They Outlast the Rest of You

When a body cannot be identified any other way, the answer is usually in the mouth. And the reason is a property of enamel that has nothing to do with teeth being important.

Enamel is the most durable thing the body makes

Bone is about 65 percent mineral by weight. Enamel is around 96 percent — almost entirely hydroxyapatite crystal, with barely any organic material and no living cells.

That composition is why enamel cannot repair itself, and it is also why it survives.

Fire. Soft tissue is gone in minutes. Teeth, protected inside the jaws and by the tongue and cheeks, routinely survive temperatures that cremate everything around them.

Water and time. There is nothing for bacteria to consume, so enamel does not decompose the way collagen-rich bone does.

Burial. Archaeologists recover teeth from sites where the skeleton has largely dissolved.

So teeth are frequently the last identifiable component of a person, and often the only one.

And the fillings are the actual signature

Here is what makes dental identification unusually powerful, and it’s a quirk of record-keeping rather than of biology.

Every filling has a shape. That shape was determined by the exact outline of a specific cavity in a specific tooth, drilled by hand on a particular afternoon. Two people do not have the same filling in the same tooth with the same margins.

And it was written down. Every dental appointment produces a chart marking which surface of which tooth was restored, with what material — and usually X-rays showing the exact outline.

So there is a detailed, dated, physical record of the inside of a person’s mouth, held by a third party, created for a completely unrelated purpose.

That is why identification can be so fast. A forensic odontologist compares the post-mortem findings against the chart and looks for concordant points. Enough matches, with no unexplainable discrepancies, and it’s a positive identification — often in hours, at a fraction of the cost of DNA analysis.

Where the method fails

One limitation, and it is total: no records, no identification.

Dental identification is comparative. It cannot tell you who somebody is from their teeth alone — it can only tell you that these teeth match that chart. Somebody who has never seen a dentist is invisible to the method entirely.

Which produces an uncomfortable pattern. The people hardest to identify this way are the people who had least access to dental care, and they are frequently the same people least likely to be reported missing.

The other limitation is administrative. Records get destroyed after retention periods expire, practices close, charts stay on paper in a filing cabinet in one country while the body is in another. Much of the work is finding the chart rather than reading the mouth.

What teeth say beyond identity

Two things, and the second is remarkable.

Age. Which teeth have erupted, in what order, and how worn they are, gives a workable estimate — very accurate in children, where the eruption sequence runs to a reliable schedule, and progressively vaguer in adults.

And where somebody grew up. This is the extraordinary one.

Enamel forms once, in childhood, from the minerals available at the time. The ratios of strontium and oxygen isotopes in local drinking water vary geographically, and whatever ratio was in the water goes into the crystal and stays there permanently. Enamel does not remodel, so it never updates.

Which means a tooth carries a chemical signature of the water somebody drank as a child, unchanged, for the rest of their life and long after. Isotope analysis of enamel has been used to establish that unidentified remains grew up in a different region or country from where they were found — narrowing a search that had nothing else to go on.

The same technique reads archaeology. Isotope work on teeth from Stonehenge-era burials showed individuals who had grown up hundreds of miles away, which is how we know how far Bronze Age people traveled.

The Tsunami and the technique

Dental identification is not a laboratory curiosity. It is the working backbone of mass-casualty identification, and INTERPOL’s disaster victim identification protocol lists it as one of the three primary identifiers alongside fingerprints and DNA.

After the 2004 Indian Ocean tsunami, teams working in Thailand identified thousands of victims, and dental comparison did a large share of the work — because fingerprints had been destroyed by water and time, DNA analysis was slow and overwhelmed, and teeth survived.

That is the practical reason it matters. When the scale is large and the conditions are bad, the mouth is what’s left.

The uncomfortable symmetry

There is something worth sitting with in all of this.

The chart your dentist fills in — surface, tooth number, material, date — is created as an administrative note about a filling. Nobody involved is thinking about identification. It is the most mundane paperwork in healthcare.

And it becomes, without anybody intending it, the most durable and specific record of a person’s physical body that exists anywhere.

Teeth get moralized about as though they were a report card on somebody’s discipline. They’re not. They are the hardest thing you’re made of, they hold a chemical memory of the water you drank as a child, and they will still be legible when nothing else about you is.

The short version

Enamel is 96 percent mineral, has no living cells, and survives fire, water, burial and time.

The fillings in it are unique shapes recorded in dated charts by a third party for a completely different reason, which makes identification fast and cheap when records exist.

And the isotopes locked into the enamel when you were a child still say where you grew up, long after everything else has stopped saying anything.