Endodontic management of a two rooted, three canaled mandibular canine with a fractured instrument.

It is important to assess the root canal morphology and its variations before initiating the endodontic procedure. This is because the inability to clean the complete root canal system forms the seat for the persistent infection which ultimately leads to endodontic treatment failure. This case reports the use of dental operating microscope for the successful endodontic management of a two rooted and three canaled mandibular canine with the fractured instrument in the middle canal of a 38-year-old healthy Asian woman. This case report highlights the need to use the dental operating microscope and ultrasonics in locating the elusive canal orifices. It is important to note the internal and external root canal morphological variations before starting the endodontic treatment without any pre-operative assumptions about the usual anatomy of the toot.

INTRODUCTION

Incompetence in locating, cleaning and shaping or obturating the complete root canal system causes primary and post-treatment infections which often lead to endodontic treatment failures.[1] However, the most significant reason for the root canal treatment failure is insufficient knowledge about the root canal morphology and its variations.[2] This is because such unexplored areas of root canal system remain unaffected by instruments and antimicrobial substances and form the seat for the persistent infection.[34] Thus, it is critical to assess the numerous morphological variations of the root canal system before initiating the endodontic procedure.[56] Mandibular canine is a single canaled, single rooted tooth. However, certain internal and external morphological variations in the mandibular canine like single or bifid roots with two or three canals have been reported in the literature.[79] Till date, no case report on management of two rooted three canaled mandibular canine with a fractured instrument has been reported in the literature. In the documented case, dental operating microscope is used to bypass the fractured instrument in the middle canal of a three canaled mandibular canine with the patients consent.

CASE REPORT

A 38-year-old healthy Asian woman was referred to the endodontic clinic by a general dentist. The patient presented to her dentist with a severe pain in left mandibular region ten days ago. The dentist initiated the root canal treatment in left mandibular canine (tooth # 22). During the cleaning and shaping procedure, an ISO # 10 K-file was accidentally fractured in one of the canals. The dentist could not bypass the fractured instrument and hence the case was opted for the referral. On clinical examination, tooth # 22 did not appear to have any coronal morphological variations and was identical to its right counterpart except it was mesially rotated. It was tender to percussion without any evidence of mobility, swelling or sinus tract. The mucosa and the underlying alveolar bone were normal on palpation. Careful pre-operative radiographic examination revealed a two rooted three canaled (i.e. buccal, middle and lingual canals) mandibular canine with a fractured instrument in the middle canal [Figure 1].

Figure 1

Pre-operative radiograph of tooth #22 showing three distinct canals – buccal (a), middle (b) and lingual (c) with a fractured instrument in the middle canal

Prior to the initiation of root canal treatment, patient was explained about the aberrant root canal morphology and presence of a separated instrument in the middle canal. Patient was administered local anesthetic solution with adrenalin (2% lidocaine with 1: 100000 epinephrine, LOX 2% Neon Lab, India). Under rubber dam isolation (Hygienic, Coltène Whaledent Inc., USA), access opening was re-defined with the help of ultrasonic tips (Pro Ultra Endo Tips No. 2 and 3, Dentsply Maillefer, New York, USA). Careful clinical explorations of access opening with a DG-16 endodontic explorer (Hu-Friedy, Chicago, IL, USA) revealed two root canal orifices in bucco-lingual direction and were present more towards the buccal side. Moreover, a bleeding point was noted lingually at the end of a developmental fusion line indicating the location of unexplored third root canal orifice. Troughing the developmental fusion line lingually with ultrasonic tips under a dental operating microscope (Carl Zeiss Surgical GmbH, Oberkochen, Germany) revealed a third root canal orifice [Figure 2].

Figure 2

All three root canal orifices – buccal (a), middle (b) and lingual (c) present alongside the developmental fusion line (d) are located with the help of ultrasonic tips and dental operating microscope

All the three root canal orifices were coronally pre-flared using a nickel-titanium (NiTi) ProTaper SX rotary file (Dentsply Maillefer, Ballaigues, Switzerland) with a brushing outstroke action to improve the straight-line access. Dental operating microscope was used to visualize the fractured instrument present in the apical third of the middle canal. The maneuver to bypass the instrument was initiated in the presence of Glyde (Dentsply Maillefer, Tulsa, OK) by wedging an ISO # 8 K-file (Dentsply Maillefer, Tulsa, OK) between the fractured instrument and the canal walls with frequent radiographic checks. The file was then advanced and withdrawn repeatedly in an attempt to widen the canal space and loosen the retained fragment from the root canal. However fractured instrument retrieval was not successful. So it was decided to prepare the entire root canal system, and incorporate the fragment into the obturation. The space created between the fractured instrument and the canal walls was enlarged with the larger sized files sequentially till ISO # 25 K-file. Working lengths for all three canals were determined with an apex locator (Root ZX; Morita, Tokyo, Japan) and were confirmed radiographically [Figure 3]. All three canals were prepared using ProTaper NiTi rotary instruments (Dentsply Maillefer, Ballaigues, Switzerland) according to manufacturer's recommendations. ProTaper S1/S2 rotary files were used with brushing outstroke action. Finishing files F1 and F2 were used with pecking motions until working length was reached. Irrigation was performed using triple distilled water, 2.5% sodium hypochlorite solution (Cmident, India) and 15% EDTA (Largal Ultra, Septodont, Saint Maur des Fosses, France). 2% chlorhexidine digluconate (R4, Septodont, Saint Maur des Fosses, France). were used as the final irrigant. The canals were dried with sterile paper points (Dentsply Maillefer, Tulsa, OK). Calcium hydroxide (Prime Dental Products Pvt. Ltd., Mumbai, India) was used as an inter-appointment medicament. The access cavity was sealed temporarily with intermediate restorative material (IRM, Caulk Dentsply, Milford, DE). The patient was recalled after a week during which the tooth was asymptomatic. The root canals were again irrigated with triple distilled water to remove the intracanal dressing of calcium hydroxide. Canals were dried. Obturation was done by a single cone technique with the use of gutta-percha cones and epoxy resin-based root canal sealer (AH plus sealer, Dentsply Maillefer, Tulsa, OK). In the middle canal, the fractured instrument was incorporated in the obturation [Figure 4a]. Tooth was restored using light cured composite resin (Z100; 3M Dental Products). Subsequent follow-up x-ray was taken at 12 months [Figure 4b].

Figure 3

Working length radiograph with fractured instrument bypassed in the middle canal

Figure 4

(a) Post-obturation radiograph with inclusion of a fractured instrument in the obturation. (b) Follow-up x-ray taken at 12-months

DISCUSSION

Essential pre-requisites for a successful endodontic treatment are careful interpretation of pre-operative radiographs, a thorough knowledge and detailed exploration of internal root canal morphology and its divergence under the magnification and illumination. Straight radiograph provides information about the mesio-distal root canal orientation where as angled radiographs (radiographs at two different horizontal angulations) provide information about the facio-lingual canal position. Any attempt to reduce the required number of radiographs runs the risk of missing information of the complex canal morphology. However, in the present case the mandibular canine was rotated mesially. So, two roots and three canals appeared separate on the radiographs. Hence, there was no need to take any additional angulated radiographs. Furthermore, a careful tracing of periodontal ligament space suggested the presence of two separate roots with three canals. The access cavity was extended buco-lingually with the help of ultrasonic tips in order to conserve the tooth structure while searching for an extra and elusive canal orifice. The internal and external morphological variations of the mandibular canine were clearly appreciable from the radiographic and clinical examination in the present case. Hence, Cone Beam Computed Tomography (CBCT) scan was not done to reduce any extra radiation dosages.

Even though the mandibular canine shows a single root and a single root canal with single apical foramen in about 92.2% of cases, clinicians should always search for any possible extra root or canal.[10] Root canal morphological variations reported in the mandibular canine include two canals and one apical foramen in 4.9% of cases, two canals and two apical foramens in 1.2% of cases and two different roots each one with one canal in 1.7% of the cases.[10] Also two distinct case reports of mandibular canine with three canals in one root or two roots were reported in the past.[89] Hence, it is always prudent to consider all anatomical variations in the mandibular canine while performing a root canal treatment. Any pre-determined assumption about the root canal morphology leads to failure to locate any morphological variation, if present. It hinders the effective cleaning and shaping and creates a nidus of infection that directly compromises the long term prognosis of the tooth.

In the documented case, the fractured K-file in the middle canal prevented the negotiation and thorough biomechanical preparation of the canal. However, the chances of uneventful retrieval of the fractured instrument were not predictable considering the impossibility of visibility of instrument under dental operating microscope, strategic importance of tooth, the location of the instrument and the limited thickness of the root. Success in management of fractured instrument is defined as the complete removal or complete bypass of the fragment without creating a perforation.[11] Hence, decision was made to bypass the instrument under dental operating microscope to enhance the visualization of operating field and to conserve the maximum root structure. During the bypassing maneuver, higher magnification was used with frequent radiographic checks to avoid intra-operative complications like root perforation, ledge formation, pushing the instrument more apically etc. The EDTA was used to soften the root canal wall dentin around separated instruments. It facilitated the negotiation of files for the negotiation of the fragment.[12]

Internal root canal anatomical variation is a rule rather than exception. So, a clear understanding of pulp anatomy and its variations is essential if effective cleaning, shaping and obturation of the pulp space are to be achieved to assure the successful and predictable outcome of endodontic treatment.[13] Mandibular canine with variations in number of roots and root canals should be treated without any pre-operative assumptions regarding its typical single rooted and single canaled anatomy. Thus the present case report highlights the endodontic management of an unusual case of mandibular canine with two roots and three canals. It also highlights the need for use of dental operating microscope and ultrasonics in locating the elusive canal orifices.

CONCLUSION

Eyes don’t see what mind doesn’t know. So it is important to note the internal and external root canal morphological variations so that similar anatomy may be predicted and managed successfully. Sometimes retrieval of a fractured instrument is impossible or undesirable. In these cases, bypassing the instrument under magnification is a valid alternative, which can lead to a favorable outcome as presented in the given case.