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Case of the Month

<< Back to 2001 Case List

October 2001 Tips for Accessing Calcified Canals

Fig. 1
October's Case of the Month features a a case that had been referred to me for completion of endodontic treatment on tooth #22. The referring dentist had attempted to access the canal but was astute enough to recognize that perforation was imminent if he continued. The canal space was smaller than normal, as the tooth had been crowned many years previously and the patient was a senior. The referral had enlarged the access more than I would have preferred. I was concerned about the retentiveness of the crown. Fig. 1

Sure enough, it wasn't more than a few moments after the dam had been placed that the crown fractured off. At this point most clinicians would normally reach for the syringe and anesthetize the tooth in order to comfortably place a rubber dam and clamp. This can be a potentially fatal error.

There are several ways that we can increase our chances of locating the calcified orifice in this case. Besides the obvious methods of magnification ( Loupes or Scopes) and transillumination ( through the buccal gingiva), there is one factor that the referring dentist did not consider. - NOT anesthetizing the case.

Fig. 2
The tooth was vital, which is especially helpful in calcified cases. One of the biggest mistakes you can make is immediately reaching for anesthesia. At this point, the patient should be informed that you need their help to locate the canal and that they should alert you if they feel any brief sharp sensation.

Instead, explore the access with a new sharp endodontic explorer. In many cases, there may be one particular area of sensitivity. Small long shank round, Mueller burs or ultrasonic tips can then be used to localize the area of sensitivity. Once a "sticking point" is found, the patient will often react sharply. Reassure them. The sharp sensation of placing a small file (#.06 or .08) in a small pinpoint exposure is different from the duller sensation of the file being placed in the PDL. This is how you can tell the difference between being in the pulp or having created a perforation. Once you are confident you are in the canal, the patient is anesthetized and the dam is then placed . The file is inserted and the working length is confirmed with assistance of an apex locator. If you have perforated, you will know immediately and the locator will indicate this. Look for the normal file length transition readings as you ease the instrument to length. Confirm with an image. Fig 2. The case was completed without incident. Figs 3 & 4. Unfortunately, the post and core crown had to remade

Fig. 3

Fig. 4

The presence of a previous access cavity is always of concern to me. If you ask most endodontists, they will tell you that they often prefer that the referral NOT make access in teeth with evidence of calcification. Why? Because the initial access is often in the wrong direction and it becomes more difficult than normal to create the proper "Glidepath". The Glidepath is they key to the effortless introduction of instruments into the access. It prevents the frustrating phenomenon of having the small exploratory file ( that may have sharp bends on it) catch in the access, before it can be placed down the canal. Burring out the access also risks loss of retention of the core, since unless you have actually prepared the tooth yourself it is impossible to tell how much actual preparation is left to hold the crown. After successful endodontics, it can be very frustrating for patients to go home, only to have the crown snap off at the gingival line a few days or weeks later.

Tips for accessing calcified canals

1. Use magnification and transillumination to locate orifices. Take frequent films if you are not sure where you are.
2. Don't be in a hurry to anesthetize the case. The patient's sensitivity can help you locate the pulp. The key is to inform them, work efficiently and confirm that you are in fact in the canal.
3. Use small round burs, Mueller burs or ultrasonic tips to avoid gouging the access. Keep the concept of "Glidepath " in mind when you are looking for the orifice. Avoid wild burr excursions in the hopes of locating the orifice.
4. The best way to avoid problems is to assess the level of difficulty of the case before you start. If you cannot locate the canal, STOP. Avoid compromising the restoration or root integrity by excessive tooth removal.