The permanent mandibular first molar is frequently involved in conventional root canal treatment due to its function and position in the oral cavity. Additional root canals mandate accurate diagnosis and conservative management to prevent any procedural errors. The first independent middle mesial canal incidence was verified in mandibular molars in 1974, with a global incidence of 10.8–27.0%. Reporting of the middle distal canal in the endodontic literature is scarce, with an incidence of 0.2–3%. The present case report describes the endodontic management of an unusual permanent mandibular first molar with three canals in the mesial and distal roots, diagnosed with irreversible pulpitis and apical periodontitis. A dental operating microscope and multiple angulated radiographs were used to identify the unusual morphology, and this was confirmed with cone-beam computed tomography imaging. The access cavity was modified to a trapezoidal shape, and the pulp chamber was carefully explored following root dentinal maps to expose additional canals by ultrasonic troughing. Incorporating a dental operating microscope and cone-beam computed tomography imaging in routine endodontic cases facilitates a better understanding and visualization of the complex root canal anatomy, making even the management of endodontically challenging cases more predictable.


1. Walton RE. Histologic evaluation of different methods of enlarging the pulp canal space. J Endod. 1976; 2(10):304-11.

2. Nosrat A, Deschenes RJ, Tordik PA, Hicks ML, Fouad AF. Middle mesial canals in mandibular molars: Incidence and related factors. J Endod. 2015; 41(1):28-32.

3. Vertucci FJ, Williams RG. Root canal anatomy of the mandibular first molar. J N J Dent Assoc. 1974; 45(3):27-8.

4. Barker BC, Parsons KC, Mills PR, Williams GL. Anatomy of root canals. III. Permanent mandibular molars. Aust Dent J. 1974; 19(6):408-13.

5. Azim AA, Deutsch AS, Solomon CS. Prevalence of middle mesial canals in mandibular molars after guided troughing under high magnification: An in vivo investigation. J Endod. 2015; 41(2):164-8.

6. de Toubes KM, Côrtes MI, Valadares MA, Fonseca LC, Nunes E, Silveira FF. Comparative analysis of accessory mesial canal identification in mandibular first molars by using four different diagnostic methods. J Endod. 2012; 38(4):436-41.

7. Akbarzadeh N, Aminoshariae A, Khalighinejad N, Palomo JM, Syed A, Kulild JC, Sadeghi G, Mickel A. The association between the anatomic landmarks of the pulp chamber floor and the prevalence of middle mesial canals in mandibular first molars: An in vivo analysis. J Endod. 2017; 43(11):1797-801.

8. Pomeranz HH, Eidelman DL, Goldberg MG. Treatment considerations of the middle mesial canal of mandibular first and second molars. J Endod. 1981; 7(12):565-8.

9. Jabali AH. Middle mesial and middle distal canals in mandibular first molar. J Contemp Dent Pract. 2018; 19(2):233-6.

10. 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(8):714-22.

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(1):12-4.

12. Calişkan MK, Pehlivan Y, Sepetçioğlu F, Türkün M, Tuncer SS. Root canal morphology of human permanent teeth in a Turkish population. J Endod. 1995; 21(4):200-4.

13. Abella F, Morales K, Garrido I, Pascual J, Duran- Sindreu F, Roig M. Endodontic applications of cone beam computed tomography: Case series and literature review. G Ital Endod. 2015; 29(2):38-50.

14. Martinez-Berna A, Badanelli P. Mandibular first molars with six root canals. J Endod. 1985; 11(8):348-52.

15. Ghoddusi J, Naghavi N, Zarei M, Rohani E. Mandibular first molar with four distal canals. J Endod. 2007; 33(12):1481-3.

16. Kontakiotis EG, Tzanetakis GN. Four canals in the mesial root of a mandibular first molar. A case report under the operating microscope. Aust Endod J. 2007; 33(2):84-8.

17. Aminsobhani M, Shokouhinejad N, Ghabraei S, Bolhari B, Ghorbanzadeh A. Retreatment of a 6-canalled mandibular first molar with four mesial canals: A case report. Iran Endod J. 2010; 5(3):138-40.

18. Ryan JL, Bowles WR, Baisden MK, McClanahan SB. Mandibular first molar with six separate canals. J Endod. 2011; 37(6):878-80.

19. Gupta S, Jaiswal S, Arora R. Endodontic management of permanent mandibular left first molar with six root canals. Contemp Clin Dent. 2012; 3(Suppl 1):S130-3.

20. Baziar H, Daneshvar F, Mohammadi A, Jafarzadeh H. Endodontic management of a mandibular first molar with four canals in a distal root by using cone-beam computed tomography: A case report. J Oral Maxillofac Res. 2014; 5(1):e5.

21. Hasan M, Rahman M, Saad N. Mandibular first molar with six root canals: A rare entity. BMJ Case Rep. 2014;2014:bcr2014205253.

22. Sinha N, Singh B, Langaliya A, Mirdha N, Huda I, Jain A. Cone beam computed topographic evaluation and endodontic management of a rare mandibular first molar with four distal canals. Case Rep Dent. 2014; 2014:306943.

23. Jain D, Reddy S, Venigalla BS, Kamishetty S. Endodontic management of a mandibular first molar with six root canal systems. J Conserv Dent. 2015; 18(5):419-22.

24. Maniglia-Ferreira C, Gomes Fde A, Sousa BC. Management of six root canals in mandibular first molar. Case Rep Med. 2015; 2015:827070.

25. Martins JN, Anderson C. Endodontic treatment of the mandibular first molar with six roots canals - Two case reports and literature review. J Clin Diagn Res. 2015; 9(4):ZD06-8.

26. Hashem A AR, Ahmed HMA. Endodontic management of a mandibular first molar with unusual canal morphology. Eur Endod J. 2017; 2(1):1-4.

27. Bhargav K, Sirisha K, Jyothi M, Boddeda MR. Endodontic management of contralateral mandibular first molars with six root canals. J Conserv Dent. 2017; 20(4):282-5.

28. Subramaniam Ramachandran V, Shankari V, Rathakrishnan M, Chandrasegaran V, Kumaraguru K. Management of three rooted mandibular first molar with six canals: A case report. Cureus. 2019; 11(12):e6280.

29. de Pablo OV, Estevez R, Péix S ánchez M , Heilborn C, Cohenca N. Root anatomy and canal configuration of the permanent mandibular first molar: A systematic review. J Endod. 2010; 36(12):1919-31.

30. 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(6):391-8.

31. De Moor RJ, Deroose CA, Calberson FL. The radix entomolaris in mandibular first molars: An endodontic challenge. Int Endod J. 2004; 37(11):789-99.

32. Ahmed HMA, Versiani MA, De-Deus G, Dummer PMH. A new system for classifying root and root canal morphology. Int Endod J. 2017; 50(8):761-70.

33. Skidmore A E, Bjor ndal A M. Root canal morphology of the human mandibular first molar. Oral Surg Oral Med Oral Pathol. 1971; 32(5):778- 84.

34. Baugh D, Wallace J. Middle mesial canal of the mandibular first molar: A case report and literature review. J Endod. 2004; 30(3):185-6.

35. Weinberg EM, Pereda AE, Khurana S, Lotlikar PP, Falcon C, Hirschberg C. Incidence of middle mesial canals based on distance between mesial canal orifices in mandibular molars: A clinical and cone-beam computed tomographic analysis. J Endod. 2020; 46(1):40-3.

36. Karapinar-Kazandag M, Basrani BR, Friedman S. The operating microscope enhances detection and negotiation of accessory mesial canals in mandibular molars. J Endod. 2010; 36(8):1289-94.

37. Yoshioka T, Kobayashi C, Suda H. Detection rate of root canal orifices with a microscope. J Endod. 2002; 28(6):452-3.

38. American Association of Endodontists, American Academy of Oral and Maxillofacial Radiology. AAE and AAOMR joint position statement: Use of cone beam computed tomography in endodontics 2015 update. J Endod. 2015; 41(9):1393-6.

39. Kottoor J, Albuquerque DV, Velmurugan N, Sumitha M. Four-rooted mandibular first molar with an unusual developmental root fusion line: A case report. Case Rep Dent. 2012; 2012:237302.

40. Tashkandi N, Alghamdi F. Effect of chemical debridement and irrigant activation on endodontic treatment outcomes: An updated overview. Cureus. 2022; 14(1):e21525.

41. Fabra-Campos H. The problem of lower first molars in endodontic treatment. Rev Esp Endodoncia. 1983; 1(3):135-53.

42. Fur ri M, Tocchio C, Bonaccorso A, Tripi TR, Cantatore G. Apical canal confluency in mandibular molars. Endod Pract Today. 2007; 1(1):53-9.

43. Reeh ES. Seven canals in a lower first molar. J Endod. 1998; 24(7):497-9.

44. Hsu YY, Kim S. The resected root surface. The issue of canal isthmuses. Dent Clin North Am. 1997; 41(3):529-40.



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