Young Bui
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 OTARY
NiTi and the endodontic microscope have revolutionized the way we do root
canal therapy. We are able to find MB2 in upper molars and third
canals in the mesial of lower molars much more easily than before due to
the introduction of the dental microscope. The NiTi files have helped
us to create the almost perfect taper in canals in a shorter time.
The end result is a nice, densely filled root canal that is aesthetically
pleasing to the eye. However, in our zeal to create a beautiful root
canal treatment, we tend to forget the most basic fundamental rule in endodontics,
and that is cleaning the canal down to the anatomical apex. Most
of us clean and fill our root canal to the radiographic apex. We
tend to doubt ourselves when the gutta-percha point is short of the radiographic
apex. We are letting aesthetics influence our judgment. When
we see a failed root canal case with the filling 1 mm short of the radiographic
apex, we attribute the failure to the short-filled canal. How do
we know whether the filling is short or not?
What are the anatomical and radiographic apexes?
The radiographic apex is the tip of the root as seen on any given x-ray.
However, the anatomical apex is different from one tooth to another.
It can be located at the tip of the root on one tooth and a couple of millimeters
away from the tip on another. The only way to know for sure where
the anatomical apex is located is to measure the length of the root using
an apex locator. The two good apex locators are Endex by Osada (which
has a needle gauge) or Root ZX by J Morita (which is digital).
When you start using the apex locator, you will
notice a number of cases in which the anatomical apex is about .5 mm to
1 mm away from the radiographic apex. The reason for this difference
is that the canal tends to take a curve at the apical end of the root before
it exits the root, as seen in Figure 1. Figure 2 shows the radiographic
apex and the anatomical apex as seen from the path of the radiation hitting
the tooth at a right angle. If you fill the canal to the radiographic
apex of this root, it will be 1 mm overfilled even though it is aesthetically
pleasing.
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FIGURE 1
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FIGURE 2
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Figure 3 shows an x-ray taken from the buccal view of a
premolar with a file in the canal to the radiographic apex. Figure
4 shows the same tooth in a mesio-distal view with the file overextending
the anatomical apex of the premolar.
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FIGURE 3
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FIGURE 4
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A good example of a misunderstanding of the difference
between a tooth’s anatomical apex and radiographic apex can be found in
a bulletin board thread on the Dentaltown website at www.dentaltown.com,
entitled by the endodontist who started the thread “Pretendodontist vs.
Endodontist.” This endodontist from Colorado took a couple of radiographs
from our website and criticized the RCT on the grounds that the fillings
are short on the two radiographs. One of the cases (the bicuspid),
which was done by Dr. Deutsch (pre-op, see Figure 5), has the final filling
2?3 mm short of the radiographic apex (see Figure 6.)
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FIGURE 5
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FIGURE 6
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However, the apex locator indicates that the length is
correct. The follow-up x-ray, Figure 6, shows healing of the large
radiolucency, which the endodontist from Colorado failed to disclose.
He also criticized my filling on a lower molar because the fill is 1 mm
short of the radiographic apex. He seems to be more concerned with
the aesthetic look of the root canal than the result. Maybe he is
a cosmetic dentist who is a pretendodontist.
July-September 2005
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