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Endo tips    Better Endo    Endo abstracts    Endo discussions

MM/isthmus protocol- Courtesy ROOTS
The opinions and photographs within this web page are not ours.
Authors have been credited
for the individual posts where they are. - www.rxroots.com

From: John A. Khademi, DDS MS
To: ROOTS
Sent: Tuesday, March 24, 2009 2:12 AM
Subject: Re:[roots] Re-post of MM/isthmus protocol for Thomas

So I have forwarded the old emails from 2005 that should go through the list-server.

Here is the protocol from 2005.
Edits for today will be in [italics]:

Thanks Benny,

That's great.  Here is how I managed these cases, because the dentin in this area 
is quite thin, and I don't recall a post on this subject matter.  The invagination 
in the blue area of Ben's post is often WORSE than is drawn.  You restorative guys, 
look at those teeth when you take them out, then ask yourself how bright it is to 
take a #2 peezo to 6mm from the end...

1) Locate and negotiate, and with a #10 or 15 establish a length.

2) Now that I have a V-Taper #10/.06, take that to length...and a little bit.
   [I skip this step  now]

3) suction out the MB and/or ML backdrawing on your NaOCl syringe.  If the MM drains 
at this point,    and the root appears thin, you may want to terminate the preparation.  
If they join this easily,    you will fill it on the squirt.  This is a relatively 
rare occurence, however.

   [I now may take a #20 HF to length and check for drainage again]

4) Brand new #2 S29/.06 to length and a bit.  Repeat step 3.  If it drains, you are done.  
   If not, check patency on all canals and repeat step 3.  If still not, go up to #3 and 
   repeat the draining    test w/ patency check.  If still not, go up to #4 and repeat 
   draining test w/ patency check.

   [This instrument is too big.  I will now take a 20.V.06 Guidance to length,
    or close to length.]


If at this point, the MM does not drain, it is prepped out large enough (#4S29/.06 = ~20/.06) 
to fit a cone and truly treat as a separate canal, regardless of whether it is or not.  
Never go past a #4 unless you have a convincing reason to do so.  Retreatment is much easier 
than retreatment + a strip perf repair... :-)

[I am able to get a fine cone down with a 20/V.06.  I have #20 standard cones for smaller 
preparations. Sometimes I just rely on squish.]

You will notice in essentially all of my MM posts that the middle canal is markedly smaller
...It almost always joins the MB or ML.

In a maxillary molar with three MB's, the DB2 and any other "fin/isthmus/whatever" canals 
I will do the same. Just finished a C-shaped lower second molar.   Took three visits, but 
all the canals drain together now, which they should, since it is one, big canal anyway.


Eric Herbranson, probably the foremost expert on endodontic anatomy pretty much agrees with 
this thinking. These isthmus canals cannot be prepared to standard shapes and sizes.
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