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September 2005 – Cracked tooth with uncertain prognosis

One of the biggest challenges that Endodontists face is to try to predict the prognosis in the case of the cracked tooth. Is the tooth worth treating and if so what are the chances for success? How “cracked” does it have to be before we recommend extraction? How deep does the fracture have to go before we see the prognosis drop so low that it isn’t worth treating?

Athough this occurs very frequently, the literature has no firm recommendations as to how to judge the prognosis for teeth like this.  Mandibular 2nd molars very often present with distal marginal ridge cracks that enter the distal canal orifice. Some clinicians suggest that once the crack reaches the level of the canal orifice (or below), the prognosis is poor. Others will try to treat teeth such as this in the hope that prompt placment of a casting can splint the two halves of the fracture together and prevent evantual migration of the fracture down the root face
.

Here is a mandibular molar I treated some years ago. It initially had a distal marginal ridge crack that extended into the distal canal orifice and slightly deeper, below the bone crest. We elected to proceed with treatment and I was initially quite happy with the results. The first image is of the recall, 6 month after treatment.  (You can tell – I was still using film back then for recall images). The tooth had been nicely restored with a casting and things seemed to be going in the right direction.  I was quite happy with the recall image. The distal canal showed multiple POEs and a lesion that was healing.

Unfortunately, the subsequent 6 year recall image was less optimistic. The tooth had developed a deep distal pocket and vertical bone less in the exact location of the previous fracture. From the appearance of the film, it seems that the PDL detached to the level of the osseous defect. There are several possible explanations for this:

  1. The microscopic crack was below the level that was visible during initial treatment.
  2. Application of vertical forces with a plugger during compaction  exaggerated or propagated the fracture
  3. Function (even with a casting) resulted in propagation of the fracture and perio defect.

In any case, after consultation with a Periodontist, the tooth was deemed untreatable and required extraction.

Figure 1  - Recall Film 6 months post op


Figure 2  - Recall Film 6 years post op


Endodontics needs a system of classification that will give guidance as to the prognosis in cases like this. There currently is none. Even still, it is virtually impossible to predict how cases with previous fractures (into the orifices of canal) will react to endodontic treatment and restoration, even if a crown is placed promptly after endodontic treatment. The best we can do is to inform the patient of the problem and let them decide whether they wish to proceed with treatment, with the understanding that prognosis is somewhat (and unpredictably) compromised. 

It also places the burden on the General Dentist to recognize this phenomenon and to try to place preventive castings on cracked teeth before they become endodontically involved or non-vital. If this occurs on one side of the mouth of a patient with bruxism or parafunctional habit, we always need to check that the contralateral molar is not similarly at risk.