Over the years, I have treated a number of patients for their wisdom teeth who were initially discouraged to have it done because as they were told: "their teeth is on top of the nerve!". The nerve spoken of is a sensory nerve that runs in the jaw bone just below the lower wisdom teeth and in very rare occasions may be in contact with the roots of the wisdom teeth. In all of these patients, the recommendations were made solely based on a panoramic x-ray or a small dental x-ray that appeared to show close proximity of the lower wisdom teeth to the canal that carries this sensory nerve. The concern during any wisdom teeth surgery is possible close relationship between the nerve and tooth, and the potential nerve irritation that may result in some degree of numbness over the lip and chin region.
The question is how valid is this concern and the recommendations given?
First, it is a known fact that in majority of patients there is a separation between the nerve and the wisdom tooth, even though it may appear otherwise on the x-ray! It's important to realize that a panorex or a small dental x-ray is a 2-dimensional image and overlapping structures on these images do not necessarily mean they are in contact.
As mentioned, there is often a separation between the nerve and roots of the wisdom teeth despite the x-ray appearance and therefore risk of nerve damage is extremely low. Even in rare instances where they are in contact, meticulous and careful techniques used by surgeon can minimize any chances of long term problems. Therefore, fear of nerve disturbance, although always possible, is largely unsupported and not removing the wisdom teeth carries much more real and significant complications in the long term. I have personally treated thousands of patients whose x-rays showed the typical 'tooth on top of the nerve' and yet the nerve was not encountered and surgery was successful with no sensory deficits.
Panorex has been considered the radiograph of choice for oral and maxillofacial surgeon when treating impacted third molars. There are 9 radiographic signs associated with an intimate anatomic relationship between the canal and the lower third molars: Radiolucent band , loss of cortex of canal, change in canal direction, canal narrowing, root deviation, bifid apex, superimposition, and contact of canal with roots of the mandibular molars. Without these positive signs, the risk of injury is considered miniscule, whereas the presence of 1 or more positive signs is not a good predictor of injury to the nerve.
Icat and three dimensional imaging is an alternative technique that can demonstrate anatomical relationships between teeth and nerve and improves diagnosis, however, there is an ongoing debate in the literature about the need for CT scans before third molar removal, even when 1 or more of the signs is noted on the panorex.
While there is no consensus or standard of care on this issue, it is felt that CT scans should be considered in selected cased, chiefly when 1 or more of the telltale signs are present on the panorex. It is also recommended to discuss it during informed consent; including potential risks and benefits of undertaking third molar removal using a CT scan compared to no CT scan. Patient should ultimately make the decision considering all the facts and involved cost.
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