What our teeth reveal about us | Science| In-depth reporting on science and technology | DW | 11.03.2019
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Science

What our teeth reveal about us

Have you lost a milk tooth or had a tooth pulled out? A group of researchers wants them. They can find out all sorts of useful medical information about you from your teeth — even predict future diseases.

A girl with a milk tooth in her hand (luna/Fotolia.com)

Don't just throw away that milk tooth

Are you always brushing your teeth? One look inside your mouth and your dentist will know. The worse the condition of the teeth, the lower on average the social status of the patient.

At the same time, teeth are like a fingerprint: forensics can use a dental impression to identify the perpetrator or the victim at a crime scene. We've known this ever since Inspector Columbo, played by Peter Falk, fished chewing gum out of a trash can in the well-known television series and solved a case.

Here's where it gets exciting: Researchers now claim to be able to draw information from a child's teeth about whether they are likely to develop mental illness. In older people, on the other hand, teeth may reveal whether they have been exposed to heavy metals and whether there is a high risk of Alzheimer's disease.

"In the field of mental health, is it possible that we have been ignoring this potential marker that literally falls out of people's mouths or is extracted and then thrown away and ends up in landfills?" asked Erin Dunn of the Massachusetts General Hospital in Boston, US. The epidemiologist for psychiatric diseases thinks that teeth, especially milk teeth, should be given much more attention. 

Read more: What to do when you break a tooth

X-Ray of dentures (picture-alliance/BSIP/AJ PHOTO)

The tooth enamel grows ring-shaped. Too much stress hormone in the blood changes the density.

Your stress levels are reflected in your teeth

At a meeting of the American Association for the Advancement of Science (AAAS) last week in Washington, D.C., researchers showed what teeth can reveal about future diseases. The most important finding was: if a child has a lot of stress during the first years of their life, you can see it in his or her teeth.

The individual layers that build up the tooth in the enamel are thinner and less dense, Thomas Boyce says. He is a health psychologist at the University of California at San Francisco: "It increases vulnerability to dental cavities." 

These changes can be measured by examining a milk tooth in a 3d model based on an X-Ray.

Stress does not just come from excessive demands at school, but also, for example, from problems with parental relationships, constant noise or even physical and/or mental abuse. Those who have a lot of stress produce a lot of the stress hormone cortisol. Its concentration can be measured in the blood and saliva, says Boyce. 

Read more: Würzburg scientists detect dental infections with gum

Watch video 03:19

Dental phobia

"But of course what we really want and what we are really after and what these snapshots fail to show is total cortisol exposure," Boyce added. 

And that's what having the actual teeth can reveal, as the stress hormone influences their development.

Stress makes you ill

From 2003 to 2005, the Peers and Wellness Study examined children in 350 families in the San Francisco Bay Area. The researchers determined the size, area, volume, color and thickness of the children's milk teeth. They found evidence that children with ADHD and impaired social behavior had thinner enamel and smaller inner pulp than the rest of the children.

"So far we have used saliva, blood and the intestinal microbiome in stool samples as biomarkers in psychiatry," Erin Dunn said. "Teeth have not really been that widely used in psychiatry."

But they could provide important information about the conditions under which a child spent the first few years of his or her life.

According to Dunn, the causes for many mental illnesses lie mostly with the experiences a person has, and not with their genes - especially during the first years of life. This includes stress. Several studies show that children exposed to stress have an increased risk of suffering from post-traumatic stress disorders, depression or eating disorders later on. So why not have every prospective school-child's milk tooth X-rayed when they start school? 

Read more: What to do to keep your teeth.

Neanderthal jaws in the archives of the California State University Northridge (Getty Images/AFP/E. Dunand)

Even archaeologists can find out all kinds of things about old teeth. Here are the teeth of a Neanderthal.

Teeth are like trees

Teeth form gradually. Milk teeth and permanent teeth are already formed in the embryo, but only develop after birth, and at different speeds, depending on the position and function of the teeth. The milk incisors form first, while the milk molars are only fully developed in three-year olds, and are the last permanent teeth to come through in teenagers.

"Teeth permanently record stressors that occur during development," says Erin Dunn. The enamel layers are formed in a circular fashion, similar to the age rings of a tree. "They tell us not only whether a potential stress occurred but when during development." Teeth are therefore even more revealing than blood or saliva samples.

Watch video 03:39

Fluoride in toothpaste

Heavy metals are stored in the teeth

If heavy metals such as lead are present during tooth formation, they are stored in the developing tooth enamel. This was demonstrated in 2005 by researchers from the University of California at Irvine in rats.

The same thing probably happens to humans.

People who are exposed to high concentrations of lead before or shortly after birth have a higher risk of becoming schizophrenic later in life, US researchers showed in 2017. These researchers proved the lead exposure stored in the milk teeth of their test group.

Marc Weisskopf, neurobiologist and epidemiologist at Harvard University in Boston, suspects that high lead concentrations could also increase the risk of Alzheimer's disease. One theory is that heavy metals aggravate the formation of amyloid plaques in the brain that are typical of Alzheimer's disease. He is currently investigating this in a study with more than 400 volunteers together with a clinic for former soldiers.

When a tooth is extracted from a patient there, the researchers take care of the valuable part. When a patient dies, a whole set of teeth is given to the scientific community - with the patient's consent, of course.

Research into teeth as a predictive tool for later diseases is still in its infancy. Much is unclear, as there have only been a few studies. But at the AAAS meeting in Washington, the researchers made one thing convincingly clear: fallen out teeth are far too valuable to just keep inside some cupboard or drawer as a memento.

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