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Why Do We Have Wisdom Teeth?
Wisdom Teeth— Why Do We Have Them?
I’ve had countless patients tell me that wisdom teeth don’t seem like a very wise idea. Why do we have wisdom teeth if we just have to get them out? That’s a good question.
So why do we have wisdom teeth anyway? One of the early theories is that through evolution our jaws have changed in size and now we can no longer fit the same number of teeth we originally had or rather our ancestors had. Well actually, scientists say that that’s much too short a time for evolution. And looking at the relative jaw sizes there is no significant difference. However, some studies were done by Dr. P.R. Begg back in 1954 and supported by work done by Varrela in 1990 and Odusanya & Abayomi in 1991 that basically support the opposite theory.
Evolutionary changes have not kept pace with dietary changes in humans over the last 500 years and that has lead to an increase in impaction rate. They studied skulls from people 500 years ago and counted the percentage of impactions they had. An impaction is when the crown of the tooth is covered by some other tissue. The crown of the tooth should be all the way in the mouth, with the roots down through the gums and into the bone. That’s the normal healthy state for a tooth. So by studying the these skulls they were able to come up with a percentage for impactions and only 500 years ago they found there was a low impaction rate. That’s much different from the 75% impaction rate that we have now.
So what happened in that 500 years? Was it evolution or lack there of? Studying the individual teeth, it’s found that people from 500 years ago had much more attrition. Attrition is where the teeth wear down from grinding hard. And they can grind down on the top and they can also grind between the teeth, on the sides because the individual teeth move slightly in their sockets. Because the diet 500 years ago was a much more coarse, what they call attritive diet, their was more attrition to the teeth and the interproximal or between tooth wear decreased the overall length of the teeth when they lied side by side, thus making it possible for wisdom teeth to fit in the dental arch in a proper way. In fact studying Aborigines today who even in today’s modern world have a very coarse attritive diet like peoples of old. They find also that Aborigines, have a very low impaction rate. Their diet consists of foods that are not well washed they have some sand and grit in them. Some of them are tough and fibrous require more chewing. Today’s diet in modern society consists of a very refined diet which basically doesn’t wear the teeth down. Another study that reconfirmed these findings and this theory was by Odusanya & Abayomi. They studied African boys who were brought up in rural area verses those brought up in urban areas and found there was an increased incidence of impactions in the urban population.
One final note is there may be an evolutionary component to impacted wisdom teeth anyway. It turns out that many people are born with fewer than the normal four wisdom teeth. I’ve seen everything from four to three to two to one and even no wisdom teeth. Since impacted wisdom teeth have been associated for a long time with deadly infections, evolutionary pressure natural selection has favored people who don’t have wisdom teeth. Anyway, if you are one of those unlucky ones who have wisdom teeth, you have two options. You can either go down under and live with the Aborigines or see your dentist.