WEDNESDAY, April 5, 2006 (HealthDay News) -- Human teeth from almost 9,000 years ago show evidence of prehistoric -- but highly developed and precise -- dental drilling and filling, anthropologists say.
The find in Pakistan, reported in this week's Nature, pushes the origins of dentistry to long before recorded history, but leaves behind another mystery, since these procedures appear to have died out after 6,500 B.C.
But the precision and placement of the drilled holes -- in teeth with evidence of cavities -- leaves little doubt they were done to treat tooth decay, according to the researchers.
"Something interesting is going on with those teeth, and it looks like it had something to do with dentistry," said David DeGusta, an assistant professor of anthropological sciences at Stanford University in Palo Alto, Calif.
DeGusta, who was not involved in the Pakistani dig, is one of the world's leading experts on "prehistoric dentistry." In the late 1990s, his team discovered a similar, precisely drilled hole in a 1,000-year-old tooth found in a burial site in Colorado. That find remains the first evidence of prehistoric dentistry in the American Southwest, and one of only two such finds in the Americas.
According to the American Dental Association, the first recorded mention of dental health comes from the ancient Sumeria of 5,000 B.C., with a text attributing dental decay to "tooth worms." The first recorded evidence of dentistry, per se, comes from a tomb inscription for Hesy-Re, a doctor-scribe who was lauded as "the greatest of those who deal with teeth and of physicians." His dental office closed up shop in about 2,600 B.C., archaeologists say.
The Pakistani site, a "neolithic cemetery" at Mehrgarh in the southwestern province of Baluchistan, goes further back, to a 1,500-year period between 5,500 B.C. and 7,000 B.C. However, the anthropological team working there said that, despite its antiquity, the site revealed that the early agricultural society they uncovered had "an increasingly rich cultural life with technological sophistication based on diverse raw materials."
The first evidence of dentistry at the burial ground emerged about five years ago, when excavators discovered two molars with tiny perfectly drilled holes.
In this latest report, anthropologists led by Dr. Roberto Macchiarelli, of the University of Poitiers in Poitiers, France, said they have since discovered 11 permanent fillings in molars from both the upper and lower jaws of four females, two males and three individuals of unknown gender.
High-tech electron microscopy revealed precise hole formations that could only have been mechanical in nature, the scientists said, and "smoothing" along the margins of the holes indicates that months or years of chewing occurred after the holes were drilled.
"The teeth of at least one individual reveal that the procedure involved not just the removal of the tooth structure by the drill, but also subsequent micro-tool carving of the cavity wall by either the operator or the patient," the anthropologists wrote in their report.
Because molars lie far back in the mouth, there's no evidence that the holes were drilled for any decorative purpose, the researchers said. Four of the 11 teeth showed definite evidence of nearby decay. According to DeGusta, "When you have people drilling teeth that had cavities, it's not a stretch to suggest that it might have been early dentistry."
Macchiarelli's team noted that the drilled holes often "exposed sensitive tooth structure, so some type of filling may have been placed in the cavity," although the scientists stressed there was no evidence to confirm that.
How did ancient humans produce such precise dental work?
DeGusta's team found that an obsidian flake mounted on the tip of a slim rod, then rotated vigorously by the palms, effectively drilled through human tooth enamel to produce conical holes similar to the one seen in the Colorado find. And in its own research, the team in Pakistan used a "bow drill" technique (using a local material, flint, instead) to similar effect.
Macchiarelli's team also noted the presence throughout the Pakistani dig of drilled, decorative beads made from turquoise, lapis lazuli, carnelian and other precious stones. Since precision drilling would be needed to create such jewelry, they speculated that "the know-how originally developed by skilled artisans for bead production" gave rise to its use in prehistoric dental offices.
Degusta called that theory "a reasonable hypothesis, but I'd like to find some way to test it. Maybe we could compare the micro-striations of the teeth with those of the beads to see if they really do match."
But one mystery remains: No evidence of dentistry has been found in Mehrgarh graves dating from later than 6,500 B.C., which suggests the highly skilled craft died out.
More information
For more on early dentistry, head to the American Dental Association.
