Table of Contents
All about Wisdom Teeth
Wisdom teeth are known as third molars in dentistry. In the X-ray film on the previous page, if you count the number of large teeth from the front of the mouth to the back, you can see that the “third” ones are impacted which means that they remain under the gums even beyond the age at which they are supposed to erupt into the mouth. They are called wisdom teeth because they erupt at about the age of 17 or 18 when people are supposed to begin to assume the mantel of adulthood (I can only assume that this name must be a hangover from centuries ago when people only lived to 25). During the course of evolution, our the human face shrank, but the number of teeth did not decrease as rapidly as the shortening of the jaws. Most people do not have enough room in the dental arches for their wisdom teeth, and they tend to remain fully or partially impacted, under the bone of the jaw, or at least partly under the gums (as in the image above). In some cases, the wisdom teeth may remain impacted all of a person’s life without causing trouble, but in a high stress society, these people are in the minority. What’s stress got to do with it? You’ll see.
The image above shows angry, swollen gums just behind a second molar. There is actually a third molar (wisdom tooth) buried under the swollen gums. You might think that a tooth that is totally buried under the gums should not come into contact with germs from the mouth, and thus should not be prone to infection. Usually, however, the enamel on the crown of the impacted wisdom tooth is in contact with the enamel on the crown of the second molar, which iserupted and immediately in front of the wisdom tooth (see arrow on illustration below). Gums cannot attach to enamel. Thus the gums lie over the crown of the wisdom tooth like a glove lies over the hand, in close approximation, but not attached to it. Germs can leak under the gums at the place where the enamel of the second molar contacts the enamel of the wisdom tooth, Therefore, there is almost always a communication between the germs that live in the mouth and the space surrounding the wisdom tooth. It is a tooth you cannot brush. When your body’s resistance is normal, the germs surrounding the impacted tooth are kept at bay by the body’s normal immune system. But if the body’s resistance is decreased, through sickness or emotional stress, the germs can get the upper hand and you find yourself with an infection around the wisdom tooth. These infections are called “pericoronitis” which means (appropriately), “an infection around the crown of an unerupted tooth”.
Once you get a case of pericoronitis, it can be controlled temporarily by a having the dentist clean around the tooth and following up with a course of antibiotics. But pericoronitis tends to return at regular intervals until the offending tooth is finally removed. Click on the image above for more on pericoronitis.
As you can see in the image above, the upper impacted wisdom tooth is in very close approximation to the maxillary sinus. As a rule impacted upper wisdom teeth cause few symptoms if no obvious oral infection is present. But in the case of peircoronitis, the infection can sometimes be transferred to the sinus causing typical sinus headaches and congestion. Conversely, the extraction of a wisdom tooth in this location can occasionally cause problems with the sinus.
People ask all the time if the problems they are having with their sinuses are caused by their otherwise non symptomatic impacted wisdom teeth. The answer is that it is always possible that there is a connection, but generally impacted wisdom teeth rarely cause sinus discomfort directly unless an obvious infection like pericoronitis is present. I usually tell my patients that in rare instances, the removal of these teeth can be associated with the relief of chronic headaches, but there is no guarantee that there is a connection between their headaches and their wisdom teeth. It is more likely that the patient is suffering from some of the symptoms of TMJ which are caused by the unconscious habit of grinding and clenching the teeth (bruxing). Click here to learn more about dentally related headaches.
Most oral surgeons prefer to wait until the roots of the wisdom teeth are between 1/2 and 2/3 formed, about age 17 for boys or 16 for girls before extracting them. The main reason for this is that during this period, the normal forces of eruption have generally allowed the tooth to erupt as much as is possible under the circumstances, while at the same time limiting the depth of the extraction socket due to the shorter roots. This means a simpler procedure involving less drilling of bone and tooth in order to effect extraction. Extraction during this ideal window of time reduces the incidence of dry socket or other post-operative complications.
Aside from pericoronitis, there are two other complications associated with impacted wisdom teeth. They both involve the uncontrolled expansion of the follicle (the space in the bone where the tooth was originally formed). This follicle is lined with cells which are supposed to transform into the lining of the sulcus of the gums when the tooth erupts. But if they are kept submerged for too long, they sometimes forget their original mission and begin to produce fluid which expands the follicle causing a cyst.
These cysts can become very large and cause distortion of the bone and face, and can lead to such weakness in the bone the jaw may be prone to fracture.
The second, very rare complication arising from uncontrolled follicular growth is a form of tumor called amyloblastoma. This tumor is not considered a cancer because it does not tend to metastasize (spread to other areas of the body), but it is locally invasive which means that it grows uncontrollably and can cause major damage and weakness in the bone if it is not thoroughly removed. Amyloblastoma is most likely to attack young adult males. It is less frequent in females or older people of either sex. Since it is always associated with an impacted tooth, usually a wisdom tooth, (but not always, as seen in the images above) it rarely occurs before the age of 18. It is difficult to remove entirely, and the surgeon will usually perform a wide excision (i.e.. he takes a lot of extra bone along with the tumor) just to be sure that he has removed it all.