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CASE REPORT Table of Contents   
Year : 2007  |  Volume : 18  |  Issue : 1  |  Page : 38-40
MB2 in maxillary second molar

Department of Conservative Dentistry and Endodontics, Meenakshi Ammal Dental College, Alapakkam Main Road, Maduravoyal, Chennai - 95, India

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Date of Submission13-Apr-2006
Date of Decision02-Nov-2006
Date of Acceptance08-Nov-2006


Occurrence of the second mesiobuccal canal (MB2) is a frequent finding. Literary reports have shown it to be found more in the cases of the maxillary first molar. However the maxillary second molars have also been found with this variation in a number of canals. This paper presents a case report on the occurrence of a second mesiobuccal canal or the MB2 in the maxillary second molar.

Keywords: Maxillary second molar, second mesiobuccal canal, MB2

How to cite this article:
Prakash R, Bhargavi N, Rajan J, Joseph R, Velmurugan N, Kandaswamy D. MB2 in maxillary second molar. Indian J Dent Res 2007;18:38-40

How to cite this URL:
Prakash R, Bhargavi N, Rajan J, Joseph R, Velmurugan N, Kandaswamy D. MB2 in maxillary second molar. Indian J Dent Res [serial online] 2007 [cited 2022 Aug 13];18:38-40. Available from:

   Introduction Top

The success of endodontic therapy is dependent on the quality of cleaning of the entire root canal system. Therefore, it is of major importance to have a thorough knowledge of the dental anatomy and its variation prior to initiation of treatment

Maxillary molars are known to have a fourth canal (Mesiobuccal second canal or mesiolingual) located in the mesiobuccal root.[1] Weine stated that one of the reasons for the failure of endodontic treatment of maxillary molars is due to the failure to locate and fill the second mesiobuccal canal.[2] A preoperative radiograph does not give a clear idea of an extra canal. Hence multiple preoperative radiographs in various angulations are a must before access opening. This paper highlights a case of a second mesiobuccal canal (MB2) in the left maxillary second molar.

   Review of literature Top

Pecora[3] studied the internal anatomy of 370 maxillary molars by clearing the roof of the pulp chamber and located a second canal in mesiobuccal root of maxillary second molars, with frequency of 42%. Stropko[4] 1999 examined 611 maxillary second molars over a period of eight years. He found an incidence of MB2 canals present in 310 (50.7%) cases. It occurred as a separate canal in 119 (45.6%) cases and joined the MB1 in 142 (54.4%) cases.

Schwarze[5], confirmed in his study that there was a high number of second canals in the mesiobuccal roots (i.e.) 48% of maxillary second molars. Peikoff et al[6] 1996 observed that 1.4% of maxillary molars may have second palatal roots. James Walcott[7] examined 2038 maxillary second molars treated consecutively over a five year period by six endodontists. The overall number of cases with MB2 was 712 (35%). Of these, in 34% of cases, MB2 was found in the initial treatment itself, whereas, the percentage of missed canals by an endodontist was 40%, it was found only during re-treatment. During re-treatment, few of the cases with sinus openings have healed provided efforts were made to locate and treat additional canals.

   Case report Top

A 27-year-old female patient was referred with complaint of severe pain in the left upper molar tooth since one week. Clinical examination revealed a deep carious lesion of the left maxillary second molar. Vitality testing gave a lingering response and radiographic investigation revealed pulpal exposure in relation to the left maxillary second molar [Figure - 1]. Hence a diagnosis of irreversible pulpitis was made. Root canal therapy was initiated under rubber dam isolation. Once the pulp chamber was deroofed, a trapezoidal shaped access opening was obtained. On careful visualization of the floor of the pulp chamber, the dentinal map showed a long groove between the palatal and the mesiobuccal orifices. Careful examination and exploration of the groove resulted in the detection of an extra mesiobuccal canal roughly about 2-3 mm away from the MB1orifice using small size instruments (6, 8, 10 Mani K-files) the canal was negotiated [Figure - 2] cleaning and shaping was done using conventional hand instruments (K-files) and Gates Glidden drills (sizes 3, 2, 1) and the canals were obturated using cold lateral compaction of gutta-percha [Figure - 3] the tooth was subsequently restored.

   Discussion Top

In today's clinical scenario a tooth is considered normal even if variation occurs in the anatomy of the roots. It is therefore the responsibility of the endodontist to locate and treat the extra canals. Weine[2] suggests that for the maxillary second molar, angulation from distal to mesial provides a profile type view of the mesiobuccal root and allows for the visualization of the presence of extra canals. If one of the canals is eccentrically located, it should immediately raise the suspicion about an extra canal.[8]

Beer and Baumann[9] suggested a geometric aid to locate an extra canal, which is adopted in this study to locate the extra canal [Figure - 4]. First a line 1 was drawn connecting the mesiobuccal and palatal canals, then a line 2 was drawn perpendicular to the line 1, at a point one third the intercanal distance from the palatal canal such that this line passes over the distobuccal canal. A fourth canal lies somewhere along line 3, which deviates approximately 10.

Most of the MB2 canals, however, can be best identified by means of an operating microscope. It was found that 33.3% of cases with MB2 was identified using a 2x magnifying loupe, whereas 95.8% were identified using an operating microscope.[1]

The MB2 canal is challenging to negotiate. The canal has a marked incline immediately apical to its orifice in the coronal 1-3 mm. When an attempt is made to instrument MB2, the tip of the file tends to catch against the mesial wall of the canal, preventing apical progress. This is because MB2 canal is smaller and usually narrower than MB1. After locating the MB2 orifice, inclining the dental handpiece to the distal, as far as the access preparation permits us to enter the first few millimeters of this overlying "roof" of calcified tissue to be safely eliminated. After this "refinement" of the access preparation, a more desired straight line access can be achieved. Sometimes, the MB2 lies in the same orifice as MB1.[4] When there was a shared or common orifice, many times the opening was more oval in shape. Infrequently, but on occasion, the MB2 orifice was harbored within or just apical to, that of the palatal canal.[4]

There is a range of variations of MB2 in root canals of maxillary second molars. They can have a single common opening into the pulp chamber, sometimes both canals exit apically through a single canal as a type II configuration, rarely they exist as two separate canals and exit separately. In the present case, it was found that the two canals had a single opening into the pulp chamber.

Apart from preoperative radiographs of varying horizontal angulations, various intraoperative procedures of detecting extra canals are available. They may be adequate access widening for enhanced visualization, careful observation and exploration of the dentinal map, looking for bleeding spots and uncovering calcifications from the chamber floor.[10],[11]

Few other investigations also help in identification of MB2. The Champagne / bubble test with warmed 2.6% NaOCl and observed under magnification, staining the chamber with 1% methylene blue and ophthalmic dyes are used to trace and locate canals. Fibre-optic transilluminations are used to locate the developmental line between the MB1 and MB2 orifices, a computed tomography can also help in identifying an extra canal.[11]

   Conclusion Top

Varying morphology in human teeth is a common occurrence. Thorough knowledge of these variations is essential prior to initiation of endodontic therapy. Hence the endodontist must have an open mind to accept the possibilities of extra canals for better management and a successful treatment outcome.

   References Top

1.Baratto-Filho F, Fariniuk LF, Ferreira EL, Pecora JD, Cruz-Filho M, Sousa-Neto MD. Clinical and macroscopic study of maxillary molars with two palatal roots. Int Endod J 2002;35:796-801.  Back to cited text no. 1    
2.Weine FS. Endodontic therapy. 5th ed. 1996.  Back to cited text no. 2    
3.Pecora JD, Woelfel JB, Sousa Neto MD, Issa EP. Morphologic study of the maxillary molars part II: Internal anatomy. Braz Dent J 1992;3:53-7.  Back to cited text no. 3  [PUBMED]  
4.Stropko JJ. Canal morphology of maxillary molars: Clinical observations of canal configurations. J Endod 1999;25:446-50.  Back to cited text no. 4  [PUBMED]  
5.Schwarze T, Baethge C, Stecher T, Geurtsen W. Identification of second canals in the mesiobuccal root of maxillary first and second molars using magnifying loupes or an operating microscope. Aust Endod J 2002;28:57-60.  Back to cited text no. 5  [PUBMED]  
6.Peikoff MD, Christie WH, Fogel HM. The maxillary second molar: Variations in the number of roots and canals. Int Endod J 1996;29:365-9.  Back to cited text no. 6  [PUBMED]  
7.Wolcott J, Ishley D, Kennedy W, Johnson S, Minnich S, Meyers J. A 5 yr clinical investigation of second mesiobuccal canals in endodontically treated and re-treated maxillary molars. J Endod 2005;31:262-4.  Back to cited text no. 7  [PUBMED]  [FULLTEXT]
8.Velmurugan N, Parameswaran A, Kandaswamy D, Smitha A, Vijayalakshmi D, Sowmya N. Maxillary second premolar with three roots and three separate canals: Case report. Aust Endod J 2005;31:73-5.  Back to cited text no. 8  [PUBMED]  
9.Rudolf B, Michael AB. Color atlas of dental medicine. Endodontology 2000. p. 51-2.  Back to cited text no. 9    
10.Ruddle CJ. Microendodontics: Identification and treatment of the MB2 system. J Calif Dent Assoc 1997;25:313-7.  Back to cited text no. 10  [PUBMED]  
11.Bhargavi N, Velmurugan N, Kandaswamy D. The hunt for elusive canals. Endodontology 2005;17:18-23.  Back to cited text no. 11    

Correspondence Address:
Jeyavel Rajan
Department of Conservative Dentistry and Endodontics, Meenakshi Ammal Dental College, Alapakkam Main Road, Maduravoyal, Chennai - 95
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0970-9290.30922

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[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4]


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