Archaeologists have found out what was used to blacken teeth in ancient Vietnam

Scientists have found in Vietnam the earliest direct scientific evidence that people deliberately "blackened" their teeth - it happened about 2000 years ago, during the Iron Age.

The discovery was made at the Dong Xa archaeological site in the north of the country: teeth with black pigment were found in one of the burials, and dating of materials from the grave showed an age of about two millennia.

Why it matters In the past, dark spots on ancient teeth were often attributed to chance - for example, diet or habits like betel nut chewing. But in this case, the researchers decided to test whether the staining was accidental, or a deliberate cosmetic procedure.

The team took samples from the three people they found and examined the surface of the teeth without destroying the remains - using scanning electron microscopy and portable X-ray fluorescence. The analysis showed unusually high levels of iron and sulphur on the enamel. Such a "chemical signature" matches well with iron and tannin-based formulations (similar to iron-tannate mixtures) that are known in traditional tooth blackening recipes.

To make sure, the scientists reproduced the procedure in the laboratory: they stained a modern animal tooth with a mixture similar to traditional formulations (based on iron-gallic components) and compared the result with ancient teeth. The chemical pattern turned out to be very close - reinforcing the conclusion that the ancient inhabitants had indeed applied a special composition, rather than "getting the colour by chance".

The authors suggest that the practice may have begun during the Dong Son culture and existed for centuries as part of a shared cultural identity among communities linked by human exchange and movement.