Mb2 Mesiobuccal Canal

MB2: THE MISSED CANAL

A source of great frustration associated with the endodontic therapy of maxillary molars is whether or not a second mesiobuccal canal (MB2) exists, and to what extent practitioners should go in pursuit of locating it. Failure to find and to fill a canal influences the prognosis of endodontic treatment. The frequency of second canal in mesiobuccal root of maxillary molars is quite high, so time should be devoted in its location and treatment. The present article describes the possible location of these canals and various methods proposed to help in locating the fourth canal. It is almost axiomatic to accept the fact that the root system of the mesiobuccal root of maxillary molars frequently has a root canal system
Developmentally, there is often a dentinal cornice, or rounded growth of dentin, found in the middle of the mesial surface of the pulp chamber which conceals entry into the MB2 canal. Likewise, during development due to dentin deposition, the ML area of the MB root first moves slightly mesially and lingually, exiting at a distance of about 1.8mm from the MB canal. The MB1 canal normally departs the pulpal floor with only a slight mesial inclination. However, the MB2 canal usually has a marked mesial incline immediately apical to its orifice in the coronal 1 to 3mm. When an attempt is made to instrument the MB2, the tip of the file tends to catch against the mesial wall of the canal, preventing apical progress. Finding and instrumenting the MB2 canal can be made more difficult due to the fact that the canal is usually smaller and can become calcified over time when exposed to irritants such as mesial proximal caries and deep
Every system has some inbuilt taper (4, 6, 7, 8, 9% etc.). However every root in every tooth has a different thickness. For example, roots of maxillary 2nd molars are smaller than roots of maxillary 1st molars. In the same tooth itself, MB and DB are thinner than the palatal. So external anatomy (width of the root) is also very significant along with internal anatomy of canals (calcification, width of canal) while cleaning and shaping. Using the same size and taper for MB/DB and palatal roots may take out too much of dentin out of the smaller MB and DB roots leaving little radicular dentin behind and thus weaker roots susceptible to fracture. So it is always preferable to use different tapers according to the external anatomy also.
So many endodontists at times prefer to fill MB1 and MB2 with 4% (25 or 30) gutta-percha points with thinner accessory cones (or thermoplasticized gutta-percha techniques). This helps in conserving the radicular dentin resulting in stronger roots. Files like HERO Shaper allow you to do circumferential filing and can join the canals without