken (figure 4). The root canals were then dried with paper point and obturated with gutta-percha using the lateral condensation method and AH Plus sealer (De Trey; Dentsply, Konstanz, Germany) (figure 5). The access cavity was temporarily filled with cavit (3M ESPE, USA).

Figure 3.

Working length radiograph.

Figure 4.

Master cone radiograph.

Figure 5.

Postoperative radiograph after obturation.

The patient was recalled after 3 days. The temporary access filling was removed. Post space preparation was done using Peeso reamer up to number 2, leaving the apical 5 mm of gutta-percha in the lingual canal (figure 6). Orange wood oil was used for softening the gutta-percha. Fibre post try in was done and cemented with dual cure resin (MulticCore Flow, Ivoclar Vivadent Schaan Liechtenstein) according to the manufacturer’s instructions (figure 7). Tooth preparation was done to recieve a porcelain fused to metal crown; rubber base impression was taken; and the crown was cemented in the next appointment after 3 days (figures 8 and 9).

Figure 6.

Postspace preparation in lingual canal.

Figure 7.

Radiograph after fibre postcementation.

Figure 8.

After crown cementation.

Figure 9.

Postoperative clinical photograph.

Outcome and follow-up

A periapical radiolucency was observed after 1 month, which was reduced in size in the further follow-up period.

Discussion

The case presented in this report had two root canals in his mandibular right central incisor. Occurrence of this canal morphology has been reported in the literature before. Vertucci in 1974 reported a second canal in 25% of mandibular lateral incisors.^{7 8} In this case, the central incisor had two separate, distinct canals extending from the pulp chamber to the apex (Vertucci type IV configuration). In 1984, Vertucci reported that the incidence of type IV canal configuration in mandibular central incisor is 3%, which is very rare.⁹ In 1988, Walker reported that the second canal in mandibular incisors is infrequent in people of East Asian origin but more frequent in people of European origin.¹⁰ In 1997, Miyashita et al found second canal in 12.4% of extracted mandibular incisors; however, only 3% had two apical foramina.¹¹ In a study conducted by Al-Qudah and Awawdeh in 2006, 26.2% of mandibular anterior teeth had second canal.⁵ In the year 2011, Boruah et al evaluated morphological characteristics of root canal of mandibular incisor in north-east Indian population. They found 36% had two canals, but none of the sample (0%) showed type IV configuration.¹² Lenin et al in 2016 found that the frequency of Vertucci type IV configuration in the south Indian population is 3%.¹³ So there is always a chance that the second canal can be present. However, most of these studies have been done under stereomicroscope after teeth have been extracted and decalcified. What makes this case unique is the placement of fibre post in one of the canals of these incisors with two canals. Because the remaining radicular dentin between two canals after endodontic treatment is very less, it is difficult to prepare a post space in these teeth. There is always a chance of vertical root fracture or joining of two canals because of removal of excess dentin present between the canals. In this case, post space was prepared precisely under magnification.

Improved field of vision and illumination with a microscope or loupe can increase the success rate of endodontic treatment. Das et al found that while using a microscope, detection of additional canal increases to 54% compared with direct vision at 36%.¹⁴ Buhrley et al evaluated the frequency of MB2 canal detection for the microscope, dental loupes and no magnification. Results showed frequencies of 71.1%, 62.5% and 17.2% for microscope, dental loupes and no magnification, respectively.¹⁵ In our case, a microscope with ×2.5 magnification was used to identify and treat the second canal.

In case of vital tooth, after thorough instrumentation, if there is continuous bleeding from the pulp chamber, the clinician should suspect the presence of a second canal.¹⁶ However, in non-vital tooth, the presence of an apical rarefaction on the lateral root surface may indicate the presence of a second canal. When there is a ‘catch’ on the canal wall during instrumentation of an unobstructed root canal, the eccentric location of an endodontic file in a working length radiograph or an inconsistent apex locator reading indicates the presence of an extra canal. In the present case, a second canal was not detected in periapical radiograph taken in standard horizontal angulation. A clear canal pattern was visible after changing the horizontal angulation. So for a successful endodontic treatment, a clinician should have at least two periapical radiographs taken from two different angulations.

Most of the time, a second canal is not located because of inadequate access cavity preparation, which leaves a lingual shelf of dentine over the canal.¹² Clinicians must always consider the presence of a bifurcated canal in mandibular incisors and further extend the cavity to remove the lingual part of the pulp chamber roof to access the lingual canal. The access cavity must be extended labiolingually as well as incisogingivally to remove the lingual shelf of dentin.¹ Always thorough probing of the pulp chamber should be done, along with careful inspection of the access cavity.

Learning points.

• Proper clinical and radiographical diagnosis is important for discovering unusual canal morphology.

• Additional radiographs should be taken in different angulations and the cavity should be modified for endodontic access.

• For successful endodontic treatment, it is important for a clinician to have thorough knowledge of the anatomy of the teeth.

• Magnification has an added advantage for predictable success.

• Postspace preparation in the mandibular incisor should be done precisely to prevent vertical root fracture.