Middle Mesial Canal In a Lower Molar By: Mark Dreyer, DMD, PA

As posted on the Case Presentation section of www.dentaltown.com, followed by Townie Comments

As is often the situation with three mesial canals, there are not three separate orifices. In the following case, two of the canals shared a single orifice

Conclusion:
This was a two-step case done with an interim CaOH dressing. The appointments were one month apart. The case was done this way because I couldn’t dry the distal canal on the initial visit.

Dr. Mark Dreyer, DMD
• BS Mathematics Univ of Florida 1981
• DMD Univ of Florida College of Dentistry 1986
• In private practice of general dentistry in Central Florida 1987-2000
• In group practice as associate-dentist limited to endodontics 2000-Fall 2003
• Started private practice as general dentist limited to endo September, 2003

Endo courses I’ve taken and forums on which I’ve learned:
Dr. John Schoeffel, Dr. Kit Weathers, Dr. Steven Buchanan, Dr. Clifford Ruddle, Dr. John Stropko, Dr. Gary Carr, Dr. Barry Musikant

Numerous dentists on the various internet based forums on which I participate: Dental Town, Internet Dental Forum, Roots Forum, TDO Forum I average completion of 1200-1500 endodontic cases/year.

Dr. Mark Dreyer can be reached at his Office at 407-933-0885, his home at 407 870 5041 or by cell at 321 443-1562. His email address is: mdreyer@cfl.rr.com

gobucks | Posts: 7 | Posted 12/20/2003 | 11:51:41 AM
How often does that third canal occur and does it usually merge with the ML or MB canal? Looks like the tricky MB2 canals on max 1st molars. Thanks for sharing.

dr-adelramadan | Posts: 5 | Posted 12/20/2003 | 3:32:36 PM
Thanks for sharing, but what is the bleach soaking? Did you use the dam? How often does this happen and can you explain how you found it?

Mark Dreyer | Posts: 634 | Posted 12/21/2003 | 5:33:31 AM
The middle mesial canal occurs in lower molars approximately 1-2% of the time if I recall correctly from the literature I’ve seen quoted on this.

On every tooth I treat, there is bleach in the chamber (not until the tissue is out on a vital tooth, and during the whole procedure on a necrotic tooth). That photo was taken after shaping of the middle mesial canal and the bleach just happened to be there as is typically the case on any tooth I treat.

As for how I find these middle mesial canals, if you look at the one photo with the arrows, you see that ledge of dentin, which is really just a piece of the roof of the chamber. This ledge becomes obvious after shaping of the MB & ML canals including coronal opening with the larger GG burs. Up until that point, the ledge is not as noticeable. Anyhow, I remove this ledge with the pear shaped troughing tip at full power in my ultrasonic unit (I have a Satelec P5 in one room and a Sybron-Analytic mini-Endo in the other room). The tip I use is incredibly aggressive and it takes this ledge out in about 5-10 seconds. It is called the pear shaped troughing tip and I buy it from Dr. Gary Carr, and endodontist in San Diego. You can inquire about it at his website at www.endotips.com. There are other similar tips sold by the big companies, but this one is less expensive and it works great. I call it the “Carr Killer Tip”.

Once that ledge is removed I can frequently see a small isthmus. (You’re probably not going to see this without some pretty high-powered loupes or a scope, in which case you might be able to find it by tactile sensation. I take my size 6 file and try to get a catch in that area. If I get a catch, I watch wind and can tell pretty fast if there’s another canal. If there is, I continue with the size 8, 10, etc. I find it helps to instrument this small canal if I keep 17% EDTA in the chamber during this process.

doctored | Posts: 3523 | Posted 12/21/2003 | 6:11:42 AM
Hello Mark. After you did the resin access buildup you probably could have done this case without a dam (wink). The angled image looks like there indeed is a third portal. Gotta’ love these cases. The more you look the more you find. Wish you were local. I would love to watch you work sometime.

Mark Dreyer | Posts: 634 | Posted 12/21/2003 | 6:19:53 AM
Doctored, thanks for the comments. No rubber dam? Is that a trick question?

windmill | Posts: 1283 |Posted 12/22/2003 | 11:54:32 AM
This is beautiful work, but it gives me nightmares about future lower molar endo. As if searching for MB2s wasn’t mind-racking enough.

Mark Dreyer | Posts: 634 | Posted 12/22/2003 | 12:22:59 PM
Windmill, thanks for the compliment. I’m not meaning to give you nightmares––sorry! My point in posting this is to educate primarily and secondarily my point is to promote the incorporation of the scope. The scope has made such a difference in my practice, and I just want to share it with others. It can really make your endodontic treatment easier and a lot more fun. They aren’t that expensive either, compared to some of the other toys us dentists spend good $$ for.

karid | Posts: 80 | Posted 12/29/2003 | 7:10:02 PM
Dear Mark, when presenting this case, picture no. 2 does not belong to this case as you have stated. There are other ways to discover third mesial canals, most often you will see a bleeding point between two orifices in a vital case or when you place a paper point in a cleaned canal there is blood on the paper point other than the tip, then one can suspect the third canal (bleeding can come from tissue web between two canals also).

Do you routinely cut with ultrasonics between the two mesial orifices?

Mark Dreyer | Posts: 634 | Posted 12/29/2003 | 7:30:45 PM
Hi Karid, yes, I routinely use the ultrasonics for this purpose. Dr. Gary Carr sells a really heavy-duty tip that works like a charm for that purpose. You can inquire at his site at www.endotips.com. Of course, a surgical length round bur would do the job also, but this particular tip does the job cleaner and faster.