Doug Kase
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often while doing endodontics, what you see is not what you actually may
get. Frequently, root anatomy and canal position will be so closely superimposed
that clinical or radiographic identification may be very difficult. If
it is difficult to see the problem on your final film, you may shrug your
shoulders and walk away with a false sense of satisfaction. This difficulty
commonly leads to non-negotiated, unclean, and unfilled canals, resulting
in ultimate failure down the road. Of course this occurs (using Murphy’s
Law of Dentistry) just after you have permanently cemented a multi-unit
restoration. So it becomes very important to identify these anatomical
situations before you obturate the obvious canals.
First, we must identify the common culprits that
give us this pain in our nether region. The mesiobuccal root of the
maxillary first molar may be a good candidate. We all know of the
existence of either a second canal or even a second root occurring at a
varying position on a line between the mesiobuccal canal and the palatal
canal. Another candidate is one of the lower bicuspids. Usually, the first
bicuspid is the more frequent problem. It is important to look for
a lingual canal that branches from the main and larger buccal canal about
1/4 to 1/2 way down its length. This canal can represent the existence
of a completely separate root. This condition can also occur in the second
bicuspid as well, but is much less frequent. Watch for two canals, usually
within one root, when it comes to lower central incisors. An even
rarer, but not unheard-of occurrence is the presence of two canals or even
two roots in the lower canines. A common mistake is assuming that,
in lower first and second molars, a large distal canal, the kind you can
drive a Mack truck down, means that there is only one canal! Very
often there is another.
So how do we fix the problem, or—more importantly—how
do we avoid the problem? Taking angled radiographs and observing
the position of canal orifices relative to external crown and root anatomy
is the way to avoid the pitfalls. A dead-on parallel starting film
may be more important than an angled film for diagnostics such as caries
proximity to the pulp, depth of existing restorations, marginal integrity,
bone height, existence of periapical pathosis and approximate root length.
It certainly gives a more realistic and one to one relationship of tooth
to radiograph. It also may show a large canal that drops out on the
radiograph mid-root. This may be an indication that the canal splits
into two at this level. However, a second mesially angulated film
is equally as important, especially if diverse root and canal anatomy is
suspected. If a tooth is rotated, make sure whatever angle you take your
radiograph from, the radiograph separates the canals on the film.
A mesial angulated x ray on a tooth with a rotation toward the distal will
cause superimposition of the canals. Also, it is important to see how an
orifice is positioned on the pulpal floor in relation to the others and
to the external aspect of the tooth. If a distal canal on a lower molar
seems to be oriented too far to one side of the tooth and for the most
part not centered then suspect another canal.
Trying to ascertain the existence of these canals
is obviously more advantageous before obturation, so don’t be shy about
taking an extra radiograph before starting and even a working film (not
to establish measurement) if you suspect extra canal and root anatomy.
Also if you discover this fact on your final film, try to correct it on
the same visit if possible. The set sealer may block your ability to access
the canal.
Figure 1, the starting radiograph of tooth
# 19, shows a mid-root drop-out. The canals were instrumented and it appeared
that there was only one large distal canal. The tooth was obturated and
an angled final film (Figure 2) was taken to make sure that the canals
were filled properly. Oops! The angled film showed me that
a distolingual canal existed. The gutta-percha was removed quite easily
from the distobuccal canal, and, using a #2 slow-speed round bur and a
fine Spartan ultrasonic file, the lingual aspect of the existing distal
canal was slowly excavated. With a pre-curved number 10 file, I was
able to find the mid-root split. The canals were instrumented and obturated
and the final result was confirmed (Figure 3).
May-June 2002
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FIGURE 1: starting radiograph
of tooth #19, showing a mid-root drop-out.
FIGURE 2: angled film showing
a distolingual canal.
FIGURE 3: confirming the
final result.
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