Endodontic management of contralateral mandibular first molars with six root canals.

The knowledge of variations in root canal morphology is essential for a successful endodontic outcome. Contralateral mandibular molar with six root canals is a rare entity. Root canal treatment of mandibular molars with aberrant canal configuration can be diagnostically and technically challenging. While dealing with variant mandibular molars, mishaps may happen. This case report describes variations in contralateral mandibular molars and also an endodontic mishap while managing them.

INTRODUCTION

The outcomes of nonsurgical and surgical endodontic procedures are influenced by highly variable anatomic structures.[1] Although the role of a preoperative radiograph is indispensable, it does not always reveal the exact number of canals present in a root.[2] This increases the risk of missing a root canal. Krasner and Rankow[3] proposed specific laws; law of symmetry, law of color change, and laws of orifice location to locate canal orifices in a systematic manner. Various diagnostic aids such as conventional angled radiographs, advanced radiographic techniques such as spiral computed tomography (SCT) and cone-beam CT (CBCT), dyes, optical loupes, and operating microscope facilitate detection of atypical root canal morphology.[4]

Many studies have been carried out to understand the internal anatomy of mandibular first molar. Although most prevalent root canal system configuration found are Type IV and Type I in mesial and distal roots, respectively, it is common to find other complexities in mandibular first molar.[5] Earlier few authors have reported mandibular first molars with additional canals.[678] This case report describes endodontic management of bilateral mandibular first molar with radix and diverse canal configurations in their mesial roots.

CASE REPORT

A 38-year-old female patient reported with a complaint of severe pain in the lower right back tooth region. There was a history of occasional pain in the same for the past 1 month. Her medical history was noncontributory. Intraoral examination revealed severe attrition in the right and left mandibular first molars. Tooth #30 was tender to percussion. There was no palpation tenderness in the vestibular region. Tooth mobility and periodontal probing around the teeth were within normal limits. Thermal and electrical pulp testing elicited a lingering response in both the teeth.

Radiographic examination [Figure 1a and Figure 2a] revealed three-rooted mandibular first molars on both sides. Periapical index rarefaction (PAI score 4)[9] was observed for tooth #30 [Figure 1a] whereas periapical area of tooth #19 appeared to be normal [Figure 2a]. A diagnosis of acute irreversible pulpitis with apical periodontitis in tooth #30 and chronic irreversible pulpitis in tooth #19 was made. Root canal therapy was planned for both mandibular first molars and patient's signature was obtained in the consent form. As the condition necessitated emergency access opening, CT could not be planned.

Figure 1

Endodontic therapy for the right mandibular first molar. (a) Preoperative radiograph, (b) working length radiograph, (c) access cavity with six orifices, (d) extruded gutta-percha and master cones, (e) postoperative radiograph, (f) recall (1 year) radiograph

Figure 2

Endodontic therapy for the left mandibular first molar. (a) Preoperative radiograph, (b) working length radiograph, (c) access cavity with six orifices, (d) master cone radiograph, (e) postoperative radiograph, (f) recall (1 year) radiograph

Endodontic management of #30

After local anesthesia, rubber dam isolation and disinfection of the field access cavity were prepared with Endo Access Bur No. 1 (Dentsply, Maillefer, Switzerland). The first distal canal was found more buccally indicating the possibility of a lingual canal. Thorough examination of pulpal floor revealed six distinct root canal orifices: four mesially (two mesiobuccal [MB1] and MB2 and two mesiolingual [ML1] and ML2) Type XIV Sert and Bayirli canal configuration,[10] one in distobuccal root, and another in distolingual root radix entomolaris (RE) [Figure 1c]. All the canals were explored with #10 K-files (Maillefer, Dentsply, Switzerland). Working length was determined with electronic method (Root Zx, J Morita, Japan) and confirmed radiographically. After estimating the working length with an apex locator, working length was confirmed radiographically [Figure 1b]. A #15 K-file (Maillefer, Dentsply, Switzerland) fractured while shaping MB2. An attempt was made to By-passed and retrieves the fractured fragment. Other canals were blocked with 20-size 2% taper gutta-percha points to prevent slippage of the fine fragment into the remaining canals. Ultrasonics (Satelec, Acteon, India) was used to remove the fractured fragment. During the instrument retrieval, accidental placement of the ultrasonic file into MB1 pushed the 20-size gutta-percha point beyond the apex. Later, the fractured instrument was bypassed and instrumentation of the canals was completed with 4% tapered Mtwo (VDW, Munich, Germany) instruments and intermittent irrigation with 5% sodium hypochlorite solution. Calcium hydroxide intracanal medicament was placed, and the patient was recalled after a week. During the second visit, root canals were irrigated with ethylenediaminetetraacetic acid and saline, dried with paper points, and obturated with cold, lateral compaction [Figure 1d and e]. The access cavity was restored with a resin composite restoration (Tetric N Ceram, Ivoclar Vivadent, Schaan, Liechtenstein, UK). The patient was reviewed periodically every 3 months for 1 year [Figure 1f].

Endodontic management of #19

After local anesthesia and rubber dam isolation, straight-line access was gained to the pulp chamber. Unlike its contralateral tooth, pulpal floor revealed six distinct root canal orifices: three were detected mesially (mesiobuccal, middle mesial, and mesiolingual) indicating the Type XV Sert and Bayirli canal configuration,[10] two canals in distobuccal root (DB1 and DB2) with Type II Vertucci canal configuration, and one in radix [Figure 2c]. The canals were explored with #10 K-files. To ascertain the presence of six canals, dental imaging with a SCT was planned due to the unavailability of CBCT at that moment. After obtaining the informed consent from the patient, SCT of the mandible was performed and the root and canal morphology was confirmed (two in distobuccal root, one in distolingual root, and three in mesial root) [Figure 3a]. After determining the working length with an apex locator (Root Zx, J Morita, Japan), working length was confirmed radiographically [Figure 2b] with files in all the six canals. Cleaning and shaping was performed using a crown-down technique with Mtwo (VDW, Munich, Germany) using 5% sodium hypochlorite irrigation. The tooth was temporized after calcium hydroxide medication. At the second visit after 1 week, root canals were dried and obturated with laterally condensed gutta-percha [Figure 2d and e]. The access cavity was restored with a resin composite restoration, and the patient was recalled after 3 months.

Figure 3

Spiral computed tomography image for the mandible. (a) Preoperative radiograph of tooth #19, (b) postoperative radiograph of tooth #19

Review evaluation

The patient was reviewed every 3 months for 1 year [Figures 1f and 2f]. SCT was repeated at 3-month recall evaluation [Figure 3b]. One-year recall radiographs revealed considerable reduction of the periapical radiolucency with a PAI score of 2 [Figure 1f] in tooth #30 indicating a definite treatment outcome.

DISCUSSION

Thorough knowledge about root canal morphology and configuration plays a vital role for successful endodontic treatment. In the present case, the patient had RE in both mandibular first molars #19 and #30. Endodontic success in teeth with additional canals requires a meticulous clinical and radiographic examination. Angled preoperative radiographs, CBCT/SCT images, examination of the pulp-chamber floor with a sharp explorer, troughing of the grooves with ultrasonic tips, staining the chamber floor with 1% methylene blue dye, performing the sodium hypochlorite “champagne bubble test,” and visualizing canal bleeding points are all essential aids in locating the root canal orifices.[1] The search for additional orifices is also abetted by the use of microscopes, magnifying loupes, and fiber-optic transillumination to locate the developmental line between the mesiobuccal and mesiolingual orifices.[11]

The major aberration in mandibular first molar is usually the presence of an additional third root, a supernumerary root which can be found distolingually. This additional root, RE, was first mentioned in the literature by Carabelli (1844). The incidence of RE among the Indian population was found to be very low (0.2%). However, few studies reported higher prevalence (2.19%–13.3%).[12] Many reported RE cases revealed the presence of two canals in the distobuccal root.[13] RE was classified by Ribeiro and Consolaro (1997) into three groups on the basis of the curve of the root/root canal. Type I refers to a straight root/root canal, Type II to an initially curved entrance and the continuation as a straight root/root canals, and Type III to an initial curve in the coronal third of the root canal and a second buccally orientated curve starting from the middle till apical third.[14] Both the teeth (#19 and #30) of this patient exhibited Type I RE.

Incidence of the middle mesial canals in mandibular molars was found to be more than 50% in patients with age <40 years.[15] Goel et al. reported that 60% of the mesial root of permanent mandibular first molars presented two foramina (Vertucci Type IV), whereas 6.7 and 3.3% of these molars had three (Vertucci Type VIII) and four foramina (Sert and Bayirli Type XX), respectively.[16] Few researchers[6717] reported the presence of six canals in mandibular first molars, but none of these reported contralateral molars with diverse morphologies.

Root canals are formed due to the secondary dentin apposition that occurs during tooth maturation resulting in dentinal vertical partitions inside the root canal cavity. A third root canal may also be created inside the root canal cavity of mandibular molars by this process. These third canals are situated centrally between the two main buccal and lingual root canals. The diameter of such middle canals is usually smaller than that of the other two.[18] The third mesial canal is defined as being independent when a distinct coronal orifice and apical foramen are observed[19] and defined as being confluent when converging into one of the other two main canals and terminating at a common apical foramen.[20] Earlier literature[2122] reported the prevalence of a third canal in the mesial root of mandibular first molars. Guided troughing under high magnification enables the location of middle mesial canal.[23]

Preventing an intracanal file separation can be partially accomplished by careful handling of instruments. Instruments no. 08 and 10 should be used only once. Smaller instruments, such as nos. 08, 10, 15, and 20, should be examined thoroughly for signs of stress during their usage. These smaller instruments should not be forced or wedged into a canal; they should be teased gently into place. An instrument that cannot be inserted to the desired depth should be removed and the tip should be modified slightly by bending before resuming the pathfinding process. The use of a canal lubricant is also helpful. This process should be repeated several times before the path of the canal is negotiated. Two other important points that will aid in preventing an intracanal file separation are sequential instrumentation, using the “quarter-turn” technique, and increasing the file size only after the current working file fits loosely into the canal without binding.[24]

The following are some important recommendations to be considered to minimize the incidence of endodontic file separation:

Awareness of root canal anatomy using CBCT or SCT in suspected cases

Establishment of glide path before commencing the cleaning and shaping

Appropriate training before using files of new design

Examination of new files before their usage as some defects can occur while being manufactured

Periodic examination of files and use of magnification for file examination as some defects cannot be seen by naked eye

Adherence to the manufacturer's recommendations during their usage.

Key points to remember

Contralateral teeth always may not have similar root canal morphology. There can be variations

Before using ultrasonic instrumentation for retrieval of broken fragment, remaining canals should be obturated and orifices should be plugged with resin-modified glass ionomer cement (GIC).

CONCLUSION

Usually, a prudent inspection of the pulp-chamber floor by proper visualization allows the clinician to search for additional canals. Proper and thorough instrumentation is one of the key factors in the success of endodontic therapy; therefore, the clinician should be aware of the incidence of these extra canals in the mandibular first molars.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.