Management of mandibular first molar with four canals in mesial root.

Successful root canal treatment depends on adequate cleaning, shaping, and filling of the root canal system. The presence of middle mesial (MM) root canal of mandibular molars has been reported by various authors. But incidence of four canals in mesial root of mandibular molar is very rare. The aim of this case report is to present and describe the identification and management of a mandibular first molar with four canals in the mesial root and single canal in the distal root.

INTRODUCTION

Post treatment apical periodontitis or endodontic failure is associated with persistence of microbial infection in the root canal system and/or the periradicular area.[1] Microorganisms present in untouched areas such as missed canals, isthmuses, and irregularities may remain unaffected by endodontic disinfection procedures. These microorganisms continue to multiply to significant number and gain access to the periradicular region, causing inflammation in the periradicular tissues.[2] Therefore, the successful root canal treatment depends on adequate cleaning, shaping, and filling of the root canal system. There have been numerous studies that describe the complex morphology of teeth, including mandibular first molars. In 1974, Vertucci and Williams, as well as Barker et al., described the presence of an independent middle mesial (MM) canal.[34] The presence of MM root canal of mandibular molars has been reported to have an incidence rate of 1-15% in various in vitro studies and case reports. The incidence of four canals in mesial root of mandibular molar have been reported by two authors ininvitro studies[56] and by three authors as case reports.[789] The aim of this case report is to present and describe the management of a mandibular first molar with four canals in the mesial root and single canal in the distal root.

CASE REPORT

A 37-year-old male patient with a noncontributory medical history reported to our department with discomfort and pain in the right mandibular region. History of present illness showed that there were few episodes of recurrent pain in that region for the past 1 year. There was a large carious lesion and a draining sinus in relation to left mandibular first molar with pain on palpation in the periapical region. Pulp testing with cold and electric pulse tester (EPT) was nonresponsive. Intraoral periapical (IOPA) radiograph revealed a large radiolucency around the periapex of left mandibular first molar [Figure 1a]. Gutta-percha tracing of sinus showed that the sinus originated from the periapical radiolucency around the tooth. It was diagnosed as pulpal necrosis with symptomatic apical periodontitis. Treatment plan was explained to the patient and endodontic treatment was initiated under rubber dam isolation. Three canals were located, two in the mesial and one in the distal. Under magnification, it was evident that the mesiobuccal (MB) and mesiolingual (ML) were placed well apart with an isthmus joining the two canals. With the above mentioned pulpal floor anatomy over the mesial root, a possibility of MMcanalwas anticipated in the isthmus between MB and ML. On exploration with DG-16, there was a “catch” or a “stick” feeling where a MM canal was located close to MB canal. The distance between the MM canal and ML canal with a prominent isthmus between the two, prompted us to look for a second MM canal. Further exploration on the isthmus revealed one more “stick” feeling which on penetration with profinder revealed to be a second MM located closer to the ML canal [Figure 1b]. IOPA radiograph revealed one MM joining the MB canal and another joining the ML canal in the middle third [Figure 1c]. The orifices were enlarged using #2 GatesGlidden Drill (Mani, Japan) to enhance access and visualization. After confirming the working length with an apex locator (Root ZX, J Morita, Tokyo, Japan), the mesial canals were enlarged up to size 25-6% (M two, DentsplyMaillefer) and the distal canal was instrumented with hand K-files (DentsplyMaillefer) by crown down method with apex enlarged to size40. Intracanal medicament of 2% chlorhexidine was placed and closed dressing was given. Since the anatomy was unusual, a cone beam computed tomography (CBCT) image was taken to confirm the anatomy [Figure 1d]. CBCT image confirmed the presence of two MM canals of which one joined the MB and another joined the ML canal at the middle third and exited as a single canal at the apex. This was followed by an intracanal medication with CaOH (Dentocal, Anabond Stedman) with chlorhexidine (Asep-RC, Anabond Stedman) after a week for 3 weeks. CaOH was not placed in the first sitting as the radiopaque CaOH may obscure the CBCT image. Obturation was performed at the third appointment using cold lateral compaction of gutta-percha and AH-26 (Dentsply Maillefer) as a root canal sealer. Figure 2a and b shows the IOPA images immediately after obturation in buccal and distal view. Figure 2c is 6 month follow-up image showing a good healing of the periapical lesion.

Figure 1

(a) Preoperative IOPA radiograph of tooth #36. (b) Intraoral image showing four canals in the mesial root. (c) IOPA radiograph showing four canals in the mesial root. (d) Cone beam computerised tomography image showing the presence offour canals in the mesial root

Figure 2

(a) IOPA radiograph after obturation, buccal view. (b) IOPA radiograph after obturation, distal view. (c) IOPA radiograph after 6 months

DISCUSSION

The incidence of MM canal ranges from 1 to 15%.[10] Pomeranz et al.,[11] in a report of 100 cases found that 12 molars had MM canals and classified them into three morphologic categories as follows: Fin, confluent, and independent. Fin, where there is free communication between all three canals and confluent, where MM canal joins one of the main canals. According to Fabra-Campos, this MM canal more commonly joins the MB canal.[12] In a systematic review by de Pablo et al., the MM canal was present in 2.6% mandibular first molars. They reported that intracanal communications existed in about 55% of mesial roots of the first molar.[13]

The pulpal floor of first molar may or may not show a clear isthmus between the two canals. The isthmus is generally obscured by a dentinal projection which can be removed with specialized ultrasonic tip or one-fourth round bur. If the isthmus isevident clinically, presence of a MM canal should always be anticipated. Hsu and Kim[14] classified isthmus configurations, where type V (single, broad, and elongated canal) was the most frequent among mesial roots of mandibular molars. According to a study by Yesilsoy et al.,[15] the groove between the MB and ML can be as deep as 3.5 mm from the orifice and between 4 and 6 mm from the apical foramen.[16] This groove is a potential area to be addressed and there is a need to modify the access to disinfect the root canal system effectively. Careful probing of this area will show a “catch” or a “stick” feeling if there is a canal in the isthmus. This isthmus could also be broad, with a fin type of MM canal. A fin type MM canal may be seen in younger age patients as canal differentiation in isthmus region with complete division of the root canal system starts only after 16 years of age and is seen in all roots only after the age of 30 years. And if numerous partitions form, extensive differentiation of the root canal system results in a reticular form in which three or more vertical canals are present with lateral interconnections.[17] Thus, a possibility of additional canals should be expected in patients above the age of 30 years. Most of the reported cases of third mesial canal have been in patients of 40 years of age or more. Though the presence of a third mesial canal has been reported by many authors, presence of fourth mesial canal has been reported only thrice.[789] Goel et al., in an in vitro study on Indian population reported an incidence of 3.3% of four canals in the mesial root of mandibular first molar.[18] Another in vitro study by Wasti et al., in Pakistan, which is of a similar ethnic population as this patient (Indian), one out of 30 teeth showed a Vertucci typeVIII configuration.[19]

In a study on 2,800 teeth by Sert and Bayirli,[5] 36 teeth showed morphology which does not come under Vertucci's classification and it occurred twice as often inmandibular teeth. They described four canals in mesial root exiting as one canal, but does not mention a 4-2-1pattern as seen in this case. Gulabivala et al., described a four canal pattern, but exiting as two canals, in Burmese population[6] as type XI. Thus, an absence of report of such a pattern and with only three previous case reports of four canals in the mesial root makes this report unique and worth mentioning to understand the complexity of root canal system of mandibular first molar.

Despite report of such extra canals, Mortman and Ahn[20] describes these extra mesial canals are a sequelae of instrumenting the isthmus between the MB and ML canals. But according to Navarro et al., if preparing a ‘canal’ in an isthmus can assist in cleaning and reshaping it, as many canals as necessary (without damaging the root structure) may be prepared so as to divide the isthmus and make it easier for the disinfectants to penetrate the spaces that cannot be reached with a file.[21] Care should be taken while instrumenting such confluent canals with nickel-titanium rotary instruments, as they have a tendency to break where two canals join at a sharp angle into one small canal.[6]

CONCLUSION

Failure to locate and clean extra canals decreases the long-term prognosis of endodontic treatment. Endodontic management of aberrant root canal is often challenging. Adequate knowledge of aberrancies, the will to search for them, combined with usage of magnification, and modern imaging techniques will beget us greater success. This case report describes a successful management of an aberrant morphology in a mandibular molar with four canals in the mesial root and one canal in the distal root.