Retreatment of a Maxillary Canine with Five Canals

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I KNOW. When you read the title of this article, you probably said, “What? Five canals in a canine? Impossible! ” Yes, it is possible, and it is called dens in dente, or tooth within a tooth. As you may remember, dens in dente is a developmental abnormality in which the outer surface (enamel) folds inward. There are three types, classified according to the depth of the invagination. Type I is a superficial invagination that stays within the coronal part of the tooth. Type II is a deeper one that passes beyond the cementoenamel junction. Type III goes all the way down through the root. Dens in dente occurs most frequently in maxillary lateral incisors. Many of these teeth result in pulpal necrosis shortly after they erupt into the oral cavity because the lumen of the invagination contains soft tissue, and that tissue loses its vascular supply after eruption.

A thirty-year-old patient presented to me in need of a retreatment of #6. Normally, this procedure is a piece of cake, but when I saw the pre-operative x-ray (Figure 1), I realized that this was definitely not the normal single-canaled tooth that we usually see. The patient explained that several years ago an endodontist in California did the root canal treatment. She was informed that the prognosis for the tooth was guarded. She said that she was asymptomatic but recently developed a slight tenderness to percussion and palpation. I explained that the prognosis was still very guarded and that extracting the tooth might be better than doing a retreatment. However, the patient wanted to give it another chance since it was an anterior tooth. I initially thought about recommending apicoectomy. However, when a cone beam CT (CBCT) scan was taken, it was clear that there were three areas inside the tooth (invaginations) that were untouched and thus unclean. Apicoectomy would fail.

Since the patient was desperate to save the tooth, I started the retreatment by removing the old gutta-percha to take a look at the anatomy of the orifices (Figures 2–4). It basically looked like two C-shaped canals with three other separate canals. These canals were found with the help of the CBCT scan, ultrasonics, and lots of patience. It is important to use irrigants—such as sodium hypochlorite, ethylenediamine tetraacetic acid, or 2 percent chlorhexidine—because these solutions will, we hope, go into areas where instrumentation cannot be done. After flooding the inside of the tooth with calcium hydroxide for at least a week, retreatment was finished in a second visit when the patient was asymptomatic (Figure 5).

Because the complex anatomy of these dens in dente cases makes results unpredictable, root canal treatment is not recommended. However, with the help of the CBCT scan, which can visually show if all the invaginations are cleaned and filled, endodontic treatment becomes more likely to succeed.

January - March 2012

Figure 1
FIGURE 1: Pre-op.
Figure 2
FIGURE 2: Mid-op.
Figure 3
FIGURE 3: Mid-op.
Figure 4
FIGURE 4: Mid-op.
Figure 5
FIGURE 5: Post-op.