There are a vast number of things in our bodies that we take for granted. Perhaps at the top of that list is our tooth design.
Our teeth have to withstand chewing motions that spread forces around. They must be able to hold, fracture, and fragment food items without being broken themselves and do this millions of times over a lifetime. Their opposing surfaces must align to a fraction of a millimeter. They also exist in an environment that is teeming with life. Our mouth is populated by some 700 different species of bacteria, some of which produce lactic acid, which attacks the enamel.
The bacteria are essential because they fight disease, help with digestion, and regulate various body functions. In ancient times the bacteria were limited because of the diet of ancient humans. Now with massive amounts of sugar in our diet, the bacteria are catalyzed in their reproduction. Our saliva buffers teeth against the lactic acid and bathes them in calcium phosphate, which remineralizes their surface.
Teeth have hard enamel caps made up of calcium phosphate. The material is composed of thousands of rods called crystallites, which are 1000th the width of a human hair. These are grouped together in bundles called prisms with tens of thousands of prisms per square millimeter. These prisms run parallel to each other, weaving and twisting as they go from the surface of the tooth to the underlying dentin. Dentin is made of tiny collagen fibers that run between structures called tubules. This tooth design resists cracks and gives toughness and impressive durability.
So if these things are true, why do I have cavities, problems with wisdom teeth, and expensive trips to the dentist? The answer to that question is diet. When we study ancient humans, we don’t see decays in their teeth, impacted wisdom teeth, or evidence of gum disease. In the animal world, it is rare to see a cavity or a decayed tooth. The struggles we have with our teeth is because we have softer and more sugary foods than our ancestors ate.
In the April 2020 issue of Scientific American (page 45), there is a wonderful article titled “The Trouble with Teeth” by Peter Ungar. He attributes this “miracle of design” and “elegant configuration” to evolutionary processing. We suggest that the tooth design speaks of wisdom and intelligence beyond that of blind chance.
— John N. Clayton © 2020