So wisdom teeth are also known as third molars but did you know that there are also fourth molars in a small subset of patients?
A recent study was performed by the United States at an Air Base in Japan which is currently in press to appear in the Journal of Oral and Maxillofacial Surgery titeld Prevalence and Management of Fourth Molars: A Retrospective Study and Literature Review by Khurram M. Shahzad and Lawrence E. Roth, 2011.
In the study conducted 409 patients were referred for a third molar (wisdom teeth) consultation. Two of 227 white patients (0.9%) had a fourth molar and 6 of 94 black patients (6.4%) had a fourth molar. One of the other 84 patients (1.2%) also had a fourth molar.
Of these patients with a fourth molar 5 out of 9 (55%) had only 1 fourth molar and 4 out of 9 (45%) had 2 fourth molars. In 7 of the 9 (78%) of the patients the fourth molars were in the maxilla (upper) and in 2 of the 9 patients (22%) the fourth molars were in the mandible (lower). No patients had fourth molars in both the maxilla and mandible.
All of the mandibular (lower) fourth molars were found to be smaller than the mandible (lower) wisdom teeth but similar in their shape. While the maxillary (upper) fourth molars were smaller than the maxillary (upper) wisdom teeth but appeared with a peg shape which did not represent the shape of the wisdom teeth.
The prevalence in this study of fourth molars was 2.2% and this is similar to the prevalence found from a few other studies were it was between 1% and 2%.
The authors recommend:
“The presence of fourth molars as well as the risks and benefits of extraction versus observation should be discussed with the patients and an individualized treatment plan should be fabricated.”
The authors comment that fhe fourth molars have a possibility of being displaced in the infratemporal fossa or the maxillary sinus during surgery and note that this is more likely to occur if the bone distal to the fourth molars is thin. (Note these are known complications of wisdom teeth removal as discussed on the complications page http://www.teethremoval.com/complications.html)
The authors of course recommend that each patient should have a panoramic x-ray and/or computerized tomography performed.
The authors also say it is even possible to remove a third molar (wisdom tooth) and leave the fourth molar in place which may allow the fourth molar to migrate down and after some time (a few years) a safer extraction can be performed.
Of course the risks of leaving a fourth molar are similar as leaving a third molar (wisdom tooth) for observation http://www.teethremoval.com/risks_of_keeping_wisdom_teeth.html
Below I have added the 2 panoramic radiographs that are in the journal article and I have added some labels for the fourth molars.
Looking at these x-rays removing a fourth molar appears to be even more risky than removing a third molar (wisdom tooth), so hopefully you are fortunate enough to not have a fourth molar.