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Case of the Month

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March 2002Taking a Second Look - Finding that Elusive Calcified Canal Orifice

April's Case of the month deals with a problem that is becoming more common. Today, elderly patients frequently attempt to retain their dentition rather than have teeth extracted as they have in the past. The consequences of this are that many teeth are "patched" and that these patches often cause endodontic involvement that is particularly difficult to treat.

In this case an 89 year old gentleman was referred to me for endodontic treatment of a mandibular first molar. He had a history of diffuse toothache that had since abated slightly. The tooth was the distal bridge abutment of a 20 year old 4 unit fixed bridge. The referring dentist told me that there was a history of attempted amalgam repair of a carious distobuccal crown margin. This was significant for several reasons. Firstly, the patients symptoms occurred fairly soon after the amalgam was placed (possible devitalization?). Secondly, the size and position of the amalgam could influence access of the distal canal, should endodontics be required.

Radiographic examination confirmed a lesion of endodontic origin associated with the mesial root apex. There was also some suggestion of developing pathology in the distal apical area. Thermal tests were negative but I considered them unreliable because this patient generally did not respond to Endo Ice cold tests of any of his teeth. ( This is not uncommon in elderly patients with calcified canals and/or heavily restored teeth.)

A rubber dam was placed and the tooth was accessed WITHOUT local anesthesia. This cavity test confirmed my diagnosis of necrosis. Under Loupe magnification, the mesial canal orifices were located fairly quickly and working lengths established. (Fig. 1) But, I had great difficulty locating the distal canal because , as I suspected, amalgam had been literally packed into the this area of the distal canal orifice

Fig. 1

After almost 2 hours of treatment I still had not found the distal orifice. The situation was made more difficult than normal because vital tissue was NOT present in the distal canal and therefore the unanesthetized patient could not give us assistance in letting us know when we were close to the orifice. If the tissue in the canal had been vital ( such as in Case of the Month October 2001) it would have been much easier to locate the canal because of the patient's reactions and sensitivity. Compounding this problem was the presence of the amalgam covering and impinging on the orifice as well as the proximity to the furca. The amalgam tended to deflect slow speed burs and reduced the effectiveness of ultrasonics. It also made the use of an apex locator difficult because of the file's interaction with the metal of the alloy.( Was the file in the canal ? in a perforation? or just touching the amalgam ?)It also made it impossible to tell where I was ( radiographically) because of the radio-opacity of the amalgam on the film. Even careful excavation in the furca area without knowing exactly where we were risked perforation. Although it would have been a huge advantage to remove the entire alloy and redo the bridge, this was not an option at this point for financial reasons.

After another 15 minutes of concentrated effort a decision was made to pack the mesial canals and bring the patient back for another appointment. It was frustrating to be able to see the canal fairly clearly on the film ( Fig. 2) but still be unable to locate the orifice as the canal disappeared under the image of the amalgam filling. But experience had taught me that at this point a set of "Fresh Eyes" was needed.

Fig. 2

One week later, the tooth was reopened. Within a few minutes of access, I located the distal orifice and obtained a working length. (Fig. 3)

Fig. 3

The canal was cleaned and shaped and a gutta cone was fit with a small amount of sealer. (Fig. 4)

Fig. 4

The case was then completed without further problems and the access was closed with amalgam. (Fig.5)

Fig. 5

As the dental population ages, we will be faced with greater challenges when treating elderly patients. Because of limited finances ( and in some cases a limited life span of the patient), heroic repair of root caries, patching of crown margins and less than optimal dental procedures are sometimes performed. Performing Endodontic treatment on elderly patients who have previous history of these types of procedures can be very challenging.

One of the Endodontist's most important tools is patience. These procedures cannot be rushed. When faced with a situation like this, it is not uncommon for appointments to extend past the scheduled time. Frustration can set in. Patients (especially elderly ones) get tired

After concentrating on a small area for such a long period of time, it is natural for the clinician to develop a " Can't see the forest for the trees" optical syndrome. The more one focuses on the small area, the less "clear" the situation becomes. Frustration makes it tempting to perform "wild excursions" to try to find the orifice, or to get more aggressive with dentin removal than normal. Before reaching that point, it is prudent to close the case, dismiss the patient and wait for the next appointment to allow the clinician to "get a fresh pair of eyes" .

During the next appointment, it is very common for me to find the orifice within a only few minutes of accessing the case. Why does this occur? The "fresh eyes" have a better overall perspective of the case. They are often able to "see" things that were not apparent in the previous long appointment. Everything doesn't blend together, and the landmarks seem much clearer. It is a difficult phenomenon to explain but anyone who does cases like this understands exactly what I mean.

With the acceptance of the surgical microscope, I believe such cases will occur less frequently. The magnification allows for better visualization of the pulpal floor and deeper into the access. However, when you have blockages such as those that occurred in this case, it is still very important to always know "where you are" with respect to the furca and the rootface. That is something that a microscope can help you with, but it cannot make the decision of where and how much tooth structure/restoration to remove to ensure proper access.


1. Try NOT to anesthetize cases like this. Use the patient's reactions ( within reason) to help you find when you are "close" to the canals.

2. Always use radiography to know "'where you are" when accessing a calcified case.

3. When you become fatigued or disoriented when trying to find a canal or orifice CLOSE THE CASE AND BRING THE PATIENT BACK FOR A SUBSEQUENT APPOINTMENT.

4. Know when to "give up" for that day. Opening the case again at a subsequent appointment can often reveal the location of the canal within a few minutes of access. USE YOU "NEW EYES" to avoid perforating or ruining the case.