Teeth

I have been thinking about teeth.  Jerry and I watch a Teaching Company lecture every night before bed and this month it has been a course on Evolution.  Much of what is known about animals of the past comes from looking at fossil teeth.  After death teeth last better than any other part of the body, so often the only clue to a long gone creature’s existence is its teeth.  Paleontologists can tell fish from amphibian, amphibian from reptile and reptile from mammal by examining teeth. Mammals have milk teeth and their teeth are differentiated for different specific functions.

Recently there was a find in Alaska of an 11,500 year old site that showed the earliest evidence of human habitation there.  At the site they found the teeth of a young child. The teeth showed the baby to have been about 3 when he or she died.  The child had apparently been cremated in the camp fire, and then the site was abandoned.

You might think that the only function of teeth is to chew food — or to catch it in the case of animals like sharks or crocodiles. In primates, and perhaps in other animals, teeth have a social function which has evolved along with their morphology.  Chimps have big canines. This is not related to diet, but rather the chimp “grin” (not friendly) is meant to threaten other chimps.  It may be used in sexual rivalries between males.  Chimps bare their teeth and rush around flapping branches and waving their arms in dominance displays. The human smile, with its puny little canines, is a friendly, sociable greeting meaning peace.

As humans evolved from ape like ancestors their teeth evolved reflecting changes in diet. As the African climate changed during the ice ages — it got progressively cooler and dryer — the teeth of our primate ancestors changed to cope with a wide variety of foods. They gradually shifted from a diet that was mostly soft fruits and leaves to one that included meat, potato like roots, seeds, parts of grasses, insects, flowers and nuts. Pretty much anything they could get their hands on.

Some people have inferred a rather specific prehistoric diet from the structure of teeth.  This is the so called “paleo” diet, supposed to include the things that humans ate in the Paleolithic era, presumably before agriculture but probably not before cooking.  It seems probable that the diets of paleolithic people differed depending on the environment that a particular population lived in.  Some ate more meat and seafood, some more insects (ugh), some more fruits, some more roots, seeds of grasses and nuts.  They ate what was available.

According to some researchers it was when people learned how to cook that tooth trouble started.  Cooked food is softer.  Teeth got smaller and more crowded.  When agriculture began this got worse. We didn’t need our wisdom teeth any more. Our occlusion got sloppy.  We needed orthodontia and dentures.  And implants.

Implants are another reason I have been thinking about teeth.  Like other animals of my species, my teeth are the result of the evils of agriculture and cooking. I was genetically lacking two permanent teeth, the second molars in my upper jaw.  The baby teeth lasted into middle age, when they finally became loose and I had bridges made.  This meant that four other teeth, two on either side of the missing teeth, had to be ground down. Recently one of the bridges failed and one of the ground down teeth became abscessed. Woe is me!

My choice was between more bridge work (more ground down teeth) or implants.  I chose implants, despite the horrendous cost. Of course it’s partly vanity; I don’t want to go around with big dark gaps between my teeth that would show when I smile.

Ancient people cared about this too.  The skull of a young Mayan woman of around 600 AD was found with tooth shaped pieces of shell implanted in the bone of her jaw. At first archeologists thought that this was done to prepare her body for burial, but when the bone was studied microscopically it was found that bone tissue had grown around the implanted shells, indicating that they were placed during her life.

Implants today are done in stages. My first appointment with the implant specialist was for x-rays and evaluation to make sure I had enough bone left in my jaw (though my regular dentist declared that I had “oodles of bone.”)
The implant specialist’s office was in Burlington, dreary town of strip malls about 30 miles from Bellingham.  There were 3 pleasant receptionists and technicians, all of whom had really beautiful teeth. One of them took the 3-d x-rays of my jaw and neck.

The dentist introduced himself and shook my hand.  “I’m Curtis Wade,” he said.  I liked that.  He didn’t say, “I’m Dr. Wade.” He was short and nice looking, in his late 50’s I would guess, though I find it hard these days to tell how old people are.  He wore surgical scrubs and a cap with a trout fishing fly pattern. White curls escaped from the band of his cap.  He showed me the x-rays — a scan of the bones of my head and neck.  I saw my jaws and teeth, the arthritis in my neck, my hyoid bone (one of the things that makes me human and gives me the ability to talk.) Dr. Wade explained it all.

The next day, as he was screwing the titanium rod into my jaw bone all the way up to the sinus, he said, “It’s sort of like working on a car.”

The next time I had an opportunity to speak I asked, “Do you have a little wrench in there?”

They keep everything behind you so you have no idea what they’re doing.  Every now and then he would say, “You’re going to hear a pop,” or “You’re going to feel pressure,” or “You’re going to hear a lot of grinding.” It isn’t something I’d want to experience often.

The procedure took less than an hour.  I have 2 titanium rods in my jaw.  In 4 months I get teeth screwed on them.  In the meantime I have a “flipper,” or what my dentist calls “party teeth.”  I am not yet allowed to wear it, so I have to cover one side of my face when I smile.

I think I’ll be allowed to use the flipper next Thursday at the Mah Jongg game.