The standards of beauty have always varied from one culture to another. But few have refined it as much as this one. In Vietnam, for two millennia, the most desirable mouth had the blackest teeth, according to a new study.
Dong Xa, the archaeological site that provided the oldest evidence of tooth blackening
The Dong Xa site was formally excavated in 2001 and 2004. Among the 72 human remains unearthed, three teeth caught the researchers’ attention. Two came from Iron Age burials, dated between 2,157 and 1,830 years before our era. The third came from a more recent tomb, dated around 400 years old. All three teeth had a consistently dark coating too regular to be accidental.
Published in the journal Archaeological and Anthropological Sciences, the study analyzed these three teeth without destroying them. The researchers used electron microscopy to examine the enamel on a microscopic scale, combined with X-ray fluorescence analysis. All three samples yielded the same result. High concentrations of iron and sulfur, far too high for an ordinary tooth. It was the signature of an intentional treatment.
Fer and tannins, the two ingredients that explain 2,000 years of black teeth in Vietnam
Iron is the key ingredient in Vietnamese teeth blackening. Mixed with tannin-rich plant extracts, it produces a simple but formidable chemical reaction. The tannins cling to iron ions and together form a dense pigment. The air then oxidizes the mixture, fixing a durable black layer on the enamel. The researchers tested this mechanism in the laboratory by treating a modern animal tooth with iron gall ink. The chemical result obtained precisely matched the teeth from Dong Xa.
What this analysis also proves is that tooth blackening has nothing to do with betel chewing. Betel leaves reddish-brown traces, not black. This chemical distinction now allows the two practices to be separated in archaeological records, which was not possible until now. A black tooth and a brown tooth tell two very different stories.
Why Vietnamese tooth blackening was the most elaborate in Asia
Tooth blackening existed in many regions of Asia, the Pacific, and even Amazonia. But the Vietnamese method was in a league of its own. The complete process could last 20 days. It started by abrading the enamel with acidic agents for three days. Next came a red dye phase with shellac juice, followed by the final black layer, obtained with a mixture of tannins, spices, and sometimes vitriol. It ended with polishing with coconut shell tar.
The result was spectacular and long-lasting, with no touch-ups needed for two to three years. Chinese texts from the Han period already mentioned a “kingdom of black teeth” located in what is now Vietnam, between 25 and 220 AD. The teeth from Dong Xa now bridge the gap between these written descriptions and archaeological reality. Among the Dong Son individuals studied, at least one-fifth had colored teeth, and some estimates reach 40%. Black teeth were not a curiosity. They were the norm.
