By: Tia Ghose, www.livescience.com
That gnawing, throbbing pain, the sharp jolt from a cup of hot coffee — almost everyone alive today has experienced the intense pain of a toothache.
But why exactly do we get toothaches?
In short, it is because, unlike hair or nails, teeth are made up of living tissue, said Christine Wall, an evolutionary anthropologist at Duke University who studies the evolution of teeth. Pain is the brain’s way of knowing something has gone wrong in the tissue, she said.
“Under the cap of enamel, there are two other layers that are living,” Wall told Live Science.
Those living tissues are threaded with nerves that send signals to the brain, when encountering hot and cold foods, or when experiencing forces so high that a tooth could break, Wall said. [Chew on This: 8 Foods for Healthy Teeth]
Teeth are made up of several layers: The outer, hard surface, called enamel, is nonliving, but the inner portion of the tooth is made up of hard, bony cells called dentin. Below that, the pulp — soft tissue filled with blood vessels and nerves — anchors the root of the tooth into the gum and extends from the tooth crown to the root.
Cavities, or holes that occur when the enamel gets eroded, are the likeliest culprits in tooth pain. Carbohydrates, especially from highly processed, sugary foods, are gobbled up by the bacteria that form plaque on teeth.
“The metabolic waste from the plaque bacteria is what rots the teeth,” said Peter Ungar, a dental anthropologist at the University of Arkansas, and the author of the forthcoming book “Evolution’s Bite” (Princeton University Press).
Once the enamel erodes, the exposed dentin registers pain in response to heat, cold and pressure. If bacteria invade the pulp cavity, they can also cause inflammation and infection. Nerves in the cavity will scream with every sip of hot coffee, every bite of cold ice cream, and will often require a root canal, which scoops out the inflamed pulp and replaces it with a rubbery material, according to the American Association of Endodontics (AAE). Cracked teeth can also cause pain when chewing as the outer tooth fragments jostle against the pulp, irritating the sensitive inner portion of the tooth, according to the AAE.
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