Researcher explores the history of dental issues, and possibilities for avoiding orthodontia for youths

Dental issues are distinctly a human issue, and according to dental anthropologist Peter S Ungar, most vertebrate creatures do not have crooked teeth, cavities or gum disease.

Human teeth are intriguing under a microscope – the enamel crystallites in one tooth are like one-one thousandth the width of a human hair. Together they create the enamel cap, from the surface to the dentin. The dentin is the part of the tooth beneath the enamel.

“Engineers have much to learn from teeth,” Unger wrote in Scientific American. “Their remarkable strength comes from an ingenious structure that gives them the hardness and the toughness to resist the start and spread of cracks. Both properties result from the combination of two components: a hard external cap of enamel made almost entirely of calcium phosphate and an internal layer of dentin, which also has organic fibers that make the tissue flexible.”

This design evolved over hundreds of millions of years, Unger writes in the April 2020 edition of Scientific American. He reports that the first vertebrates did not have a jaw, or teeth, but descendants of these fish had toothlike plates of calcium phosphate that created a sort of armor to protect the fish.

It was approximately 415 million years ago when enamel first appeared in the scales of a group of animals known as the sarcopterygians. Ungar suggests that enamel started in skin structures and moved to the mouth later.

Chewing evolved, according to Ungar, in response to the mammalian need to extract every possible calorie from each bite. In order to chew mammals need teeth that align “to a fraction of a millimeter.” Ungar says that explains why mammals have two sets of teeth, not many that grow in when other teeth wear out. He says that enamel came as part of the same adaptive package that swapped the ability to chew with the ability to grow new teeth as others wore out.

And, it’s the same thing that makes teeth strong that also explains why they fall short of what we need them to do, writes Ungar.

“The basic idea is that structures evolve to operate within a specific range of environmental conditions, which in the case of our teeth include the chemicals and bacteria in the mouth, as well as strain and abrasion. It follows that changes to the oral environment can catch our teeth off guard,” Ungar wrote. 

“Such is the case with our modern diets, which are unlike any in the history of life on our planet. The resulting mismatch between our biology and our behavior explains the dental caries (cavities), impacted wisdom teeth and other orthodontic problems that afflict us.”

Cavities happen when the harmful and beneficial bacteria are out of balance, the pH reduced and there’s a “shift in balance wherein a few harmful species outcompete those that normally dominate the oral microbiome.” Then, saliva can’t do its job to protect the enamel.

Enamel cannot regrow because it is built from the inside out and once the tooth cap is formed the surface cells die. But dentin can regrow and will work to heal diseased areas throughout an individual’s life. Unless cavities are growing which overwhelm the natural defenses and may cause an infection in the pulp, killing the tooth.

Treatments to keep teeth healthy or aligned may not even be required with the proper diet.Ungar suggests.

“Perhaps if we fed our children foods requiring vigorous chewing from an earlier age, like our ancient ancestors did, we could spare many of them the need for such interventions,” Ungar wrote.