When I took Sophomore Endodontics in dental school we had to memorize that little chart that showed the percentages of variations of canals in teeth. I remember that chart said that about two-thirds of all maxillary first molars have a mesio-buccal 2 canal.  Now I read consistently in different publications that around 90-95% of maxillary first molars have an MB2 canal.  Why the difference?  Was the Endo department trying to make us feel better about not finding MB2 most of the time?  I don’t know…but what I do know is that I just automatically assume that ever maxillary first molar I access for endodontic therapy has an MB2.  The question is can I find it?

Sometimes I can, sometimes I can’t.  Most of the time, if I can’t find MB2 at the pulpectomy appointment, I go ahead and refer the patient to the endodontist.  I don’t really have any special tricks for finding it.  I just look for it.  If anyone does have any tricks for finding MB2, please share them with us in the comments.

Here is tooth #3 that I just completed access on about 3 minutes ago.

As you can see, MB2 was located about half-way between MB1 and the palatal root.  This seems to be a pretty common spot for it, but it can vary greatly.  On every pulpectomy I do, after locating all the canals I try to get a 10 K-file to an estimated working length.  If this can be done in all canals, I open the orifices using Gates-Glidden drills.  There are all sorts of other orifice opening burs available, but I really like plain jane ol’ Gates.  They seem to work well in my hands.  The photo above shows the canal orifices after using Gates-Glidden drills size 1 and 2.

Nothing special today…just a reminder to keep a look out for those MB2’s. They can be total PITA’s most of the time.  Thank God for endodontists!

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