Archaeologists have traced Vietnam's ancient tradition of blackened teeth back 2,000 years, discovering that Iron Age people used iron oxide to achieve the striking cosmetic effect. The study, published in Archaeological and Anthropological Sciences, analyzed skeletons from Dong Xa in northern Vietnam's Red River delta, revealing high concentrations of iron and sulfur in the discolored dental enamel.

Using advanced techniques including X-ray fluorescence and SEM-EDS, researchers identified the chemical signature of iron salts combined with tannic acids. Lead author Yue Zhang from the Australian National University explained that this iron-tannin mixture, likely applied over weeks, created a permanent black coloration that required touch-ups every few years. The practice persists today across Southeast Asia, though modern methods incorporate botanical materials alongside iron-based substances.

The discovery connects archaeological evidence with contemporary tooth-blackening traditions, suggesting the practice emerged during the Iron Age when iron tools became widely available. While the original purpose remains unclear, researchers speculate it may have evolved from tooth ablation rituals or as an enhancement to betel-nut chewing stains. This finding establishes blackened teeth as one of Southeast Asia's oldest continuous cultural practices, with the same fundamental chemical process maintaining its distinctive appearance for millennia.