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Case of the Month

<< Back to 2001 Case List

June 2001 Bridge Recementation - A Good Treatment?

Fig. 1

June's case of the month features a problem related to recementation of an old bridge. A 45 year old female in good health was referred to my office for endodontic consideration of tooth #25. The tooth was the mesial abutment of a bridge #25-26-27 that had a history of coming loose. Rather than immediately insisting that the bridge be remade, the dentist recemented the bridge at the insistence of the patient. The chain of events that followed led to extensive attempts at rehabilitation but eventual treatment failure. It is often said that we learn more from our failures than from our successes and I offer this case as a good example.

Endodontic treatment was performed through the crown. At that time I told the patient that the crown margin was inadequate, there was recurrent decay and the bridge would have to be remade. It was. Endodontic treatment was also performed on #27 prior to remake of the bridge.

Fig. 2


Two years later, the patient returned with a buccal fistula adjacent to the tooth.

Fig. 3


The fistula was traced with a gutta percha cone and found to be associated with the mesial side of the root of #25. Periodontal findings were normal and there was no probable pocket on the mesial aspect of #25. I noted with some alarm that the post was very large and appeared to be perilously close to the mesial root face. (Fig. 3) I suspected a post perforation. The patient was scheduled for exploratory surgery.

Fig. 4


A surgical flap was raised and the area of pathology was readily visible. (Fig.)

Fig. 5


Removal of the granulation tissue revealed a small area of discoloration where the tip of the post was visible on the mesial rootface. (Fig.5)

Fig. 6


A round bur was used to explore the site of the perforation. I noted what appeared to be a fracture extending apically. (Fig.6)

Fig. 7


I resected the end of the root to ensure that any apical accessory canals were removed and to ensure that I did not miss a second unfilled canal. I then prepared an "inverted L" shaped slot preparation. Because of the minimal root length I wished to preserve as much root as possible for this abutment tooth. A retrofilling of Super EBA cement was placed and the case was closed. (Fig. 7)

Fig. 8


Two months later the case appeared to be healing well and the patient was asymptomatic.(Fig.8) The patient then left the country and I heard nothing further from her until two years later. I was informed that the tooth had been extracted with the bridge and I requested that the specimen be sent to me for examination. These are the photos of the specimen:

Fig. 9


Mesial-apical view. Retrofill material is gone and the post is plainly visible.(Fig.9) There is also evidence of a Vertical Root Fracture, although the next two pictures show it more clearly.

Fig.10


(Fig.10) Distal view of #25. Note vertical fracture line extending from to crown margin.

Fig. 11


A mesial view of the tooth clearly shows the Vertical Root Fracture. The tip of the Parapost is also visible.

Conclusion
The Vertical Root fracture that resulted in eventual extraction of this tooth could have been the result of any of these factors:
  1. Stresses to the root during initial Warm Vertical Compaction of Gutta Percha (UNLIKELY)
  2. Possible stresses during post space preparation or cementation or occlusion
  3. Weakening of the tooth by retropreparation with a slot.
  4. Previous microfractures exaggerated by all of the above.
In any case, we will never know the true answer.

What we can say with certainty is that the initial recementation of the loose bridge was unwise. Once the abutment tooth lost its seal due to wash out of cement or caries, the fit was compromised. Attempting to recement a bridge abutment in this way only invites carious involvement that often necessitates endodontic treatment. Post preparation increases the risk of perforation and fracture in single rooted, thin walled abutments. When fixed prostheses do become loose, it is very important to determine whether the margin fit is adequate. If not, the abutment should be re-prepared and the crown remade. Posts should be avoided where possible. Choosing the "cheap" recementation solution in the short term can lead to potential catastrophic failure in the long term as clearly shown in the above example.