Barry Musikant
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THOSE OF YOU who have followed the discussion of the EZ-Fill®
SafeSider™ instrumentation techniques, it is obvious that straight canals
are a lot easier to shape than curved ones. In fact, the greater the curve,
the harder the shaping process. If you think about it, and probably even
if you don’t, the reasons are also obvious.
The straighter the canal, the greater the depth that the
No. 2 Peeso can gain before it meets resistance. If a canal measures
21 mm to the incisal edge and is perfectly straight, at some point in the
instrumentation the No. 2 Peeso, can attain the depth of 19 mm, its complete
extension from the slow-speed handpiece. The only portion not shaped
by the No. 2 Peeso would be the most apical 2 millimeters.
On the other hand, if a 21 mm canal is highly curved,
as in a molar, the Peeso will go a shorter distance down the root.
The pulp chamber might take up 11 mm of the length, leaving 10 mm for the
canal. Of that length, the Peeso may only be able to go down 4 mm,
leaving a distance of 6 mm to the apex.
In both the straight and curved canals, a .05mm/mm
taper would be prepared with a 1 mm stepback from instruments sized 25
through 40 in the most apical 4 mm of the canal.
In the straight canal, the No. 2 Peeso would be
able to go so far apically that it would prepare the canal space into the
stepback area. In the highly curved canal, a space would exist between
the most coronal extension of the stepback (4 mm from the apex) and the
most apical extension of the No. 2 Peeso reamer, a length of 2 mm.
(The full canal length is 21 mm minus the 11 mm of pulp chamber access
minus the 4 mm the Peeso was able to go apically minus the 4 mm coronal
extension from the stepback; 21 - 11 - 4 - 4 = 2 mm.) I call this space
“no man’s land.”
For whatever length “no man’s land” has, its taper
is 2 mm/mm, starting at .40 mm. If the length is 2 mm, the coronal
extension of this space is .44 mm in width. (.40 mm + [2 x .02 mm]
= .44 mm).
The final shaping instruments in the SafeSider technique
include 30/.04 and a 25/.08 manual reamers. The longer “no man’s
land” is, the more these greater tapered NiTi instruments must cut.
This is not a problem, but it is something the dentist should be aware
of.
Fortunately, canals that are so curved that they
prevent the No. 2 Peeso from approaching the coronal end of the stepback
are rare. When they do occur, the remaining NiTi instruments must
do more work, but the technique and sequencing is designed to minimize
the stress developed within these instruments and produce the final taper
quickly, efficiently, and predictably. (Remember: you should always test-bend
the instruments before using them in the canal.)
The concept of “no man’s land” gives the dentist
a clear understanding of the potential of the No. 2 Peeso reamer. While
this instrument cannot be forced around a curve, the No. 2 Peeso reamer
should extend as apically as possible in a straight line at right angles
to the occlusal surface of the tooth. With a light touch, the No.
2 Peeso will find its own depth for each canal without any fear of perforation
or ledging. Combining the No. 2 Peeso reamer with the SafeSider sequencing
allows the dentist to shape all canals to at least an .08 mm/mm taper,
generally in five minutes per canal or less.
As usual, if any dentist wants help in attaining
these skills, just call me at (212) 582-8161 and I’ll set up an evening
to teach you. I never teach more than two dentists on any given night,
so I do get booked up at times. The course takes about an hour and
a half, after which you won’t believe how straightforward and simple the
technique is. There is no charge for this course. I have been doing
it as an exercise in good will for the last six years and personally enjoy
it. I believe you will too.
November-December 2001
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The concept
of “no man’s land” gives the dentist a clear understanding of the potential
of the No. 2 Peeso reamer.
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Perforation
of a molar does not mean that the tooth is a lost cause.
