Endo Tribune U.S. No. 3, 2011
Critical thinking: the missing link in endodontic education
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ENDO TRIBUNE
The World’s Endodontic Newspaper · U.S. Edition
March 2011
www.endo-tribune.com
Vol. 6, No. 3
Critical thinking: the missing
link in endodontic education
By Barry Lee Musikant, DMD
After years of teaching at endodontic
programs around the country, I can say
with strong conviction that the process
of critical thinking has not been applied
to the mechanics of endodontics. Not
for one moment am I critical of a program’s emphasis on diagnosis, histology and pathology. The incorporation
of microscopes has vastly improved
dentists’ abilities to seek out fine structure that can be the difference between
success and failure.
Where critical thinking is missing is
in the selection of the design and utilization of the instruments used to shape
the canals. For the most part, K-files
are the instruments recommended for
the initial shaping of canals. I have
never detected any evidence that the
decision to use K-files resulted from an
analysis of what works best. It is simply
a tool that has been handed down from
generation to generation to either perform the entire shaping procedure or to
create a glide path for the subsequent
use of rotary NiTi files.
If K-files had been chosen as the
most appropriate instrument to use
after critical analysis, we would expect
these instruments to at least initially
shape canals more easily than other
instruments. That such problems as
loss of length because of the apical
impaction of debris, distortion to the
outside wall, elbowing and frank perforation would be less inclined to occur
because of superior design and method
of usage. Yet K-files are associated
with all the above problems while their
counterpart, K-reamers, are far less
likely to produce such issues. In fact,
critical thinking was not applied to the
choice of instruments. Tradition, inertia and simple prejudice take the place
of effective analysis.
Let’s examine how critical analysis
would prevent this widespread mistake
that is perpetrated on our student bodies over the years. Take a look at a photograph of a K-file (Fig. 1). Please note
that the shank is composed of 30 flutes
along its 16 mm of working length. The
greater the number of flutes, the more
horizontally oriented they are. Compare the 30 flutes on a K-file to the
16 that are present on the shank of
a reamer. Also, please note that with
approximately half the flute number,
each flute is significantly more vertically oriented along the length of the
reamer shank. Fewer flutes lead to less
engagement along length. Resistance in
Fig. 2
(Photos/Provided by Dr. Barry L. Musikant)
Fig. 1: Photo of a K-file. Note the high number of flutes that are more horizontal in
nature.
Fig. 2: Illustration of an asymmetrical
instrument’s ability to distinguish and clean
an oval-shaped canal.
Fig. 3: Photo of a relieved reamer. Note the
flat side and the vertical flutes.
Fig. 1
apical negotiation is directly related to
the reduction in engagement.
A watch-winding motion is the recommended way to use both the reamers and the K-files. Yet, when a watchwinding motion is applied to the more
horizontally oriented flutes of a K-file,
the threads tend to imbed themselves
into the canal walls without shaving
any of the dentin away in the process.
Increasing the amount of engagement
does not help in shaping the canal.
Compare the action of these flutes
with the more vertical orientation of
the flutes on the reamer. Using the
same watch-winding stroke applied to
the K-files, the blades being more at
right angles to the plane of motion will
immediately start shaving dentin from
the walls of the canal, further reducing
the degree of engagement and the subsequent resistance encountered as the
reamers negotiate apically.
Clinically, the dentist encounters less
resistance when using reamers because
there is less engagement along length,
resulting from fewer flutes to begin
with and their greater ability to shave
dentin rather than embedding into it.
Embedment leads to increased resistance. Shaving dentin further reduces
the smaller amount of engagement that
was already present. The design and
utilization of the K-file works against
the very goals it wants to attain. Reamers are designed and utilized in a way
Fig. 3
that is compatible with their goals. Critical thinking would make these basic
points obvious. Controlled clinical testing of both designs would immediately
demonstrate the superiority of reamers
over K-files.
The comparison could easily stop at
this point, and reamers would be the
unquestioned winner, but there are
other advantages that accrue to the
user as well. With less engagement
along length, a cutting blade more or
less at right angles to the plane of
motion that removes dentin rather
than embedding into it, a more flexible instrument that is a consequence
of fewer twists along the length of the
shank, the reamer gives the dentist a
superior tactile perception, giving him
the ability to differentiate between the
tip of the instrument hitting a solid wall
or engaged within a tight canal. Both
situations will either stop or slow down
apical progress.
However, if the tip of the instrument
is hitting a wall, there will be no tugback
when the reamer is withdrawn, telling
the dentist he must not attempt to proceed further. Rather, he must remove
the reamer from the canal, place a
45-degree bend at the tip and, with a
light peck-and-twist motion, attempt to
negotiate around the obstacle. On the
other hand, if tugback is present from
the outset, the dentist knows to continue apical negotiation using either the
recommended watch-winding motion
or a twist-and-pull motion until the
apex is reached.
A K-file that is already so heavily
engaged along length cannot make the
distinction between a solid wall and a
tight canal. The resistance along length
obscures what the tip of the instrument
is encountering. Using a K-file, all a
dentist may know is that he is short
of length. Using an aggressive twistand-pull motion, the proper length can
be regained even when employing a
K-file with a non-cutting tip. However,
too often the dentist will discover that
the original anatomy has been lost with
the apical third transported to the outside wall of a curved canal. This is the
effect when a solid wall or impacted
debris is encountered, but not recognized as such because of the excessive
engagement of the K-file along length.
The absence of critical thinking is
recapitulated by maintaining the continued use of K-files. First we abdicate
the use of reamers without making
any comparisons. Worse, while not
learning the benefits of reamers, we
also lose our evolutionary potential to
improve upon a tool that in its present
state is superior to K-files.
Critical thinking demonstrates that
reamers are superior to K-files for
several reasons, one of the main ones
being reduced engagement along
length. By placing a flat along the
entire working length of the reamer,
we now have a reamer that has even
less engagement along its working
length. The result is an instrument that
is even more flexible because it is thinner in cross-section, includes two vertical columns of chisels that cut equally
effectively in both the clockwise and
counterclockwise direction and is
asymmetrical in cross-section, giving
it the ability to differentiate between
a round and oval canal. No symmetric
instrument can differentiate between
a round and oval canal. The ability to
make this distinction tells the dentist
when to widen the canals to greater
dimensions for superior mechanical
cleansing as well as better chemical
debridement via the irrigants (Fig. 2).
Without critical thinking, no one
knows that a reamer is superior to a
K-file and without that knowledge, no
one knows that a reamer can be modified to further improve its functionality. Perhaps, most importantly, without
the benefit of critical thinking, those
g ET page 2B
[2] =>
2B
Industry Opinion
f ET page 1B
designing instruments to eliminate the
shortcomings of K-files don’t eliminate them. They merely reduce them,
still incorporating their use in the creation of the glide path1, and then proceed to introduce rotary NiTi systems
that, while overcoming the limitations
of K-files, introduce significant new
problems that add cost, anxiety and
unpredictability to canal shaping.
In the meantime, critical thinking would clearly demonstrate that
relieved reamers (Fig. 3) are not only
good for glide path creation but work
far more safely when used for the
entire shaping procedure. Stainlesssteel relieved reamers are quite effective at recording the curvatures of a
canal.2 Unlike NiTi, they do not snap
back to the straight position, a property that increasingly distorts the apical
AD
end of curved canals as the tip size and
taper of the instruments increase.
The greater stiffness of stainless
steel is compensated for by the relieved
reamer design, never exceeding a
02 taper and routinely straightening
the coronal curve prior to the use of
larger-tipped instruments. Used either
in a tight watch-winding stroke or in
a 30-degree reciprocating handpiece
(Fig. 4), the tip of the instruments confined to such a short arc of motion
always stay centered in the canal. As
long as patency is maintained, these
relieved reamers will not deviate from
the original pathway. Patency3 is maintained by going 0.5 mm beyond the constriction through a 25 relieved reamer,
a technique that is easy to master and
is completely predictable in its results.
Unless one is exposed to the critical
thinking needed to open one’s mind to
better working alternatives, the entire
Endo Tribune | March 2011
ENDO TRIBUNE
The World’s Endodontic Newspaper · U.S. Edition
Publisher & Chairman
Torsten R. Oemus
t.oemus@dental-tribune.com
Fig. 4: The Endo-Express® reciprocating handpiece.
Chief Operations Officer
Eric Seid
e.seid@dental-tribune.com
Group Editor & Designer
Robin Goodman
r.goodman@dental-tribune.com
Editor in Chief Endo Tribune
Frederic Barnett, DMD
BarnettF@einstein.edu
International Editor Endo Tribune
Prof. Dr. Arnaldo Castellucci
Fig. 5: Radiograph showing clinical
results achieved with relieved reamers in a reciprocating handpiece.
Managing Editor/Designer
Implant, Endo & Lab Tribunes
Sierra Rendon
s.rendon@dental-tribune.com
Managing Editor/Designer
Ortho Tribune & Show Dailies
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k.colker@dental-tribune.com
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Dental Tribune America, LLC
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Published by Dental Tribune America
© 2011 Dental Tribune America.
All rights reserved.
Dental Tribune America makes every effort
to report clinical information and manufacturer’s product news accurately, but cannot
assume responsibility for the validity of product claims, or for typographical errors. The
publishers also do not assume responsibility
for product names or claims, or statements
made by advertisers. Opinions expressed by
authors are their own and may not reflect
those of Dental Tribune America.
Editorial Advisory Board
Frederic Barnett, DMD (Editor in Chief)
Roman Borczyk, DDS
L. Stephen Buchanan, DDS, FICD, FACD
Gary B. Carr, DDS
Prof. Dr. Arnaldo Castellucci
Joseph S. Dovgan, DDS, MS, PC
Unni Endal, DDS
Fernando Goldberg, DDS, PhD
Vladimir Gorokhovsky, PhD
Fabio G.M. Gorni, DDS
James L. Gutmann, DDS, PhD (honoris causa),
Cert Endo, FACD, FICD, FADI
William “Ben” Johnson, DDS
Kenneth Koch, DMD
Sergio Kuttler, DDS
John T. McSpadden, DDS
Richard E. Mounce, DDS, PC
John Nusstein, DDS, MS
Ove A. Peters, PD Dr. med dent., MS, FICD
David B. Rosenberg, DDS
Dr. Clifford J. Ruddle, DDS, FACD, FICD
William P. Saunders, Phd, BDS, FDS, RCS Edin
Kenneth S. Serota, DDS, MMSc
Asgeir Sigurdsson, DDS
Yoshitsugu Terauchi, DDS
John D. West, DDS, MSD
[3] =>
cascade of learning is stopped before
it starts.
Without critical thinking, one will
never learn that reamers are safer,
more efficient and more effective than
K-files. Without learning the superiority of reamers, one will never learn
that relieved reamers are superior to
non-relieved reamers. If one does not
use reamers, one will not be exposed to
the advantages of non-distorted shaping using a 30-degree reciprocating
handpiece. Without the exposure to
a 30-degree reciprocating handpiece,
one will never appreciate the absence
of torsional stress and cyclic fatigue4
that plagues rotary NiTi, leading to
Industry Opinion & Products 3B
unpredictable separation. And, without the appreciation that instruments
will simply not break, one will not
confidently shape canals to the larger
dimensions that are often required to
ensure proper debridement and irrigation. For examples of cases done with
relieved reamers in a reciprocating
handpiece, see Figures 5–7.
We have been indoctrinating our
students for too long. It is about time
that we educate them. Critical thinking is the way for students to make
rational decisions. They will become
better dentists and serve the needs of
their patients better when these skills
are honed. There may be those out
ET About the author
Dr. Barry Lee Musikant is a
member of the American Dental
Association, American Association
of Endodontists, Academy of General Dentistry, The Dental Society
of N.Y., First District Dental Society,
Academy of Oral Medicine, Alpha
Omega Dental Fraternity and the
American Society of Dental Aesthetics. He is also a fellow of the American College of Dentistry (FACD).
Musikant’s lecture schedule has
taken him to more than 250 international and domestic locations.
He has co-authored more than 300
articles in dentistry in various inter-
there who dispute the conclusions that
critical thinking will produce, but I defy
anyone who says this is not the proper
way to educate. ET
References are available from the
publisher upon request.
Fig. 6
national
dental journals.
As
a
partner in
the largest
endodontic
practice in
Manhattan,
Musikant’s
35-plus
years
of
practice
experience have established him
as one of the top authorities in endodontics.
Figs. 6, 7: Radiographs showing
clinical results achieved with relieved
reamers in a reciprocating handpiece.
Fig. 7
Seiler iQ: 3-step
microscope model
Photo/Provided by Seiler Instrument
ENDO Tribune | March 2011
The Seiler iQ is a 3-step microscope model that comes equipped
with an ultra-bright 50W metal
halide lightsource and a standard
halogen backup.
High-end German optics and a
0-220 inclinable head are also standard, which makes the iQ a perfect
entry-level microscope.
The iQ offers the core magnifications needed for any general
dentist or endodontic specialist.
For more information, call (800)
489-2282, see www.seilermicro.com
or e-mail micro@seilerinst.com.
AD
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