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Year : 2019  |  Volume : 22  |  Issue : 2  |  Page : 285-288

Middle distal canal of mandibular first molar: A case report and literature review

Department of Endodontics, Faculty of Dentistry, Akdeniz University, Antalya, Turkey

Date of Acceptance14-Aug-2018
Date of Web Publication7-Feb-2019

Correspondence Address:
Dr. D O Kirici
Department of Endodontics, Faculty of Dentistry, Akdeniz University, Antalya
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/njcp.njcp_315_18

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A successful root canal treatment can only be achieved by gaining adequate access to all root canals, ensuring adequate mechanical preparation, and disinfection as well as placing a three-dimensional impermeable filling in these root canals. Practitioners must be very careful when detecting the root canals in mandibular first molar tooth, because it shows a wide variety of root canal variations and it is the first permanent tooth erupted in the mouth that frequently requires endodontic treatment. Our case report presents the endodontic retreatment of a left permanent mandibular first molar having two roots that consist of three distal canals and two mesial canals (Type XVIII root canal pattern). After all the root canals were identified with endodontic explorer adequate preparation and disinfection were provided, the root canals were filled with calcium hydroxide-based canal sealer and gutta-percha and the crown was restored with resin composite at the second appointment. In addition, a short review of literature for similar cases is presented in this paper.

Keywords: Mandibular first molar, middle distal canal, root canal treatment

How to cite this article:
Kirici D O, Koc S. Middle distal canal of mandibular first molar: A case report and literature review. Niger J Clin Pract 2019;22:285-8

How to cite this URL:
Kirici D O, Koc S. Middle distal canal of mandibular first molar: A case report and literature review. Niger J Clin Pract [serial online] 2019 [cited 2022 May 24];22:285-8. Available from:

   Introduction Top

Successful root canal treatment can only be achieved by appropriate preparation and impermeable root canal filling.[1] It is important that the clinician must have good knowledge of root canal morphology to achieve a successful root canal treatment. A standardized root canal anatomical classification was suggested by Vertucci,[2] and a clinically more appropriate categorization of the root canal anatomy was recommended by Weine.[3] Sert and Bayirli described 14 new canal variations.[4] However, many variations exist, and it is important to evaluate each individual case for variations.[5] The morphology of mandibular first molar has shown many variations and it is the first permanent tooth to erupt, therefore, it frequently requires an endodontic treatment.[6] The practitioner should be aware of this anatomical complexity that could be present in this tooth type. The aim of this case report was to state the successful nonsurgical endodontic treatment of a left permanent mandibular first molar having two roots that consist of three distal canals and two mesial canals (Type XVIII root canal pattern).[4] This status resulted as a consequence of the failure of the first endodontic treatment performed, where middle distal canal was undetected and untreated and mesial canals unfilled.

   Case Report Top

A 31-year-old female patient whose major complaint was “severe pain in her left lower back tooth” arrived at our clinic. On first examination, there was a porcelain crown on tooth 36, which had tenderness on percussion. There was no significant finding in the medical history of the patient. The tooth had no mobility and no problems from periodontal aspect.

The radiograph taken preoperatively showed a radiolucent periapical area with changes in periodontal ligament space and lamina dura in relation to the apical part of mesial root. From the clinical and radiographic findings, a diagnosis of unsuccessful root canal treatment including insufficient root canal filling and obturation with chronic apical periodontitis was made for tooth 36, and a retreatment was scheduled [Figure 1].
Figure 1: Preoperative radiograph of tooth 36

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Periapical radiography demonstrated a regular root canal anatomy. After administration of local anesthesia with 2% articaine containing 1:200.000 epinephrine (Fullcaine; Onfarma Ltd, Samsun, Turkey), the porcelain crown was removed and the tooth no. 36 was isolated with rubber-dam. After the isolation, the endodontic access cavity was prepared.

A trapezoidal cavity was prepared to provide a straight-line access to all distal and mesial canals. During these procedures we noticed that the middle distal canal could not be detected in old endodontic treatment. The tooth had two mesial (mesiobuccal and mesiolingual) and three distal canals (distobuccal, distolingual, and middle distal) on examination [Figure 2].
Figure 2: Access opening showing three canals in distal canal

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Following the detection of the root canals, an electronic apex locator, Dr's Finder NEO (Good Doctors, Incheon, Korea) was used to determine the working length and a radiographical confirmation of these working lengths was taken. ProTaper Next X1 and X2 rotary files (Dentsply Maillefer, Ballaigues, Switzerland) were used for root canal preparation and 5.25% sodium hypochlorite was used for irrigation between each instrument and following this a saline irrigation was performed. Calcium hydroxide with barium sulfate (Meta Biomed Co, Ltd, Chungbuk, Korea) was delivered into the canals, after the canals were dried with paper points and the cavity was closed with temporary filling material (Cavitimi; Imicryl, Konya, Turkey). A second appointment was scheduled after 10 days.

At the next appointment, the previous pain on percussion had subsided. The calcium hydroxide was removed with sonic instruments and 5.25% sodium hypochlorite, 17% ethylenediaminetetraacetic acid (EDTA), and 2% chlorhexidine were used for final irrigation procedure, respectively.

Paper points were used for drying the canals and they were filled by lateral condensation using Gutta-percha and Dia-ProSeal (DiaDent Group Int., Seoul, Korea) [Figure 3]. After restoration of the tooth with a posterior composite resin core (Arabesk; VOCO, Cuxhaven, Germany) original crown was cemented with polycarboxylated cement.
Figure 3: Postobturation radiograph of tooth 36

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   Discussion Top

Mandibular first molar teeth often requires endodontic treatment, as they are the first permanent posterior teeth to erupt into oral cavity and due to different variations in the root canal anatomy, they must be treated with caution.[7] Although the tooth generally has two roots, it may have three. The mesial root can consist of two or three canals and the distal can be made up one or two canals. The incidence of four canals in mandibular molar is 35%.[8] The incidence of three canals in the distal root is 0.2–3% [Table 1]. If only one canal is present in distal root it is called the distal canal, and if more than one is present the root may have distobuccal, distolingual, and middle distal canals. Also a developmental groove connects the orifices to these canals.[6]
Table 1: Prevalence of a third canal in the distal root of mandibular first molar according to different authors

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A case report by Baugh and Wallace found that the incidence of a middle mesial canal in mandibular first molar was 1–15%, but a distal root of the mandibular first molar with three canals is a rare case.[7] A study by Kottoor et al. was a single case report about this subject that we can reach during the literature review.[9] Jabali, reported a middle mesial and a middle distal canal in the same tooth using a dental operation microscope.[10]

In our case report, the root canal variation of tooth 36 was assumed as a Type XVIII configuration. Sert and Bayirli described the Type XVIII configuration as joining of all three distal canals at the apical third of the distal root.[4] Therefore, in this retreatment case, the inadequate filling of the root canals as well as the fact that the middle distal canal could not be identified in the previous endodontic treatment could be the cause of failure in old root canal treatment.

Nowadays, CT scan is likely to be the method of choice in these situations to be certain of the root canal configuration.[11] But for this case, cone beam computed tomography (CBCT) was not necessary therefore clinical and conventional radiographic finding were enough to verify the presence of extra canals. Due to the increased radiation exposure, the benefits of its use must outweigh the risks.

In conclusion, missing a supplementary canal, poor cleaning–shaping–obturation will lead to endodontic failure. Clinicians should possess a thorough knowledge of not only the normal anatomy of the root canal system, but also aberrations. Thus, they should explore the groves in between root canals because sometimes extra root canals may be found.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


   References Top

Aminsobhani M, Bolhari B, Shokouhinejad N, Ghorbanzadeh A, Ghabraei S, Rahmani MB, et al. Mandibular first and second molars with three mesial canals: A case series. Iran Endod J 2010;5:36-9.  Back to cited text no. 1
Vertucci FJ. Root canal anatomy of the human permanent teeth. Oral Surg Oral Med Oral Pathol 1984;58:589-99.  Back to cited text no. 2
Weine FS. Endodontic Therapy. St. Louis, Missour, USA: Mosby Co.; 2004.  Back to cited text no. 3
Sert S, Bayirli GS. Evaluation of the root canal configurations of the mandibular and maxillary permanent teeth by gender in the Turkish population. J Endod 2004;30:391-8.  Back to cited text no. 4
Slowey RR. Radiographic aids in the detection of extra root canals. Oral Surg Oral Med Oral Pathol 1974;37:762-72.  Back to cited text no. 5
Hargreaves KM, Berman LH. Cohen's Pathways of the Pulp. 11th edition: Elsevier Health Sciences; 2015.  Back to cited text no. 6
Baugh D, Wallace J. Middle mesial canal of the mandibular first molar: A case report and literature review. J Endod 2004;30:185-6.  Back to cited text no. 7
Ballullaya SV, Vemuri S, Kumar PR. Variable permanent mandibular first molar: Review of literature. J Conserv Dent 2013;16:99-110.  Back to cited text no. 8
[PUBMED]  [Full text]  
Kottoor J, Sudha R, Velmurugan N. Middle distal canal of the mandibular first molar: A case report and literature review. Int Endod J 2010;43:714-22.  Back to cited text no. 9
Jabali AH. Middle mesial and middle distal canals in mandibular first molar. J Contemp Dent Pract 2018;19:233-6.  Back to cited text no. 10
Durack C, Patel S. Cone beam computed tomography in endodontics. Braz Dent J 2012;23:179-91.  Back to cited text no. 11
Goel NK, Gill KS, Taneja JR. Study of root canals configuration in mandibular first permanent molar. J Indian Soc Pedod Prev Dent 1991;8:12-4.  Back to cited text no. 12
Calişkan MK, Pehlivan Y, Sepetçioǧlu F, Türkün M, Tuncer SS. Root canal morphology of human permanent teeth in a Turkish population. J Endod 1995;21:200-4.  Back to cited text no. 13
Sperber GH, Moreau JL. Study of the number of roots and canals in senegalese first permanent mandibular molars. Int Endod J 1998;31:117-22.  Back to cited text no. 14
Gulabivala K, Aung TH, Alavi A, Ng YL. Root and canal morphology of burmese mandibular molars. Int Endod J 2001;34:359-70.  Back to cited text no. 15
Gulabivala K, Opasanon A, Ng YL, Alavi A. Root and canal morphology of thai mandibular molars. Int Endod J 2002;35:56-62.  Back to cited text no. 16
Ahmed HA, Abu-bakr NH, Yahia NA, Ibrahim YE. Root and canal morphology of permanent mandibular molars in a Sudanese population. Int Endod J 2007;40:766-71.  Back to cited text no. 17
Al-Qudah AA, Awawdeh LA. Root and canal morphology of mandibular first and second molar teeth in a Jordanian population. Int Endod J 2009;42:775-84.  Back to cited text no. 18
Zhang R, Wang H, Tian YY, Yu X, Hu T, Dummer PM, et al. Use of cone-beam computed tomography to evaluate root and canal morphology of mandibular molars in Chinese individuals. Int Endod J 2011;44:990-9.  Back to cited text no. 19
Pattanshetti N, Gaidhane M, Al Kandari AM. Root and canal morphology of the mesiobuccal and distal roots of permanent first molars in a Kuwait population – A clinical study. Int Endod J 2008;41:755-62.  Back to cited text no. 20
Mukhaimer RH. Evaluation of root canal configuration of mandibular first molars in a Palestinian population by using cone-beam computed tomography: An ex vivo study. Int Sch Res Notices 2014;2014:583621.  Back to cited text no. 21
Caputo BV, Noro Filho GA, de Andrade Salgado DM, Moura-Netto C, Giovani EM, Costa C, et al. Evaluation of the root canal morphology of molars by using cone-beam computed tomography in a Brazilian population: Part I. J Endod 2016;42:1604-7.  Back to cited text no. 22
Silva EJ, Nejaim Y, Silva AV, Haiter-Neto F, Cohenca N. Evaluation of root canal configuration of mandibular molars in a Brazilian population by using cone-beam computed tomography: An in vivo study. J Endod 2013;39:849-52.  Back to cited text no. 23


  [Figure 1], [Figure 2], [Figure 3]

  [Table 1]


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