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  Troughing advice needed
The opinions within this web page are not ours. Authors have been credited for the individual posts where they are. - www.rxroots.com Images courtesy: Doug R
From: GURPREET SINGH
Sent: Friday, December 30, 2005 7:24 AM
To: ROOTS
Subject: [roots] troughing advice needed

Please guide me about troughing between mesials of lower molars and mb and palatal to find mb1 as since last month
I have found  mb1 in almost every upper  first molar  but getting to prepare them needed troughing so i was only able
to prepare 10% less canals than the # I found as I could not  get the file past the opening of the canal and  files #8
n 10  tips used to bend like  question mark ? - Dr.Gurpreet Singh

Satelec P5 ultrasonic unit, a BUC 1 tip, rubber dam, microscope..follow the white lines in the pulpal floor..
98-99% of it is SEEING!!!!!.......

What you are basically asking is equivalent to the question :  can someone help me get this key I have here in to the
lock of that door over there while I have my eyes closed

The simple answer to the question is : open your eyes

Plain and simple there is nothing to be taught other than the value of light and magnification - Craig

First, realize that while upwards of 90% of maxillary first molars have a second canal in the MB root, only about 10% of
mandibular first molars do. In neither location can they always be negotiated. The maxillary molar is common, however,
so let's consider that one.

As John West is fond of saying, negotiating the MB2 is "not a big job, it's a smart job." The problem is that the MB2 is
very curved at the coronal limit of the canal. The shelf of dentin that grows over and obscures the (minute) orifice has
the effect of moving the canal entrance distal to the true path. When you insert your file, it immediatedly runs into a
wall of dentin on the mesial side of the canal, and the extremely narrow confines of these typically very small canals
will not allow the file to negotiate the abrupt curvature. Excessive vertical work merely crumples the file tip and risks
ledging. Therefore, access must be created.




You do this by working the tip of the file to the point where resistance is met, and then pulling it to the mesial to
file away the overhanging dentin. When your file first engages, you will note that the it "points" almost straight to
the mesial, with the handle at a radical distal angle (see illustration). Realize, there may only be 2 or three flutes
of the file that are engaged.As you do this you will observe that the MB2 orifice moves far to the mesial from where it
began. later you will gain experience and become quite artful in your troughing so as to make for the mesial extent of
the canal more directly. I often alternate ultrasonics with a small round bur (eg, LN burs); the sonics strip away the
overhang while the round bur polishes the dentin, making the orifice highly visible in the scope.When you have accessed
sufficiently, you will note that the file begins to drop vertically as you work it; this will coincide with in creasingly
vertical file orientation. You will, of course, use up a number of small files, less with experience. You want to avoid a
lot of work with the tip early on, as the possibility of ledging the mesial wall is quite high at first; you should be
"taking what the canal will give" and using the side flutes to remove what Ruddle calls the triangle of dentin that
obscures the true path.

It will become easier, with experience. But it never becomes EASY. Good luck and good hunting! ......DougR

G'day Doug,

Thank you for taking the time to distil your thoughts regarding Gurpreet's question on this subject - I thought it was so
clearly explained it didn't take a second reading.

Would you mind posting your thoughts on what should be going through our minds when "chasing the white line" during a
search for missing orifices?  I'm prompted to ask for two reasons:

I've had a few iatrogenic perforations in 2005 during this phase of endodontic treatment despite exploration with
ultrasonic tips at 10+  x's magnification, and

I enjoyed the clarity of your explanation for Gurpreet's question.

Wonderful effort; this is what Roots is about - a colleague calls for help and an hour later there is knowledgeable
advice to be considered.  - Michael Moran

G'day Mike, Remember, "access outline for the first molar (upper or lower, by the way) should approach the height of
contour of the MB cusp." What is not obvious, however, is that the orifice to the MB2 in upper molars is often located
MESIAL to the orifice of the MB. This effectively places the "true orifice", i.e., the one that will let you into the
canal proper, UNDER the mesial marginal ridge.

Initial troughing vertically means that you are essentially troughing the floor of the pulp directly overthe furcation
(a-a' in the diagram). If you use a light touch initially and clear away the overhanging dentin toward the MMR, and if
you alternate ultrasonics with light polishing with a round bur, the white line will show up and THIS you can be a bit
more aggressive in pursing vertically. It is very helpful to occasionally "true-up" the mesial wall adjacent to your
access trough (safe-end diamond) as more light will be refracted on the work (hat tip to Ruddle). This approach has the
added advantage of not weakening the MB root by excessively thinning the furcation at the junction of the MB root to the
furcation.

After a while, differences in the color of the dentin will tip you early as to where you are within the pulp floor.
If, for example, explorer pressure on the dentin leads to visible blanching of the underlying dentin color--you're getting
a might thin partner!




Avoid using a lot of explorer pressure in hunting for the canal orifice for at least 2 reasons. One, explorer gouges will
appear just like a real canal and can fool you into chasing your own, personal orifice to your man-made communication with
the periodontium. Second, the tip of the explorer will often raise a scallop of dentin (Like a wood shaving curling ahead
of a wood chisel) which obscures the entrance to what may indeed be the true canal, preventing ingress of the far more
delicate tip of a #6,8, or 10 file. Do your exploring with the file itself. Good hunting - DougR

Doug, Great information- the diagram really helped me "get it" - Arturo R. Garcia, DMD