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Ancient Maya tooth sealant glued gemstones in place—and may have prevented tooth decay

The ancient Maya believed their breath was a link to the divine. To purify it, many people filed, notched, and polished their teeth, some even decorating them with gemstones. Now, a fresh analysis suggests the sealant used to hold these jewels in place may have had therapeutic properties, which could have helped prevent infections.

During the Classic period (200 to 900 C.E.), many lowland Maya people in what is now Guatemala, Belize, and Mexico affixed colored stones such as jade, turquoise, and pyrite to the front of their teeth. Maya dentists drilled holes into the enamel and dentine, then fit the stones and applied a sealant, usually as part of a rite of passage to adulthood.

This dental adhesive has proved remarkably durable: More than half of such modified teeth from archaeological digs still have their stone inlays intact. Previous analyses of the adhesive found inorganic materials similar to cement, and hydroxyapatite, a mineral obtained from ground teeth and bones. These materials helped strengthen the mixture, but likely wouldn’t have been sticky enough to hold the stones in place. The nature of the binding agent has long been a mystery.

So Gloria Hernández Bolio, a biochemist at the Center for Research and Advanced Studies of the National Polytechnic Institute in Mexico, and colleagues analyzed the sealants in eight teeth found in burial sites across the Maya empire. They used two techniques: One distinguishes groups of organic compounds based on the amount of light they absorb; the other separates chemical mixtures using heat, before counting individual molecules.

In the sealants, the researchers found 150 organic molecules common in plant resins, they reported last month in the Journal of Archaeological Science: Reports. Each sample had a binding component like plant resin or gum, which have also been used for their water-repelling and gluelike properties since antiquity. Statistical analysis revealed the sealants could be separated into four groups based on that location, suggesting local practitioners each had their own recipes. The mixtures appear to have been well thought out, Hernández Bolio says. “Each ingredient has a specific task.”

Most samples included ingredients found in pine trees, which other research suggests can fight bacteria that cause tooth decay. Two teeth showed evidence of sclareolide, a compound found in Salvia plants that has antibacterial and antifungal properties, and is currently used as an aroma fixative in the perfume industry. Sealants from the remote outer Copán region, near the border of modern Honduras and Guatemala, included essential oils from mint plants whose components potentially have anti-inflammatory effects. This ingredient wasn’t found elsewhere, possibly reflecting connections with other Maya groups or traditions, the authors say.

“Most important for them was the binding properties,” says Hernández Bolio, whose grandfather is Yucatec, a group that’s part of the historic Maya civilization. Today’s Maya still use these plants for medicinal purposes, she says, so ancient people may well have been aware of their effects.

The study finally addresses the long-standing question of how these stones were affixed, says Cristina Verdugo, an anthropologist from the University of California, Santa Cruz. Not only were the Maya dentists good at their work, but they also knew “how to avoid potential unwanted side effects,” such as infection or other dental issues postmodification, she says.

But Joel Irish, a dental anthropologist at Liverpool John Moores University, says he’d like to see more evidence concerning the antiseptic and therapeutic properties. “It is a key takeaway that relies on previous, though compelling, research.”

Oral hygiene was important to the Maya, says co-author Vera Tiesler, a bioarchaeologist at the Autonomous University of Yucatán. She points to Janaab’ Pakal, the Maya king of Palenque, who died in 683 C.E. at the age of 80 with nearly all his teeth and no signs of decay in those that remained—a tribute to the remarkable dental skills of his people.

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