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February 2001 – Lower 2nd Bicuspid - Vital or Non-Vital?

Fig. 1

A 37 year old female in good health arrived in my office with buccal swelling adjacent to tooth #35. The tooth had been restored 2 years ago with a large deep MOD amalgam filling. Thermal tests indicated no response. Periodontal findings were normal. Percussion and palpation were both mildly positive. Mobility was greater than normal. (Fig. 1) A diagnosis of necrosis was made and endodontic treatment was initiated.

In my office, suspected necrotic teeth are NEVER opened under anesthesia. A cavity test is always the final pulp test that is performed in order confirm the diagnosis. As I suspected, the coronal pulp was non-vital. However, when I attempted to place a working length file into the canal, the patient was sensitive to file placement, even though the file was quite short of the radiographic terminus. (Fig 2.) Sensitivity to a file at this level? This far away from the apex of a necrotic tooth? How was that possible?

Fig. 2 - Sensitivity at this level!?

I removed the rubber dam, anesthetized the patient and completed treatment. The solution to the mystery became obvious once the canal was filled. As is typical in necrotic cases, fully one third have lesions of endodontic origin that are not at the apex of the tooth. The canal fill revealed a lateral canal at the level of the apical third. (Fig.3) This canal was at least as large (or perhaps larger) than the "main canal". It appears that there was sufficient diameter in this canal to have the necrotic contents leak out in this lateral direction, while the apical section of the canal remained vital. The working length file, having traveled past this lateral canal, encountered this vital apical tissue and resulted in the patient's reaction.


Fig 3. Lateral canal into lesion

So, was the case vital or non-vital ? The answer is : BOTH. The coronal section of this "single canal" tooth was indeed necrotic. The most apical section was vital. This illustrates the complexity of the root canal SYSTEM. It also underscores the need to use thermoplastic based obturation techniques that assure three dimensional seal. This is best achieved with warm gutta percha combined with application of vertical forces. Six months later, the area is healing nicely.

Fig. 4 - Six mo. Recall film

Traditional Pulp tests cannot determine the status of the entire canal system

1. Suspected necrotic teeth should always have a cavity test to ensure that the diagnosis is correct.
2. Whenever a "lateral" radiolucency is present, the clinician should automatically suspect a lateral or accessory canal is present and that it should be filled during obturation.
3. Because of the complex anatomy of the canal system, even " single canal " teeth have the ability to contain both vital and nonvital tissue.