A Surprise Inside.

Morphology, Retreatment May 3rd, 2007

I’m almost finished posting all of my interesting archived cases. Just one more to go after this one:

This one is from about 6 years ago, which explains the multiple backfill voids in the obturation. Anyway, I don’t know how many of my peers would attempt a retreat on this tooth. That post which looks like it would tack down drywall appears menacing to remove. It actually came out extremely easily. That was a pleasant surprise. The other surprise was the fifth canal.



That’s one mutant tooth.


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  • Dr. Mommy, D.D.S.

    cool! i’ve seen 5 canal lower molars, but never on an upper! where was the orifice in relation to the MB1 and DB? is this something i should look for regularly when i do my next upper 6?

    also, what is the exact percentage of upper molars that have an MB2? at the dentsply course i took in september the moderator said that almost all 6s have a fourth canal, they are very commonly missed, and that you should really look for them. i felt really silly last upper 6 i did because i had a beautiful access, perfect working length measurements, but i was convinced there was a calcified fourth canal so i sent it to the specialist. turned out there was none. i could have finished the tooth myself!!! better cautious than not, right? grrr…

  • Ameloblast

    The fifth canal showed up as an extra palatal orifice (mesial to the regular palatal canal). This is rare (speaking from experience), so you can’t really be faulted for not looking for or finding it.

    I enter upper molars expecting to find a fourth canal. It takes me longer to work the ones that only have 3 because I spend more time trying to find 4.

    This is the study that endodontists like to quote to GPs regarding the incidence of MB2 canals. Other studies have shown a lower incidence and some have a stronger sample size:

    ***
    J Endod. 1990 Jul;16(7):311-7.

    Incidence and configuration of canal systems in the mesiobuccal root of maxillary first and second molars.

    * Kulild JC,
    * Peters DD.

    US Army Dental Corps, Ft. Gordon, GA.

    The anatomy of the mesiobuccal (MB) root of 51 maxillary first and 32 maxillary second molars was studied. Initially, an attempt was made to locate all canals using a standard access and hand instruments. A bur was next used carefully to locate any additional second mesiobuccal (mesiolingual (ML)) canals. Finally, after crown removal, the teeth were reduced horizontally in 1-mm increments and examined by microscope. A second ML canal was located in the coronal half of 95.2% of the roots: by hand instruments in 54.2%; bur in 31.3%; and microscope in 9.6%. There were no root perforations when the bur was used as described. The ML canal orifice averaged 1.82 mm lingual to the MB canal orifice. The difference in incidence of ML canals between the first and second molars was not statistically significant. The canal systems were type 1, 4.8%; type 2, 49.4%, and type 3, 45.8%.
    ***

    The percentage is quite high and only slightly lower for upper 7′s. What’ll happen fairly often, though, is once both canals are located and instrumented, they end up coalescing into one larger canal (just because of how close they sometimes are to each other). This is similar to what we sometimes see with the DB and DL canals in lower molars.

  • nazlihaffiz

    A mutant 5 canal upper 6. Dang!

    My fiance (she’s the one with the interest in endodontics, I’d rather deal with orthodontic brackets and such hehe) would be having a field day if she comes across one like the mutant 6.

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