Young Bui
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HOPE THAT the following three cases will enlighten you about some of the
reasons that root canal therapy fails if the canals are not treated properly.
The first case is a failure of tooth #31 (see
Figure 1). The radiograph shows a large post in the distal canal,
and the mesial and distal roots are filled short. We would assume
right away that the short fill is the main cause of the failure. I vibrated
the post loose with an ultrasonic CPR 1 tip and then unscrewed it with
a Dentatus post remover. I cleaned the floor of the tooth using a
slow-speed #8 round bur. I noticed one mesial canal and one distal
canal situated at center on either end. I used an endo explorer to
probe around the groove along the buccal and lingual wall to check for
other canals. I found one more canal sitting right on the buccal
groove between the mesial and distal canals; it had not been cleaned out.
First I removed most of the old gutta percha by using a #2 Gates Glidden.
You can remove the gutta percha by running the slow-speed handpiece at
full speed and pecking at the gutta percha lightly. Friction will
generate enough heat to melt the gutta percha away. Do not apply force
if the instrument stops because you will block yourself out. Once
I had reached the maximum depth with the Gates Glidden, I then filled the
chamber with chloroform and instrumented by hand with a #15 Hedstrom to
get to the working length, using an apex locator. Once the working
length was attained, I flooded the chamber with sodium hypochlorite (NaOCl)
and proceeded to clean and shape the canal, using the SafeSiders® technique.
The canals were washed with liquid EDTA and then soaked with 2 percent
chlorhexidine for two minutes. The canals were then dried with paperpoints.
EZ-Fill® cement was used to coat the canals, and gutta percha was used
to fill the canals. You can see the third canal in the radiograph
shown in Figure 2.
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FIGURE 1: Showing a
large post in the distal canal and the mesial and distal roots filled short.
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FIGURE 2: Showing the
third canal.
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When looking at the second case, in Figure
3, you will notice a large radiolucency on the distal root about 4 mm from
the apex. This tells you that there is either a lateral canal at
that level or that the canal exits there. Upon instrumenting the
canals, I noticed that the two distal canals joined at the apex.
Neither of the canals created a sharp bend on the instrument, indicating
that the area was caused by a lateral canal. I then instrumented
all the canals using the SafeSiders technique while flooding the chamber
with NaOCl. NaOCl will dissolve any dead tissues in the lateral canal
if you open the main canal wide and taper it enough to get the solution
down that far. After the canals had been cleaned and shaped, I washed
them with EDTA. I placed an ultrasonic tip in the solution to heat
it and create a vibration to dissolve any tissue left in the canals.
The canals were then soaked with 2 percent chlorhexdine for two minutes.
I then filled the canals, using EZ-Fill cement and a single gutta percha
point. You can see the EZ-Fill cement extruding out of the lateral
canal in Figure 4.
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FIGURE 3: Notice a large
radiolucency on the distal root about 4 mm from the apex.
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FIGURE 4: Showing EZ-Fill
cement extruding out of the lateral canal.
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Figure 5 shows a radiograph of a normal-looking tooth
#19 with mesial decay in an area more along the furcation side of the mesial
root but not much at the apex. This looked as if it would be a straightforward
root canal procedure. I first made access and then removed all the
decay in the mesial wall. I built up the tooth using Ketac cement
to create a proper isolation. When first looking down the chamber, I thought
that the tooth had four canals (MB, ML, DB, and DL). However, there was
a groove connecting the MB and ML canals. I took a #8 reamer and
inserted it into the groove to see whether there was another canal there.
Most of the time there is a mid-mesial canal, but it joins one of the other
two. For the first time in my life, I found a mid-mesial canal that
was separate from the other two. So, in all, I had three distinct
mesial canals. The canals were cleaned and filled using the technique
described above. You can see in Figure 6 that the mid-mesial canal
was the one that curved to the furcation where the area was. When
doing root canal therapy, you should smooth out all deep grooves with a
slow-speed #2 to make sure that there are no other canals present.
Use a sharp explorer to probe into the groove to check for extra canals.
I hope you enjoyed this article.
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FIGURE 5: Showing a
radiograph of a normal-looking tooth #19 with mesial decay along the furcation
side of the mesial root.
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FIGURE 6: Showing that
the mid-mesial canal was the one that curved to the furcation.
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April - June 2007
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