Dentaltown June 2022 - 37

by Dr. Allen Ali Nasseh
Dr. Allen Ali Nasseh received his
dental degree from Northwestern
University Dental School and
completed his postdoctoral
endodontic training at Harvard
School of Dental Medicine, where he
also earned a master's degree in the
area of bone physiology. He has been
a clinical instructor in the postdoctoral endo department
at Harvard School of Dental Medicine since 1994.
Nasseh is the current president and CEO of Real World
Endo and the editor of the Harvard Dental Bulletin and
several other dental journals and periodicals. He has a solo
private endodontic practice and an endodontic educational
institute in downtown Boston.
I
t's been drilled into our heads by most of our mentors
that the cleaning component of the endodontic triad
of cleaning, shaping and obturation is the most
important determinant of clinical success in root
canal therapy. However, we tend to spend more time
and effort evaluating the latest instrumentation method or
finding ways to enhance the final look of our radiographs
by incorporating more radio-opaque cements into our
clinical armamentarium instead of focusing on improving
our irrigation protocol and, by proxy, our outcomes.
To make things worse, when we finally decide to
focus on irrigation, we find that we either are facing a
complicated irrigation protocol shared by many experts
on the field or are told that we need expensive laser-based
or sound-based devices to facilitate the irrigation process,
forcing us to either increase our fees or face a greater
overhead. How can we simplify our irrigation protocol
without expensive gadgets and complicated initial and
final irrigation protocols?
Before we set out to simplify our irrigation protocol,
it would be worthwhile to review the important concepts
that apply to effective irrigation, which chemicals are
commonly used and the objective for their use. I'll briefly
discuss some of the physical and chemical parameters in
irrigation process and irrigation solutions and potential
interactions between the reagents commonly used.
Physical parameters
and limitations
The root canal anatomy can be intricate, with many
curves, fins and anastomoses. And while the coronal pulp
chamber and the coronal root have many dentinal tubules
that can act as potential sites of microbial penetration, these
spaces constitute a very small volume. The root canal has
a volume of 20-40 microliters,1
with an average of about
0.025 cubic centimeters (cc), equal to the volume of about
half a drop of water. Therefore, each cc of irrigation solution
will displace 20-40 root canal volumes. This is important
considering the fact that volume is a key component of
effective irrigation. However, we don't know exactly
how much volume replacement is enough for effectively
cleaning and whether the chemistry of chemicals used can
catalyze this event. We do know that heat increases the
kinetic energy of the solution and will therefore catalyze
the rate of reaction.2,3
Beyond the volume, the delivery of the solutions into
the root canal is also important. Positive-pressure irrigation
is when the solution is pushed through the syringe with
the use of a needle deep in the root canal. Needles with
different tip designs distribute the irrigants differently.
Closed-ended, side-vented needles are currently the safest
needles for use because they reduce the risk of irrigation
extrusion from inside the canal. However, while these
needles must be placed deep in the canal to be effective,
it's important to use the thinnest needle available and make
sure it's not binding in the canal during irrigation. To help
reduce the odds of accidental extrusion, negative-pressure
systems were recently developed where the vacuum force
is moved to the apex with the aid of a thin needle/cannula
and the irrigation solution is deposited coronally in the
access opening. This method helps reduce the odds of
solution extrusion. The downside of negative pressure,
however, is the ergonomics of the system and the chance
of the small suction needle getting blocked prematurely.
dentaltown.com \\ JUNE 2022 37
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Dentaltown June 2022

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